PCSK9 promotes aging-related cardiac calcification by inducing osteogenic differentiation of cardiac fibroblasts

Cardiac calcification is an age-associated pathological process that contributes to cardiac dysfunction, arrhythmia, and sudden cardiac death, yet its underlying mechanisms remain unclear. Cardiac fibroblasts (CFs) have emerged as key mediators of ectopic calcification through osteogenic differentiation. Proprotein convertase subtilisin/kexin type 9 (PCSK9), a key regulator of Cholesterol metabolism, has been implicated in cardiovascular pathology beyond its canonical role, but its involvement in cardiac calcification is unknown. In this study, aged mice exhibited cardiac dysfunction, interstitial fibrosis, and myocardial calcium deposition, accompanied by upregulation of osteogenic markers, including RUNX2, OCN, and Osx. PCSK9 expression was increased in aged hearts and enriched in DDR2-positive cells. In vitro, senescent CFs displayed enhanced osteogenic differentiation, characterized by increased calcium deposition, Alkaline Phosphatase activity, and elevated expression of osteogenic markers. Recombinant PCSK9 promoted osteogenic differentiation in young CFs, whereas genetic deletion of PCSK9 attenuated these effects in senescent CFs. Pharmacological experiments suggest that PCSK9-mediated osteogenic differentiation is associated with activation of the ATF4 pathway and upregulation of RUNX2 expression. These findings support a role for the PCSK9-ATF4-Runx2 signaling axis in osteogenic differentiation of CFs, providing new insights into age‑related cardiac calcification and identifying this pathway as a hypothesis‑generating candidate for future investigation.