Butyrate enhances erastin-induced ferroptosis of osteosarcoma cells via regulating ATF3/SLC7A11 pathway.

Osteosarcoma (OS) is a highly fatal bone tumor characterized by high degree of malignancy and early lung metastasis. Traditional chemotherapy fails in improving the efficacy and survival rate of patients with OS. Butyrate (NaBu) has been reported as a new antitumor drug for inhibiting proliferation and inducing apoptosis in various cancer cells. However, the effect of NaBu on the ferroptosis of OS is still unknown. This study aimed to investigate whether NaBu promotes erastin-induced ferroptosis in OS cells and to uncover the underlying mechanism. Here, we found that NaBu significantly enhanced erastin-induced ferroptosis in vitro and in vivo. Compared with the group that erastin used alonely, pre-treating with NaBu exacerbated erastin-meditated GSH depletion, lipid peroxidation, and mitochondrial morphologic changes in OS cells. In a subcutaneous OS model, NaBu combined with erastin significantly reduced tumor growth and increased the levels of 4-HNE. Mechanistically, NaBu downregulated SLC7A11 transcription via regulating ATF3 expression. Overexpression of ATF3 facilitated erastin to induce ferroptosis, while ATF3 knockdown attenuated NaBu-induced ferroptosis sensitivity. In conclusion, our findings revealed a previously unidentified role of NaBu in erastin-induced ferroptosis by regulating SLC7A11, suggesting that NaBu may be a potential therapeutic agent for OS treatment.

Discovery of Muscle-Tendon Progenitor Subpopulation in Human Myotendinous Junction at Single-Cell Resolution.

The myotendinous junction (MTJ) is a complex and special anatomical area that connects muscles and tendons, and it is also the key to repairing tendons. Nevertheless, the anatomical structure and connection structure of MTJ, the cluster and distribution of cells, and which cells are involved in repairing the tissue are still unclear. Here, we analyzed the cell subtype distribution and function of human MTJ at single-cell level. We identified four main subtypes, including stem cell, muscle, tendon, and muscle-tendon progenitor cells (MTP). The MTP subpopulation, which remains the characteristics of stem cells and also expresses muscle and tendon marker genes simultaneously, may have the potential for bidirectional differentiation. We also found the muscle-tendon progenitor cells were distributed in the shape of a transparent goblet; muscle cells first connect to the MTP and then to the tendon. And after being transplanted in the MTJ injury model, MTP exhibited strong regenerative capability. Finally, we also demonstrated the importance of mTOR signaling for MTP maintenance by in vitro addition of rapamycin and in vivo validation using mTOR-ko mice. Our research conducted a comprehensive analysis of the heterogeneity of myotendinous junction, discovered a special cluster called MTP, provided new insights into the biological significance of myotendinous junction, and laid the foundation for future research on myotendinous junction regeneration and restoration.

[Modified Chevron osteotomy in the treatment of moderate and severe hallux valgus].

OBJECTIVE: To investigate the method and clinical effect of modified Chevron osteotomy of the distal end of the first metatarsal in the treatment of moderate and severe hallux valgus. METHODS: From January 2015 to January 2019, 28 patients(30 feet) with moderate and severe hallux valgus were treated with modified Chevron osteotomy combined with lateral soft tissue release of the first metatarsophalangeal joint, including 2 males (2 feet) and 26 females (28 feet). The age ranged from 35 to 74 (57.3±9.3) years;10 feet on the left, 16 feet on the right, 2 cases on both sides(4 feet);the course of disease was 3 to 12 (9.32±3.89) years. The changes of hallux valgus angle(HVA), intermetatarsal angle(IMA) between the first and second metatarsals and distal metatarsal articular angle(DMAA) of the first metatarsal were measured and compared before and 6 months after operation. The American Orthopaedic Foot and Ankle Society(AOFAS) thumb joint scoring system was used to evaluate the curative effect. RESULTS: All 28 patients were followed up for 8 to 16 (11.28±3.42) months. The incision healed well in all patients, and there were no complications such as incision infection and metatarsal head necrosis. The healing time of osteotomy site was 6 to 10(7.12±1.34) weeks. Preoperative HVA, IMA, DMAA and AOFAS were (36.06±6.02) °, (21.78±4.16) °, (8.21±2.65) ° and (52.90±10.97) respectively, at six months after operation, they were (8.87±2.46) °, (11.66±2.84) °, (3.65±1.00) ° and (87.45±10.55) respectively, there was significant difference between preoperative and 6 months after operation(P<0.05). At 6 months after operation, AOFAS score was excellent in 20 feet, good in 7 feet and poor in 3 feet. Among the 3 patients with poor scores, 2 were excellent after revision, and 1 was significantly improved after using custom insoles. CONCLUSION: Modified Chevron can effectively correct HVA, IMA and DMAA and improve functional recovery. The modified Chevron osteotomy increases the moving distance and the contact of the osteotomy surface. It can be fixed with multiple screws, has strong correction ability, and can exercise early. It is one of the optional methods for the treatment of moderate and severe hallux valgus.

Acacetin inhibits RANKL-induced osteoclastogenesis and LPS-induced bone loss by modulating NFATc1 transcription.

Osteolytic disorders are characterized by impaired bone volume and trabecular structure that leads to severe fragility fractures. Studies have shown that excessive osteoclast activity causes impaired bone microstructure, a sign of osteolytic diseases such as osteoporosis. Approaches of inhibiting osteoclastogenesis and bone resorption specifically could prevent osteoporosis and other osteolytic disorders. Acacetin is a potent molecule extracted from plants with anti-cancer and anti-inflammatory bioactivities. Here, we demonstrated, for the first time, that acacetin repressed osteoclastogenesis, formation of F-actin rings, bone resorption activity, and osteoclast-related gene expression in vitro through modulating ERK, P38, and NF-κB signaling pathways and preventing expression of NFATc1. Micro-CT and H & E staining results indicated that acacetin alleviated LPS-induced osteolysis in vivo. Overall, our findings suggested that acacetin could help to prevent osteoporosis and other osteoclast-related osteolytic disorders.

Molecular mechanisms of mechanical load-induced osteoarthritis.

INTRODUCTION: Mechanical loading enhances the progression of osteoarthritis. However, its molecular mechanisms have not been established. OBJECTIVE: The aim of this review was to summarize the probable mechanisms of mechanical load-induced osteoarthritis. METHODS: A comprehensive search strategy was used to search PubMed and EMBASE databases (from the 15th of January 2015 to the 20th of October 2020). Search terms included "osteoarthritis", "mechanical load", and "mechanism". RESULTS: Abnormal mechanical loading activates the interleukin-1ß, tumour necrosis factor-α, nuclear factor kappa-B, Wnt, transforming growth factor-ß, microRNAs pathways, and the oxidative stress pathway. These pathways induce the pathological progression of osteoarthritis. Mechanical stress signal receptors such as integrin, ion channel receptors, hydrogen peroxide-inducible clone-5, Gremlin-1, and transient receptor potential channel 4 are present in the articular cartilages. CONCLUSION: This review highlights the molecular mechanisms of mechanical loading in inducing chondrocyte apoptosis and extracellular matrix degradation. These mechanisms provide potential targets for osteoarthritis prevention and treatment.