Leukocyte-poor Platelet-rich Plasma Research Articles

Nonoperative and Operative Soft Tissue, Cartilage, and Bony Regeneration and Orthopaedic Biologics of the Elbow and Upper Extremity: An Orthoregeneration Network (ON) Foundation Review Authors:

Orthoregeneration is defined as a solution for orthopaedic conditions that harnesses the benefits of biology to improve healing, reduce pain, improve function, and optimally, provide an environment for tissue regeneration. Options include drugs, surgical intervention, scaffolds, biologics as a product of cells, and physical and electromagnetic stimuli. The goal of regenerative medicine is to enhance the healing of tissue after musculoskeletal injuries as both isolated treatment and adjunct to surgical management, using novel therapies to improve recovery and outcomes. Various orthopaedic biologics (orthobiologics) have been investigated for the treatment of pathology involving the elbow and upper extremity including the tendons (lateral epicondylitis, medial epicondylitis, biceps tendonitis, triceps tendonitis), articular cartilage (osteoarthritis, osteochondral lesions), and bone (fractures, non-unions, avascular necrosis, osteonecrosis). Promising and established treatment modalities include hyaluronic acid (HA); botulinum toxin; corticosteroids; leukocyte-rich and leukocyte-poor platelet-rich plasma (PRP); autologous blood; bone marrow aspirate (BMA) comprising mesenchymal stromal cells (alternatively termed medicinal signaling cells and frequently mesenchymal stem cells) and BMA concentrate (BMAC); MSC harvested from adipose and skin (dermis) sources; vascularized bone grafts; bone morphogenic protein (BMP) scaffold made from osteoinductive and -conductive -tricalcium phosphate (-TCP) and poly-ε- caprolactone (PCL) with hydrogels, human MSC, and matrix metalloproteinases (MMPs); and collagen sponge. Autologous blood preparations such as autologous blood injections and platelet-rich plasma show positive outcomes for non-responsive tendinopathy. In addition, cellular therapies such as tissue-derived tenocyte-like cells and MSC show a promising ability to regulate degenerative processes by modulating tissue response to inflammation and preventing continuous degradation and support tissue restoration

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).

A Comparative Study of Intra-Articular Knee Injection of Leukocyte-Poor Platelet-Rich Plasma Compared to Corticosteroids and Local Anesthetics in Patients with Knee Osteoarthritis

Background: Knee osteoarthritis (OA) is the most common reason for orthopedic secondary care referral. And it is one of the main causes of disability in adults worldwide. It is estimated to affect between 10 to 25% of patients over the age of 60. Intra-articular corticosteroid injection (IA CS) and physical therapy were the two choices in an attempt to provide symptomatic management or deferred surgery. There is a growing trend is intra-articular platelet-rich plasma (IA PRP) injection to reduce pain and improve function in OA patients. PRP is divided into two types: leukocyte-poor platelet-rich plasma (LP-PRP) and leukocyte-rich platelet-rich plasma (LR-PRP). It was shown that LR-PRP increases pro-inflammatory factors and also decreases anti-catabolic mediators, and LP-PRP has the opposite aspect.&#x0D; Methods: In our research 40 patients were divided into two equal groups, IA corticosteroid and leukocyte-poor platelet-rich plasma (LP-PRP) 40 cc of blood from the basilic vein of the upper limb is used with two step centrifugation. The final samples were 4 millilitres product injected intra-articular. group two (corticosteroid (CS)) received an intra-articular injection of triamcinolone acetate (Kenalog) 40 mg/ml along with 4 ml of lidocaine 0.02% (Abureyhan Co.) for a total of 5 ml. The needle used is a 22-gauge pencil-point Quincke needle (Dr. Japan Co, Ltd), which is performed with the Sonosite Edge II ultrasound guide and in an anterior-lateral manner in the knee joint. Pain was assessed on a visual analogue scale (VAS range 0-10 points) before, one week, one month, two month and 3 months after the operation. The WOMAC questionnaire was also filled before injection and three months following injection and other variables were examined.&#x0D; Results: There were no significant differences between the groups across all the baseline parameters including age, sex, body mass index and comorbidities including high blood pressure, diabetes and smoking. Both injection groups were effective in reducing patients' pain from one week to three months after injection. The level of pain in the first week after injection was significantly lower in the corticosteroid group than in the PRP group. In the first month and the third month after the injection, the pain reduction according to mean scores of VAS was the same in both groups.&#x0D; Conclusion: In short, one injection of PRP can reduce the pain of patients with osteoarthritis of the knee as much as corticosteroids during a three-month treatment process. Considering the possible side effects of corticosteroids, this alternative treatment can be considered with further investigation.

