[Cytogenetic characteristics of hematopoietic and stromal progenitor cells in myelodysplastic syndrome].

Aim: To study and compare cytogenetic abnormalities in the bone marrow (BM) and peripheral blood (PB) CD34+ hematopoietic progenitor cells and in the BM mesenchymal stromal cells (MSCs) in patients with myelodysplastic syndrome (MDS). Subjects and methods. The results of a cytogenetic analysis of the total population of BM cells (BMC), CD34+ hematopoietic progenitor cells from BM and PB, and BM MSCs were analyzed in 35 patients (29 patients with MDS and 6 with MDS transformed into acute myeloid leukemia (AML)) and 7 healthy BM donors. Cytogenetic examinations were performed by G-banding of chromosomes and fluorescence in situ hybridization (FISH).

Results: The BMC karyotype was abnormal in 17 (49%) of the 35 patients (13 with MDS and 4 with AML); the others were found to have a normal BM karyotype. The FISH analysis confirmed the same cytogenetic abnormalities in the BM and PB CD34+ hematopoietic progenitor cells in all the examinees with an abnormal karyotype. The mean abnormal clone sizes in the total population of BMCs and BM and PB CD34+ progenitor cells did not differ and constituted 65.8, 73.1, and 74.8%, respectively. The patients with a normal BM karyotype had no chromosome abnormalities in the CD34+ cells either. The karyotype of MSCs was analyzed in 23 (19 with MDS and 4 with AML) of the 35 patients. No karyotype abnormalities were revealed in the patients with MDS transformed into AML. There were structural chromosome aberrations in 2 (11%) of the 19 patients with MDS (one with constitutional inv(9)(p1 3q21) was found to have non-clonal translocation t(2;22)(p10;q1 1) and the other had a clone with an additional segment of the long arm of chromosome 2 in 35% of the cells. No numerical MSC karyotype abnormalities were detected. A normal MSC karyotype was defined in 7 healthy BM donors.

Conclusion: The cytogenetic analysis of hematopoietic and mesenchymal progenitor cells showed that the chromosome abnormalities revealed in these cell populations were different in the patients with MDS. The isolated CD34+ cells displayed the same cytogenetic abnormalities as in a total population of BMC. Examination of the latter could reveal no cytogenetic abnormalities in the majority of the patients. A normal BMC karyotype was detectable in the patients with AML. Two (11%) patients with MDS were found to have structural chromosome abnormalities that differed from those detected in the total population of BMC and in isolated CD34+ cells. The differences of chromosome abnormalities in the hematopoietic and mesenchymal progenitor cells point to the fact that the stromal microenvironment is not part of the abnormal clone in MDS, however, it may be of great importance in the pathogenesis of the disease.