New surgical model of post-traumatic osteoarthritis: isolated intra-articular bone injury in the rabbit

Alpha-2-Macroglobulin Attenuates Posttraumatic Osteoarthritis Cartilage Damage by Inhibiting Inflammatory Pathways With Modified Intra-articular Drilling in a Yucatan Minipig Model

BACKGROUND

Posttraumatic osteoarthritis (PTOA) arises secondarily to joint trauma and is driven by catabolic inflammatory pathways. Alpha-2-macroglobulin (α2M) is a naturally occurring proteinase inhibitor found in human serum and synovial fluid that binds proteases as well as proinflammatory cytokines involved in the pathogenesis of PTOA.

PURPOSE

(1) To investigate the therapeutic potential of intra-articular α2M injections during the acute stages of PTOA by inhibiting inflammatory pathways driven by the cytokines expressed by the synovium in a large preclinical Yucatan minipig model and (2) to determine if 3 intra-articular α2M injections have greater chondroprotective effects compared with 1 intra-articular injection.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 48 Yucatan minipigs were randomized into 4 groups (n = 12 each): (1) modified intra-articular drilling (mIAD) and saline (mIAD + saline), (2) mIAD and 1 intra-articular α2M injection (mIAD +α2M-1), (3) mIAD and 3 α2M injections (mIAD +α2M-3), and (4) sham control. Surgical hindlimbs were harvested at 15 weeks after surgery. Cartilage degeneration, synovial changes, inflammatory gene expression, and matrix metalloproteinase levels were evaluated. Gait asymmetry was measured before and after surgery using a pressure-sensing walkway system.

RESULTS

Macroscopic lesion areas and microscopic cartilage degeneration scores were lower in the mIAD +α2M-1 and mIAD +α2M-3 groups compared with the mIAD + saline group (P < .05) and similar to those in the sham group (P > .05). Synovial membrane scores of the mIAD +α2M-1 and mIAD +α2M-3 groups were lower than that of the mIAD + saline group (P < .05) and higher than that of the sham group (P < .05). Interleukin-1 beta, nuclear factor kappa B, and tumor necrosis factor alpha mRNA expression in the synovium and matrix metalloproteinase-1 levels in synovial fluid were significantly lower in the mIAD +α2M-1 and mIAD +α2M-3 groups compared with the mIAD + saline group (P < .05). No significant differences were observed between the mIAD +α2M-1 and mIAD +α2M-3 groups for all measured outcomes. There were early changes in gait (P < .05) between preoperative and postoperative time points for the mIAD + saline, mIAD +α2M-1, and mIAD +α2M-3 groups that normalized by 15 weeks.

CONCLUSION

Animals receiving early α2M treatment exhibited less cartilage damage, milder synovitis, and lower inflammation compared with animals with no α2M treatment. These results exemplify the early anti-inflammatory effects of α2M and provide evidence that intra-articular α2M injections may slow the progression of PTOA.

CLINICAL RELEVANCE

In patients presenting with an acute joint injury, an early intervention with α2M may have the potential to reduce cartilage degeneration from catabolic pathways and delay the development of PTOA.

Molecular biomarker approaches to prevention of post-traumatic osteoarthritis

Up to 50% of individuals develop post-traumatic osteoarthritis (PTOA) within 10 years following knee-joint injuries such as anterior cruciate ligament rupture or acute meniscal tear. Lower-extremity PTOA prevalence is estimated to account for ≥12% of all symptomatic osteoarthritis (OA), or approximately 5.6 million cases in the USA. With knowledge of the inciting event, it might be possible to 'catch PTOA in the act' with sensitive imaging and soluble biomarkers and thereby prevent OA sequelae by early intervention. Existing biomarker data in the joint-injury literature can provide insights into the pathogenesis and early risk trajectory related to PTOA and can help to elucidate a research agenda for preventing or slowing the onset of PTOA. Non-traumatic OA and PTOA have many clinical, radiological and genetic similarities, and efforts to understand early risk trajectories in PTOA might therefore contribute to the identification and classification of early non-traumatic OA, which is the most prevalent form of OA.

