Platelet-rich plasma: the PAW classification system

Platelet Rich plasma injection of the vocal folds in benign vocal pathologies

PURPOSE

There are few options for treatment of dysphonia secondary to vocal pathology related to lamina propria scar, atrophy, sulcus, or inflammatory disorders. Platelet rich plasma (PRP) may provide anti-inflammatory and regenerative properties seen with other tissue engineering therapies without the risks associated with these treatments. We evaluated vocal fold (VF) injection of PRP for feasibility, phonatory effects, patient satisfaction and durability.

METHODS

Patients with dysphonia secondary to vocal fold scar, atrophy, sulcus and inflammatory lesions were included. PRP injections were administered in office, to bilateral vocal folds. Patients were followed up at 1 week, 1 month, 3 months and 6 months to assess outcomes (GRBAS scale, maximum phonation time, vocal fatigue index (VFI), voice handicap index (VHI-10) and stroboscopy).

RESULTS

75 intracordal PRP injections were administered to 48 patients. All injections were completed, and no adverse reactions were experienced. Improvements in VHI-10 scores at 1,3,6 months were seen (mean VHI 21.73 at baseline, 15.62 at six months, p < 0.001). 72.3% rated improvement at 7 or above on Likert scale. 95.7% of patients would consider a future PRP injection. Secondary outcomes VFI, MPT, and GRBAS also demonstrated significant improvements over time. Patients receiving a single PRP injection (n = 26) still demonstrated significant VHI-10 improvements at 1,3 and 6 months.

CONCLUSIONS

VF office PRP injections are feasible and safe and can provide phonatory benefit and reduce vocal effort in benign VF disorders. A single PRP injection is sufficient to provide sustained benefit in some cases.

LEVEL OF EVIDENCE

Level III: prospective cohort study.

Platelet-Rich Plasma Promotes the Expansion of Human Myoblasts and Favors the In Vitro Generation of Human Muscle Reserve Cells in a Deeper State of Quiescence

Stem cell therapy holds significant potential for skeletal muscle repair, with in vitro-generated human muscle reserve cells (MuRCs) emerging as a source of quiescent myogenic stem cells that can be injected to enhance muscle regeneration. However, the clinical translation of such therapies is hampered by the need for fetal bovine serum (FBS) during the in vitro generation of human MuRCs. This study aimed to determine whether fresh allogeneic human platelet-rich plasma (PRP) combined or not with hyaluronic acid (PRP-HA) could effectively replace xenogeneic FBS for the ex vivo expansion and differentiation of human primary myoblasts. Cells were cultured in media supplemented with either PRP or PRP-HA and their proliferation rate, cytotoxicity and myogenic differentiation potential were compared with those cultured in media supplemented with FBS. The results showed similar proliferation rates among human myoblasts cultured in PRP, PRP-HA or FBS supplemented media, with no cytotoxic effects. Human myoblasts cultured in PRP or PRP-HA showed reduced fusion ability upon differentiation. Nevertheless, we also observed that human MuRCs generated from PRP or PRP-HA myogenic cultures, exhibited increased Pax7 expression and delayed re-entry into the cell cycle upon reactivation, indicating a deeper quiescent state of human MuRCs. These results suggest that allogeneic human PRP effectively replaces FBS for the ex vivo expansion and differentiation of human myoblasts and favors the in vitro generation of Pax7High human MuRCs, with important implications for the advancement of stem cell-based muscle repair strategies.

Is There a Need for an Exogenous Activator Along with PRP for Early Knee Osteoarthritis? A Triple-Blinded Randomized Control Trial

Background

In addition to other variables associated with PRP injections for Knee Osteoarthritis (OA), some confusion exists about the role of exogenous activators. The current study looks at matched groups getting PRP injections with or without activator (Calcium gluconate) in early knee OA patients.

Methods

Patients of early OA knee meeting inclusion criteria were randomly divided into 2 groups; Group A (43 patients) received 8 ml PRP injection alone, and Group B (48 patients) received 8 ml PRP along with 2 ml Calcium gluconate as activator. The patients were evaluated at baseline, 6 weeks, 3 months and 6 months for WOMAC Pain and Total WOMAC scores; secondary variables assessed were VAS score and patient satisfaction.

Results

The baseline characteristics of both groups were comparable. Leucocyte-depleted PRP with 5 times concentration and average absolute platelet numbers of 7.144 billion per knee was injected. Mean Pain WOMAC scores decreased in both groups from baseline (group A-8.68, group B-9.09) to final follow-up (group A-4.67, group B-5.11). Similarly, Mean Total WOMAC scores decreased from baseline (group A-37.81, group B-37.41) to (group A-21, group B-21.36) at the final follow-up in both groups. There was no significant difference between both groups, and both showed similar trends. Similar findings were noted for VAS scores. Patient satisfaction was also not different (group A, 90.69%, group B, 89.58%) at the end of 6 months.

Conclusion

Our study concluded doubtful role of adding exogenous activator to PRP preparation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43465-024-01159-7.

Immunoregulatory role of platelet derivatives in the macrophage-mediated immune response

Background

Macrophages are innate immune cells that display remarkable phenotypic heterogeneity and functional plasticity. Due to their involvement in the pathogenesis of several human conditions, macrophages are considered to be an attractive therapeutic target. In line with this, platelet derivatives have been successfully applied in many medical fields and as active participants in innate immunity, cooperation between platelets and macrophages is essential. In this context, the aim of this review is to compile the current evidence regarding the effects of platelet derivatives on the phenotype and functions of macrophages to identify the advantages and shortcomings for feasible future clinical applications.

Methods

A total of 669 articles were identified during the systematic literature search performed in PubMed and Web of Science databases.

Results

A total of 27 articles met the inclusion criteria. Based on published findings, platelet derivatives may play an important role in inducing a dynamic M1/M2 balance and promoting a timely M1-M2 shift. However, the differences in procedures regarding platelet derivatives and macrophages polarization and the occasional lack of information, makes reproducibility and comparison of results extremely challenging. Furthermore, understanding the differences between human macrophages and those derived from animal models, and taking into account the peculiarities of tissue resident macrophages and their ontogeny seem essential for the design of new therapeutic strategies.

Conclusion

Research on the combination of macrophages and platelet derivatives provides relevant information on the function and mechanisms of the immune response.

Platelet-Rich Plasma in Young and Elderly Humans Exhibits a Different Proteomic Profile

As people age, their ability to resist injury and repair damage decreases significantly. Platelet-rich plasma (PRP) has demonstrated diverse therapeutic effects on tissue repair. However, the inconsistency of patient outcomes poses a challenge to the practical application of PRP in clinical practice. Furthermore, a comprehensive understanding of the specific impact of aging on PRP requires a systematic investigation. We derived PRP from 6 young volunteers and 6 elderly volunteers, respectively. Subsequently, 95% of high-abundance proteins were removed, followed by mass spectrometry analysis. Data are available via ProteomeXchange with the identifier PXD050061. We detected a total of 739 proteins and selected 311 proteins that showed significant differences, including 76 upregulated proteins in the young group and 235 upregulated proteins in the elderly group. Functional annotation and enrichment analysis unveiled upregulation of proteins associated with cell apoptosis, angiogenesis, and complement and coagulation cascades in the elderly. Conversely, IGF1 was found to be upregulated in the young group, potentially serving as the central source of enhanced cell proliferation ability. Our investigation not only provides insights into standardizing PRP preparation but also offers novel strategies for augmenting the functionality of aging cells or tissues.

Leukocyte-Poor Platelet-Rich Plasma as an Adjuvant to Arthroscopic Rotator Cuff Repair Reduces the Retear Rate But Does Not Improve Functional Outcomes: A Double-Blind Randomized Controlled Trial

BACKGROUND

Whether the use of PRP as an adjuvant of rotator cuff repairs leads to improved tendon healing and better functional outcomes remains unclear in clinical evidence.

PURPOSE

The main purpose of this study was to assess whether the use of leukocyte-poor platelet-rich plasma (LP-PRP) as an adjuvant to arthroscopic rotator cuff repair (ARCR) decreases the rate of retears compared with a control group. The secondary objective was to analyze whether LP-PRP improves patient-reported outcomes.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

This was a double-blind randomized controlled trial at a single center. A consecutive series of 96 patients with rotator cuff tears <3 cm were enrolled and randomly allocated to the control group (double-row suture-bridge ARCR alone [n = 48]) and the PRP group (double-row suture-bridge repair, followed by 1 LP-PRP injection during surgery [n = 48]). The visual analog scale (VAS) for pain, the American Shoulder and Elbow Surgeons (ASES) score, the Single Assessment Numeric Evaluation (SANE), and the Pittsburgh Sleep Quality Index (PSQI) were administered preoperatively and at 6- and 12-month follow-up. Magnetic resonance imaging (MRI) was performed to evaluate tendon integrity at 6-month follow-up. Both patients and assessors were blinded to the intervention received during surgery.

RESULTS

The mean patient age was 56.1 ± 2.98 years. Of the 96 patients, 90 had MRI performed at 6 months after surgery (94% radiological follow-up). The retear rate in the PRP group was 15.2% (7/46 [95% CI, 6%-28%]), which was lower than that in the control group of 34.1% (15/44 [95% CI, 20%-49%]) (P = .037). Therefore, the risk ratio of ruptures in patients exposed to LP-PRP was 0.44 (95% CI, 0.2-0.9; P = .037). Overall, the ASES, VAS, SANE, and PSQI scores showed a statistical improvement after surgery (P < .001). There were no significant differences in functional scores between the groups. Most of the patients exceeded the minimal clinically important difference for the ASES, SANE, and VAS without significant differences between the groups.

