Effect of clodronate on gene expression in the peripheral blood of horses.

There are two FDA-approved bisphosphonate products, clodronate (Osphos®) and tiludronate (Tildren®), for use in horses. It is hypothesized that bisphosphonates can produce analgesic effects and prevent proper healing of microcracks in bone. Therefore, bisphosphonate use is banned in racehorses. However, bisphosphonates have a short detection window in the blood before sequestration in the skeleton, making the reliability of current drug tests questionable. Seven exercising Thoroughbred horses were administered clodronate (1.8 mg/kg i.m.), and four were administered saline. RNA was isolated from peripheral blood mononuclear cells (PBMCs) collected immediately before a single dose of clodronate or saline and then on Days 1, 6, 28, 56 and 182 post-dose. mRNA was sequenced and analysed for differentially expressed transcripts. While no single transcripts were differentially expressed, pathway analysis revealed that p38 MAPK (p = .04) and Ras (p = .04) pathways were upregulated, and cadherin signalling (p = .02) was downregulated on Day 1. Previously investigated biomarkers, cathepsin K (CTSK) and type 5 acid phosphatase (ACP5), were analysed with RT-qPCR in a targeted gene approach, with no significant difference observed. A significant effect of time on gene expression for ACP5 (p = .03) and CTSK (p < .0001) was observed. Thus, these genes warrant further investigation for detecting clodronate use over time.

Pharmacokinetics and metabolism of lidocaine HCl 2% with epinephrine in horses following a palmar digital nerve block.

BACKGROUND: Lidocaine is a local anesthetic that is sometimes administered in combination with epinephrine. The addition of epinephrine increases the time lidocaine remains at the site of administration, thus prolonging the duration of effect. Due to their potential to prevent the visual detection of lameness, the administration of local anesthetics is strictly regulated in performance and racehorses. Recent reports of positive regulatory findings for lidocaine in racehorses suggests a better understanding of the behavior of this drug is warranted. The objective of the current study was to describe serum and urine concentrations and the pharmacokinetics of lidocaine and its primary metabolites following administration in combination with epinephrine, as a palmar digital nerve block in horses. Twelve horses received a single administration of 1 mL of 2% lidocaine HCl (20 mg/horse) with epinephrine 1:100,000, over the palmar digital nerve. Blood samples were collected up to 30 h and urine samples up to 48 h post administration. Lidocaine and metabolite concentrations were determined by liquid chromatography- mass spectrometry and pharmacokinetic (non-compartmental and compartmental) analysis was performed. RESULTS: Serum concentrations of lidocaine and 3-hydroxylidocaine were above the LOQ of the assay at 30 h post administration and monoethylglycinexylidide (MEGX) and glycinexylidide (GX) were below detectable levels by 24 and 48 h, respectively. In urine, lidocaine, MEGX and GX were all non-detectable by 48 h post administration while 3-hydroxylidocaine was above LOQ at 48 h post administration. The time of maximal concentration for lidocaine was 0.26 h (median) and the terminal half-life was 3.78 h (mean). The rate of absorption (Ka) was 1.92 1/h and the rate of elimination (Kel) was 2.21 1/h. CONCLUSIONS: Compared to previous reports, the terminal half-life and subsequent detection time observed following administration of lidocaine in combination with epinephrine is prolonged. This is likely due to a decrease in systemic uptake of lidocaine because of epinephrine induced vasoconstriction. Results of the current study suggest it is prudent to use an extended withdrawal time when administering local anesthetics in combination with epinephrine to performance horses.

Identification of putative orthologs of clinically relevant antimicrobial peptides in the equine ocular surface and amniotic membrane.

OBJECTIVES: This study aimed to define the antimicrobial peptide (AMP) expression pattern of the equine ocular surface and amniotic membrane using a targeted qPCR approach and 3'Tag-sequencing. It will serve as a reference for future studies of ocular surface innate immunity and amniotic membrane therapies. PROCEDURES: A targeted qPCR approach was used to investigate the presence of orthologs for three of the most highly expressed beta-defensins (DEFB1, DEFB4B, and DEFB103A) of the human ocular surface and amniotic membrane in equine corneal epithelium, conjunctiva, and amniotic membrane. 3'Tag-sequencing was performed on RNA from one sample of corneal epithelium, conjunctiva, and amniotic membrane to further characterize their AMP expression. RESULTS: Equine corneal epithelium, conjunctiva, and amniotic membrane expressed DEFB1, DEFB4B, and DEFB103A. DEFB103A was expressed at the highest amounts in corneal epithelium, while DEFB4B was most highly expressed in conjunctiva and amniotic membrane. 3'Tag-sequencing from all three tissues confirmed these findings and identified expression of five additional beta-defensins, 11 alpha-defensins and two cathelicidins, with the alpha-defensins showing higher normalized read counts than the beta-defensins. CONCLUSIONS: This study identified AMP expression in the equine cornea and conjunctiva, suggesting that they play a key role in the protection of the equine eye, similar to the human ocular surface. We also determined that equine amniotic membrane expresses a substantial number of AMPs suggesting it could potentiate an antimicrobial effect as a corneal graft material. Future studies will focus on defining the antimicrobial activity of these AMPs and determining their role in microbial keratitis.

