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

Hyaluronic acid and platelet-rich plasma for the management of knee osteoarthritis

PURPOSE

Symptomatic knee osteoarthritis (OA) remains a substantial cause of pain and disability worldwide and effective management in young patients without indications for total knee arthroplasty remains challenging. Intra-articular injections represent a viable option in the non-operative treatment of knee OA. Hyaluronic acid (HA) and platelet-rich plasma (PRP) are two commonly utilized intra-articular treatment modalities that are of particular clinical interest in the current literature. The purpose of this manuscript is to provide a concise review of the current literature on the use of HA, PRP, and HA-PRP conjugates for the treatment of symptomatic knee OA.

METHODS

A review of the literature utilizing PubMed, OVID/Medline, and Cochrane databases on basic science and clinical literature pertaining to preparation, composition, and outcomes of HA, PRP, and HA-PRP conjugates in patients with symptomatic knee OA.

RESULTS

Both HA and PRP have been shown to be efficacious for the treatment of symptomatic knee OA, with HA injections providing limited short-term improvement, while PRP may provide greater therapeutic relief, particularly with the use of leukocyte-poor (LP-PRP) formulations. Despite limited data, the combination of different formulations of HA-PRP conjugates may provide a synergistic effect, resulting in a clinically significant improvement in both pain and function.

CONCLUSION

In patients with symptomatic knee OA, intra-articular HA and PRP provide short-term improvement in pain and function, while the efficacy of HA-PRP conjugates warrants further study.

Leucocyte-Rich Platelet-Rich Plasma Enhances Fibroblast and Extracellular Matrix Activity: Implications in Wound Healing

Background: Platelet-rich plasma (PRP) is an autologous blood product that contains a high concentration of platelets and leucocytes, which are fundamental fibroblast proliferation agents. Literature has emerged that offers contradictory findings about leucocytes within PRP. Herein, we elucidated the effects of highly concentrated leucocytes and platelets on human fibroblasts. Methods: Leucocyte-rich, PRP (LR-PRP) and leucocyte-poor, platelet-poor plasma (LP-PPP) were compared to identify their effects on human fibroblasts, including cell proliferation, wound healing and extracellular matrix and adhesion molecule gene expressions. Results: The LR-PRP exhibited 1422.00 ± 317.21 × 10³ platelets/µL and 16.36 ± 2.08 × 10³ white blood cells/µL whilst the LP-PPP demonstrated lower concentrations of 55.33 ± 10.13 × 10³ platelets/µL and 0.8 ± 0.02 × 10³ white blood cells/µL. LR-PRP enhanced fibroblast cell proliferation and cell migration, and demonstrated either upregulation or down-regulation gene expression profile of the extracellular matrix and adhesion molecules. Conclusion: LR-PRP has a continuous stimulatory anabolic and ergogenic effect on human fibroblast cells.

Platelet-rich plasma for treatment of chronic proximal hamstring tendinopathy

Aim: To determine whether platelet-rich plasma (PRP) can successfully treat symptoms associated with proximal hamstring tendinopathy. Materials & methods: Charts were retrospectively reviewed of patients with a diagnosis of chronic proximal hamstring tendinopathy who underwent an ultrasound-guided leukocyte-rich PRP injection to assess reported outcomes at baseline and final follow-up post-intervention. Results: In 22 patients with a mean age of 48.7 years and mean symptom duration of 26.5 months, mean Numeric Pain Rating Scale and Victorian Institute of Sport Assessment Scale for Proximal Hamstring Tendinopathy subscores demonstrated statistically significant improvements (p < 0.05) at a mean of 7.91 months follow-up. Sixty-eight percent of patients demonstrated ≥50% reduction of pain. Conclusion: Pain and functional outcomes improved following injection of PRP.

Platelet-rich plasma and regenerative dentistry

Regenerative dentistry is an emerging field of medicine involving stem cell technology, tissue engineering and dental science. It exploits biological mechanisms to regenerate damaged oral tissues and restore their functions. Platelet‐rich plasma (PRP) is a biological product that is defined as the portion of plasma fraction of autologous blood with a platelet concentration above that of the original whole blood. A super‐mixture of key cytokines and growth factors is present in platelet granules. Thus, the application of PRP has gained unprecedented attention in regenerative medicine. The rationale underlies the utilization of PRP is that it acts as a biomaterial to deliver critical growth factors and cytokines from platelet granules to the targeted area, thus promoting regeneration in a variety of tissues. Based on enhanced understanding of cell signalling and growth factor biology, researchers have begun to use PRP treatment as a novel method to regenerate damaged tissues, including liver, bone, cartilage, tendon and dental pulp. To enable better understanding of the regenerative effects of PRP in dentistry, this review describes different methods of preparation and application of this biological product, and provides detailed explanations of the controversies and future prospects related to the use of PRP in dental regenerative medicine.

Use of Platelet-Rich Plasma in Treating Low Back Pain: A Review of the Current Literature

Low back pain (LBP) is a common problem encountered by physicians. It is a considerable cause of morbidity and socioeconomic loss and is one of the most expensive musculoskeletal disorders. Conventional treatments include bed rest, analgesics, therapeutic exercises, lumbar or caudal epidural corticosteroids, and surgery. Several new biological therapies are being investigated for use in LBP and one of these is platelet-rich plasma (PRP). In this article, we summarize the current literature published on PRP concerning its composition, classification, and application in LBP. We believe our review will prove useful to clinicians and academics alike, interested in new developing therapies for LBP.

