Analysis of the mechanism for organogenesis in mouse embryo and its application to therapeutic transplantation to human fetus

在本项目中，我们根据小鼠胚胎造血显示了以下结果。(1)小鼠胚胎发育过程中，卵黄囊（YS）卵黄囊（dpc）的原始造血与成人骨髓的最终造血具有不同的巨核细胞生成。(2) 10.5 dpc小鼠胚胎主动脉-性腺-中肾（AGM）区基质细胞可支持终代造血中造血干细胞（HSC）的发育。(3) 10.5 dpc小鼠胚胎中来自AGM区的基质细胞，在8.0 dpc时，在YS与胚胎没有血管连接的情况下，不仅可以刺激AGM区，还可以刺激YS产生最终的造血。(4)将8.25 dpc小鼠YS移植到同阶段供体胚胎的YS上，形成YS-YS嵌合胚胎。嵌合胚胎孵育66小时后，我们在嵌合体中鉴定出来自供体YS的B细胞，这表明小鼠胚胎发生中至少有一部分最终造血是由YS产生的。(5)基质细胞也能够支持人胎儿造血源性脐带血造血干细胞的发育。(6)在小鼠胎儿和新生儿中，c-Kit+ HSC上表达CD34，但随着年龄的增长，CD34在HSC上的表达减少，在10周龄以上的小鼠中，大部分HSC都包含在CD34阴性部分。这些结果对再生医学的进一步发展和哺乳动物器官发生的分析具有重要意义。

In this project, we indicated the following results according mouse embryonic hematopoiesis.(1)In mouse embryogenesis, the primitive hematopoiesis in 7.5 days postcoitum (dpc) yolk sac (YS) has megakryocytopoiesis different from that of the definitive hematopoiesis in adult bone marrow.(2)Stromal cells derived from aorta-gonad-mesonephros (AGM) region in 10.5 dpc mouse embryo can support the development of hematopoietic stem cells (HSC) in the definitive hematopoiesis.(3)The Stromal cells from AGM region in 10.5 dpc mouse embryo can stimulate the generation of definitive hematopoiesis from not only AGM region but also YS at 8.0 dpc, a time when YS and embryo are not connected by blood vessels.(4)8.25 dpc mouse YS was engrafted upon YS of donor embryo at the same stage to make YS-YS chimeric embryo. After the incubation of the chimeric embryo for 66 hours, we identified B cells originated from donor YS in the chimera, suggesting that a part of definitive hematopoiesis at least is generated from YS in mouse embryogenesis.(5) The stromal cells are also capable of supporting the development of cord blood HSC derived from human fetal hematopopiesis.(6) While CD34 is expressed on c-Kit+ HSC in mouse fetuses and neonates, the expression on HSC decreased with aging, and in mice older than 10 weeks, most of HSC are included in CD34-negative fraction.These results are useful for the further development of regenerative medicine, and the analysis of mammalian organogenesis.