Extensive apoptosis of bone marrow cells as evaluated by the in situ end-labelling (ISEL) technique may be the basis for ineffective haematopoiesis in patients with myelodysplastic syndromes

: Apoptosis is a gene-directed cellular self-destruction which begins with internucleosomal cleavage of DNA and ends eventually with fragmentation of the nucleus. We have shown that the technique of ISEL of fragmented DNA appears to be an accurate and reliable measurement of the early stages of apoptosis. The present study was undertaken in order to define the incidence of programmed cell death in bone marrow (BM) haematopoietic and stromal cells of myelodysplastic syndromes (MDS). The ISEL technique was employed in 21 BM biopsies of MDS patients. The analysis showed that in 11/21 patients, >70% cells (high score) were undergoing programmed cell death while 5 patients showed up to 1/3 of the biopsy containing apoptotic cells and 2 patients had only few occasional ISEL positive cells. Stromal cells including fat cells, endothelial cells and fibroblasts were frequently in apoptosis in large clusters. Our results indicate that extensive apoptosis of haematopoietic cells documented in BM biopsies of MDS patients may be the explanation for the ineffective haematopoiesis which is the hallmark of these disorders.