Autologous platelet-rich plasma isolated using the Haemonetics Cell Saver 5 and Haemonetics MCS+ for the preparation of platelet gel

PRP in wound healing applications

Platelets play a crucial role in hemostasis, tissue regeneration and host defense. Based on these settings, platelet-rich plasma (PRP) and its derivatives are therapeutically used to promote wound healing in several scenarios. This review summarizes the biological mechanisms underlying the most traditional as well as innovative applications of PRP in wound healing. These mechanisms involve the combined action of platelet-derived growth factors and cytokines, together with the role of plasma-derived fibrillar, antioxidant and homeostatic factors. In addition, regenerative treatments with PRP consist of personalized and non-standardized methods. Thus, the quality of PRP varies depending on endogenous factors (e.g., age; gender; concomitant medication; disease-associated systemic factors; nutrition) and exogenous factors (anticoagulants and cellular composition). This review also analyses whether these factors affect the biological mechanisms of PRP in wound healing applications.

Assessment of Quality of Platelet-Rich Plasma Produced With Desktop Centrifuge and Comparison With Standardized Commercially Available Platelet-rich plasma

Aims:

The aim of this study was to assess the quality of platelet-rich plasma (PRP) produced by in-house desktop centrifuge method and compare it with that of standardized commercial PRP.

Materials and Methods:

REMI desktop centrifuge was used to prepare PRP and to compare with standardized commercial PRP by calculating the quantity of platelets using Beckman Coulter cell counter in 10 PRP samples and assessing the morphological quality of platelets using JEOL JEM transmission electron microscope (TEM).

Statistical Analysis Used:

The t test for platelet count in desktop PRP with the test value of therapeutic PRP was 12.618. The P value was <0.001, which was significant statistically. The data followed a normal distribution in normal Q-Q plot for platelet count in desktop centrifuge. So the test samples were not much deviated.

Results:

The platelet count was lesser than that of standardized commercial PRP. When viewed under JEOL JEM transmission electron microscope, the α granules in platelets were intact and the morphological quality of the PRP was good.

Conclusions:

With this study, we have determined that the morphological quality of PRP produced by the in-house desktop centrifuge method is comparable to that of standardized commercial PRP. Though the quantity of platelets was less than 1 million cells/μL, the clinical results were good with desired bone formation, thereby providing good avenue for further research.

Anticoagulants Interfere With the Angiogenic and Regenerative Responses Mediated by Platelets

Background and aims

Platelet rich plasma (PRP) obtained from blood anticoagulated with acid-citrate-dextrose (ACD) or sodium-citrate (SC) is used for regenerative medicine as source of platelet-derived growth factors. Allergic reactions against citrate were reported in patients after local injection of PRP allowing us to hypothesize that anticoagulants exert a harmful and local effect that interferes with the regenerative proprieties of platelets. Herein we test this hypothesis by analyzing the effect of ACD and SC on angiogenic and regenerative responses mediated by platelets.

Methods

PRP was obtained from SC- or ACD-anticoagulated blood; platelets were lysed to release growth factors; and PRP releasates (PRPr) were used to induce in vitro endothelial proliferation and 2D-migration, and regeneration of mouse skin wounds.

Results

We first compared proliferation and migration of endothelial cells mediated by anticoagulated-PRPr supplemented or not with CaCl₂. Alteration of endothelial adhesion and impediment of proliferation and migration was observed without CaCl₂. Although endothelial morphology was normalized in SC- and ACD-PRPr after calcium restitution, angiogenic responses were only markedly induced by SC-PRPr. In vivo studies revealed a delay in mouse skin regeneration after treatment with anticoagulated-PRPr without CaCl₂. Healing was only induced after calcium restitution in SC- but ACD-PRPr. Moreover, the development of inflammatory intradermal papules was evidenced after injection of ACD-PRPr. Supplementation of SC-PRPr with the equivalent concentration of dextrose (D-Glucose, 18 mM) present in ACD-PRPr resulted in reduction of endothelial proliferation and migration, delay of mouse skin regeneration and development of intradermal papules. Finally, collecting blood with half amount of SC significantly improved all the angiogenic and regenerative responses mediated by PRPr. In contrast, the delay of skin regeneration and the development of inflammatory papules remained stable after dilution of ACD.