Platelet-rich plasma-enhanced osseointegration of decellularized bone matrix in critical-size radial defects in rabbits

Background

Bone defects represent a common orthopedic condition. With its vast array of donor sources, xenogeneic bone shows considerable potential as a bone defect repair material but may also be associated with immune rejection and reduced osteogenic capacity. Thus, reducing the risks for immune rejection of xenogeneic bone, while improving its osseointegration, are key technical challenges.

Methods

Decellularized bone matrix scaffolds (DBMs) were fabricated by thorough ultrasonic vibration and subjection to chemical biological agents to remove cells and proteins. The DBMs were then mixed with platelet-rich plasma (PRP) under negative pressure. Growth factor concentrations of PRP, as well as the microstructures and biomechanical properties of the system, were examined. Furthermore, osseointegration capacities in the critical-size radial defect rabbit model were verified.

Results

Complete decellularization of the scaffold and limited reductions in mechanical strength were observed. Moreover, the obtained PRP demonstrated various growth factors. Radiographic evaluation and histological analysis verified that more new bone formation occurred in the DBM mixed with PRP group at 6 and 12 weeks after implantation compared with both the blank group and the DBM without PRP group.

Conclusions

Thorough physical and chemical treatments can reduce the probability of immune rejection of DBMs. The novel composite of DBMs mixed with PRP can serve as a promising bone regeneration material.

Platelet Concentrates in Musculoskeletal Medicine

Platelet concentrates (PCs), mostly represented by platelet-rich plasma (PRP) and platelet-rich fibrin (PRF) are autologous biological blood-derived products that may combine plasma/platelet-derived bioactive components, together with fibrin-forming protein able to create a natural three-dimensional scaffold. These types of products are safely used in clinical applications due to the autologous-derived source and the minimally invasive application procedure. In this narrative review, we focus on three main topics concerning the use of platelet concentrate for treating musculoskeletal conditions: (a) the different procedures to prepare PCs, (b) the composition of PCs that is related to the type of methodological procedure adopted and (c) the clinical application in musculoskeletal medicine, efficacy and main limits of the different studies.

Orthobiologics for the Hip Region: A Narrative Review

Management of hip region disorders is challenging. Orthobiologic treatments including platelet rich plasma (PRP), mesenchymal stem cells, and amniotic injectables have gained popularity as promising treatments despite a lack of robust evidence for their effectiveness. We review rationale and current evidence for orthobiologics for three common hip region conditions: hip osteoarthritis, gluteal tendinopathy, and proximal hamstring tendinopathy. Overall, the current state of evidence is extremely limited for orthobiologic treatments and is predominantly relevant to PRP injections. There is currently a lack of data to support the use of mesenchymal stem cells or amniotic injectables in these conditions of the hip.

Regenerative Medicine for Axial and Radicular Spine-Related Pain: A Narrative Review

INTRODUCTION

Regenerative injection-based therapy has established itself as a therapeutic option for the management of a variety of painful musculoskeletal conditions. The aim of this work was to review the current literature regarding regenerative injection therapy for axial/radicular spine pain.

METHODS

A comprehensive literature review was conducted on the use of regenerative medicine for axial/radicular spine pain. Eligible articles analyzed the therapeutic injection effects of platelet-rich plasma (PRP), prolotherapy, or mesenchymal signaling cells (MSCs) via intradiscal, facet joint, epidural, or sacroiliac joint delivery.

RESULTS

Regarding intradiscal PRP, there are level I/IV studies supporting its use. Regarding intradiscal prolotherapy, there are level III to IV studies supporting its use. Regarding intradiscal MSCs, there are level I/IV studies supporting its use with the exception of one level IV study that found no significant improvement at 12 months. Regarding facet joint injections with PRP, there are level I/IV studies supporting its use. Regarding facet joint injections with prolotherapy, there are level IV studies supporting its use, though the one level I study did not demonstrate any statistical significance supporting its use. Regarding epidural injections with PRP, there are level I/IV studies supporting its use. Regarding epidural injections with prolotherapy, there are level IV studies supporting its use, though the one level I study did not demonstrate statistical significance beyond 48 hours. Regarding sacroiliac joint injections with PRP, there are level I/IV studies supporting its use. Regarding sacroiliac joint injections with prolotherapy, there are level I/III studies supporting its use.

CONCLUSIONS

Currently, there are level I studies to support the use of PRP and MSC injections for discogenic pain; facet joint injections with PRP; epidural injections of autologous conditioned serum and epidural prolotherapy; and PRP and prolotherapy for sacroiliac joint pain. One level I study showed that facet joint prolotherapy has no significant benefit. Notably, no intervention has multiple published level I studies.

Effects of PRP and LyPRP on osteogenic differentiation of MSCs

Platelet-rich plasma (PRP) is rich in a variety of growth factors and plays an important role in the proliferation and differentiation of mesenchymal stem cells (MSCs). It has been reported that the preparation of freeze-dried platelets (lyophilized platelets [LyPRP]) from platelets could be an effective strategy to preserve the bioactivity of platelets for a long time. In this study, the osteogenic induction effects of PRP and LyPRP on MSCs were evaluated. The rabbit arterial blood was drawing to preparation of PRP by secondary centrifugation. Whole blood was prepared by lyophilization buffer to prepare LyPRP, which were activated by chloride and their surface morphology was observed. It was observed using a scanning electron microscope that platelets were evenly distributed on the surface of PRP and LyPRP. Growth factors were slowly released from PRP and LyPRP during the first 7 days and detected by the enzyme-linked immunosorbent assay kit. Cell proliferation assays and fluoresceindiacetate/propidium iodide (FDA/PI) staining demonstrated that PRP and LyPRP could promote cell proliferation. PRP and LyPRP were also shown to promote osteogenic differentiation of MSCs in vitro by osteogenesis characteristic staining and qPCR quantitative detection of osteogenic related gene expression. Both PRP and LyPRP could promote the proliferation and osteogenic differentiation of MSCs effectively. Moreover, PRP exhibited a better osteogenic induction effect on MSC than LyPRP.

