Abstract
Cartilage regeneration is still a challenge for clinicians because of avascularity, denervation, load-bearing, synovial movement, and the paucity of endogenous repair cells. We constructed a multilayered osteochondral bionic scaffold and examined its repair capacity using a rabbit osteochondral defect model. The cartilage phase and interface layer of the scaffold were prepared by freeze-drying, whereas the bone phase of the scaffold was prepared by high-temperature sintering. The three-phase osteochondral bionic scaffold was formed by joining the hydroxyapatite (HAp) and silk fibroin (SF) scaffolds using the repeated freeze-thaw method. Different groups of scaffolds were implanted into the rabbit osteochondral defect model, and their repair capacities were assessed using imaging and histological analyses. The cartilage phase and the interface layer of the scaffold had a pore size of 110.13 ± 29.38 and 96.53 ± 33.72 μm, respectively. All generated scaffolds exhibited a honeycomb porous structure. The polydopamine- (PDA-) modified scaffold released platelet-derived growth factor (PDGF) for 4 weeks continuously, reaching a cumulative release of 71.74 ± 5.38%. Synovial mesenchymal stem cells (SMSCs) adhered well to all scaffolds, but demonstrated the strongest proliferation ability in the HSPP (HAp-Silk-PDA-PDGF) group. Following scaffold-induced chondrogenic differentiation, SMSCs produced much chondrocyte extracellular matrix (ECM). In in vivo experiments, the HSPP group exhibited a significantly higher gross tissue morphology score and achieved cartilage regeneration at an earlier stage and a significantly better repair process compared with the other groups (P < 0.05). Histological analysis revealed that the new cartilage tissue in the experimental group had a better shape and almost filled the defect area, whereas the scaffold was nearly completely degraded. The new cartilage was effectively fused with the surrounding normal cartilage, and a substantial amount of chondrocyte ECM was formed. The SF/HAp three-layer osteochondral bionic scaffold exhibited favorable pore size, porosity, and drug sustained-release properties. It demonstrated good biocompatibility in vitro and encouraging repair effect at osteochondral defect site in vivo, thereby expected to enabling the repair and regeneration of osteochondral damage.
Highlights
Due to low cellularity and lack of vascularity and innervation, damaged articular hyaline cartilage often cannot repair itself spontaneously [1] and is prone to further degeneration when subjected to exercise and load, resulting in pain and dysfunction [2]
In consideration of the tissue sections of normal rabbit knee joint and the requirements of tissue engineering scaffolds suitable for different cell growth, we selected the concentration of silk fibroin (SF) according to the pore size distribution and porosity under electron microscope
We found that the porosity of each experimental group was not significantly changed compared to that of the blank group (P > 0:05), which was maintained at approximately 45%
Summary
Due to low cellularity and lack of vascularity and innervation, damaged articular hyaline cartilage often cannot repair itself spontaneously [1] and is prone to further degeneration when subjected to exercise and load, resulting in pain and dysfunction [2]. Besides providing a frame for seed cells to adhere, proliferate, and differentiate, scaffolds can serve as a carrier for the release of growth factors They can offer a mechanically stable environment to facilitate tissue regeneration [6,7,8]. HAp is a calcium phosphate mineral that has gained widespread attention because of the similarity of its chemical composition and crystal structure to those of natural bone minerals. It has been successfully used in clinical bone repair and has produced satisfactory curative results [10]
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