CONCLUSION

In patients with rotator cuff tears <3 cm undergoing double-row suture-bridge repair, a 5-mL dose of LP-PRP injected at the tendon-bone interface significantly reduced the retear rate. However, the use of LP-PRP in terms of postoperative pain and patient-reported outcomes failed to show clinically meaningful effects.

REGISTRATION

NCT04703998 (ClinicalTrials.gov identifier).

The Role of Platelet-Rich Plasma Injection for Muscle Strains in Athletes

Muscle tears/strains are among the most common musculoskeletal injuries, posing a serious challenge for sports medicine. Aiming to reduce the time to return to play and the rate of reinjuries, apart from the traditional conservative treatments and rehabilitation protocols, new and innovative therapeutic options have emerged, particularly platelet-rich plasma (PRP). This study aims to present the available evidence regarding PRP injection for the treatment of muscle strains in athletes. Two databases were searched for articles published between January 2012 and December 2022 in Portuguese or English. The query used for the PubMed database was ("Muscles/injuries"[Mesh]) AND ("Athletes"[Mesh] OR "Athletic Injuries"[Mesh]) AND "Platelet-Rich Plasma"[Mesh], while for the Web of Science database the search was performed for "Platelet-rich plasma" AND "Muscle injuries" AND ("Athletes" OR "Athletic injuries"). Eleven studies involving athletes diagnosed with muscle injuries who received treatment with PRP injection alone, or in combination with traditional conservative treatment, compared to a control group, were included. Four randomized controlled trials, four systematic reviews/meta-analyses, two retrospective studies, and one comparative study were included. Current evidence from the highest-quality studies does not support the hypothesis of reduction of time to return to play and the rate of reinjuries after PRP injection, even though some studies reported positive results. However, the available evidence suggests that PRP might have a beneficial effect on the pain perceived by athletes following an acute muscle strain. It is challenging to arrive at definitive conclusions and translate these findings into a clinical context for treating muscle strains in athletes. The existing trials present several inconsistencies and limitations, with a heterogeneous set of patients and injuries, as well as the use of different and inconsistent methods for preparing, administering, and measuring the effects of PRP. To achieve consistent outcomes, standardizing PRP administration procedures is essential.

Platelet-Rich Plasma Injections in Chronic Lateral Ankle Instability: A Case Series

The platelet-rich plasma (PRP) approach may be an effective treatment for joint and cartilage pathologies. However, the rationale for its effectiveness on joint instability is limited. This study aimed to assess the safety and effectiveness of PRP injections in patients with chronic lateral ankle instability (CLAI). This retrospective study was performed at a single-center outpatient clinic between January 2015 and February 2023 and included pre-intervention assessment and short-term follow-up. Patients were excluded if they had received previous surgical treatment or had constitutional hyperlaxity, systemic diseases, or grade II or III osteoarthritis. The clinical and functional evaluation consisted of the Karlsson score, the Cumberland Ankle Instability Tool (CAIT), Good's grading system, the patient's subjective satisfaction level, and the time required to return to exercise. The entire PRP therapy regime consisted of three PRP administrations at 7-day intervals and follow-up appointments. PRP was administered both intraarticularly and into talofibular ligaments. A total of 47 consecutive patients with CLAI were included, 11 were female (23.4%), with a mean age at intervention of 31.19 ± 9.74 years. A statistically significant improvement was found in the CAIT and Karlsson scores at 3 months (27.74 ± 1.68 and 96.45 ± 4.28, respectively) relative to the pre-intervention status (10.26 ± 4.33 and 42.26 ± 14.9, respectively, p < 0.000). The mean follow-up of patients with CLAI was 17.94 ± 3.25 weeks. This study represents successful short-term functional and clinical outcomes in patients with CLAI after PRP treatment, with no adverse effects. It demonstrates the feasibility of a randomized controlled trial to further assess this therapy.

Review of Dohan Eherenfest et al. (2009) on "Classification of platelet concentrates: From pure platelet-rich plasma (P-PRP) to leucocyte- and platelet-rich fibrin (L-PRF)"

This classic discusses the original publication of Dohan Eherenfest et al. on "Classification of platelet concentrates: from pure platelet-rich plasma (P-PRP) to leucocyte- and platelet-rich fibrin (L-PRF)", in which the authors propose four categories of platelet concentrates depending on their leucocyte and fibrin content (P-PRP, leucocyte- and platelet-rich plasma (L-PRP), pure platelet-rich fibrin (P-PRF), and L-PRF) to group a "jungle" of products in which the term platelet-rich plasma (PRP) was used indistinctly. They were able to identify common factors such as: (1) the use of anticoagulants and immediate centrifugation of the blood after its collection; (2) most preparation techniques allowed platelet concentrate preparation within an hour; (3) the centrifugation aimed to separate the blood in layers that would allow the extraction of specific fractions; and (4) the product was activated with thrombin or calcium chloride. The reviewed manuscript has been listed among the most cited PRP articles in regenerative medicine, with more than 800 citations, driving current scientific research and clinical practise by categorising L-PRP and P-PRP (now, leucocyte-poor PRP). The classification has also opened the door to understanding intrinsic biological mechanisms between platelets, leukocytes, fibrin, and growth factors, which will later be considered for studying the proliferation and differentiation of cells in different tissues affected by PRP. Since the initial classification of platelet concentrates, several other classification systems have been proposed and published in the current literature such as platelet, activation, white blood cell (PAW), Mishra, platelet, leucocyte, red blood cells, and activation (PLRA), dose of platelet, efficiency, purity, and activation (DEPA), method, activation, red blood cells, spin, platelets, image guidance, leukocytes, and light activation (MARSPILL), etc. These classifications have identified important aspects of PRP that affect the biological composition and, ultimately, the indications and outcomes. To date, there is still a lack of standardisation in sample preparation, cohort heterogeneity, and incomplete reporting of sample preparation utilised, leading to a lack of clarity and challenging researchers and clinicians.

Safety and feasibility of percutaneous needle tunneling with platelet-rich plasma injections for Peyronie's disease in the outpatient setting: a pilot study

The objective of this study is to evaluate the safety and feasibility of the combined simultaneous percutaneous needle tunneling coupled with injection of platelet-rich plasma in the outpatient department for the treatment of Peyronie's disease. This prospective, non-randomized, cohort and preliminary study included patients who underwent this procedure from November 2020 to July 2022. The main outcome was an improvement in penile curvature. Fifty-four patients were enrolled and underwent 6 sessions under local anesthesia followed by vacuum therapy for the treatment of Peyronie's disease in our outpatient unit. The amendment of the curvature angle was significant with a median correction percentage of -44.40% interquartile range (-66.70 to (-39.70)), [p-value = 0.001, 95% CI (-29.76 to (-18.02)), paired Student's t-test]. The median pre-treatment curvature angle was 45° (40-75), and the median post-treatment was 30° (20-40). The median score for pain during the procedure was 3 (0-4.25) according to a 10-point visual analogic scale. After two hours, 20.37% of patients still had pain but none required any pain medication. 50% of patients had a minor hematoma and 75.93% patients reported penile ecchymosis. A single patient reported an injection site skin infection. In our experience percutaneous needle tunneling with platelet-rich plasma injections for Peyronie's disease in the outpatient setting is a safe, effective, and feasible treatment of penile deformity for PD.

Most Publications Regarding Platelet-Rich Plasma Use in the Knee Are From Asia, Investigate Injection for Osteoarthritis, and Show Outcome Improvement: A Scoping Review

PURPOSE

To evaluate and synthesize the available literature related to platelet-rich plasma (PRP) treatment of knee pathologies and to provide recommendations to inform future research in the field.

METHODS

PubMed, CINAHL, and Scopus databases were queried on October 6, 2023. All identified citations were collated and uploaded into Covidence for screening and data extraction. Studies were included if they were human studies published in English with adult cohorts that received PRP as a procedural injection or surgical augmentation for knee pathologies with patient-reported outcome measures (PROMs) and level of evidence Levels I-IV.

RESULTS

Our search yielded 2,615 studies, of which 155 studies from 2006 to 2023 met the inclusion criteria. Median follow-up was 9 months (±11.2 months). Most studies (75.5%) characterized the leukocyte content of PRP, although most studies (86%) did not use a comprehensive classification scheme. In addition, most studies were from Asia (50%) and Europe (32%) and were from a single center (96%). In terms of treatment, 74% of studies examined PRP as a procedural injection, whereas 26% examined PRP as an augmentation. Most studies (68%) examined treatment of knee osteoarthritis. Many studies (83%) documented significant improvements in PROMs, including 93% of Level III/IV evidence studies and 72% of Level I/II evidence studies, although most studies (70%) failed to include minimal clinically important difference values. The visual analog scale was the most-used PROM (58% of studies), whereas the Short Form Health Survey 36-item was the least-used PROM (5% of studies).

CONCLUSIONS

Most published investigations of knee PRP are performed in Asia, investigate procedural injection for osteoarthritis, and show significant outcome improvements. In addition, this review highlights the need for better classification of PRP formulations.

LEVEL OF EVIDENCE

Level IV, scoping Review of level I-IV studies.

