Directing the Fate of Cells to Myogenic Lineages

描述(申请人提供)：基于细胞的再生医学是发育生物学的自然延伸。胚胎干细胞(ES细胞)形成整个胚胎，并具有修复成人病变组织的潜力。细胞分化之前有规范，这是一个将这些多能细胞限制到特定谱系的过程。组织再生依赖于特定于所需谱系的干细胞并促进其分化的因子的可用性。鉴于患病组织的环境不太可能与发育中的胚胎的环境相同，干细胞可能需要在植入之前或期间进行“调理”。指导这项研究的总体假设是：(1)多能干细胞的命运可以由先前致力于特定谱系的干细胞在体外和体内决定，(2)诱导过程是由可溶性因素和细胞-细胞黏附的组合介导的。本项目建立在我们已发表的观察结果的基础上，体内表达MyoD mRNA的鸡上皮细胞通过释放一种抑制骨形态发生蛋白信号通路并促进N-钙粘附素表达的因子(S)，在体外向骨骼肌谱系招募多能上皮细胞。在没有MyoD阳性的上皮细胞的情况下，更多的多能细胞形成心肌。肌肉分化中的一个关键事件是E-钙粘附素的下调。初步研究表明，切除上胚层中的MyoD阳性细胞会导致器官通过腹侧体壁突出，并导致体节中骨骼肌的减少。本研究旨在探讨MyoD阳性上皮细胞在体内促进骨骼肌发生的机制，并确定在体外调节钙粘附素转换和细胞向骨骼肌谱系和心肌谱系募集的因素。这些实验将集中在Wnt、7GF-/3、BMP和BMP抑制物家族成员在这些过程中的作用。这些研究可能揭示体内调节骨骼肌生成的新机制，并导致干细胞条件处理方法的发展，以确保干细胞在植入疾病组织之前偏向于沿着所需的途径分化并表达适当的细胞-细胞黏附蛋白。

DESCRIPTION (provided by applicant): Cell-based regenerative medicine is a natural extension of developmental biology. Embryonic stem cells (ES cells) give rise to the entire embryo and have the potential to repair diseased tissues in the adult. Cell differentiation is preceded by specification, a process that restricts these pluripotent cells to a particular lineage. Tissue regeneration is dependent on the availability of factors that specify stem cells to the desired lineage and promote their differentiation. Given that the environment of diseased tissues is unlikely to be the same as that of the developing embryo, stem cells may require "conditioning" prior to or during implantation. The overall hypotheses guiding the proposed research are: (1) the fate of pluripotent stem cells can be directed in vitro and in vivo by stem cells previously committed to a particular lineage, and (2) the induction process is mediated by a combination of soluble factors and cell-cell adhesions. This project builds on our published observations that chick epiblast cells expressing MyoD mRNA in vivo recruit pluripotent epiblast cells to the skeletal muscle lineage in vitro by releasing a factor(s) that inhibits the bone morphogenetic protein (BMP) signaling pathway and promotes the expression of N-cadherin. In the absence of MyoD positive epiblast cells, more pluripotent cells form cardiac muscle. A key event in muscle differentiation is the downregulation of E-cadherin. Preliminary studies demonstrate that ablation of MyoD positive cells in the epiblast results in herniation of the organs through the ventral body wall and a reduction in skeletal muscle in the somites. The proposed studies are designed to explore the mechanism whereby MyoD positive epiblast cells promote skeletal myogenesis in the somites in vivo, and to identify the factors that regulate cadherin switching and recruitment of cells to the skeletal and cardiac muscle lineages in vitro. The experiments will focus on the roles of Wnt, 7GF-/3, BMP, and BMP inhibitor family members in these processes. The proposed studies may reveal a novel mechanism for regulating skeletal myogenesis in vivo, and lead to the development of methods for conditioning stem cells to ensure that they are biased to differentiate along the desired pathway and express the appropriate cell-cell adhesion proteins prior to their implantation into diseased tissues.