Establishment of a sequential dual tracer 18 F-NaF/18 F-FDG PET protocol for imaging the equine foot.

The combination of 18 F-Sodium Fluoride (18 F-NaF) and 18 F-FluoroDeoxyGlucose (18 F-FDG) for positron emission tomography (PET) imaging of the equine foot is appealing for detection of both osseous and soft tissue lesions in a single scan. As the combination of tracers could lead to a loss of information, a sequential approach, consisting in imaging with one tracer prior to injecting the second tracer, might be valuable. The goals of this prospective, methods comparison, exploratory study were to establish the order of tracer injection and timing for imaging. Six research horses were imaged under general anesthesia with 18 F-NaF PET, 18 F-FDG PET, dual 18 F-NaF/18 F-FDG PET, and CT. Proper uptake could be identified in tendon lesions as early as 10 min after 18F-FDG injection. Bone uptake was limited when 18F-NaF was injected under general anesthesia, even at 1 h after injection, when compared with 18 F-NaF injection prior to anesthesia. The sensitivity and specificity of the dual tracer scans were 0.77 (0.63 to 0.86) and 0.98 (0.96 to 0.99) respectively, to assess 18 F-NaF uptake and 0.5 (0.28 to 0.72) and 0.98 (0.95 to 0.99), respectively, for 18F-FDG uptake. These results suggest that the sequential dual tracer approach is a pertinent technique to optimize the PET data gained from a single anesthetic episode. Based on dynamics of tracer uptake, the optimal protocol consists in injecting 18F-NaF prior to anesthesia, acquire 18F-NaF data then inject 18F-FDG and start acquisition of dual tracer PET data 10 min later. This protocol should be further validated in a larger clinical study.

Fibro-Osseous Lesions Of The Craniofacial Complex In Horses: 30 Cases (2001-2019).

OBJECTIVE: To describe the presentation, diagnosis, treatment, and outcome for horses with fibro-osseous lesions of the craniofacial complex. STUDY DESIGN: Retrospective multicenter case series. ANIMALS: Thirty horses evaluated for fibro-osseous lesions of the skull from January 1, 2001 through December 31, 2019 in four centers. METHODS: Medical records were reviewed for signalment, clinical presentation, histological and diagnostic imaging findings, treatment instituted, and outcome. Long-term outcome information was obtained by owner questionnaire or the medical record. RESULTS: Diagnoses included ossifying fibroma in 20 of 30 horses, osteoma in eight of 30 horses, and fibrous dysplasia in two of 30 horses. Twelve of 30 lesions were diagnosed in horses <1 year old, and 20 of 30 lesions originated from the rostral mandible. The most common treatment was rostral mandibulectomy. Recurrence was not reported after complete excision. Incomplete excision was confirmed in eight horses (four ossifying fibromas, three osteomas, and one fibrous dysplasia), and follow-up information was available for seven horses. Recurrence occurred in one horse, while six horses had long-term resolution of clinical signs. Prognosis for survival and return to use was excellent in 23 horses with long-term follow-up. CONCLUSION: Fibro-osseous lesions were uncommon in this multicenter study; they were most commonly diagnosed in young animals and most frequently affected the rostral mandible. Long-term survival was excellent. CLINICAL SIGNIFICANCE: The definitive diagnosis of fibro-osseous lesions of the craniofacial complex in horses is made from results of histopathology and cannot be determined on the basis of clinical presentation alone. Surgical excision is indicated, and prognosis can be favorable even when complete surgical margins are not obtained.

18 Fluorine-fluorodeoxyglucose positron emission tomography for assessment of deep digital flexor tendinopathy: An exploratory study in eight horses with comparison to CT and MRI.

