The forkhead box O (FOXO) proteins are transcription factors involved in the differentiation of many cell types. Type II collagen (Col2) Cre-Foxo1-knockout and Col2-Cre-Foxo1,3,4 triple-knockout mice exhibit growth plate malformation. Moreover, recent studies have reported that in some cells, the expressions and activities of FOXOs are promoted by transforming growth factor β1 (TGFβ1), a growth factor playing a key role in chondrogenic differentiation. Here, using a murine chondrogenic cell line (ATDC5), mouse embryos, and human mesenchymal stem cells, we report the mechanisms by which FOXOs affect chondrogenic differentiation. FOXO1 expression increased along with chondrogenic differentiation, and FOXO1 inhibition suppressed chondrogenic differentiation. TGFβ1/SMAD signaling promoted expression and activity of FOXO1. In ATDC5, FOXO1 knockdown suppressed expression of sex-determining region Y box 9 (Sox9), a master regulator of chondrogenic differentiation, resulting in decreased collagen type II α1 (Col2a1) and aggrecan (Acan) expression after TGFβ1 treatment. On the other hand, chemical FOXO1 inhibition suppressed Col2a1 and Acan expression without suppressing Sox9. To investigate the effects of FOXO1 on chondrogenic differentiation independently of SOX9, we examined FOXO1's effects on the cell cycle. FOXO1 inhibition suppressed expression of p21 and cell-cycle arrest in G0/G1 phase. Conversely, FOXO1 overexpression promoted expression of p21 and cell-cycle arrest. FOXO1 inhibition suppressed expression of nascent p21 RNA by TGFβ1, and FOXO1 bound the p21 promoter. p21 inhibition suppressed expression of Col2a1 and Acan during chondrogenic differentiation. These results suggest that FOXO1 is necessary for not only SOX9 expression, but also cell-cycle arrest during chondrogenic differentiation via TGFβ1 signaling.

Objective NF‐κB–dependent signaling is an important modulator in osteoarthritis (OA), and G protein–coupled receptor kinase 5 (GRK5) regulates the NF‐κB pathway. This study was undertaken to investigate the functional involvement of GRK5 in OA pathogenesis. Methods GRK5 expression in normal and OA human knee joints was analyzed immunohistochemically. Gain‐ or loss‐of‐function experiments were performed using human and mouse chondrocytes. OA was induced in GRK5‐knockout mice by destabilization of the medial meniscus, and histologic examination was performed. OA was also induced in wild‐type mice, which were then treated with an intraarticular injection of amlexanox, a selective GRK5 inhibitor, every 5 days for 8 weeks. Results GRK5 protein expression was increased in human OA cartilage. In vitro, expression levels of OA‐related factors and NF‐κB transcriptional activation were down‐regulated by suppression of the GRK5 gene in human OA chondrocytes (3.49‐fold decrease in IL6 [P < 0.01], 2.43‐fold decrease in MMP13 [P < 0.01], and 2.66‐fold decrease in ADAMTS4 [P < 0.01]). Conversely, GRK5 overexpression significantly increased the expression of OA‐related catabolic mediators and NF‐κB transcriptional activation. On Western blot analysis, GRK5 deletion reduced IκBα phosphorylation (up to 4.4‐fold decrease [P < 0.05]) and decreased p65 nuclear translocation (up to 6.4‐fold decrease [P < 0.01]) in mouse chondrocytes. In vivo, both GRK5 deletion and intraarticular amlexanox protected mouse cartilage against OA. Conclusion Our results suggest that GRK5 regulates cartilage degradation through a catabolic response mediated by NF‐κB signaling, and is a potential target for OA treatment. Furthermore, amlexanox may be a major compound in relevant drugs.

