HISTONE DEACETYLASE INHIBITION AMELIORATES RENAL FIBROSIS BY INDUCING DEDIFFERENTIATION AND APOPTOSIS OF MYOFIBROBLASTS

Chronic kidney disease (CKD) affects more than 10% of the global population. However, effective treatment strategies are lacking, due to a limited understanding of its complex molecular pathology. Tubulointerstitial fibrosis is a common pathologic feature across various manifestations of CKD, driven by the emergence and proliferation of myofibroblasts that highly produce the extracellular matrix (ECM). This makes fibrosis a plausible target for therapeutic intervention. Lineage tracing has demonstrated that most renal myofibroblasts in fibrotic kidneys originate from tubular interstitial fibroblasts, which possess erythropoietin (EPO)-producing capability. Given that the transformation of fibroblasts into myofibroblasts in injured kidneys is reversible (Souma et al., J Am Soc Nephrol 2013), this study aimed to identify methods—specifically those that restore fibroblastic properties to myofibroblasts—as therapeutic strategies against renal fibrosis and, eventually, CKD.

Because we previously reported that histone deacetylase (HDAC) inhibitors restored EPO-producing capability to neural cells derived from EPO-producing embryonic cells (Iwamura et al., Mol Cell Biol 2025), we investigated the effects of HDAC inhibitors (romidepsin, trichostatin A, and oxamflatin) on the cell fate of two models: Replic cells (a myofibroblast cell line derived from murine renal EPO-producing fibroblasts, Sato et al., Sci Rep 2019) and primary renal myofibroblasts non-invasively obtained from the urine of a patient with CKD. Kidney sections from mice subjected to unilateral ureteral obstruction (UUO) were also analyzed (Souma et al., J Am Soc Nephrol 2016). We analyzed gene expression related to myofibroblast activation and hypoxia-inducible EPO production in cells and tissues after HDAC inhibitor administration. CD73, encoded by the Nt5e gene, was used as a fibroblast marker in immunohistochemistry and flow cytometry. Tissue fibrosis was estimated using Elastica-Masson staining and anti-alpha smooth muscle actin antibody staining on kidney sections. Additionally, we used RNA interference to knock down the expression of HDAC1 and HDAC2 in Replic cells.

HDAC inhibitors altered the gene expression signature of Replic cells from myofibroblast to renal interstitial fibroblast, accompanied by morphological changes and CD73 induction. The gene expression data indicated that HDAC inhibition induces the dedifferentiation and apoptosis of activated myofibroblasts. Knockdown of HDAC2 in Replic cells partially recapitulated these effects, whereas HDAC1 knockdown failed due to inducing severe cell death. In a mouse model of kidney injury (UUO), HDAC inhibition attenuated renal fibrosis and tubular damage (Figure). Furthermore, HDAC inhibition restored the EPO-producing capability and fibroblastic signatures (including CD73 expression, Figure) to the primary myofibroblasts obtained from the urine of a patient with CKD.

HDAC inhibition promotes the dedifferentiation of renal myofibroblasts into fibroblasts and induces apoptosis in activated, highly ECM-producing myofibroblasts. This strategy offers a novel therapeutic approach that could potentially not only suppress renal fibrosis but also ameliorate associated tubular damage and EPO deficiency.