Longitudinal in vivo cationic contrast-enhanced computed tomography classifies equine articular cartilage injury and repair.

Cationic contrast-enhanced computed tomography (CECT) capitalizes on increased contrast agent affinity to the charged proteoglycans in articular cartilage matrix to provide quantitative assessment of proteoglycan content with enhanced images. While high resolution microCT has demonstrated success, we investigate cationic CECT use in longitudinal in vivo imaging at clinical resolution. We hypothesize that repeated administration of CA4+ will have no adverse side effects or complications, and that sequential in vivo imaging assessments will distinguish articular cartilage repair tissue from early degenerative and healthy cartilage in critically sized chondral defects. In an established equine translational preclinical model, lameness and synovial effusion scores are similar to controls after repeated injections of CA4+ (eight injections over 16 weeks) compared to controls. Synovial fluid total protein, leukocyte concentration, and sGAG and PGE2 concentrations and articular cartilage and synovial membrane scores are also equivalent to controls. Longitudinal in vivo cationic CECT attenuation in repair tissue is significantly lower than peripheral to (adjacent) and distantly from defects (remote sites) by 4 weeks (p < 0.001), and this difference persists until 16 weeks. At the 6- and 8-week time points, the adjacent locations exhibit significantly lower cationic CECT attenuation compared with the remote sites, reflecting peri-defect degeneration (p < 0.01). Cationic CECT attenuation at clinical resolution significantly correlates with cationic CECT (microCT) (r = 0.69, p < 0.0001), sGAG (r = 0.48, p < 0.0001), and ICRS II histology score (r = 0.63, p < 0.0001). In vivo cationic CECT imaging at clinical resolution distinguishes fibrous repair tissue from degenerative and healthy hyaline cartilage and correlates with molecular tissue properties of articular cartilage.

IL-1ra gene therapy in equine osteoarthritis improves physiological, anatomical, and biological outcomes of joint degeneration.

OBJECTIVE: To evaluate the effects of a gene transfer approach to IL-1ß inhibition in an equine osteochondral chip fragment model of joint injury using a self-complementary adeno-associated virus with interleukin receptor antagonist transgene cassette (scAAVIL-1ra), as posttraumatic osteoarthritis in horses, similar to people, is a significant clinical problem. ANIMALS: 16 horses were utilized for the study. METHODS: All horses had an osteochondral chip fragment induced arthroscopically in one middle carpal joint while the contralateral joint was sham operated. Eight horses received either scAAVIL-1ra or saline in the osteoarthritis joint. Horses were evaluated over 70 days clinically (lameness, imaging, and biomarker analysis) and euthanized at 70 days and evaluated grossly, with imaging and histopathology. RESULTS: The following findings were statistically significant. Injection of scAAVIL-1ra resulted in high synovial fluid levels of IL-1ra (0.5 to 9 µg/mL) throughout the duration of the experiment (70 days). Over the duration, we observed scAAVIL-1ra to improve lameness (lameness score relative improvement of 1.2 on a scale of 0 to 5), cause suppression of prostaglandin E2 (a relative decline of 30 pg/mL), and result in histological improvement in articular cartilage (decreased chondrocyte loss and chondrone formation) and subchondral bone (less osteochondral splitting and osteochondral lesions). Within the synovial membrane of scAAVIL-1ra-treated joints, we also observed perivascular infiltration with CD3-positive WBCs, suggesting lymphocytic T-cell perivascular infiltration commonly observed with viral transduction. CLINICAL RELEVANCE: These data provide support for further evaluation and optimization of scAAVIL-1ra gene therapy to treat equine osteoarthritis.

Use of quantitative mass spectrometry-based proteomics and ELISA to compare the alpha 2 macroglobulin concentration in equine blood-based products processed by three different orthobiologic devices.

