Triptolide has been widely reported to exhibit potential therapeutic value in multiple inflammatory diseases, such as rheumatoid arthritis, systemic lupus erythematosus, and psoriasis. Although its safety and efficacy as an anti-inflammatory agent have been verified by many studies, the effect of triptolide on osteoarthritis (OA) was not clearly understood. In this study, we found that triptolide prevented OA development in a surgical destabilization of the medial meniscus (DMM) mouse model. In addition, triptolide inhibited both DMM-induced and LPS-induced expression of pro-inflammatory cytokines in the human monocytic cell line THP-1. Further mechanistic studies showed that the reduction of pro-inflammatory cytokines by triptolide was mediated by the upregulation of nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing protein 3 (NLRP3) and downregulation of caspase-1. Finally, we identified that hsa-miR-20b, a microRNA targeting the NLRP3 gene, was downregulated by triptolide. This study provides a novel insight into the effect on triptolide in preventing OA pathogenesis.

Tanshinone IIA (TSA) is a lipophilic diterpene purified from the Chinese herb Danshen, which exhibits potent antioxidant and anti-inflammatory properties. Effect of TSA remains largely uninvestigated on the osteogenic differentiation of bone marrow mesenchymal stem cells (BM-MSCs), which are widely used in cell-based therapy of bone diseases. In the present study, both ALP activity at day 7 and calcium content at day 24 were upregulated during the osteogenesis of mouse BM-MSCs treated with TSA (1 and 5 μM), demonstrating that it promoted the osteogenesis at both early and late stages. We found that TSA promoted osteogenesis and inhibited osteoclastogenesis, evident by RT-PCR analysis of osteogenic marker gene expressions. However, osteogenesis was inhibited by TSA at 20 μM. We further revealed that TSA (1 and 5 μM) upregulated BMP and Wnt signaling. Co-treatment with Wnt inhibitor DKK-1 or BMP inhibitor noggin significantly decreased the TSA-promoted osteogenesis, indicating that upregulation of BMP and Wnt signaling plays a significant role and contributes to the TSA-promoted osteogenesis. Of clinical interest, our study suggests TSA as a promising therapeutic strategy during implantation of BM-MSCs for a more effective treatment of bone diseases.