Microparticles for Diagnosis of Graft-Versus-Host Disease After Allogeneic Stem Transplantation

Circulating extracellular vesicles as a predictive biomarker for acute graft-versus-host disease

The diagnosis and management of graft-versus-host disease (GVHD) have remained important challenges in allogeneic stem cell transplantation (allo-SCT). Novel diagnostic methods and therapeutic interventions are needed to further improve on patient outcomes. Extracellular vesicles (EV) are microvesicles formed by the inversion of the phospholipid bilayer of different cellular subtypes and have been described as biomarkers of cellular damage, activation, and intercellular signaling in numerous clinical scenarios. We studied the association between the levels of EV and the incidence of acute GVHD (aGVHD). Forty patients undergoing allo-SCT for hematological malignancies had their plasma collected at neutrophil engraftment. Using flow cytometry combined with fluorescent beads, the total circulating EV count (TEV) was established with annexin V positivity; CD61 positivity was used for platelet-derived EV (PEV), and CD235 positivity, for erythrocyte-derived EV (EryEV). TEV counts greater than 516/μL were associated with a higher cumulative incidence (CI) of grade II to IV aGVHD (54% vs. 21%; p = 0.02), as were EryEV counts above 357 /μL (CI of aGVHD: 59% vs. 26%; p = 0.04). In patients who are exposed to reduced intensity conditioning (RIC), stronger associations of both high TEV and EryEV counts with aGVHD were observed (77% vs. 22%; p = 0.003 and 89% vs. 27%; p = 0.002, respectively). PEV levels were not associated with the risk of aGVHD. Our data suggest that the measurement of cell-derived EV at engraftment can be used as a preemptive biomarker for acute GVHD.

Potential Novel Biomarkers in Chronic Graft-Versus-Host Disease

Prognostic, diagnostic or predictive biomarkers are urgently needed for assessment of chronic graft-versus-host disease (cGvHD), a major risk for patients undergoing allogeneic hematopoietic stem cell transplantation. The main goal of this review generated within the COST Action EUROGRAFT "Integrated European Network on Chronic Graft Versus Host Disease" was to identify potential novel biomarkers for cGvHD besides the widely accepted molecular and cellular biomarkers. Thus, the focus was on cellular biomarkers, alloantibodies, glycomics, endothelial derived particles, extracellular vesicles, microbiome, epigenetic and neurologic changes in cGvHD patients. Both host-reactive antibodies in general, and particularly alloantibodies have been associated with cGvHD and require further consideration. Glycans attached to IgG modulate its activity and represent a promising predictive and/or stratification biomarker for cGVHD. Furthermore, epigenetic changes such as microRNAs and DNA methylation represent potential biomarkers for monitoring cGvHD patients and novel targets for developing new treatment approaches. Finally, the microbiome likely affects the pathophysiology of cGvHD; bacterial strains as well as microbial metabolites could display potential biomarkers for dysbiosis and risk for the development of cGvHD. In summary, although there are no validated biomarkers currently available for clinical use to better inform on the diagnosis, prognosis or prediction of outcome for cGvHD, many novel sources of potential markers have shown promise and warrant further investigation using well characterized, multi-center patient cohorts.

Human bone marrow contains high levels of extracellular vesicles with a tissue-specific subtype distribution

Introduction

Extracellular vesicles (EV) are shed from a broad variety of cells and play an important role in activation of coagulation, cell to cell interaction and transport of membrane components. They are usually measured as circulating EV in peripheral blood (PB) and other body fluids. However, little is known about the distribution, presence and impact of EV and their subpopulations in bone marrow (BM). In our study, we focused on the analysis of different EV subtypes in human BM as compared to EV subsets in PB.

Methods

EV in BM and PB from 12 healthy stem cell donors were measured by flow-cytometry using Annexin V and cell-specific antibodies for hematopoietic stem cells, leucocytes, platelets, red blood cells, and endothelial cells. Additionally, concentrations of tissue factor-bearing EV were evaluated.

Results

High numbers of total EV were present in BM (median value [25–75 percentile]: 14.8 x10⁹/l [8.5–19.3]). Non-significantly lower numbers of total EV were measured in PB (9.2 x10⁹/l [3.8–14.5]). However, distribuation of EV subtypes showed substantial differences between BM and PB: In PB, distribution of EV fractions was similar as previously described. Most EV originated from platelets (93.9%), and only few EV were derived from leucocytes (4.5%), erythrocytes (1.8%), endothelial cells (1.0%), and hematopoietic stem cells (0.7%). In contrast, major fractions of BM-EV were derived from red blood cells or erythropoietic cells (43.2%), followed by megacaryocytes / platelets (27.6%), and by leucocytes as well as their progenitor cells (25,7%); only low EV proportions originated from endothelial cells and hematopoietic stem cells (2.0% and 1.5%, respectively). Similar fractions of tissue factor—bearing EV were found in BM and PB (1.3% and 0.9%).