Introduction: Alpha 2 macroglobulin (A2M), a multi-functional protein in the plasma protease inhibitor class, regulates proinflammatory cytokines and the clearance of chondrodestructive enzymes in cases of joint injury and osteoarthritis (OA). The purpose of this study was to compare A2M concentrations in equine plasma samples processed by three commercial devices developed for stall-side regenerative joint therapy. Methods: Plasma samples were obtained from healthy adult horses (N = 13). Mass spectrometry analysis was used to determine the concentration of protein analytes in each sample. Selected reaction monitoring measured a specific A2M peptide as a surrogate of the whole A2M protein. A2M concentrations produced by each test device were compared for two sample types: a pre-concentrate or platelet-poor (PP) component and a final component for use in the horse. Results: There was no significant difference (p > 0.05) in the geometric mean (GM) concentration of A2M in the final concentration samples produced by the Alpha2EQ® device (N horses = 13) and the single-centrifugation PP samples produced by the Pro-Stride® APS (autologous protein solution) device (N = 13) and the Restigen® PRP (platelet-rich plasma) device (N = 11). When A2M content in final concentration samples produced by each device was compared, the Pro-Stride APS and Restigen PRP samples had significantly greater GM A2M content (p < 0.0001) compared to the Alpha2EQ samples, and the Pro-Stride APS final concentration samples had significantly greater GM A2M concentration (p < 0.0001) versus that for the Restigen PRP final samples. Discussion: This comparison demonstrated that the volume and A2M concentration of an Alpha2EQ final concentrate are no different than the volume and concentration of A2M in the PP from Pro-Stride or Restigen devices.

Targeted transcriptomic analysis of synovial tissues from horses with septic arthritis treated with immune-activated mesenchymal stromal cells reveals induction of T-cell response pathways.

OBJECTIVE: To investigate mechanistically the reported beneficial effects of immune-activated mesenchymal stromal cell (MSC) therapy to treat equine septic arthritis, leveraging Nanostring technology. ANIMALS: 8 Quarter Horses with induced tibiotarsal Staphylococcus aureus septic arthritis treated IA with either Toll-like receptor-3 agonist polyinosinic:polycytidylic acid-activated MSCs + vancomycin antimicrobials (TLR-MSC-VAN; n = 4) or antimicrobials (VAN; 4). METHODS: Synovial tissues were collected and fixed in neutral-buffered 10% formalin, and formalin-fixed paraffin-embedded synovial and osteochondral tissues were sequenced using a custom-designed 200-gene equine Nanostring nCounter immune panel to directly quantify expression of key immune and cartilage-related genes. Immunohistochemistry to detect CD3+ T cells was performed on synovial tissues to further quantify T-cell infiltration in TLR-MSC-VAN- versus VAN-treated joints. RESULTS: Comparison of synovial transcriptomes between groups revealed moderate changes in differential gene expression, with upregulated expression of 9 genes and downregulated expression of 17 genes with fold change ≥ 2 or ≤ -2 and a significant false discovery rate-adjusted P value of ≤ .05. The most upregulated genes in TLR-MSC-VAN-treated horses included those related to T-lymphocyte recruitment and function, while pathways related to innate immune activation and inflammation were significantly downregulated. Immunohistochemistry and quantitation of CD3+ T-cell infiltrates revealed a numerically greater infiltrate in synovial tissues of TLR-MSC-VAN-treated horses, which did not reach statistical significance in this small sample set (P = .20). CLINICAL RELEVANCE: Targeted transcriptomic analyses using an equine Nanostring immune and cartilage health panel provided new mechanistic insights into how innate and adaptive immune cells within synovial tissues respond to TLR-activated MSC treatment when used to treat septic arthritis.

Subchondral bone sequestrum formation in the proximal intra-articular and osteochondral region of the third metatarsal bone of an Appaloosa mare treated for septic arthritis.

