Pathological mechanisms and therapeutic outlooks for arthrofibrosis

Relaxin as a treatment for musculoskeletal fibrosis: What we know and future directions

Fibrotic changes in musculoskeletal diseases arise from the abnormal buildup of fibrotic tissue around the joints, leading to limited mobility, compromised joint function, and diminished quality of life. Relaxin (RLX) attenuates fibrosis by accelerating collagen degradation and inhibiting excessive extracellular matrix (ECM) production. Further, RLX disrupts myofibroblast activation by modulating the TGF-β/Smads signaling pathways, which reduces connective tissue fibrosis. However, the mechanisms and effects of RLX in musculoskeletal pathologies are emerging as increasing research focuses on relaxin's impact on skin, ligaments, tendons, cartilage, joint capsules, connective tissues, and muscles. This review delineates the actions of relaxin within the musculoskeletal system and the challenges to its clinical application. Relaxin shows significant potential in both in vivo and in vitro studies for broadly managing musculoskeletal fibrosis; however, challenges such as short biological half-life and sex-specific responses may pose hurdles for clinical use.

Adenosine, lidocaine, and magnesium therapy augments joint tissue healing following experimental anterior cruciate ligament rupture and reconstruction

Aims

Adenosine, lidocaine, and Mg2+ (ALM) therapy exerts differential immuno-inflammatory responses in males and females early after anterior cruciate ligament (ACL) reconstruction (ACLR). Our aim was to investigate sex-specific effects of ALM therapy on joint tissue repair and recovery 28 days after surgery.

Methods

Male (n = 21) and female (n = 21) adult Sprague-Dawley rats were randomly divided into ALM or Saline control treatment groups. Three days after ACL rupture, animals underwent ACLR. An ALM or saline intravenous infusion was commenced prior to skin incision, and continued for one hour. An intra-articular bolus of ALM or saline was also administered prior to skin closure. Animals were monitored to 28 days, and joint function, pain, inflammatory markers, histopathology, and tissue repair markers were assessed.

Results

Despite comparable knee function, ALM-treated males had reduced systemic inflammation, synovial fluid angiogenic and pro-inflammatory mediators, synovitis, and fat pad fibrotic changes, compared to controls. Within the ACL graft, ALM-treated males had increased expression of tissue repair markers, decreased inflammation, increased collagen organization, and improved graft-bone healing. In contrast to males, females had no evidence of persistent systemic inflammation. Compared to controls, ALM-treated females had improved knee extension, gait biomechanics, and elevated synovial macrophage inflammatory protein-1 alpha (MIP-1α). Within the ACL graft, ALM-treated females had decreased inflammation, increased collagen organization, and improved graft-bone healing. In articular cartilage of ALM-treated animals, matrix metalloproteinase (MMP)-13 expression was blunted in males, while in females repair markers were increased.

Conclusion

At 28 days, ALM therapy reduces inflammation, augments tissue repair patterns, and improves joint function in a sex-specific manner. The study supports transition to human safety trials.

Acute Anterior Cruciate Ligament Reconstruction Performed Within 10 Days of Injury Does Not Increase Risk of Postoperative Arthrofibrosis: A Systematic Review and Meta-analysis

BACKGROUND

The optimal timing of anterior cruciate ligament (ACL) reconstruction (ACLR) remains a controversial topic. Previous reviews have demonstrated that there are no differences between early and delayed ACLR; however, these studies have been limited by heterogeneous definitions of acute ACL injury.

PURPOSE

To evaluate postoperative patient functional outcomes and risk for arthrofibrosis after acute arthroscopic ACLR performed ≤10 days after injury.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

A systematic review was performed according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines using multiple medical databases. Inclusion criteria were studies that evaluated postoperative range of motion outcomes for patients undergoing ACLR ≤10 days after initial ACL injury. For included comparative studies comparing patient groups undergoing ACLR ≤10 days and patients undergoing "delayed" ACLR after ≥3 weeks of initial injury, quantitative analysis was performed to assess for differences in postoperative arthrofibrosis, reoperation rates, and patient-reported outcomes between groups. DerSimonian-Laird binary random-effects models were constructed to quantitatively describe the association between the ACLR time period and patient outcomes by generating effect estimates in the form of odds ratios with 95% CIs. Qualitative analysis was performed to describe variably reported patient outcomes and the risk of arthrofibrosis after ACLR for noncomparative studies.

RESULTS

Screening yielded 6 full-text articles with 448 patients who underwent ACLR (296 ACLR <10 days, 152 ACLR >3 weeks), with a pooled mean age of 28.1 years. For studies amenable to quantitative analysis, there were no significant differences between ACLR performed ≤10 days and ACLR performed at the 3-week point or after in terms of postoperative stiffness (3 studies; odds ratio, 1.27; P = .508), Tegner scores (2 studies; mean difference, -0.056; P = .155), or reoperation for stiffness (3 studies; odds ratio, 0.869; P = .462). The overall incidence of postoperative arthrofibrosis after 12 months of follow-up was 11 of 296 (3.7%) for ACLRs performed ≤10 days versus 6 of 152 (3.9%) for those performed at the 3-week point or after.

CONCLUSION

ACLR performed ≤10 days after the inciting injury does not increase the risk of postoperative arthrofibrosis and demonstrates similar patient-reported outcomes compared with ACLR performed at the 3-week point or after.

Investigating cartilage-related diseases by polarization-resolved second harmonic generation (P-SHG) imaging

Establishing quantitative parameters for differentiating between healthy and diseased cartilage tissues by examining collagen fibril degradation patterns facilitates the understanding of tissue characteristics during disease progression. These findings could also complement existing clinical methods used to diagnose cartilage-related diseases. In this study, cartilage samples from normal, osteoarthritis (OA), and rheumatoid arthritis (RA) tissues were prepared and analyzed using polarization-resolved second harmonic generation (P-SHG) imaging and quantitative image texture analysis. The enhanced molecular contrast obtained from this approach is expected to aid in distinguishing between healthy and diseased cartilage tissues. P-SHG image analysis revealed distinct parameters in the cartilage samples, reflecting variations in collagen fibril arrangement and organization across different pathological states. Normal tissues exhibited distinct χ33/χ31 values compared with those of OA and RA, indicating collagen type transition and cartilage erosion with chondrocyte swelling, respectively. Compared with those of normal tissues, OA samples demonstrated a higher degree of linear polarization, suggesting increased tissue birefringence due to the deposition of type-I collagen in the extracellular matrix. The distribution of the planar orientation of collagen fibrils revealed a more directional orientation in the OA samples, associated with increased type-I collagen, while the RA samples exhibited a heterogeneous molecular orientation. This study revealed that the imaging technique, the quantitative analysis of the images, and the derived parameters presented in this study could be used as a reference for disease diagnostics, providing a clear understanding of collagen fibril degradation in cartilage.

Risk Factors for the Development of Arthrofibrosis After Anterior Cruciate Ligament Reconstruction in Children and Adolescents

BACKGROUND

Arthrofibrosis is a fibrotic joint disorder resulting in restricted joint motion and pain. Risk factors associated with the development of postoperative arthrofibrosis include female sex, type of graft, and quicker time to reconstruction. These patients have typically benefitted from manipulation under anesthesia or arthroscopic lysis of adhesions. The purpose of this study was to retrospectively review the rate of arthrofibrosis in children and adolescents who previously underwent anterior cruciate ligament (ACL) reconstruction.

MATERIALS AND METHODS

This was a retrospective chart review examining patients 18 years or younger who underwent ACL reconstruction between 2013 and 2023. Data collected included age, body mass index, reconstruction technique, concomitant meniscal or ligamentous pathology, and need for revision surgery for arthroscopic lysis of adhesions vs manipulation under anesthesia.

RESULTS

A total of 461 patients 18 years or younger who underwent ACL reconstruction were included in this study. Eighteen (3.90%) patients required reoperation for the development of arthrofibrosis. Skeletally immature patients were found to have a statistically significant lower rate of arthrofibrosis compared with skeletally mature patients (0% vs 4.80%; P=.0184). Patients with a higher weight and body mass index had an increased rate of arthrofibrosis (P=.0485 and P=.0410, respectively). Graft type did not have a significant impact on arthrofibrosis rates. There were no significant findings in terms of concomitant injuries and rate of arthrofibrosis.

CONCLUSION

Arthrofibrosis developed in 3.90% of patients after ACL reconstruction. Skeletal immaturity may be protective against the development of arthrofibrosis. No association was found between graft type or concomitant knee pathology and arthrofibrosis. [Orthopedics. 202x;4x(x):xx-xx.].

Specific Preoperative Factors Increase Manipulations under Anesthesia Following Primary TKA

Arthrofibrosis following primary total knee arthroplasty (TKA) can result in pain and limit postoperative range of motion (ROM), jeopardizing clinical outcomes and patient satisfaction. This study aims to identify preoperative risk factors associated with necessitating a manipulation under anesthesia (MUA) following primary TKA.We retrospectively reviewed 950 cases of consecutive primary TKAs performed at one institution by three arthroplasty surgeons between May 2017 and May 2019. Recorded preoperative variables included smoking status, race, preoperative ROM, presence of effusion or positive anterior drawer, and medical comorbidities. Demographic characteristics were compared with Student's t-tests or chi-square tests as appropriate. For each preoperative factor, we obtained an odds ratio (OR) for MUA risk using multivariate logistic regression.Twenty (2.3%) patients underwent MUA following their index primary TKA surgery. History of ipsilateral knee surgery (OR: 2.727, p = 0.047) and diagnosed hypertension (OR: 4.764, p = 0.016) were identified as risk factors associated with significantly increased risk of MUA. The greater the preoperative ROM, the higher likelihood needed of MUA (OR: 1.031, p = 0.034).Patients who had diagnosed hypertension or a history of prior ipsilateral knee surgery were associated with increased risk of necessitating an MUA following primary TKA. Additionally, a greater total arc of motion preoperatively increased the odds of needing MUA.Level III of evidence was present.

