Innate Immunity and Sex: Distinct Inflammatory Profiles Associated with Murine Pain in Acute Synovitis.

Joint pain severity in arthritic diseases differs between sexes and is often more pronounced in women. This disparity is thought to stem from biological mechanisms, particularly innate immunity, yet the understanding of sex-specific differences in arthritic pain remains incomplete. This study aims to investigate these disparities using an innate immunity-driven inflammation model induced by intra-articular injections of Streptococcus Cell Wall fragments to mimic both acute and pre-sensitized joint conditions.

Early pain in females is linked to late pathological features in murine experimental osteoarthritis.

Background: Osteoarthritis (OA) is a progressive joint disease and a major cause of chronic pain in adults. The prevalence of OA is higher in female patients, who tend to have worse OA outcomes, partially due to pain. The association between joint pain and OA pathology is often inconclusive.

Identification of Transcription Factors Responsible for a Transforming Growth Factor-β-Driven Hypertrophy-like Phenotype in Human Osteoarthritic Chondrocytes.

During osteoarthritis (OA), hypertrophy-like chondrocytes contribute to the disease process. TGF-β's signaling pathways can contribute to a hypertrophy(-like) phenotype in chondrocytes, especially at high doses of TGF-β. In this study, we examine which transcription factors (TFs) are activated and involved in TGF-β-dependent induction of a hypertrophy-like phenotype in human OA chondrocytes.

Prediction of the Effect of the Osteoarthritic Joint Microenvironment on Cartilage Repair.

Osteoarthritis (OA) is characterized by progressive articular cartilage loss. Human mesenchymal stromal cells (MSCs) can be used for cartilage repair therapies based on their potential to differentiate into chondrocytes. However, the joint microenvironment is a major determinant of the success of MSC-based cartilage formation.

Interleukin-37 Protects Stem Cell-Based Cartilage Formation in an Inflammatory Osteoarthritis-Like Microenvironment.

Catabolic factors present in a damaged joint inhibit chondrogenic differentiation of mesenchymal stem cells, thereby reducing the chance for successful cartilage formation. By improving stem cell-based cartilage repair with interleukin-37 (IL37), we might be able to inhibit the worsening progression of focal cartilage defects and prevent further development of joint diseases such as osteoarthritis. This will avoid chronic pain and impaired joint mobility for patients and reduce costs for society.

Interleukin 1 β-induced SMAD2/3 linker modifications are TAK1 dependent and delay TGFβ signaling in primary human mesenchymal stem cells.

Background: Chondrogenic differentiation of mesenchymal stem cells (MSC) requires transforming growth factor beta (TGFβ) signaling. TGFβ binds to the type I receptor activin-like kinase (ALK)5 and results in C-terminal SMAD2/3 phosphorylation (pSMAD2/3C). In turn pSMAD2/3C translocates to the nucleus and regulates target gene expression.

IL37 dampens the IL1β-induced catabolic status of human OA chondrocytes.

Objective: A crucial feature of OA is cartilage degradation. This process is mediated by pro-inflammatory cytokines, among other factors, via induction of matrix-degrading enzymes. Interleukin 37 (IL37) is an anti-inflammatory cytokine and is efficient in blocking the production of pro-inflammatory cytokines during innate immune responses.

Activin Receptor-Like Kinase Receptors ALK5 and ALK1 Are Both Required for TGFβ-Induced Chondrogenic Differentiation of Human Bone Marrow-Derived Mesenchymal Stem Cells.

Introduction: Bone marrow-derived mesenchymal stem cells (BMSCs) are promising for cartilage regeneration because BMSCs can differentiate into cartilage tissue-producing chondrocytes. Transforming Growth Factor β (TGFβ) is crucial for inducing chondrogenic differentiation of BMSCs and is known to signal via Activin receptor-Like Kinase (ALK) receptors ALK5 and ALK1. Since the specific role of these two TGFβ receptors in chondrogenesis is unknown, we investigated whether ALK5 and ALK1 are expressed in BMSCs and whether both receptors are required for chondrogenic differentiation of BMSCs.