The Effects of an Osteoarthritic Joint Environment on ACL Damage and Degeneration: A Yucatan Miniature Pig Model

Posttraumatic osteoarthritis (PTOA) arises secondary to joint injuries and is characteristically driven by inflammatory mediators. PTOA is often studied in the setting of ACL tears. However, a wide range of other injuries also lead to PTOA pathogenesis. The purpose of this study was to characterize the morphological changes in the uninjured ACL in a PTOA inflammatory environment. We retrospectively reviewed 14 ACLs from 13 Yucatan minipigs, 7 of which had undergone our modified intra-articular drilling (mIAD) procedure, which induced PTOA through inflammatory mediators. Seven ACLs were harvested from mIAD minipigs (PTOA) and seven ACLs from control minipigs with no cartilage degeneration (non-PTOA). ACL degeneration was evaluated using histological scoring systems. IL-1β, NF-κB, and TNF-α mRNA expression in the synovium was measured using qRT-PCR. PTOA minipigs demonstrated significant ACL degeneration, marked by a disorganized extracellular matrix, increased vascularity, and changes in cellular shape, density, and alignment. Furthermore, IL-1β, NF-κB, and TNF-α expression was elevated in the synovium of PTOA minipigs. These findings demonstrate the potential for ACL degeneration in a PTOA environment and emphasize the need for anti-inflammatory disease-modifying therapies following joint injury.

Arthritic Microenvironment-Dictated Fate Decisions for Stem Cells in Cartilage Repair

The microenvironment and stem cell fate guidance of post-traumatic articular cartilage regeneration is primarily the focus of cartilage tissue engineering. In articular cartilage, stem cells are characterized by overlapping lineages and uneven effectiveness. Within the first 12 weeks after trauma, the articular inflammatory microenvironment (AIME) plays a decisive role in determining the fate of stem cells and cartilage. The development of fibrocartilage and osteophyte hyperplasia is an adverse outcome of chronic inflammation, which results from an imbalance in the AIME during the cartilage tissue repair process. In this review, the sources for the different types of stem cells and their fate are summarized. The main pathophysiological events that occur within the AIME as well as their protagonists are also discussed. Additionally, regulatory strategies that may guide the fate of stem cells within the AIME are proposed. Finally, strategies that provide insight into AIME pathophysiology are discussed and the design of new materials that match the post-traumatic progress of AIME pathophysiology in a spatial and temporal manner is guided. Thus, by regulating an appropriately modified inflammatory microenvironment, efficient stem cell-mediated tissue repair may be achieved.

Improved Understanding of the Inflammatory Response in Synovial Fluid and Serum after Traumatic Knee Injury, Excluding Fractures of the Knee: A Systematic Review

BACKGROUND

Traumatic knee injury results in a 4- to 10-fold increased risk of post-traumatic osteoarthritis (PTOA). Currently, there are no successful interventions for preventing PTOA after knee injury. The aim of this study is to identify inflammatory proteins that are increased in serum and synovial fluid after acute knee injury, excluding intra-articular fractures.

METHODS

A literature search was done according to the PRISMA guidelines. Articles reporting about inflammatory proteins after knee injury, except fractures, up to December 8, 2021 were collected. Inclusion criteria were as follows: patients younger than 45 years, no radiographic signs of knee osteoarthritis at baseline, and inflammatory protein measurement within 1 year after trauma. Risk of bias was assessed of the included studies. The level of evidence was determined by the Strength of Recommendation Taxonomy.

RESULTS

Ten studies were included. All included studies used a healthy control group or the contralateral knee as healthy control. Strong evidence for interleukin 6 (IL-6) and limited evidence for CCL4 show elevated concentrations of these proteins in synovial fluid (SF) after acute knee injury; no upregulation in SF for IL-2, IL-10, CCL3, CCL5, CCL11, granulocyte colony-stimulating factor (G-CSF), and granulocyte-macrophage colony-stimulating factor (GM-CSF) was found. Limited evidence was found for no difference in serum concentration of IL-1β, IL-6, IL-10, CCL2, and tumor necrosis factor alpha (TNF-α) after knee injury.

CONCLUSION

Interleukin 6 and CCL4 are elevated in SF after acute knee injury. Included studies failed to demonstrate increased concentration of inflammatory proteins in SF samples taken 6 weeks after trauma. Future research should focus on SF inflammatory protein measurements taken less than 6 weeks after injury.

Synovial and cartilage responsiveness to peri-operative hyaluronic acid ± dexamethasone administration following a limited injury to the rabbit stifle joint

Posttraumatic osteoarthritis (PTOA) can develop after an injury to the knee. Previous studies have indicated that an intra-articular (IA) injection of the potent glucocorticoid dexamethasone (DEX) may significantly prevent induction of PTOA. The aim of the present study was to investigate the effectiveness of a single IA injection of hyaluronic acid (HA), alone and in combination with DEX following a localized intra-articular injury as a PTOA-preventing treatment option. An established rabbit model of surgical injury consisting of dual intra-articular (IA) drill holes in a non-cartilaginous area of the femoral notch near the origin of the anterior cruciate ligament (ACL) to allow for bleeding into the joint space was used. Immediately following surgery, subjects were treated with HA, HA + DEX, or received no treatment. An uninjured control group was used for comparison (N = 5/group). Rabbits were sacrificed and investigated at 9 weeks post-injury. At 9 weeks post-injury, there was a significant protective capacity of the single IA treatment of DEX + HA on the histological grade of the synovial tissue, and some variable location-specific effects of HA alone and HA + DEX interactions on cartilage damage. Thus, it is possible that co-treatment with HA may interfere with the effectiveness of the DEX. In vitro friction testing indicated that DEX did not interfere with the lubricating ability of HA or synovial fluid on cartilage. These results suggest that a single IA administration of HA in combination with DEX following an IA injury is not recommended for inhibition of PTOA progression in this model.

