Traditional Chinese medicine (TCM) has been practiced for thousands of years with clinical efficacy. Natural products and their effective agents such as artemisinin and paclitaxel have saved millions of lives worldwide. Artificial intelligence is being increasingly deployed in TCM. By summarizing the principles and processes of deep learning and traditional machine learning algorithms, analyzing the application of machine learning in TCM, reviewing the results of previous studies, this study proposed a promising future perspective based on the combination of machine learning, TCM theory, chemical compositions of natural products, and computational simulations based on molecules and chemical compositions. In the first place, machine learning will be utilized in the effective chemical components of natural products to target the pathological molecules of the disease which could achieve the purpose of screening the natural products on the basis of the pathological mechanisms they target. In this approach, computational simulations will be used for processing the data for effective chemical components, generating datasets for analyzing features. In the next step, machine learning will be used to analyze the datasets on the basis of TCM theories such as the superposition of syndrome elements. Finally, interdisciplinary natural product-syndrome research will be established by unifying the results of the two steps outlined above, potentially realizing an intelligent artificial intelligence diagnosis and treatment model based on the effective chemical components of natural products under the guidance of TCM theory. This perspective outlines an innovative application of machine learning in the clinical practice of TCM based on the investigation of chemical molecules under the guidance of TCM theory. Machine learning, which involves learning relationships from data using computer science, has been successfully applied to solve complicated tasks such as computer vision, speech recognition, and natural language processing , 2. The TCM is one of the oldest healthcare systems in the world and is being increasingly used as a complementary medicine system worldwide . As a fuCNN is a deep feedforward neural network with the characteristics of local connection and weight-sharing that uses a stack of convolution layers to extract features. It is widely used in image classification , facial rfitting . The mosrfitting . The poorfitting .The Elman RNN, also named as a simple recurrent network, was the first RNN among feedback neural networks and was specifically designed for processing time-dependent sequential data. The Elman RNN is often used in natural language processing . It showThe LSTM is an advanced variant of RNN with the capability of preserving long-term dependencies by using internal feedback . EssentiGAN is a promising framework composed of two components: a generator and a discriminator. The generator generates false data samples and tries to deceive the discriminator. The discriminator tries to distinguish between true and false samples, which compete with each other in the training phase . By repenslation .Multilayer perceptron (MLP) uses a neural network with fully connected layers in a nonlinear model, including an input layer, several hidden layers, and an output layer with the capability to calculate the weighted sum of its inputs and then apply an activation function to transform a signal to the next neuron  Fig. 5)5). The RThe support vector machine (SVM) algorithm is a generalized linear classifier model for binary classification . By usinFrom the original AlexNet in 2012 through the VGG in 2014 and ResNet in 2015, CNNs have been predominantly used in the field of computer vision  and natuMLP is a simple and easy-to-implement algorithm with good generalization ability that is often used for identification, classification, and prediction . HoweverDeep learning offers absolute advantages in computer vision and natural language processing. Its powerful processing capabilities for features such as image and time series features are beyond the reach of traditional machine learning algorithms. Deep learning methods such as generative adversarial algorithms and reinforcement learning ensure continuous improvements in the calculation accuracy, which is also beyond the reach of traditional machine learning algorithms. However, for small datasets, deep learning is prone to overfitting and shows no advantage over traditional machine learning algorithms. Thus, the development of artificial intelligence techniques for TCM will require a combination of deep learning and traditional machine learning. Deep learning is preferred in feature extraction, such as semantic segmentation data fitting and image feature extraction. In contrast, traditional machine learning algorithms such as MLP and RF may be more suitable for small data classification and regression problems Table .Table 1Deep learning is widely used in the research and development of natural products Table . NaturalPolygonum multiflorum Thunb, and provided a powerful tool to screen large datasets for toxicants. He [Although the majority of natural products appear inherently safe, clinicians and researchers should also pay attention to the potential for drug-induced injury. The liver which is the major organ of drug metabolism is more likely to show drug-induced injuries than other organs, and these injuries may lead to hepatitis, liver fibrosis, liver failure, and even death . The kidants. He  establisants. He  developeWith the application of AI technology in TCM, AI-assisted disease diagnosis has emerged as a promising research field. With TCM symptoms corresponding to features in the machine learning literature, syndrome elements serve as classes or labels , and macClinical information for TCM diagnosis is collected by the diagnostic methods of looking, listening and smelling, asking, and touching. Intelligent auxiliary diagnosis methods based on these four diagnostic methods in TCM are constantly developing with the accumulation of clinical diagnosis and treatment records, experimental records, TCM databases, books, medical literature, and the other knowledge. Diagnosis based on visual examination is an important method to obtain disease information, and tongue and eye diagnoses are its main components. TCM tongue diagnosis involves interpretation of tongue images obtained by doctors on the basis of the theory of TCM after observing the tongue coating, quality, shape, and other tongue-related information. Tongue diagnosis provides much information about the state of the body, and the diagnostic points of tongue diagnosis include the color and state of the tongue coating, color, texture, shape, and characteristics of the sublingual vein and tongue body parts, etc., which are important features in tongue diagnosis data collection. Traditional machine learning algorithms such as SVM , DT, neuAlthough SVM, RF, and MLP have been shown to be effective for simple image classification, they are not satisfactory for complex tasks. With advancements in machine learning, deep learning is being gradually applied for complex task processing for intelligent tongue diagnosis. CNN models are good at image classification, and have been shown to be better than other traditional algorithms in this field . The AleEye evaluations can realize intelligent auxiliary diagnosis through fundus image analysis. Retinal vessels are the only visible blood vessels that can be evaluated by simple fundus photography, and this approach provides a convenient method to evaluate cardiovascular status. One study found that retinal features were associated with stroke, and the researchers used the CNN model of the ResNet50 network structure to conduct a stroke risk assessment using retinal images . Sun 7878 used CTraditional auscultation mainly involves listening to sounds. With advancements in medical treatment, auscultation using equipment is now also utilized in TCM. The combination of an electronic stethoscope with artificial intelligence technology can allow digital acquisition of heart sounds, providing an objective basis for heart sound auscultation. Traditional machine learning methods for heart sound auscultation usually involve segmentation, feature extraction, and classification. Although traditional machine learning methods allows rapid model training, they usually require complex preprocessing and post-processing steps. However, advancements in deep learning, especially in the CNN model, have yielded favorable results for intelligent diagnosis based on heart sounds. The intelligent heart sound auscultation process includes signal acquisition, signal preprocessing, heart sound feature extraction, and model training . FernandPulse diagnosis is one of the most important diagnostic methods in TCM. Doctors use three fingers to touch the wrist at three specific positions, namely, inch, off, and ruler, to examine the pulse and determine the health of patients. With advancements in sensors, detectors, and sensor technologies, digital palpation data can now be obtained from the same location, enabling AI technology to process palpation data and make diagnoses . At presMachine learning has recently been successfully applied in disease treatment and effect evaluation of TCM, such as in prescription recommendation, transition prediction, and treatment prognosis Table . The tredan shen and san qi, were identified as the potential TCM preparations for the treatment of myocardial infarction. By utilizing machine learning , fingerprint, and network pharmacology, Li [Wolfiporia cocos. Yuan [The continuous advancement of information technology and biotechnology has yielded substantial biomarker data for TCM investigations using machine learning. Zhang  used RF logy, Li  screenedos. Yuan  used RF os. Yuan  utilizedOur team proposed that algorithm ensemble is more suitable for TCM data models. Although an algorithm model can realize the construction of a prediction model based on the data for certain characteristics, the lack of universality and transferability limits the applicability of such models in systematic research on the diagnosis and treatment process of symptom-syndrome-treatment-prescription-natural products. Therefore, considering the current status of artificial intelligence in TCM, unification