Optimized preparation method of platelet-concentrated plasma and noncoagulating platelet-derived factor concentrates: maximization of platelet concentration and removal of fibrinogen

Photopolymerizable Platelet Lysate Hydrogels for Customizable 3D Cell Culture Platforms

3D cell culture platforms have emerged as a setting that resembles in vivo environments replacing the traditional 2D platforms. Over the recent years, an extensive effort has been made on the development of more physiologically relevant 3D cell culture platforms. Extracellular matrix-based materials have been reported as a bioactive and biocompatible support for cell culture. For example, human plasma derivatives have been extensively used in cell culture. Despite all the promising results, in most cases these types of materials have poor mechanical properties and poor stability in vitro. Here plasma-based hydrogels with increased stability are proposed. Platelet lysates are modified by addition of methacryloyl groups (PLMA) that polymerize in controlled geometries upon UV light exposure. The hydrogels could also generate porous scaffolds after lyophilization. The results show that PLMA materials have increased mechanical properties that can be easily adjusted by changing PLMA concentration or modification degree. Cells readily adhere, proliferate, and migrate, exhibiting high viability when encapsulated in PLMA hydrogels. The innovation potential of PLMA materials is based on the fact that it is a complete xeno-free solution for human cell culture, thus an effective alternative to the current gold standards for 3D cell culture based on animal products.

Blood Plasma Derivatives for Tissue Engineering and Regenerative Medicine Therapies

Platelet-rich plasma (PRP) and its derivatives have been investigated and applied in regenerative medicine. The use of PRP as a supplement of cell culture media has consistently shown to potentiate stem cell proliferation, migration, and differentiation. In addition, the clinical utility of PRP is supported by evidence that PRP contains high concentrations of growth factors (GFs) and proteins which contribute to the regenerative process. PRP based therapies are cost effective and also benefit from the accessibility and safety of using the patient's own GFs. In the last years, a great development has been witnessed on PRP based biomaterials, with both structural and functional purposes. In this study we overview the most relevant PRP applications encompassing PRP based materials for tissue engineering and regenerative medicine. This review also summarizes the challenges in the fields of tissue engineering and regenerative medicine and provides a perspective on future directions.

Impact of incubation method on the release of growth factors in non-Ca2+-activated PRP, Ca2+-activated PRP, PRF and A-PRF

The aim of this study was to investigate the influence of different incubation methods on the growth factor content of lysates of platelet-rich fibrin (PRF), advanced-platelet-rich fibrin (A-PRF) and platelet-rich plasma (PRP) products. A comparison of related studies suggests that the method of sample preparation has a significant influence on growth factor content. There are few reports on the comparison of non-Ca²⁺-activated PRP, Ca²⁺-activated PRP, A-PRF, and PRF, along with a lack of information on the release of PDGF-BB, TGF-β1, and VEGF among the different incubation methods. The lysate preparation was made of non-Ca²⁺-activated PRP, Ca²⁺-activated PRP, PRF, and A-PRF, using a room-temperature, 37 °C, or freeze-thaw-freeze incubation method. Afterwards the VEGF, PDGF-BB, and TGF-β1 content was investigated by running ELISA tests. Growth factor levels were significantly increased in the non-Ca²⁺-activated PRP with freeze-thaw-freeze incubation, and in the PRF preparation there was a significant disadvantage to using room temperature incubation for releasing growth factors. In conclusion, the freeze-thaw-freeze method is sufficient for releasing growth factors, and calcium activation is not necessary. Finally, the study demonstrates the possibility of preparing PRP products from platelet concentrates, so that preoperative blood sampling might not be required.

A high glucose level is associated with decreased aspirin-mediated acetylation of platelet cyclooxygenase (COX)-1 at serine 529: A pilot study

Diabetes is a major risk factor for cardiovascular diseases. Although aspirin is considered a cornerstone of the prevention and treatment of atherothrombotic-related ischemic events, this antiplatelet drug appears to be less effective in patients with poorly controlled diabetes. It has been suggested that the glycation of platelet proteins plays a pivotal role in poor responsiveness to aspirin. However, a direct effect on the critical residue (serine 529, or Ser 529) of the catalytic pocket of cyclooxygenase 1 (COX-1) has never been demonstrated. This pilot study aimed to elucidate the impact of hyperglycaemia on aspirin acetylation of COX-1 using a targeted mass spectrometry approach. We observed that high glucose concentration had a direct impact on the level of acetylation of the COX-1 Ser 529 residue, whereas it's overall acetylation level remained unchanged. Moreover, the functional aspirin-induced inhibition of COX-1 was dose-dependently impaired as glucose concentrations increased. These in vitro findings were in line with data obtained using platelets from diabetic patients. These data provide new insights into the interplay between glucose and aspirin on platelet proteins and their effects on platelet COX-1. They also suggest a potential mechanistic explanation for the phenomenon of poor response to aspirin in diabetic patients. Data are available via ProteomeXchange with identifier PXD011204. SIGNIFICANCE: Deciphering the mutual interplay between glucose and aspirin-mediated acetylation on platelet COX-1, might be of great interest as there is still a lack of information of the mechanism underlying this process that may contribute to the less-than expected response of platelets to aspirin, often observed in diabetes.

1H-NMR and MALDI-TOF MS as metabolomic quality control tests to classify platelet derived medium additives for GMP compliant cell expansion procedures

Introduction

Ex vivo cell expansion under Good Manufacturing Practice (GMP) guidelines can be performed using medium additives containing human growth factors from platelets. These products can differently affect proliferation of adipose mesenchymal stromal stem cells (ASC). Qualification of medium additive performance is required for validation under GMP regulations: assessment of growth factor concentrations is not sufficient to predict the biological activity of the product batch. Proton nuclear magnetic resonance spectrometry (¹H-NMR) and matrix-assisted laser desorption/ionization time of flight mass spectroscopy (MALDI-TOF MS) provide wide molecular characterization of samples.

