Platelet alpha-granules

Human Serum for Culture of Articular Chondrocytes

In the field of cell and tissue engineering, culture expansion of human cells in monolayer plays an important part. Traditionally, cell cultures have been supplemented with serum to support attachment and proliferation, but serum is a potential source of foreign protein contamination and viral protein transmission. In this study, we evaluated the use of human serum for experimental human articular chondrocyte expansion and to develop a method for preparation of large volumes of high-quality human serum from healthy blood donors. Human autologous serum contained high levels of epidermal-derived growth factor and platelet-derived growth factor-AB and supported proliferation up to 7 times higher than FCS in primary chondrocyte cultures. By letting the coagulation take place in a commercially available transfusion bag overnight, up to 250 ml of growth factor-rich human serum could be obtained from one donor. The allogenic human serum supported high proliferation rate without loosing expression of cartilage-specific genes. The expanded chondrocytes were able to redifferentiate and form cartilage matrix in comparable amounts to autologous serums. In conclusion, the transfusion bags allow preparation of large volumes of growth factor-rich human serum with the capacity to support in vitro cell expansion. The data further indicate that by controlling the coagulation process there are possibilities of optimizing the release of growth factors for other emerging cell therapies.

Platelet-rich plasma with keratinocytes and fibroblasts enhance healing of full-thickness wounds

Advances in tissue engineering led to the development of various tissue-engineered skin substitutes (TESS) for the treatment of skin injuries. The majority of the autologous TESS required lengthy and costly cell expansion process to fabricate. In this study, we determine the possibility of using a low density of human skin cells suspended in platelet-rich plasma (PRP)-enriched medium to promote the healing of full-thickness skin wounds. To achieve this, full-thickness wounds of size 1.767 cm² were created at the dorsum part of nude mice and treated with keratinocytes (2 × 10⁴ cells/cm²) and fibroblasts (3 × 10⁴ cells/cm²) suspended in 10% PRP-enriched medium. Wound examination was conducted weekly and the animals were euthanized after 2 weeks. Gross examination showed that re-epithelialization was fastest in the PRP+cells group at both day 7 and 14, followed by the PRP group and NT group receiving no treatment. Only the PRP+cells group achieved complete wound closure by 2 weeks. Epidermal layer was presence in the central region of the wound of the PRP+cells and PRP groups but absence in the NT group. Comparison between the PRP+cells and PRP groups showed that the PRP+cells-treated wound was more mature as indicated by the presence of thinner epidermis with single cell layer thick basal keratinocytes and less cellular dermis. In summary, the combination of low cell density and diluted PRP creates a synergistic effect which expedites the healing of full-thickness wounds. This combination has the potential to be developed as a rapid wound therapy via the direct application of freshly harvested skin cells in diluted PRP.

Platelets in liver disease, cancer and regeneration

Although viral hepatitis treatments have evolved over the years, the resultant liver cirrhosis still does not completely heal. Platelets contain proteins required for hemostasis, as well as many growth factors required for organ development, tissue regeneration and repair. Thrombocytopenia, which is frequently observed in patients with chronic liver disease (CLD) and cirrhosis, can manifest from decreased thrombopoietin production and accelerated platelet destruction caused by hypersplenism; however, the relationship between thrombocytopenia and hepatic pathogenesis, as well as the role of platelets in CLD, is poorly understood. In this paper, experimental evidence of platelets improving liver fibrosis and accelerating liver regeneration is summarized and addressed based on studies conducted in our laboratory and current progress reports from other investigators. In addition, we describe our current perspective based on the results of these studies. Platelets improve liver fibrosis by inactivating hepatic stellate cells, which decreases collagen production. The regenerative effect of platelets in the liver involves a direct effect on hepatocytes, a cooperative effect with liver sinusoidal endothelial cells, and a collaborative effect with Kupffer cells. Based on these observations, we ascertained the direct effect of platelet transfusion on improving several indicators of liver function in patients with CLD and liver cirrhosis. However, unlike the results of our previous clinical study, the smaller incremental changes in liver function in patients with CLD who received eltrombopag for 6 mo were due to patient selection from a heterogeneous population. We highlight the current knowledge concerning the role of platelets in CLD and cancer and anticipate a novel application of platelet-based clinical therapies to treat liver disease.

The effect of intraarticular serum rich in growth factors (SRGF) on knee osteoarthritis in the rat model

Osteoarthritis (OA) is a degenerative joint disease with high incidence in world. Various treatments have been used for decreasing pain and improving physical function without clearly beneficial evidences. Nowadays, platelet-rich therapy is used as a novel approach in field of regenerative medicine. The present study evaluated the effect of intraarticular serum rich in growth factors (SRGF) on the monosodium iodoacetate induced-osteoarthritis in rat model. SRGF was injected 3 times weekly. Femorotibial joints were examined 2 weeks after last injection. Histopathologic results showed remarkable articular regeneration in the SRGF treated rats. Our findings were less surface irregularities and articular clefts, proliferation of chondrocytes and increasing synthesis of matrix proteoglycan with toluidine blue staining. Destroyed articular cartilage was repaired by fibro-hyaline cartilage in contrast to the OA rats that filled with fibrovascular tissues. The microscopic score had decreased in the treatment group. We concluded that SRGF, as a source of growth factors, have chondroinductive capacity with regard to enhancement of cartilage regeneration.

Coagulation Management in Jersey Calves: An ex vivo Study

OBJECTIVE

Jersey calves are frequently used as an experimental animal model for in vivo testing of cardiac assist devices or orthopedic implants. In this ex vivo study, we analyzed the coagulation system of the Jersey calves and the potential of human-based coagulation management to circumvent perioperative bleeding complications during surgery. Experimental Procedure: Blood from 7 Jersey calves was subjected to standard laboratory tests and thromboelastometry analysis. An ex vivo model of dilutional coagulopathy was used to study the effects of fibrinogen or prothrombin complex concentrate supplementation. Fibrinolysis was induced with tissue plasminogen activator to identify potential therapeutic strategies involving tranexamic acid or aprotinin. Furthermore, anticoagulation strategies were evaluated by incubating the blood samples with dabigatran or rivaroxaban.

RESULTS

Baseline values for thromboelastometry and standard laboratory parameters, including prothrombin time, activated partial thromboplastin time, fibrinogen, antithrombin III, and D-dimers, were established. Fifty percent diluted blood showed a statistically significant impairment of hemostasis. The parameters significantly improved after the administration of fibrinogen or prothrombin complex concentrate. Tranexamic acid and aprotinin ameliorated tissue plasminogen activator-induced fibrinolysis. Both dabigatran and rivaroxaban significantly prolonged the coagulation parameters.

CONCLUSIONS

In this ex vivo study, coagulation factors, factor concentrate, antifibrinolytic reagents, and anticoagulants regularly used in the clinic positively impacted coagulation parameters in Jersey calf blood.

