Migrasomes provide regional cues for organ morphogenesis during zebrafish gastrulation

Calcium ions promote migrasome formation via Synaptotagmin-1

Migrasomes, organelles crucial for cell communication, undergo distinct stages of nucleation, maturation, and expansion. The regulatory mechanisms of migrasome formation, particularly through biological cues, remain largely unexplored. This study reveals that calcium is essential for migrasome formation. Furthermore, we identify that Synaptotagmin-1 (Syt1), a well-known calcium sensor, is not only enriched in migrasomes but also indispensable for their formation. The calcium-binding ability of Syt1 is key to initiating migrasome formation. The recruitment of Syt1 to migrasome formation sites (MFS) triggers the swelling of MFS into unstable precursors, which are subsequently stabilized through the sequential recruitment of tetraspanins. Our findings reveal how calcium regulates migrasome formation and propose a sequential interaction model involving Syt1 and Tetraspanins in the formation and stabilization of migrasomes.

Fluorescent, phosphorescent, magnetic resonance contrast and radioactive tracer labelling of extracellular vesicles

This review focusses on the significance of fluorescent, phosphorescent labelling and tracking of extracellular vesicles (EVs) for unravelling their biology, pathophysiology, and potential diagnostic and therapeutic uses. Various labeling strategies, such as lipid membrane, surface protein, luminal, nucleic acid, radionuclide, quantum dot labels, and metal complex-based stains, are evaluated for visualizing and characterizing EVs. Direct labelling with fluorescent lipophilic dyes is simple but generally lacks specificity, while surface protein labelling offers selectivity but may affect EV-cell interactions. Luminal and nucleic acid labelling strategies have their own advantages and challenges. Each labelling approach has strengths and weaknesses, which require a suitable probe and technique based on research goals, but new tetranuclear polypyridylruthenium(II) complexes as phosphorescent probes have strong phosphorescence, selective staining, and stability. Future research should prioritize the design of novel fluorescent probes and labelling platforms that can significantly enhance the efficiency, accuracy, and specificity of EV labeling, while preserving their composition and functionality. It is crucial to reduce false positive signals and explore the potential of multimodal imaging techniques to gain comprehensive insights into EVs.

Low-intensity pulsed ultrasound improves myocardial ischaemia‒reperfusion injury via migrasome-mediated mitocytosis

During myocardial ischaemia‒reperfusion injury (MIRI), the accumulation of damaged mitochondria could pose serious threats to the heart. The migrasomes, newly discovered mitocytosis-mediating organelles, selectively remove damaged mitochondria to provide mitochondrial quality control. Here, we utilised low-intensity pulsed ultrasound (LIPUS) on MIRI mice model and demonstrated that LIPUS reduced the infarcted area and improved cardiac dysfunction. Additionally, we found that LIPUS alleviated MIRI-induced mitochondrial dysfunction. We provided new evidence that LIPUS mechanical stimulation facilitated damaged mitochondrial excretion via migrasome-dependent mitocytosis. Inhibition the formation of migrasomes abolished the protective effect of LIPUS on MIRI. Mechanistically, LIPUS induced the formation of migrasomes by evoking the RhoA/Myosin II/F-actin pathway. Meanwhile, F-actin activated YAP nuclear translocation to transcriptionally activate the mitochondrial motor protein KIF5B and Drp1, which are indispensable for LIPUS-induced mitocytosis. These results revealed that LIPUS activates mitocytosis, a migrasome-dependent mitochondrial quality control mechanism, to protect against MIRI, underlining LIPUS as a safe and potentially non-invasive treatment for MIRI.

Migrasome biogenesis: when biochemistry meets biophysics on membranes

Migrasomes, newly identified organelles, play crucial roles in intercellular communication, contributing to organ development and angiogenesis. These vesicles, forming on retraction fibers of migrating cells, showcase a sophisticated architecture. Recent research reveals that migrasome biogenesis is a complicated and highly regulated process. This review summarizes the mechanisms governing migrasome formation, proposing a model in which biogenesis is understood through the lens of membrane microdomain assembly. It underscores the critical interplay between biochemistry and biophysics. The biogenesis unfolds in three distinct stages: nucleation, maturation, and expansion, each characterized by unique morphological, biochemical, and biophysical features. We also explore the broader implications of migrasome research in membrane biology and outline key unanswered questions that represent important directions for future investigation.

Localized, highly efficient secretion of signaling proteins by migrasomes

Migrasomes, enriched with signaling molecules such as chemokines, cytokines and angiogenic factors, play a pivotal role in the spatially defined delivery of these molecules, influencing critical physiological processes including organ morphogenesis and angiogenesis. The mechanism governing the accumulation of signaling molecules in migrasomes has been elusive. In this study, we show that secretory proteins, including signaling proteins, are transported into migrasomes by secretory carriers via both the constitutive and regulated secretion pathways. During cell migration, a substantial portion of these carriers is redirected to the rear of the cell and actively transported into migrasomes, driven by the actin-dependent motor protein Myosin-5a. Once at the migrasomes, these carriers fuse with the migrasome membrane through SNARE-mediated mechanisms. Inhibiting migrasome formation significantly reduces secretion, suggesting migrasomes as a principal secretion route in migrating cells. Our findings reveal a specialized, highly localized secretion paradigm in migrating cells, conceptually paralleling the targeted neurotransmitter release observed in neuronal systems.

Biophysical aspects of migrasome organelle formation and their diverse cellular functions

The transient cellular organelles known as migrasomes, which form during cell migration along retraction fibers, have emerged as a crutial factor in various fundamental cellular processes and pathologies. These membrane vesicles originate from local membrane swellings, encapsulate specific cytoplasmic content, and are eventually released to the extracellular environment or taken up by recipient cells. Migrasome biogenesis entails a sequential membrane remodeling process involving a complex interplay between various molecular factors such as tetraspanin proteins, and mechanical properties like membrane tension and bending rigidity. In this review, we summarize recent studies exploring the mechanism of migrasome formation. We emphasize how physical forces, together with molecular factors, shape migrasome biogenesis, and detail the involvement of migrasomes in various cellular processes and pathologies. A comprehensive understanding of the exact mechanism underlying migrasome formation and the identification of key molecules involved hold promise for advancing their therapeutic and diagnostic applications.

The migrasome, an organelle for cell-cell communication

Migrasomes, newly identified extracellular organelles produced by migrating cells, are observed widely across both in vivo and in vitro studies. These organelles, rich in signaling and bioactive molecules, are pivotal in a range of physiological functions. This opinion summarizes current understanding of migrasomes, highlighting their importance as a versatile mechanism for cell-cell communication. Furthermore, it examines their roles in health and disease and potential diagnostic and therapeutic applications, and addresses the emerging challenges and open questions in this developing field.

