Abstract
Purpose: :
Patients with keratoconus are normally regarded as having a low risk of transplant rejection. However, in several studies, including one from our group, rejection episodes occur in as many 35% of transplanted patients. The aim of this study was to examine the keratoconic corneas of transplanted patients and compare histological changes between subsequently rejected and non rejected corneal transplants.
Methods: :
The original keratoconic corneas from 36 patients undergoing corneal transplant surgery for keratoconus at the Manchester Eye Hospital between 1996 and 2003 were used in this study. Patients were followed up for a minimum of 5 years. 8 of these patients went on to have at least one episode of tranplant rejection. Haematoxylin and Eosin (H&E) and Periodic Acid Schiff (PAS) staining were used to identify breaks in Bowman’s membranes. TIMP3 expression was identified by immunohistochemistry and apoptosis was detected by TUNEL.
Results: :
Breaks in Descemet’s membrane were found in 50% of patients who underwent an episode of endothelial rejection in comparison to 10% in patients who did not suffer rejection (p=0.03). Breaks in Bowman’s membrane were found in both groups of patients with similar frequency between the two groups. However, the histological and immunohistochemical make up of the break showed distinct differences between the two groups. Breaks in the rejecters stained very strongly for TIMP3 and unidentified cells with condensed nuclei were seen at the site of the break. Further immunohistochemistry showed these cells did not stain for epithelial or keratocyte cell markers. TUNEL staining showed that these cells were, however, apoptotic. These "atypical" breaks were found in 87.5% of patients who went on to reject but only in 17.8% of those that did not (p=0.0006).
Conclusions: :
There are histopathological differences between the keratoconus of patients who subsequently proceed to episodes of endothelial rejection compared to those that do not reject.
Keywords: keratoconus • transplantation • immunohistochemistry