Pathophysiology and first-line treatment of osteoarthritis

PKR activation causes inflammation and MMP-13 secretion in human degenerated articular chondrocytes

Osteoarthritis (OA) is a degenerative joint disease affecting a large population of people. Although the elevated expression of PKR (double stranded RNA-dependent protein kinase) and MMP-13 (collagenase-3) have been indicated to play pivotal roles in the pathogenesis of OA, the exact mechanism underlying the regulation of MMP-13 by PKR following inflammatory stimulation was relatively unknown. The purpose of this study was to determine the signaling pathway involved in the PKR-mediated induction of MMP-13 after TNF-α-stimulation. In this study, cartilages of knee joint were obtained from OA subjects who underwent arthroplastic knee surgery. Cartilages were used for tissue analysis or for chondrocytes isolation. In results, the upregulated expression of PKR was observed in damaged OA cartilages as well as in TNF-α-stimulated chondrocytes. Phosphorylation of PKC (protein kinase C) was found after TNF-α administration or PKR activation using poly(I:C), indicating PKC was regulated by PKR. The subsequent increased activity of NADPH oxidase led to oxidative stress accumulation and antioxidant capacity downregulation followed by an exaggerated inflammatory response with elevated levels of COX-2 and IL-8 via ERK/NF-κB pathway. Activated ERK pathway also impeded the inhibition of MMP-13 by PPAR-γ. These findings demonstrated that TNF-α-induced PKR activation triggered oxidative stress-mediated inflammation and MMP-13 in human chondrocytes. Unraveling these deregulated signaling cascades will deepen our knowledge of OA pathophysiology and provide aid in the development of novel therapies.

Clinical efficacy of certain Unani herbs in knee osteoarthritis: A pretest and post-test evaluation study

Objectives:

This study was conducted to evaluate the efficacy of preparations of certain Unani herbs on Lequesne Algo-Functional Index of knee osteoarthritis (OA).

Materials and Methods:

A prospective, pre- and post test evaluation study was conducted on 20 diagnosed patients of OA recruited from the Nizamia General Hospital, Hyderabad. Internally, a combination (formula) of Unani herbs was administered, which was as follows: 3.5 g powder of Asarun (2 g), Tukhme karafs (2 g), and Filfil daraz (3 g) was administered internally twice daily. Externally, the concoction of Gule baboona (20 g) and Gule tesu (40 g) made in 1 l water was poured over the affected knee, daily once for 40 days. The primary outcome was to assess the efficacy of Unani test drugs with the modified Lequesne Algo-Functional Index for knee OA.

Results:

The mean percentage reduction of Lequesne Algo-Functional Index score was 71.09%. The mean and standard deviation was 10.55 (1.70) and 3.05 (2.30) before treatment and after treatment, respectively. The pre- and post test evaluation showed reduction in Lequesne Algo-Functional Index score (P < 0.0001).

Conclusion:

In this study, the Unani treatment module was found to be effective in reducing the severity of disease in patients with osteoarthritis of knees.

Effects of enzymatic treatments on the depth-dependent viscoelastic shear properties of articular cartilage

Osteoarthritis (OA) is a disease that involves the erosion and structural weakening of articular cartilage. OA is characterized by the degradation of collagen and proteoglycans in the extracellular matrix (ECM), particularly at the articular surface by proteinases including matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTSs).(1) Degradation of collagen and proteoglycans is known to alter shear mechanical properties of cartilage, but study of this phenomenon has been focused on bulk tissue properties. The purpose of this study was to assess microscale cartilage damage induced by trypsin or collagenase using a technique to measure the local shear viscoelastic properties. Safranin-O histology revealed a decrease in proteoglycans near the articular surface after collagenase and trypsin digestions, with proteoglycan depletion increasing in time. Similarly, confocal reflectance micrographs showed increasing collagen degradation in collagenase treated samples, although the collagen network remained intact after trypsin treatment. Both treatments induced changes in shear modulus that were confined to a narrow range (∼400µm) near tissue surface. In addition, collagenase altered the total energy dissipation distribution by up to a factor of 100, with longer digestion times corresponding to higher energy dissipation. The ability to detect local mechanical signatures in tissue composition and mechanics is an important tool for understanding the spatially non-uniform changes that occur in articular cartilage diseases such as OA.

Clinical outcome of autologous chondrocyte implantation is correlated with infrared spectroscopic imaging-derived parameters

OBJECTIVE

To investigate whether Fourier transform infrared imaging spectroscopy (FT-IRIS), a modality based on molecular vibrations, is a viable alternative to histology and immunohistochemistry (IHC) for assessment of tissue quality and patient clinical outcome.

