Isolation methodology is essential to the evaluation of the extracellular vesicle component of the senescence-associated secretory phenotype

RAB27B-regulated exosomes mediate LSC maintenance via resistance to senescence and crosstalk with the microenvironment

The fate of leukaemia stem cells (LSCs) is determined by both their inherent mechanisms and crosstalk with their niches. Although LSCs were confirmed to be eradicated by restarting senescence, the specific key regulators of LSC resistance to senescence and remodelling of the niche to obtain a microenvironment suitable for stemness remain unknown. Here, we found that RAB27B, a gene regulating exosome secretion, was overexpressed in LSCs and associated with the poor prognosis of acute myeloid leukaemia (AML) patients. The increased RAB27B in LSCs prevented their senescence and maintained their stemness in vitro and in vivo. Mechanically, the increased RAB27B expression in LSCs selectively promoted the loading and release of exosomes rich in senescence-inducing proteins by direct combination. Furthermore, RAB27B-regulated LSC-derived exosomes remodelled the niche and induced senescence of mesenchymal stem cells (MSCs) with increased RAB27B expression ex vivo and in vivo. The increased RAB27B in the senescent MSCs conversely promoted LSC maintenance ex vivo and in vivo via selective excretion of exosomes rich in stemness-promoting proteins. Therefore, we identified the specifically increased RAB27B in LSCs and their educated senescent MSCs as a hub molecule for LSC resistance to senescence and maintenance through crosstalk with its niche via selective exosome excretion.

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.

The role of extracellular vesicles in cellular senescence

Cellular senescence, an evolutionarily conserved mechanism that prevents the proliferation of damaged cells, is a very relevant cellular response involved in both physiological and pathological conditions. Even though senescent cells are stably growth arrested, they exhibit a complex and poorly understood secretory phenotype, known as senescence-associated secretory phenotype, composed of soluble proteins and extracellular vesicles (EVs). Extracellular vesicles were initially described as a waste management mechanism to remove damaged components of cellular metabolism, but increasing evidence shows that EVs could also play important roles in intercellular communication. Recently, some studies showed that EVs could have fundamental functions during cellular senescence. Our purpose in this review is to clarify the increasing literature on the role of EVs in cellular senescence as key mediators in cell-to-cell communication.

Nanoscale biophysical properties of small extracellular vesicles from senescent cells using atomic force microscopy, surface potential microscopy, and Raman spectroscopy

Cells secrete extracellular vesicles (EVs) carrying cell-of-origin markers to communicate with surrounding cells. EVs regulate physiological processes ranging from intercellular signaling to waste management. However, when senescent cells (SnCs) secrete EVs, the EVs, which are newly regarded as senescence-associated secretory phenotype (SASP) factors, can evoke inflammation, senescence induction, and metabolic disorders in neighboring cells. Unlike other soluble SASP factors, the biophysical properties of EVs, including small EVs (sEVs), derived from SnCs have not yet been investigated. In this study, sEVs were extracted from a human IMR90 lung fibroblast in vitro senescence model. Their biomechanical properties were mapped using atomic force microscopy-based quantitative nanomechanical techniques, surface potential microscopy, and Raman spectroscopy. The surfaces of sEVs derived from SnCs are slightly stiffer but their cores are softer than those of sEVs secreted from non-senescent cells (non-SnCs). This inversely proportional relationship between deformation and stiffness, attributed to a decrease in the concentration of genetic and protein materials inside the vesicles and the adsorption of positively charged SASP factors onto the vesicle surfaces, respectively, was found to be a peculiar characteristic of SnC-derived sEVs. Our results demonstrate that the biomechanical properties of SnC-derived sEVs differ from those of non-SnC-derived sEVs and provide insight into the mechanisms underlying their formation and composition.

A cryostat-based frozen section method to increase the yield of extracellular vesicles extracted from different tissues

Extracellular vesicles (EVs) are small vesicles mediating intercellular communications that have been widely used in disease diagnosis. Extracting EVs from tissues is of great importance, but current approaches are finite and the EV yield is limited. Here, the authors introduced a new method to increase EV yield based on frozen sectioning. With a standardized, semiautomated tissue-slicing procedure in a cryostat, the authors successfully isolated EVs from hearts, kidneys and stomachs. The morphology, size distribution and purity of those isolated EVs were evaluated. Additionally, compared with the traditional scalpel section method, they confirmed the higher yield of tissue-derived EVs with the cryostat-based method. The authors believe that the new method they developed would largely facilitate the research and clinical application of EVs.

Senescence-associated morphological profiles (SAMPs): an image-based phenotypic profiling method for evaluating the inter and intra model heterogeneity of senescence

Senescence occurs in response to a number of damaging stimuli to limit oncogenic transformation and cancer development. As no single, universal senescence marker has been discovered, the confident classification of senescence induction requires the parallel assessment of a series of hallmarks. Therefore, there is a growing need for “first-pass” tools of senescence identification to streamline experimental workflows and complement conventional markers.