Mitochondrial mechanisms in the pathogenesis of chronic inflammatory musculoskeletal disorders

Chronic inflammatory musculoskeletal disorders characterized by prolonged muscle inflammation, resulting in enduring pain and diminished functionality, pose significant challenges for the patients. Emerging scientific evidence points to mitochondrial malfunction as a pivotal factor contributing to these ailments. Mitochondria play a critical role in powering skeletal muscle activity, but in the context of persistent inflammation, disruptions in their quantity, configuration, and performance have been well-documented. Various disturbances, encompassing alterations in mitochondrial dynamics (such as fission and fusion), calcium regulation, oxidative stress, biogenesis, and the process of mitophagy, are believed to play a central role in the progression of these disorders. Additionally, unfolded protein responses and the accumulation of fatty acids within muscle cells may adversely affect the internal milieu, impairing the equilibrium of mitochondrial functioning. The structural discrepancies between different mitochondrial subsets namely, intramyofibrillar and subsarcolemmal mitochondria likely impact their metabolic capabilities and susceptibility to inflammatory influences. The release of signals from damaged mitochondria is known to incite inflammatory responses. Intriguingly, migrasomes and extracellular vesicles serve as vehicles for intercellular transfer of mitochondria, aiding in the removal of impaired mitochondria and regulation of inflammation. Viral infections have been implicated in inducing stress on mitochondria. Prolonged dysfunction of these vital organelles sustains oxidative harm, metabolic irregularities, and heightened cytokine release, impeding the body's ability to repair tissues. This review provides a comprehensive analysis of advancements in understanding changes in the intracellular environment, mitochondrial architecture and distribution, biogenesis, dynamics, autophagy, oxidative stress, cytokines associated with mitochondria, vesicular structures, and associated membranes in the context of chronic inflammatory musculoskeletal disorders. Strategies targeting key elements regulating mitochondrial quality exhibit promise in the restoration of mitochondrial function, alleviation of inflammation, and enhancement of overall outcomes.

CD151-enriched migrasomes mediate hepatocellular carcinoma invasion by conditioning cancer cells and promoting angiogenesis

BACKGROUND

The tetraspanin family plays a pivotal role in the genesis of migrasomes, and Tetraspanin CD151 is also implicated in neovascularization within tumorous contexts. Nevertheless, research pertaining to the involvement of CD151 in hepatocellular carcinoma (HCC) neovascularization and its association with migrasomes remains inadequate.

METHODS

To investigate the correlation between CD151 and migrasome marker TSPAN4 in liver cancer, we conducted database analysis using clinical data from HCC patients. Expression levels of CD151 were assessed in HCC tissues and correlated with patient survival outcomes. In vitro experiments were performed using HCC cell lines to evaluate the impact of CD151 expression on migrasome formation and cellular invasiveness. Cell lines with altered CD151 expression levels were utilized to study migrasome generation and in vitro invasion capabilities. Additionally, migrasome function was explored through cellular aggregation assays and phagocytosis studies. Subsequent VEGF level analysis and tissue chip experiments further confirmed the role of CD151 in mediating migrasome involvement in angiogenesis and cellular signal transduction.

RESULTS

Our study revealed a significant correlation between CD151 expression and migrasome marker TSPAN4 in liver cancer, based on database analysis of clinical samples. High expression levels of CD151 were closely associated with poor survival outcomes in HCC patients. Experimentally, decreased CD151 expression led to reduced migrasome generation and diminished in vitro invasion capabilities, resulting in attenuated in vivo metastatic potential. Migrasomes were demonstrated to facilitate cellular aggregation and phagocytosis, thereby promoting cellular invasiveness. Furthermore, VEGF-enriched migrasomes were implicated in signaling and angiogenesis, accelerating HCC progression.

CONCLUSIONS

In summary, our findings support the notion that elevated CD151 expression promotes migrasome formation, and migrasomes play a pivotal role in the invasiveness and angiogenesis of liver cancer cells, thereby facilitating HCC progression. This finding implies that migrasomes generated by elevated CD151 expression may constitute a promising high-priority target for anti-angiogenic therapy in HCC, offering crucial insights for the in-depth exploration of migrasome function and a renewed comprehension of the mechanism underlying liver cancer metastasis.

Migrasome, a migration-dependent organelle

Migrasomes are organelles produced by migrating cells that form on retraction fibers and are released during cell migration. Migrasomes are involved in physiological and pathological processes such as intercellular communication, cell homeostasis maintenance, signal transduction, disease occurrence and development, and cancer metastasis. In addition, methods and techniques for studying migrasomes are constantly evolving. Here, we review the discovery, formation process, regulation, and known functions of migrasomes, summarize the commonly used specific markers of migrasomes, and the methods for observing migrasomes. Meanwhile, this review also discusses the potential applications of migrasomes in physiological processes, disease diagnosis, treatment, and prognosis, and looks forward to their wider application in biomedicine. In addition, the study of migrasomes will also reveal a new perspective on the mechanism of intercellular communication and promote the further development of life science.

Quantification of urinary podocyte-derived migrasomes for the diagnosis of kidney disease

Migrasomes represent a recently uncovered category of extracellular microvesicles, spanning a diameter range of 500 to 3000 nm. They are emitted by migrating cells and harbour a diverse array of RNAs and proteins. Migrasomes can be readily identified in bodily fluids like serum and urine, rendering them a valuable non-invasive source for disease diagnosis through liquid biopsy. In this investigation, we introduce a streamlined and effective approach for the capture and quantitative assessment of migrasomes, employing wheat germ agglutinin (WGA)-coated magnetic beads and flow cytometry (referred to as WBFC). Subsequently, we examined the levels of migrasomes in the urine of kidney disease (KD) patients with podocyte injury and healthy volunteers using WBFC. The outcomes unveiled a substantial increase in urinary podocyte-derived migrasome concentrations among individuals with KD with podocyte injury compared to the healthy counterparts. Notably, the urinary podocyte-derived migrasomes were found to express an abundant quantity of phospholipase A2 receptor (PLA2R) proteins. The presence of PLA2R proteins in these migrasomes holds promise for serving as a natural antigen for the quantification of autoantibodies against PLA2R in the serum of patients afflicted by membranous nephropathy. Consequently, our study not only pioneers a novel technique for the isolation and quantification of migrasomes but also underscores the potential of urinary migrasomes as a promising biomarker for the early diagnosis of KD with podocyte injury.

Tetraspanins: structure, dynamics, and principles of partner-protein recognition

Tetraspanins are a large, highly conserved family of four-pass transmembrane (TM) proteins that play critical roles in a variety of essential cellular functions, including cell migration, protein trafficking, maintenance of membrane integrity, and regulation of signal transduction. Tetraspanins carry out these biological functions primarily by interacting with partner proteins. Here, we summarize significant advances that have revealed fundamental principles underpinning structure-function relationships in tetraspanins. We first review the structural features of tetraspanin ectodomains and full-length apoproteins, and then discuss how recent structural studies of tetraspanin complexes have revealed plasticity in partner-protein recognition that enables tetraspanins to bind to remarkably different protein families, viral proteins, and antibody fragments. Finally, we discuss major questions and challenges that remain in studying tetraspanin complexes.

