PODOCYTE DAMAGE DRIVES MYELOID SKEWING, LINKING CKD TO CARDIO-RENAL DYSFUNCTION

Chronic kidney disease (CKD) is a major risk factor for cardiovascular disease. We previously demonstrated that podocyte DNA damage is associated with kidney prognosis. To investigate this further, we utilized podocyte-specific I-PpoI expressing mice, which induce non-mutagenic DNA double-strand breaks in podocytes. Using this model, we found that podocyte DNA damage alters the immune environment through aberrant DNA methylation in peripheral blood cells, thereby promoting CKD progression. Because alterations in hematopoietic stem cells (HSCs) can influence peripheral immune cell composition and are implicated in both CKD and cardiovascular risk, here we focused on the impact of podocyte DNA damage on HSC reprogramming.

Using the I-PpoI mouse model, we investigated how podocyte DNA damage influences HSC phenotypes and contributes to systemic pathophysiology. HSCs were isolated for RNA sequencing (RNA-seq) and DNA methylation analysis. Genomic DNA was isolated from peripheral blood for whole-exome sequencing (WES) analysis. Cardiac and renal functions were also evaluated. . To validate HSC-derived effects, we performed bone marrow transplantation and subsequently assessed immune cell composition and cardiac and renal function. To identify upstream signals, we conducted cytokine profiling and single-cell RNA sequencing (scRNA-seq) of bone marrow cells. Finally, clinical relevance was examined by correlating podocyte DNA damage with LYN promoter methylation in human samples.

I-PpoI mice exhibited a myeloid-biased hematopoietic shift in the bone marrow. HSCs showed reduced expression of DNA methylation-related genes, including Dnmt3a, which can induce epigenetic instability and broad genomic deregulation. As a result, although promoter DNA methylation was globally decreased, focal hypermethylation within the promoter region of Lyn, a key regulator of myeloid differentiation, was observed, accompanied by a subsequent decrease in its expression. WES analysis also identified a somatic mutation in the Lyn gene. Given that downregulation of Dnmt3a and Lyn in HSCs is known to drive myeloid skewing, these alterations likely underlie the myeloid shift observed in I-PpoI mice, leading to remarkable cardiac dysfunction and kidney inflammation. Transplantation of I-PpoI bone marrow cells into wild-type recipients recapitulated the myeloid shift, indicating that podocyte DNA damage induces reprogramming of HSCs. The resulting inflammatory myeloid cells preferentially accumulated in the heart and kidneys, contributing to cardiac dysfunction and kidney impairment. Cytokine profiling and scRNA-seq of bone marrow cells further revealed that these HSC alterations are driven by inflammatory cytokines induced by podocyte DNA damage and by signaling interactions between activated immune cells and HSCs. In human samples, podocyte DNA damage positively correlated with LYN promoter methylation in peripheral blood samples. 

These findings uncover a novel mechanism in which podocyte DNA damage reprograms hematopoiesis through alterations in DNA methylation, leading to a myeloid-biased shift that contributes to cardiorenal dysfunction. Because proteinuria is a major risk factor for cardiovascular disease, podocyte DNA damage-induced HSC reprogramming may represent a promising therapeutic target to prevent both CKD progression and cardiovascular complications.