Comparative study of collagen hydrogels modified in two ways using the model of ectopic cartilage construction with diffusion-chamber in immunocompetent host

Collagen-Based Hydrogels for Cartilage Regeneration

Cartilage regeneration remains difficult due to a lack of blood vessels. Degradation of the extracellular matrix (ECM) causes cartilage defects, and the ECM provides the natural environment and nutrition for cartilage regeneration. Until now, collagen hydrogels are considered to be excellent material for cartilage regeneration due to the similar structure to ECM and good biocompatibility. However, collagen hydrogels also have several drawbacks, such as low mechanical strength, limited ability to induce stem cell differentiation, and rapid degradation. Thus, there is a demanding need to optimize collagen hydrogels for cartilage regeneration. In this review, we will first briefly introduce the structure of articular cartilage and cartilage defect classification and collagen, then provide an overview of the progress made in research on collagen hydrogels with chondrocytes or stem cells, comprehensively expound the research progress and clinical applications of collagen-based hydrogels that integrate inorganic or organic materials, and finally present challenges for further clinical translation.

Material-induced chondrogenic differentiation of mesenchymal stem cells is material-dependent

Certain materials may mimic natural cartilage to provide an amenable cellular microenvironment for the chondrogenic differentiation of mesenchymal stem cells. The chondrogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) has been demonstrated to be induced by collagen-based hydrogels in vivo, but whether the induction is material-driven or self-differentiation has not been elucidated. In the present study, BMSCs were encapsulated in porous materials, namely, a biphasic calcium phosphate ceramic (BCP), silk fibroin protein matrix (SFP) and collagen sponge (CS), to further study the chondrogenic effects of various materials. Diffusion chambers that allow the body fluid to permeate and deter the host cells from invasion were also loaded with the cell-scaffold constructs. Chambers containing the scaffold-BMSC composites were implanted subcutaneously in the dorsa of rabbits. The specimens in the chamber were harvested for histological and immunohistochemical analyses eight weeks after implantation. The results showed that no chondrogenic differentiation of the BMSCs occurred when the BMSCs were encapsulated in BCP, SFP and CS, indicating that chondrogenesis induced by materials is material-dependent and that these particular porous materials are not suitable for inducing chondrogenesis. However, the diffusion chamber was effective in preventing host immune rejection, host cell invasion and vascular invasion. The results are likely to serve as a valuable clinical reference when selecting an appropriate scaffold for cartilage repair.