Intra-articular injection of a substance P inhibitor affects gene expression in a joint contracture model

Biomechanical outcomes of pharmacological therapies for post-traumatic arthrofibrosis in preclinical animal models: a systematic review and meta-analysis

PURPOSE/AIM OF THE STUDY

There is still no evidence of which drug has the greatest therapeutic potential for post-traumatic arthrofibrosis. The aim of this study is to systematically review the literature for quality evidence and perform a meta-analysis about the pharmacological therapies of post-traumatic arthrofibrosis in preclinical models.

MATERIALS AND METHODS

A comprehensive and systematic search strategy was performed in three databases (MEDLINE, EMBASE and Web of Science) retrieving studies on the effectiveness of pharmacological therapies in the management of post-traumatic arthrofibrosis using preclinical models in terms of biomechanical outcomes. Risk of bias assessment was performed using the SYRCLE's risk of bias tool. A meta-analysis using a random-effects model was conducted if a minimum of three studies reported homogeneous outcomes for drugs with the same action mechanism.

RESULTS

Forty-six studies were included in the systematic review and evaluated for risk of bias. Drugs from 6 different action mechanisms of 21 studies were included in the meta-analysis. Overall, the methodological quality of the studies was poor. Statistically significant overall effect in favor of reducing contracture was present for anti-histamines (Chi2 p = 0.75, I2 = 0%; SMD (Standardized Mean Difference) = -1.30, 95%CI: -1.64 to -0.95, p < 0.00001) and NSAIDs (Chi2 p = 0.01, I2 = 63%; SMD= -0.93, 95%CI: -1.58 to -0.28, p = 0.005).

CONCLUSIONS

Anti-histamines, particularly ketotifen, have the strongest evidence of efficacy for prevention of post-traumatic arthrofibrosis. Some studies suggest a potential role for NSAIDs, particularly celecoxib, although heterogeneity among the included studies is significant.

The effect of losartan on the development of post-traumatic joint stiffness in a rat model

Post-traumatic joint stiffness (PTJS) is accompanied by a multidimensional disturbance of joint architecture. Pharmacological approaches represent promising alternatives as the traumatic nature of current therapeutic standards may lead to PTJS' progression. Losartan is an auspicious candidate, as it has demonstrated an antifibrotic effect in other organs. Forty-eight Sprague Dawley rats were randomized into equally sized losartan or control groups. After a standardized knee trauma, the joint was immobilized for either 2 weeks (n = 16), 4 weeks (n = 16) or 4 weeks with re-mobilization for an additional 4 weeks (n = 16). Pharmacotherapy with losartan or placebo (30 mg/kg/day) was initiated on the day of trauma and continued for the entire course. Joint contracture was measured alongside histological and molecular biological assessments. There were no significant biomechanical changes in joint contracture over time, comparing short-term (2 weeks) with long-term losartan therapy (4 weeks). However, comparing the formation of PTJS with that of the control, there was a trend toward improvement of joint mobility of 10.5° (p 0.09) under the influence of losartan. During the re-mobilization phase, no significant effect of losartan on range of motion (ROM) was demonstrated. At a cellular level, losartan significantly reduced myofibroblast counts by up to 72 % (4 weeks, p ≤ 0.001) without effecting the capsular configuration. Differences in expression levels of profibrotic factors (TGF-β, CTGF, Il-6) were most pronounced at week 4. The antifibrotic properties of losartan are not prominent enough to completely prevent the development of PTJS after severe joint injury.

