In Utero Fetal Denervation Affects Nephron Progenitor Dynamics During Kidney Development

Background: Proper kidney function is intricately regulated by intrinsic mechanisms and extrinsic signals from peripheral nerves. Our lab has recently established that peripheral neurons composed of both sympathetic and sensory fibers innervate the kidney concomitantly during arterial differentiation, following guidance cues released by renal stromal cells. Moreover, renal nerves establish neuroeffector junctions with renal structures during development. Yet, it remains unknown whether renal nerves actively direct organogenesis. Preliminary studies from our lab showed that whole animal Ntrk1 (TrkA) knockout leads to total renal denervation which results in a reduced number of glomeruli, and thereby nephrons, with an increase in glomerular diameter at postnatal day 0.5 (P0.5). Thus, we hypothesize that renal nerves, likely via sympathetic signaling, support proper nephrogenesis through modulation of nephron progenitor proliferation or differentiation. Methods: To determine which type of nerve was responsible, we began by selectively ablating sympathetic nerves using a floxed-STOP Diphtheria Toxin A (DTA) allele crossed with a DBHCre/+ driver. We quantitatively asses number of nephron formed at P0.5 and P3.5. In addition, to identify the impact onto nephron progenitor, we used 3D light-sheet imaging to determine the total niche number and nephron progenitor cells number per niche between wild-type and Ntrk1 (TrkA) knockout kidneys at P0.5. Results: Using 3D light-sheet imaging and IMARIS analysis on control and DTA-ablated kidneys, we determined that sympathetic nerve ablation resulted in a decrease in total glomerular/nephron number and an increase in glomerular diameter at P0.5 and P3.5. Further, our results revealed a decrease in the nephron progenitor niche number and an increase in the number of nephron progenitor cells (NPCs) per niche in denervated kidneys when compared to littermate controls. Conclusion: Taken together, these results suggest that signals from renal nerves could be essential for maintaining the balance between the self-renewal and differentiation of nephron progenitors. Funding: NIDDK Support, Private Foundation Support