Aims

We aimed to assess if ¹H-NMR and MALDI-TOF MS techniques can be used as quality control test potentially predicting the impact of a medium additive on cell proliferation.

Methods

We tested the impact on ASC growth rate (cell proliferation assessment and cell morphology analysis) of four medium additives, obtained by different methods from human platelet apheresis product. In order to classify each medium additive, we evaluated growth factor concentrations and spectra obtained by ¹H-NMR and by MALDI-TOF MS.

Results

Medium additive obtained by CaCl₂ activation of platelet rich products induced higher proliferation rate vs additive derived from platelet depleted ones. Additives obtained by freeze-and-thaw methods weakly induced ASC proliferation. As expected, principal component analysis of growth factor concentrations did not unravel specific biochemical features characterizing medium additives in relation with their biological activity. Otherwise, while ¹H-NMR showed a partial resolution capacity, analysis of MALDI-TOF MS spectra allowed unambiguous distinction between the medium additives we used to differently stimulate cell growth in vitro.

Discussion

MALDI-TOF and, despite limitations, ¹H-NMR are promising cost effective and reliable quality controls to classify the potential of a medium additive to promote ASC growth. This can represent, after further investigations and appropriate validation, a significant advantage for GMP compliant manufacturing of advanced cell therapy products.

Hyperacute serum has markedly better regenerative efficacy than platelet-rich plasma in a human bone oxygen-glucose deprivation model

AIM

Platelet-rich plasma (PRP) and hyperacute serum (HAS) were compared in a novel human model of ex vivo bone damage induced by oxygen-glucose deprivation (OGD).

MATERIALS & METHODS

Osteoarthritic subchondral bone pieces were harvested from discarded femoral heads during hip replacement surgery and subjected to transient OGD.

RESULTS

Proteome profiling revealed that PRP is more angiopoietic, whereas HAS is more antiangiopoietic in composition. However, treatment of OGD-exposed bone with multiple PRP preparations had no effect on cell counts, whereas HAS restored cell proliferation capacity and rescued viable cell number following OGD.

CONCLUSION

A similar pro-proliferation effect was observed with recombinant growth factors, indicating that HAS may be an alternative agent for enhancing the regeneration of damaged bone cells.

Advancements in Regenerative Strategies Through the Continuum of Burn Care

Burns are caused by several mechanisms including flame, scald, chemical, electrical, and ionizing and non-ionizing radiation. Approximately half a million burn cases are registered annually, of which 40 thousand patients are hospitalized and receive definitive treatment. Burn care is very resource intensive as the treatment regimens and length of hospitalization are substantial. Burn wounds are classified based on depth as superficial (first degree), partial-thickness (second degree), or full-thickness (third degree), which determines the treatment necessary for successful healing. The goal of burn wound care is to fully restore the barrier function of the tissue as quickly as possible while minimizing infection, scarring, and contracture. The aim of this review is to highlight how tissue engineering and regenerative medicine strategies are being used to address the unique challenges of burn wound healing and define the current gaps in care for both partial- and full-thickness burn injuries. This review will present the current standard of care (SOC) and provide information on various treatment options that have been tested pre-clinically or are currently in clinical trials. Due to the complexity of burn wound healing compared to other skin injuries, burn specific treatment regimens must be developed. Recently, tissue engineering and regenerative medicine strategies have been developed to improve skin regeneration that can restore normal skin physiology and limit adverse outcomes, such as infection, delayed re-epithelialization, and scarring. Our emphasis will be centered on how current clinical and pre-clinical research of pharmacological agents, biomaterials, and cellular-based therapies can be applied throughout the continuum of burn care by targeting the stages of wound healing: hemostasis, inflammation, cell proliferation, and matrix remodeling.

Improved GMP compliant approach to manipulate lipoaspirates, to cryopreserve stromal vascular fraction, and to expand adipose stem cells in xeno-free media

Background

The stromal vascular fraction (SVF) derived from adipose tissue contains adipose-derived stromal/stem cells (ASC) and can be used for regenerative applications. Thus, a validated protocol for SVF isolation, freezing, and thawing is required to manage product administration. To comply with Good Manufacturing Practice (GMP), fetal bovine serum (FBS), used to expand ASC in vitro, could be replaced by growth factors from platelet concentrates.

Methods

Throughout each protocol, GMP-compliant reagents and devices were used. SVF cells were isolated from lipoaspirates by a standardized enzymatic protocol. Cells were cryopreserved in solutions containing different albumin or serum and dimethylsulfoxide (DMSO) concentrations. Before and after cryopreservation, we analyzed: cell viability (by Trypan blue); immunophenotype (by flow cytometry); colony-forming unit-fibroblast (CFU-F) formation; and differentiation potential. ASC, seeded at different densities, were expanded in presence of 10% FBS or 5% supernatant rich in growth factors (SRGF) from platelets. The differentiation potential and cell transformation grade were tested in expanded ASC.

Results

We demonstrated that SVF can be obtained with a consistent yield (about 185 × 10³ cells/ml lipoaspirate) and viability (about 82%). Lipoaspirate manipulation after overnight storage at +4 °C reduced cell viability (−11.6%). The relative abundance of ASC (CD34⁺CD45⁻CD31^–) and endothelial precursors (CD34⁺CD45⁻CD31⁺) in the SVF product was about 59% and 42%, respectively. A period of 2 months cryostorage in autologous serum with added DMSO minimally affected post-thaw SVF cell viability as well as clonogenic and differentiation potentials. Viability was negatively affected when SVF was frozen at a cell concentration below 1.3 × 10⁶ cells/ml. Cell viability was not significantly affected after a freezing period of 1 year.