The Safety of Adiponectin Receptor Agonist AdipoRon in a Rabbit Model of Arthrofibrosis

AdipoRon is an adiponectin receptor 1, 2 (ADIPOR1 and ADIPOR2) agonist with numerous reported physiological benefits in murine models of human disease, including a proposed reduction in fibrosis. However, AdipoRon has never been investigated in rabbits, which provide a robust model for orthopedic conditions. We examined the safety of intravenous (IV) AdipoRon in New Zealand White (NZW) female rabbits surgically stressed by a procedure that mimics human arthrofibrosis. Fifteen female NZW rabbits were prospectively studied using increasing AdipoRon doses based on established literature. AdipoRon was dissolved in dimethyl sulfoxide (DMSO), diluted in normal saline, and administered IV preoperatively and for 5 subsequent days postoperatively. The primary outcome was overall toxicity to rabbits, whereas secondary outcomes were change in rabbit weights and hemodynamics and defining acid-base characteristics of the drug formulation. Two rabbits expired during preoperative drug administration at 25 mg/kg. Remaining rabbits received preoperative doses of DMSO (vehicle), 2.5, 5, or 10 mg/kg of AdipoRon without complications. On postoperative day 1, one rabbit sustained a tonic-clonic seizure after their second dose of 10 mg/kg AdipoRon. The remaining 12 rabbits (4 in each group) received six serial doses of vehicle, 2.5, or 5 mg/kg of AdipoRon without adverse effects. All formulations of AdipoRon were within safe physiological pH ranges (4-5). We are the first to report the use of IV AdipoRon in a surgically stressed rabbit model of orthopedic disease. AdipoRon doses of 5 mg/kg or less appear to be well-tolerated in female NZW rabbits. Impact statement We provided the first in vivo toxicity assessment and dose optimization of a new antifibrotic experimental medication, AdipoRon, in a surgically stressed rabbit model of knee arthrofibrosis.

Immune cell populations differ in patients undergoing revision total knee arthroplasty for arthrofibrosis

Arthrofibrosis following total knee arthroplasty (TKA) is a debilitating condition typically diagnosed based on clinical findings. To gain insight into the histopathologic immune cell microenvironment of arthrofibrosis, we assessed the extent of tissue fibrosis and quantified immune cell populations in specific tissue regions of the posterior capsule. We investigated specimens from three prospectively-collected, matched cohorts, grouped as patients receiving a primary TKA for osteoarthritis, revision TKA for arthrofibrosis, and revision TKA for non-arthrofibrotic, non-infectious reasons. Specimens were evaluated using hematoxylin and eosin staining, picrosirius red staining, immunofluorescence, and immunohistochemistry with Aperio®-based digital image analysis. Increased collagen deposition and increased number of α-SMA/ACTA2 expressing myofibroblasts were present in the arthrofibrosis group compared to the two non-arthrofibrotic groups. CD163 + macrophages were the most abundant immune cell type in any capsular sample with specific enrichment in the synovial tissue. CD163 + macrophages were significantly decreased in the fibrotic tissue region of arthrofibrosis patients compared to the patients with primary TKA, and significantly increased in adipose tissue region of arthrofibrotic specimens compared to non-arthrofibrotic specimens. Synovial CD117 + mast cells were significantly decreased in arthrofibrotic adipose tissue. Together, these findings inform diagnostic and targeted therapeutic strategies by providing insight into the underlying pathogenetic mechanisms of arthrofibrosis.

Pleiotropic Long-Term Effects of Atorvastatin on Posttraumatic Joint Contracture in a Rat Model

The antifibrotic effect of atorvastatin has already been demonstrated in several organ systems. In the present study, a rat model was used to investigate the effect of atorvastatin on posttraumatic joint contracture. Forty-eight Sprague Dawley rats were equally randomized into an atorvastatin group and a control group. After initial joint trauma, knee joints were immobilized for intervals of 2 weeks (n = 16) or 4 weeks (n = 16) or immobilized for 4 weeks with subsequent remobilization for another 4 weeks (n = 16). Starting from the day of surgery, animals received either atorvastatin or placebo daily. After euthanasia at week 2, 4 or 8, joint contracture was determined, histological examinations were performed, and gene expression was assessed. The results suggest that the joint contracture was primarily arthrogenic. Atorvastatin failed to significantly affect contracture formation and showed a reduction in myofibroblast numbers to 98 ± 58 (control: 319 ± 113, p < 0.01) and a reduction in joint capsule collagen to 60 ± 8% (control: 73 ± 9%, p < 0.05) at week 2. Gene expression of α-smooth muscle actin (α-SMA), collagen type I, transforming growth factor β1 (TGF-β1) and interleukin-6 (IL-6) was not significantly affected by atorvastatin. Atorvastatin decreases myofibroblast number and collagen deposition but does not result in an improvement in joint mobility.

