Coupling plowing of cartilage explants with gene expression in models for synovial joints

Cartilage strips harvested from bovine nasal septa of 12-months-old calves were subjected for 2 h to a plowing-regime with indenter normal force of 50 or 100 N and a sliding speed of 10 mm s−1. 50 N produced a tractional force of 1.2±0.3 N, whereas 100 N generated a tractional force of 8.0±1.4 N. Furthermore, quantitative-real-time polymerase chain reaction experiments showed that TIMP-1 was 2.5x up-regulated after 50 N plowing and 2x after 100 N plowing, indicating an ongoing remodeling process. The expression of collagen type-I was not affected after 50 N plowing but it was up-regulated (6.6x) after 100 N plowing, suggesting a possible progression to an injury stage of the cartilage, as previously reported in cartilage of osteoarthritic patients. We conclude that plowing as performed by our mimetic system at the chosen experimental parameters induces changes in gene expression depending on the tractional force, which, in turn, relates to the applied normal force.