The E3 ubiquitin-protein ligase UHRF1 promotes adipogenesis and limits fibrosis by suppressing GPNMB-mediated TGF-β signaling

The E3 ubiquitin-ligase UHRF1 is an epigenetic regulator coordinating DNA methylation and histone modifications. However, little is known about how it regulates adipogenesis or metabolism. In this study, we discovered that UHRF1 is a key regulatory factor for adipogenesis, and we identified the altered molecular pathways that UHRF1 targets. Using CRISPR/Cas9-based knockout strategies, we discovered the whole transcriptomic changes upon UHRF1 deletion. Bioinformatics analyses revealed that key adipogenesis regulators such PPAR-γ and C/EBP-α were suppressed, whereas TGF-β signaling and fibrosis markers were upregulated in UHRF1-depleted differentiating adipocytes. Furthermore, UHRF1-depleted cells showed upregulated expression and secretion of TGF-β1, as well as the glycoprotein GPNMB. Treating differentiating preadipocytes with recombinant GPNMB led to an increase in TGF-β protein and secretion levels, which was accompanied by an increase in secretion of fibrosis markers such as MMP13 and a reduction in adipogenic conversion potential. Conversely, UHRF1 overexpression studies in human cells demonstrated downregulated levels of GPNMB and TGF-β, and enhanced adipogenic potential. In conclusion, our data show that UHRF1 positively regulates 3T3-L1 adipogenesis and limits fibrosis by suppressing GPNMB and TGF-β signaling cascade, highlighting the potential relevance of UHRF1 and its targets to the clinical management of obesity and linked metabolic disorders.

Arthrofibrosis of the knee in pediatric orthopedic surgery

Arthrofibrosis is a challenging complication associated with knee injuries in both children and adults. While much is known about managing arthrofibrosis in adults, it is necessary to understand its unique aspects and management strategies in the pediatric population. This paper provides an overview of arthrofibrosis in pediatric orthopedic surgery, focusing on its causes, implications, classifications, and management. This paper is a comprehensive review of the literature and existing research on arthrofibrosis in pediatric patients. Arthrofibrosis is characterized by excessive collagen production and adhesions, leading to restricted joint motion and pain. It is associated with an immune response and fibrosis within and around the joint. Arthrofibrosis can result from various knee injuries in pediatric patients, including tibial spine fractures, ACL and PCL injuries, and extra-articular procedures. Technical factors at the time of surgery play a role in the development of motion loss and should be addressed to minimize complications. Preventing arthrofibrosis through early physical therapy is recommended. Non-operative management, including dynamic splinting and serial casting, has shown some benefits. New pharmacologic approaches to lysis of adhesions have shown promise. Surgical interventions, consisting of arthroscopic lysis of adhesions (LOA) and manipulation under anesthesia (MUA), can significantly improve motion and functional outcomes. Arthrofibrosis poses unique challenges in pediatric patients, demanding a nuanced approach that includes prevention, early intervention with non-operative means, and improvements in surgical techniques. Modern pharmacological interventions offer promise for the future. Customized interventions and research focused on pediatric patients are critical for optimal outcomes.

Clinical reasoning of ultrasound imaging-guided manual passive manipulation for adhesion prevention in a patient with total knee arthroplasty: a case report

INTRODUCTION

Patients with total knee arthroplasty occasionally develop postoperative abnormalities such as posttraumatic knee stiffness and arthrofibrosis, which may affect activities of daily living. However, there are no clear assessment methods or interventions for knee stiffness. Musculoskeletal ultrasound imaging enables real-time evaluation of mobility and flexibility of tissues. The purpose of this case report was to describe the use of musculoskeletal ultrasound imaging for evaluating the optimal location and methods of passive manipulation.

CASE DESCRIPTION

The patient was an 82-year-old woman who had undergone total knee arthroplasty. She was unable to climb stairs due to limited knee flexion. Based on the results of musculoskeletal ultrasound imaging assessment, we hypothesized that the knee flexion limitation was caused by decreased sliding movement of the suprapatellar pouch. Hence, we performed passive manipulation on the tissue with decreased sliding under musculoskeletal ultrasound guidance.

OUTCOMES

The patient's knee flexion angle increased from 90° to 110° within 1 week of intervention, and her gait speed improved from 16.48 to 13.2 s per 10 m. Furthermore, after the intervention, she was able to climb 10 steps using a handrail.

DISCUSSION

Ultrasound imaging is important because it allows the examination of tissues with mobility changes such as in arthrofibrosis. Our work highlights the use of musculoskeletal ultrasound imaging for identifying the target region for therapy and for providing guidance during passive manipulation.

Female Sex, Older Age, Earlier Surgery, Anticoagulant Use, and Meniscal Repair Are Associated With Increased Risk of Manipulation Under Anesthesia or Lysis of Adhesions for Arthrofibrosis After Anterior Cruciate Ligament Reconstruction: A Systematic Review

PURPOSE

To determine what patient or surgical factors are associated with an increased risk of arthrofibrosis requiring manipulation under anesthesia (MUA) or lysis of adhesions (LOA) after anterior cruciate ligament reconstruction (ACLR).

METHODS

A systematic review was performed in adherence to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Cochrane, Embase, and Medline databases were searched for studies published through February 2023. Inclusion criteria were studies that identified risk factors for MUA and/or LOA after ACLR. Studies investigating arthrofibrosis after multiligamentous knee injuries or ACL repair were excluded.

RESULTS

Eleven studies including a total of 333,876 ACLRs with 4,842 subsequent MUA or LOA (1.45%) were analyzed. Increasing age was associated with an increased risk in 3 studies (P < .001, P < .05, P < .01) but was found to have no association another two. Other factors that were identified by multiple studies as risk factors for MUA/LOA were female sex (4 studies), earlier surgery (5 studies), use of anticoagulants other than aspirin (2 studies), and concomitant meniscal repair (4 studies).

CONCLUSIONS

In total, 1.45% of the patients who underwent ACLR and were included in this systematic review had to undergo a subsequent MUA/LOA to treat arthrofibrosis. Female sex, older age, earlier surgery, use of anticoagulants other than aspirin, and concomitant meniscal repair were associated with increased risk of MUA/LOA. The modifiable risks, including use of anticoagulants and time between injury and surgery, can be considered when making treatment decisions.

LEVEL OF EVIDENCE

Level IV, systematic review of Level III-IV studies.

The efficacy of vitamin E in preventing arthrofibrosis after joint replacement

BACKGROUND

Arthrofibrosis is a joint disorder characterized by excessive scar formation in the joint tissues. Vitamin E is an antioxidant with potential anti-fibroblastic effect. The aim of this study was to establish an arthrofibrosis rat model after joint replacement and assess the effects of vitamin E supplementation on joint fibrosis.

METHODS

We simulated knee replacement in 16 male Sprague-Dawley rats. We immobilized the surgical leg with a suture in full flexion. The control groups were killed at 2 and 12 weeks (n = 5 per group), and the test group was supplemented daily with vitamin E (0.2 mg/mL) in their drinking water for 12 weeks (n = 6). We performed histological staining to investigate the presence and severity of arthrofibrosis. Immunofluorescent staining and α2-macroglobulin (α2M) enzyme-linked immunosorbent assay (ELISA) were used to assess local and systemic inflammation. Static weight bearing (total internal reflection) and range of motion (ROM) were collected for functional assessment.

RESULTS

The ROM and weight-bearing symmetry decreased after the procedure and recovered slowly with still significant deficit at the end of the study for both groups. Histological analysis confirmed fibrosis in both lateral and posterior periarticular tissue. Vitamin E supplementation showed a moderate anti-inflammatory effect on the local and systemic levels. The vitamin E group exhibited significant improvement in ROM and weight-bearing symmetry at day 84 compared to the control group.

CONCLUSIONS

This model is viable for simulating arthrofibrosis after joint replacement. Vitamin E may benefit postsurgical arthrofibrosis, and further studies are needed for dosing requirements.

Shoulder Adhesive Capsulitis Prior to Total Knee Arthroplasty is Associated With Increased Rates of Postoperative Stiffness Requiring Manipulation Under Anesthesia and Arthroscopic Lysis of Adhesions

BACKGROUND

Arthrofibrosis following total knee arthroplasty (TKA) and adhesive capsulitis (AC) of the shoulder develop via a similar pathologic process. The purpose of this study was to examine the relationship between these two conditions.

METHODS

This was a retrospective cohort study using a large nationwide claims database. Patients who had a history of shoulder AC prior to TKA were compared to TKA patients who did not have AC history comparing rates of postoperative stiffness, manipulation under anesthesia (MUA), arthroscopic lysis of adhesions (LOAs), and revision arthroplasty at postoperative timepoints (3 months, 6 months, 1 year, and 2 years).

RESULTS

Within 3 months, 6 months, 1 year, and 2 years of their TKAs, patients who had a history of AC prior to TKA were significantly more likely to experience stiffness (OR [odds ratio] = 1.29, 1.28, 1.32, and 1.36, respectively) and LOAs (OR = 6.78, 3.65, 2.99, and 2.81, respectively). They also showed increased risk of MUA within 6 months, 1 year, and 2 years (OR = 1.15, 1.15, and 1.16, respectively) of their TKAs. Patients having a preoperative diagnosis of AC did not have an increased risk of undergoing revision surgery 1 year or 2 years after their TKAs (P > .05).

CONCLUSIONS

Patients diagnosed with AC prior to TKA experience higher rates of postoperative stiffness, resulting in additional interventions such as MUA and LOAs. These findings identify a particularly high-risk patient population that may benefit from additional interventions prior to and following TKA.

