Nociceptive nerve activity in an experimental model of knee joint osteoarthritis of the guinea pig: Effect of intra-articular hyaluronan application

Clinical and Biochemical Implications of Hyaluronic Acid in Musculoskeletal Rehabilitation: A Comprehensive Review

Hyaluronic acid (HA) naturally occurs as a biopolymer in the human body, primarily in connective tissues like joints and skin. Functioning as a vital element of synovial fluid, it lubricates joints, facilitating fluid movement and diminishing bone friction to protect articular well-being. Its distinctive attributes encompass notable viscosity and water retention capacities, ensuring flexibility and absorbing shock during motion. Furthermore, HA has gained significant attention for its potential benefits in various medical applications, including rehabilitation. Ongoing research explores its properties and functions, especially its biomedical applications in several clinical trials, with a focus on its role in improving rehabilitation outcomes. But the clinical and biochemical implications of HA in musculoskeletal rehabilitation have yet to be fully explored. This review thoroughly investigates the properties and functions of HA while highlighting its biomedical applications in different clinical trials, with a special emphasis on its role in rehabilitation. The presented findings provide evidence that HA, as a natural substance, enhances the outcomes of musculoskeletal rehabilitation through its exceptional mechanical and biochemical effects.

Concurrent Imaging and Clinical Study of the Efficacy of Hyaluronic Acid Injection for Knee Osteoarthritis: A Synovial Membrane Investigation with Ultrasound Imaging

We investigated whether hyaluronic acid (HA) injections can ameliorate ultrasound-detected synovitis in knee osteoarthritis (OA). We recruited 103 patients with symptomatic knee OA and ultrasound-detected synovitis and performed two ultrasound-guided fluid drainage procedures, followed by the administration of a low-molecular-weight HA injection (2.5 mL) in the subpatellar bursa, at a 2-week interval. Knee ultrasound imaging evaluations were performed before injection (baseline) and at 1 and 6 months after the second injection and included the measurements of synovial vascularity by using color Doppler ultrasound, synovial fluid depth over the suprapatellar bursa (SF), and synovial hypertrophy (SH). Initial clinical assessments included a visual analog scale (VAS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). VAS scores decreased significantly at both 1-month and 6-month evaluations (p < 0.001). WOMAC scores also significantly decreased at 1 month (p < 0.001), but not at 6 months (p = 0.23). The ultrasound parameters did not significantly change, except color Doppler grading, which tended to decrease at the 6-month evaluation (p = 0.059). Our findings revealed that two ultrasound-guided HA injections following fluid drainage improved pain and knee function but did not considerably influence imaging-detected synovitis in patients with knee OA.

Piezo2 expressing nociceptors mediate mechanical sensitization in experimental osteoarthritis

Non-opioid targets are needed for addressing osteoarthritis pain, which is mechanical in nature and associated with daily activities such as walking and climbing stairs. Piezo2 has been implicated in the development of mechanical pain, but the mechanisms by which this occurs remain poorly understood, including the role of nociceptors. Here we show that nociceptor-specific Piezo2 conditional knock-out mice were protected from mechanical sensitization associated with inflammatory joint pain in female mice, joint pain associated with osteoarthritis in male mice, as well as both knee swelling and joint pain associated with repeated intra-articular injection of nerve growth factor in male mice. Single cell RNA sequencing of mouse lumbar dorsal root ganglia and in situ hybridization of mouse and human lumbar dorsal root ganglia revealed that a subset of nociceptors co-express Piezo2 and Ntrk1 (the gene that encodes the nerve growth factor receptor TrkA). These results suggest that nerve growth factor-mediated sensitization of joint nociceptors, which is critical for osteoarthritic pain, is also dependent on Piezo2, and targeting Piezo2 may represent a therapeutic option for osteoarthritis pain control.

Does the Presence of Neuropathic Pain Influence the Response to Hyaluronic Acid in Patients with Knee Osteoarthritis?

OBJECTIVES

Up to 50% of patients with symptomatic knee osteoarthritis (OA) present with neuropathic pain (NP) features. We assessed the impact of NP according to DN4 (Douleurs Neuropathiques 4 questions) score on the response to intra-articular (IA) hyaluronic acid (HA) injections and the effects of HA injections on NP.

MATERIALS AND METHODS

We conducted a post hoc analysis from a multicenter, randomized, double-blind, noninferiority trial comparing the efficacy of 2 HA in symptomatic knee OA at 24 weeks. At baseline, demographic, anthropometric, radiologic data, and symptoms were recorded. The symptomatic effect of HA was assessed by VAS pain, patient global assessment (PGA), WOMAC, DN4, and OMERACT-OARSI response.

RESULTS

A total of 187 patients were included. NP according to DN4 score was present in 20 patients (10.7%) at baseline. Most common positive DN4 items were tingling (36.9%) and burning (36.4%). NP was associated with WOMAC pain score (P = 0.02). The presence of NP at baseline did not affect the symptomatic improvement after HA injections according to the VAS pain (P = 0.71), PGA (P = 050), WOMAC pain (P = 0.89), WOMAC function (P = 0.52), and rate of OMERACT-OARSI responders (P = 0.21). The prevalence of patients with NP decreased by 50% (n = 10) at 24 weeks after HA injections. Most improved DN4 items were itching (90%), hypoesthesia to pinprick (88%), and burning (50%).

CONCLUSION

In our study, NP was associated with pain severity, but did not influence the response to IA HA. On the other hand, HA injections reduced some NP features, especially itching, sting hypoesthesia, and burning.

PI3Kγ/AKT Signaling in High Molecular Weight Hyaluronan (HMWH)-Induced Anti-Hyperalgesia and Reversal of Nociceptor Sensitization

High molecular weight hyaluronan (HMWH), a well-established treatment for osteoarthritis pain, is anti-hyperalgesic in preclinical models of inflammatory and neuropathic pain. HMWH-induced anti-hyperalgesia is mediated by its action at cluster of differentiation 44 (CD44), the cognate hyaluronan receptor, which can signal via phosphoinositide 3-kinase (PI3K), a large family of kinases involved in diverse cell functions. We demonstrate that intrathecal administration of an oligodeoxynucleotide (ODN) antisense to mRNA for PI3Kγ (a Class I PI3K isoform) expressed in dorsal root ganglia (DRGs), and intradermal administration of a PI3Kγ-selective inhibitor (AS605240), markedly attenuates HMWH-induced anti-prostaglandin E₂ (PGE₂) hyperalgesia, in male and female rats. Intradermal administration of inhibitors of mammalian target of rapamycin (mTOR; rapamycin) and protein kinase B (AKT; AKT Inhibitor IV), signaling molecules downstream of PI3Kγ, also attenuates HMWH-induced anti-hyperalgesia. In vitro patch-clamp electrophysiology experiments on cultured nociceptors from male rats demonstrate that some HMWH-induced changes in generation of action potentials (APs) in nociceptors sensitized by PGE₂ are PI3Kγ dependent (reduction in AP firing rate, increase in latency to first AP and increase in slope of current ramp required to induce AP) and some are PI3Kγ independent [reduction in recovery rate of AP afterhyperpolarization (AHP)]. Our demonstration of a role of PI3Kγ in HMWH-induced anti-hyperalgesia and reversal of nociceptor sensitization opens a novel line of research into molecular targets for the treatment of diverse pain syndromes.SIGNIFICANCE STATEMENT We have previously demonstrated that high molecular weight hyaluronan (HMWH) attenuates inflammatory hyperalgesia, an effect mediated by its action at cluster of differentiation 44 (CD44), the cognate hyaluronan receptor, and activation of its downstream signaling pathway, in nociceptors. In the present study, we demonstrate that phosphoinositide 3-kinase (PI3K)γ and downstream signaling pathway, protein kinase B (AKT) and mammalian target of rapamycin (mTOR), are crucial for HMWH to induce anti-hyperalgesia.