of different diagnosis and treatment rules on the basis of syndrome elements through a combination of multiple algorithms may facilitate accurate calculation of the entire diagnosis and treatment process in symptom-syndrome-treatment-prescription-natural products. The general structure of an ensemble learning algorithm consists of a set of “individual learners”, which are used to create an ensemble using a certain policy . Using tThe diagnosis and treatment theory in TCM shows the characteristics of diversified intersection. TCM treatment based on syndrome differentiation involves eight principal forms of differentiation, qi and blood fluid syndrome differentiation, zang-fu differentiation, and meridian syndrome differentiation. On the other hand, the compatibility rules include monarch and minister compatibility, flavor compatibility, and component compatibility. In addition, differences in the diagnosis and treatment rules among TCM sects and TCM physicians have made it difficult to reserve large high-quality TCM data of the same rule system. To address this problem, our team proposed syndrome elements that could link the symptoms, treatment, natural products, and prescriptions, and thereby unify different diagnosis and treatment rules . The teaThe effective chemical components of natural products have attracted attention worldwide. Rapid screening and identification of potential candidate compounds are very vital to determine the mechanisms underlying the therapeutic effects of drugs and can greatly ameliorate the development of new drugs. Since the successful development of artemisinin, the expectations for discovery of novel drugs with high efficacy and minimal adverse effects from TCM have increased. In this regard, a combination of the knowledge of effective chemical components of natural products with computational biology and machine learning under the optimization of TCM syndrome differentiation theory can facilitate disease treatment to realize effective development of machine learning in TCM clinical practice. The team proposed machine learning using a combination of computational biology of natural products and TCM theory. In this approach, computational biology is first used to study the pharmacology of natural products. Using the key molecular targets of disease as the research aspect, computational biology is used to simulate and screen the effective components of natural products for the key molecular target of disease. Based on molecular mechanisms identified in natural products screening, machine learning is performed on the selected natural products to establish a prediction model of molecular characteristics of natural products compounds and attributes, TCM syndrome differentiation, and meridians. For disease clinical data collection, the establishment of patient syndrome model in combination with a TCM theory screening model can allow optimization of the final therapeutic drugs.The study used computational biology methods to analyze and screen natural products. Computational biology can unravel the seemingly impenetrable complexity of biological systems by an integrated approach which employed high-performance computers, state-of-the art software and algorithms, mathematical modeling, and statistical analyses . Moleculhttp://www.tcmip.cn/Syndrome/front/#/) which is a network-based evaluation tool of multi-way associations among diseases, syndrome differentiation, and prescriptions could facilitate the understanding of syndrome differentiation and natural products from the perspective of molecular biology, enriched gene ontology terms or signaling pathways associated with syndrome differentiation [Syndrome differentiation and treatment form the core of TCM theory. The development of intelligent diagnosis based on machine learning provides a dialectical basis for TCM syndrome differentiation. The use of machine learning in the research and development of TCM provides a basis for syndrome differentiation, while the unified diagnosis and treatment rules based on syndrome elements provide a direction for syndrome differentiation. Machine learning with molecular basis underlying syndrome elements may better classify diseases and improve clinical treatment effectiveness. Now, a web platform named SoFDA (ntiation . SyndromIn summary, this study reviewed the applications of machine learning in TCM research, including the principles of deep learning and traditional machine learning algorithms, the application of machine learning algorithms in TCM research, and an analysis of promising research directions. Machine learning has been applied in natural product research, TCM disease diagnosis, disease treatment and effect evaluation, and prediction of biomarkers in TCM. Traditional machine learning algorithms such as SVM, RF, DT and MLP are widely used in TCM learning. With advancements in machine learning, deep learning has found additional applications in TCM. Deep learning shows higher prediction performance than traditional machine learning algorithms. Although the clinical diagnosis and treatment process in TCM produces large amounts of data, the diversity in diagnosis and treatment models has resulted in a lack of uniform standards. Thus, the use of syndrome elements as a unified standard is important for addressing the difficulties in developing artificial intelligence-based techniques for TCM. The multi-algorithm rule integration proposed herein is more suitable for a TCM data model. Natural products contain many chemical components that influence the therapeutic effects. By utilizing computational simulation, these medicines can be screened at the molecule level. TCM theory serves as the guideline for the use of natural products, and the integration of machine learning with TCM theory, natural product, and computational simulation can yield an intelligent artificial intelligence-driven diagnosis and treatment model based on the effective chemical components of natural products under the guidance of TCM theory. Thus, the combination of machine learning with our understanding of effective chemical components of TCM and TCM theory offers a practical direction for the use of artificial intelligence in TCM, which can be expected to have far-reaching implications.Although the development of machine learning in TCM is a promising study, the challenges and difficulties cannot be ignored. Effectiveness and safety are issues that need to be paid attention to in the development of artificial intelligence in TCM. The accurate application of machine learning in TCM theory which is the guiding program of TCM is related to the clinical effectiveness of TCM artificial intelligence research, and is a difficulty and challenge that TCM artificial intelligence needs to solve. The clinical effectiveness of intelligent diagnosis and treatment of the chemical molecular mechanism of natural products under the guidance of correct TCM theory is a worth working. Safety in TCM intelligent diagnosis and treatment is another key point that influence its development. The potential for drug-induced injury should be taken into account in TCM artificial intelligence research.


Microglial cells are specialized macrophage cells of the central nervous system responsible for the innate immunity of the spinal cord and the brain. They protect the brain and spinal cord from invaders, microbes, demyelination, trauma and remove defective cells and neurons. For immune protection, microglial cells possess a significant number of receptors and chemical mediators that allow them to communicate rapidly and specifically with all cells of the nervous tissue. The contribution of microglia in neuropathic pain challenges conventional concepts toward neurons being the only structure responsible for the pathophysiological changes that drive neuropathic pain. The present study is a narrative review focusing on the literature concerning the complex interaction between neurons and microglia in the development of neuropathic pain. Injury in the peripheral or central nervous system may result in maladaptive changes in neurons and microglial cells. In neuropathic pain, microglial cells have an important role in initiating and maintenance of pain and inflammation. The interaction between neural and microglial cells has been proven extremely crucial for chronic pain. The study of individual mechanisms at the level of the spinal cord and the brain is an interesting and groundbreaking research challenge. Elucidation of the mechanisms by which neurons and immune cells interact, could constitute microglial cells a new therapeutic target for the treatment of neuropathic pain. Neuropathic pain is defined by the International Association for the Study of Pain as “pain caused by a lesion or a disease of the somatosensory nervous system.” Unlike nociceptive pain, which is the normal response to noxious stimuli, neuropathic pain is a maladaptive response to an injury of the nervous system . In neurRegardless of etiology, location, intensity, or other individual characteristics, neuropathic pain is characterized by changes in the normal processing of sensory signals. Despite the absence of tissue damage, the pain is maintained through the development of peripheral and central maladaptive mechanisms. The disorder develops gradually for weeks or months after damage, decisively affecting patients’ quality of life. Once neuropathic pain is generated, the sensory hypersensitivity typically persists for prolonged periods, even though the original etiological cause may have long since disappeared, as after nerve trauma. Symptom persistence ultimately causes changes in the genetic expression of the neurons of the somatosensory system and extension of the cortical representation in areas of the primary sensory cortex . First-lMicroglia, first described in 1920 by del Río Hortega, are a specialized population of mononuclear macrophages that are located in the central nervous system (CNS) and comprise ~10-15% of all glial cells. They participate in immune surveillance and homeostatic control of inflammation and regulate the innate immune response of the brain and spinal cord. They develop from the progenitor hematopoietic stem cells (myeloid progenitor cells) during early embryogenesis and migrate initially to the brain in relatively small numbers . HoweverMicroglial cells