Sustained intra-articular delivery of IL-1RA from a thermally-responsive elastin-like polypeptide as a therapy for post-traumatic arthritis

Therapeutic Controlled Release Strategies for Human Osteoarthritis

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

IL-1 receptor antagonist: etiological and drug delivery systems overview

OBJECTIVE

This article is aims to provide an overview of studies reported in the literature to investigate the etiological role of IL-1/IL-1ra in various disease conditions and the different drug delivery systems developed to achieve IL-1ra as a possible therapeutic option.

METHODS

Studies reported in PubMed, Google scholar, and other open-source literature related to etiological involvement of IL-1ra in pathophysiological conditions and various drug delivery schemes developed for IL-1ra for its efficacy evaluation as a possible treatment for different disease conditions were surveyed.

RESULTS AND CONCLUSIONS

The pathophysiological conditions involving IL-1/IL-1 ra spanned CNS-related disorders, Diabetes, Cardiac disorders, Ocular disease conditions, Gastrointestinal conditions, Tumor growth & metastasis, and miscellaneous conditions. The drug delivery systems developed for IL-1ra included a commercial drug product, Gene therapy, Antibody fusions, Extended-release delivery systems, and Pegylated-IL-1ra systems.

Mode of injury and level of synovitis alter inflammatory chondrocyte gene expression and associated pathways

Although various joint injuries result in post-traumatic osteoarthritis (PTOA), differences in chondrocyte response to specific injuries, such as blunt compression or fracture, are unclear. Furthermore, the role of underlying joint inflammation, or synovitis, is often not considered. We investigated how injury mechanisms and underlying synovitis affect chondrocyte gene expression using osteochondral injury models with synovial co-culture. We hypothesized that the state of synovitis as well as the mechanism of biomechanical cartilage injury differentially alter the gene expression of chondrocytes and that these responses are regulated by the pro-inflammatory cytokine interleukin 1 (IL-1). The mechanism of injury and level of synovial inflammation both significantly regulated chondrocyte gene expression and associated pathways, uncovering distinct characteristics of fracture and compression injury mechanisms. Targeting IL-1 following injury reduced the inflammatory response and could have clinical implications. The results from this study show that crosstalk between biomechanics and inflammation in the context of synovitis and cartilage injury mechanism is an important consideration for PTOA.

A synoptic literature review of animal models for investigating the biomechanics of knee osteoarthritis

Osteoarthritis (OA) is a common chronic disease largely driven by mechanical factors, causing significant health and economic burdens worldwide. Early detection is challenging, making animal models a key tool for studying its onset and mechanically-relevant pathogenesis. This review evaluate current use of preclinical in vivo models and progressive measurement techniques for analysing biomechanical factors in the specific context of the clinical OA phenotypes. It categorizes preclinical in vivo models into naturally occurring, genetically modified, chemically-induced, surgically-induced, and non-invasive types, linking each to clinical phenotypes like chronic pain, inflammation, and mechanical overload. Specifically, we discriminate between mechanical and biological factors, give a new explanation of the mechanical overload OA phenotype and propose that it should be further subcategorized into two subtypes, post-traumatic and chronic overloading OA. This review then summarises the representative models and tools in biomechanical studies of OA. We highlight and identify how to develop a mechanical model without inflammatory sequelae and how to induce OA without significant experimental trauma and so enable the detection of changes indicative of early-stage OA in the absence of such sequelae. We propose that the most popular post-traumatic OA biomechanical models are not representative of all types of mechanical overloading OA and, in particular, identify a deficiency of current rodent models to represent the chronic overloading OA phenotype without requiring intraarticular surgery. We therefore pinpoint well standardized and reproducible chronic overloading models that are being developed to enable the study of early OA changes in non-trauma related, slowly-progressive OA. In particular, non-invasive models (repetitive small compression loading model and exercise model) and an extra-articular surgical model (osteotomy) are attractive ways to present the chronic natural course of primary OA. Use of these models and quantitative mechanical behaviour tools such as gait analysis and non-invasive imaging techniques show great promise in understanding the mechanical aspects of the onset and progression of OA in the context of chronic knee joint overloading. Further development of these models and the advanced characterisation tools will enable better replication of the human chronic overloading OA phenotype and thus facilitate mechanically-driven clinical questions to be answered.

Engineered human osteoarthritic cartilage organoids

The availability of human cell-based models capturing molecular processes of cartilage degeneration can facilitate development of disease-modifying therapies for osteoarthritis [1], a currently unmet clinical need. Here, by imposing specific inflammatory challenges upon mesenchymal stromal cells at a defined stage of chondrogenesis, we engineered a human organotypic model which recapitulates main OA pathological traits such as chondrocyte hypertrophy, cartilage matrix mineralization, enhanced catabolism and mechanical stiffening. To exemplify the utility of the model, we exposed the engineered OA cartilage organoids to factors known to attenuate pathological features, including IL-1Ra, and carried out mass spectrometry-based proteomics. We identified that IL-1Ra strongly reduced production of the transcription factor CCAAT/enhancer-binding protein beta [2] and demonstrated that inhibition of the C/EBPβ-activating kinases could revert the degradative processes. Human OA cartilage organoids thus represent a relevant tool towards the discovery of new molecular drivers of cartilage degeneration and the assessment of therapeutics targeting associated pathways.

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.

Gelatin/O-carboxymethyl chitosan injectable self-healing hydrogels for ibuprofen and naproxen dual release

Recently, a significantly greater clinical benefit has been reported with a combination of glucosamine sulfate and nonsteroidal anti-inflammatory drugs (NSAIDs) compared to either treatment alone for the growing osteoarthritis (OA) disease. So, this study introduces hydrogels using O-carboxymethyl chitosan (O-CMC, structurally akin glucosamine glycan), and Gelatin type A (GA) in a 1:2 ratio with β-glycerophosphate (βGPh) at varying percentages (5 %, 12.5 %, and 15 %). We show that hydrogel properties, adaptable for drug delivery or tissue engineering, can be fine-tuned based on OCMC:βGPh ratio. CMC/GA/βGPh-12.5 exhibited a swelling rate of 189 %, compressive stress of 164 kPa, and compressive modulus of 3.4 kPa. The self-healing hydrogel also exhibited excellent injectability through a 21-gauge needle, requiring only 5 N of force. Ibuprofen and Naproxen release from CMC/GA/βGPh-12.5 and CMC/GA/βGPh-15 of designed dimensions (bi-layer structures of different diameter and height) were measured, and drug release kinetics were estimated using mathematical equations (MATLAB and polyfit program). CMC/GA/βGPh-12.5 demonstrated significant antibacterial effects against E. coli and S. aureus, a high cell survival rate of 89 % against L929 fibroblasts, and strong cell adhesion, all indicating biocompatibility. These findings underscore potential of these hydrogels as promising candidates for treating inflammatory diseases such as osteoarthritis.

Immunomodulatory Strategies for Cartilage Regeneration in Osteoarthritis

Osteoarthritis (OA) is the most prevalent musculoskeletal disorder and a leading cause of disability globally. Although many efforts have been made to treat this condition, current tissue engineering (TE) and regenerative medicine strategies fail to address the inflammatory tissue environment that leads to the rapid progression of the disease and prevents cartilage tissue formation. First, this review addresses in detail the current anti-inflammatory therapies for OA with a special emphasis on pharmacological approaches, gene therapy, and mesenchymal stromal cell (MSC) intra-articular administration, and discusses the reasons behind the limited clinical success of these approaches at enabling cartilage regeneration. Then, we analyze the state-of-the-art TE strategies and how they can be improved by incorporating immunomodulatory capabilities such as the optimization of biomaterial composition, porosity and geometry, and the loading of anti-inflammatory molecules within an engineered structure. Finally, the review discusses the future directions for the new generation of TE strategies for OA treatment, specifically focusing on the spatiotemporal modulation of anti-inflammatory agent presentation to allow for tailored patient-specific therapies. Impact statement Osteoarthritis (OA) is a prevalent and debilitating musculoskeletal disorder affecting millions worldwide. Despite significant advancements in regenerative medicine and tissue engineering (TE), mitigating inflammation while simultaneously promoting cartilage tissue regeneration in OA remains elusive. In this review article, we discuss current anti-inflammatory therapies and explore their potential synergy with cutting-edge cartilage TE strategies, with a special focus on novel spatiotemporal and patient-specific anti-inflammatory strategies.

A New Method for Creating Impact-Induced Intra-Articular Fractures in a Rabbit Model Induces Severe Post-Traumatic Osteoarthritis

OBJECTIVES

The objective of this work was to develop a model of intra-articular fracture (IAF) in a rabbit and document the speed and severity of degenerative joint changes after fracture fixation.