Sexually Dimorphic Role of Toll-like Receptor 4 (TLR4) in High Molecular Weight Hyaluronan (HMWH)-induced Anti-hyperalgesia

High molecular weight hyaluronan (HMWH), a prominent component of the extracellular matrix binds to and signals via multiple receptors, including cluster of differentiation 44 (CD44) and toll-like receptor 4 (TLR4). We tested the hypothesis that, in the setting of inflammation, HMWH acts at TLR4 to attenuate hyperalgesia. We found that the attenuation of prostaglandin E2 (PGE2)-induced hyperalgesia by HMWH was attenuated by a TLR4 antagonist (NBP2-26245), but only in male and ovariectomized female rats. In this study we sought to evaluated the role of the TLR4 signaling pathway in anti-hyperalgesia induced by HMWH in male rats. Decreasing expression of TLR4 in nociceptors, by intrathecal administration of an oligodeoxynucleotide (ODN) antisense to TLR4 mRNA, also attenuated HMWH-induced anti-hyperalgesia, in male and ovariectomized female rats. Estrogen replacement in ovariectomized females reconstituted the gonad-intact phenotype. The administration of an inhibitor of myeloid differentiation factor 88 (MyD88), a TLR4 second messenger, attenuated HMWH-induced anti-hyperalgesia, while an inhibitor of the MyD88-independent TLR4 signaling pathway did not. Since it has previously been shown that HMWH-induced anti-hyperalgesia is also mediated, in part by CD44 we evaluated the effect of the combination of ODN antisense to TLR4 and CD44 mRNA. This treatment completely reversed HMWH-induced anti-hyperalgesia in male rats. Our results demonstrate a sex hormone-dependent, sexually dimorphic involvement of TLR4 in HMWH-induced anti-hyperalgesia, that is MyD88 dependent. PERSPECTIVE: The role of TLR4 in anti-hyperalgesia induced by HMWH is a sexually dimorphic, TLR4 dependent inhibition of inflammatory hyperalgesia that provides a novel molecular target for the treatment of inflammatory pain.

Comparison of the effect of hyaluronic acid injection versus extracorporeal shockwave therapy on chronic plantar fasciitis: Protocol for a randomized controlled trial

BACKGROUND

Plantar fasciitis is the most common cause of pain in the plantar region of the heel, and extracorporeal shockwave therapy (ESWT) is an option used in cases where conservative treatment fails. Hyaluronic acid (HA), initially used for osteoarthrosis, is a treatment option because it has been applied to extra-articular regions, such as tendons, ligaments, and fascia. The aim of the present study will be to evaluate the outcomes of pain, function, and personal satisfaction after a single injection of HA and to compare the results with those of ESWT in patients with chronic plantar fasciitis.

METHODS

The study will include 80 patients who will be randomized to receive three sessions of ESWT (n = 40) or a single ultrasound-guided HA injection in the plantar fascia (n = 40). The outcomes will include the visual analog pain scale score, American Orthopaedic Foot and Ankle Society (AOFAS) score, and Foot and Ankle Outcome Score (FAOS). All of the assessments will be performed at baseline and 3, 6, and 12 months after treatment. Statistical analysis will be performed using the repeated measures ANOVA (analysis of variance test) for primary and secondary outcomes and also Fisher's Least Significant Difference, a Post-Hoc test. We will use R software for statistical analysis, randomization, and sample size calculation.

RESULTS

Recruitment and data collection will begin in November 2020, with completion scheduled for November 2022 and final publication available in March 2023.

CONCLUSION

This trial will evaluate the effects of a single ultrasound-guided HA injection for the treatment of chronic plantar fasciitis.

TRIAL REGISTRATION

Brazilian Clinical Trials Registry (Register Number: RBR-97vkx4) http://www.ensaiosclinicos.gov.br/rg/RBR-97vkx4/.

The effect of viscosupplementation on early-stage knee osteoarthritis: Clinical evaluation and assessment of cartilage in vivo with 7 T MRI

INTRODUCTION

Viscosupplementation is a well-known strategy for managing early stages knee Osteoarthritis. However, despite its effectiveness in reducing symptoms, it has not yet been found to have an effect on joint cartilage. The aim of this study is to evaluate the clinical efficacy of a new product with gel-like behaviour and its in vivo effects on joint cartilage.

METHODS

20 patients were treated by 2 consecutive injections of hyaluronan derivative Hymovis® at one-week interval. Clinical evaluation was performed before the treatment and at each time point during the follow-up using WOMAC and VAS. A 7 T magnet was used for cartilage evaluation at each MRI time point: T2 Relaxation Time (RT), T2∗ RT and cartilage parameters were evaluated before the first injection, after 45 days and at 6 months follow-up. Statistical analysis was obtained for each reported data.

RESULTS

We report significantly reduction in symptoms with an increase in knee and global activity functions. The T2 RT for lateral tibial compartment and T2∗ RT for Patello-Femoral compartment significantly decreased. A T2 RT reduction was observed in all knee compartments except for the medial tibial one, while a T2∗ RT reduction was observed in all knee compartments. We report an increase in cartilage volume and thickness in most of patients with a reduction of cartilage defects in 9 patients, but we didn't find MRI signals clearly referable to cartilage regeneration.

CONCLUSIONS

MRI results have confirmed the possibility to employ 7T magnets to evaluate early changes in cartilage structure in vivo. HA VS has provided good clinical outcomes and an improvement in the global assessment of the knee joint, but it doesn't seem to significantly modify the cartilage over the time.

Effects of Oral Hyaluronic Acid Administration in Dogs Following Tibial Tuberosity Advancement Surgery for Cranial Cruciate Ligament Injury

Hyaluronic acid (HA) intraarticular injection is used in the management of osteoarthritis in veterinary medicine. However, HA oral administration is less common given the scarce currently available scientific evidence. This study was aimed at evaluating the effects of oral HA administration on synovial fluid concentrations of several selected biomarkers in dogs with cranial cruciate ligament (CCL) injury operated on using the tibial tuberosity advancement (TTA) technique. Fifty-five dogs were included in this prospective, randomized, double-blind, clinical study; they were randomly assigned to receive either a placebo (group A; n = 25) or HA (group B; n = 30) orally for 10 weeks. Synovial fluid samples were obtained before surgery, and at 10 weeks postoperatively to measure concentrations of HA, haptoglobin, nitric oxide, and paraoxonase-1. After 10 weeks, group HA showed a significant increase in HA concentration (p = 0.0016) and a significant decrease in PON-1 concentration (p = 0.011) compared to baseline. In conclusion, post-op oral HA administration in canine patients with CCL injury leads to improvements in osteoarthritis biomarkers, namely higher synovial fluid HA concentrations and reduced synovial fluid paraoxonase-1 concentrations. These findings support the bioavailability of orally-administered HA and its usefulness in improving biomarkers of osteoarthritis.

Animal models of pain: Diversity and benefits

Chronic pain is a maladaptive neurological disease that remains a major health problem. A deepening of our knowledge on mechanisms that cause pain is a prerequisite to developing novel treatments. A large variety of animal models of pain has been developed that recapitulate the diverse symptoms of different pain pathologies. These models reproduce different pain phenotypes and remain necessary to examine the multidimensional aspects of pain and understand the cellular and molecular basis underlying pain conditions. In this review, we propose an overview of animal models, from simple organisms to rodents and non-human primates and the specific traits of pain pathologies they model. We present the main behavioral tests for assessing pain and investing the underpinning mechanisms of chronic pathological pain. The validity of animal models is analysed based on their ability to mimic human clinical diseases and to predict treatment outcomes. Refine characterization of pathological phenotypes also requires to consider pain globally using specific procedures dedicated to study emotional comorbidities of pain. We discuss the limitations of pain models when research findings fail to be translated from animal models to human clinics. But we also point to some recent successes in analgesic drug development that highlight strategies for improving the predictive validity of animal models of pain. Finally, we emphasize the importance of using assortments of preclinical pain models to identify pain subtype mechanisms, and to foster the development of better analgesics.