Biochemical and biomechanical characterization of an autologous protein-based fibrin sealant for regenerative medicine

Accidental events or surgical procedures usually lead to tissue injury. Fibrin sealants have proven to optimize the healing process but have some drawbacks due to their allogeneic nature. Autologous fibrin sealants present several advantages. The aim of this study is to evaluate the performance of a new autologous fibrin sealant based on Endoret®PRGF® technology (E-sealant). One of the most widely used commercial fibrin sealants (Tisseel®) was included as comparative Control. E-sealant´s hematological and biological properties were characterized. The coagulation kinetics and the microstructure were compared. Their rheological profile and biomechanical behavior were also recorded. Finally, the swelling/shrinkage capacity and the enzymatic degradation of adhesives were determined. E-sealant presented a moderate platelet concentration and physiological levels of fibrinogen and thrombin. It clotted 30 s after activation. The microstructure of E-sealant showed a homogeneous fibrillar scaffold with numerous and scattered platelet aggregates. In contrast, Control presented absence of blood cells and amorphous protein deposits. Although in different order of magnitude, both adhesives had similar rheological profiles and viscoelasticity. Control showed a higher hardness but both adhesives presented a pseudoplastic hydrogel nature with a shear thinning behavior. Regarding their adhesiveness, E-sealant presented a higher tensile strength before cohesive failure but their elastic stretching capacity and maximum elongation was similar. While E-sealant presented a significant shrinkage process, Control showed a slight swelling over time. In addition, E-sealant presented a high enzymatic resorption rate, while Control showed to withstand the biodegradation process in a significant way. E-sealant presents optimal biochemical and biomechanical properties suitable for its use as a fibrin sealant with regenerative purposes.

Synergistic Hepatoprotective Effects of Mesenchymal Stem Cells and Platelet-Rich Plasma in a Rat Model of Bile Duct Ligation-Induced Liver Cirrhosis

Liver cirrhosis poses a global health challenge marked by significant prevalence and mortality. Current therapeutic options are limited by high costs and immune-mediated rejection, necessitating the exploration of innovative strategies to enhance hepatic self-rehabilitation, and counteract the underlying pathological mechanisms. We evaluated the hepatoprotective activity of rat adipose-derived mesenchymal stem cells (ADMSCs) in combination with platelet-rich plasma (PRP) and recombinant human hepatocyte growth factor (rh-HGF) on a rat model of liver fibrosis/cirrhosis induced by bile duct ligation (BDL). Treatment with PRP or rh-HGF alone did not yield significant hepatoprotection in the BDL-induced liver cirrhosis model. However, ADMSC transplantation alone exhibited the potential to alleviate impaired liver conditions. The combination of PRP and rh-HGF demonstrated superior ameliorative effects compared to either treatment alone. Notably, the combination of ADMSC + PRP or ADMSC + rh-HGF significantly enhanced hepatoprotective capacity compared to individual or combined PRP and rh-HGF therapies. Injection of ADMSC via the tail vein reduced inflammation, hepatocyte damage, and collagen deposition, improving overall liver function. This improvement was more pronounced when ADMSC was administered with PRP and rh-HGF versus monotherapy. Our study concludes that ADMSCs exert antifibrotic effects by inhibiting hepatic stellate cell proliferation, collagen synthesis, and inducing apoptosis. ADMSCs also demonstrate immune-modulatory effects and transdifferentiate into hepatic progenitor cells, secreting trophic factors, cytokines, and chemokines that promote impaired liver regeneration. The observed arrest in liver fibrosis progression highlights the potential therapeutic impact of these interventions.

Recent Achievements in the Development of Biomaterials Improved with Platelet Concentrates for Soft and Hard Tissue Engineering Applications

Platelet concentrates such as platelet-rich plasma, platelet-rich fibrin or concentrated growth factors are cost-effective autologous preparations containing various growth factors, including platelet-derived growth factor, transforming growth factor β, insulin-like growth factor 1 and vascular endothelial growth factor. For this reason, they are often used in regenerative medicine to treat wounds, nerve damage as well as cartilage and bone defects. Unfortunately, after administration, these preparations release growth factors very quickly, which lose their activity rapidly. As a consequence, this results in the need to repeat the therapy, which is associated with additional pain and discomfort for the patient. Recent research shows that combining platelet concentrates with biomaterials overcomes this problem because growth factors are released in a more sustainable manner. Moreover, this concept fits into the latest trends in tissue engineering, which include biomaterials, bioactive factors and cells. Therefore, this review presents the latest literature reports on the properties of biomaterials enriched with platelet concentrates for applications in skin, nerve, cartilage and bone tissue engineering.

Advances with Platelet-Rich Plasma for Bone Healing

Despite significant advances in the understanding and delivery of osteosynthesis, fracture non-union remains a challenging clinical problem in orthopaedic surgery. To bridge the gap, basic science characterization of fracture healing provides a platform to identify and target biological strategies to enhance fracture healing. Of immense interest, Platelet-rich plasma (PRP) is a point of care orthobiologic that has been extensively studied in bone and soft tissue healing given its relative ease of translation from the benchtop to the clinic. The aim of this narrative review is to describe and relate pre-clinical in-vitro and in-vivo findings to clinical observations investigating the efficacy of PRP to enhance bone healing for primary fracture management and non-union treatment. A particular emphasis is placed on the heterogeneity of PRP preparation techniques, composition, activation strategies, and delivery. In the context of existing data, the routine use of PRP to enhance primary fracture healing and non-union management cannot be supported. However, it is acknowledged that extensive heterogeneity of PRP treatments in clinical studies adds obscurity; ultimately, refinement (and consensus) of PRP treatments for specific clinical indications, including repetition studies are warranted.

A systematic review and meta-analysis of the efficacy of platelet-rich plasma products for treatment of equine joint disease

BACKGROUND

Equine joint disease including septic arthritis (SA) and osteoarthritis (OA) is a critical cause of equine lameness. Platelet-rich plasma (PRP) is one of the most popular regenerative therapies to treat equine OA, even SA, but the evidence in support of the treatment is conflicting.

OBJECTIVES

The aim of the study was to systematically review the current evidence on PRP products used for SA and OA, as well as the efficacy of PRP products as treatment for OA on the basis of a meta-analysis of the available literature.

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

A systematic search of relevant databases (PubMed, Web of Science, Scopus) was performed to identify studies published from 2013 to 2023, in accordance with the PRISMA guidelines. Randomised controlled trials, non-randomised trials and controlled laboratory studies that used at least one type of PRP products were included. Dichotomous outcomes were presented using odds ratios (ORs) and 95% confidence intervals (95% CIs).

RESULTS

A total of 21 publications were identified in the systematic review and 5 of them in the meta-analysis. These publications involved various types of PRP products and reported different outcomes. Although most of the studies were associated with a high risk of bias, the overall estimated effect was consistent with a significant improvement in the PRP products treatment group compared with the control group (OR: 15.32; 95% CI: 3.00-78.15; p < 0.05). There was a significant improvement in clinical performance outcomes between the groups (OR: 36.64; 95% CI: 3.69-364.30; p < 0.05).

CONCLUSION

PRP products as intra-articular treatment are likely efficacious for treatment of equine OA and have potential for treating SA. These conclusions might be affected by the limited number of randomised controlled studies and high variability of different types of PRP products. To better evaluate the efficacy of PRP, a widely recognised classification system and the utilisation of randomised, blinded, equivalency or non-inferiority trials are required.

An Update on Orthobiologics: Cautious Optimism

Orthobiologics are rapidly growing in use given their potential to augment healing for multiple musculoskeletal conditions. Orthobiologics consist of a variety of treatments including platelet-rich plasma and stem cells that provide conceptual appeal in providing local delivery of growth factors and inflammation modulation. The lack of standardization in nomenclature and applications within the literature has led to a paucity of high-quality evidence to support their frequent use. The purpose of this review was to describe the current landscape of orthobiologics and the most recent evidence regarding their use.

Patient Outcomes Are Not Improved by Platelet-Rich Plasma Injection Onto the Capsule at the Time of Closure During Hip Arthroscopy for Femoroacetabular Impingement Syndrome

Purpose

To determine the effect of platelet-rich plasma (PRP) injection onto the capsule at time of closure on outcomes of patients undergoing hip arthroscopy for femoroacetabular impingement syndrome.

Methods

Patients who underwent hip arthroscopy between January 2014 and December 2021 were retrospectively identified. The first cohort included patients who received PRP injection onto the capsule following capsular closure at the conclusion of the case. The second cohort did not receive PRP. Pain scores on a visual analog scale, Modified Harris Hip Scores, Single Assessment Numeric Evaluation (SANE), as well as Patient-Reported Outcomes Measurement Information System Physical Function scores were obtained preoperatively as well as at multiple time points postoperatively up to 2 years.

Results

In total, 345 patients were included in the study, with 293 in the PRP cohort and 52 in the non-PRP cohort. There was no significance difference in age (P = .69), sex, or preoperative pain (P = .92) and patient-reported outcome scores between the 2 groups (modified Harris Hip Score, P = .38; Patient-Reported Outcomes Measurement Information System Physical Function, P = .48), except for preoperative SANE scores, which had a greater baseline in the PRP group (P < .001). Using both observed data as well as repeated measure analysis of variance model to estimate for missing data after baseline, we found there were no differences in visual analog scale pain scores nor patient-reported outcome scores at any time point. There was similarly no difference in change from baseline for SANE scores. There was no difference in rate of revision surgery between the 2 cohorts (P = .66).

Conclusions

Based on the results of this study, intraoperative PRP injection onto the capsule at the time of capsular closure does not improve outcomes of patients undergoing hip arthroscopy for femoroacetabular impingement syndrome.

