Transmission electron microscopy analysis of epithelial basement membrane repair in rabbit corneas with haze.
PURPOSE
To assess the ultrastructure of the epithelial basement membrane using transmission electron microscopy (TEM) in rabbit corneas with and without subepithelial stroma opacity (haze).


METHODS
Two groups of eight rabbits each were included in this study. Photorefractive keratectomy (PRK) was performed using an excimer laser. The first group had -4.5-diopter (-4.5D) PRK and the second group had -9.0D PRK. Contralateral eyes were unwounded controls. Rabbits were sacrificed at 4 weeks after surgery. Immunohistochemical analysis was performed to detect the myofibroblast marker α-smooth muscle actin (SMA). TEM was performed to analyze the ultrastructure of the epithelial basement membrane and stroma.


RESULTS
At 4 weeks after PRK, α-SMA+ myofibroblasts were present at high density in the subepithelial stroma of rabbit eyes that had -9.0D PRK, along with prominent disorganized extracellular matrix, whereas few myofibroblasts and little disorganized extracellular matrix were noted in eyes that had -4.5D PRK. The epithelial basement membrane was irregular and discontinuous and lacking typical morphology in all corneas at 1 month after -9D PRK compared to corneas at 1 month in the -4.5D PRK group.


CONCLUSIONS
The epithelial basement membrane acts as a critical modulator of corneal wound healing. Structural and functional defects in the epithelial basement membrane correlate to both stromal myofibroblast development from precursor cells and continued myofibroblast viability, likely through the modulation of epithelial-stromal interactions mediated by cytokines. Prolonged stromal haze in the cornea is associated with abnormal regeneration of the epithelial basement membrane.
['Torricelli|Andre A M|AA|', 'Singh|Vivek|V|', 'Agrawal|Vandana|V|', 'Santhiago|Marcony R|MR|', 'Wilson|Steven E|SE|']
D000199:Actins D000818:Animals D001485:Basement Membrane D002452:Cell Count D003319:Corneal Stroma D004195:Disease Models, Animal D019573:Epithelium, Corneal D005260:Female D046529:Microscopy, Electron, Transmission D058628:Myofibroblasts D018903:Photorefractive Keratectomy D011817:Rabbits D012038:Regeneration D014463:Ultrasonography D014945:Wound Healing
basement membrane haze myofibroblasts corneal wound healing corneal epithelium