Mechanisms Mediating High-Molecular-Weight Hyaluronan-Induced Antihyperalgesia

We evaluated the mechanism by which high-molecular-weight hyaluronan (HMWH) attenuates nociceptor sensitization, in the setting of inflammation. HMWH attenuated mechanical hyperalgesia induced by the inflammatory mediator prostaglandin E2 (PGE₂) in male and female rats. Intrathecal administration of an oligodeoxynucleotide antisense (AS-ODN) to mRNA for cluster of differentiation 44 (CD44), the cognate hyaluronan receptor, and intradermal administration of A5G27, a CD44 receptor antagonist, both attenuated antihyperalgesia induced by HMWH. In male rats, HMWH also signals via Toll-like receptor 4 (TLR4), and AS-ODN for TLR4 mRNA administered intrathecally, attenuated HMWH-induced antihyperalgesia. Since HMWH signaling is dependent on CD44 clustering in lipid rafts, we pretreated animals with methyl-β-cyclodextrin (MβCD), which disrupts lipid rafts. MβCD markedly attenuated HMWH-induced antihyperalgesia. Inhibitors for components of intracellular signaling pathways activated by CD44, including phospholipase C and phosphoinositide 3-kinase (PI3K), also attenuated HMWH-induced antihyperalgesia. Furthermore, in vitro application of HMWH attenuated PGE₂-induced sensitization of tetrodotoxin-resistant sodium current, in small-diameter dorsal root ganglion neurons, an effect that was attenuated by a PI3K inhibitor. Our results indicate a central role of CD44 signaling in HMWH-induced antihyperalgesia and suggest novel therapeutic targets, downstream of CD44, for the treatment of pain generated by nociceptor sensitization.SIGNIFICANCE STATEMENT High-molecular-weight-hyaluronan (HMWH) is used to treat osteoarthritis and other pain syndromes. In this study we demonstrate that attenuation of inflammatory hyperalgesia by HMWH is mediated by its action at cluster of differentiation 44 (CD44) and activation of its downstream signaling pathways, including RhoGTPases (RhoA and Rac1), phospholipases (phospholipases Cε and Cγ1), and phosphoinositide 3-kinase, in nociceptors. These findings contribute to our understanding of the antihyperalgesic effect of HMWH and support the hypothesis that CD44 and its downstream signaling pathways represent novel therapeutic targets for the treatment of inflammatory pain.

Injection therapies for patellar tendinopathy

Patellar tendinopathy, or jumper's knee is a common musculoskeletal condition characterized by progressive activity-related pain on the anterior aspect of the knee and tenderness on the patellar tendon. A conservative method is often the first choice of treatment, which can include anti-inflammatory medication, injection therapies, physiotherapy, eccentric exercises, extra corporeal shock wave therapy, orthosis, etc. Although there are several treatment options available, the management of patellar tendinopathy is still controversial. The literature reveals many different injection methods are being used by clinicians for the treatment of patellar tendinopathy. Platelet rich plasma, corticosteroids, autologous blood, and aprotinin are the most commonly used injection treatments. Injection therapies give promising results in the management of Patellar tendinopathy. However, due to low quality research and variation in the protocol and population it is difficult to provide a firm conclusion on its effectiveness. More high-quality clinical studies are recommended to determine the effectiveness of injections and at which stage of Patellar tendinopathy they are the most effective. This review can provide insight to clinicians involved in the management of this condition.

Quantitative characterization of viscoelastic properties of synovial fluid from forelimb joints of orthopedically normal Thoroughbreds and warmblood horses

OBJECTIVE

To determine whether differences existed in the viscoelastic properties of synovial fluid samples from the metacarpophalangeal, intercarpal, and distal interphalangeal joints of orthopedically normal athletic horses.

ANIMALS

45 warmblood horses and 30 Thoroughbreds (age range, 4 to 16 years).

PROCEDURES

Synovial fluid samples were aseptically obtained via arthrocentesis from 1 metacarpophalangeal, intercarpal, and distal interphalangeal joint of each horse, and nucleated cell counts were performed. A commercial ELISA was used to measure sample hyaluronic acid concentrations, and full rheological characterization of samples was performed to measure the elastic or storage modulus G' and viscous or loss modulus G" at 37.5°C (representing the body temperature of horses). Findings were compared among joints and between breed groups by means of ANOVA.

RESULTS

Significant differences in synovial fluid G' and G" values were identified between Thoroughbreds and warmblood horses for the metacarpophalangeal joint, between the metacarpophalangeal and intercarpal joints of Thoroughbreds, and between the metacarpophalangeal and distal interphalangeal joints and intercarpal and distal interphalangeal joints of warmblood horses. No significant differences were identified between breed groups or among joints in synovial fluid hyaluronic concentrations or nucleated cell counts.

CONCLUSIONS AND CLINICAL RELEVANCE

Viscoelastic properties of the forelimb joints of orthopedically normal Thoroughbreds and warmblood horses differed within and between these 2 groups, mainly as a function of the evaluated joint. To the authors' knowledge, this was the first study of its kind, and additional research is warranted to better understand the viscoelastic properties of synovial fluid in horses to optimize their locomotive function.

Joint nociceptor nerve activity and pain in an animal model of acute gout and its modulation by intra-articular hyaluronan

Supplemental Digital Content is Available in the Text.

Gouty pain nocifensive signs and enhanced joint nociceptor nerve activity in urate-injected rats develop in parallel and are decreased by intra-articular injection of hyaluronan.

The mechanisms whereby deposition of monosodium urate (MSU) crystals in gout activates nociceptors to induce joint pain are incompletely understood. We tried to reproduce the signs of painful gouty arthritis, injecting into the knee joint of rats suspensions containing amorphous or triclinic, needle MSU crystals. The magnitude of MSU-induced inflammation and pain behavior signs were correlated with the changes in firing frequency of spontaneous and movement-evoked nerve impulse activity recorded in single knee joint nociceptor saphenous nerve fibers. Joint swelling, mechanical and cold allodynia, and hyperalgesia appeared 3 hours after joint injection of MSU crystals. In parallel, spontaneous and movement-evoked joint nociceptor impulse activity raised significantly. Solutions containing amorphous or needle-shaped MSU crystals had similar inflammatory and electrophysiological effects. Intra-articular injection of hyaluronan (HA, Synvisc), a high-MW glycosaminoglycan present in the synovial fluid with analgesic effects in osteoarthritis, significantly reduced MSU-induced behavioral signs of pain and decreased the enhanced joint nociceptor activity. Our results support the interpretation that pain and nociceptor activation are not triggered by direct mechanical stimulation of nociceptors by MSU crystals, but are primarily caused by the release of excitatory mediators by inflammatory cells activated by MSU crystals. Intra-articular HA decreased behavioral and electrophysiological signs of pain, possibly through its viscoelastic filtering effect on the mechanical forces acting over sensitized joint sensory endings and probably also by a direct interaction of HA molecules with the transducing channels expressed in joint nociceptor terminals.

