Biodynamic performance of hyaluronic acid versus synovial fluid of the knee in osteoarthritis

Impact of degeneration and material pairings on cartilage friction: Cartilage versus glass

The association of knee joint osteoarthritis and altered frictional properties of the degenerated cartilage remains ambiguous, because previous in vitro studies did not consider the characteristic loads and velocities during gait. Therefore, the aim of this study was to quantify the friction behavior of degenerated human cartilage under characteristic stance and swing phase conditions. A dynamic pin-on-plate tribometer was used to test the tribological systems of cartilage against cartilage and cartilage against glass, both with synthetic synovial fluid as lubricant. Using the International Cartilage Repair Society classification, the cartilage samples were assigned to a mildly or a severely degenerated group before testing. Friction coefficients were calculated under stance and swing phase conditions at the beginning of the test and after 600 s of testing. The most important finding of this study is that cartilage against glass couplings displayed significantly higher friction for the severely degenerated samples compared to the mildly degenerated ones, whereas cartilage against cartilage couplings only indicated slight tendencies under the observed test conditions. Consequently, care should be taken when transferring in vitro findings from cartilage against cartilage couplings to predict the friction behavior in vivo. Therefore, we recommend in vitro tribological testing methods which account for gait-like loading conditions and to replicate physiological material pairings, particularly in preclinical medical device validation studies.

Functional nano drug delivery system with dual lubrication and immune escape for treating osteoarthritis

Local drug delivery via inter-articular injection offers a promising scenario to treat the most common joint disease, osteoarthritis (OA), which is closely associated with the increased friction or cartilage degeneration and the inflammatory syndrome of synovium. Therefore, it is quite necessary to improve the retention of drug delivery system within synovial joint, simultaneously restore the lubrication of degraded cartilage and meanwhile alleviate the inflammation. In this study, we propose a hydrophilic coating modified nano-liposome drug carrier (PMPC-Lipo) to achieve these functions. A modified chain transfer agent was utilized to polymerize 2-methacryloyloxyethyl phosphorylcholine (MPC), the obtained polymer, combined with lecithin and cholesterol, formed a liposome (PMPC-Lipo) where poly (MPC) acted as hydrophilic coating. PMPC-Lipo was found to restore the lubrication of mechanically damage cartilage (mimicking OA conditions) to the level like healthy cartilage due to the hydration lubrication. Additionally, due to the presence of poly (MPC), we also found PMPC-Lipo avoid the recognition of macrophage and thus escape from the phagocytosis to prolong its retention in synovial joint. Furthermore, after encapsulating gallic acid (GA) into PMPC-Lipo, the obtained GA-PMPC-Lipo can effectively scavenge reactive oxygen species and restore the imbalance of matrix secretion in inflammatory chondrocytes. Collectively, the proposed GA-PMPC-Lipo may provide a new idea for osteoarthritis treatment by providing both long-term effective drug action and excellent lubrication properties.

Impact of hyaluronic acid injection on the knee joint friction

PURPOSE

The purpose of this in vitro study was to investigate whether or not hyaluronic acid supplementation improves knee joint friction during osteoarthritis progression under gait-like loading conditions.

METHODS

Twelve human cadaveric knee joints were equally divided into mild and moderate osteoarthritic groups. After initial conservative preparation, a passive pendulum setup was used to test the whole joints under gait-like conditions before and after hyaluronic acid supplementation. The friction-related damping properties given by the coefficient of friction µ and the damping coefficient c (in kg m2/s) were calculated from the decaying flexion-extension motion of the knee. Subsequently, tibial and femoral cartilage and meniscus samples were extracted from the joints and tested in an established dynamic pin-on-plate tribometer using synthetic synovial fluid followed by synthetic synovial fluid supplemented with hyaluronic acid as lubricant. Friction was quantified by calculating the coefficient of friction.

RESULTS

In the pendulum tests, the moderate OA group indicated significantly lower c0 values (p < 0.05) under stance phase conditions and significantly lower µ0 (p = 0.01) values under swing phase conditions. No degeneration-related statistical differences were found for µend or cend. Friction was not significantly different (p > 0.05) with regard to mild and moderate osteoarthritis in the pin-on-plate tests. Additionally, hyaluronic acid did not affect friction in both, the pendulum (p > 0.05) and pin-on-plate friction tests (p > 0.05).

