Regulation of microsomal prostaglandin E2 synthase-1 and 5-lipoxygenase-activating protein/5-lipoxygenase by 4-hydroxynonenal in human osteoarthritic chondrocytes

Epithelial-mesenchymal interaction protects normal colonocytes from 4-HNE-induced phenotypic transformation

INTRODUCTION

Recent studies have shown that epithelial-stromal interactions could play a role in the development of colorectal cancer. Here, we investigated the role of fibroblasts in the transformation of normal colonocytes induced by 4-HNE.

METHODS

Normal Co colonocytes and nF fibroblasts from the same mouse colon were exposed, in monoculture (m) or coculture (c), to 4-HNE (5 μM) twice weekly for 3 weeks. Gene expression was then analysed and the ability of Co colonocytes to grow in anchorage-independent conditions was tested in soft agar. Fibroblasts previously treated or not with 4-HNE were also seeded in culture inserts positioned above the agar layers to allow paracrine exchanges with colonocytes.

RESULTS

First, 60% of the genes studied were modulated by coculture in Co colonocytes, with notably increased expression of BMP receptors. Furthermore, while 4-HNE increased the ability of monoculture-treated Co colonocytes to form colonies, this effect was not observed in coculture-treated Co colonocytes. Adding a selective BMPR1 inhibitor during the treatment phase abolished the protective effect of coculture. Conversely, addition of a BMP4 agonist to the medium of monoculture-treated Co colonocytes prevented phenotypic transformation by 4-HNE. Second, the presence of nF(m)-HNE fibroblasts during the soft agar assay increased the number and size of Co(m) colonocyte colonies, regardless of whether these cells had been previously treated with 4-HNE in monoculture. For soft agar assays performed with nF(c) and Co(c) cells initially treated in coculture, only the reassociation between Co(c)-HNE and nF(c)-HNE resulted in a small increase in the number of colonies.

CONCLUSIONS

During the exposure phase, the epithelial-mesenchymal interaction protected colonocytes from 4-HNE-induced phenotypic transformation via activation of the BMP pathway. This intercellular dialogue also limited the ability of fibroblasts to subsequently promote colonocyte-anchorage-independent growth. In contrast, fibroblasts pre-exposed to 4-HNE in monoculture strongly increased the ability of Co(m) colonocytes to form colonies.

MOntelukast as a potential CHondroprotective treatment following Anterior cruciate ligament reconstruction (MOCHA Trial): study protocol for a double-blind, randomized, placebo-controlled clinical trial

BACKGROUND

After anterior cruciate ligament (ACL) reconstruction, patient-reported outcomes are improved 10 years post-surgery; however, cytokine concentrations remain elevated years after surgery with over 80% of those with combined ACL and meniscus injuries having posttraumatic osteoarthritis (PTOA) within 10-15 years. The purpose of this multicenter, randomized, placebo-controlled trial is to assess whether a 6-month course of oral montelukast after ACL reconstruction reduces systemic markers of inflammation and biochemical and imaging biomarkers of cartilage degradation.

METHODS

We will enroll 30 individuals undergoing primary ACL reconstruction to participate in this IRB-approved multicenter clinical trial. This trial will target those at greatest risk of a more rapid PTOA onset (age range 25-50 with concomitant meniscus injury). Patients will be randomly assigned to a group instructed to take 10 mg of montelukast daily for 6 months following ACL reconstruction or placebo. Patients will be assessed prior to surgery and 1, 6, and 12 months following surgery. To determine if montelukast alters systemic inflammation following surgery, we will compare systemic concentrations of prostaglandin E2, monocyte chemoattractant protein-1, and pro-inflammatory cytokines between groups. We will also compare degradative changes on magnetic resonance imaging (MRI) collected 1 and 12 months following surgery between groups with reductions in early biomarkers of cartilage degradation assessed with urinary biomarkers of type II collagen breakdown and bony remodeling.

