Inflammation in Osteoarthritis

Therapeutic Controlled Release Strategies for Human Osteoarthritis

Osteoarthritis is a progressive, irreversible debilitating whole joint disease that affects millions of people worldwide. Despite the availability of various options (non-pharmacological and pharmacological treatments and therapy, orthobiologics, and surgical interventions), none of them can definitively cure osteoarthritis in patients. Strategies based on the controlled release of therapeutic compounds via biocompatible materials may provide powerful tools to enhance the spatiotemporal delivery, expression, and activities of the candidate agents as a means to durably manage the pathological progression of osteoarthritis in the affected joints upon convenient intra-articular (injectable) delivery while reducing their clearance, dissemination, or side effects. The goal of this review is to describe the current knowledge and advancements of controlled release to treat osteoarthritis, from basic principles to applications in vivo using therapeutic recombinant molecules and drugs and more innovatively gene sequences, providing a degree of confidence to manage the disease in patients in a close future.

Acute systemic macrophage depletion in osteoarthritic mice alleviates pain-related behaviors and does not affect joint damage

Background

Osteoarthritis (OA) is a painful degenerative joint disease and a leading source of years lived with disability globally due to inadequate treatment options. Neuroimmune interactions reportedly contribute to OA pain pathogenesis. Notably, in rodents, macrophages in the DRG are associated with onset of persistent OA pain. Our objective was to determine the effects of acute systemic macrophage depletion on pain-related behaviors and joint damage using surgical mouse models in both sexes.

Methods

We depleted CSF1R+ macrophages by treating male macrophage Fas-induced apoptosis (MaFIA) transgenic mice 8- or 16-weeks post destabilization of the medial meniscus (DMM) with AP20187 or vehicle control (10 mg/kg i.p., 1x/day for 5 days), or treating female MaFIA mice 12 weeks post partial meniscectomy (PMX) with AP20187 or vehicle control. We measured pain-related behaviors 1-3 days before and after depletion, and, 3-4 days after the last injection we examined joint histopathology and performed flow cytometry of the dorsal root ganglia (DRGs). In a separate cohort of male 8-week DMM mice or age-matched naïve vehicle controls, we conducted DRG bulk RNA-sequencing analyses after the 5-day vehicle or AP20187 treatment.

Results

Eight- and 16-weeks post DMM in male mice, AP20187-induced macrophage depletion resulted in attenuated mechanical allodynia and knee hyperalgesia. Female mice showed alleviation of mechanical allodynia, knee hyperalgesia, and weight bearing deficits after macrophage depletion at 12 weeks post PMX. Macrophage depletion did not affect the degree of cartilage degeneration, osteophyte width, or synovitis in either sex. Flow cytometry of the DRG revealed that macrophages and neutrophils were reduced after AP20187 treatment. In addition, in the DRG, only MHCII+ M1-like macrophages were significantly decreased, while CD163+MHCII- M2-like macrophages were not affected in both sexes. DRG bulk RNA-seq revealed that Cxcl10 and Il1b were upregulated with DMM surgery compared to naïve mice, and downregulated in DMM after acute macrophage depletion.

Conclusions

Acute systemic macrophage depletion reduced the levels of pro-inflammatory macrophages in the DRG and alleviated pain-related behaviors in established surgically induced OA in mice of both sexes, without affecting joint damage. Overall, these studies provide insight into immune cell regulation in the DRG during OA.

Matrix in Medicine: Health Consequences of Mutant Cartilage Oligomeric Matrix Protein and its relationship to abnormal growth and to joint degeneration

Cartilage oligomeric matrix protein (COMP), an extracellular matrix protein, has been shown to enhance proliferation and mechanical integrity in the matrix, supporting functions of the growth plate and articular cartilage. Mutations in COMP cause pseudoachondroplasia (PSACH), a severe dwarfing condition associated with premature joint degeneration and significant lifelong joint pain. The MT (mutant)-COMP mouse mimics PSACH with decreased limb growth, early joint degeneration and pain. Ablation of endoplasmic reticulum stress CHOP signaling eliminated pain and prevented joint degeneration. The health effects of mutant COMP are discussed in relation to cellular/chondrocyte stress in the growth plate, articular cartilage and nearby tissues, and the implications for therapeutic approaches. There are many similarities between osteoarthritis and mutant-COMP protein-induced joint degeneration, suggesting that the relevance of findings in the joints may extend beyond PSACH to idiopathic primary OA.