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Osteoarthritis (OA), the most prevalent joint disease, is characterized by the progressive loss of articular cartilage. Autophagy, a lysosomal degradation pathway, maintains cellular homeostasis, and autophagic dysfunction in chondrocytes is a hallmark of OA pathogenesis. However, the cause of autophagic dysfunction in OA chondrocytes remains incompletely understood. Recent studies have reported that decidual protein induced by progesterone (C10orf10/DEPP) positively regulates autophagic functions. In this study, we found that DEPP was involved in mitochondrial autophagic functions of chondrocytes, as well as in OA pathogenesis. DEPP expression decreased in human OA chondrocytes in the absence or presence of pro‐inflammatory cytokines, and was induced by starvation, hydrogen peroxide (H2O2), and hypoxia (cobalt chloride). For functional studies, DEPP knockdown decreased autophagic flux induced by H2O2, whereas DEPP overexpression increased autophagic flux and maintained cell viability following H2O2 treatment. DEPP was downregulated by knockdown of forkhead box class O (FOXO) transcription factors and modulated the autophagic function regulated by FOXO3. In an OA mouse model by destabilization of the medial meniscus, DEPP‐knockout mice exacerbated the progression of cartilage degradation with TUNEL‐positive cells, and chondrocytes isolated from knockout mice were decreased autophagic flux and increased cell death following H2O2 treatment. Subcellular fractionation analysis revealed that mitochondria‐located DEPP activated mitochondrial autophagy via BCL2 interacting protein 3. Taken together, our data demonstrate that DEPP is a major stress‐inducible gene involved in the activation of mitochondrial autophagy in chondrocytes, and maintains chondrocyte viability during OA pathogenesis. DEPP represents a potential therapeutic target for enhancing autophagy in patients with OA.

Background Adipose-derived mesenchymal stem cells (ADMSCs) are a promising source of material source for medical regeneration of cartilage. Growth factors, including transforming growth factor-β (TGFβ) subfamily members and bone morphogenetic proteins (BMPs), play important roles in inducing and promoting chondrogenic differentiation of MSCs. However, these exogenous growth factors have some drawbacks related to their cost, biological half-life, and safety for clinical application. Several studies have reported that statins, the competitive inhibitors of 3-hydroxy-2-methylglutaryl coenzyme A (HMG-CoA) reductase, induce the expression of BMP2 in multiple cell types as the pleotropic effects. The objective of this study was to investigate the effects of fluvastatin during chondrogenic differentiation of human ADMSCs (hADMSCs). Methods The effects of fluvastatin were analyzed during chondrogenic differentiation of hADMSCs in the pellet culture without exogenous growth factors by qRT-PCR and histology. For functional studies, Noggin, an antagonist of BMPs, mevalonic acid (MVA) and geranylgeranyl pyrophosphate (GGPP), metabolites of the mevalonate pathway, ROCK inhibitor (Y27632), or RAC1 inhibitor (NSC23766) were applied to cells during chondrogenic differentiation. Furthermore, RhoA activity was measured by RhoA pulldown assay during chondrogenic differentiation with or without fluvastatin. Statistically significant differences between groups were determined by Student’s t-test or the Tukey–Kramer test. Results Fluvastatin-treated cells expressed higher levels of BMP2, SOX9, ACAN, and COL2A1 than control cells, and accumulated higher levels of glycosaminoglycans (GAGs). Noggin significantly inhibited the fluvastatin-mediated upregulation of ACAN and COL2A1. Both MVA and GGPP suppressed the effects of fluvastatin on the expressions of BMP2, SOX9, ACAN, and COL2A1. Furthermore, fluvastatin suppressed the RhoA activity, and inhibition of RhoA–ROCK signaling by Y27632 increased the expressions of BMP2, SOX9, ACAN, and COL2A1, as well as fluvastatin. Conclusions Our results suggest that fluvastatin promotes chondrogenic differentiation of hADMSCs by inducing endogenous BMP2, and that one of the mechanisms underlying the effects is inhibition of RhoA–ROCK signaling via suppression of GGPP. Fluvastatin is a safe and low-cost compound that holds promise for use in transplantation of hADMSCs for cartilage regeneration.