are considered as the fastest and most flexible cells in the brain. They have a small cell body and several long processes with multiple branches that allow them to monitor each neuron individually while "slipping" among them by extending and shrinking their branches . They arThe present study is a narrative review focusing on the literature concerning the complex interaction between neurons and microglia in the development of neuropathic pain.Following a peripheral nerve injury, the system of pain management and treatment malfunctions. Research efforts and pharmacological approaches have focused on neural tissue dysfunction. However, evidence suggests that in addition to nerve cells, specialized non-neural cells that regulate the innate immune response of neural tissue against pathogens, play an important role in this dysfunction, which ultimately leads to neuropathic pain -14. An iLaboratory experiments using modern tools of molecular genetics have shown that microglia participate in the onset, maintenance, mediation, and expansion of neuropathic pain ,18. In mNeuroglial cells , besides the support and nutrition of neurons, actively participate in the reception, transmission, processing, and modification of nerve stimuli. Glial cells and neurons closely cooperate aiming at homeostasis and optimal functioning of the sensory synapses. In pain and tissue damage, neurons are assisted by glial cells that are activated at the dorsal root ganglia and the posterior horns of the spinal cord. Glial cells are co-responsible to some extent for the expansion of pain. Many non-opioid and opioid peptides act on microglial cells, which respond by producing pro- or anti-inflammatory agents to a continuous supplementation of neurons with excitatory chemical signals ,23.From the peripheral nerves to the spinal cordIn nerve damage , inflammatory irritants fill the space around the free nerve endings, peripheral receptors, axons, or peripheral stumps. The sensory nerves, through their special channels, including transient receptor potential vanilloid 1 (TRPV1), prostaglandin receptors, tendon-sensitive ion channels, etc.), convert chemical stimuli into electrical energy potentials. Glial cells around the spinal synapses respond to both electrical and chemical stimuli; tensile cells in the cell membrane "sense" the intensity of nerve activity and respond to it with hyperstimulation. Astrocytes and microglial cells, which are scattered but regularly arranged throughout the CNS and along the somatosensory pathway, express receptors for most of the substances that act on the spinal sensory synapsis. On the membrane of glial cells, there are glutamic acid receptors , gamma-aminobutyric acid receptors (GABA A & GABA B), norepinephrine receptors , acetylcholine receptors , cannabinoid receptors (CB2) and receptors of bradykinin, dopamine (D1 & D2), purines, adenosine, and opioids .Some transmembrane receptors are expressed in resting microglia and others in the activated state. Toll-like receptor 4 is overexpressed in microglial cells after their activation. Its overexpression promotes the production of nitric oxides, prostaglandins, leukotrienes, nerve growth factors, stimulant amino acids, neurotoxic peroxides, and cytokines, such as interleukin-1 (IL-1), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). These substances further stimulate the perisynaptic region in the microglia-axons positive feedback loop. This toxic compound of chemical substances originating from nerve cells, astrocytes, and microglial cells is responsible for chronic and persistent neuroinflammation -27.Evidence has led to the hypothesis of "microgliopathic pain," a pain syndrome for which dysfunctional microglia are responsible. It has been thought that the theory of dysfunctional microglia in chronic pain may be the "missing link" in pain physiology. Dysregulated microglial activation, neuroinflammation, and altered neuronal communication contribute to the amplification of pain signals and the transition from acute to chronic pain. By targeting microglial-related mechanisms, researchers are striving to develop effective treatments that can provide relief to individuals suffering from chronic pain .Events in the spinal cordAfter peripheral nerve damage, the resting microglia of the spinal cord rapidly changes both morphologically and functionally. Resting microglial cells have small cell bodies and long-branched processes. As microglial cells are activated, the cells undergo morphological changes in which the cell body becomes relatively large, and the processes become shorter. These changes are accompanied by an increase in the number of microglia in the spinal cord, either by migration or proliferation, a phenomenon known as gliosis or microgliosis . These aBesides cellular hypertrophy, overexpression of the complement receptor CR3 on the microglial cell surface is presented, changes that are observed within the first 24 hours of nerve damage. Two to three days after nerve injury, microglia begin to proliferate, reaching the maximum number of cells on the 4th to 7th day. Within the first seven days, the most prominent changes in the immunophenotype are observed, with more frequent increased expression of major histocompatibility complex (MHC) antigens. The changes are reversible regardless of the severity of the damage and usually are over one month after the start of the damage. Temporal continuity was one of the reasons for accepting the role of microglia in the structural changes of sensory cells and in the genesis of neuropathic pain -36.CSF-1 has been identified as the key chemoattractant of microglial cells, which invites them to colonize and expand at the site of the lesion. Concurrently, its receptor, CSF1R, located on the surface of glial cells of the spinal cord, increases in number proportionally . It simuThe fractalkine receptor, C-X3-C motif chemokine receptor 1 (CX3CR1), participates in microglial activation as well. This receptor is expressed on the cell membrane of microglial cells of the spinal cord and brain, it binds to fractalkine (chemokine-adhesion molecule) and is overexpressed in the spinal cord during inflammation and nerve damage ,45. The Summarizing, three main elements could be reported in the mechanism of activation of the spinal microglia. First, nerve damage leads to de novo CSF-1 induction in the dorsal root ganglion. From here, CSF-1 reaches the ends of the sensory neuron (reciprocating movement) and recruits the CSF-1 receptors (CSF-1Rs). Second, the presence of CSF-1 is considered a capable and necessary condition for the proliferation, migration, and activation of microglia. Finally, the activation simultaneously affects the entire reflex arc, the sensory neurons of the dorsal horn, the medial neurons, and the corresponding anterior horn motor neurons. The purine (ATP) and fractalkine pathways are rather involved in the maintenance and perpetuation of pain than in the initial activation and sensitization.Activation of the spinal neuroglia is observed in the initial phase (onset phase) of neuropathic pain and precedes the activation of astrocytes (astrogliosis), supporting the hypothesis that microglia contribute to the initiation of neuropathic pain while astrocytes participate in its maintenance ,50. TherEvents in the brainThe role of neurotransmitters in the function of microglia has been examined in the brain. Neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), pituitary adenylate cyclase-activating peptide (PACAP), somatostatin, cortistatin, tachykinins, calcitonin gene-related peptide (CGRP), leptin, ghrelin, and neuropeptides derived from the POMC gene , such as adenocorticotropin-releasing hormone (ACTH), melanocyte-stimulating hormone (MSH), and opioid peptides  directly affect the function of microglial cells. Microglial cells express membrane receptors for all the above-mentioned neuropeptides, thus participating in the regulation of pain sensitivity ,54.The role of brain microglia in chronic neuropathic pain also emerged from animal studies ,56. It wTargeting microglia as a therapeutic strategy in treating neuropathic painSince the involvement of microglia in the development and maintenance of neuropathic pain has been confirmed, the investigation of new drugs able to modify the function of immune cells of the CNS is a priority and a challenge for researchers . There iPeripheral nerve damage and peripheral inflammation are known causes of chronic pain. In situations of sensitization, prolonged activation of the primary sensory nerves in the periphery is followed by increased activity of the terminal nerve cells in the posterior horn of the spinal cord. However, hyperactivity of the nerves in the area has the effect of activating non-nerve cells (immune cells) at the site of the lesion . Microglial cells are thus involved in nervous pathology (disease or injury) dynamically; they proliferate, change morphologically, and secrete substances that make local synapses even more sensitive. Therefore, a condition of positive stimulus feedback is established, leading to chronicity. Activation of microglia is more likely after nerve damage than after inflammation. They are found along the entire length of the somatosensory pathway, where immune cells are present at each synapsis. Microglia participate in all processes of the mechanism that produces chronic neuropathic pain (gliopathy). The interaction between neurons and microglial cells is considered critical for chronic pain and inflammation. The disruption of the two-way relationship between neurons and immune cells is associated not only with chronic neuropathic pain but is considered the pathogenetic factor for a number of inflammatory diseases of the peripheral and central nervous system, which are called neurodegenerative diseases.Concluding, the somatosensory system is a key regulator of the innate immune response of organisms. To achieve this, it interacts and cooperates with the cells of the immune system, in particular with microglia. Understanding this communication, which we have tried to describe in detail in this review, will unfold new cellular mechanisms, lead research into interesting biochemical molecular pathways, and turn medical thought to a more holistic view of the organic systems involved in chronic pain (neuro-immune-endocrine coupling).


