Repair of osteochondral defects with a construct of mesenchymal stem cells and a polydioxanone/poly(vinyl alcohol) scaffold

The purpose of the present study was to test the potential of an MSC (mesenchymal stem cell)/PDO/PVA [polydioxanone/poly(vinyl alcohol)] hybrid scaffold construct to repair cartilage defects. For the in vitro study, MSCs were isolated from human bone marrow and cultured in PDO/PVA scaffolds for 4 weeks. Gross and microscopic examinations were performed, as well as RT-PCR (reverse-transcription PCR) analyses for cartilage-specific genes. For the in vivo study, MSCs isolated from rabbits were cultured in the PDO/PVA scaffolds and tissue-engineered into neocartilage, then implanted into the osteochondral defect on the distal femur of the same rabbits. Gross and histological evaluations were performed at 8 weeks after the implantation. The results of the in vitro study demonstrated that the physical stability of the cell-cultured hybrid scaffold was maintained until 4 weeks after initial placement. Scanning electronmicroscopy indicated the infiltration of the cells into, and appropriate interactions with, the scaffolds. RT-PCR showed an expression of cartilage-specific genes similar to that seen with pellet-cultured MSCs. From the in vivo study, the defect area of the experimental group showed smooth consistent glistening white tissue resembling articular cartilage, whereas the control group showed a red irregular tissue with surface depression. The regenerated cartilage of the experimental group showed metachromasia on both Safranin-O and dense staining for type II collagen, whereas the control group showed little metachromatic staining and less intense staining for type II collagen. A histological score of the quality of cartilage formation indicated that the MSC/PDO/PVA hybrid scaffold successfully produced neocartilage in vitro and enhanced the repair of the osteochondral defect in vivo. Further in vivo studies will be necessary to elucidate further the value of PDO/PVA as a scaffold material for cartilage regeneration.