Age-related Macular Degeneration (AMD) is an up-to-date untreatable chronic neurodegenerative eye disease of multifactorial origin, and the main causes of blindness in over 65 y.o. people. It is characterized by a slow progression and the presence of a multitude of factors, highlighting those related to diet, genetic heritage and environmental conditions, present throughout each of the stages of the illness. Current therapeutic approaches, mainly consisting on intraocular drug delivery, are only used for symptoms relief and/or to decelerate the progression of the disease. Furthermore, they are overly simplistic and ignore the complexity of the disease and the enormous differences in the symptomatology between patients. Due to the wide impact of the AMD and the up-to-date absence of clinical solutions, Due to the wide impact of the AMD and the up-to-date absence of clinical solutions, different treatment options have to be considered. Cell therapy is a very promising alternative to drug-based approaches for AMD treatment. Cells delivered to the affected tissue as a suspension have shown poor retention and low survival rate. A solution to these inconveniences has been the encapsulation of these cells on biomaterials, which contrive to their protection, gives them support, and favor their retention of the desired area. We offer a two-papers critical review of the available and under development AMD therapeutic approaches, from a biomaterials and biotechnological point of view. We highlight benefits and limitations and we forecast forthcoming alternatives based on novel biomaterials and biotechnology methods. In this second part we review the preclinical and clinical cell-replacement approaches aiming at the development of efficient AMD-therapies, the employed cell types, as well as the cell-encapsulation and cell-implant systems. We discuss their advantages and disadvantages and how they could improve the survival and integration of the implanted cells. Age-Related Macular Degeneration (AMD) is a multifactorial degenerative eye disease, estimated to affect nearly 290 million people by 2040 . It is cThe retina is the inner component of the eyeball . It is aThe choroid is a vascularized layer that supplies oxygen and nutrients to the whole retina. Additionally, it serves as physical support and it also contributes to the maintenance of the intraocular pressure and the regulation of eye’s temperature . BrM is Since choroid, BrM and RPE provide physical support for the neural retina, and since they are in charge for both, the interchange of the metabolic molecules and the correct physiological functioning of the photoreceptors, any degenerative pathology affecting one of these layers, would also impair or even kill the photoreceptors with the consequent visual impairment or even blindness. In AMD, BrM weakens and thickens, thus losing its permeability and diffusive properties . Low perIn the human eye, there are approximately 137 million photoreceptors: 7 million cones and 130 million rods. Cones are concentrated in the center of the eye (in the fovea) and their density decreases radially from the center to the periphery. Rods are concentrated at about 20° from the center (approx. 6 mm from the fovea) and their density also decreases toward the periphery but, slower than the cones. Photoreceptors’ degeneration is irreversible because all cellular regeneration and repair processes are inhibited by the unfavorable molecular conditions that prevail throughout the central nervous system. Among them, the absence or inappropriate concentration of neurotrophic and/or neurotropic factors, the appearance of inflammatory processes, astrocytic reactions and inhibitory molecular signals (myelin binding proteins or excess of neurotransmitters and ions), as well as the presence of myelin-associated factors and/or glial scar .in situ neuroprotective and neuroregenerative biomolecules , macrophage migration-inhibitory factor, and soluble CD95L (which regulates the innate immune response) . FurtherHowever, at the same time, the eye is one of the few immunoprivileged tissues, characterized by the presence of negative regulators which prevent the activation of local inflammatory processes  and wherImmunoprivileged conditions are the result of a synergy of physical, molecular and cellular barriers  implemenBlood-retina barrier and the indirect draining of the ocular microenvironment by the lymphatic system constitute the physical barriers. Blood-retina barrier is formed by the endothelial junctions of RPE cells which impede immune system cells to leak into the eye . The indAge-related macular degeneration-originated damages of the RPE alter this state of the eye. Cellular and tissue engineering AMD therapy procedures, either injections or surgical implants, also contribute to the worsening of the situation.The retina, the tissue most severely by AMD is an easy target for cell and tissue engineering therapeutical approaches, because of its location and its small size, which allow easy surgical accessibility and transplantation of smaller amounts of replacement cells compared to other organs. Besides, the availability of a large number of clinical variables for the assessment of the visual function, facilitated the precise evaluation of the effectiveness of novel AMD therapies  and fostBiomolecules can be used for therapeutic reasons on a neural tissue, through two, non-mutually exclusive mechanisms. On one side, through the application of neuroprotective and neuroregenerative factors  which diffuse into the host tissue and rescue the degenerating cells. On the other, by implanting healthy cells into the host tissue and replacing the damaged/degenerated cells by the new ones. In the first case, to avoid molecules/cells dispersion into the host tissue, encapsulation can be employed. Porous materials permits the signals of the damaged environment to reach the implanted cells and stimulate the production of neuroprotective biomolecules, as well as to allow the diffusion of the secreted molecules to the damaged tissue . HoweverCells source is a key component to the success of any cell therapy. We can identify three main sources for retinal implants:They represent an attractive source due to their ability to self-renew and differentiate into any type of cell in the body (pluripotent). However, they also present serious disadvantages, e.g., difficult and expensive cell differentiation and cell expansion protocols, complex bioengineering processes, tumor formation risks, rejection risks, possibility of harboring donor’s genetic defects, possible ethical challenges, etc. .They are a source of autologous multipotent cells. However, these cells could be hard to obtain and they could harbor the genetic cause of the disease .They are a relatively new source of stem cells developed by directly reprogramming adult somatic cells to transit to a pluripotent state. The use of iPSCs is exciting because iPSCs can be derived from the patient’s own tissue and are associated with fewer ethical concerns than ESCs. Using a combination of soluble factors, iPSCs can be expanded and differentiated into various types of retinal cells, including rods, cones, and retinal ganglion cells. They present a very low rejection risk, however, they could conserve epigenetic characteristics of the original cells, harbor the disease genes from the donor and lead to tumor formation . The posAt the present, cell encapsulation represents the preferred therapeutic approach since direct injection of cells has been proven to be suboptimal, due to cell losses from the rapid dispersion into the host tissue, along with glia and host immune system attacks.In their attempt to create artificial BrM,  generatein vitro study they showed that their device had better drug absorption, increased antiangiogenic potential, and prolonged inhibition of vascular endothelial growth factor (VEGF) activity compared to the free drug solution  approval for AMD treatment :NT-501  is a non-biodegradable polysulfone scaffold to encapsulate genetically engineered human RPE cells. The device is injected intravitreally and provides a sustained delivery of ciliary neurotrophic factor for months. The device is sutured into the sclera by a titanium loop to avoid migration risks and requires surgery to get removed. The device is in Phase III clinical trials and it has been effective for up to 18 months providing photoreceptor protection , g.NT-503 (Neurotech Pharma) is a non-biodegradable polyethylene terephthalate semipermeable hollow fiber membrane that encapsulates genetically engineered human RPE cells that synthesize and secrete a VEGF receptor fragment crystallizable region. This device is implanted intravitreally through a peritomy and subsequent 3 mm sclerotomy and it has been shown to maintain therapeutic effects for 12 months in W-AMD and was 20 times more efficient than injections of Ranibizumab. As with NT-501, the device gets fixed to the sclera to avoid migration and also requires surgery to be removed. This device is in Phase II clinical trials .iTrack275 Microcatheter  is a micro-calibrated pump for supra-choroidal drug/cell delivery, surgically inserted through a non-biodegradable microcatheter that includes an optical fiber illuminator to guide the insertion of the device. This suprachoroidal pump allows an improved supply of drugs, a longer duration and a greater penetration into the tissue due to the proximity to the choroid and the BrM, with the consequent avoidance of blurred vision, changes in the lens and in the vitreous (traction exerted), compared to pharmacological delivery by intravitreal or periocular injection. The device has been used in combination with Bevacizumab in advanced AMD and with cells derived from human umbilical tissue (CNTO 2476) for dry-AMD (D-AMD), showing good safety and efficacy with no serious complications . Phase IEarly attempts of AMD tissue reconstruction consisted of either autologous (translocated explants) or allogenic  RPE transplants, to replace the damaged retinal tissue  by substRetinal pigment epithelium degeneration can lead to the development of more advanced AMD stages so, transplants of healthy RPE cells have been considered as candidates for the deceleration of the disease . Vision in vitro and/or in vivo with comparable results: gelatin -modified membranes were developed to serve as a substrate for RPE growth . The surin vitro or in vivo, with only a few of these are in clinical trials  between the retina and the native RPE cells.Safety and tolerability of subretinally transplanted hESC-RPE cells in suspension in patients with advanced D-AMD has been assessed in a Phase I/II trial . The traRegarding RPE monolayers transplantation, a Phase I Trial tested the safety of an ESCs-RPE patch on a vitronectin-coated polyester membrane subretinally implanted in two patients affected by W-AMD . ImplantParylene and PLGA membranes are in Phases I/II and Phase I/II Clinical Trials, respectively . A PhaseIt is worthy to state that a sheet of iPSC-derived RPE implanted in a W-AMD patient after removal of the neovascular membrane did not show visual acuity improvement and provoked a macular edema 1 year after surgery , while aResuming, up to now, both, RPE cells injected in suspension and implanted as monolayers on artificial BrMs showed good preliminary results in terms of safety and tolerability. RPE cells injected in suspension have several drawbacks such as the necessity to migrate from the injection site and the tendency of suspended RPE to de-differentiate, problems not present in implanted scaffolded RPE monolayers. No positive results are available in terms of AMD therapy and visual acuity recovery.Different types of cells have been used for neural retinal cell replacement, including photoreceptor precursor cells (PPCs), photoreceptors, and retinal stem cells (RSCs)   . hiPSC-da model) . Rat RPEa model) .An interesting approach was taken by Both synthetic polymers and biological materials can be used in the fabrication of scaffolding structures for photoreceptors implants: natural materials like alginate, collagen, etc., are suitable for imitating natural architectures ; synthetScaffolds for retinal progenitor cells (RPCs) transplants can be cylindrical, mimicking the vertical disposition of cells in the retina, fibrous, mimicking the microstructure of the extracellular matrix or made by hydrogels, to mimic the mechanical properties of the retina . The empin vitro (in vitro. Transplanted RPCs-PCL integrated well into the host retina and expressed specific markers of photoreceptors (A 3D biodegradable poly-caprolactone (PCL)-microfabricated scaffold promoted good RPCs retention in vitro . Anotherin vitro . PCL scaeceptors . And -retinal extracellular matrix hybrids allowed adhesion of the hRPCs cells and helped their differentiation toward the photoreceptor phenotype in vitro . Interphin vitro . Tucker in vitro 3 months post-seed in the scaffold.Although preclinical studies have shown that all, RPCs, photoreceptor precursors and mature photoreceptors could potentially replace damaged retinal cells, clinical trials for these approaches are limited.