At present, most precious compounds are still obtained by plant cultivation such as ginsenosides, glycyrrhizic acid, and paclitaxel, which cannot be easily obtained by artificial synthesis. Plant tissue culture technology is the most commonly used biotechnology tool, which can be used for a variety of studies such as the production of natural compounds, functional gene research, plant micropropagation, plant breeding, and crop improvement. Tissue culture material is a basic and important part of this issue. The formation of different plant tissues and natural products is affected by growth conditions and endogenous substances. The accumulation of secondary metabolites are affected by plant tissue type, culture method, and environmental stress. Multi-domain technologies are developing rapidly, and they have made outstanding contributions to the application of plant tissue culture. The modes of action have their own characteristics, covering the whole process of plant tissue from the induction, culture, and production of natural secondary metabolites. This paper reviews the induction mechanism of different plant tissues and the application of multi-domain technologies such as artificial intelligence, biosensors, bioreactors, multi-omics monitoring, and nanomaterials in plant tissue culture and the production of secondary metabolites. This will help to improve the tissue culture technology of medicinal plants and increase the availability and the yield of natural metabolites. The increment in the global demand for medicinal plant resources, a diversified use of plants, and the reduction in cultivated land have accelerated the lack of plant resources. Large-scale culture of plant cells and tissues is considered to be a suitable method to alleviate this situation. In the past, due to the differences in plant species and varieties, the immaturity of culture conditions, and the solidification of research thinking, the development of plant cell and tissue culture technology was relatively slow . AlthougWhether for solid or liquid culture of plant tissue, the prediction and optimization of culture conditions have always been the focus of research. Data-driven modeling technology such as artificial intelligence (AI) , optimisWOX5) is crucial in the identity and maintenance of QC and the mutant WOX5 showed an aberrant differentiation pattern of stem cells [During the late period of plant embryonic development, stem cells are located in the apical niche of meristem, and stem cells will divide and differentiate to maintain the constitution of meristem, which can grow into different tissues and organs such as callus, adventitious roots (ARs), etc. ,19. Rootem cells .Zea mays L. [Panax ginseng [Abrus precatorius Linn [Callus induction is a key step in plant suspension cell culture such as  mays L. , Panax g ginseng , and Abrius Linn . The higius Linn ,27. Althius Linn . Somaticius Linn . Abnormaius Linn . Mechaniius Linn . Callus ius Linn ,33 (see Adventitious root (AR) cultures show the characteristics of high root proliferation and biomass, and have the potential to synthesize specific bioactive compounds. Adventitious roots are a reliable source of natural chemicals due to their genetic and biosynthetic stability. ARs can be induced from various explants  in in vitro conditions. Factors affecting the morphogenesis of ARs include indole-3-acetic acid (IAA), nitrous oxide, and light . Among tPlant development can be manipulated by adding PGRs at specific stages of growth or maturation by adding plant hormones such as IAA, naphthaleneacetic acid (NAA), 6-furfurylaminopurine (KT), 6-benzylaminopurine (6-BA), ethylene, abscisic acid (ABA), brassinolide (BL), jasmonic acid (JA), salicylic acid (SA), etc. . All of Plant secondary metabolites are the main active ingredients of pharmaceuticals. Plant growth regulators have been used in recent years as elicitors to stimulate the production of secondary metabolites. Plant growth regulators stimulate the synthesis of different types of secondary metabolites such as terpenoids and phenols , tannins, sulfur containing secondary metabolites , and nitrogen containing secondary metabolites  . Some stAt present, although the specific mechanism of PGRs has not been elucidated, some studies have confirmed some parts of the mechanism of plant hormone response. Studies have shown that secondary metabolic clusters such as terpenoids share a common gene evolutionary history with the major metabolic pathways of plant growth hormone synthesis , which mA biosensor is an integrated receptor–transducer device that can convert a biological response into an electrical signal, biosensors for a wide range of applications such as health care and disease diagnosis, environmental monitoring, water and food quality monitoring, and drug delivery . The intFluorescence biosensors are particularly effective for monitoring the spatial and temporal distribution of small signal molecules, which can be used to study the distribution and content of plant hormones in the subcellular . The disIn order to successfully and efficiently carry out plant tissue culture, we need to scientifically improve the culture conditions including light, temperature and humidity, appropriate medium composition, plant growth regulators, etc. However, the cultivation of plants of different species and different tissues of the same plant has great differences. It is very tedious and inefficient to screen the most suitable culture conditions through the experiments. For example, in the prediction of a medium formula, the mineral and hormone composition of the plant micropropagation medium is an important factor in the growth of explants, but the different plant species lead to different nutritional and hormone requirements. Blindly testing the types and proportions of various hormones and minerals is time-consuming, laborious, and costly work, and does not often succeed. Most of the optimization of plant tissue culture medium is improved on the basis of previous experiments. This method requires a lot of control experiments. Second, it is also necessary to effectively develop and optimize the new medium. Understanding the role of minerals and hormones and their interaction with other medium components and different plant tissues is critical to the successful in vitro culture of plant tissues ,74. HoweThe modeling method of artificial intelligence (AI) is more effective than other modeling techniques and is a potential modeling tool for plant tissue culture . AI and Previous studies have focused on predicting the effects of various components of the medium and hormones on plant explants through traditional multi-layer perceptron neural network (MLPNN) and multiple linear regression (MLR) methods. Genetic programming (GP) is one of the most traditional and widely used evolutionary algorithms. GEP technology involves computer programs encoded by linear chromosomes of different sizes and shapes, which is an effective alternative to traditional GP. Jamshidi et al.  used GEPAt present, data-driven modeling technology has become a predictive tool for modeling complex biological research and plays an important role in plant tissue culture. Scientific prediction greatly reduces the workload of researchers and reduces the cost of in vitro culture. In the future, the development of modeling technology may make the in vitro culture of plant tissue become more automated and mechanized.Panax ginseng and Panax notoginseng, the large-scale production of secondary metabolites by a bioreactor will be very competitive to solve existing problems such as the high cost of planting cultivation. By constructing the best environment for the effective growth and production of bioactive substances, the culture results can be significantly affected, which can be used to produce secondary metabolites, recombinant proteins, microbial fermentation, etc. From an economic point of view, the final purpose of the design of the bioreactor is to decrease the cost of planting production. To achieve this goal, a consideration of the cost of equipment, substrate cost, time, and the final total output is required [Many secondary metabolites of plants still cannot be obtained by artificial synthesis. The cell and tissue culture of medicinal plants is still the main source of secondary metabolite production . Bioreacrequired .Bioreactors should be able to control environmental conditions and allow the aseptic operation of different bioreactors to have a great influence on the state of secondary metabolites in plant tissue or cell culture. Agnieszka Szopa  comparedTypical plant cell and tissue culture bioreactors are made of glass or stainless steel . The morStirred tank reactors (STRs) are currently the most functional bioreactors in PTCC. Airlift and bubble column systems were basically designed to improve the biological oxygen demand of the culture. Helical and double helical ribbon impellers appeared to be efficient for the suspension culture of high-density plants. An important advance in plant cell and tissue culture is the use of disposable bioreactors. A disposable reactor replaces the stainless-steel material in the device with plastic products, which greatly reduces the preparation time and cost of the reactor. Another advantage of disposable bioreactors is that they do not require cleaning, which will reduce the probability of contamination. At present, due to limited experience in the use of disposable reactors, a lack in the physical strength of plastic materials, and other reasons, this type of reactor is not widely used . A largeA variety of detecting techniques for omics research such as high-performance liquid phase (HPLC), mass spectrum (MS), and nuclear magnetic resonance (NMR) can be used to determine the type and content of animal and plant metabolites. Some have been used to monitor robust and high-yield biological production processes. The conventional physical parameters that should be detected are pH, temperature, and dissolved oxygen. Sensors for bioreactor detection need to accurately measure the concentration of various nutrients and metabolites in the culture medium without affecting the normal production process. For nutrients and metabolites in reactors, spectroscopy is currently used for monitoring. Spectroscopy is particularly important for the biotechnology industry because it can be easily conducted and achieve online real-time measurement. The overview of spectroscopy is to study the interaction between matter and electromagnetic radiation. Analytical instruments include infrared spectroscopy, fluorescence spectroscopy, etc. Finally, statistical and mathematical techniques are used to analyze the chemical data of the monitored material. Each spectral method has its own advantages and disadvantages, which means that different spectral methods have different components and bioreactor matrices to analyze. Spectroscopy for bioreactor monitoring has been used in microbial fermentation, cell culture, etc. . NMR is Nanomaterials have a wide range of applications in biotechnology, and have played a great role in medical, agricultural, pharmaceutical, and other fields. They can be used in sensor development, agricultural chemical degradation, soil remediation, drug delivery, and so on. Various materials are used to manufacture NPs such as metal oxides, ceramics, silicates, magnetic materials, semiconductor quantum dots (QDs), lipids, and polymers. Dendritic macromolecules and emulsion encapsulated polymer nanomaterials have controlled and distressed release capabilities, and metal-based nanomaterials have a size dependence. Nanomaterial formulations increase system activity due to higher surface area, solubility, and smaller particle size . In the An elicitor stimulates the accumulation of secondary metabolites by stimulating the defense system in plant metabolism. Biological elicitors and abiotic elicitors are commonly used in plant tissue culture. Nanomaterials have been widely used in medicine, energy, biotechnology, and other fields due to their unique properties. In recent years, studies have found that using nanomaterials as elicitors can greatly increase the accumulation of secondary metabolites. The properties of nanomaterials can be precisely controlled by controlling the shape, size, and chemical composition of the materials. Nanoparticles can increase the production of reactive oxygen species and hydroxyl radicals that distort cell membranes, leading to changes in penetrability, facilitating the entry of nanoparticles into plant cells, and stimulating the production of secondary metabolites . The proMelissa officinalis