Effect of Different Storage Conditions on Platelet Aggregation in Horse

Comparison of Citrated Whole Blood to Native Whole Blood for Coagulation Testing Using the Viscoelastic Coagulation Monitor (VCM Vet™) in Horses

Viscoelastic monitoring of horse coagulation is increasing due to its advantages over traditional coagulation testing. The use of a point-of-care viscoelastic coagulation monitor (VCM Vet™) has been validated for use in horses using native whole blood (NWB) but has not been assessed using citrated whole blood (CWB), a technique that might have advantages in practicality and precision. Blood was collected from 70 horses, tested in duplicate immediately using NWB (T0), and stored at room temperature as CWB for testing in duplicate at 1 (T1) and 4 (T4) hours after venipuncture for comparison to NWB. Of these horses, 20 were classified as clinically healthy and used to determine reference intervals for CWB at 1 and 4 h post-collection. There were clinically relevant differences in all measured viscoelastic parameters of CWB compared to NWB meaning that they cannot be used interchangeably. These differences were not consistent at T1 and T4 meaning the resting time of CWB influences the results and should be kept consistent. The use of CWB in this study also resulted in more machine errors when compared to NWB resulting in measurements that might not be interpretable.

Comparison of hematologic variables among Warmbloods, Thoroughbreds, and Western stock horse breeds

BACKGROUND

Hematology is a diagnostic tool used to evaluate the health status of horses. However, breed differences are often not considered.

OBJECTIVES

The objective was to compare complete blood count variables among Warmbloods, Thoroughbreds, and stock horses (SH).

METHODS

Ninety-six healthy horses were grouped by breed (Warmbloods, Thoroughbreds, and SH). Samples were collected through venipuncture for complete blood count analysis. One-way ANOVA with Tukey's tests or Kruskal-Wallis with Dunn's post hoc tests were used to compare hematologic variables among groups.

RESULTS

Warmbloods had a significantly lower total white blood cell (WBC) count (6.08 ± 1.11 × 109/L) and lymphocyte count (1.76 ± 0.41 × 109/L) than Thoroughbreds (7.28 ± 1.45; 2.28 ± 5.16 × 109/L, respectively; P < .001) and SH (7.21 ± 1.18 × 109/L, P < .01; 2.10 ± 5.17 × 109/L; P < .05). Warmbloods had a significantly lower red blood cell count (7.7 ± 0.8 × 1012/L) and higher mean corpuscular volume (MCV, 49.4 ± 2.2 fL) than Thoroughbreds (8.42 ± 1.2 × 1012/L, P < .01; 47.3 ± 3.0 fL). Warmbloods had lower MCVs than SH (49.4 ± 2.2 vs 51.2 ± 2.6 fL). The mean cell hemoglobin concentration (MCHC) was higher in Warmbloods (35.0, 33.8-36.2 g/dL) and Thoroughbreds (34.9, 33.4-35.7 g/dL) than in SH breeds (34.0, 33.4-35.4 g/dL; P < .001, both). Total protein concentrations were significantly lower in Thoroughbreds (67, 59-80 g/L) compared with SH (71, 64-83 g/dL) (P < .05).

CONCLUSIONS

Warmbloods had decreased WBC and lymphocyte counts compared with Thoroughbreds and SH, and Thoroughbreds had increased red blood cell counts. Thoroughbreds had lower total protein concentrations than SH. Clinicians should consider breed differences when interpreting hematologic values.

Different training schedules influence platelet aggregation in show jumping horses

Depending on the intensity, duration and type of physical exercise, equine metabolism has to adapt to nervous, cardiovascular, endocrine and respiratory system requirements. In horses, exercise and training are known to have considerable effects on the mechanisms of hemostatic system involving platelet activity. The aim of the present study was to evaluate the effect of different training schedules on platelet aggregation in 15 Italian Saddle jumping horses. Animals were divided into three equal groups: Group A was subjected to a high intensity-training program; group B to a light training program, group C included sedentary horses. From each animal, blood samples were collected by jugular venipuncture at rest on the 1st, 3rd and 5th days, and afterwards, once a week, for a total of 5 weeks data recording, in order to assess the maximum degree of platelet aggregation and the initial velocity of aggregation (slope) platelet aggregation. Two-way analysis of variance (ANOVA) showed a significant effect of the different training schedules on studied parameters. The results revealed a different degree of platelet aggregation and a different initial velocity of platelet aggregation that changes during the different training schedules in horses that could represent a different protective endothelial mechanism. These findings could have an important role for a clearer knowledge of the physiological reference values of platelet aggregation and for a better interpretation of these variations during the training.

Criopreservação do plasma rico em plaquetas de equinos

Avaliou-se o congelamento do plasma rico em plaquetas (PRP) de equinos, a -196ºC em nitrogênio líquido, utilizando-se como crioprotetor o DMSO em duas concentrações (3% e 6%), e, como ponto final, a avaliação da morfologia e da agregometria plaquetária. Foram utilizadas 12 amostras de PRP em duas repetições. Previamente ao congelamento, as amostras foram submetidas a um resfriamento lento (-0,07ºC/minuto) até a temperatura final de 4-5ºC. A criopreservação do PRP equino, incluindo um resfriamento lento a 4-5ºC, previamente ao congelamento a -197ºC em nitrogênio líquido, foi similar para as concentrações do crioprotetor DMSO a 3% ou 6%, quando avaliado o percentual de ativação e de agregação plaquetária.

Influence of cryopreservation and mechanical stimulation on equine Autologous Conditioned Plasma (ACP®)

OBJECTIVE

To determine the influence of cryopreservation at two different temperatures on platelet concentration, growth factor (GF) levels and platelet activation parameters in equine ACP®; moreover, to determine if adding mechanical ACP® stimulation to freeze-thaw activation amplifies GF release from platelets.