N-(3-hydroxymethyl-β-carboline-1-yl-ethyl- 2-yl)-l-Phe: development toward a nanoscaled antitumor drug capable of treating complicated thrombosis and inflammation

It is well documented that the surfaces of cancer cells, activated platelets and inflammatory cells are rich in P-selectin. N-(3-hydroxymethyl-β-carboline-1-yl-ethyl-2-yl)-l-Phe (HMCEF) is a P-selectin inhibitor capable of simultaneously inhibiting thrombosis and inflammation. Based on the knowledge that P-selectin is a common target for antithrombotic, anti-inflammatory and antitumor drugs, the aim of this study article was to estimate the possibility of HMCEF as a nanoscaled antitumor drug. Images of transmission electron micro scopy, scanning electron microscopy and atomic force microscopy proved that HMCEF forms nanoparticles with a diameter of <120 nm that promote delivery in blood circulation. In vitro HMCEF intercalates into calf thymus DNA, cuts off DNA pBR22 and inhibits the proliferation of cancer cells. In vivo HMCEF dose dependently (0.2, 2 and 200 nmol/kg per day) slows tumor growth in treated S180 mice, and has a minimal effective dose of 2 nmol/kg per day. At 200 nmol/kg per day, HMCEF does not affect the liver and the kidney of the treated S180 mice, and at 20,000 nmol/kg HMCEF does not affect the liver and the kidney of the treated healthy ICR mice. HMCEF is a promising antitumor drug, which is characterized by its high safety and efficacy in the prevention of the complications of thrombosis and inflammation in patients.

Cardiovascular and Hemostatic Disorders: SOCE and Ca2+ Handling in Platelet Dysfunction

Among the Ca²⁺ entry mechanisms in platelets, store-operated Ca²⁺ entry (SOCE) plays a prominent role as it is necessary to achieve full activation of platelet functions and replenish intracellular Ca²⁺ stores. In platelets, as in other non-excitable cells, SOCE has been reported to involve the activation of plasma membrane channels by the ER Ca²⁺ sensor STIM1. Despite electrophysiological studies are not possible in human platelets, indirect analyses have revealed that the Ca²⁺-permeable channels involve Orai1 and, most likely, TRPC1 subunits. A relevant role for the latter has not been found in mouse platelets. There is a body of evidence revealing a number of abnormalities in SOCE or in its molecular regulators that result in qualitative platelet disorders and, as a consequence, altered platelet responsiveness upon stimulation with multiple physiological agonists. Platelet SOCE abnormalities include STIM1 and Orai1 mutations. This chapter summarizes the current knowledge in this field, as well as the disorders associated to platelet SOCE dysfunction.

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.

Biological Treatment Approaches for Degenerative Disc Disease: A Review of Clinical Trials and Future Directions

Biologic-based treatment strategies for musculoskeletal diseases have gained traction over the past 20 years as alternatives to invasive, costly, and complicated surgical interventions. Spinal degenerative disc disease (DDD) is among the anatomic areas being investigated among this group, notably due to its high incidence and functional debilitation. In this review, we report the literature encompassing the use of biologic-based therapies for DDD. Articles published between January 1995 and November 2015 were reviewed, with a subset meeting the primary and secondary inclusion criteria of clinical trial results that could be sub-classified into bimolecular, cell-based, or gene therapies, as well as studies investigating the utility of allogeneic and tissue-engineered intervertebral discs. Ongoing clinical trials that have not yet published results are also mentioned to present the current state of the field. This exciting area has demonstrated positive and encouraging results across multiple strategies; thus, future bimolecular and regenerative techniques and understanding will likely lead to an increase in the number of human clinical trials assessing these therapies.

TULA-2 (T-Cell Ubiquitin Ligand-2) Inhibits the Platelet Fc Receptor for IgG IIA (FcγRIIA) Signaling Pathway and Heparin-Induced Thrombocytopenia in Mice

OBJECTIVE

The objective of this study is to investigate the role of T-cell ubiquitin ligand-2 (TULA-2) in the platelet Fc receptor for IgG IIA (FcγRIIA) pathway and in the pathogenesis of heparin-induced thrombocytopenia (HIT).

APPROACH AND RESULTS

HIT is a life-threatening thrombotic disease in which IgG antibodies against the heparin-platelet factor 4 complex activate platelets via FcγRIIA. We reported previously differential expression of TULA-2 in human population was linked to FcγRIIA responsiveness. In this study, we investigated the role of TULA-2, a protein phosphatase, in the FcγRIIA pathway and HIT pathogenesis by crossing TULA-2^-/- mice with transgenic FcγRIIA ^+/+ mice. Ablation of TULA-2 resulted in hyperphosphorylation of spleen tyrosine kinase, linker for the activation of T cells, and phospholipase Cγ2 in platelets via FcγRIIA activation. Platelet integrin activation, granule secretion, phosphatidylserine exposure, and aggregation were also enhanced in TULA-2^-/- murine platelets. Compared with wild-type mice, TULA-2^-/- mice showed aggravated antibody-mediated thrombocytopenia, augmented thrombin generation, and shortened tail bleeding time. In contrast, there was no significant difference between TULA-2^-/- and TULA-2^+/+ platelets in platelet spreading and clot retraction. Of note, heterozygous TULA-2^+/- mice, whose platelets contained 50% as much protein as the TULA-2^+/+ platelets, showed significantly increased platelet reactivity and more severe thrombocytopenia in vivo compared with TULA-2^+/+ mice.

CONCLUSIONS

Together, the data demonstrate that not only the absence of TULA-2 but also the relative level of TULA-2 expression modulates FcγRIIA-mediated platelet reactivity and HIT in vivo. TULA-2 expression could be a valuable marker for HIT and inhibiting TULA-2 may serve as a potential therapy to reverse the bleeding adverse effect of anticoagulants.

Analysis of experimental tendinitis in rats treated with laser and platelet-rich plasma therapies by Raman spectroscopy and histometry

The objective of this controlled experimental study was to analyze the changes in the Achilles tendons of rats with experimentally induced tendinitis after treatment with platelet-rich plasma (PRP) and/or laser therapies by histometry to quantify fibroblasts and by Raman spectroscopy to determine the biochemical concentration of collagen types I and III. Fifty-four male Wistar rats were divided into six treatment groups: control (G1); PRP only (G2); irradiation with 660 nm laser (G3); irradiation with 830 nm laser (G4); PRP plus 660 nm laser irradiation (G5); and PRP plus 830 nm laser irradiation (G6). Injuries (partial tenotomy) were inflicted in the middle third of the Achilles tendon, with PRP added prior to suture in the appropriate experimental groups. A diode laser (model Laser Flash® III, DMC Equipamentos Ltda, São Carlos, SP, Brazil) that can be operated in two wavelengths 660 and 830 nm was used for irradiation treatments. The irradiation protocol was energy density of 70 J/cm², 20 s irradiation time, and 0.028 cm² spot area, per point in three points in the injured. The histometry was made in micrographical images of the H&E stained sections and evaluated by ImageJ (version 1.46r)®. Raman spectra were collected using a dispersive spectrometer at 830 nm excitation, 200 mW power, and 10 s integration time (P-1 Raman system, Lambda Solutions, Inc. MA, USA). The relative amount of type I collagen was significantly greater in the PRP plus 830 nm laser irradiation group (468 ± 188) than in the control (147 ± 137), 630 nm laser only (191 ± 117), and 830 nm laser only (196 ± 106) groups (p < 0.01), while the quantity of type III collagen was significantly greater in the PRP-only group compared to both irradiated groups without PRP (p < 0.05). Treatment with PRP combined with irradiation at 830 nm resulted in a larger number of fibroblasts and increased concentration of type I collagen, thus accelerating the healing of the injured tendon.

