p75NTR敲除对小鼠股骨矿化发育的抑制作用

目的 对比野生型和p75 neurotrophin receptor(p75 NTR)敲除小鼠股骨骨质的改变,探讨p75 NTR敲除对小鼠股骨矿化发育的影响.方法 取同窝p75 NTR+/+(野生型)和p75 NTR-/-(敲除型)雄性小鼠,出生后8周龄时行股骨Micro-CT扫描,检测股骨松质骨的骨量(BV)、骨体积分数(BV/TV)、骨小梁数(Tb.N)、骨小梁厚度(Tb.Th)、骨表面积/骨量(BS/BV)、骨小梁分离度(Tb.Sp)和皮质骨的骨量(Ct.BV)、骨皮质厚度(Ct.TbTh)、骨皮质的骨表面积/骨量(Ct.BS/BV);出生后40 d分别取同窝两种基因型雄性小鼠行钙黄绿素荧光双标实验,以检测股骨的矿化沉积速率;提取4周龄大小鼠股骨总RNA及蛋白质,RT-PCR和Western blot检测ALP、Runx2的表达.结果 Micro-CT结果显示:p75 NTR--小鼠股骨的BV、BV/TV、Tb.N、Tb.Th、Ct.BV、Ct.TbTh明显低于同窝p75 NTR+/+小鼠(P＜0.05),同时,p75 NTR-/-小鼠的BS/BV、Tb.Sp、Ct.BS/BV明显高于p75 NTR+/+小鼠(P＜0.01);钙黄绿素荧光双标检测结果显示:p75 NTR-/-小鼠股骨的矿化速率明显低于同窝p75 NTR+/+小鼠(P＜0.01);RT-PCR及Western blot结果显示:p75 NTR--小鼠的ALP、Runx2表达均明显低于p75 NTR+/+小鼠(P＜0.01).结论 p75 NTR敲除对小鼠股骨的矿化发育有一定的抑制作用.

Knocking out p75 neurotrophin receptor suppresses mineralization in the femurs of mice

Objective To compare the quantitative parameters of the femoral bone between wild-type mice and p75 neurotrophin receptor knockout (p75NTR-/-) mice and explore the impact of p75NTR knockout on mineralization and development of the femoral bone in mice.Methods The left femurs of p75NTR-/-and wild-type (p75NTR+/+) male mice (8 weeks old) were scanned with micro-CT for measurement of the cancellous bone volume (BV),bone volume fraction (BV/TV),number of bone trabecula (Tb.N),trabecular thickness (Tb.Th),bone surface area/bone volume ratio (BS/BV),trabecular separation (Tb.Sp),cortical bone volume (Ct.BV),cortical bone thickness (Ct.Tb.Th),and cortical bone surface area/ bone volume ratio (Ct.BS/BV).The mineral apposition rate (MAR) of the femurs of the p75NTR-/-mice and their wild-type littermates was analyzed on day 40 after birth using calcein double fluorescent labeling.At the 4th week,the femurs were taken to detect the expression of Runx2 and ALP using real-time PCR and Western blotting.Results Micro-CT imaging data showed significantly lower BV,BV/TV,Tb.N,Tb.Th,Ct.BV and Ct.TbTh (P ＜ 0.05) and significantly higher BS/BV,Tb.Sp and Ct.BS/BV (P ＜0.01) in p75NTR-/-mice than in p75NTR+/+ mice.Calcein double fluorescent labeling showed that the MAR of the femur was significantly lower in in p75NTR-/-mice (P ＜ 0.01).PCR and Western blotting results showed significantly decreased expressions of Runx2 and ALP in the femurs of p75NTR-/-mice as compared with those in p75NTR+/+ mice (P ＜ 0.01).Conclusion Knocking out p75NTR suppresses mineralization in the femoral bone of mice.