Use of intraarticular injections of platelet-rich plasma in the treatment of knee osteoarthritis: A review article

Osteoarthritis is one of the most common degenerative conditions affecting knee joint. As our understanding in the disease pathogenesis is evolving, so do the treatment modalities. One of the postulated mechanisms suggests the production of inflammatory cytokines secondary to repeated micro trauma than in turn lead to cartilage damage overtime. Cartilage being avascular structure has limited potential for repair. Based on this, recent studies have been focusing on stimulating cartilage-healing process by growth factors. This is where platelet-rich plasma comes in to light. Literature is showing promising results of platelet-rich plasma in treating knee osteoarthritis. In this review we have discussed the preparation, composition, classification, uses of platelet-rich plasma as well as evidence for its efficacy and complications.

Classification systems for platelet-rich plasma

There is good scientific rationale to support the use of growth factors to promote musculoskeletal tissue regeneration. However, the clinical effectiveness of platelet-rich plasma (PRP) and other blood-derived products has yet to be proven. Characterization and reporting of PRP preparation protocols utilized in clinical trials for the treatment of musculoskeletal disease is highly inconsistent, and the majority of studies do not provide sufficient information to allow the protocols to be reproduced. Furthermore, the reporting of blood-derived products in orthopaedics is limited by the multiple PRP classification systems available, which makes comparison of results between studies challenging. Several attempts have been made to characterize and classify PRP; however, no consensus has been reached, and there is lack of a comprehensive and validated classification. In this annotation, we outline existing systems used to classify preparations of PRP, highlighting their advantages and limitations. There remains a need for standardized universal nomenclature to describe biological therapies, as well as a comprehensive and reproducible classification system for autologous blood-derived products.

Cite this article: Bone Joint J 2019;101-B:891–896.

Platelet-rich plasma affects the proliferation of canine bone marrow-derived mesenchymal stromal cells in vitro

BACKGROUND

Reported efficacy of platelet-rich plasma (PRP) in regenerative medicine is contradictory. We validated the effects of PRP on proliferation of canine bone marrow-derived multipotent mesenchymal stromal cells (K9BMMSCs) in vitro. PRP was extracted from blood of six dogs with osteoarthritis. K9BMMSCs were established from bone marrow and characterized for CD90 and CD19 expression by immunocytochemistry. Effects of PRP concentrations on viability of matching autologous K9BMMSCs were validated using MTS assay.

RESULTS

Positive CD90 and negative CD19 expression confirmed MSC origin. PRP at 40% volume/volume concentration increased, while PRP at 80 and 100% v/v concentrations suppressed viability of tested K9BMMSCs.

CONCLUSION

PRP concentration plays an important role in K9BMMSCs viability, which could affect tissue repairs in vivo.

Production and evaluation of leukocyte- and thrombocyte-rich fibrin membranes in birds

The aim of this study was the preparation and histological evaluation of Leukocyte- and Thrombocyte-Rich Fibrin (L-TRF) membranes obtained from the blood of four bird species. Forty adult healthy birds were divided into four groups of equal size: G1 - macaws, G2 - domestic chickens, G3 - parrots, G4 - toco toucans. A total of 0.5 mL of blood was collected from each bird, put into a glass tube without anticoagulant and centrifuged at 3000 rpm for 10 min. L-TRF membranes produced after compression of the clot were processed for histological analysis. The ratio of thrombocytes/area was not significantly different among Groups G2, G3 and G4, but a significant difference was found between Groups G1 and G2 with the highest thrombocyte concentration/area in G1. The groups did not differ statistically in the number of leukocytes/area. The fibrin-to-cells ratio did not vary statistically among Groups G1, G2 and G3, but this ratio was significantly higher in Group G4 than in the other groups. The thrombocyte-to-leukocyte ratio was the highest in Group G1, but it did not differ among Groups G2, G3 and G4. In conclusion, the centrifugation protocol allowed the production of L-TRF membranes in the four bird species studied. Histologically, cell ratios were analogous in domestic chickens and parrots, and macaws had the highest ratio of thrombocytes.

Assessing clinical implications and perspectives of the pathophysiological effects of erythrocytes and plasma free hemoglobin in autologous biologics for use in musculoskeletal regenerative medicine therapies. A review

Autologous biologics, defined as platelet-rich plasma (PRP) and bone marrow aspirate concentrate (BMC), are cell-based therapy treatment options in regenerative medicine practices, and have been increasingly used in orthopedics, sports medicine, and spinal disorders. These biological products are produced at point-of-care; thereby, avoiding expensive and cumbersome culturing and expansion techniques.

Numerous commercial PRP and BMC systems are available but reports and knowledge of bio-cellular formulations produced by these systems are limited. This limited information hinders evaluating clinical and research outcomes and thus making conclusions about their biological effectiveness. Some of their important cellular and protein properties have not been characterized, which is critical for understanding the mechanisms of actions involved in tissue regenerative processes. The presence and role of red blood cells (RBCs) in any biologic has not been addressed extensively. Furthermore, some of the pathophysiological effects and phenomena related to RBCs have not been studied. A lack of a complete understanding of all of the biological components and their functional consequences hampers the development of clinical standards for any biological preparation.

This paper aims to review the clinical implications and pathophysiological effects of RBCs in PRP and BMC; emphasizes hemolysis, eryptosis, and the release of macrophage inhibitory factor; and explains several effects on the microenvironment, such as inflammation, oxidative stress, vasoconstriction, and impaired cell metabolism.

