BMSCs and ASCs response to 17 β-estradiol (E2)

Estrogens confer skeletal protective effects, facilitating osteogenesis and suppressing bone-resorption. 17β estradiol (E2) effect on progenitor cells (MSCs) has been largely studied, nevertheless data are still controversial. Since Mesenchymal Stem Cells from bone marrow (BMSCs) and adipose tissue (ASCs) are widely used in bone-tissue engineering research, we evaluated in vitro the effect of E2 on their proliferation, viability and osteogenic ability. E2 did not influence cell viability and proliferation; in particular, MSCs treated with E2 (1-1000 nM) for 14 days behaved as the untreated ones and no modifications in morphology and proliferation rate was observed after 35 days of treatment. In order to verify a pro-osteogenic effect, MSCs were pre-treated with 10, 100 nM E2 for 7, 21, 35 days and then osteo-differentiated for 14 days. During the osteo-differentiative process E2 increased significantly BMSC ALP activity (+50%), and this marker was further induced by 7 days pre-treatment (+158% 10 nM, +185% 100 nM) and maintained by longer pre-treatments. In contrast, E2 never influenced the osteogenic ability of ASCs at the doses and time points considered. Next, since E2 seems to be involved in telomerase activation, we wanted to evaluate its gene expression and enzymatic activity in our cells. We were unable to detect it by RT-PCR, and its activity was randomly modulated. Our data suggest a difference of E2 treatment on BMSC and ASC response which could be due to the different expression of one of its receptors. We analysed ERα expression by western blot and, surprisingly, an ERα variant of about 37 KDa is expressed by both BMSCs and ASCs, whereas the classic 66 KDa isoform was faintly or even not depicted. In conclusion, E2 improved osteogenic differentiation just on BMSCs without effect on ASCs; further studies are now in progress to elucidate the ERα variant function in MSCs.