A Comprehensive Summary of the Meta-Analyses and Systematic Reviews on Platelet-Rich Plasma Therapies for Knee Osteoarthritis.

Osteoarthritis (OA), including that of the knee joint, represents a significant proportion of musculoskeletal injuries in the Canadian Armed Forces (CAF) due to the frequent, high-stress physical activity for which member participation is necessary. Platelet-rich plasma (PRP) is a conservative, autologous treatment that has the potential to relieve symptoms and improve functionality of military members to decrease the impact of the disease and ultimately strengthen the CAF. A search of systematic reviews and meta-analyses was conducted to determine the efficacy of PRP injections in treating knee OA. The Scopus database, PubMed database, and Omni academic search tools were scoped for relevant publications. English literature, published up to and including March 2023, that investigated only clinically randomized controlled trials (RCTs) was eligible for inclusion. The results of network meta-analyses were investigated and summarized independent of reviews and non-network meta-analyses. A total of 225 unique systematic reviews and meta-analyses were initially identified, of which 39 publications, including 7 network meta-analyses, adhered to the defined inclusion and exclusion criteria. PRP was found to significantly alleviate symptoms of pain based on the visual analog scale and Western Ontario and McMaster Universities Arthritis Index pain scores within the 12-month follow-up. Function, activity, sport, quality of life, and stiffness were additionally determined to generally improve to a greater extent from PRP treatment compared to controls, while adverse effects were minor and temporary. PRP placed in the top 3 in 9 reported surface under the cumulative ranking curves, while individually reported rankings of leukocyte-poor and leukocyte-rich PRP both placed in the top 4. The clinical recommendations made were generally positive, with 17 publications acknowledging the benefits of PRP, 3 supporting possible efficacy, and an additional 8 recommending that it be an option for the conservative treatment of knee OA. The results of this review support the efficacy of PRP for relieving symptoms of pain and improving function, stiffness, and quality of life for patients experiencing knee OA within 12 months. As a result, leukocyte-poor-PRP could be considered for members of the CAF with mild to moderate knee OA (Kellgren-Lawrence grades 1-3) to slow the progression of OA and extend the military careers of CAF members. There continues to be a need for future studies to investigate the longer-term effects of PRP to verify sustained benefits at follow-up points greater than 12 months, including findings of improvement in a delayed fashion at the 3- and 6-month timeframe compared to hyaluronic acid treatment.

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

To explore the best centrifuge condition for preparing rabbit leukocyte-poor platelet-rich plasma (LP-PRP) by using single centrifugation method. Sixteen healthy New Zealand rabbits, aged 3-4 months, were utilized in the investigation. A total of 15 mL anticoagulated blood was extracted from the central ear artery of each rabbit, with a repeat of the blood collection procedure after 1 and 2 months. The obtained blood specimens were individually subjected to centrifugation at a radius of 16.7 cm and speeds of 1 200, 1 300, 1 400, and 1 500 r/min (equivalent to centrifugal forces of 269× g, 315× g, 365× g, and 420× g) for durations of 2, 3, 4, and 5 minutes, resulting in a total of 16 groups. Following centrifugation, collect plasma from each group to a distance of 1.5 mL from the separation plane. The volumes, platelet enrichment coefficient, and platelet recovery rates of LP-PRP in each group, under varying centrifugation conditions, were methodically computed and subsequently compared. The volume of LP-PRP obtained under all centrifugation conditions ranged from 1.8 to 7.6 mL. At a consistent centrifugal speed, an extension of centrifugation time leaded to a significant increase in the volume of LP-PRP, accompanied by a declining trend in the platelet enrichment coefficient of LP-PRP. When centrifuged for 2 minutes, the volume of LP-PRP at speeds of 1 200 and 1 300 r/min was less than 2.0 mL, while the volume of LP-PRP obtained under other conditions was more than 2.0 mL. When centrifuged for 4 and 5 minutes, the volume of LP-PRP obtained at each speed was more than 4 mL. LP-PRP with a platelet enrichment coefficient more than 2.0 could be prepared by centrifuging at 1 200 r/min for each time group and 1 300 r/min for 2 and 3 minutes, and the highest LP-PRP platelet enrichment coefficient could be obtained by centrifugation for 2 minutes at a speed of 1 200 r/min. The platelet recovery rates of LP-PRP obtained by centrifugation at 1 200 r/min for 4 and 5 minutes, as well as centrifugation at 1 400 r/min for 5 minutes, were both greater than 60%. There was no significant difference between the groups when centrifuged at 1 200 r/min for 4 and 5 minutes ( P>0.05). In the process of preparing rabbit LP-PRP using a single centrifugation method, collecting 15 mL of blood and centrifuging at a radius of 16.7 cm and speed of 1 200 r/min for 4 minutes can prepare LP-PRP with a volume exceeding 2.0 mL, platelet enrichment coefficient exceeding 2.0, and platelet recovery rate exceeding 60%. This centrifugal condition can achieve the optimal LP-PRP action parameters in the shortest possible time.