Applications of Stem Cell-Derived Extracellular Vesicles in Nerve Regeneration

Extracellular vesicles (EVs), including exosomes, microvesicles, and other lipid vesicles derived from cells, play a pivotal role in intercellular communication by transferring information between cells. EVs secreted by progenitor and stem cells have been associated with the therapeutic effects observed in cell-based therapies, and they also contribute to tissue regeneration following injury, such as in orthopaedic surgery cases. This review explores the involvement of EVs in nerve regeneration, their potential as drug carriers, and their significance in stem cell research and cell-free therapies. It underscores the importance of bioengineers comprehending and manipulating EV activity to optimize the efficacy of tissue engineering and regenerative therapies.

Deposited footprints let cells switch between confined, oscillatory, and exploratory migration

For eukaryotic cells to heal wounds, respond to immune signals, or metastasize, they must migrate, often by adhering to extracellular matrix (ECM). Cells may also deposit ECM components, leaving behind a footprint that influences their crawling. Recent experiments showed that some epithelial cell lines on micropatterned adhesive stripes move persistently in regions they have previously crawled over, where footprints have been formed, but barely advance into unexplored regions, creating an oscillatory migration of increasing amplitude. Here, we explore through mathematical modeling how footprint deposition and cell responses to footprint combine to allow cells to develop oscillation and other complex migratory motions. We simulate cell crawling with a phase field model coupled to a biochemical model of cell polarity, assuming local contact with the deposited footprint activates Rac1, a protein that establishes the cell's front. Depending on footprint deposition rate and response to the footprint, cells on micropatterned lines can display many types of motility, including confined, oscillatory, and persistent motion. On two-dimensional (2D) substrates, we predict a transition between cells undergoing circular motion and cells developing an exploratory phenotype. Small quantitative changes in a cell's interaction with its footprint can completely alter exploration, allowing cells to tightly regulate their motion, leading to different motility phenotypes (confined vs. exploratory) in different cells when deposition or sensing is variable from cell to cell. Consistent with our computational predictions, we find in earlier experimental data evidence of cells undergoing both circular and exploratory motion.

Fascin-1 Promotes Cell Metastasis through Epithelial-Mesenchymal Transition in Canine Mammary Tumor Cell Lines

Canine mammary tumors (CMTs) are the most common type of tumor in female dogs. In this study, we obtained a metastatic key protein, Fascin-1, by comparing the proteomics data of in situ tumor and metastatic cell lines from the same individual. However, the role of Fascin-1 in the CMT cell line is still unclear. Firstly, proteomics was used to analyze the differential expression of Fascin-1 between the CMT cell lines CHMm and CHMp. Then, the overexpression (CHMm-OE and CHMp-OE) and knockdown (CHMm-KD and CHMp-KD) cell lines were established by lentivirus transduction. Finally, the differentially expressed proteins (DEPs) in CHMm and CHMm-OE cells were identified through proteomics. The results showed that the CHMm cells isolated from CMT abdominal metastases exhibited minimal expression of Fascin-1. The migration, adhesion, and invasion ability of CHMm-OE and CHMp-OE cells increased, while the migration, adhesion, and invasion ability of CHMm-KD and CHMp-KD cells decreased. The overexpression of Fascin-1 can upregulate the Tetraspanin 4 (TSPAN4) protein in CHMm cells and increase the number of migrations. In conclusion, re-expressed Fascin-1 could promote cell EMT and increase lamellipodia formation, resulting in the enhancement of CHMm cell migration, adhesion, and invasion in vitro. This may be beneficial to improve female dogs' prognosis of CMT.

Deposited footprints let cells switch between confined, oscillatory, and exploratory migration

For eukaryotic cells to heal wounds, respond to immune signals, or metastasize, they must migrate, often by adhering to extracellular matrix. Cells may also deposit extracellular matrix components, leaving behind a footprint that influences their crawling. Recent experiments showed that some epithelial cells on micropatterned adhesive stripes move persistently in regions they have previously crawled over, where footprints have been formed, but barely advance into unexplored regions, creating an oscillatory migration of increasing amplitude. Here, we explore through mathematical modeling how footprint deposition and cell responses to footprint combine to allow cells to develop oscillation and other complex migratory motions. We simulate cell crawling with a phase field model coupled to a biochemical model of cell polarity, assuming local contact with the deposited footprint activates Rac1, a protein that establishes the cell's front. Depending on footprint deposition rate and response to the footprint, cells on micropatterned lines can display many types of motility, including confined, oscillatory, and persistent motion. On two-dimensional substrates, we predict a transition between cells undergoing circular motion and cells developing an exploratory phenotype. Small quantitative changes in a cell's interaction with its footprint can completely alter exploration, allowing cells to tightly regulate their motion, leading to different motility phenotypes (confined vs exploratory) in different cells when deposition or sensing is variable from cell to cell. Consistent with our computational predictions, we find in earlier experimental data evidence of cells undergoing both circular and exploratory motion.

Novel insights into the roles of migrasome in cancer

Cell migration, a hallmark of cancer malignancy, plays a critical role in cancers. Improperly initiated or misdirected cell migration can lead to invasive metastatic cancer. Migrasomes are newly discovered vesicular cellular organelles produced by migrating cells and depending on cell migration. Four marker proteins [NDST1 (bifunctionalheparan sulfate N-deacetylase/N-sulfotransferase 1), EOGT (Epidermal growth factor domains pecific O-linked N-acetylglucosaminetransferase), CPQ (carboxypeptidase Q), and PIGK (phosphatidylinositol glycan anchor biosynthesis, class K)] of migrasomes were successfully identified. There are three marker proteins (NDST1, PIGK, and EOGT) of migrasome expressed in cancer. In this review, we will discuss the process of migrasome discovery, the formation of migrasome, the possible functions of migrasome, and the differences between migrasomes and exosomes, especially, the biological functions of migrasome marker proteins in cancer, and discuss some possible roles of migrasomes in cancer. We speculate that migrasomes and migracytosis can play key roles in regulating the development of cancer.

Migrasomes from adipose derived stem cells enrich CXCL12 to recruit stem cells via CXCR4/RhoA for a positive feedback loop mediating soft tissue regeneration

BACKGROUND

Adipose-derived stem cells (ASCs) represent the most advantageous choice for soft tissue regeneration. Studies proved the recruitment of ASCs post tissue injury was mediated by chemokine CXCL12, but the mechanism by which CXCL12 is generated after tissue injury remains unclear. Migrasomes are newly discovered membrane-bound organelles that could deliver CXCL12 spatially and temporally in vivo. In this study, we sought to investigate whether migrasomes participate ASC-mediated tissue regeneration.

METHODS

Discrepant and asymmetrical soft tissue regeneration mice model were established, in which HE staining, immunofluorescent staining, western blot and qPCR were conducted to confirm the role of CXCL12 and migrasomes in ASC-mediated tissue regeneration. Characterization of ASC-derived migrasomes were carried out by confocal microscopy, scanning electron microscopy, transmission electron microscopy as well as western blot analysis. The function and mechanism of migrasomes were further testified by assisting tissue regeneration with isolated migrasomes in vivo and by in vitro transwell combined with co-culture system.

