FGF2 modulates cardiac remodeling in an isoform- and sex-specific manner

Pathological cardiac hypertrophy and cardiac fibrosis are remodeling events that result in mechanical stiffness and pathophysiological changes of the myocardium. Both humans and animal models display a sexual dimorphism where females are more protected from pathological remodeling. Fibroblast growth factor 2 (FGF2) mediates cardiac hypertrophy, cardiac fibrosis and protection against cardiac injury and is made in high molecular weight and low molecular weight isoforms (Hi FGF2 and Lo FGF2, respectively). Although some light has been shed on isoform-specific functions in cardiac pathophysiology, their roles in pathologic cardiac remodeling have yet to be determined. We tested the hypothesis that Lo FGF2 and Hi FGF2 modulate pathological cardiac remodeling in an isoform-specific manner. Young adult male and female mice between 8-12 weeks of age of mixed background that were deficient in either Hi FGF2 or Lo FGF2 (Hi KO or Lo KO, respectively) were subjected to daily injections of isoproterenol (Iso) for four days after which their hearts were compared to wildtype cohorts. Post-Iso treatment, female Lo KO hearts don't exhibit significant differences in their hypertrophic and fibrotic response, while female Hi KO hearts present with a blunted hypertrophic response. In male animals Lo KO hearts present with an exacerbated fibrotic response and increased alpha-smooth muscle actin protein expression while Hi KO hearts present with a blunted fibrotic response and increased atrial natriuretic factor protein expression Thus, in female hearts Hi FGF2 mediate cardiac hypertrophy while in male hearts Lo FGF2 and Hi FGF2 display an antithetical role in cardiac fibrosis where Lo FGF2 is protective while Hi FGF2 is damaging. In conclusion, cardiac remodeling following catecholamine overactivation is modulated by FGF2 in isoform- and sex-specific manners.