Cell Sorting Strategies:
For placentae of E10.0 and E11.0, 80,000 CD34+ cells were isolated by FACS and pooled together with 20,000 CD34- cells at a ratio of 4:1 to enrich hematopoietic and endothelial cells . For placentae of E12.0, about 20,000 CD34+ CD45+ hematopoietic progenitors, 20,000 CD34+ cells and 10,000 CD34- cells were separately isolated, and then pooled together with CD34- cells at a ratio of 2:2:1 to enrich hematopoietic progenitors, hematopoietic and endothelial cells, respectively.