METHODS

With Institutional Animal Care & Use Committee approval, impact-induced IAFs were created in the distal tibia of 16 New Zealand White rabbits. Fractures were fixed with a plate and screws. Pain and function were monitored at regular postoperative intervals with limb loading analysis. Twelve or 26 weeks after fracture, animals were euthanized for histological assessment of cartilage degeneration and micro-computed tomography analysis of bone histomorphometry.

RESULTS

Eleven animals successfully completed the study. Maximum foot force in the fractured limb was 41% ± 21% lower than preoperative values ( P = 0.006) 12 weeks after fracture and remained 25% ± 13% lower ( P = 0.081) after 26 weeks. Cortical bone mineral density in micro-computed tomography images was 34% ± 13% lower 12 weeks after fracture ( P < 0.001) and remained (42% ± 8%) lower 26 weeks after fracture ( P < 0.001). Twelve weeks after fracture, Mankin scores of cartilage degeneration were significantly higher in the medial talus ( P = 0.007), lateral talus ( P < 0.001), medial tibia ( P = 0.017), and lateral tibia ( P = 0.002) of the fractured limb compared with the uninjured contralateral limb. Average Mankin scores in the talus increased from 12 to 26 weeks (5.9 ± 0.9 to 9.4 ± 0.4; P < 0.001 lateral; 5.4 ± 1.8 to 7.8 ± 2.0; P = 0.043 medial), indicating substantial and progressive joint degeneration.

CONCLUSIONS

The ankle joint of the New Zealand White rabbit provides the smallest available model of impact-induced IAF that can be treated with clinically relevant techniques and replicates key features of healing and degeneration found in human patients.

Effect of anti-inflammatory treatments on patient outcomes and concentrations of inflammatory modulators in the post-surgical and post-traumatic tibiofemoral joint setting: a narrative review

Background and Objective

There are several anti-inflammatory therapeutic options that can be used in the context of post-surgical and post-traumatic knee settings. Each of these options carries with it certain benefits, as well as potential issues depending on the duration and administration of each therapy. An understanding of how these anti-inflammatory drugs modulate various biomarkers of inflammation is also necessary in understanding how they can affect patient and objective outcomes following acute knee injury or surgery. This review covers the many traditional therapeutic options that have been used in treating knee injuries, as well as some natural therapeutics that have shown anti-inflammatory properties.

Methods

A current review of the literature was conducted and synthesized into this narrative review.

Key Content and Findings

Many traditional anti-inflammatory therapeutics have been shown to be beneficial in both post-traumatic and post-surgical tibiofemoral joint settings at reducing inflammation and improving patient outcomes. However, many of these treatments have risks associated with them, which becomes problematic with prolonged, repeated administration. Natural anti-inflammatory compounds may also have some benefit as adjunctive treatment options in these settings.

Conclusions

There are multiple different therapeutic options that can be used in acute knee settings, but the specific mechanism of injury or surgical context should be weighed when determining the best clinical approach.

Effect of Targeted Cytokine Inhibition on Progression of Post-Traumatic Osteoarthritis Following Intra-Articular Fracture

Intra-articular fractures (IAF) result in significant and prolonged inflammation, increasing the chances of developing post-traumatic osteoarthritis (PTOA). Interleukin-one beta (IL-1β) and Tumor Necrosis Factor-alpha (TNF-α) are key inflammatory factors shown to be involved in osteochondral degradation following IAF. As such, use of targeted biologics such as Infliximab (INX), a TNF-α inhibitor, and Anakinra (ANR), an interleukin-one (IL-1) receptor antagonist (IL1RA), may protect against PTOA by damping the inflammatory response to IAF and reducing osteochondral degradation. To test this hypothesis, IAFs were induced in the hindlimb knee joints of rats treated with INX at 10 mg/kg/day, ANR at 100 g/kg/day, or saline (vehicle control) by subcutaneous infusion for a period of two weeks and healing was evaluated at 8-weeks post injury. Serum and synovial fluid (SF) were analyzed for soluble factors. In-vivo microcomputed tomography (µCT) scans assessed bone mineral density and bone morphometry measurements. Cationic CA4+ agent assessed articular cartilage composition via ex vivo µCT. Scoring according to the Osteoarthritis Research Society International (OARSI) guidelines was performed on stained histologic tibia sections at the 56-day endpoint on a 0-6 scale. Systemically, ANR reduced many pro-inflammatory cytokines and reduced osteochondral degradation markers Cross Linked C-Telopeptide Of Type II (CTXII, p < 0.05) and tartrate-resistant acid phosphatase (TRAP, p < 0.05). ANR treatment resulted in increased chemokines; macrophage-chemotractant protein-1 (MCP-1), MPC-3, macrophage inhibitory protein 2 (MIP2) with a concomitant decrease in proinflammatory interleukin-17A (IL17A) at 14 days post-injury within the SF. Microcomputed tomography (µCT) at 56 days post-injury revealed ANR Treatment decreased epiphyseal degree of anisotropy (DA) (p < 0.05) relative to saline. No differences were found with OARSI scoring but contrast-enhanced µCT revealed a reduction in glycosaminoglycan content with ANR treatment. These findings suggest targeted cytokine inhibition, specifically IL-1 signaling, as a monotherapy has minimal utility for improving IAF healing outcomes but may have utility for promoting a more permissive inflammatory environment that would allow more potent disease modifying osteoarthritis drugs to mitigate the progression of PTOA after IAF.

Sustained intra-cartilage delivery of interleukin-1 receptor antagonist using cationic peptide and protein-based carriers

OBJECTIVE

Blocking the interleukin-1 (IL-1) catabolic cascade following joint trauma can be achieved using its receptor antagonist, IL-1Ra. However, its clinical translation for osteoarthritis therapy has been unsuccessful due to its rapid joint clearance and lack of targeting and penetration into deep cartilage layers at therapeutic concentrations. Here, we target the high negative charge of cartilage aggrecan-glycosaminoglycans (GAGs) by attaching cationic carriers to IL-1Ra. IL-1Ra was conjugated to the cartilage targeting glycoprotein, Avidin, and a short length optimally charged cationic peptide carrier (CPC+14). It is hypothesized that electro-diffusive transport and binding properties of IL-1Ra-Avidin and IL-1Ra-CPC+14 will create intra-cartilage depots of IL-1Ra, resulting in long-term suppression of IL-1 catabolism with only a single administration.

DESIGN

IL-1Ra was conjugated to Avidin or CPC+14 using site specific maleimide linkers, and confirmed using gel electrophoresis, high-performance liquid chromatography (HPLC), and mass spectrometry. Intra-cartilage transport and retention of conjugates was compared with native IL-1Ra. Attenuation of IL-1 catabolic signaling with one-time dose of IL-1Ra-CPC+14 and IL-1Ra-Avidin was assessed over 16 days using IL-1α challenged bovine cartilage and compared with unmodified IL-1Ra.

RESULTS

Positively charged IL-1Ra penetrated through the full-thickness of cartilage, creating a drug depot. A single dose of unmodified IL-1Ra was not sufficient to attenuate IL-1-induced cartilage deterioration over 16 days. However, when delivered using Avidin, and to a greater extent CPC+14, IL-1Ra significantly suppressed cytokine induced GAG loss and nitrite release while improving cell metabolism and viability.

CONCLUSION

Charge-based cartilage targeting drug delivery systems hold promise as they can enable long-term therapeutic benefit with only a single dose.

Posttraumatic osteoarthritis: from basic science to clinical implications

Posttraumatic osteoarthritis (PTOA) is a subset of osteoarthritis that occurs after joint injury and is associated with degradation of articular cartilage and subchondral bone. As compared with primary osteoarthritis, PTOA occurs in a time window initiated by a traumatic event resulting in damage to layers of joint structure and alterations in joint shape. As techniques in open reduction and internal fixation continue to mature, our success in preventing posttraumatic osteoarthritis has not kept pace. Advances in research in the subchondral bone, inflammatory response, and joint mechanics continue to open our understanding of this posttraumatic process. In addition, there are possibilities emerging as biological agents to therapeutically alter the progression of PTOA.

Recombinant protein drugs-based intra articular drug delivery systems for osteoarthritis therapy

Osteoarthritis (OA) is the most prevalent chronic degenerative joint disease. It weakens the motor function of patients and imposes a significant economic burden on society. The current medications commonly used in clinical practice do not meet the need for the treatment of OA. Recombinant protein drugs (RPDs) can treat OA by inhibiting inflammatory pathways, regulating catabolism/anabolism, and promoting cartilage repair, thereby showing promise as disease-modifying OA drugs (DMOADs). However, the rapid clearance and short half-life of them in the articular cavity limit their clinical translation. Therefore, the reliable drug delivery systems for extending drug treatment are necessary for the further development. This review introduces RPDs with therapeutic potential for OA, and summarizes their research progress on related drug delivery systems, and make proper discussion on the certain keys for optimal development of this area.