Lesions of the deep digital flexor tendon (DDFT) are a cause for foot lameness in horses. Positron emission tomography (PET) could provide valuable information regarding the metabolic activity of these lesions. The aims of this exploratory, prospective, methods comparison study were to assess the ability of 18 fluorine-fluorodeoxyglucose (18 F-FDG) PET to detect DDFT lesions and to compare the PET findings with CT and MRI findings. Eight horses with lameness due to pain localized to the front feet were included. Both front limbs of all horses were imaged with 18 F-FDG PET, noncontrast CT, and arterial contrast-enhanced CT; 11 limbs were also assessed using MRI. Two observers graded independently 18 F-FDG PET, noncontrast CT, arterial contrast CT, T1-weighted (T1-w) MRI, and T2-weighted (T2-w)/STIR MRI. Maximal standardized uptake values were measured. Lesions were found in seven of 16 DDFT on PET, 12 of 16 DDFT on noncontrast CT, six of 15 DDFT on arterial contrast CT, eight of 11 DDFT on T1-w MRI, and six of 11 DDFT on T2-w/STIR MRI. Positron emission tomography was in better agreement with arterial contrast CT (Kappa-weighted 0.40) and T2-w/STIR MRI (0.35) than with noncontrast CT (0.28) and T1-w MRI (0.20). Maximal standardized uptake values of lesions ranged from 1.9 to 4.6 with a median of 3.1. Chronic lesions with scar tissues identified on noncontrast CT or T1-w MRI did not have increased 18 F-FDG uptake. These results demonstrated that 18 F-FDG PET agreed more closely with modalities previously used to detect active tendon lesions, i.e. arterial contrast CT and T2-w/STIR MRI. 18 Fluorine-fluorodeoxyglucose PET can be used to identify metabolically active DDFT lesions in horses.

Assessment and Revision of the Veterinary Internship and Residency Matching Program Standardized Letter of Reference.

The Veterinary Internship and Residency Matching Program (VIRMP) recently revised its electronic standardized letter of reference (SLOR) to improve the quality and usefulness of the data obtained from it and to enhance the relevance of non-cognitive and cognitive candidate attributes assessed. We used a stepwise process including a broad survey of SLOR readers and writers, analysis of past SLORs, and a multi-wave iterative revision that included key stakeholders, such as residency and internship program directors from academia and private practice. Data from the SLOR survey and analysis of past SLOR responses identified opportunities to improve applicant differentiation, mitigate positive bias, and encourage response consistency. The survey and other analytics identified and confirmed performance domains of high relevance. The revised SLOR assesses four performance domains: knowledge base and clinical skills, stress and time management, interpersonal skills, and personal characteristics. Ratings within the revised SLOR are predominantly criterion-referenced to enhance discernment of candidate attributes contained within each domain. Questions assessing areas of strength and targeted mentoring were replaced with free-text boxes, which allow writers to comment on positive and neutral/negative ratings of attributes within domains. Minor revisions were made to certain questions to enhance readability, streamline responses, or address targeted concerns identified in the SLOR survey or stakeholder review. The revised SLOR was deployed in the 2020 VIRMP; data from a survey of writers (n = 647) and readers (n = 378) indicate that the redesign objectives were achieved.

Incidence of incisional complications after exploratory celiotomy in equids affected with enterolithiasis.

This study reports the prevalence of and risk factors for incisional complications in equids after ventral midline celiotomy for enterolithiasis. This study covered the years 2008 to 2015 and included 72 equids. Enteroliths were removed from the ascending or descending colon through 1 or more enterotomies. Complications were defined as surgical site infection and/or incisional hernia formation. Follow-up by telephone questionnaire or medical records determined that 10/72 (13.9%) equids experienced complications, with 6/72 (8.3%) developing a surgical site infection and 5/72 (6.9%) a hernia. Seven of ten were presented for chronic abdominal discomfort (> 24 hours), and 8/10 had right dorsal colon and pelvic flexure enterotomies. All equids that developed an incisional hernia and 4 with surgical site infection had enteroliths > 15 cm diameter removed from the right dorsal colon. Antimicrobial powder applied to the ventral midline incision during closure significantly reduced incisional complications. Removal of > 15 cm diameter enteroliths from the right dorsal colon may predispose to postoperative incisional complications.

