microRNA and Kidney Transplantation.

The kidney serves as the main clearance organ of our body, filtrating and excreting metabolic waste products. Various intrinsic and extrinsic conditions can lead to kidney injury, roughly 0.1% of the population suffer from end stage renal disease. Renal transplantation reinstitutes an almost normal quality of life; again it is cost effective and thus the preferred treatment of terminal renal failure. miRNAs play pivotal roles in immune responses and inflammation, which makes them particularly interesting in the field of transplantation and in understanding the molecular pathways of allograft pathologies such as delayed function or cellular and antibody mediated rejection. As kidney biopsy is part of the routine disease monitoring, the identification of miRNA pattern is feasible in different stages of the injury. Furthermore miRNAs are easy to detect not only in tissue samples but also in body fluids such as blood and urine. Their regulatory capacity of biological processes together with their stability makes them excellent candidates for noninvasive monitoring of kidney pathology. There is an accumulating knowledge about diseases-specific miRNA signatures in distinct kidney injuries. In the following chapter we present the current understanding of miRNAs regulation of intragraft processes after kidney transplantation.