Inhibition of TAK1 and/or JAK can rescue impaired chondrogenic differentiation of human mesenchymal stem cells in osteoarthritis-like conditions.

Objective: To rescue chondrogenic differentiation of human mesenchymal stem cells (hMSCs) in osteoarthritic conditions by inhibition of protein kinases.

Methods: hMSCs were cultured in pellets. During early chondrogenic differentiation, these were exposed to osteoarthritic synovium-conditioned medium (OAS-CM), combined with the Janus kinase (JAK)-inhibitor tofacitinib and/or the transforming growth factor β-activated kinase 1 (TAK1)-inhibitor oxozeaenol.

Canonical Wnt signaling skews TGF-β signaling in chondrocytes towards signaling via ALK1 and Smad 1/5/8.

Background: Both Wnt signaling and TGF-β signaling have been implicated in the regulation of the phenotype of many cell types including chondrocytes, the only cell type present in the articular cartilage. A changed chondrocyte phenotype, resulting in chondrocyte hypertrophy, is one of the main hallmarks of osteoarthritis. TGF-β signaling via activin-like kinase (ALK)5, resulting in Smad 2/3 phosphorylation, inhibits chondrocyte hypertrophy.

Enhanced suppressor of cytokine signaling 3 in arthritic cartilage dysregulates human chondrocyte function.

Objective: To determine the expression of suppressor of cytokine signaling 3 (SOCS-3) in human articular chondrocytes and its functional consequences.

Methods: Chondrocytes were isolated from the cartilage of patients with osteoarthritis (OA), patients with rheumatoid arthritis (RA), and trauma patients and from the healthy cartilage of patients with a femoral neck fracture. The human chondrocyte cell line G6 and primary bovine chondrocytes were used in validation experiments.

Increase in ALK1/ALK5 ratio as a cause for elevated MMP-13 expression in osteoarthritis in humans and mice.

During osteoarthritis (OA) chondrocytes show deviant behavior resembling terminal differentiation of growth-plate chondrocytes, characterized by elevated MMP-13 expression. The latter is also a hallmark for OA. TGF-beta is generally thought to be a protective factor for cartilage, but it has also displayed deleterious effects in some studies.

Involvement of the Wnt signaling pathway in experimental and human osteoarthritis: prominent role of Wnt-induced signaling protein 1.

Objective: Wnt signaling pathway proteins are involved in embryonic development of cartilage and bone, and, interestingly, developmental processes appear to be recapitulated in osteoarthritic (OA) cartilage. The present study was undertaken to characterize the expression pattern of Wnt and Fz genes during experimental OA and to determine the function of selected genes in experimental and human OA.

Methods: Longitudinal expression analysis was performed in 2 models of OA.

Oral administration of the NADPH-oxidase inhibitor apocynin partially restores diminished cartilage proteoglycan synthesis and reduces inflammation in mice.

Apocynin, an inhibitor of NADPH-oxidase, is known to partially reverse the inflammation-mediated cartilage proteoglycan synthesis in chondrocytes. More recently, it was reported that apocynin prevents cyclooxygenase (COX)-2 expression in monocytes. The present study aimed to investigate whether these in vitro features of apocynin could be confirmed in vivo.

Inhibition of endogenous TGF-beta during experimental osteoarthritis prevents osteophyte formation and impairs cartilage repair.

Osteoarthritis has as main characteristics the degradation of articular cartilage and the formation of new bone at the joint edges, so-called osteophytes. In this study enhanced expression of TGF-beta1 and -beta3 was detected in developing osteophytes and articular cartilage during murine experimental osteoarthritis. To determine the role of endogenous TGF-beta on osteophyte formation and articular cartilage, TGF-beta activity was blocked via a scavenging soluble TGF-beta-RII.