Nerve regeneration in cornea after penetrating keratoplasty in rabbit, with special reference to relationship between regenerating nerves and basal laminae.

The pattern of nerve regeneration in the grafted rabbit cornea was investigated by electron microscopy. Grafted corneas were excised 2, 7, 14 and 28 days after grafting, and processed for observation by conventional electron microscopy. In the normal, unoperated cornea Schwann cell basal laminae are, unlike those of ordinary peripheral nerves, discontinuous and fragmentary on the fibers coursing through the corneal stroma. In the early stage of regeneration, while numbers of regenerating axons extended through the Schwann cell columns of regenerating axons extended through the Schwann cell columns in the grafts, many other regenerating axons elongated as single fibers through the corneal stroma outside the Schwann cell columns. These single naked axons were later enveloped by Schwann cell cytoplasm, contributing to the overall dense irregular pattern of regenerated nerves in the grafted cornea. It was thought that the regenerating axons can extend throughout the stroma without the guidance of basal lamina tubes, making the corneal stroma a favorable environment for nerve regeneration.