Ectopic Osteogenesis And Chondrogenesis Of Bone Marrow Stromal Stem Cells In Alginate System

Object: In orthopaedics, the regeneration and repair of cartilage or bone defects resulting from trauma, cancer or metabolic disorders, is still a major clinical challenge. With developmental plasticity, bone marrow mesenchymal stem cells (BMSCs) are considered as important seed cells for musculoskeletal tissue engineering approach. This study was to determine the ectopic osteogenic and chondrogenic ability of BMSCs in combination with a scaffolding material comprising alginate gel.Method: After isolation from bone marrow of BALB/C mice, BMSCs were expanded in vitro and induced to chondrogenesis or osteogenesis for 14 days respectively. Then these induced cells were seeded into alginate gel and the constructs were implanted into BALB/C nude mice subcutaneously for up to 8 weeks. Histological analysis, scanning and transmission electron microscopy, immunohistochemical staining and RT-PCR of the retrieved specimens at applied at various intervals to determine whether there are trends of ectopic cartilage or bone formation with alteration of cellular phenotype.Results: Histological analysis, scanning and transmission electron microscopy of the retrieved specimens at various intervals showed obvious trends of ectopic cartilage or bone formation with alteration of cellular phenotype. Simultaneously, results of immunohistochemical staining and RT-PCR confirmed the expression of specific extracellular matrix (ECM) markers for cartilaginous tissue such as collagen type II (Col-II), SOX9 and aggrecan, or markers for osteoid tissue such as osteopontin (OPN), osteocalcin (OCN) and collagen type I (Col-I). During subcutaneous implantation, the elevating production of ECM and initiation of characteristic structure were correlated closely with time increasing. In contrast, there was apparent degradation and resorption of scaffolding material in blank controls, but no newly formed tissues. Finally, the constructs made up of non-induced BMSCs almost disappeared at the 8 weeks after implantation.Conclusion: It is suggested that alginate gel combined with ultBMSCs undergoing differentiation into skeletal lineages may represent an efficient strategy for clinical reconstruction of bone and cartilage defects.