Quantitative assessment of the kinetics of growth factors release from platelet gel

Leukocyte-Rich and Platelet-Rich Fibrin for Skull Base Reconstruction After Endoscopic Endonasal Skull Base Surgery

BACKGROUND

Postoperative cerebrospinal fluid (CSF) leak is one of the most common complications after endoscopic endonasal approach to the skull base.

OBJECTIVE

To analyze the effect of leukocyte-rich and platelet-rich fibrin (L-PRF) as part of a standardized endonasal skull base repair protocol on postoperative infection and CSF leak rate.

METHODS

One hundred three patients who underwent an endoscopic endonasal approach and were reconstructed using a standard technique (Group A) were compared with 139 patients using the same protocol with the addition of L-PRF (Group B). Postoperative intracranial infection and CSF leak at 6 months were analyzed.

RESULTS

In patients with intraoperative CSF leak, postoperative leak occurred in 10.8% in Group A and 2.6% in Group B ( P .024), and in patients with intraoperative high-flow leaks, the incidences were 11.7% and 3.1%, respectively ( P .048). L-PRF reduced postoperative CSF leak by 76% in cases with intraoperative CSF leak (relative risk 0.24, 95% CI 0.06-0.87) and by 73% of patients with high-flow leak (relative risk 0.27, 95% CI 0.07-0.99). In patients undergoing surgery for diagnoses other than adenomas, there were no cases of postoperative leak in Group B, whereas in Group A occurred in 13.4% of those with intraoperative leaks ( P .047) and 15.8% with high-flow intraoperative leaks ( P .033). No significant differences were found in patients with pituitary adenoma. Meningitis occurred in 0.97% in Group A vs 2.16% in Group B ( P .639), without differences between subgroups.

CONCLUSION

L-PRF reduced the rate of postoperative CSF leaks in patients with intraoperative leaks, without differences on postoperative meningitis.

An Evaluation of the Effect of Activation Methods on the Release of Growth Factors from Platelet-Rich Plasma

BACKGROUND

Activation of platelets in platelet-rich plasma may improve growth factor release, thus enhancing regenerative properties. The authors investigated whether different methods of platelet-rich plasma activation affected growth factor release kinetics over time.

METHODS

Platelet-rich plasma from 20 healthy volunteers was processed by six different methods: (1) control (nonactivated); (2) activation with calcium chloride; (3) activation with calcium chloride and ethanol; (4) activation with calcium chloride and ethanol at 4°C; (5) activation with calcium chloride and ethanol with vitamin C; (6) activation with calcium chloride and ethanol with vitamin C at 4°C. Concentration of secreted vascular endothelial growth factor (VEGF), platelet-derived growth factor (PDGF), and insulin-like growth factor over 24 hours was measured by immunoassay.

RESULTS

Calcium chloride-activated platelet-rich plasma produced significantly more insulin-like growth factor at 1 hour compared to cold and vitamin C platelet-rich plasma, and calcium chloride plus ethanol produced significantly more at 24 hours compared to vitamin C platelet-rich plasma. The addition of vitamin C reduced release of PDGF over time. Activation with calcium chloride and ethanol with or without cold temperature produced a gradual PDGF release as opposed to calcium chloride alone, which caused higher PDGF within 4 hours. There were no significant differences between groups for VEGF, although calcium chloride and cooled platelet-rich plasma approached significance for producing more than vitamin C platelet-rich plasma.

CONCLUSIONS

Activation of platelet-rich plasma does not significantly improve growth factor secretion, which is made worse by the addition of vitamin C, a platelet inhibitor. Ethanol does not negatively impact growth factor production and may offer a more gradual release.

CLINICAL RELEVANCE STATEMENT

These findings will help guide platelet-rich plasma preparation methods where therapeutic growth factors are used.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

Autologous platelet rich plasma promotes the healing of non-ischemic diabetic foot ulcers. A randomized controlled trial

INTRODUCTION

DFU (diabetic foot ulcer) represents a major global health and socioeconomic problem and a leading cause of lower limb amputation. Although many therapies have been tested, none has been proposed as a dominant wound healing treatment. We performed a prospective randomized controlled study in order to assess the role of autologous platelet rich plasma (PRP) for the promotion of non-ischemic DFU healing.

MATERIALS AND METHODS

After full vascular assessment, a total of 80 patients were randomized in 1:1 ratio to receive either PRP injection in the healing edge and the floor of the targeted DFU (Group A), or have usual standard care with moist dressing with or without collagenase ointment (Group B). We calculated the total surface area (TSA) for the ulcer in both groups (cm²) before, after treatment and every week up to 12 weeks of follow-up.

RESULTS

A total of four patients (10%) experienced major amputation in group B, while no major amputation was performed in patients of Group A (p<0.001). A ≥ 50% reduction in TSA occurred earlier in Group A (at 2.5 weeks), compared to Group B (4.5 weeks); p<0.001. Complete wound healing rate was 95% (n=38) and it was achieved earlier (6^th week) for patients of group A, contrary to 77.8% (n=28) of patients (9^th week) for Group B (p<0.001). Superficial wound infection was noted in 10% (n=4) of the cases in the PRP arm, while in group B, 45% (n=18) of cases had a variable degree of infection ranging from superficial to deep wound infection and cellulites (p<0.001). PRP treatment was cost-effective, with 247.50$ vs. 437.50$ for the total cost of treatment for patients of Group B.

CONCLUSION

PRP is a cost-beneficial novel modality of treatment that can accelerate wound healing and decrease the rate of local infection in DFU, compared to other conventional treatment modalities.

Objective assessment of Platelet-Rich Plasma (PRP) potentiality in the treatment of Chronic leg Ulcer: RCT on 80 patients with Venous ulcer

BACKGROUND

Chronic venous leg ulcer reduces the patients' activities and their overall quality of life. Platelet-rich plasma (PRP) was previously investigated as promising less invasive management for leg ulcers.

THIS STUDY AIMS

To re-assess the efficacy and safety of PRP in the management of chronic leg ulcers due to venous factors.

PATIENTS/METHODS

RCT enrolled 80 patients who clinically presented with chronic venous leg ulcers. Forty patients were allocated randomly for the treatment with autologous platelet-rich plasma (PRP). Intradermal and subdermal injection of PRP by 27guage syringe weekly, in all edges and in the granular floor of the ulcer for 4-6 sessions. Another 40 patients managed by conventional treatment by compression and dressing for the same period were allocated as Group B. Objective assessment achieved by the percentage of reduction of the size of the ulcer area, rate of healing, incidence of recurrence, and if side effects have been reported.

RESULTS

PRP therapy showed better results and high p value significance when compared to conventional therapy.

CONCLUSION

This study shows that PRP is effective and significant in promoting the wound healing process in chronic leg venous ulcers. PRP is simple, safe, and has a short learning curve technique.

Current applications of platelet gels in wound healing-A review

Human platelets play important roles in several physiologic and pathologic processes. Platelet concentrates are activated with thrombin or calcium, resulting in a viscous coagulum (platelet gel [PG]), composed of 95% platelets at least. PG is increasingly used for the treatment of a variety of soft and hard tissue defects, most notably in the management of chronic non-healing wounds. During wound healing, platelets not only play a critical role in primary hemostasis and thrombosis, but also release growth factors and cytokines to promote tissue regeneration, enhance collagen synthesis, and trigger an immune response. This review addresses a variety of aspects relevant to the functions of well-known platelet growth factors, animal and clinical studies of PG in the last decade, and different sources of platelets for PG. PG is used for non-healing chronic wounds, such as oral ulcerations related to epidermolysis bullosa and chronic graft-versus-host disease, for those, the traditional treatment effect is poor. PG maybe provide a new therapeutic direction for these diseases. Nevertheless, some uncertainty is present, the number of clinical studies is not enough. Hence, randomized controlled trials are still required to study the potential of the use of PG in the near future.

