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

The Regenerative Marriage Between High-Density Platelet-Rich Plasma and Adipose Tissue

The use of autologous biological preparations (ABPs) and their combinations fills the void in healthcare treatment options that exists between surgical procedures, like plastic reconstructive, cosmetic, and orthopedic surgeries; non-surgical musculoskeletal biological procedures; and current pharmaceutical treatments. ABPs, including high-density platelet-rich plasma (HD-PRP), bone marrow aspirate concentrates (BMACs), and adipose tissue preparations, with their unique stromal vascular fractions (SVFs), can play important roles in tissue regeneration and repair processes. They can be easily and safely prepared at the point of care. Healthcare professionals can employ ABPs to mimic the classical wound healing cascade, initiate the angiogenesis cascade, and induce tissue regenerative pathways, aiming to restore the integrity and function of damaged tissues. In this review, we will address combining autologous HD-PRP with adipose tissue, in particular the tissue stromal vascular fraction (t-SVF), as we believe that this biocellular combination demonstrates a synergistic effect, where the HD-PRP constituents enhance the regenerative potential of t-SVF and its adipose-derived mesenchymal stem cells (AD-MSCs) and pericytes, leading to improved functional tissue repair, tissue regeneration, and wound healing in variety of clinical applications. We will address some relevant platelet bio-physiological aspects, since these properties contribute to the synergistic effects of combining HD-PRP with t-SVF, promoting overall better outcomes in chronic inflammatory conditions, soft tissue repair, and tissue rejuvenation.

[Study of centrifuge conditions for preparing rabbit leukocyte-poor platelet-rich plasma by single centrifugation]

Objective

To explore the best centrifuge condition for preparing rabbit leukocyte-poor platelet-rich plasma (LP-PRP) by using single centrifugation method.

Methods

Sixteen healthy New Zealand rabbits, aged 3-4 months, were utilized in the investigation. A total of 15 mL anticoagulated blood was extracted from the central ear artery of each rabbit, with a repeat of the blood collection procedure after 1 and 2 months. The obtained blood specimens were individually subjected to centrifugation at a radius of 16.7 cm and speeds of 1 200, 1 300, 1 400, and 1 500 r/min (equivalent to centrifugal forces of 269× g, 315× g, 365× g, and 420× g) for durations of 2, 3, 4, and 5 minutes, resulting in a total of 16 groups. Following centrifugation, collect plasma from each group to a distance of 1.5 mL from the separation plane. The volumes, platelet enrichment coefficient, and platelet recovery rates of LP-PRP in each group, under varying centrifugation conditions, were methodically computed and subsequently compared.

Results

The volume of LP-PRP obtained under all centrifugation conditions ranged from 1.8 to 7.6 mL. At a consistent centrifugal speed, an extension of centrifugation time leaded to a significant increase in the volume of LP-PRP, accompanied by a declining trend in the platelet enrichment coefficient of LP-PRP. When centrifuged for 2 minutes, the volume of LP-PRP at speeds of 1 200 and 1 300 r/min was less than 2.0 mL, while the volume of LP-PRP obtained under other conditions was more than 2.0 mL. When centrifuged for 4 and 5 minutes, the volume of LP-PRP obtained at each speed was more than 4 mL. LP-PRP with a platelet enrichment coefficient more than 2.0 could be prepared by centrifuging at 1 200 r/min for each time group and 1 300 r/min for 2 and 3 minutes, and the highest LP-PRP platelet enrichment coefficient could be obtained by centrifugation for 2 minutes at a speed of 1 200 r/min. The platelet recovery rates of LP-PRP obtained by centrifugation at 1 200 r/min for 4 and 5 minutes, as well as centrifugation at 1 400 r/min for 5 minutes, were both greater than 60%. There was no significant difference between the groups when centrifuged at 1 200 r/min for 4 and 5 minutes ( P>0.05).

Conclusion

In the process of preparing rabbit LP-PRP using a single centrifugation method, collecting 15 mL of blood and centrifuging at a radius of 16.7 cm and speed of 1 200 r/min for 4 minutes can prepare LP-PRP with a volume exceeding 2.0 mL, platelet enrichment coefficient exceeding 2.0, and platelet recovery rate exceeding 60%. This centrifugal condition can achieve the optimal LP-PRP action parameters in the shortest possible time.