Level of Evidence

Level III, retrospective comparative study.

Orthobiologics as an adjunct in treatment of femoroacetabular impingement syndrome: cell-based therapies facilitate improved postoperative outcomes in the setting of acetabular chondral lesions-a systematic review

PURPOSE

To evaluate studies utilizing orthobiologics in the management of femoroacetabular impingement syndrome (FAIS) to (1) assess the indications for usage, and (2) analyze patient-reported outcome measures (PROM) following treatment. It was hypothesized that orthobiologics would (1) be utilized for symptomatic FAIS in the setting of labral or chondral pathology, and (2) improve PROM at most recent follow-up.

METHODS

The Pubmed, Ovid Medline, Cochrane, and Web of Science databases were searched for clinical studies evaluating orthobiologics [hyaluronic acid (HA), platelet-rich plasma (PRP), or cell-based therapy (CBT) for treatment of FAIS. Exclusion criteria included orthobiologics used in conjunction with cartilage transfer or scaffolding procedures and a primary indication other than FAIS. Data collection included patient demographics, indications, and baseline and most recent PROM.

RESULTS

Eleven studies (one level I, four level II, four level III, and two level IV evidence) met inclusion criteria, consisting of 440 patients with mean ages ranging from 32.8 to 47 years. All 11 studies demonstrated an improvement in PROM from baseline to most-recent follow-up. Four studies administered PRP either intraoperatively or the day after surgery as an adjunct to labral repair. CBT was used intraoperatively in the setting of acetabular chondral lesions (three studies) and labral repair (one study). When comparing to a control group at most recent follow-up, three PRP cohorts demonstrated similar PROM (n.s.), while one PRP group exhibited worse visual analog pain scores (2.5 vs. 3.4, p = 0.005) and modified Harris Hip Scores (mHHS) (82.6 vs. 78.7, p = 0.049). The four CBT studies reported favorable results compared to a control group, with a significantly higher mHHS at most recent follow-up or mean improvement from baseline in Hip Outcome Score-Activities of Daily Living (p < 0.05). Three studies reported on HA, which was utilized exclusively in the nonoperative setting.

CONCLUSIONS

Intraoperative PRP and CBT have been commonly reported in the setting of hip arthroscopy for labral repairs and acetabular chondral lesions, respectively. The CBT cohorts demonstrated more favorable PROM at most recent follow-up when compared to a control group, though these results should be interpreted with caution due to heterogeneity of orthobiologic preparations.

LEVEL OF EVIDENCE

IV.

Optimizing Platelet-Rich Plasma: Spin Time and Sample Source

The buff-colored layer separating the plasma from red blood cells (RBCs) in centrifuged blood was named the "buffy coat" in the late 19th century. The division of platelets (PLTs) and leukocytes (WBCs) between the buffy coat, plasma, and RBC layers in centrifuged blood has not been described before. In this study, we centrifuged 8.5 mL anticoagulated blood samples at 1000× g for 1, 2, 3, 5, 10, and 20 min. We then divided each sample into ten layers and analyzed each layer for cellular composition and mean platelet volume (MPV). Our results show that even after 20 min of centrifugation, about 15% of platelets remain in the plasma layers and 65% in the RBC layers. We found that the platelet count achieved from aspiration of 1 mL volume was optimal, with aspiration beginning 1/2 mL below the buffy coat and extending 1/2 mL above the buffy coat rather than beginning at the buffy coat itself and aspirating only plasma. Using this method of aspiration, we found that the total platelet count means reached a maximum in the 1 mL around the buffy coat after only 5 min of centrifugation.

Subacromial Platelet-Rich Plasma Injections Produce Significantly Worse Improvement in Functional Outcomes in Patients With Partial Supraspinatus Tears Than in Patients With Isolated Tendinopathy

PURPOSE

To compare the effect of subacromial leukocyte-rich platelet-rich plasma (PRP) injections in patients with isolated rotator cuff tendinopathy (RCT) and those with partial-thickness rotator cuff tears (PTRCTs) based on functional outcomes, pain improvement, sleep disturbances, and return to sports.

METHODS

Between November 2019 and March 2021, 150 patients underwent PRP injections at our institution for refractory rotator cuff tendinopathy and partial rotator cuff tears (105 RCTs and 45 PTRCTs). The American Shoulder and Elbow Surgeons (ASES) score, the visual analog scale (VAS) for pain, the Single Assessment Numeric Evaluation (SANE) and The Pittsburgh Sleep Quality Index were evaluated at 2-, 6-, and 12-month follow-up. Return to sports was also evaluated. An ultrasound examination was performed to evaluate structural outcomes 12 months after the injection.

RESULTS

The mean age was 36.6 years (±9.08). Overall, the ASES, VAS, SANE, and Pittsburgh scores showed statistical improvement after the injection (P < .01). Specifically, the improvement in the ASES score, which was the primary outcome measure was significantly greater in the group without tears than in the group with PTRCTs at all follow-up times. Moreover, 94% of the patients in the isolated RCT group and 49% in the PTRCTs group achieved a substantial clinical benefit at 12 months follow-up. Ten out of the 50 patients (20%) who received PRP injections due to a partial RC tear underwent surgery due to the lack of clinical improvement.

CONCLUSIONS

Subacromial PRP injections produced a significant improvement in shoulder function, pain, and sleep disturbances in most patients with RCT refractory to conservative treatment that was maintained at the 12-month follow-up. Moreover, most patients returned to sports at the same level prior to injury. However, improvement in symptoms and functional outcomes was significantly worse in patients who had a PTRCT compared with patients who had an isolated tendinopathy.

LEVEL OF EVIDENCE

Level II, prospective cohort study.

Platelets Rich Plasma Increases Antioxidant Defenses of Tenocytes via Nrf2 Signal Pathway

Tendinopathies are common disabling conditions in equine and human athletes. The etiology is still unclear, although reactive oxygen species (ROS) and oxidative stress (OS) seem to play a crucial role. In addition, OS has been implicated in the failure of tendon lesion repair. Platelet-rich plasma (PRP) is rich in growth factors that promote tissue regeneration. This is a promising therapeutic approach in tendon injury. Moreover, growing evidence has been attributed to PRP antioxidant effects that can sustain tissue healing. In this study, the potential antioxidant effects of PRP in tenocytes exposed to oxidative stress were investigated. The results demonstrated that PRP reduces protein and lipid oxidative damage and protects tenocytes from OS-induced cell death. The results also showed that PRP was able to increase nuclear levels of redox-dependent transcription factor Nrf2 and to induce some antioxidant/phase II detoxifying enzymes (superoxide dismutase 2, catalase, heme oxygenase 1, NAD(P)H oxidoreductase quinone-1, glutamate cysteine ligase catalytic subunit and glutathione, S-transferase). Moreover, PRP also increased the enzymatic activity of catalase and glutathione S-transferase. In conclusion, this study suggests that PRP could activate various cellular signaling pathways, including the Nrf2 pathway, for the restoration of tenocyte homeostasis and to promote tendon regeneration and repair following tendon injuries.

Advances in Platelet Rich Plasma-Derived Extracellular Vesicles for Regenerative Medicine: A Systematic-Narrative Review

The use of platelet-rich plasma (PRP) has gained increasing interest in recent decades. The platelet secretome contains a multitude of growth factors, cytokines, chemokines, and other biological biomolecules. In recent years, developments in the field of platelets have led to new insights, and attention has been focused on the platelets' released extracellular vesicles (EVs) and their role in intercellular communication. In this context, the aim of this review was to compile the current evidence on PRP-derived extracellular vesicles to identify the advantages and limitations fortheir use in the upcoming clinical applications. A total of 172 articles were identified during the systematic literature search through two databases (PubMed and Web of Science). Twenty publications met the inclusion criteria and were included in this review. According to the results, the use of PRP-EVs in the clinic is an emerging field of great interest that represents a promising therapeutic option, as their efficacy has been demonstrated in the majority of fields of applications included in this review. However, the lack of standardization along the procedures in both the field of PRP and the EVs makes it extremely challenging to compare results among studies. Establishing standardized conditions to ensure optimized and detailed protocols and define parameters such as the dose or the EV origin is therefore urgent. Further studies to elucidate the real contribution of EVs to PRP in terms of composition and functionality should also be performed. Nevertheless, research on the field provides promising results and a novel basis to deal with the regenerative medicine and drug delivery fields in the future.

Anti-Aging Potential of Platelet Rich Plasma (PRP): Evidence from Osteoarthritis (OA) and Applications in Senescence and Inflammaging

Aging and age-related changes impact the quality of life (QOL) in elderly with a decline in movement, cognitive abilities and increased vulnerability towards age-related diseases (ARDs). One of the key contributing factors is cellular senescence, which is triggered majorly by DNA damage response (DDR). Accumulated senescent cells (SCs) release senescence-associated secretory phenotype (SASP), which includes pro-inflammatory cytokines, matrix metalloproteinases (MMPs), lipids and chemokines that are detrimental to the surrounding tissues. Chronic low-grade inflammation in the elderly or inflammaging is also associated with cellular senescence and contributes to ARDs. The literature from the last decade has recorded the use of platelet rich plasma (PRP) to combat senescence and inflammation, alleviate pain as an analgesic, promote tissue regeneration and repair via angiogenesis-all of which are essential in anti-aging and tissue regeneration strategies. In the last few decades, platelet-rich plasma (PRP) has been used as an anti-aging treatment option for dermatological applications and with great interest in tissue regeneration for orthopaedic applications, especially in osteoarthritis (OA). In this exploration, we connect the intricate relationship between aging, ARDs, senescence and inflammation and delve into PRP's properties and potential benefits. We conduct a comparative review of the current literature on PRP treatment strategies, paying particular attention to the instances strongly linked to ARDs. Finally, upon careful consideration of this interconnected information in the context of aging, we suggest a prospective role for PRP in developing anti-aging therapeutic strategies.