Protein-engineered biomaterials for cartilage therapeutics and repair

Cartilage degeneration and injury are major causes of pain and disability that effect millions, and yet treatment options for conditions like osteoarthritis (OA) continue to be mainly palliative or involve complete replacement of injured joints. Several biomaterial strategies have been explored to address cartilage repair either by the delivery of therapeutics or as support for tissue repair, however the complex structure of cartilage tissue, its mechanical needs, and lack of regenerative capacity have hindered this goal. Recent advances in synthetic biology have opened new possibilities for engineered proteins to address these unique needs. Engineered protein and peptide-based materials benefit from inherent biocompatibility and nearly unlimited tunability as they utilize the body's natural building blocks to fabricate a variety of supramolecular structures. The pathophysiology and needs of OA cartilage are presented here, along with an overview of the current state of the art and next steps for protein-engineered repair strategies for cartilage.

Human Mesenchymal Stem Cell-Derived Miniature Joint System for Disease Modeling and Drug Testing

Diseases of the knee joint such as osteoarthritis (OA) affect all joint elements. An in vitro human cell-derived microphysiological system capable of simulating intraarticular tissue crosstalk is desirable for studying etiologies/pathogenesis of joint diseases and testing potential therapeutics. Herein, a human mesenchymal stem cell-derived miniature joint system (miniJoint) is generated, in which engineered osteochondral complex, synovial-like fibrous tissue, and adipose tissue are integrated into a microfluidics-enabled bioreactor. This novel design facilitates different tissues communicating while still maintaining their respective phenotypes. The miniJoint exhibits physiologically relevant changes when exposed to interleukin-1β mediated inflammation, which are similar to observations in joint diseases in humans. The potential of the miniJoint in predicting in vivo efficacy of drug treatment is confirmed by testing the "therapeutic effect" of the nonsteroidal anti-inflammatory drug, naproxen, as well as four other potential disease-modifying OA drugs. The data demonstrate that the miniJoint recapitulates complex tissue interactions, thus providing a robust organ chip model for the study of joint pathology and the development of novel therapeutic interventions.

Assessment of joint pharmacokinetics and consequences for the intraarticular delivery of biologics

Intraarticular (IA) injections provide the opportunity to deliver biologics directly to their site of action for a local and efficient treatment of osteoarthritis. However, the synovial joint is a challenging site of administration since the drug is rapidly eliminated across the synovial membrane and has limited distribution into cartilage, resulting in unsatisfactory therapeutic efficacy. In order to rationally develop appropriate drug delivery systems, it is essential to thoroughly understand the unique biopharmaceutical environments and kinetics in the joint to adequately simulate them in relevant experimental models. This review presents a detailed view on articular kinetics and drug-tissue interplay of IA administered drugs and summarizes how these can be translated into reasonable formulation strategies by identification of key factors through which the joint residence time can be prolonged and specific structures can be targeted. In this way, pros and cons of the delivery approaches for biologics will be evaluated and the extent to which biorelevant models are applicable to gain mechanistic insights and ameliorate formulation design is discussed.

Combination of Lidocaine and IL-1Ra Is Effective at Reducing Degradation of Porcine Cartilage Explants

BACKGROUND

Posttraumatic inflammation after joint injury, ranging from sprains to articular fracture, contributes to the development of arthritis, and the administration of interleukin 1 (IL-1) receptor antagonist (IL-1Ra) is a potential intervention to mitigate this response. Although IL-1Ra mitigates cartilage degenerative changes induced by IL-1, lidocaine is used for local pain management in acute joint injury. Intra-articular delivery of both drugs in combination would be a novel and possibly disease-modifying treatment. However, it is not known whether the interaction with lidocaine at clinical concentrations (1%) would alter the efficacy of IL-1Ra to protect cartilage from the catabolic effects of IL-1.

HYPOTHESIS

Treatment of articular cartilage with IL-1Ra in combination with a clinically relevant concentration of lidocaine (1%) will inhibit the catabolic effects of IL-1α in a manner similar to treatment with IL-1Ra alone.

STUDY DESIGN

Controlled laboratory study.

METHODS

Fresh porcine cartilage explants were harvested, challenged with IL-1α, and incubated for 72 hours with IL-1Ra or a combination of IL-1Ra and lidocaine. The primary outcome was total sulfated glycosaminoglycan (sGAG) release. Additional experiments assessed the effect of storage temperature and premixing of IL-1Ra and lidocaine on sGAG release. All explants were histologically assessed for cartilage degradation using a modified Mankin grading scale.

RESULTS

The combination of IL-1Ra and lidocaine, premixed at various time points and stored at room temperature or 4°C, was as effective as IL-1Ra alone at inhibiting IL-1α-mediated sGAG release. Mankin histopathology scores supported these findings.

CONCLUSION

Our hypothesis was supported, and results indicated that the combination of IL-1Ra and lidocaine was as efficacious as IL-1Ra treatment alone in acutely mitigating biological cartilage injury due to IL-1α in an explant model.

CLINICAL SIGNIFICANCE

The combination of IL-1Ra and lidocaine is stable when reagents are stored in advance of administration at varying temperatures, providing clinically relevant information about storage of medications. The ability to premix and store this drug combination for intra-articular delivery may provide a novel treatment after joint injury to provide pain relief and block inflammation-induced catabolism of joint tissues.

Synthetic gene circuits for preventing disruption of the circadian clock due to interleukin-1-induced inflammation

The circadian clock regulates tissue homeostasis through temporal control of tissue-specific clock-controlled genes. In articular cartilage, disruptions in the circadian clock are linked to a procatabolic state. In the presence of inflammation, the cartilage circadian clock is disrupted, which further contributes to the pathogenesis of diseases such as osteoarthritis. Using synthetic biology and tissue engineering, we developed and tested genetically engineered cartilage from murine induced pluripotent stem cells (miPSCs) capable of preserving the circadian clock in the presence of inflammation. We found that circadian rhythms arise following chondrogenic differentiation of miPSCs. Exposure of tissue-engineered cartilage to the inflammatory cytokine interleukin-1 (IL-1) disrupted circadian rhythms and degraded the cartilage matrix. All three inflammation-resistant approaches showed protection against IL-1-induced degradation and loss of circadian rhythms. These synthetic gene circuits reveal a unique approach to support daily rhythms in cartilage and provide a strategy for creating cell-based therapies to preserve the circadian clock.

Intra-articular Administration of Triamcinolone Acetonide in a Murine Cartilage Defect Model Reduces Inflammation but Inhibits Endogenous Cartilage Repair

BACKGROUND

Cartilage defects result in joint inflammation. The presence of proinflammatory factors has been described to negatively affect cartilage formation.

PURPOSE

To evaluate the effect and timing of administration of triamcinolone acetonide (TAA), an anti-inflammatory drug, on cartilage repair using a mouse model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A full-thickness cartilage defect was created in the trochlear groove of 10-week-old male DBA/1 mice (N = 80). Mice received an intra-articular injection of TAA or saline on day 1 or 7 after induction of the defect. Mice were euthanized on days 10 and 28 for histological evaluation of cartilage defect repair, synovial inflammation, and synovial membrane thickness.

RESULTS

Mice injected with TAA had significantly less synovial inflammation at day 10 than saline-injected mice independent of the time of administration. At day 28, the levels of synovitis dropped toward healthy levels; nevertheless, the synovial membrane was thinner in TAA- than in saline-injected mice, reaching statistical significance in animals injected on day 1 (70.1 ± 31.9 µm vs 111.9 ± 30.9 µm, respectively; P = .01) but not in animals injected on day 7 (68.2 ± 21.86 µm vs 90.2 ± 21.29 µm, respectively; P = .26). A thinner synovial membrane was moderately associated with less filling of the defect after 10 and 28 days (r = 0.42, P = .02; r = 0.47, P = .01, respectively). Whereas 10 days after surgery there was no difference in the area of the defect filled and the cell density in the defect area between saline- and TAA-injected knees, filling of the defect at day 28 was lower in TAA- than in saline-injected knees for both injection time points (day 1 injection, P = .04; day 7 injection, P = .01). Moreover, there was less collagen type 2 staining in the filled defect area in TAA- than in saline-injected knees after 28 days, reaching statistical significance in day 1-injected knees (2.6% vs 18.5%, respectively; P = .01) but not in day 7-injected knees (7.4% vs 15.8%, respectively; P = .27).