Conculsion

Taken together, we describe EV numbers and their subtype distribution in the BM compartment for the first time. The tissue specific EV distribution reflects BM cell composition and favours the idea of a BM–PB barrier existing not only for cells, but also for EV.

Extracellular Vesicles as Markers and Mediators in Sepsis

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. It remains a highly lethal condition in which current tools for early diagnosis and therapeutic decision-making are far from ideal. Extracellular vesicles (EVs), 30 nm to several micrometers in size, are released from cells upon activation and apoptosis and express membrane epitopes specific for their parental cells. Since their discovery two decades ago, their role as biomarkers and mediators in various diseases has been intensively studied. However, their potential importance in the sepsis syndrome has gained attention only recently. Sepsis and EVs are both complex fields in which standardization has long been overdue. In this review, several topics are discussed. First, we review current studies on EVs in septic patients with emphasis on their variable quality and clinical utility. Second, we discuss the diagnostic and therapeutic potential of EVs as well as their role as facilitators of cell communication via micro RNA and the relevance of micro-organism-derived EVs. Third, we give an overview over the potential beneficial but also detrimental roles of EVs in sepsis. Finally, we focus on the role of EVs in selected intensive care scenarios such as coagulopathy, mechanical ventilation and blood transfusion. Overall, the prospect for EV use in septic patients is bright, ranging from rapid and precise (point-of-care) diagnostics, prevention of harmful iatrogenic interventions, to using EVs as guides of individualized therapy. Before the above is achieved, however, the EV research field requires reliable standardization of the current methods and development of new analytical procedures that can close the existing technological gaps.

Extracellular vesicles in blood, milk and body fluids of the female and male urogenital tract and with special regard to reproduction

Extracellular vesicles (EVs) are released from almost all cells and tissues. They are able to transport substances (e.g. proteins, RNA or DNA) at higher concentrations than in their environment and may adhere in a receptor-controlled manner to specific cells or tissues in order to release their content into the respective target structure. Blood contains high concentrations of EVs mainly derived from platelets, and, at a smaller amount, from erythrocytes. The female and male reproductive tracts produce EVs which may be associated with fertility or infertility and are released into body fluids and mucosas of the urogenital organs. In this review, the currently relevant detection methods are presented and critically compared. During pregnancy, placenta-derived EVs are dynamically detectable in peripheral blood with changing profiles depending upon progress of pregnancy and different pregnancy-associated pathologies, such as preeclampsia. EVs offer novel non-invasive diagnostic tools which may reflect the situation of the placenta and the foetus. EVs in urine have the potential of reflecting urogenital diseases including cancers of the neighbouring organs. Several methods for detection, quantification and phenotyping of EVs have been established, which include electron microscopy, flow cytometry, ELISA-like methods, Western blotting and analyses based on Brownian motion. This review article summarises the current knowledge about EVs in blood and cord blood, in the different compartments of the male and female reproductive tracts, in trophoblast cells from normal and pre-eclamptic pregnancies, in placenta ex vivo perfusate, in the amniotic fluid, and in breast milk, as well as their potential effects on natural killer cells as possible targets.

Endothelial microparticles carrying hedgehog-interacting protein induce continuous endothelial damage in the pathogenesis of acute graft-versus-host disease

Accumulating evidence suggests that endothelial microparticles (EMPs), a marker of endothelial damage, are elevated in acute graft-versus-host disease (aGVHD), and that endothelial damage is implicated in the pathogenesis of aGVHD, but the mechanisms remain elusive. In this study, we detected the plasma EMP levels and endothelial damage in patients and mice with aGVHD in vivo and then examined the effects of EMPs derived from injured endothelial cells (ECs) on endothelial damage and the role of hedgehog-interacting protein (HHIP) carried by EMPs in these effects in vitro. Our results showed that EMPs were persistently increased in the early posttransplantation phase in patients and mice with aGVHD. Meanwhile, endothelial damage was continuous in aGVHD mice, but was temporary in non-aGVHD mice after transplantation. In vitro, EMPs induced endothelial damage, including increased EC apoptosis, enhanced reactive oxygen species, decreased nitric oxide production and impaired angiogenic activity. Enhanced expression of HHIP, an antagonist for the Sonic hedgehog (SHH) signaling pathway, was observed in patients and mice with aGVHD and EMPs from injured ECs. The endothelial damage induced by EMPs was reversed when the HHIP incorporated into EMPs was silenced with an HHIP small interfering RNA or inhibited with the SHH pathway agonist, Smoothened agonist. This work supports a feasible vicious cycle in which EMPs generated during endothelial injury, in turn, aggravate endothelial damage by carrying HHIP into target ECs, contributing to the continuously deteriorating endothelial damage in the development of aGVHD. EMPs harboring HHIP would represent a potential therapeutic target for aGVHD.