Independent of seeding density, ASC cultured in 5% SRGF exhibited higher growth rates when compared with 10% FBS. ASC expanded in both media showed unaltered identity (by flow cytometry) and were exempt from genetic lesions. Both 5% SRGF- and 10% FBS-expanded ASC efficiently differentiated to adipocytes, osteocytes, and chondrocytes.

Conclusions

This paper reports a GMP-compliant approach for freezing SVF cells isolated from adipose tissue by a standardized protocol. Moreover, an ASC expansion method in controlled culture conditions and without involvement of animal-derived additives was reported.

Use of Platelet-Rich Plasma Immediately After an Injury Did Not Improve Ligament Healing, and Increasing Platelet Concentrations Was Detrimental in an In Vivo Animal Model

BACKGROUND

Limited information in basic science and clinical trials exists to determine if ligament healing may be accelerated with the use of biological adjuvants, such as platelet-rich plasma (PRP). However, there has been widespread acceptance of PRP for use in clinical practice, despite an inadequate understanding of its biological mechanism of action.

PURPOSE

To determine whether a single dose of PRP could accelerate ligament healing and correspondingly improve histological characteristics and biomechanical properties when injected immediately postoperatively into the injured medial collateral ligament (MCL) of New Zealand White rabbits.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eighty skeletally mature New Zealand White rabbits (160 knees) were used. The MCL was torn midbody to simulate a grade 3 tear. After an acute injury of the MCL, the administration of autologous PRP at 3 different platelet concentrations (0 million/uL, platelet-poor plasma [PPP]; 0.6 million/uL, 2 times the baseline [2× PRP]; and 1.2 million/uL, 4 times the baseline [4× PRP]) was performed and compared with a saline injection control in the contralateral knee. Histological analysis and a biomechanical endpoint characterization were utilized to assess ligamentous healing and compare it to a sham surgery group.

RESULTS

The PPP ( P = .001) and 4× PRP ( P = .002) groups had a significantly lower collagen subscore than the sham surgery group. No other differences were observed among the treatment groups, including the vascularity subscore and overall ligament tissue maturity index score. Compared with saline-injected contralateral knees, the maximum load for PPP and 2× PRP was not significantly different ( P = .788 and .325, respectively). The maximum load and stiffness for knees treated with 4× PRP were significantly less than for the saline-treated contralateral knees ( P = .006 and .001, respectively).

CONCLUSION

One single dose of PPP or 2× PRP at the time of injury did not improve ligament healing. In addition, 4× PRP negatively affected ligament strength and histological characteristics at 6 weeks after the injury.

CLINICAL RELEVANCE

The current practice of treating knee ligament injuries with PRP may not improve healing at low doses of PRP. The decreased mechanical properties and histological appearance of the torn MCL suggest that high doses of PRP decrease the quality of repair tissue. Further in vivo studies are necessary to determine the dosing and timing of PRP administration after a ligament injury before the widespread use of PRP to treat ligament injuries is recommended.

PRP Therapy

Osteochondral lesions remain as a clinical challenge despite the advances in orthopedic regenerative strategies. Biologics, in particular, platelet-rich plasma, has been applied for the reparative and regenerative effect in many tissues, and osteochondral tissue is not an exception. Platelet-rich plasma is an autologous concentrate prepared from the collected blood; thus, this safe application is free of immune response or risk of transmission of disease. It has a high potential to promote regeneration, thanks to its content, and can be applied alone or can reinforce a tissue engineering strategy. The relevant works making use of platelet-rich plasma in osteochondral lesions are overviewed herein. The practical success of platelet-rich plasma is uncertain since there are many factors involved including but not limited to its preparation and administration method. Nevertheless, today, the issues and challenges of platelet-rich plasma have been well acknowledged by researchers and clinicians. Thus, it is believed that a consensus will be built it, and then with high-quality randomized controlled trials and standardized protocols, the efficacy of platelet-rich plasma therapy can be better evaluated.

HIGHLIGHTS

The need of treating the osteochondral lesions has not been yet met in the clinics. Thanks to being an autologous source of growth factors, interleukins, and other cytokines and relative ease of clinical application, i.e., during a single-step surgical procedure, the use of platelet-rich plasma is of great interest. The high theoretical potential of the role of platelet-rich plasma in the regeneration process of osteochondral lesions is known, and the efficiency needs to be confirmed by high-quality randomized controlled trials for a robust position in the treatments of osteochondral lesions in the clinics.

Theoretical prediction and validation of cell recovery rates in preparing platelet-rich plasma through a centrifugation

In the present study, we propose a theoretical framework to predict the recovery rates of platelets and white blood cells in the process of centrifugal separation of whole blood contained in a tube for the preparation of platelet-rich plasma. Compared to previous efforts to optimize or standardize the protocols of centrifugation, we try to further the physical background (i.e., based on the multiphase flow phenomena) of analysis to develop a universal approach that can be applied to widely different conditions. That is, one-dimensional quasi-linear partial differential equation to describe the centrifugal sedimentation of dispersed phase (red and white blood cells) in continuous phase (plasma) is derived based on the kinematic-wave theory. With the information of whole blood volume and tube geometry considered, it is possible to determine the positions of interfaces between supernatant/suspension and suspension/sediment, i.e., the particle concentration gradient in a tube, for a wide range of centrifugation parameters (time and acceleration). While establishing a theory to predict the recovery rates of the platelet and white blood cell from the pre-determined interface positions, we also propose a new correlation model between the recovery rates of plasma and platelets, which is found to be a function of the whole blood volume, centrifugal time and acceleration, and tube geometry. The present predictions for optimal condition show good agreements with available human clinical data, obtained from different conditions, indicating the universal applicability of our method. Furthermore, the dependence of recovery rates on centrifugal conditions reveals that there exist a different critical acceleration and time for the maximum recovery rate of platelets and white blood cells, respectively. The other parameters such as hematocrit, whole blood volume and tube geometry are also found to strongly affect the maximum recovery rates of blood cells, and finally, as a strategy for increasing the efficiency, we suggest to dilute the whole blood, increase the whole blood volume with a tube geometry fixed.

