Fibronectin regulates calvarial osteoblast differentiation.
Fibronectin regulates calvarial osteoblast differentiation.
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发表时间：
1996-06
影响因子：
4
通讯作者：
Amr M. Moursi;C. Damsky;Jonathan Lull;Jonathan Lull;D. Zimmerman;Stephen B. Doty;S. Aota;
中科院分区：
文献类型：
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作者：
Amr M. Moursi;C. Damsky;Jonathan Lull;Jonathan Lull;D. Zimmerman;Stephen B. Doty;S. Aota;
分化成骨细胞分泌的纤维连接蛋白及其在成骨部位的积聚表明纤维连接蛋白参与了骨的形成。为了直接测试这一点，我们确定了纤维连接蛋白与细胞的相互作用是否调节了培养的胎鼠颅骨成骨细胞的渐进分化。α5整合素亚单位、纤维连接蛋白、骨桥蛋白(骨涎蛋白I)和骨钙素(骨GLA蛋白)在胎鼠颅骨和培养成骨细胞形成的矿化骨样结节中的空间分布相似。在融合培养中加入抗纤维连接蛋白抗体可将随后结节的形成减少到控制值的10%以下，这表明纤维连接蛋白是正常结节形态形成所必需的。抗纤维连接蛋白抗体选择性地抑制成骨细胞分化相关基因的mRNA的稳定表达；碱性磷酸酶和骨钙素的mRNA水平被抑制，而纤维连接蛋白、I型胶原和骨桥蛋白不受影响。为了确定纤维连接蛋白的功能相关结构域，我们用可溶性纤维连接蛋白片段和多肽处理细胞。含有Arg-Gly-Asp(RGD)序列的细胞结合纤维连接蛋白片段(类型III重复6-10)阻止了结节的启动和成熟，无论它们是否包含功能协同位点。相反，添加含有RGD的多肽GRGDSPK本身并不抑制根瘤的形成，尽管它确实阻止了根瘤的成熟。因此，除了RGD序列外，大的细胞结合片段的其他特征也有助于纤维连接蛋白的全部成骨作用。在去掉抗纤维连接蛋白抗体或GRGDSPK多肽后，结节形成和成骨细胞分化恢复，表明这种抑制是可逆的，处理没有细胞毒性。在中央细胞结合域之外，来自IIICS区域的多肽和针对N端的抗体不能抑制结节的形成。我们得出结论，成骨细胞在分化早期与内源性纤维连接蛋白的中央细胞结合域相互作用，这些相互作用调节正常的形态发生和基因表达。
The secretion of fibronectin by differentiating osteoblasts and its accumulation at sites of osteogenesis suggest that fibronectin participates in bone formation. To test this directly, we determined whether fibronectin-cell interactions regulate progressive differentiation of cultured fetal rat calvarial osteoblasts. Spatial distributions of alpha 5 integrin subunit, fibronectin, osteopontin (bone sialoprotein I) and osteocalcin (bone Gla-protein) were similar in fetal rat calvaria and mineralized, bone-like nodules formed by cultured osteoblasts. Addition of anti-fibronectin antibodies to cultures at confluence reduced subsequent formation of nodules to less than 10% of control values, showing that fibronectin is required for normal nodule morphogenesis. Anti-fibronectin antibodies selectively inhibited steady-state expression of mRNA for genes associated with osteoblast differentiation; mRNA levels for alkaline phosphatase and osteocalcin were suppressed, whereas fibronectin, type I collagen and osteopontin were unaffected. To identify functionally relevant domains of fibronectin, we treated cells with soluble fibronectin fragments and peptides. Cell-binding fibronectin fragments (type III repeats 6-10) containing the Arg-Gly-Asp (RGD) sequence blocked both nodule initiation and maturation, whether or not they contained a functional synergy site. In contrast, addition of the RGD-containing peptide GRGDSPK alone did not inhibit nodule initiation, although it did block nodule maturation. Thus, in addition to the RGD sequence, other features of the large cell-binding fragments contribute to the full osteogenic effects of fibronectin. Nodule formation and osteoblast differentiation resumed after anti-fibronectin antibodies or GRGDSPK peptides were omitted from the media, showing that the inhibition was reversible and the treatments were not cytotoxic. Outside the central cell-binding domain, peptides from the IIICS region and antibodies to the N terminus did not inhibit nodule formation. We conclude that osteoblasts interact with the central cell-binding domain of endogenously produced fibronectin during early stages of differentiation, and that these interactions regulate both normal morphogenesis and gene expression.