Intra-articular celecoxib improves knee extension regardless of surgical release in a rabbit model of arthrofibrosis

Aims

Outcomes of current operative treatments for arthrofibrosis after total knee arthroplasty (TKA) are not consistently positive or predictable. Pharmacological in vivo studies have focused mostly on prevention of arthrofibrosis. This study used a rabbit model to evaluate intra-articular (IA) effects of celecoxib in treating contracted knees alone, or in combination with capsular release.

Methods

A total of 24 rabbits underwent contracture-forming surgery with knee immobilization followed by remobilization surgery at eight weeks. At remobilization, one cohort underwent capsular release (n = 12), while the other cohort did not (n = 12). Both groups were divided into two subcohorts (n = 6 each) – one receiving IA injections of celecoxib, and the other receiving injections of vehicle solution (injections every day for two weeks after remobilization). Passive extension angle (PEA) was assessed in live rabbits at 10, 16, and 24 weeks, and disarticulated limbs were analyzed for capsular stiffness at 24 weeks.

Results

IA celecoxib resulted in greater mean PEA at ten weeks (69.6° (SD 4.6) vs 45.2° (SD 9.6), p = 0.004), 16 weeks (109.8° (SD 24.2) vs 60.9° (SD10.9), p = 0.004), and 24 weeks (101.0° (SD 8.0) vs 66.3° (SD 5.8), p = 0.004). Capsular stiffness was significantly reduced with IA celecoxib (2.72 Newton per cm (N·cm)/° (SD 1.04), p = 0.008), capsular release (2.41 N·cm/° (SD 0.80), p = 0.008), and capsular release combined with IA celecoxib (3.56 N·cm/° (SD 0.99), p = 0.018) relative to IA vehicle (6.09 N·cm/° (SD 1.64)).

Conclusion

IA injections of a celecoxib led to significant improvements in passive extension angles, with reduced capsular stiffness, when administered to rabbit knees with established experimental contracture. Celecoxib was superior to surgical release, and the combination of celecoxib and a surgical release did not provide any additional value.

Cite this article: Bone Joint Res 2022;11(1):32–39.

Absence of signature inflammatory markers in synovial fluid for total knee arthroplasties revised for arthrofibrosis

INTRODUCTION

Current diagnostic criteria for arthrofibrosis are limited. Since many patients will be aspirated during their clinical course, synovial fluid analysis may supplement current diagnostic criteria for arthrofibrosis. The goal of this study was to determine a unique synovial fluid and inflammatory marker profile for diagnosing arthrofibrosis.

HYPOTHESIS

Patients with arthrofibrosis following total knee arthroplasty will have a unique synovial fluid aspirate profile compared to control patients to aid in diagnosis.

MATERIALS AND METHODS

Between 2013 and 2017, 32 patients (32 total knee arthroplasties [TKAs]) underwent revision TKAs for arthrofibrosis. Fourteen patients had pre-revision aspirations. They were 2:1 matched based on age, sex, body mass index (BMI), and year of revision to 28 patients who underwent aseptic revision TKAs for reasons other than arthrofibrosis (control group). Mean age at revision was 66years, with 64% males.

RESULTS

In TKAs revised for arthrofibrosis, mean total cell count was 828cells/uL. These aspirates contained a mean distribution of 46% macrophages (range: 4-76%), 31% lymphocytes (range: 11-68%), 21% neutrophils (range: 0-75%), 1% other cells (mainly synovial cells; range: 0-11%), and 1% eosinophils (range: 0-7%). There was no significant difference in mean total cell count (p=0.8) or mean distribution of macrophages (p=0.6), lymphocytes (p=0.1), neutrophils (p=0.2), eosinophils (p>0.9), or serum inflammatory markers (p>0.7) when compared to controls. All aspirations were culture negative for infection.