Cartilage Matrix Changes in Hindfoot Joints in Chronic Ankle Instability Patients After Anatomic Repair Using T2-Mapping: Initial Experience With 3-Year Follow-Up

BACKGROUND

Anatomic repair is widely accepted as the primary surgical treatment for chronic lateral ankle instability (CLAI). T2-mapping is a powerful tool for quantitative assessment of biochemical changes in cartilage matrix.

PURPOSE

To longitudinally evaluate cartilage matrix changes in the hindfoot joints of CLAI patients before and after anatomic repair by using T2-mapping with magnetic resonance imaging (MRI).

STUDY TYPE

Prospective.

SUBJECTS

Thirty-two CLAI patients (males/females = 20/12) and 21 healthy controls (males/females = 13/7).

FIELD STRENGTH/SEQUENCE

3 T; sagittal multi-echo spin-echo technique (T2-mapping), coronal, sagittal, and axial spin-echo PD-FS, and sagittal T1WI sequences.

ASSESSMENT

MRI examinations were performed in CLAI patients at baseline (prior to surgery) and 3 years after anatomic repair and in healthy controls. On T2-maps, the hindfoot joints were segmented into 16 cartilage subregions. The T2 value of each subregion was measured. All patients were evaluated with the American Orthopedic Foot and Ankle Society (AOFAS) scale at baseline and after surgery.

STATISTICAL TESTS

Analysis of variance (ANOVA) and Student's t-test were used. The differences corresponding to P < 0.05 were considered statistically significant.

RESULTS

At baseline, the T2 values in most cartilage subregions of talar dome and medial posterior subtalar joint (pSTJ) were higher in CLAI patients than in healthy controls. After surgery, only the T2 value of anteriomedial talar dome decreased from that at baseline (31.11 ± 3.88 msec vs. 34.27 ± 5.30 msec). The T2 values of other subregions with elevated T2 values remained higher than healthy controls. There were no significant differences in T2 values in the midtarsal joints between CLAI patients and healthy controls (P = 0.262, 0.104, 0.169, 0.103). Postoperatively, the patients' AOFAS scores improved significantly from 67.81 to 89.13.

DATA CONCLUSION

CLAI patients exhibited elevated T2 values in most subregions of talar dome and medial pSTJ. After anatomic repair, although the patients exhibited good clinical outcomes, the elevated T2 values could not be fully recovered.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY STAGE: 4.

Blood in the joint: effects of hemarthrosis on meniscus health and repair techniques

Injury to the meniscus is common and frequently leads to the development of post-traumatic osteoarthritis (PTOA). Many times meniscus injuries occur coincident with anterior cruciate ligament (ACL) injuries and lead to a bloody joint effusion. Hemarthrosis, or bleeding into the joint, has been implicated in degeneration of joint tissues. The goal of this review paper is to understand the pathophysiology of blood-induced joint damage, the possible effects of blood on meniscus tissue, and the implications for current meniscus repair techniques that involve the introduction of blood-derived products into the joint. In this review, we illustrate the similarities in the pathophysiology of joint damage due to hemophilic arthropathy (HA) and osteoarthritis (OA). Although numerous studies have revealed the harmful effects of blood on cartilage and synovium, there is currently a gap in knowledge regarding the effects of hemarthrosis on meniscus tissue homeostasis, healing, and the development of PTOA following meniscus injury. Given that many meniscus repair techniques utilize blood-derived and marrow-derived products, it is essential to understand the effects of these factors on meniscus tissue and the whole joint organ to develop improved strategies to promote meniscus tissue repair and prevent PTOA development.

Effect of infusion irrigation with different irrigating solutions on transient receptor potential vanilloid 5 and intra-articular inflammation in a post-traumatic osteoarthritis rabbit model

BACKGROUND

The incidence of post-traumatic osteoarthritis (PTOA) after anterior cruciate ligament reconstruction (ACLR) is high, but there is still a lack of intra-operative preventive measures. This study aimed to evaluate the effect of different irrigating solutions continuous irrigation on intra-articular inflammation and cartilage degeneration.