Perceived health status of women with knee osteoarthritis: a cross-sectional study of the relationships of age, body mass, pain and walking limitations

Persons with knee osteoarthritis (OA) often experience considerable physical disability. Although some studies suggest women with this condition suffer more than men, few have attempted to characterize the magnitude and that impact of this condition specifically among women with moderate knee osteoarthritis as well as the relationships that exist between their perceived health status and well established physical, emotional and perceptual factors found in this disease. This exploratory study strove to better understand factors that underpin the perceived impact of the condition, and to describe the extent of pain and function among women with mild to moderate knee osteoarthritis, and how this impacts this condition. The records of 20 women with the condition who had undergone multiple tests using a standardized protocols and validated instruments were examined. The primary outcome measure was the perceived impact of the disease using the Arthritis Impact Measurement Scale. Secondary outcome measures included six minute walking distance, fastest walking velocity, self-reported pain, pain and functional self-efficacy, body mass, and depression. The variables were subjected to t-tests, and correlational analyses. Results demonstrated pain is the clinical factor most consistently impacting the disease experience, along with deficiencies in walking ability (p <0.05). Important mediating variables of ambulatory capacity were body mass and pain self-efficacy.

Does intraarticular inflammation predict biomechanical cartilage properties?

BACKGROUND

Intact cartilage in the lateral compartment is an important requirement for medial unicompartmental knee arthroplasty (UKA). Progression of cartilage degeneration in the lateral compartment is a common failure mode of medial UKA. Little is known about factors that influence the mechanical properties of lateral compartment cartilage.

QUESTIONS/PURPOSES

The purposes of this study were to answer the following questions: (1) Does the synovial fluid white blood cell count predict the biomechanical properties of macroscopically intact cartilage of the distal lateral femur? (2) Is there a correlation between MRI grading of synovitis and the biomechanical properties of macroscopically intact cartilage? (3) Is there a correlation between the histopathologic assessment of the synovium and the biomechanical properties of macroscopically intact cartilage?

METHODS

The study included 84 patients (100 knees) undergoing primary TKA for varus osteoarthritis between May 2010 and January 2012. All patients underwent preoperative MRI to assess the degree of synovitis. During surgery, the cartilage of the distal lateral femur was assessed macroscopically using the Outerbridge grading scale. In knees with an Outerbridge grade of 0 or 1, osteochondral plugs were harvested from the distal lateral femur for biomechanical and histologic assessment. The synovial fluid was collected to determine the white blood cell count. Synovial tissue was taken for histologic evaluation of the degree of synovitis.

RESULTS

The mean aggregate modulus and the mean dynamic modulus were significantly greater in knees with 150 or less white blood cells/mL synovial fluid compared with knees with greater than 150 white blood cells/mL synovial fluid. There was no correlation among MRI synovitis grades, histopathologic synovitis grades, and biomechanical cartilage properties.

CONCLUSIONS

The study suggests that lateral compartment cartilage in patients with elevated synovial fluid white blood cell counts has a reduced ability to withstand compressive loads.

LEVEL OF EVIDENCE

Level III, diagnostic study. See the Instructions for Authors for a complete description of levels of evidence.

Involvement of the Wnt signaling pathway in experimental and human osteoarthritis: prominent role of Wnt-induced signaling protein 1

OBJECTIVE

Wnt signaling pathway proteins are involved in embryonic development of cartilage and bone, and, interestingly, developmental processes appear to be recapitulated in osteoarthritic (OA) cartilage. The present study was undertaken to characterize the expression pattern of Wnt and Fz genes during experimental OA and to determine the function of selected genes in experimental and human OA.

METHODS

Longitudinal expression analysis was performed in 2 models of OA. Levels of messenger RNA for genes from the Wnt/beta-catenin pathway were determined in synovium and cartilage, and the results were validated using immunohistochemistry. Effects of selected genes were assessed in vitro using recombinant protein, and in vivo by adenoviral overexpression.

RESULTS

Wnt-induced signaling protein 1 (WISP-1) expression was strongly increased in the synovium and cartilage of mice with experimental OA. Wnt-16 and Wnt-2B were also markedly up-regulated during the course of disease. Interestingly, increased WISP-1 expression was also found in human OA cartilage and synovium. Stimulation of macrophages and chondrocytes with recombinant WISP-1 resulted in interleukin-1-independent induction of several matrix metalloproteinases (MMPs) and aggrecanase. Adenoviral overexpression of WISP-1 in murine knee joints induced MMP and aggrecanase expression and resulted in cartilage damage.