CONCLUSION

The results of this in vitro study suggested that the friction of cadaveric knee joint tissues does not increase with progressing degeneration. Moreover, hyaluronic acid viscosupplementation does not lead to an initial decrease in knee joint friction.

Lubricants for osteoarthritis treatment: From natural to bioinspired and alternative strategies

Osteoarthritis is the most common degenerative and highly prevalent joint disease, characterized by progressive loss and destruction of articular cartilage. The damaged cartilage surface has an increased friction, which causes patients to suffer from serious pain. Restoring the lubrication ability of the joint is central to the treatment of osteoarthritis, a key topic in medical research. A variety of lubricants have been designed to reduce friction in joints and promote cartilage tissue repair to alleviate the symptoms of osteoarthritis. Herein, we review the recent progress of lubricants from the three perspectives of natural, bioinspired, and alternative strategies for osteoarthritis treatment, as well as the structural characterization and lubrication properties of such lubricants. Specifically, natural lubricants include glycosaminoglycans, lubricin and lipids in joints, bioinspired lubricants include scaffolds mimicking hyaluronic acid or lubricin, and alternative lubricants include modified lubricants based on hyaluronic acid, lipids, nanoparticles, and peptides. We also discuss the current challenges and long-term perspectives for further research in this area.

Disrupted homeostasis of synovial hyaluronic acid and its associations with synovial mast cell proteases of rheumatoid arthritis patients and collagen-induced arthritis rats

Hyaluronic acid (HA) is the main component of the extracellular matrix (ECM) of joints, and it is important for a lubricating joint during body movement. Degradation is the main metabolic process of HA in vivo. Hyaluronidases (HAase) were known for HA degradation. The inflammation-induced HA rapid-metabolism can reduce HA viscosity and concentration in joints. Mast cells (MC) containing their specific proteases were found in synovium tissue. It is unclear if MC-proteases could be involved in HA degradation pathways. This study aims to explore the correlations between HA concentration vs mast cell proteases, or matrix metalloproteinase-2/9 (MMP-2/9) and to investigate the association of MC-specific proteases with disrupted synovial HA homeostasis in rheumatoid arthritis (RA) or collagen-induced arthritis rats. The synovial fluid samples from no-RA and RA patients were collected; the collagen-induced arthritis (CIA) rat model was established; HA concentration and the activities of MC-protease and MMP-2/9 in the samples were detected, and the correlations were analyzed. In vitro interaction experiment was carried out by mixing MC-proteases with HA to observe the degradation speed. The HA concentrations in synovial fluids were decreased in RA patients and CIA rats compared with those in no-RA subjects or normal rats respectively. The activities of mast cell proteases in synovial fluids were increased and positively correlated with MMP-9, but negatively correlated with HA concentrations. In vitro study, the addition of MC-chymase and tryptase promoted the speed in HA degradation. MC-proteases may influence HA degradation pathway.

Triborheological Study under Physiological Conditions of PVA Hydrogel/HA Lubricant as Synthetic System for Soft Tissue Replacement

In soft tissue replacement, hydrophilic, flexible, and biocompatible materials are used to reduce wear and coefficient of friction. This study aims to develop and evaluate a solid/liquid triborheological system, polyvinyl alcohol (PVA)/hyaluronic acid (HA), to mimic conditions in human synovial joints. Hydrogel specimens prepared via the freeze–thawing technique from a 10% (w/v) PVA aqueous solution were cut into disc shapes (5 ± 0.5 mm thickness). Compression tests of PVA hydrogels presented a Young’s modulus of 2.26 ± 0.52 MPa. Friction tests were performed on a Discovery Hybrid Rheometer DHR-3 under physiological conditions using 4 mg/mL HA solution as lubricant at 37 °C. Contact force was applied between 1 and 20 N, highlighting a coefficient of friction change of 0.11 to 0.31 between lubricated and dry states at 3 N load (angular velocity: 40 rad/s). Thermal behavior was evaluated by differential scanning calorimetry (DSC) in the range of 25–250 °C (5 °C/min rate), showing an endothermic behavior with a melting temperature (Tm) around 231.15 °C. Scanning Electron Microscopy (SEM) tests showed a microporous network that enhanced water content absorption to 82.99 ± 1.5%. Hydrogel achieved solid/liquid lubrication, exhibiting a trapped lubricant pool that supported loads, keeping low coefficient of friction during lubricated tests. In dry tests, interstitial water evaporates continuously without countering sliding movement friction.