Biomaterials Regulating Bone Hematoma for Osteogenesis

Blood coagulation in tissue healing not only prevents blood loss, but also forms a natural scaffold for tissue repair and regeneration. As blood clot formation is the initial and foremost phase upon bone injury, and the quality of blood clot (hematoma) orchestrates the following inflammatory and cellular processes as well as the subsequent callus formation and bone remodeling process. Inspired by the natural healing hematoma, tissue-engineered biomimic scaffold/hydrogels and blood prefabrication strategies attract significant interests in developing functional bone substitutes. The alteration of the fracture hematoma ca significantly accelerate or impair the overall bone healing process. This review summarizes the impact of biomaterials on blood coagulation and provides evidence on fibrin network structure, growth factors, and biomolecules that contribute to bone healing within the hematoma. The aim is to provide insights into the development of novel implant and bone biomaterials for enhanced osteogenesis. Advances in the understanding of biomaterial characteristics (e.g., morphology, chemistry, wettability, and protein adsorption) and their effect on hematoma properties are highlighted. Emphasizing the importance of the initial healing phase of the hematoma endows the design of advanced biomaterials with the desired regulatory properties for optimal coagulation and hematoma properties, thereby facilitating enhanced osteogenesis and ideal therapeutic effects.

Different modes of foveal regeneration after closure of full-thickness macular holes by (re)vitrectomy and autologous platelet concentrate

AIM

To describe using spectral-domain optical coherence tomography the regeneration of the foveal morphology after pars plana (re)vitrectomy surgery and gas tamponade combined with injection of autologous platelet concentrate to treat full-thickness macular holes, and to describe different anatomical outcome.

METHODS

A retrospective case series of 8 eyes of 8 patients was described.

RESULTS

In all cases investigated, the platelet-assisted closure of macular holes was associated with a rapid resolution of cystic cavities in the foveal walls. In two patients, there was a regular regeneration of the foveal morphology after hole closure; the regenerated central fovea had a regular structure with a foveola and photoreceptors. In three other patients, there was an irregular regeneration of the fovea; a foveola was not formed, photoreceptor cells were absent from the foveal center, and the center was composed of Müller and retinal pigment epithelial (RPE) cells. The foveal regeneration after hole closure may proceed with or without a temporary detachment of the foveal center from the RPE, and with or without a direct contact between the central outer nuclear layer (ONL) and the RPE. Contacts between the ONL and RPE were observed only in patients with an irregular foveal regeneration after hole closure.

CONCLUSION

The data show that there are different modes of foveal regeneration after closure of macular holes with (re)vitrectomy and platelet concentrate. It is suggested that the regular regeneration of the foveal morphology proceeds by Müller cell-mediated tissue movements without cell proliferation, whereas the irregular foveal regeneration proceeds in part by proliferation of Müller and RPE cells.

Effect of cell culture biomaterials for completely xeno-free generation of human induced pluripotent stem cells

Human induced pluripotent stem cells (hiPSCs) were generated on several biomaterials from human amniotic fluid in completely xeno-free and feeder-free conditions via the transfection of pluripotent genes using a nonintegrating RNA Sendai virus vector. The effect of xeno-free culture medium on the efficiency of the establishment of human amniotic fluid stem cells from amniotic fluid was evaluated. Subsequently, the effect of cell culture biomaterials on the reprogramming efficiency was investigated during the reprogramming of human amniotic fluid stem cells into hiPSCs. Cells cultured in laminin-511, laminin-521, and Synthemax II-coated dishes and hydrogels having optimal elasticity that were engrafted with specific oligopeptides derived from vitronectin could be reprogrammed into hiPSCs with high efficiency. The reprogrammed cells expressed pluripotency proteins and had the capability to differentiate into cells derived from all three germ layers in vitro and in vivo. Human iPSCs could be generated successfully and at high efficiency (0.15-0.25%) in completely xeno-free conditions from the selection of optimal cell culture biomaterials.

The effect of human platelet lysate on the differentiation ability of human adipose-derived stem cells cultured on ECM-coated surfaces

Human mesenchymal stem cells (hMSCs), such as human adipose-derived stem cells (hADSCs), present heterogeneous characteristics, including varying differentiation abilities and genotypes. hADSCs isolated under different conditions exhibit differences in stemness. We isolated hADSCs from human fat tissues via culture on different cell culture biomaterials including tissue culture polystyrene (TCPS) dishes and extracellular matrix protein (ECM)-coated dishes in medium supplemented with 5% or 10% serum-converted human platelet lysate (hPL) or 10% fetal bovine serum (FBS) as a control. Currently, it is not clear whether xeno-free hPL in the cell culture medium promotes the ability of hMSCs such as hADSCs to differentiate into several cell lineages compared to the xenomaterial FBS. We investigated whether a synchronized effect of ECM (Matrigel, fibronectin, and recombinant vitronectin) coatings on TCPS dishes for efficient hADSC differentiation could be observed when hADSCs were cultured in hPL medium. We found that Matrigel-coated dishes promoted hADSC differentiation into osteoblasts and suppressed differentiation into chondrocytes in 10% hPL medium. Recombinant vitronectin- and fibronectin-coated dishes greatly promoted hADSC differentiation into osteoblasts and chondrocytes in 5% and 10% hPL media. hPL promoted hADSC differentiation into osteoblasts and chondrocytes compared to FBS on the fibronectin-coated surface and recombinant vitronectin-coated surface.

Optimization of leukocyte-poor platelet-rich plasma preparation: a validation study of leukocyte-poor platelet-rich plasma obtained using different preparer, storage, and activation methods

Background

Alternative methods of platelet-rich plasma (PRP) preparation, storage, and activation that can be stably reproduced are needed to improve PRP production. The purpose of this study was to investigate the effect of the preparer’s experience on the quality of prepared PRP, chronological changes occurring in PRP, and the effect of the activation procedures on the release of several growth factors from PRP, using PRP prepared with the PRGF-Endoret Kit.

Methods

Leukocyte-poor PRP samples from seventeen healthy volunteers were prepared using the PRGF-Endoret Kit and the PRGF IV System Centrifuge. The platelet and leukocyte concentrations were compared based on the preparer’s experience. The concentrations of platelets, hepatocyte growth factor (HGF), platelet-derived growth factor-BB (PDGF-BB), and insulin-like growth factor-1 (IGF-1) were determined at 0 and 60 min after PRP preparation, and compared. Concentrations of the above growth factors from PRP activated by freeze–thaw cycling and by calcium chloride (CaCl₂) were also compared.

Results

No significant difference was observed in the platelet concentrations and leukocyte contamination rates, based on the preparer’s experience. At 60 min after PRP preparation, the platelet concentration decreased significantly, while the HGF, PDGF-BB, and IGF-1 concentrations remained unchanged. Activation with CaCl₂ resulted in a significant increase in the PDGF-BB levels, although the HGF and IGF-1 concentrations remained unchanged.