RESULTS

Here, we show for the first time that migrasomes participate in soft tissue regeneration. ASCs generate migrasomes enriched with CXCL12 to mediate tissue regeneration. Migrasomes from ASCs could promote stem cells migration by activating CXCR4/RhoA signaling in vivo and in vitro. Chemoattracted ASCs facilitate regeneration, as demonstrated by the upregulation of an adipogenesis-associated protein. This positive feed-back-loop creates a favorable microenvironment for soft tissue regeneration. Thus, migrasomes represent a new therapeutic target for ASC-mediated tissue regeneration.

CONCLUSIONS

Our findings reveal a previously unknown function of ASCs in mediating tissue regeneration by generating migrasomes. The ASC-derived migrasomes can restore tissue regeneration by recruiting stem cells, which highlighting the potential application of ASC-derived migrasomes in regenerative medicine.

Mitocytosis Mediated by an Enzyme-Activable Mitochondrion-Disturbing Polymer-Drug Conjugate Enhances Active Penetration in Glioblastoma Therapy

The application of nanomedicines for glioblastoma (GBM) therapy is hampered by the blood-brain barrier (BBB) and the dense glioblastoma tissue. To achieve efficient BBB crossing and deep GBM penetration, this work demonstrates a strategy of active transcellular transport of a mitochondrion-disturbing nanomedicine, pGBEMA22-b-pSSPPT9 (GBEPPT), in the GBM tissue through mitocytosis. GBEPPT is computer-aided designed and prepared by self-assembling a conjugate of an amphiphilic block polymer and a drug podophyllotoxin (PPT). When GBEPPT is delivered to the tumor site, overexpressed γ-glutamyl transpeptidase (GGT) on the brain-blood endothelial cell, or the GBM cell triggered enzymatic hydrolysis of γ-glutamylamide on GBEPPT to reverse its negative charge to positive. Positively charged GBEPPT rapidly enter into the cell and target the mitochondria. These GBEPPT disturb the homeostasis of mitochondria, inducing mitocytosis-mediated extracellular transport of GBEPPT to the neighboring cells via mitosomes. This intracellular-to-intercellular delivery cycle allows GBEPPT to penetrate deeply into the GBM parenchyma, and exert sustainable action of PPT released from GBEPPT on the tumor cells along its penetration path at the tumor site, thus improving the anti-GBM effect. The process of mitocytosis mediated by the mitochondrion-disturbing nanomedicine may offer great potential in enhancing drug penetration through malignant tissues, especially poorly permeable solid tumors.

Seeing is believing: observation of migrasomes

Migrasomes are a novel type of cell organelle that form on the retraction fibers at the rear of migrating cells. In recent years, numerous studies have unveiled the mechanisms of migrasome formation and have highlighted significant roles of migrasomes in both physiological and pathological processes. Building upon the strategies outlined in published works and our own research experiences, we have compiled a comprehensive set of protocols for observing migrasomes. These step-by-step instructions encompass various aspects such as cell culture, labeling, imaging, in vitro reconstitution, and statistical analysis. We believe that these protocols serve as a valuable resource for researchers exploring migrasome biology.

The M2 Macrophages Derived Migrasomes From the Surface of Titania Nanotubes Array as a New Concept for Enhancing Osteogenesis

As newly discovered substrate anchored extracellular vesicles, migrasomes (Migs) may bring a new opportunity for manipulating target cells bioactivities. In this study, the M2 macrophages derived Migs are obtained by titania nanotubes surface (NTs). Due to the benefits of nanostructuring, the NTs surface is not only able to induce RAW264.7 for M2 polarization but also to generate more Migs formation, which can be internalized by following seeded mesenchymal stem cells (MSCs). Then, the NTs surface induced Migs are collected by density-gradient centrifugation for MSCs treatment. As indicated by immunofluorescence staining, alkaline phosphatase activity, and alizarin red staining, the osteogenic differentiation capacity of MSCs is significantly enhanced by Migs treatment, in line with the dosage. By RNA-sequence analysis, the enhancement of osteogenic differentiation is correlated with PI3K-AKT pathway activation that may originate from the M2 polarization state of donor cells. Finally, the Migs are coated onto Ti surface for therapeutic application. Both the in vitro and in vivo analysis reveal that the Migs coated Ti implant shows significant enhancement of osteogenesis. In conclusion, this study suggests that the nanosurface may be a favorable platform for Migs production, which may bring a new concept for tissue regeneration.

Canonical and non-canonical integrin-based adhesions dynamically interconvert

Adhesions are critical for anchoring cells in their environment, as signaling platforms and for cell migration. In line with these diverse functions different types of cell-matrix adhesions have been described. Best-studied are the canonical integrin-based focal adhesions. In addition, non-canonical integrin adhesions lacking focal adhesion proteins have been discovered. These include reticular adhesions also known as clathrin plaques or flat clathrin lattices, that are enriched in clathrin and other endocytic proteins, as well as extensive adhesion networks and retraction fibers. How these different adhesion types that share a common integrin backbone are related and whether they can interconvert is unknown. Here, we identify the protein stonin1 as a marker for non-canonical αVβ5 integrin-based adhesions and demonstrate by live cell imaging that canonical and non-canonical adhesions can reciprocally interconvert by the selective exchange of components on a stable αVβ5 integrin scaffold. Hence, non-canonical adhesions can serve as points of origin for the generation of canonical focal adhesions.

Osmotic stress induces the formation of migrasome-like vesicles

Migrasomes are extracellular vesicles that form on the retraction fibers of migrating cells. In this study, we report the formation of migrasome-like vesicles enriched in tetraspanin 4 and containing cytoplasmic components in response to hypoosmotic stress. When migrating cells were subjected to hypoosmotic stress, vesicles with a size distribution of 0.5 to 2 μm formed on the retraction fibers, and vanished in a few minutes. The vesicles are rich in cholesterol, and their number was reduced when cells were pretreated with lipoprotein-deficient serum. The formation of migrasome-like vesicles upon hypoosmotic stress may provide biophysical cues regarding the cellular response to this external stimulus in cells and tissues.

Migrasomal autophagosomes relieve endoplasmic reticulum stress in glioblastoma cells

BACKGROUND

Glioblastoma (GBM) is more difficult to treat than other intractable adult tumors. The main reason that GBM is so difficult to treat is that it is highly infiltrative. Migrasomes are newly discovered membrane structures observed in migrating cells. Thus, they can be generated from GBM cells that have the ability to migrate along the brain parenchyma. However, the function of migrasomes has not yet been elucidated in GBM cells.

RESULTS

Here, we describe the composition and function of migrasomes generated along with GBM cell migration. Proteomic analysis revealed that LC3B-positive autophagosomes were abundant in the migrasomes of GBM cells. An increased number of migrasomes was observed following treatment with chloroquine (CQ) or inhibition of the expression of STX17 and SNAP29, which are involved in autophagosome/lysosome fusion. Furthermore, depletion of ITGA5 or TSPAN4 did not relieve endoplasmic reticulum (ER) stress in cells, resulting in cell death.

