Activation of platelet-rich plasma using soluble type I collagen

Safety Window for Effective Lesion Crossing in Patients With Chronic Thromboembolic Pulmonary Hypertension

Background

Balloon pulmonary angioplasty for chronic thromboembolic pulmonary hypertension (CTEPH) is limited by a lack of safe and effective tools for crossing these lesions. We aim to identify a safety window for an intraluminal crossing device in this vascular bed by studying the piercing properties of pulmonary arterial vessel walls and intraluminal CTEPH lesion specimens. As a secondary objective, we also describe the histopathologic features of CTEPH lesions.

Methods

Specimens were procured from 9 patients undergoing pulmonary endarterectomy. The specimens were subsampled and identified grossly as arterial wall or intraluminal CTEPH lesions. The force needed for tissue penetration was measured using a 0.38-mm (0.015-in) diameter probe in an ex vivo experimental model developed in our lab. Concurrent histology was also performed.

Results

The mean force needed to penetrate the arterial wall and intraluminal CTEPH lesions was 1.75 ± 0.10 N (n = 121) and 0.30 ± 0.04 N (n = 56), respectively (P < .001). Histology confirmed the presence of intimal hyperplasia with calcium and hemosiderin deposition in the arterial wall as well as an old, organized thrombus in the lumen.

Conclusions

The pulmonary arterial wall is friable and prone to perforation during instrumentation with workhorse coronary guide wires. However, the results of this study demonstrate that a much lower force is needed for the 0.38-mm (0.015-in) probe to penetrate an intraluminal CTEPH lesion compared to pulmonary arterial intima. This finding suggests the existence of a safety window for lesion-crossing devices, enabling effective balloon pulmonary angioplasty.

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-PRP and LR-PRP were 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-PRP nor LR-PRP was 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.

Advances with Platelet-Rich Plasma for Bone Healing

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

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.

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

Background

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

Methods

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

Results

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

Conclusion

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

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

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

Efficacy of Single Injection of Platelet-Rich Plasma in Shoulder Impingement Syndrome

Introduction

To analyze the change in Visual Analog Scale (VAS), QuickDASH score, and the range of motion at the shoulder joint following a single injection of platelet-rich plasma (PRP) in shoulder impingement syndrome.

Methods

Twenty patients (21 shoulders) of either sex above the age of 18 years with a clinical diagnosis of shoulder impingement having a positive shoulder impingement test (positive Hawkins-Kennedy impingement test and/or positive Neer's impingement sign), ultrasonographic confirmation of shoulder impingement, and a failure to respond to standard non-operative methods for a minimum period of four weeks were included in this prospective interventional study. PRP was injected at the proposed site. At three months after the injection, the changes in the VAS, QuickDASH score, and the range of motion at the shoulder joint were analyzed.

Results

There were significant changes in the VAS, QuickDASH score, and range of motion at the shoulder joint following a single injection of PRP.

Conclusions

Platelet-rich plasma (PRP) injection results in a significant decrease in pain and improvement in the range of motion and an overall excellent functional outcome in shoulder impingement syndrome. However, future studies with a bigger sample size and longer follow-up are needed.

Platelet-Rich Plasma as an Orthobiologic: Clinically Relevant Considerations

Platelet-rich plasma (PRP) is an autologous blood-derived product processed to concentrate platelets and the associated growth factors. PRP has been shown to be relatively well-tolerated and safe to use for a number of conditions in humans, equines, and canines. There are multiple commercial systems that have been validated for canine use. These systems use a variety of methodologies to produce a PRP product. However, PRP products have been shown to differ greatly between systems. Further study is needed to fully elucidate optimal component concentrations for various indications.

Effects of submucosally administered platelet-rich plasma on the rate of tooth movement

OBJECTIVES

To evaluate the effects of submucosally administered platelet-rich plasma (PRP) on the rate of maxillary canine retraction. Levels of soluble receptor activator of nuclear factor-κb ligand (sRANKL) and osteoprotegerin (OPG) in the gingival crevicular fluid (GCF) were also measured over 2 months.

MATERIALS AND METHODS

This split-mouth trial involved 20 sites in 10 subjects randomly assigned to PRP (experimental) side and control side. After alignment, the freshly prepared PRP was injected submucosally distal to the experimental side maxillary canine, and retraction was performed using NiTi closed-coil springs (150 g) on 0.019 × 0.025-inch stainless steel wire. The rate of canine movement was assessed using digital model superimposition at 0, 30, and 60 days. The OPG and sRANKL were assayed using enzyme-linked immunosorbent assay from GCF collected at 0, 1, 7, 21, 30, and 60 days.

RESULTS

Twenty sites were analyzed using paired t test. The rate of tooth movement increased significantly by 35% on the PRP side compared with the control side in the first month (P = .0001) and by 14% at the end of the second month (P = .015). Using the Mann-Whitney U test, OPG levels were found to be significantly decreased on the 7th (P = .003) and 30th day on the PRP side (P = .01), while sRANKL became detectable by the third week postinjection on the PRP side (P = .069).

CONCLUSIONS

Submucosal injection of platelet-rich plasma significantly increased tooth movement during the 60-day observation period. Local injection of PRP significantly altered the levels of OPG and sRANKL in GCF.

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

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

New design to remove leukocytes from platelet-rich plasma (PRP) based on cell dimension rather than density

Platelet-rich plasma (PRP) can stimulate the proliferation of stem cells and have a positive effect on tissue repair. Although many commercialized PRP preparation kits are already on the market, first-line clinical workers are still not satisfied with most of the PRP kits. The work of commercial PRP kits is based on the density of blood elements. However, the blood elements are very close in density which makes the separation challenging. Therefore, the mentioned commercialized kits are generally contaminated by leucocytes and erythrocyte. In this study, a home-designed PRP device was developed to use a separation membrane with adequate cut-off pore size of 5 μm, 3 μm and 2 μm for the groups of H5M, H3M, and H2M, respectively, to be placed in the middle of the centrifuge tube. The home-designed H2M showed a very promising results regardless of the final volume (1.82 ± 0.09 ml), platelet yield (8.39 ± 0.44%), Red Blood Cells (0%), White Blood Cells (0%), and Relative Concentration of Platelet Increment value (225.09%). Further, it showed a good result in cell viability and cytotoxicity and confirmed a good multilineage potentials. The concentration in PRP prepared by group H2M was relatively stable and far above average. All the fibrin fibers were linked together as bridging strands or strings and turned into an inter-connected porous structure for nutrients transportation and regenerative cell migration. We believe that the home-designed group H2M should have a great potential to develop into the final product to meet the requirements of first-line clinical workers.

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The home-designed PRP device is a novel and effective method to remove leukocytes based on cell dimension.

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All the PRP products from the home-designed PRP devices have shown good the cell viability, and the multilineage potentials

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The H2M design could provide the stability of PRP compared to other groups and far above average.

