Long-term proliferation in vitro of hematopoietic progenitor cells from children with congenital bone marrow failure: effect of rhGM-CSF and rhEPO.

We have characterized the proliferation kinetics of hematopoietic cells in long-term marrow cultures (LTMC) from five normal children and seven children with congenital bone marrow failure (four with Fanconi anemia [FA] and three with congenital pure red cell aplasia [PRCA]). Total nonadherent and adherent cells, as well as nonadherent progenitors, were determined weekly in the presence or in the absence of rhGM-CSF (10 ng/ml) or rhEPO (3 U/ml). As compared to normal LTMC, hematopoiesis was drastically reduced in cultures from FA patients. Myeloid and erythroid progenitor cells reached undetectable levels after only 3 and 1 weeks of culture, respectively. This was observed even in cultures supplemented with rhGM-CSF, in which no response to this cytokine occurred. In LTMC from PRCA children, the growth of erythroid and multipotent progenitors was also drastically reduced. Myelopoiesis, on the other hand, showed normal levels during the first three weeks of culture; however, from week 4, there was a significant decrease in the levels of both progenitor and mature cells, reaching undetectable levels several weeks before normal cells did. Response to rhGM-CSF and rhEPO was transient and deficient. Our results suggest that in FA, alterations at the level of primitive progenitor cells are so severe that myeloid, erythroid and multipotent progenitors are unable to proliferate in LTMC, even in the presence of rhGM-CSF. In patients with PRCA the erythroid arm of hematopoiesis is preferentially affected and addition of rhGM-CSF and/or rhEPO to these cultures had little or no effect on erythroid cell production. Interestingly, myelopoiesis in this culture system was deficient as well and response to rhGM-CSF was defective, suggesting that the myeloid lineage is also altered in congenital PRCA.