Conclusions

The results of this study show that leukocyte-poor PRP prepared using the PRGF-Endoret Kit did not result in any qualitative difference that depended on the experience of the preparer. However, PRP preparation required standardization in terms of the time of blood count measurement. Growth factor concentrations in PRP differed according to the platelet-activation method used.

Four types of human platelet lysate, including one virally inactivated by solvent-detergent, can be used to propagate Wharton jelly mesenchymal stromal cells

There is accumulating experimental evidence that human platelet lysate (HPL) made from platelet concentrates can replace fetal bovine serum (FBS) as a xeno-free clinical-grade supplement of growth media to expand mesenchymal stromal cells (MSCs). However, uncertainties exist in regard to impacts that various manufacturing methods of HPL can exert on the expansion and differentiation capacity of MSCs. In particular, there is a need to evaluate the possibility of implementing virus-inactivation treatment during HPL production to ensure optimal safety of industrial HPL pools. Expired human platelet concentrates from four different donors were pooled and subjected to freeze-thaw cycles (-80/+37 °C), followed or not by serum-conversion by calcium chloride, heat-treatment at 56 °C for 30 min, or solvent-detergent (S/D) virus inactivation. The concentrations of total proteins, growth factors and fibrinogen, and the chemical compositions of the HPLs were characterized. The impact of HPL supplementation on the cell morphology, doubling time, immunophenotype and trilineage differentiation capacity of Wharton jelly MSCs (WJMSCs) were compared over five passages, using FBS as a control and normalizing the protein content. Data showed that WJMSCs expanded equally well, exhibited a typical fibroblast morphology, had short doubling times, maintained their immunophenotypes, and differentiated into chondrocyte, osteocyte, and adipocyte lineages in all HPL-supplemented media, all of which were more effective than FBS. In conclusion, we found minimal detectable impact of the HPL manufacturing process, including S/D virus inactivation, on the suitability of expanding WJMSCs in vitro.

Platelet-rich plasma lyophilization enables growth factor preservation and functionality when compared with fresh platelet-rich plasma

Aims: To compare levels and activity of the growth factors between fresh and lyophilized platelet-rich plasma (PRP). Methods: Analysis of platelet concentration using fibroblast and human umbilical vein endothelial cell cultures were compared between fresh and lyophilized PRP obtained from peripheral blood. Results: After lyophilization, 54% of platelets were intact whereas the fresh showed no aggregation with agonists (levels under 20%). The concentration of growth factors (VEGF, EGF, TGF-β and PDGF) in both products were similar. Fresh and lyophilized PRPs induced proliferation in the fibroblasts at 24 h (0.303 vs 0.300, respectively). Conclusion: Lyophilized PRP appears to be an alternative to fresh PRP and the results evidenced the role of growth factors as a key element in the activity of this product.

Epidermal Growth Factor (EGF) Autocrine Activation of Human Platelets Promotes EGF Receptor-Dependent Oral Squamous Cell Carcinoma Invasion, Migration, and Epithelial Mesenchymal Transition

Activated platelets release functional, high m.w. epidermal growth factor (HMW-EGF). In this study, we show platelets also express epidermal growth factor (EGF) receptor (EGFR) protein, but not ErbB2 or ErbB4 coreceptors, and so might respond to HMW-EGF. We found HMW-EGF stimulated platelet EGFR autophosphorylation, PI3 kinase-dependent AKT phosphorylation, and a Ca²⁺ transient that were blocked by EGFR tyrosine kinase inhibition. Strong (thrombin) and weak (ADP, platelet-activating factor) G protein-coupled receptor agonists and non-G protein-coupled receptor collagen recruited EGFR tyrosine kinase activity that contributed to platelet activation because EGFR kinase inhibition reduced signal transduction and aggregation induced by each agonist. EGF stimulated ex vivo adhesion of platelets to collagen-coated microfluidic channels, whereas systemic EGF injection increased initial platelet deposition in FeCl₃-damaged murine carotid arteries. EGFR signaling contributes to oral squamous cell carcinoma (OSCC) tumorigenesis, but the source of its ligand is not established. We find individual platelets were intercalated within OSCC tumors. A portion of these platelets expressed stimulation-dependent Bcl-3 and IL-1β and so had been activated. Stimulated platelets bound OSCC cells, and material released from stimulated platelets induced OSCC epithelial-mesenchymal transition and stimulated their migration and invasion through Matrigel barriers. Anti-EGF Ab or EGFR inhibitors abolished platelet-induced tumor cell phenotype transition, migration, and invasion; so the only factor released from activated platelets necessary for OSCC metastatic activity was HMW-EGF. These results establish HMW-EGF in platelet function and elucidate a previously unsuspected connection between activated platelets and tumorigenesis through rapid, and prolonged, autocrine-stimulated release of HMW-EGF by tumor-associated platelets.

Autologous platelet-rich plasma versus conventional therapy for the treatment of chronic venous leg ulcers: A comparative study

BACKGROUND

Chronic venous leg ulcers drastically reduce the quality of life of affected patients. There is heightened interest in autologous platelet-rich plasma (PRP) as one of the promising therapies for leg ulcers.

AIM

Our aim was to compare the clinical efficacy of PRP in the management of chronic venous leg ulcers vs conventional treatment.

PATIENTS/METHODS

In total, 40 patients with chronic venous leg ulcers were included in the study. Twenty patients were treated with autologous PRP weekly for 6 weeks (Group A), and 20 patients were treated with conventional treatment (compression and dressing) for 6 weeks (Group B). Treatment results were calculated by percentage of improvement in area of the ulcer.

RESULTS

Compared to conventional therapy, a highly significant improvement in the ulcer size was observed post-PRP therapy (P-value = .0001). The mean change in the area of the ulcer post-PRP and conventional therapy was 4.92 ± 11.94 cm and 0.13 ± 0.27 cm, respectively, while the mean percentage improvement in the area of the ulcer post-PRP and conventional therapy was 67.6% ± 36.6% and 13.67% ± 28.06%, respectively. Subjective improvement in pain associated with the ulcer was noted by all patients.

CONCLUSIONS

Platelet-rich plasma is a safe nonsurgical procedure for treating chronic venous leg ulcers. Additional studies with larger sample size and longer follow-up periods are required to confirm or refute our findings.

The role of platelets in autoimmunity, vasculopathy, and fibrosis: Implications for systemic sclerosis

INTRODUCTION

Systemic sclerosis (SSc) is an autoimmune disease characterized by vasculopathy, autoimmunity, and widespread dermal and visceral fibrosis. This article summarizes the current knowledge about the potential contribution of platelets in the disease process and the rationale of targeting platelets as an adjunct treatment for SSc.

METHODS

We performed an electronic search (Medline) using the keywords platelets, systemic sclerosis, autoimmunity, fibrosis, Raynaud, and pulmonary arterial hypertension.

RESULTS

The link that connects vasculopathy, autoimmunity, and fibrosis in SSc remains obscure. Experimental data suggest that platelets are not solely cell fragments regulating hemostasis but they have a pleiotropic role in several biologic processes including immune regulation, vasculopathy, fibrosis, and all key features of SSc. Platelets interplay with the impaired endothelium, can interact with immune cells, and they are storages of bioactive molecules involved in tissue injury and remodeling. The potential role of platelets in the pathogenesis of SSc is further supported by experimental data in animal models of SSc. Platelet-derived serotonin represents a novel target in SSc and serotonin blockade is currently being tested in clinical trials.

CONCLUSION

Platelets may be actively involved in the pathogenesis of SSc by activating immune responses and facilitating the fibrotic process. However, definite conclusions cannot be drawn until more data from both basic and clinical research are available.

