Alterations in the progenitor cell population follow recovery from myeloablative therapy and bone marrow transplantation

Abstract

In a previous study we showed that following recovery from bone marrow transplantation (BMT), there are persistent derangements in the clonogenic growth of hematopoietic progenitors and in the microenvironment. To characterize the abnormalities within the precursor cell population, selected BM CD34+ cells from 15 patients in remission from hematological malignancies who had received myeloablative therapy and grafts (eight allogeneic and seven autologous) were tested in dose-response studies with recombinant cytokines. Preconditioning for transplantation was accomplished with fractionated total body irradiation (fTBI) at 12 Gy, cyclophosphamide at 120 mg/kg and fractionated total lymphoid irradiation fTLI at 6 Gy. The median mononuclear cell number infused was 0.9 x 10(8)/kg (SD 0.31). At the time of BMT, the patient's median age was 26 (SD 8.65) years and eight were female. Grafts were studied at a median of 37 (SD 48.43) months from transplantation. The light density marrow population from the patients and controls was monocyte- and T-lymphocyte depleted; CD34+ precursors were then selected with immunomagnetic beads (median 90.2 and 92% blasts) and cultured in the progenitor cell assay at a cell density of 5 x 10(3) culture with incremental concentrations of recombinant human growth factors (rhGFs). BMT patients' cultures showed significantly lower colony scores at the lowest cytokine concentrations in both erythroid burst-forming units (BFU-Es) and erythroid colony forming units (CFU-Es) as well as in myeloid lineages; colony forming units-granulocyte macrophage (CFU-GM), and did not improve at the highest GF doses. No significant differences in the results were found between the autologous and allogeneic marrow sources. We conclude that following BMT, lineage restricted progenitors within the CD34+ population are significantly reduced, failing to recover even 8 years after transplantation.