METHODS

Osteochondral biopsies were obtained from patients (9-65 months post-surgery) who underwent an autologous chondrocyte implantation (ACI) procedure to repair a cartilage defect (N = 14). The repair tissue was evaluated histologically by OsScore grading, for the presence of types I and II collagen by IHC, and for proteoglycan (PG) distribution and collagen quality parameters by FT-IRIS. Patient clinical outcome was assessed by the Lysholm score.

RESULTS

Improvement in Lysholm score occurred in 79% of patients. IHC staining showed the presence of types I and II collagen in all samples, with a greater amount of collagen type II in the deep zone. The amount and location of immunostaining for type II collagen correlated to the FT-IRIS-derived parameters of relative PG content and collagen helical integrity. In addition, the improvement in Lysholm score post-ACI correlated positively with the OsScore, type II collagen (IHC score) and FT-IRIS-determined parameters. Regression models for the relation between improvement in Lysholm score and either OsScore, IHC area score or the FT-IRIS parameters all reached significance (p < 0.01). However, the FT-IRIS model was not significantly improved with inclusion of the OsScore and IHC score parameters.

CONCLUSION

Demonstration of the correlation between FT-IRIS-derived molecular parameters of cartilage repair tissue and patient clinical outcome lays the groundwork for translation of this methodology to the clinical environment to aid in the management of cartilage disorders and their treatment.

Variation in osteoarthritis biomarkers from activity not food consumption

BACKGROUND

To optimize sampling and to understand sources of variation in biomarkers for osteoarthritis (OA), we evaluated variation due to activity and food consumption.

METHODS

Twenty participants, with radiographic knee OA, provided serial serum and urine samples at 4 time points: before arising in the morning; after 1 h of light activity; 1 h after eating breakfast; and in the evening. Five serum (s) and 2 urinary (u) analytes were measured: hyaluronan (sHA); cartilage oligomeric matrix protein (sCOMP); keratan sulfate (sKS-5D4); transforming growth factor beta (sTGF-ss1); and collagen II-related epitopes (sCPII, uCTXII, and uC2C). Activity was monitored by an accelerometer.

RESULTS

All serum biomarkers increased and one of the urinary biomarkers decreased after 1 h of non-exertional activity. Food consumption following activity was associated with a return of biomarker concentrations to baseline levels. Accelerometers proved to be a novel way to monitor protocol compliance and demonstrated a positive association between the mean level of activity and sCOMP concentration. Urinary CTXII varied the least but demonstrated both true circadian variation (peak in the morning and nadir in the evening) and the most robust correlation with radiographic knee OA.

CONCLUSIONS

We confirm activity related variation in these markers. These data suggested that biomarkers also varied due to upright posture, glomerular filtration rate stimulated by food intake, and circadian rhythm in the case of uCTXII.

Biomarkers associated with clinical phenotypes of hand osteoarthritis in a large multigenerational family: the CARRIAGE family study

OBJECTIVE

To evaluate biological markers as potential quantitative traits of clinical osteoarthritis (OA) in a large multigenerational family in the Carolinas of the USA known as the CARRIAGE (CARolinas Region Interaction of Aging, Genes and Environment) family.

METHODS

During a series of three family reunions over 6 years, we ascertained 365 family members. We performed clinical hand examinations (n=287), and obtained sera (n=278) for seven OA-related biomarkers [type IIA collagen N-propeptide (PIIANP), type II procollagen carboxy-propeptide (CPII), neoepitope from cleavage of CII (C(2)C), cartilage oligomeric matrix protein (COMP), hyaluronan (HA), high-sensitive C-reactive protein (hs-CRP), and glycated serum protein (GSP)]. Three hand OA definitions were evaluated--clinical ACR (American College of Rheumatology) and GOGO (Genetics of Generalized OA) criteria, and any single hand joint involvement. Non-hand OA was defined as a negative hand examination for OA but varying prevalence of joint symptoms; the control group was defined as having neither symptoms nor evidence for clinical hand OA.

RESULTS

Mean lnHA, lnCOMP, and lnhs-CRP were significantly higher in the hand OA group, compared with the non-hand OA or control group. Adjusted for age and sex, mean lnPIIANP (a collagen II synthesis marker) was significantly lower in the hand OA group compared with the other groups. Among those without clinical hand OA, GSP was associated with hand joint symptoms.