Prognostic value of the lymphocyte-to-monocyte ratio and other inflammatory markers in malignant pleural mesothelioma

OBJECTIVES

Inflammation plays a role in malignant pleural mesothelioma (MPM) prognosis and symptoms. We investigated the roles of the new and old inflammatory indexes and markers in MPM prognosis.

METHODS

Two hundred and ninety-two MPM patients (167 male and 125 female) were included in this retrospective study. Demographic parameters were collected from the patients' files. Kaplan-Meier curves and multivariate Cox regression analyses were used for the analysis of prognosis.

RESULTS

The mean age of the patients was 58.4 years. The mean survival time was 14.6 ± 13.0 months. Twenty-four potential prognostic factors associated with a poor outcome were calculated in the univariate analysis, and 16 potential prognostic factors were associated with a poor prognosis. These 16 potential prognostic factors were also analyzed in multivariate analysis. Multivariate analysis showed that increased age, stage 3-4 disease, the non-epithelial type, a low Karnofsky performance score, a high white blood cell count, and a low lymphocyte-to-monocyte ratio (LMR) were associated with a poor prognosis. The results of the multivariate analysis showed that a decreased LMR was associated with poor survival. Patients with LMR ≤2.6 had poor survival compared with those with LMR >2.6 (mean 9.6 vs. 17.0 months, respectively; p = 0.004).

CONCLUSIONS

LMR is an independent marker of prognosis in patients with MPM and is superior to the other inflammation-based markers. The inexpensive nature and easy reproducibility of the hemogram should encourage the use of the LMR in clinical practice.

Platelet lysate as a substitute for animal serum for the ex-vivo expansion of mesenchymal stem/stromal cells: present and future

The use of fetal bovine serum (FBS) as a cell culture supplement is discouraged by regulatory authorities to limit the risk of zoonoses and xenogeneic immune reactions in the transplanted host. Additionally, FBS production came under scrutiny due to animal welfare concerns. Platelet derivatives have been proposed as FBS substitutes for the ex-vivo expansion of mesenchymal stem/stromal cells (MSCs) since platelet-derived growth factors can promote MSC ex-vivo expansion. Platelet-derived growth factors are present in platelet lysate (PL) obtained after repeated freezing–thawing cycles of the platelet-rich plasma or by applying physiological stimuli such as thrombin or CaCl₂.

PL-expanded MSCs have been used already in the clinic, taking advantage of their faster proliferation compared with FBS-expanded preparations. Should PL be applied to other biopharmaceutical products, its demand is likely to increase dramatically. The use of fresh platelet units for the production of PL raises concerns due to limited availability of platelet donors. Expired units might represent an alternative, but further data are needed to define safety, including pathogen reduction, and functionality of the obtained PL. In addition, relevant questions concerning the definition of PL release criteria, including concentration ranges of specific growth factors in PL batches for various clinical indications, also need to be addressed. We are still far from a common definition of PL and standardized PL manufacture due to our limited knowledge of the mechanisms that mediate PL-promoting cell growth. Here, we concisely discuss aspects of PL as MSC culture supplement as a preliminary step towards an agreed definition of the required characteristics of PL for the requirements of manufacturers and users.

Human platelet lysate supplementation of mesenchymal stromal cell delivery: issues of xenogenicity and species variability

Immunogenicity of fetal bovine serum (FBS) poses a problem for its use in the propagation of autologous mesenchymal stromal cells (MSCs) for cell therapy. Human platelet lysate (hPL), an enriched growth factor solution containing mitogenic and angiogenic cues, has potential utility in replacing FBS for human MSC (hMSC) delivery strategies. Despite its potentiation of hMSC number in vitro, little is known concerning its capacity to supplement implanted hMSC-seeded constructs and promote tissue regeneration in vivo. In this study, we tested the effects of incorporating hPL in cell-seeded constructs implanted subcutaneously into immunocompromised rats, investigated in vitro interactions between hPL and rat MSCs (rMSCs) and determined interspecies variability in the PL product [hPL vs rat PL (rPL)] and its effect on cultured MSCs (hPL/hMSCs vs rPL/rMSCs). The overarching aim was to determine the utility of hPL to foster MSC survival in preclinical rodent models. Exposure to hPL-supplemented media resulted in rMSC death, by a process attributable to heat-labile proteins, but not membrane attack complex formation. In the in vitro syngeneic model, the rodent product proved fundamentally distinct from the human product, with rPL having substantially lower growth factor content than hPL. Moreover, contrary to the positive effects of hPL on hMSC expansion, rPL did not reduce rMSC doubling time for the serum concentrations examined. When tested in vivo, hPL did not improve cell survival within hydrogel constructs through 2 weeks postimplantation. In summary, this study highlights the many facets of xenogenicity and interspecies variability that must be considered in the preclinical evaluation of hPL. Copyright © 2016 John Wiley & Sons, Ltd.

Smart blood cell and microvesicle-based Trojan horse drug delivery: Merging expertise in blood transfusion and biomedical engineering in the field of nanomedicine

Therapeutic and diagnostic applications of nanomedicine are playing increasingly important roles in human health. Various types of synthetic nanoparticles, including liposomes, micelles, and other nanotherapeutic platforms and conjugates, are being engineered to encapsulate or carry drugs for treating diseases such as cancer, cardiovascular disorders, neurodegeneration, and inflammations. Nanocarriers are designed to increase the half-life of drugs, decrease their toxicity and, ideally, target pathological sites. Developing smart carriers with the capacity to deliver drugs specifically to the microenvironment of diseased cells with minimum systemic toxicity is the goal. Blood cells, and potentially also the liposome-like micro- and nano-vesicles they generate, may be regarded as ideally suited to perform such specific targeting with minimum immunogenic risks. Blood cell membranes are "decorated" with complex physiological receptors capable of targeting and communicating with other cells and tissues and delivering their content to the surrounding pathological microenvironment. Blood cells, such as erythrocytes, have been developed as permeable carriers to release drugs to diseased tissues or act as biofactory allowing enzymatic degradation of a pathological substrate. Interestingly, attempts are also being made to improve the targeting capacity of synthetic nanoparticles by "decorating" their surface with blood cell membrane receptor-like biochemical structures. Research is needed to further explore the benefits that blood cell-derived microvesicles, as a Trojan horse delivery systems, can bring to the arsenal of therapeutic micro- and nanotechnologies. This short review focuses on the therapeutic roles that red blood cells and platelets can play as smart drug-delivery systems, and highlights the benefits that blood transfusion expertise can bring to this exciting and novel biomedical engineering field.

Role of autologous platelet-rich plasma in treatment of long-bone nonunions: a prospective study

PURPOSE

Fracture union is a complex biological process, which depends upon several systemic and local factors. Disturbance of any of these factors may lead to nonunion of the fracture. These nonunions have a huge impact on quality of life as well as socioeconomical aspects. The platelets on activation release a number of growth factors and differentiation factors, which play important role in fracture healing. This study aimed to look for efficacy of platelet-rich plasma in the treatment of established fracture nonunions of long bones.

METHODS

A total of 94 patients with established nonunion of long bone (35 tibia, 30 femur, 11 humerus, 4 radius, 12 ulna, 2 with both radius and ulna) were included in this study. We injected 15-20 ml of autologous platelet-rich plasma (>2,000,000 platelets/μl) under image intensifier at each nonunion site. The fracture union was evaluated clinically and radiologically regularly at monthly interval till 4 months.

