Inflammatory cytokine levels in synovial fluid 3, 4 days postoperatively and its correlation with early-phase functional recovery after anterior cruciate ligament reconstruction: a cohort study

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.

Improved Cartilage Protection with Low Molecular Weight Hyaluronic Acid Hydrogel

Traumatic joint injuries are common, leading to progressive tissue degeneration and the development of osteoarthritis. The post-traumatic joint experiences a pro-inflammatory milieu, initiating a subtle but deteriorative process in cartilage tissue. To prevent or even reverse this process, our group previously developed a tissue-penetrating methacrylated hyaluronic acid (MeHA) hydrogel system, crosslinked within cartilage to restore and/or protect the tissue. In the current study, we further optimized this approach by investigating the impact of biomaterial molecular weight (MW; 20, 75, 100 kDa) on its integration within and reinforcement of cartilage, as well as its ability to protect tissue degradation in a catabolic state. Indeed, the low MW MeHA integrated and reinforced cartilage tissue better than the high MW counterparts. Furthermore, in a 2 week IL-1β explant culture model, the 20 kDa MeHA demonstrated the most protection from biphasic mechanical loss, best retention of proteoglycans (Safranin O staining), and least aggrecan breakdown (NITEGE). Thus, the lower MW MeHA gels integrated better into the tissue and provided the greatest protection of the cartilage matrix. Future work will test this formulation in a preclinical model, with the goal of translating this therapeutic approach for cartilage preservation.

Association of Infrapatellar Fat Pad Fibrosis at 3 Months After ACL Reconstruction With Short-term Clinical Outcomes and Inflammatory Cytokine Levels in the Synovial Fluid

Background

Infrapatellar fat pad (IFP) fibrosis is reportedly associated with anterior knee pain and the progression of patellofemoral osteoarthritis after anterior cruciate ligament reconstruction (ACLR). However, causes of IFP fibrosis after ACLR have not been sufficiently investigated.

Purpose

To compare the descriptive characteristics, clinical outcomes, and inflammatory cytokine levels in the synovial fluid between patients who underwent ACLR with versus without severe IFP fibrosis.

Study Design

Cohort study; Level of evidence, 3.

Methods

Patients who underwent primary ACLR using autologous hamstring tendon were divided into 2 groups based on magnetic resonance imaging IFP fibrosis scoring (grades 0-5) at 3 months after surgery: the severe fibrosis group (grades 4 and 5) and mild fibrosis group (grades 0-3). Synovial fluid was aspirated on postoperative day 3 or 4 to measure inflammatory cytokine levels. Patient characteristics, clinical outcomes at 3 and 12 months after surgery, and inflammatory cytokine (interleukin [IL]-1β, IL-2, IL-6, IL-8, IL-10, tumor necrosis factor-α, and interferon-γ) levels were compared between the groups.

Results

Of the 36 patients included, 7 were allocated to the severe fibrosis group and 29 were allocated to the mild fibrosis group. The severe fibrosis group had a significantly longer operation time (153.0 vs 116.5 minutes for mild fibrosis; P = .007). Compared with the mild fibrosis group, the severe fibrosis group had greater pain during stair climbing (2.0 vs 0.7; P = .01) and a lower extension muscle strength ratio (operated/healthy side, 52.9% vs 76.1%; P < .001) at 3 months, and the severe fibrosis group had a lower Lysholm score (93.7 vs 97.3; P = .026) and greater knee extension (0.3° vs 1.9°; P = .043) and flexion angle restriction (142.9° vs 149.0°; P = .013) at 12 months. The severe fibrosis group demonstrated higher IL-1β (2.6 vs 1.4 pg/mL; P = .022), IL-6 (2.0 vs 1.1 ng/mL; P = .029), and interferon-γ levels (11.3 vs 4.0 pg/mL; P = .044).

Conclusion

Severe IFP fibrosis was associated with a longer operation time, higher inflammatory cytokine level in the synovial fluid, and worse clinical outcomes at 3 and 12 months after ACLR.

Bio-orthogonal Click Chemistry Methods to Evaluate the Metabolism of Inflammatory Challenged Cartilage after Traumatic Overloading

