TITLE OF PROJECT : REGULATION OF ERYTHROPOIETIC DIFFERENTIATION OF IMMORTALIZED HEMATOPOIETIC STEM CELLS

为了解骨髓基质细胞对造血的调控机制，从Dexter的长期骨髓培养中获得了2株基质依赖型造血干细胞系。克隆株DFC-a表现出与双能髓系祖细胞相似的表型，DFC-28表现为非常早期的淋巴系祖细胞。与米兰大学的Ottolenghi博士合作，将在GATA-1基因启动子调控下携带SV4O大T抗原基因的转基因小鼠的骨髓细胞培养在基质细胞上，并试图使基质依赖的红系祖细胞永生化。我们发现红系祖细胞在有促红细胞生成素的情况下生长，巨核系祖细胞在有血小板生成素的情况下的生长通过与基质细胞的共培养得到强烈的刺激。这些结果提示，表达GATA-1的造血祖细胞富含巨核细胞和红细胞双能祖细胞(CFU-EMeg)，骨髓基质细胞可能对这些双能祖细胞有刺激信号。

To know the regulatory mechanisms of hematopoiesis by bone marrow stromal cells, 2 stroma-dependent hematopoietic stem-like cell lines were generated from Dexter's long-term bone marrow culture. DFC-a, a clonal isolate, showed the phenotype similar to bipotent myeloid progenitor cells and DFC-28 showed very early lymphoid progenitor cells. All cell lines required direct cell-to-cell contact with stromal cells for their maintenance.In collaboration with Dr.Ottolenghi of Milano University, the bone marrow cells from the transgenic mice with the SV4O large T-antigen gene regulated under the promoter of GATA-1 gene were cultured on the stromal cells and tried to immortalize stroma-dependent erythroid progenitor cell lines. We found that growth of the erythroid progenitor cells in the presence of erythropoietin and megakaryocyte progenitor cells in the presence of thrombopoietin was strongly stimulated by the coculture with the stromal cells. These results suggest that GATA-1 expressing hematopoietic progenitor cells abundantly contain the bi-potent progenitor cells for megakaryocytes and erythrocytes (CFU-EMeg) and the stromal cells in bone marrow may have stimulatory signals for these bi-potent progenitor cells.