Biological efficacy of perpendicular type-I collagen protruded from TiO2-nanotubes

The aim of this study was to evaluate the biological efficacy of a unique perpendicular protrusion of type-I collagen (Col-I) from TiO2 nanotubes (NT-EPF surface). We hypothesized that the NT-EPF surface would play bifunctional roles in stimulating platelet-mediated fibroblast recruitment and anchoring fibroblast-derived Col-I to form a perpendicular collagen assembly, mimicking the connective tissue attachment around natural teeth for the long-term maintenance of dental implants. Ti surface modification was accomplished in two steps. First, TiO2 nanotubes (NT) array was fabricated via anodization. Diameters and depths of NTs were controlled by applied voltage and duration. Subsequently, an electrophoretic fusion (EPF) method was applied to fuse Col-I into nanotube arrays in a perpendicular fashion. Surface wettability was assessed by contact angle measurement. The bioactivity of modified TiO2 surfaces was evaluated in terms of NIH3T3 fibroblast attachment, platelet activation, and collagen extension. Early attachment, aggregation, and activation of platelets as well as release of platelet-related growth factors were demonstrated on NT-EPF surfaces. Platelet-mediated NIH3T3 cells migration toward NT-EPF was significantly increased and the attached cells showed a typical fibrous morphology with elongated spindle shape. A direct linkage between pseudopod-like processes of fibroblasts to NT-EPF surfaces was observed. Furthermore, the engineered EPF collagen protrusion linked with cell-derived collagen in a perpendicular fashion. Within the limitation of this in vitro study, the TiO2 nanotube with perpendicular Col-I surface (NT-EPF) promoted better cell attachment, induced a strong platelet activation which suggested the ability to create a more robust soft tissue seal.

Parylene-C coated microporous PDMS structure protecting from functional deconditioning of platelets exposed to cardiostimulants

Most elderly patients after orthopedic and dental implant surgeries are exposed to cardiostimulants to reduce potential blood pressure-related risks of cardiovascular diseases. Such treatments lead to deconditioning of platelet function, which is an important factor in wound healing treatments. We introduced an innovative parylene-C coated microporous PDMS structure that can prevent the functional deconditioning of platelets caused by certain cardiostimulants. At different concentrations of cardiostimulants (IPR; isoprenaline and DA; dopamine), pre-activation, activation, and post-activation of platelets were intensively examined under mechanical and chemical stimulation mimicking the physiological environment on four different surfaces (glass, flat parylene-C coated glass (F-PPXC), microporous PDMS structure (P-PDMS), and parylene-C-coated microporous PDMS structure (S-PPXC)). The 3D microporous structure with parylene-C (S-PPXC) surface could attenuate the deconditioning of platelet function caused by IPR. Moreover, the S-PPXC surface further enhanced the DA-dependent stimulation of platelet function. The reason for this is that the 3D microporous structure with parylene-C S-PPXC induced stable and fast adhesion of platelets through increased surface roughness and softness, resulting in a significant enhancement of platelet activity. Therefore, we propose the use of functional S-PPXC surfaces as a novel strategy in the development of biomedical products.

Functionalising Collagen-Based Scaffolds With Platelet-Rich Plasma for Enhanced Skin Wound Healing Potential

Porous collagen-glycosaminoglycan (collagen-GAG) scaffolds have shown promising clinical results for wound healing; however, these scaffolds do not replace the dermal and epidermal layer simultaneously and rely on local endogenous signaling to direct healing. Functionalizing collagen-GAG scaffolds with signaling factors, and/or additional matrix molecules, could help overcome these challenges. An ideal candidate for this is platelet-rich plasma (PRP) as it is a natural reservoir of growth factors, can be activated to form a fibrin gel, and is available intraoperatively. We tested the factors released from PRP (PRPr) and found that at specific concentrations, PRPr enhanced cell proliferation and migration and induced angiogenesis to a greater extent than fetal bovine serum (FBS) controls. This motivated us to develop a strategy to successfully incorporate PRP homogeneously within the pores of the collagen-GAG scaffolds. The composite scaffold released key growth factors for wound healing (FGF, TGFβ) and vascularization (VEGF, PDGF) for up to 14 days. In addition, the composite scaffold had enhanced mechanical properties (when compared to PRP gel alone), while providing a continuous upper surface of extracellular matrix (ECM) for keratinocyte seeding. The levels of the factors released from the composite scaffold were sufficient to sustain proliferation of key cells involved in wound healing, including human endothelial cells, mesenchymal stromal cells, fibroblasts, and keratinocytes; even in the absence of FBS supplementation. In functional in vitro and in vivo vascularization assays, our composite scaffold demonstrated increased angiogenic and vascularization potential, which is known to lead to enhanced wound healing. Upon pro-inflammatory induction, macrophages released lower levels of the pro-inflammatory marker MIP-1α when treated with PRPr; and released higher levels of the anti-inflammatory marker IL1-ra upon both pro- and anti-inflammatory induction when treated with the composite scaffold. Finally, our composite scaffold supported a co-culture system of human fibroblasts and keratinocytes that resulted in an epidermal-like layer, with keratinocytes constrained to the surface of the scaffold; by contrast, keratinocytes were observed infiltrating the PRP-free scaffold. This novel composite scaffold has the potential for rapid translation to the clinic by isolating PRP from a patient intraoperatively and combining it with regulatory approved scaffolds to enhance wound repair.

Autologous activated platelet-rich plasma injection into adult human ovary tissue: molecular mechanism, analysis, and discussion of reproductive response

In clinical infertility practice, one intractable problem is low (or absent) ovarian reserve which in turn reflects the natural oocyte depletion associated with advancing maternal age. The number of available eggs has been generally thought to be finite and strictly limited, an entrenched and largely unchallenged tenet dating back more than 50 years. In the past decade, it has been suggested that renewable ovarian germline stem cells (GSCs) exist in adults, and that such cells may be utilized as an oocyte source for women seeking to extend fertility. Currently, the issue of whether mammalian females possess such a population of renewable GSCs remains unsettled. The topic is complex and even agreement on a definitive approach to verify the process of 'ovarian rescue' or 're-potentiation' has been elusive. Similarities have been noted between wound healing and ovarian tissue repair following capsule rupture at ovulation. In addition, molecular signaling events which might be necessary to reverse the effects of reproductive ageing seem congruent with changes occurring in tissue injury responses elsewhere. Recently, clinical experience with such a technique based on autologous activated platelet-rich plasma (PRP) treatment of the adult human ovary has been reported. This review summarizes the present state of understanding of the interaction of platelet-derived growth factors with adult ovarian tissue, and the outcome of human reproductive potential following PRP treatment.

