Harmful Effects of Leukocyte-Rich Platelet-Rich Plasma on Rabbit Tendon Stem Cells In Vitro

Platelet-derived exosomes alleviate tendon stem/progenitor cell senescence and ferroptosis by regulating AMPK/Nrf2/GPX4 signaling and improve tendon-bone junction regeneration in rats

BACKGROUND

Tendon stem/progenitor cell (TSPC) senescence contributes to tendon degeneration and impaired tendon repair, resulting in age-related tendon disorders. Ferroptosis, a unique iron-dependent form of programmed cell death, might participate in the process of senescence. However, whether ferroptosis plays a role in TSPC senescence and tendon regeneration remains unclear. Recent studies reported that Platelet-derived exosomes (PL-Exos) might provide significant advantages in musculoskeletal regeneration and inflammation regulation. The effects and mechanism of PL-Exos on TSPC senescence and tendon regeneration are worthy of further study.

METHODS

Herein, we examined the role of ferroptosis in the pathogenesis of TSPC senescence. PL-Exos were isolated and determined by TEM, particle size analysis, western blot and mass spectrometry identification. We investigated the function and underlying mechanisms of PL-Exos in TSPC senescence and ferroptosis via western blot, real-time quantitative polymerase chain reaction, and immunofluorescence analysis in vitro. Tendon regeneration was evaluated by HE staining, Safranin-O staining, and biomechanical tests in a rotator cuff tear model in rats.

RESULTS

We discovered that ferroptosis was involved in senescent TSPCs. Furthermore, PL-Exos mitigated the aging phenotypes and ferroptosis of TSPCs induced by t-BHP and preserved their proliferation and tenogenic capacity. The in vivo animal results indicated that PL-Exos improved tendon-bone healing properties and mechanical strength. Mechanistically, PL-Exos activated AMPK phosphorylation and the downstream nuclear factor erythroid 2-related factor 2 (Nrf2)/glutathione peroxidase 4 (GPX4) signaling pathway, leading to the suppression of lipid peroxidation. AMPK inhibition or GPX4 inhibition blocked the protective effect of PL-Exos against t-BHP-induced ferroptosis and senescence.

CONCLUSION

In conclusion, ferroptosis might play a crucial role in TSPC aging. AMPK/Nrf2/GPX4 activation by PL-Exos was found to inhibit ferroptosis, consequently leading to the suppression of senescence in TSPCs. Our results provided new theoretical evidence for the potential application of PL-Exos to restrain tendon degeneration and promote tendon regeneration.

Safety of bone marrow derived mesenchymal stem cell extracellular vesicle injection for lumbar facet joint pain

Aim: A 3-month pilot study to evaluate the safety of injecting a bone marrow-derived mesenchymal stem cell extracellular vesicle advanced investigational product (IP) into the lumbar facet joint space as a treatment for chronic low back pain. Methods: 20 healthy adults were treated with IP injections (0.5 ml/joint) and evaluated by three functional assessments 1, 3, 7, 14, 30, 60 and 90 days later. Results: No adverse effects or complications occurred across the 3-month follow-up. There were no reports of worsening pain. After 3 months group average scores improved significantly (p < 0.0001) in the Severity Index (65.04%), Interference Index (72.09%) and Oswestry Disability Index (58.43%) assessments. Conclusion: IP injections were safe and associated with significant functional improvements.

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.

Leukocyte and Platelet-Rich Plasma (L-PRP) in Tendon Models: A Systematic Review and Meta-Analysis of in vivo/in vitro Studies

Purpose

To perform a systematic review on the application of leukocyte- and platelet-rich plasma (L-PRP) in tendon models by reviewing in vivo/in vitro studies.

Methods

The searches were performed via electronic databases including PubMed, Embase, and Cochrane Library up to September 2022 using the following keywords: ((tenocytes OR tendon OR tendinitis OR tendinosis OR tendinopathy OR tendon injury) AND (platelet-rich plasma OR PRP OR autologous conditioned plasma OR leukocyte- and platelet-rich plasma OR L-PRP OR leukocyte-richplatelet-rich plasma Lr-PRP)). Only in vitro and in vivo studies that assessed the potential effects of L-PRP on tendons and/or tenocytes are included in this study. Description of PRP, study design and methods, outcomes measured, and results are extracted from the data.

Results

A total of 17 studies (8 in vitro studies and 9 in vivo studies) are included. Thirteen studies (76%) reported leukocyte concentrations of L-PRP. Four studies (24%) reported the commercial kits. In in vitro studies, L-PRP demonstrated increased cell proliferation, cell migration, collagen synthesis, accelerated inflammation, and catabolic response in the short term. In addition, most in vivo studies indicated increased collagen type I content. According to in vivo studies reporting data, L-PRP reduced inflammation response in 71.0% of studies, while it enhanced the histological quality of tendons in 67.0% of studies. All 3 studies reporting data found increased biomechanical properties with L-PRP treatment.

Conclusions

Most evidence indicates that L-PRP has some potential effects on tendon healing compared to control. However, it appears that L-PRP works depending on the biological status of the damaged tendon. At an early stage, L-PRP may accelerate tendon healing, but at a later stage, it could be detrimental.

Leukocyte-Rich Platelet-Rich Plasma as an Effective Source of Molecules That Modulate Local Immune and Inflammatory Cell Responses

Autologous platelet-rich plasma (PRP) injection is a safe biological method used to treat various musculoskeletal diseases. By downregulation of inflammatory cytokines and stimulation of synovial fibroblasts, PRP injection is a promising adjunctive treatment for patients with chronic autoimmune inflammatory diseases such as rheumatoid arthritis. A major problem in comparing the results of clinical trials in this area is the considerable variability in the cytokine content of PRP. We presented the profile of selected growth factors and inflammatory cytokines in the obtained PRP samples and compared them with baseline serum levels to assess the efficacy of PRP as a source of those paracrine molecules. Additionally, we wanted to determine whether the difference is only quantitative, which would suggest the use of a cheaper alternative by injecting a large amount of autologous serum. For this purpose, we analyzed whole blood and PRP samples prepared using the Mini GPS III Platelet Concentration System (Biomet Inc., USA) in 31 subjects aged 35-60 years. Cellular content, seven selected growth factors, and 13 human inflammatory cytokines were evaluated. Multiplex bead immunoassays that use fluorescence-encoded beads LEGENDplex™ (BioLegend, USA) and flow cytometer measurements were used. As a result, we found a statistically significant increase in four of the growth factors tested and eight of the inflammatory cytokines tested in PRP compared to blood serum. The difference is not only quantitative but also in the composition of paracrine molecules. In conclusion, the study confirmed that PRP is an efficient source of several growth factors and some inflammatory cytokines. These data provide additional insight into the potential mechanisms of PRP’s effects on cellular metabolism and inflammatory response and may contribute to a better understanding of its clinical efficacy.

Injection of Leukocyte-Poor Platelet-Rich Plasma for Moderate-to-Large Rotator Cuff Tears Does Not Improve Clinical Outcomes but Reduces Retear Rates and Fatty Infiltration: A Prospective, Single-Blinded Randomized Study

OBJECTIVES

To determine whether leukocyte-poor platelet-rich plasma (Lp-PRP) reduced retear rates, reduced fatty infiltration, and improved functional outcomes in patients with degenerative moderate-to-large rotator cuff tears.

METHODS

This was a randomized controlled study at a single center. A consecutive series of 104 patients with moderate-to-large rotator cuff tears was enrolled and randomly allocated to a control group (double-row suture-bridge arthroscopic rotator cuff repair alone, n = 52) and a study group (double-row suture-bridge repair followed by 3 Lp-PRP injections at the tendon repair site during surgery, at days 7 and 14 after surgery, n = 52). All patients were followed up for 27.2 months (range 24-36 months), with University of California at Los Angeles (UCLA) shoulder rating scale, the Constant score, and a visual analog scale (VAS) evaluated respectively. The integrity and fatty infiltration of repaired tissue were assessed by magnetic resonance imaging using the Sugaya classification and Goutallier grade classification at 24 months after surgery. Statistical analysis was performed based on the t test, χ² test, and the Kendall tau-b correlation coefficient.