Does the Combination of Platelet-rich Plasma and Supervised Exercise Yield Better Pain Relief and Enhanced Function in Knee Osteoarthritis? A Randomized Controlled Trial.

Knee osteoarthritis is a leading cause of disability with substantial healthcare costs, and efficient nonsurgical treatment methods are still needed. Platelet-rich plasma (PRP) injections and exercise therapy are used frequently in clinical practice. Whether PRP or PRP combined with exercise is more effective than exercise alone is unclear. (1) Which treatment relieves knee osteoarthritis pain better: PRP alone, exercise, or PRP combined with exercise? (2) Does PRP alone, exercise, or PRP combined with exercise yield better results in terms of the WOMAC score, performance on the 40-m fast-paced walk test and stair climbing test, and the SF-12 health-related quality of life score? In this randomized, controlled, three-arm clinical trial, we recruited patients with mild-to-moderate (Kellgren-Lawrence Grade II or III) knee osteoarthritis with a minimum of 3 points on the 11-point numeric rating scale for pain. During the study period, 157 patients with a diagnosis of knee osteoarthritis were screened and 84 eligible volunteers were enrolled in the study. Patients were randomly allocated (1:1:1) into either the exercise group (28), PRP group (28), or PRP + exercise group (28). Follow-up proportions were similar between the groups (exercise: 89% [25], PRP: 86% [24], PRP + exercise: 89% [25]; p = 0.79). All patients were analyzed in an intention-to-treat manner. There were no between-group differences in age, gender, arthritis severity, and baseline clinical scores (pain, WOMAC, functional performance tests, and health-related quality of life). The exercise group underwent a 6-week structured program consisting of 12 supervised individual sessions focused on strengthening and functional exercises. Meanwhile, the PRP group received three weekly injections of fresh, leukocyte-poor PRP. The PRP + exercise group received a combined treatment with both interventions. The primary outcome was knee pain over 24 weeks, measured on an 11-point numeric rating scale for pain (ranging from 0 to 10, where 0 represents no pain and 10 represents the worst pain, with a minimum clinically important difference [MCID] of 2). The secondary outcome measures included the WOMAC index (ranging from 0 to 100, with lower scores indicating a lower level of disability and an MCID of 12), the durations of the 40-meter fast-paced walk test and stair climbing test, and the SF-12 health-related quality of life score. For the a priori sample size calculation, we used the numeric rating scale score for pain at 24 weeks as the primary outcome variable. The MCID for the numeric rating scale was deemed to be 2 points, with an estimated standard deviation of 2.4. Based on sample size calculations, a sample of 24 patients per group would provide 80% power to detect an effect of this size between the groups at the significance level of p = 0.05. We found no clinically important differences in improvements in pain-defined as ≥ 2 points of 10-at 24 weeks when comparing exercise alone to PRP alone to PRP + exercise (1.9 ± 0.7 versus 3.8 ± 1.8 versus 1.4 ± 0.6; mean difference between PRP + exercise group and exercise group -0.5 [95% confidence interval -1.2 to 0.4]; p = 0.69). Likewise, we found no differences in WOMAC scores at 24 weeks of follow-up when comparing exercise alone to PRP alone to PRP + exercise (10 ± 9 versus 26 ± 20 versus 7 ± 6; mean difference between PRP + exercise group and exercise group -3 [95% CI -12 to -5]; p = 0.97). There were no differences in any of the other secondary outcome metrics among the PRP + exercise and exercise groups. PRP did not improve pain at 24 weeks of follow-up in patients with mild-to-moderate knee osteoarthritis compared with exercise alone. Moreover, exercise alone was clinically superior to PRP alone, considering function and the physical component of health-related quality of life. Despite the additional costs and endeavors related to PRP products, the combination of PRP and exercise did not differ from exercise alone. The results of this randomized controlled trial do not support the use of PRP injections in the treatment of patients diagnosed with mild-to-moderate knee osteoarthritis. Consequently, exercise alone is the recommended treatment for reducing pain and enhancing function throughout this timeframe. Level I, therapeutic study.