Angiogenesis and Tissue Repair Depend on Platelet Dosing and Bioformulation Strategies Following Orthobiological Platelet-Rich Plasma Procedures: A Narrative Review

Angiogenesis is the formation of new blood vessel from existing vessels and is a critical first step in tissue repair following chronic disturbances in healing and degenerative tissues. Chronic pathoanatomic tissues are characterized by a high number of inflammatory cells; an overexpression of inflammatory mediators; such as tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1); the presence of mast cells, T cells, reactive oxygen species, and matrix metalloproteinases; and a decreased angiogenic capacity. Multiple studies have demonstrated that autologous orthobiological cellular preparations (e.g., platelet-rich plasma (PRP)) improve tissue repair and regenerate tissues. There are many PRP devices on the market. Unfortunately, they differ greatly in platelet numbers, cellular composition, and bioformulation. PRP is a platelet concentrate consisting of a high concentration of platelets, with or without certain leukocytes, platelet-derived growth factors (PGFs), cytokines, molecules, and signaling cells. Several PRP products have immunomodulatory capacities that can influence resident cells in a diseased microenvironment, inducing tissue repair or regeneration. Generally, PRP is a blood-derived product, regardless of its platelet number and bioformulation, and the literature indicates both positive and negative patient treatment outcomes. Strangely, the literature does not designate specific PRP preparation qualifications that can potentially contribute to tissue repair. Moreover, the literature scarcely addresses the impact of platelets and leukocytes in PRP on (neo)angiogenesis, other than a general one-size-fits-all statement that "PRP has angiogenic capabilities". Here, we review the cellular composition of all PRP constituents, including leukocytes, and describe the importance of platelet dosing and bioformulation strategies in orthobiological applications to initiate angiogenic pathways that re-establish microvasculature networks, facilitating the supply of oxygen and nutrients to impaired tissues.

Modifying Orthobiological PRP Therapies Are Imperative for the Advancement of Treatment Outcomes in Musculoskeletal Pathologies

Autologous biological cellular preparations have materialized as a growing area of medical advancement in interventional (orthopedic) practices and surgical interventions to provide an optimal tissue healing environment, particularly in tissues where standard healing is disrupted and repair and ultimately restoration of function is at risk. These cellular therapies are often referred to as orthobiologics and are derived from patient's own tissues to prepare point of care platelet-rich plasma (PRP), bone marrow concentrate (BMC), and adipose tissue concentrate (ATC). Orthobiological preparations are biological materials comprised of a wide variety of cell populations, cytokines, growth factors, molecules, and signaling cells. They can modulate and influence many other resident cells after they have been administered in specific diseased microenvironments. Jointly, the various orthobiological cell preparations are proficient to counteract persistent inflammation, respond to catabolic reactions, and reinstate tissue homeostasis. Ultimately, precisely delivered orthobiologics with a proper dose and bioformulation will contribute to tissue repair. Progress has been made in understanding orthobiological technologies where the safety and relatively easy manipulation of orthobiological treatment tools has been demonstrated in clinical applications. Although more positive than negative patient outcome results have been registered in the literature, definitive and accepted standards to prepare specific cellular orthobiologics are still lacking. To promote significant and consistent clinical outcomes, we will present a review of methods for implementing dosing strategies, using bioformulations tailored to the pathoanatomic process of the tissue, and adopting variable preparation and injection volume policies. By optimizing the dose and specificity of orthobiologics, local cellular synergistic behavior will increase, potentially leading to better pain killing effects, effective immunomodulation, control of inflammation, and (neo) angiogenesis, ultimately contributing to functionally restored body movement patterns.

Influence of Sexual Dimorphism, Aging, and Differential Cell Capture Efficiency of Blood Separation Systems on the Quality of Platelet-Rich Plasma

Few studies have checked the impact of the hormonal/immunological dimorphism of patients on the cellular composition of platelet-rich plasma products (PRP). Whole blood (WB) from 26 volunteers was concentrated using a device previously characterized. Platelet and white blood cell (WBC) counts in WB and PRP were compared between genders, and after the population was split into pre (≤50 years)- and post (>50 years)-menopausal ages. In WB, platelet−total WBC densities were comparable in men and women. The phagocytic cell composition differed (p ≤ 0.04). After dividing by ages, phagocytic cell discrepancies were linked to women > 50 years (p ≤ 0.05), and differences emerged in lymphocyte counts (lower in >50 years groups, within and between genders, p ≤ 0.05). In PRP, densities were significantly higher, but the PRP/WB ratios varied according to blood cell (lower for phagocytic cells) and between subjects (more favorable at a lower density of a particular blood cell in WB). This “system compensatory efficiency” reduced/reverted PRP differences in the leukocyte composition between genders/age−sex groups in WB. In PRP, neutrophils were higher in younger men than older women (p < 0.05). WB lymphocyte differences between age−sex groups persisted. Age is a more determining factor than sex in the preparation of PRP. Post-menopause, sexual dimorphism strongly influences the composition of leukocytes, also conditioned by the capture efficiency of the system.

