Rheological Properties and Growth Factors Content of Platelet-Rich Plasma: Relevance in Veterinary Biomedical Treatments

Exploring the Functional Properties of Hydrolyzed Keratin: Filling the Knowledge Gap on Surface Active, Emulsifying, and Thickening Properties

Hydrolyzed keratin (HK) refers to any hydrolysate of keratin of a different origin derived by acid, alkali, enzymatic, or other methods of hydrolysis. HK is water soluble and has distinct chemical-physical properties compared to fibrous keratin. Although HK is employed across various technological sectors, there is a notable gap in the literature regarding the detailed chemical-physical properties of commercially available HKs. This study aims to address this gap by providing a thorough analysis of the surface-active, emulsifying, and thickening properties of three commercially available HKs. The results reveal relevant differences among HKs marketed under the International Nomenclature Cosmetic Ingredient (INCI) name "Hydrolyzed Keratin," with variations in their chemical-physical properties, primarily influenced by molecular weight. Specifically, HKs with a higher average M w (>3000 Da) and protein content demonstrate enhanced emulsifying and thickening capabilities. Conversely, HKs with low M w (<1000 Da) do not show surface-active properties suitable for the preparation of emulsions. Therefore, this study underscores the need for the standardization of commercially available HK products to obtain biomaterials with tailored and specific chemical-physical properties, enhancing their potential applications in cosmetic and pharmaceutical topical formulations.

Antibacterial Effect of Canine Leucocyte Platelet-Rich Plasma (L-PRP) and Canine Platelet-Poor Plasma (PPP) Against Methicillin-Sensitive and Methicillin-Resistant Staphylococcus pseudintermedius

Staphylococcus pseudintermedius (SP) is a commensal and opportunistic pathogen of skin and mucosal surfaces, isolated from healthy dogs and from canine pyoderma cases. It has recently gained attention due to its increasing antibiotic resistance. Platelet-rich plasma (PRP) is a biological product, obtained through a blood centrifugation process, which has antibacterial properties evidenced by in vitro and in vivo studies conducted in both the human and veterinary field. This in vitro study evaluated the antimicrobial effect of canine non-activated and activated leucocyte-rich PRP (L-PRP) and platelet-poor plasma (PPP) against two strains of SP isolated from dogs with pyoderma: one a multidrug-resistant strain (MDR) and one a non-MDR strain. Twenty healthy un-sedated adult blood donor dogs were enrolled for L-PRP and PPP production via a closed semi-automatic system for veterinary use. The evaluation of antimicrobial effect was performed using the micro-inhibition in broth method, exposing SP strains to 10 L-PRP, 10 activated L-PRP and 10 PPP samples, respectively. Bacterial growth was evaluated using CFU count at three timepoints (immediately after incubation T0, after 1 h T1 and after 2 h T2). L-PRP and PPP had a significant antimicrobial effect at all three timepoints which was similar against both non-MDR and MDR SP strains. Activation appeared to reduce the duration of the antimicrobial effect in L-PRP. More studies are necessary to confirm these preliminary results.

Impact of arthroscopy on post-procedure intra-articular elbow injections: A cadaveric study

OBJECTIVE

To determine the influence of arthroscopy and injection volume on post-procedure intra-articular (IA) injection extravasation.

STUDY DESIGN

Ex vivo prospective study.

SAMPLE POPULATION

A total of 40 paired canine cadaver forelimbs.

METHODS

After radiographs and computed tomography (CT) scans with three-dimensional (3D) digital bone model reconstructions, elbows were randomly assigned to the arthroscopy or control group and randomly assigned to receive an IA injection of 2 or 4 mL of contrast. Elbow arthroscopy was performed on assigned specimens, followed by IA injections of contrast in all elbows, and imaging was repeated. 3D digital model volumes were compared. Images were interpreted and scored for extravasation by a radiologist unaware of treatment and volume assignments.

RESULTS

Based on CT images and regardless of treatment group, IA injections of 4 mL resulted in a mean extravasation score of 2.25 (SD 0.97) versus 1.55 (SD 1.05) (p = .02) for 2 mL IA injections. The change in 3D model volumes after IA injections was a mean of 13.2 cm3 (SD 5.85) after 4 mL injections, compared to 6.97 cm3 (SD 6.28) (p = .003) after 2 mL injections. On radiographic evaluation, but not CT, the mean extravasation scores were 2.45 (SD 1.15) for the arthroscopy group and 1.25 (SD 0.79) for the control group (p < .001).

CONCLUSION

A larger volume of IA injection resulted in higher CT extravasation scores and larger 3D volumes regardless of arthroscopic treatment.