leaf were compared, and it was found that the composite elicitor could increase the content of the product by 0–17% [Common nanomaterials include multiwalled carbon nanotubes (MWCNTs), single walled carbon nanotubes (SWCNTs), graphene, and fullerene C70 . Howeverby 0–17% .Nano-elicitors play an important role in the production of many natural products. The discovery and preparation of nanomaterials are key technologies. Therefore, which nanomaterials can be used as potential elicitors for plant tissue culture? To answer this question, we conducted the following analyses. First, due to the application of new nanomaterials with the development of nanotechnology, more and more new nanomaterials have been created, so there is a need to combine biotechnology and engineering to achieve multidisciplinary cooperation and development. Second, although some composite nanomaterials have not been used in plant tissue culture, they have potential capabilities such as natural polysaccharide composite nanomaterials . This maNano-transport technology can transport some chemicals into cells in a targeted and efficient manner, which can effectively reduce the environmental pollution caused by plant growth. Currently, inorganic nanoparticles have been studied for drug delivery applications . Nano-feLDH has certain advantages as transport carriers. The hydroxide component of LDH can effectively prevent external enzymes and oxygen from destroying the loaded drugs in the interlayer. The intercalated structure makes the drugs carried by LDH have a controlled release effect. LDH-drug mixed nanoparticles can achieve cell localization by adjusting the zeta potential. LDH material has low cytotoxicity , and itsVigna radiata (L.) Wilczek. The molecules of IAA are effectively inserted into LDH through the co-precipitation effect. The insertion can protect IAA molecules from enzymatic degradation, and the intercalation can achieve a sustained release performance. The results showed that the IAA–LDH complex treatment increased the rooting efficiency by 4.6 times and improved the biological activity of IAA to promote adventitious root development. Hussein et al. [Ilya Shlar et al.  found thn et al.  found thn et al.  used then et al.  used an n et al.  construcn et al.  preparedCompared with synthetic polymers, natural polymers have good biocompatibility and biodegradability. The structure of some natural polymers is similar to that of biological macromolecules, and they are more easily recognized, utilized, and metabolized by organisms . ChitosaRoselle plants. The results showed that IAA + GA3 + CNF (800 + 800 + 100 mg/L) stimulated the growth parameters of rose plants and promoted the content of healthy phytochemicals  and the improvement in plant antioxidant capacity. This indicates that the combined application of plant growth regulators and chitosan nanofibers (CNFs) has an important impact on various growth parameters and metabolite status, and reflects the positive effect of chitosan nanofibers on plants. In plant tissue culture, chitosan is mostly used as a transport carrier for plant hormones. Salicylic acid-chitosan nanoparticles ensure their continuous availability in plants by slowly releasing SA. The seedling index was 1.6 times higher than that of the control group, and the chlorophyll  content (1.46 times), ear length, grain number per ear, and grain weight per pot were also increased [Azospirillum. The results showed that the release of bacteria in saline was gradual and could be used as a bio-nano fertilizer. Different chitosan nanomaterials as plant tissue culture material transport carriers are shown in Chitosan nanomaterials have the characteristics of promoting plant growth and increasing the content of secondary metabolites. Farhad Mirheidari et al.  applied ncreased . Plant hncreased . Using Sncreased . As an encreased . Some chncreased  developePlant secondary metabolites are synthesized and accumulated in plant cells, but traditional recovery methods generally dry plant tissues, which is destructive to the tissue. In addition to destroying expensive transgenic plant cell cultures, the activity of unstable biomolecules may be lost during the solvent extraction process, resulting in reduced yields . Nano-haThe cellular uptake and excretion mechanisms of MSNPs are important in designing novel biomolecule separation and delivery applications. Positively charged MSNP particles have been shown to facilitate penetration into the membranous and cell walls. The amine-functionalized MSNPs spontaneously entered and exited the plant cells through dynamic exchange for 20 ± 5 min. Ti-functionalized weakly charged MSNPs were absorbed and excreted through a thermal activation mechanism, whereas amine-modified positively charged particles were absorbed and excreted mainly through direct cell penetration. Particle size and surface properties (charge) are the two most critical factors for cellular uptake, but the extent of uptake depends on the type of plant. Excretion mechanisms depend on the cell type, nanoparticle size, shape, and surface modification, and the surface charge may be a decisive factor in controlling transport and excretion .The nano-capture of secondary metabolites is a new biotechnology for the separation and transfer of active biological molecules in living tissues. At present, nano-harvesting technology is only applied to the capture of flavonoids, but through the modification of nanomaterials, other active ingredients are also expected to be extracted.The cultivation technology of plant cells, tissues, and organs is a modern biological means to solve the shortage of medicinal resources and the shortage of wild plant resources. The ultimate goal of plant tissue culture is to achieve large-scale biomass production and the accumulation of precious secondary metabolites. The mechanism of plant tissue growth and development is constantly being updated, and the technology in various fields is gradually being integrated into tissue culture technology. For example, data-driven modeling technology takes artificial intelligence modeling and optimization algorithm as the means of prediction, accurately and efficiently analyzes the cultivation conditions, develops new cultivation methods, and systematically and scientifically optimizes the prediction. Data-driven modeling is one of the most applicable methods and plays an important role as a predictive tool for modeling complex biological research. From another aspect, the amplification of the bioreactor culture and improvement in the dynamic monitoring system are conducive to the realization of the industrial automatic production of culture. Designing different bioreactor types will not only help to improve and maintain high productivity, but also reduce the process costs. Suitable types of reactors should be selected for different cultures. Nanotechnology has been widely used in plant tissue culture. However, nanotechnology is not limited to the content introduced in this article. Its mode of action is more extensive and can be applied in various processes of plant tissue culture. The role of nanomaterials largely depends on their chemical and mineral composition, size, and sometimes the shape and concentration of application. Technology in various fields with continuous update, and more innovative ways will be applied to the plant tissue culture process. In summary, the application of new technologies in intelligent algorithms, instrument engineering, nanomaterials, and other fields to adapt to the standardization of commercial applications has had a positive impact on plant tissue culture and the industrial production of secondary metabolites.


Amino acids have been extensively studied in nutrition, mainly as key elements for maintaining optimal protein synthesis in the body as well as precursors of various nitrogen-containing compounds. However, it is now known that amino acid catabolism is an important element for the metabolic control of different biological processes, although it is still a developing field to have a deeper understanding of its biological implications. The mechanisms involved in the regulation of amino acid catabolism now include the contribution of the gut microbiota to amino acid oxidation and metabolite generation in the intestine, the molecular mechanisms of transcriptional control, and the participation of specific miRNAs involved in the regulation of amino acid degrading enzymes. In addition, molecules derived from amino acid catabolism play a role in metabolism as they are used in the epigenetic regulation of many genes. Thus, this review aims to examine the mechanisms of amino acid catabolism and to support the idea that this process is associated with the immune response, abnormalities during obesity, in particular insulin resistance, and the regulation of thermogenesis. Amino acids are used to synthesize body proteins and serve as precursors of many molecules, including neurotransmitters, hormones, purines, pyrimidines, and some vitamins, among others. Upon fasting or when amino acids are ingested in excess of the amounts required, their catabolism serves as an energy source. When amino acids are used for energy production, they undergo the loss of their amino groups; their remaining carbon skeletons have two primary fates: conversion into glucose through gluconeogenesis or oxidation to synthesize ATP. For this reason, there must be a balance between the synthesis and continuous degradation of proteins in the body to ensure the maintenance of optimally functioning proteins. In the steady state, protein synthesis is equal to degradation, and neither the related transcription of amino acid degrading enzymes nor the metabolites generated from these processes are affected . In addiThe catabolic pathways of most amino acids take place mainly in the liver, according to the large body of evidence reported throughout the development of metabolic biochemistry, with the exception of the branched-chain amino acids (BCAA), leucine, valine, and isoleucine . The α-aAfter protein digestion, amino acids are absorbed and used not only by intestinal cells but also by the resident bacteria; once they have passed through the gut, a fraction of the amino acids are transferred to the bloodstream to reach the liver . SeveralAfter passing through the esophagus and gastric lumen, dietary protein is hydrolyzed in the small intestine by the proteases and peptidases, including trypsin, chymotrypsin, or carboxypeptidases released by the pancreas . In the Amino acids and some peptides found in the intestinal lumen after digestion can be delivered to the portal vein due to the presence of specific transporters known as solute carriers (SCL) in the brush border or apical membrane , and in the basolateral membrane of the enterocytes   Figure B. HoweveIn the colonic lumen, colonocytes can use glutamine as a fuel substrate and catabolize arginine into ornithine and nitric oxide . The conKlebsiella spp., Escherichia coli, Streptococcus spp., Succinivibrio dextrinosolvens, Mitsuokella spp., and Anaerovibrio lipolytica, can also utilize protein digestive products and play an essential role in nitrogen recycling [Studies in germ-free animals reveal that gut bacteria alter the distribution of free amino acids in the gastrointestinal tract, indicating the role of the bacteria in the synthesis or degradation of amino acids. Interestingly, the amount of dietary protein and the dietary protein source modify the gut microbiota . Consequecycling ,28.Prevotella ruminicola, Butyrivibrio fibrisolvens, Mitsuokella multiacidas, and Streptococcus bovis can secrete active dipeptidyl peptidase and dipeptidase that contribute to protein digestion and absorption of amino acids in the gut [15N incorporation into body lysine demonstrated that the N-lysine measured in the host came mainly from bacteria, indicating that amino acids can be exchanged between the host and the microbiota [Moreover, bacteria species such as  the gut . Ammonia the gut . It has crobiota .Although the digestion of dietary protein followed by amino acid absorption is a very efficient process in the small intestine, some nitrogenous material may escape digestion and be transferred into the large intestine. Undigested peptides and amino acids are usually not absorbed by the colonocytes but are fermented by gut microbes into intermediate metabolites and other end-products C, and thAmino acid catabolism involves several metabolic pathways specific to a particular group of amino acids, involving multiple enzymes, some of which are essential for regulating the flux of metabolites in these pathways and are