Unraveling the Role of Podocyte Turnover in Glomerular Aging and Injury

TLDR

Podocyte loss is a key driver of chronic kidney disease, yet the extent and role of podocyte turnover and regeneration remain poorly understood. The study aims to quantify podocyte turnover and regeneration in vivo to elucidate their mechanisms and capacity. Using genetic fate mapping combined with efficient podocyte isolation, the authors precisely measured podocyte turnover and regeneration. They found that parietal epithelial cells can generate podocytes after acute injury, but podocyte renewal is limited in aging and after nephron loss, leading to protein oxidation, aggregates, podocyte loss, and glomerulosclerosis.

Abstract

Podocyte loss is a major determinant of progressive CKD. Although recent studies showed that a subset of parietal epithelial cells can serve as podocyte progenitors, the role of podocyte turnover and regeneration in repair, aging, and nephron loss remains unclear. Here, we combined genetic fate mapping with highly efficient podocyte isolation protocols to precisely quantify podocyte turnover and regeneration. We demonstrate that parietal epithelial cells can give rise to fully differentiated visceral epithelial cells indistinguishable from resident podocytes and that limited podocyte renewal occurs in a diphtheria toxin model of acute podocyte ablation. In contrast, the compensatory programs initiated in response to nephron loss evoke glomerular hypertrophy, but not de novo podocyte generation. In addition, no turnover of podocytes could be detected in aging mice under physiologic conditions. In the absence of podocyte replacement, characteristic features of aging mouse kidneys included progressive accumulation of oxidized proteins, deposits of protein aggregates, loss of podocytes, and glomerulosclerosis. In summary, quantitative investigation of podocyte regeneration in vivo provides novel insights into the mechanism and capacity of podocyte turnover and regeneration in mice. Our data reveal that podocyte generation is mainly confined to glomerular development and may occur after acute glomerular injury, but it fails to regenerate podocytes in aging kidneys or in response to nephron loss.