METHODS

66 New Zealand rabbits were randomly divided into normal (N) group, no treatment (NT) group, sodium chloride (NaCl) group, magnesium sulfate (MgSO4) group, and calcium chloride (CaCl2) group. The right knee joint of the experimental group was utilized to construct the model of PTOA, and the left side was utilized as the normal control group. At different time points postoperatively, the blood concentration of hemoglobin and Mg2 + , the synovial fluid concentration of IL-1 β, TNF-α, tartrate-resistant acid phosphatase-5b (TRAP-5b), and Type II Collagen, the gene expression of IL-1 β and MMP-3, and the protein expression of TRPV5 and CaM were detected. Pearson's linear correlation was employed to identify the possible relationship between the expression of TRAP-5b and the expression of IL-1β, IL-6, TNF-α, and Type II collagen. The hematoxylin and eosin staining (HE), Masson's trichrome staining, and Alcian blue staining were performed at postoperative 35 days. Osteoarthritis Scoring (OA score) comprised categories including Alcian blue staining, cartilage histology, the cellular density of cartilage, degree of cell disintegration, and formation of chondrocyte cluster were blindly scored by trained researchers at postoperative 35 days.

RESULTS

There was no statistical difference (P > 0.05) in the hemoglobin concentration between different groups. The concentration of serum Mg2+ in the MgSO4 group was higher than that of the other three groups (P < 0.05) on the same day of operation, then gradually decreased. The expression of IL-1 β, IL-6, and TRAP-5b in synovial fluid increased 5 days after the operation, decreased at 15 days, and then increased again with time in the NT group, NaCl group, and NT group and NaCl group. At 35 days after the operation, the expression of IL-1 β, IL-6, TRAP-5b, and type II collagen in the MgSO4 group were lower than that in the other three groups (except group N) (P < 0.05).The correlation analysis results showed that the TRAP-5b levels correlated positively with IL-1 β, IL-6, TNF-α, and type II collagen concentrations. The histological examination revealed that the surface smoothness of cartilage, the morphology of chondrocytes, the arrangement of collagen fibers, and the density of proteoglycan in the MgSO4 group were better than those in other experimental groups. At 35 days postoperatively, the gene expression of IL-1 β and MMP-3 and the protein expression of CaM and TRPV5 in synovium in the MgSO4 group was lower than that in the NaCl group and CaCl2 group.

CONCLUSION

Intra-operative irrigation with magnesium sulfate solution can inhibit the inflammatory factors and the expression of TRPV5, which can also reduce collagen loss and delay cartilage degeneration. Therefore, the use of magnesium sulfate in intra-operative irrigation may be an ideal choice to prevent PTOA.

Intra-articular proximal jig pin placement during tibial plateau leveling osteotomy

Background:

During tibial plateau leveling osteotomy (TPLO), a TPLO jig is often used. For placement of the jig, one of the pins is placed slightly distal to the joint line. Erroneous pin placement may lead to intra-articular damage; however, the path of the pin tract has not been thoroughly investigated.

Aim:

To document the rate and identify potential risk factors of intra-articular jig pin placement in dogs undergoing TPLO with the use of a TPLO jig.

Methods:

Medical records and pre- and postoperative radiographs (2007–2017) of 696 dogs with TPLO performed with a jig were reviewed. Primary surgeon and tibial plateau angles (TPA) were recorded. Postoperative radiographs were evaluated and classified according to intra-articular jig pin placement. Medial tibial plateau jig pin placement was defined as a radiolucent tract on the osteochondral junction of the medial tibial plateau. Lateral tibial plateau placement was defined as a radiolucent tract within 3 mm of the medial tibial plateau with a pin trajectory penetrating the lateral tibial plateau. Rates of intra-articular jig pin placement were calculated, and associations between intra-articular jig pin placement and surgeon experience and TPA were assessed with a chi-squared test.

Results:

Thirty-seven (5.32%) dogs had intra-articular placement of the jig pin. Seven dogs had medial tibial plateau jig placement, and 30 had lateral tibial plateau placement. There was no relationship between the TPA or surgeon level of experience and intra-articular placement of the pin.

Conclusion:

This study serves as a reminder to be cautious when placing the proximal jig pin during TPLO to avoid intra-articular placement. In addition, guidelines for evaluating proximal jig pin placement on postoperative radiographs are provided.

