Study of hematopoietic progenitor cells in thalassemia after bone marrow transplantation.

The hematopoietic committed progenitor cells (BFU-E and CFU-GM) in blood and bone marrow were studied in thalassemic patients before and after bone marrow transplantation. Eighteen transplants were performed in 17 patients with thalassemia. Five were homozygous beta-thalassemia and 12 were beta-thalassemia/hemoglobin E disease. The age ranged from 1.2-14 years (median = 3.4 years). The conditioning regimen comprised busulfan 3.5-4 mg/kg/day for 4 days and cyclophosphamide 50 mg/kg/day for 4 days. Cyclosporin in combination with methotrexate were administered post transplant for GVHD prophylaxis. Before transplantation, BFU-E and CFU-GM in the blood of the patients were significantly higher compared with normal (p < 0.05) but were normal in the bone marrow. Only the CFU-GM in the bone marrow of the successful cases after transplantation recovered to the normal level at the first month through the 12th month whereas the BFU-E were low. Both CFU-GM and BFU-E in the blood were lower than normal after follow up to the 12th month. Inspite of the low number of progenitor cells, there was hematological recovery in the blood of the patients. It may be due to the capacity of the hematopoiesis react to stress which could be amplified the differentiation compartment or the shortened-transit time through the stem cell compartment.

Abnormalities of hematopoietic progenitor cells in patients with aplastic anemia after hematologic recovery.

Hematopoietic progenitor cells were studied in 11 patients with aplastic anemia who had hematologic recovery after androgen therapy. The mean numbers of colonies derived from erythroid and granulocyte-macrophage progenitor cells (BFU-E and CFU-GM) were markedly decreased compared to normal controls. Cell-mediated suppression of colony growth as detected by coculture studies was observed in 5 patients; 4 patients for CFU-GM and one for both CFU-GM and BFU-E. It is thus concluded that the pool of hematopoietic stem cells in patients after hematologic recovery is still not fully reconstituted. In addition, this impaired reconstitution appears due in some cases to cell mediated suppression of progenitor colony growth.

Studies on the pathogenesis of aplastic anemia in Thailand: evidence of immune-mediated mechanism.

The pathogenesis of aplastic anemia in Thailand was studied by using in vitro progenitor cells culture. In 37 patients who had active disease, the numbers of colonies derived from erythroid and granulocyte-macrophage progenitor cells (BFU-E and CFU-GM) were markedly decreased both in the blood and bone marrow as compared to normal controls. Co-culture of patients' cells with normal blood cells was performed in order to verify an immunologically mediated mechanism. In 8 of 26 patients, there were very low numbers of colonies both BFU-E and CFU-GM in the blood and bone marrow with significant suppression of colony formation in co-culture. Suppressor cells may have caused the aplasia in these patients. The rest had low colony formation and no suppression in co-culture. These patients may have absent or defective stem cells. None had normal colony formation. Therefore, aplastic anemia in Thailand may result mostly from defects involving the stem cells. Only some patients had cell mediated suppression of hematopoiesis as detected by co-culture.