Pathophysiologic Study of Aplastic Anemia by Long-term Bone Marrow Cultures

Hong, Dae Sik; Lee, Nam Su; Lee, Kyu Tack; Park, Sung Kyu; Baick, Seung Ho; Won, Jong Ho; Park, Hee Sook

Abstract

BACKGROUND: Several mechanisms have been proposed to account for bone marrow failure in aplastic anemia (AA), including deficiency in hematopoietic stem cells, a secondary stem cell defect involving immune regulation and defective marrow stroma, or microenvironment. We investigated the pathophysiology of AA through long-term bone marrow cultures (LTBMCs) using bone marrrow of AA patients before treatment and of patients responded to immunosuppressive therapy with anti-thymocyte globulin (ATG) and/or cyclosporine.
METHODS
We investigated the hematopoietic defect in severe aplastic anemia (SAA) patients by using long-term bone marrow cultures (LTBMCs). Twenty patients with SAA have been studied. In these patients, 10 had been treated with ATG plus cyclosporine and the remainders were studied before therapy was begun. Subsequent assays of the production of negative-acting hematopoietic cytokines (TNF-alpha, IFN-gamma, MIP-1alpha and TGF-beta) by AA stroma in LTBMCs were performed.
RESULTS
Initial assessment of CD34+ cells, CFU-GM and CFU-MK from LTBMCs in AA demonstrated severely reduced or absent in patients with SAA, even following hematologic recovery with immunosuppressive therapy,when compared with normal controls. Significant difference in concentrations of TNF-alpha, INF-gamma, and MIP-1alpha between the AA and control groups were apparent. Interestingly, the levels of those negative-acting hematopoietic cytokines were decreased in SAA patients receiving immunosuppressive therapy, but not the levels of controls. However, the mean TGF-beta concentrations in the AA patients and normal controls were not significantly different. The percent of CD34+ cells and CFU-MK in bone marrow was lower in SAA patients before immunosuppressive therapy was begun than that in SAA patients receiving immunosuppressive therapy and that in normal controls (mean 0.54+/-0.32% vs 0.96+/-0.32% vs 1.94+/-0.61%).
CONCLUSIONS
These results indicate the presence of a in vitro functional deficiency in the hematopoietic system of patients with AA, including those that achieved partial or complete remission after immunosuppressive treatment, and add to the available evidence for defect of microenvironment with hematopoeitic stem cell in some cases of AA.