CONCLUSIONS

Taken together, our study suggests that increasing the number of autophagosomes, through inhibition of autophagosome/lysosome fusion, generates migrasomes that have the capacity to alleviate cellular stress.

Polystyrene Nanoplastics Activate Autophagy and Suppress Trophoblast Cell Migration/Invasion and Migrasome Formation to Induce Miscarriage

Nanoplastics (NPs), as emerging pollutants, have attracted global attention. Nevertheless, the adverse effects of NPs on female reproductive health, especially unexplained miscarriage, are poorly understood. Defects of trophoblast cell migration and invasion are associated with miscarriage. Migrasomes were identified as cellular organelles with largely unidentified functions. Whether NPs might affect migration, invasion, and migrasome formation and induce miscarriage has been completely unexplored. In this study, we selected polystyrene nanoplastics (PS-NPs, 50 nm) as a model of plastic particles and treated human trophoblast cells and pregnant mice with PS-NPs at doses near the actual environmental exposure doses of plastic particles in humans. We found that exposure to PS-NPs induced a pregnant mouse miscarriage. PS-NPs suppressed ROCK1-mediated migration/invasion and migrasome formation. SOX2 was identified as the transcription factor of ROCK1. PS-NPs activated autophagy and promoted the autophagy degradation of SOX2, thus suppressing SOX2-mediated ROCK1 transcription. Supplementing with murine SOX2 or ROCK1 could efficiently rescue migration/invasion and migrasome formation and alleviate miscarriage. Analysis of the protein levels of SOX2, ROCK1, TSPAN4, NDST1, P62, and LC-3BII/I in PS-NP-exposed trophoblast cells, villous tissues of unexplained miscarriage patients, and placental tissues of PS-NP-exposed mice gave consistent results. Collectively, this study revealed the reproductive toxicity of nanoplastics and their potential regulatory mechanism, indicating that NP exposure is a risk factor for female reproductive health.

Molecular Regulation and Oncogenic Functions of TSPAN8

Tetraspanins, a superfamily of small integral membrane proteins, are characterized by four transmembrane domains and conserved protein motifs that are configured into a unique molecular topology and structure in the plasma membrane. They act as key organizers of the plasma membrane, orchestrating the formation of specialized microdomains called "tetraspanin-enriched microdomains (TEMs)" or "tetraspanin nanodomains" that are essential for mediating diverse biological processes. TSPAN8 is one of the earliest identified tetraspanin members. It is known to interact with a wide range of molecular partners in different cellular contexts and regulate diverse molecular and cellular events at the plasma membrane, including cell adhesion, migration, invasion, signal transduction, and exosome biogenesis. The functions of cell-surface TSPAN8 are governed by ER targeting, modifications at the Golgi apparatus and dynamic trafficking. Intriguingly, limited evidence shows that TSPAN8 can translocate to the nucleus to act as a transcriptional regulator. The transcription of TSPAN8 is tightly regulated and restricted to defined cell lineages, where it can serve as a molecular marker of stem/progenitor cells in certain normal tissues as well as tumors. Importantly, the oncogenic roles of TSPAN8 in tumor development and cancer metastasis have gained prominence in recent decades. Here, we comprehensively review the current knowledge on the molecular characteristics and regulatory mechanisms defining TSPAN8 functions, and discuss the potential and significance of TSPAN8 as a biomarker and therapeutic target across various epithelial cancers.

Extracellular lipidosomes containing lipid droplets and mitochondria are released during melanoma cell division

BACKGROUND

The incidence of melanoma is increasing worldwide. Since metastatic melanoma is highly aggressive, it is important to decipher all the biological aspects of melanoma cells. In this context, we have previously shown that metastatic FEMX-I melanoma cells release small (< 150 nm) extracellular vesicles (EVs) known as exosomes and ectosomes containing the stem (and cancer stem) cell antigenic marker CD133. EVs play an important role in intercellular communication, which could have a micro-environmental impact on surrounding tissues.

RESULTS

We report here a new type of large CD133+ EVs released by FEMX-I cells. Their sizes range from 2 to 6 µm and they contain lipid droplets and mitochondria. Real-time video microscopy revealed that these EVs originate from the lipid droplet-enriched cell extremities that did not completely retract during the cell division process. Once released, they can be taken up by other cells. Silencing CD133 significantly affected the cellular distribution of lipid droplets, with a re-localization around the nuclear compartment. As a result, the formation of large EVs containing lipid droplets was severely compromised.

CONCLUSION

Given the biochemical effect of lipid droplets and mitochondria and/or their complexes on cell metabolism, the release and uptake of these new large CD133+ EVs from dividing aggressive melanoma cells can influence both donor and recipient cells, and therefore impact melanoma growth and dissemination.

Deep proteomic analysis of obstetric antiphospholipid syndrome by DIA-MS of extracellular vesicle enriched fractions

Proteins in the plasma/serum mirror an individual's physiology. Circulating extracellular vesicles (EVs) proteins constitute a large portion of the plasma/serum proteome. Thus, deep and unbiased proteomic analysis of circulating plasma/serum extracellular vesicles holds promise for discovering disease biomarkers as well as revealing disease mechanisms. We established a workflow for simple, deep, and reproducible proteome analysis of both serum large and small EVs enriched fractions by ultracentrifugation plus 4D-data-independent acquisition mass spectrometry (4D-DIA-MS). In our cohort study of obstetric antiphospholipid syndrome (OAPS), 4270 and 3328 proteins were identified from large and small EVs enriched fractions respectively. Both of them revealed known or new pathways related to OAPS. Increased levels of von Willebrand factor (VWF) and insulin receptor (INSR) were identified as candidate biomarkers, which shed light on hypercoagulability and abnormal insulin signaling in disease progression. Our workflow will significantly promote our understanding of plasma/serum-based disease mechanisms and generate new biomarkers.

TSPAN4 and migrasomes in atherosclerosis regression correlated to myocardial infarction and pan-cancer progression

The migrasomes formation is mediated by the assembly of micron-scale tetraspanin macrodomains and the recruitment of tetraspanin 4 (TSPAN4). However, the physiological functions of TSPAN4 on migrasomes are less known. The TSPAN4 expression in macrophages in single-cell sequencing data, GEO datasets and TCGA database were determined. TSPAN4 expression was highly associated with atherosclerosis regression-related macrophages, intraplaque hemorrhage and ruptured plaques. TSPAN4 expression was upregulated in spontaneous MI and inducible MI mice model. Besides, TSPAN4 expression was highly correlated with tumor-associated macrophages. The study provided a critical role of TSPAN4 aberrant expression in the progression of atherosclerosis and pan-cancer, and the intervention of TSPAN4 and migrasomes may save dying patients' lives and improve their prognosis.