Platelet- Rich Plasma Treatment Supported by Ultrasound Detection of Septa in Recurrent Canine Aural Hematoma: A Case Series

Aural hematoma is a common pathological condition in veterinary practice with a high incidence rate in dogs. Drainage, corticosteroid injections, and surgical approaches represent the common treatments in these clinical cases. However, surgery leaves visible signs and is usually correlated with recurrence, scars, and deformation of the treated pinna. For this reason, more effective and less invasive methods have been proposed over the years. Platelet-Rich Plasma (PRP) is one of the most promising options due to its pro-regenerative properties and capability to modulate the inflammatory state. The present work reports 12 cases of canine aural hematoma treated with PRP. The PRP treatment was combined with an ultrasound evaluation of the pinna to detect and treat all involved septa. The results show that relatively large volumes (2 mL) of PRP associated with an ultrasound guide are safe and efficacious in the treatment of canine aural hematoma requiring a maximum of two infiltrations, both in acute and chronic conditions. All the patients recovered their normal ear thickness (compared with the controlateral one) without relapses, averaging 38.5 days from their first treatment (10-90 days; SD: 24.7). The key role of PRP combined with a tailored diagnosis process carried out by the veterinarian, which included using an ultrasound system and the proper bandage, suggests that this approach may represent a valid alternative to surgery and corticosteroids.

Platelet-rich plasma in the pathologic processes of tendinopathy: a review of basic science studies

Tendinopathy is a medical condition that includes a spectrum of inflammatory and degenerative tendon changes caused by traumatic or overuse injuries. The pathological mechanism of tendinopathy has not been well defined, and no ideal treatment is currently available. Platelet-rich plasma (PRP) is an autologous whole blood derivative containing a variety of cytokines and other protein components. Various basic studies have found that PRP has the therapeutic potential to promote cell proliferation and differentiation, regulate angiogenesis, increase extracellular matrix synthesis, and modulate inflammation in degenerative tendons. Therefore, PRP has been widely used as a promising therapeutic agent for tendinopathy. However, controversies exist over the optimal treatment regimen and efficacy of PRP for tendinopathy. This review focuses on the specific molecular and cellular mechanisms by which PRP manipulates tendon healing to better understand how PRP affects tendinopathy and explore the reason for the differences in clinical trial outcomes. This article has also pointed out the future direction of basic research and clinical application of PRP in the treatment of tendinopathy, which will play a guiding role in the design of PRP treatment protocols for tendinopathy.

Plasma Rich in Growth Factors as an Adjuvant Treatment for the Management of Frontal Fibrosing Alopecia: A Retrospective Observational Clinical Study

BACKGROUND

Frontal fibrosing alopecia (FFA) is a scarring alopecia in which the exact etiopathogenesis has not been completely elucidated and the available treatments are not very effective. Plasma rich in growth factors (PRGF) has shown to induce folliculogenesis in hair loss related disorders. However, the scientific evidence when facing FFA is scarce.

OBJECTIVES

The aim of this study was to retrospectively analyze the adjuvant use of PRGF compared to the conventional treatment in the management of FFA.

METHODS

Participants with clinically diagnosed FFA who had been treated with either conventional therapy (Control Group) or conventional therapy combined with PRGF (PRGF Group) were identified from the center's medical records. The clinical assessment was based on the "Frontal Fibrosing Alopecia Severity Score" (FFASS), which was fulfilled during a period of two and 4 years.

RESULTS

This study included 118 patients with clinically diagnosed FFA (Control Group: 57 and PRGF Group: 61). No adverse effects related to the treatments were observed. Both treatments showed to halt the steady progression of hair loss compared to baseline. PRGF treatment also induced significant hair regrowth compared to the Control Group. The scalp inflammation was reduced in response to treatments. The FFASS score indicated that PRGF Group improved the symptoms and severity of FFA in a significant manner.

CONCLUSIONS

The adjuvant use of PRGF may exert long-term beneficial effects on hair loss reduction and might reduce the symptoms and severity of FFA.

The Invasive Management of Pain: Diagnosis and New Treatment Options

Both the diagnosis and treatment of pain are evolving, especially in interventional approaches. Diagnosis of low back pain combines old and new methodologies, in particular, it involves an expanded role for ultrasound. While low back pain is a common complaint, there are many etiologies to the condition which must be explored before a final diagnosis can be made and treatment planned. Tumors and infections are rarely involved in low back pain but should be ruled out in the initial phase itself since failing to address them early can have devastating consequences. Some invasive treatments seem promising in the management of low back pain. Treating musculoskeletal pain with regenerative medicine, such as platelet-rich plasma, holds great promise. Autologous blood products are safe and may help stimulate the body's own responses for regeneration. The so-called "orthobiologics" play a role in sports medicine and the treatment of musculoskeletal pain. Neuromodulation, especially spinal cord stimulation, is undergoing a renaissance with new waveforms, devices, and a greater albeit incomplete understanding of its mechanisms of action. Spinal cord stimulation is not a first-line therapy and not all patients or all back problems respond to this treatment. Nevertheless, the therapy can be safe, effective, and cost-effective with appropriate patient selection. Radiofrequency ablation of nerves in the form of neurotomy can be effective in reducing the pain of osteoarthritis. These procedures, including the newer cooled radiofrequency neurotomy, can restore function, reduce pain, and may potentially have an opioid-sparing effect. Technical expertise in nerve and anatomy is needed for the use of this technique. This review article aims to provide updated information on some invasive intervention techniques in pain management.

Autologous microfragmented adipose tissue and leukocyte-poor platelet-rich plasma combined with hyaluronic acid show comparable clinical outcomes for symptomatic early knee osteoarthritis over a two-year follow-up period: a prospective randomized clinical trial

PURPOSE

The purpose of this prospective randomized clinical trial is to compare the clinical outcomes of three injections of leucocyte-poor platelet-rich plasma (LP-PRP) and hyaluronic acid (HA) to a single dose of autologous microfragmented adipose tissue (AMAT) in patients with mild osteoarthritis at a two-year follow-up.

METHODS

Eighty symptomatic knees in fifty patients (mean age: 62.38 ± 11.88 years) with Kellgren-Lawrence grade 0 to 2 osteoarthritis were non blinded, randomly allocated into two equal groups. Group 1 consisted of 40 knees that received autologous LP-PRP + HA; Group 2 consisted of 40 knees treated with a single dose of AMAT injection. The outcomes were measured by Tegner, Marx, Visual Analogue Scale (VAS) for pain, International Knee Documentation Committee, and Knee Injury and Osteoarthritis Outcome Score (KOOS) at 6 (T1), 12 (T2), and 24 (T3) months. Adverse events were recorded at each follow-up timepoint. To assess score differences among subjects of the same gender and age, a subgroup analysis was performed.

RESULTS

Both groups had significant clinical and functional improvement at 6, 12, and 24 months (p < 0.05). Comparing the two groups, the AMAT groups showed significantly higher pre-operative Marx score (3.35 ± 4.91 vs. 1.78 ± 3.91) and VAS score (5.03 ± 2.02 vs. 3.85 ± 1.68) (p < 0.05), higher VAS (3.89 ± 2.51 vs. 2.64 ± 2.00) at T2 and KOOS-ADL (79.60 ± 20.20 vs. 65.68 ± 23.62), and lower KOOS-Sports (50.30 ± 30.15 vs. 68.35 ± 30.39) at T3 (p < 0.05). No patient from either group had experienced major adverse effects. In the LP-PRP group 12 (30%) patients presented swelling, redness, and mild pain for one day after injection and two patients had synovitis for two days and required paracetamol and local ice. In AMAT group 5 (12.5%) patients had ecchymosis and bruising at the fat aspiration site for three days.

CONCLUSION

AMAT did not show significant superior clinical improvement compared with three LP-PRP combined with HA injections in terms of functional improvement at different follow-up points. Both procedures were safe with no major complications reporting good results at mid-term follow-up, improving knee function, pain, and quality of live regardless of age and gender.

LEVEL OF EVIDENCE

Level I-Prospective Randomized Clinical Trial.

Total Healing of a Partial Rupture of the Supraspinatus Tendon Using Barbotage Technique Associated with Platelet-Rich Plasma: A Randomized, Controlled, and Double-Blind Clinical Trial

The prevalence of partial rotator cuff tears (PRCTs) is high in the general population. Our hypothesis is that barbotage, when associated with platelet-rich plasma (PRP), is an effective method for healing these tears. The aim of this study was to compare the effects of barbotage with or without PRP on the healing of partial supraspinatus tendon tears (PSTTs). This study assessed the Western Ontario Rotator Cuff Index score and ultrasound (US) images at 6 weeks and 6 months after treatment. Patients in both groups showed clinical improvement, with no significant difference in scores at 6 weeks. However, at 6 months, the PRP group exhibited significant improvement (p = 0.019). Both groups experienced a reduction in ST tear size, but the PRP group demonstrated a significant enhancement at 6 weeks and 6 months. In conclusion, the US-guided barbotage technique, whether associated with PRP or saline solution, proved to be an effective treatment for clinical improvement and reduction in the size of PSTT. Better clinical improvement results were observed with PRP at 6 months. The combination of PRP with barbotage was superior in reducing the size of the ST tear at both 6 weeks and 6 months, resulting in complete healing in 79.3% of the tears.