Incidence des complications incisionnelles après une céliotomie exploratoire chez des équidés atteints d'entérolithiase. Cette étude rapporte la prévalence et les facteurs de risque des complications incisionnelles chez les équidés opérés pour l'entérolithiase en utilisant une celiotomie médiane ventrale de 2008 à 2015. Soixantedouze équidés ont été inclus. Les entérolithes ont été retirés du côlon ascendant ou descendant par ≥ 1 entérotomies. Les complications étaient définies comme une infection du site opératoire et/ou la formation d'une hernie incisionnelle. Le suivi a été obtenu par questionnaire téléphonique ou par dossiers médicaux. Dix des 72 (13,9 %) des équidés ont eu des complications, dont 6/72 (8,3 %) ont développé une infection du site opératoire et 5/72 (6,9 %) une hernie. Sept sur 10 ont été présentés pour un malaise abdominal chronique (> 24 heures) et 8/10 avaient des entérotomies du côlon dorsal droit et de la flexion pelvienne. Tous les équidés ayant développé une hernie incisionnelle et quatre avec une infection du site opératoire avaient des entérolithes > 15 cm de diamètre prélevés du côlon dorsal droit. La poudre antimicrobienne appliquée sur l'incision médiane ventrale lors de la fermeture réduisait significativement les complications incisionnelles. Le retrait d'entolithes de > 15 cm de diamètre du côlon dorsal droit peut prédisposer aux complications incisionnelles postopératoires.(Traduit par les auteurs).

Pathological Safety Assessment in Preclinical Neurothrombectomy Studies.

The design, production, and preclinical testing of neurothrombectomy devices is in a burgeoning phase as the demand escalates for safe and reliable treatment options following neurovascular stroke. Currently, there is a paucity of published data describing the development of iatrogenic vascular lesions occurring secondary to neurothrombectomy procedures. In an effort to test new devices, demonstrate device safety, satisfy regulatory requirements, and develop an understanding of the potential for associated vascular pathology, investigators are establishing appropriate methodology in suitable animal models. Significant challenges exist in identifying a single animal species that can be consistently utilized in all phases of device development. These aforementioned challenges are underscored by the intricacies of neurovascular pathology, thrombovascular interactions, and vascular responses to injury.

A novel ultrasonographic assisted technique for desmotomy of the palmar/plantar annular ligament in horses.

OBJECTIVES: To describe an ultrasound assisted technique for desmotomy of the palmar/plantar annular ligament (PAL), determine its efficacy and intraoperative complications. STUDY DESIGN: Cadaveric and in vivo study. ANIMALS: Cadaveric limbs (n = 12), adult horses (n = 4), and clinical cases (n = 2). METHODS: Ultrasound assisted desmotomy of the palmar/plantar annular ligament (UAD-PAL) was performed in cadaveric limbs and in standing horses with the operated limb placed in a distal limb splint. The procedure was performed under general anesthesia and was followed by tenoscopic examination in 2 clinical cases. A hook knife was developed for the procedure. Complete transection was assessed by postmortem dissection (10 forelimbs, 10 hindlimbs) and tenoscopic examination (1 forelimb, 1 hindlimb). Thickness of PAL, surgery time, other intraoperative parameters and complications associated with the procedure were recorded. RESULTS: Complete PAL transection was accomplished in 20/22 limbs. No iatrogenic damage to adjacent intrathecal structures was identified in any case. The instrument was correctly positioned on the first attempt in 19/22 cases. The most common intraoperative complication was inadvertent subcutaneous placement of the instrument (n = 2). Significant thickening of the PAL (3 mm) was present in 1/2 limbs in which complete transection was not achieved. CONCLUSIONS: UAD-PAL with the custom-made hook knife was effective at transecting the PAL with minimal intraoperative complications. The procedure can be performed in standing sedated horses. Another method should be considered in horses with thickened PAL.

ULTRASOUND-GUIDED INJECTIONS IN HORSES WITH CRANIOVENTRAL DISTENSION OF THE COXOFEMORAL JOINT CAPSULE: FEASIBILITY FOR A CRANIOVENTRAL APPROACH.

Intrasynovial access to the equine coxofemoral joint (CFJ) is inherently challenging. Blind injection techniques rely upon inconsistently palpable landmarks, and ultrasound guidance requires expertise for needle placement into the coxofemoral articulation. Aspiration is recommended to confirm intrasynovial placement and avoid sciatic nerve anesthesia. The aim of this observational, descriptive, retrospective study was to evaluate the feasibility for an alternative ultrasound-guided approach in horses with cranioventral distention of the CFJ identified during pelvic ultrasound. Thirteen horses with cranioventral CFJ distention, including 12 with severe pathology, were recruited from 2009 to 2014. Seven were excluded as they were not injected or underwent ultrasound-guided injection using a dorsal approach. The remaining six horses underwent a total of nine injections into the cranioventral recess. With the exception of one foal, all were aged horses (15-29 years) of varying breeds and uses, with prominent lameness due to subluxation (three), luxation (two), and severe osteoarthritis (one). The cranioventral recess was imaged adjacent to the proximal femur using a low-frequency curvilinear transducer placed ventral to the cranial joint margins. Using aseptic technique, spinal needles were placed cranial to the transducer and advanced caudomedially into the distended cranioventral recess. Synovial fluid was retrieved in all cases with one needle placement. Findings indicated that, when distended, ultrasound-guided access to the cranioventral CFJ recess is a feasible alternative approach and may reduce the potential for extra-synovial placement. Distention in this sample of horses was accompanied by severe pathology, also supporting the use of this approach for therapeutic interventions.