A Call for Standardization in Platelet-Rich Plasma Preparation Protocols and Composition Reporting: A Systematic Review of the Clinical Orthopaedic Literature

BACKGROUND

Platelet-rich plasma (PRP) is a blood-derived preparation whose use has grown exponentially in orthopaedic practice. However, there remains an unclear understanding of the biological properties and effects of PRP on musculoskeletal healing. Heterogeneous processing methods, unstandardized nomenclature, and ambiguous classifications make comparison among studies challenging. A comprehensive assessment of orthopaedic clinical PRP trials is key to unraveling the biological complexity of PRP, while improving standardized communication. Toward this goal, we performed a systematic review of the PRP preparation protocols and PRP composition utilized in clinical trials for the treatment of musculoskeletal diseases.

METHODS

A systematic review of the literature was performed from 2006 to 2016. Inclusion criteria were human clinical trials, English-language literature, and manuscripts that reported on the use of PRP in musculoskeletal/orthopaedic conditions. Basic-science articles, editorials, surveys, special topics, letters to the editor, personal correspondence, and nonorthopaedic applications (including cosmetic use or dental application studies) were excluded.

RESULTS

A total of 105 studies (in 104 articles) met the inclusion criteria for analysis. Of these studies, only 11 (10%) provided comprehensive reporting that included a clear description of the preparation protocol that could be used by subsequent investigators to repeat the method. Only 17 studies (16%) provided quantitative metrics on the composition of the final PRP product.

CONCLUSIONS

Reporting of PRP preparation protocols in clinical studies is highly inconsistent, and the majority of studies did not provide sufficient information to allow the protocol to be reproduced. Furthermore, the current reporting of PRP preparation and composition does not enable comparison of the PRP products being delivered to patients. A detailed, precise, and stepwise description of the PRP preparation protocol is required to allow comparison among studies and provide reproducibility.

Tenogenically Induced Allogeneic Peripheral Blood Mesenchymal Stem Cells in Allogeneic Platelet-Rich Plasma: 2-Year Follow-up after Tendon or Ligament Treatment in Horses

Poor healing of tendon and ligament lesions often results in early retirement of sport horses. Therefore, regenerative therapies are being explored as potentially promising treatment for these injuries. In this study, an intralesional injection was performed with allogeneic tenogenically induced mesenchymal stem cells and platelet-rich plasma 5-6 days after diagnosis of suspensory ligament (SL) (n = 68) or superficial digital flexor tendon (SDFT) (n = 36) lesion. Clinical, lameness and ultrasonographic evaluation was performed at 6 and 12 weeks. Moreover, a survey was performed 12 and 24 months after treatment to determine how many horses were competing at original level and how many were re-injured. At 6 weeks, 88.2% of SL (n = 68) and 97.3% of SDFT lesions (n = 36) demonstrated moderate ultrasonographic improvement. At 12 weeks, 93.1% of SL (n = 29) and 95.5% of SDFT lesions (n = 22) improved convincingly. Moreover, lameness was abolished in 78.6% of SL (n = 28) and 85.7% (n = 7) of SDFT horses at 12 weeks. After 12 months (n = 92), 11.8% of SL and 12.5% of SDFT horses were re-injured, whereas 83.8 of SL and 79.2% of SDFT returned to previous performance level. At 24 months (n = 89) after treatment, 82.4 (SL) and 85.7% (SDFT) of the horses returned to previous level of performance. A meta-analysis was performed on relevant published evidence evaluating re-injury 24 months after stem cell-based [17.6% of the SL and 14.3% of the SDFT group (n = 89)] versus conventional therapies. Cell therapies resulted in a significantly lower re-injury rate of 18% [95% confidence interval (CI), 0.11-0.25] 2 years after treatment compared to the 44% re-injury rate with conventional treatments (95% CI, 0.37-0.51) based on literature data (P < 0.0001).

Enhanced proliferation and migration capability of epidermal stem cells by PRP and PDGF stimulation

Adult epidermal stem cells renew the epithelial compartment of the skin throughout life and are the most accessible of all adult stem cells. Isolation and culture epidermal stem cells in vitro can both benefit stem cell therapy and tissue-engineering study. In this study, we successfully isolated and cultured epidermal stem cells in vitro, and demonstrated for the first time that PRP and PDGF could promote epidermal stem cell proliferation and migration, which meant PRP and PDGF addition during epidermal stem cell culture can be regarded as an optimized condition to improve the number of harvested cells in a short time. Compared with epidermal stem cells treated with K-SFM medium and platelet-poor plasma, the differences showed in cells treated with PRP and PDGF including: CCK-8 assay showed that cell proliferation was enhanced about twice; the cell cycle analysis showed 7%~12% less cells were arrested in S and G2 phases; western blot assay suggested that PCNA expression was 7-10 times higher; transwell assay also demonstrated that cell migration capability enhanced 8-11 times. These results all proved that the application of PRP and PDGF in epidermal stem cell culture may promote stem cell therapy and tissue-engineered skin study by providing high quantity of seeded cells.

