Effects of preparation method, shear force, and exposure to collagen on release of growth factors from equine platelet-rich plasma

Platelet-Rich Plasma as an Orthobiologic: Clinically Relevant Considerations

Platelet-rich plasma (PRP) is an autologous blood-derived product processed to concentrate platelets and the associated growth factors. PRP has been shown to be relatively well-tolerated and safe to use for a number of conditions in humans, equines, and canines. There are multiple commercial systems that have been validated for canine use. These systems use a variety of methodologies to produce a PRP product. However, PRP products have been shown to differ greatly between systems. Further study is needed to fully elucidate optimal component concentrations for various indications.

A Critical Overview of the Use of Platelet-Rich Plasma in Equine Medicine Over the Last Decade

In the 1990s, the role of platelets in inflammation and tissue healing was finally recognized. Since then, the clinical use of platelet-derived products (hemocomponents), such as, platelet-rich plasma (PRP), markedly increased. The promise of a more economical option of a disease-modifying treatment led to the intensive and continuous research of PRP products and to its widespread clinical use. A number of protocols and commercial kits have been developed with the intention of creating a more practical and reliable option for clinical use in equine patients. Still, the direct comparison between studies is particularly challenging due to the lack of standardization on the preparation methods and product composition. The incomplete reports on PRP cellular concentration and the poorly designed in vivo studies are additional matters that contest the clinical efficiency of this biomaterial. To overcome such challenges, several in vitro and in vivo studies have been proposed. Specifically, experiments have greatly focused in protocol optimization and its effect in different tissues. Additionally, in vivo studies have proposed different biological products envisioning the upgrade of the anti-inflammatory cytokines trusting to increase its anti-inflammatory effect. The individual variability and health status of the animal, type of tissue and condition treated, and protocol implemented are known to influence on the product's cell and cytokine composition. Such variability is a main clinical concern once it can potentially influence on PRP's therapeutic effects. Thus, lack of qualitative and quantitative evidence-based data supporting PRP's clinical use persists, despite of the numerous studies intended to accomplish this purpose. This narrative review aims to critically evaluate the main research published in the past decade and how it can potentially impact the clinical use of PRP.

Optimal double-spin method for maximizing the concentration of platelets in equine platelet-rich plasma

This study optimized the double-spin conditions for preparing equine platelet-rich plasma (PRP): leukocyte-rich PRP (L-PRP) and leukocyte-poor PRP (P-PRP). Whole blood samples were centrifuged at various double-spin conditions. Both L-PRP and P-PRP were prepared at each stage, and complete blood counts and growth factor concentrations were compared. Samples centrifuged at 160 × 900 g, 160 × 2,000 g, and 400 × 2,000 g exhibited the highest platelet counts. P-PRP had significantly lower leukocyte and erythrocyte contents than L-PRP, especially at 400 × 2,000 g. No significant differences were observed in growth factor concentrations. Our data suggest that optimum L-PRP preparation should include centrifugation under the aforementioned conditions, whereas centrifugation at 400 × 2,000 g is optimal for P-PRP.

Optimal activation methods for maximizing the concentrations of platelet-derived growth factor-BB and transforming growth factor-β1 in equine platelet-rich plasma

Platelet-rich plasma (PRP) therapy has been widely applied in various medical fields including humans and horses. This study aimed to establish an optimal activation method to stably and reproducibly maximize the concentrations of platelet-derived growth factor-BB (PDGF-BB) and transforming growth factor-β1 (TGF-β1) contained in equine PRP. Autologous PRP was prepared from 11 Thoroughbreds. For the activation test, PRP was activated by either a single freeze-thaw cycle (Fr) or adding calcium and autologous serum containing thrombin (Ca). PDGF-BB and TGF-β1 concentrations in Fr, Ca, nonactivated (No), and platelet-poor plasma (PPP) samples were determined using ELISA and compared. For repetitive freeze-thaw test, PRP was subjected to single (Fr1), double (Fr2), triple (Fr3), or quadruple (Fr4) freeze-thaw cycles and the concentrations of both growth factors in samples were compared similarly. The PDGF-BB concentration in Ca was significantly higher than that in other preparations. The TGF-β1 concentrations in Fr and Ca were significantly higher than those in PPP and No, with no significant differences between Fr and Ca. The concentrations of both factors were significantly increased in PRP treated with multiple cycles of freeze-thaw compared with that in PRP treated with a single cycle. No significant differences were noted among Fr2, Fr3, and Fr4. Our findings suggest that activation by adding calcium and autologous serum is optimal for instant use of PRP and that double freeze-thawing is an easier and optimal activation method for cryopreserved PRP.

Efficacy of a Semi Automated Commercial Closed System for Autologous Leukocyte- and Platelet-Rich Plasma (l-prp) Production in Dogs: A Preliminary Study

BACKGROUND

To characterize the cellular composition (platelets, erythrocytes, and leukocytes) and determine platelet-derived growth factor isoform BB (PDGF-BB) concentration in canine leukocyte- and platelet rich plasma (L-PRP) produced using a commercial semi-automated closed system.

METHODS

Twenty milliliters of citrated whole blood were obtained from 30 healthy un-sedated canine blood donors and processed using a semi-automated completely closed commercial system (CPUNT 20, Eltek group, Casale Monferrato, Alessandria, Italy) according to the manufacturer's instructions. Erythrocyte, leukocyte, and platelet counts were determined in both whole blood (WB) and resultant L-PRP. The PDGF-BB concentration was evaluated after bovine thrombin activation of 10 L-PRP samples.

RESULTS

This commercial system produced on average 2.3 ± 0.7 mL of L-PRP containing a high concentration of platelets (767,633 ± 291,001 μL, p < 0.001), with a 4.4 fold increase in platelet count, lower concentration of erythrocytes (528,600 ± 222,773 μL, p < 0.001) and similar concentration of leukocytes (8422 ± 6346 μL, p = 0.9918) compared with WB. L-PRP had an average of 3442 ± 2061 pg/mL of PDGF-BB after thrombin activation. Neutrophils, lymphocytes and monocytes average percent content in L-PRP was 14.8 ± 13.2, 71.7 ± 18.5 and 10.7 ± 6.4, respectively.

CONCLUSION

Sterile canine L-PRP prepared using this semi-automated closed system is easy to obtain, produces a significant increase in platelet count compared to WB and contains a detectable concentration of PDGF-BB after activation. Additional in vitro and in vivo studies are needed to assess inflammatory markers concentration and the therapeutic efficacy of this L-PRP in dogs.

