Osteogenic differentiation potential of multiple myeloma patients derived bone marrow mesenchymal stem cells

Multiple myeloma is a plasma cell neoplasia characterized by proliferation of malignant plasma cells in the bone marrow. Multiple myeloma is a kind of cancer; same as the other cancer types, resultant of genetic changes of the cells variants of geography, socio-economic conditions and ethnic origin of human. This disease is more common in men than women which commonly seen across the globe, particularly in Europe, North America and Australia. In multiple myeloma, development of a destructive bone disease that results osteolytic bone lesions, bone pain and fractures is observed. Bone fractures and intense bone pain in later stages of the disease or in treatment process, are considerably reduces the quality of life of patients. Under normal physiological conditions, osteoblast formation and differentiation from bone marrow mesenchymal stem cells and bone resorbtion through osteoclastic activity are in balance. However in multiple myeloma patients, an imbalance between osteoblastic and osteoclastic activity was present, which is induced by numerous inhibitory factors secreted by plasma cells into bone marrow microenvironment. During tumor progression, bone lesions increase consequently. Up to date, bisphosphonates which uses for the treatment of multiple myeloma bone disease, inhibits the activity of osteoclasts and induces them to apoptosis. Furthermore, by inhibiting osteoclastogenesis the formation of osteoclasts precursors are inhibited. However, in multiple myeloma, the formation of osteoblasts from mesenchymal stem cells in the bone marrow and bone formation is still unclear for the improvement of treatment strategies. The capability of self-renewal and differentiation potential of bone marrow mesenchymal stem cells into bone, cartilage, muscle and fat cells are well known. In vivo and in vitro osteogenic differentiation and proliferation abnormalities of bone marrow mesenchymal stem cells derived from patients with multiple myeloma have been shown in latest studies. The loss of differentiation capacity of bone marrow mesenchymal stem cells of multiple myeloma patients into osteoblasts might explain the reason for bone deformations. The comparative gene analysis promise better knowledge in molecular pathways of osteogenic differentiation progress between the normal and diseased cells after in vitro osteogenic differentiation without the influence of microenvironment. Until today, the studies performed co-culture systems for mimicing bone marrow microenvironment in vitro to determine negative effects of multiple myeloma plasma cells on bone marrow-derived mesenchymal stem cells osteogenic differentiation. These studies show multiple myeloma bone marrow derived mesenchymal stem cells are different from healthy donors with their phenotype and their osteogenic differentiation capacitys'looseness. However, without the influence of the microenvironment, the genes which play roles in osteogenic pathways after osteogenic induction of bone marrow derived mesenchymal stem cells have not report in the literature yet. Osteoblasts responsible for bone formation in multiple myeloma bone disease without the influence of the microenvironment, in vitro determination of behavior likely to happen in the future of stem cell therapy or regenerative medicine approaches are important. At the same time constitutes a significant portion of the bone marrow microenvironment of bone marrow mesenchymal stem cells in vitro characterization of multiple myeloma patients in the survival and invasion of the tumor to obtain significant findings will be pioneers. Our aim for this goal is to analyze the gene expressions of bone marrow mesenchymal stem cells derived from multiple myeloma patients, without the influence of the microenvironment, before and after in vitro osteogenic induction osteogenic pathways. For this purpose, bone marrows obtained from healthy donors and multiple myeloma patients in order to isolate mesenchymal stem cells. After the characterization of the mesenchymal stem cells, osteogenic induction will be performed in order to compare the gene expressions of the cells before and after of osteogenic induction. This analyses completed by Real Time PCR using expression arrays specially designed for osteogenic differentiation. The gene expressions which are important in osteogenic differentiation pathways were analysed. Data were statistically evaluated using the paired t-test. The results demonstrate that ALP activity was lower in multiple myeloma group. We compared expressions of genes that play roles in osteogenic pathway between healthy donors and multiple myeloma mesenchymal stem cells and the levels of 8 genes were significantly different expressed in multiple myeloma mesenchymal stem cells. From these genes; BMP4, CSF1, ICAM1 and VDR expressions showed a significantly increase in multiple myeloma group after osteogenic induction. But, COL3A1, ITGB1 and VEGFA genes significantly decreased. Besides this, TWIST1 gene expression significantly incrased in healthy donors after osteogenic induction, but did not change in multiple myeloma group. In conclusion the results have shown that the difference of osteogenic gene expressions of in multiple myeloma bone marrow mesenchymal stem cells and defect of alkaline phosphatase activity may be related with osteogenic disorders of multiple myeloma in addition to presence of other tumorogenic microenviroment of bone marrow.