Molecular Response of Rabbit Menisci to Surgically Induced Hemarthrosis and a Single Intra-Articular Dexamethasone Treatment

Anterior cruciate ligament reconstructive surgery can restore biomechanical stability, however, such surgery cannot reliably prevent the onset of post-traumatic osteoarthritis. The aim of this study was to elucidate the molecular response that occurs within the menisci following a surgical injury that allows bleeding into the joint space, and then to investigate the effect of dexamethasone (DEX) on this molecular response. Cell viability studies following acute controlled exposure to blood and blood plus DEX were also conducted. Forty-eight New Zealand white rabbits were randomly allocated into control, sham, surgical, and surgical  + DEX groups (each group n  =  6). Animals were sacrificed at 48 h and 9 weeks, and menisci were harvested. The messenger RNA (mRNA) expression levels for key inflammatory, and degradative proteins, as well as mRNA levels for autophagy pathway molecules were quantified, and statistically significant changes were described. Meniscal cell viability was calculated by incubating groups of medial and lateral menisci in autologous blood, or autologous blood plus DEX for 48 h (each group n  =  4; total of eight medial and eight lateral menisci), and then conducting a histological live/dead assay. Results indicated a significant reduction in only medial meniscal cell viability when the tissue was exposed to blood in combination with DEX. A single administration of DEX following surgery significantly suppresses the elevated molecular expression for key inflammatory and degradative markers within menisci at 48 h and 9 weeks post-surgery. In vitro, autologous blood did not affect cell viability, but addition of DEX uniquely impacted the medial menisci. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2043-2052, 2019.

MRI of synovitis and joint fluid

Synovitis and joint effusion are common manifestations of rheumatic disease and play an important role in the disease pathophysiology. Earlier detection and accurate assessment of synovial pathology, therefore, can facilitate appropriate clinical management and hence improve prognosis. Magnetic resonance imaging (MRI) allows unparalleled assessment of all joint structures and associated pathology. It has emerged as a powerful tool, which enables not only detection of synovitis and effusion, but also allows quantification, detailed characterization, and noninvasive monitoring of synovial processes. The purpose of this article is to summarize the pathophysiology of synovitis and to review the role of qualitative, semiquantitative, and quantitative MRI in the assessment of synovitis and joint fluid. We also discuss the utility of MRI as an outcome measure to assess treatment response, particularly with respect to osteoarthritis and rheumatoid arthritis. Emerging applications such as hybrid positron emission tomography / MRI and molecular imaging are also briefly discussed. Level of Evidence: 5 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019.

Surgical Procedures for Chronic Lateral Ankle Instability

Surgical procedures for managing chronic lateral ankle instability include anatomic direct repair, anatomic reconstruction with an autograft or allograft, and arthroscopic repair. Open direct repair is commonly used for patients with sufficient ligament quality. Reconstruction incorporating either an autograft or an allograft is another promising option in the short term, although the longevity of this procedure remains unclear. Use of an allograft avoids donor site morbidity, but it comes with inherent risks. Arthroscopic repair of chronic lateral ankle instability can provide good to excellent short- and long-term clinical outcomes, but the evidence supporting this technique is limited. Deterioration of the ankle joint after surgery is also a concern. Studies are needed on not only treating ligament insufficiency but also on reducing the risk of ankle joint deterioration.

Interleukin-17 Can Induce Osteoarthritis in Rabbit Knee Joints Similar to Hulth's Method

Interleukin-17 (IL-17) is closely related to osteoarthritis (OA), but animal studies that employ IL-17 to induce OA are currently lacking. Therefore, this study evaluated the effect of IL-17 in the rabbit knee joint. The right knees served as the control group. The left knees were divided randomly into 4 groups: a Hulth group and 3 IL-17 groups (1-ng, 10-ng, and 50-ng groups). OA was induced in the Hulth group using Hulth's method. The IL-17 groups were injected with 1, 10, or 50 ng of IL-17 as indicated. Specimens were collected at 72 h, 1 week, 3 weeks, 6 weeks, and 12 weeks after surgery or the last injection. Subsequently, the following experiments were conducted: X-ray analysis, histological evaluation, and polymerase chain reaction (PCR) analysis of the mRNA expression levels of cartilage degeneration-related markers. At 12 weeks, like the Hulth group, the 10-ng and 50-ng IL-17 groups displayed typical manifestations of OA. The X-ray results, histological scores, and mRNA expression levels showed statistically significant differences between the control group and the 10-ng and 50-ng IL-17 groups. In sum, injecting 10 ng of IL-17 into the rabbit knee joint can induce OA similar to OA induced by Hulth's method.

