TRIM28 Promotes Senescence-Associated Secretory Phenotype in Tubular Epithelial Cells and Drives Kidney Fibrosis

Background: Chronic kidney disease (CKD) is a progressive disorder characterized by nephron loss and declining kidney function, with interstitial fibrosis as the key pathological feature. Increasing evidence implicates tubular epithelial cell senescence as a major contributor to fibrosis, primarily through the senescence-associated secretory phenotype (SASP), which drives inflammation, fibroblast activation, and extracellular matrix (ECM) deposition. However, the upstream regulators of SASP in tubular cells remain incompletely defined. This study investigates the role of tripartite-motif-containing protein 28 (TRIM28) in regulating SASP in tubular cells and its contribution to kidney fibrosis. Methods: Cultured tubular epithelial cells (TECs) were used to examine the role of Trim28 in regulating markers of fibrosis, pro-inflammatory, and pro-fibrotic cytokines. Tamoxifen-inducible global TRIM28 knockout (Trim28GKO) mice and tubule-specific TRIM28 knockout (Trim28TKO) mice were generated by crossing TRIM28 floxed mice with CAG-Cre and KSP-Cre mice, respectively. Littermate Trim28f/f (Trim28CON) mice were used as controls. CKD was induced in 8- to 12-week-old male mice using the unilateral ureteral obstruction (UUO) model. Kidneys were harvested 10 days after UUO to assess SASP markers, inflammation, fibroblast activation, interstitial fibrosis, and collagen deposition. Results: In cultured TECs, TRIM28 knockout decreased ECM protein production in response to TGFβ1 treatment. RNA-sequencing analysis revealed that TRIM28 knockout reduced the expression of key SASP factors, including MMP1, TNFα, and PDGFβ, implicated in kidney fibrosis. In vivo, TRIM28 expression was significantly induced in the kidneys of wild-type mice with UUO. Trim28GKO mice displayed markedly reduced senescence, inflammation, fibroblast activation, and total collagen deposition in the kidneys following UUO. Similar kidney protective effects were obtained in Trim28TKO mice following UUO. Moreover, Trim28TKO mice had reduced expression of inflammatory cytokines and PDGFβ in the kidney compared with Trim28CON mice. Conclusion: Our results identify TRIM28 as a crucial regulator of SASP in tubular epithelial cells and a promoter of kidney fibrosis. Therefore, targeting TRIM28 or TRIM28-driven SASP pathways could represent a novel therapeutic strategy for the treatment of CKD. Funding: NIDDK Support