Regenerative effects of 3-D bioprinted gradient hydrogel scaffold in rabbit knee osteochondral defect model

Tissue engineering offers creative solutions in the treatment of osteochondral defects (OCD). Thanks to 3-D bioprinting technology, it is possible to produce tissue scaffolds that can mimic osteochondral tissue. The aim of this study is to implant the 3-D bioprinted scaffold into the rabbit knee OCD model and determine its effectiveness in healing. Chitosan-based tissue scaffold was produced in a gradient structure using microextrusion technique with a 3-D bioprinter. Peptide amphiphiles were used to mimic cartilage tissue, nano-hydroxyapatite and boron-doped nano-hydroxyapatite were used to mimic bone tissue. To increase regenerative efficiency, human umbilical cord mesenchymal stem cells were added to the scaffold. New Zealand White male rabbits were used in in-vivo experiments, and negative control (NK), positive control (PK), acellular hydrogel gradient scaffold (HGI) and cellular hydrogel gradient scaffold (h-HGI) experimental groups were formed. Macroscopic scoring, micro CT and histological evaluation were used in post-operative 6th and 12th week analyses. In macroscopic scoring, the lowest mean was seen in the NK group at the 6th and 12th weeks, while the highest mean was seen in the PK group. At the twelfth week, the HGI and h-HGI groups gave results similar to the PK group. It was observed that the bone volume/tissue volume ratio and bone mineral density values of the HGI and h-HGI groups were higher than the PK group at the 12th week. In histological examination; The best recovery findings were observed in the PK group and second in the h-HGI group. Hyaline-like cartilage formation was observed in the h-HGI group, but the results were heterogeneous. The HGI group showed much better collagen synthesis compared to the negative control group. As a result, the tissue scaffold produced showed successful results in terms of defect filling in the OCD treatment. By adding MSC, the regenerative potential of the scaffold was increased.