Methods: Under sterile conditions, cartilage strips (60x17x2 mm) were harvested from bovine nasal septum and plowed over 40mm for 2 hours at 37°C by means of a cylindrical aluminum indenter (diameter 25 mm) with 25, 50 and 100N normal force at 10mm/s (in vivo typical value for TMJ stress-field translation). We examined by real time quantitative polymerase chain reaction (RT-qPCR) gene expression of collagen type I (Coll1), collagen type II (Coll2), aggrecan (Agg), fibronectin (Fn) and stromelysin-1 (MMP-3) and its inhibitor TIMP-1 at the post-loading equilibration times of 2, 4, 24 and 48 hours. Quantitative data was analyzed by ANOVA (significance: p<0.05).
Results: RT-qPCR showed that plowing at 10mm/s at either 100 or 50N mostly leads to a catabolic reponse. In particular, cartilage strips (N=9) loaded at 100N showed up-regulation of MMP-3 up to 6.5x, whereas strips loaded at 50N showed a 5x MMP-3 expression increase. MMP-3 up-regulation decreased over time, reaching a minimum at 48 hours. Furthermore only plowing at 100N caused down-regulation of the Agg gene (2.5x), peaking at 48 hours. All other analyzed genes did not show any regulation also at 25N (here except a slight up-regulation of TIMP-1).
Conclusions: These results could be explained as catabolic reactions possibly leading to a mechanically induced remodelling process. Plowing of cartilage according to real data from TMJ dynamic stereometry can induce significant mechanobiological effects (SNSF grant #325200-110067).