LEVEL OF EVIDENCE

This is a level III prognostic study.

Postoperative Angiotensin Receptor Blocker Use is Associated With Decreased Rates of Manipulation Under Anesthesia, Arthroscopic Lysis of Adhesions, and Prosthesis-Related Complications in Patients Undergoing Total Knee Arthroplasty

BACKGROUND

The cellular mechanisms underlying excess scar tissue formation in arthrofibrosis following total knee arthroplasty (TKA) are well-described. Angiotensin receptor blockers (ARB), particularly losartan, is a commonly prescribed antihypertensive with demonstrated antifibrotic properties. This retrospective study aimed to assess the rates of 1- and 2-year postoperative complications in patients who filled prescriptions for ARBs during the 90 days after TKA.

METHODS

Patients undergoing primary TKA were selected from a large national insurance database, and the impact of ARB use after TKA on complications was assessed. Of the 1,299,106 patients who underwent TKA, 82,065 had filled at least a 90-day prescription of losartan, valsartan, or olmesartan immediately following their TKA. The rates of manipulation under anesthesia (MUA), arthroscopic lysis of adhesions (LOA), aseptic loosening, periprosthetic fracture, and revision at 1 and 2 years following TKA were analyzed using multivariable logistic regressions to control for various comorbidities.

RESULTS

ARB use was associated with decreased rates of MUA (odds ratio [OR] = 0.94, 95% confidence interval (CI), 0.90 to 0.99), arthroscopy/LOA (OR = 0.86, 95% CI, 0.77 to 0.95), aseptic loosening (OR = 0.71, 95% CI, 0.61 to 0.83), periprosthetic fracture (OR = 0.58, 95% CI, 0.46 to 0.71), and revision (OR = 0.79, 95% CI, 0.74 to 0.85) 2 years after TKA.

CONCLUSIONS

ARB use throughout the 90 days after TKA is associated with a decreased risk of MUA, arthroscopy/LOA, aseptic loosening, periprosthetic fracture, and revision, demonstrating the potential protective abilities of ARBs. Prospective studies evaluating the use of ARBs in patients at risk for postoperative stiffness would be beneficial to further elucidate this association.

Medial quadriceps tendon femoral ligament reconstruction and medial patellofemoral ligament reconstruction have no significant differences in clinical outcomes for treatment of lateral patellar instability: a matched-cohort study

OBJECTIVES

The purpose of this study was to compare clinical outcomes of medial quadriceps tendon-femoral ligament reconstruction (MQTFLR) and medial patellofemoral ligament reconstruction (MPFLR) among patients with recurrent lateral patellar instability.

METHODS

A retrospective matched-cohort study was conducted involving patients who underwent MQTFLR or MPFLR with or without tibial tubercle osteotomy (TTO) from 2019 to 2021. Subjects were matched 1:1 on age, concomitant osteochondral allograft (OCA), concomitant TTO, and follow-up time. Measured outcomes included 90-day complications, Visual Analog Scale (VAS) knee pain, return to sport/work, Kujala score, Tegner score, and MPFL-Return to Sport after Injury (MPFL-RSI) score. Outcomes were compared between groups using Mann-Whitney U-test for continuous variables and Fisher's exact test for categorical variables. P-values <0.05 were considered significant.

RESULTS

Ten MQTFLR patients (mean age 28.7 years, 80% female, mean follow-up 19.7 months) and ten MPFLR patients (mean age 29.1 years, 90% female, mean follow-up 28.3 months) were included in the study. One MQTFLR patient (10%) and three MPFLR patients (30%) underwent reoperation for postoperative arthrofibrosis. Postoperative VAS resting pain was not significantly different between the groups (MQTFLR mean 1.1, MPFLR mean 0.6, p ​= ​0.31). There were no significant differences in rates of recurrent subluxations (MQTFLR 20%, MPFLR 0%, p ​= ​0.47), return to sport (MQTFLR 50%, MPFLR 75%, p ​= ​0.61), return to work (MQTFLR 100%, MPFLR 88%, p ​= ​1.00), or MPFL-RSI pass rate (MQTFLR 75% vs. MPFLR 38%, p ​= ​0.31).

CONCLUSION

There were no significant differences in knee pain and function, return to work, and rates of recurrent patellar instability between patients who underwent MQTFLR versus MPFLR, though these results should be interpreted with caution given the small sample size and potential selection bias.

LEVEL OF EVIDENCE

III.

Interleukin-35 protein inhibits osteoclastogenesis and attenuates collagen-induced arthritis in mice

Rheumatoid arthritis (RA) is a chronic autoimmune disease. Its pathological features include synovial inflammation, bone erosion, and joint structural damage. Our previous studies have shown that interleukin (IL)-35 is involved in the pathogenesis of bone loss in RA patients. In this study, we are further evaluating the efficacy of IL-35 on collagen-induced arthritis (CIA) in the mouse model. Male DBA/1J mice (n = 10) were initially immunized, 2 μg/mouse IL-35 was injected intraperitoneally every week for 3 weeks after the establishment of the CIA model. Clinical arthritis, histopathological analysis, and three-dimensional micro-computed tomography (3D micro-CT) were determined after the mice were anesthetized on the 42th day. In vitro, RANKL/M-CSF induced mouse preosteoclasts (RAW264.7 cells line) was subjected to antiarthritis mechanism study in the presence of IL-35. The results of clinical arthritis, histopathological analysis, and 3D micro-CT, the expression of RANK/RANKL/OPG axis, inflammatory cytokines, and osteoclastogenesis-related makers demonstrated decreasing severity of synovitis and bone destruction in the ankle joints after IL-35 treatment. Furthermore, IL-35 attenuated inflammatory cytokine production and the expression of osteoclastogenesis-related makers in a mouse preosteoclasts cell line RAW264.7. The osteoclastogenesis-related makers were significantly reduced in IL-35 treated RAW264.7 cells line after blockage with the JAK/STAT1 signaling pathway. These results demonstrated that IL-35 protein could inhibits osteoclastogenesis and attenuates CIA in mice. We concluded that IL-35 can exhibit anti-osteoclastogenesis effects by reducing the expression of inflammatory cytokines and osteoclastogenesis-related makers, thus alleviating bone destruction in the ankle joint and could be a potential therapeutic target for RA.

The impact of digital healthcare systems on pain and body function in patients with knee joint pain: a systematic review and meta-analysis

The digital healthcare (DH) system has recently emerged as an advanced rehabilitation approach that promotes rehabilitation training based on virtual reality (VR) and augmented reality (AR). The purpose of this meta-analysis study is to review and assess the impact of DH systems on pain and physical function among patients diagnosed with knee joint pain. Between January 2003 and September 2023, studies that met the listed inclusion criteria were gathered from Scopus, PubMed, Web of Science, and EBSCO databases. The analysis of standardized mean difference (SMD) was carried out with 95% confidence interval (95% CI) (PROSPERO registration number: CRD42023462538). Eight research papers were selected, which collectively involved 194 males and 279 females. The meta-analysis outcomes revealed that DH intervention significantly improved balance (SMD, 0.41 [0.12, 0.69], p < 0.05) and pain level (SMD, - 1.10 [- 2.02, - 0.18], p < 0.05). The subgroup analysis of the pain level showed varied outcomes for the TKA (SMD, - 0.22 [- 0.49, 0.04], p = 0.10) or OA patients (SMD, - 2.80 [- 3.83, - 1.78], p < 0.05) Next, this study found no significant effect of DH intervention on knee joint range of motion (ROM) (SMD, 0.00 [- 0.76, 0.76], p = 1.00) and walking velocity (SMD, 0.04 [- 0.22, 0.29], p = 0.77) in patients with knee joint pain. The meta-analysis review conducted in this study revealed that DH intervention may potentially improve balance among the patients with knee joint pain. It may also alleviate the pain level particularly among OA patients.

Screening of diagnostic biomarkers for ferroptosis-related osteoarthritis and construction of a risk-prognosis model

Background

Osteoarthritis (OA) is the most prevalent and commonly chronic joint disease that frequently develops among the elderly population. It is not just a single tissue that is affected, but rather a pathology involving the entire joint. Among them, synovitis is a key pathological change in OA. Ferroptosis is a newly discovered form of cell death that results from the buildup of lipid peroxidation. However, the role and impact of it in OA are yet to be explored.

Objective

The key to this work is to uncover the mechanisms of ferroptosis-related OA pathogenesis and develop more novel diagnostic biomarkers to facilitate the diagnostic and therapeutic of OA.

Materials and methods

Download ferroptosis-related genes and OA synovial chip datasets separately from the FerrDB and Gene Expression Omnibus databases. Identify ferroptosis differentially expressed genes using R software, obtain the intersection genes through two machine learning algorithms, and obtain diagnostic biomarkers after logistic regression analysis. Verify the diagnostic and therapeutic efficacy of specific genes for OA through the construction of clinical risk prognostic models using ROC curves and nomogram. Simultaneously, correlations between specific genes and OA immune cell infiltration co-expression were constructed. Finally, verify the differential presentation of specific genes in OA and health control synovium.

Results

Obtain 38 ferroptosis differentially expressed genes through screening. Based on machine learning algorithms and logistic regression analysis, select AGPS, BRD4, RBMS1, and EGR1 as diagnostic biomarker genes. The diagnostic and therapeutic efficacy of the four specific genes for OA has been validated by ROC curves and nomogram of clinical risk prognostic models. The analysis of immune cell infiltration and correlation suggests a close association between specific genes and OA immune cell infiltration. Further revealing the diagnostic value of specific genes for OA by the differential presentation analysis of their differential presentation in synovial tissue from OA and health control.

Conclusion

This study identified four diagnostic biomarkers for OA that are associated with iron death. The establishment of a risk-prognostic model is conducive to the premature diagnosis of OA, evaluating functional recovery during rehabilitation, and guidance for subsequent treatment.