Autologous Platelet Lysate Does Not Enhance Chondrogenic Differentiation of Equine Bone Marrow-Derived Mesenchymal Stromal Cells Despite Increased TGF-β1 Concentration

Bone marrow-derived mesenchymal stromal cells (BM-MSCs) are being investigated for their potential in the treatment of musculoskeletal injuries, including tendon and ligament lesions, and cartilage lesions. Culture expansion of cells has traditionally been performed in medium supplemented with fetal bovine serum (FBS), however, concerns regarding the antigenicity and potential viral or prion contamination of FBS have prompted interest in alternative medium supplements. Platelet lysate (PL) contains elevated concentrations of growth factors, including transforming growth factor-β (TGF-β), platelet-derived growth factors, and fibroblast growth factor, released from the α-granules of platelets; therefore, PL could be an ideal medium supplement. The effect of PL on mesenchymal stromal cell (MSC) growth and differentiation has not been fully elucidated. We hypothesized that PL medium would contain significantly higher amounts of TGF-β1 than FBS medium and would be associated with enhanced osteogenic and chondrogenic differentiation. MSCs were isolated from bone marrow collected from five adult horses. Cells were cultured in traditional medium supplemented with FBS or in medium supplemented with fibrinogen depleted-PL (FD-PL). Immunophenotyping was performed using flow cytometry. Trilineage differentiation was assessed through histology and gene expression analysis using quantitative reverse transcription-polymerase chain reaction. TGF-β1 was quantified in both medium types. The immunophenotypes of BM-MSCs cultured in FBS and FD-PL medium were similar with both culture types containing cells positive for stromal cell markers [cluster of differentiation 29 (CD29), CD44, CD90, CD105, and major histocompatibility complex I (MHCI)] and negative for exclusion markers (CD45, CD79α, and MHCII). Despite significantly higher TGF-β1 concentration in FD-PL medium, chondrogenic and osteogenic differentiation were not significantly different between FBS and FD-PL supplemented cultures. PL is an appropriate alternative medium supplement for the culture of equine BM-MSCs up to passage 3. However, despite increased TGF-β1 concentration in FD-PL medium, significant changes in chondrogenic differentiation compared with FBS medium should not be expected.

Platelet-Rich Products and Their Application to Osteoarthritis

Autologous platelet-rich plasma (PRP) is a biological preparation made from the patient's own plasma that contains a platelet concentration above the whole blood baseline. Owing to the release of growth factors and other cytokines after degranulation, platelets have a central role in inflammation and in different stages of the healing process. For this reason, PRP-derived products have been used to enhance healing of musculoskeletal injuries and modulate progression of inflammatory processes, including osteoarthritis (OA). Osteoarthritis is one of the main causes of musculoskeletal disabilities in horses, and currently, there is no effective treatment for this disease. Treatments that focus on the modulation of inflammation and disease progression offer new hope for OA. Platelet-rich plasma provides a more practical and accessible option of therapy compared to other forms of biological treatment (i.e., stem cell therapies) and is believed to induce the production of functional matrix. However, several factors related to PRP production, including methods of preparation and application, and intraindividual variability, lead to an inconsistent product, precluding reliable conclusions about its efficacy for clinical use. The aim of this study was to review the benefits related to the clinical use of PRP in OA as well as factors that influence its use, the limitations of this treatment, and future directions of PRP research and therapy.

Does Double Centrifugation Lead to Premature Platelet Aggregation and Decreased TGF-β1 Concentrations in Equine Platelet-Rich Plasma?

Blood-derived autologous products are frequently used in both human and equine medicine to treat musculoskeletal disorders. These products, especially the platelet-rich plasma (PRP), may contain high concentrations of growth factors (GFs), and thus improve healing in several tissues. Nevertheless, the procedures for preparation of PRP are currently non-standardized. Several protocols, which are based on distinct centrifugation patterns (rotation speed and time), result in PRPs with different characteristics, concerning platelet and GFs concentrations, as well as platelet activation. The aim of the present study was to compare two different protocols for PRP preparation: protocol (A) that is based on a single-centrifugation step; protocol (B), which included two sequential centrifugation steps (double-centrifugation). The results here reported show that the double-centrifugation protocol resulted in higher platelet concentration, while leukocytes were not concentrated by this procedure. Although platelet activation and aggregation were increased in this protocol in comparison to the single-centrifugation one, the TGF-β1 concentration was also higher. Pearson’s correlation coefficients gave a significant, positive correlation between the platelet counts and TGF-β1 concentration. In conclusion, although the double-centrifugation protocol caused premature platelet aggregation, it seems to be an effective method for preparation of PRP with high platelet and TGF-β1 concentrations.

The effect of four different freezing conditions and time in frozen storage on the concentration of commonly measured growth factors and enzymes in equine platelet-rich plasma over six months

Background

Platelet-rich plasma (PRP) is a therapeutic biologic that is used for treatment of musculoskeletal pathologies in equine athletes. Due to the expense of PRP kits, and the volumes obtained, freezing aliquots for future dosing is common. Aliquots of PRP are also commonly frozen for later analysis of growth factor concentrations in in vitro research. A variety of freezing methods are used and storage duration until analysis is often not reported. The optimal frozen storage conditions and duration to maintain concentrations of commonly measured growth factors and enzymes in PRP are unknown. Our objectives were two-fold. First, to determine the effect of a single freeze-thaw cycle on PRP protein concentrations and establish their baseline levels. Second, to evaluate the effect of storage in -20 °C automatic defrost freezer, − 20 °C manual defrost freezer, − 80 °C manual defrost freezer, and liquid nitrogen for 1, 3, and 6 months on PRP protein concentrations, compared to the established baseline concentrations.

Results

Fold-change between fresh activated and snap frozen PRP were analyzed using paired t-test. A snap frozen-thaw cycle resulted in increased MMP-9 (p = 0.0021), and a small significant decrease in TGF-β1 (p = 0.0162), while IGF-1 and PDGF-BB were unchanged compared to fresh activated PRP. Fold-change over time within storage method were analyzed using repeated measures ANOVA and Tukey post-hoc test. IGF-1 decreased in all conditions (p < 0.0001). At all time-points at -20 °C (p < 0.0001), and at 3 and 6 months at -80 °C (p < 0.0070), PDGF-BB decreased. TGF- β1 was unchanged or increased after 6 months (p < 0.0085). MMP-9 decreased at 3-months at -20 °C, and at all times at -80 °C and in liquid nitrogen compared to snap frozen (p < 0.0001).

Conclusions

The protein profile of equine frozen-stored PRP differs from fresh PRP. For clinical applications equine PRP can be stored at -80 °C for 1 month or in liquid nitrogen for 6 months to maintain PDGF-BB and TGF-β1 concentration, but IGF-1 concentrations will be reduced. The storage temperature and duration should be reported in studies measuring protein concentrations in PRP. To accurately measure IGF-1 concentrations, PRP samples should be analyzed immediately.

Electronic supplementary material

The online version of this article (10.1186/s12917-019-2040-4) contains supplementary material, which is available to authorized users.

Comparison of the methods for platelet rich plasma preparation in horses

Platelet rich plasma (PRP) is popularly used in the horse industry to enhance regeneration of tissue injury that has limitation of blood supply. This study aimed to compare the methods for platelet rich plasma preparation since they has not been established yet. Blood was collected from six horses and platelets were concentrated by three different methods (2-step centrifugation, separated centrifugation and separated centrifugation using histopaque). Concentrated blood was analyzed using Advia hematology systems. In the result, separated centrifugation with histopaque showed the significantly lower number of red blood cells than other groups. The 2-step centrifugation showed the significantly higher number of white blood cells than other groups, while it contained the highest concentration of red blood cells among three groups. In the 2-step centrifugation, separated centrifugation and separated centrifugation with histopaque, platelets were concentrated 4.5, 5.3 and 5.6 times, respectively. And no significant difference of the platelet concentration between the three groups was found. This study demonstrated that separated centrifugation using histopaque was the best method for platelet rich plasma preparation because of the proper amount of platelets and the separation of red blood cells from platelet rich plasma.