DISCUSSION

There is a complex interplay between the pro-inflammatory intra-articular environment, underlying bone remodeling, and progressive cartilage degradation. PTOA affects multiple tissues and appears to be more similar to rheumatoid arthritis than osteoarthritis with respect to inflammation. There is currently no treatment to delay or prevent PTOA after ACL injury. Since there is a larger and more persistent inflammatory response after ACL reconstruction than the initial insult of injury, treatment may need to be initiated after surgery, sustained over a period of time, and target multiple mechanisms in order to successfully alter the disease process. This study will assess whether a 6-month postoperative course of oral montelukast affects multiple PTOA mechanisms. Because montelukast administration can be safely sustained for long durations and offers a low-cost treatment option, should it be proven effective in the current trial, these results can be immediately incorporated into clinical practice.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04572256 . Registered on October 1, 2020.

Clinical Effectiveness and Adverse Events of Bee Venom Therapy: A Systematic Review of Randomized Controlled Trials

Bee venom has been used to treat many diseases because of its anti-inflammatory and analgesic effects. However, the secretions of bee venom can also cause life-threatening adverse reactions. The objective of this paper was to review the clinical effectiveness of bee venom and adverse events induced by bee venom, regardless of the disease. Four electronic databases were searched in April 2020. The reference lists of the retrieved articles and previous review articles were also hand-searched. Randomized controlled trials (RCTs) using any type of bee venom other than live bee stings for the clinical treatment of any disease other than cancer were included. The studies were selected, the data were extracted, and the quality of the studies was assessed by two authors. Risk of bias was assessed using the Cochrane risk of bias standards. Twelve RCTs were included in this review—three on Parkinson’s disease, four on arthralgia, four on musculoskeletal disorders, and one on polycystic ovary syndrome. The types of bee venom used were acupuncture injections, ultrasound gel, and an ointment. Six studies reported adverse events, and skin reactions such as pruritus and swelling were the most common. The large-scale clinical trials of bee venom therapy are needed to verify the statistical difference, and the reporting system for adverse events is also required to increase the safety of bee venom therapy.

Etoricoxib prevents progression of osteolysis in repeated intra-articular monosodium urate-induced gouty arthritis in rats

Deposition of monosodium urate (MSU) crystals in the joint or synovium is the major factor in Gouty arthritis (GA). The clinical features of chronic and recurrent GA include pain and the subsequent development of chronic tophaceous GA with multiple tophi deposits accompanied by osteolysis. The majority of previous animal studies have focused on MSU-induced acute GA without making observations regarding osteolysis. In the study, intra-articular injections of MSU into the knee (2 times/week for 10 weeks) was used to induce chronic and recurrent attacks of GA that in turn induced progressive osteolysis. Moreover, we also evaluated whether the clinical, nonsteroidal anti-inflammatory drug (NSAID) etoricoxib attenuated the osteoclastogenesis of progressive osteolysis. The knee morphometry and the expression of osteoclastogenesis-related proteins (cathepsin K and matrix metalloproteinase-9 and -13) in the knee were examined by micro-CT and immunohistochemistry, respectively. Results showed that oral etoricoxib not only significantly attenuated the nociceptive behaviors of the rats but that it also inhibited the expression of osteoclastogenesis-related proteins in their knee joints in chronic and recurrent attacks of GA. Our findings thus suggest that NSAIDs not only inhibit nociception but also prevent the progression of osteolysis in chronic and repeated attacks of GA.

Proeryptotic Activity of 4-Hydroxynonenal: A New Potential Physiopathological Role for Lipid Peroxidation Products

Background: Eryptosis is a physiological, apoptosis-like death of injured erythrocytes crucial to prevent premature haemolysis and the pathological sequalae generated by cell-free haemoglobin. When dysregulated, the process is associated to several inflammatory-based pathologies. 4-Hydroxy-trans-2-nonenal (HNE) is an endogenous signalling molecule at physiological levels and, at higher concentrations, is involved in the pathogenesis of several inflammatory-based diseases. This work evaluated whether HNE could induce eryptosis in human erythrocytes. Methods: Measurements of phosphatidylserine, cell volume, intracellular oxidants, Ca⁺⁺, glutathione, ICAM-1, and ceramide were assessed by flow cytometry. Scanning electron microscopy evaluated morphological alterations of erythrocytes. Western blotting assessed caspases. PGE₂ was measured by ELISA. Adhesion of erythrocytes on endothelial cells was evaluated by gravity adherence assay. Results: HNE in the concentration range between 10–100 µM induces eryptosis, morphological alterations correlated to caspase-3 activation, and increased Ca⁺⁺ levels. The process is not mediated by redox-dependent mechanisms; rather, it strongly depends on PGE₂ and ceramide. Interestingly, HNE induces significant increase of erythrocytes adhesion to endothelial cells (ECs) that are in turn dysfunctionated as evident by overexpression of ICAM-1. Conclusions: Our results unveil a new physiopathological role for HNE, provide mechanistic details of the HNE-induced eryptosis, and suggest a novel mechanism through which HNE could exert pro-inflammatory effects.

