Huang H, Zettergren L D, Auerbach R
Center for Development Biology, University of Wisconsin, Madison 53706.
Exp Hematol. 1994 Jan;22(1):19-25.
The yolk sac is the first site of hematopoiesis during ontogeny. However, the source of early embryonic hematopoietic stem cells remains unresolved. Early studies have shown that cells obtained from day-8 and -9 extraembryonic yolk sacs can give rise to T cells and myeloid cells, whereas the embryo itself appears to lack such cells. Controversy remains as to whether it is the embryo itself or the extraembryonic yolk sac that contains the initial precursors capable of differentiating into B cells. This study used the approach of enriching hematopoietic stem cells by immunocytoadherence and studying cells isolated from within the embryo itself or from the yolk sac obtained at days 8 and 9 of mouse embryonic development. We report that on day 9, both yolk sac-derived and embryo-derived cells can give rise to B cells and myeloid cells in vitro. On day 8, however, cells isolated from the yolk sac but not from the embryo produce myeloid colonies in vitro; neither source of stem cells generates B cells. Our study suggests that myeloid precursors migrate from yolk sac to embryo earlier than has previously been reported but that the origin for B cell precursors remains to be determined.
卵黄囊是个体发育过程中造血的第一个部位。然而，早期胚胎造血干细胞的来源仍未明确。早期研究表明，从第8天和第9天的胚外卵黄囊中获取的细胞可分化为T细胞和髓系细胞，而胚胎本身似乎缺乏这类细胞。关于是胚胎本身还是胚外卵黄囊含有能够分化为B细胞的初始前体细胞，仍存在争议。本研究采用免疫细胞黏附法富集造血干细胞，并对从小鼠胚胎发育第8天和第9天获取的胚胎本身或卵黄囊中分离出的细胞进行研究。我们报告，在第9天，卵黄囊来源和胚胎来源的细胞在体外均可分化为B细胞和髓系细胞。然而，在第8天，从卵黄囊中而非胚胎中分离出的细胞在体外可产生髓系集落；两种干细胞来源均不能产生B细胞。我们的研究表明，髓系前体细胞从卵黄囊迁移至胚胎的时间比先前报道的更早，但B细胞前体细胞的来源仍有待确定。