Here, we utilise a high content, multidimensional phenotypic profiling-based approach, to assess the morphological profiles of senescent cells induced via a range of stimuli. In the context of senescence, we refer to these as senescence-associated morphological profiles (SAMPs), as they facilitate distinction between senescent and proliferating cells. The complexity of the profiles generated also allows exploration of the heterogeneity both between models of senescence and within an individual senescence model, providing a level of insight at the single cell level. Furthermore, we also demonstrate that these models are applicable to the assessment of senescence in vivo, which remains a key challenge for the field. Therefore, we believe SAMPs has the potential to serve as a useful addition in the repertoire of senescence researchers, either as a first-pass tool or as part of the established senescence hallmarks.

miR-6869-5p Transported by Plasma Extracellular Vesicles Mediates Renal Tubule Injury and Renin-Angiotensin System Activation in Obesity

Obesity increases the risk of other diseases, including kidney disease. Local renal tubular renin-angiotensin system (RAS) activation may play a role in obesity-associated kidney disease. Extracellular vehicles (EVs) transmit necessary information in obesity and cause remote organ damage, but the mechanism is unclear. The aim of the study was to investigate whether the plasma EVs cargo miR-6869-5p causes RAS activation and renal tubular damage. We isolated plasma EVs from obese and lean subjects and analyzed differentially-expressed miRNAs using RNA-seq. Then, EVs were co-cultured with human proximal renal tubular epithelial cells (PTECs) in vitro. Immunohistochemical pathology was used to assess the degree of RAS activation and tubule injury in vivo. The tubule damage-associated protein and RAS activation components were detected by Western blot. Obesity led to renal tubule injury and RAS activation in humans and mice. Obese-EVs induce RAS activation and renal tubular injury in PTECs. Importantly, miR-6869-5p-treated PTECs caused RAS activation and renal tubular injury, similar to Obese-EVs. Inhibiting miR-6869-5p decreased RAS activation and renal tubular damage. Our findings indicate that plasma Obese-EVs induce renal tubule injury and RAS activation via miR-6869-5p transport. Thus, miR-6869-5p in plasma Obese-EVs could be a therapeutic target for local RAS activation in obesity-associated kidney disease.

The significance of exosomal RNAs in the development, diagnosis, and treatment of pancreatic cancer

Exosomes are single-membrane, secreted organelles with a diameter of 30–200 nm, containing diverse bioactive constituents, including DNAs, RNAs, proteins, and lipids, with prominent molecular heterogeneity. Extensive studies indicate that exosomal RNAs (e.g., microRNAs, long non-coding RNAs, and circular RNAs) can interact with many types of cancers, associated with several hallmark features like tumor growth, metastasis, and resistance to therapy. Pancreatic cancer (PaCa) is among the most lethal cancers worldwide, emerging as the seventh foremost cause of cancer-related death in both sexes. Hence, revealing the specific pathogenesis and improving the clinical diagnosis and treatment process are urgently required. As the study of exosomes has become an active area of research, the functional connections between exosomes and PaCa have been deeply investigated. Among these, exosomal RNAs seem to play a significant role in the development, diagnosis, and treatment of PaCa. Exosomal RNAs delivery ultimately modulates the various features of PaCa, and many scholars have interpreted how exosomal RNAs contribute to the proliferation, angiogenesis, migration, invasion, metastasis, immune escape, and drug resistance in PaCa. Besides, recent studies emphasize that exosomal RNAs may serve as diagnostic and prognostic biomarkers or therapeutic targets for PaCa. In this review, we will introduce these recent insights focusing on the discoveries of the relationship between exosomal RNAs and PaCa, and the potentially diagnostic and therapeutic applications of exosomes in PaCa.

Isolation methodology is essential to the evaluation of the extracellular vesicle component of the senescence-associated secretory phenotype

A hallmark of senescence is the acquisition of an enhanced secretome comprising inflammatory mediators and tissue remodelling agents - the senescence-associated secretory phenotype (SASP). Through the SASP, senescent cells are hypothesised to contribute to both ageing and pathologies associated with age. Whilst soluble factors have been the most widely investigated components of the SASP, there is growing evidence that small extracellular vesicles (EVs) comprise functionally important constituents. Thus, dissecting the contribution of the soluble SASP from the vesicular component is crucial to elucidating the functional significance of senescent cell derived EVs. Here, we take advantage of a systematic proteomics based approach to determine that soluble SASP factors co-isolate with EVs following differential ultracentrifugation (dUC). We present size-exclusion chromatography (SEC) as a method for separation of the soluble and vesicular components of the senescent secretome and thus EV purification. Furthermore, we demonstrate that SEC EVs isolated from senescent cells contribute to non-cell autonomous paracrine senescence. Therefore, this work emphasises the requirement for methodological rigor due to the propensity of SASP components to co-isolate during dUC and provides a framework for future investigations of the vesicular component of the SASP.