Absence of a Direct Anabolic Effect of 17 β-Estradiol on Normal Human Bone Marrow Stromal Cells

The effects of 17 β-estradiol on the proliferation and differentiation of cultured normal human bone marrow stromal cells were investigated. Treatment of 17β-estradiol at the concentration of 10(−6)∼10(−10) M for either 48 hours or 7 days did not affect [(3)H] thymidine incorporation. 17 β-estradiol (10(−8) M) treatment for 4 or 7 days also failed to stimulate alkaline phosphatase activity. Similarly, incubation with 17 β-estradiol (10(−8) M) for 48 hours did not increase the incorporation of [(3)H] proline into collagenase digestible protein and noncollagen proteins and secretion of IGF-I and IGF binding proteins in human bone marrow stromal cells. Present data indicate that 17β-estradiol does not have a direct effect on cultured normal human bone marrow stromal cells. With previous findings that estradiol elicits few effects on normal human osteoblasts, our results strongly suggest that estrogen does not have a direct anabolic effect on normal human osteoblast lineage. Therefore, the in vivo estrogen effects may be entirely through an antiresorptive mechanism or, if any anabolic role of estrogen is present, it must be indirect and mediated by other hormones or local factors.