Platelet-Rich Plasma for Knee Osteoarthritis: What Does the Evidence Say?

The utilization of platelet-rich-plasma as a therapeutic intervention for knee osteoarthritis has gained immense attention since 2008. The increase in the number of scientific publications dedicated to this area can be attributed to the majority of favorable results reported in clinical trials and basic science studies. However, despite the growing evidence, the use of platelet-rich plasma in clinical practice still poses controversial aspects. The potential mechanisms of action described for platelet-rich-plasma so far indicate that it could serve as a disease-modifying drug, acting to counteract important aspects of knee osteoarthritis pathophysiology (cartilage breakdown, inflammation, and bone remodeling). Nevertheless, its efficacy in slowing down the progression of knee osteoarthritis remains unproven. While inconsistencies have been noted, the majority of controlled clinical trials and meta-analyses advocate for the utilization of platelet-rich-plasma in treating knee osteoarthritis, as it has demonstrated greater efficacy than hyaluronic acid and placebo, with a follow-up of at least 1 year. Despite advancements made in certain areas, significant diversity persists regarding the formulations used, therapeutic regimen, extended follow-up periods, patient selection, and assessment of clinically relevant outcomes. Consequently, the leading clinical practice guidelines do not recommend its use. In light of the emerging evidence, this narrative review aims to provide an objective evaluation of the recent available scientific literature (last 5 years) focused on randomized clinical trials and meta-analyses to present a current overview of the topic.

"Platelet-Rich Plasma" epidural injection an emerging strategy in lumbar disc herniation: a Randomized Controlled Trial

BACKGROUND

Lumbar herniated disc (HNP) is mainly treated by conservative management. Epidural steroid injection (ESI) has been an option to treat failed cases prior to surgery. Triamcinolone has been widely used due to its efficacy in bringing about pain reduction for up to three months. However, several reports have shown some severe adverse events. Platelet-rich plasma (PRP) is made from blood through centrifugation. Several studies supported the potential short to long-term effects, and safety of PRP injection in treating HNP. The study objective was to evaluate the efficacy of PRP in treatment of single-level lumbar HNP in comparison to triamcinolone.

METHODS

Thirty patients were treated by transforaminal epidural injections. PRP was obtained from 24 ml venous blood through standardized double-spin protocol. Participants included fifteen patients each being in triamcinolone and PRP groups. The same postoperative protocols and medications were applied. The visual analogue scale of leg (LegVAS), collected at baseline, 2, 6, 12, and 24 weeks, was the primary outcome. The BackVAS, Oswestry Disability Index (ODI), adverse event, and treatment failure were the secondary endpoints.

RESULTS

Platelet ratio of PRP in fifteen patients was 2.86 ± 0.85. Patients treated by PRP injections showed statistically and clinically significant reduction in LegVAS at 6, 12, and 24 weeks, and in ODI at 24 weeks. It demonstrated comparable results on other aspects. No adverse event occurred in either group.

CONCLUSION

Noncommercial epidural double-spin PRP yielded superior results to triamcinolone. Due to its efficacy and safety, the procedure is recommended in treating single level lumbar HNP.

TRIAL REGISTRATION

NCT, NCT05234840. Registered 1 January 2019, https://clinicaltrials.gov/ct2/show/record/NCT05234840 .

Advances in Platelet-Rich Plasma Treatment for Spinal Diseases: A Systematic Review

Spinal diseases are commonly associated with pain and neurological symptoms, which negatively impact patients' quality of life. Platelet-rich plasma (PRP) is an autologous source of multiple growth factors and cytokines, with the potential to promote tissue regeneration. Recently, PRP has been widely used for the treatment of musculoskeletal diseases, including spinal diseases, in clinics. Given the increasing popularity of PRP therapy, this article examines the current literature for basic research and emerging clinical applications of this therapy for treating spinal diseases. First, we review in vitro and in vivo studies, evaluating the potential of PRP in repairing intervertebral disc degeneration, promoting bone union in spinal fusion surgeries, and aiding in neurological recovery from spinal cord injury. Second, we address the clinical applications of PRP in treating degenerative spinal disease, including its analgesic effect on low back pain and radicular pain, as well as accelerating bone union during spinal fusion surgery. Basic research demonstrates the promising regenerative potential of PRP, and clinical studies have reported on the safety and efficacy of PRP therapy for treating several spinal diseases. Nevertheless, further high-quality randomized controlled trials would be required to establish clinical evidence of PRP therapy.

How Does Platelet-Rich Plasma Compare Clinically to Other Therapies in the Treatment of Knee Osteoarthritis? A Systematic Review and Meta-analysis

BACKGROUND

There has been an increase in interest in the use of biological therapies in orthopaedic conditions such as knee osteoarthritis. Platelet-rich plasma (PRP) is one of these therapies, but it still lacks consistent results.

PURPOSE

To evaluate the effects (benefits and harms) of PRP intra-articular injection compared with other nonsurgical methods for the treatment of knee osteoarthritis.

STUDY DESIGN

Systematic review and meta-analysis of randomized and quasi-randomized controlled trials; Level of evidence, 2.

METHODS

Three electronic databases were searched to identify relevant studies published before January 2021. The primary outcomes were pain, function, and failure of treatment. Risks of bias of all trials were assessed using a Cochrane risk of bias tool. The Grading of Recommendations Assessment, Development and Evaluation System was used to assess the quality of evidence of included studies.

RESULTS

A total of 40 studies with 3035 participants were included. Analysis of this review focused on comparing PRP with hyaluronic acid, corticosteroid, and saline, as we believe they are the most relevant comparisons with the most studies available. At 6-month follow-up, PRP was as effective as and in some studies more effective than other therapies regarding pain, function, and stiffness. However, current evidence is of low or very low quality and is based on trials with high risk of bias and great heterogeneity among them. No significant difference among treatments was found concerning major adverse events and treatment failure.

CONCLUSION

Although studies suggest that PRP may be more effective than or at least as effective as other modalities of nonsurgical treatment for knee osteoarthritis in terms of pain, function, and adverse events, serious limitations and methodological flaws are considerable in the current literature. Therefore, the authors are not able to make recommendations for clinical practice regarding PRP for knee osteoarthritis.

Plasma rich in growth factors versus corticosteroid injections for management of chronic rotator cuff tendinopathy: a prospective double-blind randomized controlled trial with 1 year of follow-up

BACKGROUND

Rotator cuff tendinopathy (RCT) is a painful and dysfunctional shoulder condition traditionally considered as a degenerative pathology. However, evidence is pointing to immunocompetent cells and activated stromal fibroblasts as the drivers of a nonresolved inflammatory condition in RCT. As potent anti-inflammatory agents, corticosteroid injections have been among the first-line and the most common therapeutic strategies. Recently, another adjuvant therapy to treat musculoskeletal inflammation-driven painful conditions, namely, platelet-rich plasma (PRP), has emerged as safe and effective. The aim of this study was to compare the clinical efficacy of intratendinous injections of plasma rich in growth factors (PRGF) with conventional intratendinous corticosteroid injections on patients with chronic RCT using patient-reported outcome measures.

METHODS

A total of 39 patients received PRGF treatment (3 infiltrations, 1 every other week), whereas 40 patients, as a control group, received corticosteroid (3 infiltrations, 1 every other week). Patients were evaluated before treatment and at 3, 6, and 12 months of follow-up using the University of California Los Angeles (UCLA) scale, Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH), and Constant test. The primary outcome of the study was a 15% superior improvement of the PRGF group compared with the corticosteroid group in the UCLA scale and QuickDASH test at 6 months of follow-up, considering this difference to be clinically relevant.

RESULTS

Both PRGF and corticosteroid groups showed significant clinical improvement in the 3 scores at all time points of the study compared with baseline. However, at 6 and 12 months of follow-up, the PRGF group had 22.1% and 21.2% superior improvement of the UCLA test, 14.3% and 13.5% for QuickDASH, and 16.4% and 20.2% for the Constant-Murley test, respectively, compared to the corticosteroid group.

CONCLUSIONS

Three PRGF intratendinous injections every other week in patients with chronic rotator cuff tendinopathy show significantly superior and sustained pain-relieving and functional improvements compared with corticosteroid intratendinous injections assessed by 3 patient-reported outcome scales at 6 and 12 months of follow-up.

The use of platelet-rich plasma in studies with early knee osteoarthritis versus advanced stages of the disease: a systematic review and meta-analysis of 31 randomized clinical trials

INTRODUCTION

Reports have concluded that platelet-rich plasma (PRP) is an effective and safe biological approach to treating knee osteoarthritis (OA). However, the effectiveness of PRP in advanced stages of the disease is not entirely clear. The purpose of this study was to evaluate whether the use of PRP would be as effective in studies with early-moderate knee OA patients compared to studies including patients with end-stage OA, based on the Kellgren-Lawrence classification.

MATERIALS AND METHODS

A comprehensive search in MEDLINE, EMBASE, Scopus, and Web of Science databases was conducted to identify randomized controlled trials (RCTs) comparing the effect of PRP injections versus other intra-articular treatments on pain and functionality. A meta-analysis was conducted using a random-effects model and the generic inverse variance method.