Erythrocyte sedimentation rate and fibrinogen concentration of whole blood influences the cellular composition of platelet-rich plasma obtained from centrifugation methods

Erythrocyte sedimentation rate (ESR), which reflects the sedimentation rate of platelets, leukocytes and erythrocytes in response to centrifugal force, may influence the cellular composition of platelet-rich plasma (PRP) obtained via centrifugation methods. However, no relevant studies have substantiated this. In the present study, blood was collected from 40 healthy volunteers and used to prepare PRP with two plasma-based preparation systems [YinPRP and Plasma Rich in Growth Factor (PRGF) systems] and two buffy coat-based systems (RegenPRP and WEGOPRP systems) in a single-donor model. Volumes of PRP and platelet-poor plasma (PPP) that were removed in the preparation process were recorded. Analyses of ESR, haematocrit, C-reaction protein, coagulation, serum glucose and serum lipid of the whole blood used for PRP preparation were performed to evaluate the levels of ESR and the factors known to influence it. Whole blood analysis was performed to evaluate the cellular composition of PRP. Results demonstrated that there were marked positive correlations between the ESR of the whole blood used for PRP preparation and PPP removal efficiencies, platelet concentrations, platelet capture efficiencies and platelet enrichment factors of PRP formulations obtained from plasma-based systems, and PRP yield efficiency of RegenPRP and PPP removal efficiency of WEGOPRP. Furthermore, there were marked negative correlations between ESR and concentrations and enrichment factors of platelets, leukocytes and erythrocytes of RegenPRP. Fibrinogen concentration of the whole blood, which had a marked positive correlation with ESR, also influenced the cellular composition of PRP. These findings may increase the understanding of PRP preparation and provide substantial evidence for the individualised optimisation of PRP preparation systems used in clinical practice.

Optimisation of a double-centrifugation method for preparation of canine platelet-rich plasma

Background

Platelet-rich plasma (PRP) has been expected for regenerative medicine because of its growth factors. However, there is considerable variability in the recovery and yield of platelets and the concentration of growth factors in PRP preparations. The aim of this study was to identify optimal relative centrifugal force and spin time for the preparation of PRP from canine blood using a double-centrifugation tube method.

Methods

Whole blood samples were collected in citrate blood collection tubes from 12 healthy beagles. For the first centrifugation step, 10 different run conditions were compared to determine which condition produced optimal recovery of platelets. Once the optimal condition was identified, platelet-containing plasma prepared using that condition was subjected to a second centrifugation to pellet platelets. For the second centrifugation, 12 different run conditions were compared to identify the centrifugal force and spin time to produce maximal pellet recovery and concentration increase. Growth factor levels were estimated by using ELISA to measure platelet-derived growth factor-BB (PDGF-BB) concentrations in optimised CaCl₂-activated platelet fractions.

Results

The highest platelet recovery rate and yield were obtained by first centrifuging whole blood at 1000 g for 5 min and then centrifuging the recovered platelet-enriched plasma at 1500 g for 15 min. This protocol recovered 80% of platelets from whole blood and increased platelet concentration six-fold and produced the highest concentration of PDGF-BB in activated fractions.

Conclusions

We have described an optimised double-centrifugation tube method for the preparation of PRP from canine blood. This optimised method does not require particularly expensive equipment or high technical ability and can readily be carried out in a veterinary clinical setting.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-1123-3) contains supplementary material, which is available to authorized users.

Standardization of platelet releasate products for clinical applications in cell therapy: a mathematical approach

BACKGROUND

Standardized animal-free components are required for manufacturing cell-based medicinal products. Human platelet concentrates are sources of growth factors for cell expansion but such products are characterized by undesired variability. Pooling together single-donor products improves consistency, but the minimal pool sample size was never determined.

METHODS

Supernatant rich in growth factors (SRGF) derived from n = 44 single-donor platelet-apheresis was obtained by CaCl₂ addition. n = 10 growth factor concentrations were measured. The data matrix was analyzed by a novel statistical algorithm programmed to create 500 groups of random data from single-donor SRGF and to repeat this task increasing group statistical sample size from n = 2 to n = 20. Thereafter, in created groups (n = 9500), the software calculated means for each growth factor and, matching groups with the same sample size, the software retrieved the percent coefficient of variation (CV) between calculated means. A 20% CV was defined as threshold. For validation, we assessed the CV of concentrations measured in n = 10 pools manufactured according to algorithm results. Finally, we compared growth rate and differentiation potential of adipose-derived stromal/stem cells (ASC) expanded by separate SRGF pools.

RESULTS

Growth factor concentrations in single-donor SRGF were characterized by high variability (mean (pg/ml)-CV); VEGF: 950-81.4; FGF-b: 27-74.6; PDGF-AA: 7883-28.8; PDGF-AB: 107834-32.5; PDGF-BB: 11142-48.4; Endostatin: 305034-16.2; Angiostatin: 197284-32.9; TGF-β1: 68382-53.7; IGF-I: 70876-38.3; EGF: 2411-30.2). In silico performed analysis suggested that pooling n = 16 single-donor SRGF reduced CV below 20%. Concentrations measured in 10 pools of n = 16 single SRGF were not different from mean values measured in single SRGF, but the CV was reduced to or below the threshold. Separate SRGF pools failed to differently affect ASC growth rate (slope pool A = 0.6; R² = 0.99; slope pool B = 0.7; R² 0.99) or differentiation potential.

DISCUSSION

Results deriving from our algorithm and from validation utilizing real SRGF pools demonstrated that pooling n = 16 single-donor SRGF products can ameliorate variability of final growth factor concentrations. Different pools of n = 16 single donor SRGF displayed consitent capability to modulate growth and differentiation potential of expanded ASC. Increasing the pool size should not further improve product composition.

Tri-Layered Nanocomposite Hydrogel Scaffold for the Concurrent Regeneration of Cementum, Periodontal Ligament, and Alveolar Bone

A tri-layered scaffolding approach is adopted for the complete and concurrent regeneration of hard tissues-cementum and alveolar bone-and soft tissue-the periodontal ligament (PDL)-at a periodontal defect site. The porous tri-layered nanocomposite hydrogel scaffold is composed of chitin-poly(lactic-co-glycolic acid) (PLGA)/nanobioactive glass ceramic (nBGC)/cementum protein 1 as the cementum layer, chitin-PLGA/fibroblast growth factor 2 as the PDL layer, and chitin-PLGA/nBGC/platelet-rich plasma derived growth factors as the alveolar bone layer. The tri-layered nanocomposite hydrogel scaffold is cytocompatible and favored cementogenic, fibrogenic, and osteogenic differentiation of human dental follicle stem cells. In vivo, tri-layered nanocomposite hydrogel scaffold with/without growth factors is implanted into rabbit maxillary periodontal defects and compared with the controls at 1 and 3 months postoperatively. The tri-layered nanocomposite hydrogel scaffold with growth factors demonstrates complete defect closure and healing with new cancellous-like tissue formation on microcomputed tomography analysis. Histological and immunohistochemical analyses further confirm the formation of new cementum, fibrous PDL, and alveolar bone with well-defined bony trabeculae in comparison to the other three groups. In conclusion, the tri-layered nanocomposite hydrogel scaffold with growth factors can serve as an alternative regenerative approach to achieve simultaneous and complete periodontal regeneration.

