Osteoarthritis (OA) is a severe inflammation-related disease which leads to cartilage destruction. The retinoic acid receptor gamma (RARγ) has been indicated to be involved in many inflammation processes. However, the role and mechanism of RARγ in cartilage destruction caused by inflammation in OA are still unknown. Here, we demonstrated that the RARγ was highly expressed in chondrocytes of OA patients compared with healthy people and was positively correlated with the damage degree of cartilage in OA. Cytokine TNF-α promoted the transcription and expression of RARγ through activating the NF-κB pathway in OA cartilage. In addition, the overexpression of RARγ resulted in the upregulation of matrix degradation and inflammation associated genes and downregulation of differentiation and collagen production genes in human normal chondrocyte C28/I2 cells. Mechanistically, overexpression of RARγ could increase the level of p-IκBα and p-P65 to regulate the expression of downstream genes. RARγ and IκBα also could interact with each other and had the same localization in C28/I2 cells. Moreover, the SD rats OA model induced by monosodium iodoacetate indicated that CD437 (RARγ agonist) and TNF-α accelerated the OA progression, including more severe cartilage layer destruction, larger knee joint diameter, and higher serum ALP levels, while LY2955303 (RARγ inhibitor) showed the opposite result. RARγ was also highly expressed in OA group and even higher in TNF-α group. In conclusion, RARγ/NF-κB positive feedback loop was activated by TNF-α in chondrocyte to promote cartilage destruction. Our data not only propose a novel and precise molecular mechanism for OA disease but also provide a prospective strategy for the treatment.

Objective: The aim of this study was to introduce a modified surgical procedure using anatomic locking plate (ALP) fixation and coracoclavicular (CC) stabilisation with multistrand titanium cable (MTC) to repair unstable distal clavicle fractures, and to estimate clinical effects of these people. Materials and methods: Between July 2016 and April 2018, we treated 7 patients with unstable distal clavicle fracture by ALP fixation and CC stabilisation with MTC. After the surgery, we followed up every patient for at least 24 months and analysed their clinical results. Results: The average term required for fracture healing was 9.9 (range, 9–12 weeks) and all cases are successful in fracture healing. The average Constant score was 94.6 points (range, 92–100) at the last follow-up; the modified University of California, Los Angeles (UCLA) shoulder rating scale was 33.4 points (range, 31–35) at the last follow-up. There was no infection, hardware failure and iatrogenic fracture in all the cases. Conclusions: ALP fixation and CC stabilisation with MTC is a really good method for the treatment of unstable distal clavicle fractures. This surgical technique can provide stable fixation for early functional exercise, and prevent extra shoulder joint damage.