®  injected subretinally in AMD patients  lack of vascularization, which leads to long-term necrosis in the innermost areas of the organoid (2) lack of interaction between RPE and photoreceptor layer, essential for the proper functioning of the neurons (3) impossibility of the different cell types to reach an adult state, despite the complex differentiation protocols that are carried out and (4) lack of some essential cell types, such as microglia, despite presenting a high number of cell types .The lack of certain cell types during the development of the 3D culture may be due, among other causes, to the lack of sufficient physical and environmental signals, also causing high variability between the various retinal organoid models. A possible solution to some of the limitations mentioned above in relation to this type of culture could be the use of biomaterials as a support for the organoid’s growth and differentiation and their biofunctionalization to make them able to generate the adequate physical and chemical signals (molecules of the extracellular matrix) to stimulate the correct differentiation of the cells . BiomateSummarizing, despite the promising results obtained in several studies, long-term viability of cell implants has not yet been achieved, neither significant functional integration in the host retina nor improvement of long-term visual capabilities. Up-to-day photoreceptors integration in the host retina is clearly insufficient and/or inadequate. AMD cellular therapy has three main unanswered questions: (1) RPE plays a critical role in the maintenance and function of photoreceptors but very few studies consider the interdependence between RPE cells and photoreceptors  which coAddressing these problems could allow us to identify those factors that could be used to promote cellular viability, synaptogenesis and integration of the donor cells to the host tissue. Further questions regard the safety of the transplants (depending on their origin), possibility of transferring of the pathology to the implanted healthy cells, etc. It should be noticed that the most promising results have been obtained in tissue transplantation of retinal sheets and RPE patches.Several subfoveal RPE implantation techniques have been employed in AMD patients. Most often, excision at sub-macular level is necessary for transplantation of the monolayer of fetal or adult RPE. This procedure can lead to acute tissue inflammation and a consequent eye damage that can impair the visual route, or even a higher immune reaction if the implant comes from another organism. Therefore, knowledge of the immunosuppression mechanisms is necessary to prevent rejection of RPE layers , and it in vivo.2D – 3D scaffolding approaches have been shown to be efficient for overcoming limitations like low cell survival, lack of cell integration at the transplant site or keeping the injected cells in the target area . HoweverBiodegradable polymer scaffolds for the transplantation of retinal stem cells increase survival cell rate . On the Scaffolds can actively interact with different cellular components. Furthermore, biomaterials can include biological cues  to promote cell adhesion or physical clues  to favor cell alignment and morphology. Scaffolds can also serve as supplier or repository for excitatory growth signals to accelerate tissue regeneration . BiomateBiomaterials should be biocompatible, biologically inert and sterilizable, not triggering cytotoxic processes neither inflammatory responses while promoting the proliferation, survival and migration of the implanted cells. Significant challenges are the risk of immune reactions at the implant site as well as the long-term survival and functionality of the transplanted cells.A very promising biomaterial is silkworm silk fibroin, because it fulfills all the above requirements. The encapsulation of mesenchymal stem cells in silk fibroin hydrogels promotes a substantial release of anti-inflammatory and anti-oxidant molecules with marked neuroregenerative and neuroprotective properties that could be used in AMD treatment .Current research of cell and tissue engineering approaches focuses on the preservation of photoreceptors by replacing the damaged retinal pigment epithelium since this technique has been shown to slow the degeneration of photoreceptors and even restore partial visual functions . The devin vitro and in vivo studies (Good results on biomaterials and RPE cells have been obtained from both,  studies  although studies . UnfortuIn conclusion, the use of biomaterials to generate implantable biohybrid tissue may be a potential solution to the main problems of cell transplantation, increasing the survival of implanted cells and improving their integration capacity.Cell replacement, either by using cell suspensions or by integrating cell’s sheets on a scaffolding material to promote the survival of the transplanted cells, is a promising treatment for advanced AMD stages. Pioneering studies have provided a proof-of-concept for RPE and photoreceptors transplantation as a plausible therapeutic strategy.in vitro development of artificial 3D retinal tissues, as well as the implantation and the functional integration of these constructs into the damaged retina represents the most promising therapeutic approach. Indeed, there is evidence that retinal cells on supporting biomaterials, implanted in the posterior segment of the eye, achieve a better but limited integration than injections of free cells in the same region, and slightly improve vision capabilities in different experimental models.The effective integration of the transplanted cells into the damaged retina is the principal limitation of cell therapy. The development of advanced biomaterials to support the To obtain clinically relevant therapeutic solutions, a good effectiveness of the proposed treatment must be achieved. And the key factor to increase the effectiveness of retinal implant therapies is the accomplishment of a substantial integration of the implanted cells. In this aspect an immense amount of work is still needed: the discovery of the exchange of genetic material between native and implanted photoreceptors suggests that the integration of these neurons to the host retina, reported in up-to-date studies, is probably not real, putting on the table the need to verify and reevaluate these studies. It is still unknown whether the therapeutic effect of cell transplants is due to an improvement in functionality by integration or due to production of protective factors. The elucidation of the involved mechanisms is essential for the accomplishment of this goal. Furthermore, functionality analysis of the integrated implants has to be performed.NJ-D and AG-D: bibliographic research and information synthesis, AMD course, wrote the manuscript, and equal contribution. MF-A, NS-B, and NA-L: bibliographic research and information synthesis. FA-M: clinical aspects. GG, JP-R, FR, and DK: biomaterials aspects. DG-N: biomaterials and cell and tissue therapy. GG, JP-R, DK, DG-N: manuscript revision. FP: manuscript design, information synthesis, supervision, and wrote the manuscript. All authors contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Glaucoma is a neurodegenerative disease of the visual system and leading cause of blindness worldwide. The disease is associated with sensitivity to intraocular pressure (IOP), which over a large range of magnitudes stresses retinal ganglion cell (RGC) axons as they pass through the optic nerve head in forming the optic projection to the brain. Despite clinical efforts to lower IOP, which is the only modifiable risk factor for glaucoma, RGC degeneration and ensuing loss of vision often persist. A major contributor to failure of hypotensive regimens is the multifactorial nature of how IOP-dependent stress influences RGC physiology and structure. This stress is conveyed to the RGC axon through interactions with structural, glial, and vascular components in the nerve head and retina. These interactions promote pro-degenerative pathways involving biomechanical, metabolic, oxidative, inflammatory, immunological and vascular challenges to the microenvironment of the ganglion cell and its axon. Here, we focus on the contribution of vascular dysfunction and breakdown of neurovascular coupling in glaucoma. The vascular networks of the retina and optic nerve head have evolved complex mechanisms that help to maintain a continuous blood flow and supply of metabolites despite fluctuations in ocular perfusion pressure. In healthy tissue, autoregulation and neurovascular coupling enable blood flow to stay tightly controlled. In glaucoma patients evidence suggests these pathways are dysfunctional, thus highlighting a potential role for pathways involved in vascular dysfunction in progression and as targets for novel therapeutic intervention. Glaucoma is an age-related disease of the visual system and a leading cause of irreversible blindness worldwide . ClinicaThat the ONH is a critical juncture for pathogenic processes that underlie neurodegeneration in glaucoma is underscored by its unique structure and physiology . ThroughDespite the association between systemic vascular dysfunction and glaucoma, controversy remains concerning the extent of involvement of neurovascular dysfunction in RGC degeneration during glaucoma . Much ofThe high metabolic nature of the retina necessitates a continual supply of metabolites and removal of oxidative waste . The retIn all stages of glaucoma, early through to late progression, functional and morphological changes appear in the microvasculature of both the retina and ONH, independently of IOP . Ocular In addition to blood flow, advances in fundus imaging have enabled vessel diameters close to the optic disc to be routinely performed on patients. Retinal microvascular caliber is therefore one of the most commonly reported biomarkers, with high reproducibility using semi-automated quantification methods . HoweverIn addition to vessel narrowing, further along in disease progression, OCT-angiography in glaucoma patients shows reduced vessel density in retinal capillary layers . In the 2 due to insufficient blood flow, or ‘ischemia’ . There is a higher incidence of these changes in glaucoma patients at all stages of disease progression. Interestingly, focal arterial narrowing and other microvascular changes are also associated with other non-glaucomatous optic neuropathies , suggestThe vessels of the retina and ONH have evolved mechanisms that enable blood flow to meet the dynamic metabolic demands of the tissue . Such meA, ETB1, and ETB2 receptors. ETA receptors are present in vascular smooth muscle and mediate the vasoconstrictive properties of ET-1  and endothelin-1 