The soluble protease ADAMDEC1 released from activated platelets hydrolyzes platelet membrane pro-epidermal growth factor (EGF) to active high-molecular-weight EGF

Platelets are the sole source of EGF in circulation, yet how EGF is stored or released from stimulated cells is undefined. In fact, we found platelets did not store EGF, synthesized as a single 6-kDa domain in pro-EGF, but rather expressed intact pro-EGF precursor on granular and plasma membranes. Activated platelets released high-molecular-weight (HMW)-EGF, produced by a single cleavage between the EGF and the transmembrane domains of pro-EGF. We synthesized a fluorogenic peptide encompassing residues surrounding the putative sessile arginyl residue and found stimulated platelets released soluble activity that cleaved this pro-EGF_1020-1027 peptide. High throughput screening identified chymostatins, bacterial peptides with a central cyclic arginyl structure, as inhibitors of this activity. In contrast, the matrix metalloproteinase/TACE (tumor necrosis factor-α-converting enzyme) inhibitor GM6001 was ineffective. Stimulated platelets released the soluble protease ADAMDEC1, recombinant ADAMDEC1 hydrolyzed pro-EGF_1020-1027, and this activity was inhibited by chymostatin and not GM6001. Biotinylating platelet surface proteins showed ADAMDEC1 hydrolyzed surface pro-EGF to HMW-EGF that stimulated HeLa EGF receptor (EGFR) reporter cells and EGFR-dependent tumor cell migration. This proteolysis was inhibited by chymostatin and not GM6001. Metabolizing pro-EGF Arg¹⁰²³ to citrulline with recombinant polypeptide arginine deiminase 4 (PAD4) abolished ADAMDEC1-catalyzed pro-EGF_1020-1027 peptidolysis, while pretreating intact platelets with PAD4 suppressed ADAMDEC1-, thrombin-, or collagen-induced release of HMW-EGF. We conclude that activated platelets release ADAMDEC1, which hydrolyzes pro-EGF to soluble HMW-EGF, that HMW-EGF is active, that proteolytic cleavage of pro-EGF first occurs at the C-terminal arginyl residue of the EGF domain, and that proteolysis is the regulated and rate-limiting step in generating soluble EGF bioactivity from activated platelets.

Current Evidence for Clinical Efficacy of Platelet Rich Plasma in Aesthetic Surgery: A Systematic Review

Background

Platelet rich plasma (PRP) has attracted attention in a number of surgical fields due to a wide variety of potential clinical benefits. Yet PRP has not gained wide popularity in aesthetic surgery as a result of uncertainty surrounding objective clinical evidence.

Objectives

We aim to describe the current applications, define preparation and activation, explore effectiveness, and propose a classification system to facilitate comparisons across studies.

Methods

A comprehensive review of the literature regarding the use of platelet rich plasma in aesthetic surgery was performed. Data gathered included: PRP application, study type, subject number, centrifugation, anticoagulation, activation, PRP composition, and outcomes.

Results

Thirty-eight reports were identified. Applications included injection into aging skin (29%), scalp alopecia (26%), lipofilling (21%), fractional laser (13%), and facial surgery (11%). The majority of studies (53%) were case series without controls. Leucocytes were sparsely defined (32%). The concentration of injected and/or baseline platelets was rarely clarified (18%). The mechanism of activation was described in 27 studies (71%), while anticoagulation was uncommonly elucidated (47%). While most studies (95%) claim effectiveness, objective measures were only utilized in 17 studies (47%).

Conclusions

Current studies produce context-dependent results with a lack of consistent reporting of PRP preparation, composition, and activation in aesthetic applications, making meaningful meta-analysis unrealistic. Thus the method of PRP preparation warrants increased attention. We recommend a set of descriptors, FIT PAAW (described below), to produce scientifically grounded conclusions, facilitating a clearer understanding of the situations in which PRP is effective.

Level of Evidence

4

Treatment of chronic non-healing ulcers using autologous platelet rich plasma: a case series

Background

Non-healing ulcers are a major health problem worldwide and have great impact at personal, professional and social levels, with high cost in terms of human and material resources. Recalcitrant non-healing ulcers are inevitable and detrimental to the lower limb and are a major cause of non-traumatic lower limb amputations. Application of autologous Platelet Rich Plasma (PRP) has been a major breakthrough for the treatment of non-healing and diabetic foot ulcers, as it is an easy and cost-effective method, and provides the necessary growth factors that enhance tissue healing. PRP is a conglomeration of thrombocytes, cytokines and various growth factors which are secreted by α-granules of platelets that augment the rate of natural healing process with decrease in time. The purpose of this case series was to evaluate the safety and efficacy of autologous platelet rich plasma for the treatment of chronic non-healing ulcers on the lower extremity.

Methods

Autologous PRP was prepared from whole blood utilizing a rapid, intraoperative point-of-care system that works on the principle of density gradient centrifugation. Twenty Four (24) patients with non-healing ulcers of different etiologies, who met the inclusion criteria, were treated with single dose of subcutaneous PRP injections along with topical application of PRP gel under compassionate use.

Results

The mean age of the treated patients was 62.5 ± 13.53 years and they were followed-up for a period of 24 weeks. All the patients showed signs of wound healing with reduction in wound size, and the mean time duration to ulcer healing was 8.2 weeks. Also, an average five fold increase in the platelet concentrate was observed in the final PRP product obtained using the rapid point-of-care device, and the average platelet dose administered to the patients was 70.10 × 10⁸.

Conclusion

This case series has demonstrated the potential safety and efficacy of autologous platelet rich plasma for the treatment of chronic non-healing ulcers.

Trial registration

NCT03026855, Registered 4 January 2017 ‘Retrospectively’

Solvent/Detergent Virally Inactivated Serum Eye Drops Restore Healthy Ocular Epithelium in a Rabbit Model of Dry-Eye Syndrome

Application of autologous serum eye drops (SEDs) is a recognized means to treat severe dry-eye syndrome (DES). Due to the inconvenience and difficulty of preparing SEDs from some patients, producing SEDs from allogeneic blood donations is gaining popularity. A major safety concern associated with allogeneic blood is virus transmission. We therefore herein evaluated the possibility of applying a solvent/detergent (S/D) treatment to inactivate viruses and studied the impacts of such treatment of SEDs to resolve DES in a rabbit model. Sera prepared from the blood of five rabbits were pooled and divided into two sub-pools. One was untreated (SEDs), while the other was virally-inactivated with 1% Tri-n-butyl phosphate/1% Triton X-45 at 31°C for 1 h (S/D-SEDs). DES was induced in rabbits using 0.1% benzalkonium chloride (BAC). Rabbits were divided into five groups of two rabbits each. One group was untreated (control), three were treated twice daily for 3 weeks using PBS, SEDs, or S/D-SEDs, and the last received an additional 0.1% BAC (as the negative control). The DES condition was determined by measuring aqueous tear secretion (Schirmer’s test), corneal fluorescein staining, a corneal histologic examination, TUNEL stain apoptosis, and corneal inflammatory marker (tumor necrosis factor-α, interleukin (IL)-1β, IL-8, and IL-6) expressions. We first confirmed that SEDs and S/D-SEDs had similar protein profiles and transforming growth factor (TGF)-β contents. Animal experiments showed that tear secretion did not significantly differ between the SED and S/D-SED groups but was significantly higher than in the PBS group. Eye fluorescein staining revealed dramatic improvements in epithelial defects in groups treated with SEDs or S/D-SEDs, and hematoxylin/eosin staining revealed microscopic epithelial layers similar to those of the untreated controls. Inflammatory markers and TUNEL studies showed that healthy epithelium had been restored in groups treated with SEDs or S/D-SEDs. In conclusion, this preclinical study supports the possibility of using S/D virally inactivated SEDs to treat DES and restore a normal epithelium.