CONCLUSION

This study included a comprehensive characterization of Wnt and Frizzled gene expression in experimental and human OA articular joint tissue. The data demonstrate, for the first time, that WISP-1 expression is a feature of experimental and human OA and that WISP-1 regulates chondrocyte and macrophage MMP and aggrecanase expression and is capable of inducing articular cartilage damage in models of OA.

Should we use non-steroidal anti-inflammatory drugs?

Both the relative efficacy and inefficacy of non-steroidal antiinflammatory drugs (NSAIDs) contribute to their use in chronic rheumatic diseases. There are also sociological trends in patients, and in the population as a whole, increasing demand for treatment. In view of the risks of such treatment, the most rational approach to prescribing would be the use of a scientific risk-benefit analysis. Unfortunately, the data, especially those related to symptom relief, are inadequate for such an analysis. Until more meaningful figures are produced, good clinical practise concentrates on the responsibilities of physicians who both start and stop drugs, and makes it essential that strategies to minimize risk are produced.

Osteophytes, juxta-articular radiolucencies and cancellous bone changes in the proximal tibia of patients with knee osteoarthritis

OBJECTIVE

To determine differences in tibial cancellous bone organisation in knee osteoarthritis (OA) between the central weight-bearing region and juxta-articular radiolucencies adjacent to small, medium or large marginal osteophytes.

METHODS

Patients with medial compartment OA (n = 60; F = 39), mean (SD) age 60.0 (9.7) years, and non-OA reference subjects (n = 21; F = 5), mean (SD) age 36.8 (11.5) years, had x4 macroradiographs digitised by laser scanner. Using a modified Osteoarthritis Research Society (OARS) Atlas, right and/or left knees were graded according to marginal osteophyte size into those with small (n = 30), medium (n = 30) or large (n = 27) marginal osteophytes, identified as OPH1, OPH2 and OPH3, respectively. Non-OA knees (n = 30) were anatomically normal. Computerised method of Fractal Signature Analysis (FSA) quantified differences in cancellous bone structure between non-OA and osteophyte subgroups at two regions of interest (ROIs); central weight-bearing and tibial margin.

RESULTS

Compared to non-OA, vertical trabecular number increased significantly (P < 0.05) in all osteophyte subgroups (width range 0.12-1.14 mm) within both ROIs. In OPH3, this increase was significantly (P < 0.05) greater compared to OPH2 in the central ROI, and to OPH2 and OPH1 in the marginal ROI at most trabecular widths (0.12-1.14 mm). In the marginal ROI, compared to non-OA, horizontal trabeculae number decreased in all osteophyte subgroups. This decrease was significantly greater in OPH3 compared to OPH2 and OPH1 at small to medium trabecular widths (0.12-0.54 mm).

CONCLUSION

Compared to disease associated bone loss at the central ROI of the tibia, the extent of juxta-articular bone loss appears to be associated with the size of the marginal osteophytes.

Postnatal expression in hyaline cartilage of constitutively active human collagenase-3 (MMP-13) induces osteoarthritis in mice

It has been suggested that increased collagenase-3 (MMP-13) activity plays a pivotal role in the pathogenesis of osteoarthritis (OA). We have used tetracycline-regulated transcription in conjunction with a cartilage-specific promoter to target a constitutively active human MMP-13 to the hyaline cartilages and joints of transgenic mice. Postnatal expression of this transgene resulted in pathological changes in articular cartilage of the mouse joints similar to those observed in human OA. These included characteristic erosion of the articular cartilage associated with loss of proteoglycan and excessive cleavage of type II collagen by collagenase, as well as synovial hyperplasia. These results demonstrate that excessive MMP-13 activity can result in articular cartilage degradation and joint pathology of the kind observed in OA, suggesting that excessive activity of this proteinase can lead to this disease.

The pathobiology of osteoarthritis and the rationale for the use of pentosan polysulfate for its treatment

OBJECTIVES

Structure-modifying osteoarthritis (OA) drugs (SMOADs) may be defined as agents that reverse, retard, or stabilize the underlying pathology of OA, thereby providing symptomatic relief in the long-term. The objective of this review was to evaluate the literature on sodium pentosan polysulfate (NaPPS) and calcium pentosan polysulfate (CaPPS), with respect to the pathobiology of OA to ascertain whether these agents should be classified as SMOADs.

