Investigation for bone mass and trabecular bone turnover through transient regulation of marrow osteogenic and osteoclastogenic potentials follow by climbming exercise

导读：在机械载荷骨中，骨量增加与局部骨形成和骨吸收之间的关系尚不清楚。材料与方法：选取8周龄的C57BL/6J小鼠65只，随机分为5组：基线对照组和地面对照组、攀爬运动组各2、4周。老鼠被安置在一个100厘米高的塔中，它们必须爬上塔顶的瓶子喝水。结果：与地面对照组相比，攀爬组小鼠左股骨骨密度（BMD）在4周时增加。在第2周和第4周，攀爬小鼠骨膜表面骨形成率（BFR/BS）、横截面积和转动惯量均增加，而骨膜表面BFR/BS和侵蚀面（ES/BS）无显著差异。攀爬小鼠胫骨近端骨小梁体积（BV/TV）增加，破骨细胞表面（Oc.S/BS）和破骨细胞数量减少。4周时BV/TV升高，骨形成参数矿化面、矿物质附着率、骨形成率升高。在胫骨骨髓细胞培养中，攀爬小鼠碱性磷酸酶阳性集落形成单位-成纤维细胞数量和矿化结节形成面积增加，2周时破骨细胞样抗酒石酸酸性磷酸酶阳性多核细胞数量减少。在第4周，骨髓细胞培养的这些参数恢复到地面对照的水平。结论：我们的研究结果表明，攀爬增加了骨小梁的体积，减少了骨吸收，随后增加了骨形成。间歇性攀爬最初下调骨髓破骨细胞，上调成骨细胞，但进一步的运动似乎使它们脱敏。皮质包膜较早扩大，但对骨小梁的反应似乎不同。

Introduction : The relationship between bone mass gain and local bone formation and resorption in mechanically loaded bone are not well understood.Material and method : 65 C57BL/6J mice, 8 weeks of age, were assigned to 5 groups : a baseline control and two groups each of ground control and climbing exercise mice for 2 and 4 weeks. Mice were housed in a 100-cm tower and had to climb to drink water toward a bottle placed at the top.Results : Compared to the ground control, bone mineral density (BMD) of the left femur increased in the climbing mice at 4 weeks. At 2 and 4 weeks, bone formation rate (BFR/BS) of periosteal surface, the cross-sectional area, and moment of inertia were increased in the climbing mice, while BFR/BS and eroded surface (ES/BS) of endosteal surface did not differ. The trabecular bone volume (BV/TV) of the proximal tibia increased in climbing mice and their osteoclasts surface (Oc.S/BS) and osteoclast number decreased at 2 weeks. At 4 weeks, there were increases in BV/TV and parameters of bone formation including mineralized surface, mineral apposition rate and bone formation rate. In marrow cell cultures from the tibia, the number of alkaline phosphatase-positive colony forming units-fibroblastic and the area of mineralized nodule formation in climbing mice were increased, and the number of osteoclast like tartrate-resistant acid phosphatase-positive multinucleated cells was lower at 2 weeks. At 4 weeks, these parameters of marrow cell cultures recovered to the levels of the ground controls.Conclusion : Our results indicated that climbing increased trabecular bone volume and reduced bone resorption, with a subsequent increase in bone formation. Intermittent climbing downregulate marrow osteoclastogenic cells and upregulate osteogenic cells initially, but further exercise appeared to desensitize them. Cortical envelopes were enlarged earlier, but the response seems to differ from trabecular bone.