Micro-array profiling exhibits remarkable intra-individual stability of human platelet micro-RNA

Infiltration therapy in the context of cartilage surgery

Guideline-based surgical cartilage therapy for focal cartilage damage offers highly effective possibilities to sustainably reduce patients' complaints and to prevent or at least delay the development of early osteoarthritis. In the knee joint, it has the potential to reduce almost a quarter of the arthroses requiring joint replacement caused by cartilage damage. Biologically effective injection therapies could further improve these results. Based on the currently available literature and preclinical studies, intra- and postoperative injectables may have a positive effect of platelet-rich plasma/fibrin (PRP/PRF) and hyaluronic acid (HA) on cartilage regeneration and, in the case of HA injections, also on the clinical outcome can be assumed. The role of a combination therapy with use of intra-articular corticosteroids is lacking in the absence of adequate study data and cannot be defined yet. With regard to adipose tissue-based cell therapy, the current scientific data do not yet justify any recommendation for its use. Further studies also regarding application intervals, timing and differences in different joints are required.

Regenerative methods in osteoarthritis

Osteoarthritis (OA) is the most common type of arthritis that can affect all joint structures. The primary goals of osteoarthritis treatment are to alleviate pain, reduce functional limitations, and improve quality of life. Despite its high prevalence, treatment options for osteoarthritis are limited, with most therapeutic approaches focusing on symptom management. Tissue engineering and regenerative strategies based on biomaterials, cells, and other bioactive molecules have emerged as viable options for osteoarthritis cartilage repair. Platelet-rich plasma (PRP) and mesenchymal stem cells (MSCs) are the most commonly used regenerative therapies today to protect, restore, or increase the function of damaged tissues. Despite promising results, there is conflicting evidence regarding the efficacy of regenerative therapies, and their efficacy remains unknown. The data suggest that more research and standardization are required for the use of these therapies in osteoarthritis. This article provides an overview of the application of MSCs and PRP applications.

Contents in tumor-educated platelets as the novel biosource for cancer diagnostics

Liquid biopsy, a powerful non-invasive test, has been widely used in cancer diagnosis and treatment. Platelets, the second most abundant cells in peripheral blood, are becoming one of the richest sources of liquid biopsy with the capacity to systematically and locally respond to the presence of cancer and absorb and store circulating proteins and different types of nucleic acids, thus called "tumor-educated platelets (TEPs)". The contents of TEPs are significantly and specifically altered, empowering them with the potential as cancer biomarkers. The current review focuses on the alternation of TEP content, including coding and non-coding RNA and proteins, and their role in cancer diagnostics.

AMD Genomics: Non-Coding RNAs as Biomarkers and Therapeutic Targets

Age-related macular degeneration (AMD) is a progressive neurodegenerative disease that is the world’s leading cause of blindness in the aging population. Although the clinical stages and forms of AMD have been elucidated, more specific prognostic tools are required to determine when patients with early and intermediate AMD will progress into the advanced stages of AMD. Another challenge in the field has been the appropriate development of therapies for intermediate AMD and advanced atrophic AMD. After numerous negative clinical trials, an anti-C5 agent and anti-C3 agent have recently shown promising results in phase 3 clinical trials, in terms of slowing the growth of geographic atrophy, an advanced form of AMD. Interestingly, both drugs appear to be associated with an increased incidence of wet AMD, another advanced form of the disease, and will require frequent intravitreal injections. Certainly, there remains a need for other therapeutic agents with the potential to prevent progression to advanced stages of the disease. Investigation of the role and clinical utility of non-coding RNAs (ncRNAs) is a major advancement in biology that has only been minimally applied to AMD. In the following review, we discuss the clinical relevance of ncRNAs in AMD as both biomarkers and therapeutic targets.

New Insights Into Platelet-enriched miRNAs: Production, Functions, Roles in Tumors, and Potential Targets for Tumor Diagnosis and Treatment

In view of the increasing number of malignant tumors worldwide and their high mortality, efforts are being made to find effective biomarkers for early detection and effective treatment measures of cancer. In recent years, the roles of platelets in tumors have attracted considerable attention. Although platelets do not have nuclei, they are rich in miRNAs, which are important molecules in platelet regulation of tumors. Platelet miRNA expression in tumor patients is abnormal and tumor-specific. Platelet miRNAs have higher accuracy and specificity than conventional tumor detection markers and circulating miRNAs in tumor diagnosis. Platelets enriched miRNAs are involved in the regulation of tumor proliferation, metastasis, tumor-related immunity, tumor-related thrombosis, and antitumor therapy. To understand the role of platelet miRNAs in tumors, this article reviews the biological functions of miRNAs in platelets and summarizes the regulatory roles of platelet miRNAs in tumors and the potential roles of platelet miRNAs in tumor diagnosis and treatment.