CONCLUSION

Intra-articular injection of TAA reduced synovial inflammation but negatively affected cartilage repair. This implies that inhibition of inflammation may inhibit cartilage repair or that TAA has a direct negative effect on cartilage formation.

CLINICAL RELEVANCE

Our findings show that TAA can inhibit cartilage defect repair. Therefore, we suggest not using TAA to reduce inflammation in a cartilage repair setting.

Efficacy and Safety of FX201, a Novel Intra-Articular IL-1Ra Gene Therapy for Osteoarthritis Treatment, in a Rat Model

Osteoarthritis (OA) is a disabling, degenerative disease characterized by progressive cartilage and bone damage. There remains a need for local therapies that, following a single injection, can provide long-term pain relief and functional improvement and potentially delay disease progression. FX201 is a novel, intra-articular (IA), interleukin-1 receptor antagonist (IL-1Ra) gene therapy in development for the treatment of OA. In this study, we assessed the efficacy, biodistribution, and safety of helper-dependent adenovirus (HDAd)-ratIL-1Ra, the rat surrogate of FX201, and the biodistribution of FX201, in the anterior cruciate ligament transection (ACLT) rat OA model. A single IA injection of HDAd-ratIL-1Ra administered 7 days post-ACLT mitigated OA-related changes to cartilage, bone, and the synovial membrane at week 12 following surgery. Furthermore, FX201 and HDAd-ratIL-1Ra persisted for at least 92 days in the injected joint and proximal tissues with minimal evidence of vector spreading peripherally. Finally, HDAd-ratIL-1Ra showed a favorable safety profile without any local or systemic adverse effects. In conclusion, HDAd-ratIL-1Ra demonstrated local therapeutic and disease-modifying effects and was well tolerated, supporting further clinical development of FX201.

Intra-articular drug delivery systems for osteoarthritis therapy: shifting from sustained release to enhancing penetration into cartilage

Osteoarthritis (OA) is a progressive chronic inflammation that leads to cartilage degeneration. OA Patients are commonly given pharmacological treatment, but the available treatments are not sufficiently effective. The development of sustained-release drug delivery systems (DDSs) for OA may be an attractive strategy to prevent rapid drug clearance and improve the half-life of a drug at the joint cavity. Such delivery systems will improve the therapeutic effects of anti-inflammatory effects in the joint cavity. Whereas, for disease-modifying OA drugs (DMOADs) which target chondrocytes or act on mesenchymal stem cells (MSCs), the cartilage-permeable DDSs are required to maximize their efficacy. This review provides an overview of joint structure in healthy and pathological conditions, introduces the advances of the sustained-release DDSs and the permeable DDSs, and discusses the rational design of the permeable DDSs for OA treatment. We hope that the ideas generated in this review will promote the development of effective OA drugs in the future.

Intra-Articular Synovial Fluid With Hematoma After Ankle Fracture Promotes Cartilage Damage In Vitro Partially Attenuated by Anti-Inflammatory Agents

BACKGROUND

Intra-articular ankle fracture (IAF) causes posttraumatic osteoarthritis (PTOA), but the exact mechanism is unknown. Proinflammatory mediators have been shown to be present in the synovial fluid fracture hematoma (SFFH) but have not been linked to cartilage damage. The purpose of this study was to determine if the SFFH causes cartilage damage and whether this damage can be attenuated by commercially available therapeutic agents.

METHODS

Synovial fluid was obtained from 54 IAFs and cultured with cartilage discs from the dome of fresh allograft human tali and randomly assigned to one of the following groups: (A) control-media only, (B) SFFH from days 0 to 2 after fracture, (C) SFFH from days 3 to 9, (D) SFFH from days 10 to 14, (E) group B + interleukin 1 receptor antagonist (IL-1Ra), and (F) group B + doxycycline. The cartilage discs underwent histological evaluation for cell survival and cartilage matrix components. The spent media were analyzed for inflammatory mediators.

RESULTS

Cartilage discs cultured with SFFH in groups B, C, and D demonstrated significantly increased production of cytokines, metalloproteinases (MMPs), and extracellular matrix breakdown products. Safranin O staining was significantly decreased in group B. The negative effects on cartilage were partially attenuated with the addition of either IL-1RA or doxycycline. There was no difference in chondrocyte survival among the groups.

CONCLUSION

Exposure of uninjured cartilage to IAF SFFH caused activation of cartilage damage pathways evident through cartilage disc secretion of inflammatory cytokines, MMPs, and cartilage matrix fragments. The addition of IL-1Ra or doxycycline to SFFH culture partially attenuated this response.

CLINICAL RELEVANCE

IAFs create an adverse intra-articular environment consisting of significantly increased levels of inflammatory cytokines and MMPs able to damage cartilage throughout the joint. These data suggest that the acute addition of specific inflammatory inhibitors may decrease the levels of these proinflammatory mediators.

In vivo methodologies to assist preclinical development of topical fixed-dose combinations for pain management

The combination in a fixed dose of two or more active pharmaceutical ingredients in the same pharmaceutical dosage form is an approach that has been used successfully in the treatment of several pathologies, including pain. In the preclinical development of a topical fixed-dose combination product with analgesic and anti-inflammatory activities for pain management, the main objective is to establish the nature of the interaction between the different active pharmaceutical ingredients while obtaining data on the medicinal product safety and efficacy. Despite the improvement of in vitro assays, animal models remain a fundamental strategy to characterise the interaction, efficacy and safety of active pharmaceutical ingredients at the physiological level, which cannot be reached by in vitro assays. Thus, the main goal of this review is to systematise the available animal models to evaluate the efficacy and safety of a new fixed-dose combination product for topical administration indicated for pain management. Particular emphasis is given to animal models that are accepted for regulatory purposes.

Injectable recombinant block polymer gel for sustained delivery of therapeutic protein in post traumatic osteoarthritis

Protein-based biomaterials offer several advantages over synthetic materials, owing to their unique stimuli-responsive properties, biocompatibility and modular nature. Here, we demonstrate that E5C, a recombinant protein block polymer, consisting of five repeats of elastin like polypeptide (E) and a coiled-coil domain of cartilage oligomeric matrix protein (C), is capable of forming a porous networked gel at physiological temperature, making it an excellent candidate for injectable biomaterials. Combination of E5C with Atsttrin, a chondroprotective engineered derivative of anti-inflammatory growth factor progranulin, provides a unique biochemical and biomechanical environment to protect against post-traumatic osteoarthritis (PTOA) onset and progression. E5C gel was demonstrated to provide prolonged release of Atsttrin and inhibit chondrocyte catabolism while facilitating anabolic signaling in vitro. We also provide in vivo evidence that prophylactic and therapeutic application of Atsttrin-loaded E5C gels protected against PTOA onset and progression in a rabbit anterior cruciate ligament transection model. Collectively, we have developed a unique protein-based gel capable of minimally invasive, sustained delivery of prospective therapeutics, particularly the progranulin-derivative Atsttrin, for therapeutic application in OA.

Monocytes, Macrophages, and Their Potential Niches in Synovial Joints - Therapeutic Targets in Post-Traumatic Osteoarthritis?

Synovial joints are complex structures that enable normal locomotion. Following injury, they undergo a series of changes, including a prevalent inflammatory response. This increases the risk for development of osteoarthritis (OA), the most common joint disorder. In healthy joints, macrophages are the predominant immune cells. They regulate bone turnover, constantly scavenge debris from the joint cavity and, together with synovial fibroblasts, form a protective barrier. Macrophages thus work in concert with the non-hematopoietic stroma. In turn, the stroma provides a scaffold as well as molecular signals for macrophage survival and functional imprinting: “a macrophage niche”. These intricate cellular interactions are susceptible to perturbations like those induced by joint injury. With this review, we explore how the concepts of local tissue niches apply to synovial joints. We introduce the joint micro-anatomy and cellular players, and discuss their potential interactions in healthy joints, with an emphasis on molecular cues underlying their crosstalk and relevance to joint functionality. We then consider how these interactions are perturbed by joint injury and how they may contribute to OA pathogenesis. We conclude by discussing how understanding these changes might help identify novel therapeutic avenues with the potential of restoring joint function and reducing post-traumatic OA risk.

Novel Protein Therapeutics Created Using the Elastin-Like Polypeptide Platform

Elastin-like polypeptides (ELPs) are bioengineered proteins that have a unique physical property, a thermally triggered inverse phase transition, that can be exploited for drug delivery. ELP-fusion proteins can be used as soluble biologics, thermally targeted drug carriers, self-assembling nanoparticles, and slow-release drug depots. Because of their unique physical characteristics and versatility for delivery of nearly any type of therapeutic, ELP-based drug delivery systems represent a promising platform for biologics development.