Conclusion

Our findings indicate that (1) calcium restitution is required to impair the cellular and tissue alterations induced by citrated-anticoagulants contained in PRP; (2) ACD-derived dextrose confers anti-angiogenic, anti-regenerative and pro-inflammatory proprieties to PRP; and (3) half concentration of SC improves the angiogenesis and regeneration mediated by PRP.

Efficacy of platelet-rich plasma for non-transfusion use: Overview of systematic reviews

INTRODUCTION

Platelet-rich plasma (PRP) is a blood component therapy with a supraphysiological concentration of platelets derived from allogenic or, more commonly, autologous blood. PRP has been used in different non-transfusion indications because of its role in the promotion of tissue repair and healing, in fields such as Traumatology, Dermatology and Dentistry.

OBJECTIVE

To provide a synthesis of the efficacy of PRP for different clinical situations.

METHODS

Systematic searches were carried out in MEDLINE, Embase, Cochrane Library and LILACS in July 2018 to identify systematic reviews (SRs) of randomized clinical trials (RCTs) focusing on PRP for non-transfusion use. Two authors independently screened all retrieved references in two stages (titles and abstracts at a first stage and full texts at a second stage). The methodological quality of SRs that met the eligibility criteria was appraised by AMSTAR 2. Conclusions were based on the most recent SRs with highest quality.

RESULTS

One thousand two hundred and forty references were retrieved. After checking the inclusion criteria, 29 SRs of RCTs related to three different fields (wound care, Orthopedics and Dentistry) were included. The results suggest the benefit of PRP for different clinical situations, such as diabetic wounds, acute lesions of musculoskeletal system, rotator cuff lesions, tendinopathies, knee and hip osteoarthritis, total knee arthroplasty, allogenic bone graft for dental implants and periodontal intrabony defects.

CONCLUSION

There is low to moderate quality evidence supporting the efficacy of PRP for specific clinical situations. The low quality of the evidence limits the certainty of these findings. Well-planned and well-conducted RCTs are still needed to further assess the efficacy of PRP.

Clinical and Structural Evaluations of Rotator Cuff Repair With and Without Added Platelet-Rich Plasma at 5-Year Follow-up: A Prospective Randomized Study

BACKGROUND

Platelet-rich plasma (PRP) has been studied with the objective of reducing the retear rate and improving functional outcomes after rotator cuff repair. Only one study to date has reported its midterm effect.

HYPOTHESIS

PRP promotes better functional and structural results in arthroscopic rotator cuff repair.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

All patients underwent arthroscopic single-row repair of small to medium supraspinatus tears. At the end of the surgical procedure, liquid PRP prepared by apheresis with autologous thrombin was applied in the tendon-to-bone interface in the PRP group. The outcomes were assessed by the University of California, Los Angeles (UCLA) and Constant scales and the visual analog scale (VAS) for pain at 6, 12, 24, and 60 months after surgery and magnetic resonance imaging at 12 and 60 months.

RESULTS

Of 54 patients initially randomized, we analyzed the clinical outcomes in 51 (25 control, 26 PRP) and the structural outcomes in 44 (22 each group). At 60-month follow-up, the mean UCLA scores were 32.5 ± 3.8 and 32.1 ± 4.6 in the control and PRP groups, respectively ( P = .992). The mean Constant scores were 82.0 ± 9.5 in the control group and 82.1 ± 11.0 in the PRP group ( P = .699). The mean VAS scores were 1.4 ± 1.8 and 1.5 ± 2.1 in the control and PRP groups, respectively ( P = .910). None of the clinical assessments at 6, 12, and 24 months in either group produced statistically significant differences, and both groups showed significant improvements throughout the follow-up time in the 3 evaluations ( P < .001). The control group exhibited 1 full-thickness retear (Sugaya type IV) and 11 partial-thickness retears (Sugaya type III), while the PRP group had 7 partial-thickness retears (Sugaya type III). The overall number of retears did not differ between groups ( P = .203).

