Abstract P130: Estrogen Receptor β Mediates the Rescue of Cardiac Function in Advanced Heart Failure by Promoting Neoangiogenesis and Reducing Fibrosis

Estrogen can act via the estrogen receptor alpha (ERa) or estrogen receptor beta (ERb) to exert its biological effects, and both of these receptors are present in the heart. We have previously shown that short-term estrogen (E2) treatment can rescue pressure overload-induced decompensated heart failure (HF) in mice, and that this rescue is achieved mainly through the ERb. Furthermore, E2 has been shown to regulate angiogenesis in different tissues. Because HF has been associated with decreased angiogenesis and increased fibrosis, here we investigated whether the E2-induced rescue of HF by the selective ERb agonist DPN can regulate cardiac fibrosis and neoangiogenesis. We used transaortic constriction to induce HF, and once the ejection fraction (EF) reached ∼30%, one group of animals was sacrificed (HF group), and the other three groups received either 17b-estradiol via a subcutaneous pellet implant (0.012mg/pellet, n=16), selective ERa agonist (PPT, 0.625mg/kg/day), or selective ERb agonist (DPN, 0.625mg/kg/day) for 10 days. Serial echocardiography was performed to monitor cardiac structure and function. As expected, E2 rescued HF by restoring EF from 33.17±1.12% to 53.05±1.29%. Mice treated with DPN had a significant EF improvement from 33.17±1.12% to 45.25±2.1% (n=7), while the EF of PPT-treated mice did not improve (31.09±2.3%, n=6). Similarly, only the fractional shortening of DPN-treated mice improved from 15.7±0.58% in HF to 21.95±1.65% with DPN treatment vs. 14.72±1.24% with PPT. Next, we examined whether promotion of cardiac neoangiogenesis and suppression of fibrosis by the selective ERb agonist are possible mechanisms in the rescue action of HF by DPN. DPN treatment was able to reverse the interstitial and perivascular fibrosis observed in HF, while PPT had no effect. The selective ERb agonist also stimulated neoangiogenesis, as the capillary density was increased from 0.46±0.04 microvessels/cardiomyocyte in HF to 0.67±0.07 with DPN treatment, whereas PPT treatment had no effect (0.43±0.03). Our data strongly suggests that upregulation of cardiac neoangiogenesis and reversal of fibrosis are pivotal mechanisms in rescuing advanced HF by the estrogen receptor beta agonist DPN.