RESULTS

Four patients refused follow-up, and 11 patients had incomplete data. Eventually, a total of 89 patients were available for 24 months follow-up. The mean UCLA score increased from 14.80 ± 2.53 to 29.37 ± 2.06 in control group and from 13.74 ± 3.30 to 30.14 ± 2.32 in study group (P = .103). The mean Constant score increased from 46.56 ± 5.90 to 86.83 ± 4.94 in control group and from 44.37 ± 7.92 to 88.80 ± 4.92 in study group (P = .063). The VAS score decreased from 3.22 ± 1.24 to 0.97 ± 1.12 in control group and in 3.49 ± 1.52 to 1.16 ± 0.99 in study group (P = .41). All differences in UCLA score, Constant score, and VAS between pre- and postoperation achieved minimal clinically important differences proposed for arthroscopic rotator cuff repair. Of the 89 patients, 76 had magnetic resonance imaging performed at 24 months after surgery. The retear rate was 17.6% in study group, which was lower than that in control group (38.1%, P = .049). In addition, the Goutallier grade was found to be significant difference between groups postoperatively (Kendall tau-b -0.24, P = .03) but no significant difference preoperatively (Kendall tau-b -0.18, P = .11). There were no complications in the patients.

CONCLUSIONS

Our procedures involving repeated injections of Lp-PRP during surgery and at days 7 and 14, as described in this study, have positive effects on reducing retear rate and promoting Goutallier grade in patients following arthroscopic rotator cuff repair and could also provide substantial clinical outcomes that reach the minimal clinically important difference for surgical treatment. However, given the numbers available for analysis, it did not promote better clinical results when compared with the control group.

LEVEL OF EVIDENCE

II, randomized controlled study.

Leukocyte-Rich Platelet-Rich Plasma Has Better Stimulating Effects on Tenocyte Proliferation Compared With Leukocyte-Poor Platelet-Rich Plasma

Background:

Rotator cuff (RC) tendinopathy is one of the most common causes of shoulder pain. Platelet-rich plasma (PRP) has been frequently used in clinical scenarios, but its efficacy remains inconsistent.

Purpose:

To investigate the different responses of human tenocytes from torn RCs to leukocyte-rich PRP (LR-PRP) and leukocyte-poor PRP (LP-PRP) in a 2-chamber coculture device.

Study Design:

Controlled laboratory study.

Methods:

PRP was prepared using different platelet and leukocyte concentrations according to 5 groups: (1) LR-PRP with 5000 platelets/µL, (2) LR-PRP with 10,000 platelets/µL, (3) LP-PRP with 5000 platelets/µL, (4) LP-PRP with 10,000 platelets/µL, and (5) control with only culture medium supplementation and without PRP stimulation. Platelet-derived growth factor–AB (PDGF-AB) and transforming growth factor–β1 (TGF-β1) were measured in LR-PRP and LP-PRP via enzyme-linked immunosorbent assay. Microscopy, water-soluble tetrazolium salt assay, and quantitative real-time polymerase chain reaction were used to investigate the morphology, proliferation, and gene expression of RC tenocytes exposed to different PRP formulations. Data were collected from at least 3 independent measurements. The results were analyzed via 1-way analysis of variance, followed by the post hoc Bonferroni test.

Results:

The ratio of leukocytes to 5000 platelets/µL was 29.5 times higher in LR-PRP than in LP-PRP (P < .05). In the 5000 platelets/µL groups, the levels of TGF-β1 and PDGF-AB were both significantly higher in LR-PRP versus LP-PRP (TGF-β1: 367.0 ± 16.5 vs 308.6 ± 30.3 pg/mL, respectively [P = .043]; PDGF-AB: 172.1 ± 1.8 vs 94.1 ± 4.2 pg/mL, respectively [P < .001]). Compared with the control group, RC tenocyte proliferation was 1.42 ± 0.01 and 1.41 ± 0.03 times higher in the LR-PRP groups with 5000 platelets/µL and 10,000 platelets/µL, respectively (P < .05). The expression of tenocyte-related genes was higher in tenocytes cultured in LR-PRP.

Conclusion:

Both the LR-PRP groups with 5000 platelets/µL and 10,000 platelets/µL induced more growth factor release and increased RC tenocyte proliferation than did the LP-PRP groups.

Clinical Relevance:

In RC repair, LR-PRP may be better than LP-PRP for increasing the proliferation of tenocytes.

Why might ovarian rejuvenation fail? Decision analysis of variables impacting reproductive response after autologous platelet-rich plasma

Experience with platelet-rich plasma (PRP) has accumulated from use in dental restoration, post-infarct myocardial repair, tendon surgery, pain management, and aesthetic enhancements. Reproductive medicine joined this arena in 2016, beginning with reports of menopause reversal and fertility recovery after autologous PRP for senescent ovaries. Although recent publications have highlighted benefits of 'ovarian rejuvenation', the absence of randomized placebo-controlled clinical trial data has limited its acceptance. Because selection bias tends to underreport negative outcomes, reliable estimates cannot be calculated for how often intraovarian PRP is unsuccessful. Ample information is available, however, to permit an operational root-cause analysis when failures are considered. This assessment uses a PRP treatment care path with a decision theory model to critique pre-intake screening, baseline audit, sample processing, ovarian tissue placement method, equipment selection, and follow-up monitoring. These branched choice points enable interventions likely to determine outcome. Specimen handling for intraovarian PRP merits particular scrutiny, since enormous variation in platelet protocols already exists across unrelated clinical areas. As a new addition to fertility practice, intraovarian PRP requires validation of safety and efficacy to gain wider support. Borrowing PRP knowledge from other domains can facilitate this goal, ideally with appreciation of aspects unique to intraovarian use.

Classification and coding of platelet-rich plasma derived from New Zealand white rabbits for tissue engineering and regenerative medicine applications

BACKGROUND AND OBJECTIVE

Platelet-rich plasma (PRP) is a category of platelet concentrate that has been widely used as a therapeutic modality in musculoskeletal medicine. The present study was conducted to classify and code the non-activated platelet-rich plasma (nPRP) derived from New Zealand white rabbits for tissue engineering and other regenerative medicine applications.

METHODS

PRP was prepared from the whole blood by double centrifugation protocol using a laboratory centrifuge. The prepared nPRP was characterized using the parameters such as platelet dose, the relative composition of platelets, WBC, and RBC. The production protocol was described using the parameters such as platelet enrichment factor, factor increase in WBC concentration, platelet capture efficiency, WBC-reducing efficiency, and RBC-reducing efficiency. The nPRP was also classified and coded using the most recent and universally accepted classification and coding systems.

RESULTS

The non-activated leukocyte-poor red cell-rich PRP had an average platelet count of 1875.75 × 10⁹/L, which is higher than the basal platelet concentration in the whole blood. Furthermore, the protocol used in this study has a mean platelet capture efficiency of 47.43 ± 6.42%.

CONCLUSION

The protocol described in this study can be used to prepare non-activated leukocyte-poor red cell-rich PRP (Red-PRP IC1) from rabbits that can be coded as 318-00-00.

Platelet-Rich Plasma Content of Active Spinal Cord Injured Patients: A Controlled Laboratory Study

OBJECTIVE

Platelet-rich plasma has potential uses for patients with spinal cord injuries. However, no study has quantified the cellular and growth factor content of platelet-rich plasma in this population. This study aimed to analyze (1) platelet-rich plasma content of spinal cord injury subjects and (2) the effect of high-intensity interval exercise on their platelet-rich plasma.

DESIGN

Ten spinal cord injury patients and 10 controls were enrolled. At rest, platelet-rich plasma was created from both groups. The spinal cord injury group then performed high-intensity interval exercise and underwent a second blood draw to create post-high-intensity interval exercise platelet-rich plasma. Complete blood counts and growth factor analysis (via enzyme-linked immunosorbent assay) was performed on all platelet-rich plasma.

RESULTS

The spinal cord injury group had lower platelets (305,700 ± 85,697/μl vs 380,800 ± 57,301/μl, P = 0.015) and transforming growth factor β (12.84 ± 1.58 vs 14.33 ± 0.63 ng/ml, P = 0.023). Four minutes of high-intensity interval exercise increased the platelets (305,700 ± 85,697/μl to 399,200 ± 96,251/μl, P = 0.004), leukocytes (906 ± 930 vs 2504 ± 3765/μl, P = 0.002) and transforming growth factor β (12.84 ± 1.58 to 14.28 ± 1.21 ng/ml, P = 0.020).

CONCLUSIONS

Spinal cord injury patients have fewer platelets and transforming growth factor β in their platelet-rich plasma at baseline compared with controls. Exercise increased platelet, leukocyte, and transforming growth factor β yield, compensating for the baseline deficits.

