IL1B and chondrosarcoma: IL-1β downregulates peroxisome proliferator–activated receptor γ (PPARγ) and increases expression of MMPs.45 Results from a study focused on inflammatory gene expression in IL-1β–stimulated human chondrosarcoma cells indicate that HMW HA increases the expression of PPARγ and decreases that for COX-2, MMP-1, and MMP-13.