Long term graft survival following a kidney allograft remains a leading limitation to transplantation, despite newer, potent immunosuppressive regimens. The leading cause of late graft loss is chronic allograft nephropathy (CAN). This disease is manifest by proteinuria, hypertension and renal failure associated with a progressive fibrosis of the graft. While the etiology of this disorder is not certain, both immunologic and non-immunologic factors are implicated in the pathogenesis. Furthermore, there is no specific therapy for this disease, and renal function fails over a period of months to years. The goal of this project is to identify new targets for the treatment of CAN, and importantly, to identify biomarkers of disease. Our hypothesis is that CAN is mediated by growth factor(s) that are induced either by TGFbeta or via other signals following transplantation, specifically connective tissue growth factor (CTGF), a downstream effector of TGFbeta. Furthermore, disruption of the matrix deposition cascade, via inhibition of these factors or by blocking matrix production, may ameliorate the development of CAN. We have accomplished the following over the past year: 1. We have firmly established a mouse model of kidney transplantation that has the features of the human disease. In this model, increased levels of TGF?O and CTGF mRNA are expressed compared to grafts without the disease. These increased levels of mRNA can be detected as early as one week after transplant, 5 weeks before the disease is manifest. Furthermore, we can disrupt the process of CAN by inhibiting matrix deposition using novel inhibitors of prolyl-4-hydroxylase, an essential enzyme in collagen synthesis. 2. We have established a clinical protocol, 03-DK-0132, The Expression of Connective Tissue Growth Factor and Other Mediators in the Pathogenesis of Chronic Allograft Nephropathy, and have enrolled 53 patients. In this protocol, we are prospectively collecting urine, serum, urine pellet, and biopsy tissue at periodic intervals after transplantation and analyzing for the expression of not only CTGF but other relevant growth factors. Biopsies are evaluated in a masked fashion and the results correlated to CTGF measurements. To date, we have determined that urine and serum levels are highly elevated in transplant recipients, and highest in patients with CAN. Furthermore, CTGF mRNA expression is dramatically elevated in kidney biopsies with CAN, as well as following reperfusion of the transplant. 3. We have identified a mouse kidney cell line that expressed CTGF and can be induced to express high levels following hypoxic injury. In preliminary studies, CTGF mRNA is induced in vivo following renal ischemic injury. This may indicate a possible role for CTGF in ischemia/reperfusion injury. These results are supporting further study in our human donor population as well as in the immediate post-transplant period. 4. We have prospectively characterized the presence of Polyoma virus in all transplant recipients in this program to analyze the natural history and to assess whether chronic viral infection may contribute to CAN. Transcriptional analysis suggests that polyoma virus infection induced a cytotoxic T cell response that is different from acute cellular rejection.
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