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Autologous therapies using platelet-rich plasma (PRP) need meticulous preparation—currently, no standardised preparation technique exists. Processing Quantitative Standards (PQSs) define manufacturing quantitative variables (such as time, volume and pressure). Processing Qualitative Standards (PQLSs) define the quality of the materials and methods of manufacturing. The aim of this review is to use existing PQSs and PQLs to report the in vivo/in vitro results obtained by using different Kits, that utilise different procedures (classified as Closed-Technique and Opened-Technique) to isolate autologous human activated (AA-PRP) or non-activated PRP (A-PRP). PQSs included the volumes of blood collected as well as the reagents used, the time/gravity of centrifugation, and the duration, temperature and tilt level/speed of centrifugation. PQLSs included the use of Calcium Chloride CaCl2, Kit weight, transparency of Kit components, the maintenance of a closed sterile processing environment and the use of a small centrifuge. Eight CE marked devices for PRP extraction were evaluated: Angel®, Biomed®, Cascade® and Selphyl®, Mag-18®, i-Stem®, MyCells® and Regenlab®. Using a Kit with the PQSs and PQLSs described in this study enables the isolation of A-PRP, thereby meeting consensus quality criteria. As our understanding of Critical Quality Attributes (CQAs) of A-PRP continues to evolve, especially with respect to purity and potency, adjustments to these benchmark PQSs and PQLs will hopefully help isolate A-PRP of desired CQAs with greater reproducibility, quality, and safety. Confirmatory studies will no doubt need to be completed.

The number of studies evaluating platelet-rich plasma (PRP) concentration has substantially grown in the last fifteen years. A systematic review on this field has been realized by evaluating in the identified studies the in vitro PRP concentration—also analyzing the platelet amount—and the in vivo PRP effects in tissue regeneration compared to any control. The protocol has been developed in agreement with the Preferred Reporting for Items for Systematic Reviews and Meta-Analyses-Protocols (PRISMA-P) guidelines. Multistep research of the PubMed, MEDLINE, Embase, PreMEDLINE, Ebase, CINAHL, PsycINFO, Clinicaltrials.gov, Scopus database and Cochrane databases has permitted to identify articles on different concentrations of PRP in vitro and related in vivo impact for tissue repair. Of the 965 articles initially identified, 30 articles focusing on PRP concentration have been selected and, consequently, only 15 articles have been analyzed. In total, 40% (n = 6) of the studies were related to the fixed PRP Concentration Group used a fixed PRP concentration and altered the platelet concentration by adding the different volumes of the PRP (lysate) to the culture. This technique led to a substantial decrease in nutrition available at higher concentrations. Sixty percent (n = 9) of the studies were related to the fixed PRP Volume Group that used a fixed PRP-to-media ratio (Vol/Vol) throughout the experiment and altered the concentration within the PRP volume. For both groups, when the volume of medium (nutrition) decreases, a lower rate of cell proliferation is observed. A PRP concentration of 1.0 × 106 plt/μL, appears to be optimal thanks to the constant and plentiful capillary nutrition supply and rapid diffusion of growth factors that happen in vivo and it also respects the blood decree-law. The PRP/media ratio should provide a sufficient nutrition supply to prevent cellular starvation, that is, PRP ≤ 10% (Vol/Vol) and thus best mimic the conditions in vivo.

Background Platelet-rich plasma (PRP) provides a nonsurgical approach for treating osteoarthritis (OA). Exosomes that play vital roles in intercellular communication have been studied extensively. Here, we investigated the therapeutic potential and molecular mechanism of exosomes derived from PRP (PRP-Exos) in alleviating OA. Methods Exosomes derived from PRP(PRP-Exos) were isolated and purified using the exoEasy Maxi Kit and then identified and analyzed. Primary rabbit chondrocytes were isolated and treated with interleukin 1 beta (IL-1β) to establish the OA model in vitro. Proliferation, migration, and apoptosis assays were measured and compared between PRP-Exos and activated PRP (PRP-As) to evaluate the therapeutic effects on OA. The mechanism involving the Wnt/β-catenin signaling pathway was investigated by Western blot analysis. In vivo, we established animal knee OA model by surgery to compare the therapeutic effect of PRP-Exos and PRP-As. Results We successfully isolated and purified exosomes from PRP using the exoEasy Maxi Kit. We also isolated and identified chondrocytes from the New Zealand white rabbit and established the IL-1β-induced OA model; meanwhile, PRP-Exos and PRP-As both inhibited the release of tumor necrosis factor-α(TNF-α) and there was no statistically significant difference between the two. In proliferation, migration, scratch assay, the promoting effect of PRP-Exos was significantly more better than PRP-As. Furthermore, PRP-Exos could significantly decreased apoptotic rate of OA chondrocyte compared with PRP-As. In Western blot analysis, the expression of β-catenin, and RUNX2, Wnt5a were increased in IL-1β-treated chondrocytes, but PRP-Exos and PRP-As could both reverse these changes, and the reversal effect of the former was better than the latter. In vivo, we found that both PRP-Exos and PRP-As displayed the progression of OA, and the effect of PRP-Exos was obviously better than PRP-As by chondrocyte count and Osteoarthritis Research Society International (OARSI) scoring system. Conclusion The therapeutic effects of PRP-Exos on OA were similar or better compared with those of PRP-As in vitro or in vivo. PRP-Exos acting as carriers containing growth factors derived from PRP present a novel therapy for OA by activating the Wnt/β-catenin signaling pathway.