OBJECTIVE: To raise awareness of the potential for intra-articular subchondral bone sequestrum formation secondary to a traumatic or septic process to enable more rapid identification of this uncommon but possible outcome in future cases. ANIMAL: A client-owned 12-year-old Appaloosa mare. CLINICAL PRESENTATION, PROGRESSION, AND PROCEDURES: The mare had a wound to the lateral aspect of the fourth metatarsal bone (MT4) that communicated with the distal tarsal joints. Radiographs revealed a displaced, comminuted fracture of MT4. TREATMENT AND OUTCOME: The horse underwent aggressive debridement of the wound and MT4 as well as, on 2 occasions, needle joint lavage. Systemic, regional, and IA antibiotic therapy was also performed together with a bone graft from the tuber coxae. The horse's comfort improved, and the wound appeared to be healing. Five weeks following discharge, the horse re-presented with a non-weight-bearing lameness and radiographs revealed marked osteomyelitis of the tarsometatarsal and distal intertarsal joints. Postmortem examination of the limb identified a sequestrum within the proximal articular surface of the third metatarsal bone. CLINICAL RELEVANCE: The present report highlights the importance of arthroscopic lavage to visualize the cartilage surface and the benefits of advanced imaging to detect associated changes within the bone earlier than conventional radiographs. To our knowledge, no reports exist of intra-articular subchondral bone sequestra in the tarsometatarsal joint in horses.

Computed tomography and fluoroscopy versus radiographic guidance for internal fixation of simulated dorsomedial-plantarolateral central tarsal bone fractures in nonracehorses.

OBJECTIVE: The aim of this study was to assess screw placement in simulated dorsomedial-plantarolateral central tarsal bone (CTB) fractures using two imaging guidance techniques - computed tomography (CT) with fluoroscopy compared to digital radiography alone (DR). STUDY DESIGN: Experimental study. SAMPLE POPULATION: Equine cadaver hindlimbs (n = 10 pairs). METHODS: One tarsus per pair was randomly assigned to have a 4.5 mm cortical screw placed across the CTB using CT and fluoroscopy (CT/F group) or digital radiography alone (DR group). Postoperative CT was performed on all limbs. Variables related to marker placement, procedure time, and screw positioning were recorded and compared using a paired t-test for dependent means (p < .05). RESULTS: Time for marker placement was longer for the CT/F group (p = .001), with no difference in total procedure time (p = .12). CT/F was not superior to radiography alone (p > .05) for parameters related to screw positioning. Based on the 95% CI, there was greater range in relative screw length using radiography (76.5%-91.2%) versus CT/F (78.4%-84.0%). CONCLUSION: Internal fixation of CTB fractures can be successfully performed using either technique for imaging guidance. CT and fluoroscopy did not result in faster or more accurate screw placement compared to radiographs alone, except in determining screw length. CLINICAL SIGNIFICANCE: Mild adjustments in fluoroscopic or radiographic angle appeared to be a point of variability in the perception of screw placement. While CT is recommended for improved understanding of fracture configuration and surgical planning, radiographic guidance may be a suitable alternative for internal fixation of dorsomedial-plantarolateral fractures.

A polymer network architecture provides superior cushioning and lubrication of soft tissue compared to a linear architecture.

We report the relationships between linear vs. network polymer architecture and biomechanical outcomes including lubrication and cushioning when the polymers are applied to the surface of articulating knee cartilage. Aqueous formulations of the bioinspired polymer poly(2-methacryloyloxylethyl phosphorylcholine) (pMPC) exhibit tuneable rheological properties, with network pMPC exhibiting increased elasticity and viscosity compared to linear pMPC. Application of a polymer network, compared to a linear one, to articulating tissue surfaces reduces friction, lessens tissue strain, minimizes wear, and protects tissue - thereby improving overall tissue performance. Administration of the network pMPC to the middle carpal joint of skeletally mature horses elicits a safe response similar to saline as monitored over a 70 day period.

Extracellular vesicles in the treatment and prevention of osteoarthritis: can horses help us translate this therapy to humans?