Cell-Based Therapies for Joint Disease in Veterinary Medicine: What We Have Learned and What We Need to Know

Biological cell-based therapies for the treatment of joint disease in veterinary patients include autologous-conditioned serum, platelet-rich plasma, and expanded or non-expanded mesenchymal stem cell products. This narrative review outlines the processing and known mechanism of action of these therapies and reviews current preclinical and clinical efficacy in joint disease in the context of the processing type and study design. The significance of variation for biological activity and consequently regulatory approval is also discussed. There is significant variation in study outcomes for canine and equine cell-based products derived from whole blood or stem cell sources such as adipose and bone marrow. Variation can be attributed to altering bio-composition due to factors including preparation technique and source. In addition, study design factors like selection of cases with early vs. late stage osteoarthritis (OA), or with intra-articular soft tissue injury, influence outcome variation. In this under-regulated field, variation raises concerns for product safety, consistency, and efficacy. Cell-based therapies used for OA meet the Food and Drug Administration’s (FDA’s) definition of a drug; however, researchers must consider their approach to veterinary cell-based research to meet future regulatory demands. This review explains the USA’s FDA guidelines as an example pathway for cell-based therapies to demonstrate safety, effectiveness, and manufacturing consistency. An understanding of the variation in production consistency, effectiveness, and regulatory concerns is essential for practitioners and researchers to determine what products are indicated for the treatment of joint disease and tactics to improve the quality of future research.

Influence of calcium salts and bovine thrombin on growth factor release from equine platelet-rich gel supernatants

Objective: To compare five activation methods in equine platelet-rich plasma (PRP) by determination of platelet-derived growth factor BB (PDGF-BB) and transforming growth factor beta 1 (TGF-β1) concentrations in platelet-rich gel (PRG) supernatants.

Methods: Platelet-rich plasma from 20 horses was activated by calcium chloride (CC), calcium gluconate (CG), bovine thrombin (BT), and their combinations, BTCC and BTCG. Both growth factor concentrations in PRG supernatants were measured by ELISA and compared with plasma and platelet ly-sates (PL) over time.

Results: Growth factor concentrations were significantly lower in plasma and higher for all PRG supernatants. Platelet lysates contained a significantly lower concentration of PDGF-BB than PRG supernatants and a significantly higher concentration of TGF-β1 than PRG supernatants. Clots from PRP activated with sodium salts were more stable over time and had significant growth factor release, whereas CC produced gross salt deposition. Significant correlations were noticed for platelet with leukocyte concentrations in PRP (rs: 0.76), platelet counts in PRP with TGF-β1 concentrations in PRG supernatants (rs: 0.86), platelet counts in PRP with PDGF-BB concentrations in PRG super-natants (rs: 0.78), leukocyte counts in PRP with TGF-β1 concentrations in PRG supernatants (rs: 0.76), and PDGF-BB concentrations with activating substances (rs: 0.72).

Clinical significance: Calcium gluconate was the better substance to induce PRP activation. It induced growth factor release free from calcium precipitates in the clots. Use of BT alone or combined with calcium salts was not advantageous for growth factor release.

Extracorporeal Shockwave Therapy Increases Growth Factor Release from Equine Platelet-Rich Plasma In Vitro

Introduction

Extracorporeal shockwave therapy (ESWT) and platelet-rich plasma (PRP) are common treatments for soft tissue injuries in horses. Shockwave triggers cell specific responses to promote healing. Growth factors released from PRP also promote healing. It has been hypothesized that greater growth factor release would amplify the healing process. The combination of ESWT and PRP could promote healing in injured tendons and ligaments in the horse. The objective of this study was to determine if application of shockwaves to PRP samples increases the concentration of transforming growth factor-β₁ (TGF-β₁) and platelet-derived growth factor ββ (PDGF-ββ) released from the platelets in vitro.

Materials and methods

PRP was produced from blood drawn from six horses. The PRP from each horse was exposed to the following treatments: (1) positive control (freeze-thaw cycle), (2) untreated negative control, or shockwaves with either (3) a "standard probe" (ESWT-S) with a 2 cm focal width and medium energy density or (4) a "power probe" (ESWT-P) with a 1 cm focal width and high energy density. After each treatment, the samples were centrifuged, and the supernatant was harvested. The supernatant was then used for growth factor quantification via commercially available ELISA kits for TGF-β₁ and PDGF-ββ.

Results

Concentrations of TGF-β₁ and PDGF-ββ in PRP that underwent a freeze-thaw cycle were significantly increased compared with all other treatments. Both ESWT-S and ESWT-P resulted in significantly increased TGF-β₁ concentrations, 46 and 33%, respectively, when compared with the negative control. Both ESWT-S and ESWT-P resulted in significantly increased PDGF-ββ concentrations, 219 and 190%, respectively, when compared with the negative control.

Discussion

These data indicate that the application of ESWT to PRP increases the expression of growth factors in vitro. This suggests that the combination therapy of local PRP injection followed by ESWT may stimulate release of growth factors from platelets after they have been injected into the area of injury.

Conclusion

The combination of PRP and ESWT might result in synergism of two modalities previously utilized individually for tendon and ligament injuries in horses.

Uterine clinical findings, fertility rate, leucocyte migration, and COX-2 protein levels in the endometrial tissue of susceptible mares treated with platelet-rich plasma before and after AI

Persistent mating-induced endometritis (PMIE) results in decreased fertility in horses, thereby causing a significant impact in the horse market. Platelet-rich plasma (PRP), a modulator of the inflammatory response, has been largely used in veterinary medicine. Here, we investigated the effects of PRP on uterine inflammation, conception rate, endometrial polymorphonuclear neutrophil (PMN) migration, and COX-2 protein levels in the endometrial tissue. Thirteen PMIE-susceptible mares were used for artificial insemination (AI). The mares were inseminated with fresh semen in three consecutive cycles in a cross-over study design. The following cycle classifications were used: control cycle, no pharmacological interference; pre-AI, 20 mL of PRP was infused 24 h before AI; and post-AI, 20 mL of PRP was infused four h after AI. Follicular dynamics were monitored daily by transrectal ultrasound. When a follicle larger than 35 mm was detected, ovulation was induced with deslorelin acetate (1 mg, im). AI was performed 24 h after ovulation induction. Intrauterine fluid (FLU) was evaluated by ultrasonography before and 24 h after AI. PMNs in uterine cytology (CYT) and biopsy (HIS) were also observed before and 24 h after AI. Pregnancy was determined within 14 days after ovulation. Number of COX-2 positive cells was evaluated by immunohistochemistry. Both PRP treatments resulted in a decrease of PMNs in the CYT after breeding when compared to controls. FLU did not differ between cycles; however, the conception rates were significantly higher in the PRP mares. Mares positive for endometritis decreased in both treatment groups, and a more intense positive COX-2 labeling was observed in the control group when compared to the two treatment groups. In conclusion, PRP beneficially reduces inflammatory response in PMIE mares independent of when treatments were administered, thus increasing chances of successful pregnancy.