ET-1; . NO is a of ET-1 . ETB1 redilation . ETB2 re vessels .Aside from its role in regulating blood flow, ET-1 mediates a multitude of responses in the retina through targeting ET-1 receptors on several cell types. In rodents, intravitreal and peribulbar administration of ET-1 activates receptors on RGCs altering the rate of RGC axonal transport and promotes apoptotic cell death of RGCs . ET-1 reIn vascular autoregulation, a delicate balance between concentrations of NO and ET-1 mediates appropriate vessel response to maintain blood flow . In glauPatients with glaucomatous optic neuropathy have abnormal autoregulatory responses due to the dysfunction of the cells involved in these processes . CellulaA and ETB receptors results in increased blood flow through the retina, choroid and ONH. In DBA/2J mouse studies, delivery of bodentan, a dual ETA and ETB receptor blocker, significantly protects against glaucomatous damage at the ONH , an enzyme activated by NO and responsible for the production of cGMP), develop POAG over time, characterized by RGC axon loss, modest increases in IOP and impaired retinal vascular function  Ca2+ channels to close, reducing Ca2+ influx, leading to vasorelaxation of vascular smooth muscle cells. This chain of events leads to vasodilation and increased blood flow  and small molecules such as ATP/ADP, glutamate, and glucose, and second messengers (e.g., NO, cGMP, and cAMP; In the retina and optic nerve, gap junction channels between cells mediate intercellular communication, such as the communication between astrocytes and blood vessels. This communication can occur from glial cell to glial cell, or through glial cells communication to other cell types. The concept of neuron-glial connectivity, or ‘gliotransmission,’ was initially introduced to account for the active transfer of neuroactive molecules, from glia to neurons . Initialn slices . IncreasIn vitro studies show that an increase in hydrostatic pressure leads to loss of gap junction communication and redistribution in human astrocytes (In the retinal NVU, gap junctions are integral in the maintenance of the blood–retinal-barrier , and in trocytes . Converstrocytes .In vitro, elevated hydrostatic pressure causes astrocytes to alter localization and phosphorylation state of Cx43 (in vivo evidence for increased connectivity between astrocytes under glaucoma stress but suggest that glaucoma-related stresses can alter the connectivity of astrocyte gap junction proteins and their activity.In the optic nerve and ONH, the processes of astrocytes are interconnected via gap junction proteins Cx30 and Cx43, allowing intercellular communication that contributes to maintaining a homeostatic cellular environment . Express of Cx43 . Increas of Cx43 , whereas of Cx43  or an in of Cx43 . These sThe role of gap junctions in the vasculature of the retina and ONH is less well established. Direct electrical communication of vascular cells via gap junctions has been shown to mediate the vasomotor tone and propagation of vasomotor response in the retina . Most reThe observation that systemic and ocular vascular dysfunctions are correlated with the incidence of glaucoma raises an important question; does vascular dysfunction precede glaucomatous optic neuropathy, increasing the sensitivity of RGCs to pressure at the ONH, or is it merely a secondary consequence of other pathological changes in the disease, e.g., increased inflammation? Treatments so far have focused on the anterior chamber with current therapies aimed at lowering IOP, the only modifiable risk factor for the disease. Such drugs address IOP by modulating the amount of aqueous humor produced by the ciliary body, or by improving outflow through the trabecular meshwork . These tThe fact that glaucomatous optic neuropathy occurs at all levels of IOP, and that patients progress regardless of interventions to regulate IOP suggests that there are other factors that contribute to the degeneration of RGCs and their axons in the visual projection. As we have outlined, these factors include increased vascular dysfunction, and ocular hemodynamics are critical players in the progression of glaucoma . Systemiin vivo imaging of vasculature in the retina and ONH of glaucoma patients improve, evidence is mounting in support of vascular abnormalities coinciding with optic neuropathy in glaucoma. A key question moving forward in glaucoma research is how can we target vascular function in the design and development of new treatments? Vascular dysfunction in glaucoma likely arises from impaired functioning of cells in the NVU, and a loss of connectivity between neurons, glia, and endothelial cells. Thus, future research into the pathways involved in this intercellular communication, as outlined in this review, is key to our understanding of the role of NVC in glaucomatous disease and efforts to delineate the temporal changes in NVC and RGC death require urgent investigation. Vascular dysfunction occurs at all levels of IOP and can affect RGC health directly, however, we do not fully understand the role of these pathways in RGC survival. Further work in these areas will lead to therapies that are aimed at mediating proper vascular regulation and therapies that promote neurovascular interactions. Both of these are attractive novel areas to explore in the search for neuroprotective therapies in glaucoma.As technologies for LW and DC collected the analysis and wrote the manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


The computer-vision-based surface defect detection of metal planar materials is a research hotspot in the field of metallurgical industry. The high standard of planar surface quality in the metal manufacturing industry requires that the performance of an automated visual inspection system and its algorithms are constantly improved. This paper attempts to present a comprehensive survey on both two-dimensional and three-dimensional surface defect detection technologies based on reviewing over 160 publications for some typical metal planar material products of steel, aluminum, copper plates and strips. According to the algorithm properties as well as the image features, the existing two-dimensional methodologies are categorized into four groups: statistical, spectral, model, and machine learning-based methods. On the basis of three-dimensional data acquisition, the three-dimensional technologies are divided into stereoscopic vision, photometric stereo, laser scanner, and structured light measurement methods. These classical algorithms and emerging methods are introduced, analyzed, and compared in this review. Finally, the remaining challenges and future research trends of visual defect detection are discussed and forecasted at an abstract level. Metal planar materials  are widely used in automobile manufacturing, bridge construction, aerospace, and other pillar industries, which make immense contributions to the modern social development and the betterment of life. Nevertheless, in the actual industrial production process, the processing equipment damage or the harsh industrial environment will inevitably lead to certain quality problems of metal planar materials products. Some products surface defects showing large-area or periodic characteristics not only impact on the subsequent production but also threaten the quality of terminal products, which bring huge economic and reputational losses to the manufacturing enterprises. The number, degree, and distribution of surface defects areas are significant factors to determine the quality of industrial metal planar materials. The damage detection methods based on vibro-acoustic modulation , wirelesThe metal planar materials such as steel, aluminum, copper plates and strips along with the similar appearance characteristics have the unified quality requirement that can be summarized as “precise size, homogeneous, and finish surface”, which means that the thickness and width of the metal planar materials should meet the specified precision requirements, and the surface should be clean and free of scales, cracks, scratches, roll marks and bubbles, etc. The defects on the surface of planar materials not only damage the appearance of planar products but may become the weak link of stress concentration as the source of cracking and corrosion. The AVI equipment for surface defects of metal planar materials has two main functions: defect detection and defect classification. The former aims to accurately detect and locate defects on-line in the industrial production process without identifying the types of defects, so that the industrial site can adjust the corresponding continuous casting/rolling equipment according to the degree and frequency of defects, so as to lose no time in controlling the massive diffusion of similar defects and effectively avoid economic losses caused by quality problems. Meanwhile, defect classification is to recognize and label the detected defects to support the grading of finished products. The classification accuracy is directly determined by the precision of defect detection; thus, the overall performance of an AVI system is mainly limited by the accuracy, time efficiency, and robustness of various algorithms in the process of defect detection, which is the focus of this paper.The online surface defect detection of metal planar materials faces the following severe challenges in the production process:(1) High surface reflectanceThe surface of steel, aluminum, copper strips, and other extremely thin strips is smooth, and their high surface reflectivity is liable to bring high light and shadow area; then, the phenomenon of inconsistent gray value increases the possibility of false edge detection.(2) Pseudo defect interferencePseudo defects such as water droplets, water cloth, rain line, water mist, and other real defects produced in the process of laminar cooling lead to frequent false alarms of AVI equipment .(3) Random elastic deformationCaused by continuous rolling equipment vibration, roll speed differential, side guide plate heterotopia, rolling speed fluctuation, atmospheric turbulence-like effect, and so on, the random elastic deformation presents random image distortion on the charge coupled device (CCD) camera side .