Osteoarthritis (OA) is a common joint disease affecting humans and horses, resulting in significant morbidity, financial expense, and loss of athletic use. While the pathogenesis is incompletely understood, inflammation is considered crucial in the development and progression of the disease. Mesenchymal stromal cells (MSCs) have received increasing scientific attention for their anti-inflammatory, immunomodulatory, and pro-regenerative effects. However, there are concerns about their ability to become a commercially available therapeutic. Extracellular vesicles (EVs) are now recognized to play a crucial role in the therapeutic efficacy observed with MSCs and offer a potentially novel cell-free therapeutic that may negate many of the concerns with MSCs. There is evidence that EVs have profound anti-inflammatory, immunomodulatory, and pro-regenerative effects equal to or greater than the MSCs they are derived from in the treatment of OA. Most of these studies are in small animal models, limiting the translation of these results to humans. However, highly translational animal models are crucial for further understanding the efficacy of potential therapeutics and for close comparisons with humans. For this reason, the horse, which experiences the same gravitational impacts on joints similar to people, is a highly relevant large animal species for testing. The equine species has well-designed and validated OA models, and additionally, therapies can be further tested in naturally occurring OA to validate preclinical model testing. Therefore, the horse is a highly suitable model to increase our knowledge of the therapeutic potential of EVs.

Antimicrobial Properties of Equine Stromal Cells and Platelets and Future Directions.

Increasing antimicrobial resistance in veterinary practice has driven the investigation of novel therapeutic strategies including regenerative and biologic therapies to treat bacterial infection. Integration of biological approaches such as platelet lysate and mesenchymal stromal cell (MSC) therapy may represent adjunctive treatment strategies for bacterial infections that minimize systemic side effects and local tissue toxicity associated with traditional antibiotics and that are not subject to antibiotic resistance. In this review, we will discuss mechanisms by which biological therapies exert antimicrobial effects, as well as potential applications and challenges in clinical implementation in equine practice.

The use of radiofrequency in equine orthopedic surgery.

The use of radiofrequency energy (RFE) has become increasingly popular in equine orthopedic surgery in recent years, particularly for the debridement of cartilage lesions and soft tissue resection. However, despite considerable advancements in the technology, the safety and efficacy of RFE have continued to be questioned. While studies investigating the use of RFE for chondroplasty in the equine population are lacking, there is an abundance of research studies in the human literature assessing its effect on healthy chondrocytes, and researchers are seeking to develop guidelines to minimize collateral damage. This review article provides a concise and thorough summary of the current use of RFE in equine orthopedics, in addition to discussing the recent evidence surrounding its use for chondroplasty in both the human and equine populations.

Distinct differences in immunological properties of equine orthobiologics revealed by functional and transcriptomic analysis using an activated macrophage readout system.