METHODS

Published studies on NaPPS and CaPPS were selected on the basis of their relevance to the known pathobiology of OA, which also was reviewed.

RESULTS

Both NaPPS and CaPPS exhibit a wide range of pharmacological activities. Of significance was the ability of these agents to support chondrocyte anabolic activities and attenuate catabolic events responsible for loss of components of the cartilage extracellular matrix in OA joints. Although some of the anti-catabolic activities may be mediated through direct enzyme inhibition, NaPPS and CaPPS also have been shown to enter chondrocytes and bind to promoter proteins and alter gene expression of matrix metalloproteinases and possibly other mediators. In rat models of arthritis, NaPPS and CaPPS reduced joint swelling and inflammatory mediator levels in pouch fluids. Moreover, synoviocyte biosynthesis of high-molecular-weight hyaluronan, which is diminished in OA, was normalized when these cells were incubated with NaPPS and CaPPS or after intraarticular injection of NaPPS into arthritic joints. In rabbit, canine, and ovine models of OA, NaPPS and CaPPS preserved cartilage integrity, proteoglycan synthesis, and reduced matrix metalloproteinase activity. NaPPS and CaPPS stimulated the release of tissue plasminogen activator (t-PA), superoxide dismutase, and lipases from vascular endothelium while concomitantly decreasing plasma levels of the endogenous plasminogen activator inhibitor PAI-1. The net thrombolytic and lipolytic effects exhibited by NaPPS and CaPPS may serve to improve blood flow through subchondral capillaries of OA joints and improve bone cell nutrition. In geriatric OA dogs, NaPPS and CaPPS reduced symptoms, as well as normalized their thrombolytic status, threshold for platelet activation, and plasma triglyceride levels. These hematologic parameters were shown to be abnormal in OA animals before drug treatment. Similar outcomes were observed in OA patients when CaPPS or NaPPS were given orally or parenterally in both open and double-blind trials.

CONCLUSIONS

The data presented in this review support the contention that NaPPS and CaPPS should be classified as SMOADs. However, additional long-term clinical studies employing methods of assessing joint structural changes will be needed to confirm this view.

Comparison of aceclofenac with piroxicam in the treatment of osteoarthritis

A multicentre, double-blind, randomised, parallel group study was undertaken to investigate the efficacy and safety of aceclofenac (123 patients, 100 mg twice daily) in comparison to piroxicam (117 patients, 20 mg once daily and placebo once daily) in patients with osteoarthritis of the knee. The treatment period of two months was preceded by a washout period of one week duration. On completion of the study, patients in both aceclofenac and piroxicam-treated groups exhibited significant improvement in pain intensity and functional capacity of the affected knee, as represented by the Osteoarthritis Severity Index (OSI) (p < 0.0001 and p < 0.001 respectively). This was further substantiated following the patient's assessment of pain intensity using the Visual Analogue Scale (VAS), in which significant improvements were demonstrated at all time points for each treatment group (p < 0.001). Although both treatment groups showed a significant improvement in all investigator's clinical assessments (functional exploration of the knee, knee flexion and extension (EXT)), there were no significant differences between the groups. There was, however, a more rapid improvement in knee flexion in the aceclofenac group after 15 days of treatment. Both aceclofenac and piroxicam were well tolerated by patients, the most commonly reported adverse events being gastrointestinal, although their incidence was low. Only 24 patients on aceclofenac, as opposed to 33 on piroxicam complained of dyspepsia, epigastralgia and pyrosis. While 7 patients in each group were withdrawn because of adverse events, only one patient with piroxicam was withdrawn because of severe upper gastrointestinal bleeding. Twice as many reports of fecal blood loss were made in the piroxicam group in comparison to the aceclofenac group. In summary, this study confirms the therapeutic efficacy of aceclofenac and suggests that it is a well-tolerated alternative NSAID to piroxicam in the treatment of osteoarthritis.