Objective Platelet‐rich plasma（PRP), with different concentration of leukocytes, may lead to varying effects in the treatment of cartilage lesions. So far, current research has not shown enough evidence on this. To evaluate the clinical efficacy and safety of intra‐articular injection with pure platelet‐rich plasma (P‐PRP) versus those of leukocyte platelet‐rich plasma (L‐PRP) in treating knee cartilage lesions, we conducted a double‐blind, randomized controlled clinical trial with a larger sample and longer follow‐up period. Methods From October 2019 to October 2020, 95 patients were invited to participate in our study, and 60 (63.2%) were randomized to P‐PRP (n = 30) or L‐PRP (n = 30) groups. Patients from the two groups were treated with knee intra‐articular injections of P‐PRP or L‐PRP. Visual analog scale (VAS) and Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores were assessed using an unpaired t‐test for independent samples preoperatively and at 6 weeks, 12 weeks, 6 months, and 12 months after intervention. Results We followed up 27 cases in the P‐PRP group and 26 cases in the L‐PRP group. No significant differences in VAS and WOMAC scores were found between the two groups before the intervention (p > 0.05). The WOMAC Pain and VAS‐Motions scores of the P‐PRP group were significantly lower than those of the L‐PRP group at 6 weeks after the intervention (p < 0.05). While the long‐term clinical efficacy of both injections was similar and weakened after 12 months, more adverse events were found in the L‐PRP group. Conclusions The short‐term results demonstrate a positive effect in reducing pain and improving function in patients with knee cartilage lesions in the two groups. While the P‐PRP injection showed better clinical efficacy in the early phase of postoperative rehabilitation and resulted in fewer adverse events, long‐term follow‐up showed similar and weakened efficacy after 12 months. Trial Registration ChiCTR1900026365. Registered on October 3, 2019, http://www.chictr.org.cn/showproj.aspx?proj=43911. To evaluate the clinical efficacy and safety of intra‐articular injection with pure platelet‐rich plasma (P‐PRP) versus those of leukocyte platelet‐rich plasma (L‐PRP) in treating knee cartilage lesions, we conducted a double‐blind, randomized controlled clinical trial with a larger sample and longer follow‐up period. From October 2019 to October 2020, 95 patients were invited to participate in our study, and 60 (63.2%) were randomized to P‐PRP (n = 30) or L‐PRP (n = 30) groups. Patients from the two groups were treated with knee intra‐articular injections of P‐PRP or L‐PRP. VAS and WOMAC scores were assessed preoperatively and at 6 weeks, 12 weeks, 6 months, and 12 months after intervention. The short‐term results of our study are encouraging and demonstrate that both L‐PRP and P‐PRP intra‐articular injections reduce pain and improve function in patients with knee cartilage lesions. Compared with the L‐PRP injection, the P‐PRP injection (which had a lower risk of early inflammation caused by leukocytes) showed better clinical efficacy in the early phase of postoperative rehabilitation and resulted in fewer adverse events. However, long‐term clinical efficacy for both injections were similar and weakened after 12 months.

Platelet concentrates have emerged as innovative autologous blood products that enhance tissue healing and regeneration in regenerative therapy. A common feature of these products is their higher than baseline platelet concentration, which improves wound healing and tissue repair. Four main categories of products can be easily defined, based on their leukocyte content and fibrin architecture: pure platelet‐rich plasma, such as Cell Separator PRP or Anitua' PRGF; leukocyte‐ and platelet‐rich plasma (L‐PRP), such as PCCS or Ace PRP; pure platelet‐rich fibrin (P‐PRF), such as Fibrinet PRFM; and leukocyte‐ and platelet‐rich fibrin (L‐PRF), such as Choukroun's PRF. Two families contain significant concentrations of leukocytes: L‐PRP and L‐PRF. These four families of products have different biological signatures and mechanisms and obviously different clinical applications. An L‐PRF membrane releases growth factors and matrix proteins over a period longer than 7 days, whereas a PRP gel matrix releases and disperses its growth factors in a relatively quick download. In the near future, simple and inexpensive products such as L‐PRF are expected to have applications in oral‐maxillofacial surgery, periodontal surgery, plastic surgery, orthopedic surgery, and sports medicine. Leukocytes substantially affect the intrinsic biology and properties of platelet concentrates, not only because they enhance immune function and antibacterial potential, but also because they have essential roles in the wound healing process. Unfortunately, their impact has been almost completely neglected in the literature. Improved understanding of the effects of leukocytes in wound healing is essential for development of new clinical applications of platelet concentrates.