known as amino acid degrading enzymes (AADEs). AADEs are mainly located in the liver but are now known to be found in other extrahepatic tissues; they are specific for the utilization of each amino acid, and the transcription of the genes encoding them is highly regulated . The stuAmino acids metabolized by bacteria present in the gut contribute to the survival and proliferation of these bacteria, but also provide amino acids and key metabolites to the host . The genDietary protein supply can also regulate amino acid catabolism indirectly via changes in the gut microbiota D. The coAs indicated above, each amino acid has a specific catabolic pathway regulated by key enzymes that play a central role in controlling the flux of the pathway metabolites , enzymesInterestingly, the increased activity of these enzymes is due to an up regulation of AADE gene expression, as several studies have reported in mice or rats fed increasing amounts of dietary proteins showing an increment in the abundance of AADE mRNA in the liver, and the higher the amount of dietary proteins, the higher the expression of most of the enzymes ,44,51. I4+ production and an increase in the amino acid carbon skeletons. As a consequence, the enzymes of the urea cycle increase their expression with a high-protein diet [4+. Other studies have shown that not only an excess of dietary protein induces the expression of these enzymes, but that prolonged fasting or the ingestion of very low concentrations of dietary protein increases muscle protein breakdown, releasing amino acids into the circulation, particularly glutamine and alanine, that are catabolized in the liver [In addition, other conditions can induce the expression of specific AADEs. BCAA catabolism also increases in the fetal liver during gestation ,66 and tein diet  to elimihe liver .In addition to transcriptional control, post-transcriptional control mechanisms can regulate the expression of AADE, particularly by some microRNAs (miRNAs). miRNAs are short 18–22 nucleotide, single-stranded RNA molecules that regulate gene expression by binding to 3′-UTR regions of mRNA target genes, leading to their degradation and/or translational repression . TherefoAnother example of the importance of miRNAs in the regulation of AADE is that of miR-122, which regulates glutamine metabolism in the liver by inhibiting mitochondrial glutaminase (Gls) and its transporter, Slc1a5, thereby inhibiting glutaminolysis and enhancing gluconeogenesis in humans and mice . Since mNutrients can regulate the metabolic activities of living organisms through epigenetic mechanisms, including DNA methylation, histone modification, and RNA regulation . Amino aMoreover, amino acid degradation produces downstream metabolites that are critical for embryonic stem cell (ESC) function and differentiation. Evidence from several laboratories reports that differentiation and self-renewal of mouse ESCs are dependent on proline catabolism. Likewise, catabolism of either threonine (mouse) or methionine (human) generates molecules used in histone methylation and acetylation involved in ESC differentiation and growth .Amino acid catabolism provides metabolites that serve as substrates or are responsible for activating signaling pathways involved in the physiology of different organs. For example, the regulation of amino acid catabolism is key for the immune system since its functions depend on an adequate supply of amino acids, and individual amino acids and their metabolites can affect immune responses . SimilarAll cells, including those involved in immune responses, depend on nutrient availability to maintain their functionality . When thBesides BCAA, the AADE that have been mainly studied for their response to inflammation are those involved in tryptophan and arginine catabolism, such as tryptophan 2,3-dioxygenase (TDO), IDO1, the arginase isoforms , and the inducible nitric oxide synthase (iNOS), respectively .+ synthesis, which is necessary to control ATP production and macrophage activation and function. Although both enzymes catalyze the same reaction, they differ in expression and function [TDO and IDO catalyze the cleavage of the C2–C3 bond of the indolic ring of L-tryptophan to form N-formyl-kynurenine . Noteworfunction . TDO is function , which, function . Also, ifunction .IDO1, the rate-limiting step of tryptophan degradation, is extrahepatic and is induced by lipopolysaccharide (LPS), TNF-α (tumor necrosis factor-α), and IFN-γ (interferon-γ) ,99 FiguA. The laL-arginine is a common substrate for arginase-1 (Arg1) and inducible nitric oxide synthase (iNOS); thus, its regulation is essential for proper cellular functioning . Arg1 prAn adequate amino acid catabolism is crucial to maintaining plasma amino acid concentration. Disturbances in plasma amino acid concentration have been associated with alterations in individual health . In a crThe alteration of BCAA catabolism has physiological consequences in two aspects. First, leucine is likely the most potent mTORC1 activator among all amino acids. In physiological conditions, mTORC1 activation inhibits autophagy, activates adipogenesis and lipogenesis in white adipose tissue, and inhibits insulin signaling through the inactivation of the insulin receptor substrate 1 (IRS1) C. Thus, Furthermore, leucine catabolism contributes 30% to the acetyl-CoA lipogenic pool . and aceSecond, a reduction in the BCAA catabolic enzymes causes an inefficient production of anaplerotic substrates from BCAA, causing suboptimal activity of the Krebs cycle ,126. TheAlthough progress has been made in understanding the participation of BCAA catabolism in the maintenance of adipocyte function, further research is needed to understand the role of catabolism of other amino acids such as aspartate, proline, tyrosine, and tryptophan, among others, that can modify mitochondrial activity and therefore metabolic flexibility in the adipocyte.In addition to BCAAs, tryptophan (Trp) is another essential amino acid for humans, . ConsumeIn addition to white adipose tissue, it has been demonstrated that BAT may play an essential role in the control of body thermogenesis . This efAs previously mentioned, white adipose tissue plays an important role in the utilization of BCAAs, which is associated with improving insulin sensitivity. However, now BAT is also considered an essential catabolic organ of these amino acids, decreasing circulating levels of BCAA that are associated with increased insulin sensitivity.Amino acid catabolism has been considered in nutrition as a mechanism used by the body to eliminate excess circulating amino acids due to high-protein intake or a catabolic state of the organism, as occurs during fasting or in specific pathologies. However, research in nutrition and metabolism has shown that amino acid catabolism plays an essential role in different metabolic processes, even though it has long been overlooked. It is now important to consider it as a key element of metabolism whose abnormalities may be associated with the development of several chronic diseases. Amino acid catabolism enzymes have been found in different cell types or organs and perform specific functions, generating end-products that can be used for ATP synthesis and gluconeogenesis. However, its role is now known to have additional functions of great relevance, such as the regulation of the immune response, the development of insulin resistance, and even body thermogenesis. It is important to comprehensively consider not only the utilization of dietary amino acids as precursors for the synthesis of proteins and other nitrogenous compounds, but also that their utilization by the catabolism machinery generates important metabolites that have an impact on the regulation of gene expression that directly or indirectly impacts the fine regulation of numerous processes in various cell types of various organs or tissues. Interestingly, new important players in the orchestration of amino acid catabolism have been discovered, particularly the gut microbiota. Thus, the field of nutrition must take into more profound and more applicative consideration the effects of amino acid catabolism. In particular, the catabolism of BCAAs needs to be studied in greater depth, as current evidence strongly suggests its implications in various metabolic processes, and it is therefore important to conduct more clinical trials to use this information in the development of dietary guidelines or therapeutic strategies involved in the future of personalized nutrition.


Viral infections have a major impact on physiology and behavior. The clinical symptoms of human rotavirus and norovirus infection are primarily diarrhea, fever, and vomiting, but several other sickness symptoms, such as nausea, loss of appetite, and stress response are never or rarely discussed. These physiological and behavioral changes can be considered as having evolved to reduce the spread of the pathogen and increase the chances of survival of the individual as well as the collective. The mechanisms underlying several sickness symptoms have been shown to be orchestrated by the brain, specifically, the hypothalamus. In this perspective, we have described how the central nervous system contributes to the mechanisms underlying the sickness symptoms and behaviors of these infections. Based on published findings, we propose a mechanistic model depicting the role of the brain in fever, nausea, vomiting, cortisol-induced stress, and loss of appetite. Rotavirus and norovirus are two major causes of acute gastroenteritis and are characterized by vomiting, fever, and diarrhea. While norovirus is quite common in adults who can communicate their illness experience very well, rotavirus occurs mainly in children below the age of 5, which have difficulty conveying their illness. Our knowledge of how rotavirus causes illness has therefore mainly been obtained from investigating the mechanisms of diarrhea –6. Altho–In this perspective, we discuss the mechanisms of certain sickness behaviors and symptoms coordinated by the brain and associated with rotavirus and norovirus infections .In addition to vomiting, fever, and diarrhea, the clinical illness of rotavirus and norovirus can include nausea, headache, abdominal discomfort, myalgias, fever, fatigue, and loss of appetite –15, coll–16–The gut-brain axis is a bidirectional communication between the central and the enteric nervous systems  , which ppromote a metabolic state similar to fasting, the brain and particularly the hypothalamus, seem to drive the adaptive physiological and behavioral changes necessary for the suppression of appetite during viral infections.Norovirus  and probThermoregulation and central control of body temperature are mainly governed by the hypothalamus . A not u13–Nausea and vomiting are hallmarks of the sickness symptoms of rotavirus and particularly norovirus, which causes the winter vomiting disease. While being common symptoms, surprisingly little information is available on how these viruses trigger nausea and vomiting , 43, 44.3 receptor antagonist, has been found to reduce rotavirus symptoms in children (Enterochromaffin (EC) cells constitute the largest population of epithelial enteroendocrine cells and are sensory cells that release serotonin (5-hydroxytryptamine [5-HT]) upon stimulation . Releasechildren . Throughchildren  upregulaBased on the above findings, the key sites involved in the mediation of vomiting following viral gut infection are as follows: (i) the sensory epithelial EC cells, which are present in the mucosa of the gastrointestinal tract; (ii) the enteric nervous system and the vagus nerve; (iii) the brainstem dorsal vagal complex emetic nuclei such as the area postrema (AP), the NTS, and the dorsal motor nucleus of the vagus (DMV). However, further investigations into the underlying neuroanatomical and neurochemical mechanisms are required to translate these observations into a mechanistic model of rotavirus and norovirus vomiting and nausea , 4.Although the ENS can work independently of CNS and control most of the intestinal functions, CNS can trough the autonomic nervous system modulate intestinal motility and gut homeostasis . The inhInfections are associated with stress, as indicated by the concomitant release of the steroid hormone cortisol . When thIn this perspective, we have discussed how the central nervous system contributes to the mechanisms underlying the sickness symptoms and behaviors during virus infection of the gut. To further increase understanding, new approaches such as organoid models and three-dimensional (3D) light sheet microscopy of gut and brain may be of benefit.


