Apoptosis in myelodysplasia: Association with patient age, bone marrow cellularity and karyotypes

Background: Myelodysplastic syndrome (MDS) comprises a heterogeneous group of clonal hematopoietic stem cell diseases, characterized by dysplasias and apoptosis in bone marrow (BM) and cytopenias in peripheral blood. In this study, we analyzed apoptosis in MDS to verify associations with patient age, bone marrow cellularity and karyotypes and to investigate the role of apoptosis in MDS pathogenesis. Methods: Bone marrow cells were collected from 81 patients with primary MDS, of which 60 were adults and 21 children. BM cells were also collected from 10 healthy donors for bone marrow transplants, 5 adults and 5 children, as controls. The patients and controls came from public onco-hematology institutions in Rio de Janeiro. The percentage of apoptotic BM cells was assessed by flow cytometry using two combinations: annexin V-FITC/CD34PE/CD45PerCP and annexin V-FITC/CD14PE/CD45PerCP in BM cells. Cytogenetic analysis was performed by G-banding. Results: The comparison between adult and pediatric patients showed that these patients show a similar behavior with regard to apoptotic cells percentages in BM samples. Apoptosis occurs independently of BM cellularity, being more prominent in patients with hyper/normocellular BM. Patients with normal karyotypes, del(5q), del(17p) had higher apoptosis rates than patients with del(11q) and complex karyotypes. Cells committed to a differentiation program were associated with high rates of apoptosis, suggesting that apoptosis may be a consequence of inefficient hematopoiesis, such that the hematopoietic system may eliminate dysplastic cells at the beginning of the disease. Conclusions: Our results suggest that apoptosis is an important characteristic of BM cells from adult and pediatric MDS patients and may be a consequence of inefficient hematopoiesis. In addition, we suggest that apoptosis is not the main mechanism associated with hypocellular MDS, and it occurs preferentially in MDS cases of hyper/normocellular BM and is associated with a good prognosis. Keywords: Myelodysplastic Syndrome; Apoptosis; Patient age; Bone marrow cellularity; Karyotypes.