Background Chronic refractory wounds refer to wounds that cannot be repaired timely. Platelet‐rich plasma (PRP) has significant potential in chronic wound healing therapy. The exosomes isolated from PRP were proved to exhibit more effectiveness than PRP. However, the therapeutic potential of exosomes from PRP on chronic refractory wounds remained elusive. Hence, this study aimed to clarify the action of exosomes from PRP on chronic refractory wounds by evaluating the response of macrophages to exosomes. Methods Pure platelet‐rich plasma (P‐PRP) and leukocyte platelet‐rich plasma (L‐PRP) were prepared from the fasting venous blood of healthy volunteers. Exosomes were extracted from P‐PRP and L‐PRP using ultracentrifugation and identified by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and western blot. Macrophages were obtained by inducing THP‐1 cells with phorbol‐12‐myristate‐13 acetate (PMA). The internalization of exosomes into macrophages was observed utilizing confocal laser scanning microscopy after being labeled with PKH67. Cell viability was determined by CCK‐8 assay. Cell apoptosis was measured utilizing a flow cytometer. The polarization status of M1 and M2 macrophages were evaluated by detecting their markers. Nitric oxide (NO) detection was conducted using the commercial kit. Results Exosomes from P‐PRP and L‐PRP were absorbed by macrophages. Exosomes from L‐PRP restrained viability and induced apoptosis of macrophages. Besides, exosomes from P‐PRP promoted M2 polarization, and exosomes from L‐PRP promoted M1 polarization. Furthermore, exosomes from L‐PRP promoted NO generation of macrophages. Conclusion Exosomes from L‐PRP restrained viability, induced apoptosis and NO generation of macrophages, and promoted M1 polarization, while exosomes from P‐PRP increased M2 polarization. The exosomes from L‐PRP presented a more effective effect on macrophages than that from P‐PRP, making it a promising strategy for chronic refractory wound management. Exosomes from L‐PRP restrained viability, induced apoptosis and NO generation of macrophages, and promoted M1 polarization, while exosomes from P‐PRP increased M2 polarization. The exosomes from L‐PRP presented a more effective effect on macrophages than that from P‐PRP, making it a promising strategy for chronic refractory wound management.

Storing platelet-rich plasma (PRP) for future use is a compelling approach, presuming the retention of biological properties is maintained. However, certain factors in PRP preparations have deleterious effects for the treatment of certain musculoskeletal conditions. The purpose of this study was to measure and compare matrix metalloproteinase protein (MMP) concentrations between fresh and freeze-thawed leukocyte-rich PRP (LR-PRP) inactivated (LR-I) and activated (LR-A) preparations, and leukocyte-poor PRP (LP-PRP) inactivated (LP-I) and activated (LP-A) preparations. A volume of 60 mL of whole blood was drawn from 19 healthy donors. LP-I and LR-I samples were processed using a manual extraction and centrifugation methodology. LP-A and LR-A products were activated with 10% CaCl2 and recombinant thrombin. Blood fractions were either immediately assayed and analyzed or stored at −80 °C for 24, 72 and 160 h. Multiplex immunoassay was used to measure MMP-1, MMP-2, MMP-3, MMP-9, MMP-10, and MMP-12. MMP-1 concentrations increased in LR-A (p < 0.05) and MMP-9 significantly increased in LR-I (p < 0.05), while MMP-2 significantly decreased in LR-I (p < 0.05) and MMP-3 concentrations significantly decreased in LR-A (p < 0.05). MMP-12 concentrations also significantly decreased in LR-I (p < 0.05) from baseline concentrations. There were no significant differences between LP-A and LP-I preparations and MMP concentrations. MMP-10 concentrations in all PRP samples compared to each freezing time point were also not significantly different. MMPs regulate components of the extracellular matrix (ECM) in the remodeling phase of musculoskeletal injury. In this study, we observed a significant increase and decrease in MMP concentrations in response to a single freeze–thaw cycle in inactivated PRP and activated PRP preparations. This evidence contributes to the growing body of literature on the optimization of PRP preparation and storage strategies prior to delivery. Our findings suggest that specific PRP preparations after a single freeze–thaw may be more advantageous for certain musculoskeletal applications based on the presence of MMP concentrations.