CLINICAL SIGNIFICANCE

IA injections performed immediately after arthroscopy resulted in 50% or less extravasation, especially with a smaller IA injection volume.

Dilutional rheology of Radiesse: Implications for regeneration and vascular safety

BACKGROUND

Calcium hydroxylapatite-carboxymethylcellulose (CaHA-CMC) injectables have emerged as dual-purpose fillers with bioregenerative and direct filling capabilities.

AIMS

This study investigates the rheological properties of CaHA-CMC and its CMC carrier gel at various dilutions.

METHODS

The storage modulus (G'), loss modulus (G″), complex viscosity (η*), loss factor (tan δ), cohesivity, and extrusion force were evaluated for a range of CaHA-CMC aqueous dilutions with an oscillatory rheometer, drop weight testing, and force analysis, respectively.

RESULTS

Results revealed a significant decrease in G', η*, and increase in tan(δ) with increasing dilution, indicating a decline in the product's direct filling capabilities. Cohesivity decreased dramatically with dilution, potentially enhancing tissue biointegration and the product's biostimulatory effects. The CMC gel carrier displayed inelastic and non-resilient properties, with rheological changes differing from CaHA-CMC. Dilutional rheology was also correlated with previously published dilution-dependent biostimulatory data where hyperdiluted CaHA-CMC (>1:2) demonstrated a regenerative profile and diluted or hypodiluted mixtures retained meaningful filling properties and increased regeneration.

CONCLUSIONS

These findings offer a continuum for tailoring the product's rheological profile to match specific tissue requirements. Customizable rheology allows CaHA-CMC to be tuned for either filling and contouring or optimal regenerative effects. Importantly, safety implications related to vascular occlusion suggest that dilutional rheomodulation decreases the risk of vascular events. In conclusion, this study highlights the significant impact of aqueous dilution on the rheological properties of CaHA-CMC and its carrier gel. The findings support the clinical application of tailored dilutions to achieve desired outcomes, providing versatility and safety for aesthetic applications.

In vitro antibacterial efficacy of autologous conditioned plasma and amniotic membrane eye drops

OBJECTIVE

To determine the in vitro antibacterial efficacy of equine and canine autologous conditioned plasma (ACP) and amniotic membrane extract eye drops (AMEED) against aerobic bacteria common to the corneal surface.

PROCEDURES

Canine (n = 4) and equine (n = 4) anticoagulated whole blood samples were sterilely collected, pooled for each species, and processed using the Arthrex ACP® Double-Syringe System. Platelet counts were performed on ACP and pooled blood. AMEED were obtained from a commercial source. An electronic medical records search (2013-2022) identified aerobic bacteria cultured from canine and equine corneal ulcers at Mississippi State University College of Veterinary Medicine (MSU-CVM). Ten commonly isolated bacteria for each species were collected from cultures submitted to the MSU-CVM Microbiology Diagnostic Service and frozen at -80°C. The Kirby-Bauer disk diffusion method was used to determine the sensitivities of these isolates to ACP and AMEED. Bacterial isolates were plated onto Mueller-Hinton +5% sheep blood agar and blank sterile discs saturated with 20 μL of ACP or AMEED were tested in duplicate. Imipenem discs served as positive controls and blank discs as negative controls. Zones of inhibition were measured at 18 h.

RESULTS

ACP platelet counts were 1.06 and 1.65 times higher than blood for equine and canine samples, respectively. Growth of a multi-drug resistant Enterococcus faecalis was partially inhibited by canine and equine ACP. AMEED did not inhibit growth of any examined bacteria.

CONCLUSIONS

Canine and equine ACP partially inhibited E. faecalis growth in vitro. Further studies using varying concentrations of ACP against bacterial isolates from corneal ulcers are warranted.

Use of platelet lysate for in-vitro embryo production and treatment of repeat breeding in cows

