Tissue-engineering strategies to repair joint tissue in osteoarthritis: nonviral gene-transfer approaches

Gene Delivery of TGF-β3 and BMP2 in an MSC-Laden Alginate Hydrogel for Articular Cartilage and Endochondral Bone Tissue Engineering

Incorporating therapeutic genes into three-dimensional biomaterials is a promising strategy for enhancing tissue regeneration. Alginate hydrogels have been extensively investigated for cartilage and bone tissue engineering, including as carriers of transfected cells to sites of injury, making them an ideal gene delivery platform for cartilage and osteochondral tissue engineering. The objective of this study was to develop gene-activated alginate hydrogels capable of supporting nanohydroxyapatite (nHA)-mediated nonviral gene transfer to control the phenotype of mesenchymal stem cells (MSCs) for either cartilage or endochondral bone tissue engineering. To produce these gene-activated constructs, MSCs and nHA complexed with plasmid DNA (pDNA) encoding for transforming growth factor-beta 3 (pTGF-β3), bone morphogenetic protein 2 (pBMP2), or a combination of both (pTGF-β3-pBMP2) were encapsulated into alginate hydrogels. Initial analysis using reporter genes showed effective gene delivery and sustained overexpression of the transgenes were achieved. Confocal microscopy demonstrated that complexing the plasmid with nHA before hydrogel encapsulation led to transport of the plasmid into the nucleus of MSCs, which did not happen with naked pDNA. Gene delivery of TGF-β3 and BMP2 and subsequent cell-mediated expression of these therapeutic genes resulted in a significant increase in sulfated glycosaminoglycan and collagen production, particularly in the pTGF-β3-pBMP2 codelivery group in comparison to the delivery of either pTGF-β3 or pBMP2 in isolation. In addition, stronger staining for collagen type II deposition was observed in the pTGF-β3-pBMP2 codelivery group. In contrast, greater levels of calcium deposition were observed in the pTGF-β3- and pBMP2-only groups compared to codelivery, with a strong staining for collagen type X deposition, suggesting these constructs were supporting MSC hypertrophy and progression along an endochondral pathway. Together, these results suggest that the developed gene-activated alginate hydrogels were able to support transfection of encapsulated MSCs and directed their phenotype toward either a chondrogenic or an osteogenic phenotype depending on whether TGF-β3 and BMP2 were delivered in combination or isolation.

Regeneration of hyaline-like cartilage in situ with SOX9 stimulation of bone marrow-derived mesenchymal stem cells

Microfracture, a common procedure for treatment of cartilage injury, induces fibrocartilage repair by recruiting bone marrow derived mesenchymal stem cells (MSC) to the site of cartilage injury. However, fibrocartilage is inferior biomechanically to hyaline cartilage. SRY-type high-mobility group box-9 (SOX9) is a master regulator of chondrogenesis by promoting proliferation and differentiation of MSC into chondrocytes. In this study we aimed to test the therapeutic potential of cell penetrating recombinant SOX9 protein in regeneration of hyaline cartilage in situ at the site of cartilage injury. We generated a recombinant SOX9 protein which was fused with super positively charged green fluorescence protein (GFP) (scSOX9) to facilitate cell penetration. scSOX9 was able to induce chondrogenesis of bone marrow derived MSC in vitro. In a rabbit cartilage injury model, scSOX9 in combination with microfracture significantly improved quality of repaired cartilage as shown by macroscopic appearance. Histological analysis revealed that the reparative tissue induced by microfracture with scSOX9 had features of hyaline cartilage; and collagen type II to type I ratio was similar to that in normal cartilage. This short term in vivo study demonstrated that when administered at the site of microfracture, scSOX9 was able to induce reparative tissue with features of hyaline cartilage.