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Different biological formulations optimize disease specific regenerative treatment protocols.

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Disintegrated RBC's release harmful components to regenerative therapy treatment vials.

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The effectiveness of MSC injection depends on the quality of the bone marrow aspiration procedure.

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PRP and BMC should contain minimal to no erythrocytes.

Effects of Aspirin on Growth Factor Release From Freshly Isolated Leukocyte-Rich Platelet-Rich Plasma in Healthy Men: A Prospective Fixed-Sequence Controlled Laboratory Study

BACKGROUND

The benefits of platelet-rich plasma (PRP) are believed to be in part dependent on growth factor release after platelet activation. Platelet activation is complex and involves multiple mechanisms. One important mechanism is driven by cyclooxygenase 1 (COX-1)-mediated conversion of arachidonic acid (AA) to precursor prostaglandins that then mediate proinflammatory responses that trigger growth factor release. Acetylsalicylic acid (ASA; also known as aspirin) is known to irreversibly inhibit COX-1, thereby blocking AA-mediated signaling; however, it is unclear whether ASA use alters growth factor release from freshly isolated PRP.

PURPOSE

To assess the effects of low-dose ASA use on activation of growth factor release from freshly isolated human PRP via AA and thrombin (TBN).

STUDY DESIGN

Controlled laboratory study.

METHODS

Twelve healthy men underwent blood collection and leukocyte-rich PRP (LR-PRP) preparation through a double-spin protocol to obtain baseline whole blood and PRP counts the same day. PRP was aliquoted into 3 groups: nonactivated, AA activated, and TBN activated. Immediately after activation, the concentrations of transforming growth factor β1 (TGF-β1), vascular endothelial growth factor (VEGF), and platelet-derived growth factor AB (PDGF-AB) were measured using enzyme-linked immunosorbent assays (ELISAs). The same 12 participants were then placed on an 81-mg daily dose of oral ASA for 14 days. Repeat characterization of whole blood and PRP analyses was done on day 14, followed by repeat ELISAs of growth factors under the same nonactivated and activated settings as previously stated.

RESULTS

Fourteen days of daily ASA had no effect on the number of platelets and leukocytes measured in whole blood and LR-PRP. Compared with nonactivated LR-PRP, AA- and TBN-mediated activation led to significant release of VEGF and PDGF-AB. In contrast, release of TGF-β1 from LR-PRP was observed only with activation by AA, not with TBN. Consistent with its inhibitory role in AA signaling, ASA significantly inhibited AA-mediated release of all 3 growth factors measured in this study. Although ASA had no effect on TBN-mediated release of VEGF and TGF-β1 from LR-PRP, ASA did partially block TBN-mediated release of PDGF-AB, although the mechanism remains unclear.

CONCLUSION

Daily use of low-dose ASA reduces VEGF, PDGF-AB, and TGF-β1 expression in freshly isolated human LR-PRP when activated with AA.

CLINICAL RELEVANCE

Reduction in growth factor release attributed to daily use of low-dose ASA or other COX inhibitors can be mitigated when PRP samples are activated with TBN. Clinical studies are needed to determine whether activation before PRP injection is needed in all applications where ASA is in use and to what extent ASA may inhibit growth factor release in vivo at the site of injury.

Platelet-Rich Plasma Use in Musculoskeletal Disorders: Are the Factors Important in Standardization Well Understood?

Platelet-rich plasma (PRP) is a novel therapeutic treatment option for joint and tendon disease, but preparation methods are varied. This article summarizes research on uses of PRP, compares classification systems to standardize various PRP compositions, and discusses the most common methodologies to produce PRP. Even with advances in understanding PRP, there are unknowns about the factors and processes that may have an impact on treatment efficacy for musculoskeletal conditions. PRP studies should pursue determining optimal PRP preparation, setting a standard to evaluate PRP mixtures and preparation methods, assessing efficacy of PRP for various musculoskeletal conditions, and managing and reducing costs.

Platelet-rich plasma in osteoarthritis treatment: review of current evidence

Platelet-rich plasma (PRP) is defined as a volume of plasma with a platelet concentration higher than the average in peripheral blood. Many basic, preclinical and even clinical case studies and trials report PRP’s ability to improve musculoskeletal conditions including osteoarthritis, but paradoxically, just as many conclude it has no effect. The purpose of this narrative review is to discuss the available relevant evidence that supports the clinical use of PRP in osteoarthritis, highlighting those variables we perceive as critical. Here, recent systematic reviews and meta-analyses were used to identify the latest randomized controlled trials (RCTs) testing a PRP product as an intra-articular treatment for knee osteoarthritis, compared with an intra-articular control (mostly hyaluronic acid). Conclusions in the identified RCTs are examined and compared. In total, five recent meta-analyses and systematic reviews were found meeting the above criteria. A total of 19 individual trials were identified in the five reviews but only 9 were level of evidence I RCTs, and many had moderate or high risks of bias. At present, results from these RCTs seem to favor PRP use over other intra-articular treatments to improve pain scales in the short and medium term (6–12 months), but the overall level of evidence is low. As a result, clinical effectiveness of PRP for knee osteoarthritis treatment is still under debate. This is, prominently, the result of a lack of standardization of PRP products, scarceness of high quality RCTs not showing high risks of bias, and poor patient stratification for inclusion in the RCTs.