RESULTS

Eighty-two patients had their fracture united at the end of 4 months. Thirty-four patients showed bridging trabeculae on X-rays at the end of 2 months, while 41 patients showed bridging trabeculae at the end of third month. Twelve patients did not show any attempt of union at 4 months and were labeled as failure of treatment. There were no complications.

CONCLUSION

Platelet-rich plasma is a safe and effective treatment for the treatment of nonunions. More studies are needed to look into molecular mechanism of this fracture healing acceleration by platelet-rich plasma.

An In Vitro Investigation of Platelet-Rich Plasma-Gel as a Cell and Growth Factor Delivery Vehicle for Tissue Engineering

Platelet-rich plasma (PRP) has been used for different applications in human and veterinary medicine. Many studies have shown promising therapeutic effects of PRP; however, there are still many controversies regarding its composition, properties, and clinical efficacy. The aim of this study was to evaluate the influence of different platelet concentrations on the rheological properties and growth factor (GF) release profile of PRP-gels. In addition, the viability of incorporated bone marrow-derived human mesenchymal stem cells (MSCs) was investigated. PRP (containing 1000 × 10(3), 2000 × 10(3), and 10,000 × 10(3) platelets/μL) was prepared from human platelet concentrates. Platelet activation and gelification were achieved by addition of human thrombin. Viscoelastic properties of PRP-gels were evaluated by rheological studies. The release of GFs and inflammatory proteins was measured using a membrane-based protein array and enzyme-linked immunosorbent assay. MSC viability and proliferation in PRP-gels were assessed over 7 days by cell viability staining. Cell proliferation was examined using DNA quantification. Regardless of the platelet content, all tested PRP-gels showed effective cross-linking. A positive correlation between protein release and the platelet concentration was observed at all time points. Among the detected proteins, the chemokine CCL5 was the most abundant. The greatest release appeared within the first 4 h after gelification. MSCs could be successfully cultured in PRP-gels over 7 days, with the highest cell viability and DNA content found in PRP-gels with 1000 × 10(3) platelets/μL. The results of this study suggest that PRP-gels represent a suitable carrier for both cell and GF delivery for tissue engineering. Notably, a platelet concentration of 1000 × 10(3) platelets/μL appeared to provide the most favorable environment for MSCs. Thus, the platelet concentration is an important consideration for the clinical application of PRP-gels.

An overview of the role of microparticles/microvesicles in blood components: Are they clinically beneficial or harmful?

Blood cells and tissues generate heterogeneous populations of cell-derived vesicles, ranging from approximately 50 nm to 1 µm in diameter. Under normal physiological conditions and as an essential part of an energy-dependent natural process, microparticles (MPs) are continuously shed into the circulation from membranes of all viable cells such as megakaryocytes, platelets, red blood cells, white blood cells and endothelial cells. MP shedding can also be triggered by pathological activation of inflammatory processes and activation of coagulation or complement systems, or even by shear stress in the circulation. Structurally, MPs have a bilayered phospholipid structure exposing coagulant-active phosphatidylserine and expressing various membrane receptors, and they serve as cell-to-cell shuttles for bioactive molecules such as lipids, growth factors, microRNAs, and mitochondria. It was established that ex vivo processing of blood into its components, involving centrifugation, processing by various apheresis procedures, leucoreduction, pathogen reduction, and finally storage in different media and different types of blood bags, can impact MP generation and content. This is mostly due to exposure of the collected blood to anticoagulant/storage media and due to shear stresses or activation, contact with artificial surfaces, or exposure to various leucocyte-removal filters and pathogen-reduction treatments. Such artificially generated MPs, which are added to the original pool of MPs collected from the donor, may exhibit specific functional characteristics, as MPs are not an inert element of blood components. Not surprisingly, MPs' roles and functionality are therefore increasingly seen to be fully relevant to the field of transfusion medicine, and as a parameter of blood safety that must be considered in haemovigilance programmes. Continual advancements in assessment methods of MPs and storage lesions are gradually leading to a better understanding of the impacts of blood collection on MP generation, while clinical research should clarify links of MPs with transfusion reactions and certain clinical disorders. Harmonization and consensus in sampling protocols, sample handling and processing, and assessment methods are needed to achieve consensual interpretations. This review focuses on the role of MPs as an essential laboratory tool and as a most effective player in transfusion science and medicine and in health and disease.

Epithelial cells supply Sonic Hedgehog to the perinatal dentate gyrus via transport by platelets

Dentate neural stem cells produce neurons throughout life in mammals. Sonic hedgehog (Shh) is critical for maintenance of these cells; however, the perinatal source of Shh is enigmatic. In the present study, we examined the role of Shh expressed by hair follicles (HFs) that expand perinatally in temporal concordance with the proliferation of Shh-responding dentate stem cells. Specific inhibition of Shh from HFs or from epithelial sources in general hindered development of Shh-responding dentate stem cells. We also found that the blood–brain barrier (BBB) of the perinatal dentate gyrus (DG) is leaky with stem cells in the dentate exposed to blood-born factors. In attempting to identify how Shh might be transported in blood, we found that platelets contain epithelial Shh, provide Shh to the perinatal DG and that inhibition of platelet generation reduced hedgehog-responsive dentate stem cells.

DOI:http://dx.doi.org/10.7554/eLife.07834.001

Although most of the neurons in the brain have been made by the time we are born, new neurons develop throughout life in part of the brain called the hippocampus. These neurons are thought to help with learning and forming memories. Conditions such as depression and Alzheimer's disease have been linked to not being able to produce enough new neurons.

The neurons develop from a pool of stem cells in part of the hippocampus. A protein called Sonic Hedgehog (Shh) helps to ensure there are enough stem cells and control when they develop into new neurons. The brain cells that produce Shh in adult mice do not appear until a week after birth, by which point the stem cells are already present and generating neurons. This has led scientists to question where these cells get Shh from around the time of birth.

One idea is that cells outside of the brain contribute the Shh such as hair follicles—the structures that hairs grow out of—in the scalp. Hair follicles produce Shh, develop at around the same time as the brain stem cells, and are known to regulate the development of other nearby stem cells. So, Choe et al. conducted a series of experiments in genetically engineered newborn mice and found that the brain stem cells multiply at around the same time that the hair follicles start to produce Shh. Furthermore, reducing the amount of Shh produced by the hair follicles hampered the growth of these stem cells and caused fewer neurons to develop from the stem cell pool.

These results raised the question of how Shh gets from the hair follicles to the stem cell pool in the developing brain. In adult animals, a barrier exists between the brain and the blood supply to protect the brain from infection. However, parts of this barrier are still leaky before birth, which might allow blood cells to carry Shh to the brain. Cloe et al. found that platelets—the blood cells responsible for clotting—are able to carry Shh to the brain stem cell pool. Further experiments showed that preventing platelets from forming caused fewer stem cells to develop.

The suggestion that Shh from the epithelium—the tissue layer that hair follicles are found in—is able to signal to the brain during a specific window of time raises several questions that require further study. Does epithelial Shh also signal to other organs during embryonic or postnatal development? Does injury to the nervous system that increases the permeability of the blood–brain barrier lead to the delivery of Shh to the brain via the circulation in adult animals?

