oxalylglycine and Osteoarthritis

Osteoarthritis (OA) is characterized by cartilage degradation, inflammation, and hypertrophy. Therapies are mainly symptomatic and aim to manage pain. Consequently, medical community is waiting for new treatments able to reduce OA process. This study aims to develop an in vitro simple OA model useful to predict drug ability to reduce cartilage hypertrophy. Human primary OA chondrocytes were incubated with transforming growth factor beta 1 (TGF-β1). Hypertrophy was evaluated by Runx2, type X collagen, MMP13, and VEGF expression. Cartilage anabolism was investigated by Sox9, aggrecan, type II collagen, and glycosaminoglycan expression. In chondrocytes, TGF-β1 increased expression of hypertrophic genes and activated canonical WNT pathway, while it decreased dramatically cartilage anabolism, suggesting that this treatment could mimic some OA features in vitro. Additionally, EZH2 inhibition, that has been previously reported to decrease cartilage hypertrophy and reduce OA development in vivo, attenuated COL10A1 and MMP13 upregulation and SOX9 downregulation induced by TGF-β1 treatment. Similarly, pterosin B (an inhibitor of Sik3), and DMOG (a hypoxia-inducible factor prolyl hydroxylase which mimicks hypoxia), repressed the expression of hypertrophy markers in TGF-β stimulated chondrocytes. In conclusion, we established an innovative OA model in vitro. This cheap and simple model will be useful to quickly screen new drugs with potential anti-arthritic effects, in complementary to current inflammatory models, and should permit to accelerate development of efficient treatments against OA able to reduce cartilage hypertrophy.

Topics: Aged; Aged, 80 and over; Amino Acids, Dicarboxylic; Benzamides; Biphenyl Compounds; Cartilage, Articular; Chondrocytes; Drug Evaluation, Preclinical; Enhancer of Zeste Homolog 2 Protein; Humans; Hypertrophy; Indans; Middle Aged; Models, Biological; Morpholines; Osteoarthritis; Primary Cell Culture; Pyridones; Transforming Growth Factor beta1; Wnt Signaling Pathway

Mitochondrial dysfunction leads to osteoarthritis (OA) and disc degeneration. Hypoxia inducible factor-1α (HIF-1α) mediated mitophagy has a protective role in several diseases. However, the underlying mechanism of HIF-1α mediated mitophagy in OA remains largely unknown. This current study was performed to determine the effect of HIF-1α mediated mitophagy on OA. Therefore, X-ray and tissue staining including HE staining, safranin O-fast green (S-O) and Alcian Blue were used to assess imageology and histomorphology differences of mouse knee joint. Transcriptional analysis was used to find the possible targets in osteoarthritis. Western blot analysis, RT-qPCR and immunofluorescence staining were used to detect the changes in gene and protein levels in the vitro experiment. The expression of HIF-1α was increased in human and mouse OA cartilage. HIF-1α knockdown by siRNA further impair the hypoxia-induced mitochondrial dysfunction; In contrast, HIF-1α mediated protective role was reinforced by prolylhydroxylase (PHD) inhibitor dimethyloxalylglycine (DMOG). In addition, HIF-1α stabilization could alleviate apoptosis and senescence via mitophagy in chondrocytes under hypoxia condition, which could also ameliorate surgery-induced cartilage degradation in mice OA model. In conclusion, HIF-1α mediated mitophagy could alleviate OA, which may serve as a promising strategy for OA treatment.

Topics: Amino Acids, Dicarboxylic; Animals; Apoptosis; Autophagy; Cartilage, Articular; Cell Hypoxia; Cellular Senescence; Chondrocytes; Cytoprotection; Disease Models, Animal; Extracellular Matrix; Female; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Male; Meniscus; Mice, Inbred C57BL; Middle Aged; Mitochondria; Mitophagy; Osteoarthritis; Protein Stability; Reactive Oxygen Species

To investigate crosslinks between catabolic and anabolic pathways in articular cartilage by examining the synthesis and distribution pattern of microsomal prostaglandin E synthase 1 (mPGES-1) in healthy and osteoarthritic (OA) cartilage and analyzing its functional relationship to hypoxia-inducible factor 1alpha (HIF-1alpha) in primary articular chondrocytes.. Normal cartilage and OA cartilage were subjected to immunohistochemical staining for mPGES-1 and HIF-1alpha. Isolated chondrocytes were cultivated under 21% or 1% O(2). Microarray analysis and quantitative reverse transcriptase-polymerase chain reaction were used to detect genes differentially expressed in chondrocytes cultured under normoxic compared with hypoxic conditions. Immunoblotting was conducted to evaluate intracellular protein levels of mPGES and nuclear accumulation of HIF-1alpha under different oxygen tension levels and with different stimulatory or inhibitory chemical agents.. We found enhanced levels of expression of the mPGES-1 gene and an increased number of OA chondrocytes showing staining for mPGES-1 in OA cartilage. Microarray analysis demonstrated that mPGES-1 was among the genes that were up-regulated to the greatest degree in primary chondrocytes exposed to 1% O(2). In vitro, hypoxia led to an enhanced synthesis of mPGES-1, coinciding with a nuclear accumulation of the transcription factor HIF-1alpha. In chondrocyte culture, stimulation with dimethyloxaloylglycine promoted the expression of mPGES-1, phosphoglycerate kinase 1, and cyclooxygenase 2 (COX-2) by stabilizing HIF-1alpha protein levels. A reduction of mPGES-1 synthesis was detected after treatment with 2-methoxyestradiol, correlating with lower HIF-1alpha activity. In contrast, synthesis of mPGES-1 was not influenced by treatment with the specific COX-2 inhibitor NS398.. These findings suggest that the transcription factor HIF-1alpha is involved in the up-regulation of mPGES-1 and may therefore play an important role in the metabolism of OA cartilage.

Topics: 2-Methoxyestradiol; Aged; Amino Acids, Dicarboxylic; Cartilage, Articular; Cell Hypoxia; Cells, Cultured; Chondrocytes; Cyclooxygenase 2; Cyclooxygenase Inhibitors; Estradiol; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Intramolecular Oxidoreductases; Microsomes; Middle Aged; Nitrobenzenes; Osteoarthritis; Prostaglandin-E Synthases; Prostaglandins; Sulfonamides; Tubulin Modulators; Up-Regulation