Background To further improve rheumatoid arthritis (RA) treatment, it is necessary to understand each RA patient’s satisfaction and to identify the factors affecting their satisfaction. Despite the rise in medical costs for RA, little is known about the factors that influence patient satisfaction with the cost of treatment in RA patients. Methods This is a multicenter observational study of Japanese RA patients from the FRANK Registry with data analyzed from March 2017 to August 2020. We collected data on demographic characteristics, clinical data, quality of life which was evaluated using the EuroQol 5-dimensional questionnaire (EQ5D), and patient satisfaction. The four categories of patient satisfaction were evaluated individually (i.e., cost, treatment efficacy, activities of daily living [ADL], and global treatment satisfaction). We analyzed the factors that affected each patient’s satisfaction, such as age, sex, EQ5D, disease duration, disease activity, and treatment. Results This study included 2235 RA outpatients (406 males, 1829 females). In RA patients, “very satisfied” and “satisfied” were given for nearly half of each satisfaction aspect (cost 49%; efficacy 72%; ADL 58%; global treatment 66%) at the time of the initial registration. To investigate the factors influencing each satisfaction, multivariate analysis has revealed that the use of b/tsDMARDs increased satisfaction of treatment effect (odds ratio [OR] 0.66) and ADL (OR 0.78) but decreased cost satisfaction (OR 2.21). Age (50–64 years; OR 0.91; 65–74 years, 0.55: ≥ 75 years, 0.35), female (OR 0.81), and history of musculoskeletal surgery (OR 0.60) all increased cost satisfaction. Patients with lower disease activity and higher EQ5D scores had higher levels of satisfaction in all areas. Conclusions In this study, patient satisfaction in terms of cost, treatment effect, ADL, and overall treatment was generally higher, but some patients were dissatisfied. The cost of satisfaction increased with age and a history of musculoskeletal surgery, while it decreased with a lower EQ5D score and the use of b/tsDMARDs.

Desmoid-type fibromatoses are pathologically benign but locally aggressive tumors. We report the case of a desmoid tumor that disappeared spontaneously after recurrence. A 21-year-old woman was referred to our hospital because of left lower limb weakness during menstruation. The following day this weakness had disappeared but menstrual colic remained; consequently, the patient underwent an internal examination that revealed an intrapelvic tumor. Magnetic resonance imaging demonstrated an enhanced mass (diameter, 8 cm) arising from the internal obturator muscle and attached to the urinary bladder. The tumor was diagnosed as a desmoid-type fibromatosis after histologic evaluation of a transvaginal biopsy; marginal resection was carried out at < 1 month after the first hospital admission. The patient experienced recurrence at 2 years after surgery, which was confirmed as two enhanced masses (diameter, 1 cm) using magnetic resonance imaging. Eleven months later, the diameters of these masses had increased to 1.8 cm; however, there was no further increase in size beyond this point. The patient delivered successfully at 5 and 7 years after surgery; at 8 years, the recurrent tumors had disappeared completely as confirmed by magnetic resonance imaging. This case involving recurrence is rare for two reasons. The first was that no change in the size of the tumors occurred during pregnancy and after delivery, and the second was that the patient experienced complete remission of the recurrent tumors after only simple observation. Thus, it is important to recognize that even a recurrent desmoid tumor can sometimes exhibit spontaneous regression.

G protein-coupled receptor kinase 5 (GRK5) regulates inflammatory responses via the nuclear factor-kappa B (NF-κB) pathway. This study investigated the functional involvement of GRK5 in the pathogenesis of inflammatory arthritis. Immunohistochemically, rheumatoid arthritis (RA) synovium had a significantly higher proportion of GRK5-positive cells in the synovial lining layer than healthy control synovium. Gene expression and NF-κB activation in lipopolysaccharide-stimulated human SW982 synovial cells were significantly suppressed by silencing of the GRK5 gene. Similarly, GRK5 kinase activity inhibition in human primary RA synovial cells attenuated gene expressions of inflammatory factors. In a murine model of collagen antibody-induced arthritis, arthritis scores and serum IL6 production of GRK5 knockout (GRK5-/-) mice were significantly lower than those of wild-type mice. Histologically, the degree of synovitis and cartilage degeneration in GRK5-/- mice was significantly lower than in wild-type mice. In in vitro analyses using activated murine macrophages and fibroblast-like synoviocytes, gene expression of inflammatory factors and p65 nuclear translocation were significantly lower in GRK5-/- mice compared to wild-type mice. In conclusion, our results suggested that GRK5 is deeply involved in the pathogenesis of inflammatory arthritis, therefore, GRK5 inhibition could be a potential therapeutic target for types of inflammatory arthritis such as RA.