Bisdemethoxycurcumin, a curcumin, protects chondrocytes, and reduces cartilage inflammation via the NRF2/HO-1/NLRP3 pathway

BACKGROUND

The objective of this thesis is to evaluate the effect of bisdemethoxycurcumin (BDMC) on osteoarthritis (OA) and comprehensively evaluate the role of the Nuclear Factor erythroid 2-Related Factor 2 (Nrf2) signalling pathway in chondrocytes.

METHOD

In our study, we treated chondrocytes with BDMC in an in vitro chondrocyte assay and measured its influence on extracellular matrix (ECM) expression, downstream heme oxygenase-1 (HO-1) and NOD-like receptor thermal protein domain associated protein 3 (NLRP3) levels.

RESULTS

Our study indicates that BDMC significantly activates the Nrf2 signaling pathway in chondrocytes in vitro. Furthermore, the expression of matrix metalloproteinase 3, interleukin 1β, recombinant a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)4 and (ADAMTS)5 was significantly suppressed by BDMC.

CONCLUSION

This study confirms the potential for BDMC to activate the Nrf2/HO-1/NLRP3 signalling pathway and alleviate OA symptoms. Therefore, BDMC is a promising therapeutic agent for OA that offers new insights and treatment methods.

Arthroscopic Arthrolysis of Knee: Timing, Technique and Results

Aim

To evaluate the functional outcomes of patients undergoing arthroscopic arthrolysis of the knee and find the ideal timing for arthrolysis to achieve maximum range of motion (ROM) of the knee.

Methods

All patients who underwent arthroscopic arthrolysis for post-operative joint stiffness following surgery for injuries around knee joint at a tertiary care centre from 2009 to 2023 were included in this study. The patients' details such as primary injury, time interval between the index surgery and arthrolysis, improvement in knee range of ROM and Lysholm score from prior to arthrolysis to last follow-up post arthrolysis were retrieved from hospital database and analysed.

Results

Total of 42 patients who underwent arthroscopic arthrolysis of knee from 2009 to 2023 were included in this study. Follow-up range was 6 months to 6 years. ROM after arthrolysis significantly improved in the early and delayed arthrolysis groups as compared to late arthrolysis groups (mean 126.25 and 115.62 vs 106.3, p < 0.05). Patients treated with early arthroscopic arthrolysis (within 3 months) showed significant increase in post operative Lysholm score compared to other groups (p < 0.05). ROM of 120° and beyond was achieved in 75% of cases in early arthrolysis group compared to 62.8% and 39% in delayed and late arthrolysis group (p < 0.05).

Conclusions

Arthroscopic arthrolysis done within 6 months (with maximum effect when done within 3 months) after the primary surgery leads to significant improvement in ROM and functional scores as compared to those with late arthrolysis group.

Single-cell atlas of human infrapatellar fat pad and synovium implicates APOE signaling in osteoarthritis pathology

The infrapatellar fat pad (IPFP) and synovium play essential roles in maintaining knee joint homeostasis and in the progression of osteoarthritis (OA). The cellular and transcriptional mechanisms regulating the function of these specialized tissues under healthy and diseased conditions are largely unknown. Here, single-cell and single-nuclei RNA sequencing of human IPFP and synovial tissues were performed to elucidate the cellular composition and transcriptional profile. Computational trajectory analysis revealed that dipeptidyl peptidase 4+ mesenchymal cells function as a common progenitor for IPFP adipocytes and synovial lining layer fibroblasts, suggesting that IPFP and synovium represent an integrated tissue unit. OA induced a profibrotic and inflammatory phenotype in mesenchymal lineage cells with biglycan+ intermediate fibroblasts as a major contributor to OA fibrosis. Apolipoprotein E (APOE) signaling from intermediate fibroblasts and macrophages was identified as a critical regulatory factor. Ex vivo incubation of human cartilage with soluble APOE accelerated proteoglycan degeneration. Inhibition of APOE signaling by intra-articular injection of an anti-APOE neutralizing antibody attenuated the progression of collagenase-induced OA in mice, demonstrating a detrimental effect of APOE on cartilage. Our studies provide a framework for designing further therapeutic strategies for OA by describing the cellular and transcriptional landscape of human IPFP and synovium in healthy versus OA joints.

Reversible SAHH inhibitor ameliorates MIA-induced osteoarthritis of rats through suppressing MEK/ERK pathway

Osteoarthritis (OA) is characterized by gradual articular cartilage degradation, accompanied by persistent low-grade joint inflammation, correlating with radiographic and pain-related progression. The latent therapeutic potential of DZ2002, a reversible inhibitor of S-adenosyl-L-homocysteine hydrolase (SAHH), holds promise for OA intervention. This study endeavored to examine the therapeutic efficacy of DZ2002 within the milieu of OA. The cytotoxicity of DZ2002 was evaluated using the MTT assay on bone marrow-derived macrophages. The inhibitory impact of DZ2002 during the process of osteoclastogenesis was assessed using TRAP staining, analysis of bone resorption pits, and F-actin ring formation. Mechanistic insights were derived from qPCR and Western blot analyses. Through the intra-articular injection of monosodium iodoacetate (MIA), an experimental rat model of OA was successfully instituted. This was subsequently accompanied by a series of assessments including Von Frey filament testing, analysis of weight-bearing behaviors, and micro-CT imaging, all aimed at assessing the effectiveness of DZ2002. The findings emphasized the effectiveness of DZ2002 in mitigating osteoclastogenesis induced by M-CSF/RANKL, evident through a reduction in TRAP-positive OCs and bone resorption. Moreover, DZ2002 modulated bone resorption-associated gene and protein expression (CTSK, CTR, Integrin β3) via the MEK/ERK pathway. Encouragingly, DZ2002 also alleviates MIA-induced pain, cartilage degradation, and bone loss. In conclusion, DZ2002 emerges as a potential therapeutic contender for OA, as evidenced by its capacity to hinder in vitro M-CSF/RANKL-induced osteoclastogenesis and mitigate in vivo osteoarthritis progression. This newfound perspective provides substantial support for considering DZ2002 as a compelling agent for osteoarthritis intervention.

Manipulation Under Anesthesia is Safe and Effective for Management of Early Postoperative Knee Arthrofibrosis in Adolescent Patients

BACKGROUND

Management of postoperative knee arthrofibrosis can be challenging and the preferred time for intervention remains controversial. The purpose of this study is to evaluate the safety and efficacy of early (<3 mo postoperatively) manipulation under anesthesia (MUA) for the treatment of knee arthrofibrosis in adolescent patients. We hypothesized that early MUA could restore normal knee motion with a low complication rate and without the need for more invasive intervention.

METHODS

In a retrospective review, 57 patients who underwent MUA for postoperative knee arthrofibrosis were identified. The time between the index surgery and MUA as well as changes in range of motion (ROM) before and after MUA were analyzed. Descriptive statistics with median and interquartile range were used to analyze this non-parametric study cohort. Repeated measures ANOVA was performed to assess improvement in ROM over time. A P value <0.05 denoted statistical significance.

RESULTS

The median age of the cohort at time of MUA was 14.5 years [interquartile range (IQR) 12.9 to 17.6)]. 54.4% were male. Median time to MUA was 64 days (IQR 52 to 79) after index surgery. ROM before MUA was 90.0 degrees (IQR 75 to 100), which improved to 130 degrees (120 to 135) after MUA. At final median follow-up of 8.9 months (IQR 5.1 to 16.1), mean ROM was 133 degrees (130 to 140). There were no iatrogenic fractures or physeal separations associated with MUA. 12.3% (n=7/57) failed MUA either due to the need for subsequent repeat MUA (n=2), need for lysis of adhesions (n=3) or need for surgery after MUA (n=2). Those who failed early MUA and required subsequent procedures had ROM >120 degrees at final follow-up.

CONCLUSIONS

Postoperative knee arthrofibrosis can be safely and effectively treated with early (<3 mo postoperative) MUA. There were no iatrogenic fractures or physeal separations during MUA. Patients who had recurrence of motion deficits after early MUA and required further intervention, regained satisfactory knee motion at final follow-up. Although further research is warranted to better characterize risk factors for knee arthrofibrosis in adolescent patients, early recognition and MUA is a safe and effective treatment for arthrofibrosis to help patients regain full ROM without invasive intervention.

LEVEL OF EVIDENCE

Therapeutic Study - Level IV.

Computational screening of biomarkers and potential drugs for arthrofibrosis based on combination of sequencing and large nature language model

Background

Arthrofibrosis (AF) is a fibrotic joint disease resulting from excessive collagen production and fibrous scar formation after total knee arthroplasty (TKA). This devastating complication may cause consistent pain and dramatically reduction of functionality. Unfortunately, the conservative treatments to prevent the AF in the early stage are largely unknown due to the lack of specific biomarkers and reliable therapeutic targets.

Methods

In this study, we extracted1782 fibrosis related genes (FRGs) from 373,461published literature based on the large natural language processing models (ChatGPT) and intersected with the 2750 differential expressed genes (DEGs) from mRNA microarray (GSE135854). A total of 311 potential AF biomarker genes (PABGs) were obtained and functional analysis were performed including gene ontology (GO) annotation and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Subsequently, we accomplished validation in AF animal models with immobilization of the unilateral knee joints of 16 rabbits for 1-week, 2-weeks, 3-weeks and 4-weeks. Finally, we tested the biomarkers in a retrospective cohort enrolled 35 AF patients and 35 control group patients.

Results

We identified G-protein-coupled receptor 17 (GPR17) as a reliable therapeutic biomarker for AF diagnosis with higher AUC (0.819) in the ROC curve. A total of 21 potential drugs targeted to GPR17 were screened. Among them, pranlukast and montelukast have achieved therapeutic effect in animal models. In addition, we established an online AF database for data integration (https://chenxi2023.shinyapps.io/afdbv1).

