Baseline podocyte‐associated state and persistent cell–matrix transcriptional programs are associated with BALB /c substrain differences in adriamycin nephropathy

BACKGROUND: Adriamycin (ADR)-induced nephropathy is a widely used murine model of glomerular injury. Although strain-dependent susceptibility is well recognized, variation among closely related substrains remains insufficiently explored. METHODS: We compared early responses to ADR between two BALB/c substrains, BALB/cAJcl (AJcl) and BALB/cByJcl (ByJcl), focusing on baseline podocyte-associated features and early glomerular transcriptional programs. RESULTS: Following ADR administration, ByJcl mice developed significantly greater albuminuria at Day 7 compared with AJcl mice. At Day 7, ByJcl mice also showed lower WT1-positive nuclei counts and diminished nephrin immunoreactivity than AJcl mice; notably, these differences were already evident at baseline. Glomerulus-enriched RNA sequencing showed that extracellular matrix organization and integrin signaling were already enriched in ByJcl at baseline and remained enriched at Day 5, when coordinated suppression of podocyte-associated transcriptional programs was also evident. CONCLUSION: Substrain-dependent differences in baseline podocyte-associated readouts and a pre-existing cell-matrix transcriptional state that persists after ADR are associated with divergent trajectories of ADR-induced injury. Because WT1-based counts cannot distinguish podocyte number from WT1 expression, these baseline differences are best described as an attenuated podocyte-associated state rather than a definitive reduction in podocyte number. Careful documentation of substrain origin is critical for experimental reproducibility in nephropathy research.