Platelet-Rich Plasma: A Comprehensive Review of Emerging Applications in Medical and Aesthetic Dermatology

Platelet-rich plasma (PRP) has been integrated into numerous treatment regimens for medical and aesthetic dermatology. While some of these approaches are well-established, many uses are underreported in the literature. We sought to identify and summarize the emerging dermatologic applications for PRP by conducting a comprehensive PubMed search of studies published between 2000 and 2020. These studies were reviewed to synthesize collection methods, treatment schedule, adverse effects, and the impact of therapy for new and emerging uses for PRP. In general, we identified positive treatment outcomes for skin rejuvenation, scar revision, alopecia, pigmentary disorders, lichen sclerosus, leprosy-induced peripheral neuropathy, plaque psoriasis, and nail disorders. Widely, therapy was well-tolerated and suitable for all reported phototypes. The variations in collection and application sequences make concrete recommendations difficult to discern, underscoring the need for a standardized approach to preparation and treatment methods. We hope this review serves as an outline for new and interesting uses for PRP and will help readers familiarize themselves with this exciting technology for comfortable integration into their practices.

Commercial blood cell separation systems versus tube centrifugation methods for the preparation of platelet-rich plasma: a preliminary cross-sectional study

OBJECTIVE

Clinical studies claim that platelet-rich plasma (PRP) accelerates tissue healing due to its high concentration of growth factors and that the combination with leukocytes improves the antimicrobial effect of the concentrate. Most of these studies obtained PRP using different separation systems, and few analyzed the content of the PRP used for treatment. This study characterized the composition of PRP and white blood cells (WBC) from a single donor produced by three commercially available PRP separation systems and two anticoagulated general analytical tubes.

METHODS

Five patients donated 50 mL of blood, which was processed to produce PRP and WBC using three PRP concentration systems (i.e., Easy PRP Kit, GloPRP, and Wego) and two tubes for general analysis anticoagulated with ethylenediaminetetraacetic acid (EDTA) and citrate. Platelets and WBC in combination with their concentrates were analyzed by automated systems in a clinical laboratory.

RESULTS

There were no significant differences in the average concentrations of PRP platelets and WBC between GloPRP and the tubes for general analysis with EDTA and citrate; however, the Easy PRP Kit gave results much superior to the rest of the methods, especially comparing it with the Wego Kit, whose concentrates were especially low, even nonexistent for WBC.

CONCLUSIONS

The Easy PRP Kit concentrates WBC-rich PRP, resulting in increased WBC concentrations, compared with low WBC-low PRP of GloPRP and general tube methods for EDTA and citrate analysis and the even lower concentration of PRP from the Wego Kit, with the absence of leukocytes.

Enrichment of plasma in platelets and extracellular vesicles by the counterflow to erythrocyte settling

In order to prepare optimal platelet and extracellular vesicle (EV)-rich plasma for the treatment of chronic temporal bone inflammation, we studied effects of centrifugation parameters on redistribution of blood constituents in blood samples of 23 patients and 20 volunteers with no record of disease. Concentrations of blood cells and EVs were measured by flow cytometry. Sample content was inspected by scanning electron microscopy. A mathematical model was constructed to interpret the experimental results. The observed enrichment of plasma in platelets and EVs after a single spin of blood depended on the erythrocyte sedimentation rate, thereby indicating the presence of a flow of plasma that carried platelets and EVs in the direction opposite to settling of erythrocytes. Prolonged handling time correlated with the decrease of concentration of platelets and larger EVs in platelet and EV-rich plasma (PVRP), R = -0.538, p = 0.003, indicating cell fragmentation during the processing of samples. In further centrifugation of the obtained plasma, platelet and EV enrichment depended on the average distance of the sample from the centrifuge rotor axis. Based on the agreement of the model predictions with observations, we propose the centrifugation protocol optimal for platelet and EV enrichment and recovery in an individual sample, adjusted to the dimensions of the centrifuge rotor, volume of blood and erythrocyte sedimentation rate.[Figure: see text].

Autologous Platelet- and Extracellular Vesicle-Rich Plasma Is an Effective Treatment Modality for Chronic Postoperative Temporal Bone Cavity Inflammation: Randomized Controlled Clinical Trial

Purpose

To determine the efficacy of autologous platelet- and extracellular vesicle-rich plasma (PVRP) to treat chronic postoperative temporal bone cavity inflammation (CPTBCI) after exhausting surgical and standard conservative therapies.