(4) Massive image dataThe high speed of the real-world production line, the fast pace of coil change, and the demand for fine defects detection in hot rolling mill make the image acquisition front-end continuously generate massive image data, and its peak speed is as high as 5.12 Gbps , which rIn different processes, the process operations of different types of industrial equipment make the surface textures have great differences, and the corresponding metal plates and strips also have different detection difficulties. This paper focuses on the latest theory and algorithm of two-dimensional (2D) defect detection methods based on AVI, as well as the attempt and development process of three-dimensional (3D) technologies in the field of surface defects detection, which will serve as an important reference and inspire scholars to develop methods more suitable for various application scenarios.The content of this paper is arranged as follows. Firstly, the research background and challenges of the project are introduced. In the second section, the hardware facilities of the 2D surface quality inspection system are described in detail. In the third section, some previous related survey papers are briefly reviewed. The fourth section presents several commonly used performance evaluation criteria for industrial surface defect detection tasks. In the fifth section, four kinds of 2D defect detection methods are introduced in detail, and the classical algorithms and new methods in each category are introduced, analyzed, and compared. Then, in the sixth section, the imaging equipment and detection algorithms of 3D defect detection technology are introduced. Finally, the challenges and future research trends of defect visual inspection are discussed and prospected.The traditional manual visual inspection methods with the disadvantages of low detection rate, poor real-time performance, low detection confidence, and poor environmental adaptability are not sufficient for the requirements of high precision and fast speed of industrial surface defect detection. With the rapid development of machine vision technology, the automated surface defect detection methods based on machine vision have gradually become the mainstream methods and have been widely used in the surface defect detection of glass bottles , mobile The hardware of the image acquisition subsystem usually consists of lighting, a lens, and a sensor. Lighting conditions have a great impact on image quality; favorable illumination helps to reduce noise, shadow, and reflection and enhance image contrast, so as to improve the success rate of image processing and analysis, and the commonly used light sources are incandescent lamps, fluorescent lamps, halogen lamps, etc. The lens focuses the light reflected from the surface of the target object to generate a clear image on the sensor. The most momentous part of a camera is the digital sensor, which converts the image into analog or digital video signals. The two main sensors are the CCD (charge coupled device) and CMOS . The communication interface receives digital signals and converts them into images in computer memory. An ROI detection subsystem is used to determine whether there are defects on the image surface. It originates in the visual attention technology, which can quickly focus the vision on important targets. In the past 30 years, numerous scholars have carried out in-depth research on ROI detection algorithms, and in the fifth section, we will mainly overview these algorithms.Taking the strip surface defect detection system as an example, its hardware framework mainly consists of lighting facilities, a CCD camera, and an image processing computer and server, and its lighting facilities adopt a special infrared light source array. The CCD line scanning camera group is arranged horizontally on the strip steel production line, and the horizontal and vertical visual ranges overlap each other to ensure no missing inspection. The images collected by the CCD camera are transmitted to the image processing computer group via the optical fiber for image processing and pattern recognition. Then, the results, together with the relevant information of the production line are sent to the server database for further processing, and various on-site production information statistical reports are generated. Users can evaluate the quality grade of steel coils according to these reports or analyze the causes of the abnormal production line, so as to realize the real-time monitoring of the production line. In recent years, great breakthroughs have been made in image processing, computer vision, artificial intelligence, and other related fields, which makes the surface defect detection systems of industrial metal planar materials continuously optimized. In 1900, Matti et al. developed a prototype of the automated online visual inspection system, which collected images by a CCD linear scanning camera, concentrated a strong field light source, and detected defects by combining morphology and statistical algorithms. This system was successfully applied to the surface defects detection and classification of copper alloy strips . In 1995Over the past 30 years, researchers have conducted in-depth researches on AVI, and various theories and algorithms have emerged in an endless stream. Some scholars have summarized and compared the relevant research results ,23,24,25In the task of surface defect detection, we usually evaluate the relevant methods quantitatively according to statistical results, which can be divided into four categories: true positive (TP) indicates the actual defect is detected as a defect, true negative (TN) means the actual defect is mistakenly detected as a background, false positive (FP) means the actual background is wrongly detected as a defect, and false negative (FN) indicates the actual background is detected as a background. Obviously, in the ideal case, the larger the TP and FN, the better the detection effect, while the larger the TN and FP, the worse the detection effect. Nine indicators are consequently defined as follows:True Positive Rate (TPR):True Negative Rate (TNR):False Positive Rate (FPR):False Negative Rate (FNR):Precision Rate:Recall Rate:Accuracy Rate:G-Mean Value:F-Measure Value:Among them, G-mean measures the accuracy of these two categories in a combined way, and a larger G-mean means higher TPR and TNR, which is also the requirement of defect detection application. On the other hand, F-measure evaluates the overall performance of defect detection based on the accuracy and recall rate.In this section, the existing two-dimensional vision technologies and models of metal planar materials surface defect detection methods are comprehensively reviewed, and the discussions and prospects are also carried out, the overall structure of detection method taxonomy is shown in From the perspective of statistical methods, the image texture is regarded as a random phenomenon. Statistical methods study the regular and periodic distribution of pixel strength by measuring the statistical characteristics of pixel spatial distribution, so as to detect the defects on the metal planar materials surface. The following is a brief introduction to five representative statistical approaches and the comparison of several typical approaches of these five categories is given in Edge detection is essentially the detection of grayscale or structural mutation in the tested image. The difference of gray level between the defect area and the background results in an obvious edge at the boundary, which can be applied to detect surface defects of metal planar materials. Owing to the discontinuity of pixels at the edge of the image, researchers usually employ local image differentiation technology to obtain edge detection operators, and the commonly used edge detection templates of metal planar materials surface defects include Prewitt , Sobel ,44, and In practice, various differential operators are generally used to realize differential operation by a small region template and image convolution, which is extremely sensitive to noise and uneven illumination, so image preprocessing is necessary when using differential operators to detect the edge. Generally speaking, the edge detection operators are deficient in the images with complex gray changes and rich details, and they are even less ideal once the noise interferes. For this reason, some other edge detection methods have been proposed continuously. Zhao and Yan et al.  proposedHough transform (HT) utilizes the global characteristics of the image to detect the target contour directly and connect the edge pixels to form the region closed boundary. As for the application on metal planar materials, Sharifzadeh et al.  utilizedDue to the uneven reflection caused by the surface morphology and texture as well as the change of ambient light, the pixel intensity difference between the defect area and background is quite large. The probability distribution of pixel intensity is estimated from a set of images without defects, which is used to select pixels with outliers as candidate defects pixels. Choi et al.  first emLocal binary pattern (LBP) marks the difference between the center pixel and its neighborhood pixel by threshold, and it is commonly used in image local feature comparison. LBP proposed by Ojala et al.  in 1994 Gray level co-occurrence matrix (GLCM) describes the spatial dependence of pixel gray level, which can be used to extract the feature parameters of image texture on the surface of the plane workpiece, and these feature parameters are significant information for analyzing image primitives and arrangement structure. In 1973, Haralick et al.  first prMany statistical methods are not reliable in the case of illumination variation and pseudo defects interference. Fortunately, researchers have found that images are more likely to be separated out information of different characteristics in the transform domain, and it is possible to find a better defect detection method than the direct processing method in the pixel domain. Some transformation domain methods are summarized as bellow and the comparison of several typical approaches of these categories is given in Fourier transform can transform images into the frequency domain and represent texture by spectral energy or spectrum entropy, which realizes translation invariance, unfolding invariance, and rotation invariance. The defect images directly obtained from the steel production line normally contain background noise; therefore, for removing the noise, Yazdchi et al.  used theFourier transform plays an important role in the frequency domain analysis of the whole time period, but it lacks the ability to describe the spatial local information of the signal, so most of the local description information is ignored in the spatial domain. The Gabor filter can effectively make up this disadvantage by modulating Gaussian kernel function on a sine wave of a specific frequency in the spatial domain and frequency domain. On the basis of the Gabor filter, Yun et al.  detectedAdmittedly, the performance of Fourier transform in local feature analysis is unsatisfactory. The Gabor filter overcomes the drawback to a limited extent, whereas the immutability of the sliding window function determines the fixity of the time-frequency resolution. Compared with the Gabor filter, wavelet transform has a more powerful adaptive ability and is in line with human visual characteristics ideally, which could not only locomote the time-frequency window but also automatically modify the window size according to the variation of the window center frequency ,78. FiguIn addition to statistical- and spectrum-based methods, there is a type of approach with a different work scheme, which is called the model-based approach. The model-based method projects the original texture distribution of the image block to the low-dimensional distribution through the special structure model enhanced by parameter learning, so as to detect various defects better. Several model-based approaches are briefly discussed below and the comparison of several typical approaches of these categories is given in In 1983, Cross et al.  regardedMathematically speaking, fractals are extremely complex and fragmented geometric figures with inherent laws, and fractal dimension (FD) has ideal self-similarity—that is, the overall information can be represented by local features. The grayscale statistics of defect images actually contain features of FD’s self-similarity; Yazdchi et al.  applied Research exhibits that the human visual system keeps the ability to quickly search and locate objects of interest in the face of natural scenes. By introducing the visual attention mechanism, namely visual saliency, into computer vision tasks, the difficulties of visual information processing tasks are significantly abated ,90,91,92In addition to the above model-based defect detection methods, new model-based methods have been proposed continuously in recent years. In With the rapid development of artificial intelligence technology, widely applied machine learning has shown good results in various fields. Duan et al.  and Zu eThe essence of machine learning is to analyze and learn data (features) and then make accurate decisions or predictions. In 2005, Liu et al.  used a dIn the field of machine learning, using unlabeled image samples to detect surface defects of strip steel is called unsupervised learning, which aims to find sample groups with similar information in input data, so it is also called clustering. Based on the similarity between pixels, the clustering method mines the