Background: Platelet-rich plasma (PRP) has been extensively used as a treatment in tissue healing in tendinopathy, muscle injury, and osteoarthritis. However, there is variation in methods of extraction, and this produces different types of PRP. Purpose: To determine the composition of PRP obtained from 4 commercial separation kits, which would allow assessment of current classification systems used in cross-study comparisons. Study Design: Controlled laboratory study. Methods: Three normal adults each donated 181 mL of whole blood, some of which served as a control and the remainder of which was processed through 4 PRP separation kits: GPS III (Biomet Biologics), Smart-Prep2 (Harvest Terumo), Magellan (Arteriocyte Medical Systems), and ACP (Device Technologies). The resultant PRP was tested for platelet count, red blood cell count, and white blood cell count, including differential in a commercial pathology laboratory. Glucose and pH measurements were obtained from a blood gas autoanalyzer machine. Results: Three kits taking samples from the “buffy coat layer” were found to have greater concentrations of platelets (3-6 times baseline), while 1 kit taking samples from plasma was found to have platelet concentrations of only 1.5 times baseline. The same 3 kits produced an increased concentration of white blood cells (3-6 times baseline); these consisted of neutrophils, leukocytes, and monocytes. This represents high concentrations of platelets and white blood cells. A small drop in pH was thought to relate to the citrate used in the sample preparation. Interestingly, an unexpected increase in glucose concentrations, with 3 to 6 times greater than baseline levels, was found in all samples. Conclusion: This study reveals the variation of blood components, including platelets, red blood cells, leukocytes, pH, and glucose in PRP extractions. The high concentrations of cells are important, as the white blood cell count in PRP samples has frequently been ignored, being considered insignificant. The lack of standardization of PRP preparation for clinical use has contributed at least in part to the varying clinical efficacy in PRP use. Clinical Relevance: The variation of platelet and other blood component concentrations between commercial PRP kits may affect clinical treatment outcomes. There is a need for standardization of PRP for clinical use.

In this study, we aimed at performing a comparison between intra-articular injections of PRP-derived growth factor (PGRF) and hyaluronic acid regarding their effect on pain and patient's function in knee osteoarthritis, as well as their safety profiles. During our single-masked randomized clinical trial, the candidates with symptomatic knee osteoarthritis received two intra-articular injections of PRGF with 3 weeks apart or received three weekly injections of HA. The mean improvements from before treatment until the second, sixth, and twelfth months post-intervention in scores obtained by visual analog scale (VAS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Lequesne index were our primary outcomes. A total of 102 candidates were finally included in the study. Patients' mean age was 57.08±7.3 years old in the PRGF group compared to the mean age of 58.63±7.09 years old in HA patients. In the PRGF group, total WOMAC index decreased from 41.96±11.71 to 27.10±12.3 (P = 0.02), and from 39.71±10.4 to 32.41±11.8 in the HA group after 12 months (P > 0.05). Regarding the Lequesne index, pain, ADL, and global scores significantly decreased after 12 months in the PRGF group compared to the HA group (P<0.001). There was also a meaningful higher rate of satisfaction in the PRGF group compared to the HA group after 12 months of treatment (P<0.001). Besides significantly higher satisfaction belonging to the PRGF group, there was a statistically significant improvement in VAS score and global, pain, and ADL score of Lequesne by passing 12 months from injection in PRGF compared to HA.

Platelet rich plasma (PRP) was tested as a potential therapy for androgenetic alopecia (AGA) through two different clinical protocols in which one population (18 participants) received half-head treatment with autologous non-activated PRP (A-PRP) produced by CPunT Preparation System (Biomed Device, Modena, Italy) and the other half-head with placebo, and a second separated population in which all participants (n = 6, 3 participants per group) received treatment with calcium-activated PRP (AA-PRP) produced from one of two different PRP collection devices (Regen Blood Cell Therapy or Arthrex Angel System). For the A-PRP study, three treatments were administered over 30-day intervals. Trichoscan analysis of patients, three months post-treatment, showed a clinical improvement in the number of hairs in the target area (36 ± 3 hairs) and in total hair density (65± 5 hair cm2), whereas negligible improvements in hair count (1.1± 1.4 hairs) and density (1.9 ± 10.2 hair cm2) were seen in the region of the scalp that received placebo. Microscopic evaluation conducted two weeks after treatment showed also an increase in epidermal thickness, Ki67+ keratinocytes, and in the number of follicles. The AA-PRP treatment groups received a singular set of injections, and six months after the treatments were administered, notable differences in clinical outcomes were obtained from the two PRP collection devices (+90 ± 6 hair cm2 versus -73 ± 30 hair cm2 hair densities, Regen versus Arthrex). Growth factor concentrations in AA-PRP prepared from the two collection devices did not differ significantly upon calcium activation.