MMP2 and Arthritis: Some publications demonstrated that HKL could inhibit the expression of MMPs in other diseases, such as arthritis and cancer (Ahn et al., 2006; Kim et al., 2010; Chen et al., 2014; Zhang et al., 2015), however, the results of our study displayed that HKL could up-regulate the protein expression of MMP1, MMP2, MMP3, and MMP9 while down-regulate the protein expression of TIMP1 both at the lowest effective concentration at 6 μg/ml (Figures 5D–I).