Aging of human skin is a complex process leading to a decline in homeostasis and regenerative potential of this tissue. Mitochondria are important cell organelles that have a crucial role in several cellular mechanisms such as energy production and free radical maintenance. However, mitochondrial metabolism as well as processes of mitochondrial dynamics, biogenesis, and degradation varies considerably among the different types of cells that populate the skin. Disturbed mitochondrial function is known to promote aging and inflammation of the skin, leading to impairment of physiological skin function and the onset of skin pathologies. In this review, we discuss the essential role of mitochondria in different skin cell types and how impairment of mitochondrial morphology, physiology, and metabolism in each of these cellular compartments of the skin contributes to the process of skin aging. The human skin is a complex organ that acts as the main barrier of the body against environmental insults  and mainMitochondria are dynamic organelles enclosed by two membranes that are present in eukaryotic cells. They have their distinct DNA and are essential for meeting the energy and metabolic needs of cells. The primary function of mitochondria is to generate adenosine triphosphate (ATP) via cellular respiration, thereby acting as the main energy source of the cells. Beyond energy production, mitochondria play pivotal roles in the regulation of cell viability, proliferation, calcium homeostasis, and programmed cell death . FurtherWhile the research on the role of impaired mitochondrial function on aging has extensively focused on fibroblasts and keratinocytes, the investigation of mitochondrial dysfunction in other skin-residing cell types, including melanocytes, immune cells, sebocytes, and adipocytes, remains largely unexplored . In the The skin is composed of over 20 different cell types and is organized into three main compartments: the epidermis, dermis, and hypodermis . The epiKeratinocytes, derived from the ectodermal layer during embryogenesis, constitute the predominant cell type within the epidermis, forming the protective barrier of the skin. Keratinocytes differentiate as they move from the basal layer towards the skin surface, undergoing structural changes and producing keratins, fibrous proteins that contribute to skin strength and waterproofing .Melanocytes are specialized cells that originate from the neural crest. They reside in the epidermal basal layer along the dermo-epidermal junction (DEJ) and within hair follicles . MelanocThe dermis is connected to the epidermis by the DEJ and is composed of an abundant extracellular matrix (ECM) along with different functional structures and cell types. Within the skin compartments, the dermis hosts the highest cell diversity. Fibroblasts, the major cell type of the dermis, play a pivotal role in the synthesis and maintenance of the ECM, which consists of structurally relevant proteins such as collagen and elastin, glycoproteins, and glycosaminoglycans. Collectively, these elements contribute to the skin’s elasticity and strength . Other cThe hypodermis, also known as subcutaneous adipose tissue, is the bottom layer of the cutaneous tissue. It is predominantly composed of adipocytes, pre-adipocytes, and adipose-derived stem cells but also of fibroblasts, pericytes, macrophages, T-cells, and erythrocytes in a stromal vascular cell network organized within nerves, muscles, and hair follicles . The priThe skin immune system comprises a network of effector cells and molecular mediators. The skin immune system constitutes a highly sophisticated system that provides physical, chemical, and microbiological barriers, to protect the host from external insults and pathogens and helps maintain skin homeostasis .The primary structure of the skin and the cellular components that inhabit this tissue are depicted in Mitochondria are enclosed by two membranes, namely, the inner and outer mitochondrial membranes. This arrangement forms two distinct aqueous compartments: the intermembrane space and the mitochondrial matrix, which play a crucial role in supporting physiological functions of this organelle. The outer membrane is highly permeable and is composed of many large protein-based pores along with active transporter proteins, which are collectively responsible for the transit of proteins, nucleotides, ions, and metabolites between the cytosol and the intermembrane space. In contrast, the inner membrane has much more restricted permeability, much like the plasma membrane of a cell. The inner membrane forms numerous folds (cristae), which extend into the interior (or matrix) of the organelle in which the proteins involved in electron transport and ATP synthesis are embedded . The intMitochondrial metabolism orchestrates an intricate network of biochemical processes within eukaryotic cells, which collectively drive the generation of energy in the form of ATP. Mitochondria engage in oxidative phosphorylation, where electrons derived from metabolic substrates, such as glucose and fatty acids, pass through a series of protein complexes in the electron transport chain. This creates a proton gradient across the inner mitochondrial membrane, which, in turn, powers the ATP synthase enzyme to synthesize ATP . AdditioMitochondria also play a pivotal role in the intricate process of apoptosis, a controlled form of cell death essential for developmental processes and for the maintenance of tissue homeostasis. Mitochondria release factors like cytochrome c, which triggers the formation of the apoptosome a multiprotein complex that activates caspase enzymes. This cascade of events leads to the orchestrated breakdown of cellular components, ultimately resulting in cell death .The dynamic nature of the mitochondrial network, which is crucial for maintaining cellular and mitochondrial homeostasis, is regulated by mitochondrial biogenesis, trafficking, fusion and fission processes. These events shape mitochondrial morphology, distribution, and function, allowing for optimal cellular energy production, calcium homeostasis, and other essential mitochondrial activities. Furthermore, this dynamic regulation allows for the degradation of dysfunctional mitochondria, the maintenance of the redox status, and the preservation of mitochondrial integrity, including mtDNA content . Mitochoin vivo. The extent to which this mechanism is relevant for maintaining skin homeostasis or is implicated in skin pathological conditions remains an open area of exploration. Further investigations into the in vivo relevance of intercellular mitochondrial transfer within the skin will be crucial for a comprehensive understanding of its role in skin health and disease , and consequent compromised cellular energy metabolism. These alterations are related to the increased production of ROS exhibited by mitochondria during aging, the accumulation of which causes oxidative damage to mitochondrial and cell components contributing to cellular senescence  enzyme . AdditioMitochondrial dysfunction and cellular senescence are hallmarks of aging and are intricately interconnected . MitochoMitochondria of skin cells are prone to accumulate damage, which contributes to the process of skin aging . In the As keratinocytes progress from basal to suprabasal layers and undergo terminal differentiation, mitochondrial function, and morphology undergo dynamic alterations. Additionally, mitochondrial ROS acts as a signaling molecule, which regulates epidermal differentiation . Metabolin vitro . Depletion of NIX hampered epidermal maturation and disrupted the elimination of mitochondria, whereas the overexpression of NIX accelerated keratinocyte differentiation and led to premature mitochondrial fragmentation . FurtherBasal keratinocytes primarily rely on glycolysis for energy production and as they differentiate and migrate towards the upper layers of the epidermis, there is an increase in mitochondrial oxidative phosphorylation and ATP production through the TCA cycle and electron transport chain . Given tin vitro and displayed impaired mitochondrial ATP production and increased ROS production  ratio impairs keratinocyte differentiation and is associated with the acquisition of premature keratinocyte senescent phenotype , accompanied by a decrease in fusion proteins mitofusin 1 and 2 (Mfn1/2). This alteration promotes heightened production of ROS and activates the inflammatory pathways, including cGAS-STING and the NACHT, LRR and PYD domains-containing protein 3 (NLRP3) inflammasome. Primary human keratinocytes also undergo dose-dependent mitochondrial fragmentation following UVB irradiation. In these cells, depletion of Drp1 leads to mitochondria hyperfusion and attenuates UVB-induced mitochondrial fragmentation .The main mitochondrial damages observed in keratinocytes during aging, along with their resulting consequences for the skin, are displayed in Melanocytes, specialized cells residing in the basal layer of the epidermis, are responsible for producing and distributing the pigment melanin . As the Melanin synthesis is a precisely regulated process that involves various cellular mechanisms and compartments, including mitochondria. A group revealed a novel connection between melanosomes and mitochondria, facilitated by fibril bridges dependent on Mfn2. This unique linkage of melanosome-mitochondria predominantly occurs early during melanosome generation in the perinuclear area. Intriguingly, disruption in the mitochondrial function or impaired melanogenesis correlates with a reduction of interorganelle connectivity suggesting a potential involvement of this mechanism in the development of skin pigmentation disorders .Melanocytes display elevated basal levels of ROS compared to other skin cell