Platelet-rich plasma as an effective biological therapy in early-stage knee osteoarthritis: One year follow up

Objective: PRP is produced by centrifugation of whole blood containing highly concentrated platelets, associated growth factors, and other bioactive agents which has been shown to provide some symptomatic relief in early knee osteoarthritis (OA). The principal objective of our study was to evaluate the effectiveness and safety of standardized intra-articular injection of autologous PRP in early osteoarthritis knee. Methods: A total of 98 eligible symptomatic patients received two injections of standardized PRP 3 weeks apart. Clinical outcomes were evaluated using the VAS and Western Ontario and McMaster Universities Arthritis Index (WOMAC) questionnaire before treatment and at 6 weeks, 3 months, 6 months, and 1 year after treatment. Secondary objectives were safety (side effects), and the effect of PRP on the different grades of knee degeneration. Results: There was a statistically significant improvement in mean VAS and WOMAC scores at 6 weeks, 3 months, 6 months, and slight loss of improvement at 1 year follow-up. There was also a correlation between the degree of degeneration and improvement in the mean scores. The decrease in mean pain score is more in grades 1 and 2 (early OA) than in grade 3. The intraarticular injection is safe, with no major complications. Conclusion: PRP is a safe and effective biological regenerative therapy for early OA Knees. It provides a significant clinical improvement in patients with some loss of improvement with time. More studies will be needed to confirm our findings.

Circulating non-coding RNAs in biomarker-guided cardiovascular therapy: a novel tool for personalized medicine?

Current clinical guidelines emphasize the unmet need for technological innovations to guide physician decision-making and to transit from conventional care to personalized cardiovascular medicine. Biomarker-guided cardiovascular therapy represents an interesting approach to inform tailored treatment selection and monitor ongoing efficacy. However, results from previous publications cast some doubts about the clinical applicability of biomarkers to direct individualized treatment. In recent years, the non-coding human transcriptome has emerged as a new opportunity for the development of novel therapeutic strategies and biomarker discovery. Non-coding RNA (ncRNA) signatures may provide an accurate molecular fingerprint of patient phenotypes and capture levels of information that could complement traditional markers and established clinical variables. Importantly, ncRNAs have been identified in body fluids and their concentrations change with physiology and pathology, thus representing promising non-invasive biomarkers. Previous publications highlight the translational applicability of circulating ncRNAs for diagnosis and prognostic stratification within cardiology. Numerous independent studies have also evaluated the potential of the circulating non-coding transcriptome to predict and monitor response to cardiovascular treatment. However, this field has not been reviewed in detail. Here, we discuss the state-of-the-art research into circulating ncRNAs, specifically microRNAs and long non-coding RNAs, to support clinical decision-making in cardiovascular therapy. Furthermore, we summarize current methodological and conceptual limitations and propose future steps for their incorporation into personalized cardiology. Despite the lack of robust population-based studies and technical barriers, circulating ncRNAs emerge as a promising tool for biomarker-guided therapy.

The Role of microRNAs in Organismal and Skin Aging

The aging process starts directly after birth and lasts for the entire lifespan; it manifests itself with a decline in an organism’s ability to adapt and is linked to the development of age-related diseases that eventually lead to premature death. This review aims to explore how microRNAs (miRNAs) are involved in skin functioning and aging. Recent evidence has suggested that miRNAs regulate all aspects of cutaneous biogenesis, functionality, and aging. It has been noted that some miRNAs were down-regulated in long-lived individuals, such as let-7, miR-17, and miR-34 (known as longevity-related miRNAs). They are conserved in humans and presumably promote lifespan prolongation; conversely, they are up-regulated in age-related diseases, like cancers. The analysis of the age-associated cutaneous miRNAs revealed the increased expression of miR-130, miR-138, and miR-181a/b in keratinocytes during replicative senescence. These miRNAs affected cell proliferation pathways via targeting the p63 and Sirtuin 1 mRNAs. Notably, miR-181a was also implicated in skin immunosenescence, represented by the Langerhans cells. Dermal fibroblasts also expressed increased the levels of the biomarkers of aging that affect telomere maintenance and all phases of the cellular life cycle, such as let-7, miR-23a-3p, 34a-5p, miR-125a, miR-181a-5p, and miR-221/222-3p. Among them, the miR-34 family, stimulated by ultraviolet B irradiation, deteriorates collagen in the extracellular matrix due to the activation of the matrix metalloproteinases and thereby potentiates wrinkle formation. In addition to the pro-aging effects of miRNAs, the plausible antiaging activity of miR-146a that antagonized the UVA-induced inhibition of proliferation and suppressed aging-related genes (e.g., p21WAF-1, p16, and p53) through targeting Smad4 has also been noticed. Nevertheless, the role of miRNAs in skin aging is still not fully elucidated and needs to be further discovered and explained.