DOI:http://dx.doi.org/10.7554/eLife.07834.002

Immunodiagnosis of platelet activation in immune thrombocytopenia through scFv antibodies cognate to activated IIb3 integrins

Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder characterized by low platelet count and presence of IgG autoantibodies to platelet surface glycoproteins, such as α IIbβ3 and GPIb/IX. Our previous work has shown that platelets in ITP patients exist in an activated state. Two different marker-based approaches are used to study the course of platelet activation: (1) binding of PAC-1 antibody, signifying a change in αIIbβ3 conformation, and (2) expression of P-selectin, signifying alpha granule content release from platelets. Here, we describe the development of a new scFv antibody (R38) that, compared with PAC-1, appears to better distinguish between platelets of ITP patients and healthy controls. Notably, R38 was generated using commercially sourced resting-state integrin that was coated on a microtiter plate. Its ability to distinguish between ITP patients and healthy controls thus suggests that inadvertent integrin activation caused by coating involves a conformational change and exposure of a cryptic epitope. This report also describes for the first time the potential use of an scFv antibody in the immunodiagnosis of platelet activation in ITP patients.

Platelet-rich Plasma as a Potential Treatment for Noncicatricial Alopecias

Androgenetic alopecia (AGA) and alopecia areata (AA) are common hair loss disorders affecting both men and women. Despite available therapeutic options, search for new, more effective treatment is constant. Platelet-rich plasma (PRP) could be effective in promoting hair growth: (1) To present PRP and its mechanism of action in promoting hair growth and (2) to evaluate its preparation methods and its therapeutic potential in noncicatrial alopecias in a systematic review. An international bibliography search, through five databases, was conducted to find articles regarding PRP's action on hair loss. Growth factors in platelets’ granules of PRP bind in the bulge area of hair follicle, promoting hair growth. In our systematic review, 14 articles matched our criteria, including 12 articles for AGA and two for AA. PRP is a potential useful therapeutic tool for alopecias, without major adverse effects. Nevertheless, due to the small number of conducted trials, further studies are required to investigate its efficacy.

Platelet-delivered therapeutics

We have proposed that modified platelets could potentially be used to correct intrinsic platelet defects as well as for targeted delivery of therapeutic molecules to sights of vascular injury. Ectopic expression of proteins within α-granules prior to platelet activation has been achieved for several proteins, including urokinase, factor (F) VIII, and partially for FIX. Potential uses of platelet-directed therapeutics will be discussed, focusing on targeted delivery of urokinase as a thromboprophylactic agent and FVIII for the treatment of hemophilia A patients with intractable inhibitors. This presentation will discuss new strategies that may be useful in the care of patients with vascular injury as well as remaining challenges and limitations of these approaches.

P-selectin and subclinical and clinical atherosclerosis: the Multi-Ethnic Study of Atherosclerosis (MESA)

OBJECTIVE

P-selectin is a cellular adhesion molecule that has been shown to be crucial in development of coronary heart disease (CHD). We sought to determine the role of P-selectin on the risk of atherosclerosis in a large multi-ethnic population.

METHODS

Data from the Multi-Ethnic Study of Atherosclerosis (MESA), including 1628 African, 702 Chinese, 2393 non-Hispanic white, and 1302 Hispanic Americans, were used to investigate the association of plasma P-selectin with CHD risk factors, coronary artery calcium (CAC), intima-media thickness, and CHD. Regression models were used to investigate the association between P-selectin and risk factors, Tobit model for CAC, and Cox regression for CHD events.

RESULTS

Mean levels of P-selectin differed by ethnicity and were higher in men (P<0.001). For all ethnic groups, P-selectin was positively associated with measures of adiposity, blood pressure, current smoking, LDL, and triglycerides and inversely with HDL. A significant ethnic interaction was observed for the association of P-selectin and prevalent diabetes; however, P-selectin was positively associated with HbA1c in all groups. Higher P-selectin levels were associated with greater prevalence of CAC. Over 10.1 years of follow-up, there were 335 incident CHD events. There was a positive linear association between P-selectin levels and rate of incident CHD after adjustment for traditional risk factors. However, association was only significant in non-Hispanic white Americans (HR: 1.81, 95% CI 1.07 to 3.07, P=0.027).

CONCLUSION

We observed ethnic heterogeneity in the association of P-selectin and risk of CHD.

Restoration of responsiveness of phospholipase Cγ2-deficient platelets by enforced expression of phospholipase Cγ1

Receptor-mediated platelet activation requires phospholipase C (PLC) activity to elevate intracellular calcium and induce actin cytoskeleton reorganization. PLCs are classified into structurally distinct β, γ, δ, ε, ζ, and η isoforms. There are two PLCγ isoforms (PLCγ1, PLCγ2), which are critical for activation by tyrosine kinase-dependent receptors. Platelets express both PLCγ1 and PLCγ2. Although PLCγ2 has been shown to play a dominant role in platelet activation, the extent to which PLCγ1 contributes has not been evaluated. To ascertain the relative contributions of PLCγ1 and PLCγ2 to platelet activation, we generated conditionally PLCγ1-deficient, wild-type (WT), PLCγ2-deficient, and PLCγ1/PLCγ2 double-deficient mice and measured the ability of platelets to respond to different agonists. We found that PLCγ2 deficiency abrogated αIIbβ3-dependent platelet spreading, GPVI-dependent platelet aggregation, and thrombus formation on collagen-coated surfaces under shear conditions, which is dependent on both GPVI and αIIbβ3. Addition of exogenous ADP overcame defective spreading of PLCγ2-deficient platelets on immobilized fibrinogen, suggesting that PLCγ2 is required for granule secretion in response to αIIbβ3 ligation. Consistently, αIIbβ3-mediated release of granule contents was impaired in the absence of PLCγ2. In contrast, PLCγ1-deficient platelets spread and released granule contents normally on fibrinogen, exhibited normal levels of GPVI-dependent aggregation, and formed thrombi normally on collagen-coated surfaces. Interestingly, enforced expression of PLCγ1 fully restored GPVI-dependent aggregation and αIIbβ3-dependent spreading of PLCγ2-deficient platelets. We conclude that platelet activation through GPVI and αIIbβ3 utilizes PLCγ2 because PLCγ1 levels are insufficient to support responsiveness, but that PLCγ1 can restore responsiveness if expressed at levels normally achieved by PLCγ2.

Principles and Methods of Preparation of Platelet-Rich Plasma: A Review and Author's Perspective

The utility of platelet-rich plasma (PRP) has spanned various fields of dermatology from chronic ulcer management to trichology and aesthetics, due to its role in wound healing. Though PRP is being used over a long time, there is still confusion over proper terminology to define, classify and describe the different variations of platelet concentrates. There is also a wide variation in the reported protocols for standardization and preparation of PRP, in addition to lack of accurate characterization of the tested products in most articles on the topic. Additionally, the high cost of commercially available PRP kits, precludes its use over a larger population.

In this article, we review the principles and preparation methods of PRP based on available literature and place our perspective in standardizing a safe, simple protocol that can be followed to obtain an optimal consistent platelet yield.