The Role of Hyaluronic Acid in Cartilage Boundary Lubrication

Hydration lubrication has emerged as a new paradigm for lubrication in aqueous and biological media, accounting especially for the extremely low friction (friction coefficients down to 0.001) of articular cartilage lubrication in joints. Among the ensemble of molecules acting in the joint, phosphatidylcholine (PC) lipids have been proposed as the key molecules forming, in a complex with other molecules including hyaluronic acid (HA), a robust layer on the outer surface of the cartilage. HA, ubiquitous in synovial joints, is not in itself a good boundary lubricant, but binds the PC lipids at the cartilage surface; these, in turn, massively reduce the friction via hydration lubrication at their exposed, highly hydrated phosphocholine headgroups. An important unresolved issue in this scenario is why the free HA molecules in the synovial fluid do not suppress the lubricity by adsorbing simultaneously to the opposing lipid layers, i.e., forming an adhesive, dissipative bridge between them, as they slide past each other during joint articulation. To address this question, we directly examined the friction between two hydrogenated soy PC (HSPC) lipid layers (in the form of liposomes) immersed in HA solution or two palmitoyl-oleoyl PC (POPC) lipid layers across HA-POPC solution using a surface force balance (SFB). The results show, clearly and surprisingly, that HA addition does not affect the outstanding lubrication provided by the PC lipid layers. A possible mechanism indicated by our data that may account for this is that multiple lipid layers form on each cartilage surface, so that the slip plane may move from the midplane between the opposing surfaces, which is bridged by the HA, to an HA-free interface within a multilayer, where hydration lubrication is freely active. Another possibility suggested by our model experiments is that lipids in synovial fluid may complex with HA, thereby inhibiting the HA molecules from adhering to the lipids on the cartilage surfaces.

Potential of Natural Biomaterials in Nano-scale Drug Delivery

BACKGROUND

The usage of natural biomaterials or naturally derived materials intended for interface with biological systems has steadily increased in response to the high demand of amenable materials, which are suitable for purpose, biocompatible and biodegradable. There are many naturally derived polymers which overlap in terms of purpose as biomaterials but are equally diverse in their applications.

METHODS

This review examines the applications of the following naturally derived polymers; hyaluronic acid, silk fibroin, chitosan, collagen and tamarind polysaccharide (TSP); further focusing on the biomedical applications of each as well as emphasising on individual novel applications.

RESULTS

Each of the polymers was found to demonstrate a wide variety of successful biomedical applications fabricated as wound dressings, scaffolds, matrices, films, sponges, implants or hydrogels to suit the therapeutic need. Interestingly, blending and amelioration of polymer structures were the two selection strategies to modify the functionality of the polymers to suit the purpose. Further, these polymers have shown promise to deliver small molecule drugs, proteins and genes as nano-scale delivery systems.

CONCLUSION

The review highlights the range of applications of the aforementioned polymers as biomaterials. Hyaluronic acid, silk fibroin, chitosan, collagen and TSP have been successfully utilised as biomaterials in the subfields of implant enhancement, wound management, drug delivery, tissue engineering and nanotechnology. Whilst there are a number of associated advantages (i.e. biodegradability, biocompatibility, non-toxic, nonantigenic as well as amenability) the selected disadvantages of each individual polymer provide significant scope for their further exploration and overcoming challenges like feasibility of mass production at a relatively low cost.