Platelet-rich plasma does not accelerate the healing of damaged muscle following muscle strain.

Although platelet-rich plasma (PRP)has been widely used regardless of the severity of muscle strain, there have been very few basic studies in which its effects on muscle injury were examined by using models that accurately mimic the clinical muscle strain injury process. Therefore, the aim of this study was to confirm by physiological and structural analyses whether PRP purified by a general preparation method has a muscle healing effect on muscle damage caused by eccentric contraction (ECC).Male Wistar rats were subjected to muscle injury induced by ECC in bilateral plantar flexor muscles using electrical stimulation and an automatically dorsiflexing footplate. The rats were randomly assigned to three groups by type of injection: phosphate-buffered saline (PBS),leukocyte-poor PRP (LP-PRP),or leukocyte-rich PRP (LR-PRP)injection into gastrocnemius muscles three times at weekly intervals. The platelet concentrations of the LP-PRPand LR-PRPwere three to five times higher than that of whole blood. The recovery process of torque strength in the plantar flexor muscle, signal changes in MRI images, and histological evaluation 3 weeks after injury showed no obvious differences among the three groups, and every muscle recovered well from the injury without marked fibrosis. The results that neither LP-PRPnor LR-PRPwas found to accelerate healing of muscle injuries suggested that conventional preparation and use of PRP for simple muscle injuries caused by muscle strain should be carefully considered, and further basic research using models that accurately mimic clinical practice should be carried out to determine the optimal use of PRP.

Platelet-rich Plasma Injection for the Treatment of Partial Achilles Tendon Rupture: A Case Report

Introduction: Achilles tendon rupture is one of the most common adult tendon injuries and continues to increase in incidence. This case report outlines a comprehensive approach for stand-alone leukocyte-poor platelet-rich plasma treatment of a partial subacute Achilles tendon rupture in a professional athlete who had received prior autologous conditioned serum injections with an interleukin-1 receptor antagonist. Patient History: A 32-year-old male professional ice hockey player presented with persistent left ankle pain approximately seven months after suffering a partial acute Achilles tendon tear. Imaging confirmed a subacute partial Achilles tendon rupture. Injection: Following local anesthesia, a 25-gauge 1.5-inch needle was advanced to the target structure under ultrasound guidance and 3 mL of autologous platelet-rich plasma was divided amongst several areas of the patient's Achilles tendon, while simultaneously tenotomizing the tendon. No complications were observed. Imaging: Follow-up magnetic resonance imaging approximately 9 months after platelet-rich plasma injection revealed complete resolution of the Achilles tendon rupture. Conclusion: Ultrasound-guided leukocyte-poor platelet-rich plasma injection could be considered an effective treatment option for acute Achilles tendon rupture during the subacute stages of tendon healing, leading to complete radiographic resolution of the tear and enabling a return to high-level athletics.

Safety and Efficacy of Bone Marrow-Derived Mesenchymal Stem Cells for Chronic Patellar Tendinopathy (With Gap >3 mm) in Patients: 12-Month Follow-up Results of a Phase 1/2 Clinical Trial.

In a previous study, the authors found that at 6 months after treatment with a 20 × 106 dose of bone marrow-derived mesenchymal stem cells (BM-MSCs), patients showed improved tendon structure and regeneration of the gap area when compared with treatment using leukocyte-poor platelet-rich plasma (Lp-PRP). The Lp-PRP group (n = 10), which had not seen tendon regeneration at the 6-month follow-up, was subsequently offered treatment with BM-MSCs to see if structural changes would occur. In addition, the 12-month follow-up outcomes of the original BM-MSC group (n = 10) were evaluated. To evaluate the outcomes of all patients (n = 20) at 12 months after BM-MSC treatment and observe if the Lp-PRP pretreated group experienced any type of advantage. Cohort study; Level of evidence, 2. Both the BM-MSC and original Lp-PRP groups were assessed at 12 months after BM-MSC treatment with clinical examination, the visual analog scale (VAS) for pain during daily activities and sports activities, the Victorian Institute of Sport Assessment-Patella score for patellar tendinopathy, dynamometry, and magnetic resonance imaging (MRI). Differences between the 2 groups were compared with the Student t test. The 10 patients originally treated with BM-MSCs continued to show improvement in tendon structure in their MRI scans (P < .0001), as well as in the clinical assessment of their pain by means of scales (P < .05). Ten patients who were originally treated with Lp-PRP and then with BM-MSCs exhibited an improvement in tendon structure in their MRI scans, as well as a clinical pain improvement, but this was not significant on the VAS for sports (P = .139). Thus, applying Lp-PRP before BM-MScs did not yield any type of advantage. The 12-month follow-up outcomes after both groups of patients (n = 20) received BM-MSC treatment indicated that biological treatment was safe, there were no adverse effects, and the participants showed a highly statistically significant clinical improvement (P < .0002), as well as an improvement in tendon structure on MRI (P < .0001). Preinjection of Lp-PRP yielded no advantages.