Conclusions

These results unveiling therapeutic biomarkers for AF diagnosis, and provide potential drugs for clinical treatment.

The translational potential of this article

Our study demonstrated that GPR17 holds significant promise as a potential biomarker and therapeutic target for arthrofibrosis. Moreover, pranlukast and montelukast targeted to GPR17 that could be instrumental in the treatment of AF.

Lentivirus-based shRNA of Caspase-3 gene silencing inhibits chondrocyte apoptosis and delays the progression of surgically induced osteoarthritis

Chondrocyte apoptosis is an important pathological feature of osteoarthritis (OA). Excessive apoptosis of chondrocytes disrupts the dynamic balance of cell proliferation and apoptosis, with a marked reduction in chondrocytes and cartilage matrix disintegration, which represents the main pathology of OA. Caspases, especially Caspase-3, play a central role in cell apoptosis. In this study, a lentiviral vector was used to transduce caspase-3 short hairpin RNA (shRNA) into rat chondrocytes (RCs), and the apoptotic and phenotypic genes of RCs were analyzed using real-time PCR and western blotting in vitro. In addition, in vivo intra-articular injection of Caspase-3 shRNA lentivirus was performed in a surgically induced OA rat model. Our results showed that Caspase-3 gene silencing could down-regulate the TNF-α-mediated inflammatory gene expression of TNFR1, FADD, and IL-1β, apoptotic gene expression of APAF1, Caspase-3, and Caspase-9, thereby attenuating the apoptotic pathway in vitro. Caspase-3 gene silencing also attenuated TNF-α-mediated decreased gene expression of ACAN, Col1-a1, and Col2-a1. Furthermore, Caspase-3 gene silencing could effectively reduce the OARSI score, and gene expression of Caspase-3, Caspase-9, MMP13, and TNF-α in a surgically induced OA rat model. Caspase-3 gene silencing may serve as a novel therapeutic strategy for cartilage injury and OA.

Evaluating the Efficacy of a Thermoresponsive Hydrogel for Delivering Anti-Collagen Antibodies to Reduce Posttraumatic Scarring in Orthopedic Tissues

Excessive posttraumatic scarring in orthopedic tissues, such as joint capsules, ligaments, tendons, muscles, and peripheral nerves, presents a significant medical problem, resulting in pain, restricted joint mobility, and impaired musculoskeletal function. Current treatments for excessive scarring are often ineffective and require the surgical removal of fibrotic tissue, which can aggravate the problem. The primary component of orthopedic scars is collagen I-rich fibrils. Our research team has developed a monoclonal anti-collagen antibody (ACA) that alleviates posttraumatic scarring by inhibiting collagen fibril formation. We previously established the safety and efficacy of ACA in a rabbit-based arthrofibrosis model. In this study, we evaluate the utility of a well-characterized thermoresponsive hydrogel (THG) as a delivery vehicle for ACA to injury sites. Crucial components of the hydrogel included N-isopropylacrylamide, poly(ethylene glycol) diacrylate, and hyaluronic acid. Our investigation focused on in vitro ACA release kinetics, stability, and activity. Additionally, we examined the antigen-binding characteristics of ACA post-release from the THG in an in vivo context. Our preliminary findings suggest that the THG construct exhibits promise as a delivery platform for antibody-based therapeutics to reduce excessive scarring in orthopedic tissues.

The effect of extracorporeal shock wave on joint capsule fibrosis based on A2AR-Nrf2/HO-1 pathway in a rat extending knee immobilization model

Joint capsule fibrosis, a common complication of joint immobilization, is mainly characterized by abnormal collagen deposition. The present study aimed to investigate the effect of extracorporeal shock wave therapy (ESWT) on reduced collagen deposition in the joint capsule during immobilization-induced joint capsule fibrosis. Additionally, the potential involvement of the adenosine A2A receptor (A2AR)-Neurotrophic factor e2-related factor 2 (Nrf2)/Haem oxygenase-1 (HO-1) pathway was explored. Thirty 3-month-old male Sprague-Dawley rats were randomly assigned to five groups: control (C), immobilization model (IM), natural recovery (NR), ESWT intervention (EI), and ESWT combined with A2AR antagonist SCH 58261 intervention (CI). After the left knee joints of rats in the IM, NR, EI and CI groups were immobilized using a full-extension fixation brace for 4 weeks, the EI and CI groups received ESWT twice a week for 4 weeks. The CI group was also treated with ESWT following intraperitoneal injection of SCH 58261 (0.01 mg/kg) for 4 weeks. The range of motion of the left knee joint was measured, and the protein levels of collagens I and III, A2AR, phosphorylated-protein kinase A/protein kinase A (p-PKA/PKA), p-Nrf2/Nrf2, and HO-1 were analysed by Western blotting. The IM and NR groups showed significantly greater arthrogenic contracture than the C group (P < 0.05). Compared to the NR group, the EI and CI groups exhibited significant improvement in arthrogenic contracture (P < 0.05). Conversely, the EI group showed lower contracture than the CI group (P < 0.05). Similar results were observed for collagen deposition and the protein levels of collagens I and III. The intervention groups (EI and CI groups) showed higher levels of p-Nrf2/Nrf2 and HO-1 than the NR group (P < 0.05). Moreover, the EI group exhibited higher levels of p-PKA/PKA, p-Nrf2/Nrf2, and HO-1 than the CI group (P < 0.05). However, no significant difference was found in the A2AR levels among the five groups (P > 0.05). ESWT may activate A2AR, leading to the phosphorylation of PKA. Subsequently, Nrf2 may be activated, resulting in the upregulation of HO-1, which then reduces collagen deposition and alleviates immobilization-induced joint capsule fibrosis.

Enzyme targeted delivery of sivelestat loaded nanomicelle inhibits arthritic severity in experimental arthritis

AIMS

Rheumatoid arthritis (RA) is chronic inflammatory disorder mainly affects the lining of articular cartilage of synovial joints characterized by severe inflammation and joint damage. The expression of proteolytic enzymes like MMP-2 and Neutrophil Elastase (NE) worsens the RA condition. To address this concern, we have synthesized dual enzyme targeted chlorotoxin conjugated nanomicelles loaded with sivelestat as broad spectrum treatment for RA.

MATERIALS AND METHODS

Conjugation of the chlorotoxin over nanomicelle and incorporation of sivelestat in nanomicelle provide it dual targeting potential. The sivelestat loaded nanomicelle (SLM) evaluated for the drug release and in-vitro cytocompatibility. Further, investigated its in-vivo anti-arthritic potential on collagen-induced arthritis in wistar rats.

KEY FINDINGS

The microscopic observation of SLM showed spherical ball like appearance with size ranging from 190 to 230 nm. SLM showed good drug loading and encapsulation efficiency along with no cytotoxicity against healthy cell lines. In-vivo therapeutic assessment on collagen induced arthritis rat model showed potential chondroprotection. The microscopic visualization of articular cartilage by staining showed that it restores the cartilage integrity and lowers the expression of pro-inflammatory enzymes showed by Immunohistochemistry and Immunofluorescence. We observed that, it restrain the mediators of synovial inflammation by simultaneous inhibition of the proteolytic enzymes involved in swelling, cartilage destruction and joint damage which provides strong chondroprotection.

SIGNIFICANCE

We report that significant alleviation of inflammation and inhibition of proteolytic enzymes together might provide enhanced potential for the treatment and management of RA.

Arthrofibrosis After Total Knee Arthroplasty: A Critical Analysis Review

» Arthrofibrosis after total knee arthroplasty (TKA) is the new formation of excessive scar tissue that results in limited ROM, pain, and functional deficits.» The diagnosis of arthrofibrosis is based on the patient's history, clinical examination, absence of alternative diagnoses from diagnostic testing, and operative findings. Imaging is helpful in ruling out specific causes of stiffness after TKA. A biopsy is not indicated, and no biomarkers of arthrofibrosis exist.» Arthrofibrosis pathophysiology is multifactorial and related to aberrant activation and proliferation of myofibroblasts that primarily deposit type I collagen in response to a proinflammatory environment. Transforming growth factor-beta signaling is the best established pathway involved in arthrofibrosis after TKA.» Management includes both nonoperative and operative modalities. Physical therapy is most used while revision arthroplasty is typically reserved as a last resort. Additional investigation into specific pathophysiologic mechanisms can better inform targeted therapeutics.

Continuous detrimental activity of intra-articular fibrous scar tissue in correlation with posttraumatic ankle osteoarthritis

Posttraumatic osteoarthritis is primarily characterized by articular cartilage destruction secondary to trauma or fracture events. Even while intra-articular scar tissue can be observed following ankle fractures, little is known about its nature and molecular events linking its biological activity and cartilage deterioration. Here, we investigated scar tissue's histological and molecular characteristics, and its relationship with localized articular cartilage alterations consistent with early osteoarthritic degeneration. Intra-articular scar tissues from sixty-two patients who underwent open reduction internal fixation for ankle fracture were obtained at hardware removal time (6-44 months after fracture). Histological analysis demonstrated that scar tissue has the nature of fibrosis with fibrous tissue hyperplasia, fibroblast proliferation, and chondrometaplasia. These fibrous scar tissues showed overexpressed pro-inflammatory cytokines and high mRNA expression levels of osteoarthritis-related markers (cytokines, chemokines, and enzymes) compared to the normal synovium. Furthermore, those transcriptional levels were significantly correlated with the grade of talar chondral degeneration. Our findings suggest that following an ankle fracture, the intra-articular fibrous scar tissue exhibits high catabolic and inflammatory activity, which has a long-lasting negative impact correlated to cartilage deterioration in the development of posttraumatic osteoarthritis.

