We previously found that the combination of an autologous bone mesenchymal stem cell-derived extracellular matrix (aBMSC-dECM) scaffold with bone marrow stimulation could enhance hyaline cartilage regeneration. We suspected that chondrogenic differentiation could be induced by the aBMSC-dECM scaffold. This study aimed to investigate whether aBMSC-dECM scaffolds could promote chondrogenic differentiation without exogenous growth factors. BMSCs were seeded on aBMSC-dECM scaffolds and cultured in vitro with or without TGF-β3 (E+ or E- group). Atelocollagen scaffolds were used as controls (C+ or C- group). The chondrogenic differentiation was evaluated by histological, biochemical and real-time PCR assays. After 3 weeks, cartilage-like tissue with a homogeneous structure, a high cartilaginous matrix content (proteoglycan and type II collagen) and high expression levels of cartilage-associated genes (COL2A1, ACAN and SOX9) was observed in the E+, E- and C+ groups. In addition, BMSCs in each scaffold (E group or C group) were preconditioned with chondrogenic media in vitro for 1 week and then implanted in the backs of nude mice for 3 weeks. Three weeks later, cartilage matrix formation (proteoglycan and type II collagen) was achieved only in the E group, confirmed by safranin O staining and immunohistochemical staining for type II collagen. Taken together, these results indicate that aBMSC-dECM scaffolds could induce chondrogenic differentiation. Thus they could be successful candidate scaffolds for cartilage tissue engineering.

Many researches have investigated the changes associated with immobilization-induced osteoarthritis (OA). However, there are only few studies focusing on the effect of unilateral knee immobilization on cartilage matrix changes in the contralateral mobile knee. The aim of the present study was to investigate the influence of immobilization on the cartilage matrix in the contralateral mobile knees in a rabbit model of OA induced by immobilization. Right knees (experimental knees) of eighteen mature female rabbits were immobilized at an extension of 180° with orthopedic casting tape for 2, 4, or 8 weeks. Left knees (contralateral knees) of the immobilized rabbits were not subjected to immobilization. The knees of six non-immobilized rabbits were designated as control knees. Following immobilization, cartilage specimens from the medial femoral condyle underwent macroscopic, histological, immunohistochemical, and biochemical evaluations. Roughness of cartilage surface was detected in the experimental knees at 2 weeks, and cartilage degeneration was further developed. In the contralateral knee, cartilage showed degenerative changes after 4 weeks. Safranin-O staining and glycosaminoglycan (GAG) contents were reduced in the experimental knees following immobilization and in the contralateral intact knees after 4 and 8 weeks. Type II collagen staining was gradually reduced, type I collagen accumulation was obviously detected in the upper and middle layers of cartilage in experimental knees after 8 weeks, and the collagen orientation was gradually disorganized in both knees at 4 and 8 weeks. For both experimental and contralateral knees, collagen contents were significantly decreased at 8 weeks, and Mankin and Osteoarthritis Research Society International (OARSI) scores increased over time. OA developed in the contralateral intact knee with the progress of OA in the immobilized knee in a rabbit model of immobilization-induced OA.

This study aimed to evaluate the effects of cell-derived (BMSCs and chondrocytes) extracellular matrix (ECM) scaffolds incorporating bone marrow aspirate concentrate (BMAC) on cartilage regeneration, and to determine whether BMAC-loaded BMSCs-derived (BM-d) ECM scaffolds were comparable to chondrocytes-derived (Ch-d) ECM scaffolds in terms of cartilage regeneration. In this study, BMSCs and chondrocytes were harvested and isolated, then developed into BM-d and Ch-d ECM scaffolds. The scaffolds were fully immersed in BMAC and subsequently utilized for inducing chondrogenic differentiation in vitro and cartilage regeneration in vivo. The in vitro results demonstrated that chondrogenesis was effectively promoted, accompanied by scaffold biodegradation, in both BM-d and Ch-d ECM groups as culture progressed over time. The ex vivo results, obtained using nude mice, showed that cartilage-like appearance gradually developed and cartilage matrix accumulation gradually increased in both groups over time. However, more significant calcium deposition was observed in the BM-d ECM group as time progressed. After 12 weeks of in vivo cartilage repair, white and smooth cartilage-like tissues had formed in the defect areas of both ECM groups. The regenerated tissues in both ECM groups fully integrated with the surrounding host tissues and exhibited higher mechanical properties compared to those in the microfracture group. Moreover, the in vivo histological and biochemical results indicated that more hyaline-like cartilage regenerated in both ECM groups, whereas more fibrocartilage formed in the microfracture group. In summary, our results suggest that BM-d and Ch-d ECM scaffolds loaded with BMAC can effectively promote cartilage regeneration both in vitro and in vivo, with BM-d ECM scaffolds being comparable to Ch-d ECM scaffolds.