Materials and Methods

Patients were randomly allocated to treatment with PVRP (PVRP group) or standard conservative methods (control group) in a setting of four once-monthly checkups and subsequent follow-up. The treatment outcome was measured with the Chronic Otitis Media Questionnaire-12 (COMQ-12), CPTBCI focus surface area, and CPTBCI symptom-free time after the fourth checkup.

Results

Eleven patients from each group completed the trial; 95% of patients suffered from chronically discharging mastoid cavity (the type of CPTBCI). Within four checkups, the COMQ-12 score decreased statistically significantly in the PVRP group (p < 0.001) but not in the control group (p = 0.339). The CPTBCI foci surface area decreased statistically significantly between the first and second checkups (p < 0.0005) but not between other checkups (p > 0.05) in the PVRP group. No statistically significant differences in CPTBCI foci surface area were detected between checkups in the control group (p = 0.152). Nine patients from the PVRP group and three patients from the control group were CPTBCI symptom-free at the fourth checkup. The median symptom-free time was 9.2 months (95% CI [7.4, 11.9]) in the PVRP group. Cumulatively, 49% of patients in the PVRP group remained CPTBCI symptom-free for 12.7 months after the fourth checkup.

Conclusion

Autologous PVRP represents a novel additional and successful treatment modality for a chronically discharging radical mastoid cavity when the surgical and standard conservative treatment methods have been exhausted.

Trial Number

https://clinicaltrials.gov (NCT04281901).

Age-based inter-subject variability in platelet and white blood cell concentrations of platelet-rich plasma prepared using a new application to blood separation system

The benefit of autologous platelet‐rich plasma (PRP) treatment is still under discussion. Variations in PRP products, consequence of the lack of a standardised protocol for the multitude of commercially available blood separation systems and the lack of knowledge of the optimal composition of PRP or its suitability for the proposed indication are some of the reasons behind clinical inconsistencies. The impact of inter‐subject variability in PRP has received less attention in comparison. The purpose of this study was to determine the inter‐subject variability, based on age, in the concentrates prepared by a new blood concentration system. Twenty‐six healthy volunteers of both genders (29‐93 years) were enrolled. Whole blood (WB) was collected from each participant to prepare PRP using the Easy PRP kit. Platelets and white blood cells (WBC) from WB and PRP were analysed after split population by age; patients younger than 65 years (n = 13) and patients ≥65 years old (n = 13). Among the demographic characteristics tested, only age was significantly different between the groups. Cell capture efficiency of the system was specific for each type of blood cell and identical for both age groups. Platelets and WBC in PRP were higher than in WB (P < .001). In WB, platelets and WBC concentrations were significantly lower in older group (P ≤ .035). These differences persisted in the prepared PRP (P ≤ .004). The ageing of population has a strong influence on the haematocrit and therefore on the composition of PRP. Because the efficiency of blood separator system seems to be constant across individuals, the inter‐subject haematocrit variability based on age could be used as a predictor of resulting PRP. The clinical application of PRP should be restricted to the specific cell capture capacity of the different commercial devices.

Enhanced Diamagnetic Repulsion of Blood Cells Enables Versatile Plasma Separation for Biomarker Analysis in Blood

A hemolysis-free and highly efficient plasma separation platform enabled by enhanced diamagnetic repulsion of blood cells in undiluted whole blood is reported. Complete removal of blood cells from blood plasma is achieved by supplementing blood with superparamagnetic iron oxide nanoparticles (SPIONs), which turns the blood plasma into a paramagnetic condition, and thus, all blood cells are repelled by magnets. The blood plasma is successfully collected from 4 mL of blood at flow rates up to 100 µL min^-1 without losing plasma proteins, platelets, or exosomes with 83.3±1.64% of plasma volume recovery, which is superior over the conventional microfluidic methods. The theoretical model elucidates the diamagnetic repulsion of blood cells considering hematocrit-dependent viscosity, which allows to determine a range of optimal flow rates to harvest platelet-rich plasma and platelet-free plasma. For clinical validations, it is demonstrated that the method enables the greater recovery of bacterial DNA from the infected blood than centrifugation and the immunoassay in whole blood without prior plasma separation.

Automatic medium exchange for micro-volume cell samples based on dielectrophoresis

Cell medium exchange is a crucial step for life science and medicine. However, conventional cell medium exchange methods, including centrifuging and filtering, show limited ability for micro-volume cell samples such as circulating tumor cell (CTC) and circulating fetal cell (CFC). In this paper, we proposed an automatic medium exchange method for micro-volume cell samples based on dielectrophoresis (DEP) in microfluidic chip. Fresh medium and cell suspension were introduced into the microfluidic channel as the laminar flow. Plane stair-shaped interdigital electrodes were employed to drive the cells from the cell suspension to fresh media directly by DEP force. Additionally, we characterized and optimized the cell medium exchange according to both the theory and experiments. In the end, we achieved a 96.9% harvest rate of medium exchange for 0.3 μL samples containing micro-volume cells. For implementing an automatic continuous cell medium exchange, the proposed method can be integrated into the automatic cell processing system conveniently. Furthermore, the proposed method is a great candidate in micro-volume cell analysis and processing, cell electroporation, single cell sequencing, and other scenarios.