Regenerative medicine curriculum for next-generation physicians

Regenerative sciences are poised to transform clinical practice. The quest for regenerative solutions has, however, exposed a major gap in current healthcare education. A call for evidence-based adoption has underscored the necessity to establish rigorous regenerative medicine educational programs early in training. Here, we present a patient-centric regenerative medicine curriculum embedded into medical school core learning. Launched as a dedicated portal of new knowledge, learner proficiency was instilled by means of a discovery–translation–application blueprint. Using the “from the patient to the patient” paradigm, student experience recognized unmet patient needs, evolving regenerative technologies, and ensuing patient management solutions. Targeted on the deployment of a regenerative model of care, complementary subject matter included ethics, regulatory affairs, quality control, supply chain, and biobusiness. Completion of learning objectives was monitored by online tests, group teaching, simulated clinical examinations along with longitudinal continuity across medical school training and residency. Success was documented by increased awareness and proficiency in domain-relevant content, as well as specialty identification through practice exposure, research engagement, clinical acumen, and education-driven practice advancement. Early incorporation into mainstream medical education offers a tool to train next-generation healthcare providers equipped to adopt and deliver validated regenerative medicine solutions.

Influence of Platelet-Rich and Platelet-Poor Plasma on Endogenous Mechanisms of Skeletal Muscle Repair/Regeneration

The morpho-functional recovery of injured skeletal muscle still represents an unmet need. None of the therapeutic options so far adopted have proved to be resolutive. A current scientific challenge remains the identification of effective strategies improving the endogenous skeletal muscle regenerative program. Indeed, skeletal muscle tissue possesses an intrinsic remarkable regenerative capacity in response to injury, mainly thanks to the activity of a population of resident muscle progenitors called satellite cells, largely influenced by the dynamic interplay established with different molecular and cellular components of the surrounding niche/microenvironment. Other myogenic non-satellite cells, residing within muscle or recruited via circulation may contribute to post-natal muscle regeneration. Unfortunately, in the case of extended damage the tissue repair may become aberrant, giving rise to a maladaptive fibrotic scar or adipose tissue infiltration, mainly due to dysregulated activity of different muscle interstitial cells. In this context, plasma preparations, including Platelet-Rich Plasma (PRP) and more recently Platelet-Poor Plasma (PPP), have shown advantages and promising therapeutic perspectives. This review focuses on the contribution of these blood-derived products on repair/regeneration of damaged skeletal muscle, paying particular attention to the potential cellular targets and molecular mechanisms through which these products may exert their beneficial effects.

Current concepts in intraosseous Platelet-Rich Plasma injections for knee osteoarthritis

Knee osteoarthritis (OA) is a degenerative process that slowly destroys the joints producing pain and loss of function, and diminishes the quality of life. Current treatments alleviate this symptomatology but do not stop the disease, being total knee arthroplasty the only definitive solution. Among the emerging treatments, Platelet-Rich Plasma (PRP) has shown promising results in the treatment of OA. However, to improve its effectiveness, it is necessary to approach this pathology targeting the whole joint, not only the cartilage, but including other tissues such as subchondral bone. The pathological processes that occur in the subchondral bone have influence of the cartilage loss, aggravating the disease. The combination of intraarticular infiltrations with intraosseous infiltrations regulates the biological processes of the tissues, reducing the inflammatory environment and modulating the overexpression of biomolecules that generate an aberrant cellular behavior. Although the first clinical results using this technique are promising, further research and developing adequate protocols are necessary to achieve good clinical results.

Pure platelet-rich plasma and supernatant of calcium-activated P-PRP induce different phenotypes of human macrophages

AIM

This study aimed to evaluate the effect of two platelet preparations used in the clinic, pure platelet-rich plasma (P-PRP) and the supernatant of calcium-activated P-PRP (S-PRP), on the phenotype of human macrophages.

MATERIALS & METHODS

Surface markers and cytokine production of human monocyte-derived macrophages were analyzed after 24 h stimulation with P-PRP or S-PRP.

RESULTS

P-PRP and S-PRP present no difference in the expression of CD206, a M2 tissue-repair macrophage-related marker. However, these same macrophages presented different levels of CD163, CD86 as well as different IL-10 secretion capacities after 24 h incubation.

CONCLUSION

These platelet preparations do not have an equivalent biological effect over macrophages, which suggest that they may present different clinical regenerative potentials.

Comparative effect of platelet-rich plasma, platelet-poor plasma, and fetal bovine serum on the proliferative response of periodontal ligament cell subpopulations

OBJECTIVES

Cell-based therapies involve the need to expand cell cultures ex vivo for their subsequent implantation in an autologous manner. An important limitation regarding this technology is the use of fetal bovine serum (FBS) that has critical safety limitations. Platelet-derived fractions represent an autologous source of growth factors that may be used for the expansion of these cell cultures. Periodontal ligament (PDL) cells comprise a heterogeneous cell population that may not necessarily respond in a uniform manner to proliferative stimuli. The aim of this study was to evaluate the ability of two platelet-derived fractions, platelet-rich plasma (PRP) and platelet-poor plasma (PPP) and FBS on the proliferative response of different subpopulations of PDL cell cultures.

MATERIALS AND METHODS

PDL cells were characterized and then exposed to PRP, PPP, or FBS during 2, 5, or 14 days to analyze cell proliferation and clonogenic capability. Cell proliferation was evaluated through immunofluorescence for Ki67 and by tracing carboxyfluorescein diacetate succinimidyl ester (CFSE) dye in combination with mesenchymal stem cell markers using flow cytometry.

RESULTS

Both PRP and PPP stimulated PDL cell proliferation and their clonogenic ability. We found a significant increase of CD73- and CD90-positive cells after PRP or PPP treatment, compared to FBS. Otherwise, no differences were found regarding the response of CD146-or CD105-positive cells when stimulated with PRP, PPP, or FBS.