Introduction: Multiple biological therapies for orthopedic injuries are marketed to veterinarians, despite a lack of rigorous comparative biological activity data to guide informed decisions in selecting a most effective compound. Therefore, the goal of this study was to use relevant bioassay systems to directly compare the anti-inflammatory and immunomodulatory activity of three commonly used orthobiological therapies (OTs): mesenchymal stromal cells (MSC), autologous conditioned serum (ACS), and platelet rich plasma (PRP). Methods: Equine monocyte-derived macrophages were used as the readout system to compare therapies, including cytokine production and transcriptomic responses. Macrophages were stimulated with IL-1ß and treated 24 h with OTs, washed and cultured an additional 24 h to generate supernatants. Secreted cytokines were measured by multiplex immunoassay and ELISA. To assess global transcriptomic responses to treatments, RNA was extracted from macrophages and subjected to full RNA sequencing, using an Illumina-based platform. Data analysis included comparison of differentially expressed genes and pathway analysis in treated vs. untreated macrophages. Results: All treatments reduced production of IL-1ß by macrophages. Secretion of IL-10 was highest in MSC-CM treated macrophages, while PRP lysate and ACS resulted in greater downregulation of IL-6 and IP-10. Transcriptomic analysis revealed that ACS triggered multiple inflammatory response pathways in macrophages based on GSEA, while MSC generated significant downregulation of inflammatory pathways, and PRP lysate induced a mixed immune response profile. Key downregulated genes in MSC-treated cultures included type 1 and type 2 interferon response, TNF-α and IL-6. PRP lysate cultures demonstrated downregulation of inflammation-related genes IL-1RA, SLAMF9, ENSECAG00000022247 but concurrent upregulation of TNF-α, IL-2 signaling, and Myc targets. ACS induced upregulation of inflammatory IL-2 signaling, TNFα and KRAS signaling and hypoxia, but downregulation of MTOR signaling and type 1 interferon signaling. Discussion: These findings, representing the first comprehensive look at immune response pathways for popular equine OTs, reveal distinct differences between therapies. These studies address a critical gap in our understanding of the relative immunomodulatory properties of regenerative therapies commonly used in equine practice to treat musculoskeletal disease and will serve as a platform from which further in vivo comparisons may build.

Evaluation of a modified subchondroplasty technique in an equine full-thickness cartilage defect model: a pilot study.

OBJECTIVE: To perform a pilot study with the intent of assessing the feasibility of a modified subchondroplasty (mSCP) technique in a validated preclinical equine model of full-thickness articular cartilage loss and evaluate the short-term patient response to the injected materials. ANIMALS: 3 adult horses. PROCEDURES: Two 15-mm-diameter full-thickness cartilage defects were created on the medial trochlear ridge of each femur. Defects were treated with microfracture and then filled by 1 of 4 techniques: (1) autologous fibrin graft (FG) via subchondral injection of fibrin glue (FG), (2) autologous fibrin graft via direct injection of FG, (3) subchondral injection of a calcium phosphate bone substitute material (BSM) with direct injection of FG, and (4) untreated control. Horses were euthanized after 2 weeks. Patient response was evaluated via serial lameness examination, radiography, magnetic resonance imaging, computed tomography, gross evaluation, microcomputed tomography, and histopathology. RESULTS: All treatments were successfully administered. The injected material perfused through the underlying bone into the respective defects without adversely affecting the surrounding bone and articular cartilage. Increased new bone formation was seen at the margins of the trabecular spaces containing BSM. There was no treatment effect on the amount or composition of tissue within defects. CLINICAL RELEVANCE: The mSCP technique was a simple, well-tolerated technique in this equine articular cartilage defect model without significant adverse effects to host tissues after 2 weeks. Larger studies with long-term follow-ups are warranted.

Serotype-specific transduction of canine joint tissue explants and cultured monolayers by self-complementary adeno-associated viral vectors.

A formal screening of self-complementary adeno-associated virus (scAAV) vector serotypes in canine joint tissues has not been performed to date. Selecting appropriate serotypes is crucial for successful treatment due to their varying levels of tissue tropism. The objective of this study is to identify the most optimal scAAV vector serotype that maximizes transduction efficiencies in canine cell monolayer cultures (chondrocytes, synoviocytes, and mesenchymal stem cells) and tissue explant cultures (cartilage and synovium). Transduction efficiencies of scAAV serotypes 1, 2, 2.5, 3, 4, 5, 6, 8, and 9 were evaluated in each culture type in three different vector concentrations by encoding a green fluorescent protein. It was found that scAAV2 and 2.5 showed the overall highest transduction efficiency among serotypes with dose-response. Since possible immune response against conventional AAV2 was previously reported in dogs, the chimeric scAAV2.5 may be more suitable to use. Evaluation of the safety and efficacy of the scAAV2.5 vector with an appropriate therapeutic gene in vivo is indicated.

TLR-activated mesenchymal stromal cell therapy and antibiotics to treat multi-drug resistant Staphylococcal septic arthritis in an equine model.

