Characterization of senescence in human cardiac fibroblasts

Abstract

Abstract Funding Acknowledgements None. Background Recent studies suggest that senescence of cardiac fibroblasts (cFib) plays a significant role in cardiac aging and disease. However, senescence of cultured cFib in response to classical pro-senescent stimuli has not been characterized yet. Purpose We thoroughly studied oncogene- and stress-induced senescence, as well as replicative senescence, in primary human cFib. Methods Human cFib were isolated from specimens of right atrial appendages, collected during cardiac surgery with extracorporeal circulation. These cells were subjected to oncogene-induced senescence by overexpression of HRasV12, were exposed to ionizing radiation (IR, 5 Gy) to recapitulate stress-induced senescence, and were passaged until replicative senescence was reached (P12-P14). Senescence was assessed by staining for senescence associated (SA) β-galactosidase and EdU and by RT-PCR for CDKN1A, CDKN2A, and LamB1. Results The main results are summarized in the graphical abstract. HRasV12 overexpression, IR, and prolonged culturing consistently caused senescence of cFib: in fact, all senescent models showed a significant increase in SA-β-gal activity and CDKN1A expression and a decrease in EdU uptake and LamB1 expression over control cells. Interestingly, cFib with HRasV12 overexpression exhibited a peculiar morphological phenotype with vacuoles and showed higher levels of the typical markers of senescence compared to control and to IR-treated or extensively passaged cFib. Moreover, only cFib with HRasV12 overexpression showed a strong downregulation of CDKN2A. Conclusions Cultured primary human cFib undergo senescence in response to established inducers of senescence. HRasV12 overexpression uniquely causes vacuolization of senescent cFib, which is currently being further characterized by transmission electron microscopy.