Does the injection of platelet-rich plasma induce changes in the gene expression and morphology of intact Thoroughbred skeletal muscle?

Platelet-rich plasma (PRP) therapy is promising for treating skeletal muscle injuries in human athletes by promoting muscle regeneration. It might also be useful for treating muscle injuries in equine athletes. In the present study, muscle regeneration induced by injection of PRP into intact muscle of Thoroughbred was investigated. Autologous PRP and saline were injected twice into intact left and right gluteus medius muscles of seven clinically healthy Thoroughbreds. Muscle samples were collected from the injection sites by needle biopsy at 2 and 7 days after PRP injection. Immunohistochemical staining to identify the types of myosin heavy chains (MHCs) and satellite cells was performed to compare morphological changes among intact (pre-injection), saline-, and PRP-injected muscles. The expression of marker genes related to muscle regeneration (MHC-I, MHC-II, and embryonic MHC [MHC-e]), satellite cell activity (CK, Pax7, MyoD, and myogenin), and proinflammatory and promyogenic cytokines (IL-6, IGF-1, and HGF) was analyzed and compared between saline- and PRP-injected muscles. There were no obvious morphological differences among the three treatments. There were no significant differences in gene expression associated with satellite cell activity between saline and PRP injection at 7 days after injection. MHC genes showed significantly higher expression levels with PRP than with saline, including MHC-e at 2 days and MHC-I at 7 days after injection. It is suggested that injection of PRP into intact skeletal muscle does not induce specific morphological changes, but upregulate the expression of genes related to muscle regeneration.

Evaluation of Platelet-Rich Plasma and Neutrophil Antimicrobial Extract as Two Autologous Blood-Derived Agents

The platelet-rich plasma (PRP) and antimicrobial peptides neutrophil extract (AMP extract) were prepared from rabbit neutrophils as two autologous blood-derived preparations, which could be applied locally to enhance healing process of tissues. Both preparations were analyzed using the MALDI TOF method for accurate qualitative assay. Growth factors (PDGF and VEGF) and microbicidal protein were reported in PRP. In AMP extract α-defensins, namely; NP-1, -2, -3a, -3b, -4, and -5 and cathelicidins represented among other by 15-kDa antibacterial protein (p15s) were detected. In the second part of our study the influence of antimicrobial extract on macrophages in vitro was tested. Then, degranulation of neutrophils in vitro and generation of reactive intermediates by these cells under the influence of AMP extract were assessed. As estimated, the addition of AMP extract into cultures of macrophages decreased superoxide anion generation after 5 days of incubation. Furthermore, AMP extract inhibited degranulation and respiratory burst in neutrophils, therefore in this regard it suppress proinflammatory effect of two studied populations of leukocytes.

Influence of Cellular Composition and Exogenous Activation on Growth Factor and Cytokine Concentrations in Canine Platelet-Rich Plasmas

OBJECTIVE

The purposes of this study were to (1) evaluate correlations among platelet, leukocyte, growth factor, and cytokine concentrations in canine platelet-rich plasmas (PRPs) produced from five different canine PRP-concentrating systems and (2) compare the effects of different activation protocols on platelet activation and growth factor release from one of these PRPs.

METHODS

PRP was made using blood from 15 dogs and each of 5 different PRP systems in a cross-over design. Complete blood counts were performed to quantify platelet and leukocyte concentrations. PRPs were activated, or not, according to manufacturer instructions, and transforming growth factor-β1 (TGF-β1), platelet-derived growth factor-BB (PDGF-BB), vascular endothelial growth factor, and tumor necrosis factor-alpha (TNF-α) were quantified. Differences among platelet, leukocyte, and growth factor concentration were compared among the different systems. Correlations between platelet and anabolic growth factor concentrations were assessed. Subsequently, PRP was made from 12 additional dogs using one of the devices. Each PRP was divided into three aliquots that were activated with calcium chloride (CaCl₂), human γ-thrombin (HGT), or not activated. Expression of CD62P and platelet-bound fibrinogen (CAP1) was quantified for each activation group. Concentrations of TGF-β1, PDGF-BB, and TNF-α were also quantified for each activation group and a fourth group that was frozen/thawed. Differences among activation groups were assessed by a Friedman test.

RESULTS

There were statistically significant differences among the PRPs made with difference devices with regard to platelet, leukocyte, TGF-β1, and PDGF-BB concentrations (p < 0.0001). There were weak to moderate correlations (R² = 0.07-0.58) between platelet and anabolic growth factor concentrations but it appeared that activation had a greater effect on growth factor concentration than did cellular composition. Intentional platelet activation significantly increased CD62P and CAP1 expression as well as TGF-β1 and PDGF-BB concentrations in the one PRP in which all activation methods were assessed. Activation with HGT resulted in the greatest platelet activation, and CaCl₂ and freeze/thaw elicited moderate increases in either growth factor release or CD62P and CAP1 expression.

CONCLUSION

There are positive correlations between platelet and anabolic growth factor concentrations in canine PRPs. However, intentional platelet activation has a greater effect on growth factor delivery than platelet concentration. Thrombin provides more robust activation than CaCl₂.

Validation of commercial ELISAs for quantifying anabolic growth factors and cytokines in canine ACD-A anticoagulated plasma

Platelet-rich plasma has been studied extensively in dogs, but validation of enzyme-linked immunosorbent assays (ELISAs) for quantifying anabolic growth factors and inflammatory cytokines in canine plasma prepared with citrate-based anticoagulants is not available. We performed a validation of commercial ELISAs for transforming growth factor-beta 1 (TGF-β1), platelet-derived growth factor-BB (PDGF-BB), vascular endothelial growth factor (VEGF), tumor necrosis factor-alpha (TNF-α), and interleukin-1 beta (IL-1β) for use with canine plasma prepared with acid-citrate-dextrose, solution A (ACD-A). Platelet-poor plasma (PPP) anticoagulated with ACD-A as well as PPP anticoagulated with ACD-A and spiked with the relevant canine recombinant proteins were evaluated with each ELISA to calculate the efficiency of spike recovery. Replicates of the spiked PPP were also assessed in 2 additional assays to quantify intra-assay and interassay precision. The efficiency of spike recovery was within 75-125% of the expected concentration for the TGF-β1, PDGF-BB, and VEGF ELISAs. The intra- and interassay variability were <25% for the TGF-β1, PDGF-BB, VEGF, and TNF-α ELISAs. The TGF-β1, PDGF-BB, and VEGF ELISAs demonstrate acceptable efficiency of spike recovery and intra- and interassay variability, whereas the TNF-α and IL-1β ELISAs did not meet industry standards of performance with ACD-A anticoagulated canine plasma.

