Tougu Xiaotong capsule inhibits the tidemark replication and cartilage degradation of papain-induced osteoarthritis by the regulation of chondrocyte autophagy

Abstract

The tidemark is located between calcified and non-calcified cartilage matrices. Tidemark replication plays an important role in the pathogenesis of osteoarthrosis (OA). Autophagy, or cellular self-digestion, is an essential cellular homeostasis mechanism that was found to be deficient in osteoarthritic cartilage. This study evaluated the effects of Tougu Xiaotong capsule (TXC) on the tidemark replication and cartilage degradation, and also investigated LC3 I/II, which executes autophagy, the potential role of ULK1, an inducer of autophagy, and Beclin1, a regulator of autophagy, in the development of a papain-induced OA in rat knee joints. Using a papain-injected knee rat model, standard histological methods were used to validate our model as well as treatment with TXC or glucosamine (GlcN). After 12 weeks of treatment, the changes of cartilage structure were observed by digital radiography (DR), optical microscopy, scanning electron microscopy and transmission electron microscopy, and the LC3 I/II, ULK1 and Beclin1 levels were measured by western blotting. Cartilage degradation was evaluated by the Mankin score on paraffin-embedded sections stained with Safranin O-fast green. TXC was found to improve the arrangement of subchondral bone collagen fibers and calcium phosphate crystals, inhibit the tidemark replication and delay the cartilage degradation in the papain-induced OA. Our results also showed that LC3 I/II, ULK1 and Beclin1 levels in both the TXC+OA and GlcN+OA groups were significantly increased compared to those in the OA group. The results indicate that TXC could inhibit the tidemark replication and cartilage degradation by the regulation of chondrocyte autophagy.

Tougu Xiaotong capsule promotes chondrocyte autophagy by regulating the Atg12/LC3 conjugation systems

“…Accordingly, the development of novel drugs from natural herbs, which can provide cartilage protection and be safely used in the prolonged treatment of OA, is required. TXC has been used to control tidemark replication and cartilage degradation by inhibiting chondrocyte apoptosis and promoting chondrocyte autophagy (18,19). Therefore, in the present study, we sought to determine the efficacy of TXC on chondrocyte autophagy, as a chondroprotective agent.…”

“…The number of lysosomes increases in the process of autophagy, accompanied by an increased expression of beclin 1 and LC3 (33). Beclin 1, forming a complex with type III PI3 kinase and Vps34, participates in the nucleation of the autophagic vesicle (19). The involvement of LC3 in the protein conjugation system is required in the expansion of the autophagosome.…”

“…TXC has been widely used for the therapy of OA in the Second People's Hospital affiliated to Fujian University of TCM for 2 decades and has been shown to control pain and improve dysfunction in patients with OA (18). We have previously reported that TXC inhibits tidemark replication and cartilage degradation by the regulation of chondrocyte autophagy (19). However, the precious molecular and cellular mechanisms responsible for the effects of TXC on the regulation of chondrocyte autophagy remain largely unknown.…”

Protective effects of the Tougu Xiaotong capsule on morphology and osteoprotegerin/nuclear factor-κB ligand expression in rabbits with knee osteoarthritis

“…TGXTC, a traditional Chinese medicine, has been demonstrated to be clinically effective in the treatment of OA, which has been indicated by in vitro and in vivo studies where TGXTC was observed to reverse cartilage degeneration in OA (11)(12)(13)(14)(15)(16)(17)(18)(19)(20). However, whether TGXTC has a protective effect on subchondral bone remodeling remains unclear.…”

“…The Tougu Xiaotong capsule (TGXTC), characterized as a multi-target and multi-channel compound (11), contains a proven recipe for OA treatment, consisting of Morinda officinalis, Paeonia lactiflora, Ligusticum chuanxiong and Sarcandra glabra (12). Previous studies have demonstrated that this compound may inhibit chondrocyte apoptosis, promote chondrocyte proliferation (13)(14)(15)(16), suppress expression of matrix metalloproteinases and inflammatory cytokines (17)(18)(19), improve the structure and function of cartilage (20) and promote osteoblast proliferation and activation (21). However, the regulatory effects of TGXTC on subchondral bone remodeling remain largely unclear.…”