Abstract
Abstract: :
Purpose: We have previously presented evidence supporting the hypothesis that the basement membrane is important to the maintenance of the corneal epithelium. We undertook an electron microscopic analysis with emphasis on the basement membrane zone of the corneas of 2 patients who underwent stem cell transplants which failed. Methods: Case 1: A man suffered alkali burns to both eyes. He required an amniotic membrane transplant, symblepharon reduction, and stem cell transplant. The cornea underwent surface failure and scleral melt requiring a second stem cell transplant. A corneal perforation occurred and lamellar keratoplasty was performed. When the surface was stable he underwent penetrating keratoplasty. Tissue was submitted for light and electron microscopic analysis. Subsequently, there were areas of stem cell failure and additional stem cells were transplanted. Case 2: A man was splashed over his left face with Freon chemical. He developed surface failure. After repeated tarsorrhaphy, an amniotic membrane transplant was performed. When the corneal surface stabilized, he underwent penetrating keratoplasty. The patient again developed a persistent epithelial defect and stem cell transplantation was done. He developed a cornea perforation, which required a lamellar keratoplasty. Tissue was submitted for analysis. Results: Case 1: Light microscopy showed differences between the two sides of the corneal specimen. On one side, the surface cells were flattened. There were 7 layers of epithelial cells made up of 2 layers of partially nucleated surface cells and 5 layers of wing cells. The basal cells were not uniform and there were no goblet cells. On the other side of the specimen, there were 3 layers of surface cells, and 13 layers of wing cells. The basal cells were not uniform. Electron microscopic analysis revealed an absence of basement membrane components such as hemidesmosomes, lamina densa and anchoring fibrils. An amorphous material replaced Bowman’s layer. Case 2: Electron microscopic analysis revealed no goblets cells. There were no basement membrane zone components and Bowman’s layer was replaced by amorphous and cellular material. Conclusions:The absence of goblet cells and columnar epithelial cells suggested that the cells from the kerato–limbal graft had retained the epithelial morphology. However, at the electron microscopic level, there was an absence of normal basement membrane components, which may be one explanation for the failure of these stem cell transplants.
Keywords: pathology: human • cornea: epithelium