Platelet-rich plasma (PRP) is a biological hemocomponent derived from blood after the complete removal of red blood cells and the partial or complete removal of white blood cells to concentrate platelets in an appropriate volume of plasma. Platelets have important growth factors, cytokines, and active metabolites that improve the endometrial environment and positively affect implantation. This study evaluated the effect of the addition of activated PRP (platelets lysate; PL) on in vitro bovine oocyte maturation and embryonic development and the effect of intrauterine (IU) infusion of autologous PL in repeat breeder (RB) cows. Experiment 1 examined the effects of allogeneic PL, fetal calf serum (FCS), mixed PL + FCS, or platelet-poor plasma (PPP) supplementations to in vitro maturation and development media on in vitro oocyte maturation and embryo development in good- and poor-quality oocytes of Japanese Black cows. Experiment 2 examined the IU infusion of autologous PL, 24 h post-insemination, in 21 RB Holstein-Friesian dairy cows. The cleavage rate of good-quality oocytes was higher in the PL group (85.93 ± 2.50%) than in the PPP group (67.16 ± 3.41%) (P < 0.05), while the cleavage rate of the poor-quality oocytes was higher in the PL alone (76.13 ± 4.04%) and mixed PL + FCS treated (73.59 ± 4.22%) groups than in the PPP group (54.64 ± 2.93%) (P < 0.05). The blastocyst rate of the good-quality oocytes was higher in the PL group (40.97 ± 3.03%) than in the FCS (27.97 ± 3.31%) and PPP (25.33 ± 2.15%) groups (P < 0.05). The blastocyst rate of poor-quality oocytes and the hatching rates of both good and poor-quality oocytes showed no significant differences among all groups. The conception rate in the autologous PL-treated group was 41.67% (5/12), while it was 11.11% (1/9) in the control group. The platelets' count in the pregnant PL-treated cows (n = 5; mean ± SEM, 1.07 ± 0.10 × 109/mL) was higher than in the non-pregnant ones (n = 7; 0.67 ± 0.10 × 109/mL) (P < 0.05). In conclusion, allogeneic PL was effective in stimulating the in vitro oocyte maturation and embryonic development in both good and poor-quality bovine oocytes, and post-insemination IU infusion of autologous PL derived from high platelets' count-PRP would be recommended for the treatment of RB cows.

Optimization of a Two-Step Centrifugation Protocol for Bovine Platelet-Rich Plasma

Platelet-rich plasma ( PRP), an autologous platelet concentrated in plasma, is a source of diverse growth factors and is extensively utilized to promote tissue healing. Most of the clinical and laboratory investigations in veterinary medicine have focused on horses and dogs. Consequently, the types and detailed conditions of the PRP preparation method are based on those species. However, in bovine medicine, only a few studies have investigated the species-specific characteristics of bovine platelets. The aim of this study was to optimize the conditions of a two-step centrifugation method for bovine PRP. Whole blood samples were obtained from eight healthy lactating Holstein-Friesian cows. Eight running conditions for the first and second centrifugations each were evaluated based on the platelet recovery rate, the concentration of growth factors, and the adenosine diphosphate (ADP)-induced aggregation response, which reflects the premature platelet activation caused by the centrifugation process. The results of this study showed that for the first and second centrifugations, 900×g for 10 minutes and 1250×g for 15 minutes, respectively, were the most suitable conditions for the platelet recovery rate, and the concentration of growth factors was highest under these conditions without significant activation of premature platelet aggregation. Thus, we established an optimal two-step centrifugation protocol for bovine PRP that should provide a better understanding of bovine platelets.

Emerging Delivery Strategies of Platelet-Rich Plasma with Hydrogels for Wound Healing

Platelet-rich plasma (PRP), a platelet-rich plasma concentrate obtained from whole blood, has been widely used to treat wounds due to its high contents of growth factors that can not only play a role in the hemostasis, repair, and anti-infection of wounds but also promote cell proliferation, maturation, and angiogenesis. However, after PRP activation, its clinical effect was limited because of burst and uncontrolled release of growth factors and poor mechanical properties of PRP gels. In recent years, increasing attention has been moved to the loading and sustained release of growth factors in PRP by polymeric carriers. Hydrogels, as an interesting carrier, enable controlled delivery of growth factors by structural designs. Moreover, using hydrogels to encapsulate PRP is favorable to controlling the mechanical properties and water maintenance of PRP gels, which can provide a stable and moist wound repair environment to promote coordinated operations of skin tissue cells and cytokines as well as wound healing. In this review, the state of the art of hydrogels that have been used to load PRP for wound treatments is introduced, and further prospects in the research area are proposed.