RESULTS

We included 31 clinical trials that reported data of 2705 subjects. Meta-analysis revealed an overall significant improvement of both pain [MD, - 1.05 (95% CI - 1.41 to - 0.68); I² = 86%; P ≤ 0.00001] and function [SMD, - 1.00 (95% CI - 1.33, to - 0.66); I² = 94%; P ≤ 0.00001], favoring PRP. Subanalysis for pain and functional improvement showed a significant pain relief in studies with 1-3 and 1-4 Kellgren-Lawrence OA stages and a significant functional improvement in studies with 1-2, 1-3 and 1-4 knee OA stages, favoring PRP.

CONCLUSION

Our results indicate that including patients with advanced knee OA does not seem to affect the outcomes of clinical trials in which the effectiveness of the PRP in knee OA is assessed.

Global research trends on platelet-rich plasma for tendon and ligament injuries from the past two decades: A bibliometric and visualized study

Background

In sports medicine, tendon and ligament injuries are the most prevalent conditions, and with the booming of sports competition, the incidence of sports injuries is gradually increasing, investigating more potent therapeutic options is therefore becoming increasingly crucial. Platelet-rich plasma therapy has gained popularity as an effective and secure treatment in recent years. Currently, a faceted systematic and clear visual analysis is lacking in this research area.

Methods

The literature related to using platelet-rich plasma to treat ligament and tendon injuries from 2003 to 2022 in the core dataset of the Web of Science database was collected and analyzed visually using Citespace 6.1 software. Research hotspots and development trends were analyzed in terms of high-impact countries or regions, authors, research institutions, keywords, and cited literature.

Results

The literature comprised a total of 1,827 articles. The annual publication volume of relevant literature has demonstrated a significant development tendency as the field of platelet-rich plasma research for tendon and ligament injuries has heated up in recent years. With 678 papers, the United States came in top place, followed by China with 187 papers. Hosp Special Surg ranked first with 56 papers. The hot research topics analyzed by keywords were tennis elbow, anterior cruciate ligament, rotator cuff repair, achilles tendon, mesenchymal stem cells, guided tissue regeneration, network meta analysis, chronic patellar tendinopathy, and follow up.

Conclusion

Analysis of the research literature over the past 20 years shows that the United States and China will continue to dominate in terms of volume of publications based on annual volume and trends, with some collaboration among high-impact authors and further collaboration still needed in different countries and institutions. Platelet-rich plasma is widely used in the treatment of tendon ligament injuries. Its clinical efficacy is influenced by a number of factors, the main ones being the inconsistency in the preparation and composition of platelet-rich plasma and its related preparations, and the differences in efficacy due to different activation methods of platelet-rich plasma, as well as factors such as injection time, injection site, administration method, number of administrations, acidity and evaluation methods, In addition, the applicability to different injury diseases remains controversial. In recent years, the molecular biology of platelet-rich plasma for tendon ligament therapy has received increasing attention.

Autologous Platelet and Extracellular Vesicle-Rich Plasma as Therapeutic Fluid: A Review

The preparation of autologous platelet and extracellular vesicle-rich plasma (PVRP) has been explored in many medical fields with the aim to benefit from its healing potential. In parallel, efforts are being invested to understand the function and dynamics of PVRP that is complex in its composition and interactions. Some clinical evidence reveals beneficial effects of PVRP, while some report that there were no effects. To optimize the preparation methods, functions and mechanisms of PVRP, its constituents should be better understood. With the intention to promote further studies of autologous therapeutic PVRP, we performed a review on some topics regarding PVRP composition, harvesting, assessment and preservation, and also on clinical experience following PVRP application in humans and animals. Besides the acknowledged actions of platelets, leukocytes and different molecules, we focus on extracellular vesicles that were found abundant in PVRP.

Freeze-dried Platelet-rich Plasma and Stem Cell-conditioned Medium for Therapeutic Use in Horses

This study investigated platelet-rich plasma (PRP) and adipose stem cell-conditioned medium (ASC-CM) use as a strategy to accelerate tissue healing. Platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) were quantified in fresh and freeze-dried PRP and ASC-CM, and a stability test was performed in the freeze-dried samples (90 and 180 days of storage). A cell proliferation test was performed using equine mesenchymal stem cell culture in reconstituted PRP gel mesh after freeze-drying. In vivo PRP, ASC-CM applications, or their association were performed in induced wounds at 15 and 9-day intervals, according to the treatments: saline solution (control), PRP, ASC-CM, or ASC-CM + PRP. Horses were monitored through photographs and wound area measurements on days 5, 7, 15, and 24 after lesion induction. Skin biopsies were obtained on days 15 and 24 of the experiment. PDGF and VEGF quantification did not differ between fresh or freeze-dried treatments, was similar after freeze-drying or 90 days of storage, but showed a significant reduction after 180 days of storage. Comparing all treatments, no differences were observed in the histopathological analyses. For inflammation, fibroplasia, and collagen formation, only the time effect between the first and second biopsies was significant. The cell proliferation test revealed intense multiplication in the PRP gel mesh. Healing time was similar among all treatments. In conclusion, our results showed the possibility to produce and maintain freeze-dried PRP and ASC-CM for 90 days. Further studies are needed to better explore the in vivo therapeutic PRP and ASC-CM effects.

The Efficacy of Platelet-Rich Plasma Injection Therapy in the Treatment of Patients with Achilles Tendinopathy: A Systematic Review and Meta-Analysis

BACKGROUND

Over the past few years, many studies have been conducted to evaluate the effectiveness of platelet-rich plasma (PRP) in treating musculoskeletal conditions. However, there is controversy about its benefits for patients with Achilles tendinopathy.

OBJECTIVE

This study aimed to investigate whether platelet-rich plasma injections can improve outcomes in patients with Achilles tendinopathy.

METHODS

A comprehensive literature search was conducted in PubMed, Embase, Cochrane Library, Web of Science, China Biomedical CD-ROM, and Chinese Science and Technology Journal databases to identify randomised controlled clinical trials that compared the efficacy of PRP injection in patients with Achilles tendinopathy (AT) versus placebo, published between 1 January 1966 and 1 December 2022. Review Manager 5.4.1 software was used for the statistical analysis, and the Jadad score was used to assess the included literature. Only 8 of the 288 articles found met the inclusion criteria.

RESULTS

Our work suggests that: The PRP treatment group had a slightly higher VISA-A score than the placebo group at 6 weeks [MD = 1.92, 95% CI (-0.54, 4.38), I² = 34%], at 12 weeks [MD = 0.20, 95% CI (-2.65 3.05), I² = 60%], and 24 weeks [MD = 2.75, 95% CI (-2.76, 8.26), I² = 87%]). However, the difference was not statistically significant. The Achilles tendon thickness was higher at 12 weeks of treatment in the PRP treatment group compared to the control group [MD = 0.34, 95% CI (-0.04, 0.71), p = 0.08], but the difference was not statistically significant. The VAS-improvement results showed no significant difference at 6 and 24 weeks between the two groups, respectively (MD = 6.75, 95% CI = (-6.12, 19.62), I² = 69%, p = 0.30), and (MD = 10.46, 95% CI = (-2.44 to 23.37), I² = 69%, p = 0.11). However, at 12 weeks of treatment, the PRP injection group showed a substantial VAS improvement compared to the control group (MD = 11.30, 95% CI = (7.33 to 15.27), I² = 0%, p < 0.00001). The difference was statistically significant. The return to exercise rate results showed a higher return to exercise rate in the PRP treatment group than the placebo group [RR = 1.11, 95% CI (0.87, 1.42), p = 0.40]; the difference was not statistically significant.

CONCLUSION

There is no proof that PRP injections can enhance patient functional and clinical outcomes for Achilles tendinopathy. Augmenting the frequency of PRP injections may boost the outcomes, and additionally, more rigorous designs and standardised clinical randomised controlled trials are needed to produce more reliable and accurate results.

Advances in the Clinical Application of Platelet-Rich Plasma in the Foot and Ankle: A Review

Autologous and recombinant biologic substances have been generated as a result of the research into the cellular features of the healing process. Orthobiologics are increasingly being used in sports medicine and musculoskeletal surgery. Nevertheless, clinical data are limited; consequently, further studies are required, particularly in foot and ankle pathologies. This review aims to provide evidence of the most recent literature results and ignite the interest of orthopedic specialists eager for an update about the most current discussion on platelet-rich plasma (PRP) clinical applications in the foot and ankle fields. Previous studies have shown that platelet-rich plasma can be beneficial in treating various conditions, such as chronic foot ulcers, osteoarthritis, Achilles tendinopathy, etc. Despite the positive effects of PRP on various musculoskeletal conditions, more prospective studies are needed to confirm its effectiveness at treating ankle and foot pathologies. In addition to clinical trials, other factors, such as the quality of the research and the procedures involved, must be considered before they can be used in patients. More long-term evaluations are needed to support or oppose its application in treating foot and ankle disorders. We present the most extensive review of PRP's clinical applications in the foot and ankle field.

Individual immune cell and cytokine profiles determine platelet-rich plasma composition

OBJECTIVE

Platelet-rich plasma (PRP) therapy is increasingly popular to treat musculoskeletal diseases, including tendinopathies and osteoarthritis (OA). To date, it remains unclear to which extent PRP compositions are determined by the immune cell and cytokine profile of individuals or by the preparation method. To investigate this, we compared leukocyte and cytokine distributions of different PRP products to donor blood samples and assessed the effect of pro-inflammatory cytokines on chondrocytes.

