Osteochondral regeneration using scaffold-free constructs of adipose tissue-derived mesenchymal stem cells made by a bio three-dimensional printer with a needle-array in rabbits.

Osteoarthritis is a major joint disease for which medical interventions have been extensively investigated in humans and animals. In this study, we examined the regeneration of articular cartilage and subchondral bone using a scaffold-free construct consisting of adipose tissue-derived mesenchymal stem cells (AT-MSCs) fabricated using a bio three-dimensional (3D) printer. AT-MSCs were isolated from three rabbits and cultured to a number of sufficient for creation of 3D-printed constructs. One construct consisted of 960 spheroids obtained from 3.5 × 104 autologous AT-MSCs. The construct was then implanted into an osteochondral defect (diameter 4 mm and depth 4 mm) surgically bored into the left femoral trochlear groove of each rabbit. Three months after implantation, healing was assessed by computed tomography, magnetic resonance (MR) imaging, and pathology. MR images were evaluated based on a modified two-dimensional (2D)-magnetic resonance observation of cartilage repair tissue (MOCART) grading system, and gross and microscopic histology were scored according to the International Cartilage Repair Society scale. At the time of imaging, treated defects had become radiopaque, while control defects remained radiolucent. Total 2D-MOCART scores were higher in the implanted defects than in the controls, but not to a statistically significant extent. Similarly, average histological scores were comparable among all groups, although average gross scores were significantly higher in implanted defects than in controls. This is the first demonstration of a scaffold-free 3D-printed construct consisting of autologous AT-MSCs regenerating cartilage and subchondral bone within three months.