Visualization of Peripheral Neuron Sensitization in a Surgical Mouse Model of Osteoarthritis by In Vivo Calcium Imaging

OBJECTIVE

To develop a method for analyzing sensory neuron responses to mechanical stimuli in vivo, and to evaluate whether these neuronal responses change after destabilization of the medial meniscus (DMM).

METHODS

DMM or sham surgery was performed in 10-week-old male C57BL/6 wild-type or Pirt-GCaMP3^+/- mice. All experiments were performed 8 weeks after surgery. Knee and hind paw hyperalgesia were assessed in wild-type mice. The retrograde label DiI was injected into the ipsilateral knee to quantify the number of knee-innervating neurons in the L4 dorsal root ganglion (DRG) in wild-type mice. In vivo calcium imaging was performed on the ipsilateral L4 DRG of Pirt-GCaMP3^+/- mice as mechanical stimuli (paw pinch, knee pinch, or knee twist) were applied to the ipsilateral hind limb.

RESULTS

Eight weeks after surgery, mice subjected to DMM had more hyperalgesia in the knee and hind paw compared to mice subjected to sham surgery. Intraarticular injection of DiI labeled similar numbers of neurons in the L4 DRG of mice subjected to sham surgery and mice subjected to DMM. Increased numbers of sensory neurons responded to all 3 mechanical stimuli in mice subjected to DMM, as assessed by in vivo calcium imaging. The majority of responses in mice subjected to sham surgery and mice subjected to DMM were in small to medium-sized neurons, consistent with the size of nociceptors. The magnitude of responses was similar between mice subjected to sham surgery and mice subjected to DMM.

CONCLUSION

Our findings indicate that increased numbers of small to medium-sized DRG neurons respond to mechanical stimuli 8 weeks after DMM surgery, suggesting that nociceptors have become sensitized by lowering the response threshold.

Osteoarthritis pain: What are we learning from animal models?

All experimental models of osteoarthritis (OA)-like joint damage are accompanied by behaviors indicative of pain. In experimental knee OA, evoked pain responses to exogenously applied stimuli suggest that animals become sensitized to mechanical stimuli. Neurobiological techniques including electrophysiology and in vivo calcium imaging confirm that joint damage is associated with mechanical stimuli through peripheral sensitization. Several mediators present in the OA joint can cause peripheral sensitization, most notably the neurotrophin nerve growth factor (NGF). Furthermore, experimental OA is associated with neuroinflammation in the peripheral nervous system and central nervous system (CNS), including macrophage infiltration of the dorsal root ganglia and microglial activation in the spinal cord. Increasingly, researchers are employing models that are slowly progressive, and this approach has revealed that distinct pain mechanisms operate in a time-dependent manner, which may have important translational significance. While the study of pain in experimental OA is rapidly evolving, with the application of increasingly sophisticated techniques to assess pain and unravel the neurobiology of its genesis, important gaps and limitations in our current approaches exist, which our research community needs to address.

No Effects of Early Viscosupplementation After Arthroscopic Partial Meniscectomy: A Randomized Controlled Trial

BACKGROUND

The management of the postoperative period after knee arthroscopic surgery may be challenging because surgical trauma deeply alters the joint microenvironment, causing the release of several catabolic molecules and proinflammatory factors that might slow down functional recovery. The possibility of using hyaluronic acid (HA) to promote postoperative pain relief and expedite functional improvement seems attractive, considering its biological properties.

PURPOSE

The aim of the present double-blind randomized controlled trial was to evaluate the effects, in terms of pain control and functional recovery, provided by a single HA injection performed at the end of arthroscopic meniscectomy.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

A total of 90 patients, 18 to 55 years old, were included according to the following criteria: (1) chronic, symptomatic meniscal tears requiring partial resection; (2) a healthy contralateral knee; (3) no previous surgery on the index knee; and (4) no other concurrent articular lesions requiring surgical treatment (eg, cartilage or ligament injuries). Patients were randomized into 2 treatment groups: one underwent meniscectomy alone, whereas the other also received an injection of 3 mL HA at the end of the procedure. All patients were evaluated at baseline and then at 15, 30, 60, and 180 days using the following tools: International Knee Documentation Committee (IKDC) subjective, Knee injury and Osteoarthritis Outcome Score (KOOS), visual analog scale (VAS) for pain, VAS for general health status, and Tegner scores. The transpatellar circumference and active and passive ranges of motion were also recorded during the follow-up evaluations.

RESULTS

No major adverse events were reported using HA postoperatively. A statistically significant increase in all the clinical scores was reported in both treatment groups, but no significant intergroup difference was documented at any follow-up evaluation. No difference was observed also in the objective measurements. The mean time to return to full sports activity was not different between groups, and a comparable satisfaction rate was recorded in both treatment groups.

CONCLUSION

Early postoperative viscosupplementation did not provide significant clinical benefits after arthroscopic meniscectomy. Despite the lack of major adverse events, the administration of a single HA injection at the end of the surgical procedure is not a successful strategy to provide either faster functional recovery or symptomatic improvement after meniscectomy.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02629380.

Novel effects of sarcopenic osteoarthritis on metabolic syndrome, insulin resistance, osteoporosis, and bone fracture: the national survey

This study compared the effects sarcopenic osteoarthritis on metabolic syndrome, insulin resistance, osteoporosis, and bone fracture. By using national survey data, we suggest that the relationship between sarcopenia and metabolic syndrome or insulin resistance is potentiated by the severity of osteoarthritis and is independent of body weight.

INTRODUCTION

Sarcopenia and osteoarthritis are known risk factors for metabolic syndrome. However, their combined effects on metabolic syndrome, insulin resistance and osteoporosis remain uncertain.

METHODS

We used data from the fifth Korean National Health and Nutrition Examination Survey using a total of 3158 adults (age >50 years). Sarcopenia was defined as a skeletal muscle index score (appendicular skeletal muscle mass/body weight) within the fifth percentile of sex-matched younger reference participants. Radiographic knee osteoarthritis was defined as a Kellgren-Lawrence (K-L) grade of 2 or greater. Metabolic syndrome was diagnosed using the National Cholesterol Education Program criteria. Insulin resistance was evaluated using the homeostasis model assessment-estimated insulin resistance index (HOMA-IR). Osteoporosis was defined using the World Health Organization T-score criteria.

RESULTS

In multivariable logistic regression analysis, the sarcopenic osteoarthritis group had a higher odds ratio (OR) for metabolic syndrome (OR = 11.00, 95 % confidential interval (CI) = 2.12-56.99, p = 0.013) than the non-sarcopenic osteoarthritis (OR = 1.02, 95 % CI = 0.65-1.62, p = 0.972) and sarcopenic non-osteoarthritis groups (OR = 7.15, 95 % CI = 1.57-32.53, p = 0.027). Similarly, sarcopenic osteoarthritis had a greater OR of highest HOMA-IR quartiles (OR = 8.19, 95 % CI = 2.03-33.05, p = 0.003) than the other groups. Overall, the association between the K-L grade and body mass index was significant; however, this significance was lower in individuals with sarcopenia and was lost in those with sarcopenic osteoarthritis. Additionally, osteoporosis and bone fracture were not associated to sarcopenic osteoarthritis (p > 0.05).

CONCLUSIONS

These results suggest that the relationship between sarcopenia and metabolic syndrome or insulin resistance is potentiated by the severity of osteoarthritis and is independent of body weight.

