Margolis David S, Kim Devin, Szivek John A, Lai Li-Wen, Lien Yeong-Hau H
Orthopaedic Research Lab, Department of Orthopaedic Surgery, University of Arizona, Tucson, AZ 85721, USA.
Bone. 2006 Sep;39(3):477-84. doi: 10.1016/j.bone.2006.02.064. Epub 2006 May 2.
In vitro studies indicate that Calbindin-D28k, a calcium binding protein, is important in regulating the life span of osteoblasts as well as the mineralization of bone extracellular matrix. The recent creation of a Calbindin-D28k knockout mouse has provided the opportunity to study the physiological effects of the Calbindin-D28k protein on bone remodeling in vivo. In this experiment, histomorphometry, microCT, and bend testing were used to characterize bones in Calbindin-D28k KO (knockout) mice. The femora of Calbindin-D28k KO mice had significantly increased cortical bone volume (60.4% +/- 3.1) compared to wild-type (WT) mice (45.4% +/- 4.6). The increased bone volume was due to a decrease in marrow cavity area, and significantly decreased endosteal perimeters (3.397 mm +/- 0.278 in Calbindin-D28k KO mice, and 4.046 mm +/- 0.450 in WT mice). Similar changes were noted in the analysis of the tibias in both mice. The bone formation rates were similar in the femoral and tibial cortical bones of both mice. microCT analysis of the trabecular bone in the tibial plateau indicated that Calbindin-D28k KO mice had an increased bone volume (35.2% +/- 3.1) compared to WT mice (24.7% +/- 4.9) which was primarily due to increased trabecular number (8.99 mm(-1) +/- 0.94 in Calbindin-D28k KO mice compared to 6.75 mm(-1) +/- 0.85 in WT mice). Bone mineral content analysis of the tibias indicated that there is no difference in the calcium or phosphorus content between the Calbindin-D28k KO and WT mice. Cantilever bend testing of the femora demonstrated significantly lower strains in the bones of Calbindin-D28k KO mice (4135 micro strain/kg +/- 1266) compared to WT mice (6973 micro strain/kg +/- 998) indicating that the KO mice had stiffer bones. Three-point bending demonstrated increased failure loads in bones of Calbindin-D28k KO mice (31.6 N +/- 2.1) compared to WT mice (15.0 N +/- 1.7). In conclusion, Calbindin-D28k KO mice had increased bone volume and stiffness indicating that Calbindin-D28k plays an important role in bone remodeling.
体外研究表明，钙结合蛋白钙结合蛋白-D28k在调节成骨细胞寿命以及骨细胞外基质矿化方面具有重要作用。最近培育出的钙结合蛋白-D28k基因敲除小鼠为研究钙结合蛋白-D28k蛋白在体内对骨重塑的生理作用提供了契机。在本实验中，采用组织形态计量学、显微CT和弯曲试验对钙结合蛋白-D28k基因敲除（KO）小鼠的骨骼进行表征。与野生型（WT）小鼠（45.4%±4.6）相比，钙结合蛋白-D28k基因敲除小鼠的股骨皮质骨体积显著增加（60.4%±3.1）。骨体积增加是由于骨髓腔面积减小，骨内膜周长显著减小（钙结合蛋白-D28k基因敲除小鼠为3.397 mm±0.278，野生型小鼠为4.046 mm±0.450）。在对两种小鼠胫骨的分析中也发现了类似变化。两种小鼠股骨和胫骨皮质骨的骨形成率相似。对胫骨平台小梁骨的显微CT分析表明，与野生型小鼠（24.7%±4.9）相比，钙结合蛋白-D28k基因敲除小鼠的骨体积增加（35.2%±3.1），这主要是由于小梁数量增加（钙结合蛋白-D28k基因敲除小鼠为8.99 mm-1±0.94，野生型小鼠为6.75 mm-1±0.85）。对胫骨的骨矿物质含量分析表明，钙结合蛋白-D28k基因敲除小鼠和野生型小鼠的钙或磷含量没有差异。对股骨的悬臂弯曲试验表明，与野生型小鼠（6973微应变/kg±998）相比，钙结合蛋白-D28k基因敲除小鼠骨骼中的应变显著降低（4135微应变/kg±1266），这表明基因敲除小鼠的骨骼更硬。三点弯曲试验表明，与野生型小鼠（15.0 N±1.7）相比，钙结合蛋白-D28k基因敲除小鼠骨骼的破坏载荷增加（31.6 N±2.1）。总之，钙结合蛋白-D28k基因敲除小鼠的骨体积和硬度增加，表明钙结合蛋白-D28k在骨重塑中起重要作用。