CONCLUSION

PRP obtained by apheresis and applied in liquid form with the addition of thrombin at the end of single-row repair of supraspinatus tears did not promote better clinical or structural results at 60-month follow-up.

REGISTRATION

NCT01029574 ( ClinicalTrials.gov identifier).

Platelet-rich plasma in rotator cuff repair: a prospective randomized study

BACKGROUND

Although platelet-rich plasma (PRP) has been used in rotator cuff repair, most authors have been unable to report the advantages of this method in clinical trials.

HYPOTHESIS

The use of PRP promotes better functional and structural results in arthroscopic rotator cuff repair.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

This was a prospective, randomized, double-blind study with 2 groups of 27 patients each (PRP group and control group). Complete supraspinatus tears with retraction of less than 3 cm were subjected to arthroscopic single-row repair; at the end of the surgical procedure, liquid PRP prepared by apheresis was given to the patients in the PRP group with autologous thrombin. The outcomes were assessed by the University of California at Los Angeles (UCLA) and Constant scales, visual analog scale (VAS) for pain, and magnetic resonance imaging (MRI) before and 3, 6, 12, and 24 months after surgery. The significance level was 5%.

RESULTS

The 2 groups of patients exhibited significant clinical improvement (P < .001). Between the preoperative assessment and 24-month follow-up, the mean UCLA score increased from 13.63 ± 3.639 to 32.70 ± 3.635 and from 13.93 ± 4.649 to 32.44 ± 4.318 in the control and PRP groups, respectively (P = .916). The mean Constant score increased from 47.37 ± 11.088 to 85.15 ± 9.879 in the control group and from 46.96 ± 11.937 to 84.78 ± 14.048 in the PRP group (P = .498). The mean VAS score varied from 7.00 ± 1.939 and 6.67 ± 1.617 before surgery to 1.15 ± 1.916 and 0.96 ± 2.244 at the 24-month assessment in the control and PRP groups, respectively (P = .418). The only difference was in the mean UCLA score at 12 months, with 30.04 ± 4.528 in the control group and 32.30 ± 3.506 in the PRP group (P = .046). The control group exhibited 1 case of a complete retear and 4 partial retears, and the PRP group exhibited 2 cases of partial retears (P = .42).

CONCLUSION

Platelet-rich plasma prepared by apheresis and applied in the liquid state with thrombin did not promote better clinical results at 24-month follow-up. Given the numbers available for analysis, the retear rate also did not change.

Optimizing platelet-rich plasma gel formation by varying time and gravitational forces during centrifugation

Despite the increasing clinical use of topical platelet-rich plasma (PRP) to enhance tissue healing and regeneration, there is no properly standardized method of autologous PRP gel preparation. This study examined the effect of the centrifugation time and gravitational force (g) on the platelet recovery ratio of PRP and determined the most effective centrifugation conditions for preparing PRP. Two-step centrifugations for preparing PRP were used in 39 subjects who had consented prior to the study's start. The separating centrifugation (Step 1, used to separate whole blood into its two main components: red blood cells and plasma) was tested from 500g to 1900g at 200g increments for 5 minutes (min), and from 100g to 1300g at 200g increments for 10 minutes. After separating centrifugation, upper plasma layer was transferred to another plain tube for the condensation centrifugation and remaining lower cell layer was discarded. The condensation centrifugation (Step 2, used to condense the platelets in the separated plasma) was tested at 1000g for 15 min, 1500g for 15 min, 2000g for 5 min and 3000g for 5 min, additionally at 1000g for 10 min and 1500g for 10 min. Platelet gelation was induced by adding 10% calcium gluconate to final PRP with volume ratio of 1:10. The optimal separating centrifugation conditions were followed by 900g for 5 minutes and the condensation conditions were followed by 1500g for 15 minutes, of which recovery ratios were 92.0 ± 3.1% and 84.3 ± 10.0%, respectively.