DISCUSSION

The profile of arthrofibrotic synovial fluid aspirates and serum inflammatory marker values were similar to patients revised for non-arthrofibrotic aseptic etiologies. This suggests synovial fluid and serum inflammatory markers in non-infected knees with arthrofibrosis should expect to have characteristics similar to synovial fluid and inflammatory marker profiles in other aseptic diagnoses.

LEVEL OF EVIDENCE

III; retrospective case-control study.

Suppression of TGF-beta activity with remobilization attenuates immobilization-induced joint contracture in rats

BACKGROUND

Joint contracture is a common complication of joint injury. This study aimed to assess the effect of inhibiting the transforming growth factor-β (TGF-β) signaling during joint immobilization and remobilization on immobilization-induced joint contracture in rats.

METHODS

The knees of rats were immobilized using Kirschner wires following trauma to the femoral condyles to generate joint contracture. After immobilization, levels of TGF-β and passive extension range of motion (ROM) were measured at different time points, joints were histologically analyzed by hematoxylin and eosin (H&E) and Masson trichrome staining, and the expression of inflammatory or fibrosis-related mediators, including interleukin-1β (IL-1β), phosphorylated Smad2/3 (p-Smad2/3), α-smooth muscle actin (α-SMA) and collagen types I (Col 1) and III (Col 3), were examined in joint capsules using immunohistochemistry and quantitative real-time polymerase chain reaction (qRT-PCR). Rats were also treated with LY2157299, a TGF-β receptor I kinase inhibitor, at different stages of immobilization and remobilization.

RESULTS

TGF-β1 levels in the serum and the number of p-Smad2/3⁺ cells in the joint capsule were significantly elevated after immobilization. ROM decreased during the 6 weeks of immobilization and partly recovered after remobilization. After treatment with LY2157299 during immobilization, the restricted ROM moderately increased, but this effect was stronger when combined with active motion. Mechanistically, the expression of IL-1β, TGF-β, fibrosis-related factors, and the density of collagen significantly decreased after treatment with LY2157299.

CONCLUSIONS

Inhibiting TGF-β signaling paired with active motion effectively attenuated the formation of immobilization-induced joint contracture in rats.

Reduction of arthrofibrosis utilizing a collagen membrane drug-eluting scaffold with celecoxib and subcutaneous injections with ketotifen

The dense formation of abnormal scar tissue after total knee arthroplasty results in arthrofibrosis, an unfortunate sequela of inflammation. The purpose of this study was to use a validated rabbit model to assess the effects on surgically-induced knee joint contractures of two combined pharmacological interventions: celecoxib (CXB) loaded on an implanted collagen membrane, and subcutaneously (SQ) injected ketotifen. Thirty rabbits were randomly divided into five groups. The first group received no intervention after the index surgery. The remaining four groups underwent intra-articular implantation of collagen membranes loaded with or without CXB at the time of the index surgery; two of which were also treated with SQ ketotifen. Biomechanical joint contracture data were collected at 8, 10, 16, and 24 weeks. At the time of necropsy (24 weeks), posterior capsule tissue was collected for messenger RNA and histopathologic analyses. At 24 weeks, there was a statistically significant increase in passive extension among rabbits in all groups treated with CXB and/or ketotifen compared to those in the contracture control group. There was a statistically significant decrease in COL3A1, COL6A1, and ACTA2 gene expression in the treatment groups compared to the contracture control group (P < .001). Histopathologic data also demonstrated a trend towards decreased fibrous tissue density in the CXB membrane group compared to the vehicle membrane group. The present data suggest that intra-articular placement of a treated collagen membrane blunts the severity of contracture development in a rabbit model of arthrofibrosis, and that ketotifen and CXB may independently contribute to the prevention of arthrofibrosis. Statement of clinical significance: Current literature has demonstrated that arthrofibrosis may affect up to 5% of primary total knee arthroplasty patients. For that reason, novel pharmacologic prophylaxis and treatment modalities are critical to mitigating reoperations and revisions while improving the quality of life for patients with this debilitating condition.