First clinical experience with a new injectable recombinant human collagen scaffold combined with autologous platelet-rich plasma for the treatment of lateral epicondylar tendinopathy (tennis elbow)

BACKGROUND

Lateral epicondylitis is a tendinopathy of the common extensor origin at the elbow. When traditional conservative treatment fails, more effective therapies are needed. Vergenix Soft Tissue Repair (STR) Matrix (CollPlant Ltd., Ness-Ziona, Israel) is an injectable gel composed of cross-linked bioengineered recombinant human type I collagen combined with autologous platelet-rich plasma (STR/PRP). The complex forms a collagen-fibrin matrix that promotes cell migration and tissue repair. Based on positive outcomes from preclinical trials, this study is the first clinical trial of STR/PRP on tendinopathy. We hypothesized that STR/PRP would be a safe and effective treatment for lateral epicondylar tendinopathy.

METHODS

Patients with chronic lateral epicondylitis underwent treatment with STR/PRP. Outcome assessment included grip strength, functional disability, and changes in sonographic tendon appearance for up to 6 months after treatment.

RESULTS

The study enrolled 40 patients. No systemic or local severe adverse events were reported. Clinical evaluation revealed an improvement in the mean Patient-Rated Tennis Elbow Evaluation score from 64.8 before treatment and showed a 59% reduction at 6 months. The 12-Item Short-Form Health Survey questionnaire showed improvement from a mean score of 30.7 to 37.7 at the final follow-up. Grip strength increased from 28.8 kg at baseline to 36.8 kg at 6 months. Improvements in sonographic tendon appearance were evident among 68% of patients.

CONCLUSION

STR/PRP is a safe treatment that effectively induces clinically significant improvements in elbow symptoms and general well-being as well as objective measures of strength and imaging of the common extensor tendon within 6 months of treatment of elbow tendinopathy recalcitrant to standard treatments.

Cartilage Regeneration in Humans with Adipose Tissue-Derived Stem Cells and Adipose Stromal Vascular Fraction Cells: Updated Status

Adipose tissue-derived stem cells (ASCs) in the form of stromal vascular fraction (SVF) and cultured expansion have been applied in clinical settings in some countries to treat osteoarthritis (OA) of knees, one of the most common debilitating, incurable disorders. Since the first report of successful cartilage-like tissue regeneration with autologous adipose SVF containing ASCs, there has been a gradual increase in the number of publications confirming such results. Thus far, most of the reports have been limited to treatments of OA of knees. Recently, successful applications of adipose SVF in treating OA of ankles and hips have been reported. In addition, several groups have reported modified methods of applying adipose SVF, such as combining bone marrow stimulation with adipose SVF or adding additional extracellular matrix (ECM) in treating OA. Here, we present an updated, systematic review of clinical effectiveness and safety in treating OA of knees, ankles, and one hip since 2016 using ASCs in the form of adipose SVF or in cultured expansion, along with a description and suggestion of potential biological mechanisms of cartilage regeneration.

Blood derivatives awaken in regenerative medicine strategies to modulate wound healing

Blood components play key roles in the modulation of the wound healing process and, together with the provisional fibrin matrix ability to selectively bind bioactive molecules and control its spatial-temporal presentation, define the complex microenvironment that characterize this biological process. As a biomimetic approach, the use of blood derivatives in regenerative strategies has awakened as a source of multiple therapeutic biomolecules. Nevertheless, and despite their clinical relevance, blood derivatives have been showing inconsistent therapeutic results due to several factors, including proper control over their delivery mechanisms. Herein, we highlight recent trends on the use biomaterials to protect, sequester and deliver these pools of biomolecules in tissue engineering and regenerative medicine approaches. Particular emphasis is given to strategies that enable to control their spatiotemporal delivery and improve the selectivity of presentation profiles of the biomolecules derived from blood derivatives rich in platelets. Finally, we discussed possible directions for biomaterials design to potentiate the aimed regenerative effects of blood derivatives and achieve efficient therapies.

Development of a co-culture device for the study of human tenocytes in response to the combined stimulation of electric field and platelet rich plasma (PRP)

One of the objectives of rotator cuff repairs is to achieve biological healing and recovery in the tendon-bone zone. Some clinical evaluations reported the feasibility of tendon healing based on the stimulations of electric field and platelet-rich plasma (PRP). However, because of lack of appropriate tool for in vitro primary culture under complicated conditions, the efficacy and standard protocol of these healing approaches are still controversial among clinical experts. In this study, a novel co-culture device was developed for the study of tenocytes proliferation under single and combined stimulations of electric field and PRP. The device was a culture well divided into three sub-chambers separated by a barrier and embedded with a pair of parallel plate electrodes. Tenocytes and PRP gel could be respectively loaded into the sub-chambers and cultured with interlinked medium. Hence, tenocytes could concurrently receive a uniform electric field and platelet-derived growth factors by diffusion. Results revealed that the proliferation of tenocytes could be significantly enhanced by these stimulations. The device provides a precise and practical approach for the in vitro study of tendon healing, especially for PRP study. Moreover, optimization of the conditions of electric field and PRP could be determined by in vitro screening procedure before surgery to provide a personalized therapy.

Use of a Cyclooxygenase-2 Inhibitor Does Not Inhibit Platelet Activation or Growth Factor Release From Platelet-Rich Plasma

BACKGROUND

It remains unestablished whether use of cyclooxygenase (COX)-2 inhibitors impairs platelet activation and anabolic growth factor release from platelets in platelet-rich plasma (PRP).

PURPOSE

The purpose of this study was to assess the effects of a COX-2 inhibitor on platelet activation and anabolic growth factor release from canine PRP when using a clinically applicable PRP activator and to determine whether a 3-day washout would be sufficient to abrogate any COX-2 inhibitor-related impairment on platelet function.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten healthy dogs underwent blood collection and PRP preparation. Dogs were then administered a COX-2 inhibitor for 7 days, after which PRP preparation was repeated. The COX-2 inhibitor was continued for 4 more days and PRP preparation performed a third time, 3 days after discontinuation of the COX-2 inhibitor. Immediately after PRP preparation, the PRP was divided into 4 aliquots: 2 unactivated and 2 activated using human γ-thrombin (HGT). One activated and 1 unactivated sample were assessed using flow cytometry for platelet expression of CD62P and platelet-bound fibrinogen using the canine activated platelet-1 (CAP1) antibody. The 2 remaining samples were centrifuged and the supernatant assayed for transforming growth factor-β1 (TGF-β1), platelet-derived growth factor-BB (PDGF-BB), and thromboxane B2 (TXB2) concentrations. Differences in platelet activation and TGF-β1, PDGF-BB, and TXB2 concentrations over the 3 study weeks were evaluated using a 1-way repeated-measures ANOVA, and comparisons between activated and unactivated samples within a study week were assessed with paired t tests.

RESULTS

There were no statistically significant ( P > .05) effects of the COX-2 inhibitor on percentage of platelets positive for CD62P or CAP1 or on concentrations of TGF-β1, PDGF-BB, or TXB2. All unactivated samples had low levels of activation or growth factor concentrations and significantly ( P < .05) greater activation and growth factor concentrations in HGT-activated samples.

