MMP1 and osteoarthritis: Liu et al. (2021) administered pure PSO in doses of 0.95 g/kg, 1.27 g/kg, and 1.59 g/kg to rats with osteoarthritis via gavage. They compared these doses with a model group that received 1.59 g/kg of normal saline via gavage. The mRNA expression of matrix metalloproteinase-1 in chondrocytes decreased significantly (p < 0.01), while mRNA expression of type II collagen (CoII) increased significantly (p < 0.01).