INTEGRIN-EXTRACELLULAR MATRIX INTERACTIONS AND OSTEOBLAST DIFFERENTIATION

这项建议的总体目标是理解信号的作用 由细胞-细胞外基质(ECM)相互作用所致 成骨细胞的分化。相当多的数据支持这样的观点 成骨细胞系来源于多潜能间充质干细胞。 也具有形成其他结缔组织细胞的能力的细胞 类型。最近已经建立了几个多潜能细胞系 在体外可以分化为具有成骨细胞的细胞 特征，给予适当的刺激。最近的 特征性大鼠C26成骨细胞系表达极低水平 成骨细胞分化的早期标志，如碱性 磷酸酶，并在汇合处形成肌管。然而，C26细胞可以 被刺激表现出分化的成骨细胞表型 通过在I型胶原凝胶中培养或暴露于BMP-2，一种类似转化生长因子的β-BMP 生长因子。根据这些数据，需要检验的假设是 整合素成员介导的特异性细胞-ECM相互作用 细胞外基质受体家族在促进成骨细胞中发挥关键作用 差异化。一种可能发生这种情况的机制预测 细胞外基质配体通过其整合素受体调节转化生长因子-1的表达 类贝塔生长因子。此外，整合素-ECM相互作用和 转化生长因子-β样生长因子可能起协同或协同作用 在成骨细胞分化中。目前，人们对此知之甚少 细胞表面ECM受体在临界状态下表达的特性 OB分化的各个阶段，或者说关于他们在 矩阵。此外，这种细胞-细胞外基质相互作用的机制 可能暗示间充质前体细胞沿 成骨途径和保持稳定的成骨细胞表型是 人们对此知之甚少。这项建议是为了增进理解 这些重要领域。具体地说，我们将：1)描述 C26细胞对某些细胞外基质成分的成骨反应 优化ECM诱导C26细胞向成骨细胞分化的目标； 2)检验ECM与特定变量之间相互作用的假设 整合素受体是成骨细胞分化所必需的；3) 确定特定的整合素-ECM相互作用是否调节 转化生长因子-β在成骨细胞中的表达 4)确定选定的转化生长因子-β成员是否 超家族和ECM成分协同作用促进 C26细胞向成骨细胞分化；5)检验假设 特征性成骨细胞外基质的蓄积和稳定 涉及基质金属蛋白酶及其抑制物的调节 特定的整合素-ECM相互作用。更好地理解 成骨细胞分化的调控机制应该导致 致力于开发更有效的修复材料 因衰老、关节炎、手术、创伤而导致的骨骼缺陷 和先天缺陷。

The overall goal of this proposal is to understand the role of signals resulting from cell-extracellular matrix (ECM) interactions in the differentiation of osteoblasts. Considerable data support the idea that the osteoblast lineage is derived from a multipotential mesenchymal stem cell that also has the capacity to form other connective tissue cell types. Several multipotential cell lines have recently been established that can differentiate in vitro into cells with osteoblastic characteristics, given the appropriate stimulus. The recently characterized rat C26 osteoblastic cell line expresses very low levels of early markers of osteoblastic differentiation, such as alkaline phosphatase, and forms myotubes at confluence. However, C26 cells can be stimulated to exhibit a differentiated osteoblastic phenotype either by culture in type I collagen gels or exposure to BMP-2, a TGF-beta-like growth factor. Based on these data, the hypothesis to be tested is the specific cell-ECM interactions, mediated by members of the integrin family of ECM receptors, play a critical role in promoting osteoblastic differentiation. One mechanism by which this might occur predicts that ECM ligands, via their integrin receptors, regulate expression of TGF- beta-like growth factors. Alternatively integrin-ECM interactions and TGF-beta-like growth factors might play a cooperative or synergistic role in osteoblastic differentiation. At present, little is known about the identities of specific cell surface ECM receptors expressed at critical stages in the differentiation of OB, or about their targets in the matrix. In addition, the mechanisms by which such cell-ECM interactions might signal mesenchymal precursors to differentiate along the osteoblastic pathway and to maintain a stable osteoblastic phenotype are poorly understood. This proposal is designed to increase understanding of these important areas. Specifically, we will: 1) Characterize the osteogenic response of C26 cells to selected ECM constituents, with the goal of optimizing ECM-induced osteoblastic differentiation of C26 cells; 2) test the hypothesis that interactions between ECM and specific integrin receptors are required for osteoblastic differentiation; 3) determine whether particular integrin-ECM interactions regulate expression of TGF-beta-like growth factors during osteoblastic differentiation; 4) determine whether selected members of the TGF-beta superfamily and ECM constituents act synergistically to promote osteoblastic differentiation of C26 cells; 5) test the hypothesis that accumulation and stabilization of the characteristic osteoblastic ECM involves regulation of matrix-metalloproteinases and their inhibitors by specific integrin-ECM interactions. Greater understanding of the mechanisms by which osteoblast differentiation is regulated should lead to development of more effective materials for the restoration of skeletal deficiencies resulting from aging, arthritis, surgery, trauma and congenital defects.