Ovarian hormones induce TGF-beta(3) and fibronectin mRNAs but exhibit a disparate action on cardiac fibroblast proliferation.

UNLABELLED: Prior to menopause, women have a lower risk of cardiovascular disease compared to age-matched men. Despite the well-documented beneficial physiological effects of ovarian hormones on vascular reactivity and growth, very little is known with regard to the direct action on cardiac cells.
OBJECTIVE: The following study examined the pattern of ovarian hormone receptor subtype expression in cardiac fibroblasts, the modulator role of 17 beta-estradiol and progesterone on growth and their respective influence on putative molecular events of extracellular matrix remodeling. METHODS AND
RESULTS: Neonatal rat cardiac fibroblasts were isolated from 1- to 3-day-old Sprague--Dawley rats. Immunofluorescence and Western blot analysis revealed the presence of estrogen receptor-alpha (ER-alpha), and -beta (ER-beta) subtypes, with the ER-alpha subtype localized on the plasma membrane. Likewise, both progesterone receptor-A (PR-A), and -B (PR-B) subtypes were expressed in cardiac fibroblasts, and the PR-B appeared to be the predominant subtype associated with the plasma membrane. Despite the presence of both ER subtypes, the treatment of cardiac fibroblasts with 1 microM 17 beta-estradiol exerted a modest decrease in DNA synthesis. By contrast, progesterone treatment caused a dose-dependent decrease in [3H]thymidine uptake, without a concomitant induction of apoptosis. The progesterone-mediated decrease in DNA synthesis was associated with the upregulation of the cyclin-dependent kinase inhibitor p27(Kip1), whereas p21(cip) and proliferating cell nuclear antigen protein levels were unchanged. Lastly, despite the modest effect on DNA synthesis, 17 beta-estradiol increased the steady-state mRNA levels of transforming growth factor-beta(3) and fibronectin. Likewise, progesterone increased the expression of both transforming growth factor-beta(3), and fibronectin mRNA.
CONCLUSION: Collectively, these data are the first to highlight the presence of estrogen and progesterone receptor subtypes on the plasma membrane of neonatal rat cardiac fibroblasts, and further underscore the ability of ovarian hormones to directly suppress DNA synthesis, and influence putative molecular events associated with extracellular matrix remodeling.