Erythropoiesis in murine long-term marrow cultures following transfer of the erythropoietin cDNA into marrow stromal cells

Long-term bone marrow cultures (LTMC) have provided a useful in vitro system to study stem cell self-renewal and myeloid differentiation. However, standard murine LTMC are devoid of erythroid differentiation within 2 weeks of establishment. In an attempt to develop a model system to study erythropoiesis in vitro, we have used a recombinant retrovirus vector to transfer the erythropoietin cDNA into stromal cells making up the hematopoietic microenvironment of murine LTMC. Three weeks after infection, erythroid differentiation was evident macroscopically, with clumps of hemoglobinized red blood cells present in the infected cultures. Hemoglobinization was confirmed by benzidine staining of nonadherent cells, which showed that up to 70% of nucleated cells were benzidine positive. In combination with LTMC, the use of recombinant retrovirus vectors to transfer growth factor genes may provide useful models to study the interactions of hematopoietic stem cells, hematopoietic microenvironment, and growth factors in vitro.