Adhesion and activation of platelets from subjects with coronary artery disease and apparently healthy individuals on biomaterials

On the basis of the clinical studies in patients with coronary artery disease (CAD) presenting an increased percentage of activated platelets, we hypothesized that hemocompatibility testing utilizing platelets from healthy individuals may result in an underestimation of the materials' thrombogenicity. Therefore, we investigated the interaction of polymer-based biomaterials with platelets from CAD patients in comparison to platelets from apparently healthy individuals. In vitro static thrombogenicity tests revealed that adherent platelet densities and total platelet covered areas were significantly increased for the low (polydimethylsiloxane, PDMS) and medium (Collagen) thrombogenic surfaces in the CAD group compared to the healthy subjects group. The area per single platelet-indicating the spreading and activation of the platelets-was markedly increased on PDMS treated with PRP from CAD subjects. This could not be observed for collagen or polytetrafluoroethylene (PTFE). For the latter material, platelet adhesion and surface coverage did not differ between the two groups. Irrespective of the substrate, the variability of these parameters was increased for CAD patients compared to healthy subjects. This indicates a higher reactivity of platelets from CAD patients compared to the healthy individuals. Our results revealed, for the first time, that utilizing platelets from apparently healthy donors bears the risk of underestimating the thrombogenicity of polymer-based biomaterials.

Morphology of platelet Golgi apparatus and their significance after acute cerebral infarction

Blood samples were harvested from the antecubital vein of 20 fasting patients with acute cerebral infarction at 1, 7 and 15 days after onset to prepare blood platelet suspension. Fasting antecubital vein blood was collected from an additional 20 normal adults as controls. Under transmission tron microscope, platelet Golgi tubules and vesicles became significantly thickened, enlarged, and irregular after acute cerebral infarction. Alpha granules in platelets significantly reduced in number, especially 1 day after cerebral infarction. Under immunoelectron microscopy, a few alpha granules aggregated around Golgi tubules and vesicles after infarction. These results suggested that platelet Golgi apparatus displayed significant morphological changes, which were possibly associated with enhanced synthetic and secretory functions of activated platelets after acute cerebral infarction. This study used Golgi apparatus blocking agent Brefeldin A to block Golgi apparatus in an aim to study the effects of Golgi apparatus on CD40L expression on the surface of activated platelets. Flow cytometry revealed that CD40L expression on activated platelet surfaces decreased significantly when Golgi apparatus was blocked, which indicated that Golgi apparatus participated in the synthesis and transport of CD40L to the platelet surface.

D, Forleo M, Dasi LP. Theory to predict shear stress on cells in turbulent blood flow

Shear stress on blood cells and platelets transported in a turbulent flow dictates the fate and biological activity of these cells. We present a theoretical link between energy dissipation in turbulent flows to the shear stress that cells experience and show that for the case of physiological turbulent blood flow: (a) the Newtonian assumption is valid, (b) turbulent eddies are universal for the most complex of blood flow problems, and (c) shear stress distribution on turbulent blood flows is possibly universal. Further we resolve a long standing inconsistency in hemolysis between laminar and turbulent flow using the theoretical framework. This work demonstrates that energy dissipation as opposed to bulk shear stress in laminar or turbulent blood flow dictates local mechanical environment of blood cells and platelets universally.

A secreted tyrosine kinase acts in the extracellular environment

Although tyrosine phosphorylation of extracellular proteins has been reported to occur extensively in vivo, no secreted protein tyrosine kinase has been identified. As a result, investigation of the potential role of extracellular tyrosine phosphorylation in physiological and pathological tissue regulation has not been possible. Here, we show that VLK, a putative protein kinase previously shown to be essential in embryonic development, is a secreted protein kinase, with preference for tyrosine, that phosphorylates a broad range of secreted and ER-resident substrate proteins. We find that VLK is rapidly and quantitatively secreted from platelets in response to stimuli and can tyrosine phosphorylate coreleased proteins utilizing endogenous as well as exogenous ATP sources. We propose that discovery of VLK activity provides an explanation for the extensive and conserved pattern of extracellular tyrosine phosphophorylation seen in vivo, and extends the importance of regulated tyrosine phosphorylation into the extracellular environment.

Validating laboratory results in a national observational cohort study without field centers: the Reasons for Geographic and Racial Differences in Stroke cohort

OBJECTIVES

The REasons for Geographic and Racial Differences in Stroke (REGARDS) study is a prospective cohort of 30,239 Americans in the contiguous United States; the first of this scale to use home visits to obtain, process, and ship biologic samples to a core laboratory. Pre-analytical factors resulting from this study design may affect the results of some laboratory assays. We investigated the impact of REGARDS processing on a variety of analytes.

DESIGN AND METHODS

In REGARDS, blood samples were processed in the field by technicians who were trained on standardized methods for phlebotomy and sample processing. Field processing included centrifugation using varying non-uniform equipment and shipping overnight on ice to the University of Vermont, where samples were re-centrifuged for 30,000 ×g-minutes and stored at -80 °C. We assessed the effects of REGARDS sample handling by processing split samples from 20 volunteers using either ideal procedures or simulated REGARDS procedures. Assays for 19 analytes for potential study in REGARDS were then run on both samples and results compared.

RESULTS

Spearman correlation coefficients for analytes measured in ideal versus REGARDS processed samples ranged from 0.11 to 1.0. Thirteen of 19 analytes were highly correlated (>0.75), but platelet proteins were more variable.

CONCLUSIONS

Simulation of non-optimal field processing and shipment to a central laboratory showed high variability in analytes released by platelets. The majority of other analytes produced valid results, but platelet contamination in REGARDS samples makes measurement of platelet proteins unadvisable in these samples. Future analytes considered by REGARDS or similar studies should undergo similar pilot testing.

Role of platelet-released growth factors in detoxification of reactive oxygen species in osteoblasts

INTRODUCTION

Oxidative stress can impair fracture healing. To protect against oxidative damage, a system of detoxifying and antioxidative enzymes works to reduce the cellular stress. The transcription of these enzymes is regulated by antioxidant response element (ARE). The nuclear factor (erythroid-derived 2)-like2 (Nrf2) plays a major role in transcriptional activation of ARE-driven genes. Recently it has been shown that vascular endothelial growth factor (VEGF) prevents oxidative damage via activation of the Nrf2 pathway in vitro. Platelet-released growth factor (PRGF) is a mixture of autologous proteins and growth factors, prepared from a determined volume of platelet-rich plasma (PRP). It has already used to enhance fracture healing in vitro. The aim of the present study was to elucidate if platelets can lead to upregulation of VEGF and if platelets can regulate the activity of Nrf2-ARE system in primary human osteoblast (hOB) and in osteoblast-like cell line (SAOS-2).

METHODS

Platelets and PRGF were obtained from healthy human donors. HOB and SAOS-2 osteosarcoma cell line were used. The ARE activity was analysed using a dual luciferase reporter assay system. We used Western blot to detect the nuclear accumulation of Nrf2 and the amount of cytosolic antioxidant Thioredoxin Reductase-1 (TXNRD-1), Heme Oxygenase-1 (HO-1) and NAD(P)H quinine oxidoreductase-1 (NQO1). Gene expression analysis was performed by real-time RT PCR. ELISA was used for the quantification of growth factors.

RESULTS

The activity of ARE was increased in the presence of PRGF up to 50%. Western blotting demonstrated enhanced nuclear accumulation of Nrf2. This was followed by an increase in the protein expression of the aforementioned downstream targets of Nrf2. Real-time RT PCR data showed an upregulation in the gene expression of the VEGF after PRGF treatment. This was confirmed by ELISA, where the treatment with PRGF induced the protein level of VEGF in both cells.

