Olivier M. Lepage

Effects of platelet-rich plasma on the repair of wounds on the distal aspect of the forelimb in horses.

OBJECTIVE To evaluate the effect of platelet-rich plasma on wounds on the distal aspect of the forelimb in horses. ANIMALS 6 mixed-breed 10- to 15-year-old mares. PROCEDURES 3 wounds were created on metacarpal regions in each of 6 horses (n = 36 wounds total). Eighteen wounds were treated with platelet-rich plasma and bandaged, whereas 18 control wounds were similarly bandaged with no prior topical treatment. Decrease in wound surface area and the required number of excisions of exuberant granulation tissue were recorded until complete healing. Tissue specimens were taken from wounds at 1 week for histologic examination and measurement of transforming growth factor-beta1 concentrations and at closure for histologic examination, biomechanical evaluation, and measurement of collagen type I and type III mRNA. RESULTS Platelet-rich plasma favored excessive development of granulation tissue and significantly slowed wound healing at 1, 2, and 3 weeks after surgery. Transforming growth factor-beta1 had a 1.6-fold higher concentration in treated wounds, compared with untreated wounds. Histologic, biomechanical, and gene expression data did not differ significantly between treated and control wounds. CONCLUSIONS AND CLINICAL RELEVANCE Topical application of autologous platelet-rich plasma did not accelerate or improve the quality of repair of small granulating wounds on limbs of horses. This treatment may better suit wounds with massive tissue loss or, alternatively, chronic wounds that would benefit from a fresh source of mediators to accelerate the healing process.

Trans-arterial coil embolization of the internal carotid artery in standing horses.

Objectives To develop transarterial coil embolization (TACE) for occlusion of the internal carotid artery (ICA), in normal standing horses, and to evaluate it use for prevention of hemorrhage in horses with guttural pouch mycosis (GPM). Study Design Prospective study. Animals Normal horses (n = 8) and 5 with GPM. Methods Horses had TACE of the ICA in standing position under fluoroscopic guidance. Four normal horses were euthanatized 2 weeks after TACE for morphologic assessment and 4 were followed for 6 months. The 5 clinically affected horses were evaluated for long-term (10–12 months) success rate and complications. Results No complications related to the TACE were noted. Up to 30 mL warmed meglumine ioxithalamate was injected and well tolerated. Standing angiography confirmed complete occlusion of all vessels, and coils were positioned as intended; the procedure did not alter local hemodynamics. At 2 weeks, maturing to mature continuous thrombi was seen at the site of the coils. Two clinically affected horses died at day 3 and 12 after surgery from other problems. In the 3 surviving horses, mycotic lesions completely resolved without additional treatment. Conclusions TACE under fluoroscopic guidance in standing horses provided a safe, minimally invasive, and effective method for ICA occlusion and should be recommended for individuals at risk of general anesthesia. Residual neurologic deficits are a common sequela, but they do not reflect a treatment failure.OBJECTIVES To develop transarterial coil embolization (TACE) for occlusion of the internal carotid artery (ICA), in normal standing horses, and to evaluate it use for prevention of hemorrhage in horses with guttural pouch mycosis (GPM). STUDY DESIGN Prospective study. ANIMALS Normal horses (n = 8) and 5 with GPM. METHODS Horses had TACE of the ICA in standing position under fluoroscopic guidance. Four normal horses were euthanatized 2 weeks after TACE for morphologic assessment and 4 were followed for 6 months. The 5 clinically affected horses were evaluated for long-term (10-12 months) success rate and complications. RESULTS No complications related to the TACE were noted. Up to 30 mL warmed meglumine ioxithalamate was injected and well tolerated. Standing angiography confirmed complete occlusion of all vessels, and coils were positioned as intended; the procedure did not alter local hemodynamics. At 2 weeks, maturing to mature continuous thrombi was seen at the site of the coils. Two clinically affected horses died at day 3 and 12 after surgery from other problems. In the 3 surviving horses, mycotic lesions completely resolved without additional treatment. CONCLUSIONS TACE under fluoroscopic guidance in standing horses provided a safe, minimally invasive, and effective method for ICA occlusion and should be recommended for individuals at risk of general anesthesia. Residual neurologic deficits are a common sequela, but they do not reflect a treatment failure.

