Jamie A. Textor

Objectives: (1) To report the clinical and synovial effects of a platelet‐rich product (PRPr) in normal equine joints, (2) to assess the persistence of platelets within synovial fluid after intra‐articular injection, (3) to compare responses to different preparations of that product, and (4) to evaluate a gravity filtration system for PRPr preparation in horses.Study Design: Experimental.Methods: A platelet‐rich saline product (PRPr) was prepared from 7 normal horses using a proprietary preparation device and was divided into 3 treatments: resting, CaCl₂‐activated (23 mM, final), and bovine thrombin‐activated (10 U/mL, final). Each horse had 3 concurrent randomly assigned intra‐articular PRPr treatments administered in their metacarpophalangeal/metatarsophalangeal joints; the fourth limb was injected with saline (0.9% NaCl) solution as a control. Clinical assessments, cytologic analysis of synovial fluid and hemograms were performed at 6, 24, 48, and 96 hours after injection. PRPr composition and growth factor content were analyzed.Results: The gravity filtration system produced a moderately concentrated PRPr. At 6 and 24 hours, when compared to control values, all PRPr treatments caused a significant increase in synovial WBC concentration (P < .0059) and neutrophil percentage (P < .0005). Bovine thrombin‐activated PRPr injection consistently caused increased effusion scores and periarticular signs. At all time points, the synovial WBC concentration after thrombin‐activated PRPr was significantly greater (P < .001) than for the control, CaCl₂‐activated or resting PRPr. Intact platelets could be observed in synovial fluid for up to 5 days after intra‐articular PRPr injection.Conclusions: Resting and CaCl₂‐activated PRPr may be safely used to treat equine joints, but bovine thrombin activation is not recommended at 10 U/mL. A PRPr can be prepared using a gravity filtration system, eliminating the need for centrifugation.

Objective: To investigate and compare clinically relevant Platelet‐rich plasma (PRP) activation methods.Study Design: Experimental.Methods: PRP was prepared from 6 equine subjects. Activation of the PRP was performed by 4 methods (autologous thrombin, bovine thrombin, calcium chloride (CaCl₂), or freeze‐thaw). The resultant PDGF‐BB (where PDGF is platelet‐derived growth factor) and TGFβ1 (where TGFβ is transforming growth factor beta) levels in PRP releasates were quantified by Enzyme‐linked immunosorbent assay (ELISA) and compared. Growth factor contents were also compared between platelet‐rich clots produced by thrombin or CaCl₂. The composition and function of equine autologous thrombin were characterized by Western blot analysis and platelet aggregometry.Results: CaCl₂ (23 mM) activation of PRP yielded significantly greater PDGF release than did any other method. TGFβ release was comparable after PRP activation by CaCl₂, bovine thrombin, and freeze thaw. Autologous thrombin was significantly less effective than all other activation methods in eliciting platelet growth factor release and induced significantly less platelet aggregation than bovine thrombin at 5 U/mL. Clots retained substantial concentrations of growth factor, and the amount in the releasate versus the clot differed between activation methods.Conclusions: PRP activation methods differ in terms of growth factor output as well as logistical considerations. Autologous thrombin is not recommended for PRP activation. CaCl₂ (23 mM) is an effective and inexpensive method of PRP activation. The PRP releasate derived from CaCl₂ activation contains 80% of the total PDGF content and is easily produced, making it a convenient product for clinical use.