4-Hydroxy-Trans-2-Nonenal in the Regulation of Anti-Oxidative and Pro-Inflammatory Signaling Pathways

Recent studies indicate that 4-hydroxy-trans-2-nonenal (HNE), a major oxidative stress triggered lipid peroxidation-derived aldehyde, plays a critical role in the pathophysiology of various human pathologies including metabolic syndrome, diabetes, cardiovascular, neurological, immunological, and age-related diseases and various types of cancer. HNE is the most abundant and toxic α, β-unsaturated aldehyde formed during the peroxidation of polyunsaturated fatty acids in a series of free radical-mediated reactions. The presence of an aldehyde group at C1, a double bond between C2 and C3 and a hydroxyl group at C4 makes HNE a highly reactive molecule. These strong reactive electrophilic groups favor the formation of HNE adducts with cellular macromolecules such as proteins and nucleic acids leading to the regulation of various cell signaling pathways and processes involved in cell proliferation, differentiation, and apoptosis. Many studies suggest that the cell-specific intracellular concentrations of HNE dictate the anti-oxidative and pro-inflammatory activities of this important molecule. In this review, we focused on how HNE could alter multiple anti-oxidative defense pathways and pro-inflammatory cytotoxic pathways by interacting with various cell-signaling intermediates.

Early growth response 1 reduction in peripheral blood involving condylar subchondral bone loss

OBJECTIVES

To detect whether early growth response 1 (EGR1) in peripheral blood leucocytes (PBLs) indicates temporomandibular joint (TMJ) osteoarthritis (OA) lesions.

MATERIALS AND METHODS

Egr1 mRNA expression levels in PBLs were detected in eight malocclusion patients without temporomandibular disorder (TMD) signs and 16 malocclusion patients with clinical TMD signs with (eight) or without (eight) imaging signs of TMJ OA. Twelve 6-week-old rats were randomized to a control group and a unilateral anterior crossbite (UAC) group and were sampled at 4 weeks. The Egr1 mRNA expression levels in PBLs and protein expression levels in different orofacial tissues were measured.

RESULTS

Patients with TMD signs with/without TMJ OA diagnosis showed lower Egr1 mRNA expression levels in PBLs than patients without TMD signs. The lower Egr1 mRNA expression was also found in the PBLs of UAC rats, which were induced to exhibit early histo-morphological signs of TMJ OA lesions. In subchondral bone of UAC rats, EGR1 protein expression was decreased, co-localization of EGR1 with osterix or dentin matrix protein-1 was identified, and the number of EGR1 and osterix double-positive cells was reduced (all p < .05).

CONCLUSION

Egr1 reduction in PBLs potentially indicates subchondral bone OA lesions at an early stage.

Effect of the Lipid Peroxidation Product 4-Hydroxynonenal on Neuroinflammation in Microglial Cells: Protective Role of Quercetin and Monochloropivaloylquercetin

Objectives

The lipid peroxidation-derived aldehyde 4-hydroxynonenal (HNE) has been implicated in a number of oxidative stress-induced inflammatory pathologies such as neurodegenerative diseases and aging. In this regard, we investigated the effects of HNE on neuroinflammatory responses by measuring cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) induction with cytokine production. In addition, we measured nuclear factor erythroid 2-related factor 2 (Nrf-2)/Kelch-like ECH-associated protein 1 (Keap1) signaling proteins, and antioxidant enzymes heme oxygenase-1 (HO-1) and nicotinamide adenine dinucleotide phosphate dehydrogenase, quinone 1 (NQO1), and compared the results with quercetin and monochloropivaloylquercetin (MPQ) pretreated microglial cells.

Materials and Methods

Cytotoxicity was determined by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and production of cytokines was determined by cytokine array. Furthermore, intracellular Nfr2/Keap1 signaling proteins, HO-1, NQO1, and COX-2 expression were analyzed by western blot in 2.5 μM HNE treated BV-2 cells.

