Blood extracellular vesicles from healthy individuals regulate hematopoietic stem cells as humans age

Exercise, healthy ageing, and the potential role of small extracellular vesicles

Extracellular vesicles (EVs) can be released from most cells in the body and act as intercellular messengers transferring information in their cargo to affect cellular function. A growing body of evidence suggests that a subset of EVs, referred to here as 'small extracellular vesicles' (sEVs), can accelerate or slow the processes of ageing and age-related diseases dependent on their molecular cargo and cellular origin. Continued exploration of the vast complexity of the sEV cargo aims to further characterise these systemic vehicles that may be targeted to ameliorate age-related pathologies. Marked progress in the development of mass spectrometry-based technologies means that it is now possible to characterise a significant proportion of the proteome of sEVs (surface and cargo) via unbiased proteomics. This information is vital for identifying biomarkers and the development of sEV-based therapeutics in the context of ageing. Although exercise and physical activity are prominent features in maintaining health in advancing years, the mechanisms responsible are unclear. A potential mechanism by which plasma sEVs released during exercise could influence ageing and senescence is via the increased delivery of cargo proteins that function as antioxidant enzymes or inhibitors of senescence. These have been observed to increase in sEVs following acute and chronic exercise, as identified via independent interrogation of high coverage, publicly available proteomic datasets. Establishing tropism and exchange of functionally active proteins by these processes represents a promising line of enquiry in implicating sEVs as biologically relevant mediators of the ageing process.

RNA landscapes of brain tissue and brain tissue-derived extracellular vesicles in simian immunodeficiency virus (SIV) infection and SIV-related central nervous system pathology

Introduction

Antiretroviral treatment regimens can effectively control HIV replication and some aspects of disease progression. However, molecular events in end-organ diseases such as central nervous system (CNS) disease are not yet fully understood, and routine eradication of latent reservoirs is not yet in reach. Brain tissue-derived extracellular vesicles (bdEVs) act locally in the source tissue and may indicate molecular mechanisms in HIV CNS pathology. Regulatory RNAs from EVs have emerged as important participants in HIV disease pathogenesis. Using brain tissue and bdEVs from the simian immunodeficiency virus (SIV) model of HIV disease, we profiled messenger RNAs (mRNAs), microRNAs (miRNAs), and circular RNAs (circRNAs), seeking to identify possible networks of RNA interaction in SIV infection and neuroinflammation.

Methods

Postmortem occipital cortex tissue were collected from pigtailed macaques: uninfected controls and SIV-infected subjects (acute phase and chronic phase with or without CNS pathology). bdEVs were separated and characterized in accordance with international consensus standards. RNAs from bdEVs and source tissue were used for sequencing and qPCR to detect mRNA, miRNA, and circRNA levels.

Results

Multiple dysregulated bdEV RNAs, including mRNAs, miRNAs, and circRNAs, were identified in acute infection and chronic infection with pathology. Most dysregulated mRNAs in bdEVs reflected dysregulation in their source tissues. These mRNAs are disproportionately involved in inflammation and immune responses, especially interferon pathways. For miRNAs, qPCR assays confirmed differential abundance of miR-19a-3p, let-7a-5p, and miR-29a-3p (acute SIV infection), and miR-146a-5p and miR-449a-5p (chronic with pathology) in bdEVs. In addition, target prediction suggested that several circRNAs that were differentially abundant in source tissue might be responsible for specific differences in small RNA levels in bdEVs during SIV infection.

Conclusions

RNA profiling of bdEVs and source tissues reveals potential regulatory networks in SIV infection and SIV-related CNS pathology.

The profile of circulating extracellular vesicles depending on the age of the donor potentially drives the rejuvenation or senescence fate of hematopoietic stem cells

Blood donor age has become a major concern due to the age-associated variations in the content and concentration of circulating extracellular nano-sized vesicles (EVs), including exosomes. These EVs mirror the state of their parental cells and transfer it to the recipient cells via biological messengers such as microRNAs (miRNAs, miRs). Since the behavior of hematopoietic stem cells (HSCs) is potentially affected by the miRs of plasma-derived EVs, a better understanding of the content of EVs is important for the safety and efficacy perspectives in blood transfusion medicine. Herein, we investigated whether the plasma-derived EVs of young (18-25 years) and elderly human donors (45-60 years) can deliver "youth" or "aging" signals into human umbilical cord blood (hUCB)-derived HSCs in vitro. The results showed that EVs altered the growth functionality and differentiation of HSCs depending on the age of the donor from which they are derived. EVs of young donors could ameliorate the proliferation and self-renewal potential of HSCs whereas those of aged donors induced senescence-associated differentiation in the target cells, particularly toward the myeloid lineage. These findings were confirmed by flow cytometric analysis of surface markers and microarray profiling of genes related to stemness (e.g., SOX-1, Nanog) and differentiation (e.g., PU-1). The results displayed an up-regulation of miR-29 and miR-96 and a down-regulation of miR-146 in EVs derived from elderly donors. The higher expression of miR-29 and miR-96 contributed to the diminished expression of CDK-6 and CDKN1A (p21), promoting senescence fate via cell growth suppression, while the lower expression of miR-146 positively regulates TRAF-6 expression to accelerate biological aging. Our findings reveal that plasma-derived EVs from young donors can reverse the aging-associated changes in HSCs, while vice versa, the EVs from elderly donors rather promote the senescence process.