Background: Rapid development of antibiotic resistance necessitates advancement of novel therapeutic strategies to treat infection. Mesenchymal stromal cells (MSC) possess antimicrobial and immunomodulatory properties, mediated through antimicrobial peptide secretion and recruitment of innate immune cells including neutrophils and monocytes. TLR-3 activation of human, canine and equine MSC has been shown to enhance bacterial killing and clearance in vitro, in rodent Staphylococcal biofilm infection models and dogs with spontaneous multi-drug-resistant infections. The objective of this study was to determine if intra-articular (IA) TLR-3-activated MSC with antibiotics improved clinical parameters and reduced bacterial counts and inflammatory cytokine concentrations in synovial fluid (SF) of horses with induced septic arthritis. Methods: Eight horses were inoculated in one tarsocrural joint with multidrug-resistant Staphylococcus aureus (S. aureus). Bone marrow-derived MSC from three unrelated donors were activated with TLR-3 agonist polyinosinic, polycytidylic acid (pIC). Recipient horses received MSC plus vancomycin (TLR-MSC-VAN), or vancomycin (VAN) alone, on days 1, 4, 7 post-inoculation and systemic gentamicin. Pain scores, quantitative bacterial counts (SF, synovium), SF analyses, complete blood counts, cytokine concentrations (SF, plasma), imaging changes (MRI, ultrasound, radiographs), macroscopic joint scores and histologic changes were assessed. Results were reported as mean ± SEM. Results: Pain scores (d7, P=0.01, 15.2±0.2 vs. 17.9±0.5), ultrasound (d7, P=0.03, 9.0±0.6 vs. 11.8±0.5), quantitative bacterial counts (SF d7, P=0.02, 0±0 vs. 3.4±0.4; synovium P=0.003, 0.4±0.4 vs. 162.7±18.4), systemic neutrophil (d4, P=0.03, 4.6±0.6 vs. 7.8±0.6) and serum amyloid A (SAA) (d4, P=0.01, 1,106.0±659.0 vs. 2,858.8±141.3; d7, P=0.02, 761.8±746.2 vs. 2,357.3±304.3), and SF lactate (d7, P<0.0001, 5.4±0.2 vs. 15.0±0.3), SAA (endterm, P=0.01, 0.0 vs. 2,094.0±601.6), IL-6 (P=0.03, 313.0±119.2 vs. 1,328.2±208.9), and IL-18 (P=0.02, 11.1±0.5 vs. 13.3±3.8) were improved in TLR-MSC-VAN vs. VAN horses. Study limitations include the small horse sample size, short study duration, and lack of additional control groups. Conclusions: Combined TLR-activated MSC with antibiotic therapy may be a promising approach to manage joint infections with drug resistant bacteria.

Gene therapy approaches for equine osteoarthritis.

With an intrinsically low ability for self-repair, articular cartilage injuries often progress to cartilage loss and joint degeneration resulting in osteoarthritis (OA). Osteoarthritis and the associated articular cartilage changes can be debilitating, resulting in lameness and functional disability both in human and equine patients. While articular cartilage damage plays a central role in the pathogenesis of OA, the contribution of other joint tissues to the pathogenesis of OA has increasingly been recognized thus prompting a whole organ approach for therapeutic strategies. Gene therapy methods have generated significant interest in OA therapy in recent years. These utilize viral or non-viral vectors to deliver therapeutic molecules directly into the joint space with the goal of reprogramming the cells' machinery to secrete high levels of the target protein at the site of injection. Several viral vector-based approaches have demonstrated successful gene transfer with persistent therapeutic levels of transgene expression in the equine joint. As an experimental model, horses represent the pathology of human OA more accurately compared to other animal models. The anatomical and biomechanical similarities between equine and human joints also allow for the use of similar imaging and diagnostic methods as used in humans. In addition, horses experience naturally occurring OA and undergo similar therapies as human patients and, therefore, are a clinically relevant patient population. Thus, further studies utilizing this equine model would not only help advance the field of human OA therapy but also benefit the clinical equine patients with naturally occurring joint disease. In this review, we discuss the advancements in gene therapeutic approaches for the treatment of OA with the horse as a relevant patient population as well as an effective and commonly utilized species as a translational model.

