Differential Hematopoietic Supportive Potential and Gene Expression of Stroma Cell Lines from Midgestation Mouse Placenta and Adult Bone Marrow

Abstract

During mouse embryogenesis, hematopoietic development takes place in several distinct anatomic locations. The microenvironment of different hematopoietic organs plays an important role in the proliferation and maturation of the hematopoietic cells. We hypothesized that fetal stromal cells would be distinct to adult bone marrow (BM)-derived stromal cells because the BM contributes mainly to the homeostasis of hematopoietic stem cells (HSCs), while extensive expansion of HSCs occurs during fetal development. Here we report the establishment of stromal cell lines from fetal hematopoietic organs, namely aorta-gonad-mesonephros (AGM), midgestation placenta (PL), and fetal liver (FL) together with adult bone marrow (BM). The growth patterns and hematopoietic supportive potential were studied. Their phenotypic and molecular gene expression profiles were also determined. Stromal cell lines from each tissue were able to support cobblestone area formation of BM c-Kit+Sca-1+ hematopoietic cells: 22 (22/47) from AGM, three (3/4) from PL, three (3/4) from FL, and three (3/3) from BM. There were similar levels of expansion of total mononuclear cells (TMNs) when HSCs were cocultured with fetal stroma and adult BM stroma. However, PL-derived stromal cells supported higher levels of generation of colony-forming progenitor cell (CFU-C), indicated by more colonies and colonies with significantly larger size. Flow cytometric analysis of the PL1 cells demonstrated a phenotype of CD45-, CD105+, Sca-1+, CD34+, and CD49d+, compared to adult BM1 cells, which were CD45-, CD105+, Sca-1+, CD34-, and CD49d-. Using Affymetrix microarray analysis, we identified that genes specifically express in endothelial cells, such as Tie1, Tek, Kdr, Flt4, Emcn, Pecam1, Icam2, Cdh5, Esam1, Prom1, Cd34, and Sele were highly expressed in stroma PL1, consistent with an endothelial phenotype, while BM1 expressed a mesenchymal stromal phenotype. In summary, these data demonstrate distinct characteristics of stromal cells that provide insights into the microenvironmental control of HSCs.