Growth-promoting action and growth factor release by different platelet derivatives

Abstract Platelet derivatives are commonly used in wound healing and tissue regeneration. Different procedures of platelet preparation may differentially affect growth factor release and cell growth. Preparation of platelet-rich fibrin (PRF) is accompanied by release of growth factors, including platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF) and transforming growth factor β1 (TGFβ1), and several cytokines. When compared with the standard procedure for platelet-rich plasma (PRP), PRF released 2-fold less PDGF, but >15-fold and >2-fold VEGF and TGFβ1, respectively. Also, the release of several cytokines (IL-4, IL-6, IL-8, IL-10, IFNγ, MIP-1α, MIP-1β and TNFα) was significantly increased in PRF-conditioned medium (CM), compared to PRP-CM. Incubation of both human skin fibroblasts and human umbilical vein endothelial cells (HUVECs) with PRF-derived membrane (mPRF) or with PRF-CM enhanced cell proliferation by >2-fold (p<0.05). Interestingly, PRP elicited fibroblast growth at a higher extent compared to PRF. At variance, PRF effect on HUVEC growth was significantly greater than that of PRP, consistent with a higher concentration of VEGF in the PRF-CM. Thus, the procedure of PRP preparation leads to a larger release of PDGF, as a possible result of platelet degranulation, while PRF enhances the release of proangiogenic factors.

BLOOD-DERIVED, TISSUE ENGINEERING BIOMATERIALS

Fibrin sealant and platelet gels are human blood-derived, biodegradable, non toxic, surgical products obtained by mixing a fibrinogen concentrate or a platelet rich plasma with thrombin, respectively. Fibrin sealant is now a well known surgical tool increasingly used to stop or control bleeding, or to provide air and fluid tightness in many surgical situations. Platelet gels are newly developed preparations that are of specific interest because they contain numerous physiological growth factors and cytikines that are released upon the activation of blood platelets by thrombin. These growth factors, including PDGF, TGF-β 1, BMP, and VEGF have been shown to stimulate cell growth and differentiation with special clinical benefits for soft and bony tissue healing and regeneration. Platelet gels allow surgeons to manipulate the cellular environment of surgical sites and to guide tissue regeneration. A specific interest of such products is observed for the induction of osteogenesis and chondrogenesis. Advances in the preparation, clinical use, and safety of these two important classes of blood-derived biomaterials are reviewed.

PLATELET-RICH PLASMA IN ARTHROSCOPIC REPAIRS OF COMPLETE TEARS OF THE ROTATOR CUFF

Objective: To evaluate shoulder functional results and the retear rate of arthroscopic repair of the rotator cuff augmented with platelet-rich plasma (PRP).Methods: Prospective case series with single-row arthroscopic repair of the rotator cuff augmented with PRP. Only cases of isolated supraspinatus tears with retraction of less than 3 cm were included in this series. The PRP used was obtained by apheresis. It was applied on liquid consistency in its activated form, with the addition of autologous thrombin. Patients were evaluated after 12 months of the surgical procedure. The Constant-Murley, UCLA and VAS scales were used, and the retear rate was assessed using magnetic resonance imaging (MRI). Results: Fourteen patients were evaluated (14 shoulders). The mean Constant-Murley score was 45.64 ± 12.29 before the operation and evolved to 80.78 ± 13.22 after the operation (p < 0.001). The UCLA score increased from 13.78 ± 5.66 to 31.43 ± 3.9 (p < 0.001). The patients’ pain level decreased from a median of 7.5 (p25% = 6, p75% = 8) to 0.5 (p25% = 0, p75% = 3) (p = 0.0013) according to the VAS score. None of the patients presented complete retear. Three patients (21.4%) showed partial retear, without transfixation. Only one patient developed complications (adhesive capsulitis). Conclusion: Patients submitted to arthroscopic rotator cuff repair augmented with PRP showed significant functional improvement and none of them had complete retearing.

