Endocytosis blocks the vesicular secretion of exosome marker proteins

Sigma1 inhibitor suppression of adaptive immune resistance mechanisms mediated by cancer cell derived extracellular vesicles

Adaptive immune resistance in cancer describes the various mechanisms by which tumors adapt to evade anti-tumor immune responses. IFN-γ induction of programmed death-ligand 1 (PD-L1) was the first defined and validated adaptive immune resistance mechanism. The endoplasmic reticulum (ER) is central to adaptive immune resistance as immune modulatory secreted and integral membrane proteins are dependent on ER. Sigma1 is a unique ligand-regulated integral membrane scaffolding protein enriched in the ER of cancer cells. PD-L1 is an integral membrane glycoprotein that is translated into the ER and processed through the cellular secretory pathway. At the cell surface, PD-L1 is an immune checkpoint molecule that binds PD-1 on activated T-cells and blocks anti-tumor immunity. PD-L1 can also be incorporated into cancer cell-derived extracellular vesicles (EVs), and EV-associated PD-L1 can inactivate T-cells within the tumor microenvironment. Here, we demonstrate that a selective small molecule inhibitor of Sigma1 can block IFN-γ mediated adaptive immune resistance in part by altering the incorporation of PD-L1 into cancer cell-derived EVs. Sigma1 inhibition blocked post-translational maturation of PD-L1 downstream of IFN-γ/STAT1 signaling. Subsequently, EVs released in response to IFN-γ stimulation were significantly less potent suppressors of T-cell activation. These results suggest that by reducing tumor derived immune suppressive EVs, Sigma1 inhibition may promote antitumor immunity. Sigma1 modulation presents a novel approach to regulating the tumor immune microenvironment by altering the content and production of EVs. Altogether, these data support the notion that Sigma1 may play a role in adaptive immune resistance in the tumor microenvironment.

Fetoplacental extracellular vesicles deliver conceptus-derived antigens to maternal secondary lymphoid tissues for immune recognition

Pregnancy is an immunological paradox where despite a competent maternal immune system, regulatory mechanisms at the fetoplacental interface and maternal secondary lymphoid tissues (SLTs) circumvent rejection of semi-allogeneic concepti. Small extracellular vesicles (sEVs) are a vehicle for intercellular communication; nevertheless, the role of fetoplacental sEVs in transport of antigens to maternal SLTs has not been conclusively demonstrated. Using mice in which the conceptus generates fluoroprobe-tagged sEVs shed by the plasma membrane or released from the endocytic compartment, we show that fetoplacental sEVs are delivered to immune cells in the maternal spleen. Injection of sEVs from placentas of females impregnated with Act-mOVA B6 males elicited suboptimal activation of OVA-specific CD8+ OT-I T cells in virgin females as occurs during pregnancy. Furthermore, when OVA+ concepti were deficient in Rab27a, a protein required for sEV secretion, OT-I cell proliferation in the maternal spleen was decreased. Proteomics analysis revealed that mouse trophoblast sEVs were enriched in antiinflammatory and immunosuppressive mediators. Translational relevance was tested in humanized mice injected using sEVs from cultures of human trophoblasts. Our findings show that sEVs deliver fetoplacental antigens to the mother's SLTs that are recognized by maternal T cells. Alterations of such a mechanism may lead to pregnancy disorders.

The Potential Role of Exosomes in Communication Between Astrocytes and Endothelial Cells

Exosomes are extracellular vesicles secreted by almost all types of cells. Their release allows for the transport of specific regulatory cargo into the recipient cells and the modulation of their activity. Vesicular communication has also been identified as an important mechanism for the regulation of numerous cellular activities in the brain tissue, contributing to proper neuronal functions and brain homeostasis. In this work, we focus on the role of exosomes and extracellular vesicles in the communication between astrocytes and brain endothelial cells, two major components of the blood-brain barrier. We perform a comprehensive review of the latest studies highlighting the role of exosomes in astrocyte-endothelial cell crosstalk within the blood-brain barrier. We have also described the role of particular exosomal miRNAs in the regulation of astrocytes and brain endothelial cell functions, and discuss some future implications.

Microglial TMEM119 binds to amyloid-β to promote its clearance in an Aβ-depositing mouse model of Alzheimer's disease

The progression of Alzheimer's disease (AD) involves temporal dynamics of microglial activation. Restoring or maintaining microglial homeostasis has emerged as a promising therapeutic strategy to combat AD. Transmembrane protein 119 (TMEM119) is a homeostatic marker of microglia but has not been fully studied under AD pathological conditions. Here, we observed that amyloid-beta (Aβ) induced a decrease in TMEM119 expression in microglia, and TMEM119 deficiency increased AD progression in the 5×FAD mouse model. TMEM119 bound to Aβ oligomers and recruited low-density lipoprotein receptor 1, which in turn degraded TMEM119 itself. Overexpression of TMEM119 in microglia enhanced their phagocytic activity and alleviated cognitive deficits in 5xFAD mice. Administration of the small molecules Kartogenin and SRI-011381, which we found enhanced TMEM119 expression, substantially promoted Aβ clearance and improved cognitive function in AD mice, even during the mid-stage of the disease. These findings identify TMEM119 as a promising therapeutic target for AD.