CONCLUSIONS

These results provide a new insight into PRGF's mode of action in osteoblasts. PRGF not only leads to increase the endogenous VEGF, but also it may be involved in preventing oxidative damage through the Nrf2-ARE signalling. Nrf2 activation via PRGF may have great potential as an effective therapeutic drug target in fracture healing.

Sustained delivery of biomolecules from gelatin carriers for applications in bone regeneration

Local delivery of therapeutic biomolecules to stimulate bone regeneration has matured considerably during the past decades, but control over the release of these biomolecules still remains a major challenge. To this end, suitable carriers that allow for tunable spatial and temporal delivery of biomolecules need to be developed. Gelatin is one of the most widely used natural polymers for the controlled and sustained delivery of biomolecules because of its biodegradability, biocompatibility, biosafety and cost–effectiveness. The current study reviews the applications of gelatin as carriers in form of bulk hydrogels, microspheres, nanospheres, colloidal gels and composites for the programmed delivery of commonly used biomolecules for applications in bone regeneration with a specific focus on the relationship between carrier properties and delivery characteristics.

Platelet-Rich Preparations to Improve Healing. Part I: Workable Options for Every Size Practice

Numerous studies have demonstrated that platelet-rich preparations applied to surgical sites, injuries, or wounds are a safe and effective way to promote soft tissue healing and bone growth. Various protocols have been developed for preparing platelet-rich preparations, with subtle but important differences between them. Unfortunately, only a minority of clinicians use platelet-rich preparations, such as platelet-rich plasma and platelet-rich fibrin, in their practice, possibly due to confusion about the different methods and their advantages and disadvantages. Therefore, the different types of preparations are described to help guide the selection of the best method for any size practice. Classic methods generally require large volumes of blood and can be expensive, complicated, and time-intensive. Simpler protocols have been developed recently, which require relatively inexpensive equipment and small blood volumes and, thus, may be more applicable for small clinical practices. Platelet-rich preparations accelerate healing at earlier time points to reduce discomfort and the potential for adverse outcomes, including infection, poor wound closure, and delays in forming strong bone for subsequent procedures (such as implants). However, platelet-rich preparations may also improve long-term outcomes in patients expected to have impaired healing, such as with lifestyle choices (eg, smoking), medications (eg, steroids), diseases (eg, diabetes, osteoporosis, atherosclerosis), and aging, by supplementing the deficient wound environment to restore proper healing. Therefore, both large and small clinical practices would benefit from utilizing platelet-rich preparations to enhance healing in their patients.

Platelet microparticles: detection and assessment of their paradoxical functional roles in disease and regenerative medicine

There is increasing research on and clinical interest in the physiological role played by platelet microparticles (PMPs). PMPs are 0.1-1-μm fragments shed from plasma membranes of platelets that are undergoing activation, stress, or apoptosis. They have a phospholipid-based structure and express functional receptors from platelet membranes. As they are the most abundant microparticles in the blood and they express the procoagulant phosphatidylserine, PMPs likely complement, if not amplify, the functions of platelets in hemostasis, thrombosis, cancer, and inflammation, but also act as promoters of tissue regeneration. Their size and structure make them instrumental in platelet-cell communications as a delivery tool of platelet-borne bioactive molecules including growth factors, other signaling molecules and micro (mi)RNA. PMPs can therefore be a pathophysiological threat or benefit to the cellular environment when interacting with the blood vasculature. There is also increasing evidence that PMP generation is triggered during blood collection, separation into components, and storage, a phenomenon potentially leading to thrombotic and inflammatory side effects in transfused patients. Evaluating PMPs requires strict pre-analytical and analytical procedures to avoid artifactual generation and ensure accurate assessment of the number, size repartitioning, and functional properties. This review describes the physical and functional methods developed for analyzing and quantifying PMPs. It then presents the functional roles of PMPs as markers or triggers of diseases like thrombosis, atherosclerosis, and cancer, and discusses the possible detrimental immunological impact of their generation in blood components. Finally we review the potential function of PMPs in tissue regeneration and the prospects for their use in therapeutic strategies for human health.

Role of platelets in chronic liver disease and acute liver injury

Platelets contain not only hemostatic factors but also many growth factors that play important roles in wound healing and tissue repair. Platelets have already been used for the promotion of tissue regeneration in the clinical setting, such as dental implantation and plastic surgery. Thrombocytopenia, which is frequently found in patients with chronic liver disease and cirrhosis, is due to various causes such as decreased thrombopoietin production and accelerated platelet destruction caused by hypersplenism. However, the relationship between thrombocytopenia and hepatic pathogenesis and the role of platelets in chronic liver disease are poorly understood. In acute liver injury, it is reported that platelets are recruited to the liver and contribute to liver damage by promoting the induction of chemotactic factors and the accumulation of leukocytes in the liver, whereas platelets or mediators released by platelets can have a protective effect against liver injury. In this review, we highlight the recent accumulated knowledge concerning the role of platelets in chronic liver disease and acute liver injury.

The bone integration effects of platelet-rich fibrin by removal torque of titanium screw in rabbit tibia

Platelet-rich fibrin (PRF) is nowadays often used in various fields, but no removal torque studies have yet been done to evaluate the effects of the platelet-rich fibrin on the bone integration at the initial healing period. An experimental study have been performed in rabbits to evaluate whether the complete PRF clots can accelerate the bone integration of implants at the initial healing period after creating bone defects in tibias. The effect of the complete PRF clots on bone integration was studied in two rabbit groups, 4-week group (group A) and 6-week group (group B) after preparing bony defects. Artificial bony defects were prepared in the tibias of rabbits. The complete PRF clots was applied to the defects in the experimental group, whereas the defects were unfilled in the control group. Four weeks later, machined implants were installed into the rabbit tibias (group A). Six weeks after installation, the removal torque from nine rabbits was measured to examine the bone healing effect of PRF. In another rabbits (group B), 6 weeks after preparing bony defects, installation was performed, and another 6 weeks after installation, the removal torque from nine rabbits was measured. The authors found a positive significant effect of the complete PRF clots on bone integration (higher bone density) in group A installed at 4 weeks after preparing bony defects (p = 0.008; t-test), but not in group B installed at 6 weeks after preparing bony defects (p = 0.677).

Orthobiologics and platelet rich plasma

Orthobiologics have evolved to the extent that they significantly influence modern orthopedic surgical practice. A better understanding of the role of various growth factors and cells in the process of tendon healing, ligament repair, cartilage regeneration and bone formation has stimulated focused research in many chronic musculoskeletal ailments. Investigators have published results of laboratory as well as clinical studies, using orthobiologics like platelet rich plasma, stem cells, autologous conditioned serum etc., with variable results. However, a clear consensus over the best orthobiologic substance and the method of preparation and usage of these substances is lacking. Much of the confusion is due to the fact that studies ranging from RCTs to case reports present variable results, and the interpretations are wide-ranging. We have reviewed the available orthobiologics related data with a focus on platelet rich plasma in orthopedic conditions.