microRNAs as promising biomarkers of platelet activity in antiplatelet therapy monitoring

Given the high morbidity and mortality of cardiovascular diseases (CVDs), novel biomarkers for platelet reactivity are urgently needed. Ischemic events in CVDs are causally linked to platelets, small anucleate cells important for hemostasis. The major side-effect of antiplatelet therapy are life-threatening bleeding events. Current platelet function tests are not sufficient in guiding treatment decisions. Platelets host a broad spectrum of microRNAs (miRNAs) and are a major source of cell-free miRNAs in the blood stream. Platelet-related miRNAs have been suggested as biomarkers of platelet activation and assessment of antiplatelet therapy responsiveness. Platelets release miRNAs upon activation, possibly leading to alterations of plasma miRNA levels in conjunction with CVD or inadequate platelet inhibition. Unlike current platelet function tests, which measure platelet activation ex vivo, signatures of platelet-related miRNAs potentially enable the assessment of in vivo platelet reactivity. Evidence suggests that some miRNAs are responsive to platelet inhibition, making them promising biomarker candidates. In this review, we explain the secretion of miRNAs upon platelet activation and discuss the potential use of platelet-related miRNAs as biomarkers for CVD and antiplatelet therapy monitoring, but also highlight remaining gaps in our knowledge and uncertainties regarding clinical utility. We also elaborate on technical issues and limitations concerning plasma miRNA quantification.

Uncontrolled Diabetes Mellitus Has No Major Influence on the Platelet Transcriptome

BACKGROUND

Diabetes mellitus (DM) has been associated with increased platelet reactivity as well as increased levels of platelet RNAs in plasma. Here, we sought to evaluate whether the platelet transcriptome is altered in the presence of uncontrolled DM.

METHODS

Next-generation sequencing (NGS) was performed on platelet RNA for 5 patients with uncontrolled DM (HbA1c 9.0%) and 5 control patients (HbA1c 5.5%) with otherwise similar clinical characteristics. RNA was isolated from leucocyte-depleted platelet-rich plasma. Libraries of platelet RNAs were created separately for long RNAs after ribosomal depletion and for small RNAs from total RNA, followed by next-generation sequencing.

RESULTS

Platelets in both groups demonstrated RNA expression profiles characterized by absence of leukocyte-specific transcripts, high expression of well-known platelet transcripts, and in total 6,343 consistently detectable transcripts. Extensive statistical bioinformatic analysis yielded 12 genes with consistently differential expression at a lenient FDR < 0.1, thereof 8 protein-coding genes and 2 genes with known expression in platelets (MACF1 and ITGB3BP). Three of the four differentially expressed noncoding genes were YRNAs (RNY1, RNY3, and RNY4) which were all downregulated in DM. 23 miRNAs were differentially expressed between the two groups. Of the 13 miRNAs with decreased expression in the diabetic group, 8 belonged to the DLK1-DIO3 gene region on chromosome 14q32.2.

CONCLUSIONS

In this study, uncontrolled DM had a remote impact on different components of the platelet transcriptome. Increased expression of MACF1, together with supporting predicted mRNA-miRNA interactions as well as reduced expression of RNYs in platelets, may reflect subclinical platelet activation in uncontrolled DM.

Platelet-Enriched MicroRNAs and Cardiovascular Homeostasis

SIGNIFICANCE

Platelets are anucleate blood cells that are involved in hemostasis and thrombosis. Although no longer able to generate ribonucleic acid (RNA) de novo, platelets contain messenger RNA (mRNA), YRNA fragments, and premature microRNAs (miRNAs) that they inherit from megakaryocytes. Recent Advances: Novel sequencing techniques have helped identify the unexpectedly large number of RNA species present in platelets. Throughout their life time, platelets can process the pre-existing pool of premature miRNA to give the fully functional miRNA that can regulate platelet protein expression and function.

CRITICAL ISSUES

Platelets make a major contribution to the circulating miRNA pool but platelet activation can have major consequences on Dicer levels and thus miRNA maturation, which has implications for studies that are focused on screening-stored platelets.

FUTURE DIRECTIONS

It will be important to determine the importance of platelets as donors for miRNA-containing microvesicles that can be taken up and processed by other (particularly vascular) cells, thus contributing to homeostasis as well as disease progression. Antioxid. Redox Signal. 29, 902-921.