Use of pre-clinical surgically induced models to understand biomechanical and biological consequences of PTOA development

Post-traumatic osteoarthritis (PTOA) development is often observed following traumatic knee injuries involving key stabilising structures such as the cruciate ligaments or the menisci. Both biomechanical and biological alterations that follow knee injuries have been implicated in PTOA development, although it has not been possible to differentiate clearly between the two causal factors. This review critically examines the outcomes from pre-clinical lapine and ovine injury models arising in the authors' laboratories and differing in severity of PTOA development and progression. Specifically, we focus on how varying severity of knee injuries influence the subsequent alterations in kinematics, kinetics, and biological outcomes. The immediate impact of injury on the lubrication capacity of the joint is examined in the context of its influence on biomechanical alterations, thus linking the biological changes to abnormal kinematics, leading to a focus on the potential areas for interventions to inhibit or prevent development of the disease. We believe that PTOA results from altered cartilage surface interactions where biological and biomechanical factors intersect, and mitigating acute joint inflammation may be critical to prolonging PTOA development. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:454-465, 2017.

Operative Treatment for Osteochondral Lesions of the Talus: Biologics and Scaffold-Based Therapy

OBJECTIVE

Numerous basic science articles have published evidence supporting the use of biologic augmentation in the treatment of osteochondral lesions of the talus (OLT). However, a comprehensive evaluation of the clinical outcomes of those treatment modalities in OLT has yet to be published. The purpose of this review is to provide an evidence-based overview of clinical outcomes following biologic augmentation to surgical treatments for OLT.

DESIGN

A comprehensive literature review was performed. Two commonly used surgical techniques for the treatment of OLT-bone marrow stimulation and osteochondral autograft transfer-are first introduced. The review describes the operative indications, step-by- step operative procedure, clinical outcomes, and concerns associated with each treatment. A review of the currently published basic science and clinical evidence on biologic augmentation in the surgical treatments for OLT, including platelet-rich plasma, concentrated bone marrow aspirate, and scaffold-based therapy follows.

RESULTS

Biologic agents and scaffold-based therapies appear to be promising agents, capable of improving both clinical and radiological outcomes in OLT. Nevertheless, variable production methods of these biologic augmentations confound the interpretation of clinical outcomes of cases treated with these agents.

CONCLUSIONS

Current clinical evidence supports the use of biologic agents in OLT cases. Nonetheless, well-designed clinical trials with patient-specific, validated and objective outcome measurements are warranted to develop standardized clinical guidelines for the use of biologic augmentation for the treatment of OLT in clinical practice.

Dexamethasone Release from Within Engineered Cartilage as a Chondroprotective Strategy Against Interleukin-1α

While significant progress has been made toward engineering functional cartilage constructs with mechanical properties suitable for in vivo loading, the impact on these grafts of inflammatory cytokines, chemical factors that are elevated with trauma or osteoarthritis, is poorly understood. Previous work has shown dexamethasone to be a critical compound for cultivating cartilage with functional properties, while also providing chondroprotection from proinflammatory cytokines. This study tested the hypothesis that the incorporation of poly(lactic-co-glycolic acid) (PLGA) (75:25) microspheres that release dexamethasone from within chondrocyte-seeded agarose hydrogel constructs would promote development of constructs with functional properties and protect constructs from the deleterious effects of interleukin-1α (IL-1α). After 28 days of growth culture, experimental groups were treated with IL-1α (10 ng/mL) for 7 days. Reaching native equilibrium moduli and proteoglycan levels, dexamethasone-loaded microsphere constructs exhibited tissue properties similar to microsphere-free control constructs cultured in dexamethasone-supplemented culture media and were insensitive to IL-1α exposure. These findings are in stark contrast to constructs containing dexamethasone-free microspheres or no microspheres, cultured without dexamethasone, where IL-1α exposure led to significant tissue degradation. These results support the use of dexamethasone delivery from within engineered cartilage, through biodegradable microspheres, as a strategy to produce mechanically functional tissues that can also combat the deleterious effects of local proinflammatory cytokine exposure.

The infrapatellar fat pad is affected by injury induced inflammation in the rabbit knee: use of dexamethasone to mitigate damage

OBJECTIVE AND DESIGN

The health of the infrapatellar fat pad (IFP) has been linked to pain, joint inflammation, and the onset of post-traumatic osteoarthritis. Thus, early inflammation effects on the IFP could have long term sequelae on joint integrity. This study was designed to characterize the natural history of the IFP in a model of surgically induced knee injury and inflammation, and to test the efficacy of one intra-articular (IA) administration of dexamethasone (DEX) immediately following surgery.

METHODS

An IA bone drill hole injury to the rabbit knee was conducted and immediately treated with DEX (n = 12). Early and late post-surgical time-points were investigated (48 h and 9 weeks) and the outcome measures were analysis of IFP histology, mRNA levels for relevant molecules, and protein levels for a subset of cytokines. Data were analyzed against a surgical control (injury without treatment; n = 12), a surgical sham (capsular incision only; n = 12), and normal control (n = 6).