Efeito do Plasma Rico em Plaquetas na apoptose pós-traumática de condrócitos

OBJETIVO: Avaliar se a injeção intra-articular de Plasma rico em plaquetas (PRP) pode reduzir a apoptose pós-traumática de condrócitos. MÉTODOS: Foi desenvolvido um estudo experimental duplo-cego com quatro joelhos de coelhos adultos. Após a anestesia, os animais foram submetidos à contusão padronizada dos joelhos. Depois foi injetado 1ml de PRP humano nos dois joelhos esquerdos e 1ml de solução fisiológica (SF) nos dois joelhos direitos. Os dois coelhos foram mantidos no mesmo ambiente sob controle de temperatura, de atividades diárias e de alimentação. A eutanásia dos animais ocorreu dez dias após a intervenção e foram realizadas biópsias da cartilagem de cada joelho. As peças foram preparadas para análise em microscopia eletrônica (ME). RESULTADOS: Quatro preparados para ME foram obtidos, cada um correspondendo a um joelho. Os joelhos-PRP apresentaram as taxas de apoptose de 47,62% (50/105) e de 48,36% (59/122), respectivamente. Nos joelhos-SF as taxas de apoptose foram, respectivamente, 56,67% (17/30) e 70,40% (88/125). A diferença do índice de apoptose nos joelhos-PRP (48,02%) e nos joelhos-SF (67,74%) foi significante (p<0,001) e OR=0,439 (IC95%=0.287-0.673). CONCLUSÃO: A injeção intra-articular de PRP imediatamente ao trauma, reduz as taxas de apoptose (pós-traumática) de condrócitos de coelhos.

Comparison between Platelet-Rich Plasma and Autologous Iliac Grafts for Tibial Osteotomy

OBJECTIVE

Platelet-rich plasma (PRP) has the capacity to improve the bone-healing process. The aim of this pilot study was to investigate the occurrence of bone healing and the time taken to achieve this in patients submitted to medial opening wedge high tibial osteotomy (MOWHTO), comparing platelet-rich plasma with bone marrow aspirate to autologous iliac graft.

DESIGN

Twenty-five patients who underwent tibial osteotomy were randomly divided into 2 groups: a control group, which received autologous iliac grafts (14 patients), and a study group, which received a compound of PRP and bone marrow aspirate (11 patients).

RESULTS

The bone-healing rates achieved were 100% in the control group and 91% in the study group. There was no difference in the time taken to achieve bone healing between the groups.

CONCLUSIONS

The use of a combination of PRP and bone marrow aspirate, as a bone substitute, did not demonstrate any advantage over the use of an autologous iliac graft in MOWHTO.

The Clinical Use of Human Culture-Expanded Autologous Bone Marrow Mesenchymal Stem Cells Transplanted on Platelet-Rich Fibrin Glue in the Treatment of Articular Cartilage Defects: A Pilot Study and Preliminary Results

OBJECTIVE: To test the hypothesis that platelet-rich fibrin glue (PR-FG) can be used clinically as a scaffold to deliver autologous culture-expanded bone marrow mesenchymal stem cells (BM-MSCs) for cartilage repair and to report clinical results 1 y after implantation of MSCs PR-FG. PATIENTS AND METHODS: Autologous BM-MSCs were culture expanded, placed on PR-FG intraoperatively, and then transplanted into 5 full-thickness cartilage defects of femoral condyles of 5 patients and covered with an autologous periosteal flap. Patients were evaluated clinically at 6 and 12 mo by the Lysholm and Revised Hospital for Special Surgery Knee (RHSSK) scores and radiographically by x-rays and magnetic resonance imaging (MRI) at the same time points. Repair tissue in 2 patients was rated arthroscopically after 12 mo using the International Cartilage Repair Society (ICRS) Arthroscopic Score. STUDY DESIGN: Case series; level of evidence 4. RESULTS: All patients' symptoms improved over the follow-up period of 12 mo. Average Lysholm and RHSSK scores for all patients showed statistically significant improvement at 6 and 12 mo postoperatively (P < 0.05). There was no statistically significant difference between the 6 and 12 mo postoperative clinical scores (P = 0.18). ICRS arthroscopic scores were 8/12 and 11/12 (nearly normal) for the 2 patients who consented to arthroscopy. MRI of 3 patients at 12 mo postoperatively revealed complete defect fill and complete surface congruity with native cartilage, whereas that of 2 patients showed incomplete congruity. CONCLUSION: Autologous BM-MSC transplantation on PR-FG as a cell scaffold may be an effective approach to promote the repair of articular cartilage defects of the knee in human patients.

