FAILURE TO DETECT SPINDLE-SHAPED FIBROBLASTOID CELL PROGENITORS IN PBPC COLLECTIONS

We assessed the development of an adherent stromal layer in peripheral blood progenitor cells (PBPC) collections of 17 patients with solid t umors and hematological malignancies (n = 38), as well as in normal an d disease-free bone marrow samples (n = 14). Light-density mononuclear cells from peripheral blood leukapheresis maintained in long term cul ture (LTC) conditions for at least 3 weeks failed to develop a stromal layer as was observed in all bone marrow samples. We found no differe nces with regard to CFU-GM growth, CD34+ percentage or cytological mor phology. Our results indicate that spindle-shaped fibroblastoid cell p rogenitors present in the bone marrow are not mobilized towards periph eral blood by chemotherapy and/or growth factor stimulation, contrasti ng with hematopoietic progenitors, which, as is well known, are able t o circulate. The absence of stromal progenitors in PBPC autografts doe s not appear to be relevant for a successful hematopoietic engraftment .