Platelet RNA as a circulating biomarker trove for cancer diagnostics

Platelets are multifunctional cell fragments, circulating in blood in high abundance. Platelets assist in thrombus formation, sensing of pathogens entering the blood stream, signaling to immune cells, releasing vascular remodeling factors, and, negatively, enhancing cancer metastasis. Platelets are 'educated' by their environment, including in patients with cancer. Cancer cells appear to initiate intraplatelet signaling, resulting in splicing of platelet pre-mRNAs, and enhance secretion of cytokines. Platelets can induce leukocyte and endothelial cell modeling factors, for example, through adenine nucleotides (ATP), thereby facilitating extravasation of cancer cells. Besides releasing factors, platelets can also sequester RNAs and proteins released by cancer cells. Thus, platelets actively respond to queues from local and systemic conditions, thereby altering their transcriptome and molecular content. Platelets contain a rich repertoire of RNA species, including mRNAs, small non-coding RNAs and circular RNAs; although studies regarding the functionality of the various platelet RNA species require more attention. Recent advances in high-throughput characterization of platelet mRNAs revealed 10 to > 1000 altered mRNAs in platelets in the presence of disease. Hence, platelet RNA appears to be dynamically affected by pathological conditions, thus possibly providing opportunities to use platelet RNA as diagnostic, prognostic, predictive, or monitoring biomarkers. In this review, we cover the literature regarding the platelet RNA families, processing of platelet RNAs, and the potential application of platelet RNA as disease biomarkers.

MicroRNA Biomarkers and Platelet Reactivity: The Clot Thickens

Over the last few years, several groups have evaluated the potential of microRNAs (miRNAs) as biomarkers for cardiometabolic disease. In this review, we discuss the emerging literature on the role of miRNAs and other small noncoding RNAs in platelets and in the circulation, and the potential use of miRNAs as biomarkers for platelet activation. Platelets are a major source of miRNAs, YRNAs, and circular RNAs. By harnessing multiomics approaches, we may gain valuable insights into their potential function. Because not all miRNAs are detectable in the circulation, we also created a gene ontology annotation for circulating miRNAs using the gene ontology term extracellular space as part of blood plasma. Finally, we share key insights for measuring circulating miRNAs. We propose ways to standardize miRNA measurements, in particular by using platelet-poor plasma to avoid confounding caused by residual platelets in plasma or by adding RNase inhibitors to serum to reduce degradation. This should enhance comparability of miRNA measurements across different cohorts. We provide recommendations for future miRNA biomarker studies, emphasizing the need for accurate interpretation within a biological and methodological context.

Hyperglycaemia suppresses microRNA expression in platelets to increase P2RY12 and SELP levels in type 2 diabetes mellitus

Megakaryocyte (MK)-derived miRNAs have been detected in platelets. Here, we analysed the expression of platelet and circulating miR-223, miR-26b, miR-126 and miR-140 that might be altered with their target mRNAs in type 2 diabetes mellitus (DM2). MiRNAs were isolated from leukocyte-depleted platelets and plasma samples obtained from 28 obese DM2, 19 non-DM obese and 23 healthy individuals. The effect of hyperglycaemia on miRNAs was also evaluated in MKs using MEG-01 and K562 cells under hyperglycaemic conditions after 8 hours up to four weeks. Quantitation of mature miRNA, pre-miRNAs and target mRNA levels (P2RY12 and SELP) were measured by RT-qPCR. To prove the association of miR-26b and miR-140 with SELP (P-selectin) mRNA level, overexpression or inhibition of these miRNAs in MEG-01 MKs was performed using mimics or anti-miRNAs, respectively. The contribution of calpain substrate Dicer to modulation of miRNAs was studied by calpain inhibition. Platelet activation was evaluated via surface P-selectin by flow cytometry. Mature and pre-forms of investigated miRNAs were significantly reduced in DM2, and platelet P2RY12 and SELP mRNA levels were elevated by two-fold at increased platelet activation compared to controls. Significantly blunted miRNA expressions were observed by hyperglycaemia in MEG-01 and K562-MK cells versus baseline values, while the manipulation of miR-26b and miR-140 expression affected SELP mRNA level. Calpeptin pretreatment restored miRNA levels in hyperglycaemic MKs. Overall, miR-223, miR-26b, miR-126 and miR-140 are expressed at a lower level in platelets and MKs in DM2 causing upregulation of P2RY12 and SELP mRNAs that may contribute to adverse platelet function.

