Research Background
Renal fibrosis represents the final common pathological outcome of chronic kidney disease (CKD) and is a major determinant of progression to end-stage renal failure. A hallmark event driving renal fibrosis is the abnormal activation of renal interstitial fibroblasts and their transition into matrix-producing myofibroblasts, a process known as fibroblast–myofibroblast transition (FMT). Despite extensive investigation, effective therapeutic strategies capable of reversing fibrotic remodeling remain lacking.
RAS protein activator-like 1 (RASAL1) is a key antifibrotic regulator that restrains fibroblast activation and extracellular matrix production. Previous studies have shown that RASAL1 is persistently silenced in fibrotic kidneys; however, the epigenetic mechanisms responsible for its sustained repression and their functional significance in renal fibrosis have not been fully elucidated.
Histone deacetylase 3 (HDAC3) is a central epigenetic regulator involved in chromatin remodeling and transcriptional control, yet its role in fibroblast activation and its transcriptional partners in renal fibrosis remain poorly understood. This study aimed to define the epigenetic mechanism underlying RASAL1 repression and to clarify its contribution to fibroblast activation and renal fibrogenesis.
Research Progress
Using two well-established murine models of renal fibrosis—unilateral ureteral obstruction (UUO) and aristolochic acid I (AAI)-induced injury—the researchers observed a consistent increase in HDAC3 expression accompanied by marked suppression of RASAL1 in fibrotic kidneys. Molecular and histological analyses revealed that these changes were closely associated with enhanced fibroblast activation and extracellular matrix deposition. Importantly, analyses of human renal biopsy samples further confirmed that elevated HDAC3 levels and reduced RASAL1 expression correlated with the severity of renal interstitial fibrosis.
Functional studies demonstrated that fibroblast-specific deletion of Hdac3 or pharmacological inhibition using the selective HDAC3 inhibitor RGFP966 effectively restored RASAL1 expression, suppressed fibroblast–myofibroblast transition, and significantly attenuated renal fibrosis in vivo. These findings establish HDAC3 as a critical epigenetic driver of fibroblast activation and fibrotic remodeling.
At the mechanistic level, the study revealed that HDAC3 does not act alone but cooperates with the transcription factor Yin Yang 1 (YY1) to repress RASAL1 transcription. HDAC3 and YY1 were shown to form a repressive complex that directly binds to the RASAL1 promoter, inducing histone deacetylation and transcriptional silencing. Chromatin immunoprecipitation and promoter reporter assays confirmed that YY1 functions as an essential cofactor enabling HDAC3-mediated epigenetic repression of RASAL1.
To determine whether RASAL1 mediates the antifibrotic effects of HDAC3 inhibition, the researchers performed targeted knockdown of RASAL1 in RGFP966-treated mice. Strikingly, silencing RASAL1 largely abolished the protective effects of HDAC3 inhibition, leading to reactivation of fibroblast–myofibroblast transition and aggravated renal fibrosis. These results provide causal evidence that derepression of RASAL1 is essential for the antifibrotic function of HDAC3 inhibition.
Future Prospects
Currently, therapeutic options for renal fibrosis are extremely limited, with most treatments focused on slowing disease progression rather than reversing fibrotic remodeling. This study identifies epigenetic repression of RASAL1 mediated by HDAC3 in cooperation with YY1 as a previously unrecognized mechanism driving fibroblast activation and renal fibrosis.
The findings suggest that targeting HDAC3 activity or restoring RASAL1 expression may represent promising therapeutic strategies for renal fibrosis and potentially other fibrotic diseases. Given that HDAC3-selective inhibitors are already under development, this work provides an important theoretical foundation for future translational studies aimed at epigenetic therapy in chronic kidney disease.
The complete study is accessible via DOI:10.34133/research.1073