# Intermitt Dynamic Compression Conters Anabolic Effects in Articular Cartilage
## 3 Results
### Inhibition of the TGF-\(\beta\) Type I Receptor ALK5 Blocks Cartilage Remodeling  
Given the lack of compression effect in TGF-\(\beta\)1-treated explants, we investigated whether the ALK5-inhibitor, SB-525334, could inhibit compression-induced cartilage turnover. Treatment with 2 uM SB-525334 strongly inhibited the metabolic activity in compressed naive explants (SB-525334 + compression vs. w/o + compression) and explants treated with 50 ng/mL TGF-\(\beta\)1 (SB-525334 + TGF-\(\beta\)1 vs. TGF-\(\beta\)1) at day 14 and 21 of culture (all \(p\) < 0.0001). Explants were, however, still viable (Figure 5A,B). PRO-C2 was increased by compression in naive ex  
Figure 3: Effect of dynamic compression on IGF-1-induced cartilage remodeling. Cartilage ECM turnover biomarkers released to explant conditioned media over a three-week culture period. Bovine cartilage explants (\(n\) = 12 for each condition) were cultured in IGF-1 [100 ng/mL] in the absence of loading (IGF-1) or with 5 times weekly compression (IGF-1 + compression). Explants cultured in culture media without (w/o) or including compression (w/o + compression) were co-cultured. (**A**) Alamar Blue metabolic activity assessment of explants at day 0, 7, 14 and 21 of culture. (**B**) Metabolic activity at day 21. (**C**) PRO-C2 release from explants into conditioned media measured at day 0, 7, 14 and 21 of culture. (**D**) PRO-C2 release at day 21. (**E**) FBN-C release into conditioned media at day 0, 7, 14 and 21 of culture. (**F**) FBN-C measured at day 21. Data point and bars represent geometric least-squares (LS) mean values and error bars represent 95% confidence levels. (**A**,**C**,**E**) are presented on a logarithmic scale and (**B**,**D**,**F**) are presented on a linear scale. Asterisks (* or +) indicate Tukey-adjusted \(p\)-values: */+: \(p\) < 0.05, **/++: \(p\) < 0.01, ***/++: \(p\) < 0.001.  
plants, compared to naive unloaded explants on day 21 (\(p\) = 0.0106) (Figure 5C,D). SB-525334 inhibited the release of PRO-C2 in compressed naive explants and TGF-\(\beta\)1-stimulated explants, compared to the untreated counterparts (all \(p\) < 0.0001 at day 7, 14 and 21) (Figure 5C,D). PRO-C2 release was below the lower limit of detection with SB-525334 treatment in most explants on day 14, indicating that type II collagen formation was blocked from day 14 and onward culture by accumulation of the inhibitor. SB-525334 treatment strongly inhibited FBN-C release in compressed naive- and TGF-B1-treated explants, compared to their unloaded counterparts (all \(p\) < 0.0001 at day 7, 14 and 21). As for PRO-C2, FBN-C release with SB-525334 treatment was below the lower limit of detection in most explants on day 14, indicating a blockade in FBN-C turnover (Figure 5E,F).  
Figure 4: Effect of dynamic compression on TGF-\(\beta\)1-induced cartilage remodeling. Cartilage ECM turnover biomarkers released to the explant conditioned media over a three-week culture period. Bovine cartilage explants (\(n\) = 12 for each condition) were cultured in TGF\(\beta\)-1 [50 ng/mL] in the absence of loading (TGF\(\beta\)-1) or with 5 times weekly compression (TGF\(\beta\)-1 + compression). (**A**) Alamar Blue metabolic activity assessment of explants at day 0, 7, 14 and 21 of culture. (**B**) Metabolic activity at day 21. (**C**) PRO-C2 release measured at day 0, 7, 14 and 21 of culture. (**D**) PRO-C2 release at day 21. (**E**) FBN-C release measured at day 0, 7, 14 and 21 of culture. (**F**) FBN-C measured at day 21. Data point and bars represent geometric least-squares (LS) mean values and error bars represent 95% confidence levels. (**A,C,E**) are presented on a logarithmic scale and (**B,D,F**) are presented on a linear scale. Asterisks (* or +) indicate Tukey-adjusted \(p\)-values: */+: \(p\) < 0.05, **/++: \(p\) < 0.01, ***/++: \(p\) < 0.001, ***/++++: \(p\) < 0.0001.