Sequential Variations in the Content of Bone Marrow Colony-forming Cells in Individual Patients with Aplastic Anemia Before and After Immunosuppressive Therapy

Abstract

Previous studies have shown that the levels of hematopoietic progenitor cells (colony-forming cells; CFC) are drastically reduced in the vast majority of patients with aplastic anemia (AA). This has been observed both in patients before and after immunosuppressive therapy. In those studies, however, both groups of patients were usually formed by different individuals, thus it was not possible to follow the kinetics of such cells in each particular patient. In the present study, we have determined the content of myeloid and erythroid CFC in individual AA patients before and after therapy. Treated patients were studied at two different times (8–18 months apart) to detect any possible variations due to the ongoing treatment. At diagnosis, the levels of both myeloid and erythroid CFC were drastically reduced, as compared to normal bone marrow, in all the patients studied. This correlated with very low levels of leukocytes and hemoglobin in circulation. After the patients entered an immunosuppressive treatment, all of them showed significant increments in their CFC levels, and this correlated with increments in their hematological parameters in peripheral blood. However, in most patients CFC levels were still below the normal range. When the second sample after treatment was obtained, great variations in CFC numbers were observed. In terms of erythroid CFC levels, a further increase was seen in most patients, and this correlated with a further increase in hemoglobin levels. In contrasts, the levels of myeloid CFC were increased in only some of the patients, whereas in others, significant reductions were evident. Interestingly, in this latter group of patients, CFC never reached the levels observed before treatment. Our results indicate that, in a significant proportion of patients, a common pattern seems to exist. That is to say, low CFC numbers are present before treatment; an increase in the numbers of such cells results as an effect of the immunosuppressive therapy and further variations in CFC numbers (within individual limits that may differ significantly from one patient to another) take place as long as the treatment continues. Finally, we observed a correlation between CFC levels and the clinical status of the patients, i.e., those patients that showed a complete or a partial response to treatment showed higher levels of both myeloid and erythroid CFC than those patients that did not respond to therapy.

Keywords:

• Aplastic anemia
• colony-forming cells
• hematopoiesis
• in vitro culture