Renal blood flow and oxygenation drive nephron progenitor differentiation

Abstract

During kidney development, the vasculature develops via both angiogenesis (branching from major vessels) and vasculogenesis (de novo vessel formation). The formation and perfusion of renal blood vessels are vastly understudied. In the present study, we investigated the regulatory role of renal blood flow and O2 concentration on nephron progenitor differentiation during ontogeny. To elucidate the presence of blood flow, ultrasound-guided intracardiac microinjection was performed, and FITC-tagged tomato lectin was perfused through the embryo. Kidneys were costained for the vasculature, ureteric epithelium, nephron progenitors, and nephron structures. We also analyzed nephron differentiation in normoxia compared with hypoxia. At embryonic day 13.5 (E13.5), the major vascular branches were perfused; however, smaller-caliber peripheral vessels remained unperfused. By E15.5, peripheral vessels started to be perfused as well as glomeruli. While the interior kidney vessels were perfused, the peripheral vessels (nephrogenic zone) remained unperfused. Directly adjacent and internal to the nephrogenic zone, we found differentiated nephron structures surrounded and infiltrated by perfused vessels. Furthermore, we determined that at low O2 concentration, little nephron progenitor differentiation was observed; at higher O2 concentrations, more differentiation of the nephron progenitors was induced. The formation of the developing renal vessels occurs before the onset of blood flow. Furthermore, renal blood flow and oxygenation are critical for nephron progenitor differentiation.

Kidney Regeneration: Lessons from Development

“…Patterning of the renal vasculature is not completely understood, but the formation of glomerular capillaries is regulated by epithelium and mesangial cell-derived factors 32, 33 , while global patterning of renal vasculature is dependent on the stromal mesenchyme itself 34 . Conversely, tissue oxygenation from vascular perfusion is required for CM differentiation during the last trimester of pregnancy (after 15.5 days post-fertilization in mice) 35 . As far as we are aware, there are no published data on the functional role of macrophages in kidney development.…”

Effect of fluid shear stress on in vitro cultured ureteric bud cells

“…Irrespective of the underlying mechanism, it is generally thought that in embryonic kidneys, urine flow initiates around E15.5 when blood flow and glomerular filtration take place, 20 and since UB tip cells are known to be the proliferating progenitor cells that contribute to branching morphogenesis and development of the collecting system in the kidney, 29 our finding that FSS led to an enrichment of tip cell population in the in vitro cultured UB cells derived from E15.5 embryonic kidneys could have an important implication for the development and function of the kidney.…”

“…Thereafter, mutual interactions among these progenitor cells control their self-renewal and differentiation, leading to the formation of glomeruli and nephron tubules from MM cells, the collecting system and ureter from UB cells, and supportive interstitial tissues from SM cells 15–19 . Since the initiation of blood flow and urine flow takes place in embryonic kidneys during kidney development, 20 it is possible that FSS may influence the development of embryonic kidneys. However, thus far, there has been no report on the effect of FSS on embryonic kidney cells.…”

Role of hypoxia during nephrogenesis

“…Mouse kidney explant studies demonstrate that the nephrogenic zone of the developing kidney does not receive blood flow, and that the differentiation of nephron progenitors appears to be induced by vascular perfusion and the accompanying increase in oxygen tension [52]. However, how this process is regulated by hypoxia is poorly understood.…”