Platelet-Rich Plasma: The Choice of Activation Method Affects the Release of Bioactive Molecules

Platelet-Rich Plasma (PRP) is a low-cost procedure to deliver high concentrations of autologous growth factors (GFs). Platelet activation is a crucial step that might influence the availability of bioactive molecules and therefore tissue healing. Activation of PRP from ten voluntary healthy males was performed by adding 10% of CaCl₂, 10% of autologous thrombin, 10% of a mixture of CaCl₂ + thrombin, and 10% of collagen type I. Blood derivatives were incubated for 15 and 30 minutes and 1, 2, and 24 hours and samples were evaluated for the release of VEGF, TGF-β1, PDGF-AB, IL-1β, and TNF-α. PRP activated with CaCl₂, thrombin, and CaCl₂/thrombin formed clots detected from the 15-minute evaluation, whereas in collagen-type-I-activated samples no clot formation was noticed. Collagen type I produced an overall lower GF release. Thrombin, CaCl₂/thrombin, and collagen type I activated PRPs showed an immediate release of PDGF and TGF-β₁ that remained stable over time, whereas VEGF showed an increasing trend from 15 minutes up to 24 hours. CaCl₂ induced a progressive release of GFs from 15 minutes and increasing up to 24 hours. The method chosen to activate PRP influences both its physical form and the releasate in terms of GF amount and release kinetic.

Arcabouço de PRP-gel associado a células tronco mesenquimais: uso em lesões condrais em modelo experimental equino

Resumo: O plasma rico em plaquetas (PRP) é conhecido por apresentar propriedades anabólicas, anti-inflamatórias e capacidade de gelificação. Atualmente o PRP é considerado eficaz na reparação da cartilagem, sendo sua capacidade de formação de gel indicada para o preenchimento de defeitos condrais. O objetivo desse estudo foi analisar o uso do PRP ativado, no formato de arcabouço, como suporte para o implante de células tronco mesenquimais (CTM), no preenchimento e tratamento de lesões condrais induzidas em equinos. Doze equinos foram submetidos a uma cirurgia artroscópica no tempo zero do experimento (T0), onde foi induzida uma lesão condral de 15 mm de diâmetro na tróclea medial femoral dos membros pélvicos direito. As 12 articulações foram divididas em dois grupos distintos com seis articulações cada (GA e GB). As articulações do GA foram submetidas ao tratamento com o implante de CTM em gel de PRP. As articulações de GB foram o grupo controle do experimento. As CTMs foram extraídas do tecido adiposo e o PRP em gel foi obtido por protocolo de dupla centrifugação seguido da adição de trombina liofilizada. Após cinco meses (T150) foi realizada nova artroscopia para avaliação macroscópica do local, coleta de amostras do tecido de reparação para análises de microscopia eletrônica, sendo realizadas imagens ressonância magnética e tomografia computadorizada no local do implante no GA. Observamos que o gel de PRP associado às CTM demonstrou ser adequado no tratamento de defeitos condrais experimentais dos equinos. GA evidenciou um melhor aspecto macroscópico e microscópico do tecido de reparação, sendo que GB mostrou maior desorganização das fibras colágenas. Nas imagens de ressonância magnética e tomografia computadorizada apenas foi relevante o local da lesão condral. O arcabouço de gel de PRP demonstrou ser apropriado no suporte do tratamento com as CTMs, sendo de fácil aplicação e efetivo, demonstrando resultados promissores na reparação de lesões condrais induzidas.

Method to obtain platelet-rich plasma from rabbits (Oryctolagus cuniculus )

Abstract: Platelet-rich plasma (PRP) is a product easy and inxpesnsive, and stands out to for its growth factors in tissue repair. To obtain PRP, centrifugation of whole blood is made with specific time and gravitational forces. Thus, the present work aimed to study a method of double centrifugation to obtain PRP in order to evaluate the effective increase of platelet concentration in the final product, the preparation of PRP gel, and to optimize preparation time of the final sample. Fifteen female White New Zealand rabbits underwent blood sampling for the preparation of PRP. Samples were separated in two sterile tubes containing sodium citrate. Tubes were submitted to the double centrifugation protocol, with lid closed and 1600 revolutions per minute (rpm) for 10 minutes, resulting in the separation of red blood cells, plasma with platelets and leucocytes. After were opened and plasma was pipetted and transferred into another sterile tube. Plasma was centrifuged again at 2000rpm for 10 minutes; as a result it was split into two parts: on the top, consisting of platelet-poor plasma (PPP) and at the bottom of the platelet button. Part of the PPP was discarded so that only 1ml remained in the tube along with the platelet button. This material was gently agitated to promote platelets resuspension and activated when added 0.3ml of calcium gluconate, resulting in PRP gel. Double centrifugation protocol was able to make platelet concentration 3 times higher in relation to the initial blood sample. The volume of calcium gluconate used for platelet activation was 0.3ml, and was sufficient to coagulate the sample. Coagulation time ranged from 8 to 20 minutes, with an average of 17.6 minutes. Therefore, time of blood centrifugation until to obtain PRP gel took only 40 minutes. It was concluded that PRP was successfully obtained by double centrifugation protocol, which is able to increase the platelet concentration in the sample compared with whole blood, allowing its use in surgical procedures. Furthermore, the preparation time is appropriate to obtain PRP in just 40 minutes, and calcium gluconate is able to promote the activation of platelets.

Immunohistochemical Expression of Collagens in the Skin of Horses Treated with Leukocyte-Poor Platelet-Rich Plasma

This study evaluated the immunohistochemical expression of type I (COL I) and III (COL III) collagens during the healing process of skin treated with leukocyte-poor platelet-rich plasma (LP-PRP). Seven healthy gelding crossbred horses aged 16 to 17 years were used. Two rectangle-shaped wounds were created surgically in the right and left gluteal regions. Twelve hours after wound induction, 0.5 mL of the LP-PRP was administered in each edge of the wounds of one of the gluteal regions. The contralateral region was used as control (CG). Three samples were obtained: after wound induction (T0), 14 days (T1) of healing process, and after complete closure of the skin (T2). The normal skin (T0) showed strong staining for type III and I collagen in papillary and reticular dermis, respectively. In the scar of the treated group, COL III showed important (p < 0.05) increase in immunoreaction in T2 compared with T1. The administration of a single dose of LP-PRP 12 h after induction of wound in horses does not influence formation of collagens I and III. However, the intense labeling for COL III suggests that the tissue was still weak during the macroscopic closure of the wound, demonstrating that healing was not completely finished.

Equine platelet lysate as an alternative to fetal bovine serum in equine mesenchymal stromal cell culture - too much of a good thing?

REASONS FOR PERFORMING STUDY

Multipotent mesenchymal stromal cells (MSC) are often culture-expanded in vitro. Presently, expansion medium (EM) for MSC is supplemented with fetal bovine serum (FBS). However, increasing cost, variable composition and potential risks associated with bovine antigens call for alternatives. Platelet lysate (PL) has shown promise as an alternative supplement.

OBJECTIVES

To determine how equine umbilical cord blood (CB) MSC proliferate in EM enriched with PL or FBS at various concentrations.

STUDY DESIGN

Randomised dose escalation study.

