Changes on the Structural Architecture and Growth Factor Release, and Degradation in Equine Platelet-Rich Fibrin Clots Cultured Over Time

Biostimulation effect of platelet-rich fibrin augmented with decellularized bovine pericardium on full-thickness cutaneous wound healing in Donkeys (Equus asinus)

AIM

The current research aimed to evaluate the potential effect of adding platelet-rich fibrin (PRF) to the decellularized bovine pericardium (DBP) on the distal limb of donkeys' full-thickness cutaneous wounds healing (Equus asinus).

MATERIALS AND METHODS

Healthy male donkeys (n = 12) were used in this study. Under general anesthesia, 6 cm2 full-thickness incisions were made on the middle dorsolateral surface of both forelimbs' metacarpi. The left forelimbs were control wounds, while the right wounds were treated with PRF/DBP. Control wounds were bandaged with a standard dressing after saline irrigation and were evaluated at days 4, 7, 10, 13, 16, 19, 22, 25, and 28 post-wounding. PRF/DBP-treated wounds were dressed with a combination of PRF/DBP at the first, second, and third weeks post-wounding. Clinical and histopathological examinations of the wounds were performed to assess the healing process. Additionally, the immunohistochemical evaluation and gene expression profiles of myofibroblastic and angiogenic genes (transforming growth factor-β1, vascular endothelial growth factor-A, fibroblast growth factor 7 (FGF-7), and collagen type 3α1) were analyzed.

RESULTS

PRF/DBP wounds had a significantly faster healing process (61.3 ± 2.6 days) than control wounds (90.3 ± 1.4 days) (p < 0.05). The immunohistochemical examination and gene expression profile revealed significant enrichment in PRF/DBP wounds compared to control wounds.

CONCLUSION

PRF/DBP dressing can be considered a natural and cost-effective biomaterial for enhancing the recovery of donkeys' distal limb injuries.

Bacterial exclusion and wound healing potential of horizontal platelet-rich fibrin (H-PRF) membranes when compared to 2 commercially available collagen membranes

OBJECTIVES

The aim of the present study was to compare the barrier function during bacterial invasion and wound healing properties of 3 commonly used membranes including horizontal platelet-rich fibrin (H-PRF) against two commercially available resorbable collagen membranes.

MATERIALS AND METHODS

H-PRF membranes were prepared by collecting venous blood from 3 healthy volunteers using a 700 g for 8-min centrifugation protocol followed by compression into membranes. To evaluate their barrier function, 3 groups (H-PRF membrane, collagen membrane A (Bio-Gide, Geistlich), collagen membrane B (Megreen, Shanxi Ruisheng Biotechnology Co) were placed between an inner chamber and outer chamber and inoculated with S. aureus. At 2 h, 24 h, and 48 h post-inoculation, cultures from the inner and outer chambers were assessed for bacterial CFUs. Then, scanning electron microscope (SEM) was utilized to visualized the morphological destruction by bacteria of the inner and outer surfaces of the membranes. To assess the wound healing properties of each membrane, leachates from each group were applied to human gingival fibroblasts (HGF) and a scratch assay was performed at 24 h and 48 h.

RESULTS

S. aureus showed a minimal bacterial attachment or invasion rate through either collagen membranes at 2 h post-inoculation, yet over time demonstrated rapid degradation, especially on the rougher surface. While PRF demonstrated higher number of CFUs after 2 h, no significant penetration/degradation of the H-PRF membranes was observed at 24 h and 48 h in the H-PRF group. Both collagen membranes demonstrated significant morphological changes 48 h post-bacterial innoculation, while minimal obvious morphological changes were observed in the H-PRF group. The wound healing assay also demonstrated significantly better wound closure rates in the H-PRF group.

CONCLUSION

H-PRF membranes exhibited better barrier function towards S. aureus over 2 days of innoculation and better wound healing ability when compared to two commercially available collagen membranes.

CLINICAL RELEVANCE

This study provides further evidence for the application of H-PRF membranes during guided bone regeneration by minimizing bacterial invasion. Furthermore, H-PRF membranes have significantly better ability to promote wound healing.

