Identification and Characterization of the Presomitic Mesoderm Progenitor

描述(申请人提供)：身体中胚层组织的疾病，包括伤口愈合、关节炎、骨质疏松症和肌肉萎缩疾病，影响着全球数百万人。如果从容易获得的、患者匹配的干细胞中有效地获得中胚层组织的现有障碍能够被克服，这些疾病就可以用基于干细胞的再生医学来治疗。不幸的是，从胚胎干细胞(ESC)和诱导多能干细胞(IPSC)中定向分化中胚层目前仅限于心血管和血液衍生品。用于肌肉、软骨和结缔组织分化的可重复方案，或者更具体地说，那些仅由体细胞前中胚层(PSM)产生的中胚层衍生物，尚未出现。虽然可以从人类胚胎干细胞中获得某些类型的后中胚层细胞，但在这些组织的再生程序可行之前，这些效率(通常为1%)必须得到极大的提高。以前的研究表明，在原始条纹和Hensen‘s结节(PSM-Pr小生境)的交界处存在内源性PSM-Pr细胞。PSM-Pr的后代定植于近轴中胚层并产生体节，体节进而产生胚胎的骨骼肌、软骨和结缔组织。这里描述的工作的主要焦点是识别和详尽地描述组成和维持内源性祖细胞干细胞及其生态位的细胞类型。在这个项目中，我们将(1)确定位于边界的所有单元格类型 评估关键信号通路在维持PSM-Pr和PSM-Pr生态位中的作用。这些目标的成功完成将为体细胞中胚层的产生提供前所未有的洞察力，并使产生临床使用的具有治疗意义的中胚层细胞类型的新方法成为可能。

DESCRIPTION (provided by applicant): Diseases of the mesodermal tissues of the body including wound healing, arthritis, osteoporosis and muscular wasting diseases, affect millions of people across the globe. If existing barriers to the efficient derivation of mesodermal tissues from readily-available, patient-matched stem cells could be overcome, these diseases could be treated with stem cell-based regenerative medicine. Unfortunately, robust directed differentiation of mesoderm from embryonic stem cells (ESC) and induced pluripotent stem cells (IPSC) is currently limited to cardiovascular and blood derivatives. Reproducible protocols for the differentiation of muscle, cartilage, and connective tissues, or more specifically, those mesodermal derivatives produced solely from pre-somitic mesoderm (PSM), have yet to emerge. While it is possible to obtain some cell types of the posterior mesoderm from human ESC, these efficiencies (commonly <1%) must be vastly improved before regenerative procedures for these tissues will be feasible. Previous studies have indicated the presence of an endogenous PSM-progenitor (PSM-Pr) cell located at the border of the primitive streak and Hensen's node (the PSM-Pr niche). Progeny of the PSM-Pr colonize the paraxial mesoderm and give rise to the somites, which in turn produce the skeletal muscle, cartilage, and connective tissue of the embryo. The primary focus of the work described here is to identify and exhaustively characterize the cell types that comprise and maintain the endogenous progenitor stem cell and its niche. In this project we will (1) identify all cell types located in the border region and (2) evaluate the role of key signaling pathways in the maintenance of the PSM-Pr and the PSM-Pr niche. Successful completion of these goals will provide unprecedented insight into the generation of somitic mesoderm and enable novel approaches to the generation of therapeutically relevant mesodermal cell types for clinical use.