FRACTURE OF THE CENTRAL TARSAL BONE IN NONRACEHORSES: FOUR CASES.

Fractures of the central tarsal bone are a rarely recognized cause of acute severe hind limb lameness in nonracehorses. Diagnosis of these fractures can be challenging and little is known about their configuration or outcome. The objectives of this retrospective case series study were to describe the clinical features, imaging findings, and outcomes of fractures of the central tarsal bone in a sample of nonracehorses. Medical records from 2001 to 2014 were searched for cases of central tarsal bone fractures in nonracehorses. All available imaging findings including radiography, ultrasound, computed tomography (CT), and/or nuclear scintigraphy were reviewed. History, clinical presentation, and outcome were collected from the records. Four horses met the inclusion criteria. All had a similar configuration as a simple nondisplaced slab fracture in a dorsomedial to plantarolateral orientation. Initial radiographs failed to reveal the fracture in three of four cases. When additional plantarolateral-dorsomedial oblique radiographic views were obtained, the fracture could be identified in all cases. Fractures of the central tarsal bone seemed to occur in a consistent dorsomedial to plantarolateral orientation in this sample of nonracehorses, which is different from the configuration previously reported in racehorses. While CT can be used for detection and assessment of these fractures, authors propose that radiography can also identify these fractures with the appropriate view. Authors recommend the use of several plantarolateral to dorsomedial radiographic projections at varying degrees of obliquity for horses with a suspected central tarsal bone fracture.

POSITRON EMISSION TOMOGRAPHY OF THE EQUINE DISTAL LIMB: EXPLORATORY STUDY.

Positron emission tomography (PET) is a highly sensitive, noninvasive imaging technique for quantifying biological functions of tissues. However, at the time of this study, PET imaging applications had not been reported in the horse. The aim of this exploratory study was to determine whether a portable high-resolution PET scanner could be used to image the equine distal limb. Images of the front feet and fetlocks of three research horses, with known lesions localized to the distal front limbs, were acquired under general anesthesia after administration of 18 F-fluorodeoxyglucose (18 F-FDG), with doses ranging from 1.5 to 2.9 MBq/kg. The radiation exposure measured during imaging was slightly higher than 99m Technetium scintigraphy. However, the use of general anesthesia allowed the proximity and the contact time with the patient to be minimized for the staff involved. 18 F-FDG uptake was evident throughout the soft tissues, with the highest uptake in the coronary band and the lowest uptake in the tendons. Anatomic structures could be discriminated due to the high contrast between soft tissue and bone. Detected lesions included lysis of the flexor cortex of the navicular bone, lesions of flexor tendons and suspensory ligament, and abnormal uptake through the lamina of a laminitic subject. Findings indicated that tomographic molecular imaging is feasible in the equine distal limb and could be useful as a future diagnostic technique for clinical and research studies, especially those involving tendinopathy/desmopathy and laminitis.

Intra-articular injection of an extended-release flavopiridol formulation represents a potential alternative to other intra-articular medications for treating equine joint disease.

OBJECTIVE: To establish the pharmacokinetics of the cyclin-dependent kinase-9 inhibitor flavopiridol in equine middle carpal joints, using an extended-release poly lactic-co-glycolic acid (PLGA) microparticle formulation. ANIMALS: 4 healthy horses without evidence of forelimb lameness. METHODS: A 6-week longitudinal pharmacokinetic study was conducted in 2 phases (6 weeks each) in 4 healthy horses. The PLGA microparticles containing 122 µg flavopiridol in 3 mL saline were administered by intra-articular injection into 1 middle carpal joint, with empty PLGA microparticles injected into the contralateral joint as a control. Synovial fluid and plasma were collected at time points out to 6 weeks, and drug concentrations in synovial fluid and plasma were determined using validated protocols. Synovial fluid total protein and total nucleated cell count and differential, CBC, serum biochemistry, and lameness exams were performed at each of the time points. RESULTS: Synovial fluid flavopiridol averaged 19 nM at week 1, gradually reduced to 1.4 nM by 4 weeks, and was generally below the detection limit at 5 and 6 weeks. There was no detectable flavopiridol in the plasma samples, and no adverse effects were observed at any time point. CLINICAL RELEVANCE: Intra-articular injection of PLGA microparticle-encapsulated flavopiridol was well tolerated in horses, with detectable levels of flavopiridol in the synovial fluid out to 4 weeks with negligible systemic exposure. Flavopiridol is a cyclin-dependent kinase-9 inhibitor with potent anti-inflammatory and analgesic activity. The extended-release microparticle formulation promotes intra-articular retention of the drug and it may be an alternative to other intra-articular medications for treatment of equine joint disease.