Effects of local platelet-rich plasma injection on the rate of orthodontic tooth movement in a rat model: A histomorphometric study

INTRODUCTION

The aims of this study were to determine the effects of different concentrations of platelet-rich plasma (PRP) on alveolar bone density and orthodontic tooth movement.

METHODS

Seventy-six rats were divided into 2 groups: a moderate concentration PRP injection group (n = 38) and a high concentration PRP injection group (n = 38). In each group, 5 time points were studied: 3, 7, 14, 21, and 60 days. Before orthodontic mesialization of the maxillary first molars, moderate and high concentrations of PRP were injected on the right sides of the molar buccal sulcus, and the left sides served as the controls. Tooth movements were measured on 3-dimensional digital models. Alveolar bone volume density and osteoclastic activity in the first molar intraradicular areas were evaluated by histomorphometric analysis.

RESULTS

Alveolar bone density was decreased in the experimental groups compared with the control groups (P = 0.0001) at 3, 7, 14, and 21 days. On day 3, osteoclastic activity of the experimental groups was higher than that of the controls (P = 0.044, P = 0.0001). On day 21, the amounts of tooth movement in the high-concentration experimental group were 1.7 times greater than in the high-concentration control group and 1.4 times greater than in the moderate-concentration experimental group (P = 0.001). On day 60, alveolar bone density increased to the original levels in all groups.

CONCLUSIONS

Injection of both moderate and high concentrations of PRP may accelerate orthodontic tooth movement by decreasing alveolar bone density on paradental tissues by enhancing osteoclastic activity in a transient way.

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

Platelet-derived Factor Concentrates with Hyaluronic Acid Scaffolds for Treatment of Deep Burn Wounds

Supplemental Digital Content is available in the text.

A deep burn wound is a critical condition that generally necessitates vascularized tissue coverage. We performed the injection of platelet-derived factor concentrates combined with non–cross-linked hyaluronic acid scaffolds for 2 patients with critical burn wounds with bone and tendon exposure and achieved successful healing. Hyaluronic acid was considered to have served as a controlled-release carrier of platelet-derived factors, being clinically effective for the treatment of deep burn wounds.

Concise Review: The Use of Adipose-Derived Stromal Vascular Fraction Cells and Platelet Rich Plasma in Regenerative Plastic Surgery

Tissue engineering has emerged at the intersection of numerous disciplines to meet a global clinical need for technologies to promote the regeneration of tissues. Recently, many authors have focused their attention on mesenchymal stem/stromal cells (MSCs) for their capacity to differentiate into many cell lineages. The most widely studied cell types are bone marrow mesenchymal stem cells and adipose-derived stem cells (ASCs), which display similar results. Biomaterials, cells, and growth factors are needed to design a regenerative plastic surgery approach in the treatment of organ and tissue defects, but not all tissues are created equal. The aim of this article is to describe the advances in tissue engineering through the use of ASCs, platelet rich plasma, and biomaterials to enable regeneration of damaged complex tissue. Stem Cells 2017;35:117-134.

High-throughput acoustic separation of platelets from whole blood

Platelets contain growth factors which are important in biomedical and clinical applications. In this work, we present an acoustic separation device for high-throughput, non-invasive platelet isolation. In particular, we separated platelets from whole blood at a 10 mL min(-1) throughput, which is three orders of magnitude greater than that of existing acoustic-based platelet separation techniques. Without sample dilution, we observed more than 80% RBC/WBC removal and platelet recovery. High throughput, high separation efficiency, and biocompatibility make this device useful for many clinical applications.

Platelet-Rich Plasma Obtained with Different Anticoagulants and Their Effect on Platelet Numbers and Mesenchymal Stromal Cells Behavior In Vitro

There are promising results in the use of platelet-rich plasma (PRP) for musculoskeletal tissue repair. However, the variability in the methodology for its obtaining may cause different and opposing findings in the literature. Particularly, the choice of the anticoagulant is the first definition to be made. In this work, blood was collected with sodium citrate (SC), ethylenediaminetetraacetic acid (EDTA), or anticoagulant citrate dextrose (ACD) solution A, as anticoagulants, prior to PRP obtaining. Hematological analysis and growth factors release quantification were performed, and the effects on mesenchymal stromal cell (MSC) culture, such as cytotoxicity and cell proliferation (evaluated by MTT method) and gene expression, were evaluated. The use of EDTA resulted in higher platelet yield in whole blood; however, it induced an increase in the mean platelet volume (MPV) following the blood centrifugation steps for PRP obtaining. The use of SC and ACD resulted in higher induction of MSC proliferation. On the other hand, PRP obtained in SC presented the higher platelet recovery after the blood first centrifugation step and a minimal change in MSC gene expression. Therefore, we suggest the use of SC as the anticoagulant for PRP obtaining.

Clinical-grade quality platelet-rich plasma releasate (PRP-R/SRGF) from CaCl2 -activated platelet concentrates promoted expansion of mesenchymal stromal cells

BACKGROUND AND OBJECTIVES

The aim of our study was to test a platelet-rich plasma releasate (PRP-R/SRGF) from CaCl2 -activated platelets as a source of growth factors for the expansion of mesenchymal stromal cells (MSCs). PRP-R/SRGF, obtained with a low-cost procedure, is characterized by a reduced variability of growth factor release.