Creating 2 Unique Platelet-rich Plasma Products From a Single Batch of Whole Blood With a Single Processing Kit

Introduction: Platelet-rich plasma (PRP) is effective for knee osteoarthritis (OA) and certain tendinopathies. Current recommendations support the use of leukocyte-poor PRP for OA and leukocyte-rich PRP for tendinopathy. If a patient presents with both OA and tendinopathy, very few systems can create multiple PRP products in the same treatment session. The Angel device processes multiple cycles to produce different PRP products. Methods: Ten healthy volunteers donated 156 mL whole blood (WB) that was mixed with 24 mL of anticoagulant citrate dextrose solution, solution A. The first PRP was produced by processing 120 mL at the 0% hematocrit setting and the second PRP was created by processing the remaining 60 mL at the 15% hematocrit setting. WB and PRP underwent complete blood counts and growth-factor analysis. Results: Ten patients donated WB for processing. The 0% setting yielded 3.7 ± 0.15 mL PRP, whereas the 15% setting produced 4.7 ± 0.33 mL. The 0% and 15% settings both concentrated platelets significantly more than WB (1101.5 ± 281.7 K/uL and 1357.8 ± 363.7 vs 184.3 ± 39.1 K/uL, P = 0.000). The 0% setting reduced total leukocytes, but this was not statistically significant. The 15% setting concentrated total leukocytes to 24 ± 8.72 K/uL, which was significantly higher than WB (P = 0.000). Neutrophil concentration was significantly reduced in the 0% PRP compared with 15% (0.032 ± .02 vs 6.75 ± 5.76 K/uL, P = 0.000). Discussion: Two unique PRP products were created from the same batch of WB using a single commercial kit by processing aliquots at different settings.

Leukocyte-poor platelet-rich plasma and leukocyte-rich platelet-rich plasma promote myoblast proliferation through the upregulation of cyclin A, cdk1, and cdk2.

Muscle injuries are common among athletes and often treated with platelet-rich plasma (PRP). However, whether the leukocyte concentration affects the efficacy of PRP in treating muscle injuries remains unclear. This study investigated the effects of leukocyte-poor platelet-rich plasma (LP-PRP) and leukocyte-rich platelet-rich plasma (LR-PRP) on myoblast proliferation and the molecular mechanisms underlying these effects. Myoblasts were treated with 0.5% LP-PRP, 0.5% LR-PRP, 1% LP-PRP, or 1% LR-PRP for 24 h. The gene expression of the LP-PRP- and LR-PRP-treated myoblasts was determined using RNA sequencing analysis. Cell proliferation was evaluated using an bromodeoxyuridine (BrdU) assay, and cell cycle progression was assessed through flow cytometry. The expression of cyclin A, cyclin-dependent kinase 1 (cdk1), and cdk2 was examined using Western blotting. The expression of myoblast determination protein 1 (MyoD1) was examined through Western blotting and immunofluorescence staining. The LP-PRP and LR-PRP both promoted the proliferation of myoblasts and increased differential gene expression of myoblasts. Moreover, the LP-PRP and LR-PRP substantially upregulated the expression of cyclin A, cdk1, and cdk2. MyoD1 expression was induced in the LP-PRP and LR-PRP-treated myoblasts. Our results corroborate the finding that LP-PRP and LR-PRP have similar positive effects on myoblast proliferation and MyoD1 expression.

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 etal. 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.

Statistical Fragility of Randomized Controlled Trials Evaluating Platelet-Rich Plasma Use for Knee Osteoarthritis: A Systematic Review.