Therapeutic Effect of Platelet-Rich Plasma Improves Bladder Overactivity in the Pathogenesis of Ketamine-Induced Ulcerative Cystitis in a Rat Model

The present study attempted to elucidate whether intravesical instillation of platelet-rich plasma (PRP) could decrease bladder inflammation and ameliorate bladder hyperactivity in ketamine ulcerative cystitis (KIC) rat model. Female Sprague Dawley (S-D) rats were randomly divided into control group, ketamine-treated group, ketamine with PRP treated group, and ketamine with platelet-poor plasma (PPP) treated group. Cystometry and micturition frequency/volume studies were performed to investigate bladder function. The morphological change of bladder was investigated by Mason’s trichrome staining. Western blotting analysis were carried out to examine the protein expressions of inflammation, urothelial differentiation, proliferation, urothelial barrier function, angiogenesis and neurogenesis related proteins. The results revealed that treatment with ketamine significantly deteriorated bladder capacity, decreased voiding function and enhanced bladder overactivity. These pathological damage and interstitial fibrosis may via NF-κB/COX-2 signaling pathways and muscarinic receptor overexpression. PRP treatment decreased inflammatory fibrotic biosynthesis, attenuated oxidative stress, promoted urothelial cell regeneration, and enhanced angiogenesis and neurogenesis, thereafter recovered bladder dysfunction and ameliorate the bladder hyperactivity in KIC rat model. These findings suggested that the PRP therapy may offer new treatment options for those clinical KIC patients.

Antibacterial Properties of Canine Platelet-Rich Plasma and Other Non-Transfusional Hemo-Components: An in vitro Study

This in vitro study was carried out to evaluate the potential antibacterial properties of canine non-transfusional hemo-components. Therapeutic formulations commonly used for regenerative medicine purposes (platelet-rich plasma, platelet gel, platelet lysate, fibrin glue), considering both leukocyte-rich and leukocyte-poor formulations, but also platelet-poor plasma and activating substances (thrombin, calcium gluconate), were tested to detect elements with potential antimicrobial properties. The antibacterial effect was tested on different bacterial strains (Staphylococcus aureus subspecies aureus, Staphylococcus cohnii subspecies cohnii, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae subspecies pneumoniae) isolated from canine wounds and classified as susceptible, multidrug-, extensively, and pandrug-resistant bacteria toward a known panel of human and veterinary antibiotics. The evaluation was carried out by agar gel diffusion method (Kirby-Bauer) and micro-inhibition in broth using microplates and spectrophotometer reading. The study findings confirmed the hypothesized antibacterial properties of canine non-transfusional hemo-components. A more effective bacteriostatic effect was found against Gram-negative bacteria, drug-resistant too. The presence of leukocytes or platelets does not appear to be essential for the antibacterial effect. Further studies should be conducted to evaluate the exact mechanism of action of the antimicrobial activity. However, non-transfusional hemo-components could be a useful natural aid in controlling bacterial infections in dogs.

Therapeutic Potential of Platelet-Rich Plasma in Canine Medicine

Platelets are the reservoir of growth factors and play a major role in several physiological processes, such as coagulation, angiogenesis, immune response, and tissue repair. Platelet concentrates are broadly classified into two groups depending on their fibrin content, namely platelet-rich plasma (PRP) and platelet-rich fibrin (PRF). They are further divided based on their leucocyte contents. The PRP is plasma containing supra-physiological concentrations of the platelets. The growth factors present in the PRP play a crucial role in the promotion of local angiogenesis, regulation of cellular activity, stem cell homing, proliferation and differentiation of different stem cells, and deposition of matrix proteins contributing to tissue regeneration. This review aimed to establish the therapeutic potential of PRP in canine medicine with a particular focus on the applications in ophthalmology, dermatology, and musculoskeletal disorders. A systematic literature review was performed to identify the literature published during the past 20 years (2001-2021) using authentic academic databases, such as PubMed, Science Direct, Google Scholar, and Scopus. In the initial search, 556 articles were identified and based on the specific inclusion and exclusion criteria, 59 articles were selected for further analysis. The clinical efficacy of PRP depends on the number of platelets and the growth factor concentration. The PRP-based biological therapy has broad clinical applications in musculoskeletal pathologies. It is a simple, safe, and cost-effective method that can be used to treat various diseases and disorders in canine practice. For example, PRP is used for managing corneal ulcers, corneal erosion, alkali burn, keratoconjunctivitis sicca, burn wounds, chronic wounds, cutaneous ulcers, acute traumatic bone fractures, tendinopathies, cartilage pathologies, osteoarthritis, and abdominal wall defects either as monotherapy or as an adjunctive therapeutic agent. In addition, PRP is widely used as a carrier of mesenchymal stem cells for transplanting into bone defects. Therefore, allogeneic PRP therapy can be considered a simple, safe, and cost-effective method for the treatment of various diseases and disorders in canine practice. The therapeutic application of PRP in canine medicine is limited in the present study due to the lack of consensus for collection, characterization, and clinical use. Hence, further studies are required to establish the actual worth of PRP-based regenerative strategies in canine medicine.

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.