In vitro evaluation of the direct effect of estradiol on human osteoblasts (HOB) and human mesenchymal stem cells (h-MSCs).

Estrogen may increase the proliferation of osteoblasts depending upon their differentiation stage. Our objective was to test the hypothesis that estradiol could stimulate the proliferation of primary human osteoblast (HOB) cells or human mesenchymal stem cells (h-MSCs). To test this hypothesis, we investigated two synthetic estradiol preparations: (a) a commercially available one (in clinical use) whose effect was evaluated using MTT assay, trypan blue cell counts and total protein assays; (b) a novel synthetic preparation (not in clinical use) using Alamar Blue assays and scanning electron microscopy (SEM). Commercial estradiol increased HOB proliferation in a concentration-dependant manner between 1 nM and 8 nM reaching significance at a concentration of 8 nM (p<0.001). Small doses of 1 nM and 2 nM increased h-MSC proliferation (p<0.001) but higher doses had no effect. All novel synthetic estradiol preparations decreased HOB proliferation (p<0.001) whereas no direct effect was observed on h-MSCs. Commercial estradiol appears to induce proliferation of HOBs, although its effects on h-MSCs appears to be highly dose-dependent and requires further investigation.