MATERIALS AND METHODS

PRP-R/SRGF is a clinical-grade quality solution obtained from CaCl2 -activated platelets. Its activity was evaluated by measuring the proliferation, the phenotype, the differentiation potential and the immunosuppressive properties of MSCs derived from bone marrow (BM) and adipose tissue (AT).

RESULTS

PRP-R/SRGF was more active than FBS to expand BM- and AT-derived MSCs. PRP-R/SRGF treatment did not affect the expression of typical MSCs surface markers, neither MSCs differentiation potential nor their capability to inhibit activated T-cell proliferation.

CONCLUSIONS

The clinical-grade PRP-R/SRGF may be used in the clinical setting for the expansion of MSCs.

Use of platelet lysate for bone regeneration - are we ready for clinical translation?

Current techniques to improve bone regeneration following trauma or tumour resection involve the use of autograft bone or its substitutes supplemented with osteoinductive growth factors and/or osteogenic cells such as mesenchymal stem cells (MSCs). Although MSCs are most commonly grown in media containing fetal calf serum, human platelet lysate (PL) offers an effective alternative. Bone marrow - derived MSCs grown in PL-containing media display faster proliferation whilst maintaining good osteogenic differentiation capacity. Limited pre-clinical investigations using PL-expanded MSCs seeded onto osteoconductive scaffolds indicate good potential of such constructs to repair bone in vivo. In an alternative approach, nude PL-coated scaffolds without seeded MSCs have been proposed as novel regenerative medicine devices. Even though methods to coat scaffolds with PL vary, in vitro studies suggest that PL allows for MSC adhesion, migration and differentiation inside these scaffolds. Increased new bone formation and vascularisation in comparison to uncoated scaffolds have also been observed in vivo. This review outlines the state-of-the-art research in the field of PL for ex vivo MSC expansion and in vivo bone regeneration. To minimise inconsistency between the studies, further work is required towards standardisation of PL preparation in terms of the starting material, platelet concentration, leukocyte depletion, and the method of platelet lysis. PL quality control procedures and its "potency" assessment are urgently needed, which could include measurements of key growth and attachment factors important for MSC maintenance and differentiation. Furthermore, different PL formulations could be tailor-made for specific bone repair indications. Such measures would undoubtedly speed up clinical translation of PL-based treatments for bone regeneration.

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

This journal requires that authors assign a level of evidence to each submission to which Evidence-Based Medicine rankings are applicable. This excludes Review Articles, Book Reviews, and manuscripts that concern Basic Science, Animal Studies, Cadaver Studies, and Experimental Studies. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Is Platelet-Rich Plasma a Future Therapy in Pain Management?

Platelet-rich plasma (PRP) has the potential to regenerate tissues and decrease pain through the effects of bioactive molecules and growth factors present in alpha granules. Several PRP preparation systems are available with varying end products, doses of growth factors, and bioactive molecules. This article presents the biology of PRP, the preparation of PRP, and the effects PRP-related growth factors have on tissue healing and repair. Based on available evidence-based literature, the success of PRP therapy depends on the method of preparation and composition of PRP, the patient's medical condition, anatomic location of the injection, and the type of tissue injected.

Accuracy of a New Platelet Count System (PLT-F) Depends on the Staining Property of Its Reagents

Background

Platelet count is essential for the diagnosis and management of hemostasis abnormalities. Although existing platelet count methods installed in common hematology analyzers can correctly count platelets in normal blood samples, they tend to miscount platelets in some abnormal samples. The newly developed PLT-F channel in the XN-Series hematology analyzer (Sysmex) has been reported to be a reliable platelet count system, even in abnormal samples. However, how the PLT-F platelet counting system achieves such accuracy has not been described in scientific articles.

Methods

Isolated platelets, erythrocytes, and fragmented erythrocytes were examined using an automated hematology analyzer. The samples were labeled by combining PLT-F reagents and anti-CD62p, CD63, Grp75, Calreticulin, CD41, or CD61 antibody, and analyzed using confocal laser scanning microscopy or flow cytometry.

Results

The PLT-F system correctly discriminated platelets in erythrocytes. Its reagents strongly stained some intraplatelet organelles labeled with anti-Grp75, but only faintly stained the plasma membrane of both platelets and erythrocytes. Microscopic observation and flow cytometric examination revealed that all of these strongly stained cells were also labeled with platelet-specific anti-CD41 and anti-CD61 antibodies.

Conclusions

This study revealed that the staining property of the PLT-F reagents, by which platelets and fragmented erythrocytes are clearly distinguished, contributes to the platelet-counting accuracy of the PLT-F system.

Tenogenically Induced Allogeneic Mesenchymal Stem Cells for the Treatment of Proximal Suspensory Ligament Desmitis in a Horse

Suspensory ligament injuries are a common injury in sport horses, especially in competing dressage horses. Because of the poor healing of chronic recalcitrant tendon injuries, this represents a major problem in the rehabilitation of sport horses and often compromises the return to the initial performance level. Stem cells are considered as a novel treatment for different pathologies in horses and humans. Autologous mesenchymal stem cells (MSCs) are well known for their use in the treatment of tendinopathies; however, recent studies report a safe use of allogeneic MSCs for different orthopedic applications in horses. Moreover, it has been reported that pre-differentiation of MSCs prior to injection might result in improved clinical outcomes. For all these reasons, the present case report describes the use of allogeneic tenogenically induced peripheral blood-derived MSCs for the treatment of a proximal suspensory ligament injury. During conservative management for 4 months, the horse demonstrated no improvement of a right front lameness with a Grade 2/5 on the American Association of Equine Practitioners (AAEP) scale and a clear hypo-echoic area detectable in 30% of the cross sectional area. From 4 weeks after treatment, the lameness reduced to an AAEP Grade 1/5 and a clear filling of the lesion could be noticed on ultrasound. At 12 weeks (T₄) after the first injection, a second intralesional injection with allogeneic tenogenically induced MSCs and platelet-rich plasma was given and at 4 weeks after the second injection (T₅), the horse trotted sound under all circumstances with a close to total fiber alignment. The horse went back to previous performance level at 32 weeks after the first regenerative therapy and is currently still doing so (i.e., 20 weeks later or 1 year after the first stem cell treatment). In conclusion, the present case report demonstrated a positive evolution of proximal suspensory ligament desmitis after treatment with allogeneic tenogenically induced MSCs.