Septic inflammation of the bicipital bursa: clinical, imaging, and surgical findings in nine horses.

OBJECTIVE: To describe the etiologies, clinicopathologic findings, diagnostic modalities employed, treatments, and outcome associated with cases of septic bicipital bursitis. ANIMALS: 9 horses. CLINICAL PRESENTATION AND PROCEDURES: Medical records of horses diagnosed with septic bicipital bursitis between 2000 and 2021 were reviewed. Horses were included if synoviocentesis of the bicipital bursa revealed a total nucleated cell count of ≥ 20,000 cells/µL with a neutrophil proportion of ≥ 80%, a total protein concentration of ≥ 4.0 g/dL, and/or the presence of bacteria on cytology, or positive culture of the synovial fluid. Information retrieved from medical records included signalment, history, clinicopathologic variables, diagnostic imaging findings, treatment, and outcome. RESULTS: Trauma was the most common inciting cause (n = 6). Synoviocentesis using ultrasonographic guidance was performed in all cases and showed alterations consistent with septic synovitis. Radiography identified pathology in 5 horses, whereas ultrasonography identified pathology in all horses. Treatment consisted of bursoscopy (n = 6) of the bicipital bursa of which 1 was performed under standing sedation, through-and-through needle lavage (3), bursotomy (2), or medical management alone (2). Five (55.6%) horses survived to discharge. Long-term follow-up was available for 3 horses and all were serviceably sound, with 2 in training as pleasure horses and 1 case continuing retirement. CLINICAL RELEVANCE: Ultrasonography was the most informative imaging modality and paramount in obtaining synovial fluid samples for definitive diagnosis of septic bicipital bursitis. Bursoscopy performed under standing sedation is a feasible treatment option. Horses treated for bicipital septic bursitis have a fair prognosis for survival and may return to some level of athletic performance.

Examining the Effects of In Vitro Co-Culture of Equine Adipose-Derived Mesenchymal Stem Cells With Tendon Proper and Peritenon Cells.

Tendinopathies remain the leading contributor to career-ending injuries in horses because of the complexity of tendon repair. As such, cell-based therapies like injections of adipose-derived mesenchymal stem cells (ADMSCs, or MSCs) into injured tendons are becoming increasingly popular though their long-term efficacy on a molecular and wholistic level remains contentious. Thus, we co-cultured equine MSCs with intrinsic (tendon proper) and extrinsic (peritenon) tendon cell populations to examine interactions between these cells. Gene expression for common tenogenic, perivascular, and differentiation markers was quantified at 48 and 120 hours. Additionally, cellular metabolism of proliferation was examined every 24 hours for peritenon and tendon proper cells co-cultured with MSCs. MSCs co-cultured with tendon proper or peritenon cells had altered expression profiles demonstrating trend toward tenogenic phenotype with the exception of decreases in type I collagen (COL1A1). Peritenon cells co-cultured with MSCs had a trending and significant decrease in biglycan (BGN) and CSPG4 at 48 hours and 120 hours but overall significant increases in lysyl oxidase (LOX), mohawk (MKX), and scleraxis (SCX) within 48 hours. Tendon proper cells co-cultured with MSCs also exhibited increases in LOX and SCX at 48 hours. Furthermore, cell proliferation improved overall for tendon proper cells co-cultured with MSCs. The co-culture study results suggest that adipose-derived MSCs contribute beneficially to tenogenic stimulation of peritenon or tendon proper cells.

Comparison of 18 F-sodium fluoride positron emission tomography and computed tomography for imaging of the fetlock in 25 nonracehorses.