A 3D-printed PRP-GelMA hydrogel promotes osteochondral regeneration through M2 macrophage polarization in a rabbit model

Osteochondral regeneration is an orchestrated process of inflammatory immunity, host cell response, and implant degradation in tissue engineering. Here, the effects of a platelet-rich plasma (PRP)-gelatin methacryloyl (GelMA) hydrogel scaffold fabricated using the digital micro-mirror device (DMD) technique for osteochondral repair were investigated in a rabbit model. GelMA hydrogels with different PRP concentrations were fabricated, and their roles in bone marrow mesenchymal stem cells (BMSCs) and macrophage polarization in vitro were investigated. The incorporation of 20% PRP into the hydrogel showed optimal effects on the proliferation, migration, and osteogenic and chondrogenic differentiation of BMSCs. The 20% PRP-GelMA (v/v) hydrogel also promoted M2 polarization with high expression of Arg1 and CD206. Compared to the 20% PRP group, the 50% PRP group showed similar biological roles in BMSCs but less extent of osteogenesis. In the vivo study, the 20% PRP-GelMA composite was used for osteochondral reconstruction and showed more cartilage and subchondral bone regeneration than that observed using the pure GelMA hydrogel. The PRP-GelMA group exhibited more M2 macrophage infiltration and less M1 macrophage presentation at three time points as compared to the nontreatment group. The expression of Arg1 in the PRP-GelMA group increased significantly at 6 weeks but decreased to a lower level at 12 weeks, while CD163 showed sustained high expression until 18 weeks. Our findings demonstrated that the 3D-printed PRP-GelMA composite could promote osteochondral repair through immune regulation by M2 polarization and could be a potential candidate for osteochondral tissue engineering. STATEMENT OF SIGNIFICANCE: PRP-GelMA hydrogels promoted the migration and osteogenic and chondrogenic differentiation of BMSCs. PRP-GelMA hydrogels participated in immune regulation and M1-to-M2 transition of macrophages. PRP-GelMA hydrogels coordinated and promoted several overlapping osteochondral repair events, including dynamic immune regulation, chemotaxis of MSCs, and osteochondral differentiation. PRP-GelMA hydrogels showed superior cartilage and subchondral bone repair properties.

Effects of leukocyte- and platelet-rich plasma on tendon disorders based on in vitro and in vivo studies (Review)

Tendon-related disorders are common musculoskeletal system disorders in clinical practice, accounting for 30-50% of all sports-related injuries, and they are difficult to treat due to the hypovascular structure of the tendons. Platelet-rich plasma (PRP), including pure PRP and leukocyte- and platelet-rich plasma (L-PRP), has been attracting increasing attention, as it may stimulate tissue regeneration through the release of growth factors and cytokines. The aim of the present review was to provide a summary of the effects of L-PRP on tendon disorders and the underlying mechanisms through a comprehensive examination of the published literature, including in vitro, animal and clinical studies. It has been demonstrated that L-PRP results in comparatively greater pain relief and improved function in patients suffering from tendon disorders. Furthermore, L-PRP may exert its effects through a diverse range of mechanisms, such as neovascularization, cell proliferation and differentiation of tendon/progenitor stem cells into tenocytes, as well as extracellular matrix reorganization by transforming type III to type I collagen fibers. It has also been indicated that the effects of leukocytes in L-PRP depend on the biological state of the injured tissue and its surrounding microenvironment. L-PRP is beneficial and promotes tendon healing at the early stage, whereas it is likely detrimental to the repair of tendon at a later stage because of the risk of excessive catabolic and inflammatory responses. Overall, the application of L-PRP in tendon disorders appears to be a promising field that is worthy of further research.

Characterization of Tendon-Derived Stem Cells and Rescue Tendon Injury

The natural healing ability of tendon is limited, and it cannot restore the native structure and function of tendon injuries. Tendon-derived stem cells (TDSCs) are a new type of pluripotent stem cells with multi-directional differentiation potential and are expected to become a promising cell-seed for the treatment of tendon injuries in the future. In this review, we outline the latest advances in the culture and identification of TDSCs. In addition, the influencing factors on the differentiation of TDSCs are discussed. Moreover, we aim to discuss recent studies to enhance TDSCs treatment of injured tendons. Finally, we identify the limitations of the current understanding of TDSCs biology, the main challenges of using their use, and potential therapeutic strategies to inform cell-based tendon repair.

Platelet-Rich Plasma in Patients With Partial-Thickness Rotator Cuff Tears or Tendinopathy Leads to Significantly Improved Short-Term Pain Relief and Function Compared With Corticosteroid Injection: A Double-Blind Randomized Controlled Trial

PURPOSE

To perform a randomized controlled trial comparing platelet-rich plasma (PRP) with standard corticosteroid (CS) injection in providing pain relief and improved function in patients with rotator cuff tendinopathy and partial-thickness rotator cuff tears (PTRCTs).

METHODS

This double-blind randomized controlled trial enrolled patients with ultrasound-proven or magnetic resonance imaging-proven PTRCTs who received either an ultrasound-guided PRP or CS injection. Patients completed patient-reported outcome assessments at baseline and at 6 weeks, 3 months, and 12 months after injection. The primary outcome was improvement in the visual analog scale (VAS) score for pain. Secondary outcomes included changes in American Shoulder and Elbow Surgeons (ASES) and Western Ontario Rotator Cuff Index (WORC) scores. Treatment failure was defined as subsequent injection, consent to undergo surgery, or operative intervention.

RESULTS

We followed up 99 patients (47 in the PRP group and 52 in the CS group) until 12 months after injection. There were no differences in baseline patient demographic characteristics including age, sex, or duration of symptoms. Despite randomization, patients in the PRP group had worse baseline VAS (46.0 vs 34.7, P = .01), ASES (53.9 vs 61.8, P = .02), and WORC (42.2 vs 49.5, P = .03) scores. At 3 months after injection, the PRP group had superior improvement in VAS (-13.6 vs 0.4, P = .03), ASES (13.0 vs 2.9, P = .02), and WORC (16.8 vs 5.8, P = .03) scores. There were no differences in patient-reported outcomes at 6 weeks or 12 months. There was no difference in the rate of failure (P = .31) or conversion to surgery (P = .83) between groups.

CONCLUSIONS

Patients with PTRCTs or tendinopathy experienced clinical improvement in pain and patient-reported outcome scores after both ultrasound-guided CS and PRP injections. Patients who received PRP obtained superior improvement in pain and function at short-term follow-up (3 months). There was no sustained benefit of PRP over CS at longer-term follow-up (12 months).

LEVEL OF EVIDENCE

Level I, randomized controlled trial.

PRP in wound healing applications

Platelets play a crucial role in hemostasis, tissue regeneration and host defense. Based on these settings, platelet-rich plasma (PRP) and its derivatives are therapeutically used to promote wound healing in several scenarios. This review summarizes the biological mechanisms underlying the most traditional as well as innovative applications of PRP in wound healing. These mechanisms involve the combined action of platelet-derived growth factors and cytokines, together with the role of plasma-derived fibrillar, antioxidant and homeostatic factors. In addition, regenerative treatments with PRP consist of personalized and non-standardized methods. Thus, the quality of PRP varies depending on endogenous factors (e.g., age; gender; concomitant medication; disease-associated systemic factors; nutrition) and exogenous factors (anticoagulants and cellular composition). This review also analyses whether these factors affect the biological mechanisms of PRP in wound healing applications.

Platelet-Rich Plasma Therapy in the Treatment of Diseases Associated with Orthopedic Injuries

Platelet-rich plasma (PRP) is an autologous platelet concentrate prepared from the whole blood that is activated to release growth factors (GFs) and cytokines and has been shown to have the potential capacity to reduce inflammation and improve tissue anabolism for regeneration. The use of PRP provides a potential for repair due to its abundant GFs and cytokines, which are key in initiating and modulating regenerative microenvironments for soft and hard tissues. Among outpatients, orthopedic injuries are common and include bone defects, ligament injury, enthesopathy, musculoskeletal injury, peripheral nerve injury, chronic nonhealing wounds, articular cartilage lesions, and osteoarthritis, which are caused by trauma, sport-related or other types of trauma, or tumor resection. Surgical intervention is often required to treat these injuries. However, for numerous reasons regarding limited regeneration capacity and insufficient blood supply of the defect region, these treatments commonly result in unsatisfactory outcomes, and follow-up treatment is challenging. The aim of the present review is to explore future research in the field of PRP therapy in the treatment of diseases associated with orthopedic injuries. Impact statement In recent years, platelet-rich plasma (PRP) has become widely used in the treatment of diseases associated with orthopedic injuries, and the results of numerous studies are encouraging. Due to diseases associated with orthopedic injuries being common in clinics, as a conservative treatment, more and more doctors and patients are more likely to accept PRP. Importantly, PRP is a biological product of autologous blood that is obtained by a centrifugation procedure to enrich platelets from whole blood, resulting in few complications, such as negligible immunogenicity from an autologous source, and it is also simple to produce through an efficient and cost-effective method in a sterile environment. However, the applicability, advantages, and disadvantages of PRP therapy have not yet been fully elucidated. The aim of the present review is to explore future research in the field of PRP therapy in the treatment of diseases associated with orthopedic injuries, as well as to provide references for clinics.