Intra-Articular Injection of Cross-Linked Hyaluronic Acid-Dexamethasone Hydrogel Attenuates Osteoarthritis: An Experimental Study in a Rat Model of Osteoarthritis

Cross-linked hyaluronic acid hydrogel (cHA gel) and dexamethasone (Dex) have been used to treat knee osteoarthritis (OA) in clinical practice owing to their chondroprotective and anti-inflammatory effects, respectively. The aim of the present study was to compare the treatment effects of the cHA gel pre-mixed with/without Dex in a surgery-induced osteoarthritis model in rats. Anterior cruciate ligament transection (ACLT) surgery was performed on the right knee of rats to induce OA. Male 2-month-old Sprague-Dawley rats were randomly divided into five groups (n = 10/per group): (1) ACLT + saline; (2) ACLT + cHA gel; (3) ACLT + cHA-Dex (0.2 mg/mL) gel; (4) ACLT + cHA-Dex (0.5 mg/mL) gel; (5) Sham + saline. Intra-joint injections were performed four weeks after ACLT in the right knee. All animals were euthanized at 12 weeks post-surgery. Cartilage damage and changes in the synovial membrane were assessed by micro X-ray, Indian ink articular surface staining, Safranin-O/Fast Green staining, immunohistochemistry, hematoxylin and eosin staining of the synovial membrane, and quantitative reverse transcription-polymerase chain reaction for changes in gene expression. Micro X-ray revealed that the knee joint treated with the cHA-Dex gel was wider than those treated with cHA gel alone or saline. The cHA-Dex gel group had less Indian ink staining (indicator of cartilage fibrillation) than the cHA gel or saline injection groups. Safranin-O/Fast Green staining indicated that increased proteoglycan staining and less cartilage damage were found in the cHA-Dex gel group compared with the cHA gel or saline injection groups. Quantification of histology findings from saline, cHA gel, cHA-Dex (0.2 mg/mL) gel, cHA-Dex (0.5 mg/mL) gel, and sham groups were 5.84 ± 0.29, 4.50 ± 0.87, 3.00 ± 1.00, 2.00 ± 0.48, and 0.30 ± 0.58 (p < 0.05), respectively. A strong staining of type II collagen was found in both the cHA-Dex gel groups compared with saline group or cHA alone group. Similar result was found for the mRNA level of aggrecan and opposite result for type X collagen. Hematoxylin and eosin staining in the synovial membrane showed less synovial lining cell layers and reduced inflammatory cell infiltration in cHA-Dex gel-treated animals compared with saline or cHA only groups. Altogether, cHA-Dex gel has better chondroprotective and anti-inflammatory effects in rat surgery-induced osteoarthritis than cHA alone.

[Injection treatment with hyaluronic acid]

This article presents the spectrum of indications for the use of hyaluronic acid (HA) based on the recommendations of the European League Against Rheumatism (EULAR), the American College of Rheumatology (ACR), the Osteoarthritis Research Society International (OARSI), the International Institute for Health and Clinical Excellence (NICE) and the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO) taking the reality of patient care in Europe into account.

Hyaluronan modulates TRPV1 channel opening, reducing peripheral nociceptor activity and pain

Hyaluronan (HA) is present in the extracellular matrix of all body tissues, including synovial fluid in joints, in which it behaves as a filter that buffers transmission of mechanical forces to nociceptor nerve endings thereby reducing pain. Using recombinant systems, mouse-cultured dorsal root ganglia (DRG) neurons and in vivo experiments, we found that HA also modulates polymodal transient receptor potential vanilloid subtype 1 (TRPV1) channels. HA diminishes heat, pH and capsaicin (CAP) responses, thus reducing the opening probability of the channel by stabilizing its closed state. Accordingly, in DRG neurons, HA decreases TRPV1-mediated impulse firing and channel sensitization by bradykinin. Moreover, subcutaneous HA injection in mice reduces heat and capsaicin nocifensive responses, whereas the intra-articular injection of HA in rats decreases capsaicin joint nociceptor fibres discharge. Collectively, these results indicate that extracellular HA reduces the excitability of the ubiquitous TRPV1 channel, thereby lowering impulse activity in the peripheral nociceptor endings underlying pain.

Hyaluronan is a major component of the extracellular matrix, and is used to treat joint pain in osteoarthritis. In this study, Caires et al. show hyaluronan achieves its analgesic effects by targeting TRPV1 and stabilising the channel in its closed state.

Sorbitol-modified hyaluronic acid reduces oxidative stress, apoptosis and mediators of inflammation and catabolism in human osteoarthritic chondrocytes

OBJECTIVE AND DESIGN

Our study was designed to elucidate the precise molecular mechanisms by which sorbitol-modified hyaluronic acid (HA/sorbitol) exerts beneficial effects in osteoarthritis (OA).

METHODS

Human OA chondrocytes were treated with increasing doses of HA/sorbitol ± anti-CD44 antibody or with sorbitol alone and thereafter with or without interleukin-1beta (IL-1β) or hydrogen peroxide (H2O2). Signal transduction pathways and parameters related to oxidative stress, apoptosis, inflammation, and catabolism were investigated.

RESULTS

HA/sorbitol prevented IL-1β-induced oxidative stress, as measured by reactive oxygen species, p47-NADPH oxidase phosphorylation, 4-hydroxynonenal (HNE) production and HNE-metabolizing glutathione-S-transferase A4-4 expression. Moreover, HA/sorbitol stifled IL-1β-induced metalloproteinase-13, nitric oxide (NO) and prostaglandin E2 release as well as inducible NO synthase expression. Study of the apoptosis process revealed that this gel significantly attenuated cell death, caspase-3 activation and DNA fragmentation elicited by exposure to a cytotoxic H2O2 dose. Examination of signaling pathway components disclosed that HA/sorbitol prevented IL-1β-induced p38 mitogen-activated protein kinase and nuclear factor-kappa B activation, but not that of extracellular signal-regulated kinases 1 and 2. Interestingly, the antioxidant as well as the anti-inflammatory and anti-catabolic effects of HA/sorbitol were attributed to sorbitol and HA, respectively.

CONCLUSIONS

Altogether, our findings support a beneficial effect of HA/sorbitol in OA through the restoration of redox status and reduction of apoptosis, inflammation and catabolism involved in cartilage damage.

Blockade of nociceptive sensory afferent activity of the rat knee joint by the bradykinin B2 receptor antagonist fasitibant

OBJECTIVE

The aim of this study was to determine in intact and inflamed knee joints of the rat, the effect of the bradykinin (BK) B2 receptor antagonist fasitibant (MEN16132) on nociceptor mechanosensitivity and hyperalgesia.

METHODS

Joint afferent sensory fibers of the medial articular nerve of anesthetized animals were electrophysiologically recorded, measuring nerve impulse activity evoked by passive innocuous and noxious movements of the joint, in intact and kaolin and carrageenan-injected joints. Knee joints of rats were also acutely inflamed by intra-articular injection of carrageenan alone. Long term duration of fasitibant antinociceptive effects were behaviorally evaluated using the incapacitance test.

RESULTS

BK (100 μM) injected into the saphenous artery, induced excitation and sensitization of multi- and single unit recordings. Fasitibant (300 μM) injected prior to BK, reduced its excitatory effects as well as the overall increase of movement-evoked activity resulting from repeated injections of BK. Fasitibant did not affect movement-evoked activity of sensory fibers of intact, non-inflamed knee joints. Intra-articular fasitibant (100 μg/knee) significantly reduced the carrageenan-induced inflammatory hyperalgesia measured with the incapacitance test up to four days after treatment. This antinociceptive effect was not obtained with systemic endovenous injection of the drug.

CONCLUSIONS

Fasitibant prevents B2 receptor-mediated activation and sensitization of peripheral joint afferents and the ensuing inflammatory hyperalgesia, and may be a useful, novel drug for arthritis pain treatment.