Objective—To determine whether CT provides unique information about the treatment or prognosis for horses with ethmoid hematoma (EH). Design—Retrospective case series. Animals—16 horses with EH. Procedures—Horses with a diagnosis of EH that had undergone a diagnostic CT study were included. Clinical features, treatment, outcome, radiographic and CT images, and histologic specimens were reviewed. Results—CT provided new diagnostic information that affected treatment in 10 of 16 horses. Bilateral disease occurred in 8 of 16 horses and was undetected in 5 horses prior to CT. Paranasal sinus involvement occurred in all horses, but was incompletely defined prior to CT in 7 of 16 horses. The sphenopalatine sinus was affected in 6 of 16 horses as detected on CT; 4 of 6 of these were bilaterally affected. Medical and surgical treatments were performed. Six of 10 horses had a successful outcome, with recurrence in 4 of 10. Five of 6 patients in which treatment addressed all lesion sites identified by CT had a successful outcome. Bilateral disease did not confer a poor prognosis when all affected sites were treated. Sphenopalatine sinus involvement may have been associated with recurrence. Conclusions and Clinical Relevance—CT provided anatomic information that may facilitate effective treatment of horses with EH, particularly in patients with bilateral disease and paranasal sinus involvement. Computed tomography is recommended for patients in which the lesion cannot be viewed endoscopically, when sinus involvement or multifocal disease are suspected, or when the lesion has been unresponsive to treatment.

Objective—To test the hypotheses that preparation method, exposure to shear force, and exposure to collagen affect the release of growth factors from equine platelet-rich plasma (PRP). Sample Population—PRP obtained from 6 horses. Procedures—PRP was prepared via 2 preparation methods (tube and automated) and subjected to 6 treatment conditions (resting, detergent, exposure to shear via 21- and 25-gauge needles, and exposure to collagen [10 and 20 μg/mL]). Concentrations of platelet-derived growth factor, isoform BB (PDGF-BB); transforming growth factor β, isoform 1 (TGFβ₁); and insulin-like growth factor, isoform 1 (IGF-1) were quantified by use of ELISAs. Statistical analysis was conducted via repeated-measures ANOVA. Results—Platelet numbers were significantly higher in tube-prepared PRP than in automated-prepared PRP Growth factor concentrations did not differ significantly between preparation methods. Mean PDGF-BB concentration ranged from 134 to 7,157 pg/mL, mean TGFβ₁ concentration ranged from 1,153 to 22,677 pg/mL, and mean IGF-1 concentration ranged from 150 to 280 ng/mL. Shear force did not affect growth factor concentrations. Dose-dependent increases in PDGF-BB and TGFβ₁ were detected in response to collagen, but equalled only 10% of the estimated total platelet content. Concentrations of IGF-1 were not significantly different among treatments and negative or positive control treatments. Serum concentrations of PDGF-BB and TGFβ₁ exceeded concentrations in PRP for most treatment conditions. Conclusions and Clinical Relevance—Release of growth factors from equine PRP was negligible as a result of the injection process alone. Investigation of platelet-activation protocols is warranted to potentially enhance PRP treatment efficacy in horses.

The role of cardiac function or dysfunction in the pathogenesis of exercise-induced pulmonary hypertension and haemorrhage in horses has been minimally investigated. We hypothesize that pericardiotomy would enhance diastolic function and attenuate pulmonary vascular pressures in maximally exercising horses. Our objective was to evaluate diastolic function and cardiopulmonary pressures before and after pericardiotomy, at rest and at maximal exercise. Study design was both self- and externally controlled. Five horses underwent pericardiotomy after a baseline exercise test. They subsequently performed the same exercise protocol at 1 week and 13 weeks post-operatively. An external, unoperated control group of five horses performed the same experimental protocol. Pulmonary arterial pressure (PAP), pulmonary artery wedge pressure (PWP), right ventricular pressure, heart rate (HR) and oesophageal pressure were measured continuously at rest and at maximal exercise; maximum rates of ventricular pressure decrease (−dP/dt_max), relaxation half-time (t_1/2), time constant of isovolumic relaxation (τ) and pulmonary capillary pressures (PcapP) were derived. Statistical analysis was performed using two-tailed Wilcoxon's signed-rank and rank-sum tests, with significance set at P<0.05. No significant differences were found in any variable after pericardiotomy was performed or between the experimental and external control groups. We conclude that during a 13-week study period, pericardiotomy does not alter pulmonary or ventricular pressures or rate of ventricular relaxation in the resting or maximally exercising horse. Results indicate that, in past and future studies requiring an open pericardium in normal horses, the cardiopulmonary parameters measured here are not affected by reduced pericardial pressure.