Growth Factor Release from Lyophilized Porcine Platelet-Rich Plasma: Quantitative Analysis and Implications for Clinical Applications

BACKGROUND

Freeze-dried platelet-rich plasma (FD PRP) is of potential value for clinical applications. However, growth factors released from FD PRP have not been well studied. Our study investigates growth factor release from FD PRP preparations, compared with other PRP samples, to further facilitate such clinical use.

METHODS

We used four experimental groups: (1) Fresh porcine PRP (PRP), (2) PRP activated by calcium chloride (CaCl2) (Ca PRP), (3) PRP activated by CaCl2, followed by freeze drying (Ca-FD PRP), and (4) PRP freeze-dried first, then activated by CaCl2 (FD-Ca PRP). All FD PRP samples were kept for up to 4 weeks at room temperature (22 °C) and reconstituted prior to analysis. Transforming growth factor-β1 (TGF-β1), platelet-derived growth factor AB (PDGF-AB), and vascular endothelial growth factor (VEGF) were quantitated by ELISA at 15 min and 1 h incubation times.

RESULTS

The concentrations of all growth factors in Ca PRP, measured at 1 h, were significantly higher than those in PRP (p < 0.05). PDGF-AB concentrations in FD-Ca PRP were not significantly different than in Ca PRP (p > 0.05). Levels of VEGF in Ca-FD PRP were not significantly different than in Ca PRP (p > 0.05). However, TGF-β1 concentrations in Ca-FD PRP, measured at 15 min, were higher than those in Ca PRP (p < 0.05).

CONCLUSIONS

PRP was activated efficiently by calcium chloride. Freeze-dried PRP remained rich in growth factors after storage for 4 weeks at room temperature, indicating its ease of use and wider possibilities for clinical applications.

NO LEVEL ASSIGNED

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An In Vitro Investigation of Platelet-Rich Plasma-Gel as a Cell and Growth Factor Delivery Vehicle for Tissue Engineering

Platelet-rich plasma (PRP) has been used for different applications in human and veterinary medicine. Many studies have shown promising therapeutic effects of PRP; however, there are still many controversies regarding its composition, properties, and clinical efficacy. The aim of this study was to evaluate the influence of different platelet concentrations on the rheological properties and growth factor (GF) release profile of PRP-gels. In addition, the viability of incorporated bone marrow-derived human mesenchymal stem cells (MSCs) was investigated. PRP (containing 1000 × 10(3), 2000 × 10(3), and 10,000 × 10(3) platelets/μL) was prepared from human platelet concentrates. Platelet activation and gelification were achieved by addition of human thrombin. Viscoelastic properties of PRP-gels were evaluated by rheological studies. The release of GFs and inflammatory proteins was measured using a membrane-based protein array and enzyme-linked immunosorbent assay. MSC viability and proliferation in PRP-gels were assessed over 7 days by cell viability staining. Cell proliferation was examined using DNA quantification. Regardless of the platelet content, all tested PRP-gels showed effective cross-linking. A positive correlation between protein release and the platelet concentration was observed at all time points. Among the detected proteins, the chemokine CCL5 was the most abundant. The greatest release appeared within the first 4 h after gelification. MSCs could be successfully cultured in PRP-gels over 7 days, with the highest cell viability and DNA content found in PRP-gels with 1000 × 10(3) platelets/μL. The results of this study suggest that PRP-gels represent a suitable carrier for both cell and GF delivery for tissue engineering. Notably, a platelet concentration of 1000 × 10(3) platelets/μL appeared to provide the most favorable environment for MSCs. Thus, the platelet concentration is an important consideration for the clinical application of PRP-gels.

Platelet-Rich Plasma Promotes Axon Regeneration, Wound Healing, and Pain Reduction: Fact or Fiction

Platelet-rich plasma (PRP) has been tested in vitro, in animal models, and clinically for its efficacy in enhancing the rate of wound healing, reducing pain associated with injuries, and promoting axon regeneration. Although extensive data indicate that PRP-released factors induce these effects, the claims are often weakened because many studies were not rigorous or controlled, the data were limited, and other studies yielded contrary results. Critical to assessing whether PRP is effective are the large number of variables in these studies, including the method of PRP preparation, which influences the composition of PRP; type of application; type of wounds; target tissues; and diverse animal models and clinical studies. All these variables raise the question of whether one can anticipate consistent influences and raise the possibility that most of the results are correct under the circumstances where PRP was tested. This review examines evidence on the potential influences of PRP and whether PRP-released factors could induce the reported influences and concludes that the preponderance of evidence suggests that PRP has the capacity to induce all the claimed influences, although this position cannot be definitively argued. Well-defined and rigorously controlled studies of the potential influences of PRP are required in which PRP is isolated and applied using consistent techniques, protocols, and models. Finally, it is concluded that, because of the purported benefits of PRP administration and the lack of adverse events, further animal and clinical studies should be performed to explore the potential influences of PRP.

Removal of transmissible spongiform encephalopathy prion from large volumes of cell culture media supplemented with fetal bovine serum by using hollow fiber anion-exchange membrane chromatography

Cases of variant Creutzfeldt-Jakob disease in people who had consumed contaminated meat products from cattle with bovine spongiform encephalopathy emphasize the need for measures aimed at preventing the transmission of the pathogenic prion protein (PrPSc) from materials derived from cattle. Highly stringent scrutiny is required for fetal bovine serum (FBS), a growth-medium supplement used in the production of parenteral vaccines and therapeutic recombinant proteins and in the ex vivo expansion of stem cells for transplantation. One such approach is the implementation of manufacturing steps dedicated to removing PrPSc from materials containing FBS. We evaluated the use of the QyuSpeed D (QSD) adsorbent hollow-fiber anion-exchange chromatographic column (Asahi Kasei Medical, Tokyo, Japan) for the removal of PrPSc from cell culture media supplemented with FBS. We first established that QSD filtration had no adverse effect on the chemical composition of various types of culture media supplemented with 10% FBS or the growth and viability characteristics of human embryonic kidney (HEK293) cells, baby hamster kidney (BHK-21) cells, African green monkey kidney (Vero) cells, and Chinese hamster ovary (CHO-k1) cells propagated in the various culture-medium filtrates. We used a 0.6-mL QSD column for removing PrPSc from up to 1000 mL of Dulbecco's modified Eagle's medium containing 10% FBS previously spiked with the 263K strain of hamster-adapted scrapie. The Western blot analysis, validated alongside an infectivity assay, revealed that the level of PrPSc in the initial 200mL flow-through was reduced by 2.5 to > 3 log10, compared with that of the starting material. These results indicate that QSD filtration removes PrPSc from cell culture media containing 10% FBS, and demonstrate the ease with which QSD filtration can be implemented in at industrial-scale to improve the safety of vaccines, therapeutic recombinant proteins, and ex vivo expanded stem cells produced using growth media supplemented with FBS.