Early decrease of serum biomarkers of type II collagen degradation (Coll2-1) and joint inflammation (Coll2-1 NO₂ ) by hyaluronic acid intra-articular injections in patients with knee osteoarthritis: a research study part of the Biovisco study

To measure the evolution of the serum levels of specific Osteoarthritis (OA) biomarker, Coll2-1 and Coll2-1 NO₂ in knee osteoarthritic patients after viscosupplementation (VS). Fifty-one patients with unilateral symptomatic knee were recruited for this prospective open label study. They received three intra-articular injections of 2 ml of hyaluronic acid (Hylan GF-20) and were followed for 3 months. Walking pain was evaluated and serum samples were taken at each visit. Coll2-1 and Coll2-1 NO₂ were measured in the serum using specific immunoassays. Variations over time of each parameter and predictive factor of response were studied. Forty-five patients were analyzed. The serum concentrations of Coll2-1 and Coll2-1 NO₂ were significantly higher in KL III/IV patients compared to KL I/II patients at baseline and decreased systematically over time after VS. Its effect was ever more pronounced in patients with KL III/IV. The serum concentration of Coll2-1 was significantly lower at baseline in responders than in non-responders. This study suggests a rapid slowdown of type II collagen degradation and joint inflammation after VS with Hylan G-20 and gives additional information for the validation of accurate biomarkers for OA. The serum level of Coll2-1 appeared to be a predictive factor for response to treatment.

Injectable hyaluronic-acid-doxycycline hydrogel therapy in experimental rabbit osteoarthritis

Background

Osteoarthritis (OA) is a common joint disease that causes disabilities in elderly adults. However, few long-lasting pharmacotherapeutic agents with low side effects have been developed to treat OA. We evaluated the therapeutic effects of intra-articular injections of hydrogels containing hyaluronic acid (HA) and doxycycline (DOX) in a rabbit OA model.

Results

Thirteen week old New Zealand White rabbits undergone a partial meniscectomy and unilateral fibular ligament transection were administered with either normal saline (NT), HA, DOX or HA-DOX hydrogels on day 0, 3, 6, 9 and 12; animals were also examined the pain assessment in every three days. The joint samples were taken at day 14 post-surgery for further histopathological evaluation. The degree of pain was significantly attenuated after day 7 post-treatment with both HA and HA-DOX hydrogels. In macroscopic appearance, HA-DOX hydrogel group showed a smoother cartilage surface, no or minimal signs of ulceration, smaller osteophytes, and less fissure formation in compare to HA or DOX treatment alone. In the areas with slight OA changes, HA-DOX hydrogel group exhibited normal distribution of chondrocytes, indicating the existence of cartilage regeneration. In addition, HA-DOX hydrogels also ameliorated the progression of OA by protecting the injury of articular cartilage layer and restoring the elastoviscosity.

Conclusion

Overall, from both macroscopic and microscopic data of this study indicate the injectable HA-DOX hydrogels presented as a long-lasting pharmacotherapeutic agent to apply for OA therapy.

Efficacy Evaluation of a New Hyaluronan Derivative HYADD® 4-G to Maintain Cartilage Integrity in a Rabbit Model of Osteoarthritis

Objective: To test the efficacy of a hyaluronan derivative (HYADD^®4-G) in a model of osteoarthritis (anterior cruciate ligament [ACLT]) and to compare its efficacy with the injection of growth factors. Design: In a first experimental set-up, specially selected for treatment scheme with published studies on hyaluronan or growth factor efficacy in osteoarthritis, saline, HYADD^®4-G, rh-BMP-7, and the treatments of rh-BMP-7 or rh-BMP-2 with HYADD^®4-G were injected after ACLT, for five times starting 3 weeks after ACLT. Euthanasia was at day 70. The knees were evaluated by gross morphological observation, x-ray, and histology (Study A). In a second experimental set-up selected to evaluate the efficacy of three viscosupplement injections, starting 4 weeks after ACTL, HYADD^®4-G was compared to saline (Study B). Results: (A) X-ray analysis showed more damage in the saline group than all other treatment groups (2.67 ± 0.61 for saline, 0.83 ± 0.26 for HYADD^®4-G, 1.67 ± 0.82 for HYADD^®4-G with rh-BMP-2, 0.75 ± 0.76 for HYADD^®4-G with rh-BMP-7, and 1.58 ± 0.49 for rh-BMP-7), P < 0.05. In the femoral condyle, the Mankin's score for HYADD^®4-G with rh-BMP-2, HYADD^®4-G with rh-BMP-7, and rh-BMP7 alone was statistically lower compared to saline in the medial part; in the lateral part a significant lower value was observed in the HYADD^®4-G with the rh-BMP-2 group. (B) The Kellgren and Lawrence score and Mankin's score was lower in the HYADD^®4-G group than in the saline group (P < 0.002 and P = 0.0031). Conclusions: These two studies suggest that HYADD^®4-G delayed the cartilage degeneration and that the association of HYADD^®4-G with growth factors is synergistic.

Hyaluronic acid concentrations in synovial fluid of dogs with different stages of osteoarthritis

To compare hyaluronic acid (HA) concentrations measured in synovial fluid (SF) of joints with different stages of canine secondary osteoarthritis (OA), clinical-orthopedic, radiographic, macroscopic intra-operative and SF findings of 49 joints were assessed. The sum of single findings was correlated to HA concentrations measured by a commercially available ELISA. Joints were categorized into three OA-groups: non-osteoarthritic, mildly osteoarthritic, and severely osteoarthritic. A significant negative correlation was found between severity of OA and HA concentrations (r=-0.696; P<0.001). Median values of HA concentrations decreased with increasing severity of the disease. Statistically significant differences in HA concentrations were observed between the OA-groups (P<0.001). Due to overlapping values between groups, it was concluded that synovial HA concentrations may only indicate a trend of osteoarthritic disease activity, but is not suitable for staging the disease.

Hyaluronan injection therapy for athletic patients with patellar tendinopathy

BACKGROUND

Patellar tendinopathy produces activity-related pain and focal tenderness at the attachment of the patellar tendon at the lower pole of the patella. It frequently causes a reduction in athletic ability. An injection of hyaluronan was found to be useful for patellar tendinopathy, provided the indication is appropriate, based on the authors' pilot cases. The purpose of this study was to summarize the clinical experience of and to describe the appropriate indication for this injection therapy.

METHODS

Fifty patients were treated from January 1999 to December 2006. The observation period averaged 25.7 months (range 6-88). All patients were graded stage 2 or 3 by Blazina's classification. Each treatment was counted separately for 9 patients (10 knees) who had more than one treatment period with 3 months or more between the injections. There were 4 bilaterally injected patients. Patellar tendinopathy was classified into 4 types according to the degree of tenderness and the regions that are tender. Hyaluronan was injected into the interface between the patellar tendon and the infrapatellar fat pad at the proximal insertion, or into the region of maximum tenderness.

RESULTS

The total number of injections was 135, and there were an average of 2.0 injections per case (range 1-11). Following treatment, 54 % of the cases were rated in excellent condition, as they were able to return to their previous athletic activities with little difficulty, while 40 % of the cases were rated in good condition-these patients were able to return to their previous sporting activities with some degree of limitation.

CONCLUSIONS

Hyaluronan injection therapy for athletic patients with patellar tendinopathy is an optional but effective treatment.