TREATMENT

Single IA injection of DEX (0.5 mg/kg), administered at the completion of surgery.

RESULTS

IFPs from injured joints exhibited significantly increased cellularity and early fibrosis at 48 h post surgery. While the histological inflammation from a capsular incision alone resolved, knee injured animals progressed to a significantly more fibrotic IFP by 9 weeks. DEX significantly lowered histological scores at 48 h, but not at the 9 weeks. DEX did not influence mRNA levels for IL-1β, 6, and 8, however, protein analysis indicated that IL-8 levels were lower in DEX treated joints. DEX resulted in significantly elevated expression of mRNA for MCP-1, leptin, and VEGF.

CONCLUSION

One IA administration of a glucocorticoid appears to mitigate the initial inflammation within the joint, but is not sufficient to protect the joint to 9 weeks post-surgery.

Single intra-articular dexamethasone injection immediately post-surgery in a rabbit model mitigates early inflammatory responses and post-traumatic osteoarthritis-like alterations

Despite surgical reconstruction of the anterior cruciate ligament, a significant number of patients will still develop post-traumatic osteoarthritis (PTOA). Our objective was to determine if mitigating aspects of the acute phase of inflammation following a defined knee surgery with a single administration of a glucocorticoid could prevent the development of PTOA-like changes within an established rabbit model of surgically induced PTOA. An early and late post-surgical time-point was investigated in this study (48 h and 9 weeks post-surgery) in which the following groups were repeated (each n=6, for a total of 24 rabbits per time-point, and 48 rabbits used in the study): control (age/sex matched), sham (arthrotomy), drill injury (arthrotomy+two drill holes to a non-cartilaginous area of the femoral notch), and drill injury+single intra-articular (IA) injection of dexamethasone (DEX). At 48 h post-surgery, DEX treatment significantly lowered the mRNA levels for a subset of pro-inflammatory mediators, and significantly lowered the histological grade. Nine weeks post surgery, DEX treatment significantly lowered the histological scores (presented as effect size) for synovium (3.8), lateral femoral condyle (3.9), and lateral tibial cartilage (5.1) samples. Thus, DEX likely acts to prevent injury induced inflammation that could contribute to subsequent joint damage.

Inflammation in joint injury and post-traumatic osteoarthritis

Inflammation is a variable feature of osteoarthritis (OA), associated with joint symptoms and progression of disease. Signs of inflammation can be observed in joint fluids and tissues from patients with joint injuries at risk for development of post-traumatic osteoarthritis (PTOA). Furthermore, inflammatory mechanisms are hypothesized to contribute to the risk of OA development and progression after injury. Animal models of PTOA have been instrumental in understanding factors and mechanisms involved in chronic progressive cartilage degradation observed after a predisposing injury. Specific aspects of inflammation observed in humans, including cytokine and chemokine production, synovial reaction, cellular infiltration and inflammatory pathway activation, are also observed in models of PTOA. Many of these models are now being utilized to understand the impact of post-injury inflammatory response on PTOA development and progression, including risk of progressive cartilage degeneration and development of chronic symptoms post-injury. As evidenced from these models, a vigorous inflammatory response occurs very early after joint injury but is then sustained at a lower level at the later phases. This early inflammatory response contributes to the development of PTOA features including cartilage erosion and is potentially modifiable, but specific mediators may also play a role in tissue repair. Although the optimal approach and timing of anti-inflammatory interventions after joint injury are yet to be determined, this body of work should provide hope for the future of disease modification tin PTOA.

Using diet-induced obesity to understand a metabolic subtype of osteoarthritis in rats

Osteoarthritis (OA) in obese individuals is often attributed to joint loading. However, a subtype of OA, Metabolic OA, may be due to obesity-related intrinsic factors but remains to be evaluated experimentally against a known OA progression model.

OBJECTIVE

To evaluate if obesity contributes to OA onset using a high fat/high sucrose diet-induced obesity (DIO) model with anterior cruciate ligament-transected rats (ACL-X).

METHODS

Sprague Dawley rats (n = 33) consumed high fat/high sucrose or chow diets for 12 weeks, were randomized to one of three groups: a unilateral ACL-X group, sham surgery group, or naïve non-surgical group. These animals were followed for an additional 16 weeks. At sacrifice, body composition, knee joint Modified Mankin scores, and 27 serum and synovial fluid cytokines and adipokines were measured.

RESULTS

Experimental limbs of obese ACL-X, obese Sham, and lean ACL-X animals had similar Modified Mankin scores that were greater than those obtained from lean Sham and naïve animals. Obese contralateral limbs had similar OA damage as ACL-X and Sham limbs of obese and ACL-X limbs of lean animals. Obese contralateral limb Modified Mankin scores had a strong correlation (r = 0.75, P < 0.001) with body fat percentage. Serum leptin and synovial fluid IP10/CXCL10 best described Modified Mankin scores in contralateral limbs of obese animals.

