Osteochondral Regeneration using PLGA Scaffolds under Short-term Continuous Passive Motion in a Rabbit Model

Abstract

Cells, scaffolds, and stimulation are three important components in cartilage tissue engineering. Osteochondrosis is a disorder of endochondral ossification in epiphyseal growth plate, leading to the osteoarthritis or the degenerative joint cartilage. Continuous passive motion (CPM), a natural physiological stimulation, should promote cell proliferation in joint defect regeneration. To better understand how continuous passive motion affects on the formation of repairing tissue in full-thickness cartilage defects, this study evaluated the effects of CPM in articular defects in rabbit model by macroscopic observation, computed tomography scanning, and histological evaluation. A 3-mm depth from the articular surface was produced in the patella groove and the medial condyle respectively to represent the high- and low- weight-bearing regions. Poly DL-lactic-co-glycolic acid (PLGA) that is a biodegradable polymer approved by FDA is widely used in biomaterial products. PLGA scaffolds were fabricated into the cylinder porous sponges by salt-leaching technique. The scaffolds were placed into the osteochondral defects for experimental group. Thirty-six rabbits were separated into six groups which were treated in individual study: with/without PLGA scaffold with immobilization on week 4 and 12; with/without PLGA scaffold with free cage activity for 4 and 12 weeks; and with/without PLGAscaffold with CPM on week 4 and 12. The results at four weeks showed the use of PLGA scaffold provided the mechanical functions at the medial condyle. Even though the histological scores of the immobilization treated with PLGA scaffold showed the highest, there was osteophyte which can limit the range of motion on the joint. After 12 weeks post-operation, the healing process of scaffold treated CPM were significantly better than that CPM alone at the medial condyle (p = 0.048). In conclusion, the articular cartilage function, and cell differentiation and proliferation are important to regenerate hyaline cartilage. This study showed that the scaffolds in combination of CPM can induce both chondrogenesis and osteogenesis in repaired area and would be a possible method for articular cartilage repair in clinic and cartilage tissue engineering.