Temporal Release and Denature of Several Mediators in Pure Platelet-Rich Plasma and Temperature-Induced Platelet Lysates Derived from a Similar Bovine Platelet Concentrate

There is scarce information about bovine platelet-rich plasma/platelet-rich gel (PRP/PRG) and related hemocomponents (HCs), such as platelet lysates (PLs), including growth factor (GF) and cytokine concentrations, and how the stability of these biomolecules could be affected by time and temperature. This study aimed to evaluate the release and stability of transforming growth factor beta 1 (TGF-β₁), interleukin 4 (IL-4), and tumor necrosis factor alpha (TNF-α) contained in bovine pure PRP (P-PRP) and temperature-induced PL (TIPL) coming from a similar platelet concentrate (PC) at 4 and 37°C at 3 and 96 h. Platelet concentrates (PCs) presented a 1.7-fold concentration of platelets (PLTs) with negligible counts of white blood cells (WBCs) when compared to the counts for these cells in whole blood. TGF-β₁ concentrations were significantly lowest in plasma followed by TIPL, chemical-induced PL (CIPL), and P-PRP. IL-4 and TNF-α concentrations did not differ between HCs. TGF-β₁ concentrations were negatively affected in P-PRPs stored at 4°C at 3 and 96 h, whereas those from P-PRP maintained at 37°C presented similar concentrations to TIPL stored at both temperatures over time. IL-4 and TNF-α concentrations were not affected by time or temperature in any of the HCs evaluated. Pure PRGs released additional quantities of GF and cytokines over time when compared with HCs stored over 96 h at 4 and 37°C. The method, either chemical or physical, used for platelet activation or damage produces a different GF and cytokine release pattern, which makes to each evaluated HCs different despite they come from a similar bovine PC. P-PRP activated with calcium gluconate and maintained at 37°C, which polymerizes in P-PRG, showed the best GF and cytokine release/denature profile compared with the rest of the HCs evaluated.

Production Protocol Standardisation, Macroscopic and Histological Evaluation, and Growth Factor Quantification of Canine Leukocyte-and Platelet-Rich Fibrin Membranes

Leukocyte-Platelet-Rich Fibrin (L-PRF) is a second generation of platelet concentrates; it was widely used, as an autologous platelet-based wound sealant and hemostatic agent in surgical wound healing. L-PRF clot or membrane is a solid fibrin-based biomaterial, with a specific 3D distribution of the leukocytes and platelet aggregates. This biological scaffold releases growth factors (i.e., TGF- β1, PDGF-AB, VEGF) and matrix proteins (fibronectin, vitronectin and thrombospondin-1) during the healing process after the application. To the Authors' knowledge both in human and veterinary medicine a single standardised protocol was not reported. This prospective study aimed to apply Crisci's L-PRF protocol (which is characterised by 30” of acceleration, 2' at 2,700 rpm, 4' at 2,400 rpm, 3' at 3,000 rpm, and 36” of deceleration and arrest) sin canine species, evaluate macroscopically and histologically the L-PRF membranes obtained by using Wound Box to standardise the L-PRF protocol in dogs and to evaluate the clinical feasibility of using L-PRF membranes by quantitative in vitro analysis of growth factors over 7 days. One hundred twenty-eight dogs in good general condition with no history of recent NSAIDs intake (15 days of washout) and/or any medication or disease related to coagulation process met inclusion criteria and therefore were enrolled. We obtained 172 membrane L-PRF membranes by 86 dogs: half of them underwent macroscopic and histological analysis, the other 86 underwent ELISA analysis. The Wound Box gave a membrane of mean (±SD) length (cm), width (cm) and weight (g) of 1.97 (±0.89), 0.95 (±0.36), 0.46 (±0.20) respectively. Histology analysis confirmed a well-defined histoarchitecture with five layers reproducing density and distribution of blood cells in this biomaterial. Finally, the ELISA assay performed with 22 L-PRF membranes showed a peak in growth factors at 6 h after membrane production, followed by a decrease in release at 24 and 72 h and a second peak in release at 168 h after production. Statistical analysis of demographic variables (age, sex, and body condition score BCS) and the average of growth factors determined by the ELISA assay did not reveal statistical significance, except for the BCS factor compared with the production of VEGF. Our data confirm the effectiveness of this protocol and of Wound Box to produce L-PRF membranes in dogs.

