A comparison of shear- and compression-induced mechanotransduction in SW1353 chondrocytes

Mechanotransduction is a biological phenomenon where mechanical stimuli are converted to biochemical responses. A model system for studying mechanotransduction are the chondrocytes of articular cartilage. Breakdown of this tissue results in decreased mobility, increased pain, and reduced quality of life. Either disuse or overloading can disrupt cartilage homeostasis, but physiological cyclical loading promotes cartilage homeostasis. To model this, we exposed SW1353 cells to cyclical mechanical stimuli, shear and compression, for different durations of time (15 and 30 min). By utilizing liquid chromatography-mass spectroscopy (LC-MS), metabolomic profiles were generated detailing metabolite features and biological pathways that are altered in response to mechanical stimulation. In total, 1,457 metabolite features were detected. Statistical analyses identified several pathways of interest. Taken together, differences between experimental groups were associated with inflammatory pathways, lipid metabolism, beta-oxidation, central energy metabolism, and amino acid production. These findings expand our understanding of chondrocyte mechanotransduction under varying loading conditions and time periods.

Early detection of osteoarthritis in the rat with an antibody specific to type II collagen modified by reactive oxygen species

Background: Osteoarthritis (OA) is a disease of the whole joint, with articular cartilage breakdown as a major characteristic. Cartilage degradation is mostly driven by chondrocytes which produce inflammatory mediators, proteases and oxidants. Nevertheless, the early pathogenesis events are still unclear. We employed antibody that is specific to oxidative post-translationally modified collagen type II (anti-oxPTM-CII) to detect early cartilage pathogenic changes in two rat models of OA. Methods: The animals underwent surgery for destabilization of the medial meniscus (DMM) and were sacrificed at 3, 5, 7, 14 and 28 days or anterior cruciate ligament transection with partial meniscectomy (ACLT+pMx) and were sacrificed after 1, 3, 5, 7 and 14 days. Joints were stained with toluidine blue and Saffron du Gatinais for histological scoring, anti-oxPTM-CII and anti- collagen type X antibodies (anti-CX). Results: We observed oxPTM-CII staining as early as 1 or 3 days after ACLT+pMx or DMM surgeries respectively, before overt cartilage lesions were visible. It was located mostly in the deep zone of the medial tibial cartilage, in the pericellular and territorial matrix of hypertrophic chondrocytes and co-localized with CX staining. Both staining were weak or absent for the lateral compartment or the contralateral knees except at later timepoints. Conclusion: The results demonstrate that oxidants production and chondrocytes hypertrophy occur very early in the onset of OA, possibly initiating the pathogenic events of OA. We propose to use anti-oxPTM-CII as an early biomarker for OA ahead or radiographic changes.

Early Detection of Osteoarthritis in the Rat With an Antibody Specific to Type II Collagen Modified by Reactive Oxygen Species

Background Osteoarthritis (OA) is a disease of the whole joint, with articular cartilage breakdown as a major characteristic. Cartilage degradation is mostly driven by chondrocytes which produce inflammatory mediators, proteases and oxidants. Nevertheless, the early pathogenesis events are still unclear. We employed antibody that is specific to oxidative post-translationally modified collagen type II (anti-oxPTM-CII) to detect early cartilage pathogenic changes in two rat models of OA. Methods The animals underwent surgery for destabilization of the medial meniscus (DMM) and were sacrificed at 3, 5, 7, 14 and 28 days or anterior cruciate ligament transection with partial meniscectomy (ACLT + pMx) and were sacrificed after 1, 3, 5, 7 and 14 days. Joints were stained with toluidine blue and Saffron du Gatinais for histological scoring, anti-oxPTM-CII and anti- collagen type X antibodies (anti-CX). Results We observed oxPTM-CII staining as early as 1 or 3 days after ACLT + pMx or DMM surgeries respectively, before overt cartilage lesions were visible. It was located mostly in the deep zone of the medial tibial cartilage, in the pericellular and territorial matrix of hypertrophic chondrocytes and co-localized with CX staining. Both staining were weak or absent for the lateral compartment or the contralateral knees except at later timepoints. Conclusion The results demonstrate that oxidants production and chondrocytes hypertrophy occur very early in the onset of OA, possibly initiating the pathogenic events of OA. We propose to use anti-oxPTM-CII as an early biomarker for OA ahead or radiographic changes.

New Therapeutic Strategies for Osteoarthritis by Targeting Sialic Acid Receptors

Osteoarthritis (OA) is the most common degenerative joint disease characterized by articular cartilage degradation and joint degeneration. The articular cartilage is mainly formed by chondrocytes and a collagen-proteoglycan extracellular matrix that contains high levels of glycosylated proteins. It was reported that the shift from glycoproteins containing α-2,6-linked sialic acids to those that contain α-2,3 was associated with the onset of common types of arthritis. However, the pathophysiology of α-2,3-sialylation in cartilage has not been yet elucidated. We show that cartilage from osteoarthritic patients expresses high levels of the α-2,3-sialylated transmembrane mucin receptor, known as podoplanin (PDPN). Additionally, the Maackia amurensis seed lectin (MASL), that can be utilized to target PDPN, attenuates the inflammatory response mediated by NF-kB activation in primary chondrocytes and protects human cartilage breakdown ex vivo and in an animal model of arthritis. These findings reveal that specific lectins targeting α-2,3-sialylated receptors on chondrocytes might effectively inhibit cartilage breakdown. We also present a computational 3D molecular model for this interaction. These findings provide mechanistic information on how a specific lectin could be used as a novel therapy to treat degenerative joint diseases such as osteoarthritis.

IgE-mediated mast cell activation promotes inflammation and cartilage destruction in osteoarthritis

Osteoarthritis is characterized by articular cartilage breakdown, and emerging evidence suggests that dysregulated innate immunity is likely involved. Here, we performed proteomic, transcriptomic, and electron microscopic analyses to demonstrate that mast cells are aberrantly activated in human and murine osteoarthritic joint tissues. Using genetic models of mast cell deficiency, we demonstrate that lack of mast cells attenuates osteoarthritis in mice. Using genetic and pharmacologic approaches, we show that the IgE/FcεRI/Syk signaling axis is critical for the development of osteoarthritis. We find that mast cell-derived tryptase induces inflammation, chondrocyte apoptosis, and cartilage breakdown. Our findings demonstrate a central role for IgE-dependent mast cell activation in the pathogenesis of osteoarthritis, suggesting that targeting mast cells could provide therapeutic benefit in human osteoarthritis.Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (<xref ref-type="decision-letter" rid="SA1">see decision letter</xref>).