Bone marrow mesenchymal stem cells in myelodysplastic syndromes: cytogenetic characterization

Phenotypic and Cytogenetic Characterization of Mesenchymal Stromal Cells in De Novo Myelodysplastic Syndromes

Bone marrow (BM) mesenchymal stem/stromal cells (MSCs) are vital in hematopoiesis. Whether BM-MSCs alter their characteristics in Myelodysplastic Syndromes (MDS) is still controversial. We characterized MSCs of de novo MDS patients in Sri Lanka who have not been reported previously in the literature. We also analyzed MSCs derived from different MDS subtypes. MSCs were culture-expanded, characterized by flow cytometry, and induced towards osteogenic and adipogenic differentiation. Growth properties were determined using growth curves and population doubling times. Karyotyping and FISH were performed on MSCs. Cell morphology, differentiation potential, and CD marker expression of MDS-MSCs of all subtypes were comparable to those of control-MSCs. No significant growth differences were observed between control MSCs and MDS-MSCs of all subtypes (p > 0.05). 31% of MDS-MSCs had chromosomal aberrations (der(3),del(6q),del(7p), loss of chromosomes) whose BM karyotypes were normal. Highest percentage of karyotypic abnormalities was observed in RCMD-MSCs. Patients with abnormal BM karyotypes had no aberrant MSC clones. Results show that in spite of presence of genetically abnormal clones in MDS-MSC populations, in vitro phenotypic and growth characteristics of MSCs in MDS remain unchanged. Further, the occurrence of genetic abnormalities in BM-MSCs in MDS could be considered as an autonomous event from that of their hematopoietic counterparts.

Biological differences between native and cultured mesenchymal stem cells: implications for therapies

We describe the current knowledge of the surface marker phenotype of native bone marrow mesenchymal stem/stromal cells (MSCs) in humans and in mouse models, highlighting similarities in the MSC marker "signature" between the two species. The chapter proceeds to discuss the published literature pertaining to native MSC topography and their interactions with hematopoietic stem cells and their progeny, as well as with blood vessels and nerve endings. Additionally, the chapter describes phenotypic and functional "drifts" that occur in MSC preparations as they are taken out of their native bone marrow microenvironment and induced to proliferate in vitro (in the presence of animal or human serum). We propose that the understanding of the biology of MSCs in their native niches in the bone marrow could lead to future developments in the treatment of hematological diseases such as multiple myeloma. Additionally, this knowledge would assist in the development of more "natural" MSC culture conditions, best preserving MSC functionality including their homing potential in order to optimize MSC transplantation in the context of graft-versus-host and other diseases.

Impaired osteogenic differentiation of mesenchymal stem cells derived from bone marrow of patients with lower-risk myelodysplastic syndromes

The pathogenesis of myelodysplastic syndromes (MDS) has not been completely understood, and insufficiency of the hematopoietic microenvironment can be an important factor. Mesenchymal stem cells (MSCs) and osteoblasts are key components of the hematopoietic microenvironment. Here, we measured the expression of multiple osteogenic genes in 58 MSCs from MDS patients with different disease stages and subtypes by real-time PCR and compared the osteogenic differentiation of MSCs from 20 MDS patients with those of MSCs from eight normal controls quantitatively and dynamically. The mRNA level of Osterix and RUNX2, two key factors involved in the early differentiation process toward osteoblasts, was significantly reduced in undifferentiated MSCs from lower-risk MDS. After osteogenic induction, lower-risk MDS showed lower alkaline phosphatase activity, less intense alizarin red S staining, and lower gene expression of osteogenic differentiation markers; however, higher-risk MDS was normal. Finally, in bone marrow biopsy, the number of osteoblasts was significantly decreased in lower-risk MDS. These results indicate that MSCs from lower-risk MDS have impaired osteogenic differentiation functions, suggesting their insufficient stromal support in MDS.