Combined intra-articular injection of corticosteroid and hyaluronic acid reduces pain compared to hyaluronic acid alone in the treatment of knee osteoarthritis

PURPOSE

Intra-articular injections of corticosteroid (CS) and hyaluronic acid (HA) have individually demonstrated efficacy for knee osteoarthritis (OA); however, both treatments are limited by the trajectory of symptom relief. The combination of CS and HA in the management of knee OA may provide improved symptomatic relief for patients who are candidates for intra-articular therapies.

METHODS

Electronic databases Medline, EMBASE and Cochrane Library were used to identify relevant publications. Randomized controlled trials (RCT) that evaluated intra-articular injections of combined CS and HA in comparison to HA alone were included. Outcomes eligible for meta-analysis were WOMAC pain, WOMAC total, OMERACT-OARSI responder rate, and treatment-related adverse events. Standardized mean differences (SMD) were calculated for continuous outcomes using an inverse variance method and a random-effects model. Odds ratios (OR) were calculated for dichotomous outcomes using the Mantel-Haenszel method and a random-effects model. Heterogeneity was assessed using the I² statistic.

RESULTS

Eight trials (n = 751 patients) were included. Reduction in WOMAC pain scores at 2-4 weeks favoured the combined CS and HA group compared to HA alone [SMD 0.60, 95% CI (0.23, 0.97); p = 0.002, I² = 75%]. Longer term improvements at 24-26 and 52 weeks WOMAC pain scores also favoured the combined CS and HA group {[SMD 0.25, 95% CI (0.09, 0.41); p = 0.002, I² = 0%] and [SMD 0.39, 95% CI (0.01, 0.77); p = 0.05, I² = 0%]} compared to HA alone, respectively. There were no significant differences in WOMAC total scores, OMERACT-OARSI responder rate, or treatment-related adverse events.

CONCLUSION

Combined intra-articular injections of CS and HA led to reductions in pain at 2-4, 24-26 and 52 weeks compared to HA injections alone.

LEVEL OF EVIDENCE

Level II-meta-analysis.

Fullerene-like MoS2 Nanoparticles as Cascade Catalysts Improving Lubricant and Antioxidant Abilities of Artificial Synovial Fluid

Intraarticular injection of hyaluronic acid (HA) for viscosupplementation is a nonsurgical therapy for osteoarthritis (OA). However, HA fails to lubricate under a significant load and tends to be depolymerized by the overproduction of reactive oxygen species (ROS) in inflammation. Here, we for the first time reported that fullerene-like MoS₂ (F-MoS₂) nanoparticles are efficient lubricants and antioxidants for artificial synovial fluid. A model of arthrosis was built, to evaluate the tribological behavior of F-MoS₂ nanoparticles. The tests showed that they significantly improve the antiwear and friction-reducing abilities of the artificial synovial fluid. More importantly, the F-MoS₂ nanoparticles possess intrinsic dual-enzyme-like activity, mimicking superoxide dismutases (SOD) and catalases (CAT) under physiological conditions (pH 7.4, 25 °C). By coupling of these unique properties, a self-organized cascade catalytic system was constructed, which includes the disproportionation of superoxide radicals (O₂^•-) to hydrogen peroxide (H₂O₂) and subsequently the disproportionation of H₂O₂ into oxygen (O₂). The effectiveness of the detox system was evaluated by human umbilical vein endothelial cells (HUVEC) models exposed to oxidative stress. After that, F-MoS₂ nanoparticles were used to regulate the ROS level in artificial synovial fluid containing HA. Relative viscosity measurements showed the excellent protective effect of F-MoS₂ nanoparticles against HA oxidative damage offered by O₂^•-. These results indicate that F-MoS₂ nanoparticles are promising candidates for treatment of OA and other diseases caused by lubrication deficiency or oxidative stress.

