Effect of leptin on the differentiation and function of osteoclast induced from bone marrow in mice

Objective More and more evidence suggest that leptin is not only an energy-regulating hormone but also has a role in bone metabolism. Leptin may both stimulate bone formation and decrease bone resorption via direct peripheral effects on stromal precursor cells. To observe the effect of leptin on the differentiation and function of osteoclasts and investigate the biologic effects of leptin on the bone resorption. Methods: Femurs and humerus from 4-week mice were dissected and bone marrow cells collected and cultured. The culture system was divided into 7 groups: group A containing M-CSF(50 ng/ml) and RANKL(50 ng/ml); group B containing not only M-CSF and RANKL but also different concentration leptin (The concentration of leptin of group from B to F was respectively 80 ng/ml, 160 ng/ml, 240 ng/ml, 320 ng/ml, 400 ng/ml.); group G, control group. On the seventh day, the cultural cells were fixed and were stained for tartrate-resistant acid phossphatase(TRAP).The formation of osteoclasts was quantified by counting the number of TRAP~+ multinuclear cells. On the tenth day, bone slices were stained toluidine blue and the percentage of the bone surface that was resorbed was quantified with scanning electron microscopy.Results: The appearance of reduced mice osteoclasts was typical. Compared with group A, the number of TRAP~+ multinuclear cells of group B and group C did not significantly decrease (P0.05), but the ratio of bone resorption of all groups from B to F obviously decreased(P0.05).Conclusions: Leptin can inhibit osteoclasts formation and bone resorption.