CONCLUSION

This COX-2 inhibitor did not impair platelet activation, growth factor release, or TXB2 production in this canine PRP when using HGT as an activator. Studies are warranted to determine whether COX-2 inhibitors affect platelet activation and growth factor release from human PRPs.

CLINICAL RELEVANCE

These results suggest that there is no need to withhold a COX-2 inhibitor before PRP preparation, particularly if thrombin is going to be used to activate the PRP. This is clinically relevant information because many patients who are candidates for PRP therapy for treatment of musculoskeletal injury are also using COX-2 inhibitors.

Plantar Fasciitis-A Comparison of Treatment with Intralesional Steroids versus Platelet-Rich Plasma A Randomized, Blinded Study

BACKGROUND

Many treatment options for plantar fasciitis currently exist, some with great success in pain relief. The objective of our study was to compare the use of intralesional steroids with platelet-rich plasma (PRP), using pain scales and functional evaluation, in patients with plantar fasciitis who did not respond to conservative treatment.

METHODS

A controlled, randomized, blinded clinical assay was performed. Patients were assigned to one of the two groups by selecting a sealed envelope. The steroid treatment group received 8 mg of dexamethasone plus 2 mL of lidocaine as a local anesthetic. The PRP treatment group received 3 mL of PRP activated with 0.45 mL of 10% calcium gluconate. All of the patients were evaluated at the beginning of the study, and at 2, 4, 8, 12, and 16 weeks post-treatment with the Visual Analog Scale (VAS), Foot and Ankle Disability Index (FADI), and American Orthopedic Foot and Ankle Society (AOFAS) scale.

RESULTS

The right foot was the most frequently affected foot (63%). The average age of the patients was 44.8 years (range, 24-61 years). All scales used (VAS, FADI and AOFAS) showed that the difference was not statistically significant between the two groups.

CONCLUSIONS

We can conclude that the use of PRP is an effective treatment method for patients with plantar fasciitis who do not respond to conservative treatment because PRP demonstrates an efficacy equal to that of steroids. However, the cost and the time for preparation the PRP are two of the disadvantages of this treatment.

Impact of Source and Manufacturing of Collagen Matrices on Fibroblast Cell Growth and Platelet Aggregation

Collagen is a main component of the extracellular matrix. It is often used in medical applications to support tissue regeneration, hemostasis, or wound healing. Due to different sources of collagen, the properties and performance of available products can vary significantly. In this in vitro study, a comparison of seven different collagen matrices derived from bovine, equine, and porcine sources was performed. As performance indicators, the scaffold function for fibroblasts and platelet aggregation were used. We found strong variation in platelet aggregation and fibroblast growth on the different collagen materials. The observed variations could not be attributed to species differences alone, but were highly dependent on differences in the manufacturing process.

Influence of Cellular Composition and Exogenous Activation on Growth Factor and Cytokine Concentrations in Canine Platelet-Rich Plasmas

OBJECTIVE

The purposes of this study were to (1) evaluate correlations among platelet, leukocyte, growth factor, and cytokine concentrations in canine platelet-rich plasmas (PRPs) produced from five different canine PRP-concentrating systems and (2) compare the effects of different activation protocols on platelet activation and growth factor release from one of these PRPs.

METHODS

PRP was made using blood from 15 dogs and each of 5 different PRP systems in a cross-over design. Complete blood counts were performed to quantify platelet and leukocyte concentrations. PRPs were activated, or not, according to manufacturer instructions, and transforming growth factor-β1 (TGF-β1), platelet-derived growth factor-BB (PDGF-BB), vascular endothelial growth factor, and tumor necrosis factor-alpha (TNF-α) were quantified. Differences among platelet, leukocyte, and growth factor concentration were compared among the different systems. Correlations between platelet and anabolic growth factor concentrations were assessed. Subsequently, PRP was made from 12 additional dogs using one of the devices. Each PRP was divided into three aliquots that were activated with calcium chloride (CaCl₂), human γ-thrombin (HGT), or not activated. Expression of CD62P and platelet-bound fibrinogen (CAP1) was quantified for each activation group. Concentrations of TGF-β1, PDGF-BB, and TNF-α were also quantified for each activation group and a fourth group that was frozen/thawed. Differences among activation groups were assessed by a Friedman test.

RESULTS

There were statistically significant differences among the PRPs made with difference devices with regard to platelet, leukocyte, TGF-β1, and PDGF-BB concentrations (p < 0.0001). There were weak to moderate correlations (R² = 0.07-0.58) between platelet and anabolic growth factor concentrations but it appeared that activation had a greater effect on growth factor concentration than did cellular composition. Intentional platelet activation significantly increased CD62P and CAP1 expression as well as TGF-β1 and PDGF-BB concentrations in the one PRP in which all activation methods were assessed. Activation with HGT resulted in the greatest platelet activation, and CaCl₂ and freeze/thaw elicited moderate increases in either growth factor release or CD62P and CAP1 expression.

CONCLUSION

There are positive correlations between platelet and anabolic growth factor concentrations in canine PRPs. However, intentional platelet activation has a greater effect on growth factor delivery than platelet concentration. Thrombin provides more robust activation than CaCl₂.

Use of platelet concentrates in oral and maxillofacial surgery: an overview

OBJECTIVE

To describe and provide a comprehensive overview on the development, use and efficacy of autologous platelet concentrates in different in vitro and in vivo studies focusing on oral and maxillofacial pathologies.

MATERIALS AND METHODS

Present work employs an extensive critical overview of the literature on the development and application of platelet concentrates.

RESULTS

Platelet concentrates are innovative endogenous therapeutic agents which gained a lot of interest in different medical and dental disciplines due to their potential ability to stimulate and increase regeneration of soft and hard tissues. The effect of platelet-derived products is considered to be a result of the high number of platelets which contain a wide range of growth factors. They are not just therapeutic products but autologous blood concentrates containing active molecules. The quality of platelet concentrates may vary according to the individual physical state of donors making it difficult to to compare the outcomes of their application. Although, there are many studies analyzing the properties of these biomaterials both in vivo and in vitro, a consensus regarding their efficacy still has to be reached.

CONCLUSION

Evidences described in the literature on the efficacy of platelet concentrates in procedures in oral and maxillofacial region are controversial and limited. In order to clarify the real advantages and priorities for the patients, when the blood-derived products are applied, further in vitro and in vivo research about the activity of PRP and PRF on the dental cells biology should be conducted.