Results

Inducible nitric oxide synthase (iNOS) and COX-2 mRNA levels were measured with reverse transcription-quantitative polymerase chain reaction. HNE induced both COX-2 mRNA and protein levels, iNOS mRNA expression, and cytokine production. In addition, HNE markedly increased Keap1 levels and decreased cytoplasmic Nrf-2 expression with antioxidant enzyme HO-1 levels. Quercetin and monochloropivaloylquercetin treatment alleviated neuroinflammatory responses in microglial cells, by decreasing COX-2 mRNA expression. Monochloropivaloylquercetin decreased cytoplasmic Keap1 levels and increased nuclear translocation of Nrf-2 resulted in induction of HO-1 and NQO1 expression.

Conclusion

These results suggest that HNE could be a link between oxidative stress and inflammation in BV-2 microglia cells. In particular, monochloropivaloylquercetin alleviated inflammation, probably by decreasing the expression of proinflammatory genes and strengthening the antioxidant defense system.

Disease-modifying effects of COX-2 selective inhibitors and non-selective NSAIDs in osteoarthritis: a systematic review

Osteoarthritis (OA) is a potentially disabling disease whose progression is dependent on several risk factors. OA management usually involves the use of non-steroidal anti-inflammatory drugs (NSAIDs) that are the primary pharmacological treatments of choice. However, NSAIDs have often been associated with unwanted side effects. Cyclooxygenase (COX)-2 specific inhibitors, such as celecoxib, have been successfully used as an alternative in the past for OA treatment and have demonstrated fewer side effects. While abundant data are available for the clinical efficacy of drugs used for OA treatment, little is known about the disease-modifying effects of these agents. A previous review published by Zweers et al. (2010) assessed the available literature between 1990 and 2010 on the disease-modifying effects of celecoxib. In the present review, we aimed to update the existing evidence and identify evolving concepts relating to the disease-modifying effects of not just celecoxib, but also other NSAIDs. We conducted a review of the literature published from 2010 to 2016 dealing with the effects, especially disease-modifying effects, of NSAIDs on cartilage, synovium, and bone in OA patients. Our results show that celecoxib was the most commonly used drug in papers that presented data on disease-modifying effects of NSAIDs. Further, these effects appeared to be mediated through the regulation of prostaglandins, cytokines, and direct changes to tissues. Additional studies should be carried out to assess the disease-modifying properties of NSAIDs in greater detail.

An overview of the role of lipid peroxidation-derived 4-hydroxynonenal in osteoarthritis

BACKGROUND

Over the years, many theories have been proposed and examined to better explain the etiology and development of osteoarthritis (OA). The characteristics of joint destruction are one of the most important aspects in disease progression. Therefore, investigating different factors and signaling pathways involved in the alteration of extracellular matrix (ECM) turnover, and the subsequent catabolic damage to cartilage holds chief importance in understanding OA development. Among these factors, reactive oxygen species (ROS) have been at the forefront of the physiological and pathophysiological OA investigation.

FINDINGS

In the last decades, research studies provided an enormous volume of data supporting the involvement of ROS in OA. Most interestingly, published data regarding the effect of exogenous antioxidant therapy in OA lack conclusive results from clinical trials to back up in vitro data. Accordingly, it is rational to suggest that there are other reactive species in OA that are not taken into account. Thus, our present review is focused on our current understanding of the involvement of lipid peroxidation-derived 4-hydroxynonenal (HNE) in OA.

CONCLUSION

Our findings, like those in the literature, illustrate the central role played by HNE in the regulation of a number of factors involved in joint homeostasis. HNE could thus be considered as an attractive therapeutic target in OA.

Naproxen induces type X collagen expression in human bone-marrow-derived mesenchymal stem cells through the upregulation of 5-lipoxygenase