Early effect of hyaluronic acid intra-articular injections on serum and urine biomarkers in patients with knee osteoarthritis: An open-label observational prospective study

The aim of the study was to investigate the effect of hyaluronic acid (HA) intra articular injections (IA) on osteoarthritis (OA) biomarkers in patients with knee OA. Prospective open label study. Fifty-one patients with unilateral symptomatic K-OA received IA injections of 2mL of HA on days (D) 1, 7, 14 and were followed 3 months. At D-15 patients were examined and X-rays performed, to exclude patients with bilateral K-OA, or those with more than three symptomatic OA joints. From 15 days (D-15) before the first injection to D90 concomitant therapies were unchanged. Walking pain (WP) on VAS was obtained at each visit. Urine (U) and serum (S) samples were obtained at D-15, D1, D30, and D90. S-C2C, S-Cartilage oligomeric matrix protein, S-HA, S-CS 846 epitope, S-type II collagen propeptide, and U-type II collagen C telopeptide (U-CTX II/creatinin) were assayed. Predictive factors of response were analyzed using logistic regression. Correlations between variables were obtained using Spearman test. Forty-five patients were analyzed. Between D-15 and D1 there was no difference for any biomarkers At D1, WP (SD) was correlated with U-CTX II/creat (p = 0.006). Between D1 and D90: U-CTX II/creat decreased significantly. After adjustment for confounding variables there was a significant correlation between clinical response and U-CTX II/creat variation. U-CTX II and S-HA at baseline were independently predictive of clinical response. This study showed that 90 days after HA IA injections, U-CTX II levels significantly decrease compared to baseline, suggesting a slowdown of type II collagen degradation.

The protective effect of xanthan gum on interleukin-1β induced rabbit chondrocytes

We have previously shown that intra-articular injection of xanthan gum (XG) could protect the joint cartilage and reduce osteoarthritis progression. In this study, we investigated the preliminary cytotoxicity of XG on chondrocytes, evaluated the effects of XG on the proliferation and the protein expression of matrix metalloproteinases (MMPs), tissue inhibitors of metalloproteinase-1 (TIMP-1) in interleukin-1β (IL-1β)-induced rabbit chondrocytes. Primary rabbit chondrocytes were cultured. After treatment with various concentrations of XG with or without 10 ng/mL IL-1β, the proliferation of chondrocytes was evaluated using the MTT assay and the expression levels of MMPs and TIMP-1 were evaluated using ELISA. The results showed that XG alone displayed no adverse effects on cell viability and reversed significantly IL-1β-reduced cell proliferation in a dose-dependent manner. Furthermore, XG showed a dose-dependent inhibition in the IL-1β-induced release of MMPs while increasing TIMP-1 expression. These results strongly suggest that XG affords protection on IL-1β induced rabbit chondrocytes.

Spontaneous firing in C-fibers and increased mechanical sensitivity in A-fibers of knee joint-associated mechanoreceptive primary afferent neurones during MIA-induced osteoarthritis in the rat

OBJECTIVE

Osteoarthritis (OA) pain mechanisms are poorly understood. We used the monosodium iodoacetate (MIA) model of knee OA to characterize changes in excitability during the course of OA in different classes of mechanosensitive afferents projecting to joint-associated tissues, and examine whether these afferent responses and pain behavior are correlated.

METHODS

Rats were injected intra-articularly with MIA (1mg in 50 μl). Hind-limb weight bearing was studied 3 (MIA3) and 14 (MIA14) days after MIA, followed by deep anesthesia and teased-nerve-fiber recordings. Spontaneous activity (SA) and mechanically evoked responses of A- and C-mechanosensitive fibers (AM and CM respectively, probably nociceptive) innervating tissues associated with the ipsilateral knee joint were examined.

RESULTS

MIA3 and MIA14 rats exhibited reduced ipsilateral weight bearing. SA (>0.02 impulses/s) occurred in ∼50% of CMs from MIA rats vs 0% in normals. SA firing rates in CMs were significantly higher than normal; decreased weight bearing was correlated with increased CM SA rates. Neither percentages of AMs with SA (20%) nor their firing rates (0-0.01 impulses/s) significantly increased after MIA. In contrast, in MIA rats AMs, but not CMs, exhibited decreased mechanical thresholds and increased firing rates in response to suprathreshold mechanical stimulation.

CONCLUSIONS

These findings of increased SA firing rate in CMs but not AMs and increased mechanical sensitivity of AMs, but not CMs, have not previously been reported. These are two distinct important physiological mechanisms that may underpin spontaneous pain (CMs) and stimulus-evoked pain (AMs) in OA. Our data contribute to a mechanism-based understanding of OA pain.

Intra-articular Duration of Durolane™ after Single Injection into the Rabbit Knee

OBJECTIVE

The aim of the present study was to investigate the intra-articular duration of Durolane™ in a rabbit model to allow comparison between Durolane™ residence time and data reported for other hyaluronic acid products as well as native hyaluronic acid.

DESIGN

(14)C-labeled Durolane™ was manufactured by labeling the cross-linker used for stabilization. A single injection of approximately 0.3 mL (14)C-labeled Durolane™ was administered intra-articularly in both knee joints of male New Zealand White rabbits. At days 1, 2, 3, 7, 28, 60, 96, and 120 after injection, the knee joints of 4 animals were collected, and the radioactivity of the remaining gel was measured. The obtained data were fitted by exponential models to calculate the half-life of the gel. Two additional rabbits were used for histology of the joint 127 days after the injection.

RESULTS

The elimination of (14)C-labeled Durolane™ followed first-order kinetics with an apparent half-life of approximately 32 days. Histology showed no morphological changes in the knee joints.

CONCLUSIONS

This study shows that Durolane™ has a half-life of 32 days in the rabbit knee joint, which is much longer compared to literature data on hyaluronic acid and other modified hyaluronic acid products.

Evaluation of long-term antinociceptive properties of stabilized hyaluronic acid preparation (NASHA) in an animal model of repetitive joint pain

Introduction

Clinical trials provided controversial results on whether the injection of hyaluronan preparations into osteoarthritic joints reduces pain. Problems of clinical studies may be the substantial placebo effects of intra-articular injections, different severity and rate of progression of the disease and others. We hypothesize that the use of preclinical pain models may help to clarify whether a certain hyaluronan exerts antinociceptive effects upon intra-articular injection. In the present study we tested in the bradykinin/prostaglandin E₂ (PGE₂) model primarily the putative antinociceptive effect of stabilized hyaluronic acid from a non animal source (NASHA), a stabilized hyaluronic acid based gel for intra-articular treatment of OA. We established a dose-response relationship for NASHA and we compared NASHA to other hyaluronans with different formulations that are in clinical use.

Methods

To induce transient joint pain episodes bradykinin and PGE₂ were repetitively administered intra-articularly and unilaterally into rat knee joints during short anaesthesia. After establishment of the predrug nociceptive responses, a single intra-articular injection of saline or NASHA at different concentrations was administered and pain responses to further bradykinin/PGE₂ injections were monitored up to 56 days after NASHA. Furthermore, the obtained effective dose was compared to clinically defined concentrations of Hylan GF20 and sodium hyaluronate. The primary outcome measures were primary mechanical hyperalgesia at the knee joint and pain-induced weight bearing.

Results

On day 1 after injection, all tested hyaluronan preparations showed an antinociceptive effect >50% compared to saline. Single injections of higher doses of NASHA (50, 75 and 100 μl) were antinociceptive up to 56 days. When injection volumes in rat knee joints were adapted to clinical injection volumes in humans, the antinociceptive effects of the cross-linked NASHA and Hylan GF20 had a longer duration than that of the non cross-linked sodium hyaluronate (with a slightly better effect of NASHA than Hylan GF20).

Conclusions

In the bradykinin/PGE₂ model of joint pain a single injection of all hyaluronan preparations provided significant antinociceptive effects compared to saline. It appeared that the duration of the antinociceptive effect of the cross-linked hyaluronan preparations NASHA and Hylan GF20 was more prolonged. In addition, the gel beads structure allowing only a slow release of hyaluronic acid (NASHA) may even enhance this prolonged antinociceptive effect.