Role of embedded pure xenogenous bovine platelet gel on experimental tendon healing, modelling and remodelling

BACKGROUND AND OBJECTIVES

Surgical reconstruction of large tendon defects is technically demanding. In addition, tendon healing has poor quality and is associated with development of peritendinous adhesions. Tissue engineering and regenerative medicine is an option. A combination of scaffolds and factors that promote healing, such as a bioactive graft, could be a valuable strategy for treatment of the injured tendons. Different forms of platelets have been used for tendon healing. Since the availability and cost effectiveness of biomaterials are important in tissue engineering, bovine platelets could be a valuable alternative option for the autograft platelets. We investigated whether bovine platelet gel embedded within an artificial tendon could be effective in tendon healing and regeneration, in vivo.

METHODS

After in vitro evaluations, a large tendon defect model was produced in rabbits and the defect maintained align using Kessler suture. The animals were divided into four groups of control (no implant), treatment with collagen implant, collagen implant-polydioxanone sheath, and collagen implant-polydioxanone sheet-bovine platelet gel. The healing and regeneration were assessed by gross- micro- and nano-morphologic analyses, biomechanical testing, biochemistry, bioelectricity, and clinical evaluations at 60 and 120 days after injury.

RESULTS

Bovine platelet gel induced cellular proliferation and enhanced cell viability in vitro. In vivo, it significantly increased inflammation in the short term, enhanced cellular distribution, proliferation, migration, differentiation and matrix production at mid-term and finally it facilitated graft degradation, incorporation and acceptance in the newly regenerated tendon. Compared with the control groups, the platelet-treated neotendon had significantly higher mechanical strength which was due to the collagen fibril's better density, diameter, number, differentiation and distribution, collagen fibril to fiber and fiber bundle differentiation and lower peritendinous adhesion, muscle fibrosis and atrophy.

CONCLUSION

Bovine platelet gel-embedded artificial tendon could be considered as a new option in reconstruction and healing of large tendon defects.

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.

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.

Mesenchymal stem cell therapies in the treatment of musculoskeletal diseases

The application of regenerative strategies to musculoskeletal ailments offers extraordinary promise to transform management of the conditions of numerous patients. The use of cell-based therapies and adjunct strategies is under active investigation for injuries and illnesses affecting bones, joints, tendons, and skeletal muscle. Of particular interest to the field is the mesenchymal stem cell, an adult stem cell found in bone marrow and adipose tissue. This cell type can be expanded ex vivo, has allogeneic application, and has the capacity for engraftment and differentiation into mesodermal lineages. Also of major interest in the field is the use of platelet-rich plasma, a strategy to concentrate endogenous cytokines and growth factors with reparative potential. Here we review the biological basis, clinical studies, safety, and current state of mesenchymal stem cell and platelet-rich plasma therapies in the treatment of musculoskeletal disease.

A New Economic Method for Preparing Platelet-rich Plasma

BACKGROUND

Although platelet-rich plasma (PRP) is nowadays a common method in various medical fields, including cosmetic surgery or dermatology, the expensiveness of the kit for processing is still a hurdle.

METHODS

A new unique economic method for preparing PRP was reported. The method consists in a simple modification of a disposable 5-mL syringe that allows insertion into a common centrifuge and positioning of the syringe on the centrifuge so the PRP separates next to the tip of the syringe. Platelet-derived growth factor BB in PRP was measured under anticoagulant dextrose solution A (ACD-A) or heparin as anticoagulant and with or without prostaglandin E1 (PGE1) as a platelet aggregation suppressant.

RESULTS

The new method successfully created PRP with high platelet-derived growth factor BB in all conditions, and the highest value was obtained by using ACD-A and PGE1.

CONCLUSIONS

The new method is useful, and the use of ACD-A and PGE1 is the most recommended.

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.

Prediction and modulation of platelet recovery by discontinuous centrifugation of whole blood for the preparation of pure platelet-rich plasma

The aim of this study was to describe the behavior of the separation of red blood cells (RBCs) by discontinuous centrifugation (DC) of whole blood to modulate and control the platelet recovery in the preparation of pure platelet-rich plasma (P-PRP). P-PRP is a platelet-rich plasma (PRP) in which the white blood cell layer is not included. To achieve this goal, an analytical model was derived that takes into account the packing of RBCs and predicts the behavior of platelet and plasma recovery efficiencies (PtPlRE) based on the volume of whole blood, the hematocrit, and the volume of supernatant, as a function of the operating variables, centrifugal acceleration, and time. The model was derived from the basic equation of DC, which originates from the equilibrium balance of forces on a particle, and included the addition of one factor that corrected the terminal velocity of RBCs and was also correlated to the PtPlRE in the supernatant. This factor was the ratio between the fractional volume concentrations of plasma and RBCs in the centrifugation pellet after centrifugation. The model was validated and the variability of the data was determined using experimental data from 10 healthy donors in the age range of 25-35 years. The predicted behavior for the packing of RBCs and the PtPlRE was consistent with the behavior seen in the experimental data. Thus, the PtPlRE could be modulated and controlled through centrifugal acceleration, time, and hematocrit. Use of this model based on a physical description of events is the first step of a reliable standardization of PRP preparations.