Comparative pharmacokinetics of two intravenous administration regimens of tiludronate in healthy adult horses and effects on the bone resorption marker CTX-1

Bioavailability and pharmacological effects of tiludronate were compared when administered as an intravenous (i.v.) bolus at a dosage of 0.1 mg/kg body weight (b.w.) once daily for 10 consecutive days (group 1, n = 6) and as a single constant rate infusion (CRI) at a total dose of 1 mg/kg b.w. (group 2, n = 6) in healthy adult horses. Tiludronate and carboxy-terminal cross-linking telopeptide of type I collagen (CTX-1) were measured in plasma and urine. There was no statistically significant difference in area under the curve (AUC) and clearance (Cl) between the two groups. Bioavailability of the CRI was 103% (not significantly different) that of the 10 daily i.v. bolus doses. Cumulative urine tiludronate excretion could not be compared between groups because of poor sensitivity of the assay in urine. Plasma and urine CTX-1 levels were not different between groups throughout the study. However, interindividual variations were greater in group 1 than in group 2. A significant decrease in CTX-1 levels was observed in plasma after the first administration in group 1, but not in urine; while in group 2, a significant decrease in CTX-1 concentrations was observed after treatment in both plasma and urine. In conclusion, both dosage regimens of tiludronate produced similar plasma exposure and pharmacological effects in adult healthy horses.

Small Intestine Adenocarcinoma in Conjunction with Multiple Adenomas Causing Acute Colic in a Horse

An 11-year-old Andalusian stallion developed marked signs of colic associated with an acute small intestine obstruction. Exploratory laparotomy revealed a distal jejunum full-thickness wall induration and multiple small adherent intraluminal masses. Fifteen centimeters of jejunum, including the induration, and several intraluminal masses were resected. Histologic examination revealed an adenocarcinoma and multiple polypoid adenomas. The horse was discharged, and no complications were reported 12 months postoperatively. Colic was considered secondary to partial jejunal lumen obstruction by the adenocarcinoma. Adenocarcinoma recurrence or transformation from remaining adenomas into an adenocarcinoma is still a major risk.

Utility of a Mouse Model of Osteoarthritis to Demonstrate Cartilage Protection by IFNγ-Primed Equine Mesenchymal Stem Cells

Objective Mesenchymal stem cells isolated from adipose tissue (ASC) have been shown to influence the course of osteoarthritis (OA) in different animal models and are promising in veterinary medicine for horses involved in competitive sport. The aim of this study was to characterize equine ASCs (eASCs) and investigate the role of interferon-gamma (IFNγ)-priming on their therapeutic effect in a murine model of OA, which could be relevant to equine OA. Methods ASC were isolated from subcutaneous fat. Expression of specific markers was tested by cytometry and RT-qPCR. Differentiation potential was evaluated by histology and RT-qPCR. For functional assays, naïve or IFNγ-primed eASCs were cocultured with peripheral blood mononuclear cells or articular cartilage explants. Finally, the therapeutic effect of eASCs was tested in the model of collagenase-induced OA (CIOA) in mice. Results The immunosuppressive function of eASCs on equine T cell proliferation and their chondroprotective effect on equine cartilage explants were demonstrated in vitro. Both cartilage degradation and T cell activation were reduced by naïve and IFNγ-primed eASCs, but IFNγ-priming enhanced these functions. In CIOA, intra-articular injection of eASCs prevented articular cartilage from degradation and IFNγ-primed eASCs were more potent than naïve cells. This effect was related to the modulation of eASC secretome by IFNγ-priming. Conclusion IFNγ-priming of eASCs potentiated their antiproliferative and chondroprotective functions. We demonstrated that the immunocompetent mouse model of CIOA was relevant to test the therapeutic efficacy of xenogeneic eASCs for OA and confirmed that IFNγ-primed eASCs may have a therapeutic value for musculoskeletal diseases in veterinary medicine.