DESIGN

For each of three PRP preparations (ACP®, Angel™, and nSTRIDE® APS), products were derived using whole blood samples from twelve healthy donors. The cellular composition of PRP products was analyzed by flow cytometry using DURAClone antibody panels (DURAClone IM Phenotyping Basic and DURAClone IM T Cell Subsets). The MESO QuickPlex SQ 120 system was used to assess cytokine profiles (V-PLEX Proinflammatory Panel 1 Human Kit, Meso Scale Discovery). Primary human chondrocyte 2D and 3D in vitro cultures were exposed to recombinant IFN-γ and TNF-α. Proliferation and chondrogenic differentiation were quantitatively assessed.

RESULTS

All three PRP products showed elevated portions of leukocytes compared to baseline levels in donor blood. Furthermore, the pro-inflammatory cytokines IFN-γ and TNF-α were significantly increased in nSTRIDE® APS samples compared to donor blood and other PRP products. The characteristics of all other cytokines and immune cells from the donor blood, including pro-inflammatory T cell subsets, were maintained in all PRP products. Chondrocyte proliferation was impaired by IFN-γ and enhanced by TNF-α treatment. Differentiation and cartilage formation were compromised upon treatment with both cytokines, resulting in altered messenger ribonucleic acid (mRNA) expression of collagen type 1A1 (COL1A1), COL2A1, and aggrecan (ACAN) as well as reduced proteoglycan content.

CONCLUSIONS

Individuals with elevated levels of cells with pro-inflammatory properties maintain these in the final PRP products. The concentration of pro-inflammatory cytokines strongly varies between PRP products. These observations may help to unravel the previously described heterogeneous response to PRP in OA therapy, especially as IFN-γ and TNF-α impacted primary chondrocyte proliferation and their characteristic gene expression profile. Both the individual's immune profile and the concentration method appear to impact the final PRP product.

TRIAL REGISTRATION

This study was prospectively registered in the Deutsches Register Klinischer Studien (DRKS) on 4 November 2021 (registration number DRKS00026175).

Comparison of the clinical effectiveness of activated and non-activated platelet-rich plasma in the treatment of knee osteoarthritis: a systematic review and meta-analysis

INTRODUCTION/OBJECTIVES

Platelet-rich plasma (PRP) has shown to be clinically effective in the treatment of knee osteoarthritis (OA). Notwithstanding, some inconsistences remain due to methodological differences in PRP preparation such as the use (or not) of activation strategies. We aimed to evaluate whether the use of non-activated PRP would be as effective as activated PRP in patients with knee OA.

METHOD

All randomized, placebo-controlled trials were identified through a search in MEDLINE, EMBASE, Scopus, and Web of Science up to June 2022. Pre- and post-injection pain and function scores were collected. The meta-analysis was conducted with a random-effects model and generic inverse variance method. Effect sizes were estimated using standardized mean differences (SMD).

RESULTS

Fourteen clinical trials involving 1292 subjects were included for meta-analysis. Exogenous activation of PRP revealed a significant pain relief (SMD, - 1.05 [95% CI - 1.58 to - 0.52]; p = 0.0001) and a significant functional improvement (SMD, - 1.21 [95% CI - 1.75 to - 0.67]; p < 0.0001) unlike studies describing the use of a non-activated PRP. The sensitivity analysis indicated that the effect size for both outcomes was not influenced by a single study.

CONCLUSIONS

The results of this systematic review suggest that the use of an exogenously activated PRP is more effective in improving both pain and functional scores in patients with knee OA. Key Points • Results from meta-analysis suggest that exogenously activated PRP is clinically more effective than non-activated PRP. • The use of an activated PRP was more frequently reported by the included studies. • The most frequent method for activation was the use of calcium chloride (CaCl₂).

Biomimetic Approaches in Clinical Endodontics

In the last few decades, biomimetic concepts have been widely adopted in various biomedical fields, including clinical dentistry. Endodontics is an important sub-branch of dentistry which deals with the different conditions of pulp to prevent tooth loss. Traditionally, common procedures, namely pulp capping, root canal treatment, apexification, and apexigonesis, have been considered for the treatment of different pulp conditions using selected materials. However, clinically to regenerate dental pulp, tissue engineering has been advocated as a feasible approach. Currently, new trends are emerging in terms of regenerative endodontics which have led to the replacement of diseased and non-vital teeth into the functional and healthy dentine-pulp complex. Root- canal therapy is the standard management option when dental pulp is damaged irreversibly. This treatment modality involves soft-tissue removal and then filling that gap through the obturation technique with a synthetic material. The formation of tubular dentine and pulp-like tissue formation occurs when stem cells are transplanted into the root canal with an appropriate scaffold material. To sum up tissue engineering approach includes three components: (1) scaffold, (2) differentiation, growth, and factors, and (3) the recruitment of stem cells within the pulp or from the periapical region. The aim of this paper is to thoroughly review and discuss various pulp-regenerative approaches and materials used in regenerative endodontics which may highlight the current trends and future research prospects in this particular area.

Study protocol for a randomised placebo controlled trial of platelet-rich plasma injection to prevent post-traumatic knee osteoarthritis after anterior cruciate ligament reconstruction

INTRODUCTION

The elevated cytokine levels in patients suffering from anterior cruciate ligament (ACL) rupture may lead to acute post-traumatic arthritis (APTA) and post-traumatic osteoarthritis (PTOA). Due to its chondrogenerative and anti-inflammatory effect, platelet-rich plasma (PRP) therapy is expected to show a positive outcome in APTA and PTOA. The proposed trial aims to quantitatively measure the efficacy of PRP injection in arresting post-traumatic cartilage degeneration among patients after ACL reconstruction.

METHODS AND ANALYSIS

This will be a single-blind, randomised, prospective, controlled clinical trial designed following the Consolidated Standards of Reporting Trials guidelines. After ACL reconstruction, 80 patients will be randomised to receive either leucocyte-poor PRP injection after joint aspiration or a placebo control group receiving only joint aspiration. Participants (age 20-49 years) will be those who have undergone ACL reconstruction within the past 2 weeks with a body mass index<35 and Kellgren Lawrence osteoarthritis grade<2. The primary outcome will include MRI-T2 values of knee cartilage at 6 months. The secondary outcomes will include pain assessment by Visual Analogue Scale, Knee injury and Osteoarthritis Outcome Score, blood and urine test, physical findings, measurements for muscle strength and joint stability.

ETHICS AND DISSEMINATION

The study was approved by The Independent Ethics Committee for Clinical Trials of the Japanese Association for the Promotion of State-of-the-Art Medicine. Results of the trial and each of the outcomes will be shared via conferences and publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

jRCTb030200391.

Encapsulation of rat bone marrow-derived mesenchymal stem cells (rBMMSCs) in collagen type I containing platelet-rich plasma for osteoarthritis treatment in rat model

Osteoarthritis (OA) is the most common form of degenerative joint disease, affecting more than 25% of the adults despite its prevalence in the elderly population. Most of the current therapeutic modalities aim at symptomatic treatment which lingers the disease progression. In recent years, regenerative medicine such as stem cell transplantation and tissue engineering has been suggested as a potential curative intervention for OA. The objective of this current study was to assess the safety and efficacy of an injectable tissue-engineered construct composed of rat bone marrow mesenchymal stem cells (rBMMSCs), platelet-rich plasma (PRP), and collagen type I in rat model of OA. To produce collagen type I, PRP and rBMMSCs, male Wistar rats were ethically euthanized. After isolation, culture, expansion and characterization of rBMMSCs, tissue-engineered construct was formed by a combination of appropriate amount of collagen type I, PRP and rBMMSCs. In vitro studies were conducted to evaluate the effect of PRP on chondrogenic differentiation capacity of encapsulated cells. In the following, the tissue-engineered construct was injected in knee joints of rat models of OA (24 rats in 4 groups: OA, OA + MSC, OA + collagen + MSC + PRP, OA + MSC + collagen). After 6 weeks, the animals were euthanized and knee joint histopathology examinations of knee joint samples were performed to evaluate the effect of each treatment on OA. Tissue-engineered construct was successfully manufactured and in vitro assays demonstrated the relevant chondrogenic genes and proteins expression were higher in PRP group than that of others. Histopathological findings of the knee joint samples showed favorable regenerative effect of rBMMSCs + PRP + collagen group compared to others. We introduced an injectable tissue-engineered product composed of rBMMSCs + PRP + collagen with potential regenerative effect on cartilage that has been damaged by OA.

The Top 100 Most Cited Articles on Platelet-Rich Plasma Use in Regenerative Medicine-A Bibliometric Analysis-From the ESSKA Orthobiologic Initiative

Over the past few decades, more and more articles about platelet-rich plasma (PRP) use in regenerative medicine have been published. The aim of this study was to determine which articles have been most influential in this field by identifying and analyzing the characteristics of the 100 most cited articles. Articles on the use of PRP in regenerative medicine were identified via the Thomson ISI Web of Science database. A majority of the articles originated from the USA (36%). The top journal in terms of number of articles was American Journal of Sports Medicine (12%). Musculoskeletal system and orthopedics (54%) were the most popular fields of applications. Preclinical studies were the most represented study type, from which only 8 from 46 (17.4%) provided a complete numerical description of the injected product. Analysis showed a time-dependent trend of increasing quality of the clinical studies (p = 0.004), although none of them provided a complete biological characterization of the injected PRP. This study demonstrated that the use of PRP in regenerative medicine is a growing and popular area of research, mainly focused on orthopedic applications. Studies on PRP-derived exosomes, biological characterization, and correlation with clinical results might be areas of future trends.