Abstract
Abstract: :
Purpose: The microvilli of corneal endothelial cells project into the aqueous humor and amplify the apical surface area of the cells. The function of the microvilli of corneal endothelial cells has been the subject of much speculation, but remains elusive. We hypothesized that microvilli may play a nutritional role in the avascular cornea and thus predicted that cells of the peripheral cornea would possess fewer microvilli than those of the central cornea, because of proximity to capillaries in the limbus. Methods: Corneas were dissected from bovine eyes acquired from a local abattoir, fixed in 2.5% glutaraldehyde and processed separately for SEM and TEM. Pieces from 3 corneas (from 3 different animals) were designated as central, peripheral (medial), or peripheral (lateral) based on their location. A total of 12 cells were selected at random from each region of each cornea (n = 108) and photographed at 3,500-5,000X with the SEM. The number of microvilli on each cell was then counted separately by three individuals. Results: TEM showed microvilli 0.1 – 0.5 µm in diameter and 0.2 – 2.5 µm in length. Our fixation failed to reveal the presence of cytoskeletal elements in the microvilli, but showed endocytotic events in the endothelial cells. Bovine corneal endothelial cells displayed a lack of a central cilium and possessed between 9 and 149 microvilli per cell ( mean = 46.4 ± 23.8 SD ). A comparison of central vs. peripheral regions revealed no significant difference in the number of microvilli per cell (p = 0.35). Conclusions: The results do not support the hypothesis, however, they certainly do not rule out a nutritional function for the microvilli of corneal endothelial cells.
Keywords: cornea: endothelium • anatomy • microscopy: electron microscopy