The objective of this study was to determine the effect of birch leaf (Betula pendula) extract (BPE) on corneal inflammation following keratoplasty in the rat model. T cells were stimulated in vitro in the presence of BPE. Proliferation, activation phenotype and the number of apoptotic/necrotic cells in cell culture were analyzed by flow cytometry. Corneal transplantation was performed between Fisher and Lewis rats. Recipient rats were either treated with cyclosporine A at a low dosage (Low-dose CsA=LDCsA) or received LDCsA in combination with BPE (2×1ml/day). Clinical signs for corneal inflammation and rejection time points were determined. Infiltrating leukocytes were analyzed histologically. BPE specifically inhibited T cell proliferation in vitro by inducing apoptosis. The phenotype was not affected. In vivo, BPE significantly delayed the onset of corneal opacification (p<0.05). The amount of infiltrating CD45(+) leukocytes and CD4(+) T cells (p<0.001) was significantly reduced by BPE, whereas infiltration of CD163(+) macrophages was not significantly different between the two groups. BPE selectively induces apoptosis of activated T cells. Accordingly, BPE treatment significantly reduces infiltrating T cells and subsequent corneal opacification following keratoplasty. Our findings suggest BPE as a promising anti-inflammatory drug to treat corneal inflammation.
Copyright © 2012. Published by Elsevier Ltd.