METHODS

Platelet concentrate was generated from 5 equine whole blood samples through a double centrifugation method and standardised to 1 × 10(12) platelets/l prior to a freeze/thaw cycle to produce PL. Pooled PL or pooled FBS was added to EM at concentrations of 5% to 60%. Proliferation of 4 equine CB-MSC cultures was determined after 4 days using a resazurin semiquantitative assay.

RESULTS

Cord blood-MSC proliferated with a dose-dependent response with no significant difference found between PL and FBS up to a 30% concentration. Beyond 30%, proliferation fell in the PL-cultured cells, while continued dose-dependent proliferation was noted in the FBS-cultured cells. Despite reduced cell numbers in high PL concentrations, live/dead staining revealed that adherent cells remained viable.

CONCLUSIONS

Expansion medium enriched with PL can support short-term equine CB-MSC proliferation at conventional culture concentrations. Based on the unexpected suppression of CB-MSC at higher PL concentrations, an in vivo dose study is indicated to investigate if combinational therapies of CB-MSC and platelet-rich plasma are associated with synergistic or antagonistic effect on CB-MSC function.

Platelet-rich plasma in orthopedic therapy: a comparative systematic review of clinical and experimental data in equine and human musculoskeletal lesions

BACKGROUND

This systematic review aimed to present and critically appraise the available information on the efficacy of platelet rich plasma (PRP) in equine and human orthopedic therapeutics and to verify the influence of study design and methodology on the assumption of PRP's efficacy. We searched Medline, PubMed, Embase, Bireme and Google Scholar without restrictions until July 2013. Randomized trials, human cohort clinical studies or case series with a control group on the use of PRP in tendons, ligaments or articular lesions were included. Equine clinical studies on the same topics were included independently of their design. Experimental studies relevant to the clarification of PRP's effects and mechanisms of action in tissues of interest, conducted in any animal species, were selected.

RESULTS

This review included 123 studies. PRP's beneficial effects were observed in 46.7% of the clinical studies, while the absence of positive effects was observed in 43.3%. Among experimental studies, 73% yielded positive results, and 7.9% yielded negative results. The most frequent flaws in the clinical trials' designs were the lack of a true placebo group, poor product characterization, insufficient blinding, small sampling, short follow-up periods, and adoption of poor outcome measures. The methods employed for PRP preparation and administration and the selected outcome measures varied greatly. Poor study design was a common feature of equine clinical trials. From studies in which PRP had beneficial effects, 67.8% had an overall high risk of bias. From the studies in which PRP failed to exhibit beneficial effects, 67.8% had an overall low risk of bias.

CONCLUSIONS

Most experimental studies revealed positive effects of PRP. Although the majority of equine clinical studies yielded positive results, the human clinical trials' results failed to corroborate these findings. In both species, beneficial results were more frequently observed in studies with a high risk of bias. The use of PRP in musculoskeletal lesions, although safe and promising, has still not shown strong evidence in clinical scenarios.

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.

Effects of sodium citrate and acid citrate dextrose solutions on cell counts and growth factor release from equine pure-platelet rich plasma and pure-platelet rich gel

Background

There is a lack information on the effects of the most commonly used anticoagulants for equine platelet rich plasmas (PRPs) elaboration on cell counts and growth factor release from platelet rich gels (PRGs). The aims of this study were 1) to compare the effects of the anticoagulants sodium citrate (SC), acid citrate dextrose solution A (ACD-A) and ACD-B on platelet (PLT), leukocyte (WBC) and on some parameters associated to platelet activation including mean platelet volume (MPV) and platelet distribution width (PDW) between whole blood, pure PRP (P-PRP) and platelet-poor plasma (PPP); 2) to compare transforming growth factor beta 1 (TGF-β₁) and platelet-derived growth factor isoform BB (PDGF-BB) concentrations in supernatants from pure PRG (P-PRG), platelet-poor gel (PPG), P-PRP lysate (positive control) and plasma (negative control); 3) to establish the possible correlations between all the studied cellular and molecular parameters.

Results

In all cases the three anticoagulants produced P-PRPs with significantly higher PLT counts compared with whole blood and PPP. The concentrations of WBCs were similar between P-PRP and whole blood, but significantly lower in PPP. The type of anticoagulant did not significantly affect the cell counts for each blood component. The anticoagulants also did not affect the MPV and PDW parameters. Independently of the anticoagulant used, all blood components presented significantly different concentrations of PDGF-BB and TGF-β₁. The highest growth factor (GF) concentrations were observed from P-PRP lysates, followed by PRG supernatants, PPP lysates, PPG supernatants and plasma. Significant correlations were observed between PLT and WBC counts (ρ = 0.80), PLT count and TGF-β₁ concentration (ρ = 0.85), PLT count and PDGF-BB concentration (ρ = 0.80) and PDGF-BB and TGF-β₁ concentrations (ρ = 0.75). The type of anticoagulant was not correlated with any of the variables evaluated.

Conclusions

The anticoagulants did not significantly influence cell counts or GF concentrations in equine PRP. However, ACD-B was apparently the worst anticoagulant evaluated. It is necessary to perform additional research to determine the effect of anticoagulants on the kinetics of GF elution from P-PRG.

Concentration of platelets and growth factors in platelet-rich plasma from Goettingen minipigs

In minipigs little is known about the concentration of growth factors in plasma, despite their major role in several patho-physiological processes such as healing of fractures. This prompted us to study the concentration of platelets and selected growth factors in plasma and platelet-rich plasma (PRP) preparation of sixteen Goettingen minipigs.

Platelet concentrations increased significantly in PRP in comparison to native blood plasma. Generally, significant increase in the concentration of all growth factors tested was observed in the PRP in comparison to the corresponding plasma or serum. Five of the plasma samples examined contained detectable levels of bone morphogenic protein 2 (BMP-2) whereas eleven of the plasma or serum samples contained minimal amounts of vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF-bb) respectively. On the other hand variable concentrations of bone morphogenic protein 7 (BMP-7) and transforming growth factor β1 (TGF-β1) were measured in all plasma samples. In contrast, all PRP samples contained significantly increased amounts of growth factors. The level of BMP-2, BMP-7, TGF-β1, VEGF and PDGF-bb increased by 17.6, 1.5, 7.1, 7.2 and 103.3 fold, in comparison to the corresponding non-enriched preparations. Moreover significant positive correlations were found between platelet count and the concentrations of BMP-2 (r=0.62, p<0.001), TGF-β1 (r=0.85, p<0.001), VEGF (r=0.46, p<0.01) and PDGF-bb (r=0.9, p<0.001). Our results demonstrate that selected growth factors are present in the platelet-rich plasma of minipigs which might thus serve as a source of autologous growth factors.