Crosstalk between synovial macrophages and fibroblasts in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease associated with chronic inflammation of joints. Abnormally activated cells such as synovial macrophages and synovial fibroblasts induce RA pathogenesis and ultimately joint destruction. Since macrophages can change their own characteristics depending on the microenvironmental condition, it has been suggested that activation and remission of RA are regulated by crosstalk between synovial macrophages and other cells. Moreover, recent findings of heterogeneity of synovial macrophages and fibroblasts support the idea that complex interactions regulate RA from its onset to remission. Importantly, an understanding of the intercellular crosstalk in RA is far from complete. Here, we summarize the molecular mechanisms underlying the pathological development of RA with particular reference to the crosstalk between synovial macrophages and fibroblasts.

ASIC1a-CMPK2-mediated M1 macrophage polarization exacerbates chondrocyte senescence in osteoarthritis through IL-18

PURPOSE

Identification of a role for, and the mechanism of action of, the acid-sensing ion channel 1a (ASIC1a) in M1 macrophage polarization, which results in osteoarthritis (OA)-associated chondrocyte senescence.

METHOD

ASIC1a expression in synovial M1 macrophages of OA patients was assessed by immunofluorescence. A role for ASIC1a in M1 macrophage and chondrocyte senescence was assessed in a mouse OA model.

RESULTS

ASIC1a expression was found to be upregulated in synovial M1 macrophages of OA patients. Extracellular acidification (pH 6.0) promoted M1 polarization of bone marrow derived macrophages (BMDMs), which was reversed by PcTx-1 or ASIC1a-siRNA. RNA-seq transcriptome results demonstrated a downregulation of M1 macrophage-associated genes in BMDMs after PcTx-1 treatment. Mechanistically, a role for the ASIC1a-cytidine/uridine monophosphate kinase 2 (CMPK2) axis in M1 macrophage polarization was demonstrated. The concentration of IL-18 was elevated in synovial fluid and supernatants of acid-activated BMDMs. In vitro, IL-18 stimulation or co-culture with acid-activated macrophages promoted chondrocyte senescence. In vivo, intra-articular administration of PcTx-1 reduced articular cartilage destruction and chondrocytes senescence in OA mice, which related to reduced numbers of M1 macrophages and IL-18 in affected joints.

CONCLUSION

These results demonstrate a novel pathogenic process that results in OA cartilage damage, in which M1 macrophage derived IL-18 induces articular chondrocytes senescence. Further, the ASIC1a-CMPK2 axis was shown to positively regulate M1 macrophage polarization. Hence, ASIC1a is a promising treatment target for M1 macrophage-mediated diseases, such as OA.

Adhesions in the setting of hip arthroscopy

With the growing number of primary arthroscopies performed, patients requiring revision hip arthroscopies for various issues is high including postoperative adhesion formation, a source of pain, mechanical symptoms, range of motion limitation, stiffness, and microinstability. Adhesions are a consequence of biological pathways that have been stimulated by injury or surgical interventions leading to an increased healing response. Preventative efforts have included surgical adjuncts during/after primary hip arthroscopy, biologic augmentation, and postoperative rehabilitation. Treatment options for adhesion formation includes surgical lysis of adhesions with or without placement of biologic membranes aimed at inhibiting adhesion reformation as well as systemic medications to further reduce the risk. Postoperative rehabilitation exercises have also been demonstrated to prevent adhesions as a result of hip arthroscopy. Ongoing clinical trials are further investigating pathways and prevention of adhesion formation.

Replenishing decoy extracellular vesicles inhibits phenotype remodeling of tissue-resident cells in inflammation-driven arthritis

The interleukin 6 (IL6) signaling pathway plays pleiotropic roles in regulating the inflammatory milieu that contributes to arthritis development. Here, we show that activation of IL6 trans-signaling induces phenotypic transitions in tissue-resident cells toward an inflammatory state. The establishment of arthritis increases the serum number of extracellular vesicles (EVs), while these EVs express more IL6 signal transducer (IL6ST, also known as gp130) on their surface. Transferring these EVs can block IL6 trans-signaling in vitro by acting as decoys that trap hyper IL6 and prevent inflammatory amplification in recipient arthritic mice. By genetically fusing EV-sorting domains with extracellular domains of receptors, we engineered EVs that harbor a higher quantity of signaling-incompetent decoy receptors. These exogenous decoy EVs exhibit significant potential in eliciting efficient anti-inflammatory effects in vivo. Our findings suggest an inherent resistance of decoy EVs against inflammation, highlighting the therapeutic potential of efficient decoy EVs in treating inflammatory diseases.

Arthrofibrosis risk factors after anterior cruciate ligament reconstruction

Introduction

Knee arthrofibrosis is a disabling complication after anterior cruciate ligament reconstruction (ACLr). Different risk factors have been studied but are still controversial because of a diagnosis made only during reoperations for the treatment of the stiffness, which underestimates the occurrence rate. We aimed to confirm risk factors of arthrofibrosis after ACLr in case of clinically made diagnoses.

Methods

Ninety-two athletes with clinically diagnosed arthrofibrosis, complicating a primary ACLr, were compared to 482 athletes with ACLr without any complications. Usually considered risk factors were studied: age under 18, female, Body Mass Index (BMI ≥ 25), high sport level, time from ACL injury to ACLr < 1 month, Bone-Patella-Tendon-Bone surgical procedure (BPTB), meniscal repair, and intensive rehabilitation. Binary logistic regression was carried out to confirm or refute these risk factors.

Results

Female, time from ACL injury to ACLr < 1 month, BPTB procedure, meniscal repair, and BMI ≥ 25 were not confirmed as risk factors. Previous competitive sport level assessed by Tegner score was the only risk factor identified, OR: 3.56 (95%IC: 2.20-5.75; p = 0.0001). Age < 18, OR: 0.40 (95%IC: 0.19-0.84; p = 0.015) and inpatient rehabilitation program, OR: 0.28 (95%IC: 0.17-0.47; p = 0.0001), were protective factors.

Discussion

Competitive athletes are at risk of arthrofibrosis after ACLr and should benefit from protective inpatient rehabilitation program.

Leveraging osteoclast genetic regulatory data to identify genes with a role in osteoarthritis

There has been a growing interest in the role of the subchondral bone and its resident osteoclasts in the progression of osteoarthritis (OA). A recent genome-wide association study (GWAS) identified 100 independent association signals for OA traits. Most of these signals are led by noncoding variants, suggesting that genetic regulatory effects may drive many of the associations. We have generated a unique human osteoclast-like cell-specific expression quantitative trait locus (eQTL) resource for studying the genetics of bone disease. Considering the potential role of osteoclasts in the pathogenesis of OA, we performed an integrative analysis of this dataset with the recently published OA GWAS results. Summary data-based Mendelian randomization (SMR) and colocalization analyses identified 38 genes with a potential role in OA, including some that have been implicated in Mendelian diseases with joint/skeletal abnormalities, such as BICRA, EIF6, CHST3, and FBN2. Several OA GWAS signals demonstrated colocalization with more than one eQTL peak, including at 19q13.32 (hip OA with BCAM, PRKD2, and BICRA eQTL). We also identified a number of eQTL signals colocalizing with more than one OA trait, including FAM53A, GCAT, HMGN1, MGAT4A, RRP7BP, and TRIOBP. An SMR analysis identified 3 loci with evidence of pleiotropic effects on OA-risk and gene expression: LINC01481, CPNE1, and EIF6. Both CPNE1 and EIF6 are located at 20q11.22, a locus harboring 2 other strong OA candidate genes, GDF5 and UQCC1, suggesting the presence of an OA-risk gene cluster. In summary, we have used our osteoclast-specific eQTL dataset to identify genes potentially involved with the pathogenesis of OA.

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.

Satisfactory Outcomes and Improved Range of Motion With Arthroscopic Lysis of Adhesions and Manipulation for Arthrofibrosis After Multiligamentous Knee Reconstruction

Purpose

To (1) evaluate the efficacy of surgery for arthrofibrosis (AF), as measured by preoperative and postoperative range of motion (ROM), and (2) evaluate patient-reported outcomes at mid- to long-term follow-up.

Methods

We performed a retrospective review of a prospectively collected database including patients who sustained multiligamentous knee injuries (MLKIs) managed surgically, sustained loss of ROM after surgical intervention, and underwent subsequent lysis of adhesions (LOA) and/or manipulation under anesthesia (MUA). Loss of ROM was defined as clinically symptomatic loss of terminal extension (flexion deformity) and/or flexion compared with the contralateral side.

Results

In total, 12 patients (6 male and 6 female patients; age, 36.0 ± 8.7 years; body mass index, 36.3 ± 8.7) met the inclusion criteria and underwent LOA and/or MUA at a mean of 14 ± 27 months (median, 4.0 months; interquartile range, 3.5-9.3 months) after MLKI surgery. Prior to AF intervention, patients showed mean flexion of 75.9° ± 36.0° (range, 30°-129°), mean extension of 3.2° ± 5.2° (range, 0°-12°), and a mean arc of motion of 72.7° ± 34.1° (range, 30°-117°). At a mean follow-up of 7.0 ± 3.9 years (range, 2.4-16.6 years) after AF intervention, patients showed a significant increase in knee flexion of 49° (P = .003), a significant increase in arc of motion of 51° (P = .002), and an increase in extension of 3° (P = .086). The mean final International Knee Documentation Committee score was 59.5 ± 23.9; Lysholm score, 72.1 ± 20.6; Tegner activity scale score, 5.6 ± 2.8; visual analog scale score at rest, 1.0 ± 1.6; and visual analog scale score with use, 3.3 ± 2.5. At final follow-up, 2 patients (17%) had undergone conversion to total knee arthroplasty (TKA) at 10.3 and 24.8 years after MLKI surgery. Of the 10 patients who did not go on to TKA, 9 (90%) reported that they were satisfied or very satisfied with their AF knee surgery.