Numerous studies have been published on the use of platelet-rich plasma (PRP) for knee osteoarthritis (OA), with conflicting results. To determine the fragility index (FI) and fragility quotient (FQ) of randomized controlled trials (RCTs) that evaluated the use of PRP to treat knee OA. Systematic review. RCTs evaluating the efficacy of PRP injections for knee OA from 2000 to 2020 were included for analysis according to PRISMA guidelines. The FI was determined by calculating the number of outcome event reversals required to change the statistical significance. The associated FQ was determined by dividing the FI by the sample size. Our initial search resulted in 41,149 studies, of which 8 RCTs (678 patients, 72 outcome events) were included in the analysis. One study failed to report PRP formulation details, whereas 87.5% of studies reported using either leukocyte-rich or leukocyte-poor PRP. The platelet concentration was reported in 25% of the included trials. The overall FI of the 72 outcome events was 8.5. Accounting for sample size, the associated FQ was determined to be 0.14, suggesting that the reversal of 14% of outcome events was required to change outcome significance. There were 51 statistically significant outcomes, of which the FI and FQ were 12 and 0.164, respectively. Comprehensive fragility analysis suggested that the published literature evaluating the efficacy of PRP use for knee OA may lack statistical stability. We recommend the reporting of both an FI and FQ in addition to P value analysis to provide a clear and thorough understanding of the statistical integrity of studies reporting on PRP use for knee OA.

Knee Osteoarthritis: Clinical and MRI Outcomes After Multiple Intra-Articular Injections With Expanded Autologous Adipose-Derived Stromal Cells or Platelet-Rich Plasma.

To directly compare clinical and MRI outcomes of multiple intra-articular injections of adipose-derived stromal cells (ASCs) or platelet-rich plasma (PRP) in patients with knee osteoarthritis (OA). We retrospectively compared 24-month outcomes in (1) 27 patients receiving 3-monthly intra-articular injections with a total of 43.8 million ASCs and (2) 23 patients receiving 3-monthly injections of 3-ml preparation of PRP. All patients had Kellgren-Lawrence grade 1, 2, or 3 knee OA with failed conservative medical therapy. The Numeric Pain Rating Scale (NPRS) scores; Knee injury and Osteoarthritis Outcome Score (KOOS) at baseline, 6, 12, and 24 months after the first injection; and the MRI Osteoarthritis Knee Score (MOAKS) at 12 and 24 months were considered as outcomes. No major complications occurred in any patient. Both groups significantly improved in pain NPRS score and KOOS at 6 months. At 12- and 24-month evaluations, the ASC group significantly decreased scores to a greater degree (P < 0.001) than the PRP group. MOAKS scores indicated a decrease in disease progression in the ASC group. Both ASCs and PRP were safe and resulted in clinical improvement in patients with knee OA at 6 months; however, at 12 and 24 months, ASCs outperformed leukocyte-poor PRP in clinical and radiological outcomes.

Leukocyte-Poor Platelet Rich Plasma As An Adjuvant Of Arthroscopic Rotator Cuff Repairs Reduces Retears Rates But Does Not Improve Functional Outcomes A Double-Blind Randomized Controlled Trial

Leukocyte-Poor Platelet Rich Plasma As An Adjuvant Of Arthroscopic Rotator Cuff Repairs Reduces Retears Rates But Does Not Improve Functional Outcomes A Double-Blind Randomized Controlled Trial

Leukocyte-Poor Platelet-Rich Plasma Injections Improve Cartilage T1ρ and T2 and Patient-Reported Outcomes in Mild-to-Moderate Knee Osteoarthritis

To use T1ρ and T2 magnetic resonance imaging to evaluate the effect of leukocyte-poor platelet-rich plasma (LP-PRP) injections on knee cartilage health and to correlate structural changes with patient-reported outcome measurements. Ten patients with symptomatic unilateral mild-to-moderate knee osteoarthritis (Kellgren-Lawrence Grade 1-2) underwent T1ρ and T2 magnetic resonance imaging of both the symptomatic and contralateral knee before injection and 6 months after injection with LP-PRP. Patient-reported outcome questionnaires (Knee Osteoarthritis Outcome Score and International Knee Documentation Committee) that evaluate the domains of pain, symptoms, activities of daily living, sports function, and quality of life were completed at baseline, 3 months, 6 months, and 12 months after injection. T1ρ and T2 relaxation times, which are correlated with the proteoglycan and collagen concentration of cartilage, were measured in compartments with and without chondral lesions. Ten patients were prospectively enrolled (9 female, 1 male) with a mean age of 52.9 years (range, 42-68) years and mean body mass index of 23.2 ± 1.9. Significant increases in Knee Osteoarthritis Outcome Score for all subscales and International Knee Documentation Committee scores were observed 3 months after injection and the improvements were sustained at 12 months. T1ρ and T2 values of compartments with chondral lesions were observed to significantly decrease by 6.0% (P= .036) and 7.1% (P= .017) 6 months after LP-PRP injection, respectively. No significant associations between T1ρ and T2 relaxation times and improvement in patient-reported outcomes were observed. Patients undergoing LP-PRP injections for the treatment of mild-to-moderate knee osteoarthritis had increased proteoglycan and collagen deposition in the cartilage of affected compartments by 6 months after injection. Patient-reported outcomes scores improved 3 months after injection and were sustained through 1 year after injection, but these improvements were not associated with the changes in proteoglycan and collagen deposition in knee cartilage. Level II, prospective cohort study.

