Roelofsen J, Klein-Nulend J, Burger E H
Department of Oral Cell Biology, ACTA-Free University, Amsterdam, The Netherlands.
J Biomech. 1995 Dec;28(12):1493-503. doi: 10.1016/0021-9290(95)00097-6.
In a previous study of the cellular mechanism underlaying Wolff's law we showed that mechanical stimulation by intermittent hydrostatic compression (IHC) increases bone formation in cultured fetal mouse calvariae compared to non-stimulated cultures. To test whether mechanical stimuli may modulate bone-specific gene expression, we studied the effect of IHC on alkaline phosphatase (AP) expression and enzyme activity as well as collagen and actin mRNA levels in neonatal mouse calvariae and calvarial bone cells. Two cell populations, one resembling osteoprogenitor (OPR) cells and another resembling osteoblasts (OB) were obtained from calvariae by sequential digestion. IHC was applied by intermittently (0.3 Hz) compressing the gas- phase of a closed culture chamber (peak stress 13kPa, peak stress rate 32.5 kPas-1). In control cultures of calvariae as well as OB and OPR cells, AP activity and AP-, collagen-, and actin-mRNA levels all decreased after one or more days, with the exception of OPR cell collagen expression which increased during culture. IHC treatment upregulated AP, collagen and actin expression and AP activity in calvariae and OB cells, but decreased collagen expression in OPR cells. These results suggest that treatment with IHC promotes the osteoblastic phenotype in bone organ cultures and in osteoblasts. Osteoprogenitor cells seem to react somewhat differently to mechanical stress than osteoblasts. The loss of bone-specific gene expression under control culture conditions, in the absence of mechanical stimuli, suggests that the mechanical environment is important in maintaining the differentiated phenotype of bone cells, and that IHC treatment partially restores this environment in bone cell- and organ cultures.
在先前一项关于沃尔夫定律细胞机制的研究中，我们发现，与未受刺激的培养物相比，间歇性流体静压（IHC）产生的机械刺激可增加培养的胎鼠颅骨中的骨形成。为了测试机械刺激是否可调节骨特异性基因表达，我们研究了IHC对新生小鼠颅骨及颅骨骨细胞中碱性磷酸酶（AP）表达、酶活性以及胶原蛋白和肌动蛋白mRNA水平的影响。通过连续消化从颅骨中获得了两类细胞群体，一类类似于骨祖细胞（OPR），另一类类似于成骨细胞（OB）。通过间歇性（0.3Hz）压缩封闭培养箱的气相来施加IHC（峰值应力13kPa，峰值应力速率32.5kPas-1）。在颅骨以及OB和OPR细胞的对照培养物中，AP活性以及AP、胶原蛋白和肌动蛋白的mRNA水平在一天或多天后均下降，但OPR细胞胶原蛋白表达在培养期间有所增加。IHC处理上调了颅骨和OB细胞中的AP、胶原蛋白和肌动蛋白表达以及AP活性，但降低了OPR细胞中的胶原蛋白表达。这些结果表明，IHC处理可促进骨器官培养物和成骨细胞中的成骨细胞表型。骨祖细胞对机械应力的反应似乎与成骨细胞有所不同。在无机械刺激的对照培养条件下骨特异性基因表达的丧失表明，机械环境对于维持骨细胞的分化表型很重要，并且IHC处理可在骨细胞和器官培养物中部分恢复这种环境。
