Liver sinusoidal endothelial cells promote lymphohematopoietic differentiation from murine embryonic stem cells: role of soluble factors.

Liver sinusoid endothelial cells (LSEC) constitute an in vitro and in vivo microenvironment for the proliferation and differentiation of hematopoietic stem cells (HSC). Previously, we have shown that LSEC support the survival and growth of murine embryonic stem cells (ESC). In this study, we investigated the capacity of LSEC to promote hematopoietic differentiation from the murine ESC cell line, CGR8. Undifferentiated ESC were cultured on LSEC monolayers in the absence of exogenous cytokines. After 10 and 20 days, cells were harvested and examined by their morphology, phenotype and capacity of hematopoietic colony formation. Microscopic observation of LSEC/ESC cocultures showed the presence of cobblestone areas formation, which indicates active hematopoiesis. Morphological analysis of cell from these foci showed the presence of hematopoietic cells at different stages of differentiation. Cells expressing B lymphoid markers (B220 and CD19) were detected by flow cytometry, and clonogenic assays showed the formation of CFU-pre B colonies. Similar results were observed when ESC were cultured with LSEC conditioned media. Myeloid precursors were also detected by the presence of CFU-GM colonies and cells expressing myeloid markers. These results indicate that LSEC provided an in vitro microenvironment mainly for B cell development, but also myeloid differentiation from ESC. Coculture of ESC with LSEC may constitute a very powerful tool to study the mechanisms involved in B cell generation from ESC.