Subcutaneous transplantation of marrow- derived murine mesenchymal stem cells cultivated in alginate and their chondrogenesis

Background and ObjectivesMesenchymal stem cells are appropriate candidates to treat diseases including articular cartilage defects. There are plenty of researches being conducted to make the application of these cells possible. The purpose of this study was to cultivate murine mesenchymal stem cells (MSCs) in alginate gel and transplant them subcutaneously to immuno-suppressed rats to examine their chondrogenic potential in vivo.Materials and Methods 4-6 week old NMRI mice were sacrificed and their bone marrow cells were cultivated in 6-cell plates at the density of 500 cell/cm2. The pure fibroblastic cells appeared after two passages. 2×106 fibroblastic cells were mixed with 1 ml of alginate solution and converted into gel by being exposed to calcium chloride solution. MSCs-embedded alginate gel were then transplanted subcutaneously to 6 rats that had received an immunosuppressive drug (cyclosporine) for transplant rejection to be avoided. 5 weeks after transplantation, the alginate gels were removed and evaluated by histochemistry, RT-PCR for certain cartilage markers, and transmission electron microscopy.Results5 weeks after transplantation, the skin was incised and the alginate gel with its surrounding vascular connective tissue were removed. Tuloidine blue staining indicates that the cells within the gel assumed oval morphology and occupied lacuna-like cavities. RT-PCR analysis revealed that in these cells the mRNA of some cartilage markers such as collagen II (the marker of hyaline cartilage), collagen X (hypertrophied chondrocyte marker in osteogenesis), and aggreacan were largely produced. Ultra-thin sections analysis showed that the cells within the lacuna-like cavity of alginate gel contain a large amount of expanded rough endoplasmic reticulum and secret fibrillar extra cellular matrix. ConclusionsTransplanted murine MSCs cultivated in alginate gel can differentiate into hyaline cartilage with the sign of osteogenic initiation.