QUALITY AND FUNCTIONAL-CAPACITY OF THE BONE-MARROW MICROENVIRONMENT OF AUTOLOGOUS BLOOD STEM-CELL TRANSPLANTATION (ABSCT) RECIPIENTS

We have previously reported that the rate of haematopoietic recovery f ollowing Autologous Blood Stem Cell Transplantation (ABSCT) could be i nfluenced by the type of conditioning regimen or by the underlying dis ease. Furthermore, Peripheral Blood Stem Cell (PBSC) growth was found to be sensitive to stimulation by irradiated allogeneic stromal layers . in the present study, we used the long term culture system (LTC) to investigate the quality of the bone marrow (BM) microenvironment from patients who had undergone ABSCT for either Malignant Lymphoma (ML, 13 patients) or Multiple Myeloma (MM, 8 patients) after conditioning reg imens comporting myeloablative chemotherapy (CT) or Total Body irradia tion (TBI). Among the 13 ML patients, 10 received CT conditioning and 9 of the 10 BM samples developed a complete confluent stromal layer. T he remaining 3 ML patients received TBI prior to ABSCT and 2 of the 3 samples developed confluent stroma. In contrast, when LTC were establi shed with BM from the 8 MM patients, all of whom were treated with TBI prior to ABSCT, only 3 of the 8 marrow samples developed a complete c onfluent stromal layer Thus BM from patients who had received CT condi tioning therapy tended to form confluent stroma more often than BM fro m those who had received TBI (p = 0.08). CFU-GM production was also ev aluated for the stromal layers derived from all transplanted patients. The type of disease (ML vs MM), the conditioning regimen prior to ABS CT (TBI vs CT) or the presence or absence of a confluent stromal layer did not influence the day 7 or day 14 production of CFU-GM by these s tromal layers. There was no correlation between the formation of a con fluent layer and the time interval from ABSCT to LTC or from diagnosis to cytapheresis. Nor was there any correlation with the number of nuc leated cells and CFU-GM used for transplantation. interestingly, when we examined the ability of confluent and non confluent stromal layers to support haematopoiesis, we observed no difference in the total cumu lative production of nucleated cells or CFU-GM, suggesting that the qu ality of the BM microenvironment after ABSCT as evaluated by the LTC s ystem cannot explain the differences seen in the rate of haematopoieti c reconstitution.