Conclusions

At mid-term follow-up, LOA and/or MUA for symptomatic AF after multiligamentous knee surgery results in high rates of patient satisfaction and improved knee ROM and pain scores, as well as durable and satisfactory functional outcomes in patients not undergoing TKA.

Level of Evidence

Level IV, therapeutic case series.

Arthroscopic Lysis of Adhesions for Arthrofibrosis After Anterior Cruciate Ligament Reconstruction

BACKGROUND

Arthrofibrosis (AF) after anterior cruciate ligament reconstruction (ACLR) remains a challenge. There is a paucity of data on arthroscopic interventions for AF after ACLR.

PURPOSE

To (1) describe the patient, injury, and surgical characteristics and patient-reported outcomes (PROs) of those requiring an arthroscopic intervention for loss of motion after ACLR and (2) compare outcomes between patients undergoing an early intervention (within 3 months) versus those undergoing a late intervention (after 3 months).

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Patients with a history of ACLR and a subsequent operative procedure for postoperative AF at a single institution between 2000 and 2018 were retrospectively identified. Arthroscopic interventions included lysis of adhesions, capsular release with or without manipulation under anesthesia, and excision of cyclops lesions. Patients were excluded if they had a knee dislocation or multiple-ligament injury, a periarticular fracture, or less than 2-year follow-up from the arthroscopic intervention. PROs including the Tegner activity score, visual analog scale pain score, and International Knee Documentation Committee score as well as knee range of motion (ROM) were recorded.

RESULTS

A total of 40 patients were included with a mean age of 27.2 years (range, 11.0-63.8 years) at surgery and a mean follow-up of 10.0 years (range, 2.9-20.7 years). The mean preoperative flexion and extension were 102° (range, 40°-150°) and 8° (range, 0°-25°), respectively. The mean postoperative flexion and extension were 131° (range, 110° to 150°) and 0° (range, -10° to 5°), respectively. After the arthroscopic intervention, the mean ROM improved from 94° (range, 40°-140°) preoperatively to 131° (range, 107°-152°) at final follow-up (P < .001), and the visual analog scale pain score improved from 3.0 preoperatively to 1.2 postoperatively (P = .001). Overall, 13 patients (32.5%) underwent an intervention within 3 months and 27 (67.5%) after 3 months. The early intervention group had a higher postoperative International Knee Documentation Committee score compared with the late intervention group (86.8 vs 71.7, respectively; P = .035).

CONCLUSION

An arthroscopic intervention for AF after ACLR successfully improved knee ROM and pain. Patients who underwent either early or late surgery obtained satisfactory motion and function, although improved PROs were observed when the intervention occurred within 3 months of the primary procedure.

Manipulation Under Anesthesia and/or Lysis of Adhesions After Anterior Cruciate Ligament Reconstruction in Female Basketball Players: Does Race Play a Role?

BACKGROUND

Arthrofibrosis can limit function and return to sport after anterior cruciate ligament (ACL) reconstruction. Previously reported risk factors for developing arthrofibrosis after ACL reconstruction include female sex, age <18 years, time from injury to surgery <28 days, concomitant meniscal repair, prolonged immobilization, and genetic factors. There is a lack of evidence regarding whether race plays a significant role.

HYPOTHESIS

The risk of undergoing manipulation under anesthesia (MUA) and/or lysis of adhesions (LOA) after primary ACL reconstruction with bone-patellar tendon-bone (BTB) autograft in female basketball players is higher in African American players than in White players.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Using a computerized relational database, the authors identified competitive female basketball players who underwent primary ACL reconstruction with BTB autograft by the senior author over a 13-year period. Data previously entered from examinations and surgical findings were reviewed retrospectively. Univariate statistics and multivariable logistic regression were used to assess the relationship between undergoing subsequent MUA and/or LOA and study predictors.

RESULTS

A total of 186 knees (114 African American knees and 72 White knees) met inclusion criteria. The overall rate of MUA and/or LOA was 8.6%. Thirteen African American knees (11.4%) and 3 White knees (4.2%) underwent MUA and/or LOA for treatment of arthrofibrosis. No study predictor was found to have a statistically significant relationship with the rate of MUA and/or LOA on univariate analysis. However, when controlling for body mass index and previously described risk factors (age <18 years, time from injury to surgery ≤28 days, and concomitant meniscal repair) in the logistic regression model, the authors found that MUA and/or LOA was more likely in African American (odds ratio, 4.01 [95% CI, 1.01-15.92]; P = .049) than in White female players and in patients who underwent ACL reconstruction within 28 days of injury (odds ratio, 4.01 [95% CI, 1.18-13.57]; P = .026) compared with those with surgery delayed beyond 28 days.

CONCLUSION

In female basketball players, the present study found a statistically significantly increased risk for undergoing MUA and/or LOA after primary ACL reconstruction with BTB autograft in African American females compared with White females and in patients who underwent ACL reconstruction within 28 days of injury.

Single-cell and bulk tissue sequencing unravels the heterogeneity of synovial microenvironment in arthrofibrosis

Arthrofibrosis (AF) is a debilitating complication that occurs after trauma or surgery, leading to functional impairment and surgical failures worldwide. This study aimed to uncover the underlying mechanism of AF. A total of 141 patients were enrolled, and synovial samples were collected from both patients and animal models at different time points. Single-cell RNA-sequencing (scRNA-seq) and bulk tissue RNA sequencing (bulk-seq) were employed to profile the distinct synovial microenvironment. This study revealed changes in cell proportions during AF pathogenesis and identified Engrailed-1 (EN1) as a key transcription factor strongly associated with disease severity and clinical prognosis. Additionally, the researchers discovered a specific type of synovial fibroblast called DKK3-SLF, which played a critical role in driving AF development. These findings shed light on the composition and heterogeneity of the synovial microenvironment in AF, offering potential avenues for identifying therapeutic targets and developing clinical treatments for AF and other fibrotic diseases.

Adhesive Capsulitis of the Ankle (Frozen Ankle): An Infrequent Syndrome

Adhesive capsulitis, characterized by progressive fibrosis, causes a gradual, painful loss of both active and passive articular motion, leading to the final contracture of the joint capsule. The condition commonly referred to as "frozen ankle" (FA), which Goldman was the first to use, relates to the ankle joint and is challenging to both diagnose and treat. Data acquired from people who suffer from this type of damage in other joints such as the shoulder, hip, and wrist also exists. Despite the fact that a well-defined model for the medical management of FA does not exist, a wide spectrum of local treatments, both surgical and non-surgical, exist. This review gives an overview of the current scientific position of the frozen ankle in terms of evolutionary factors, etiology, the different mechanisms of action involved, current treatment options, and other possible interventions based on recent discoveries of pathophysiological mechanisms. The application of extracorporeal shockwave therapy, stretching exercises, and corticosteroid injections combined with physical therapy modalities that enhance pain management, range of motion, and functional capacity is highly advisable for the treatment of adhesive capsulitis, commonly known as "frozen joints". Furthermore, the addition of interventions both impacting and analyzing chronic hypoxia, low-grade inflammation, and sedentary life is proposed.

Minoxidil weakens newly synthesized collagen in fibrotic synoviocytes from osteoarthritis patients

PURPOSE

Synovial fibrosis (SFb) formation and turnover attributable to knee osteoarthritis (KOA) can impart painful stiffness and persist following arthroplasty. To supplement joint conditioning aimed at maximizing peri-operative function, we evaluated the antifibrotic effect of Minoxidil (MXD) on formation of pyridinoline (Pyd) cross-links catalyzed by Plod2-encoded lysyl hydroxylase (LH)2b that strengthen newly synthesized type-I collagen (COL1) in fibroblastic synovial cells (FSCs) from KOA patients. MXD was predicted to decrease Pyd without significant alterations to Col1a1 transcription by FSCs stimulated with transforming growth factor (TGF)β1.

METHODS

Synovium from 10 KOA patients grouped by SFb severity was preserved for picrosirius and LH2b histology or culture. Protein and RNA were purified from fibrotic FSCs after 8 days with or without 0.5 µM MXD and/or 4 ng/mL of TGFβ1. COL1 and Pyd protein concentrations from ELISA and expression of Col1a1, Acta2, and Plod2 genes by qPCR were compared by parametric tests with α = 0.05.

RESULTS

Histological LH2b expression corresponded to SFb severity. MXD attenuated COL1 output in KOA FSCs but only in the absence of TGFβ1 and consistently decreased Pyd under all conditions with significant downregulation of Plod2 but minimal alterations to Col1a1 and Acta2 transcripts.

CONCLUSIONS

MXD is an attractive candidate for local antifibrotic pharmacotherapy for SFb by compromising the integrity of newly formed fibrous deposits by FSCs during KOA and following arthroplasty. Targeted antifibrotic supplementation could improve physical therapy and arthroscopic lysis strategies aimed at breaking down joint scarring. However, the effect of MXD on other joint-specific TGFβ1-mediated processes or non-fibrotic components requires further investigation.

Uncommon, foreign-body induced knee arthrofibrosis in a pediatric patient

Arthrofibrosis is defined as an excessive fibrotic tissue response within a joint leading to a painful loss of motion. This pathological scar formation process with dysregulated, inordinate extracellular matrix formation, especially collagen, may occur in any joints, although is frequently localized in the knee. Different etiologies have been described and most of them are related to trauma, infection or recent surgical procedure. Although arthrofibrosis affects people of all ages, it is unusual in pediatric population. We present a case report of an uncommon, foreign body induced knee arthrofibrosis in a 14-year old boy. We also review the current literature regarding diagnostic procedures and treatment rationale for arthrofibrosis of the knee.