Several studies have shown that type X collagen (COL X), a marker of late-stage chondrocyte hypertrophy, is expressed in mesenchymal stem cells (MSCs) from osteoarthritis (OA) patients. We recently found that Naproxen, but not other nonsteroidal anti-inflammatory drugs (NSAIDs) (Ibuprofen, Celebrex, Diclofenac), can induce type X collagen gene (COL10A1) expression in bone-marrow-derived MSCs from healthy and OA donors. In this study we determined the effect of Naproxen on COL X protein expression and investigated the intracellular signaling pathways that mediate Naproxen-induced COL10A1 expression in normal and OA hMSCs. MSCs of OA patients were isolated from aspirates from the intramedullary canal of donors (50-80 years of age) undergoing hip replacement surgery for OA and were treated with or without Naproxen (100 μg/mL). Protein expression and phosphorylation were determined by immunoblotting using specific antibodies (COL X, p38 mitogen-activated protein kinase [p38], phosphorylated-p38, c-Jun N-terminal kinase [JNK], phosphorylated-JNK, extracellular signal-regulated kinase [ERK], and phosphorylated-ERK). Real-time reverse transcription polymerase chain reaction (RT-PCR) was performed to determine the expression of COL10A1 and Runt-related transcription factor 2 gene (Runx2). Our results show that Naproxen significantly stimulated COL X protein expression after 72 h of exposure both in normal and OA hMSCs. The basal phosphorylation of mitogen-activated protein kinases (MAPKs) (ERK, JNK, and p38) in OA hMSCs was significantly higher than in normal. Naproxen significantly increased the MAPK phosphorylation in normal and OA hMSCs. NSAID cellular effects include cyclooxygenase, 5-lipoxygenase, and p38 MAPK signaling pathways. To investigate the involvement of these pathways in the Naproxen-induced COL10A1 expression, we incubated normal and OA hMSCs with Naproxen with and without inhibitors of ERK (U0126), JNK (BI-78D3), p38 (SB203580), and 5-lipoxygenase (MK-886). Our results showed that increased basal COL10A1 expression in OA hMSCs was significantly suppressed in the presence of JNK and p38 inhibitors, whereas Naproxen-induced COL10A1 expression was suppressed by 5-lipoxygenase inhibitor. This study shows that Naproxen induces COL X both at transcriptional and translational levels in normal and OA hMSCs. Elevated basal COL10A1 expression in OA hMSCs is probably through the activation of MAPK pathway and Naproxen-induced COL10A1 expression is through the increased 5-lipoxygenase signaling.

Epithelium-dependent modulation of responsiveness of airways from caveolin-1 knockout mice is mediated through cyclooxygenase-2 and 5-lipoxygenase

BACKGROUND AND PURPOSE

Acute silencing of caveolin-1 (Cav-1) modulates receptor-mediated contraction of airway smooth muscle. Moreover, COX-2- and 5-lipoxygenase (5-LO)-derived prostaglandin and leukotriene biosynthesis can influence smooth muscle reactivity. COX-2 half-life can be prolonged through association with Cav-1. We suggested that lack of Cav-1 modulated levels of COX-2 which in turn modulated tracheal contraction, when arachidonic acid signalling was disturbed by inhibition of COX-2.

EXPERIMENTAL APPROACH

Using tracheal rings from Cav-1 knockout (KO) and wild-type mice (B6129SF2/J), we measured isometric contractions to methacholine and used PCR, immunoblotting and immunohistology to monitor expression of relevant proteins.

KEY RESULTS

Tracheal rings from Cav-1 KO and wild-type mice exhibited similar responses, but the COX-2 inhibitor, indomethacin, increased responses of tracheal rings from Cav-1 KO mice to methacholine. The phospholipase A₂ inhibitor, eicosatetraynoic acid, which inhibits formation of both COX-2 and 5-LO metabolites, had no effect on wild-type or Cav-1 KO tissues. Indomethacin-mediated hyperreactivity was ablated by the LTD₄ receptor antagonist (montelukast) and 5-LO inhibitor (zileuton). The potentiating effect of indomethacin on Cav-1 KO responses to methacholine was blocked by epithelial denudation. Immunoprecipitation showed that COX-2 binds Cav-1 in wild-type lungs. Immunoblotting and qPCR revealed elevated levels of COX-2 and 5-LO protein, but not COX-1, in Cav-1 KO tracheas, a feature that was prevented by removal of the epithelium.

CONCLUSION AND IMPLICATIONS

The indomethacin-induced hypercontractility observed in Cav-1 KO tracheas was linked to increased expression of COX-2 and 5-LO, which probably enhanced arachidonic acid shunting and generation of pro-contractile leukotrienes when COX-2 was inhibited.

