HDAC1 Modulates Cell Cycle and Proliferation of Myofibroblasts in the Kidneys

Background: Ischemia-reperfusion injury (IRI) can cause acute kidney injury (AKI) leading to renal interstitial fibrosis. Histone deacetylase 1 (HDAC1), a regulator of transcription, is implicated in mediating renal injury and fibrosis post-IRI. Understanding its role post-IRI may lead to novel therapeutic approaches for improving health outcomes. We hypothesized that fibroblast HDAC1 activation after IRI leads to fibrosis by promoting cell cycle progression and proliferation of myofibroblasts. Methods: Male, floxed HDAC1 (control), and floxed HDAC1 mice with hemizygous Col1A2-CreER (iFibHDAC1KO mice, littermates) received tamoxifen i.p. in adulthood and this resulted in fibroblast HDAC1 knockdown in Cre+ mice. Mice underwent 18-min kidney bilateral IRI or sham surgery. AKI was confirmed 24 h post-surgery by serum creatinine levels and glomerular filtration rate (GFR). Interstitial fibrosis was evaluated after four weeks of recovery using picrosirius red. Normal rat kidney fibroblasts (NRK49F) were transfected with empty vector control or HDAC1 and cell cycle was determined by flow cytometry. Cells were also treated for 24 h with 2 ng/ml TGFβ1 to induce myofibroblast transition. Cells were collected for bulk RNA-seq to assess gene expression profiles. Results: All IRI mice experienced a 50% reduction in GFR 24 h post-surgery compared to shams. iFibHDAC1KO IRI mice had significantly lower renal fibrosis compared to control IRI mice (0.47 ± 0.1% vs/ 1.16±0.2, p = 0.0011, n=5-7). HDAC1 overexpression in NRK49F cells led to a shift in the cell cycle with greater percentage of cells in the S (11 ± 0.2 vs 4 ±0.2, p< 0.001, n=3) and G2 phases (19 ± 0.4 vs 7 ± 0.1, p< 0.001). These cells also had increased expression of 44 cell cycle, and 65 proliferation related genes compared to control cells (adjusted P < 0.05). Although TGFβ1 treatment for 24 h didn’t lead to a further shift in cell cycle, there were 2 additional cell cycle and 7 proliferation-related genes increased. HDAC1 overexpression lead to the cyclin gene Ccna2 and proliferation marker Mki67 upregulation in both conditions. Conclusion: HDAC1 may be profibrotic through shifting the cell cycle and increasing fibroblast/myofibroblast proliferation. Targeting HDAC1-mediated pathways could offer a therapeutic solution for mitigating renal fibrosis progression. Funding: NIDDK Support - NIDDK Support, NIDDK Support, Private Foundation Support