Pharmacological Therapies for Connective Tissue Fibrosis in Orthopaedics

Fibrosis is a common and debilitating pathological process that affects many organ systems and contributes to connective tissue disorders in orthopaedics. Tendons heal after acute and chronic injury through a process of fibrovascular scar tissue formation, and soft tissue joint capsules can be affected after traumatic joint injury, leading to arthrofibrosis. Although the precise underlying mechanisms are still being elucidated, fibrosis is thought to be a consequence of dysregulated immune and cytokine signaling that leads to myofibroblast activation and proliferation and subsequent excessive collagen deposition. Current treatments for connective tissue fibrosis include physical therapy and surgery, but there are no therapies that directly target the underlying cellular and molecular mechanisms of fibrosis. Many pharmacological agents have been used to successfully target fibrosis in other tissues and organ systems and thus are a promising treatment option to fill this gap. However, limited evidence is available to guide the use of these agents in musculoskeletal connective tissues. This article provides an overview of pharmacological therapies that have potential to treat connective tissue fibrosis in patients with musculoskeletal conditions, along with the current supporting evidence and future uses of each therapy.

Changes in passive stiffness and length of the semitendinosus muscles in rats with arthritis-induced knee flexion contracture

BACKGROUND

Arthritis-induced joint contracture is caused by arthrogenic and myogenic factors. The arthrogenic factor, localized within the joint, is naturally accepted as the cause of contracture. However, the detailed mechanisms underlying arthritis-induced myogenic contracture are largely unknown. We aimed to elucidate the mechanisms of arthritis-induced myogenic contracture by examining the muscle mechanical properties.

METHODS

Knee arthritis was induced in rats by injecting complete Freund's adjuvant into the right knees, while the untreated contralateral knees were used as controls. After one or four weeks of injection, passive stiffness, length, and collagen content of the semitendinosus muscles were assessed, along with passive knee extension range of motion.

FINDINGS

After one week of injection, flexion contracture formation was confirmed by a decreased range of motion. Range of motion restriction was partially relieved by myotomy, but still remained even after myotomy, indicating the contribution of both myogenic and arthrogenic factors to contracture formation. After one week of injection, the stiffness of the semitendinosus muscle was significantly higher in the injected side than in the contralateral side. After four weeks of injection, the stiffness of the semitendinosus muscle in the injected side returned to levels comparable to the contralateral side, parallel to partial improvement of flexion contracture. Muscle length and collagen content did not change due to arthritis at both time points.

INTERPRETATION

Our results suggest that increased muscle stiffness, rather than muscle shortening, contributes to myogenic contracture detected during the early stage of arthritis. The increased muscle stiffness cannot be explained by excess collagen.

Understanding of arthrofibrosis: New explorative insights into extracellular matrix remodeling of synovial fibroblasts

Arthrofibrosis following total knee arthroplasty is a fibroproliferative joint disorder marked by dysregulated biosynthesis of extracellular matrix proteins, such as collagens and proteoglycans. The underlying cellular events remain incompletely understood. Myofibroblasts are highly contractile matrix-producing cells characterized by increased alpha-smooth muscle actin expression and xylosyltransferase-I (XT-I) secretion. Human XT-I has been identified as a key mediator of arthrofibrotic remodeling. Primary fibroblasts from patients with arthrofibrosis provide a useful in vitro model to identify and characterize disease regulators and potential therapeutic targets. This study aims at characterizing primary synovial fibroblasts from arthrofibrotic tissues (AFib) regarding their molecular and cellular phenotype by utilizing myofibroblast cell culture models. Compared to synovial control fibroblasts (CF), AFib are marked by enhanced cell contractility and a higher XT secretion rate, demonstrating an increased fibroblast-to-myofibroblast transition rate during arthrofibrosis. Histochemical assays and quantitative gene expression analysis confirmed higher collagen and proteoglycan expression and accumulation in AFib compared to CF. Furthermore, fibrosis-based gene expression profiling identified novel modifier genes in the context of arthrofibrosis remodeling. In summary, this study revealed a unique profibrotic phenotype in AFib that resembles some traits of other fibroproliferative diseases and can be used for the future development of therapeutic interventions.

Effect of Trainee Level on Surgical Time and Postoperative Complications of Anterior Cruciate Ligament Reconstruction

PURPOSE

The objective of this study was to investigate the association between trainee level and surgical time and postoperative complications of anterior cruciate ligament reconstruction (ACLR).

METHODS

A retrospective chart review of patients who underwent ACLR at an academic orthopaedic ambulatory surgery center collected demographic and clinical information, including the number of trainees present and trainee level. Unadjusted and adjusted regression analyses assessed the association between trainee number and level with surgical time (time from skin incision to closure) and postoperative complications.

RESULTS

Of 799 patients in this study operated on by one of five academic sports surgeons, 87% had at least one trainee involved. The average surgical time overall was 93 ± 21 minutes and by trainee level was 99.7 (junior resident), 88.5 (senior residents), 96.6 (fellows), and 95.6 (no trainees). Trainee level was significantly associated with surgical time (P = 0.0008), with increased surgical time in cases involving fellows (0.0011). Fifteen complications (1.9%) were observed within 90 days of surgery. No notable risk factors of postoperative complications were identified.

CONCLUSION

Resident trainee level does not have a notable effect on surgical time or postoperative complications for ACLR at an ambulatory surgery center, although cases involving fellows had longer surgical times. Trainee level was not associated with risk of postoperative complications.

Metformin improves fibroblast metabolism and ameliorates arthrofibrosis in rats

Background

Emerging studies have suggested an essential role of fibroblast metabolic reprogramming in the pathogenesis of arthrofibrosis. The metabolic modulator metformin appears to be a therapeutic candidate for fibrotic disorders. However, whether metformin could alleviate arthrofibrosis has not been defined. In this study we have determined if treatment with metformin has beneficial effect on arthrofibrosis and its underlying mechanism.

Methods

Articular capsule samples were collected from patients with/without arthrofibrosis to perform gene and protein expression analysis. Arthrofibrosis animal model was established to examine the anti-fibrotic effect of metformin. Cell culture experiments were conducted to determine the mechanism by which metformin inhibits fibroblast activation.

Results

We found that glycolysis was upregulated in human fibrotic articular capsules. In an arthrofibrosis animal model, intra-articular injection of metformin mitigated inflammatory reactions, downregulated expression of both fibrotic and glycolytic markers, improved range of motion (ROM) of the joint, and reduced capsular fibrosis and thickening. At the cellular level, metformin inhibited the activation of fibroblasts and mitigated the abundant influx of glucose into activated fibroblasts. Interestingly, metformin prompted a metabolic shift from oxidative phosphorylation to aerobic glycolysis in activated fibroblasts, resulting in the anti-fibrotic effect of metformin.

Conclusion

Metformin decreased glycolysis, causing a metabolic shift toward aerobic glycolysis in activated fibroblasts and has beneficial effect on the treatment of arthrofibrosis.The translational potential of this article: The findings of this study demonstrated the therapeutic effect of metformin on arthrofibrosis and defined novel targets for the treatment of articular fibrotic disorders.

Exercise builds the scaffold of life: muscle extracellular matrix biomarker responses to physical activity, inactivity, and aging

Skeletal muscle extracellular matrix (ECM) is critical for muscle force production and the regulation of important physiological processes during growth, regeneration, and remodelling. ECM remodelling is a tightly orchestrated process, sensitive to multi-directional tensile and compressive stresses and damaging stimuli, and its assessment can convey important information on rehabilitation effectiveness, injury, and disease. Despite its profound importance, ECM biomarkers are underused in studies examining the effects of exercise, disuse, or aging on muscle function, growth, and structure. This review examines patterns of short- and long-term changes in the synthesis and concentrations of ECM markers in biofluids and tissues, which may be useful for describing the time course of ECM remodelling following physical activity and disuse. Forces imposed on the ECM during physical activity critically affect cell signalling while disuse causes non-optimal adaptations, including connective tissue proliferation. The goal of this review is to inform researchers, and rehabilitation, medical, and exercise practitioners better about the role of ECM biomarkers in research and clinical environments to accelerate the development of targeted physical activity treatments, improve ECM status assessment, and enhance function in aging, injury, and disease.

The combined effects of treadmill exercise and steroid administration on anterior cruciate ligament reconstruction-induced joint contracture and muscle atrophy in rats

Rehabilitation protocols to treat joint contracture and muscle atrophy following anterior cruciate ligament (ACL) reconstruction have not been established. In this study, we examined the combined effects of exercise therapy and steroid administration on joint contracture and muscle atrophy following ACL reconstruction. Rats received ACL transection and reconstructive surgery in one knee. After surgery, they were divided into four groups: no intervention, treadmill exercise (started from day three post-surgery, 12 m/min, 60 min/d, 6 d/week), treatment with the steroidal drug dexamethasone (250 μg/kg on days 0-5, 7, and 9 post-surgery), and dexamethasone treatment plus treadmill exercise. Age-matched untreated rats were used as controls. At day 10 or 30 post-surgery, we assessed ACL-reconstruction-induced joint contracture, joint capsule fibrosis, osteophyte formation, and muscle atrophy of the rectus femoris and gastrocnemius. Treadmill exercise after ACL reconstruction improved several indicators of muscle atrophy in both muscles, but it did not have positive effects on joint contracture. Dexamethasone treatment after ACL reconstruction improved joint contracture and joint capsule fibrosis at both timepoints and partially attenuated osteophyte formation at day 10 post-surgery, but delayed recovery from atrophy of the rectus femoris at day 30 post-surgery. The two treatments combined improved both joint contracture and atrophy of the rectus femoris and gastrocnemius. Exercise therapy combined with steroid administration may therefore be a novel therapeutic strategy for joint contracture and muscle atrophy following ACL reconstruction.