CONCLUSIONS

Mechanical factors produced OA damage in experimental limbs, as expected. Interestingly, OA damage in obese contralateral limbs was similar to mechanically perturbed limbs, suggesting that obesity may induce OA in a non-mechanical manner.

Development and retranslational validation of an in vitro model to characterize acute infections in large human joints

Bacterial infections can destroy cartilage integrity, resulting in osteoarthritis. Goal was to develop an in vitro model with in vivo validation of acute joint inflammation. Inflammation in cocultivated human synovial fibroblasts (SFB), chondrocytes (CHDR), and mononuclear cells (MNC) was successively relieved for 10 days. Articular effusions from patients with (n = 7) and without (n = 5) postoperative joint infection in healthy patients (ASA 1-2) were used as model validation. Inflammation in vitro resulted in an enormous increase in IL-1 and a successive reduction in SFB numbers. CHDR however, maintained metabolic activity and proteoglycan synthesis. While concentrations of bFGF in vivo and in vitro rose consistently, the mRNA increase was only moderate. Concurring with our in vivo data, cartilage-specific IGF-1 steadily increased, while IGF-1 mRNA in the CHDR and SFB did not correlate with protein levels. Similarly, aggrecan (ACAN) protein concentrations increased in vivo and failed to correlate in vitro with gene expression in either the CHDR or the SFB, indicating extracellular matrix breakdown. Anabolic cartilage-specific BMP-7 with highly significant intra-articular levels was significantly elevated in vitro on day 10 following maximum inflammation. Our in vitro model enables us to validate early inflammation of in vivo cell- and cytokine-specific regulatory patterns. This trial is registered with MISSinG, DRKS 00003536.

Dexamethasone inhibits inflammation and cartilage damage in a new model of post-traumatic osteoarthritis

Corticosteroids are used in musculoskeletal diseases, and offer patient relief. Injections of corticosteroids are recommended for management of osteoarthritis (OA). Current data have shown the role of corticosteroids in ameliorating pain. We hypothesized that repeated intra-articular injections of high dose dexamethasone would protect the cartilage from damage in a post-traumatic model of OA. Eighteen female New Zealand White rabbits were used. Twelve underwent surgery to induce OA; six of them received intra-articular injections of dexamethasone every 3 days for 3 weeks. The other six rabbits served as operated controls. Six additional rabbits served as non-operated controls. All animals were euthanized 3 weeks post-surgery. Knees were assessed grossly. Cartilage, synovium, and fat pad were assessed histologically. Synovium and fat pad were analyzed with qPCR and Western blots. Surgical controls had cartilage damage which was supressed with dexamethasone. Dexamethasone significantly decreased synovial expression of interleukin-1β and collagen I, and a trend to decrease synovial matrix metalloproteinase3 expression. There were also significantly lower levels of interleukin-1β protein with dexamethasone treatment. Dexamethasone significantly decreased fat pad expression of matrix metalloproteinase13, basic fibroblast growth factor, and interleukin8, and a trend to decrease matrix metalloproteinase3 and transforming growth factorβ expression. Dexamethasone decreased joint inflammation and joint tissue degradation and was chondroprotective in this unique model of PTOA.

Biodegradation of a magnesium alloy implant in the intercondylar femoral notch showed an appropriate response to the synovial membrane in a rabbit model in vivo

Degradable magnesium alloys are promising biomaterials for orthopedic applications. The aim of this study was to evaluate the potential effects on both the synovial membrane (synovialis) and the synovial fluid (synovia) of the degradation products of a MgYREZr-pin implanted in the intercondylar femoral notch in a rabbit model. Thirty-six animals were randomized into two groups (MgYREZr or Ti6Al4V alloy) of 18 animals each. Each group was then divided into three subgroups with implantation periods of 1, 4, and 12 weeks, with six animals in each subgroup. The initial inflammatory reaction caused by the surgical trauma declined after 12 weeks of implantation, and elucidated a progressive recovery of the synovial membrane. Compared with control Ti6Al4V pins, there were no significant differences between the groups. However, after 12 weeks, recovery of the synovial membrane was more advanced in the titanium group, in which 92% showed no signs of synovitis, than in the magnesium group. A cytotoxicity test with L929 cells and human osteoblasts (HOB) was also conducted, according to EN ISO 10993-5/12, and no toxic leachable products were observed after 24 h of incubation. In conclusion, the MgYREZr alloy seems to be a suitable material for intra-articular degradable implants.