CONCLUSIONS

This is the first report, to our knowledge, showing an association of OA biomarkers and hand OA based on physical examination alone. Analyses using these biomarkers as quantitative traits could reveal novel genetic loci and facilitate exploration of the genetic susceptibility to OA.

Fourier transform infrared imaging and MR microscopy studies detect compositional and structural changes in cartilage in a rabbit model of osteoarthritis

Assessment of subtle changes in proteoglycan (PG) and collagen, the primary macromolecular components of cartilage, which is critical for diagnosis of the early stages of osteoarthritis (OA), has so far remained a challenge. In this study we induced osteoarthritic cartilage changes in a rabbit model by ligament transection and medial meniscectomy and monitored disease progression by infrared fiber optic probe (IFOP) spectroscopy, Fourier transform infrared imaging spectroscopy (FT-IRIS), and magnetic resonance imaging (MRI) microscopy. IFOP studies combined with chemometric partial least-squares analysis enabled us to monitor progressive cartilage surface changes from two to twelve weeks post-surgery. FT-IRIS studies of histological sections of femoral condyle cartilage revealed that compared with control cartilage the OA cartilage had significantly reduced PG content 2 and 4 weeks post-surgery, collagen fibril orientation changes 2 and 4 weeks post-surgery, and changes in collagen integrity 2 and 10 weeks post-surgery, but no significant changes in collagen content at any time. MR microscopy studies revealed reduced fixed charge density (FCD), indicative of reduced PG content, in the OA cartilage, compared with controls, 4 weeks post-surgery. A non-significant trend toward higher apparent MT exchange rate, k(m), was also found in the OA cartilage at this time point, suggesting changes in collagen structural features. These two MR findings for FCD and k(m) parallel the FT-IRIS findings of reduced PG content and altered collagen integrity, respectively. MR microscopy studies of the cartilage at the 12-week time point also found a trend toward longer T (2) values and reduced anisotropy in the deep zone of the OA cartilage, consistent with increased hydration and less ordered collagen. These studies reveal that FT-IRIS and MR microscopy provide complementary data on compositional changes in articular cartilage in the early stages of osteoarthritic degradation.

Fourier transform infrared imaging spectroscopy investigations in the pathogenesis and repair of cartilage

Significant complications in the management of osteoarthritis (OA) are the inability to identify early cartilage changes during the development of the disease, and the lack of techniques to evaluate the tissue response to therapeutic and tissue engineering interventions. In recent studies several spectroscopic parameters have been elucidated by Fourier transform infrared imaging spectroscopy (FT-IRIS) that enable evaluation of molecular and compositional changes in human cartilage with progressively severe OA, and in repair cartilage from animal models. FT-IRIS permits evaluation of early-stage matrix changes in the primary components of cartilage, collagen and proteoglycan on histological sections at a spatial resolution of approximately 6.25 microm. In osteoarthritic cartilage, the collagen integrity, monitored by the ratio of peak areas at 1338 cm(-1)/Amide II, was found to correspond to the histological Mankin grade, the gold standard scale utilized to evaluate cartilage degeneration. Apparent matrix degradation was observable in the deep zone of cartilage even in the early stages of OA. FT-IRIS studies also found that within the territorial matrix of the cartilage cells (chondrocytes), proteoglycan content increased with progression of cartilage degeneration while the collagen content remained the same, but the collagen integrity decreased. Regenerative (repair) tissue from microfracture treatment of an equine cartilage defect showed significant changes in collagen distribution and loss in proteoglycan content compared to the adjacent normal cartilage, with collagen fibrils demonstrating a random orientation in most of the repair tissue. These studies demonstrate that FT-IRIS is a powerful technique that can provide detailed ultrastructural information on heterogeneous tissues such as diseased cartilage and thus has great potential as a diagnostic modality for cartilage degradation and repair.

Diurnal variation of serum and urine biomarkers in patients with radiographic knee osteoarthritis

OBJECTIVE

To evaluate diurnal variation of biomarkers in subjects with osteoarthritis (OA) of the knee.

METHODS

Twenty subjects with radiographic knee OA were admitted to the General Clinical Research Center of Duke University for an overnight stay to undergo serial blood and urine sampling. Biomarkers measured included serum hyaluronan (HA), cartilage oligomeric matrix protein (COMP), keratan sulfate (KS-5D4), aggrecan neoepitope (CS846), high-sensitivity C-reactive protein (hsCRP), osteocalcin, transforming growth factor beta1 (TGFbeta1), and type II collagen (CII)-related epitopes (neoepitope from cleavage of CII [C2C], carboxy-terminus of three-quarter peptide from cleavage of CI and CII [C1,2C], and type II procollagen carboxy-propeptide [CPII] in serum, and C-terminal telopeptides of CII [CTX-II] and C2C in urine).