Principles and Methods of Preparation of Platelet-Rich Plasma: A Review and Author's Perspective

The utility of platelet-rich plasma (PRP) has spanned various fields of dermatology from chronic ulcer management to trichology and aesthetics, due to its role in wound healing. Though PRP is being used over a long time, there is still confusion over proper terminology to define, classify and describe the different variations of platelet concentrates. There is also a wide variation in the reported protocols for standardization and preparation of PRP, in addition to lack of accurate characterization of the tested products in most articles on the topic. Additionally, the high cost of commercially available PRP kits, precludes its use over a larger population.

In this article, we review the principles and preparation methods of PRP based on available literature and place our perspective in standardizing a safe, simple protocol that can be followed to obtain an optimal consistent platelet yield.

Advanced platelet-rich fibrin: a new concept for cell-based tissue engineering by means of inflammatory cells

Choukroun's platelet-rich fibrin (PRF) is obtained from blood without adding anticoagulants. In this study, protocols for standard platelet-rich fibrin (S-PRF) (2700 rpm, 12 minutes) and advanced platelet-rich fibrin (A-PRF) (1500 rpm, 14 minutes) were compared to establish by histological cell detection and histomorphometrical measurement of cell distribution the effects of the centrifugal force (speed and time) on the distribution of cells relevant for wound healing and tissue regeneration. Immunohistochemistry for monocytes, T and B -lymphocytes, neutrophilic granulocytes, CD34-positive stem cells, and platelets was performed on clots produced from four different human donors. Platelets were detected throughout the clot in both groups, although in the A-PRF group, more platelets were found in the distal part, away from the buffy coat (BC). T- and B-lymphocytes, stem cells, and monocytes were detected in the surroundings of the BC in both groups. Decreasing the rpm while increasing the centrifugation time in the A-PRF group gave an enhanced presence of neutrophilic granulocytes in the distal part of the clot. In the S-PRF group, neutrophils were found mostly at the red blood cell (RBC)-BC interface. Neutrophilic granulocytes contribute to monocyte differentiation into macrophages. Accordingly, a higher presence of these cells might be able to influence the differentiation of host macrophages and macrophages within the clot after implantation. Thus, A-PRF might influence bone and soft tissue regeneration, especially through the presence of monocytes/macrophages and their growth factors. The relevance and feasibility of this tissue-engineering concept have to be proven through in vivo studies.

Clinical and structural outcomes after arthroscopic repair of full-thickness rotator cuff tears with and without platelet-rich product supplementation: a meta-analysis and meta-regression

PURPOSE

The purpose of this study was to perform a systematic review, meta-analysis, and meta-regression of all Level I and Level II studies comparing the clinical or structural outcomes, or both, after rotator cuff repair with and without platelet-rich product (PRP) supplementation.

METHODS

A literature search of the PubMed and EMBASE databases was performed to identify all Level I or II studies comparing the clinical or structural outcomes, or both, after arthroscopic repair of full-thickness rotator cuff tears with (PRP+ group) and without (PRP- group) PRP supplementation. Data included outcome scores (American Shoulder and Elbow Surgeons [ASES], University of California Los Angeles [UCLA], Constant, Simple Shoulder Test [SST] and visual analog scale [VAS] scores) and retears diagnosed with imaging studies. Meta-analyses compared preoperative, postoperative, and gain in outcome scores and relative risk ratios for retears. Meta-regression compared the effect of PRP treatment on outcome scores and retear rates according to 6 covariates. Minimum effect sizes that were detectable with 80% power were also calculated for each study.

RESULTS

Eleven studies were included in this review and a maximum of 8 studies were used for meta-analyses according to data availability. There were no statistically significant differences between the PRP+ and PRP- groups for overall outcome scores or retear rates (P > .05). Overall gain in the Constant score was decreased when liquid PRP was injected over the tendon surface compared with PRP application at the tendon-bone interface (-6.88 points v +0.78 points, respectively; P = .046); however, this difference did not reach the previously reported minimum clinically important difference (MCID) for Constant scores. When the initial tear size was greater than 3 cm in anterior-posterior length, the PRP+ group exhibited decreased retear rates after double-row repairs when compared with the PRP- group (25.9% v 57.1%, respectively; P = .046). Sensitivity power analyses revealed that most included studies were only powered to detect large differences in outcome scores between groups.

CONCLUSIONS

There were no statistically significant differences in overall gain in outcome scores or retear rates between treatment groups. Gain in Constant scores was significantly increased when PRPs were applied at the tendon-bone interface when compared with application over the top of the repaired tendon. Retear rates were significantly decreased when PRPs were used for the treatment of tears greater than 3 cm in anterior-posterior length using a double-row technique. Most of the included studies were only powered to detect large differences in outcome scores between treatment groups. In addition, an increased risk for selection, performance, and attrition biases was found.

LEVEL OF EVIDENCE

Level II, meta-analysis of Level I and Level II studies.

Considerations on the use of platelet-rich plasma, specifically for burn treatment

Platelet-rich plasma (PRP) is a fraction of blood plasma with a platelet concentration above baseline. After activation of the platelets, growth factors are released, which are involved in wound-healing processes. Application of a multitude of growth factors seems to boost the healing process. In this review the authors provide a comprehensive overview of the many different aspects of PRP; this is followed by a short outline of the evidence for a wide range of applications and finally narrowing down to a more in-depth analysis of the literature on the potential use of PRP in burn treatment. The authors performed an extensive search on PRP and the different biological, as well as practical aspects for the different applications. Furthermore, we performed a systematic search on PRP in the treatment of burn wounds. A high variety exists in PRP products, procedures, and content. This makes interpretation and comparison of the evidence difficult. PRP has been reported to have beneficial effects on wound healing in different fields of surgery and in the treatment of acute, chronic, and diabetic wounds. Literature on the use of PRP in burns is scarce. Separate growth factors have shown beneficial results in the treatment of burns. Furthermore, an animal study and several case reports showed improved burn wound-healing time after the application of PRP. A deep dermal burn could benefit from PRP through its hemostatic antimicrobial abilities and the positive effects seen in wound healing. However, burn patients have an altered physiological state and it is unknown how this may affect platelet function and quality. Furthermore, the effect of PRP on scarring has not been evaluated properly. Future research is needed to elucidate the role of PRP in the treatment of burns.

Platelet derivatives in regenerative medicine: an update

Prior preclinical and clinical studies support the use of platelet-derived products for the treatment of soft and hard tissue lesions. These regenerative effects are controlled by autocrine and paracrine biomolecules including growth factors and cytokines contained in platelet alpha granules. Each growth factor is involved in a phase of the healing process, such as inflammation, collagen synthesis, tissue granulation, and angiogenesis collectively promoting tissue restitution. Platelet derivatives have been prepared as platelet-rich plasma, platelet gel, platelet-rich fibrin, and platelet eye drops. These products vary in their structure, growth factors, composition, and cytokine concentrations. Here, we review the current use of platelet-derived biological products focusing on the rationale for their use and the main requirements for their preparation. Variation in the apparent therapeutic efficacy may have resulted from a lack of reproducible, standardized protocols for preparation. Despite several individual studies showing favorable treatment effects, some randomized controlled trials as well as meta-analyses have found no constant clinical benefit from the application of platelet-derived products for prevention of tissue lesions. Recently, 3 published studies in dentistry showed an improvement in bone density. Seven published studies showed positive results in joint regeneration. Five published studies demonstrated an improvement in the wound healing, and an improvement of eye epithelial healing was observed in 2 reports. Currently, at least 14 ongoing clinical trials in phase 3 or 4 have been designed with large groups of treated patients (n > 100). Because the rationale of the therapy with platelet-derived compounds is still debated, a definitive insight can be acquired only when these large randomized trials will be completed.

