Spatially Patterned Podocyte State Transitions Coordinate Aging of the Glomerulus.

<h4>Background</h4>Glomerular aging is accompanied by podocyte loss, glomerulosclerosis, and declining kidney function, yet the cellular states and intercellular programs underlying these changes remain incompletely defined. Thus, we tested whether aging produces coordinated, cell type-specific transcriptional changes that differ between outer cortical and juxtamedullary nephrons.<h4>Methods</h4>Single-nucleus RNA sequencing was performed in micro-dissected outer cortical and juxtamedullary kidney regions from mice aged 4, 20, and 25 months. Region prediction, lineage-specific sub-clustering, gene-set enrichment, trajectory inference, and ligand-receptor analyses were used to define spatially and age-associated kidney cell states and inferred glomerular communication.<h4>Results</h4>Analysis of 860,869 nuclei revealed transcriptional identities linked to anatomical region across multiple cell types, including juxtamedullary enrichment of Napsa. In proximal tubule heterogeneity primarily reflected segment and functional state, without age-dependent redistribution. Conversely, in podocytes, one of the five transcriptionally connected transcriptional states was a stress-adaptive state. It was enriched in the juxtamedullary region and exhibited the greatest aging-, senescence(definition)-, and inflammatory gene-set activity. Yet, like parietal epithelial, glomerular endothelial, and mesangial cell states, podocytes showed little compositional remodeling with age. The inferred glomerular communication architecture was largely preserved across age and region, with podocytes having the greatest outgoing and mesangial cells the greatest incoming interaction burden. Aging selectively altered only a limited number of candidate ligand-receptor programs such as juxtamedullary podocyte-to-parietal epithelial cell Egf and Lpl signaling.<h4>Conclusions</h4>In healthy mice, anatomical location was a stronger determinant than chronological age. Aging did not produce widespread expansion of discrete aging-associated populations, but instead selectively modified transcriptional and communication programs within an anatomically patterned glomerular landscape. In fact, the juxtamedullary-enriched, stress-associated podocyte state provides a mechanistic explanation for recognized regional-specific glomerular vulnerability.