Curcumin alleviates osteoarthritis in mice by suppressing osteoclastogenesis in subchondral bone via inhibiting NF-κB/JNK signaling pathway.

This study explored the mechanism of curcumin (CUR) suppressing osteoclastogenesis and evaluated its effects on osteoarthritis (OA) mouse. Bone marrow-derived macrophages were isolated as osteoclast precursors. In the presence or absence of CUR, cell proliferation was detected by CCK-8, osteoclastogenesis was detected by tartrate-resistant acid phosphatase (TRAP) staining, F-actin rings formation was detected by immunofluorescence, bone resorption was detected by bone slices, IκBα, nuclear factor kappa-B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways were detected using western blot, osteoclastogenesis-related gens were measured using quantitative polymerase chain reaction. A knee OA mouse model was designed by destabilizing the medial meniscus (DMM). Thirty-six male mice were divided into sham+vehicle, OA+vehicle, and OA+CUR groups. Mice were administered with or without CUR at 25 mg/kg/d from the first post-operative day until sacrifice. After 4 and 8 weeks of OA induction, micro-computed tomography was performed to analyze microstructure changes in subchondral bone, hematoxylin and eosin staining was performed to calculate the thickness of the calcified and hyaline cartilage layers, toluidine blue O staining was performed to assess the degenerated cartilage, TRAP-stained osteoclasts were counted, and NF-κB, phosphorylated Jun N-terminal Kinases (p-JNK), and receptor activator of nuclear factor κB ligand (RANKL) were detected using immunohistochemistry. CUR suppressed osteoclastogenesis and bone resorption without cytotoxicity. CUR restrained RANKL-induced activation of NF-κB, p-JNK and up-regulation of osteoclastogenesis-related genes. CUR delayed cartilage degeneration by suppressing osteoclastogenesis and bone resorption in early OA. The mechanism of CUR inhibiting osteoclastogenesis might be associated with NF-κB/JNK signaling pathway, indicating a novel strategy for OA treatment.

Cardamonin inhibits osteogenic differentiation by downregulating Wnt/beta-catenin signaling and alleviates subchondral osteosclerosis in osteoarthritic mice.

Osteoarthritis (OA) is a common degenerative joint disease, and subchondral osteosclerosis is an important pathological change that occurs in its late stages. Cardamonin (CD) is a natural flavonoid isolated from Alpinia katsumadai that has anti-inflammatory activity. The objectives of this study were to investigate the therapeutic effects and potential mechanism of CD in regulating OA subchondral osteosclerosis at in vivo and in vitro settings. Eight-week-old male C57BL/6J mice were randomly divided into four groups: sham operation, anterior cruciate ligament transection (ACLT)-induced OA model, low-dose and high-dose CD treated ACLT-OA model groups. Histological assessment and immunohistochemical examinations for chondrocyte metabolism-related markers metalloproteinase-13, ADAMTS-4, Col II, and Sox-9 were performed. Microcomputed tomography was used to assess the sclerosis indicators in subchondral bone. Further, MC3T3-E1 (a mouse calvarial preosteoblast cell line) cells were treated with various concentrations of CD to reveal the influence and potential molecular pathways of CD in osteogenic differentiations. Animal studies suggested that CD alleviated the pathological changes in OA mice such as maintaining integrity and increasing the thickness of hyaline cartilage, decreasing the thickness of calcified cartilage, decreasing the Osteoarthritis Research Society International score, regulating articular cartilage metabolism, and inhibiting subchondral osteosclerosis. In vitro investigation indicated that CD inhibited alkaline phosphatase expression and production of calcium nodules during osteogenic differentiation of MC3T3-E1 cells. In addition, CD inhibited the expression of osteogenic differentiation-related indicators and Wnt/ß-catenin pathway-related proteins. In conclusion, CD inhibits osteogenic differentiation by downregulating Wnt/ß-catenin signaling and alleviating subchondral osteosclerosis in a mouse model of OA.

Understanding Learners' Metacognition of Online Teacher Feedback Amid COVID-19: A Case Study in a University Livestream Instruction Context.

While research on metacognition in second language (L2) learning has burgeoned in the past two decades, its relation to actual teaching behaviors, such as teacher feedback, remains to be fully described and explained in L2 classroom, especially in livestream English teaching settings. To fill this gap, this case study examined how learners utilize and regulate metacognition of online teacher feedback during COVID-19 in a Chinese inner land university. Data were gathered through semi-structured interviews. With qualitative and interpretive analysis, it is revealed that leaners positively receive online teacher feedback for its detrimentalness together with a growth mindset and high levels of resilience, but, on the whole, there is a metacognitive deficit: they misinterpret self-consciousness about online feedback which is underpinned by a conception of tasks that characterizes online L2 learning. This research expands our understanding of L2 learning processes pertaining to awareness and management of teacher feedback receiving and may also shed light on solutions to empower livestream teaching by building external scaffolding devices to compensate weaknesses of online L2 education during the pandemic and beyond.