Renal Transplant Injury and the Renin-Angiotensin System in Kids (RETASK)

Kidney damage activates the traditional renin-angiotensin (Ang) system (RAS), characterized by Ang-converting enzyme (ACE)/Ang II/Ang II type 1 receptor. The Ang-converting enzyme 2 (ACE2)/Ang-(1-7)/Mas pathway counteracts this damage. The balance, or ratio, between levels of the ACE/Ang II and ACE2/Ang-(1-7) pathways may be clinically important because Ang-(1-7) counteracts Ang II-mediated injury. An increase in ACE and Ang II expression and a decrease in ACE2 and Ang-(1-7) expression on tubular cells may promote renal injury. Tubular damage may increase urinary loss of protective ACE2 and Ang-(1-7), propagating renal damage by allowing ACE and Ang II to stimulate inflammation and fibrosis unopposed. The investigators hypothesis is that a shift in the urinary ACE-to-ACE2 and Ang II-to-Ang-(1-7) ratios towards ACE2 and Ang-(1-7) predicts acute graft injury diagnosed on renal biopsy and predicts chronic graft damage on renal biopsy.