Extracellular matrix control mesenchymal stem cell fate

骨髓的间充质干细胞（MSC）复制以产生相同的子代干细胞， 可以分化成许多不同的细胞类型，包括成骨细胞。然而，MSC失去了其独特的 当在组织培养塑料上培养时，这表明骨髓的一个重要特征 在这样的培养系统中缺少有利于保持干细胞特性的微环境-- 这种情况损害了MSC的研究并限制了其治疗潜力。在其他组织中， 细胞外基质（ECM）通过调控干细胞的生长， 接触生长因子。还已知ECM的蛋白聚糖组分双糖链蛋白聚糖（biglycan）在ECM中起作用。 在MSC号码和功能的维护中发挥重要作用。初步研究表明， 在由鼠骨髓来源的基质细胞制成的无细胞ECM上的MSC保留了它们的干细胞特性， 包括自我更新的能力，维持未分化的状态，以及对 外源性BMP-2的促成骨细胞生成作用。这一发现可以解释的证据表明，ECM 隔离由基质细胞分泌的内源性BMP-2。上述意见构成了 假设骨髓基质细胞产生的ECM特异性地支配MSC的能力， 自我更新和分化成一个特定的谱系，至少部分，通过调节细胞暴露于因子 控制它们的复制和分化。提出实验来识别主要的胶原蛋白， 应用免疫组织化学方法检测小鼠骨髓基质细胞衍生的ECM的粘附蛋白和蛋白聚糖组分 免疫染色和共聚焦显微镜;并确定基质细胞衍生的ECM是否是独特的 保持MSC特性的能力。此外，促成骨细胞生成因子的量，包括 将测定基质细胞来源的ECM中的IGF-1、TGF-β、PDGF、VEGF和BMP-2; 将研究双糖链聚糖缺陷对ECM中这些生长因子水平的影响。最后 关于在该ECM上生长的MSC是否保留其干细胞特性的问题将在体内进行测试， 移植到免疫缺陷小鼠中。这些研究将为调查年龄是否- 相关的骨丢失部分是由于骨ECM的改变引起的异常MSC行为 骨髓

Mesenchymal stem cells (MSCs) of the bone marrow replicate to produce identical daughter stem cells and can differentiate into many different cell types inculding osteoblasts. However, MSCs lose their unique properties when cultured on tissue culture plastic. This indicates that a critical feature of the marrow microenvironment that facilitates retention of stem cell properties is missing in such culture systems - a situation that impairs the study of MSCs and limits their therapeutic potential. In other tissues, the extracellular matrix (ECM) plays an important role in controlling stem cell behavior by governing their exposure to growth factors. It is also known that a proteoglycan component of the ECM, biglycan, plays an important role in the maintenance of MSC number and function. Preliminary studies indicated that culture of MSCs on a cell-free ECM made by murine marrow-derived stromal cells preserved their stem cell properties, including the capacity to self-renew, the maintenance of an undifferentiated state, and responsiveness to the pro-osteoblastogenic effect of exogenous BMP-2. This finding may be explained by evidence that the ECM sequestered endogenous BMP-2 secreted by the stromal cells. The above observations form the basis of the hypothesis that the ECM made by marrow stromal cells specifically governs the ability of MSCs to both self-renew and differentiate into a particular lineage, at least in part, by regulating exposure of cells to factors that control their replication and differentiation. Experiments are proposed to identify the principal collagen, adhesion protein and proteoglycan components of murine marrow stromal cell-derived ECM using immunostaining and confocal microscopy; and to determine whether the stromal cell-derived ECM is unique in its ability to preserve MSC properties. In addition, the amount of pro-osteoblastogenic factors, including IGF-I, TGF-(3, PDGF, VEGF, and BMP-2, in the stromal cell-derived ECM will be determined; and the impact of biglycan deficiency on the level of these growth factors in this ECM will be investigated. Finally, the question of whether MSCs grown on this ECM retain their stem cell properties will be tested in vivo following transplantation into immunodeficient mice. These studies will set the stage for investigating whether age- related bone loss is due in part to aberrant MSC behavior caused by alteration in the ECM of the bone marrow.