CONCLUSION

PRP and PPP can stimulate the proliferation and clonogenicity of PDL cell populations including cells positive for CD90 and CD73 markers.

CLINICAL RELEVANCE

These findings may have implications for future therapies aiming to stimulate periodontal regeneration using autologous growth factors.

Platelet-rich plasma for androgenetic alopecia: A review of the literature and proposed treatment protocol

Androgenetic alopecia (AGA) is a common hair loss disorder caused by genetic and hormonal factors that are characterized by androgen-related progressive thinning of scalp hair in a defined pattern. By the age of 60 years, 45% of men and 35% of women develop AGA. Currently, U.S. Food and Drug Administration-approved treatments for AGA include oral finasteride and topical minoxidil. Due to the limited number of effective therapies for AGA, platelet-rich plasma (PRP) has become an effective alternative treatment. PRP is an autologous concentration of platelets in plasma with numerous growth factors that contribute to hair regeneration. The growth factors contained within the alpha granules of platelets act on stem cells in the bulge area of the hair follicles and stimulate the development of new follicles along with neovascularization. PRP has become a promising treatment modality for AGA. Although there have been several studies previously reported, a standard practice for PRP preparation and administration as well as a method to evaluate results have not been established. This literature review was conducted to evaluate the effectiveness of PRP for AGA and discuss the various treatment protocols that have been proposed.

Comparison of the Regenerative Effects of Platelet-Rich Fibrin and Plasma Rich in Growth Factors on Injured Peripheral Nerve: An Experimental Study

PURPOSE

The aim of this study was to investigate the effects of platelet-rich fibrin (PRF) and plasma rich in growth factors (PRGF) on peripheral nerve injury in the early period of healing.

MATERIAL AND METHODS

Thirty Wistar albino rats were used in this study. Rats were divided into control (C), damaged (D), PRF, and PRGF groups. The left sciatic nerves of each group were identified as group C. Crush-type injury was performed on the right sciatic nerves of the D, PRF, and PRGF groups. In the PRF and PRGF groups, blood 2 mL was obtained to prepare the PRF and PRGF and the biomaterials were applied to the injured nerve area. After 8 weeks, functional, electrophysiologic, and stereological evaluations were performed.

RESULTS

For the electrophysiologic evaluation, the latency and amplitude values in the D, PRF, and PRGF groups were significantly lower than those in the C group (P > .05). According to the sciatic functional index result, there were significant differences between groups D and PRF and between groups D and PRGF (P = .000). For the stereological evaluations, although no significant difference was observed between the PRGF and C groups (P > .05), a significant difference was observed among the D, PRF, and PRGF groups for myelinated axon number. There were significant differences between groups D and PRF and between groups D and PRGF for axon area (P = .021 and .001, respectively). No significant difference was observed among the D, PRF, and PRGF groups for myelin sheath thickness and ratio of axon area to myelin sheath thickness (P > .05).

CONCLUSIONS

The results of this study suggest that PRGF increases nerve regeneration in the early period of healing and that the limited early action of PRF should be re-evaluated in the late period.

Regenerative Sports Medicine: Past, Present, and Future (Adapted From the PASSOR Legacy Award Presentation; AAPMR; October 2016)

Regenerative medicine has shown dramatic expanse and evolution in the past decade. Within that milieu, physiatrists are taking an active role in research, clinical care delivery, and education. The purpose of this review is to provide a balance among evidence, theory, experience, clinical trends, and the foreseeable future. We focus on the literature that reports the research with the best methodology in each practice area, recognizing that the level of evidence varies substantially among different treatment modalities and conditions. The following elements are included: an overview of the evolution of currently available regenerative techniques, evidence base for each available modality (prolotherapy, platelet rich plasma, bone marrow aspirate concentrate and stem cells, adipose-derived stem cells, and amniotic tissue products), general principles in the application of these treatments, and discussion and a vision of what lies ahead. We expect that practitioners will use this review to facilitate clinical decision making and to provide a core knowledge base to assist when counseling patients. LEVEL OF EVIDENCE: IV.

Platelet-rich plasma in tendon-related disorders: results and indications

PURPOSE

Platelet-rich plasma (PRP) is currently the most exploited strategy in the clinical practice to provide a regenerative stimulus for tendon healing. The aim of the present study was to systematically review the available evidence on the treatment of the main tendon disorders where PRP is currently applied.

METHODS

A systematic review of the literature was performed on the use of PRP as a treatment for tendinopathies focusing on the following sites: Achilles tendon, patellar tendon, rotator cuff tendons, and lateral elbow tendons. The following inclusion criteria for relevant articles were used: clinical trials written in English language up to 21 June 2016 on the use of PRP in the conservative or surgical treatment of the aforementioned tendinopathies.

RESULTS

The research identified the following clinical trials dealing with the application of PRP in the selected tendons: 19 papers on patellar tendon (6 being RCTs: 4 dealing with PRP conservative application and 2 surgical), 24 papers on Achilles tendon (4 RCTs: 3 conservative and 1 surgical), 29 on lateral elbow tendons (17 RCTs, all conservative), and 32 on rotator cuff (22 RCTs: 18 surgical and 3 conservative).

CONCLUSION

Patellar tendons seem to benefit from PRP injections, whereas in the Achilles tendon, PRP application is not indicated neither as a conservative approach nor as a surgical augmentation. Lateral elbow tendinopathy showed an improvement in most of the high-level studies, but the lack of proven superiority with respect to the more simple whole-blood injections still questions its use in the clinical practice. With regard to rotator cuff pathology, the vast majority of surgical RCTs documented a lack of beneficial effects, whereas there is still inconclusive evidence concerning its conservative application in rotator cuff disorders.