Nanoparticle Properties for Delivery to Cartilage: The Implications of Disease State, Synovial Fluid, and Off-Target Uptake

A major hurdle limiting the ability to treat and cure osteoarthritis, a common and debilitating disease, is rapid joint clearance and limited cartilage targeting of intra-articular therapies. Nanoscale drug carriers have the potential to improve therapeutic targeting and retention in the joint after direct injection; however, there still lacks a fundamental understanding of how the physicochemical properties of nanoparticles (NPs) influence localization to the degenerating cartilage and how joint conditions such as disease state and synovial fluid impact NP biodistribution. The goal of this study was to assess how physicochemical properties of NPs influence their interactions with joint tissues and, ultimately, cartilage localization. Ex vivo models of joint tissues were used to study how poly(lactide- co-glycolide) (PLGA) and polystyrene (PS) NP size, charge, and surface chemistry influence cartilage retention under normal and disease-mimicking conditions. Of the particles investigated, PLGA NPs surface-modified with a quaternary ammonium cation had the greatest retention within cartilage explants; however, retention was diminished 2- to 2.9-fold in arthritic tissue and in the presence of synovial fluid. Interactions with synovial fluid induced changes to NP surface properties and colloidal stability in vitro. The impact of NP charge on "off-target" synoviocyte uptake was also dependent on synovial fluid interactions. The results suggest that the design of nanocarriers for targeted drug delivery within the joint cannot be based on a single parameter such as zeta potential or size, and that the fate of injected delivery systems will likely be influenced by the disease state of the joint and the presence of synovial fluid.

Mesenchymal Stem Cells in Combination with Hyaluronic Acid for Articular Cartilage Defects

Mesenchymal stem cells (MSCs) and hyaluronic acid (HA) have been found in previous studies to have great potential for medical use. This study aimed to investigate the therapeutic effects of bone marrow mesenchymal stem cells (BMSCs) combined with HA on articular cartilage repair in canines. Twenty-four healthy canines (48 knee-joints), male or female with weight ranging from 5 to 6 kg, were operated on to induce cartilage defect model and divided into 3 groups randomly which received different treatments: BMSCs plus HA (BMSCs-HA), HA alone, and saline. Twenty-eight weeks after treatment, all canines were sacrificed and analyzed by gross appearance, magnetic resonance imaging (MRI), hematoxylin-eosin (HE) staining, Masson staining, toluidine blue staining, type II collagen immunohistochemistry, gross grading scale and histological scores. MSCs plus HA regenerated more cartilage-like tissue than did HA alone or saline. According to the macroscopic evaluation and histological assessment score, treatment with MSCs plus HA also lead to significant improvement in cartilage defects compared to those in the other 2 treatment groups (P < 0.05). These findings suggested that allogeneic BMSCs plus HA rather than HA alone was effective in promoting the formation of cartilage-like tissue for repairing cartilage defect in canines.

Phospholipid Vesicles in Media for Tribological Studies against Live Cartilage

Introduction

Pre-clinical testing of hemiarthroplasty devices requires that the tribological conditions present in vivo with live cartilage be closely duplicated. A current limitation in the tribological testing of live cartilage involves the use of cell-culture media as lubricant.

Study Aim

to develop and test a new hyaluronan-phospholipid based medium (HA-phospholipid medium) that combines the rheological and frictional properties of synovial fluid with the nourishing properties of culture media to keep cells alive.

Materials and Methods

The HA-phospholipid medium consisted of culture medium with added phospholipid dipalmitoylphosphatidylcholine (0.3 mg/mL), and hyaluronic acid (2.42 mg/mL). A standard cell culture medium was used as the control. The rheology of each medium was determined using a flat plate configuration. Bovine calf cartilage was used to assess cell viability and friction in each medium. For friction measurements, a cobalt-chrome alloy ball was articulated against cartilage disks immersed in medium.

Results

Lipid vesicles 0.1 to 50 μm in diameter were identified in the HA-phospholipid medium. Cartilage cell viability was significantly higher in the HA-phospholipid medium (62% ± 8%, 95% CI) than in control medium (49.5% ± 5%) (p = 0.009). The HA-phospholipid medium exhibited strong shear-thinning behavior, similar to synovial fluid, with viscosities ~100-fold higher at 10 s^-1 and 5-fold higher at 20,000 s^-1 than the approximately Newtonian control medium. The HA-phospholipid medium also yielded 20% lower friction values than the control medium after one hour of testing.

Conclusions

The rheological and friction results indicate that the HA-phospholipid medium is superior to the control cell culture medium in emulating the shear thinning and lubricative properties of natural synovial fluid, making it more clinically relevant for in vitro wear and friction testing with live cartilage.