Ageing and rejuvenation of tissue stem cells and their niches

Most adult organs contain regenerative stem cells, often organized in specific niches. Stem cell function is critical for tissue homeostasis and repair upon injury, and it is dependent on interactions with the niche. During ageing, stem cells decline in their regenerative potential and ability to give rise to differentiated cells in the tissue, which is associated with a deterioration of tissue integrity and health. Ageing-associated changes in regenerative tissue regions include defects in maintenance of stem cell quiescence, differentiation ability and bias, clonal expansion and infiltration of immune cells in the niche. In this Review, we discuss cellular and molecular mechanisms underlying ageing in the regenerative regions of different tissues as well as potential rejuvenation strategies. We focus primarily on brain, muscle and blood tissues, but also provide examples from other tissues, such as skin and intestine. We describe the complex interactions between different cell types, non-cell-autonomous mechanisms between ageing niches and stem cells, and the influence of systemic factors. We also compare different interventions for the rejuvenation of old regenerative regions. Future outlooks in the field of stem cell ageing are discussed, including strategies to counter ageing and age-dependent disease.

A Computational Approach to Identification of Candidate Biomarkers in High-Dimensional Molecular Data

Complex high-dimensional datasets that are challenging to analyze are frequently produced through ‘-omics’ profiling. Typically, these datasets contain more genomic features than samples, limiting the use of multivariable statistical and machine learning-based approaches to analysis. Therefore, effective alternative approaches are urgently needed to identify features-of-interest in ‘-omics’ data. In this study, we present the molecular feature selection tool, a novel, ensemble-based, feature selection application for identifying candidate biomarkers in ‘-omics’ data. As proof-of-principle, we applied the molecular feature selection tool to identify a small set of immune-related genes as potential biomarkers of three prostate adenocarcinoma subtypes. Furthermore, we tested the selected genes in a model to classify the three subtypes and compared the results to models built using all genes and all differentially expressed genes. Genes identified with the molecular feature selection tool performed better than the other models in this study in all comparison metrics: accuracy, precision, recall, and F1-score using a significantly smaller set of genes. In addition, we developed a simple graphical user interface for the molecular feature selection tool, which is available for free download. This user-friendly interface is a valuable tool for the identification of potential biomarkers in gene expression datasets and is an asset for biomarker discovery studies.

Cell and Cell-Free Therapies to Counteract Human Premature and Physiological Aging: MSCs Come to Light

The progressive loss of the regenerative potential of tissues is one of the most obvious consequences of aging, driven by altered intercellular communication, cell senescence and niche-specific stem cell exhaustion, among other drivers. Mesenchymal tissues, such as bone, cartilage and fat, which originate from mesenchymal stem cell (MSC) differentiation, are especially affected by aging. Senescent MSCs show limited proliferative capacity and impairment in key defining features: their multipotent differentiation and secretory abilities, leading to diminished function and deleterious consequences for tissue homeostasis. In the past few years, several interventions to improve human healthspan by counteracting the cellular and molecular consequences of aging have moved closer to the clinic. Taking into account the MSC exhaustion occurring in aging, advanced therapies based on the potential use of young allogeneic MSCs and derivatives, such as extracellular vesicles (EVs), are gaining attention. Based on encouraging pre-clinical and clinical data, this review assesses the strong potential of MSC-based (cell and cell-free) therapies to counteract age-related consequences in both physiological and premature aging scenarios. We also discuss the mechanisms of action of these therapies and the possibility of enhancing their clinical potential by exposing MSCs to niche-relevant signals.

An Isolation System to Collect High Quality and Purity Extracellular Vesicles from Serum

Purpose

Extracellular vesicles (EVs) are membrane-encapsulated nanoparticles that function as carriers and play a role in intercellular communication. There are a large number of EVs in the blood and serve as an indicator of pathophysiological conditions. Studies on the basics and application of EVs are hampered by the limitations of current protocols to isolate EVs from blood. However, current isolation methods are difficult to achieve a balance between yield and purity.

Methods

Firstly, we use Sepharose-4B to build a self-made size exclusion chromatography (SEC) column and perform separation and characteristics. Then, we use the SEC column to systematically compare the efficiency with the most common EV isolation methods: Ultracentrifugation (UC) and total exosomes isolation commercial kit (TEI). The EVs isolated through different methods were characterized the yield and size of EVs, analyzed their protein profiles, the morphology and purity were observed under the transmission electron microscope. To further improve the quality and purity, we combined SEC and UC methods and established a two-steps method to isolated EVs from serum.

Results

Self-made SEC column can well separate EVs from complex serum protein, and EVs enriched in the 8–13 fractions with good morphology and yield. By systematically compare SEC with the commonly used UC and TEI kit, SEC is outstanding in all aspects and balances both isolation purity and yield. However, using the SEC method alone still has certain limitations and residual impurities. The SEC+UC combined method can cleverly solve the shortcomings of SEC and optimize the quality and purity of EVs from serum, which is much better than using one method alone.

Conclusion

Our study presents the combination of size-exclusion chromatography and ultracentrifugation as a feasible and time-saving method to isolate high-quality and purity extracellular vesicles from serum.

Extracellular vesicles tell all: How vesicle-mediated cellular communication shapes hematopoietic stem cell biology with increasing age

Extracellular vesicles (EVs) are small lipid bilayer particles containing biologically important cargo and impart regulatory changes in target cells. Despite the importance of EVs in cellular communication, there remains a gap in our understanding of how EVs influence HSC fate and, in turn, how aging and longevity are affected. This review summarizes the current literature dealing with how age-altered intercellular communication mediated by EVs influences HSC biology.

Extracellular Vesicles and Hematopoietic Stem Cell Aging

[Figure: see text].