Platelet-Rich Plasma: The Choice of Activation Method Affects the Release of Bioactive Molecules

Platelet-Rich Plasma (PRP) is a low-cost procedure to deliver high concentrations of autologous growth factors (GFs). Platelet activation is a crucial step that might influence the availability of bioactive molecules and therefore tissue healing. Activation of PRP from ten voluntary healthy males was performed by adding 10% of CaCl₂, 10% of autologous thrombin, 10% of a mixture of CaCl₂ + thrombin, and 10% of collagen type I. Blood derivatives were incubated for 15 and 30 minutes and 1, 2, and 24 hours and samples were evaluated for the release of VEGF, TGF-β1, PDGF-AB, IL-1β, and TNF-α. PRP activated with CaCl₂, thrombin, and CaCl₂/thrombin formed clots detected from the 15-minute evaluation, whereas in collagen-type-I-activated samples no clot formation was noticed. Collagen type I produced an overall lower GF release. Thrombin, CaCl₂/thrombin, and collagen type I activated PRPs showed an immediate release of PDGF and TGF-β₁ that remained stable over time, whereas VEGF showed an increasing trend from 15 minutes up to 24 hours. CaCl₂ induced a progressive release of GFs from 15 minutes and increasing up to 24 hours. The method chosen to activate PRP influences both its physical form and the releasate in terms of GF amount and release kinetic.

Characteristics of Reconstituted Lyophilized Tendon Hydrogel: An Injectable Scaffold for Tendon Regeneration

BACKGROUND

The authors have developed a tendon hydrogel that may be injected into the site of tendon injury to improve speed and strength of repair. The aim of this study was to compare the biological and physical properties of fresh, hydrated tendon hydrogel with its reconstituted lyophilized counterpart with the goal of increasing clinical feasibility.

MATERIALS

Hydrogel was prepared from fresh human cadaveric flexor tendon. Fresh gel was compared to gel aliquots that were lyophilized and reconstituted with sterile deionized water. Scanning electron microscopy was used to examine the microarchitecture of gelated samples. Rat adipose-derived stem cells were seeded in hydrogel, and cell viability was assessed after 7 days. MTS colorimetric assay was used to evaluate both the effect of prolonged storage on gel and the ability of reconstituted lyophilized hydrogel to activate platelet-rich plasma. The viability and proliferation of luciferase-transfected adipose-derived stem cells embedded within hydrogel in vivo was assessed by a bioluminescence in vivo imaging system.

RESULTS

Reconstituted lyophilized hydrogel demonstrated similar handling properties compared to fresh gel. Adipose-derived stem cells remained viable 7 days after reseeding in both conditions. Lyophilized hydrogel retained its ability to activate platelet-rich plasma and retained 95 percent of its maximal proliferative capacity at 30 days. The in vivo imaging system demonstrated similar cell proliferation, with signal persisting through day 13.

CONCLUSIONS

Reconstitution of lyophilized hydrogel stimulated cell proliferation and platelet-rich plasma activation to a greater degree than did fresh hydrogel. Efficacy after prolonged storage was also shown to be superior. Therefore, this lyophilized formulation of tendon hydrogel may have wider clinical applicability.

Extracellular matrix-blood composite injection reduces post-traumatic osteoarthritis after anterior cruciate ligament injury in the rat

The objective of this study was to determine if an injection of a novel extracellular matrix scaffold and blood composite (EMBC) after anterior cruciate ligament (ACL) injury would have a mitigating effect on post-traumatic osteoarthritis (PTOA) development in rat knees. Lewis rats underwent unilateral ACL transection and were divided into three groups as follows: (1) no further treatment (ACLT; n = 10); (2) an intra-articular injection of EMBC on day 0 (INJ0; n = 11); and (3) an intra-articular injection of EMBC on day 14 (INJ14; n = 11). Ten additional animals received capsulotomy only (n = 10, SHAM group). The OARSI histology scoring of the tibial cartilage and micro-CT of the tibial epiphysis were performed after 35 days. The ratio of intact/treated hind limb forces during gait was determined using a variable resistor walkway. The OARSI cartilage degradation sum score and total degeneration width were significantly greater in the ACLT group when compared to the INJ0 (p = 0.031, and p = 0.005) and INJ14 (p = 0.022 and p = 0.04) group. Weight bearing on the operated limb only decreased significantly in the ACLT group (p = 0.048). In the rat ACL transection model, early or delayed injection of EMBC ameliorated the significant decrease in weight bearing and cartilage degradation seen in knees subjected to ACL transection without injection. The results indicate that the injection of EMBC may slow the process of PTOA following ACL injury and may provide a promising treatment for PTOA. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:995-1003, 2016.

Platelets and plasma stimulate sheep rotator cuff tendon tenocytes when cultured in an extracellular matrix scaffold

The addition of platelet-rich plasma (PRP) to rotator cuff repair has not translated into improved outcomes after surgery. However, recent work stimulating ligament healing has demonstrated improved outcomes when PRP or whole blood is combined with an extracellular matrix carrier. The objective of this study was to evaluate the effect of three components of blood (plasma, platelets, and macrophages) on the in vitro activity of ovine rotator cuff cells cultured in an extracellular matrix environment. Tenocytes were obtained from six ovine infraspinatus tendons and cultured over 14 days in an extracellular matrix scaffold with the following additives: (1) plasma (PPP), (2) plasma and platelets (PAP), (3) plasma and macrophages (PPPM), (4) plasma, platelets and macrophages (PAPM), (5) phosphate buffered saline (PBS), and (6) PBS with macrophages (PBSM). Assays measuring cellular metabolism (AlamarBlue), proliferation (Quantitative DNA assay), synthesis of collagen and cytokines (SIRCOL, TNF-α and IL-10 ELISA, and MMP assay), and collagen gene expression (qPCR) were performed over the duration of the experiment, as well as histology at the conclusion. Plasma was found to stimulate cell attachment and spreading on the scaffold, as well as cellular proliferation. Platelets also stimulated cell proliferation, cellular metabolism, transition of cells to a myofibroblast phenotype, and contraction of the scaffolds. The addition of macrophages did not have any significant effect on the sheep rotator cuff cells in vitro. In vivo studies are needed to determine whether these changes in cellular function will translate into improved tendon healing.

Effect of autologous platelet-rich plasma application on cutaneous wound healing in dogs

This study was conducted to identify the effectiveness of platelet-rich plasma (PRP) and efficacy of intralesional injection as a method of application to acute cutaneous wounds in dogs. Healthy adult beagles (n = 3) were used in this study. Autologous PRP was separated from anticoagulant treated whole blood in three dogs. Cutaneous wounds were created and then treated by intralesional injection of PRP in the experimental group, while they were treated with saline in the control group on days 0, 2 and 4. The healing process was evaluated by gross examination throughout the experimental period and histologic examination on day 7, 14 and 21. In PRP treated wounds, the mean diameter was smaller and the wound closure rate was higher than in the control. Histological study revealed that PRP treated wounds showed more granulation formation and angiogenesis on day 7, and faster epithelialization, more granulation formation and collagen deposition were observed on day 14 than in control wounds. On day 21, collagen deposition and epithelialization were enhanced in PRP treated groups. Overall, PRP application showed beneficial effects in wound healing, and intralesional injection was useful for application of PRP and could be a good therapeutic option for wound management in dogs.