types, primarily due to their engagement in the ROS-generating process of melanogenesis . The rolMitochondrial dynamics play a peculiar role in melanocytes . It has A recent study examined the impact of mtDNA depletion on melanocyte function and structure using a mtDNA-depleted mice model . This stRecent studies demonstrate that melanocytes also actively contribute to skin aging through their secretory activity. The secretome of senescent melanocytes was shown to affect surrounding cells such as keratinocytes impairing their proliferation and leading to changes in the skin microenvironment . The appWhile melanocytes significantly impact the skin microenvironment through their secretome, their function and metabolism are also regulated by secretory factors such as extracellular vesicles, cytokines, and other soluble factors originating from various cells, including keratinocytes, fibroblasts, and sebocytes . This prThe main mitochondrial damages observed in skin melanocytes during aging, along with their resulting consequences for the skin, are displayed in Skin or dermal fibroblasts play a vital role in supporting the structure and function of the skin. They are responsible for synthesizing and maintaining the ECM and actively participate in other skin-related processes such as wound healing. Being energy-demanding cells, fibroblasts heavily rely on mitochondria to carry out their crucial functions, including ECM synthesis, secretion of growth factors and cytokines, and cellular signaling. Furthermore, mitochondrial function is critical for sustaining fibroblast viability, promoting proliferation, and facilitating collagen synthesis, all of which are essential for maintaining tissue integrity .During aging, fibroblasts aggregate damaged mitochondria and mtDNA deletions leading to structural and functional alterations in the ECM and the induction of inflammation, which in turn, accelerates the formation of skin wrinkles . FibroblIrradiation of fibroblasts can lead to mtDNA mutations. These mutations, in turn, result in mitochondrial dysfunction, oxidative stress, and reduced collagen production which consequently promotes the expression of collagen-degrading proteins like matrix metalloproteases . These mRecent research by Recent studies have shed light on mechanisms of intercellular communication elicited by factors secreted by senescent fibroblasts ultimately leading to skin aging. For instance, the relationship between skin pigmentation and components of the SASP secreted by senescent dermal fibroblasts, including SDF-1 and GDF15 has recently been addressed . These fA distinct form of cellular senescence, arising from mitochondrial dysfunction and distinguished by a unique secretion profile lacking the inflammatory interleukin-1 (IL-1) arm has been identified in human fibroblasts and named mitochondrial dysfunction-associated senescence (MiDAS). In this study, the authors demonstrated that the senescence-associated secretory phenotype of fibroblasts induced by MiDAS stimulates keratinocyte differentiation supporting the hypothesis that the secretome of MiDAS cells induce the rapid accumulation of senescent-like keratinocytes, which show enhanced differentiation and might drive aging phenotypes and age-related pathologies in the skin .UV exposure leads to decreased barrier function, alterations in skin physiology, and changes in mitochondrial morphology and function in comparison to non-exposed skin . It was The main mitochondrial damages observed in skin fibroblasts during aging, along with their resulting consequences for the skin, are displayed in During aging, the progressive decline of immune function and reduction in the immune system’s ability to respond effectively to new and emerging challenges leads to immunosenescence which is characterized by the deregulation of immune responses, impaired healing, and poor tissue restoration and function . The agiMitochondria are essential for regulating immune cell activation, differentiation, metabolism, effector functions, and immune survival. Therefore, cells from the innate and adaptive immune system rely heavily on mitochondria to maintain their fate and function . It is wM and ATP turnover and coupling efficiency, reduced baseline OXPHOS, and increased proton leakage and ROS generation. These alterations in mitochondrial bioenergetics cause a depletion of phagocytic and antigen cross-presenting capacity of DCs and consequent alterations in immune response 4+ T lymphocytes in the elderly (+ T cells from old mice and whether such transfer changed CD4+ T cell function. The results of this study demonstrated that mitochondrial transfer improved the redox status and function of CD4+ T cells from old mice. These findings support the notion that mitochondria can serve as targets of therapeutic intervention in aging (During aging of the skin, the number and function of T cells decrease, impairing the immune response. This decline in T cells is mainly due to thymic involution, a process in which the thymus gland shrinks and loses its ability to produce new T cells. Additionally, the remaining T cells become less efficient in recognizing and responding to antigens, leading to a weakened immune system. This decline in T cell function contributes to the development of age-related skin diseases and impaired wound healing . Several elderly . A recenin aging . Anotherin aging . HoweverThe main mitochondrial damages observed in skin immune cells during aging, along with their resulting consequences for the skin, are displayed in Sebaceous glands are exocrine glands that are responsible for the secretion of lipid-rich sebum, a critical component of epidermal barrier function, thermoregulation, skin elasticity, and skin/hair microbiome management . SebaceoAs we age, our skin undergoes a number of changes that affect the function and appearance of sebaceous glands and sebocytes. These changes are driven by several factors, including hormonal shifts, oxidative stress, and the accumulation of cellular damage over time . DisordeThe main mitochondrial damages observed in skin sebocytes during aging, along with their resulting consequences for the skin, are displayed in INK4a, reduced insulin-dependent glucose transport, and hypertrophic expansion of adipocytes (During aging the adipose tissue undergoes significant changes in mass and distribution, characterized by an increase in visceral fat and a decrease in subcutaneous fat. Visceral adipose tissue is associated with detrimental metabolic effects, while subcutaneous adipose tissue is considered metabolically beneficial. Age-related peripheral fat loss may be attributed to defects in adipogenesis and heightened inflammation in subcutaneous fat. Mitochondrial dysfunction in adipose tissue during aging is linked to cellular senescence, chronic inflammation, and decline in stem cell activity, as well as obesity and insulin resistance . Senesceipocytes .The main mitochondrial damages observed in skin adipocytes during aging, along with their resulting consequences for the skin, are displayed in Recent studies have laid the foundation for understanding the cell type-specific nuances in mitochondrial dynamics and function within the skin. One emerging direction of research is the exploration of mitochondrial interactions among different skin cell types and their implications for tissue physiology. Investigating the crosstalk between keratinocytes, melanocytes, and dermal fibroblasts is anticipated to shed light on how mitochondrial dynamics collectively contribute to skin homeostasis and responses to external stressors.The importance of mitochondria in human health is evidenced by the consideration of artificial mitochondrial transplant as a possible therapeutic approach to treat damage of several tissues, including the skin . FurtherYet, several important questions remain to be answered. Firstly, how do distinct mitochondrial dynamics in different skin cell types harmonize to maintain overall skin health? Secondly, what role does mitochondrial trafficking play in cellular communication within the skin microenvironment? Additionally, can we harness the knowledge of cell type-specific mitochondrial dynamics to develop targeted interventions for skin conditions, such as aging, inflammation, or UV damage? Furthermore, the identification of key regulators governing mitochondrial dynamics in specific cell types and their potential as therapeutic targets holds great promise. Addressing these questions and delving into the intricacies of mitochondrial behavior across different skin cell types is the next frontier in advancing our understanding of skin biology and paving the way for innovative approaches in dermatology.Mitochondria act as dynamic hubs, orchestrating energy production, metabolism, and cellular signaling pathways critical for keratinocytes, fibroblasts, melanocytes, and immune cells. The integrity of mitochondrial function is indispensable for sustaining the specialized functions of each cell type, from keratinocyte differentiation to fibroblast collagen production, melanin synthesis, and immune surveillance. However, as cells age, mitochondrial damage accumulates, impairing their function and triggering a cascade of events that contribute to the multifaceted process of skin aging. This includes disruptions in energy production, increased oxidative stress, and altered cellular signaling, collectively culminating in diminished skin health and the visible signs of aging. Understanding the intricacies of mitochondrial function and dysfunction in these diverse skin cell populations not only sheds light on the molecular mechanisms underlying skin aging but also paves the way for innovative therapeutic strategies targeting mitochondrial health to promote more youthful and resilient skin.