RESULTS

Levels of serum HA, COMP, KS-5D4, and TGFbeta1 increased significantly from T0 (before arising from bed) to T1 (1 hour after arising). More diurnal variation in HA was observed in patients with higher daily mean HA concentrations. CPII increased significantly from T0 to T2 (4 hours after arising). Urinary concentrations of CTX-II were also found to vary with morning activity, decreasing significantly from T0 to T2. Urinary C2C concentrations increased significantly from T0 until T3 (early evening). No diurnal variations in CS846, hsCRP, osteocalcin, serum C2C, or C1,2C were observed. Six biomarkers (serum C2C, C1,2C, COMP, KS-5D4, TGFbeta1, and urinary CTX-II) were associated with radiographic knee OA (expressed as the sum of Kellgren/Lawrence radiographic severity grades), with the strongest correlations observed with measurements obtained at later time points (either T2 or T3).

CONCLUSION

Our study results suggest that serum and urine sampling for HA, COMP, KS-5D4, TGFbeta1, CPII, urinary CTX-II, and urinary C2C should be standardized in future OA clinical trials. Serum and urine sampling at late midday time points may be the optimal approach for OA studies, although this result should be validated in a larger cohort.

Early diagnosis of osteoarthritis using cathepsin B sensitive near-infrared fluorescent probes

OBJECTIVE

Osteoarthritis is currently diagnosed utilizing X-ray and MRI-techniques, both of which are based on the morphological changes of tissue. However, once changes are detected, the tissue has an irreversible defect. This study investigates early diagnosis of OA on a molecular basis using a recently developed cathepsin B sensitive near-infrared (NIR) fluorescent probe.

METHOD

Twelve male nude mice were induced osteoarthritis by intra-articular injection of collagenase (1.0%, w/v) into the right knee joint. The left knee joint served as the negative control. The cathepsin B NIR probe is activated by arthritis-associated cathepsin B, thus resulting in the emission of an intensive NIR fluorescence signal which can be detected in vivo. NIR fluorescence signals were acquired on an optical imaging system using an excitation wavelength of 610-650 nm and an emission wavelength of 680-720 nm.

RESULTS

Mild to moderate degenerative cartilage was observed 1 month after collagenase injection. NIR fluorescence imaging of mice showed approximately a 3-fold difference in signal intensity between osteoarthritic and normal joints 24 h after intravenous injection of the reporter probe. Immunohistochemical evaluation also revealed cathepsin B expression in the arthritic lesion of femorotibial joints, and not in the control contra-lateral knee joints.

CONCLUSION

As the cathepsin B activatable NIR fluorescent imaging showed a significant difference between the osteoarthritic and normal joints, the cathepsin B activatable NIR fluorescent probe thus offers a potential new imaging technology for early OA diagnosis.

Paracetamol in the Treatment of Osteoarthritis Pain

Osteoarthritis (OA) is the most common joint disease and OA of the knee, in particular, is the major cause of chronic disability among people > 65 years. Because nonsteroidal anti-inflammatory drugs (NSAIDs) improve symptoms in many patients with OA, it is widely considered that OA pain is due to synovial inflammation. However, OA pain may arise also from subchondral bone, the joint capsule ligaments, tendons, entheses and periarticular muscle spasm. In many patients, the relief of OA pain and overall satisfaction with therapy may be as great with paracetamol (acetaminophen [APAP]) as with an NSAID. Cyclo-oxygenase (COX)-1-sparing NSAIDs (coxibs) are no more effective in the treatment of OA pain than non-selective NSAIDs and, although they may significantly decrease the risk of serious adverse effects related to gastrointestinal ulcers (GI) and ulcer complications, their gastroprotective effect may be reduced by concomitant administration of low-dose aspirin. Also, they may increase the risk of myocardial infarction in predisposed individuals. Because coxibs do not inhibit platelet aggregation, if prophylaxis against thromboembolic disease is required in patients being treated with a selective COX-2 inhibitor, low-dose aspirin should be used in conjunction with the coxib. Furthermore, nonselective NSAIDs and coxibs may have adverse effects on the kidney, fracture healing and salt and water homeostasis. This paper discusses the relative positioning of APAP, NSAIDs and coxibs in the management of OA, on the basis of considerations of tolerability, efficacy and costs.