Leukocyte-Rich Platelet-Rich Plasma Is Predominantly Anti-inflammatory Compared With Leukocyte-Poor Platelet-Rich Plasma in Patients With Mild-Moderate Knee Osteoarthritis: A Prospective, Descriptive Laboratory Study

Background: Platelet-rich plasma (PRP) has been used extensively in clinical practice to treat patients with symptomatic knee osteoarthritis (OA). Leukocyte-poor PRP (LP-PRP) has been clinically preferred over leukocyte-rich PRP (LR-PRP); however, it is unclear which cytokine mediators of pain and inflammation are present in LR-PRP and LP-PRP from patients with mild to moderate knee OA in order to rationalize a specific formulation. Hypothesis: LP-PRP would be predominantly anti-inflammatory and have reduced nociceptive pain mediators compared with LR-PRP from the same individual with mild to moderate knee OA. Study Design: Controlled laboratory study. Methods: A total of 24 unique samples of PRP were prepared in order to assess 48 samples of LR-PRP and LP-PRP taken from 12 patients (6 male and 6 female) with symptomatic knee OA of Kellgren-Lawrence grade 2 to 3. Patients underwent blood collection for LR-PRP and LP-PRP preparation through a double-spin protocol to obtain baseline whole blood, platelet concentration, and white blood cell subtypes. LR-PRP and LP-PRP from the same patient were produced at the same time and underwent a comprehensive panel through Luminex (multicytokine profiling) to assess key mediators of inflammation: interleukin 1 receptor antagonist (IL-1Ra), interleukin 4, 6, 8, and 10 (IL-4, IL-6, IL-8, and IL-10), IL-1β, tissue necrosis factor α (TNF-α), and matrix metalloproteinase 9 (MMP-9). To assess mediators of nociceptive pain, nerve growth factor (NGF) and tartrate resistant acid phosphatase 5 (TRAP5) were also assessed. Results: LR-PRP from patients with mild to moderate knee OA expressed significantly more IL-1Ra, IL-4, IL-8, and MMP-9 compared with LP-PRP formulations from the same patients. No significant differences were found between LR-PRP and LP-PRP in mediators of nociceptive pain—namely, NGF and TRAP5. Other mediators including TNF-α, IL-1β, IL-6, and IL-10 were also found to have no significant expression differences between LR-PRP and LP-PRP. Conclusion: LR-PRP expressed significantly more IL-1Ra, IL-4, and IL-8, suggesting that LR-PRP may be more anti-inflammatory than LP-PRP. MMP-9 was expressed in higher concentrations in LR-PRP, suggesting that LR-PRP may be more chondrotoxic than LP-PRP. Clinical Relevance: LR-PRP was found to have a robust expression of anti-inflammatory mediators compared with LP-PRP and may be beneficial to patients with long-term knee OA where chronic low-grade inflammation is present. Mechanistic clinical trials are needed to elucidate the key mediators in both LR-PRP and LP-PRP to assess their effect on long-term progression of knee OA.

Biological injection therapy with leukocyte-poor platelet-rich plasma induces cellular alterations, enhancement of lubricin, and inflammatory downregulation in vivo in human knees: A controlled, prospective human clinical trial based on mass spectrometry imaging analysis.