BACKGROUND: 18 F-sodium fluoride (18 F-NaF) positron emission tomography (PET) has been validated as a useful imaging technique in the racehorse fetlock. The use of 18 F-NaF PET in the nonracehorse fetlock has not been reported. OBJECTIVES: To describe 18 F-NaF PET findings in nonracehorse fetlocks, to compare with computed tomography (CT) findings and to compare PET findings between horses with and without fetlock pain. STUDY DESIGN: Retrospective observational study. METHODS: All horses undergoing 18 F-NaF PET and CT imaging of the fetlock between October 2016 and March 2021 were included in the study. Medical records were reviewed for associated lameness information. RESULTS: Thirty-six fetlocks (33 front and 3 hind) from 25 horses were included. The interobserver agreement for PET [0.62 (95% confidence interval [CI] 0.59-0.65)] was higher than for CT [0.47 (95% CI 0.43-0.51)]. Increased 18 F-NaF uptake was most common in the medial subchondral bone of the proximal phalanx (23/36), the dorsomedial (20/36) and dorsosagittal (16/36) metacarpal/metatarsal distal subchondral bone, whereas sclerosis was identified on CT in these areas in 22 of 36 (p > 0.9), 33 of 36 (p = 0.001) and 23 of 36 (p = 0.15), respectively. Significant correlations were found between PET grades and both subchondral sclerosis and resorption CT grades (p < 0.001, Spearman r = 0.19 and 0.21, respectively). Abnormal 18 F-NaF uptake in the proximal sesamoid bones (PSBs) was identified in 12 of 36 of the fetlocks, which was more common than CT abnormalities (3/36, p = 0.02). Periarticular increased uptake was seen in 7 of 36 fetlocks, whereas osteophytosis was recognised on CT in 20 of 36 (p = 0.1). Maximal standardised uptake values (SUVmax) were significantly higher in painful than in nonpainful fetlocks (22.0 and 11.9, respectively, p = 0.038). MAIN LIMITATIONS: Retrospective study and limited sample size. CONCLUSIONS: Overall PET and CT findings follow a similar distribution in their location. PET identified more abnormalities in the PSBs than CT. SUVmax is a pertinent factor to take into consideration for the assessment of the clinical significance of findings.

Clodronate detection and effects on markers of bone resorption are prolonged following a single administration to horses.

BACKGROUND: Clodronate is a potent antiresorptive agent labelled for use in horses over 4 years of age, for the treatment of navicular syndrome. Concerns regarding the extra-label use of clodronate in equine athletes, such as racehorses, have been raised as inhibition of osteoclast activity by clodronate has been postulated to interfere with normal bone healing, which is imperative to the repair of microfractures. The paucity of data describing the long-term pharmacokinetics of clodronate and effects on biomarkers of bone resorption necessitates further study. OBJECTIVES: (1) To determine clodronate concentrations in blood and urine over a 6-month period in horses undergoing treadmill exercise and (2) to assess the effects of clodronate on protein biomarkers of bone remodelling in this same group of horses. STUDY DESIGN: Randomised controlled experimental study. METHODS: Seven exercised Thoroughbred horses received a single im administration of 1.8 mg/kg clodronate and four horses received an equivalent volume of saline. Blood and urine samples were collected prior to, during and for 182 days post drug administration for drug concentration determination using liquid chromatography-tandem mass spectrometry, and determination of protein biomarker (CTX-1 and TRAcP5B) concentrations. RESULTS: Clodronate was detectable in blood for 14-175 days and for up to 175 days in urine. For some horses, concentrations were nondetectable at one time point but detectable at a subsequent time point. The terminal serum half-life ranged from 1.80 to 283.9 days. CTX-1 concentrations were significantly higher, relative to baseline, in both treated and control groups while concentrations of TRAcP5B were significantly lower in the treated group. MAIN LIMITATIONS: Relatively small number of horses studied. CONCLUSIONS: Based on assessment of protein biomarkers, clodronate appears to influence osteoclasts at label doses. Furthermore, results of this study support racing regulations that preclude horses administered bisphosphonates for medical reasons, from racing for a prolonged period of time.