Hyperglycaemia-induced reciprocal changes in miR-30c and PAI-1 expression in platelets

Type 2 diabetic mellitus (DM2) is associated with accelerated thrombotic complications and is characterized by high levels of plasminogen activator inhibitor-1 (PAI-1). Recent studies show that human platelets have high levels of miR-30c and synthesize considerable active PAI-1. The underlying mechanism of how PAI-1 expression is upregulated in DM2 is poorly understood. We now report that hyperglycaemia-induced repression of miR-30c increases PAI-1 expression and thrombus formation in DM2. Bioinformatic analysis and identification of miRNA targets were assessed using luciferase assays, quantitative real-time PCR and western blots invitro and in vivo. The changes in miR-30c and PAI-1 levels were identified in platelets from healthy and diabetic individuals. We found that miR-30c directly targeted the 3′ UTR of PAI-1 and negatively regulated its expression. miR-30c was negatively correlated with glucose and HbA1c levels in DM2. In HFD-fed diabetic mice, increasing miR-30c expression by lenti-miR-30c significantly decreased the PAI-1 expression and prolonged the time to occlusion in an arterial thrombosis model. Platelet depletion/reinfusion experiments generating mice with selective ablation of PAI-1 demonstrate a major contribution by platelet-derived PAI-1 in the treatment of lenti-miR-30c to thrombus formation. These results provide important implications regarding the regulation of fibrinolysis by platelet miRNA under diabetic mellitus.

Development of a circulating miRNA assay to monitor tumor burden: From mouse to man

Circulating miRNA stability suggests potential utility of miRNA based biomarkers to monitor tumor burden and/or progression, particularly in cancer types where serial biopsy is impractical. Assessment of miRNA specificity and sensitivity is challenging within the clinical setting. To address this, circulating miRNAs were examined in mice bearing human SCLC tumor xenografts and SCLC patient derived circulating tumor cell explant models (CDX). We identified 49 miRNAs using human TaqMan Low Density Arrays readily detectable in 10 μl tail vein plasma from mice carrying H526 SCLC xenografts that were low or undetectable in non-tumor bearing controls. Circulating miR-95 measured serially in mice bearing CDX was detected with tumor volumes as low as 10 mm(3) and faithfully reported subsequent tumor growth. Having established assay sensitivity in mouse models, we identified 26 miRNAs that were elevated in a stage dependent manner in a pilot study of plasma from SCLC patients (n = 16) compared to healthy controls (n = 11) that were also elevated in the mouse models. We selected a smaller panel of 10 previously reported miRNAs (miRs 95, 141, 200a, 200b, 200c, 210, 335#, 375, 429) that were consistently elevated in SCLC, some of which are reported to be elevated in other cancer types. Using a multiplex qPCR assay, elevated levels of miRNAs across the panel were also observed in a further 66 patients with non-small cell lung, colorectal or pancreatic cancers. The utility of this circulating miRNA panel as an early warning of tumor progression across several tumor types merits further evaluation in larger studies.

Platelets and Their Interactions with Other Immune Cells

Platelets are anucleate blood cells, long known to be critically involved in hemostasis and thrombosis. In addition to their role in blood clots, increasing evidence reveals significant roles for platelets in inflammation and immunity. However, the notion that platelets represent immune cells is not broadly recognized in the field of Physiology. This article reviews the role of platelets in inflammation and immune responses, and highlights their interactions with other immune cells, including examples of major functional consequences of these interactions.

PRP and articular cartilage: a clinical update

The convincing background of the recent studies, investigating the different potentials of platelet-rich plasma, offers the clinician an appealing alternative for the treatment of cartilage lesions and osteoarthritis. Recent evidences in literature have shown that PRP may be helpful both as an adjuvant for surgical treatment of cartilage defects and as a therapeutic tool by intra-articular injection in patients affected by osteoarthritis. In this review, the authors introduce the trophic and anti-inflammatory properties of PRP and the different products of the available platelet concentrates. Then, in a complex scenario made of a great number of clinical variables, they resume the current literature on the PRP applications in cartilage surgery as well as the use of intra-articular PRP injections for the conservative treatment of cartilage degenerative lesions and osteoarthritis in humans, available as both case series and comparative studies. The result of this review confirms the fascinating biological role of PRP, although many aspects yet remain to be clarified and the use of PRP in a clinical setting has to be considered still exploratory.

Dicer cleavage by calpain determines platelet microRNA levels and function in diabetes

RATIONALE

MicroRNAs (miRNAs) are short noncoding RNA species generated by the processing of longer precursors by the ribonucleases Drosha and Dicer. Platelets contain large amounts of miRNA that are altered by disease, in particular diabetes mellitus.

OBJECTIVE

This study determined why platelet miRNA levels are attenuated in diabetic individuals and how decreased levels of the platelet-enriched miRNA, miR-223, affect platelet function.