Percutaneous Ultrasound‐Guided Arterial Angiography for Transarterial Coil Placement in Anesthetized and Standing Horses

OBJECTIVE To (1) describe ultrasound-guided percutaneous introduction of a transarterial angiographic catheter into the common carotid artery (CCA); (2) investigate the feasibility of using angiography of the carotid arteries in the guttural pouch region and assess transarterial coil (TAC) placement into the internal carotid artery (ICA). STUDY DESIGN Experimental study. ANIMALS Healthy Standardbred horses (n = 6), aged 5-8 years. METHODS Six horses had ultrasound-guided percutaneous CCA catheterization and angiography under general anesthesia. Catheterization sites were ultrasonographically evaluated postoperatively. Ten weeks later using the same horses sedated and standing, the same procedure was combined with placement of a TAC in the ICA. RESULTS Agitated contrast ultrasonography confirmed successful catheterization of the CCA. Needle puncture and introducer-set penetration of the CCA were the main technical difficulties. Radiography and fluoroscopy confirmed successful angiography and TAC placement. Mild hematoma formation was recorded in 4 of 12 procedures. CONCLUSION Angiography and TCA placement in the ICA can be safely performed using a percutaneous approach to the CCA under ultrasound guidance, in standing or anesthetized horses. This approach might be used for TAC embolization procedure; however, technical difficulties and hematoma formation can impair the procedure.Objective To (1) describe ultrasound-guided percutaneous introduction of a transarterial angiographic catheter into the common carotid artery (CCA); (2) investigate the feasibility of using angiography of the carotid arteries in the guttural pouch region and assess transarterial coil (TAC) placement into the internal carotid artery (ICA). Study Design Experimental study. Animals Healthy Standardbred horses (n = 6), aged 5–8 years. Methods Six horses had ultrasound-guided percutaneous CCA catheterization and angiography under general anesthesia. Catheterization sites were ultrasonographically evaluated postoperatively. Ten weeks later using the same horses sedated and standing, the same procedure was combined with placement of a TAC in the ICA. Results Agitated contrast ultrasonography confirmed successful catheterization of the CCA. Needle puncture and introducer-set penetration of the CCA were the main technical difficulties. Radiography and fluoroscopy confirmed successful angiography and TAC placement. Mild hematoma formation was recorded in 4 of 12 procedures. Conclusion Angiography and TCA placement in the ICA can be safely performed using a percutaneous approach to the CCA under ultrasound guidance, in standing or anesthetized horses. This approach might be used for TAC embolization procedure; however, technical difficulties and hematoma formation can impair the procedure.

Development of an Equine Groove Model to Induce Metacarpophalangeal Osteoarthritis: A Pilot Study on 6 Horses

The aim of this work was to develop an equine metacarpophalangeal joint model that induces osteoarthritis that is not primarily mediated by instability or inflammation. The study involved six Standardbred horses. Standardized cartilage surface damage or “grooves” were created arthroscopically on the distal dorsal aspect of the lateral and medial metacarpal condyles of a randomly chosen limb. The contralateral limb was sham operated. After 2 weeks of stall rest, horses were trotted 30 minutes every other day for 8 weeks, then evaluated for lameness and radiographed. Synovial fluid was analyzed for cytology and biomarkers. At 10 weeks post-surgery, horses were euthanized for macroscopic and histologic joint evaluation. Arthroscopic grooving allowed precise and identical damage to the cartilage of all animals. Under the controlled exercise regime, this osteoarthritis groove model displayed significant radiographic, macroscopic, and microscopic degenerative and reactive changes. Histology demonstrated consistent surgically induced grooves limited to non-calcified cartilage and accompanied by secondary adjacent cartilage lesions, chondrocyte necrosis, chondrocyte clusters, cartilage matrix softening, fissuring, mild subchondral bone inflammation, edema, and osteoblastic margination. Synovial fluid biochemistry and cytology demonstrated significantly elevated total protein without an increase in prostaglandin E2, neutrophils, or chondrocytes. This equine metacarpophalangeal groove model demonstrated that standardized non-calcified cartilage damage accompanied by exercise triggered altered osteochondral morphology and cartilage degeneration with minimal or inefficient repair and little inflammatory response. This model, if validated, would allow for assessment of disease processes and the effects of therapy.

Experimental induction of mycotic plaques in the guttural pouches of horses.

