ß-catenin inhibition disrupts the homeostasis of osteogenic/adipogenic differentiation leading to the development of glucocorticoid-induced osteonecrosis of the femoral head.

Glucocorticoid-induced osteonecrosis of the femoral head (GONFH) is a common refractory joint disease characterized by bone damage and the collapse of femoral head structure. However, the exact pathological mechanisms of GONFH remain unknown. Here, we observed abnormal osteogenesis and adipogenesis associated with decreased ß-catenin in the necrotic femoral head of GONFH patients. In vivo and in vitro studies further revealed that glucocorticoid exposure disrupted osteogenic/adipogenic differentiation of bone marrow mesenchymal cells (BMSCs) by inhibiting ß-catenin signaling in glucocorticoid-induced GONFH rats. Col2+ lineage largely contributes to BMSCs and was found an osteogenic commitment in the femoral head through 9 mo of lineage trace. Specific deletion of ß-catenin gene (Ctnnb1) in Col2+ cells shifted their commitment from osteoblasts to adipocytes, leading to a full spectrum of disease phenotype of GONFH in adult mice. Overall, we uncover that ß-catenin inhibition disrupting the homeostasis of osteogenic/adipogenic differentiation contributes to the development of GONFH and identify an ideal genetic-modified mouse model of GONFH.

Improving Precipitation in Cryogenic Rolling 6016 Aluminum Alloys during Aging Treatment.

This study systematically investigated the performance and microstructure characterization of cryogenic rolling (CR) and room-temperature rolling (RTR) Al-Mg-Si alloys. The result showed that the hardness of the CR alloys decreased at the early aging stage, but that the hardness of the RTR alloys increased at the early aging stage. Retrogression phenomena were apparent in the CR alloys at the early aging stage. Despite undergoing the same solid solution treatment, a few substructures were still observed in the CR alloys, and the degree of recrystallization in the CR alloys was significantly inferior to that in the RTR alloys. After aging for 50 h, the strength and precipitates' density in the CR 75 alloy were higher than that in the other alloys; this indicated that the substructures were beneficial to precipitation and precipitate growth. A precipitation strength model was employed to illustrate the precipitation contribution at different aging stages. The results showed that the CR 75 alloy obtained the strongest precipitation strengthening.

Case Report: First Documented Hip Arthroplasty on Chinese Patient with Ochronotic Arthropathy.

Alkaptonuria (AKU) is a rare autosomal recessive disorder caused by homogentisc acid (HGA) accumulation, the deposition of which in the joints usually causes ochronotic arthropathy. With no specific therapy for AKU currently, total joint arthroplasty in ochronotic arthropathy is applied to relieve the symptoms. A 63-year-old female patient came to our Orthopedic Surgery Department in 2019, complaining of severe limitation of movement and pain in the right hip for more than one year. A right total hip arthroplasy (THA) was performed due to the ineffective conservative therapy. At a follow-up of more than 15 months, the woman had full mobility with no complaining of pains. Since there is no relevant case reported about THA therapy for Chinese AKU patients, this report provides a feasible scheme, which makes clinical data more comprehensive.