Cordycepin inhibits chondrocyte hypertrophy of mesenchymal stem cells through PI3K/Bapx1 and Notch signaling pathway

Mesenchymal stem cells (MSCs) are widely used in cartilage tissue engineering to repair articular cartilage defects. However, hypertrophy of chondrocytes derived from MSCs might hinder the stabilization of hyaline cartilage. Thus, it is very important to find a suitable way to maintain the chondrogenic phenotype of chondrocytes. It has been reported that cordycepin has anti-inflammatory and anti-tumor functions. However, the role of cordycepin in chondrocyte hypertrophy remains unclear. Therefore, the objective of this study was to determine the effect of cordycepin on chondrogenesis and chondrocyte hypertrophy in MSCs and ATDC5 cells. Cordycepin upregulated chondrogenic markers including Sox9 and collagen type II while down-regulated hypertrophic markers including Runx2 and collagen type X. Further exploration showed that cordycepin promoted chondrogenesis through inhibiting Nrf2 while activating BMP signaling. Besides, cordycepin suppressed chondrocyte hypertrophy through PI3K/Bapx1 pathway and Notch signaling. Our results indicated cordycepin had the potential to maintain chondrocyte phenotype and reconstruct engineered cartilage. [BMB Reports 2016; 49(10): 548-553]

Repair of cartilage defects in osteoarthritis rats with induced pluripotent stem cell derived chondrocytes

Background

The incapacity of articular cartilage (AC) for self-repair after damage ultimately leads to the development of osteoarthritis. Stem cell-based therapy has been proposed for the treatment of osteoarthritis (OA) and induced pluripotent stem cells (iPSCs) are becoming a promising stem cell source.

Results

Three steps were developed to differentiate human iPSCs into chondrocytes which were transplanted into rat OA models induced by monosodium iodoacetate (MIA). After 6 days embryonic body (EB) formation and 2 weeks differentiation, the gene and protein expression of Col2A1, GAG and Sox9 has significantly increased compare to undifferentiated hiPSCs. After 15 weeks transplantation, no immune responses were observed, micro-CT showed gradual engraftment and the improvement of subchondrol plate integrity, and histological examinations demonstrated articular cartilage matrix production.

Conclusions

hiPSC could be an efficient and clinically translatable approach for cartilage tissue regeneration in OA cartilages.

A controlled double-duration inducible gene expression system for cartilage tissue engineering

Cartilage engineering that combines competent seeding cells and a compatible scaffold is increasingly gaining popularity and is potentially useful for the treatment of various bone and cartilage diseases. Intensive efforts have been made by researchers to improve the viability and functionality of seeding cells of engineered constructs that are implanted into damaged cartilage. Here, we designed an integrative system combining gene engineering and the controlled-release concept to solve the problems of both seeding cell viability and functionality through precisely regulating the anti-apoptotic gene bcl-2 in the short-term and the chondrogenic master regulator Sox9 in the long-term. Both in vitro and in vivo experiments demonstrated that our system enhances the cell viability and chondrogenic effects of the engineered scaffold after introduction of the system while restricting anti-apoptotic gene expression to only the early stage, thereby preventing potential oncogenic and overdose effects. Our system was designed to be modular and can also be readily adapted to other tissue engineering applications with minor modification.

Kartogenin-Incorporated Thermogel Supports Stem Cells for Significant Cartilage Regeneration

Recently, cartilage tissue engineering (CTE) attracts increasing attention in cartilage defect repair. In this work, kartogenin (KGN), an emerging chondroinductive nonprotein small molecule, was incorporated into a thermogel of poly(L-lactide-co-glycolide)-poly(ethylene glycol)-poly(L-lactide-co-glycolide) (PLGA-PEG-PLGA) to fabricate an appropriate microenvironment of bone marrow mesenchymal stem cells (BMSCs) for effective cartilage regeneration. More integrative and smoother repaired articular surface, more abundant characteristic glycosaminoglycans (GAGs) and collagen II (COL II), and less degeneration of normal cartilage were obtained in the KGN and BMSCs coloaded thermogel group in vivo. In conclusion, the KGN-loaded PLGA-PEG-PLGA thermogel can be utilized as an alternative support for BMSCs to regenerate damaged cartilage in vivo.

Cartilage Tissue Engineering Using Combination of Chitosan Hydrogel and Mesenchymal Stem Cells

A novel chitosan hydrogel with high porosity was fabricated by a crosslinking method. Cartilage tissue engineering formed after mesenchymal stem cells was cultured on this hydrogel scaffold for 12 weeks. The immunohistochemistry tests demonstrated that the obtained cartilage had the specific histological properties of natural cartilage. And the qPCR tests also proved that the genes for type II collagen in the obtained cartilage were expressed the same as in the natural one.