Guttural pouch mycosis (GPM) is a rare but potentially life-threatening condition in horses. GPM is caused by a fungal invasion into the mucosal lining of the guttural pouches and, frequently, the associated neurovascular structures. Although several species of fungi have been associated with this disease, Aspergillus spp. appear to be the most common isolated from the guttural pouches. However, it remains unclear which are the predisposing factors leading to the development of the infection. The objectives of the present study were to experimentally reproduce an infection by Aspergillus fumigatus and to follow the natural evolution of the mycosis. Eight guttural pouches from four horses were experimentally infected by endoscopy-guided intrapouch inoculation of A. fumigatus culture. Horses were monitored for clinical signs and development of fungal plaques through endoscopic examination. Mycotic lesions were observed in all the horses and a spontaneous regression was observed within 15-28 days. No development of clinical signs was noticed. In conclusion, we were able to induce the development of mycotic lesions and to observe a natural regression of these lesions without clinical signs.

LOW‐FIELD MAGNETIC RESONANCE IMAGING APPEARANCE OF POSTARTHROSCOPIC MAGNETIC SUSCEPTIBILITY ARTIFACTS IN HORSES

An awareness of magnetic susceptibility artifacts is important for interpreting prepurchase and postoperative magnetic resonance imaging (MRI) studies in horses. These artifacts occur when a metallic or a paramagnetic substance creates a local magnetic field deformity. Aims of the current experimental study were to determine prevalence of these artifacts after arthroscopy in a sample of nonlame horses, and to describe effects of time and type of pulse sequence on low-field MRI signal intensity and detection of the artifacts. Ten, nonlame Standardbred horses were prospectively recruited. All horses underwent arthroscopy of both metacarpophalangeal joints for purposes unrelated to the study. Serial low-Field MRI examinations were performed on each horse and each joint (before, and 6 and 12 weeks postsurgery). In two horses, more detailed longitudinal evaluations were performed with additional MRI examinations. Magnetic susceptibility artifacts were detected postoperatively at the surgical access sites in eight metacarpophalangeal joints at both 6 and 12 weeks after surgery (40% prevalence). Neither of the two longitudinally followed horses had artifacts at any time. Artifacts were only detected on gradient echo (GRE) sequences. Findings indicated that magnetic susceptibility artifacts can be present in postarthroscopy MRI studies in horses and can persist up to 12 weeks after arthroscopy. For this sample of horses, the artifacts did not interfere with evaluation of the joint. Further longitudinal studies are needed to determine the full duration of magnetic susceptibility artifact persistence in affected tissues.

A novel minimal invasive closed chest myocardial ischaemia reperfusion model in rhesus monkeys (Macaca mulatta): improved stability of cardiorespiratory parameters

The aim of this study was to report the cardiorespiratory events observed during coronary artery occlusion and reperfusion in a minimally invasive closed chest myocardial occlusion–reperfusion model in rhesus monkeys. We hypothesized that a minimally invasive technique may lead to fewer cardiac arrhythmias and complications. Eight male rhesus macaques 10–15 kg and 10–15 years old were sedated with ketamine (2 mg/kg), midazolam (1.3 mg/kg), atropine (0.01 mg/kg) and buprenorphine 0.02 mg/kg intramuscularly. Etomidate 1–2 mg/kg was injected intravenously to allow tracheal intubation. Anaesthesia was maintained with isoflurane. Pulse oximetry, electrocardiogram (ECG), heart rate, mean arterial blood pressure (MAP), inspired isoflurane fractions (FIISO) and core temperature were recorded every 10 min. The coronary artery occlusion was induced by a balloon-tipped catheter advanced via the femoral artery into the left anterior descending artery and inflated to completely occlude the vessel for 20–50 min (IT) before reperfusion. Sequences of elevated ST segment, QRS complex prolongation, ventricular premature complexes and ventricular fibrillation were observed with a lower incidence than previously described in the literature. IT was (min: 17; max: 50) min long. FIISO was lower than the minimal alveolar concentration in these species. Hypotension (MAP < 70 mmHg) and hypothermia (T°C < 36°C) were observed in all macaques. This minimally invasive closed chest model was successful in providing better cardiorespiratory physiological parameters than reported in previous models. The benefit (achieving ischaemia) versus risk (lethal arrhythmia) of the duration of the coronary occlusion should be considered.