Abstract
Purpose: :
To investigate the ultra-fine features of epithelial cells developing on human corneas that had previously underwent amniotic membrane transplantation
Methods: :
The buttons of 7 human corneas obtained from penetrating keratoplasties were prepared for electron microscopy. All corneas had previously been transplanted with cryopreserved amniotic membranes, epithelial-side-up. Main corneal pathology: Alkali injury (n=1), Bullous keratopathy (n=2). Neurotrophic Keratopathy (n=1) Rejected corneal graft (n=2)Preparation for electron microscopy included:CuttingGlutaraldehyde fixationInfiltration with buffered osmium solutionDehydration in graded ethanol solutionsEPON embeddingMicrotome tissue sectioningUranylium staining
Results: :
Many atypical and degenerated forms of epithelial cells as well as reduced population & atypical forms of surface microvilli were found. Intercellular projections appeared connecting neighboring cells. Desmosomes showed abnormal distribution. Cell organelles indicated high metabolic activity while plethora of actin fibrils was constantly found There was also a remarkable lack of basal hemidesmosomes while typical epithelial basal membrane was frequently absent. Basal layer cells displayed many philopodia that served as anchoring projections Amniotic membrane remnants were recognized even in cases where amniotic membrane was transplanted 12-18 months ago
Conclusions: :
Regenerated corneal epithelium that develops over transplanted amniotic membrane seems to lack proper differentiation by ultra-structural means. Epithelial cells display mixed morphological features of corneal and conjunctival epithelia. Intra-epithelial connections and basal layer anchoring appear to be more vulnerable to stress while corneal surface may suffer insufficient tear stability and lubrication.
Keywords: cornea: basic science • microscopy: electron microscopy • cornea: epithelium