METHODS AND RESULTS

Dicer levels were altered in platelets from diabetic mice and patients, a change that could be attributed to the cleavage of the enzyme by calpain, resulting in loss of function. Diabetes mellitus in human subjects as well as in mice resulted in decreased levels of platelet miR-142, miR-143, miR-155, and miR-223. Focusing on only 1 of these miRNAs, miR-223 deletion in mice resulted in modestly enhanced platelet aggregation, the formation of large thrombi and delayed clot retraction compared with wild-type littermates. A similar dysregulation was detected in platelets from diabetic patients. Proteomic analysis of platelets from miR-223 knockout mice revealed increased levels of several proteins, including kindlin-3 and coagulation factor XIII-A. Whereas, kindlin-3 was indirectly regulated by miR-223, factor XIII was a direct target and both proteins were also altered in diabetic platelets. Treating diabetic mice with a calpain inhibitor prevented loss of platelet dicer as well as the diabetes mellitus-induced decrease in platelet miRNA levels and the upregulation of miR-223 target proteins.

CONCLUSIONS

Thus, calpain inhibition may be one means of normalizing platelet miRNA processing as well as platelet function in diabetes mellitus.

Activating stimuli induce platelet microRNA modulation and proteome reorganisation

Platelets carry megakaryocyte-derived mRNAs whose translation efficiency before and during activation is not known, although this can greatly affect platelet functions, both under basal conditions and in response to physiological and pathological stimuli, such as those involved in acute coronary syndromes. Aim of the present study was to determine whether changes in microRNA (miRNA) expression occur in response to activating stimuli and whether this affects activity and composition of platelet transcriptome and proteome. Purified platelet-rich plasmas from healthy volunteers were collected and activated with ADP, collagen, or thrombin receptor activating peptide. Transcriptome analysis by RNA-Seq revealed that platelet transcriptome remained largely unaffected within the first 2 hours of stimulation. In contrast, quantitative proteomics showed that almost half of > 700 proteins quantified were modulated under the same conditions. Global miRNA analysis indicated that reorganisation of platelet proteome occurring during activation reflected changes in mature miRNA expression, which therefore, appears to be the main driver of the observed discrepancy between transcriptome and proteome changes. Platelet functions significantly affected by modulated miRNAs include, among others, the integrin/cytoskeletal, coagulation and inflammatory-immune response pathways. These results demonstrate a significant reprogramming of the platelet miRNome during activation, with consequent significant changes in platelet proteome and provide for the first time substantial evidence that fine-tuning of resident mRNA translation by miRNAs is a key event in platelet pathophysiology.

New paradigms in thrombosis: novel mediators and biomarkers platelet RNA transfer

Platelets, anucleated cells with a central role in hemostasis and inflammation, contain messenger RNAs and microRNAs of unknown functionality and clinical relevance. Historically, platelet RNA was viewed as merely a remnant of platelet biogenesis; however, several studies now refute this assumption. Studies have shown that platelets can actively translate RNA to protein and that specific RNA profiles correlate with select human clinical phenotypes. These studies support a more fluid role for platelet RNA in platelet function and disease development. Our lab and others have recently studied the platelet's unique ability to transfer RNA to recipient cells and the effect this transfer has on the recipient cells' functions. This transfer may represent a previously unknown form of vascular cell communication and modulation. Unlike the well-characterized thrombotic properties of platelets, the nature and purpose of platelet RNA transfer has not been determined, partly due to limitations in techniques used to manipulate platelet RNA profiles. Defining the mechanism of RNA transfer and its role in the vascular system will allow for the better understanding of how platelets function in both their traditional thrombotic role and non-traditional functions, potentially having widespread implications in several fields.

A tour through the transcriptional landscape of platelets

The RNA code found within a platelet and alterations of that code continue to shed light onto the mechanistic underpinnings of platelet function and dysfunction. It is now known that features of messenger RNA (mRNA) in platelets mirror those of nucleated cells. This review serves as a tour guide for readers interested in developing a greater understanding of platelet mRNA. The tour provides an in-depth and interactive examination of platelet mRNA, especially in the context of next-generation RNA sequencing. At the end of the expedition, the reader will have a better grasp of the topography of platelet mRNA and how it impacts platelet function in health and disease.

MicroRNA expression differences in human hematopoietic cell lineages enable regulated transgene expression

Blood microRNA (miRNA) levels have been associated with and shown to participate in disease pathophysiology. However, the hematopoietic cell of origin of blood miRNAs and the individual blood cell miRNA profiles are poorly understood. We report the miRNA content of highly purified normal hematopoietic cells from the same individuals. Although T-cells, B-cells and granulocytes had the highest miRNA content per cell, erythrocytes contributed more cellular miRNA to the blood, followed by granulocytes and platelets. miRNA profiling revealed different patterns and different expression levels of miRNA specific for each lineage. miR-30c-5p was determined to be an appropriate reference normalizer for cross-cell qRT-PCR comparisons. miRNA profiling of 5 hematopoietic cell lines revealed differential expression of miR-125a-5p. We demonstrated endogenous levels of miR-125a-5p regulate reporter gene expression in Meg-01 and Jurkat cells by (1) constructs containing binding sites for miR-125a-5p or (2) over-expressing or inhibiting miR-125a-5p. This quantitative analysis of the miRNA profiles of peripheral blood cells identifies the circulating hematopoietic cellular miRNAs, supports the use of miRNA profiles for distinguishing different hematopoietic lineages and suggests that endogenously expressed miRNAs can be exploited to regulate transgene expression in a cell-specific manner.