Epithelial and Erythrocyte Microvesicles From Bronchoalveolar Lavage Fluid Are Elevated and Associated With Outcome in Chronic Lung Allograft Dysfunction

BACKGROUND

Chronic lung allograft dysfunction (CLAD) is the major outcome limitation for lung transplant recipients (LTR) after the first year, and therapies targeting immunological pathways show only limited success. Because microvesicles (MV) are biomarkers of endothelial dysfunction and coagulation but are also involved in immunological responses, we hypothesized that MV, found in bronchoalveolar lavage (BAL) fluids (BALF) of LTR at CLAD diagnosis, are elevated and potential prognostic biomarkers.

METHODS

The BALF was collected from 37 LTR at time point of CLAD diagnosis and 37 LTR without any complication at routinely performed BAL. The MV concentration and origin were determined by flow cytometry by detection of different antigens. Patient- and transplant-related risk factors were included in a retrospective statistical analysis.

RESULTS

The BALF-MV levels of epithelial and red blood cell (RBC) origin were significantly higher in CLAD patients (mean: 1533/μL and 158/μL) compared to controls (436/μL, 57/μL). The LTR with high levels of epithelial MV >580/μL showed a significantly shorter overall survival at 4 years after BAL (39.5%) compared to patients with low MV (66.4%) and this proofed to be an independent prognostic factor in multivariate Cox analysis (hazards ratio = 3.05). Furthermore, LTR with high levels of RBC MV ≥225/μL were also associated with worse disease-specific survival, with probabilities at 4 years after BAL of 85.8% vs. 36.0%.

CONCLUSIONS

Epithelial and RBC BALF-MV are elevated at CLAD diagnosis, have a potential as biomarkers, and support the hypothesis of a pathway, including activation of coagulation and complement, endothelial barrier dysfunction, and microangiopathy.

Extracellular vesicles in hematological disorders

Extracellular vesicles (EVs), comprised of exosomes, microparticles, apoptotic bodies, and other microvesicles, are shed from a variety of cells upon cell activation or apoptosis. EVs promote clot formation, mediate pro-inflammatory processes, transfer proteins and miRNA to cells, and induce cell signaling that regulates cell differentiation, proliferation, migration, invasion, and apoptosis. This paper will review the contribution of EVs in hematological disorders, including hemoglobinopathies (sickle cell disease, thalassemia), paroxysmal nocturnal hemoglobinuria, and hematological malignancies (lymphomas, myelomas, and acute and chronic leukemias).

Gateway to understanding microparticles: standardized isolation and identification of plasma membrane-derived vesicles

Microparticles (MPs) are small plasma membrane-derived vesicles that can expose molecules originating from their parental cells. As vectors of biological information they are likely to play an active role in both homeostasis and pathogenesis, making them promising biomarkers and nanomedicine tools. Therefore, there is an urgent need for standardization of MP isolation and analysis protocols to propel our understanding of MP biology to the next level. Based on current methodology and recent insights, this review proposes an optimized protocol for the isolation and biochemical characterization of MPs.

Microparticles: biomarkers and beyond

Membrane microparticles are submicron fragments of membrane shed into extracellular space from cells under conditions of stress/injury. They may be distinguished from other classes of extracellular vesicles (i.e. exosomes) on the basis of size, content and mechanism of formation. Microparticles are found in plasma and other biological fluids from healthy individuals and their levels are altered in various diseases, including diabetes, chronic kidney disease, pre-eclampsia and hypertension among others. Accordingly, they have been considered biomarkers of vascular injury and pro-thrombotic or pro-inflammatory conditions. In addition to this, emerging evidence suggests that microparticles are not simply a consequence of disease, but that they themselves may contribute to pathological processes. Thus microparticles appear to serve as both markers and mediators of pathology. The present review examines the evidence for microparticles as both biomarkers of, and contributors to, the progression of disease. Approaches for the detection of microparticles are summarized and novel concepts relating to the formation of microparticles and their biological effects are examined.

Red blood cell microparticles: clinical relevance

SUMMARY

Microparticles are small phospholipid vesicles of less than 1 µm released into the blood flow by various types of cells such as endothelial, platelet, white or red blood cells. They are involved in many biological and physiological processes including hemostasis. In addition, an elevated number of microparticles in the blood is observed in various pathological situations. In the context of transfusion, erythrocyte-derived microparticles are found in red blood cell concentrates. Their role is not elucidated, and they are considered as a type of storage lesion. The purpose of this review is to present recent data showing that erythrocyte-derived microparticles most likely play a role in transfusion medicine and could cause transfusion complications.