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

本课题通过对小鼠胚胎造血的研究发现：(1)在小鼠胚胎发育过程中，7.5日龄卵黄囊(DPC)原始造血区的原始造血细胞具有不同于成人骨髓定向造血区的巨核细胞造血活性。(2)10.5DPC小鼠胚胎的AGM区基质细胞可支持定向造血性造血干细胞(HSC)的发育。(3)10.5DPC小鼠胚胎AGM区的基质细胞不仅能刺激AGM区的定向造血细胞的生成，还能刺激8.0DPC的YS区定向造血区的定向造血细胞的生成将8.25DPC小鼠YS移植到供体胚胎的YS上，制成YS-YS嵌合胚胎。在嵌合胚胎孵育66小时后，我们在嵌合体中发现了来自供者YS的B细胞，这表明在小鼠胚胎发生中至少有一部分确定的造血来自YS。(5)基质细胞也能够支持人胎儿造血来源的脐血HSC的发育。(6)虽然CD34在小鼠胚胎和新生儿的c-Kit+HSC上表达，但HSC上的表达随着年龄的增长而减少，在10周以上的小鼠中，大多数HSC都包括在CD34阴性的组分中。这一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.