Dose-Dependent Effects of Platelet-Rich Plasma Powder on Chondrocytes In Vitro

BACKGROUND

Platelet-rich plasma (PRP) is widely used in sports medicine. However, neither preparation nor parameters for clinical application, such as concentration, timing, and number of applications, are standardized, making research and clinical utilization challenging.

PURPOSE

To investigate the effect of varying doses of PRP powder in terms of different concentrations, timing, and number of applications on human chondrocytes in a reproducible cell culture model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A standardized lyophilized platelet growth factor preparation (PRP powder) was used to stimulate human chondrocytes. Chondrocytes were cultivated for 2 weeks with different stimulation frequencies (2×, 3×, 6×) and different concentrations of PRP powders (0.5%, 1%, 5%). Cell proliferation and metabolic cell activity were analyzed on days 7 and 14. Phenotypic changes were visualized through live-dead staining. Chondrogenic differentiation was quantified with enzyme-linked immunosorbent assay to assess the synthesis of procollagen types 1 and 2. Furthermore, sulfated proteoglycans and glycosaminoglycans were analyzed.

RESULTS

Human chondrocytes exhibited a significant dose- and time-dependent increase after 14 days in cell number (1% and 5% PRP powder vs unstimulated control: 7.95- and 15.45-fold increase, respectively; 2× vs 6× stimulation with 5% PRP powder: 4.00-fold increase) and metabolic cell activity (1% and 5% PRP powder vs unstimulated control: 3.27-fold and 3.58-fold change, respectively). Furthermore, cells revealed a significant increase in the amount of bone-specific procollagen type 1 (14 days, 1.94-fold) and sulfated glycosaminoglycans (14 days, 2.69-fold); however, no significant change was observed in the amount of cartilage-specific collagen type 2.

CONCLUSION

We showed that chondrocytes exhibit a significant dose- and time-dependent increase in cell number and metabolic cell activity. The standardized use of growth factor concentrates in cell culture models can contribute to clinical knowledge in terms of dosage and timing of PRP applications.

CLINICAL RELEVANCE

Problems with PRP, such as the absence of standardization, lack of consistency among studies, and unknown dosage, could be solved by using characterized PRP powder made by pooling and lyophilizing multiple platelet concentrates. The innovative PRP powder generates new possibilities for PRP research, as well as for the treatment of patients.

Platelet and Leukocyte Concentration in Equine Autologous Conditioned Plasma Are Inversely Distributed by Layer and Are Not Affected by Centrifugation Rate

Background: Platelet rich plasma (PRP) is used extensively in equine regenerative medicine. Differences in preparation protocols give rise to significant variability in the cellular composition of PRP making it very difficult to establish a standard of care in the field. This study aimed to optimize the preparation protocol for leukocyte-reduced PRP (P-PRP).

Methods: Blood (100 mL) was collected from horses (n = 5) and divided into 2 purple top EDTA tubes and 6 (15 mL) double syringes^a with a final concentration of 10% acid citrate dextrose anticoagulant. Six double syringes^a were collected from each horse; PRP samples were prepared in duplicate and centrifuged at 1,100 rpm (188 × g), 1,300 rpm (263 × g), or 1,500 rpm (350 × g). Duplicates were subjected to +/– braking at the end of centrifugation. The total volume of PRP generated was measured and divided into thirds. Each third (top, middle, and bottom) were drawn off separately using the inner (6 mL syringe) and placed in purple top EDTA tubes. Automated complete blood counts were performed on all peripheral whole blood and PRP samples.

Results: The concentration of leukocytes was higher in the bottom layer of PRP compared to the top and middle layers (p < 0.0001). The concentration of platelets was slightly lower in the bottom layer of PRP than the middle layer (p = 0.02). Centrifugation braking increased the leukocyte concentration in the top (p = 0.03) and middle layers of PRP (p = 0.001). Centrifugation rate had no effect on the cellular composition of PRP (p = 0.1–0.6).

Conclusions: Because layer of plasma affected both platelet and leukocyte concentrations in PRP, the most important modification for the current single spin, double syringe, plasma based PRP preparation protocols is to exclude the bottom 1/3 layer of PRP.

High Intensity Interval Exercise Increases Platelet and Transforming Growth Factor-β Yield in Platelet-Rich Plasma

BACKGROUND

Platelet-rich plasma (PRP) is an emerging orthobiologic treatment for musculoskeletal conditions like osteoarthritis. Two studies have demonstrated the influence of longer duration exercise on PRP composition, but no study has ever explored the impact of high intensity interval exercise (HIIE) on PRP content.

OBJECTIVE

To quantify cellular and growth factor content changes in PRP after 4 minutes of HIIE.

DESIGN

Controlled laboratory pilot study.

SETTING

Academic sports medicine center.

PARTICIPANTS

Ten healthy volunteers (5 male, 5 female).

INTERVENTION

Volunteers had PRP prepared from 15 mL of whole blood using a single spin, plasma-based system (autologous conditioned plasma [ACP]) immediately before and after 4 minutes of HIIE on a stationary exercise bike (Tabata protocol).

MAIN OUTCOME MEASURE

The PRP was sent for complete blood counts and enzyme-linked immunosorbent assay (ELISA) to quantify transforming growth factor (TGF)-β, platelet-derived growth factor (PDGF), insulin-like growth factor (IGF)-1, and vascular endothelial growth factor (VEGF).

RESULTS

Mean platelet count in PRP increased from 367.4 ± 57.5 k/μL to 497.7 ± 93.3 k/μL after 4 minutes of HIIE (P < .001). TGF-β also increased from 8237.2 ± 7676.5 pg/mL to 21 535.7 ± 4062.6 pg/mL postexercise (P = .004). The other cellular components (leukocytes, red blood cells, and mean platelet volume) and growth factors (PDGF, IGF-1, and VEGF) were not significantly changed.

CONCLUSIONS

A short 4-minute bout of HIIE significantly increased the total platelet count and TGF-β concentration in PRP.

Comparison of Leukocyte-Rich Platelet-Rich Plasma and Leukocyte-Poor Platelet-Rich Plasma on Achilles Tendinopathy at an Early Stage in a Rabbit Model

BACKGROUND

Tendinopathy is still a great challenge in clinical practice, and the role of platelet-rich plasma (PRP) is controversial. The influence of leukocytes on tendinopathy at an early stage has not been defined so far.

PURPOSE

To compare the effects of leukocyte-rich PRP (Lr-PRP) and leukocyte-poor PRP (Lp-PRP) on Achilles tendinopathy when applied at an early stage.

STUDY DESIGN

Controlled laboratory study.

METHODS

A rabbit Achilles tendinopathy model was induced by a collagenase injection. A week later, treatments were applied randomly on local Achilles tendon lesions: (1) 200 μL of Lr-PRP (16 legs), (2) 200 μL of Lp-PRP (16 legs), and (3) 200 μL of saline (16 legs). At 3 and 6 weeks after the collagenase injection, outcomes were evaluated by histology, magnetic resonance imaging (MRI), real-time polymerase chain reaction analysis, immunohistochemistry, and transmission electron microscopy (TEM).

RESULTS

The Lr-PRP group had a lower T2 signal intensity (P = .0377) and smaller diameter (P = .0193) and cross-sectional area (P = .0194) than the Lp-PRP group on MRI. Histologically, the Lr-PRP group had better scores than the Lp-PRP group (P = .0284 and P = .0188, respectively). Compared with the Lp-PRP group, higher gene expression and more protein synthesis of collagen I (P = .0160 and P = .0309, respectively) and CD163 (P < .0001 and P = .0411, respectively) were found in the Lr-PRP group. Considering TEM and biomechanical testing, the Lr-PRP group demonstrated more mature collagen fibers (P < .0001), a larger fiber diameter (P = .0005), a higher failure load (P = .00417), and higher tensile stress (P < .0001) than the Lp-PRP group.

CONCLUSION

Lr-PRP had more beneficial effects than Lp-PRP when delivered at an early stage during tendon repair.

CLINICAL RELEVANCE

Here, we showed that tendinopathy influenced the curative effects of PRP in vivo. An early-stage application of Lr-PRP had more benefits for the repair of tendinopathy than Lp-PRP in a rabbit model, which will supplement guidelines of PRP treatment on tendinopathy clinically.

Platelet-Rich Plasma Versus Surgery for the Management of Recalcitrant Greater Trochanteric Pain Syndrome: A Systematic Review

PURPOSE

To perform a systematic review of the outcomes of platelet-rich plasma (PRP) injections as an in-office procedure versus surgical treatment for recalcitrant greater trochanteric pain syndrome (GTPS).

METHODS

The MEDLINE and Embase databases were searched in June 2019 following the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement. Clinical studies on patients with recalcitrant GTPS treated with PRP or surgery were included. Demographic characteristics, patient-reported outcomes (PROs), and complications were compared. A qualitative analysis using the Methodological Index for Non-randomized Studies and Cochrane Risk of Bias Tool scores was performed.