Membrane-tethered peptides patterned after the TRP domain (TRPducins) selectively inhibit TRPV1 channel activity

The transient receptor potential vanilloid 1 (TRPV1) channel is a thermosensory receptor implicated in diverse physiological and pathological processes. The TRP domain, a highly conserved region in the C terminus adjacent to the internal channel gate, is critical for subunit tetramerization and channel gating. Here, we show that cell-penetrating, membrane-anchored peptides patterned after this protein domain are moderate and selective TRPV1 antagonists both in vitro and in vivo, blocking receptor activity in intact rat primary sensory neurons and their peripheral axons with mean decline time of 30 min. The most potent lipopeptide, TRP-p5, blocked all modes of TRPV1 gating with micromolar efficacy (IC(50)<10 μM), without significantly affecting other thermoTRP channels. In contrast, its retrosequence or the corresponding sequences of other TRPV channels did not alter TRPV1 channel activity (IC(50)>100 μM). TRP-p5 did not affect the capsaicin sensitivity of the vanilloid receptor. Our data suggest that TRP-p5 interferes with protein-protein interactions at the level of the TRP domain that are essential for the "conformational" change that leads to gate opening. Therefore, these palmitoylated peptides, which we termed TRPducins, are noncompetitive, voltage-independent, sequence-specific TRPV1 blockers. Our findings indicate that TRPducin-like peptides may embody a novel molecular strategy that can be exploited to generate a selective pharmacological arsenal for the TRP superfamily of ion channels.

The OARSI histopathology initiative - recommendations for histological assessments of osteoarthritis in the guinea pig

OBJECTIVE

This review focuses on the criteria for assessing osteoarthritis (OA) in the guinea pig at the macroscopic and microscopic levels, and recommends particular assessment criteria to assist standardization in the conduct and reporting of preclinical trails in guinea pig models of OA.

METHODS

A review was conducted of all OA studies from 1958 until the present that utilized the guinea pig. The PubMed database was originally searched August 1, 2006 using the following search terms: guinea pig and OA. We continued to check the database periodically throughout the process of preparing this chapter and the final search was conducted January 7, 2009. Additional studies were found in a review of abstracts from the OsteoArthritis Research Society International (OARSI) conferences, Orthopaedic Research Society (ORS) conferences, and literature related to histology in other preclinical models of OA reviewed for relevant references. Studies that described or used systems for guinea pig joint scoring on a macroscopic, microscopic, or ultrastructural basis were included in the final comprehensive summary and review. General recommendations regarding methods of OA assessment in the guinea pig were derived on the basis of a comparison across studies and an inter-rater reliability assessment of the recommended scoring system.

RESULTS

A histochemical-histological scoring system (based on one first introduced by H. Mankin) is recommended for semi-quantitative histological assessment of OA in the guinea pig, due to its already widespread adoption, ease of use, similarity to scoring systems used for OA in humans, its achievable high inter-rater reliability, and its demonstrated correlation with synovial fluid biomarker concentrations. Specific recommendations are also provided for histological scoring of synovitis and scoring of macroscopic lesions of OA.

CONCLUSIONS

As summarized herein, a wealth of tools exist to aid both in the semi-quantitative and quantitative assessment of OA in the guinea pig and provide a means of comprehensively characterizing the whole joint organ. In an ongoing effort at standardization, we recommend specific criteria for assessing the guinea pig model of OA as part of an OARSI initiative, termed herein the OARSI-HISTOgp recommendations.

Hylan G-F 20 single-injection formulation

Hylan G-F 20, a cross-linked hyaluronic acid derivative, is an elastoviscous, high-molecular-weight (average 6000 kDa) fluid with rheological properties similar to those of knee synovial fluid of healthy young individuals. In a 26-week, randomized, double-blind, multicentre study in patients with symptomatic primary osteoarthritis of the knee (n = 253), one intra-articular injection of hylan G-F 20 (single-injection formulation) into the target knee significantly relieved pain (as measured by the Western Ontario and McMaster Universities Osteoarthritis Index pain [WOMAC A] subscale), including pain while walking on a flat surface (as assessed by the WOMAC A1 subscore), compared with placebo. Observer-reported disease status and patient-reported health status were also significantly improved in hylan G-F 20-treated patients compared with placebo-treated patients. A single intra-articular injection of hylan G-F 20 was generally well tolerated, with an adverse event profile similar to that of placebo. Repeat administration of hylan G-F 20 after 6 months had a similar tolerability profile to that of the initial injection. However, no patient who developed a target-knee adverse event after their first injection experienced such an event following their second injection.

Delayed onset of changes in soma action potential genesis in nociceptive A-beta DRG neurons in vivo in a rat model of osteoarthritis

BACKGROUND

Clinical data on osteoarthritis (OA) suggest widespread changes in sensory function that vary during the progression of OA. In previous studies on a surgically-induced animal model of OA we have observed that changes in structure and gene expression follow a variable trajectory over the initial days and weeks. To investigate mechanisms underlying changes in sensory function in this model, the present electrophysiological study compared properties of primary sensory nociceptive neurons at one and two months after model induction with properties in naïve control animals. Pilot data indicated no difference in C- or Adelta-fiber associated neurons and therefore the focus is on Abeta-fiber nociceptive neurons.

RESULTS

At one month after unilateral derangement of the knee by cutting the anterior cruciate ligament and removing the medial meniscus, the only changes observed in Abeta-fiber dorsal root ganglion (DRG) neurons were in nociceptor-like unresponsive neurons bearing a hump on the repolarization phase; these changes consisted of longer half width, reflecting slowed dynamics of AP genesis, a depolarized Vm and an increased AP amplitude. At two months, changes observed were in Abeta-fiber high threshold mechanoreceptors, which exhibited shorter AP duration at base and half width, shorter rise time and fall time, and faster maximum rising rate/maximum falling rate, reflecting accelerated dynamics of AP genesis.

CONCLUSION

These data indicate that Abeta nociceptive neurons undergo significant changes that vary in time and occur later than changes in structure and in nociceptive scores in this surgically induced OA model. Thus, if changes in Abeta-fiber nociceptive neurons in this model reflect a role in OA pain, they may relate to mechanisms underlying pain associated with advanced OA.

Intra-articular injections of hyaluronan solutions of different elastoviscosity reduce nociceptive nerve activity in a model of osteoarthritic knee joint of the guinea pig

OBJECTIVE

To study in guinea pigs knee joints the effects of intra-articular injection of HYADD 4-G (Fidia-Farmaceutici), a novel hyaluronan (HA)-derived elastoviscous material and of Hyalgan (Fidia-Farmaceutici), a HA product with very low viscoelasticity, on movement-evoked nociceptor impulse activity from normal and inflamed knee joints.

DESIGN

Nociceptor impulse activity was recorded from single Adelta and C fibers of the medial articular nerve either under control conditions or after induction of an experimental knee joint osteoarthritis (OA) by partial medial menisectomy and transection of the anterior cruciate ligament (PMM-TACL). The stimuli consisted of standardized innocuous and noxious inward and outward rotations of the tibia against the femur of 50s duration, repeated every 5min for 1.5h.

RESULTS

The number of movement-evoked impulses was significantly augmented 1 day and 1 week after PMM-TACL compared with intact knee joint. The enhanced impulse response to joint movements 1 week following surgery was attenuated by repeated intra-articular injection of HYADD 4-G and even more prominently by Hyalgan.

CONCLUSIONS

HA products have a reducing action on joint nociceptor discharges that appears to depend predominantly on their role as an elastoviscous filter associated with their rheological properties, but also on a chemical effect on sensitized nociceptive terminals of inflamed joint tissues, possibly linked to the HA concentration.