Treatment Effects of Intra-Articular Allogenic Mesenchymal Stem Cell Secretome in an Equine Model of Joint Inflammation.

Background: Allogenic mesenchymal stem cell (MSC) secretome is a novel intra-articular therapeutic that has shown promise in in vitro and small animal models and warrants further investigation. Objectives: To investigate if intra-articular allogenic MSC-secretome has anti-inflammatory effects using an equine model of joint inflammation. Study Design: Randomized positively and negatively controlled experimental study. Method: In phase 1, joint inflammation was induced bilaterally in radiocarpal joints of eight horses by injecting 0.25 ng lipopolysaccharide (LPS). After 2 h, the secretome of INFy and TNFα stimulated allogeneic equine MSCs was injected in one randomly assigned joint, while the contralateral joint was injected with medium (negative control). Clinical parameters (composite welfare scores, joint effusion, joint circumference) were recorded, and synovial fluid samples were analyzed for biomarkers (total protein, WBCC; eicosanoid mediators, CCL2; TNFα; MMP; GAGs; C2C; CPII) at fixed post-injection hours (PIH 0, 8, 24, 72, and 168 h). The effects of time and treatment on clinical and synovial fluid parameters and the presence of time-treatment interactions were evaluated. For phase 2, allogeneic MSC-secretome vs. allogeneic equine MSCs (positive control) was tested using a similar methodology. Results: In phase 1, the joint circumference was significantly (p < 0.05) lower in the MSC-secretome treated group compared to the medium control group at PIH 24, and significantly higher peak synovial GAG values were noted at PIH 24 (p < 0.001). In phase 2, no significant differences were noted between the treatment effects of MSC-secretome and MSCs. Main Limitations: This study is a controlled experimental study and therefore cannot fully reflect natural joint disease. In phase 2, two therapeutics are directly compared and there is no negative control. Conclusions: In this model of joint inflammation, intra-articular MSC-secretome injection had some clinical anti-inflammatory effects. An effect on cartilage metabolism, evident as a rise in GAG levels was also noted, although it is unclear whether this could be considered a beneficial or detrimental effect. When directly comparing MSC-secretome to MSCs in this model results were comparable, indicating that MSC-secretome could be a viable off-the-shelf alternative to MSC treatment.

Current use of biologic therapies for musculoskeletal disease: A survey of board-certified equine specialists.

OBJECTIVE: To evaluate the use of mesenchymal stem cells (MSCs), autologous conditioned serum (ACS), platelet-rich plasma (PRP), and autologous protein solution (APS) for the treatment of equine musculoskeletal disease by diplomates of the American College of Veterinary Surgery (ACVS), and American College of Veterinary Sports Medicine and Rehabilitation (ACVSMR). STUDY DESIGN: Cross-sectional study. SAMPLE POPULATION: Diplomates (n = 423). METHODS: An email link was sent to ACVS and ACVMR diplomates. A survey contained 59 questions regarding demographics, as well as indications, frequency, adverse effects, and limitations of use. Responses were analyzed using Fisher's exact test. RESULTS: One hundred and fifty four surveys were analyzed. Years in practice and type of practice were not associated with biologic therapy use. PRP was the most used therapy (120/137; 87.5%). PRP and MSCs were most often administered intralesionally while ACS and APS were most often administered intra-articularly. ACS (50/104; 48.1%) treatment was repeated commonly within 2 weeks of initial injection. MSCs (39/90; 43.3%) and PRP (38/100; 38%) were commonly repeated 1-2 months after initial injection and APS was typically repeated >4 months after initial injection (21/53; 39.6%). Local inflammation and expense were the most common adverse effect and limitation of use. CONCLUSION: Diplomates most commonly utilized PRP and MSC intralesionally for soft-tissue injuries, and ACS and ACP intra-articularly for joint injury. Protocols for repeated administration varied widely. Local inflammation was a clinical concern with the use of biologics. CLINICAL SIGNIFICANCE: Biologic therapies are used commonly by ACVS and ACVSMR diplomates for soft tissue and joint disease.