Standardized Platelet-Rich Fibrin (PRF) from canine and feline origin: An analysis on its secretome pattern and architectural structure

Platelet-rich fibrin (PRF) has been incorporated in surgical procedures to promote tissue and bone healing, particularly in human medicine. The rationale for the use of platelet-based products stems from the fact that platelets, after being activated, release growth factors (GFs) and other active molecules such as cytokines, that modulate inflammation and tissue repair. Although PRF has been advanced as a therapeutic treatment for veterinary use, namely in canine and feline patients (following human medicine developments), to our knowledge a full characterization of PRF therapeutic effectors has never been performed. Herein, we studied the biological properties and release profile of GFs and other cytokines throughout ten days in in vitro culture conditions, in order to investigate the potential therapeutic ability of PRF for canine and feline practice. A protocol for obtaining PRF from whole blood without anti-coagulant from both species was optimized, originating large and homogenous PRF clots. Then, PRF clots obtained from four dogs and four cats were incubated in culture medium to assess the temporal release of platelet-derived growth factor-BB (PDGF-BB), vascular endothelial factor-A (VEGF-A), transforming growth factor β-1 (TGF-β1), and interleukin-8 (IL-8). Furthermore, morphological characterization of PRF clots, fresh and after 10 days of incubation, was performed by histology and high-resolution field emission electron scanning microscopy. In standard culture conditions, PRF clots from both species released PDGF-BB, TGF- β1 and VEGF-A, in a sustained manner, up to day 10. Moreover, PRF presents an initial burst release of IL-8, a mediator of inflammatory response which plays a key role in neutrophil recruitment and degranulation. Overall, our findings show that PRF clots may be an efficient therapeutic strategy in canine and feline clinical practice, accelerating the local healing mechanism, through the sustained delivery of signalling molecules involved in the healing cascade.

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.

The distribution pattern and growth factor level in platelet-rich fibrin incorporated skin-derived mesenchymal stem cells: An in vitro study

Background and Aim:

A skin wound in an animal must be cared for to prevent further health issues. Platelet-rich fibrin (PRF) and skin-derived mesenchymal stem cells (SMSCs) have been reported to have potential in increasing the rate of wound healing. This study aimed to analyze the distribution patterns and levels of platelet-derived growth factor (PDGF), insulin-like growth factor (IGF), vascular endothelial growth factor (VEGF), and transforming growth factor-β (TGF-β) in PRF incorporated with SMSCs.

Materials and Methods:

This study employed a true experiment (in vitro) design with post-test only performed in the control group alone. PRF and SMSCs were extracted from the blood and skin of 16 rabbits. SMSCs were characterized using immunocytochemistry to examine clusters of differentiation for 45, 73, 90, and 105. PRF was incorporated into the SMSCs and then divided into four groups (N=32/n=8): Group A (PRF only), Group B (PRF+SMSCs, incubated for 1 day), Group C (PRF+SMSCs, incubated for 3 days), and Group D (PRF+SMSCs, incubated for 5 days). Scanning electron microscopy was used to examine the distribution pattern of SMSCs between groups. The supernatant serum (Group A) and supernatant medium culture (Group D) were collected for the measurement of PDGF, IGF, VEGF, and TGF-β using an enzyme-linked immunosorbent assay sandwich kit. An unpaired t-test was conducted to analyze the differences between Groups A and D (p<0.01).

Results:

Group D had the most morphologically visible SMSCs attached to the PRF, with elongated and pseudopodia cells. There was a significant difference between the levels of growth factor in Groups A and D (p=0.0001; p<0.01).

Conclusion:

SMSCs were able to adhere to and distribute evenly on the surface of PRF after 5 days of incubation. The PRF incorporated SMSCs contained high levels of PDGF, IGF, VEGF, and TGF- β, which may prove to have potential in enhancing wound healing.