hidden information in texture images and performs clustering based on the features of pixel points. Then, defect detection is realized by the multi-classification method. The clustering method mines the hidden information in the texture image according to the similarity between the image pixels. In detail, clustering is based on the characteristics of pixels, and then defect detection is realized by the multi-classification method. Bulnes et al.  analyzedFor a long time, Auto-encoder (AE) has represented strong competitiveness due to its potential to solve the above problems, but the redundant parameters limit the application of the AE method in 2D image data. To break through this limitation, Tao et al.  establisCompared with the above two categories, the semi-supervised learning method chooses a more compromised route by using both limited labeled samples and a large number of unlabeled samples. The generative adversarial network (GAN) , consistTo separate the abnormal areas from the image background of different complexity is the significant purpose of defect detection. In this section, the algorithms are divided into four detection methods based on statistical, spectrum, model, and machine learning according to their characteristics, and the existing technologies of each method are reviewed and discussed. In addition, the fundamental significance of online defect detection lies in the rapid and accurate detection of abnormal areas on the surface of high-speed moving targets, and the high-performance real-time and anti-interference detection algorithm has always been the target of defect detection. Most of the strip surface defect detection algorithms outlined in this section are tested on exposed offline databases. For example, in the literature , Song etIt is noteworthy that in recent years, the surface defect detection literature of plate and strip steel shows that the research trend has gradually moved from purely theoretical research to field application. For example, Ghorai et al.  developeThe surface defect detection research based on the existing offline database tests the performance of the new proposed algorithm easily and accelerate the iterative updating speed of the theoretical algorithm, and at the same time, rich and diversified data are needed to ensure the overall performance of the algorithm. Unfortunately, the number and variety of samples contained in the steel surface defect dataset are far from sufficient, and there are few publicly available steels surface defect texture databases. Therefore, because there is no uniform database standard, the methods of many articles cannot be compared fairly. The widely used steel surface defect databases include NEU , Dragon (1) NEU databaseThe NEU database is a public database of surface defects of the hot-rolled strips collected by the Northeastern University research team. Six typical surface defects of the hot-rolled strips are collected, namely, roll-in scale (RS), patch (Pa), crack (Cr), pitting surface (PS), inclusion (In), and scratch (Sc). The database includes 1800 gray images . (2) Dragon databaseDragon contains 18 categories of defects obtained from an actual hot rolling production line, and each class contains 300 non-overlapping samples. (3) RSDDs databaseRSDDs consists of two types of datasets: the first type is the type I RSDDs dataset captured from the fast track, which contains 67 challenging images. The second is the TYPE II RSDDs dataset, which is captured from common heavy-duty tracks and contains 128 challenging images. Each image from both datasets contains at least one defect and includes a complex background and various noise. Two-dimensional detection methods mainly rely on gray images to obtain the surface morphology of flat metal and employ gray field change to realize surface defect detection. Due to the lack of height/depth information, these kinds of methods are frequently susceptible to natural light, shadow, water, and oil stains, resulting in false defects. In spite of this, the surface defects of metal planar materials are generally accompanied by height anomalies, such as pits, bumps, depressions, and so on. High reflective spots and dark areas appear in the two-dimensional image after illumination, which is unconducive to the accurate identification of defects. Therefore, the defect detection methods led by 3D imaging technology or 3D reconstruction technology attract wide attention. Making full use of the gray, elevation, and geometric characteristics of the defects, new detection techniques are the development trend of the surface defect detection technology of metal planar materials. Three-dimensional (3D) data measurement is commonly divided into contact measurement and non-contact measurement. The former shows the characteristics of high destructiveness, high cost, and slow detection speed, and the latter mainly includes penetration measurement and reflection measurement. Penetrating measurement of radioactive substances causes potential hazards. Consequently, the non-contact and high-security advantages of reflection-type measurement turn into the choice of most people, and outstanding results have been obtained in the surface detection of 3D objects. Non-optical measurement is a type of reflection measurement, from early radar and sonar to ultrasonic imaging ,130, magNon-contact, non-destructive measurement, high precision, high speed, and high reliability are major advantages of the two-dimensional vision system, as an advanced stage of a 2D vision system, passive stereo vision system uses multi-view 2D images for 3D reconstruction; that is, it calculates the relationship between the camera image coordinate system and world coordinate system, and then uses the information in multiple 2D images to reconstruct 3D information. As shown in Photometric stereo refers to a method of estimating the surface normal by using multi-intensity images obtained with different lighting conditions. Kang et al.  developeBased on triangulation, the laser scanner works by projecting laser points (lines) onto an object and capturing its reflection with a sensor (camera). Millions of 3D point cloud data could be accurately captured to represent the surface of the target object. The working principle of triangulation is shown in Different from the single or multiple cameras and laser scanners of the stereo vision method, the active structured light method uses an optical projector to project a certain pattern of structured light onto the surface of an object and then forms a three-dimensional image modulated by the surface shape of the object to be measured. The main principle is shown in The stereo vision methods rely on the intrinsic texture information of the object surface; photometric stereo methods have the limitations of detection of non-Lambertian surfaces; laser scanning equipment shows the high cost and a large amount of computation; they are unsuitable for on-line or real-time monitoring of metal planar materials. The projector calibration of the structured light method is complicated and easy to cause errors. In order to solve the above problems, Wen and Song tried to combine the stereo vision method and structural light method to detect the surface height information of high-temperature steel products. They designed a set of static object 3D detection systems  and estaFrom simple binary image processing to high-resolution multi-gray image processing, and from general 2D information processing to 3D vision processing, machine vision, as an emerging and rapidly developing discipline, has moved from laboratory research to practical application. Different from previous reviews, this paper focuses on planar metal materials with similar quality control requirements, and it is the first one to comprehensively summarize defect detection methods from two-dimensional and three-dimensional aspects. This paper summarizes the research results of the automated visual defect detection of metal plates and strip surfaces in the last 30 years, most of which were published in last 10 years. In (1) Compared with other surface defect detection tasks based on computer vision, in real-world metal planar materials industrial manufacturing, in addition to the balance between detection accuracy and computational efficiency, the more important thing is to ensure the stability of the detection algorithm, especially the robustness to environmental changes. In addition, it is also necessary to have the ability to detect the diversity of defects, especially deformation defects without edge features. (2) The rapidity and generality of the algorithm are two key problems in the application of a real-world AVI system. As for the algorithm itself, compared with a complex learning network, online surface defect detection, as an unsupervised real-time detection task, is more inclined to use a lightweight algorithm, while machine learning or a deep network is more suitable for dealing with complex multi-class classification problems with rich datasets . As far as hardware is concerned, the concept of edge computing can be used for terminal acceleration; for example, application specific integrated circuit (ASIC), similar to field programmable gate array (FPGA), can be placed in the front end of image acquisition to complete the preprocessing of original data in real time, so as to prevent the complicated information from affecting the subsequent processing.(3) Noise smoothing and edge enhancement are important preprocessing operations for defect detection, which should be arranged as close as possible to the sensor side of imaging. In addition, the most effective denoising method of the AVI system is to make the image as clean as possible through some feasible engineering measures. For example, a blower or an ion air gun should be installed on the lens side and the surface side of the target to remove water drops, dust, fibers, etc. on the optical surface caused by the harsh industrial environment, and a light source with uniform and moderate brightness should be applied on the target side to overcome the influence of uneven light caused by the variation of illumination during the day and night. In addition, some cost-effective measures of cooling configuration and security protection for imaging devices are also of great significance for avoiding imaging degeneration caused by harsh environments such as high-temperature and mechanical vibration.(4) The latest machine learning technology provides a new way to handle this problem of data imbalance. For example, the GAN has achieved great success in generating defect samples. To avoid the problem of poor interpretability in a GAN, it can be connected with reinforcement learning, and a GAN can be applied to reverse reinforcement learning and simulation learning to improve the efficiency of the reinforcement learning, the ability to transform images and texts, and the ability of machines to understand. Since researchers conduct experiments with different methods on different datasets, it is difficult to fairly compare the detection performance of different technologies. Inspired by the research in the field of biometric identification, it will be a long-term work in this field to construct a rich and diversified database of surface defects of metal planar materials. (5) The automated visual detection of metal planar materials surface defects should strive to adapt to the new adjustment of world industrial competition pattern and seize the commanding heights of future industrial competition. Efforts should be made to promote the deep integration and organic collaboration of multiple technologies, and the study of metal planar materials surface defect detection algorithms and instruments with high detection accuracy, strong real-time performance, and high stability play an important role in the automated control and whole process management of surface quality of industrial metal planar materials.