To investigate the in vivo biological effects of leukocyte-poor platelet-rich plasma (LpPRP) treatment in human synovial layer to establish the cellular basis for a prolonged clinical improvement. Synovial tissues (n = 367) were prospectively collected from patients undergoing arthroscopic surgery. Autologous-conditioned plasma, LpPRP, was injected into the knees of 163 patients 1-7 days before surgery to reduce operative trauma and inflammation, and to induce the onset of regeneration. A total of 204 patients did not receive any injection. All samples were analyzed by mass spectrometry imaging. Data analysis was evaluated by clustering, classification, and investigation of predictive peptides. Peptide identification was done by tandem mass spectrometry and database matching. Data analysis revealed two major clusters belonging to LpPRP-treated (LpPRP-1) and untreated (LpPRP-0) patients. Classification analysis showed a discrimination accuracy of 82%-90%. We identified discriminating peptides for CD45 and CD29 receptors (receptor-type tyrosine-protein phosphatase C and integrin beta 1), indicating an enhancement of musculoskeletal stem cells, as well as an enhancement of lubricin, collagen alpha-1-(I) chain, and interleukin-receptor-17-E, dampening the inflammatory reaction in the LpPRP-1 group following LpPRP injection. We could demonstrate for the first time that injection therapy using "autologic-conditioned biologics" may lead to cellular changes in the synovial membrane that might explain the reported prolonged beneficial clinical effects. Here, we show in vivo cellular changes, possibly based on muscular skeletal stem cell alterations, in the synovial layer. The gliding capacities of joints might be improved by enhancing of lubricin, anti-inflammation by activation of interleukin-17 receptor E, and reduction of the inflammatory process by blocking interleukin-17.

The Influence of Platelet-Derived Growth Factors on the Proliferation of Germinal Epithelium After Local Irradiation with Electrons.

At present, the damage of male reproductive function caused by electron irradiation, as well as the development of methods for its correction are the relevant topics for further research. In fact, the effect of leukocyte-poor platelet-rich plasma (LP-PRP) growth factors are poorly investigated on different aspects of male fertility. In this study, Wistar rats were divided into four groups; I) control which were injected with saline; II and III) groups (n=65) whose testes were locally irradiated with electrons to a dose of 2 Gy (linear accelerator "NOVAC-11"); III) the group (n=30) which received LP-PRP for 11 weeks after irradiation; and IV) animals (n=30) which received only LP-PRP (conditional control). The testes were studied by histological, immunohistochemical (IHC), western blotting, and TUNEL methods using Ki-67, Bcl-2, and p53. Comparison between groups was performed and p<0.01 was set as the level of significance. The results showed a decrease in the expression levels of Ki-67 and Bcl-2 besides an increase in p53-positive cells by the end of the experiment (p<0.01). After injection of LP-PRP, a gradual restoration of the proliferative activity of gametes was noted, which was confirmed by an increase in the proportion of Ki-67- and Bcl-2-positive germ cells (46.4±2.3, p<0.01 and 23.5±1.1, respectively, p<0.01). Ki-67 expression and TUNEL analysis in the testes revealed a modulation of the proliferative-apoptotic balance towards apoptosis of germ cells after 2 Gy local electron irradiation. A tendency to restore the proliferative-apoptotic balance was noted after LP-PRP injections as indicated by increase in Ki-67-positive germ cells.

Intrauterine Infusion of Leukocyte-Poor Platelet-Rich Plasma Is an Effective Therapeutic Protocol for Patients with Recurrent Implantation Failure: A Retrospective Cohort Study.

The clinical application of autologous leukocyte-poor platelet-rich plasma (LP-PRP) in patients with recurrent implantation failure (RIF) is rare. This retrospective observational cohort study aimed to evaluate the efficacy of LP-PRP intrauterine infusion in patients with RIF. Patients with RIF undergoing frozen embryo transfer (FET) from January 2019 to December 2021 (n = 118) were enrolled, with those undergoing LP-PRP intrauterine infusion as the PRP group (n = 64), and those receiving no LP-PRP treatment as the control group (n = 54). The beta-human chorionic gonadotropin (β-hCG)-positive rate, clinical pregnancy rate (CPR), live birth rate (LBR), and miscarriage rate (MR) per ET cycle were compared. The β-hCG-positive rate (57.8% vs. 38.9%, p = 0.041), CPR (45.3% vs. 24.5%, p = 0.022), and LBR per ET cycle (42.2% vs. 18.5%, p = 0.009) were higher in the PRP group than in the control group, and the three variables (62.5% vs. 41.2%, p = 0.040, 47.5% vs. 23.5%, p = 0.033, and 47.5% vs. 20.6%, p = 0.027) in the PRP group transferred with the blastocyst-stage embryos were also higher than those in the control group. The MR was similar in all groups. The LP-PRP treatment could improve the β-hCG-positive rate, CPR, and LBR in RIF patients undergoing FET cycles.