Blood components for topical use in tissue regeneration: evaluation of corneal lesions treated with platelet lysate and considerations on repair mechanisms

BACKGROUND

The fields of application of topically administered platelet derivatives are numerous and increasing. The use of this blood component is based on the fact that it contains growth factors and proteins of the clotting system. Studies carried out so far have been aimed at identifying these substances, assaying their content in the various types of platelet concentrate used, determining the in vivo and in vitro mechanisms of action, and trying to standardise the production methods. However, much still remains to be discovered, not only about the growth factors, but also about all those cytokines and biochemical mediators that are involved in the processes of tissue regeneration.

METHODS

We studied the use of platelet lysate, obtained from platelet-rich plasma which had been frozen, for the treatment of corneal ulcers caused by neurotrophic keratitis and of epithelial and stromal loss following physical or chemical trauma. The platelet lysate was administered in the form of eye drops to patients who had not responded to conventional therapy and who were at risk of corneal scarring.

RESULTS

The results were satisfactory in terms of both tissue regeneration and healing time. The clinical follow-up showed a clear reduction in the time of regeneration of the damaged epithelium and stabilisation of the repair process. The epithelial defects disappeared completely in all the treated eyes within 6 to 32 days, with the time depending on the type of lesion and the severity of the damage.

CONCLUSIONS

The cornea reacts to damage by releasing numerous substances, including cytokines, growth factors, proteases and neuropeptides in order to restore its anatomical integrity. A change in the balance between inhibitory and stimulating substances can lead to the development of complications. Fast, correct re-epithelialisation is fundamental for the formation of new, transparent tissue. The use of non-gelified platelet-rich plasma was found to be effective in all cases with loss of epithelium, such as post-herpetic corneal ulcers or ulcers occurring following trauma or exposure to caustic substances.

THE USE OF PLATELET RICH PLASMA WITH BONE MARROW ASPIRATE IN PUDDU TIBIAL OSTEOTOMY

Objective: The present study was performed in order to evaluate the use of platelet rich plasma associated to bone marrow aspirate, substituting autologous iliac bone graft in medial opening wedge osteotomy (OWHTO). Methods: Twenty-five patients were submitted to tibial opening wedge osteotomy, being divided into two groups. Iliac group: 14 patients submitted to OWHTO, using autologous iliac bone graft to fill the gap. PRP group: 11 patients using platelet rich plasma associated to bone marrow aspirate to fill the gap. We evaluated bleeding (hemoglobin and hematocrit levels) and pain (visual analogic scale-VAS), then we compared the groups regarding these variables. Results: Differences between the groups were not found regarding hemoglobin levels (p=0.820) and hematocrit levels (p=0.323). The groups were not different regarding pain measured with VAS (p=0.538). Conclusion: The use of platelet rich plasma associated to bone marrow aspirate in medial opening wedge osteotomy did not offer advantages over autologous iliac bone graft regarding bleeding and pain.

Synergistic action of protease-modulating matrix and autologous growth factors in healing of diabetic foot ulcers. A prospective randomized trial

This study tests the hypothesis that addition of a protease-modulating matrix enhances the efficacy of autologous growth factors in diabetic ulcers. Fifty-one patients with chronic diabetic foot ulcers were managed as outpatients at the Democritus University Hospital of Alexandroupolis and followed up for 8 weeks. All target ulcers were > or = 2.5 cm in any one dimension and had been previously treated only with moist gauze. Patients were randomly allocated in three groups of 17 patients each: Group A was treated only with the oxidized regenerated cellulose/collagen biomaterial (Promogran, Johnson & Johnson, New Brunswick, NJ), Group B was treated only with autologous growth factors delivered by Gravitational Platelet Separation System (GPS, Biomet), and Group C was managed by a combination of both. All ulcers were digitally photographed at initiation of the study and then at change of dressings once weekly. Computerized planimetry (Texas Health Science Center ImageTool, Version 3.0) was used to assess ulcer dimensions that were analyzed for homogeneity and significance using the Statistical Package for Social Sciences, Version 13.0. Post hoc analysis revealed that there was significantly greater reduction of all three dimensions of the ulcers in Group C compared to Groups A and B (all P<.001). Although reduction of ulcer dimensions was greater in Group A than in Group B, these differences did not reach statistical significance. It is concluded that protease-modulating dressings act synergistically with autologous growth factors and enhance their efficacy in diabetic foot ulcers.