The treatment of osteoarthritis

1. The treatment of osteoarthritis is currently purely symptomatic. To enable rational therapy, careful clinical assessment is necessary to identify the origin of symptoms. Often, effective therapy can result from a biomechanical approach such as surgery, orthotics, physiotherapy and dieting. If drugs are required, there is little evidence that the current over-reliance on non-steroidal anti-inflammatory drugs (NSAIDs) is justified. Full dose regular paracetamol should be the first line of analgesic therapy. In the majority of patients, simple analgesics are probably as effective as NSAIDs. If NSAIDs are used it is necessary to review regularly their use and to be aware of potential toxicity. 2. Many alternative strategies of pain management such as topical preparations, intra-articular steroid injections, acupuncture, radiosynovectomy, transcutaneous nerve stimulation and anti-depressants, may be effective but their precise place in the armamentarium is not yet fully established. 3. The realisation that osteoarthritis is not a passive 'wear and tear' phenomenon but an active process that may be potentially modified, has led to interest in 'chondroprotective' agents, which may beneficially affect the osteoarthritic process. To date there are no convincing data available that such agents are, in fact, chondroprotective in humans.

Efficacy of cod liver oil as an adjunct to non-steroidal anti-inflammatory drug treatment in the management of osteoarthritis in general practice

A double blind, placebo controlled trial was carried out to assess the efficacy of cod liver oil as an adjunct treatment to non-steroidal anti-inflammatory drugs (NSAIDs) in the management of osteoarthritis in general practice. Eighty six patients were given 10 ml of either cod liver oil or olive oil placebo daily as a supplement to their regular NSAID treatment for 24 weeks. Patients were assessed by their general practitioner at four week intervals for joint pain/inflammation, overall interference with activities, and unwanted effects of treatment. Patients recorded on visual analogue scales their daily pain and the extent to which arthritis interfered with everyday activities. There was no significant benefit for the patients taking cod liver oil compared with those taking placebo.

Quantitative microfocal radiographic assessment of progression in osteoarthritis of the hand

We studied 32 patients with osteoarthritis who had 5x macroradiographs taken of their wrists and hands at 6-month intervals over an 18-month period. The higher magnification and resolution of microfocal radiography permitted the quantitative detection of progressive changes in 4 different features: subchondral sclerosis, the number and size of osteophytes, juxtaarticular radiolucencies, and joint space narrowing. Compared with normal control subjects, subchondral cortical thickness was greater in all patients at entry and showed a variable degree of change over the study period. Osteophytes and juxtaarticular radiolucencies were present in all patients at study entry; by the end of the study, osteophytes had increased in number and area, and juxtaarticular radiolucencies had increased in area, but not in number. At entry, 44% of the patients had joint space narrowing significantly greater than that in the control subjects; by 18 months, this proportion increased to 65%. No correlation was found between subchondral sclerosis, osteophytes, juxtaarticular radiolucencies, and joint space narrowing. We conclude that in osteoarthritis of the hand, the bony changes have progressed significantly before the occurrence of radiographically evident joint space narrowing indicative of cartilage thinning.

HLA-A, B antigens and alpha 1-antitrypsin phenotypes in nodal generalised osteoarthritis and erosive osteoarthritis

HLA-A, B and alpha 1-antitrypsin phenotypes were studied in 90 unrelated patients with established nodal generalised osteoarthritis (OA). Compared with standard reference populations, independently increased frequency of the HLA-A1B8 and MZ alpha 1-antitrypsin phenotypes were observed (27% v 11.5%, relative risk 2.79, and 12% v 3.6%, relative risk 3.73 respectively). These associations related to developed of nodal generalised OA rather than to severity as judged by the summated radiographic scores for hand OA. Ten patients had marked subchondral radiographic erosions and were further classified as erosive OA; these patients had an increased frequency of the MS alpha 1-antitrypsin phenotype (30% v 9%) and higher radiographic OA scores corrected for presence of erosions. This first report of two independent genetic markers in nodal generalised OA is of interest in relation to the increasingly recognised inflammatory component of the osteoarthritis process.

Urate-mediated inflammation in nodal osteoarthritis: clinical and roentgenographic correlations

We studied 25 patients with crystal-proven gout or roentgenographic evidence of gouty arthritis, or both, in finger joints involved with nodal osteoarthritis (OA). These patients were elderly (mean age 71.4 years), and 72% of them were receiving diuretic therapy. Roentgenographic findings, in addition to features typical of OA, included soft tissue densities (tophi), with or without calcification, large intraarticular erosions, characteristic nonmarginal cortical erosions, and periarticular osteolysis. We conclude that urate crystals mediate episodes of acute inflammation in certain patients with nodal OA. This association is noted primarily in elderly patients of both sexes, especially in those receiving diuretic therapy.