LEVEL OF EVIDENCE

Systematic review of level I-IV trials, Level IV.

Nonoperative treatment of five common shoulder injuries: A critical analysis

Economic pressure highlights the critical need for appropriate diagnosis and treatment of various shoulder pathologies since under-diagnosis and under-treatment can result in increased costs to society in the form of disability and lost production. On the other hand, aggressive over-treatment can further inflate already burgeoning health-care costs and potentially harm the patient. Therefore, it is crucial to distinguish the indications between operative and nonoperative management, especially in common shoulder pathologies such as rotator cuff tears, anterior shoulder instability, biceps tendinitis, lesions to the acromioclavicular joint, and proximal humeral fractures. As a result, a detailed analysis of individual risk factors for potential failures should be performed and treatment should be based on individualized care with consideration given to each patient’s particular injury pattern, functional demands, and long-term goals.

A Systematic Review of Autologous Platelet-Rich Plasma and Fat Graft Preparation Methods

BACKGROUND

The addition of platelet-rich plasma (PRP) to adipose tissue may improve fat graft survival, although graft retention rates vary markedly between studies. To what extent this outcome heterogeneity reflects differing methodological factors remains unknown. This systematic review aims to synthesize and critically review methodological approaches to autologous PRP and fat cotransplantation in both human and animal studies.

METHODS

In accordance with PRISMA guidelines, Ovid MEDLINE, Scopus, and Cochrane Library databases were searched from inception to April 2017. Data were extracted from all in vivo studies involving autologous PRP and fat cotransplantation. A secondary aim was to assess reporting of technical detail; authors were not contacted to provide missing data.

RESULTS

From 335 articles, 23 studies were included in the qualitative synthesis. Some 21 were performed in humans and 2 in rabbits. Six studies were randomized control trials; the remainder reported on observational data. Methods of PRP extraction and activation varied markedly between studies. Fat graft preparation was comparatively more consistent. Methods of PRP and fat mixing differed significantly, especially with regards to relative volume/volume ratios.

CONCLUSIONS

Our study represents the first systematic review of methodological factors in autologous PRP and fat cotransplantation. It demonstrates that technical factors in graft preparation and administration vary significantly between in vivo studies. Such methodological heterogeneity may explain observed differences in experimental and clinical outcomes. Reporting of key procedural information is inconsistent and often inadequate. These issues make meaningful evaluation of the PRP-enhanced fat grafting literature difficult and may limit its translation into clinical practice.

Effects of three blood derived products on equine corneal cells, an in vitro study

BACKGROUND

Despite advances in therapy of corneal ulcerative diseases in horses, a vast number of cases require surgical intervention, due to poor response to treatment. Topical application of serum has been used for many years, based on its anticollagenolytic properties and the presence of growth factors promoting corneal wound healing. However, although other blood derived products i.e. platelet rich plasma (PRP), plasma rich in growth factors (PRGF) have been widely used in equine orthopaedics and in human ophthalmology, no reports of the effects of these blood derived products exist in equine ophthalmology.

OBJECTIVES

To determine in vitro effects of PRGF and PRP on equine corneal cells compared with serum.

STUDY DESIGN

Prospective controlled cohort study.

METHODS

Blood from 35 healthy horses was used to produce serum, PRGF (Endoret^® ), and PRP (E-PET™). Limbal- and stromal cells were isolated from healthy corneas of six horses and treated with 20% serum, 20% PRGF or 20% PRP. Proliferation rates and migration capacity were analysed in single cell cultures as well as co-culture systems.

RESULTS

Cell proliferation increased with PRP treatment, remained constant in PRGF treated cells, and declined upon serum treatment over a period of 48 h. Migration capacity was significantly enhanced with PRP treatment, compared with PRGF treatment. Intact leucocytes, mainly eosinophils, were only detected in PRP.

MAIN LIMITATIONS

Due to the study design use of autologous blood products on corneal cells was not possible.

CONCLUSIONS

The results demonstrate beneficial effects of PRP on proliferation as well as migration capacity of equine corneal cells in vitro. In vivo studies are warranted to determine further beneficial effects of PRP in horses with corneal ulcers.

Platelet-Rich Plasma as an Autologous and Proangiogenic Cell Delivery System

Angiogenesis is a key factor in early stages of wound healing and is crucial for the repair of vascularized tissues such as the bone. However, supporting timely revascularization of the defect site still presents a clinical challenge. Tissue engineering approaches delivering endothelial cells or prevascularized constructs may overcome this problem. In the current study, we investigated platelet-rich plasma (PRP) gels as autologous, injectable cell delivery systems for prevascularized constructs. PRP was produced from human thrombocyte concentrates. GFP-expressing human umbilical vein endothelial cells (HUVECs) and human bone marrow-derived mesenchymal stem cells (MSCs) were encapsulated in PRP gels in different proportions. The formation of cellular networks was assessed over 14 days by time-lapse microscopy, gene expression analysis, and immunohistology. PRP gels presented a favorable environment for the formation of a three-dimensional (3D) cellular network. The formation of these networks was apparent as early as 3 days after seeding. Networks increased in complexity and branching over time but were only stable in HUVEC-MSC cocultures. The high cell viability together with the 3D capillary-like networks observed at early time points suggests that PRP can be used as an autologous and proangiogenic cell delivery system for the repair of vascularized tissues such as the bone.