Platelet-rich plasma inhibits demineralized bone matrix-induced bone formation in nude mice

BACKGROUND

It is unclear whether platelet-rich plasma is a clinically effective adjunct to osteoinductive agents such as demineralized bone matrix. It contains platelet-derived growth factor (PDGF), which decreases osteoinduction by human demineralized bone matrix in nude-mouse muscle, suggesting that platelet-rich plasma may also have a negative impact. This study tested the hypothesis that platelet-rich plasma reduces demineralized bone matrix-induced bone formation and that this effect varies with donor-dependent differences in platelet-rich plasma and demineralized bone matrix.

METHODS

Human platelet-rich plasma was prepared from blood from six men (average age [and standard error of the mean], 29.2 +/- 2.4 years). Platelet numbers were determined, and growth factors were quantified before and after platelet activation. Human demineralized bone matrix from two donors (demineralized bone matrix-1 and demineralized bone matrix-2) was mixed with activated platelet-rich plasma and was implanted bilaterally in the gastrocnemius muscle in eighty male nude mice (eight implants per variable). Fifty-six days after implantation, the hindlimb calf muscles were harvested for histological analysis. Osteoinduction was evaluated with use of a qualitative score and morphometric measurements of ossicle size, new bone formation, and residual demineralized bone matrix.

RESULTS

Compared with platelet-poor plasma, platelet-rich plasma preparations exhibited a fourfold increase in the platelet count, a fifteenfold increase in the amount of transforming growth factor-beta, a sixfold increase in the amount of PDGF-BB, a fivefold increase in the amount of PDGF-AA, and a twofold increase in the amount of PDGF-AB. Demineralized bone matrix-1 was more osteoinductive than demineralized bone matrix-2, as determined on the basis of a greater ossicle area. The effect of platelet-rich plasma was either neutral or inhibitory depending on the demineralized bone matrix batch. When used with demineralized bone matrix-1, platelet-rich plasma did not alter the qualitative score or overall ossicle size, but it decreased the new bone area. When used with demineralized bone matrix-2, platelet-rich plasma reduced the qualitative score, ossicle area, and new bone area and increased the amount of residual demineralized bone matrix. The effects on osteoinduction also varied with the donor of the platelet-rich plasma.

CONCLUSIONS

Platelet-rich plasma decreased the osteoinductivity of demineralized bone matrix implanted in immunocom-promised mice, and the activities of both demineralized bone matrix and platelet-rich plasma were donor-dependent.

Thrombin‐activated platelets induce proliferation of human skin fibroblasts by stimulating autocrine production of insulin‐like growth factor‐1

Platelet components have found successful clinical utilization to initiate or to accelerate tissue-repair mechanisms. However, the molecular pathways by which platelet factors contribute to tissue regeneration have not been fully elucidated. We have studied the effect of thrombin-activated platelets (TAPs) on cell growth in vivo and in cultured cell systems. Application of TAPs to ulcerative skin lesions of diabetic patients induced local activation of ERK1/2 and Akt/PKB. Moreover, when applied to cultured human skin fibroblasts, TAPs promoted cell growth and DNA synthesis and activated platelet-derived growth factor (PDGF) and insulin-like growth factor (IGF)-1 receptor tyrosine kinases. PDGF was released by TAPs and rapidly achieved a plateau. At variance, the release of IGF-1 was mainly provided by the TAPs-stimulated fibroblasts and progressively increased up to 48 h. The PDGF-R blocker Ag1296 reduced the activation of Akt/PKB and, at a lesser extent, of ERK1/2. Conversely, inhibition of IGF-1 signaling by Ag1024 and expression of a dominant-negative IGF-1R mutant selectively reduced the stimulation of ERK1/2 by TAPs and fibroblast-released factors, with minor changes of Akt/PKB activity. Thus, platelet factors promote fibroblast growth by acutely activating Akt/PKB and ERK1/2. Sustained activation of ERK1/2, however, requires autocrine production of IGF-1 by TAPs-stimulated fibroblasts.