Temporal Bacteriostatic Effect and Growth Factor Loss in Equine Platelet Components and Plasma Cultured with Methicillin-Sensitive and Methicillin-Resistant Staphylococcus aureus: A Comparative In Vitro Study

The aims were (1) to evaluate the bacteriostatic effect of platelet-rich plasma (PRP), platelet-rich gel (PRG), leukocyte-poor plasma (LPP), leukocyte-poor gel (LPG), plasma, and heat-inactivated plasma (IP) on both methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) over a period of 24 h; (2) to determine and to compare the concentrations and degradation over time of platelet factor 4 (PF-4), transforming growth factor beta 1 (TGF-β 1), and platelet-derived growth factor isoform BB (PDGF-BB); and (3) to identify any correlations between MSSA and MRSA growth and either the cellular, PF-4, TGF-β 1, or PDGF-BB concentrations in the blood components. PRP and its byproducts from 18 horses were obtained by the tube method. All blood components were cultured with either MSSA or MRSA. Bacterial growth, PF-4, TGF-β 1, and PDGF-BB were determined at 6 h and 24 h. At six hours, bacterial growth was significantly inhibited by all blood components, with the exception of IP. MSSA was more sensitive to the treatments than MRSA. At 24 hours, bacterial growth was significantly higher in IP. MRSA bacterial growth was significantly higher in PRP, LPP, and plasma when compared to MSSA. Growth factor concentrations were not significantly affected by bacteria.

Comparison of platelet counting technologies in equine platelet concentrates

OBJECTIVE

(1) To compare the performance of 4 platelet counting technologies in equine platelet concentrates and (2) to evaluate the ability of the Magellan platelet rich plasma (PRP) system to concentrate equine platelets.

STUDY DESIGN

Experimental study to assess method agreement.

ANIMALS

Adult mixed breed horses (n = 32).

METHODS

Acid citrate dextrose-A anti-coagulated whole blood was collected and PRP produced using the Magellan system according to the manufacturer's instructions. Platelets were quantified using 4 counting methods: optical scatter (Advia 2120), impedance (CellDyn 3700), hand counting, and fluorescent antibody flow cytometry. Platelet concentrations were compared using Passing and Bablok regression analyses and mixed model ANOVA. Significance was set at P < .05.

RESULTS

Platelet concentrations measured in identical PRP samples were consistently higher for the Advia 2120 than the CellDyn 3700. Systematic and proportional biases were observed between these 2 automated methods when analyzed by regression analysis of the larger sample size. No bias (systematic or proportional) was observed among any of the other counting methods. Despite the bias detected between the 2 automated systems, there were no significant differences on average among the 4 counting methods evaluated, based on the ANOVA. The Magellan system consistently generated high platelet concentrations as well as higher than expected WBC concentrations.

CONCLUSIONS

The Magellan system delivered desirably high platelet concentrations; however, WBC concentrations may be unacceptably high for some orthopedic applications. All 4 platelet counting methods tested were equivalent on average and therefore suitable for quantifying platelets in equine PRP used for clinical applications.

Quantificação de fatores de crescimento na pele de equinos tratada com plasma rico em plaquetas

O plasma rico em plaquetas (PRP) é um produto derivado da centrifugação do sangue total, sendo rico em fatores bioativos, como os de crescimento. Apesar da ampla utilização em processos cicatriciais, há controvérsia sobre a eficácia da terapia na cicatrização cutânea. O objetivo desse estudo foi quantificar e comparar a concentração dos fatores TGF-β1 e PDGF-BB no PRP, plasma sanguíneo e pele, durante diferentes fases do processo de cicatrização da pele tratada ou não com PRP. Foram utilizados sete equinos machos castrados, mestiços, hígidos, com idade entre 16 e 17 (16,14±0,63) anos. Três lesões em formato quadrangular (6,25cm²) foram produzidas cirurgicamente nas regiões glúteas direita e esquerda de todos os animais. Doze horas após indução das feridas, 0,5mL do PRP foi administrado em cada uma das quatro extremidades das feridas de uma das regiões glúteas (Grupo tratado = GT), escolhida aleatoriamente. A região contralateral foi utilizada como controle (GC). As feridas foram submetidas à limpeza diária com água Milli Q, e amostras foram obtidas mediante biópsias realizadas com Punch de 6mm. Foram obtidas seis biópsias de pele, sendo a primeira realizada logo após a produção da ferida (T0), e as demais com 1 (T1) 2 (T2) 7 (T3) e 14 (T4) dias após a indução da lesão. A sexta biópsia (T5) foi obtida após completo fechamento da pele, que ocorreu aproximadamente aos 37 dias (36,85±7,45, GC; 38,85±6,46, GT). Também foram obtidas amostras de sangue com EDTA em todos os tempos mencionados. A quantificação dos fatores de crescimento TGF-β1 e PDGF-BB na pele, PRP e plasma sanguíneo foi realizada pela técnica ELISA. Os dados foram analisados estatisticamente pelo teste t, correlação de Pearson e regressão, utilizando nível de significância de 5%. Não houve diferença entre os grupos, nos valores dos dois fatores de crescimento mensurados na pele, nos diferentes tempos. Também não houve correlação entre a quantidade dos fatores de crescimento presentes na pele e no plasma. Por outro lado, correlação positiva foi observada entre PRP e pele no grupo tratado, para os fatores de crescimento TGF-β1 (r=0,31) e PDGF-BB (r=0,38), bem como entre ambos os fatores de crescimento presentes no PRP (r=0,81). Considerando as concentrações dos fatores de crescimento no T0, os maiores valores cutâneos (p<0,05) do TGF-β1, em ambos os grupos, ocorreram nos tempos T3 e T5. Valores mais elevados (p<0,05) do PDGF-BB ocorreram no T4 (GT) e T5 (GC). No plasma não houve alteração nas concentrações desses fatores em relação ao T0, o que sugere que o PRP não acarreta efeito sistêmico, quando os procedimentos adotados na presente pesquisa são utilizados. A administração local de PRP no volume estudado, 12 h após indução cirúrgica de ferida cutânea na região glútea de equinos não ocasiona maiores concentrações dos fatores de crescimento TGF-β1 e PDGF-BB no plasma sanguíneo e pele, durante o processo de cicatrização.

In vitro effects of three formulations of hydroxyethyl starch solutions on coagulation and platelet function in horses

OBJECTIVE

To investigate the in vitro effects of 3 hydroxyethyl starch (HES) solutions on viscoelastic coagulation testing and platelet function in horses.

SAMPLE

Blood samples collected from 7 healthy adult horses.

PROCEDURES

Blood samples were diluted with various crystalloid and HES solutions to approximate the dilution of blood in vivo that occurs with administration of a 10 and 20 mL/kg fluid bolus to a horse (1:8 and 1:4 dilutions, respectively). Diluted samples were analyzed through optical platelet aggregometry, platelet function analysis, thromboelastography, and dynamic viscoelastic coagulometry. Colloid osmotic pressure and concentrations of von Willebrand factor and factor VIII:C were also determined for each sample.

RESULTS

For all HES products, at both dilutions, the colloid osmotic pressure was significantly higher than that in the respective carrier solutions. At the 1:4 dilution, nearly all HES solutions resulted in significant alterations in platelet function as measured via the platelet function analyzer and dynamic viscoelastic coagulometer. Significant decreases in platelet aggregation and factor concentrations were also evident. Fewer HES-associated changes were identified at the 1:8 dilutions.