Autologous platelet-rich plasma: a biological supplement to enhance adipose-derived mesenchymal stem cell expansion

Currently the use of non-autologous cell culture media (e.g., animal-derived or allogeneic serum) for clinical applications of mesenchymal stem cells (MSCs) is criticized by regulatory agencies. Autologous platelet-rich plasma (PRP) is proposed as a safer alternative medium supplement for adipose-derived mesenchymal stem cells (AT-MSC) culture. To study its efficiency on cell proliferation, AT-MSCs were cultured for 10 days in media supplemented with different concentrations of autologous non-activated PRP (nPRP) or thrombin-activated PRP (tPRP) (1-60%). AT-MSC proliferation, cell phenotype, multipotency capacity, and chromosome stability were assessed and compared to AT-MSCs expanded in a classical medium supplemented with 10% of fetal bovine serum (FBS). Culture media supplemented with nPRP showed dose-dependent higher AT-MSC proliferation than did FBS or tPRP. Twenty percent nPRP was the most effective concentration to promote cell proliferation. This condition increased 13.9 times greater AT-MSC number in comparison to culture with FBS, without changing the AT-MSC phenotype, differentiation capacity, and chromosome status. We concluded that 20% autologous nPRP is a safe, efficient, and cost-effective supplement for AT-MSC expansion. It should be considered as an alternative to FBS or other nonautologous blood derivatives. It could serve as a potent substitute for the validation of future clinical protocols as it respects good manufacturing practices and regulatory agencies' standards.

Ex vivo expansion of bovine corneal endothelial cells in xeno-free medium supplemented with platelet releasate

Clinical-grade ex vivo expansion of corneal endothelial cells can increase the availability of corneal tissues for transplantation and treatment of corneal blindness. However, these cells have very limited proliferative capacity. Successful propagation has required so far to use very complex growth media supplemented with fetal bovine serum and other xenocomponents. We hypothesized that human platelet releasates rich in multiple growth factors, and in particular neurotrophins, could potentially be a useful supplement for ex vivo expansion of corneal endothelium cells due to their neural crest origin. Platelet releasates were prepared by calcium salt activation of apheresis platelet concentrates, subjected or not to complement inactivation by heat treatment at 56°C for 30 minutes. Platelet releasates were characterized for their content in proteins and were found to contain high amount of growth factors including platelet-derived growth factor-AB (30.56 to 39.08 ng/ml) and brain-derived neurotrophic factor (30.57 to 37.11 ng/ml) neurotrophins. We compared the growth and viability of corneal endothelium cells in DMEM-F12 medium supplemented with different combinations of components, including 2.5%∼10% of the platelet releasates. Corneal endothelium cells expanded in platelet releasates exhibited good adhesion and a typical hexagonal morphology. Their growth and viability were enhanced when using the complement-inactivated platelet releasate at a concentration of 10%. Immunostaining and Western blots showed that CECs maintained the expressions of four important membrane markers: Na-K ATPase α1, zona occludens-1, phospho-connexin 43 and N-cadherin. In conclusion, our study provides the first proof-of-concept that human platelet releasates can be used for exvivo expansion of corneal endothelium cells. These findings open a new paradigm for exvivo propagation protocols of corneal endothelium cells in compliance with good tissue culture practices and regulatory recommendations to limit the use of xenogenic materials.

Relevant aspects of centrifugation step in the preparation of platelet-rich plasma

Introduction. Platelet-Rich Plasma (PRP) is rich in growth factors, playing important role in tissue healing. The wide variation of reported protocols for preparation of PRP leads to variable compositions, which induce different biological responses and prevent results comparison. This study aims to highlight relevant aspects of the centrifugation step to obtain reproducible results and overall quality. Material and Methods. Samples of blood were collected from 20 healthy donors that have signed free informed consent. Two centrifugation steps (spins) were analyzed for the influence of centrifugal acceleration, time, processed volume, and platelet gradient. The Pure Platelet-Rich Plasma (P-PRP) was characterized as platelet concentration, integrity, and viability (sP-selectin measurement). Results. Lower centrifugal accelerations favour platelet separation. The processing of 3.5 mL of blood at 100 ×g for 10 min (1st spin), 400 ×g for 10 min (2nd spin), withdrawing 2/3 of remnant plasma, promoted high platelet recovery (70–80%) and concentration (5x) maintaining platelet integrity and viability. The recovery of platelets was reduced for a larger WB volume (8.5 mL) processed. Conclusion. Centrifugal acceleration, time, WB processed volume, and minimization of the platelet gradient before sampling are relevant aspects to ensure reproducible compositions within the autologous nature of PRP.

Evaluation of the effects of homologous platelet gel on healing lower extremity wounds in patients with diabetes

The treatment of chronic diabetic wounds remains complicated, despite new insight into the cellular and molecular basis of wound healing and cutaneous regeneration. A growing body of clinical trials has shown that platelet release has a notable effectiveness on refractory ulcer healing. However, patients with chronic diabetic ulcers usually have poor general health, and the large-volume blood absence required to produce autologous platelet-rich plasma often causes adverse effects. To overcome the limitation, the homologous platelet gel (PG) from healthy donor was used for the treatment of chronic diabetic lower extremity wound in the study. We show here that homologous derived platelets significantly enhanced EVC304 cell and HaCaT cell proliferation and homologous PG was capable of prompting cell migration. Twenty-one patients with refractory diabetic lower extremity ulcers, who had no response to conventional treatments, were treated in this study. Our data indicated that homologous PG was effective for the enhancement and acceleration of diabetic lower extremity wounds healing. We propose that homologous PG appeared to enhance vascularization and epithelialization, which might induce a quicker healing process and and encourage controlled studies in future.

Single-donor allogeneic platelet fibrin glue and osteoconductive scaffold in orbital floor fracture reconstruction

BACKGROUND

Commonly used materials for orbital floor fracture reconstruction include autologous cranial bone graft and titanium mesh. We have evaluated here a biomaterial combining biphasic calcium phosphate (hydroxyapatite [HA]/β-tricalcium phosphate [TCP]) osteoconductive scaffold with single-donor allogeneic platelet fibrin glue.

METHODS

The study was conducted on 10 consecutive patients with a follow-up of up to 4 years. Platelet fibrin glue was prepared by mixing equal volumes of single-donor platelet-rich plasma and cryoprecipitate with HA/β-TCP followed by activation with human thrombin prepared by plasma activation. Postoperative evaluations included serial photographs, repeated physical examination, and 3-dimensional computed tomography scan performed 2 years after surgery.

RESULTS

The fibrin-rich platelet biomaterial was easy to mold and to apply on the surgical site allowing the surgeon to sculpt accurately the bone defect, providing mechanical stability while avoiding spillage of the scaffold. No infection of the orbit or extrusion of HA/β-TCP was observed. Ocular motility was normal, and no diplopia or enophthalmos of the injured orbit was noted. Coronal computed tomography scans of the reconstructed orbits revealed good restoration of the orbital floor defect in all 10 patients.

CONCLUSIONS

The use of single-donor platelet fibrin glue combined with an osteoconductive scaffold offers a valuable alternative to autologous cranial bone graft or titanium mesh in the reconstruction of orbital floor bone defect.