Advantages of pure platelet-rich plasma compared with leukocyte- and platelet-rich plasma in promoting repair of bone defects

Background

High levels of pro-inflammatory cytokines in leukocyte- and platelet-rich plasma (L-PRP) may activate the nuclear factor κB (NF-κB) pathway to counter the beneficial effect of the growth factors on bone regeneration. However, to date, no relevant studies have substantiated this.

Methods

L-PRP and pure platelet-rich plasma (P-PRP) were isolated. The in vitro effects of L-PRP and P-PRP on the proliferation, viability and migration of human bone marrow-derived mesenchymal stem cells (HBMSCs) and EaHy926, tube formation of EaHy926, and osteogenic differentiation of HBMSCs were assessed by cell counting, flow cytometry, scratch assay, tube formation assay, and real-time quantitative polymerase chain reaction (RT-PCR), western blotting and Alizarin red staining, respectively. The in vitro effects of L-PRP and P-PRP on the nuclear translocation of NF-κB p65, mRNA expression of inducible nitric oxide synthase and cyclooxygenase-2, and production of prostaglandin E2 and nitric oxid were assessed by western blotting, RT-PCR, enzyme-linked immunosorbent assay and Griess reaction, respectively. The in vivo effects of L-PRP or P-PRP preprocessed β-tricalcium phosphate (β-TCP) on the calvarial defects in rats were assessed by histological and immunofluorescence examinations.

Results

P-PRP, which had similar platelet and growth factors concentrations but significantly lower concentrations of leukocytes and pro-inflammatory cytokines compared with L-PRP, promoted the proliferation, viability and migration of HBMSCs and EaHy926, tube formation of EaHy926 and osteogenic differentiation of HBMSCs in vitro, compared with L-PRP. The implantation of P-PRP preprocessed β-TCP also yielded better histological results than the implantation of L-PRP preprocessed β-TCP in vivo. Moreover, L-PRP treatment resulted in the activation of the NF-κB pathway in HBMSCs and EaHy926 in vitro while the postoperative delivery of caffeic acid phenethyl ester, an inhibitor of NF-κB activation, enhanced the histological results of the implantation of L-PRP preprocessed β-TCP in vivo.

Conclusions

Leukocytes in L-PRP may activate the NF-κB pathway via the increased pro-inflammatory cytokines to induce the inferior effects on bone regeneration of L-PRP compared with P-PRP. Hence, P-PRP may be more suitable for bone regeneration compared with L-PRP, and the combined use of P-PRP and β-TCP represents a safe, simple, and effective alternative option for autogenous bone graft in the treatment of bone defects.

Optimization of an injectable tendon hydrogel: the effects of platelet-rich plasma and adipose-derived stem cells on tendon healing in vivo

INTRODUCTION

Acute and chronic tendon injuries would benefit from stronger and more expeditious healing. We hypothesize that supplementation of a biocompatible tendon hydrogel with platelet-rich plasma (PRP) and adipose-derived stem cells (ASCs) would augment the tendon healing process.

MATERIALS AND METHODS

Using 55 Wistar rats, a full-thickness defect was created within the midsubstance of each Achilles tendon with the addition of one of five experimental conditions: (i) saline control (50-μL), (ii) tendon hydrogel (50-μL), (iii) tendon hydrogel (45-μL)+PRP (5-μL), (iv) tendon hydrogel (45-μL)+2×10(6)-ASCs/mL in phosphate buffered saline (5-μL), and (v) tendon hydrogel (45-μL)+2×10(6)-ASCs/mL in PRP (5-μL). Hydrogel was developed from decellularized, human cadaveric tendons. Fresh rat PRP was obtained per Amable et al.'s technique, and green fluorescent protein/luciferase-positive rat ASCs were utilized. Rats were sacrificed at weeks 1, 2, 4, and 8 after injury. Real-time in vivo bioluminescence imaging of groups with ASCs was performed. Upon sacrifice, Achilles tendons underwent biomechanical and histological evaluation. Comparisons across groups were analyzed using the two-sample Z-test for proportions and the Student's t-test for independent samples. Significance was set at p<0.05.

RESULTS

(i) Bioluminescence imaging demonstrated that total photon flux was significantly increased for hydrogel+PRP+ASCs, versus hydrogel+ASCs for each postoperative day imaged (p<0.03). (ii) Mean ultimate failure load (UFL) was increased for hydrogel augmented with PRP and/or ASCs versus hydrogel alone at week 2 (p<0.03). By week 4, hydrogel alone reached a similar mean UFL to hydrogel augmented with PRP and/or ASCs (p>0.3). However, at week 8, hydrogel with PRP and ASCs demonstrated increased strength over other groups (p<0.05), except for hydrogel with PRP (p=0.25). (iii) Upon histological analysis, Hematoxylin and Eosin staining showed increased extracellular matrix formation in groups containing PRP and increased cellularity in groups containing ASCs. Groups containing both PRP and ASCs demonstrated both of these characteristics.

CONCLUSION

PRP and ASCs are easily accessible bioactive products that have potentiating effects on tendon hydrogel. Augmentation with these two factors encourages earlier mechanical strength and functional restoration. Thus, biochemically, tendon hydrogel augmented with PRP and/or ASCs, serves as a promising therapeutic modality for augmenting the tendon healing process after injury.

A call for a standard classification system for future biologic research: the rationale for new PRP nomenclature

Autologous cell therapies including platelet-rich plasma (PRP) and bone marrow concentrate (BMC) are increasingly popular options for soft tissue and joint-related diseases. Despite increased clinical application, conflicting research has been published regarding the efficacy of PRP, and few clinical publications pertaining to BMC are available. Preparations of PRP (and BMC) can vary in many areas, including platelet concentration, number of white blood cells, presence or absence of red blood cells, and activation status of the preparation. The potential effect of PRP characteristics on PRP efficacy is often not well understood by the treating clinician, and PRP characteristics, as well as the volume of PRP delivered, are unfortunately not included in the methods of many published research articles. It is essential to establish a standard reporting system for PRP that facilitates communication and the interpretation and synthesis of scientific investigations. Herein, the authors propose a new PRP classification system reflecting important PRP characteristics based on contemporary literature and recommend adoption of minimal standards for PRP reporting in scientific investigations. Widespread adoption of these recommendations will facilitate interpretation and comparison of clinical studies and promote scientifically based progress in the field of regenerative medicine.

Cartilage Regeneration in Human with Adipose Tissue-Derived Stem Cells: Current Status in Clinical Implications

Osteoarthritis (OA) is one of the most common debilitating disorders among the elderly population. At present, there is no definite cure for the underlying causes of OA. However, adipose tissue-derived stem cells (ADSCs) in the form of stromal vascular fraction (SVF) may offer an alternative at this time. ADSCs are one type of mesenchymal stem cells that have been utilized and have demonstrated an ability to regenerate cartilage. ADSCs have been shown to regenerate cartilage in a variety of animal models also. Non-culture-expanded ADSCs, in the form of SVF along with platelet rich plasma (PRP), have recently been used in humans to treat OA and other cartilage abnormalities. These ADSCs have demonstrated effectiveness without any serious side effects. However, due to regulatory issues, only ADSCs in the form of SVF are currently allowed for clinical uses in humans. Culture-expanded ADSCs, although more convenient, require clinical trials for a regulatory approval prior to uses in clinical settings. Here we present a systematic review of currently available clinical studies involving ADSCs in the form of SVF and in the culture-expanded form, with or without PRP, highlighting the clinical effectiveness and safety in treating OA.