Immunoengineering the next generation of arthritis therapies

Immunoengineering continues to revolutionize healthcare, generating new approaches for treating previously intractable diseases, particularly in regard to cancer immunotherapy. In joint diseases, such as osteoarthritis (OA) and rheumatoid arthritis (RA), biomaterials and anti-cytokine treatments have previously been at that forefront of therapeutic innovation. However, while many of the existing anti-cytokine treatments are successful for a subset of patients, these treatments can also pose severe risks, adverse events and off-target effects due to continuous delivery at high dosages or a lack of disease-specific targets. The inadequacy of these current treatments has motivated the development of new immunoengineering strategies that offer safer and more efficacious alternative therapies through the precise and controlled targeting of specific upstream immune responses, including direct and mechanistically-driven immunoengineering approaches. Advances in the understanding of the immunomodulatory pathways involved in musculoskeletal disease, in combination with the growing emphasis on personalized medicine, stress the need for carefully considering the delivery strategies and therapeutic targets when designing therapeutics to better treat RA and OA. Here, we focus on recent advances in biomaterial and cell-based immunomodulation, in combination with genetic engineering, for therapeutic applications in joint diseases. The application of immunoengineering principles to the study of joint disease will not only help to elucidate the mechanisms of disease pathogenesis but will also generate novel disease-specific therapeutics by harnessing cellular and biomaterial responses. STATEMENT OF SIGNIFICANCE: It is now apparent that joint diseases such as osteoarthritis and rheumatoid arthritis involve the immune system at both local (i.e., within the joint) and systemic levels. In this regard, targeting the immune system using both biomaterial-based or cellular approaches may generate new joint-specific treatment strategies that are well-controlled, safe, and efficacious. In this review, we focus on recent advances in immunoengineering that leverage biomaterials and/or genetically engineered cells for therapeutic applications in joint diseases. The application of such approaches, especially synergistic strategies that target multiple immunoregulatory pathways, has the potential to revolutionize our understanding, treatment, and prevention of joint diseases.

Mitochondria in Injury, Inflammation and Disease of Articular Skeletal Joints

Inflammation is an important biological response to tissue damage caused by injury, with a crucial role in initiating and controlling the healing process. However, dysregulation of the process can also be a major contributor to tissue damage. Related to this, although mitochondria are typically thought of in terms of energy production, it has recently become clear that these important organelles also orchestrate the inflammatory response via multiple mechanisms. Dysregulated inflammation is a well-recognised problem in skeletal joint diseases, such as rheumatoid arthritis. Interestingly osteoarthritis (OA), despite traditionally being known as a ‘non-inflammatory arthritis’, now appears to involve an element of chronic inflammation. OA is considered an umbrella term for a family of diseases stemming from a range of aetiologies (age, obesity etc.), but all with a common presentation. One particular OA sub-set called Post-Traumatic OA (PTOA) results from acute mechanical injury to the joint. Whether the initial mechanical tissue damage, or the subsequent inflammatory response drives disease, is currently unclear. In the former case; mechanobiological properties of cells/tissues in the joint are a crucial consideration. Many such cell-types have been shown to be exquisitely sensitive to their mechanical environment, which can alter their mitochondrial and cellular function. For example, in bone and cartilage cells fluid-flow induced shear stresses can modulate cytoskeletal dynamics and gene expression profiles. More recently, immune cells were shown to be highly sensitive to hydrostatic pressure. In each of these cases mitochondria were central to these responses. In terms of acute inflammation, mitochondria may have a pivotal role in linking joint tissue injury with chronic disease. These processes could involve the immune cells recruited to the joint, native/resident joint cells that have been damaged, or both. Taken together, these observations suggest that mitochondria are likely to play an important role in linking acute joint tissue injury, inflammation, and long-term chronic joint degeneration - and that the process involves mechanobiological factors. In this review, we will explore the links between mechanobiology, mitochondrial function, inflammation/tissue-damage in joint injury and disease. We will also explore some emerging mitochondrial therapeutics and their potential for application in PTOA.

Degenerative joint changes following intra-articular fracture are more severe in mice with T cell deficiency

The inflammatory response to joint injury, specifically intra-articular fracture, has been implicated in posttraumatic arthritis development. However, the role of T cells in regulating the development of posttraumatic arthritis is unclear. We hypothesized that the absence of T cells would lead to less severe posttraumatic arthritis following intra-articular fracture. T cell-deficient, athymic nude, and wild-type C57BL/6NJ mice were assessed at 8 weeks following closed articular fracture. Joints were assessed using histologic scores of arthritis, synovitis, and bone morphology via micro computed tomography. Cells were profiled in whole blood via flow cytometry, and plasma and synovial fluid derived cytokines were quantified by multiplex analysis. Compared to C57BL/6NJ mice, nude mice had significantly greater histologic evidence of arthritis and synovitis. Whole blood immune cell profiling revealed a lower percentage of dendritic cells but increased natural killer (NK) cells in nude mice. Concurrently, nude mice had significantly higher levels of NK cells in synovial tissue. Concentrations of plasma interleukin 1β (IL-1β) and tumor necrosis factor α, and synovial fluid IL-12, IL-17, and IL-6 in both knees were greater in nude mice. Outcomes of this study suggest that T cells may play a protective regulatory role against the development of posttraumatic arthritis. Clinical significance: Lack of functional T cells exacerbated the development of posttraumatic arthritis following intra-articular fracture suggesting that critical regulators of the immune responses, contained within the T cell population, are required for protection. Future research identifying the specific T cell subsets responsible for modulating disease immunopathogenesis will lead to new therapeutic targets to mitigate posttraumatic arthritis.

Anti-Inflammatory Therapeutic Approaches to Prevent or Delay Post-Traumatic Osteoarthritis (PTOA) of the Knee Joint with a Focus on Sustained Delivery Approaches

Inflammation plays a central role in the pathogenesis of knee PTOA after knee trauma. While a comprehensive therapy capable of preventing or delaying post-traumatic osteoarthritis (PTOA) progression after knee joint injury does not yet clinically exist, current literature suggests that certain aspects of early post-traumatic pathology of the knee joint may be prevented or delayed by anti-inflammatory therapeutic interventions. We discuss multifaceted therapeutic approaches that may be capable of effectively reducing the continuous cycle of inflammation and concomitant processes that lead to cartilage degradation as well as those that can simultaneously promote intrinsic repair processes. Within this context, we focus on early disease prevention, the optimal timeframe of treatment and possible long-lasting sustained delivery local modes of treatments that could prevent knee joint-associated PTOA symptoms. Specifically, we identify anti-inflammatory candidates that are not only anti-inflammatory but also anti-degenerative, anti-apoptotic and pro-regenerative.

Immune cell profiling in the joint following human and murine articular fracture

OBJECTIVE

Human and in vivo animal research implicates inflammation following articular fracture as contributing to post-traumatic arthritis. However, relevant immune cell subsets present following injury are currently undefined. Immunophenotyping human and murine synovial fluid may help to identify immune cell populations that play key roles in the response to articular fracture.

METHODS

Immunophenotyping by polychromatic flow cytometry was performed on human and mouse synovial fluid following articular fracture. Specimens were collected in patients with closed ankle fracture at the time of surgical fixation and from C57BL/6 mice with closed articular knee fracture. Immune cells were collected from injured and uninjured joints in mice via a novel cell isolation method. Whole blood samples were also collected. Immunohistochemistry (IHC) was performed on mouse synovial tissue to assess for macrophages and T cells.

RESULTS

Following intra-articular fracture, the prominent human synovial fluid immune cell subset was CD3+ T cells, containing both CD4+ and CD8+ T cells. In mice, infiltration of CD45+ immune cells in synovial fluid of the fractured limb was dominated by CD19+ B cells and CD3+ T cells at 7 days after intra-articular fracture. We also detected adaptive immune cells, including macrophages, NK cells, dendritic cells and monocytes. Macrophage and T cell findings were supported by IHC of murine synovial tissue.

CONCLUSIONS

Determining specific cell populations that mediate the immune response is essential to elucidating the chain of events initiated after injury and may be an important step in identifying potential immune signatures predictive of PTA susceptibility or potential therapeutic targets.

Prevention of posttraumatic osteoarthritis at the time of injury: Where are we now, and where are we going?