CONCLUSIONS AND CLINICAL RELEVANCE

Dilution of blood samples with all HES solutions resulted in changes in viscoelastic coagulation and platelet function that did not appear to be attributable to dilution alone. In vivo evaluations are necessary to understand the clinical impact of these in vitro changes.

Application of Platelet-Rich Plasma to Disorders of the Knee Joint

IMPORTANCE

The promising therapeutic potential and regenerative properties of platelet-rich plasma (PRP) have rapidly led to its widespread clinical use in musculoskeletal injury and disease. Although the basic scientific rationale surrounding PRP products is compelling, the clinical application has outpaced the research.

OBJECTIVE

The purpose of this article is to examine the current concepts around the basic science of PRP application, different preparation systems, and clinical application of PRP in disorders in the knee.

EVIDENCE ACQUISITION

A systematic search of PubMed for studies that evaluated the basic science, preparation and clinical application of platelet concentrates was performed. The search used terms, including platelet-rich plasma or PRP preparation, activation, use in the knee, cartilage, ligament, and meniscus. Studies found in the initial search and related studies were reviewed.

RESULTS

A comprehensive review of the literature supports the potential use of PRP both nonoperatively and intraoperatively, but highlights the absence of large clinical studies and the lack of standardization between method, product, and clinical efficacy. Conclusions and Relevance. In addition to the call for more randomized, controlled clinical studies to assess the clinical effect of PRP, at this point, it is necessary to investigate PRP product composition and eventually have the ability to tailor the therapeutic product for specific indications.

Effects of bilayer gelatin/β-tricalcium phosphate sponges loaded with mesenchymal stem cells, chondrocytes, bone morphogenetic protein-2, and platelet rich plasma on osteochondral defects of the talus in horses

Osteochondrosis (OC) is a common and clinically important joint disorder in horses. However, repair of the OC region is difficult because of the avascular nature of cartilage. This study aimed to evaluate the efficacy of bilayer gelatin/β-tricalcium phosphate (GT) sponges loaded with mesenchymal stem cells (MSCs), chondrocytes, bone morphogenetic protein-2 (BMP-2), and platelet rich plasma (PRP) for the repair of osteochondral defects of the talus in horses. Full-thickness osteochondral defects were created on both the lateral trochlear ridges of the talus (n = 6). In the test group, a basic GT sponge loaded with MSCs and BMP-2 (MSC/BMP2/GT) was inserted into the lower part of the defect, and an acidic GT sponge loaded with chondrocyte, MSCs, and PRP (Ch/MSC/PRP/GT) was inserted into the upper part of the defect. In the control group, the defect was treated only with bilayer GT sponges. Repair of osteochondral defects was assessed by radiography, quantitative computed tomography (QCT), and macroscopic and histological evaluation. The test group showed significantly higher radiographic, QCT, macroscopic, and histological scores than the control group. This study demonstrated that the bilayer scaffolds consisting of Ch/MSC/PRP/GT for the chondrogenic layer and MSC/BMP2/GT for the osteogenic layer promoted osteochondral regeneration in an equine model. The bilayer scaffolds described here may be useful for treating horses with OC.

Effects of the breed, sex and age on cellular content and growth factor release from equine pure-platelet rich plasma and pure-platelet rich gel

Background

There is no information on the effects of the breed, gender and age on the cellular content and growth factor (GF) release from equine pure-platelet rich plasma (P-PRP) and pure-platelet rich gel (P-PRG). The objectives of this study were: 1) to compare the cellular composition of P-PRP with whole blood and platelet poor plasma (PPP); 2) to compare the concentration of transforming GF beta 1 (TGF-β₁) and platelet derived GF isoform BB (PDGF-BB) between P-PRP treated with non-ionic detergent (P-PRP+NID), P-PRG (activated with calcium gluconate -CG-), PPP+NID, PPP gel (PPG), and plasma and; 3) to evaluate and to correlate the effect of the breed, gender and age on the cellular and GF concentration for each blood component. Forty adult horses, 20 Argentinean Creole Horses (ACH) and, 20 Colombian Creole Horses (CCH) were included. Data were analyzed by parametric (i.e.: t-test, one way ANOVA) and non parametric (Kruskal-Wallis test, Wilcoxon test) tests. Correlation analysis was also performed by using the Spearman and Pearson tests. A p ≤ 0.05 was set as significant for all tests. All the blood components were compared for platelet (PLT), leukocyte (WBC), TGF-β₁ and PDGF-BB concentrations. The effect of the breed, gender and age on these variables was analyzed. A P ≤ 0.05 was accepted as significant for all the tests.

Results

PLT counts were 1.8 and 0.6 times higher in P-PRP than in whole blood and PPP, respectively; WBC counts were 0.5 and 0.1 times lower in P-PRP, in comparison with whole blood and PPP, respectively. TGF-β₁ and PDGF-BB concentrations were 2.3 and 262 times higher, respectively, in P-PRG than in plasma, and 0.59 and 0.48 times higher, respectively, in P-PRG than in PPG. P-PRG derived from CCH females or young horses presented significantly (P < 0.001) higher PDGF-BB concentrations than P-PRG derived from ACH males or older horses.

Conclusions

Our results indicated that P-PRP obtained by a manual method was affected by intrinsic factors such as the breed, gender and age. Equine practitioners should be aware that cellular and GF release from P-PRP/P-PRG could change according with the intrinsic variables associated with a patient in particular.

Effects of Platelet-Rich Plasma Composition on Anabolic and Catabolic Activities in Equine Cartilage and Meniscal Explants

OBJECTIVE

To evaluate the effects of single- and double-spin preparations of platelet-rich plasma (PRP) on anabolic and catabolic activities of cartilage and meniscal explants in vitro.

METHODS

Single- and double-spin PRP was prepared using laboratory processing or commercial kits. The cellular contents were quantified, and each PRP was mixed in equal quantities with cell culture medium and added to cartilage or meniscus explant cultures, with or without interleukin 1 β (IL-1β). Extracellular matrix synthesis was quantified over 24 hours via (35)S-sulfate and (3)H-proline incorporation, while gene expression of catabolic enzymes was evaluated using real-time PCR.

RESULTS

The platelet concentration in single-spin laboratory PRP was 59% higher than blood. Platelet and white blood cell concentrations in single-spin laboratory and kit PRP were not significantly different, while the double-spin kit resulted in approximately 2.5-fold higher platelet and approximately 400-fold higher white blood cell concentrations. In cartilage cultures without IL-1β, radiolabel incorporation in single-spin PRP cultures was significantly higher than in double-spin cultures. Similar results were obtained for (35)S-sulfate incorporation in meniscus cultures without IL-1β. In IL-1β, radiolabel incorporation was largely similar among all PRPs. After 24 hours of culture, ADAMTS-4 gene expression in cartilage was lowest for single-spin PRP, while expression in the double-spin kit was not significantly different from double-spin laboratory PRP in which platelets were concentrated 6-fold.

CONCLUSIONS

This study suggests that single-spin PRP preparations may be the most advantageous for intra-articular applications and that double-spin systems should be considered with caution.