Bionic, porous, functionalized hybrid scaffolds with vascular endothelial growth factor promote rapid wound healing in Wistar albino rats

Biomimetic collagen-poly(dialdehyde) locust bean gum based hybrid scaffolds synergistically combined with vascular endothelial growth factor were prepared to regenerate tissue formation for wound healing applications.

Comparison of the Cellular Composition and Cytokine-Release Kinetics of Various Platelet-Rich Plasma Preparations

BACKGROUND

Variations in formulations used to prepare platelet-rich plasmas (PRPs) result in differences in the cellular composition and biomolecular characteristics.

PURPOSE

To evaluate the cellular composition and the cytokine-release kinetics of PRP according to differences in the preparation protocols.

STUDY DESIGN

Controlled laboratory study.

METHODS

Five preparation procedures were performed for 14 healthy subjects, including 2 manual procedures (single-spin [SS] at 900 g for 5 minutes; double-spin [DS] at 900 g for 5 minutes and then 1500 g for 15 minutes) and 3 methods with commercial kits (Arthrex ACP, Biomet GPS, and Prodizen Prosys). After evaluation of cellular composition, each preparation was divided into 4 aliquots and incubated for 1 hour, 24 hours, 72 hours, and 7 days for the assessment of cytokine release over time. The cytokine-release kinetics were evaluated by assessing platelet-derived growth factor (PDGF), transforming growth factor (TGF), vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), interleukin-1 (IL-1), and matrix metalloproteinase-9 (MMP-9) concentrations of each aliquot with bead-based sandwich immunoassay.

RESULTS

The DS PRP had a higher concentration of platelets and leukocytes than did the SS PRP. Every PRP preparation exhibited an increase in PDGF, TGF, VEGF, and FGF release when compared with whole blood samples. The FGF and TGF release occurred quickly and decreased over time, while the PDGF and VEGF release was constant and sustained over 7 days. The PDGF and VEGF concentrations were higher in the DS PRP than in the SS PRP, whereas the TGF and FGF concentrations were higher in the SS PRP than in the DS PRP. Biomet GPS had the highest VEGF and MMP-9 concentrations but the lowest TGF concentration. Arthrex ACP had the highest FGF concentration but the lowest PDGF concentration. Prodizen Prosys had the highest IL-1 concentration and higher PDGF concentration than Arthrex ACP.

CONCLUSION

The DS method generally led to a higher concentration of platelet relative to the SS method. However, the cytokine content was not necessarily proportional to the cellular composition of the PRPs, as the greater content could be different between the SS or DS method depending on the type of cytokine.

CLINICAL RELEVANCE

Physicians should select proper PRP preparations after considering their biomolecular characteristics and patient indications.

A retrospective comparison of the management of recalcitrant lateral elbow tendinosis: platelet-rich plasma injections versus surgery

BACKGROUND

The aim of this study is to compare the outcomes of platelet-rich plasma (PRP) injections to surgical release and decortication for lateral elbow tendinosis within a similar patient population.

METHODS

A retrospective chart review was performed on two groups of patients, receiving either PRP injections (n = 28) or surgery (n = 50). Patient demographics, clinical presentation, pain score, worker's compensation status, and previous steroid injections were recorded. Primary outcomes included pain and symptom improvement, range of motion, return to work, and postoperative complications.

RESULTS

Demographics, duration of symptoms, and exam findings were similar between the PRP and surgical patients. There was no significant difference in pain and symptom improvement. Pain improvement was reported in 89.3 % of PRP patients and 84 % of surgical patients, with a reported percent reduction in pain of 61.1 and 55 %, respectively. Symptoms other than pain improved in 85.7 and 88 % of the PRP and surgical patients, respectively. Tenderness to palpation at the lateral epicondyle (64.3 % PRP, 44 % surgical), pain with resisted wrist extension (35.7 % PRP, 30 % surgical), or residual symptoms other than pain (14.3 % PRP, 10 % surgical) were not significantly different between groups at last follow-up. Eighty-two percent of patients in both the PRP and surgical groups returned to work. No complications were reported. Mean follow-up was 315 vs. 352 days for the PRP and surgical groups, respectively.

CONCLUSIONS

Similar outcomes in pain improvement and return to work may be achievable with either PRP injections or surgery in recalcitrant lateral elbow tendinosis. PRP injections may be a reasonable alternative for patients apprehensive to proceed with surgery or poor surgical candidates.

The past, present and future in scaffold-based tendon treatments

Tendon injuries represent a significant clinical burden on healthcare systems worldwide. As the human population ages and the life expectancy increases, tendon injuries will become more prevalent, especially among young individuals with long life ahead of them. Advancements in engineering, chemistry and biology have made available an array of three-dimensional scaffold-based intervention strategies, natural or synthetic in origin. Further, functionalisation strategies, based on biophysical, biochemical and biological cues, offer control over cellular functions; localisation and sustained release of therapeutics/biologics; and the ability to positively interact with the host to promote repair and regeneration. Herein, we critically discuss current therapies and emerging technologies that aim to transform tendon treatments in the years to come.

Platelet activation using electric pulse stimulation: growth factor profile and clinical implications

BACKGROUND

Autologous platelet gel therapy using platelet-rich plasma has emerged as a promising alternative for chronic wound healing, hemostasis, and wound infection control. A critical step for this therapeutic approach is platelet activation, typically performed using bovine thrombin (BT) and calcium chloride. However, exposure of humans to BT can stimulate antibody formation, potentially resulting in severe hemorrhagic or thrombotic complications. Electric pulse stimulation using nanosecond PEFs (pulse electric fields) is an alternative, nonbiochemical platelet activation method, thereby avoiding exposure to xenogeneic thrombin and associated risks.

METHODS

In this study, we identified specific requirements for a clinically relevant activator instrument by dynamically measuring current, voltage, and electric impedance for platelet-rich plasma samples. From these samples, we investigated the profile of growth factors released from human platelets with electric pulse stimulation versus BT, specifically platelet-derived growth factor, transforming growth factor β, and epidermal growth factor, using commercial enzyme-linked immunosorbent assay kits.

RESULTS

Electric pulse stimulation triggers growth factor release from platelet α-granules at the same or higher level compared with BT.

CONCLUSION

Electric pulse stimulation is a fast, inexpensive, easy-to-use platelet activation method for autologous platelet gel therapy.

