Serum from post-menopausal women induces adipocytogenesis of bone progenitor cells

There is evidence to support the view that osteoporosis contributes to the bone loss and tooth loss seen in periodontal disease. However, the pathogenic mechanisms leading to chronic bone loss in both disorders remain unclear. Following menopause the porosity of mandibular bone, both cortical and alveolar, increases markedly. Menopause-related oestrogen deficiency is associated with accelerated bone loss, whereby bone resorption exceeds new bone formation during each bone remodelling cycle. We proposed previously that a deficit in osteoblast differentiation might be part of the pathogenic mechanism of chronic bone loss, since serum from post-menopausal women induced the adipocyte differentiation of human osteoprogenitor cells. We wish now to clarify whether oestrogen hormone replacement therapy (HRT) might offset the adipogenic affect of post-menopausal serum on bone progenitor cells. OBJECTIVES: To determine whether HRT could negate the adipogenic effect of post-menopausal serum on human osteoprogenitor cells. METHODS: The human adipocytic/osteoblastic cell line, hOP-7, was incubated with 10% foetal bovine serum (FBS), 10% rabbit serum (RS - a known inducer of bone marrow cell adipocytogenesis), or 10% pre- or post-(with or without 6-weeks HRT) menopausal human serum. After 4-7 days, cells were fixed and stained for lipids with Oil-Red-O. mRNA analyses were performed to determine the expression of adipocyte markers lipoprotein lipase (LPL) and glycerol phosphate 3-hydrogenase (GPD). RESULTS: RS induced adipocytogenesis of hOP-7 cells as determined by increased Oil Red O cell staining, and LPL and GDP expression. Little or no adipocytogenesis occurred in hOP-7 cells incubated with FBS, or pre-menopausal serum. A highly significant (p<0.01) increase in adipocytogenesis was seen in hOP-7 cells incubated with post-menopausal serum sampled either before or after HRT therapy. CONCLUSIONS: The adipogenic effect of serum from post-menopausal women on human bone progenitor cells is not negated by hormone replacement therapy.