For the millions living with ischaemic heart failure, cardiac fibrosis — the progressive stiffening of heart tissue — remains one of the most difficult pathological processes to reverse. New mechanistic evidence pinpoints a specific molecular driver within the heart's own blood vessel lining, potentially opening a targeted therapeutic window that existing treatments entirely miss.
The research identifies endothelial PARP1, a poly(ADP-ribose) polymerase expressed in the cells lining cardiac vasculature, as a master regulator of endothelial-to-mesenchymal transition (EndMT) in ischaemic heart failure. The proposed mechanism centers on PARylation — the enzymatic addition of poly(ADP-ribose) chains — targeting FHL2 (Four-and-a-Half LIM domain protein 2), a scaffolding protein involved in cytoskeletal organization and gene transcription. This post-translational modification of FHL2 appears to reprogram endothelial cells into fibroblast-like mesenchymal cells, actively contributing to the fibrotic remodeling that undermines cardiac function after ischaemic injury.
This finding sits at a productive intersection of two previously somewhat separate research streams: the PARP biology field, long focused on DNA damage repair and cancer therapeutics, and the cardiac fibrosis field, where EndMT has gained increasing recognition as a significant contributor to pathological remodeling. PARP inhibitors are already clinically approved in oncology, which gives this discovery immediate translational relevance — repurposing existing compounds for cardiac indications is a faster path than de novo drug development. However, critical limitations deserve acknowledgment. PARP1 has broad cellular functions, and systemic inhibition carries risks of off-target effects, particularly in tissues with high DNA repair demands. Whether these findings from experimental models translate to human ischaemic heart failure requires validation in larger, clinically representative cohorts. Still, identifying FHL2 PARylation as a discrete, druggable checkpoint in EndMT makes this finding more than incremental — it offers a mechanistically specific target where none previously existed.