Adipose stem cells exhibit mechanical memory and reduce fibrotic contracture in a rat elbow injury model

Fibrosis is driven by a misdirected cell response causing the overproduction of extracellular matrix and tissue dysfunction. Numerous pharmacological strategies have attempted to prevent fibrosis but have attained limited efficacy with some detrimental side effects. While stem cell treatments have provided more encouraging results, they have exhibited high variability and have not always improved tissue function. To enhance stem cell efficacy, we evaluated whether mechanical memory could direct cell response. We hypothesized that mechanically pre-conditioning on a soft matrix (soft priming) will delay adipose-derived stem cell (ASC) transition to a pro-fibrotic phenotype, expanding their regenerative potential, and improving healing in a complex tissue environment. Primary ASCs isolated from rat and human subcutaneous fat exhibited mechanical memory, demonstrated by a delayed cell response to stiffness following two weeks of soft priming including decreased cell area, actin coherency, and extracellular matrix production compared to cells on stiff substrates. Soft primed ASCs injected into our rat model of post-traumatic elbow contracture decreased histological evidence of anterior capsule fibrosis and increased elbow range-of-motion when evaluated by joint mechanics. These findings suggest that exploiting mechanical memory by strategically controlling the culture environment during cell expansion may improve the efficacy of stem cell-based therapies targeting fibrosis.

Mechanisms involved in the arthrofibrosis formation and treatments following bone fracture

Arthrofibrosis is a common complication for patients with bone fracture following external and internal fixation. In this review, we summarize the related factors and significant pathways for joint adhesion following fracture surgery. Moreover, the different types of treatments and related preventive measures are also discussed. Many factors related to the development and treatment of arthrofibrosis are discussed in this review in order to provide possible clues for the prospective targets to develop new medication or treatments for preventing or reducing the joint adhesion following orthopedic surgery.

Inhibition of COX-2 Pathway as a Potential Prophylaxis Against Arthrofibrogenesis in a Rabbit Model of Joint Contracture

Arthrofibrosis is a common complication following total knee arthroplasty caused by pathologic fibroblast activation and excessive collagen deposition around a synovial joint leading to debilitating loss of motion. Treatment options are limited because the pathologic mechanisms remain to be characterized. Dysregulation of the inflammatory cascade may lead to communication between myofibroblasts and immune cells triggering tissue metaplasia, and excessive collagen deposition described clinically as arthrofibrosis. We explored the novel use of celecoxib (selective cyclooxygenase-2 [COX-2] inhibitor) to disrupt the downstream effects of the post-traumatic inflammatory cascade and inhibit scar tissue formation in a validated rabbit model of arthrofibrosis combined with new parameters for quantifying the stiffness of the posterior capsule. Biomechanical and molecular analyses, of contracted rabbit knee posterior capsule tissue after COX-2 inhibition revealed increased maximal passive extension and down-regulation of collagen messenger RNA compared with controls. Histopathologic examination suggested a trend of decreased quantities of dense fibrous connective tissue with COX-2 inhibition. These data may suggest that inhibiting the inflammatory cascade could potentially reduce pathologic myofibroblast activation, thereby reducing scar tissue formation and increasing the range of motion in arthrofibrotic joints. Implementing a multi-modal pharmacologic approach may simultaneously target numerous cellular components contributing to the complex process of arthrofibrogenesis. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2609-2620, 2019.

A Drug Eluting Scaffold for the Treatment of Arthrofibrosis

INTRODUCTION

The inflammatory cascade and production of prostaglandins may play a role in the pathogenesis of arthrofibrosis, a debilitating condition after joint replacement and other orthopedic procedures. Cyclooxygenase 2 (COX-2) inhibitors may mitigate the inflammatory response and formation of arthrofibrosis, but oral delivery is associated with risk of systemic side effects in many patients. The nonsteroidal anti-inflammatory drug, celecoxib, may have therapeutic benefits for arthrofibrosis, but current methods for its local delivery (e.g., biologically derived microspheres) are not translatable to immediate clinical use. Therefore, we investigated the use of a drug scaffold for sustainable intra-articular delivery of therapeutic doses of celecoxib.

