Hematopoietic Differentiation of Human Embryonic Stem Cells in Vitro : Comparison of Three Cell Lines

Human embryonic stem cells (hES) isolated from the inner cell mass of a blastocyst have the ability to self renew indefinitely while maintaining their pluripotency to differentiate into multiple cell lineages. Therefore, hES represent an important source of cells for perspective cell therapies and serve as an essential tool for fundamental research, specifically for understanding pathophysiological mechanisms of human diseases for the development of novel pharmacological drugs. The generation of hematopoietic stem cells from hES may serve as an alternative source of cells for hematopoietic reconstitution following bone marrow transplantation and an interesting approach to understand early stages of hematopoietic development which are difficult to study in human embryos. Using two different methods, we have differentiated three hES cell lines (SA01, H1 and H9) into hematopoietic cells by generating embryoid bodies and co-culturing on the murine Op9 cell line. In both experimental approaches, we obtain cells expressing CD34 and when cultured in hematopoietic conditions, SA01 and H1 cell lines differentiate into various hematopoietic lineages as demonstrated by BFU-E, CFU-GM and CFU-GEMM colony formation, whereas H9 have almost exclusively granulo-macrophage differentiation. Cells composing these hematopoietic colonies express CD45, CD11b, CD31, CD41 and CD235 and staining with May Grundwald-Giemsa demonstrate neutrophil and erythrocyte morphology. These results demonstrate the capacity of hES to differentiate into mature hematopoietic cells in vitro. Nevertheless, there exist some quantitative and qualitative differences about hematopoietic differentiation between the hES cell lines used. However, we still have to evaluate their capacity to reconstitute hematopoiesis in vivo in an immune deficient mouse model. We will also be interested in developing in vitro methods to expand these hematopoietic precursor cells derived from hES which may be used as a viable source for future cell therapy.