Cell membranes are very complex biological systems including a large variety of lipids and proteins. Therefore, they are difficult to extract and directly investigate with biophysical methods. For many decades, the characterization of simpler biomimetic lipid membranes, which contain only a few lipid species, provided important physico-chemical information on the most abundant lipid species in cell membranes. These studies described physical and chemical properties that are most likely similar to those of real cell membranes. Indeed, biomimetic lipid membranes can be easily prepared in the lab and are compatible with multiple biophysical techniques. Lipid phase transitions, the bilayer structure, the impact of cholesterol on the structure and dynamics of lipid bilayers, and the selective recognition of target lipids by proteins, peptides, and drugs are all examples of the detailed information about cell membranes obtained by the investigation of biomimetic lipid membranes. This review focuses specifically on the advances that were achieved during the last decade in the field of biomimetic lipid membranes mimicking the mammalian plasma membrane. In particular, we provide a description of the most common types of lipid membrane models used for biophysical characterization, i.e., lipid membranes in solution and on surfaces, as well as recent examples of their applications for the investigation of protein-lipid and drug-lipid interactions. Altogether, promising directions for future developments of biomimetic lipid membranes are the further implementation of natural lipid mixtures for the development of more biologically relevant lipid membranes, as well as the development of sample preparation protocols that enable the incorporation of membrane proteins in the biomimetic lipid membranes. Cell membranes are the most external cellular envelopes, which separate the cells from the surrounding environment and, in the case of eukaryotic cells, compartmentalize them into different internal organelles . Cell meAmong the different types of mammalian cell membranes, the plasma membrane is often the target of pathogens, e.g., viruses, as well as of selective drugs . The plaThe cholesterol content in the mammalian membranes can vary between 20 and 50 mol%, and the plasma membrane is typically quite rich in cholesterol with a concentration in the range of 40–50 mol% . The remThe composition of the two layers of lipids within the lipid bilayer, i.e., the leaflets, is not identical. In the mammalian plasma membrane, the cytosolic leaflet, facing the inside of the cell, is richer in anionic phospholipids, such as PS and PI . On the Altogether, cell membranes are very complex systems, even if only their lipid components are taken into account. Thousands of different lipid species are part of the mammalian cell membranes, and the biological function of this high compositional complexity is still poorly understood ,8. IndeeThis review focuses specifically on the advances in the development of biomimetic lipid membranes for biophysical and physico-chemical studies. The discussed biomimetic lipid membranes are aimed at reproducing specific structural and functional properties of the mammalian plasma membrane. In particular, we provide a description of the most common types of biomimetic lipid membranes in solution and on surfaces , as wellBiomimetic lipid membranes can be divided into two main categories: (1) membranes in solution; (2) membranes on surfaces . These tLiposomes or vesicles are soluble spherical particles, which are composed of one or more lipid bilayers fused at their ends a. The liVesicle preparation often starts with dissolving the lipids in an organic solvent and subsequently forming a lipid film by solvent evaporation . The speSuspensions of small unilamellar vesicles (SUVs) are particularly required for scattering experiments. In order to produce SUVs, the lipid water suspension is typically sonicated or extruded ,39. IndeVesicles can be prepared with a large variety of synthetic lipids ,42. A re bilayer . Similare lipids . While Cdiseases .As mentioned in the Introduction, the plasma membrane has an asymmetric lipid composition of the inner and outer leaflet. The protocols for vesicle preparation described above typically lead to the production of symmetric vesicles, i.e., inner and outer leaflets of the bilayer exhibit the same lipid composition. However, recently, a sample preparation protocol was developed to produce asymmetric lipid vesicles . In partreported . Such asGiant unilamellar vesicles (GUVs) can be produced either by natural swelling or electroformation . In the Lipid mixtures directly extracted from natural sources, such as cells, can also be used to produce lipid membranes, which better resemble the compositional complexity of real cell membranes. In this context, the extraction of plasma membrane vesicles from mammalian cell lines allowed highly realistic models of cell membranes to be investigated . In partLipid membranes can be produced in the proximity of both a liquid or a solid surface b. In theLipid monolayers can be prepared with various lipid composition. In general, lipid monolayers are used as membrane biomimics to investigate lipid-phase transitions induced by surface pressure or temperature by collecting Langmuir isotherms . They alRecently, monolayers composed by mixtures of 1,2-dipalmitoyl-sn-glycero-3- phosphocholine (DPPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho- . In addiembranes a. This os (α-syn .Similarly to features . In partesicles) . The chal growth . In addil growth . The pre peptide . In thisragments . Additioregation ,104.Another example of the interaction between a soluble protein and lipid membranes is the recently reported study of the adsorption of the lipid interaction domain (LID) of the Nae (POPS) . In partLipid membranes are also used as platforms to investigate the interaction between the mammalian plasma membrane and viral fusion proteins or peptides. Indeed, enveloped viruses are characterized by glycoproteins in their envelopes, which have the function of favoring the fusion between the virus envelope and the mammalian plasma membrane. This membrane fusion event is fundamental for the virus RNA to enter into the host cell . Short fThe plasma membrane being among the most external cellular components, the characterization of drug-lipid interactions has a central role in the development of new and more efficient drugs of natural or synthetic origins . Among aAnti-inflammatory drugs are another large class of biologically-active compounds. The study of their interaction with the plasma membrane lipids is of great relevance for understanding their mechanism of action. Tomelin, a non-steroidal anti-inflammatory drug for the treatment of rheumatoid arthrosis, was shown to strongly interact with the DPPC lipid headgroup within both biomimetic lipid membranes in solution and on surfaces . The eleThe membrane localization and orientation of ibuprofen, as well as its influence on membrane properties were recently studied by using solid-state NMR spectroscopy and other biophysical assays on large unilamellar vesicles composed of POPC or a POPC/ cholesterol mixture . The expThe natural polyphenol resveratrol exhibits potential therapeutic activity with cardioprotective, anti-neurodegenerative, antioxidant, and antitumor action. Recently, these therapeutic actions were suggested be related to resveratrol’s interaction with the plasma membrane. In particular, by using biomimetic membranes in solution composed of egg-PC, SM, and cholesterol at different ratios, resveratrol molecules were found to be mainly located in bilayer domains rich in cholesterol and SM; see The mammalian plasma membrane is a very complex system, which is difficult to isolate and directly investigate by conventional biophysical methods . In thisMost of the discussed scientific cases focused on the investigation of biomimetic lipid membranes with a relatively simple composition, 1-3 synthetic lipids. The advantage of these lipid membranes is their relatively simple preparation protocols, which allow the concentration of each of the lipid components to be finely tuned. In addition, they are compatible with several biophysical methods, which enable a direct correlation between specific physico-chemical properties of the biomimetic lipid membranes and the presence of a specific lipid component. Evidence of such correlations was reported in the case of supported lipid bilayer prepared with the phosphoinositide PIP3  or the g3 . The lip3 ,7. We ar3 ,78,79. BBesides the implementation of more biologically relevant lipid compositions, future advancements in the development and characterization of lipid membranes as mimics of the mammalian plasma membrane should also include membrane proteins. Indeed, about 50% of the mammalian plasma membrane components are proteins, the structure and function of which strongly depend on the surrounding lipid environment . RecentlAltogether, increasing the complexity of lipid composition and incorporating membrane proteins are central aspects in the future developments of more advanced biomimetic lipid membranes. The biophysical investigation of such membranes will increase our understanding of the biological functions of the mammalian plasma membrane and will allow us to produce more biologically relevant membrane models as platforms for studying and testing protein-membrane and drug-membrane interactions. As an example, protein-membrane interaction do not only play a fundamental role in our physiological cellular processes, but are also crucial for the infection of cells by pathogens such as viruses. Advanced biomimetic lipid membranes will increase our knowledge about these kinds of interactions and will promote the development of more efficient drugs and vaccines.


