Stem cells in orthopedics: Current concepts and possible future applications

Transfection of the IHH gene into rabbit BMSCs in a simulated microgravity environment promotes chondrogenic differentiation and inhibits cartilage aging

The effect of overexpressing the Indian hedgehog (IHH) gene on the chondrogenic differentiation of rabbit bone marrow-derived mesenchymal stem cells (BMSCs) was investigated in a simulated microgravity environment. An adenovirus plasmid encoding the rabbit IHH gene was constructed in vitro and transfected into rabbit BMSCs. Two large groups were used: conventional cell culture and induction model group and simulated microgravity environment group. Each large group was further divided into blank control group, GFP transfection group, and IHH transfection group. During differentiation induction, the expression levels of cartilage-related and cartilage hypertrophy-related genes and proteins in each group were determined. In the conventional model, the IHH transfection group expressed high levels of cartilage-related factors (Coll2 and ANCN) at the early stage of differentiation induction and expressed high levels of cartilage hypertrophy-related factors (Coll10, annexin 5, and ALP) at the late stage. Under the simulated microgravity environment, the IHH transfection group expressed high levels of cartilage-related factors and low levels of cartilage hypertrophy-related factors at all stages of differentiation induction. Under the simulated microgravity environment, transfection of the IHH gene into BMSCs effectively promoted the generation of cartilage and inhibited cartilage aging and osteogenesis. Therefore, this technique is suitable for cartilage tissue engineering.

Mesenchymal stem cell sheet encapsulated cartilage debris provides great potential for cartilage defects repair in osteoarthritis

The restoration of the degenerated articular cartilage in patients with osteoarthritis (OA) is still a challenge for researchers and clinicians. Drug interventions and surgical treatments have been widely attempted for cartilage regeneration in OA. However, the results were largely unsatisfactory. Autologous chondrocyte implantation (ACI) or matrix-induced autologous chondrocyte implantation (MACI) offers potential for the regeneration of cartilage over the long-term. However, due to the limitations and disadvantages of ACI, alternative therapies for cartilage regeneration are in need. The availability of large quantities of mesenchymal stem cells (MSCs) and the multilineage differentiation, especially their chondrogenic differentiation property, have made MSCs the most promising cell source for cartilage regeneration. In addition, MSCs have been shown the ability to undergo site-specific differentiation. MSCs can be obtained as MSC sheets using the temperature-responsive culture dish method. The MSC sheet can provide amounts of cells and extracellular matrix, which might provide the continuity between the implant and host cartilage, thus improving integrative cartilage repair. Moreover, OA is associated with progressive and often severe inflammation. MSCs not only have the ability to contribute structurally to tissue repair, but also possess potent immunomodulatory and anti-inflammatory effects. Taken together, these properties make MSC sheet promising candidate for cartilage repair in OA. We hypothesize that MSC sheet encapsulated cartilage debris can efficiently promote cartilage repair in OA patients. Chondrocytes can be obtained and cultured from small cartilage debris in vitro. Therefore, the chondrocytes may grow from the debris in cartilage defect and improve cartilage regeneration. MSC sheet provide amounts of cells, ECM and protein for cartilage regeneration and integration, and may play some roles of periosteum. The operation of MSC sheet encapsulated cartilage debris for cartilage repair is simple and practical. Moreover, the cell sheet/cartilage debris constructs can be easily shaped based on the size and shape of cartilage defects. The new method might have great potential in treating cartilage defects clinically, especially for OA patients.

Cell transplantation for articular cartilage defects: principles of past, present, and future practice

As articular cartilage has very limited self-repair capability, the repair and regeneration of damaged cartilage is a major challenge. This review aims to outline the past, present, and future of cell therapies for articular cartilage defect repair. Autologous chondrocyte implantation (ACI) has been used clinically for more than 20 years, and the short, medium, and long-term clinical outcomes of three generation of ACI are extensively overviewed. Also, strategies of clinical outcome evaluation, ACI limitations, and the comparison of ACI clinical outcomes with those of other surgical techniques are discussed. Moreover, mesenchymal stem cells and pluripotent stem cells for cartilage regeneration in vitro, in vivo, and in a few clinical studies are reviewed. This review not only comprehensively analyzes the ACI clinical data but also considers the findings from state-of-the-art stem cell research on cartilage repair from bench and bedside. The conclusion provides clues for the future development of strategies for cartilage regeneration.