Platelet gel for healing cutaneous chronic wounds

Wound healing is a specific host immune response for restoration of tissue integrity. Experimental studies demonstrated an alteration of growth factors activity due to their reduced synthesis, increased degradation and inactivation. In wound healing platelets play an essential role since they are rich of alpha-granules growth factors (platelet derived growth factor--PDGF; transforming growth factor-beta--TGF-beta; vascular endothelial growth factor--VEGF). Topical use of platelet gel (PG), hemocomponent obtained from mix of activated platelets and cryoprecipitate, gives the exogenous and in situ adding of growth factors (GF). The hemocomponents are of autologous or homologous origin. We performed a technique based on: multicomponent apheretic procedure to obtain plasma rich platelet and cryoprecipitate; manual processing in an open system, in sterile environment, for gel activation. Every step of the gel synthesis was checked by a quality control programme. The therapeutic protocol consists of the once-weekly application of PG. Progressive reduction of the wound size, granulation tissue forming, wound bed detersion, regression and absence of infective processes were considered for evaluating clinical response to hemotherapy. 24 patients were enrolled. They had single or multiple cutaneous ulcers with different ethiopathogenesis. Only 3 patients could perform autologous withdrawal; in the others homologous hemocomponent were used, always considering suitability and traceability criteria for transfusional use of blood. Complete response was observed in 9 patients, 2 were subjected to cutaneous graft, 4 stopped treatment, 9 had partial response and are still receiving the treatment. In each case granulation tissue forming increased following to the first PG applications, while complete re-epithelization was obtained later. Pain was reduced in every treated patient. Topical haemotherapy with PG may be considered as an adjuvant treatment of a multidisciplinary process, useful to enhance therapy of cutaneous ulcers.

Comparison of hematologic values and transforming growth factor- and insulin-like growth factor concentrations in platelet concentrates obtained by use of buffy coat and apheresis methods from equine blood

OBJECTIVE

To evaluate the buffy coat and apheresis methods for preparation of platelet concentrates from equine blood by comparing platelet and growth factor concentrations.

ANIMALS

15 mature mixed-breed geldings.

PROCEDURE

Whole blood samples were collected and processed by use of a buffy coat or apheresis method to obtain platelet poor and platelet concentrated fractions. The PCV, WBC count, and platelet count were compared among whole blood samples, platelet poor fractions, concentrates obtained by use of the apheresis method (ie, apheresis platelet concentrates), and concentrates obtained by use of the buffy coat method (ie, buffy coat platelet concentrates). Concentrations of transforming growth factor-beta (ie,TGF-beta1 andTGF-beta2) and insulin-like growth factor were compared between buffy coat and apheresis platelet concentrates.

RESULTS

Platelet concentrations were 8.9-fold and 5.2-fold greater in buffy coat and apheresis platelet concentrates, respectively, compared with whole blood. Platelet concentrations were 13.1-fold greater in filtered apheresis platelet concentrates, compared with whole blood. TGF-beta1 concentrations were 2.8-fold and 3.1-fold greater in buffy coat and apheresis platelet concentrates, respectively, and TGF-beta1 concentrations were 10.5-fold greater in filtered apheresis platelet concentrates, compared with whole blood. TGF-beta2 concentrations were 3.6-fold greater in apheresis platelet concentrates, compared with whole blood. Platelet concentrations correlated with growth factor concentrations across all blood and platelet fractions. White blood cell counts had a significant positive correlation with TGF-beta1 concentration in buffy coat platelet concentrates.

CONCLUSIONS AND CLINICAL RELEVANCE

Platelets and TGF-beta1 can be concentrated reliably from equine blood by use of buffy coat or apheresis methods, without modification of the protocols used for humans.