RESULTS

A total of 5 PRP and 5 surgery studies met the inclusion criteria, contributing 94 and 185 patients, respectively. The mean follow-up time was shorter for the PRP studies (range, 2-26 months) than with surgery (range, 12-70 months). The mean Methodological Index for Non-randomized Studies scores for the PRP and surgery groups were 11.25 and 11.4, respectively, and the only randomized trial had a low risk of bias. Two studies in the PRP group (n = 56) reported improvements in the modified Harris Hip Score at final follow-up (from 53.8 to 82.6 and from 56.7 to 74.2). The other PRP studies reported improvements using other measures. In the surgery group, 2 studies reported improvements in the Harris Hip Score (from 53.0 to 80 and from 53.3 to 88) whereas 3 used unique PROs (Oxford score, from 20.4 to 37.3; modified Harris Hip Score, from 54.9 to 76.2; and Merle d'Aubigné and Postel score, from 10.9 to 16.7). Although significant improvement was reported in all studies included, PRP showed a large effect size whereas surgery showed a moderate to large effect size. No major complications were associated with PRP treatment; however, the surgery group reported a higher rate of complications including recurrent external snapping hip, retears resulting from falls, trochanteric fracture, venous thrombosis, and wound-related problems.

CONCLUSIONS

Both PRP and surgical intervention for the treatment of recalcitrant GTPS showed statistically and clinically significant improvements based on PROs. Although not covered by most medical insurance companies, PRP injections for recalcitrant GTPS provides an effective and safe alternative after failed physical therapy. If surgery is indicated, endoscopy is safer than the open technique.

LEVEL OF EVIDENCE

Level IV, systematic review of Level I to IV studies.

Effect of platelet-rich plasma on the degenerative rotator cuff tendinopathy according to the compositions

Background

There are controversies about platelet-rich plasma (PRP) as an established treatment option for rotator cuff (RC) tendinopathy. The purpose of the study was to find the relation of cellular component with clinical efficacy in RC tendinopathy and to find the composition of PRP in treating RC tendinopathy.

Methods

A total 30 patients were recruited and divided into PRP and control groups. In the PRP group, 2 ml of PRP solution was injected to the hypoechoic lesion of degenerative supraspinatus via 22-gauge syringe with peppering technique. Patients in the control group were taught rotator cuff strengthening exercises. American Shoulder and Elbow Surgeons (ASES), Constant-Murley score, and numeric rating scale (NRS) were measured before, 6 weeks after, 12 weeks after, and 24 weeks after the procedure. PRP compositions were analyzed using the 1 ml of PRP solution.

Results

Linear regression analysis showed no significant difference of ASES and Constant-Murley scores between the groups at 6 weeks (P = 0.582 and 0.258) and at 12 weeks (P = 0.969 and 0.795) but showed a significant difference at 24 weeks (P = 0.050 and 0.048). Independent t test showed significant group difference of NRS at 6 weeks (P = 0.031) but not at 12 and 24 weeks (P = 0.147 and 0.935). 5.19 pg/ml in IL-1β and 61.79 μg/ml in TGF-β1 were acquired as cutoff values to predict meaningful improvement. The PRP subgroup above IL-1β or TGF-β1 cutoff value showed significant differences in all clinical outcomes compared with the exercise group while the PRP subgroup below the cutoff value showed no significant differences in linear regression analysis.

Conclusions

Our study can help to find the optimal PRP condition and to enhance the effect of PRP on RC tendinopathy.

Trial registration

All the patients were registered in our Institutional Ethics Committee (approval number 2014-05-009).

Platelet-rich plasma can release nutrient factors to promote facial nerve crush injury recovery in rats

To evaluate the effects of platelet-rich plasma (PRP) on promoting neural repair after facial nerve compression in rats and the mechanism by which this occurs.  Methods: Adult Wistar rats (n=100) were divided into 3 groups: healthy controls, surgery-only, and surgery+PRP groups. The rats underwent nerve crush injury to establish a facial palsy model. The blood from the rats was used to prepare the PRP for application to the injury site. The evaluation methods included vibrissae movement, eyelid closure, and electrophysiology. Electron microscopy, immunohistochemistry, and real-time polymerase chain reaction (PCR) were used to detect nutrient factor expression in the brain and nerve sections. This study was conducted in Shandong Provincial ENT Hospital Affiliated to Shandong University,  Shandong, China between January and November 2018.  Results: Platelet-rich plasma promotes the recovery of vibrissae movement, eyelid closure, and electrophysiological function in a rat model of nerve crush injury. Hematoxylin and eosin staining, toluidine blue staining, and electron microscopy showed significant recovery of Schwann cells and axons in the PRP group. Polymerase chain reaction results showed that PRP releases growth factors, which include nerve growth factor and brain-derived neurotrophic factor. Immunohistochemistry also demonstrated higher levels of S-100 protein expression in the PRP group compared to the other groups.  Conclusions: Platelet-rich plasma releases nutrient factors in the brainstem, and the use of PRP can promote injury recovery.

Prospective Clinical Research of the Efficacy of Platelet-rich Plasma in the Outpatient-based Treatment of Rotator Cuff Tendinopathy

Background

The purpose of this study is to compare the clinical outcomes of the control group and platelet-rich plasma (PRP) group among the patients who failed to respond to conservative treatment as outpatient-based therapy for rotator cuff tendinopathy, and to compare the clinical results of leukocyte-poor (LP) PRP and leukocyte-rich (LR) PRP.

Methods

Inclusion criteria are (1) over 18-year-old, (2) patients with rotator cuff tendinopathy, no rotator cuff tear by radiologic diagnosis (ultrasonography or magnetic resonance imaging) within the last 3 months, and (3) not effective to conservative treatment for more than 1 month. Of the final 60 subjects, 33 patients in the exercise treatment group and 27 patients in the PRP injection group (LP-PRP, 13; LR-PRP, 14) were included. Clinical evaluation was carried out by assessing the outcomes of treatment using the Numeric Rating Scale pain score, the American Shoulder and Elbow Society (ASES) score, and the Constant score at baseline and at 3 and 6 months after the procedure.

Results

There was a statistically significant difference in ΔASES_3months (ASES_3months-ASES_first) score between the control and PRP groups (p=0.006). However, there was no statistical significance between LP-PRP and LR-PRP groups (p>0.05).

Conclusions

This study showed that PRP injection was more effective than exercise therapy for the first 3 months. However, there was no difference between the LP-PRP group and the LR-PRP group. Regardless of the type of PRP, clinical application of PRP injection in patients with rotator cuff tendinopathy seems to be effective in early treatment.

Impact of Platelet-Rich Plasma Use on Pain in Orthopaedic Surgery: A Systematic Review and Meta-analysis

CONTEXT

Amid extensive debate, evidence surrounding the use of platelet-rich plasma (PRP) for musculoskeletal injuries has rapidly proliferated, and an overall assessment of efficacy of PRP across orthopaedic indications is required.

OBJECTIVES

(1) Does PRP improve patient-reported pain in musculoskeletal conditions? and (2) Do PRP characteristics influence its treatment effect?

DATA SOURCES

MEDLINE, EMBASE, Cochrane, CINAHL, SPORTDiscus, and Web of Science libraries were searched through February 8, 2017. Additional studies were identified from reviews, trial registries, and recent conferences.

STUDY SELECTION

All English-language randomized trials comparing platelet-rich therapy with a control in patients 18 years or older with musculoskeletal bone, cartilage, or soft tissue injuries treated either conservatively or surgically were included. Substudies of previously reported trials or abstracts and conference proceedings that lacked sufficient information to generate estimates of effect for the primary outcome were excluded.

STUDY DESIGN

Systematic review and meta-analysis.

LEVEL OF EVIDENCE

Level 1.

DATA EXTRACTION

All data were reviewed and extracted independently by 3 reviewers. Agreement was high between reviewers with regard to included studies.

RESULTS

A total of 78 randomized controlled trials (5308 patients) were included. A standardized mean difference (SMD) of 0.5 was established as the minimum for a clinically significant reduction in pain. A reduction in pain was associated with PRP at 3 months (SMD, -0.34; 95% CI, -0.48 to -0.20) and sustained until 1 year (SMD, -0.60; 95% CI, -0.81 to -0.39). Low- to moderate-quality evidence supports a reduction in pain for lateral epicondylitis (SMD, -0.69; 95% CI, -1.15 to -0.23) and knee osteoarthritis (SMD, -0.91; 95% CI, -1.41 to -0.41) at 1 year. PRP characteristics did not influence results.

