Abstract
Scaffold-free cartilage-sheet technology can stably regenerate high-quality cartilage tissue in vivo. However, uncontrolled shape maintenance and mechanical strength greatly hinder its clinical translation. Decalcified bone matrix (DBM) has high porosity, a suitable pore structure, and good biocompatibility, as well as controlled shape and mechanical strength. In this study, cartilage sheet was prepared into engineered cartilage gel (ECG) and combined with DBM to explore the feasibility of regenerating 3D cartilage with controlled shape and mechanical strength. The results indicated that ECG cultured in vitro for 3 days (3 d) and 15 days (15 d) showed good biocompatibility with DBM, and the ECG–DBM constructs successfully regenerated viable 3D cartilage with typical mature cartilage features in both nude mice and autologous goats. Additionally, the regenerated cartilage had comparable mechanical properties to native cartilage and maintained its original shape. To further determine the optimal seeding parameters for ECG, the 3 d ECG regenerated using human chondrocytes was diluted in different concentrations (1:3, 1:2, and 1:1) for seeding and in vivo implantation. The results showed that the regenerated cartilage in the 1:2 group exhibited better shape maintenance and homogeneity than the other groups. The current study established a novel mode of 3D cartilage regeneration based on the design concept of steel (DBM)-reinforced concrete (ECG) and successfully regenerated homogenous and mature 3D cartilage with controlled shape and mechanical strength, which hopefully provides an ideal cartilage graft for the repair of various cartilage defects.
Highlights
The clinical treatment of cartilage defects is a significant challenge (Gomez et al, 2020; Mardones et al, 2020; Pattappa et al, 2020), as current methods do not provide an ideal graft for repairing the cartilage defects
Auricular cartilage was obtained from autologous goat and cut into 1.0 mm pieces, washed using phosphate-buffered solution (PBS), and digested using 0.15% collagenase (Worthington Biochemical Corp., NJ, United States) for isolating chondrocytes, as previously reported (Rodriguez et al, 1999)
Quantitative analyses showed that all quantitative indexes, including the wet weight, volume, and cartilage extracellular matrix (ECM) contents, increased significantly with decreasing dilution (Figure 8). These results indicate that an appropriate dilution is important for enhancing the cartilage regeneration efficiency and preventing excessive proliferation of the engineered cartilage gel (ECG)–Decalcified bone matrix (DBM) constructs
Summary
The clinical treatment of cartilage defects is a significant challenge (Gomez et al, 2020; Mardones et al, 2020; Pattappa et al, 2020), as current methods do not provide an ideal graft for repairing the cartilage defects. Autologous cartilage transplantation is currently the most effective method for treating cartilage defects; there is limited source tissue, and the potential exists for irreversible damage to the donor area (Schinhan et al, 2013; Ruta et al, 2016). Tissue engineering provides a new approach for treating various cartilage defects and can be used to regenerate sufficient autologous viable cartilage tissue during in vitro proliferation with a small number of chondrocytes and minimal trauma (Zheng et al, 2014; He et al, 2018; Zhou et al, 2018). Various animal and clinical experiments have demonstrated that scaffold-free cartilage-sheet technologies can stably regenerate high-quality cartilage tissue in vivo (Li et al, 2017, 2019; He et al, 2018). The application of ECG is mainly limited to minimally invasive fillings, which are not suitable for repairing cartilage defects with specific shape and strength requirements because ECG cannot be shaped, ECG does not provide adequate mechanical strength, and ECG particles are too large to seed in conventional tissue regeneration scaffolds that have a relatively small pore size
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