Controlled type II diabetes mellitus has no major influence on platelet micro-RNA expression. Results from micro-array profiling in a cohort of 60 patients

Diabetes mellitus as a major contributor to cardiovascular disease burden induces dysfunctional platelets. Platelets contain abundant miRNAs, which are linked to inflammatory responses and, thus, may play a role in atherogenesis. While diabetes mellitus affects plasma miRNAs, no data exist on platelet miRNA profiles in this disease. Therefore, this study sought to explore the miRNA profile of platelets in patients with diabetes mellitus that is unrelated to the presence or absence of coronary artery disease (CAD). Platelet miRNA profiles were assessed in stable diabetic and non-diabetic patients (each n=30); 15 patients in each group had CAD. Platelet miRNA was isolated from leucocyte-depleted platelet-rich plasma, and miRNA profiling was performed using LNA micro-array technology (miRBase18.0, containing 1,917 human miRNAs). Effects of diabetes mellitus were explored by univariate statistical tests for each miRNA, adjusted for potential confounders, and by developing a multivariable signature; evaluated by resampling techniques. Platelets in non-diabetic patients demonstrated miRNA expression profiles comparable to previous data. The miRNA profiles of platelets in diabetics were similar. Statistical analysis unveiled three miRNAs (miR-377-5p, miR-628-3p, miR-3137) with high reselection probabilities in resampling techniques, corresponding to signatures with modest discriminatory performance. Functional annotation of predicted targets for these miRNAs pointed towards an influence of diabetes mellitus on mRNA processing. We did not find major differences in platelet miRNA profiles between diabetics and non-diabetics. Minor differences pertained to miRNAs associated with mRNA processing. Thus, described differences in plasma miRNAs between diabetic and non-diabetic patients cannot be explained by plain changes in platelet miRNA profile.

MicroRNA expression profile in human macrophages in response to Leishmania major infection

Background

Leishmania (L.) are intracellular protozoan parasites able to survive and replicate in the hostile phagolysosomal environment of infected macrophages. They cause leishmaniasis, a heterogeneous group of worldwide-distributed affections, representing a paradigm of neglected diseases that are mainly embedded in impoverished populations. To establish successful infection and ensure their own survival, Leishmania have developed sophisticated strategies to subvert the host macrophage responses. Despite a wealth of gained crucial information, these strategies still remain poorly understood. MicroRNAs (miRNAs), an evolutionarily conserved class of endogenous 22-nucleotide non-coding RNAs, are described to participate in the regulation of almost every cellular process investigated so far. They regulate the expression of target genes both at the levels of mRNA stability and translation; changes in their expression have a profound effect on their target transcripts.

Methodology/Principal Findings

We report in this study a comprehensive analysis of miRNA expression profiles in L. major-infected human primary macrophages of three healthy donors assessed at different time-points post-infection (three to 24 h). We show that expression of 64 out of 365 analyzed miRNAs was consistently deregulated upon infection with the same trends in all donors. Among these, several are known to be induced by TLR-dependent responses. GO enrichment analysis of experimentally validated miRNA-targeted genes revealed that several pathways and molecular functions were disturbed upon parasite infection. Finally, following parasite infection, miR-210 abundance was enhanced in HIF-1α-dependent manner, though it did not contribute to inhibiting anti-apoptotic pathways through pro-apoptotic caspase-3 regulation.

Conclusions/Significance

Our data suggest that alteration in miRNA levels likely plays an important role in regulating macrophage functions following L. major infection. These results could contribute to better understanding of the dynamics of gene expression in host cells during leishmaniasis.

Leishmania parasites belong to different species, each one characterized by specific vectors and reservoirs, and causes cutaneous or visceral disease(s) of variable clinical presentation and severity. In its mammalian host, the parasite is an obligate intracellular pathogen infecting the monocyte/macrophage lineage. Leishmania have developed ambiguous relationships with macrophages. Indeed, these cells are the shelter of invading parasites, where they will grow and eventually will reside in a silent state for life. But macrophages are also the cells that participate, through the induction of several pro-inflammatory mediators and antigen presentation, to shape the host immune response and ultimately kill the invader. To subvert these anti-parasite responses, Leishmania manipulate the host machinery for their own differentiation and survival. We aimed to evaluate the impact of L. major (the causative agent of zoonotic cutaneous leishmaniasis) infection on deregulation of non-coding miRNAs, a class of important regulators of gene expression. Our results revealed the implication of several miRNAs on macrophage fate upon parasite infection through regulation of different pathways, including cell death. Our findings provided a new insight for understanding mechanisms governing this miRNA deregulation by parasite infection and will help to provide clues for the development of control strategies for this disease.