This overview of progress made in preventing post-traumatic osteoarthritis (PTOA) was delivered in a workshop at the Orthopaedics Research Society Annual Conference in 2019. As joint trauma is a major risk factor for OA, defining the molecular changes within the joint at the time of injury may enable the targeting of biological processes to prevent later disease. Animal models have been used to test therapeutic targets to prevent PTOA. A review of drug treatments for PTOA in rodents and rabbits between 2016 and 2018 revealed 11 systemic interventions, 5 repeated intra-articular or topical interventions, and 5 short-term intra-articular interventions, which reduced total Osteoarthritis Research Society International scores by 30%-50%, 20%-70%, and 0%-40%, respectively. Standardized study design, reporting of effect size, and quality metrics, alongside a "whole joint" approach to assessing efficacy, would improve the translation of promising new drugs. A roadblock to translating preclinical discoveries has been the lack of guidelines on the design and conduct of human trials to prevent PTOA. An international workshop addressing this in 2016 considered inclusion criteria and study design, and advocated the use of experimental medicine studies to triage candidate treatments and the development of early biological and imaging biomarkers. Human trials for the prevention of PTOA have tested anakinra after anterior cruciate ligament rupture and dexamethasone after radiocarpal injury. PTOA offers a unique opportunity for defining early mechanisms of OA to target therapeutically. Progress in trial design and high-quality preclinical research, and allegiance with patients, regulatory bodies, and the pharmaceutical industry, will advance this field.

Overcoming negatively charged tissue barriers: Drug delivery using cationic peptides and proteins

Negatively charged tissues are ubiquitous in the human body and are associated with a number of common diseases yet remain an outstanding challenge for targeted drug delivery. While the anionic proteoglycans are critical for tissue structure and function, they make tissue matrix dense, conferring a high negative fixed charge density (FCD) that makes drug penetration through the tissue deep zones and drug delivery to resident cells extremely challenging. The high negative FCD of these tissues is now being utilized by taking advantage of electrostatic interactions to create positively charged multi-stage delivery methods that can sequentially penetrate through the full thickness of tissues, create a drug depot and target cells. After decades of work on attempting delivery using strong binding interactions, significant advances have recently been made using weak and reversible electrostatic interactions, a characteristic now considered essential to drug penetration and retention in negatively charged tissues. Here we discuss these advances using examples of negatively charged tissues (cartilage, meniscus, tendons and ligaments, nucleus pulposus, vitreous of eye, mucin, skin), and delve into how each of their structures, tissue matrix compositions and high negative FCDs create barriers to drug entry and explore how charge interactions are being used to overcome these barriers. We review work on tissue targeting cationic peptide and protein-based drug delivery, compare and contrast drug delivery designs, and also present examples of technologies that are entering clinical trials. We also present strategies on further enhancing drug retention within diseased tissues of lower FCD by using synergistic effects of short-range binding interactions like hydrophobic and H-bonds that stabilize long-range charge interactions. As electrostatic interactions are incorporated into design of drug delivery materials and used as a strategy to create properties that are reversible, tunable and dynamic, bio-electroceuticals are becoming an exciting new direction of research and clinical work.

Intra-articular depletion of macrophages increases acute synovitis and alters macrophage polarity in the injured mouse knee

OBJECTIVE

Acute synovial inflammation following joint trauma is associated with posttraumatic arthritis. Synovial macrophages have been implicated in degenerative changes. In this study, we sought to elucidate the role of intra-articular macrophages in the acute inflammatory response to fracture in the mouse knee.

METHOD

A closed articular fracture was induced in two models of synovial macrophage depletion: genetically-modified MaFIA mice administered AP20187 to induce programmed macrophage apoptosis, and wild-type C57BL/6 mice administered clodronate liposomes, both via intra-articular injection. Synovial inflammation, bone morphology, and levels of F4/80+ macrophages, NOS2+ M1 macrophages, and CD206+ M2 macrophages were quantified 7 days after fracture using histology and micro-computed tomography.

RESULTS

Intra-articular macrophage depletion with joint injury did not reduce acute synovitis or the number of synovial macrophages 7 days after fracture in either macrophage-depleted MaFIA mice or in clodronate-treated C57BL/6 mice. In macrophage-depleted MaFIA mice, macrophage polarity shifted to a dominance of M1 macrophages and a reduction of M2 macrophages in the synovial stroma, indicating a shift in M1/M2 macrophage ratio in the joint following injury. Interestingly, MaFIA mice depleted 2 days prior to fracture demonstrated increased synovitis (P = 0.003), reduced bone mineral density (P = 0.0004), higher levels of M1 macrophages (P = 0.013), and lower levels of M2 macrophages (not statistically significant, P=0.084) compared to control-treated MaFIA mice.

CONCLUSION

Our findings indicate that macrophages play a critical immunomodulatory role in the acute inflammatory response surrounding joint injury and suggest that inhibition of macrophage function can have prominent effects on joint inflammation and bone homeostasis after joint trauma.

Engineering the Architecture of Elastin-Like Polypeptides: From Unimers to Hierarchical Self-Assembly

Well-defined tunable nanostructures formed through the hierarchical self-assembly of peptide building blocks have drawn significant attention due to their potential applications in biomedical science. Artificial protein polymers derived from elastin-like polypeptides (ELPs), which are based on the repeating sequence of tropoelastin (the water-soluble precursor to elastin), provide a promising platform for creating nanostructures due to their biocompatibility, ease of synthesis, and customizable architecture. By designing the sequence and composition of ELPs at the gene level, their physicochemical properties can be controlled to a degree that is unmatched by synthetic polymers. A variety of ELP-based nanostructures are designed, inspired by the self-assembly of elastin and other proteins in biological systems. The choice of building blocks determines not only the physical properties of the nanostructures, but also their self-assembly into architectures ranging from spherical micelles to elongated nanofibers. This review focuses on the molecular determinants of ELP and ELP-hybrid self-assembly and formation of spherical, rod-like, worm-like, fibrillar, and vesicle architectures. A brief discussion of the potential biomedical applications of these supramolecular assemblies is also included.

Genetically Engineered Elastin-based Biomaterials for Biomedical Applications

Protein-based polymers are some of the most promising candidates for a new generation of innovative biomaterials as recent advances in genetic-engineering and biotechnological techniques mean that protein-based biomaterials can be designed and constructed with a higher degree of complexity and accuracy. Moreover, their sequences, which are derived from structural protein-based modules, can easily be modified to include bioactive motifs that improve their functions and material-host interactions, thereby satisfying fundamental biological requirements. The accuracy with which these advanced polypeptides can be produced, and their versatility, self-assembly behavior, stimuli-responsiveness and biocompatibility, means that they have attracted increasing attention for use in biomedical applications such as cell culture, tissue engineering, protein purification, surface engineering and controlled drug delivery. The biopolymers discussed in this review are elastin-derived protein-based polymers which are biologically inspired and biomimetic materials. This review will also focus on the design, synthesis and characterization of these genetically encoded polymers and their potential utility for controlled drug and gene delivery, as well as in tissue engineering and regenerative medicine.

A Synthetic Gene Circuit for Self-Regulating Delivery of Biologic Drugs in Engineered Tissues

IMPACT STATEMENT

We engineered a synthetic transcription system based on nuclear factor kappa-light-chain-enhancer of activated B cells signaling that can attenuate the effects of the inflammatory cytokine interleukin (IL)-1α in a self-regulating manner. This system responds in a time- and dose-dependent manner to rapidly produce therapeutic levels of IL-1 receptor antagonist (IL-1Ra). The use of lentiviral gene therapy allows this system to be utilized through different transduction methods and in different cell types for a variety of applications. Broadly, this approach may be applicable in developing autoregulated biologic systems for tissue engineering and drug delivery in a range of disease applications.

Conferring extracellular matrix affinity enhances local therapeutic efficacy of anti-TNF-α antibody in a murine model of rheumatoid arthritis

BACKGROUND

Although disease in a majority of rheumatoid arthritis (RA) patients is often initially limited to one or a few joints, currently approved medications including anti-tumor necrosis factor-α antibody (α-TNF) are injected systemically. Given that α-TNF systemic injection typically does not cure RA and involves risk of treatment-related adverse events, one possible approach to enhance therapeutic efficacy and reduce α-TNF systemic exposure is to retain the antibodies in arthritic joints after local administration. The aim of this study was to evaluate the approach of conferring extracellular matrix (ECM) binding affinity to α-TNF antibodies in a RA model.

METHODS

α-TNF was chemically conjugated with a promiscuous ECM-binding peptide derived from placenta growth factor 2 (PlGF-2_123-144). The binding activity of PlGF-2_123-144-conjugated α-TNF (PlGF-2_123-144-α-TNF) against ECM proteins was assessed by ELISA and by immunostaining on human cartilage specimens. The effect of conjugation on antibody function was assessed as a neutralizing activity against osteoclast differentiation. Retention at the injection site and therapeutic efficacy of PlGF-2_123-144-α-TNF were tested in a collagen antibody-induced arthritis (CAIA) model in the mouse.