Selective sympathetic and parasympathetic pathways that act on target organs represent the terminal actors in the neurobiology of homeostasis and often become compromised during a range of neurodegenerative and traumatic disorders. Here, we delineate several neurotransmitter and neuromodulator phenotypes found in diverse parasympathetic and sympathetic ganglia in humans and rodent species. The comparative approach reveals evolutionarily conserved and non-conserved phenotypic marker constellations. A developmental analysis examining the acquisition of selected neurotransmitter properties has provided a detailed, but still incomplete, understanding of the origins of a set of noradrenergic and cholinergic sympathetic neuron populations, found in the cervical and trunk region. A corresponding analysis examining cholinergic and nitrergic parasympathetic neurons in the head, and a range of pelvic neuron populations, with noradrenergic, cholinergic, nitrergic, and mixed transmitter phenotypes, remains open. Of particular interest are the molecular mechanisms and nuclear processes that are responsible for the correlated expression of the various genes required to achieve the noradrenergic phenotype, the segregation of cholinergic locus gene expression, and the regulation of genes that are necessary to generate a nitrergic phenotype. Unraveling the neuron population-specific expression of adhesion molecules, which are involved in axonal outgrowth, pathway selection, and synaptic organization, will advance the study of target-selective autonomic pathway generation. The autonomic nervous system (ANS) in mammals functions to ensure the maintenance of body homeostasis under highly variable conditions, which allows mammals to access remarkably diverse environments, such as those experienced by diving animals  biosynthesis, tyrosine hydroxylase (TH), and the enzyme dopamine beta-hydroxylase (DBH), which is located within synaptic vesicles and completes the noradrenaline biosynthesis cascade, or the identification of their transcripts are considered to be prerequisite histological evidence for a noradrenergic transmitter phenotype , sphenopalatine (SPG) , otic (OG), and submandibular ganglia (SMG) Gaskell . An exceThe paravertebral sympathetic ganglia are integrated into a macroscopically prominent structure, the sympathetic chain, which was initially considered to be a nerve and was named the intercostal nerve Winslow . This stAt the level of the celiac, mesenteric, and renal arteries, which branch from the aorta, a set of less well-demarcated and more lobulated ganglia complement the paired sympathetic strands, including the prevertebral celiac, superior, and inferior mesenteric or aorticorenal ganglia belonging to the preaortic ganglia and plexus. In humans, an additional, less discrete ganglionic structure was recently described, referred to as the prehypogastric ganglion . These nerves reach the pelvic ganglia or plexus, which appear more or less discrete and circumscribed, depending on the mammalian species examined , and humans will be discussed here. Comparisons between rats and guinea pigs, which are the first mammalian model species that were analyzed by immunohistochemistry, suggested the conservation of gross organizational features between closely related mammalian species. This conservation extends to differences between the cholinergic and nitrergic characters of the cranial parasympathetic ganglia and the largely noradrenergic properties of the paravertebral and prevertebral sympathetic ganglia in the cervical and trunk regions, which reflect the key divide between parasympathetic and sympathetic features that have been resolved in physiological and pharmacological studies.This comparative anatomical and cell biological approach can help appreciate and identify altered and new elements of the system, which can be defined when comparing between different genders within the same species and when examining the evolutionary differences that exist between rodents and humans. The significant expansion of the noradrenergic neuronal population in the human pelvic plexus (PP), compared with the rodent major pelvic ganglia (MPG), illustrates one such alteration in neuron populations. The appearance of divergent neuropeptide combinations between male and female rodents in the same species supports the existence of sex-specific differences in neuron populations, which have not yet been analyzed in humans. In addition, the developmental data examining the acquisition of these phenotypes, which has been obtained from studies performed in mice, will also be considered. These studies focus on the central questions of how such divergent neuron populations come into existence and how distinct neurochemical profiles become realized in the different rostrocaudal domains of the ANS and are generated from distinct precursor cells.The availability of antisera against TH, NOS, and ChAT has facilitated the characterization of neuron classes in the rat cranial ganglia Table  and provIn addition to these small-molecule neurotransmitter phenotypes, the neuropeptides neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP) constitute important markers for cranial neurons. NPY is expressed in 60 to 80% of OG cells, 30% of CIL cells, and 15% of SPG cells in adult rats  , which are expressed in noradrenergic sympathetic neurons in the CEG/SMG, appear to be largely but not completely mutually exclusive  that govern gene expression programs have been identified by super-enhancer (SE) mapping. The strongest SEs have been observed at loci associated with the TFs Hand2, Phox2b, Phox2a, Gata2, and Gata3, which bind to each other’s SEs and are thought to control noradrenergic identity through cross-regulatory expression -family growth factor receptor Ret suggests a role for Ret signaling in the development of cholinergic sympathetic neurons  increase in HMX1 and TrkA expression and the near-complete absence of ChAT, VAChT, VIP, and SOM expression  signaling induced by neurokine growth factors is essential for the postnatal induction of cholinergic properties in previously noradrenergic neurons that innervate mammalian sweat glands, as demonstrated by gp130 mutational inactivation in mice   and extending into groups of fluorescent and non-fluorescent cells, in the anterior (APP) and posterior (PPP) pelvic plexus of adult guinea pigs , but not with TH  showed that 65% of neurons were NOS-positive , which significantly exceeds that in the rodent pelvic ganglia . Whether the gender-specific differences in peptide expression patterns that have been observed in rodents also exist in humans remains to be seen. Finally, changing co-expression patterns, in terms of the noradrenergic and nitrergic properties, which have been observed in human target tissues, also raises a wide range of highly relevant questions. Is such a shift also observed in rodents and can it be mechanistically explored in experimental animals? Does this shift occur due to changes in gene expression patterns in individual cells or due to the maturation of fiber connections, in possible combination with the expansion or restriction of defined neuron subpopulations? How does this shift contribute to changes in the activity patterns of pelvic organs during aging or disease and can this be modulated therapeutically?The histology and function of intramural ganglia in the bladder were investigated in the guinea pig. In newborn animals, numerous intramural ganglia were detected, lying among smooth muscle bundles and in the submucosa , the neuron subpopulation composition in the pelvic ganglia of mice was observed to be similar but not identical to those in other rodents  strategy for the identification of autonomic precursors in visceral tissues  family members, which represent a group of proteins that have been recognized for their importance in multiple steps of neural circuit formation (Peek et al. These findings indicate the need for an in-depth analysis of the role played by Pcdhns in the target-specific regulation of sympathetic effector functions, the establishment of target-specific neuronal pathways, and the developmental generation of neuronal class-specific Pcdhn gene expression patterns.The stunning observation of the progression from mixed noradrenergic/cholinergic precursors to mature cells with segregated transmitter phenotypes during sympathetic neuron development was complemented by recent studies showing the expression of noradrenergic markers in mature cholinergic sympathetic neurons, as analyzed by RNA sequencing in mice (Furlan et al. The detection of cholinergic transdifferentiation in the cardiac sympathetic nervous systems of humans and rodents during congestive heart failure and myocardial infarction, under the control of gp130-mediated mechanisms (Kanazawa et al. High levels of sympathetic drive, associated with several cardiovascular diseases, including congestive myocardial infarction and hypertension, prompt the question for the component of sympathetic hyperactivity residing at the level of post-ganglionic neurons (Grassi et al. Autonomic dysfunction constitutes a hallmark of a diverse range of neurodegenerative diseases, such as Parkinson’s disease and other synucleinopathies, diabetic neuropathies, and multiple sclerosis (Rafanelli et al. Advances in the clinical assessments of functional subsystems in the ANS have resulted from improved sudomotor testing, to complement the more conveniently recordable cardiovascular biosignals (Vinik et al. These studies exemplify approaches in which the neurotransmitter and neuromodulator features of post-ganglionic autonomic neurons are analyzed in the context of key autonomic dysfunctions and disease. This line of investigation has been pursued intensely in the human and rodent sympathetic nervous systems, in which changes in neuronal phenotypes, observed after myocardial infarctions, and alterations in peptidergic phenotypes in Parkinson’s disease and diabetes, mark particularly interesting cases. The human pelvic plexus, which has been less intensely studied along these lines, will be an even more challenging subject due to the extensive developmental regulation of neuronal phenotypes and the co-expression of noradrenergic, cholinergic, and nitrergic features. Pelvic floor dysfunctions make a particularly relevant example because of their age and gender-specific manifestations (Dieter et al. One subsystem associated with the autonomic innervation of pelvic organs, which has been characterized in some detail, is the innervation of the lower urinary tract (de Groat and Yoshimura Taken together, these results have contributed to the increasing understanding of neuronal populations in the diverse autonomic ganglia including a highly refined knowledge regarding their transcriptomes. The transcriptomes provide quantitative data on axonal outgrowth and synaptic organizer molecules to indicate players involved in the formation of target specific homeostasis circuits. Insight into disease-associated plasticity of neuronal properties, and age-dependent transformations, has changed our understanding of the autonomic neuron pools and circuits that operate in homeostasis. In combination with improving clinical assessment instruments for analyzing autonomic dysfunction, these advances will greatly improve our insights into autonomic control and the disturbances that manifest during aging and disease. These advances need to be exploited for the development of personalized treatment strategies that consider age, gender, and disease duration of individual human patients affected by autonomic dysfunction and the underlying diseases.