CONTEXTO: Clodronato é um agente antirreabsortivo potente e recomendado para o uso em cavalos com mais de 4 anos de idade, para o tratamento da síndrome do navicular. Há preocupação com o uso indiscriminado de clodronato em equinos atletas, como cavalos de corrida, já que a inibição da atividade dos osteoclastos pelo clodronato tem sido postulada em interferir na cicatrização óssea normal, o que é essencial para a cicatrização de microfraturas. A escassez de informação quanto às ações prolongadas do uso de clodronato e seus efeitos nos biomarcadores de reabsorção óssea requere mais estudos. OBJETIVOS: (1) Determinar a concentração de clodronato no sangue e urina por um período de 6 meses em cavalos submetidos ao exercício em esteira e (2) acessar os efeitos de clodronato nos biomarcadores de remodelação óssea no mesmo grupo de cavalos. DELINEAMENTO DO ESTUDO: Estudo controlado randomizado. METODOLOGIA: Sete cavalos Puro-Sangue Inglês em exercício receberam uma única dose im de 1.8 mg/kg de clodronato e 4 cavalos receberam um volume equivalente de solução fisiológica. Amostras de sangue e urina foram coletadas antes, durante e por 182 dias após a administração de clodronato. Valores de concentração da droga foram determinados utilizando cromatografia líquida-espectrometria de massa (LC-MS/MS), e determinação da concentração de biomarcadores (CTX-1 e TRAcP5B) também foi realizada. RESULTADOS: Clodronato foi detectado no sangue por 14-175 dias e por até 175 dias na urina. Para alguns equinos, a concentração foi não-detectável em um momento, mas detectável no próximo momento. O valor terminal da vida-média em soro foi 1.80-283.9 dias. A concentração de CTX-1 foi significativamente elevada, relativo às amostras iniciais, em ambos os grupos (tratamento e controle), enquanto as concentrações de TRAcP5B foram significativamente menores no grupo de cavalos tratados. PRINCIPAIS LIMITAÇÕES: Número relativamente pequenos de cavalos no estudo. CONCLUSÕES: Baseado nos resultados dos biomarcadores, clodronato parece influencia osteoclastos na dose recomendada. Além disso, os resultados deste estudo suportam o regulamento de cavalos de corrida que impedem que cavalos que receberam bifosfonatos por razão médica de competir por um período de tempo prolongado.

18F-sodium fluoride positron emission tomography provides pertinent additional information to computed tomography for assessment and management of tarsal pain in horses.

OBJECTIVE: To assess the value of 18F-sodium fluoride (18F-NaF) positron emission tomography (PET) for imaging the tarsus and proximal metatarsus and compare it with CT and lameness evaluation. ANIMALS: 25 horses with lameness localized to the tarsal and proximal metatarsal regions that underwent 18F-NaF PET/CT between 2016 and 2021. METHODS: 18F-NaF PET and CT images were retrospectively independently evaluated by 3 observers. Standardized uptake values (SUV) were used to characterize 18F-NaF uptake. Correlation between PET and CT findings with subjective and objective maximum (Max-D) and minimum pelvic height lameness data was estimated. RESULTS: The inter-observer Kappa-weighted value (κ) was higher for PET (κ = 0.66) than CT (κ = 0.6). CT and PET scores were fairly correlated (R = 0.49; P < 0.05). PET SUVratio (SUV of the main lesion/SUV talus) had the highest correlation with Max-D (R = 0.71; P < .05). PET and CT scores for the plantar region were significantly higher in Quarter Horses (P < .05) and showed consistently higher correlation with objective lameness data (CT plantar grade - Max-D [R = 0.6; P < .05], PET plantar grade - Max-D [R = 0.47; P = .04]) than other regions of the distal tarsal joints. Three Warmbloods presented marked uptake at the medial cochlea of the distal tibia. CLINICAL RELEVANCE: PET had a moderate correlation with CT for assessment of tarsal lesions. The degree of PET uptake can help differentiate active versus inactive lesions. Specific location of the uptake is important in determining clinical relevance.

Osteochondral necrosis of the femoral condyles in Thoroughbred foals: eight cases (2008-2018).

OBJECTIVE: To describe clinical, imaging, gross, and histopathological abnormalities associated with osteochondral necrosis of the femoral condyles in foals and identify features suggestive of a common pathogenesis. ANIMALS: 8 Thoroughbred foals euthanized with a presumptive diagnosis of necrosis of the femoral condyles. PROCEDURES: Postmortem CT was performed on all distal femoral epiphyseal samples. The articular epiphyseal cartilage complex (AECC) of affected distal femurs was examined grossly and histologically, focusing on lesions of interest identified on CT images. RESULTS: 7 foals were between 9 and 23 days old at the time of euthanasia; 1 foal was 85 days old. Concurrent illness (neonatal maladjustment syndrome, neonatal isoerythrolysis, or infection such as enteritis and omphalitis) was diagnosed in 7 foals. The characteristic antemortem radiographic and postmortem CT finding was a crescent-shaped osteochondral flap displaced from the affected medial femoral condyle. Synovial fluid cytology from affected joints was either within normal limits or consistent with mild inflammation. Histologically, all lesions were characterized by osteochondral necrosis and detachment of the AECC. In 6 foals, polymorphonuclear cells were found within growth cartilage canals, representing septic cartilage canals. CLINICAL RELEVANCE: Osteochondral necrosis was interpreted to be secondary to bacterial colonization of the distal femoral AECC, evidenced by septic cartilage canals identified in 6 of 8 foals. This uncommon condition was previously thought to arise from an ischemic event, but the disease process was not well understood. An improved understanding of the pathogenesis of osteochondral necrosis is the first step in formulating more successful preventative and treatment strategies.