RESULTS

PlGF-2_123-144 peptide conjugation conferred α-TNF with affinity to ECM proteins without impairment of antigen recognition. PlGF-2_123-144-α-TNF locally injected at a paw in the CAIA model was retained for at least 96 h at the injection site, whereas unmodified α-TNF was dispersed rapidly after injection. Local treatment with unmodified α-TNF did not suppress the arthritis score relative to isotype controls. By contrast, local administration of PlGF-2_123-144-α-TNF suppressed arthritis development almost completely in the treated paw even at a 1000× lower dose.

CONCLUSION

These data demonstrate that retention of α-TNF in arthritic joints can suppress arthritis development and enhance therapeutic efficacy. This simple bioengineering approach of ECM-binding peptide conjugation offers a powerful and clinically translational approach to treat RA.

Multi-arm Avidin nano-construct for intra-cartilage delivery of small molecule drugs

Targeted drug delivery to joint tissues like cartilage remains a challenge that has prevented clinical translation of promising osteoarthritis (OA) drugs. Local intra-articular (IA) injections of drugs suffer from rapid clearance from the joint space and slow diffusive transport through the dense, avascular cartilage matrix comprised of negatively charged glycosaminoglycans (GAGs). Here we apply drug carriers that leverage electrostatic interactions with the tissue's high negative fixed charge density (FCD) for delivering small molecule drugs to cartilage cell and matrix sites. We demonstrate that a multi-arm cationic nano-construct of Avidin (mAv) with 28 sites for covalent drug conjugation can rapidly penetrate through the full thickness of cartilage in high concentration and have long intra-cartilage residence time in both healthy and arthritic cartilage via weak-reversible binding with negatively charged aggrecans. mAv's intra-cartilage mean uptake was found to be 112× and 33× the equilibration bath concentration in healthy and arthritic (50% GAG depleted) cartilage, respectively. mAv was conjugated with Dexamethasone (mAv-Dex), a broad-spectrum glucocorticoid, using a combination of hydrolysable ester linkers derived from succinic anhydride (SA), 3,3-dimethylglutaric anhydride (GA) and phthalic anhydride (PA) in 2:1:1 M ratio that enabled 50% drug release within 38.5 h followed by sustained release in therapeutic doses over 2 weeks. A single 10 μM low dose of controlled release mAv-Dex (2:1:1) effectively suppressed IL-1α-induced GAG loss, cell death and inflammatory response significantly better than unmodified Dex over 2 weeks in cartilage explant culture models of OA. With this multi-arm design, <1 μM Avidin was needed - a concentration which has been shown to be safe, preventing further GAG loss and cytotoxicity. A charge-based cartilage homing drug delivery platform like this can elicit disease modifying effects as well as facilitate long-term symptomatic pain and inflammation relief by enhancing tissue specificity and prolonging intra-cartilage residence time of OA drugs. This nano-construct thus has high translational potential for enabling intra-cartilage delivery of a broad array of small molecule OA drugs and their combinations to chondrocytes, enabling OA treatment with a single injection of low drug doses and eliminating toxicity issues associated with multiple high dose injections.

Interleukin-1 receptor antagonist (IL-1Ra) is more effective in suppressing cytokine-induced catabolism in cartilage-synovium co-culture than in cartilage monoculture

Background

Most in vitro studies of potential osteoarthritis (OA) therapies have used cartilage monocultures, even though synovium is a key player in mediating joint inflammation and, thereby, cartilage degeneration. In the case of interleukin-1 (IL-1) inhibition using its receptor antagonist (IL-1Ra), like chondrocytes, synoviocytes also express IL-1 receptors that influence intra-articular IL-1 signaling and IL-1Ra efficacy. The short residence time of IL-1Ra after intra-articular injection requires the application of frequent dosing, which is clinically impractical and comes with increased risk of infection; these limitations motivate the development of effective drug delivery strategies that can maintain sustained intra-articular IL-1Ra concentrations with only a single injection. The goals of this study were to assess how the presence of synovium in IL-1-challenged cartilage-synovium co-culture impacts the time-dependent biological response of single and sustained doses of IL-1Ra, and to understand the mechanisms underlying any co-culture effects.

Methods

Bovine cartilage explants with or without synovium were treated with IL-1α followed by single or multiple doses of IL-1Ra. Effects of IL-1Ra in rescuing IL-1α-induced catabolism in cartilage monoculture and cartilage-synovium co-culture were assessed by measuring loss of glycosaminoglycans (GAGs) and collagen using DMMB (dimethyl-methylene blue) and hydroxyproline assays, respectively, nitric oxide (NO) release using Griess assay, cell viability by fluorescence staining, metabolic activity using Alamar blue, and proteoglycan biosynthesis by radiolabel incorporation. Day 2 conditioned media from mono and co-cultures were analyzed by mass spectrometry and cytokine array to identify proteins unique to co-culture that contribute to biological crosstalk.

Results

A single dose of IL-1Ra was ineffective, and a sustained dose was necessary to significantly suppress IL-1α-induced catabolism as observed by enhanced suppression of GAG and collagen loss, NO synthesis, rescue of chondrocyte metabolism, viability, and GAG biosynthesis rates. The synovium exhibited a protective role as the effects of single-dose IL-1Ra were significantly enhanced in cartilage-synovium co-culture and were accompanied by release of anti-catabolic factors IL-4, carbonic anhydrase-3, and matrilin-3. A total of 26 unique proteins were identified in conditioned media from co-cultures, while expression levels of many additional proteins important to cartilage homeostasis were altered in co-culture compared to monocultures; principal component analysis revealed distinct clustering between co-culture and cartilage and synovium monocultures, thereby confirming significant crosstalk.

Conclusions

IL-1Ra suppresses cytokine-induced catabolism in cartilage more effectively in the presence of synovium, which was associated with endogenous production of anti-catabolic factors. Biological crosstalk between cartilage and synovium is significant; thus, their co-cultures should better model the intra-articular actions of potential OA therapeutics. Additionally, chondroprotective effects of IL-1Ra require sustained drug levels, underscoring the need for developing drug delivery strategies to enhance its joint residence time following a single intra-articular injection.

Pathogenesis of Posttraumatic Osteoarthritis of the Ankle

Ankle osteoarthritis affects a significant portion of the global adult population. Unlike other joints, arthritis of the ankle often develops as a response to traumatic injury (intra-articular fracture) of the ankle joints. The full mechanism leading to posttraumatic osteoarthritis of the ankle (PTOAA) is poorly understood. These deficits in knowledge pose challenges in the management of the disease. Adequate surgical reduction of fractured ankle joints remains the gold standard in prevention. The purpose of this review is to thoroughly delineate the known pathogenesis of PTOAA, and provide critical updates on this pathology and new avenues to provide therapeutic management of the disease.

Injectable biomaterials for delivery of interleukin-1 receptor antagonist: Toward improving its therapeutic effect

Interleukin-1 receptor antagonist (IL-1Ra) is a naturally occurring anti-inflammatory cytokine that inhibits IL-1 activity and has been proposed to treat a wide variety of systemic and local inflammatory pathologies for multiple decades. However, the short half-life and high concentration required to inhibit IL-1 activity has limited its use in clinical applications. Many strategies have been developed with the goal of improving the therapeutic efficacy of IL-1Ra for a variety of pathologies, including fusing IL-1Ra to protein/peptide/polymer partners, releasing IL-1Ra from injectable polymer or mineral particles, and release of IL-1Ra from injectable coacervates and gels. This literature review examines injectable biomaterials engineered to improve IL-1Ra delivery, both locally and systemically, to increase its efficacy and ease of use in clinic. STATEMENT OF SIGNIFICANCE: Interleukin-1 receptor antagonist (IL-1Ra) is a therapeutic protein with the potential to treat numerous inflammatory conditions and diseases. However, its short biological half-life and high therapeutic concentration may limit its utility in all but a few clinical scenarios. In this review, we present the biomaterial based delivery strategies which have been explored to deliver IL-1Ra to improve its efficacy and applicability to treat inflammation.