CONCLUSION

PRP leads to a reduction in pain; however, evidence for clinically significant efficacy is limited. Available evidence supports the use of PRP in the management of lateral epicondylitis as well as knee osteoarthritis.

[Effectiveness and mechanism of pure platelet-rich plasma on osteochondral injury of talus]

Objective

To explore the effectiveness and mechanism of pure platelet-rich plasma (P-PRP) on osteochondral injury of talus.

Methods

Thirty-six patients with osteochondral injury of talus selected between January 2014 and October 2017 according to criteria were randomly divided into control group (group A), leukocyte PRP (L-PRP) group (group B), and P-PRP group (group C), with 12 cases in each group. There was no significant difference in gender, age, disease duration, and Hepple classification among the three groups ( P>0.05). Patients in the groups B and C were injected with 2.5 mL L-PRP or P-PRP at the bone graft site, respectively. Patients in the group A were not injected with any drugs. The American Orthopaedic Foot and Ankle Society (AOFAS) score and visual analogue scale (VAS) score were used to evaluate the effectiveness before operation and at 3, 6, and 12 months after operation. Study on the therapeutic mechanism of P-PRP: MC3T3-E1 cells were randomly divided into control group (group A), L-PRP group (group B), and P-PRP group (group C). Groups B and C were cultured with culture medium containing 5% L-PRP or P-PRP respectively. Group A was cultured with PBS of the same content. MTT assay was used to detect cell proliferation; ELISA was used to detect the content of matrix metalloprotein 9 (MMP-9) protein in supernatant; alkaline phosphatase (ALP) activity was measured; and real-time fluorescence quantitative PCR (qRT-PCR) was used to detect the expression of osteopontin (OPN), collagen type Ⅰ, and MMP-9 in cells. Western blot was used to detect the expression of MMP-9 in supernatant and phosphoinositide 3-kinase (PI3K), phosphorylated protein kinase B (pAKT), and phosphorylated c-Jun (p-c-Jun) in cells.

Results

All patients were followed up 13-25 months, with an average of 18 months. No complication such as wound infection and internal fixation failure occurred. MRI showed that the degree of injury was similar between the three groups before operation, and patients in the three groups all recovered at 6 months after operation. Moreover, group C was superior to groups A and B. Compared with preoperation, AOFAS scores and VAS scores in the three groups were all significantly improved at each time point after operation ( P<0.05). AOFAS score of group C was significantly higher than that of groups A and B at 3, 6, and 12 months after operation ( P<0.05); there was no significant difference in VAS score between the three groups ( P>0.05). Study on the therapeutic mechanism of P-PRP: The absorbance ( A) value, ALP activity, the relative mRNA expression of OPN and collagen type Ⅰ in group C were significantly higher than those in groups A and B ( P<0.05), and those in group B were significantly higher than those in group A ( P<0.05). The relative expression of MMP-9 protein and mRNA and the content of MMP-9 protein detected by ELISA in group B were significantly higher than those in groups A and C, while those in group C were significantly lower than those in group A ( P<0.05). Western blot detection showed that the relative expression of PI3K, pAKT, and p-c-Jun protein in group B was significantly higher than those in groups A and C ( P<0.05), but there was no significant difference between groups A and C ( P>0.05).

Conclusion

P-PRP is superior to L-PRP for osteochondral injury of talus, which may be related to the inhibition of PI3K/AKT/AP-1 signaling pathway in the osteoblast, thereby reducing the secretion of MMP-9.

Cellular Components and Growth Factor Content of Platelet-Rich Plasma With a Customizable Commercial System

BACKGROUND

Platelet-rich plasma (PRP) is an autologous orthobiologic treatment option for musculoskeletal conditions with favorable results in a limited number of high-quality clinical trials. Because different blood-processing methods result in PRP with varying cellular and growth factor content, it is critical that clinicians understand the content of the specific PRP being used in clinical practice. One adjustable system, the Angel System, has few independent laboratory reports on the specific composition of its PRP. The goal of this study was to quantify the cellular and growth factor composition of PRP produced by this system at its lowest hematocrit settings.

HYPOTHESIS

The authors hypothesized that the system would significantly concentrate platelets over baseline and, at the lowest hematocrit settings, would reduce leukocytes to produce leukocyte-poor PRP.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Ten healthy male volunteers donated 150 mL of whole blood for processing. Three separate processing cycles were performed for each sample at the 0%, 1%, and 2% hematocrit settings. The resultant PRP from each cycle was sent for complete blood counts and enzyme-linked immunosorbent assay to quantify the following growth factors: platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), insulin-like growth factor-1 (IGF-1), and vascular endothelial growth factor (VEGF).

RESULTS

The system consistently concentrated platelets 5-fold over baseline, with no significant differences among settings. Leukocytes were concentrated at all settings, between 2 and 5 times over baseline. The 0% and 1% settings had significantly lower leukocyte concentrations than the 2% setting. Lymphocytes made up >89% of the leukocyte differential, while neutrophils represented <11% of the differential at each setting. There was a significant increase in PDGF and bFGF, a significant decrease in IGF-1, and no change in VEGF, with no difference among settings.

CONCLUSION

The system consistently concentrated platelets 5 times but was unable to reduce leukocytes, therefore resulting in leukocyte-rich PRP at each setting tested. Leukocytes had a differential composition of >89% lymphocytes and <11% neutrophils. For all settings, PDGF and bFGF were concentrated; IGF-1 was reduced; and VEGF was not significantly different from baseline.

CLINICAL RELEVANCE

These data can serve to guide clinicians considering using this particular PRP system. It consistently yielded leukocyte-rich PRP with a lymphocyte-predominant/neutrophil-reduced profile. Further research is needed to better understand how to apply this specific PRP in clinical practice.

Concentrations of Blood Components in Commercial Platelet-Rich Plasma Separation Systems: A Review of the Literature

BACKGROUND

Platelet-rich plasma (PRP) has proven to be a very safe therapeutic option in the treatment of tendon, muscle, bone, and cartilage injuries. Currently, several commercial separation systems are available for the preparation of PRP. The concentrations of blood components in PRP among these separation systems vary substantially.

PURPOSE

To systematically review and evaluate the differences between the concentrations of blood components in PRP produced by various PRP separation systems.

STUDY DESIGN

Systematic review.

METHODS

MEDLINE/PubMed, the Cochrane Central Register of Controlled Trials (CENTRAL), and EMBASE were searched for studies that compared the concentrations of blood components and growth factors in PRP between various separation systems and studies that reported on the concentrations of blood components and growth factors of single separation systems. The primary outcomes were platelet count, leukocyte count, and concentration of growth factors (eg, platelet-derived growth factor-AB [PDGF-AB], transforming growth factor-β1 [TGF-β1], and vascular endothelial growth factor [VEGF]). Furthermore, the preparation protocols and prices of the systems were compared.

RESULTS

There were 1079 studies found, of which 19 studies were selected for inclusion in this review. The concentrations of platelets and leukocytes in PRP differed largely between, and to a lesser extent within, the studied PRP separation systems. Additionally, large differences both between and within the studied PRP separation systems were found for all the growth factors. Furthermore, preparation protocols and prices varied widely between systems.

CONCLUSION

There is a large heterogeneity between PRP separation systems regarding concentrations of platelets, leukocytes, and growth factors in PRP. The choice for the most appropriate type of PRP should be based on the specific clinical field of application. As the ideal concentrations of blood components and growth factors for the specific fields of application are yet to be determined for most of the fields, future research should focus on which type of PRP is most suitable for the specific field.

Variables affecting the potential efficacy of PRP in providing chronic pain relief

Although chronic pain affects about 1% of the US population, it remains largely resistant to treatment. Despite great variability in pain outcomes, the application of autologous platelet-rich plasma (PRP) has become increasingly popular in attempts to reduce chronic pain. The variability in PRP efficacy raises the question of whether PRP actually has an analgesic capacity, and if so, can that capacity be made consistent and maximized. The best explanation for the variability in PRP analgesic efficacy is the failure during PRP preparation and application to take into account variables that can increase or eliminate its analgesic capabilities. This suggests that if the variables are reduced and controlled, a PRP preparation and application protocol can be developed leading to PRP inducing reliable, complete, and long-term pain relief. The goal of this study was to examine some of the variables that influence platelets and see how they might be controlled to increase the analgesic potential of PRP. Among the variables examined are the physiological status of the patient, methods used to prepare PRP, and methods of PRP application. The goal of modifying these variables is to minimize platelet serotonin content, maximize platelet content of factors that reduce inflammation and pain, while maintaining their bioactivity, maximize platelet capacity to aggregate at injury sites, induce rapid and simultaneous release of their contents, and optimize PRP application protocols. It is concluded that controlling some or many of these variables will lead to PRP that induces reliable, maximum, and long-term relief of chronic pain.

