Bone Abstracts

The mature human skeleton is a metabolically active organ that is continuously resorbed and rebuilt by osteoclasts and osteoblasts. Dietary supplementation of selected long chain polyunsaturated fatty acids (LCPUFAs) has shown effects on bone turnover. Most research on LCPUFAs has been done using commercially available cell lines and further clarification of the cellular effects on models relevant to humans is required. After ethical approval, peripheral blood was collected from healthy young male volunteers to prepare a mononuclear CD14+ monocyte population to generate osteoclasts. The action of an ω-6 LCPUFA, arachidonic acid (AA), and an ω-3 LCPUFA, docosahexaenoic acid (DHA), on various parameters regarding osteoclast formation and bone resorption were investigated.

CD14+ monocytes were seeded at 130 000 cells/cm² with RANKL (30 ng/ml) and M-CSF (25 ng/ml). For experiments on differentiating osteoclasts, cells were exposed to the LCPUFAs at varying concentrations (20 μM, 40 μM, 60 μM and 80 μM) from day 3. For experiments on mature osteoclasts, cells were exposed to the LCPUFAs from the onset of resorption (day 11–14). Experiments were terminated a week thereafter. TRAP activity, osteoclast numbers, resorption and expression of prominent osteoclast markers were assessed. All experiments were conducted in triplicate and repeated three times with monocytes from three different donors.

AA (60 μM, 80 μM) and DHA (80 μM) decreased TRAP activity in differentiating osteoclasts. AA (all concentrations) and DHA (60 μM, 80 μM) decreased osteoclast numbers in differentiating osteoclasts. AA (60 μM, 80 μM) decreased bone resorption while not affecting cell numbers in mature osteoclasts. Both LCPUFAs (40 μM) decreased cathepsin K and TRAP protein expression in differentiating and mature osteoclasts. Both LCPUFAs (40 μM) decreased MMP-9 protein expression, in differentiating and mature osteoclasts, except DHA that showed no effect on mature osteoclasts. This data shows for the first time that LCPUFAs can affect osteoclast formation and function in a human primary cell line, in vitro.