Bioactive factors for cartilage repair and regeneration: Improving delivery, retention, and activity

Articular cartilage is a remarkable tissue whose sophisticated composition and architecture allow it to withstand complex stresses within the joint. Once injured, cartilage lacks the capacity to self-repair, and injuries often progress to joint wide osteoarthritis (OA) resulting in debilitating pain and loss of mobility. Current palliative and surgical management provides short-term symptom relief, but almost always progresses to further deterioration in the long term. A number of bioactive factors, including drugs, corticosteroids, and growth factors, have been utilized in the clinic, in clinical trials, or in emerging research studies to alleviate the inflamed joint environment or to promote new cartilage tissue formation. However, these therapies remain limited in their duration and effectiveness. For this reason, current efforts are focused on improving the localization, retention, and activity of these bioactive factors. The purpose of this review is to highlight recent advances in drug delivery for the treatment of damaged or degenerated cartilage. First, we summarize material and modification techniques to improve the delivery of these factors to damaged tissue and enhance their retention and action within the joint environment. Second, we discuss recent studies using novel methods to promote new cartilage formation via biofactor delivery, that have potential for improving future long-term clinical outcomes. Lastly, we review the emerging field of orthobiologics, using delivered and endogenous cells as drug-delivering "factories" to preserve and restore joint health. Enhancing drug delivery systems can improve both restorative and regenerative treatments for damaged cartilage. STATEMENT OF SIGNIFICANCE: Articular cartilage is a remarkable and sophisticated tissue that tolerates complex stresses within the joint. When injured, cartilage cannot self-repair, and these injuries often progress to joint-wide osteoarthritis, causing patients debilitating pain and loss of mobility. Current palliative and surgical treatments only provide short-term symptomatic relief and are limited with regards to efficiency and efficacy. Bioactive factors, such as drugs and growth factors, can improve outcomes to either stabilize the degenerated environment or regenerate replacement tissue. This review highlights recent advances and novel techniques to enhance the delivery, localization, retention, and activity of these factors, providing an overview of the cartilage drug delivery field that can guide future research in restorative and regenerative treatments for damaged cartilage.

Articular fibrocartilage - Why does hyaline cartilage fail to repair?

Once damaged, articular cartilage has a limited potential to repair. Clinically, a repair tissue is formed, yet, it is often mechanically inferior fibrocartilage. The use of monolayer expanded versus naïve cells may explain one of the biggest discrepancies in mesenchymal stromal/stem cell (MSC) based cartilage regeneration. Namely, studies utilizing monolayer expanded MSCs, as indicated by numerous in vitro studies, report as a main limitation the induction of type X collagen and hypertrophy, a phenotype associated with endochondral bone formation. However, marrow stimulation and transfer studies report a mechanically inferior collagen I/II fibrocartilage as the main outcome. Therefore, this review will highlight the collagen species produced during the different therapeutic approaches. New developments in scaffold design and delivery of therapeutic molecules will be described. Potential future directions towards clinical translation will be discussed. New delivery mechanisms are being developed and they offer new hope in targeted therapeutic delivery.

Continuous low-intensity ultrasound attenuates IL-6 and TNFα-induced catabolic effects and repairs chondral fissures in bovine osteochondral explants

BACKGROUND

Cartilage repair outcomes are compromised in a pro-inflammatory environment; therefore, the mitigation of pro-inflammatory responses is beneficial. Treatment with continuous low-intensity ultrasound (cLIUS) at the resonant frequency of 5 MHz is proposed for the repair of chondral fissures under pro-inflammatory conditions.

METHODS

Bovine osteochondral explants, concentrically incised to create chondral fissures, were maintained under cLIUS (14 kPa (5 MHz, 2.5 Vpp), 20 min, 4 times/day) for a period of 28 days in the presence or absence of cytokines, interleukin-6 (IL-6) or tumor necrosis factor (TNF)α. Outcome assessments included histological and immunohistochemical staining of the explants; and the expression of catabolic and anabolic genes by qRT-PCR in bovine chondrocytes. Cell migration was assessed by scratch assays, and by visualizing migrating cells into the hydrogel core of cartilage-hydrogel constructs.

RESULTS

Both in the presence and absence of cytokines, higher percent apposition along with closure of fissures were noted in cLIUS-stimulated explants as compared to non-cLIUS-stimulated explants on day 14. On day 28, the percent apposition was not significantly different between unstimulated and cLIUS-stimulated explants exposed to cytokines. As compared to non-cLIUS-stimulated controls, on day 28, cLIUS preserved the distribution of proteoglycans and collagen II in explants despite exposure to cytokines. cLIUS enhanced the cell migration irrespective of cytokine treatment. IL-6 or TNFα-induced increases in MMP13 and ADAMTS4 gene expression was rescued by cLIUS stimulation in chondrocytes. Under cLIUS, TNFα-induced increase in NF-κB expression was suppressed, and the expression of collagen II and TIMP1 genes were upregulated.

CONCLUSION

cLIUS repaired chondral fissures, and elicited pro-anabolic and anti-catabolic effects, thus demonstrating the potential of cLIUS in improving cartilage repair outcomes.

Effects of Anti-Inflammatory Agents on Expression of Early Responsive Inflammatory and Catabolic Genes in Ex Vivo Porcine Model of Acute Knee Cartilage Injury

Objective Early intervention therapies targeting inflammation and cell death during the acute phase of cartilage injury have the potential to prevent posttraumatic osteoarthritis. The objective of this study was to investigate the effects of interleukin receptor antagonist protein (IRAP), hyaluronan (HA), dexamethasone (DEX), and mesenchymal stem cell (MSC) treatment on the expression of established genetic markers for matrix degradation, apoptosis, and inflammation in articular cartilage during the acute phase of injury. Design A custom impact device was used to create replicable injury ex vivo to intact porcine knee joint. One hour after impact, IRAP, HA, DEX, or MSCs was intra-articularly injected. At 8 hours postinjury, cartilage and meniscus samples were harvested for genetic expression analysis. Expression of miR-27b, miR-140, miR-125b, miR-16, miR-34a, miR-146a, miR-22, ADAMTS-4, ADAMTS-5, MMP-3, IL-1β, and TNF-α was analyzed by real-time polymerase chain reaction. Results At 8 hours postinjury, expression of ADAMTS-4, ADAMTS-5, MMP-3, IL-1β, and TNF-α in cartilage was significantly decreased in IRAP- and DEX-treated joints as compared to nontreated injured joints, whereas only IRAP upregulated expression of miR-140, miR-125b, miR-27b, miR-146a, and miR-22 in cartilage. HA and MSC treatments had no significant effects on catabolic and inflammatory gene expression in cartilage. However, HA treatment significantly upregulated expression of all miRNAs except miR-16. In addition, the treatments tested also exhibited significant influences on meniscus. Conclusions This study provides a valuable starting point for further research into potential targets for and efficacy of various early intervention strategies that may delay or prevent the progression of posttraumatic osteoarthritis after acute cartilage injury.

Intra-articular drug delivery systems for joint diseases

Intra-articular (IA) injections directly deliver high concentrations of therapeutics to the joint space and are routinely used in various musculoskeletal conditions such as osteoarthritis (OA) and rheumatoid arthritis (RA). However, current IA-injected drugs are rapidly cleared and do not significantly affect the course of joint disease. In this review, we highlight recent developments in IA therapy, with a special emphasis on current and emerging therapeutic carriers and their potential to deliver disease-modifying treatment modalities for arthritis. Recent IA approaches concentrate on platforms that are safe with efficient tissue penetration, and readily translatable for controlled and sustained delivery of therapeutic agents. Gene therapy delivered by viral or non-viral vectors and cell-based therapy for cartilage preservation and regeneration are being intensively explored.

Injectable network biomaterials via molecular or colloidal self-assembly

Self-assembly is a powerful tool to create functional materials. A specific application for which self-assembled materials are ideally suited is in creating injectable biomaterials. Contrasting with traditional biomaterials that are implanted through surgical means, injecting biomaterials through the skin offers numerous advantages, expanding the scope and impact for biomaterials in medicine. In particular, self-assembled biomaterials prepared from molecular or colloidal interactions have been frequently explored. The strategies to create these materials are varied, taking advantage of engineered oligopeptides, proteins, and nanoparticles as well as affinity-mediated crosslinking of synthetic precursors. Self-assembled materials typically facilitate injectability through two different mechanisms: i) in situ self-assembly, whereby materials would be administered in a monomeric or oligomeric form and self-assemble in response to some physiologic stimulus, or ii) self-assembled materials that, by virtue of their dynamic, non-covalent interactions, shear-thin to facilitate flow within a syringe and subsequently self-heal into its reassembled material form at the injection site. Indeed, many classes of materials are capable of being injected using a combination of these two mechanisms. Particular utility has been noted for self-assembled biomaterials in the context of tissue engineering, regenerative medicine, drug delivery, and immunoengineering. Given the controlled and multifunctional nature of many self-assembled materials demonstrated to date, we project a future where injectable self-assembled biomaterials afford improved practice in advancing healthcare.