Identification of cytochrome P450s involved in the metabolism of arachidonic acid in human platelets

Although cytochrome P450s (CYPs) have been identified in most human cells, identification of CYPs in human platelets remains poorly explored. CYP expressions in human platelets were screened by using reverse transcriptase-polymerase chain reaction and western blot analysis followed by functional assays using arachidonic acid (ARA). CYP1A1, 2U1, 2J2, 4A11, 4F2, and 5A1 were expressed as both proteins and mRNAs in platelets. Ethoxyresorufin-O-deethylase activity was observed in platelets and this activity was significantly decreased after treatment with the general P450 inhibitor SKF-525A and the CYP1A inhibitor, α-naphthoflavone (40-45%, P<0.001). Seventeen ARA metabolites were detected in ARA-treated platelets. Among these, the levels of 20-hydroxyeicosatetraenoic acid and epoxyeicosatrienoic acids were significantly decreased with the treatment of the P450 ω-hydroxylase inhibitor 17-octadecynoic acid (P<0.05-0.001). In summary, multiple ARA-metabolizing P450s were identified in human platelets. These findings may provide an important resource for understanding physiological function of platelet.

MicroRNAs in platelet production and activation

Recent work by the Encyclopedia of DNA Elements project showed that non-protein-coding RNAs account for an unexpectedly large proportion of the human genome. Among these non-coding RNAs are microRNAs (miRNAs), which are small RNA molecules that modulate protein expression by degrading mRNA or repressing mRNA translation. MiRNAs have been shown to play important roles in hematopoiesis including embryonic stem cell differentiation, erythropoiesis, granulocytopoiesis/monocytopoiesis, lymphopoiesis, and megakaryocytopoiesis. Additionally, disordered miRNA biogenesis and quantitative or qualitative alterations in miRNAs and their targets are associated with hematological pathologies. Platelets contain machinery to process pre-miRNAs into mature miRNAs, and specific platelet miRNA levels have been found to correlate with platelet reactivity. This review summarizes the current state of knowledge of miRNAs in megakaryocytes and platelets, and the exciting possibilities for future megakaryocyte-platelet transcriptome research.

Sensitive PCR-based quantitation of cell-free circulating microRNAs

Cell-free microRNAs (miRNAs) that circulate in the blood are promising surrogate biomarkers of disease and physiological processes. The ease of quantifying specific miRNA species using made-to-order approaches based on Taq-polymerase has led to numerous studies that have identified changes in the abundance of circulating cell-free miRNA species that correlate with pathology or other events. The growing interest in developing miRNAs as blood biomarkers necessitates the careful consideration of the unique properties of such body fluids that can make the reproducible and quantitative assessment of RNA abundance challenging. For example, enzymes involved in the amplification and analysis of RNA can be affected by blood components that copurify with miRNA. Thus, if miRNAs are to be effectively utilized as biomarkers, it is important to establish standardized protocols for blood collection and miRNA analysis to ensure accurate quantitation. Here we outline several considerations, including the type of collection tube used in sampling, the influence of added anticoagulants and stabilizers, sample processing, enrichment of vesicular and other miRNA species, RNA extraction approaches and enzyme selection, that affect quantitation of miRNA isolated from plasma and should be considered in order to achieve reproducible, sensitive and accurate quantitation.

Platelet microRNAs: From platelet biology to possible disease biomarkers and therapeutic targets

Although anucleated, platelets contain megakaryocyte-derived messenger ribonucleic acid (mRNA) which can be translated to produce protein molecules. Recently, platelets have been found to contain small (∼23 base pair) non-coding microRNAs (miRNAs) derived from hairpin-like precursors. MiRNAs can specifically silence their mRNA targets regulating mRNA translation. Platelet miRNAs are reported to bind to important platelet target mRNAs involved in platelet reactivity including P2Y12 ADP receptor, GPIIb receptor, and cyclic AMP-dependent protein kinase A. They also regulate important functions such as platelet shape change, granules secretion, and platelet activation. Platelet miRNAs were also proposed as biomarkers of arteriosclerosis, although their role in vascular inflammation needs to be elucidated. Further, the possibility of using miRNAs as therapeutic tools has emerged. Using synthetic oligo-nucleotides that antagonize miRNAs binding to their mRNAs-targets or synthetic miRNAs mimics that enhance endogenous miRNAs function potentially will ultimately lead to the manipulation of platelet miRNAs expression and function with significant effects on specific protein levels and overall platelet reactivity.