Differences between migrasome, a 'new organelle', and exosome

The migrasome is a new organelle discovered by Professor Yu Li in 2015. When cells migrate, the membranous organelles that appear at the end of the retraction fibres are migrasomes. With the migration of cells, the retraction fibres which connect migrasomes and cells finally break. The migrasomes detach from the cell and are released into the extracellular space or directly absorbed by the recipient cell. The cytoplasmic contents are first transported to the migrasome and then released from the cell through the migrasome. This release mechanism, which depends on cell migration, is named 'migracytosis'. The main components of the migrasome are extracellular vesicles after they leave the cell, which are easy to remind people of the current hot topic of exosomes. Exosomes are extracellular vesicles wrapped by the lipid bimolecular layer. With extensive research, exosomes have solved many disease problems. This review summarizes the differences between migrasomes and exosomes in size, composition, property and function, extraction method and regulation mechanism for generation and release. At the same time, it also prospects for the current hotspot of migrasomes, hoping to provide literature support for further research on the generation and release mechanism of migrasomes and their clinical application in the future.

Chick chorioallantoic membrane model to investigate role of migrasome in angiogenensis

The development of the vascular system is essential for embryonic development, including processes such as angiogenesis. Angiogenesis plays a critical role in many normal physiological and pathological processes. It is driven by a set of angiogenic proteins, including angiogenic growth factors, chemokines, and extracellular matrix proteins. Among various animal model systems, the chorioallantoic membrane (CAM), a specialized and highly vascularized tissue of the avian embryo, has proven to be a valuable tool for analyzing the angiogenic potential of candidate cells or factors. In this protocol, we provide detailed procedures for establishing the CAM model to evaluate the function and mechanism of migrasomes in embryonic angiogenesis. This includes the CAM nylon mesh assay and CAM ex vivo sprouting assay to assess CAM angiogenesis, as well as the observation, purification, and delivery of migrasomes. Additionally, we describe the generation of T4-KO-mCherry-KI embryos using the CRISPR system within the CAM tissue to investigate the role of migrasomes in angiogenesis.

Macrophages release IL11-containing filopodial tip vesicles and contribute to renal interstitial inflammation

Macrophage filopodia, which are dynamic nanotube-like protrusions, have mainly been studied in the context of pathogen clearance. The mechanisms by which they facilitate intercellular communication and mediate tissue inflammation remain poorly understood. Here, we show that macrophage filopodia produce a unique membrane structure called "filopodial tip vesicle" (FTV) that originate from the tip of macrophages filopodia. Filopodia tip-derived particles contain numerous internal-vesicles and function as cargo storage depots via nanotubular transport. Functional studies indicate that the shedding of FTV from filopodia tip allows the delivery of many molecular signalling molecules to fibroblasts. We observed that FTV derived from M1 macrophages and high glucose (HG)-stimulated macrophages (HG/M1-ftv) exhibit an enrichment of the chemokine IL11, which is critical for fibroblast transdifferentiation. HG/M1-ftv induce renal interstitial fibrosis in diabetic mice, while FTV inhibition or targeting FTV IL11- alleviates renal interstitial fibrosis, suggesting that the HG/M1-ftvIL11 pathway may be a novel mechanism underlying renal fibrosis in diabetic nephropathy. Collectively, FTV release could represent a novel function by which filopodia contribute to cell biological processes, and FTV is potentially associated with macrophage filopodia-related fibrotic diseases. Video Abstract.

Migrasome: a new functional extracellular vesicle

Migrasome is a novel cellular organelle produced during cell migration, and its biogenesis depends on the migration process. It is generated in a variety of cells such as immune cells, metastatic tumor cells, other special functional cells like podocytes and cells in developing organisms. It plays important roles in various fields especially in the information exchange between cells. The discovery of migrasome, as an important supplement to the extracellular vesicle system, provides new mechanisms and targets for comprehending various biological or pathological processes. In this article, we will review the discovery, structure, distribution, detection, biogenesis, and removal of migrasomes and mainly focus on summarizing its biological functions in cell-to-cell communication, homeostatic maintenance, embryonic development and multiple diseases. This review also creates prospects for the possible research directions and clinical applications of migrasomes in the future.

cxcl12a plays an essential role in pharyngeal cartilage development

Background: Neural crest cells constitute a distinct set of multipotent cells that undergo migration along predefined pathways, culmination in the differentiation into a plethora of cell types, including components of the pharyngeal cartilage. The neurocranium is composite structure derived from both cranial neural crest and mesoderm cells, whereas the pharyngeal skeletal elements-including the mandibular and branchial arches-are exclusively formed by craniofacial neural crest cells. Previous studies have elucidated the critical involvement of the chemokine signaling axis Cxcl12b/Cxcr4a in craniofacial development in zebrafish (Danio rerio). Nonetheless, the function contribution of Cxcl12a and Cxcr4b-the homologous counterparts of Cxcl12b and Cxcr4a-remain largely unexplored. Methods: In the present study, mutant lines for cxcl12a and cxcr4b were generated employing CRISPR/Cas9 system. Temporal and spatial expression patterns of specific genes were assessed using in situ hybridization and dual-color fluorescence in situ hybridization techniques. High-resolution confocal microscopy was utilized for in vivo imaging to detect the pharyngeal arch or pouch patterning. Additionally, cartilage formation within the craniofacial region was analyzed via Alcian blue staining, and the proliferation and apoptosis rates of craniofacial neural crest cells were quantified through BrdU incorporation and TUNEL staining. Results: Our data reveals that the deletion of the chemokine gene cxcl12a results in a marked diminution of pharyngeal cartilage elements, attributable to compromised proliferation of post-migratory craniofacial neural crest cells. Subsequent experiments confirmed that Cxcl12a and Cxcl12b exhibit a synergistic influence on pharyngeal arch and pouch formation. Conclusion: Collectively, the present investigation furnishes compelling empirical evidence supporting the indispensable role of Cxcl2a in craniofacial cartilage morphogenesis, albeit cxcr4b mutants exert a minimal impact on this biological process. We delineate that Cxcl12a is essential for chondrogenesis in zebrafish, primarily by promoting the proliferation of craniofacial neural crest cells. Furthermore, we proposed a conceptual framework wherein Cxcl12a and Cxcl12b function synergistically in orchestrating both the pharyngeal arch and pouch morphogenesis.

Migrasomes and tetraspanins in hepatocellular carcinoma: current status and future prospects

In recent years, many studies have attempted to clarify the formation, structure and biological function of migrasomes, which are defined as specialized organelles formed by the tips and intersections of Retraction Fibrils during cell migration. It has confirmed that migrasomes were involved in various critical biological processes and diseases, and has became a new research hotspot. In this paper, we reviewed the formation and biological functions of migrasomes, explored the relationship between migrasomes, tetraspanins and hepatocellular carcinoma and discussed the potential applications of migrasomes in hepatocellular carcinoma.

