Self-Renewing Presomitic Mesoderm Progenitor Lines Reprogrammed from human urine cells [Passage bulk RNA-seq]. Self-Renewing Presomitic Mesoderm Progenitor Lines Reprogrammed from human urine cells [Passage bulk RNA-seq]

Vertebrate formation is the defining feature of all vertebrates1,2. Yet, each vertebrate species appears to have a unique timing mechanism for forming somites along the vertebral column3-5. Human vertebrate formation remains poorly studied due to technical and ethical limitations. Here we report the generation of self-renewing stem cells with characteristic presomitic mesoderm (PSM) features by reprogramming epithelial cells isolated from human urine. These induced expandable presomitic mesoderm progenitor cells (UiPSM) proliferated extensively for more than 30 passages in chemically defined conditions, robustly producing 1040 UiPSM cells. UiPSM established presomitic mesodermal transcription profile, not detected pluripotency, ectoderm and endoderm related genes. UiPSM developed into presomitic mesodermal lineage cells, such as skeletal muscle cells(skm), osteoblast and chrondroblast cells in vivo and vitro, when transplanted UiPSM derived human skm cells in muscle injury model, the skm cells can survive in vivo and contribute to muscle regeneration up to one month. Thus, UiPSM is a powerful system to study human somite development and provide strategies for regenerative medicine in musculoskeletal system Overall design: Building library and sequencing different passages of UiPSM

脊椎形成（Vertebrate formation）是所有脊椎动物的标志性特征1,2。然而，不同脊椎动物物种沿脊柱生成体节的时序调控机制各不相同3-5。由于技术与伦理层面的限制，人类脊椎形成的相关研究仍较为匮乏。本研究通过对从人类尿液中分离的上皮细胞进行重编程，成功获得了具备典型前体节中胚层（presomitic mesoderm, PSM）特征的自我更新型干细胞。此类诱导可扩增前体节中胚层祖细胞（induced expandable presomitic mesoderm progenitor cells, UiPSM）可在化学成分明确的培养体系中大量增殖，传代超过30次，最终可稳定获得10^40个UiPSM细胞。UiPSM呈现典型的前体节中胚层转录组特征，未检测到多能性、外胚层及内胚层相关基因的表达。UiPSM可在体内外分化为前体节中胚层谱系细胞，包括骨骼肌细胞（skeletal muscle cells, skm）、成骨细胞及成软骨细胞。将UiPSM诱导产生的人类骨骼肌细胞移植至肌肉损伤模型后，这些细胞可在体内存活，并参与肌肉再生长达1个月之久。综上，UiPSM是研究人类体节发育的理想模型，同时可为肌肉骨骼系统的再生医学研究提供新策略。整体实验设计：构建文库并对不同传代次数的UiPSM进行测序。