Corrigendum: Gene therapy approaches for equine osteoarthritis.

[This corrects the article DOI: 10.3389/fvets.2022.962898.].

Evaluation of Intra-Articular Amikacin Administration in an Equine Non-inflammatory Joint Model to Identify Effective Bactericidal Concentrations While Minimizing Cytotoxicity.

Septic arthritis causes significant morbidity and mortality in veterinary and human clinical practice and is increasingly complicated by multidrug-resistant infections. Intra-articular (IA) antibiotic administration achieves high local drug concentrations but is considered off-label usage, and appropriate doses have not been defined. Using an equine joint model, we investigated the effects of amikacin injected at three different doses (500, 125, and 31.25 mg) on the immune and cartilage responses in tibiotarsal joints. Synovial fluid (SF) was sampled at multiple time points over 24 h, the cell counts determined, and amikacin concentrations measured by liquid chromatography-mass spectrometry. Cytokine concentrations and collagen degradation products in SF were measured by ELISA and multiplex immunoassays. The mean amikacin concentrations in SF were greater than or equal to the minimum inhibitory concentration (MIC) (0.004 mg/ml) for most common equine joint pathogens at all time points tested to 24 h for all three amikacin doses evaluated. The inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1ß) increased significantly in SF in the highest amikacin dose group, despite the fact that increases in SF cell counts were not observed. Similarly, the biomarkers of cartilage type II collagen cleavage (C2C and C12C) were increased in SF following amikacin injection. Mechanistically, we further demonstrated using in vitro studies that chondrocytes and synoviocytes killed by exposure to amikacin underwent apoptotic cell death and were phagocytosed by macrophages in a non-inflammatory process resembling efferocytosis. Neutrophils and T cells were susceptible to amikacin cytotoxicity at clinically relevant doses, which may result in blunting of cellular inflammatory responses in SF and account for the lack of increase in total nucleated cell counts following amikacin injection. In summary, decisions on whether to inject cytotoxic antibiotics such as aminoglycosides intra-articularly and what doses to use should take into account the potential harm that antibiotics may cause and consider lower doses than those previously reported in equine practice.

USE OF INTRACARPAL INTERLEUKIN RECEPTOR ANTAGONIST PROTEIN (IRAP) AND HYALURONIC ACID IN A MULTIMODAL THERAPEUTIC REGIME FOR OSTEOARTHRITIS IN AN ASIAN ELEPHANT (ELEPHAS MAXIMUS).

An approximately 41-yr-old female Asian elephant (Elephas maximus) experiencing forelimb stiffness and decreased range of motion was diagnosed with bilateral carpal osteoarthritis (OA). Standing sedation combined with local anesthesia was used to deliver ultrasound-guided carpal articular injections of an autologous conditioned serum product, interleukin receptor antagonist protein, combined with hyaluronic acid. Within 2 mo of completing therapy, improved range and speed of motion were evident. Reduced inflammation was suggested by decreased carpal articular prostaglandin E2 levels. Subjectively improved clinical signs lasted approximately 5-6 mo, at which point carpal articular injections were repeated. Joint inflammatory markers were useful in gauging response to treatment and may provide guidance in the diagnostic and therapeutic approach to elephant OA. On the basis of the positive response noted, interarticular autologous therapy combined with hyaluronic acid should be considered for carpal OA in elephants.