The use of platelet-rich plasma for the treatment of osteoarthritis

Osteoarthritis (OA) is the most common cause of disability in the United States. With an aging population, its incidence is only likely to rise. Articular cartilage has a poor capacity to heal. The advent of regenerative medicine has heralded a new approach to early treatment of degenerative conditions such as osteoarthritis by focusing on regenerating damaged tissue rather than focusing on replacement. Platelet-rich plasma (PRP) is one such treatment that has received much recent attention and has been used particularly for tendon healing. Recent studies have focused on assessing its use on degenerative conditions such as OA. In this article, we review the evidence for the pathologic basis for the use of PRP in OA and also the clinical outcomes pertaining to its use. Finally, we also consider reasons for the inconsistent clinical success pertaining to its use.

The effect of platelet-rich plasma on muscle contusion healing in a rat model

BACKGROUND

Current therapy for muscle contusions is usually limited to nonsteroidal anti-inflammatory drugs and/or use of the RICE principle (rest, ice, compression, elevation); thus, other forms of treatment that can potentially accelerate the rate of healing are desirable.

HYPOTHESES

A local injection of platelet-rich plasma (PRP) would lead to accelerated healing rates compared with controls; also, delayed administration of PRP would lead to a blunted response compared with immediate treatment.

STUDY DESIGN

Controlled laboratory study.

METHODS

Forty-six male Lewis rats each underwent a single blunt, nonpenetrating impact to the gastrocnemius muscle via a drop-mass technique and subsequently received either a single injection of saline into the area of injury immediately after injury (controls, n = 11) or rat PRP (either immediately after injury [PRP day 0, n = 12], the first day after injury [PRP day 1, n = 12], or the third day after injury [PRP day 3, n = 11]). The primary outcome was maximal isometric torque strength of the injured muscle, which was assessed before injury as well as on postinjury days 1, 4, 7, 10, and 14. All animals were sacrificed on postinjury day 15. Histological and immunohistochemical analyses were performed on 6 specimens from each group after sacrifice.

RESULTS

The mean platelet concentration in the PRP was 2.19 × 10(6) (±2.69 × 10(5))/μL. The mean white blood cell count in the PRP was 22.54 × 10(3)/μL. Each group demonstrated statistically significant decreases in maximal isometric torque strength after injury when compared with preinjury levels, followed by significant increases back toward baseline values by postinjury day 14 (controls, 90.6% ± 7.90%; PRP day 0, 105.0% ± 7.60%; PRP day 1, 92.4% ± 7.60%; PRP day 3, 77.8% ± 7.90%) (P = .121). There were no statistically significant differences between the treatment and control groups at any of the time points. There were also no statistically significant differences between any of the groups in the percentage of centronucleated fibers (controls, 3.31% ± 5.10%; PRP day 0, 0.62% ± 1.59%; PRP day 1, 3.24% ± 5.77%; PRP day 3, 2.13% ± 3.26%) (P = .211) or the presence of inflammatory cells and macrophages.

CONCLUSION

In this rat contusion model, a local injection of PRP into the injured gastrocnemius muscle resulted in no significant differences in functional or histological outcomes, indicating no likely benefit to healing. Additionally, there was no significant difference between immediate or delayed administration of PRP.

CLINICAL RELEVANCE

Before PRP can be recommended for the treatment of muscle contusion injuries, further translational and clinical investigations need to be performed.

Treatment of tendinopathies with platelet-rich plasma

Pain and dysfunction related to tendinopathy are often refractory to traditional treatments and offer a unique challenge to physicians, because no gold standard treatment exists. Injectable biologics may represent a new modality in conjunction with a multifaceted treatment approach. Platelet-rich plasma (PRP) injections are not associated with the systemic or tendon degradation risks of corticosteroids or the inherent risks of surgery. Studies are promising but have not been replicated with high-powered evidence at the clinical level. Further evidence to expand understanding of the role of PRP in the treatment of tendinopathy is needed.

Matrix metalloproteinase content and activity in low-platelet, low-leukocyte and high-platelet, high-leukocyte platelet rich plasma (PRP) and the biologic response to PRP by human ligament fibroblasts

BACKGROUND

Recent work has shown the presence of catabolic cytokines in platelet-rich plasma (PRP), but little is known about endogenous catabolic proteases such as matrix metalloproteinases (MMPs). Hypothesis/

PURPOSE

To quantify MMP content in 2 commercially available PRP preparation systems: Arthrex Double Syringe System autologous conditioned plasma (ACP) and Biomet GPS (GPS). The hypothesis was that MMPs are actively secreted from PRP immediately after preparation.

STUDY DESIGN

Controlled laboratory study.

METHODS

PRP was prepared using either ACP (low platelet, low leukocyte) or GPS (high platelet, high leukocyte). MMP-2, MMP-3, and MMP-9 concentrations were measured using multiplex enzyme-linked immunosorbent assays for up to 6 days in 2 donors, and MMP activity was measured in 3 donors using kinetic activity kits able to detect the enzymatic cleavage of a fluorogenic peptide. Human ligament fibroblasts were cultured and exposed to both ACP and GPS from 1 donor each. MMP-2, -3, and -9 concentrations were assayed in culture media at 24 and 48 hours after exposure.

RESULTS

GPS exhibited higher total MMP-2, -3, and -9 concentrations for up to 144 hours of release, while ACP had higher platelet-normalized MMP-2 and MMP-3 concentrations. GPS had significantly higher total and endogenous MMP-2 activity (P = .004 and .014, respectively), MMP-3 activity (P = .020 and .015, respectively), and MMP-9 activity (P = .004 and .002, respectively) compared with ACP. Once normalized to platelet count, differences in MMP activity were not significant between ACP and GPS. Compared with controls, cells stimulated with interleukin-1 beta (IL-1β) and treated with ACP showed significantly higher fold changes of MMP-2 (P = .001) and MMP-3 (P = .003) concentrations at 24 hours than did cells treated with GPS. Total MMP-9 content was higher in the media of GPS-treated, IL-1β-stimulated cells compared with ACP-treated cells (P = .001). At 48 hours, IL-1β-stimulated cells treated with GPS exhibited higher fold changes of MMP-2 concentration (P = .002) compared with controls, but no difference in MMP-3 concentration was found. At 48 hours, there was a significantly higher concentration of MMP-9 in the cell culture media of ACP-treated cells compared with GPS-treated cells (P = .003).

CONCLUSION

PRP prepared as both ACP and GPS contains MMP-2, -3, and -9, which is released over a period of at least 6 days. Furthermore, a large proportion of these MMPs are in their active form, and MMP activity is dependent on platelet count within the PRP preparation. Once exposed to ligament fibroblasts, both ACP and GPS cause the fibroblasts to release MMPs, most notably 24 hours after PRP exposure, and this release is dependent on prior IL-1β stimulation.

CLINICAL RELEVANCE

The results of this study demonstrate that PRP therapy delivers ng/mL-range concentrations of catabolic proteases, which could perpetuate inflammation and inhibit tissue healing.