Molecular imaging-guided extracellular vesicle-based drug delivery for precise cancer management: Current status and future perspectives

Extracellular vesicles (EVs), the mediators of intercellular communication, have attracted the attention of researchers for the important roles they play in cancer treatment. Compared with other inorganic nano-materials, EVs possess the advantages of higher biocompatibility, better physiochemical stability, easier surface modification, and excellent biosafety. They can be used as an advanced drug delivery system with an improved therapeutic index for various therapeutic agents. Engineered EV-based imaging and therapeutic agents (engineered EVs) have emerged as useful tools in targeted cancer diagnosis and therapy. Non-invasive tracing of engineered EVs contributes to a better evaluation of their functions in cancer progression, in vivo dynamic biodistribution, therapeutic response, and drug-loading efficiency. Recent advances in real-time molecular imaging (MI), and innovative EV labeling strategies have led to the development of novel tools that can evaluate the pharmacokinetics of engineered EVs in cancer management, which may accelerate further clinical translation of novel EV-based drug delivery platforms. Herein, we review the latest advances in EVs, their characteristics, and current examples of EV-based targeted drug delivery for cancer. Then, we discuss the prominent applications of MI for tracing both natural and engineered EVs. Finally, we discuss the current challenges and considerations of EVs in targeted cancer treatment and the limitations of different MI modalities. In the coming decades, EV-based therapeutic applications for cancer with improved drug loading and targeting abilities will be developed, and better anti-cancer effects of drug delivery nanoplatform will be achieved.

Cell fragmentation in mouse preimplantation embryos induced by ectopic activation of the polar body extrusion pathway

Cell fragmentation is commonly observed in human preimplantation embryos and is associated with poor prognosis during assisted reproductive technology (ART) procedures. However, the mechanisms leading to cell fragmentation remain largely unknown. Here, light sheet microscopy imaging of mouse embryos reveals that inefficient chromosome separation due to spindle defects, caused by dysfunctional molecular motors Myo1c or dynein, leads to fragmentation during mitosis. Extended exposure of the cell cortex to chromosomes locally triggers actomyosin contractility and pinches off cell fragments. This process is reminiscent of meiosis, during which small GTPase-mediated signals from chromosomes coordinate polar body extrusion (PBE) by actomyosin contraction. By interfering with the signals driving PBE, we find that this meiotic signaling pathway remains active during cleavage stages and is both required and sufficient to trigger fragmentation. Together, we find that fragmentation happens in mitosis after ectopic activation of actomyosin contractility by signals emanating from DNA, similar to those observed during meiosis. Our study uncovers the mechanisms underlying fragmentation in preimplantation embryos and, more generally, offers insight into the regulation of mitosis during the maternal-zygotic transition.

Extracellular Vesicle Heterogeneity and Its Impact for Regenerative Medicine Applications

Extracellular vesicles (EVs) are cell-derived membrane-enclosed particles that are involved in physiologic and pathologic processes. EVs are increasingly being studied for therapeutic applications in the field of regenerative medicine. Therapeutic application of stem cell-derived EVs has shown great potential to stimulate tissue repair. However, the exact mechanisms through which they induce this effect have not been fully clarified. This may to a large extent be attributed to a lack of knowledge on EV heterogeneity. Recent studies suggest that EVs represent a heterogeneous population of vesicles with distinct functions. The heterogeneity of EVs can be attributed to differences in their biogenesis, and as such, they can be classified into distinct populations that can then be further subcategorized into various subpopulations. A better understanding of EV heterogeneity is crucial for elucidating their mechanisms of action in tissue regeneration. This review provides an overview of the latest insights on EV heterogeneity related to tissue repair, including the different characteristics that contribute to such heterogeneity and the functional differences among EV subtypes. It also sheds light on the challenges that hinder clinical translation of EVs. Additionally, innovative EV isolation techniques for studying EV heterogeneity are discussed. Improved knowledge of active EV subtypes would promote the development of tailored EV therapies and aid researchers in the translation of EV-based therapeutics to the clinic. SIGNIFICANCE STATEMENT: Within this review we discuss the differences in regenerative properties of extracellular vesicle (EV) subpopulations and implications of EV heterogeneity for development of EV-based therapeutics. We aim to provide new insights into which aspects are leading to heterogeneity in EV preparations and stress the importance of EV heterogeneity studies for clinical applications.

Migrasome, a novel organelle, differs from exosomes

Migrasomes, a newly discovered organelle produced by migrating cells, are vesicles with membranous structure that form on the tips and intersections of retraction fibers (RFs). These structures are released into the extracellular environment or taken up by surrounding cells, mediating the release of cytoplasmic contents and intercellular communication. Retractosomes, a new type of small extracellular vesicles generated from broken-off RFs, are closely related to migrasomes in their physical location and origin, but were defined later. Despite their widespread existence in cells and biological organisms, little is known about the regulatory mechanisms underlying their formation and potential function. In this review, we provide an overview of the discovery, biogenesis, distribution, and functions of migrasomes and retractosomes, as well as their differences from exosomes.

Sin3a associated protein 130 kDa, sap130, plays an evolutionary conserved role in zebrafish heart development

Hypoplastic left heart syndrome (HLHS) is a congenital heart disease where the left ventricle is reduced in size. A forward genetic screen in mice identified SIN3A associated protein 130 kDa (Sap130), part of the chromatin modifying SIN3A/HDAC complex, as a gene contributing to the etiology of HLHS. Here, we report the role of zebrafish sap130 genes in heart development. Loss of sap130a, one of two Sap130 orthologs, resulted in smaller ventricle size, a phenotype reminiscent to the hypoplastic left ventricle in mice. While cardiac progenitors were normal during somitogenesis, diminution of the ventricle size suggest the Second Heart Field (SHF) was the source of the defect. To explore the role of sap130a in gene regulation, transcriptome profiling was performed after the heart tube formation to identify candidate pathways and genes responsible for the small ventricle phenotype. Genes involved in cardiac differentiation and cardiac function were dysregulated in sap130a, but not in sap130b mutants. Confocal light sheet analysis measured deficits in cardiac output in MZsap130a supporting the notion that cardiomyocyte maturation was disrupted. Lineage tracing experiments revealed a significant reduction of SHF cells in the ventricle that resulted in increased outflow tract size. These data suggest that sap130a is involved in cardiogenesis via regulating the accretion of SHF cells to the growing ventricle and in their subsequent maturation for cardiac function. Further, genetic studies revealed an interaction between hdac1 and sap130a, in the incidence of small ventricles. These studies highlight the conserved role of Sap130a and Hdac1 in zebrafish cardiogenesis.

Fibroblasts generate topographical cues that steer cancer cell migration

Fibroblasts play a fundamental role in tumor development. Among other functions, they regulate cancer cells' migration through rearranging the extracellular matrix, secreting soluble factors, and establishing direct physical contacts with cancer cells. Here, we report that migrating fibroblasts deposit on the substrate a network of tubular structures that serves as a guidance cue for cancer cell migration. Such membranous tubular network, hereafter called tracks, is stably anchored to the substrate in a β5-integrin-dependent manner. We found that cancer cells specifically adhere to tracks by using clathrin-coated structures that pinch and engulf tracks. Tracks thus represent a spatial memory of fibroblast migration paths that is read and erased by cancer cells directionally migrating along them. We propose that fibroblast tracks represent a topography-based intercellular communication system capable of steering cancer cell migration.