Allogenic Pure Platelet-Rich Plasma Therapy for Rotator Cuff Disease: A Bench and Bed Study

BACKGROUND

Although platelet-rich plasma (PRP) is a popular option for rotator cuff disease, the underlying mechanism of PRP and its clinical indications are unclear. Further, some kinds of PRP might be detrimental to patients. Allogenic PRP prepared through a standardized process and fully characterized could eliminate variations in PRP as well as uncertainties regarding its use in each patient, which could provide clues about its mechanism of action and indications for its use.

PURPOSE

To assess the effects of pure PRP on tenocytes with or without inflammation in an in vitro study and to evaluate the safety and efficacy of a fully characterized pure PRP injection in patients with rotator cuff disease in a clinical study.

STUDY DESIGN

Controlled laboratory study and cohort study; Level of evidence, 3.

METHODS

For the in vitro study, tenocytes were enzymatically isolated and cultured from patients with rotator cuff tear and treated with or without interleukin 1β (IL-1β) and PRP. Gene expression and protein synthesis of pro- and anti-inflammatory cytokines, enzymes and their inhibitors, matrix synthesis, and cell viability were evaluated. For the clinical study, a total of 17 patients with rotator cuff disease received ultrasonography-guided subacromial PRP injection and were followed for 6 months. Pain, range of motion, muscle strength, shoulder function, and overall satisfaction in patients were compared with the results in a propensity score-matched control group who received corticosteroid (triamcinolone acetonide 40 mg).

RESULTS

PRP induced inflammation in the absence of inflammation and ameliorated inflammation in IL-1β-induced tendinopathic conditions by regulation of cytokines such as IL-1β, cyclooxygenase 2, microsomal prostaglandin E synthase 1, vasoactive intestinal peptide, and downstream matrix metalloproteinases. No general or local adverse events were noted with regard to allogenic PRP injection. Whereas steroid injection showed earlier improvement in some kinds of pain and functional scores, PRP generally showed comparable effects with steroid injection in all clinical outcomes at 6 months.

CONCLUSION

This study showed that allogenic pure PRP had pleiotropic effects on tenocytes depending on inflammation and that it did not cause adverse events but rather decreased pain and improved shoulder function to a degree comparable with steroid injection in patients with rotator cuff disease.

CLINICAL RELEVANCE

Allogenic PRP could be a treatment option for rotator cuff disease.

Differing efficacies of autologous platelet-rich plasma treatment in reducing pain following rotator-cuff injury in a single patient

Rotator-cuff tears (RCTs) are typically associated with chronic pain. The most common treatment for reducing pain is the injection of cortisone into the injury site. An alternative and increasingly used technique is the injection of autologous platelet-rich plasma (PRP). A limitation of cortisone is its pain relief is short-lived, while PRP has the limitation of providing pain relief to only about 50% of patients, making its efficacy questioned, although when it is effective, its efficacy is longer than cortisone. Little is known about what accounts for these limitations. This paper presents results from a patient with RCTs causing excruciating pain who received an injection of PRP into that shoulder resulting in complete pain elimination that was ongoing at 2 years and 2 months. When 7-month severe posttrauma pain associated with the RCT developed in the contralateral shoulder, PRP prepared the same way and injected by the same person who performed the first injection provided no pain relief. However, a subsequent single cortisone injection resulted in complete pain elimination, which was ongoing at >15 months. These observations indicate that PRP can have inconsistent effects in reducing pain, not only between patients but also within the same patient. Further, although the pain relief induced by cortisone is normally not long-lasting, when given following a PRP injection, it can induce complete pain relief lasting >15 months. This paper discusses possible reasons for the variability in PRP efficacy on pain relief and addresses the possibility that when administered together, PRP and cortisone may act in a complementary manner, leading to significantly greater and longer-lasting pain relief.

Platelet-rich plasma in the foot and ankle

PURPOSE OF REVIEW

Platelet-rich plasma has become an increasingly popular treatment option within the orthopedic community to biologically enhance and stimulate difficult-to-heal musculoskeletal tissues. This review evaluates the recent literature on platelet-rich plasma use in the treatment of foot and ankle pathologies.

RECENT FINDINGS

Recent literature has demonstrated platelet-rich plasma to have a possible benefit in the treatment of Achilles pathology, chronic plantar fasciitis, osteochondral lesions of the talus, ankle osteoarthritis, and diabetic foot ulcers. However, given the lack of standardization of platelet-rich plasma preparations and protocols and the predominance of low-quality studies, no definitive treatment indications exist. Platelet-rich plasma is a promising treatment option, but at present, there is only limited clinical evidence supporting its use in foot and ankle applications.

The effects of aging, diabetes mellitus, and antiplatelet drugs on growth factors and anti-aging proteins in platelet-rich plasma

As the aged population continues to markedly increase worldwide, the incidences of diabetes mellitus (DM) and cardiovascular disease (CVD) are increasing. In this study, we investigated the effects of aging, DM, and antiplatelet drugs on growth factors and anti-aging proteins in platelet-rich plasma (PRP). The study participants were classified into the following four groups: Group A, healthy individuals aged ≤45 years; Group B, healthy individuals aged >45 years; Group C, DM patients aged >45 years; and Group D, CVD patients aged >45 years taking antiplatelet drugs. The concentrations of epidermal growth factor (EGF), fibroblast growth factor (FGF)-2, platelet-derived growth factor (PDGF)-AA, PDGF-AB/BB, vascular endothelial growth factor (VEGF)-A, tissue inhibitor of metalloproteinase 2 (TIMP2), insulin-like growth factor 1 (IGF-1), growth differentiation factor (GDF)11, and clusterin in PRP samples were determined to analyze the effects of aging, DM, and antiplatelet drugs. Overall, the concentrations of IGF-1, TIMP2, and clusterin did not vary significantly between the four groups. The concentrations of PDGF-AB/BB (P = 0.010), VEGF-A (P = 0.000), and GDF11 (P = 0.026) were significantly different between Group A and Group B. Further, the concentrations of EGF (P = 0.000) and GDF11 (P = 0.000) were significantly different between Groups B and C. The concentrations of EGF (P = 0.001), VEGF-A (P = 0.000), and GDF11 (P = 0.002) significantly differed between Groups A and C. The concentrations of FGF-2 (P = 0.048), PDGF-AA (P = 0.03), and GDF11 (P = 0.001) were significantly different between Groups B and D. The concentrations of PDGF-AB/BB (P = 0.032), VEGF-A (P = 0.010), and GDF11 (P = 0.02) significantly differed between Groups A and D. We found that PRP contains high concentrations of the growth factors, TIMP2 and GDF11. Aging, DM, and antiplatelet drugs can decrease the concentration of some growth factors and GDF11, which weakens the regenerative capacity and anti-aging effects of PRP and reduces the quality of PRP.

Current trends in tendinopathy: consensus of the ESSKA basic science committee. Part II: treatment options

The treatment of painful chronic tendinopathy is challenging. Multiple non-invasive and tendon-invasive methods are used. When traditional non-invasive treatments fail, the injections of platelet-rich plasma autologous blood or cortisone have become increasingly favored. However, there is little scientific evidence from human studies supporting injection treatment. As the last resort, intra- or peritendinous open or endoscopic surgery are employed even though these also show varying results. This ESSKA basic science committee current concepts review follows the first part on the biology, biomechanics and anatomy of tendinopathies, to provide a comprehensive overview of the latest treatment options for tendinopathy as reported in the literature.

Pooled Platelet-Rich Plasma Lysate Therapy Increases Synoviocyte Proliferation and Hyaluronic Acid Production While Protecting Chondrocytes From Synoviocyte-Derived Inflammatory Mediators

Platelet-rich plasma (PRP) preparations are being used with moderate success to treat osteoarthritis (OA) in humans and in veterinary species. Such preparations are hindered, however, by being autologous in nature and subject to tremendous patient and processing variability. For this reason, there has been increasing interest in the use of platelet lysate preparations instead of traditional PRP. Platelet lysate preparations are acellular, thereby reducing concerns over immunogenicity, and contain high concentrations of growth factors and cytokines. In addition, platelet lysate preparations can be stored frozen for readily available use. The purpose of this study was to evaluate the effects of a pooled allogeneic platelet-rich plasma lysate (PRP-L) preparation on equine synoviocytes and chondrocytes challenged with inflammatory mediators in-vitro to mimic the OA joint environment. Our hypothesis was that PRP-L treatment of inflamed synoviocytes would protect chondrocytes challenged with synoviocyte conditioned media by reducing synoviocyte pro-inflammatory cytokine production while increasing synoviocyte anti-inflammatory cytokine production. Synoviocytes were stimulated with either interleukin-1β (IL-1β) or lipopolysaccharide (LPS) for 24 h followed by no treatment or treatment with platelet-poor plasma lysate (PPP-L) or PRP-L for 48 h. Synoviocyte growth was evaluated at the end of the treatment period and synoviocyte conditioned media was assessed for concentrations of hyaluronic acid (HA), IL-1β, tumor necrosis factor alpha (TNF-α), and interleukin-6 (IL-6). Chondrocytes were then challenged for 48 h with synoviocyte conditioned media from each stimulation and treatment group and examined for gene expression of collagen types I (COL1A1), II (COL2A1), and III (COL3A1), aggrecan (ACAN), lubricin (PRG4), and matrix metallopeptidase 3 (MMP-3) and 13 (MMP-13). Treatment of inflamed synoviocytes with PRP-L resulted in increased synoviocyte growth and increased synoviocyte HA and IL-6 production. Challenge of chondrocytes with conditioned media from PRP-L treated synoviocytes resulted in increased collagen type II and aggrecan gene expression as well as decreased MMP-13 gene expression. The results of this study support continued investigation into the use of pooled PRP-L for the treatment of osteoarthritis and warrant further in-vitro studies to discern the mechanisms of action of PRP-L.

