Rapid induction of early osteoarthritic-like lesions in the rabbit knee by continuous intra-articular infusion of mammalian collagenase or interleukin-1

Non-invasive mouse models of post-traumatic osteoarthritis

Animal models of osteoarthritis (OA) are essential tools for investigating the development of the disease on a more rapid timeline than human OA. Mice are particularly useful due to the plethora of genetically modified or inbred mouse strains available. The majority of available mouse models of OA use a joint injury or other acute insult to initiate joint degeneration, representing post-traumatic osteoarthritis (PTOA). However, no consensus exists on which injury methods are most translatable to human OA. Currently, surgical injury methods are most commonly used for studies of OA in mice; however, these methods may have confounding effects due to the surgical/invasive injury procedure itself, rather than the targeted joint injury. Non-invasive injury methods avoid this complication by mechanically inducing a joint injury externally, without breaking the skin or disrupting the joint. In this regard, non-invasive injury models may be crucial for investigating early adaptive processes initiated at the time of injury, and may be more representative of human OA in which injury is induced mechanically. A small number of non-invasive mouse models of PTOA have been described within the last few years, including intra-articular fracture of tibial subchondral bone, cyclic tibial compression loading of articular cartilage, and anterior cruciate ligament (ACL) rupture via tibial compression overload. This review describes the methods used to induce joint injury in each of these non-invasive models, and presents the findings of studies utilizing these models. Altogether, these non-invasive mouse models represent a unique and important spectrum of animal models for studying different aspects of PTOA.

Detection of changes in articular cartilage proteoglycan by T(1rho) magnetic resonance imaging

The purpose of this work is to demonstrate the feasibility of T(1rho)-weighted magnetic resonance imaging (MRI) to quantitatively measure changes in proteoglycan content in cartilage. The T(1rho) MRI technique was implemented in an in vivo porcine animal model with rapidly induced cytokine-mediated cartilage degeneration. Six pigs were given an intra-articular injection of recombinant porcine interleukin-1beta (IL-1beta) into the knee joint before imaging to induce changes in cartilage via matrix metalloproteinase (MMP) induction. The induction of MMPs by IL-1 was used since it has been extensively studied in many systems and is known to create conditions that mimic in part characteristics similar to those of osteoarthritis. The contralateral knee joint was given a saline injection to serve as an internal control. T(1rho)-weighted MRI was performed on a 4 T whole-body clinical scanner employing a 2D fast spin-echo-based T(1rho) imaging sequence. T(1rho) relaxation parameter maps were computed from the T(1rho)-weighted image series. The average T(1rho) relaxation rate, R(1rho) (1/T(1rho)) of the IL-1beta-treated patellae was measured to be on average 25% lower than that of saline-injected patellae indicating a loss of proteoglycan. There was an average reduction of 49% in fixed charge density, measured via sodium MRI, of the IL-1beta-treated patellae relative to control corroborating the loss of proteoglycan. The effects of IL-1beta, primarily loss of PG, were confirmed by histological and immunochemical findings. The results from this study demonstrate that R(1rho) is able to track proteoglycan content in vivo.

Sodium magnetic resonance imaging of proteoglycan depletion in an in vivo model of osteoarthritis

RATIONALE AND OBJECTIVES

The aim of the study was to investigate the feasibility of using sodium magnetic resonance imaging (MRI) as a noninvasive quantitative technique for measuring proteoglycan (PG) content in an in vivo porcine model of osteoarthritis (OA).

MATERIALS AND METHODS

Biochemical conditions similar to those of OA were created by an intra-articular injection of recombinant porcine interleukin-1beta (IL-1beta) into the knee joint of pigs (n = 6) before performing MRI. The contralateral knee joint was given a saline injection to serve as an internal control. Sodium MRI data were acquired on a 4-T clinical MR scanner and used to compute quantitative sodium and fixed charge density (FCD) maps based on a previously established methodology. In vivo FCD maps were compared with FCD maps obtained using ex vivo patellae harvested from the specimens. The tissue and joint fluid were subjected to histologic and immunohistochemical analyses as independent measurements of IL-1beta activity and PG loss.

RESULTS

The average FCD of IL-1beta-treated patellae was measured to be 49% lower than that of saline-treated patellae, indicating a loss of PG content. These results were supported by histologic and immunochemical findings, most notably a reduction in staining for PG and an increase in matrix metalloproteinases in the synovial fluid.

CONCLUSION

Sodium MRI can serve as a quantitative method to measure in vivo changes in PG content in an animal model of OA. The use of a noninvasive quantitative in vivo PG measurement technique such as sodium MRI on an animal model would aid greatly in efforts to monitor the efficacy of treatments for OA. Furthermore, these results indicate that early degenerative events could be detected noninvasively in vivo in humans with PG-depleting diseases such as OA.

Proteoglycan Loss in Human Knee Cartilage: Quantitation with Sodium MR Imaging—Feasibility Study

The feasibility of using sodium magnetic resonance (MR) imaging to detect proteoglycan loss in early-stage osteoarthritis is evaluated. Fixed charge density (FCD) maps were calculated from sodium MR imaging data collected in nine healthy volunteers and three individuals with symptoms of early-stage osteoarthritis by using a 4.0-T clinical MR imaging unit. Data from the healthy individuals revealed a mean FCD of -182 mmol/L +/- 9. Data from the symptomatic subjects revealed focal regions of decreased FCD, with mean values ranging from -108 to -144 mmol/L, indicating proteoglycan loss from the cartilage matrix. The data suggest that sodium MR imaging has potential for use as a quantitative diagnostic tool to measure changes in proteoglycan content in early-stage osteoarthritis.