The surgical method of complete/radical cyst excision plus Roux-en-Y hepaticojejunostomy remains the primary therapy and the only effective treatment for cystic dilation of the bile ducts (CDBDs). However, the incidence of long-term postoperative complications is still high, as is the reoperation rate, and the potential for postoperative malignant transformation still exists. In recent years, significant progress has been made in understanding the pathogenic mechanism and pathological changes of adult CDBDs. Based on which, the surgical procedures for CDBDs have been revised to further improve their effectiveness. The purpose of this review is to systematically summarize the latest concepts of the etiology and pathogenic mechanism and the pathological changes of adult CDBDs. Based on the findings of these clinical and pathological studies, a comprehensive theoretical system in the surgical treatment of CDBDs has been established, which corrects many previous theoretical misunderstandings. The specific surgical method for each type of CDBDs and the key technical notes are also described in detail. Using these principles, treatment outcomes for CDBDs can be significantly improved, and the current high complication rate, reoperation rate, and rate of postoperative malignant transformation can be reduced. Surgical treatment remains the primary therapy and the only effective treatment for cystic dilation of the bile ducts (CDBDs). Around the year 2000, the surgical method of complete/radical cyst excision plus Roux-en-Y hepaticojejunostomy was established  and subsOur medical center has treated a great number of adult patients who need reoperation due to lack of proper bile duct flow following CDBD surgery. It emphasizes the importance of standardized surgical procedures. In recent years, significant progress has been made in understanding the pathogenic mechanism and pathological changes of adult CDBDs. Based on these advances in knowledge, the surgical procedures for CDBDs have been revised to further improve their effectiveness. For over 20 years, we have been committed to improving the long-term treatment outcomes of patients with CDBDs and have published a series of reports on the surgical approaches for CDBDs, as well as the importance of radical excision and proper bile duct flow –11. At pCDBDs is defined as an isolated or multifocal cystic dilation of an extrahepatic or/and intrahepatic biliary duct. The Todani classification system classifies CDBDs into 5 types according to the location of the biliary duct dilation and anatomical characteristics  Figure , and thiThe etiology of CDBDs is not fully understood, but several theories have been proposed. The most widely accepted theory is that there is an anomalous pancreaticobiliary junction (APBJ) . An APBJIt should be emphasized that pancreaticobiliary reflux and APBJ are 2 completely different concepts. Pancreaticobiliary reflux is the consequence of an abnormal confluent pancreaticobiliary juice, while abnormal anatomical changes result in an APBJ. However, these 2 concepts are confused and frequently considered interchangeable, leading to misunderstanding of the pathogenic mechanism of CDBDs.Pancreaticobiliary reflux occurring in patients with a normal pancreaticobiliary junction is known as “occult pancreaticobiliary reflux” . SphinctPathological changes of CDBDs include the morphological changes and histological changes. Cystic dilatation can occur at any segment of the extrahepatic or intrahepatic bile ducts and can be divided into 2 types of morphological changes: cystic dilatation and fusiform dilation . The mosDuring pancreaticobiliary reflux, the pancreatic juice erodes the entire biliary tree. Unlike a tumor, there is no clear histological boundary between a lesioned and normal bile duct. During surgery, it is difficult to identify the boundary between the lesioned and the normal bile duct by visual inspection or choledochoscopy. Thus, radical resection is performed based on morphological changes rather than histological changes.According to the duration of the disease and the severity of the lesion, the dilated bile duct wall may present with different extents of histological changes. For those with a short duration or mild lesion, the histological changes are mild inflammation of the inner bile duct wall, and the bile duct mucosa shows degenerative changes. Nevertheless, the deep tissue of the bile duct wall has not been damaged, and its tissue structure is close to that of normal tissue. At this stage, the histological changes of the bile duct wall can be reversed after elimination of the cause; hence, the histological changes are reversible. In our practice, we have found that performing hepaticojejunostomy on the bile duct wall with reversible pathological changes can achieve proper bile duct flow and satisfactory outcomes .As the disease progresses, the fibrosis of the bile duct wall is aggravated, and the wall of the capsule gradually thickens and consists of dense fibrotic inflammatory tissue with little smooth muscle. There is little or no epithelium covering the mucosa, and in some cases, there are ulcers and fibrous calcification. The blood supply to the bile duct wall is impaired. At this stage, even with elimination of the cause, the pathological changes and functions of the bile duct wall cannot be restored. The irreversible nonfunctional lesioned bile duct should be radically resected as much as possible during surgical treatment.Malignant transformation of CDBDs is not uncommon, and it is important to understand that the mechanisms of preoperative and postoperative malignant transformations are completely different. The pathogenic mechanism of the long-term erosion of refluxed pancreatic juice on the bile duct wall, combined with bacterial infection, further enhances malignant transformation at the lesioned bile duct wall , 20.The mechanism of postoperative malignant transformation is because proper bile duct flow is not achieved by surgical treatment, leading to repeated postoperative reflux cholangitis and eventually malignant transformation within the cystic ducts . PostopeThe general principles of surgical treatment for CDBDs should include elimination of the cause, excision of the lesions, establishment of proper bile duct flow, and management of secondary lesions.Elimination of the etiology refers to preventing bile duct erosion from pancreatic juice due to elevated biliary pressure. This is done by establishing biliopancreatic diversion. The surgical procedure is to perform a Roux-en-Y hepaticojejunostomy to divert bile flow; this procedure has been clinically confirmed as the most practical and feasible surgical method for many years , 21.Excision of the lesioned bile duct is a crucial step of the whole surgical procedure for CDBDs. The irreversible nonfunctional lesioned bile duct should be radically resected as much as possible. The remnant lesioned bile duct may form fibrous scars at anastomotic stoma, and fibrous scar contraction will induce bile duct stricture and biliary-enteric anastomotic stricture, in turn affecting bile duct flow and causing a series of postoperative complications. Radical resection can effectively reduce the rate of postoperative complications and malignant transformation , 9, 11.Establishing proper intrahepatic bile and pancreatic secretion flow is the most important step. Our study has revealed that proper bile duct flow, rather than radical resection, is the most crucial factor determining the long-term postoperative outcomes in Todani type Ia, type Ic, and type IVa CDBDs . MoreoveThe secondary lesions in patients with CDBDs include secondary bile duct stones, secondary intrahepatic infection, bile duct stricture due to long-term repeated infection, partial liver atrophy caused by long-term biliary obstruction, and portal hypertension secondary to biliary cirrhosis. Management of these secondary conditions during surgery can further ensure proper postoperative proper bile duct flow, improve postoperative liver function, and improve the long-term surgical outcomes.The current standard treatment for type I CDBDs is radical resection of cysts and reconstruction with an end-to-side Roux-en-Y hepaticojejunostomy , 23. TheManagement of the lesioned intrapancreatic bile duct is a common issue for type Ia and type Ic cases. It should be particularly emphasized that radical resection of the lesioned intrapancreatic bile duct is necessary during primary surgery. The presence of a remnant intrapancreatic cystic, dilated duct will lead to the formation of dead space within the pancreas where pancreatic juice may be forced into due to the APBJ , 24. TheRadical resection of lesioned intrapancreatic bile ducts is challenging, especially when the cystic lesion extends deeply into the pancreas . We haveBoth intraductal and periductal approaches are combined to strip the lesioned ducts with the assistance of a choledochoscope. Separating the lesioned ducts along the gap between the outer wall and the pancreatic tissue is relatively safe and caused less bleeding. In case of massive intraoperative hemorrhage, the posterior superior pancreaticoduodenal artery is ligated. In the case of severe inflammation around the bile duct, radical resection may not be achieved in order to avoid serious postoperative complications. However, it must be emphasized that the formation of a dead space should be strictly avoided during cyst removal, which can be accomplished by suturing and destruction of the bile duct mucosa.The key points to the resection of a lesioned hilar bile duct are to prevent postoperative biliary-enteric anastomotic stricture and hilar biliary stricture and to prevent stricture-induced severe postoperative complications, including recurrent reflux cholangitis, hepatolithiasis, biliary cirrhosis, liver abscess, and cholangiocarcinoma , 29. PosFor Todani type Ic cases, after surgical resection of the extrahepatic lesioned bile duct, the hilar bile duct can be used for the biliary-enteric anastomosis because the diameter of the hilar bile duct is large enough. This anastomosis can be performed well and will not lead to postoperative biliary-enteric anastomotic stricture and hilar biliary stricture.For Todani type Ia cases , after rHilar ductoplasty is used to enlarge the diameter of the hilar bile duct at the anastomotic opening  and is tAfter hilar ductoplasty, the opening of the hilar bile duct is enlarged, and the orientation of the anastomosis between the hilar bile duct and the jejunum is similar to that between the common bile duct and the jejunum. Therefore, this surgical approach is a “side-to-side” Roux-en-Y hepaticojejunostomy. For side-to-side Roux-Y hepaticojejunostomy following hilar ductoplasty, the hilar bile duct and jejunum are anastomosed in a side-to-side manner, and the anastomotic junction is sutured with 4/0 or 5/0 absorbable sutures. The mode of anastomosis is determined based on the status of the bile ducts after hilar ductoplasty. It is recommended to use an intercostal anastomosis. If the anastomotic opening is large enough, continuous anastomosis at the posterior wall could be performed but with interrupted anastomosis at the anterior wall.In summary, the standardized surgical procedure for type Ia CDBDs is radical excision of the extrahepatic CDBD, followed by the hilar ductoplasty and a side-to-side Roux-en-Y hepaticojejunostomy , while tIn the surgical treatment of type IVa cases, it is necessary to properly manage the intrahepatic dilated lesioned bile duct, in addition to the extrahepatic lesioned bile duct . The intDespite the large morphological variations in type IVa cases, the surgical methods can be divided into 2 categories based on the need for combined partial hepatectomy : (1) radIn cases with wide distribution, but relatively slight severity of intrahepatic lesioned bile ducts, hilar ductoplasty is sufficient to achieve a proper intrahepatic bile flow. The suggested surgical procedure is radical excision of the extrahepatic lesioned ducts, followed by hilar ductoplasty and Roux-en-Y hepaticojejunostomyFor cases in which the distribution of intrahepatic lesioned bile ducts is limited, and the intrahepatic lesions are confined to a segment or a lobe of the liver, morphological radical resection can be achieved by combined partial hepatectomy. The suggested surgical procedure is radical resection of extrahepatic lesioned ducts, followed partial hepatectomy and Roux-en-Y hepaticojejunostomyIn cases with a wide distribution and relatively high severity of intrahepatic lesioned bile ducts, the suggested surgical procedure is radical excision of the extrahepatic lesioned ducts, followed by partial hepatectomy and Roux-en-Y hepaticojejunostomy. Partial hepatectomy mainly includes left or right hepatic resection, but left or right hepatic trisegmentectomy is occasionally adoptedFor cases with wide distribution and high severity of intrahepatic lesioned bile ducts, neither hilar ductoplasty nor partial hepatectomy can establish proper intrahepatic bile flow. If the patient does not have obvious clinical symptoms, surgery may be postponed with close clinical observation. If clinical symptoms are severed and bile duct infection is frequent, liver transplantation should be consideredThe method of excision of extrahepatic lesioned ducts in type IV cases is the same as that in type I cases. Owing to the involvement of intrahepatic bile ducts in type IVa cases, radical resection requires combined partial hepatectomy. The treatment of intrahepatic biliary cysts needs to be evaluated according to the severity and extent of the lesioned bile ducts . The scoBased on findings from clinical and pathological studies, a comprehensive theoretical system for the surgical treatment of CDBDs has been established, which corrects many previous theoretical misunderstandings. Using these principles, treatment outcomes for CDBDs can be improved.