Characteristics of tendon derived stem cells according to different factors to induce the tendinopathy

Tendon derived stem cells (TDSCs) have been used as a therapeutic agent and as a healing marker. However, there has been no study about the characteristics of TDSCs extracted from tendinopathic tendon tissues. The aim of this study was to find the different characteristics of TDSCs according to the factors to induce the tendinopathy. Five- and fifteen-week old Sprague Dawley rats were used for this study and chemically-induced and injury-induced tendinopathy models were made depending on the age of the animal for different types of tendinopathy. TDSCs from chemically-induced tendinopathy showed markedly low proliferation compared to those from age-matched normal control and injury-induced tendinopathy. In addition, TDSCs from chemically-induced tendinopathy progressed to osteogenesis under an osteogenic differentiation environment more than those from other groups. In contrast, TDSCs from injury-induced tendinopathy showed markedly high proliferation and high expression of type III collagen and α-SMA compared to other groups. Adipogenic potentials in TDSCs from injury-induced tendinopathy were also higher. These different characteristics might be helpful in the development new therapeutic agents for tendon regeneration according to different factors to induce the tendinopathy.

Current advances in the treatment of medial and lateral epicondylitis

Despite advances elucidating the causes of lateral and medial epicondylitis, the standard of care remains conservative management with NSAIDs, physical therapy, bracing, and rest. Scar tissue formation provoked by conservative management creates a tendon lacking the biomechanical properties and mechanical strength of normal tendon. The following review analyzes novel therapies to regenerate tendon and regain function in patients with epicondylitis. These treatments include PRP injection, BMAC, collagen-producing cell injection, and stem cell treatments. While these treatments are in early stages of investigation, they may warrant further consideration based on prospects of pain alleviation, function enhancement, and improved healing.

The use of platelet-rich plasma to treat chronic tendinopathies: A technical analysis

Platelet-rich plasma (PRP) is blood plasma with a high concentration of autologous platelets which constitute an immense reservoir of growth factors. The clinical use of PRP is widespread in various medical applications. Although highly popular with athletes, the use of PRP for the treatment of tendinopathies remains scientifically controversial, particularly due to the diversity of products that go by the name of "PRP." To optimize its use, it is important to look at the various stages of obtaining PRP. In this literature review, we take a closer look at eight parameters which may influence the quality of PRP: 1) anticoagulants used to preserve the best platelet function, 2) the speed of centrifugation used to extract the platelets, 3) the platelet concentrations obtained, 4) the impact of the concentration of red and while blood cells on PRP actions, 5) platelet activators encouraging platelet degranulation and, hence, the release of growth factors, and 6) the use or nonuse of local anesthetics when carrying out infiltration. In addition to these parameters, it may be interesting to analyze other variables such as 7) the use of ultrasound guidance during the injection with a view to determining the influence they have on potential recovery.

Biologic Approaches to Problems of the Hand and Wrist

Orthobiologics are not used as frequently in the hand and wrist as in other sites. The most frequently reported is the use of bone morphogenetic protein for the treatment of Kienböck disease. Animal studies have described improved tendon healing with the use of platelet-rich plasma (PRP), but no clinical studies have confirmed these results. PRP has been reported to produce improvements in the outcomes of distal radial fractures and osteoarthritis of the trapeziometacarpal in small numbers of patients. The use of orthobiologics in the hand and wrist are promising, but clinical trials are necessary to establish efficacy and safety.

Intratendon Delivery of Leukocyte-Poor Platelet-Rich Plasma Improves Healing Compared With Leukocyte-Rich Platelet-Rich Plasma in a Rabbit Achilles Tendinopathy Model

BACKGROUND

Chronic tendinopathy is a commonly occurring clinical problem that affects both athletes and inactive middle-aged patients. Although some studies have shown that different platelet-rich plasma (PRP) preparations could exert various therapeutic effects in vitro, the role of leukocytes in PRP has not yet been defined under tendinopathy conditions in vivo.

PURPOSE

This study compared the effects of the intratendon delivery of leukocyte-poor PRP (Lp-PRP) versus leukocyte-rich PRP (Lr-PRP) in a rabbit chronic tendinopathy model in vivo.

STUDY DESIGN

Controlled laboratory study.

METHODS

Four weeks after a local injection of collagenase in the Achilles tendon, the following treatments were randomly administered on the lesions: injections of (1) 200 μL of Lp-PRP (n = 8), (2) 200 μL of Lr-PRP (n = 8), or (3) 200 μL of saline (n = 8). Healing outcomes were assessed at 4 weeks after therapy with magnetic resonance imaging (MRI), cytokine quantification, real-time polymerase chain reaction analysis of gene expression, histology, and transmission electron microscopy (TEM).

RESULTS

MRI revealed that the Lr-PRP and saline groups displayed higher signal intensities compared with the Lp-PRP group with T2 mapping. Histologically, the Lp-PRP group displayed significantly better general scores compared with the Lr-PRP ( P = .001) and saline ( P < .001) groups. Additionally, TEM showed that the Lp-PRP group had larger collagen fibril diameters than the Lr-PRP group ( P < .001). Enzyme-linked immunosorbent assay showed a significantly lower level of catabolic cytokine IL-6 in the Lp-PRP group compared with the Lr-PRP ( P = .001) and saline ( P = .021) groups. The Lp-PRP group displayed significantly increased expression of collagen I compared with the saline group ( P = .004) but not the Lr-PRP group. Both the Lp-PRP and Lr-PRP groups exhibited significantly lower matrix metalloproteinase (MMP)-1 and MMP-3 expression levels compared with the saline group. However, only the Lp-PRP group displayed significantly higher expression of TIMP-1 than the saline group ( P = .024).

CONCLUSION

Compared with Lr-PRP, Lp-PRP improves tendon healing and is a preferable option for the clinical treatment of tendinopathy.

CLINICAL RELEVANCE

PRP is widely used in the clinical management of chronic tendinopathy. However, the clinical results are ambiguous. It is imperative to understand the influence of leukocytes on PRP-mediated tissue healing in vivo, which could facilitate the better clinical management of chronic tendinopathy. Further studies are needed to translate our findings to the clinical setting.

Effects of Platelet-Rich Plasma on Tissue Expansion in Rabbits

BACKGROUND

Tissue expansion has been widely applied in clinic practice. However, the expanded skin is always insufficient for clinical use and how to promote tissue expansion is still a challenge. Platelet-rich plasma (PRP) contains multiple tissue growth factors and has been widely utilized in hard- and soft-tissue augmentation. However, its feasibility to promote tissue expansion has not been explored. The purpose of this study was to evaluate the possible effect of PRP in tissue expansion.

METHODS

Tissue expanders were implanted in the dorsal sides of rabbit ears, and the left and right side were for the PRP group and the control group randomly. The PRP group was injected with 1.0 mL of autologous PRP in the expansion skin and the control group with the same volume of saline solution. The expanders were inflated regularly by injecting saline solution under the same pressure. After the inflation phase, the expansion skin was harvested and the inflation volume, gross specimen, and histological characteristics were assayed and evaluated.

RESULTS

The mean inflation volume of the PRP group was significantly higher than that of the control (p < 0.05). H&E staining of expanded skin sections showed more epidermal cell layers and thicker skin in the PRP group than that in the control group. There were significantly more capillaries in the expanded skin in the PRP group than those from the control group by IHC staining with its marker anti-CD31. A higher level of mRNA expression of VEGF was observed in the PRP group by real-time PCR.

CONCLUSIONS

The present study suggests that PRP plays a pivotal role in tissue expansion and skin proliferation.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors. www.springer.com/00266 .