Ultrastructural morphology and morphometry of the normal corneal endothelium of adult crossbred pig

Abstract

Corneal endothelium constitutes a monolayer of polygonal cells. The integrity and health of this layer are essential for the maintenance of normal corneal transparency. This study reported by the first time in a detailed way the ultrastructural morphology and morphometry of the corneal endothelium in normal adult crossbred pigs by using scanning electron microscopy (SEM). A regular pattern of polygonal cells, with predominantly hexagonal cells and clear cell borders, was observed. An oval nucleus that bulges in the centre of the cell, cilia (2-4) in a few peripheral cells, openings of the pinocytotic vesicles, microvilli, borders bars and interdigitated cell borders were observed. The mean endothelial cell area was significantly higher (P<0.05) in the centre than in periphery, with a lower variation coefficient in the former. The mean cell density in periphery was significantly higher (P<0.05) than in centre and 43.9% higher than data formerly reported by other authors using specular microscopy, showing the significant shrinkage caused by sample processing for SEM. The mean value of cell sides (pleomorfism) was 5.9, ie. predominant hexagonal shape. The percentage of hexagonal cells was significantly higher in central region (P<0.01), determining a more homogeneous structure. The parameters obtained in this study will be a basement for future investigations about the effect on pig corneal endothelium of drugs, intracamerular surgeries and storage solutions for transplants.