Klein-Nulend J, Roelofsen J, Sterck J G, Semeins C M, Burger E H
Department of Oral Cell Biology, ACTA-Free University, Amsterdam, The Netherlands.
J Cell Physiol. 1995 Apr;163(1):115-9. doi: 10.1002/jcp.1041630113.
We have shown earlier that mechanical stimulation by intermittent hydrostatic compression (IHC) inhibits bone resorption and stimulates bone formation in cultured fetal mouse calvariae (Klein-Nulend et al., 1986, Arthritis Rheum., 29: 1002-1009). The production of soluble bone factors by such calvariae is also modified (Klein-Nulend et al., 1993, Cell Tissue Res., 271:513-517). Transforming growth factor-beta (TGF-beta) is an important local regulator of bone metabolism and is produced by osteoblasts. In this study, the release of TGF-beta activity as a result of mechanical stress was examined in organ cultures of neonatal mouse calvariae, in primary cultures of calvariae-derived osteoprogenitor (OPR) cells, and in more differentiated osteoblastic (OB) cells. Whole calvariae and calvariae-derived cells were cultured in the presence or absence of IHC for 1-7 days and medium concentrations of active as well as total TGF-beta were measured using a bioassay. IHC (maximum 13 kPa, maximal pressure rate 32.5 kPa/sec) was generated by intermittently (0.3 Hz) compressing the gas phase above the cultures. We found that mechanical loading by IHC stimulated the release of TGF-beta activity from cultured calvariae by twofold after 1 day. IHC also stimulated the release of TGF-beta activity from calvariae-derived cells after 1 and 3 days. The absolute amounts of TGF-beta activity released were lower in OPR cells than in OB cells, but the stimulatory effect of IHC was greater in OPR cells. Total TGF-beta (active and bound) released into the medium was not affected by IHC. IHC did not change the dry weight of the organ cultures, nor the DNA or protein content of the cell cultures. These data show that mechanical perturbation of bone cells, particularly OPR cells, enhances the activation of released TGF-beta. We conclude that modulation of TGF-beta metabolism may be part of the response of bone tissue to mechanical stress.
我们之前已经表明，间歇性流体静压（IHC）产生的机械刺激可抑制培养的胎鼠颅骨中的骨吸收并刺激骨形成（Klein-Nulend等人，1986年，《关节炎与风湿病》，29：1002 - 1009）。此类颅骨产生的可溶性骨因子也会发生改变（Klein-Nulend等人，1993年，《细胞与组织研究》，271：513 - 517）。转化生长因子-β（TGF-β）是骨代谢的重要局部调节因子，由成骨细胞产生。在本研究中，我们在新生小鼠颅骨的器官培养物、颅骨来源的骨祖细胞（OPR）原代培养物以及分化程度更高的成骨细胞（OB）中，检测了机械应力导致的TGF-β活性释放情况。完整的颅骨和颅骨来源的细胞在有或无IHC的情况下培养1 - 7天，并使用生物测定法测量培养基中活性TGF-β以及总TGF-β的浓度。通过间歇性（0.3 Hz）压缩培养物上方的气相来产生IHC（最大13 kPa，最大压力速率32.5 kPa/秒）。我们发现，IHC施加的机械负荷在1天后使培养的颅骨释放的TGF-β活性增加了两倍。IHC在1天和3天后也刺激了颅骨来源细胞释放TGF-β活性。OPR细胞释放出TGF-β活性的绝对量低于OB细胞，但IHC对OPR细胞的刺激作用更大。释放到培养基中的总TGF-β（活性和结合型）不受IHC影响。IHC未改变器官培养物的干重，也未改变细胞培养物的DNA或蛋白质含量。这些数据表明，骨细胞，尤其是OPR细胞的机械扰动增强了释放的TGF-β的活化。我们得出结论，TGF-β代谢的调节可能是骨组织对机械应力反应的一部分。