The phosphatidylinositol (4,5)-bisphosphate-Rab35 axis regulates migrasome formation

Migrasomes are recently discovered organelles, which are formed on the ends or branch points of retraction fibers at the trailing edge of migrating cells. Previously, we showed that recruitment of integrins to the site of migrasome formation is essential for migrasome biogenesis. In this study, we found that prior to migrasome formation, PIP5K1A, a PI4P kinase which converts PI4P into PI(4,5)P2, is recruited to migrasome formation sites. The recruitment of PIP5K1A results in generation of PI(4,5)P2 at the migrasome formation site. Once accumulated, PI(4,5)P2 recruits Rab35 to the migrasome formation site by interacting with the C-terminal polybasic cluster of Rab35. We further demonstrated that active Rab35 promotes migrasome formation by recruiting and concentrating integrin α5 at migrasome formation sites, which is likely mediated by the interaction between integrin α5 and Rab35. Our study identifies the upstream signaling events orchestrating migrasome biogenesis.

Migrasomes released by HSV-2-infected cells serve as a conveyance for virus spread

•Cells infected with HSV-2 release migrasomes containing HSV-2 virions. •HSV-2 in the isolated migrasomes can be transmitted to uninfected cells and cause productive infection. •It is the first time that migrasomes have been found to play a role in virus spread.

The formation of migrasomes is initiated by the assembly of sphingomyelin synthase 2 foci at the leading edge of migrating cells

The migrasome is an organelle of migrating cells with diverse physiological functions. How migrasome formation is initiated is unknown. We found that sphingomyelin is enriched in migrasomes and identified sphingomyelin synthase 2 (SMS2) as an essential protein for migrasome biogenesis. SMS2 assembles into immobile foci that adhere on the basal membrane at the leading edge. When cells migrate away, the SMS2 foci 'move' out of cells and into retraction fibres, where they become migrasome formation sites and eventually grow into migrasomes. Mechanistically, SMS2 foci seed migrasomes by converting ceramide to sphingomyelin, which is essential for migrasome formation. Furthermore, CerS5, which is required for the synthesis of long-chain ceramide, and CERT, which transports ceramide from the endoplasmic reticulum to Golgi, are both required for migrasome formation. Our data reveal the essential role of ceramide and sphingomyelin in migrasome formation and suggest that SMS2 forms basal membrane-surface-connecting structures that pre-determine where migrasomes will grow.

A macrophage subpopulation promotes airineme-mediated intercellular communication in a matrix metalloproteinase-9 dependent manner

Tissue-resident macrophages are heterogeneous and perform location-dependent functions. Skin resident macrophages play intriguing roles in long-distance intercellular signaling by mediating cellular protrusions called airinemes in zebrafish. These macrophages relay signaling molecules containing airineme vesicles between pigment cells, and their absence disrupts airineme-mediated signaling and pigment pattern formation. It is unknown if the same macrophages control both these signaling and typical immune functions or if a separate subpopulation functions in intercellular communication. With high-resolution imaging and genetic ablation approaches, we identify a macrophage subpopulation responsible for airineme-mediated signaling. These seem to be distinct from conventional skin-resident macrophages by their ameboid morphology and faster or expansive migratory behaviors. They resemble ectoderm-derived macrophages termed metaphocytes. Metaphocyte ablation markedly decreases airineme extension and signaling. In addition, these ameboid/metaphocytes require matrix metalloproteinase-9 for their migration and airineme-mediated signaling. These results reveal a macrophage subpopulation with specialized functions in airineme-mediated signaling, which may play roles in other aspects of intercellular communication.

Albumosomes formed by cytoplasmic pre-folding albumin maintain mitochondrial homeostasis and inhibit nonalcoholic fatty liver disease

Hepatic mitochondrial dysfunction contributes to the progression of nonalcoholic fatty liver disease (NAFLD). However, the factors that maintain mitochondrial homeostasis, especially in hepatocytes, are largely unknown. Hepatocytes synthesize various high-level plasma proteins, among which albumin is most abundant. In this study, we found that pre-folding albumin in the cytoplasm is completely different from folded albumin in the serum. Mechanistically, endogenous pre-folding albumin undergoes phase transition in the cytoplasm to form a shell-like spherical structure, which we call the "albumosome". Albumosomes interact with and trap pre-folding carnitine palmitoyltransferase 2 (CPT2) in the cytoplasm. Albumosomes control the excessive sorting of CPT2 to the mitochondria under high-fat-diet-induced stress conditions; in this way, albumosomes maintain mitochondrial homeostasis from exhaustion. Physiologically, albumosomes accumulate in hepatocytes during murine aging and protect the livers of aged mice from mitochondrial damage and fat deposition. Morphologically, mature albumosomes have a mean diameter of 4μm and are surrounded by heat shock protein Hsp90 and Hsp70 family proteins, forming a larger shell. The Hsp90 inhibitor 17-AAG promotes hepatic albumosomal accumulation in vitro and in vivo, through which suppressing the progression of NAFLD in mice.

Emerging diversity in extracellular vesicles and their roles in cancer

Extracellular vesicles have undergone a paradigm shift from being considered as 'waste bags' to being central mediators of cell-to-cell signaling in homeostasis and several pathologies including cancer. Their ubiquitous nature, ability to cross biological barriers, and dynamic regulation during changes in pathophysiological state of an individual not only makes them excellent biomarkers but also critical mediators of cancer progression. This review highlights the heterogeneity in extracellular vesicles by discussing emerging subtypes, such as migrasomes, mitovesicles, and exophers, as well as evolving components of extracellular vesicles such as the surface protein corona. The review provides a comprehensive overview of our current understanding of the role of extracellular vesicles during different stages of cancer including cancer initiation, metabolic reprogramming, extracellular matrix remodeling, angiogenesis, immune modulation, therapy resistance, and metastasis, and highlights gaps in our current knowledge of extracellular vesicle biology in cancer. We further provide a perspective on extracellular vesicle-based cancer therapeutics and challenges associated with bringing them to the clinic.

Horizontal Transfer of Malignant Traits and the Involvement of Extracellular Vesicles in Metastasis

Metastases are responsible for the vast majority of cancer deaths, yet most therapeutic efforts have focused on targeting and interrupting tumor growth rather than impairing the metastatic process. Traditionally, cancer metastasis is attributed to the dissemination of neoplastic cells from the primary tumor to distant organs through blood and lymphatic circulation. A thorough understanding of the metastatic process is essential to develop new therapeutic strategies that improve cancer survival. Since Paget's original description of the "Seed and Soil" hypothesis over a hundred years ago, alternative theories and new players have been proposed. In particular, the role of extracellular vesicles (EVs) released by cancer cells and their uptake by neighboring cells or at distinct anatomical sites has been explored. Here, we will outline and discuss these alternative theories and emphasize the horizontal transfer of EV-associated biomolecules as a possibly major event leading to cell transformation and the induction of metastases. We will also highlight the recently discovered intracellular pathway used by EVs to deliver their cargoes into the nucleus of recipient cells, which is a potential target for novel anti-metastatic strategies.