CYTOKINE MESSENGER-RNA EXPRESSION DURING EXPERIMENTAL CORNEAL ALLOGRAFT-REJECTION

Allograft rejection is the main cause of corneal graft failure. T lymp hocytes and macrophages have been implied to be involved in corneal re jection, but little is known about the molecular mechanism in this pro cess. In this study, cytokine mRNA expression in the cornea was analys ed during experimental corneal transplantation. The donor and acceptor corneas of two groups of rats were studied after receiving an allo- ( PVG to AO rat) or autograft (AO rat). For controls, central buttons an d peripheral corneal rings of the non-transplanted contralateral eyes were used. At different post-operative days (1, 3, 7, 12 and 19), the corneas were removed and subjected to mRNA isolation. All corneal samp les underwent semi-quantitative reverse transcriptase-polymerase chain reaction analysis for interleukin-1 beta, interleukin-1 receptor anta gonist, interleukin-2, interleukin-4, interleukin-6, interleukin-10, t umor necrosis factor-alpha, interferon-gamma, monocyte chemotactic pro tein-1 and macrophage inflammatory protein-2 mRNA expression, Corneal rejection, characterized by opaque corneas with prominent neovasculari zation, was always diagnosed around day 12. Contralateral, non-grafted corneas showed constitutive mRNA expression for interleukin-1 recepto r antagonist and in a few samples also monocyte chemotactic protein-1 and macrophage inflammatory protein-2 mRNA was found. Both allo- and a utografts expressed mRNA for the cytokines found in contralateral, non -grafted tissue, as well as for interleukin-1 beta, interleukin-6, int erleukin-10 and tumor necrosis factor-alpha. in allografts, the mRNA l evels for these cytokines remained constant throughout all post-operat ive days, with increased interleukin-6 mRNA expression after post-oper ative day 12. The analysis of the autografts revealed high cytokine mR NA levels until post-operative day 3 or 7, which decreased from then o n, except for interleukin-1 receptor antagonist, mRNA for interleukin- 2, interleukin-4 and interferon-gamma was not observed in autografts a t any time point and in allografts, until post-operative day 12. Inter ieukin-2 and interferon-gamma mRNA showed maximal expression on POD 12 , while in autografts, a marked decrease was observed after POD 3. IL- 10 mRNA levels decreased immediately after POD 1 in autografted eyes, For TNF-alpha, an increased mRNA expression starting on POD 7 was foun d in recipient rings of allografted eyes, while in autografts a weak e xpression was seen in some samples. MIP-2 transcription increased on P AD 12, while in autografts, its expression was not markedly different from that detected in the contralateral, non-grafted peripheral cornea . (C) 1996 Academic Press Limited