During traumatic joint injuries, impact overloading can cause mechanical damage to the cartilage. In the following inflammation phase, excessive inflammatory cytokines (e.g., interleukin-1β (IL-1β)) can act on chondrocytes, causing over-proliferation, apoptosis, and extracellular matrix (ECM) degradation that can lead to osteoarthritis. This study investigated the combined effects of traumatic overloading and IL-1β challenge on the metabolic activities of chondrocytes. Bovine cartilage explants underwent impact overloading followed by IL-1β exposure at a physiologically relevant dosage (1 ng/mL). New click chemistry-based methods were developed to visualize and quantify the proliferation of in situ chondrocytes in a nondestructive manner without the involvement of histological sectioning or antibodies. Click chemistry-based methods were also employed to measure the ECM synthesis and degradation in cartilage explants. As the click reactions are copper-free and bio-orthogonal, i.e., with negligible cellular toxicity, cartilage ECM was cultured and studied for 6 weeks. Traumatic overloading induced significant cell death, mainly in the superficial zone. The high number of dead cells reduced the overall proliferation of chondrocytes as well as the synthesis of glycosaminoglycan (GAG) and collagen contents, but overloading alone had no effects on ECM degradation. IL-1β challenge had little effect on cell viability, proliferation, or protein synthesis but induced over 40% GAG loss in 10 days and 61% collagen loss in 6 weeks. For the overloaded samples, IL-1β induced greater degrees of degradation, with 68% GAG loss in 10 days and 80% collagen loss in 6 weeks. The results imply a necessary immediate ease of inflammation after joint injuries when trauma damage on cartilage is present. The new click chemistry methods could benefit many cellular and tissue engineering studies, providing convenient and sensitive assays of metabolic activities of cells in native three-dimensional (3D) environments.

Tackling the Challenges of Graft Healing After Anterior Cruciate Ligament Reconstruction-Thinking From the Endpoint

Anterior cruciate ligament (ACL) tear is common in sports and accidents, and accounts for over 50% of all knee injuries. ACL reconstruction (ACLR) is commonly indicated to restore the knee stability, prevent anterior–posterior translation, and reduce the risk of developing post-traumatic osteoarthritis. However, the outcome of biological graft healing is not satisfactory with graft failure after ACLR. Tendon graft-to-bone tunnel healing and graft mid-substance remodeling are two key challenges of biological graft healing after ACLR. Mounting evidence supports excessive inflammation due to ACL injury and ACLR, and tendon graft-to-bone tunnel motion negatively influences these two key processes. To tackle the problem of biological graft healing, we believe that an inductive approach should be adopted, starting from the endpoint that we expected after ACLR, even though the results may not be achievable at present, followed by developing clinically practical strategies to achieve this ultimate goal. We believe that mineralization of tunnel graft and ligamentization of graft mid-substance to restore the ultrastructure and anatomy of the original ACL are the ultimate targets of ACLR. Hence, strategies that are osteoinductive, angiogenic, or anti-inflammatory should drive graft healing toward the targets. This paper reviews pre-clinical and clinical literature supporting this claim and the role of inflammation in negatively influencing graft healing. The practical considerations when developing a biological therapy to promote ACLR for future clinical translation are also discussed.

Synovial Fluid Mesenchymal Stem Cells for Knee Arthritis and Cartilage Defects: A Review of the Literature

Mesenchymal stem cells (MSCs) are adult stem cells that have the ability to self-renew and differentiate into several cell lineages including adipocytes, chondrocytes, tenocytes, bones, and myoblasts. These properties make the cell a promising candidate for regenerative medicine applications, especially when dealing with sports injuries in the knee. MSCs can be isolated from almost every type of adult tissue. However, most of the current research focuses on MSCs derived from bone marrow, adipose, and placenta derived products. Synovial fluid-derived MSCs (SF-MSCs) are relatively overlooked but have demonstrated promising therapeutic properties including possessing higher chondrogenic proliferation capabilities than other types of MSCs. Interestingly, SF-MSC population has shown to increase exponentially in patients with joint injury or disease, pointing to a potential use as a biomarker or as a treatment of some orthopaedic disorders. In this review, we go over the current literature on synovial fluid-derived MSCs including the characterization, the animal studies, and discuss future perspectives.

Differential MMP 1 and MMP 13 expression in proliferation and ligamentization phases of graft remodeling in anterior cruciate ligament reconstruction

Purpose: Graft remodeling in anterior cruciate ligament reconstruction (ACLR) demonstrates three distinct phases: necrosis, proliferation and ligamentization. Biological enhancement involves modulating these processes, but the cellular activities related to extracellular matrix remodeling have not been investigated. We hypothesized that changes in matrix metalloproteinases (MMPs) 1 and 13 expression are involved in the transition of proliferation phase to ligamentization phase of graft remodeling.Materials and methods: Thirty-three rats underwent ACLR. Tendon grafts were harvested at week 1 (necrosis), 2 (proliferation), or 12 (ligamentization) post-operation for histological examination (n = 3), or for isolation of graft-derived cells (n = 8) for flow cytometry, proliferation assay, cell invasion assay, measurement of gene expression related to matrix remodeling (Col1A1, Col3A1, MMP1, tissue inhibitor of marix metalloproteinase 1 (TIMP1), and MMP13) and total MMP activities.Results: Increased cellularity in tendon graft was contributed by active cell proliferation and migration at week 2 post-operation, while decreased cellularity were paralleled by increased apoptosis at week 12. All genes measured (Col1A1, Col3A1, MMP1, TIMP1, and MMP13) increased significantly in week 2 cells compared to week 1 cells. MMP1 expression subsided at week 12, while MMP13 expression kept increasing till 12 weeks post-operation. Total MMP activities was 3-fold higher in cultured graft-derived cells from week 2 as compared to cells from week 12. Two distinct processes of graft remodeling were identified, characterized by increased MMP1 expression with cell proliferation and increased MMP13 expression with cell apoptosis.Conclusions: Unfavorable matrix remodeling during the proliferation phase is found with increased MMP1, while remodeling leading to ligamentization is associated with increased MMP13 expression.

