Renin as a key player of the renin-angiotensin-aldosterone system

(RAAS), regulating blood pressure and volume, is mainly released by juxtaglomerular cells in the wall of the afferent arterioles at the entrance to the glomerulus in the adult kidney. In contrast, renin-producing cells during development are distributed alongside the renal arterial vascular tree. Due to the fact that previous investigations based on extrapolations of histological slices, we developed a computer-assisted method that processes serial slices of C57/Bl6 mice kidneys and generates three- dimensional high resolution models of the renal vascular system and colocalized renin-producing cells. Analysis of the embryonic days e14 to e19 and postpartal days pp1, pp3, pp5, pp7, pp10, pp20 and adult state revealed that the first expression of renin takes place in e16 with a cliffy and discontinuous pattern. As the interlobar arteries already contain renin-positive cells at this early stage, we do not see an evidence for the migration of these cells from the renal artery to the afferent arterioles. During nephrogenesis expression becomes dominant in the circumference, but proximal islands remain. In the future, we want to compare our library of C57/Bl6 kidneys with knockout mice having received a genetic manipulation of different proteins being involved in the developmental regulation of the renin- angiotensin-aldosterone system.