[Optimized preparation method of leukocytes-rich platelet-rich plasma by varying conditions during centrifugation]

OBJECTIVE

To identify a more popularized preparation protocol of leukocytes-rich platelet-rich plasma (L-PRP) for higher tolerance rate.

METHODS

The peripheral blood samples of 76 volunteers (45.0 mL/case) were mixed with 5 mL sodium citrate injection for blood transfusion, and L-PRP was prepared by twice centrifugations. All blood samples were divided into three groups according to the parameters of twice centrifugation: experimental group A (12 cases, 400× g, 10 minutes for the first time and 1 100× g, 10 minutes for the second time), experimental group B (27 cases, 800× g, 10 minutes for the first time and 1 100× g, 10 minutes for the second time), and control group (37 cases, 1 360× g, 10 minutes for the first time and 1 360× g, 10 minutes for the second time). The platelet recovery rate and platelet and leukocyte enrichment coefficient of L-PRP in each group were calculated and compared.

RESULTS

After removal of abnormal blood samples (platelet recovery rate was more than 100% or white thrombus), the remaining 55 cases were included in the statistical analysis, including 10 cases in experimental group A, 21 cases in experimental group B, and 24 cases in control group. The platelet enrichment coefficient and platelet recovery rate of experimental group B were significantly higher than those of experimental group A and control group ( P<0.05); there was no significant difference between experimental group A and control group ( P>0.05). There was no significant difference in leukocyte enrichment coefficient between experimental groups A, B, and control group ( P>0.05).

CONCLUSION

The preparation quality of PRP is affected by various factors, including centrifugal force, centrifugal time, temperature, and operation process, etc. Twice centrifugation (800× g, 10 minutes for the first time and 1 100× g, 10 minutes for the second time) is an ideal and feasible centrifugation scheme, which can obtain satisfactory platelet recovery rate and enrichment coefficient with thicker buffy coat, which can reduce the fine operation requirements for operators, improve the fault tolerance rate and generalization.

Platelet-rich plasma and regenerative dentistry

Regenerative dentistry is an emerging field of medicine involving stem cell technology, tissue engineering and dental science. It exploits biological mechanisms to regenerate damaged oral tissues and restore their functions. Platelet‐rich plasma (PRP) is a biological product that is defined as the portion of plasma fraction of autologous blood with a platelet concentration above that of the original whole blood. A super‐mixture of key cytokines and growth factors is present in platelet granules. Thus, the application of PRP has gained unprecedented attention in regenerative medicine. The rationale underlies the utilization of PRP is that it acts as a biomaterial to deliver critical growth factors and cytokines from platelet granules to the targeted area, thus promoting regeneration in a variety of tissues. Based on enhanced understanding of cell signalling and growth factor biology, researchers have begun to use PRP treatment as a novel method to regenerate damaged tissues, including liver, bone, cartilage, tendon and dental pulp. To enable better understanding of the regenerative effects of PRP in dentistry, this review describes different methods of preparation and application of this biological product, and provides detailed explanations of the controversies and future prospects related to the use of PRP in dental regenerative medicine.

Characterization of the Dielectrophoretic Response of Different Candida Strains Using 3D Carbon Microelectrodes

Bloodstream infection with Candida fungal cells remains one of the most life-threatening complications among hospitalized patients around the world. Although most of the cases are still due to Candida albicans, the rising incidence of infections caused by other Candida strains that may not respond to traditional anti-fungal treatments merits the development of a method for species-specific isolation of Candida. To this end, here we present the characterization of the dielectrophoresis (DEP) response of Candida albicans, Candida tropicalis and Candida parapsilosis. We complement such characterization with a study of the Candida cells morphology. The Candida strains exhibited subtle differences in their morphology and dimensions. All the Candida strains exhibited positive DEP in the range 10-500 kHz, although the strength of the DEP response was different for each Candida strain at different frequencies. Only Candida tropicalis showed positive DEP at 750 kHz. The current results show potential for manipulation and enrichment of a specific Candida strain at specific DEP conditions towards aiding in the rapid identification of Candida strains to enable the effective and timely treatment of Candida infections.