IMPAIRMENT OF THE COMPARTMENT OF STROMAL CELLS IN MYELODYSPLASTIC SYNDROMES

We assessed the in vitro behavior of bone marrow stromal cells (BM-SC) in myelodysplastic syndromes (MDS) with a particular focus on hypoplastic MDS (hMDS). H-MDS is an entity characterized by cytopenia, BM hypoplasia sharing similarities with severe aplastic anemia (SAA), except for the presence of a normal number of CD34+ cells, occurrence of abnormal localized immune precursors, dysmegakaryocytopoiesis and involvement of -7/7q- chromosome. Thirty-two cases were considered: 10 refractory anemia (RA), 3 RA with ring sideroblasts (RARS), 8 RA with excess of blasts (RAEB), 5 RAEB-t and 6 cases of hMDS. BM cells were cultured with long-term culture medium to evaluate the mesenchymal clonogenic precursors (CFU-F) and the stromal layer confluence capacity in a T25 flask. MDS stromal cells gave evidence of defective cell growth capacity vs controls (see Figures 1 & 2). In hMDS, CFU-F significantly (Wilcoxon test) differed from that in controls, RA/RARS (p=0.02) and RAEB (p=0.01) groups; the same difference was maintained considering the stromal confluence (p=0.01). An increased apoptosis process involving both the hemopoietic compartment and BM-SC has been reported in MDS, with the maximum rate occurring in the RAEB-t samples (Raza et al., Blood, 1995). Our in vitro findings confirm an impairment of BM-SC in MDS, suggesting how hMDS differs from both MDS or SAA, in which the stromal cell compartment seems to be spared, adding a further clue that differentiates these two similar forms of BM failure.