The effect of autologous platelet-rich plasma on bronchial stump tissue granulation after pneumonectomy: experimental study

Objectives. Recent advances in perioperative management, antibiotics, and surgical materials, including mechanical staplers, have decreased the operative risk of pulmonary resection. However, bronchopleural fistula can still occur in some instances, the occurrence often being lethal. This study investigated whether platelet-rich plasma (PRP) promotes granulation of the bronchial stump after pneumonectomy. Methods. Ten pigs were randomized into two groups: (A) control or non-PRP group (pneumonectomy) and (B) PRP group (pneumonectomy and PRP application). PRP was obtained by spinning down the animal's own blood and collecting the buffy coat containing platelets and white blood cells. Results. Increased platelet concentration triggered the healing process. The percentage of granulation tissue formed at the stumps was significantly higher in the PRP group of animals. This observation was confirmed when statistical analysis using Mann-Whitney U test was performed (P = 0.0268). Conclusions. PRP is easily produced with minimal basic equipment and is useful in accelerating granulation of the bronchial stump, although the timing and optimum number of applications in humans require further study. Autologous PRP is a safe, feasible, and reliable new healing promoter with potential therapeutic effects.

The effects of platelet-rich clot releasate on the expression of MMP-1 and type I collagen in human adult dermal fibroblasts: PRP is a stronger MMP-1 stimulator

Platelet-rich plasma is widely used in acute and chronic ulcers due to its capacity to enhance the wound healing process. Fibroblasts are believed to be the most important cells in the production and remodeling of the extracellular matrix (ECM). Matrix metalloproteinase (MMP)-1 is the proteolytic enzyme of collagen I, and has a key role in collagen remodeling during wound healing. Whether or not platelet-rich clot releasate (PRCR) is able to effectively modulate the ECM, and the effect of PRCR on the expression of type I collagen and MMP-1 in human dermal fibroblasts was evaluated. Specifically, human adult dermal fibroblasts were incubated in PRCR-containing solutions for 24 and 48 h, after which the levels of collagen and MMP-1 were quantified by reverse transcription PCR at the transcriptional level, and ELISA and immunoblot analyses at the post-transcriptional level. PRCR markedly up-regulated the expression of MMP-1 and type I collagen in fibroblasts incubated in 20 % PRCR solutions for 48 h. These findings suggest that increased MMP-1 expression after PRCR treatment enable remodeling the ECM.

The efficacy of platelet-rich plasma in the treatment of symptomatic knee osteoarthritis: a systematic review with quantitative synthesis

PURPOSE

The purpose of this systematic review was to synthesize the available Level I and Level II literature on platelet-rich plasma (PRP) as a therapeutic intervention in the management of symptomatic knee osteoarthritis (OA).

METHODS

A systematic review of Medline, Embase, Cochrane Central Register of Controlled Trials, PubMed, and www.clinicaltrials.gov was performed to identify all randomized controlled trials and prospective cohort studies that evaluated the clinical efficacy of PRP versus a control injection for knee OA. A random-effects model was used to evaluate the therapeutic effect of PRP at 24 weeks by use of validated outcome measures (Western Ontario and McMaster Universities Arthritis Index, visual analog scale for pain, International Knee Documentation Committee Subjective Knee Evaluation Form, and overall patient satisfaction).

RESULTS

Six Level I and II studies satisfied our inclusion criteria (4 randomized controlled trials and 2 prospective nonrandomized studies). A total of 577 patients were included, with 264 patients (45.8%) in the treatment group (PRP) and 313 patients (54.2%) in the control group (hyaluronic acid [HA] or normal saline solution [NS]). The mean age of patients receiving PRP was 56.1 years (51.5% male patients) compared with 57.1 years (49.5% male patients) for the group receiving HA or NS. Pooled results using the Western Ontario and McMaster Universities Arthritis Index scale (4 studies) showed that PRP was significantly better than HA or NS injections (mean difference, -18.0 [95% confidence interval, -28.8 to -8.3]; P < .001). Similarly, the International Knee Documentation Committee scores (3 studies) favored PRP as a treatment modality (mean difference, 7.9 [95% confidence interval, 3.7 to 12.1]; P < .001). There was no difference in the pooled results for visual analog scale score or overall patient satisfaction. Adverse events occurred more frequently in patients treated with PRP than in those treated with HA/placebo (8.4% v 3.8%, P = .002).

CONCLUSIONS

As compared with HA or NS injection, multiple sequential intra-articular PRP injections may have beneficial effects in the treatment of adult patients with mild to moderate knee OA at approximately 6 months. There appears to be an increased incidence of nonspecific adverse events among patients treated with PRP.

LEVEL OF EVIDENCE

Level II, systematic review of Level I and II studies.

Scaffold-assisted cartilage tissue engineering using infant chondrocytes from human hip cartilage

OBJECTIVE

Studies about cartilage repair in the hip and infant chondrocytes are rare. The aim of our study was to evaluate the use of infant articular hip chondrocytes for tissue engineering of scaffold-assisted cartilage grafts.

METHOD

Hip cartilage was obtained from five human donors (age 1-10 years). Expanded chondrocytes were cultured in polyglycolic acid (PGA)-fibrin scaffolds. De- and re-differentiation of chondrocytes were assessed by histological staining and gene expression analysis of typical chondrocytic marker genes. In vivo, cartilage matrix formation was assessed by histology after subcutaneous transplantation of chondrocyte-seeded PGA-fibrin scaffolds in immunocompromised mice.

RESULTS

The donor tissue was heterogenous showing differentiated articular cartilage and non-differentiated tissue and considerable expression of type I and II collagens. Gene expression analysis showed repression of typical chondrocyte and/or mesenchymal marker genes during cell expansion, while markers were re-induced when expanded cells were cultured in PGA-fibrin scaffolds. Cartilage formation after subcutaneous transplantation of chondrocyte loaded PGA-fibrin scaffolds in nude mice was variable, with grafts showing resorption and host cell infiltration or formation of hyaline cartilage rich in type II collagen. Addition of human platelet rich plasma (PRP) to cartilage grafts resulted robustly in formation of hyaline-like cartilage that showed type II collagen and regions with type X collagen.

CONCLUSION

These results suggest that culture of expanded and/or de-differentiated infant hip cartilage cells in PGA-fibrin scaffolds initiates chondrocyte re-differentiation. The heterogenous donor tissue containing immature chondrocytes bears the risk of cartilage repair failure in vivo, which may be possibly overcome by the addition of PRP.

Absence of micronucleus formation in CHO-K1 cells cultivated in platelet lysate enriched medium

Human platelet lysate (PL) represents an effective substitute of fetal bovine serum (FBS) for mesenchymal stromal cell (MSC) cultivation. Compared to FBS, PL favors MSC proliferation significantly shortening the population doubling time and avoiding the risks related to the use of animal derivatives. Growth factors contained in the platelets are released upon platelet disruption following freezing/thawing cycles or as we have recently described by using ultrasound. We have investigated whether the increased cell proliferation achieved by using PL could induce mitotic stress and whether the potential formation of free radicals during PL production by ultrasound could cause chromosomal instability in mammalian cells. We have applied an image analysis assisted high content screening (HCS) in vitro micronucleus assay in the Chinese Hamster Ovarian K1 (CHO-K1) rodent mammalian cell line. PL was produced by sonication; for the micronucleus assay, CHO-K1 cells were exposed to increasing concentrations of PL. Cytokinesis was blocked by cytochalasin B, nuclei were stained with bisbenzimide and images were acquired and analyzed automatically using an HCS system, both with a 20× and a 10× objective. Our results suggest that growth stimulus induced by the use of PL did not significantly increase micronucleus formation in CHO-K1 cells compared to negative control. Micronucleus testing in conjunction with HCS could represent a valid tool to evaluate the safety of ancillary materials used in the production of cell-based medicinal products.