MATERIAL AND METHODS

Firstly, blood from five horses was used to prepare ACP®. Platelet, platelet derived growth factor BB (PDGF-BB) and transforming growth factor β1 (TGF-β1) concentrations as well as mean platelet volume (MPV) and mean platelet component (MPC) were determined in fresh and corresponding ACP® samples after 2 months cryopreservation at -20 °C and -80 °C, respectively. Secondly, ACP® was prepared from blood of nine horses. Half of ACP® was activated using one freeze-thaw-cycle at -20 °C, whereas the rest was first vortexed. Their PDGF-BB and TGF-β1 concentrations were subsequently determined.

RESULTS

Platelet concentration significantly decreased after -80 °C cryopreservation. PDGF-BB level augmented significantly after both storage methods, whereas TGF-β1 concentration was not significantly altered. MPV significantly increased after -20 °C cryopreservation. Both storage regimens induced a significant MPC decrease. No significant differences in GF concentrations between the vortexed and non-vortexed samples were detected.

DISCUSSION

Both cryopreservation methods induced platelet activation, but storage at -80 °C apparently harmed the platelets without generating higher GF release than -20 °C. The mechanical stimulation process could not enhance GF release in subsequently frozen-thawed ACP®.

CONCLUSION AND CLINICAL RELEVANCE

Storage of ACP® at -20 °C could be useful in equine practice, but, before this procedure can be recommended, further qualitative tests are needed. The mechanical stimulation technique should be adjusted in order to increase platelet activation.

Equine bone marrow volume reduction, red blood cell depletion, and mononuclear cell recovery using the PrepaCyte-CB processing system

BACKGROUND

Volume reduction and RBC depletion of equine bone marrow specimens are necessary processing steps for the immediate therapeutic use of bone marrow (BM)-derived mesenchymal stem cells (MSC), and for MSC expansion in culture.

OBJECTIVES

The purpose of the study was to evaluate the ability of the PrepaCyte-CB processing system to reduce volume, deplete RBC, and recover mononuclear cells (MNC) from equine BM specimens.

METHODS

One hundred and twenty mL of heparinized BM were obtained from each of 90 horses. A CBC was performed on the BM pre- and post-PrepaCyte-CB processing. Volume and RBC reduction, and total nucleated cell (TNC) and MNC recoveries were determined.

RESULTS

Bone marrow volume was reduced from 120 mL to 21 mL with a median RBC depletion of 90.1% (range, 62.0-96.7%). The median preprocessing total TNC count was 2.2 × 10(9) (range, 0.46-7.9 × 10(9)) and the median postprocessing TNC count was 1.7 × 10(9) (range, 0.3-4.4 × 10(9); P < .0001), with a median recovery of 73.5% (range, 22.4-216.7%). The median preprocessing total MNC count was 0.9 × 10(9) (range, 0.1-4.7 × 10(9)) and median postprocessing total MNC count was 0.8 × 10(9) (range, 0.1-2.7 × 10(9); P = .06), with a median recovery of 83.7% (range, 15.4-413.9%).

CONCLUSIONS

The PrepaCyte-CB processing system can be used to deplete both volume and RBC, and recover MNC from equine BM specimens. Further studies assessing the viability of MSC and the efficacy of MSC expansion after using the PrepaCyte-CB processing system are warranted.

ADP-induced platelet aggregation after addition of tramadol in vitro in fed and fasted horses plasma

Adenosine diphosphate (ADP)-induced platelet aggregation in fed and fasted horses after addition of tramadol hydrochloride was evaluated in vitro. On 10 horses citrated blood samples were collected 2h after feeding (fed animals) and 21 h after feeding (fasted animals). Final concentrations of ADP 1 and 0.5 μM, and tramadol hydrochloride (1, 15, 30, 45 and 60 min after the addition of tramadol) were used to determine the maximum degree and initial velocity of platelet aggregation. Repeated measures multifactor analysis of variance (MANOVA) was used to evaluate the effect of feeding/fasting condition, ADP concentration and addition of tramadol. Findings showed statistical differences (P≤0.05) on studied parameters after addition of tramadol to different ADP concentrations in fed and fasted horses. The clinical relevance of these results is that tramadol provides many advantages as a therapeutic option; in fact, it is an inexpensive and a relatively new analgesic in equine veterinary medicine. Further investigations would be appropriate to compare the effects of different opioids but also using different concentrations of tramadol associated with other drugs in order to have substances which can regulate the functional activity of the platelets and to extend the knowledges on equine platelet aggregation.

Effects of hydrocortisone and aminophylline on the aggregation of equine platelets in vitro

The purpose of this study was to evaluate in vitro the effects of hydrocortisone and aminophylline on adenosine diphosphate (ADP)-induced platelet aggregation in horses. Blood samples from 30 healthy Thoroughbred horses were collected by via jugular venipuncture to assess platelet aggregation. Platelet-rich and platelet-poor plasma were prepared from all samples by centrifugation and divided into three different aliquots. In the first aliquot, platelet aggregation was measured after platelet activation with 1 µM and 0.5 µM ADP (Group A). In the other two aliquots, the effect of a 10 min preincubation with hydrocortisone (Group B) or aminophylline (Group C) on ADP-induced aggregation at final ADP concentrations of 1 µM and 0.5 µM was observed. Platelet aggregation, recorded by an aggregometer, was evaluated by measuring the maximum degree of platelet aggregation and the initial velocities of platelet aggregation were obtained. Our results demonstrated the inhibitory effect of hydrocortisone and the induction effect of aminophylline on equine platelet responses in vitro.