Expression of stromelysin and urokinase type plasminogen activator protein in resection specimens and biopsies at different stages of osteoarthritis of the knee

This study aimed at assessing the possible diagnostic value of cartilage biopsies as a convenient marker for cartilage matrix degradation. We therefore examined cartilage specimens from 56 patients with primary osteoarthritis (OA) of the knee. Resection and biopsy cartilage specimens obtained during joint replacement surgery were used for this study. In addition to histomorphology, immunohistochemistry (ICH) was performed to determine the expression levels and distribution patterns of stromelysin and u-PA protein. The latter data were compared with the degree of histomorphological changes in osteoarthritic cartilage samples, based on a modified version of Mankin's grading score. Compared to the cartilage resection specimens, the biopsies showed comparable expression patterns for both proteinases: the strongest signals were noted in the superficial zone and, as matrix destruction increased, also in the chondrocytes of the transition and deep zones. The strongest signals were ascertained in cell clusters beneath deep matrix fissures. At the immunohistochemical level, we found a direct correlation in the expression of MMP-3 and u-PA between resection specimens and biopsies. Furthermore, in both types of cartilage samples, we noticed a positive relationship between the expression of both proteins and the Mankin score. Analysis of the expression levels revealed significant differences between deep, transition and superficial zones. Histomorphological and immunohistochemical examinations of MMP-3 and u-PA in biopsies of osteoarthritic cartilage turned out to be useful for estimating the pathological changes within osteoarthritic knee joints. Therefore, in future, cartilage biopsies from osteoarthritic knee joints might serve as a diagnostic tool and thus have an influence on further therapeutic strategies.

Niacinamide therapy for osteoarthritis--does it inhibit nitric oxide synthase induction by interleukin 1 in chondrocytes?

Fifty years ago, Kaufman reported that high-dose niacinamide was beneficial in osteoarthritis (OA) and rheumatoid arthritis. A recent double-blind study confirms the efficacy of niacinamide in OA. It may be feasible to interpret this finding in the context of evidence that synovium-generated interleukin-1 (IL-1), by inducing nitric oxide (NO) synthase and thereby inhibiting chondrocyte synthesis of aggrecan and type II collagen, is crucial to the pathogenesis of OA. Niacinamide and other inhibitors of ADP-ribosylation have been shown to suppress cytokine-mediated induction of NO synthase in a number of types of cells; it is therefore reasonable to speculate that niacinamide will have a comparable effect in IL-1-exposed chondrocytes, blunting the anti-anabolic impact of IL-1. The chondroprotective antibiotic doxycycline may have a similar mechanism of action. Other nutrients reported to be useful in OA may likewise intervene in the activity or synthesis of IL-1. Supplemental glucosamine can be expected to stimulate synovial synthesis of hyaluronic acid; hyaluronic acid suppresses the anti-catabolic effect of IL-1 in chondrocyte cell cultures, and has documented therapeutic efficacy when injected intra-articularly. S-adenosylmethionine (SAM), another proven therapy for OA, upregulates the proteoglycan synthesis of chondrocytes, perhaps because it functions physiologically as a signal of sulfur availability. IL-1 is likely to decrease SAM levels in chondrocytes; supplemental SAM may compensate for this deficit. Adequate selenium nutrition may down-regulate cytokine signaling, and ample intakes of fish oil can be expected to decrease synovial IL-1 production; these nutrients should receive further evaluation in OA. These considerations suggest that non-toxic nutritional regimens, by intervening at multiple points in the signal transduction pathways that promote the synthesis and mediate the activity of IL-1, may provide a substantially superior alternative to NSAIDs (merely palliative and often dangerously toxic) in the treatment and perhaps prevention of OA.

Cloning of the gene for interstitial collagenase-3 (matrix metalloproteinase-13) from rabbit synovial fibroblasts: differential expression with collagenase-1 (matrix metalloproteinase-1)

Cartilage, bone and the interstitial stroma, composed largely of the interstitial collagens, types I, II and III, are remodelled by three members of the metalloproteinase (MMP) family, collagenase-1 (MMP-1), collagenase-2 (MMP-8) and collagenase-3 (MMP-13). MMP-1 and MMP-13 may contribute directly to disease progression, since they are induced in patients with rheumatoid arthritis and osteoarthritis. The study of MMP-1 and MMP-13 gene regulation in models of arthritic disease has been problematic because mice and rats, which are typically used, only possess a homologue of MMP-13. Here we show that in contrast with mice and rats, rabbits possess distinct genes homologous to human MMP-1 and MMP-13. Furthermore, rabbit MMP-13 is expressed simultaneously with MMP-1 in chondrocytes and synovial fibroblasts in response to the cytokines interleukin-1 and tumour necrosis factor-alpha, or the phorbol ester PMA. The time course of MMP-13 induction is more rapid and transient than that of MMP-1, suggesting that distinct mechanisms regulate the expression of these two collagenases. We have cloned the rabbit MMP-13 gene from synovial fibroblasts and demonstrated that the rabbit gene shares greater homology with human MMP-13 than does the mouse interstitial collagenase. Together with the fact that mice and rats do not possess a homologue to human MMP-1, our data suggest that the rabbit provides an appropriate model for studying the roles of interstitial collagenases in connective-tissue diseases, such as rheumatoid arthritis and osteoarthritis.