Inflammatory and healing environment in synovial fluid after anterior cruciate ligament reconstruction: Granulocytes and endogenous opioids as new targets of postoperative pain

Background

Biological processes after anterior cruciate ligament reconstruction (ACLR) is crucial for recovery. However, alterations in the of synovial fluid cell population during the acute phase following ACLR and the relationship between these cells and postoperative pain is unclear. The goal of this study was to reveal alterations in synovial fluid cell population during the acute phase following ACLR and relationship between postoperative pain and proportion of synovial fluid cells.

Methods

Synovial fluids were obtained from all patients (n = 50) before surgery and from patients who showed hydrarthrosis at days 4 (n = 25), and 21 (n = 42) post-surgery. The cell population was analyzed by flow cytometry. IL1β, IL8, and met-enkephalin in synovial fluid were quantitated by enzyme-linked immunosorbent assay. Patients answered numerical rating scale (NRS) questionnaire at 4 days and approximately 4 weeks postoperatively.

Results

The granulocyte population was significantly higher at 4 days after surgery than at any other time points. The population of macrophages was 3.2 times and 7.7 times as high as at surgery on days 4 and 21, respectively. T cell population was significantly higher 21 days after surgery compared to 4 days after surgery. All NRS 4 weeks after surgery showed a significant negative correlation with the granulocyte population in synovial fluid 4 days after surgery. Granulocyte population in synovial fluid significantly correlated with the levels of IL1β and IL8. Postoperative pain at rest tended to decrease with an increase in met-enkephalin concentration 4 days after ACLR.

Conclusions

Synovial fluid after ACLR had an inflammatory environment at early time points and a healing environment in the subsequent phase about concerning to the cellular composition. A proportion of synovial fluid cells and endogenous opioids affected postoperative pain.

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Granulocyte population was higher at 4 days after ACLR than at other time points.

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Postoperative pain negatively correlated with the granulocyte in synovial fluid.

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Granulocyte population in synovial fluid correlate with IL1β and IL8 concentration.

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Postoperative pain tended to decrease with an increase in met-enkephalin.

Pre-operative Joint Inflammation has no Bearing on Outcome of Arthroscopic Anterior Cruciate Ligament Reconstruction at 1-Year Follow-Up; a Prospective Study

BACKGROUND

To study the effect of pre-operative joint inflammation on clinical outcome at 1 year follow-up following ACL reconstruction surgery.

METHODS

Male patients, aged 18-40 years, suffering from isolated ACL injury were included. All patients were randomly divided into two groups based on the type of graft used: Group A: semitendinosus gracilis graft with preserved insertions (STG-PI), Group B: bone-patellar tendon-bone graft (BPTB). Patients were categorised based on the time of presentation after injury: (a) within 6 weeks of injury, (b) between 6 and 12 weeks of injury, (c) after 12 weeks of injury. Synovial fluid levels of Interlukin-1, Interlukin-6 and TNF-α were measured in all the ACL deficient knees by taking a joint fluid sample intra-operatively.

RESULTS

The total number of patients in the study was 59; 23 in group A (STG-PI) and 36 in group B (BPTB). Mean age of patients was 26 ± 5.146 years. 14 out of 59 (23.7%) patients presented within 6 weeks of injury, 16 (27.11%) patients presented between 6 and 12 weeks after injury and 29 (49.1%) patients presented after 12 weeks of injury. IL-6 levels were significantly high in group with < 6 weeks of injury than in group with > 12 weeks since injury. IL-6 had significant correlation with VAS scores, KT 1000, Lysholm knee scores and Tegner level of activity. There was no difference in outcome (pain scores, mechanical stability, Lysholm knee score and Tegner level of activity) at 1 year follow-up when patients with different time intervals since injury were compared.

CONCLUSION

The clinical outcome in terms of pain score, mechanical stability, functional scores and return to sporting activity is comparable, irrespective of the time since injury, at short term follow-up.