Ramipril attenuates lipid peroxidation and cardiac fibrosis in an experimental model of rheumatoid arthritis

INTRODUCTION

Recent studies revealed that co-morbidity and mortality due to cardiovascular disease are increased in patients with rheumatoid arthritis (RA) but little is known about factors involved in these manifestations. This study aimed at characterizing the impact of arthritis on oxidative stress status and tissue fibrosis in the heart of rats with adjuvant-induced arthritis (AIA).

METHODS

AIA was induced with complete Freund's adjuvant in female Lewis rats. Animals were treated by oral administration of vehicle or angiotensin-converting enzyme inhibitor ramipril (10 mg/kg/day) for 28 days, beginning 1 day after arthritis induction. Isolated adult cardiomyocytes were exposed to 10 μM 4-hydroxynonenal (HNE) for 24 hours in the presence or absence of 10 μM ramipril.

RESULTS

Compared to controls, AIA rats showed significant 55 and 30% increase of 4-HNE/protein adducts in serum and left ventricular (LV) tissues, respectively. Cardiac mitochondrial NADP+-isocitrate dehydrogenase (mNADP-ICDH) activity decreased by 25% in AIA rats without any changes in its protein and mRNA expression. The loss of mNADP-ICDH activity was correlated with enhanced accumulation of HNE/mNADP-ICDH adducts as well as with decrease of glutathione and NADPH. Angiotensin II type 1 receptor (AT1R) expression and tissue fibrosis were induced in LV tissues from AIA rats. In isolated cardiomyocytes, HNE significantly decreased mNADP-ICDH activity and enhanced type I collagen and connective tissue growth factor expression. The oral administration of ramipril significantly reduced HNE and AT1R levels and restored mNADP-ICDH activity and redox status in LV tissues of AIA rats. The protective effects of this drug were also evident from the decrease in arthritis scoring and inflammatory markers.

CONCLUSION

Collectively, our findings disclosed that AIA induced oxidative stress and fibrosis in the heart. The fact that ramipril attenuates inflammation, oxidative stress and tissue fibrosis may provide a novel strategy to prevent heart diseases in RA.

5-Lipoxygenase metabolic contributions to NSAID-induced organ toxicity

Cyclooxygenase (COX)-1, COX-2, and 5-lipoxygenase (5-LOX) enzymes produce effectors of pain and inflammation in osteoarthritis (OA) and many other diseases. All three enzymes play a key role in the metabolism of arachidonic acid (AA) to inflammatory fatty acids, which contribute to the deterioration of cartilage. AA is derived from both phospholipase A(2) (PLA(2)) conversion of cell membrane phospholipids and dietary consumption of omega-6 fatty acids. Nonsteroidal antiinflammatory drugs (NSAIDs) inhibit the COX enzymes, but show no anti-5-LOX activity to prevent the formation of leukotrienes (LTs). Cysteinyl LTs, such as LTC(4), LTD(4), LTE(4), and leukoattractive LTB(4) accumulate in several organs of mammals in response to NSAID consumption. Elevated 5-LOX-mediated AA metabolism may contribute to the side-effect profile observed for NSAIDs in OA. Current therapeutics under development, so-called "dual inhibitors" of COX and 5-LOX, show improved side-effect profiles and may represent a new option in the management of OA.

High density micromass cultures of a human chondrocyte cell line: a reliable assay system to reveal the modulatory functions of pharmacological agents

Osteoarthritis is a highly prevalent and disabling disease for which we do not have a cure. The identification of suitable molecular targets is hindered by the lack of standardized, reproducible and convenient screening assays. Following extensive comparisons of a number of chondrocytic cell lines, culture conditions, and readouts, we have optimized an assay utilizing C-28/I2, a chondrocytic cell line cultured in high-density micromasses. Utilizing molecules with known effects on cartilage (e.g. IL-1β, TGFβ1, BMP-2), we have exploited this improved protocol to (i) evoke responses characteristic of primary chondrocytes; (ii) assess the pharmacodynamics of gene over-expression using non-viral expression vectors; (iii) establish the response profiles of known pharmacological treatments; and (iv) investigate their mechanisms of action. These data indicate that we have established a medium-throughput methodology for studying chondrocyte-specific cellular and molecular responses (from gene expression to rapid quantitative measurement of sulfated glycosaminoglycans by Alcian blue staining) that may enable the discovery of novel therapeutics for pharmacological modulation of chondrocyte activation in osteoarthritis.