The combination of nano-calcium sulfate/platelet rich plasma gel scaffold with BMP2 gene-modified mesenchymal stem cells promotes bone regeneration in rat critical-sized calvarial defects

BACKGROUND

Mesenchymal stem cells (MSCs) can be differentiated into an osteoblastic lineage in the presence of growth factors (GFs). Platelet-rich plasma (PRP), which can be easily isolated from whole blood, contains a large amount of GFs, and, therefore, promotes bone growth and regeneration. The main goal of this work was to develop and investigate the effect of a new sandwich-like bone scaffold which combines a nano-calcium sulfate (nCS) disc along with PRP fibrin gel (nCS/PRP) with BMP2-modified MSCs on bone repair and regeneration in rat critical-sized calvarial defects.

METHODS

We evaluated the cytotoxicity, osteogenic differentiation and mineralization effect of PRP extract on BMP2-modified MSCs and constructed a sandwich-like nCS/PRP scaffold (mimicking the nano-calcium matrix of bone and carrying multi GFs in the PRP) containing BMP2-modified MSCs. The capacity of this multifunctional bone regeneration system in promoting bone repair was assessed in vivo in a rat critical-sized (8 mm) calvarial bone defect model.

RESULTS

We developed an optimized nCS/PRP sandwich-like scaffold. Scanning electron microscopy (SEM) results showed that nCS/PRP are polyporous with an average pore diameter of 70-80 μm and the cells can survive in the nCS/PRP scaffold. PRP extract dramatically stimulated proliferation and differentiation of BMP2-modified MSCs in vitro. Our in vivo results showed that the combination of BMP2-modified MSCs and nCS/PRP scaffold dramatically increased new bone regeneration compared with the groups without PRP and/or BMP2.

CONCLUSIONS

nCS/PRP scaffolds containing BMP2-modified MSCs successfully promotes bone regeneration in critical-sized bone defects. This system could ultimately enable clinicians to better reconstruct the craniofacial bone and avoid donor site morbidity for critical-sized bone defects.

Rehabilitation and Prevention of Proximal Hamstring Tendinopathy

Proximal hamstring tendinopathy (PHT) comprises a small but significant portion of hamstring injuries in athletes, especially runners. PHT is a chronic condition that is clinically diagnosed but can be supported with imaging. The main presenting complaint is pain in the lower gluteal or ischial region that may or may not radiate along the hamstrings in the posterior thigh. There is little scientific evidence on which to base the rehabilitation management of PHT. Treatment is almost always conservative, with a focus on activity modification, addressing contributing biomechanical deficiencies, effective tendon loading including eccentric training, and ultrasound-guided interventional procedures which may facilitate rehabilitation. Surgery is limited to recalcitrant cases or those involving concomitant high-grade musculotendinous pathology. The keys to PHT management include early and accurate diagnosis, optimal rehabilitation to allow for a safe return to preinjury activity level, and preventative strategies to reduce risk of reinjury.

Short term storage stability at room temperature of two different platelet-rich plasma preparations from equine donors and potential impact on growth factor concentrations

Background

The increasing interest in platelet-rich plasma (PRP) based therapies is as yet accompanied by inconsistent information regarding nearly all aspects of handling and application. Among these storage stability of processed platelet-rich products may be the basis for a more flexible application mode. The objective of this study was (1) to estimate the storage stability of growth factors platelet derived growth factor BB (PDGF-BB) and transforming growth factor ß1 (TGF-ß1) in both, a single-step softspin centrifugation-based pure-PRP (P-PRP, ACP®), and a gravity filtration system-based leukocyte-rich-PRP (L-PRP, E-PET), over a six hours time span after preparation at room temperature and (2) to identify possible factors influencing these growth factor concentrations in an equine model.

Results

Growth factor concentrations remained stable over the entire investigation period in L-PRP as well as P-PRP preparations revealing a mean of 3569 pg/ml PDGF-BB for E-PET and means of 1276 pg/ml PDGF-BB and 5086 pg/ml TGF-ß1 for ACP®. Pearson correlations yielded no significant impact of whole blood platelet (PLT), white blood cell (WBC) and red blood cell (RBC) counts on resulting cytokine values. In case of ACP® no significant dependencies between PLT, WBC and RBC counts of the processed platelet-rich product and resulting cytokine content occurred with exception of TGF-ß1 concentrations showing a strong correlation with the WBC content. PDGF-BB content of E-PET preparations showed a strong positive correlation with PLT and a strong negative with WBC of these preparations but not with RBC.

Conclusions

L-PRP ad modum E-PET and P-PRP ad modum ACP® are applicable over at least a six hours time span at room temperature without loss of growth factor content. Based on the results of this study factors influencing the resulting growth factor concentrations still remain questionable. Additional studies implicating a further standardization of preparation protocols are necessary to identify consistent impact on cytokine content after PRP processing.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0920-4) contains supplementary material, which is available to authorized users.

Application of platelet-rich plasma with stem cells in bone and periodontal tissue engineering

Presently, there is a high paucity of bone grafts in the United States and worldwide. Regenerating bone is of prime concern due to the current demand of bone grafts and the increasing number of diseases causing bone loss. Autogenous bone is the present gold standard of bone regeneration. However, disadvantages like donor site morbidity and its decreased availability limit its use. Even allografts and synthetic grafting materials have their own limitations. As certain specific stem cells can be directed to differentiate into an osteoblastic lineage in the presence of growth factors (GFs), it makes stem cells the ideal agents for bone regeneration. Furthermore, platelet-rich plasma (PRP), which can be easily isolated from whole blood, is often used for bone regeneration, wound healing and bone defect repair. When stem cells are combined with PRP in the presence of GFs, they are able to promote osteogenesis. This review provides in-depth knowledge regarding the use of stem cells and PRP in vitro, in vivo and their application in clinical studies in the future.