Functional decellularized fibrocartilaginous matrix graft for rotator cuff enthesis regeneration: A novel technique to avoid in-vitro loading of cells

Rapid and functional enthesis regeneration after rotator cuff tear (RCT) remains a challenge in clinic. Current tissue-engineering strategies for solving this challenge are focused on developing grafts with the mode of in-vitro loading cells on a scaffold. However, this mode is complicated and time-inefficient, moreover the preservation of this graft outside a cell incubator is highly inconvenient, thus limiting their clinical application. Developing a cell-free graft with chemotaxis to recruit postoperative injected cells may be a promising approach to solve these problems. Herein, we prepared a recombinant SDF-1α (termed as C-SDF-1α) capable of binding collagen and chemotaxis, which were then tethered on the collagen fibers of book-shaped decellularized fibrocartilage matrix (BDFM) to fabricate this cell-free graft (C-SDF-1α/BDFM). This C-SDF-1α/BDFM is noncytotoxicity and low-immunogenicity, allows synovium-derived mesenchymal stem cells (SMSCs) attachment and proliferation, and shows superior chondrogenic inducibility. More importantly, C-SDF-1α/BDFM released the tethered SDF-1α with a sustained release profile in-vitro and in-vivo, thus steadily recruiting chemokine (C-X-C motif) receptor 4 positive (CXCR4⁺) cells. Rats with RCT were repaired acutely with C-SDF-1α/BDFM together with postoperative CXCR4⁺SMSCs injection (C-SDF-1α/BDFM + CXCR4⁺SMSCs), BDFM in-vitro pre-loaded CXCR4⁺SMSCs (BDFM/CXCR4⁺SMSCs), or direct suture only (CTL). At postoperative 14-day, compared with BDFM/CXCR4⁺SMSCs, C-SDF-1α/BDFM + CXCR4⁺SMSCs showed a little more CXCR4⁺SMSCs at the healing site. At postoperative week 4 or 8, rats treated with C-SDF-1α/BDFM + CXCR4⁺SMSCs presented a similar RC healing quality as BDFM/CXCR4⁺SMSCs, both of which were significantly better than the CTL. Collectively, compared with conventional BDFM/CXCR4⁺SMSCs, C-SDF-1α/BDFM, as a cell-free graft with chemotaxis, could recruit postoperative injected CXCR4⁺cells into the healing site to participating RC healing, thus avoiding the complex process of in-vitro loading cells on a scaffold and necessitating immense care for the graft outside cell incubator, making it very convenient for clinical application.

Exogenous stromal derived factor-1 releasing silk scaffold combined with intra-articular injection of progenitor cells promotes bone-ligament-bone regeneration

Anterior cruciate ligament (ACL) is one of the most difficult tissues to heal once injured. Ligament regeneration and tendon-bone junction healing are two major goals of ACL reconstruction. This study aimed to investigate the synergistic therapeutic effects of Stromal cell-derived factor 1 (SDF-1)-releasing collagen-silk (CSF) scaffold combined with intra-articular injection of ligament-derived stem/progenitor cells (LSPCs) for ACL regeneration and the amelioration in the long-term complication of osteoarthritis (OA). The stem cell recruitment ability of CSF scaffold and the multipotency, particularly the tendon forming ability of LSPCs from rabbits were characterized in vitro, while the synergistic effect of the CSF scaffold and LSPCs for ACL regeneration and OA amelioration were investigated in vivo at 1, 3, and 6 months with a rabbit ACL reconstruction model. The CSF scaffold was used as a substitute for the ACL, and LSPCs were injected into the joint cavity after 7 days of the ACL reconstruction. CSF scaffold displayed a controlled release pattern for the encapsulated protein for up to 7 days with an increased stiffness in the mechanical property. LSPCs, which exhibited highly I Collagen and CXCR4 expression, were attracted by SDF-1 and successfully relocated into the CSF scaffold at 1 month in vivo. At 3 and 6 months post-treatment, the CSF scaffold combined with LSPCs (CSFL group) enhanced the regeneration of ACL tissue, and promoted bone tunnel healing. Furthermore, the OA progression was impeded efficiently. Our findings here provided a new strategy that using stem cell recruiting CSF scaffold with tissue-specific stem cells, could be a promising solution for ACL regeneration.

STATEMENT OF SIGNIFICANCE

In this study, we developed a silk scaffold with increased stiffness and SDF-1 controlled release capacity for ligament repair. This advanced scaffold transplantation combined with intra-articular injection of LSPCs (which was isolated from rabbit ligament for the first time in this study) promoted the regeneration of both the tendinous and bone tunnel portion of ACL. This therapeutic strategy also ameliorated cartilage degeneration and reduced the severity of arthrofibrosis. Hence, combining LSPCs injection with SDF-1-releasing silk scaffold is demonstrated as a therapeutic strategy for ACL regeneration and OA treatment in the clinic.