Growth factor release from platelet concentrates: analytic quantification and characterization for clinical applications

BACKGROUND AND OBJECTIVES

Clinical use of plasma rich in growth factors requires biochemical product control. We aimed to measure and modulate concentrations of growth factors in solutions deriving from platelet apheresis or whole blood.

MATERIALS AND METHODS

Growth factor concentrations were measured 5', 10', 20', 30', 60' after CaCl2 was added at 40°C to platelet-apheresis products (n = 39) or after 60' in platelet concentrates from whole blood (n = 13). Growth factor release was also obtained in platelet apheresis a) by incubation at 22°C or 40°C for 10' or 30' (n = 4); b) by repeated freeze-thaw (n = 9).

RESULTS

Fibroblast growth factor (FGF), platelet-derived growth factor (PDGF) isoforms AA and AB and transforming growth factor beta (TGF-β) concentrations (pg/10(9 ) plt) were 25-60% higher in growth factors solutions from whole blood compared to platelet apheresis. Vascular endothelial growth factor (VEGF), TGF-β and PDGF isoforms were released early (5-10') during incubation: TGF-β concentration increased also at 30'. FGF and epidermal growth factor (EGF) were released only after 30'. Incubation at 40°C/10' increased VEGF (+70%) and decreased EGF (-30%) and PDGF-BB (-50%) versus 22°C/30'. Shock significantly increased TGF-β (1.6-fold), EGF (1.5-fold), FGF (4.5-fold) and lowered PDGF isoforms (0.2- to 0.5-fold) versus prolonged incubation at 40°C.

CONCLUSION

Platelets from platelet apheresis and whole-blood release all investigated growth factors. The release can be regulated controlling incubation time and/or temperature and performing cell lysis.

Treatment of nonhealing diabetic lower extremity ulcers with skin graft and autologous platelet gel: a case series

Lower extremity ulcers in diabetic patients are difficult to treat. Recently, the use of human blood platelet-derived components in this indication has been raising interest. In this study, we have evaluated the safety and efficacy of the combination of autologous platelet gel (PG) and skin graft for treating large size recalcitrant ulcers. Eight consecutive diabetic patients aged 25 to 82 with nine nonhealing lower extremity ulcers (median size of 50 cm²; range 15–150 cm²) were treated. Skin ulcer was debrided, and the wound was sprayed after 7 to 10 days with autologous platelet-rich plasma and thrombin. Thin split-thickness skin graft with multiple slits was then applied on the wound bed and fixed with staples or cat-gut sutures. There were no adverse reactions observed during the study. Eight out of 9 skin grafts took well. The interval between skin graft and complete wound healing ranged from 2 to 3 weeks in the 8 successful cases. No ulcer recurrence was noted in those patients during the follow-up period of 2 to 19 months. In this study, the combination of autologous platelet gel and skin grafting has proven beneficial to heal large-size recalcitrant ulcers.

Bio-modulators in platelet-rich plasma: a comparison of the amounts in products from healthy donors and patients produced with three different techniques

BACKGROUND

Platelet-rich plasma consists of platelets concentrated in a small volume of plasma and constitutes a reservoir of bio-modulators potentially useful in tissue repair. The amounts of bio-modulators detectable in platelet-rich plasma prepared with various commercial or "in house" methods have been reported, but virtually all the analyses described have been performed on platelet-rich plasma derived from healthy donors. Since leucocyte contamination is technically unavoidable, we investigated whether platelet-rich plasma prepared from patients could contain different amounts of bio-modulators because of a possible activated status of the leucocytes.

MATERIALS AND METHODS

We evaluated platelet-rich plasma prepared with three different techniques (the commercial Vivostat and Biomet recover GPS II systems and an "in house" method) starting from whole blood from healthy donors and patients. Specifically, we compared the levels of sHLA-I, sFasL, platelet-derived growth factor, transforming growth factors-beta and vascular endothelial growth factor in the platelet-rich plasma releasates according to the method of preparation and to the immune system activation status of the subjects.

RESULTS

With the exception of sHLA-I levels, no differences were found in the surrogate indices of lymphocyte activation between healthy donors and patients. No significant differences were found in sHLA-I, sFasL, platelet-derived growth factor, transforming growth factors-beta and vascular endothelial growth factor levels detectable in platelet-rich plasma produced with the three different methods in either healthy donors or patients.

DISCUSSION

On the whole our findings indicate that the overall content of bio-modulators in autologous platelet-rich plasma is not influenced by T-lymphocyte activation status, at least in patients with uncomplicated femoral fractures. The amounts of sFasL and sHLA-I detected in all the platelet-rich plasma releasates studied were very small, far below the amounts detectable in all clinically available blood derivatives and absolutely insufficient to induce sHLA-I and/or sFasL mediated immunomodulation.

"Reasonable compromise" to define the quality standards of platelet concentrate for non-transfusion use (CPunT)

Platelets concentrate for non-transfusion use (CPunT) is a blood component specific for regenerative medicine. This blood component has found regenerative applications in many clinical fields (orthopedic, plastic surgery, maxillofacial surgery) since platelets contain growth factors, cytokines and bioactive molecules. Plasticity and ease of preparation of this blood component has often led the user to prepare it without using standardized procedures and references to quality product standards, but to evaluate the effectiveness of treatments and to standardize clinical protocols, is essential. The complexity of establish functional and non-functional parameters to define CPunT properties is linked to three fundamental steps: variability and bioavailability of biomolecules content in platelets, variability in product preparation. Then it is very difficult to understand which are the real parameters to evaluate, but it seems a "reasonable compromise" to establish content of platelets×ml (1×10(9)ml) as reference realistic parameter for CPunT qualification.

Antimicrobial activity of platelet (PLT)-poor plasma, PLT-rich plasma, PLT gel, and solvent/detergent-treated PLT lysate biomaterials against wound bacteria

BACKGROUND

Platelet (PLT) gels exhibit antimicrobial activity useful for wound healing. The nature of the antibacterial component(s) is unknown.

STUDY DESIGN AND METHODS

PLT-poor plasma (PPP), PLT-rich plasma (PRP), PLT gel (PG), and solvent/detergent-treated PLT lysate (S/D-PL) from two donors were evaluated either native or after complement heat inactivation. Materials were spiked at a 10% ratio (vol/vol) with approximately 10(7-8) colony-forming units/mL with four Gram-positive and four Gram-negative bacteria of the wound flora. Bacterial count was determined by plate assays at time of spiking and after 3 and 48 hours at 31°C. Bacteria growth inhibition tests were also performed.

RESULTS

There was no viable Escherichia coli colony for 48 hours after spiking to the plasma and PLT materials from both donors, corresponding to greater than 7.51 to greater than 9.05 log inactivation. Pseudomonas aeruginosa, Klebsiella pneumoniae, and Staphylococcus aureus were inactivated (approx. 4.7, 7, and 2 log, respectively) 3 hours after spiking to PRP, PPP, or S/D-PL from the first donor but less (1.1, 4.6, and 0.2 log, respectively) in PG, before a regrowth at 48 hours in all materials. Similar data were obtained with the second donor. No plasma and PLT material had antimicrobial activity against Enterobacter cloacae, Bacillus cereus, Bacillus subtilis, and Staphylococcus epidermidis. Complement-inactivated samples had no antimicrobial activity.

CONCLUSION

Plasma complement is mostly responsible for the activity of plasma and PLT biomaterials against E. coli, P. aeruginosa, K. pneumoniae, and S. aureus. Activation of the coagulation to prepare PG may reduce antimicrobial activity. These findings may help optimize the control of wound infections by blood biomaterials.