MATERIALS AND METHODS

Celecoxib was eluted from clinically approved biodegradable collagen membranes over 7 days as measured by UV spectroscopy and high-performance liquid chromatography/mass spectroscopy. Eluted concentrations of celecoxib were examined for toxicity (live/dead staining) and profibrotic gene expression (real-time-quantitative polymerase chain reaction) in rabbit knee capsular fibroblasts in vitro.

RESULTS

Sustained concentrations of celecoxib eluted from the membrane over 7 days from both a wet and dry scaffold, with a burst release (30-45%) of celecoxib in the first 2 h. Rabbit cells treated with eluted concentrations experienced a toxic response to the burst release doses, and inhibitory effects on profibrotic genes were seen in response to the sustained doses eluted from the scaffold.

CONCLUSIONS

This study characterized the novel use of collagen scaffolds for intra-articular drug delivery to treat arthrofibrosis. Scaffolds exhibit celecoxib release through an initial burst release followed by sustained release of antifibrotic doses over 7 days. Thus, collagen scaffolds are promising for clinician-directed treatment of arthrofibrosis.

Pathological mechanisms and therapeutic outlooks for arthrofibrosis

Arthrofibrosis is a fibrotic joint disorder that begins with an inflammatory reaction to insults such as injury, surgery and infection. Excessive extracellular matrix and adhesions contract pouches, bursae and tendons, cause pain and prevent a normal range of joint motion, with devastating consequences for patient quality of life. Arthrofibrosis affects people of all ages, with published rates varying. The risk factors and best management strategies are largely unknown due to a poor understanding of the pathology and lack of diagnostic biomarkers. However, current research into the pathogenesis of fibrosis in organs now informs the understanding of arthrofibrosis. The process begins when stress signals stimulate immune cells. The resulting cascade of cytokines and mediators drives fibroblasts to differentiate into myofibroblasts, which secrete fibrillar collagens and transforming growth factor-β (TGF-β). Positive feedback networks then dysregulate processes that normally terminate healing processes. We propose two subtypes of arthrofibrosis occur: active arthrofibrosis and residual arthrofibrosis. In the latter the fibrogenic processes have resolved but the joint remains stiff. The best therapeutic approach for each subtype may differ significantly. Treatment typically involves surgery, however, a pharmacological approach to correct dysregulated cell signalling could be more effective. Recent research shows that myofibroblasts are capable of reversing differentiation, and understanding the mechanisms of pathogenesis and resolution will be essential for the development of cell-based treatments. Therapies with significant promise are currently available, with more in development, including those that inhibit TGF-β signalling and epigenetic modifications. This review focuses on pathogenesis of sterile arthrofibrosis and therapeutic treatments.

Genomewide Association Study of Fracture Nonunion Using Electronic Health Records

Nonunion is a clinically significant complication of fracture associated with worse outcomes, including increased pain, disability, and higher healthcare costs. The risk for nonunion is likely to be complex and multifactorial, and as such, the biology underlying such risk remains poorly understood. Genetic studies represent one approach to identify implicated biology for further investigation, but to date the lack of large cohorts for study has limited such efforts. We utilized the electronic health records of two large academic medical centers in Boston to identify individuals with fracture nonunion and control individuals with fracture but no evidence of nonunion. We conducted a genomewide association study among 1760 individuals of Northern European ancestry with upper or lower extremity fracture, including 131 with nonunion, to examine whether common variants were associated with nonunion in this cohort. In all, one locus in the Calcyon (CALY) gene exceeded a genomewide threshold for statistical significance (p = 1.95e-8), with eight additional loci associated with p < 5e-7. Previously reported candidate genes were not supported by this analysis. Electronic health records should facilitate identification of common genetic variations associated with adverse orthopedic outcomes. The loci we identified in this small cohort require replication and further study to characterize mechanism of action, but represent a starting point for the investigation of genetic liability for this costly outcome.