Microfluidics-based label-free SERS profiling of exosomes with machine learning for osteosarcoma diagnosis

Osteosarcoma (OS) calls for early diagnosis to significantly improve patient survival rates. Exosomes hold significant potential as noninvasive biomarkers for the early diagnosis of cancer. Here, we design a microfluidic device to purify and analyze plasma-derived exosomes by label-free surface-enhanced Raman spectroscopy (SERS) profiling for OS diagnosis. Exosomes were isolated, purified, and enriched using a size-dependent microfluidic chip with tangential flow filtration, achieving a high recovery rate of 82 %. The isolated exosomes were then analyzed by label-free SERS using a nanoarray chip with self-assembly monolayers of gold nanoparticles (GNPs). Exosomes originating from different OS cell types were differentiated based on the intrinsic SERS signals. Our approach was further employed to analyze the plasma-derived exosomes from healthy donors and OS patients without the need for specific biomarker labeling. A machine learning-based diagnostic model for OS was constructed, achieving an accuracy of 93 %. The findings indicate that our method is valuable for noninvasive and precise diagnosis of OS and could be generalized to other diseases in the future.

Novel extracellular vesicle release pathway facilitated by toxic superoxide dismutase 1 oligomers

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease resulting in paralysis and death within three to five years. Mutations in over forty different proteins have been linked to ALS, leading to controversy whether ALS is one disease or many diseases with a similar phenotype. Mutations in Cu,Zn superoxide dismutase 1 (SOD1) are only found in 2-3% of ALS cases, yet misfolded SOD1 is found in both sporadic (sALS) and familial (fALS) patients. Yet, mutations in TDP-43 or FUS increase the level of misfolded SOD1 on extracellular vesicles (EVs). Additionally, small EVs isolated from ALS patient samples caused cell death of wild type motor neurons and myotubules. The toxicity and protein alterations of ALS EVs have led to the theory that EVs are responsible for the spread of ALS. We hypothesize that previously-identified toxic trimeric SOD1 is spreading on EVs in ALS and altering the spread of other ALS-related proteins, linking them to a common mechanism. To test our hypothesis, we isolate EVs from motor neuron-like cells expressing trimer stabilizing mutations and perform a sandwich enzyme-linked immunoassay (ELISA) (CD9 capture antibody) to quantify whether misfolded SOD1 and 17 other ALS-related proteins increase or decrease on EVs with trimer stabilization. We identify which EV release pathway is being affected by trimeric SOD1 utilizing endocytosis and exocytosis inhibitors, and determine if any specific EV-related proteins are altered with trimer stabilization. We establish that VAPB, VCP, and Stathmin-2 increase on EVs with trimer stabilization. The common pathway between SOD1 and three other ALS-associated proteins is affected by multiple pathways, including the Caveolae endocytosis pathway, suggesting a novel hybrid pathway of EV release present in ALS.

Tetraspanin CD9 alters cellular trafficking and endocytosis of tetraspanin CD63, affecting CD63 packaging into small extracellular vesicles

Small extracellular vesicles (sEVs) are particles secreted from cells that play vital roles both in normal physiology and in human disease. sEVs are highly enriched in tetraspanin proteins, such as CD9 and CD63, and contain tetraspanin-enriched membrane microdomains involved in loading of sEVs with macromolecule cargoes and in sEV biogenesis. However, the precise roles of individual tetraspanins in sEV biogenesis and cargo loading remain poorly understood. Here, we report that CD9 negatively regulated CD63 trafficking to tetraspanin-enriched microdomains and its subsequent packaging into sEVs, whereas CD63 had no discernable effect on CD9 localization or packaging. Using super resolution microscopy of individual vesicles, we showed that CD9 governs the fraction of sEVs that are loaded with CD63. Interestingly, CD9-dependent suppression of CD63 packaging was rescued by pharmacological blockade of endocytosis. Together, our data support a model where CD9 contributes to the regulation and secretion of CD63 in an endocytosis-dependent manner to reprogram the contents of sEVs and tetraspanin-enriched microdomains.

Leveraging nature's nanocarriers: Translating insights from extracellular vesicles to biomimetic synthetic vesicles for biomedical applications

Naturally occurring extracellular vesicles (EVs) and synthetic nanoparticles like liposomes have revolutionized precision diagnostics and medicine. EVs excel in biocompatibility and cell targeting, while liposomes offer enhanced drug loading capacity and scalability. The clinical translation of EVs is hindered by challenges including low yield and heterogeneity, whereas liposomes face rapid immune clearance and limited targeting efficiency. To bridge these gaps, biomimetic synthetic vesicles (SVs) have emerged as innovative platforms, combining the advantageous properties of EVs and liposomes. This review emphasizes critical aspects of EV biology, such as mechanisms of EV-cell interaction and source-dependent functionalities in targeting, immune modulation, and tissue regeneration, informing biomimetic SV engineering. We reviewed a broad array of biomimetic SVs, with a focus on lipid bilayered vesicles functionalized with proteins. These include cell-derived nanovesicles, protein-functionalized liposomes, and hybrid vesicles. By addressing current challenges and highlighting opportunities, this review aims to advance biomimetic SVs for transformative biomedical applications.

Mesenchymal stromal cell exosomes for drug delivery of prostate cancer treatments: a review

Interest in prostate cancer as a research topic has gradually increased. As a result, a series of innovative treatment strategies have emerged with an in-depth understanding of the disease. Owing to their unique biological characteristics, mesenchymal stromal cell exosomes (MSC-Exos) have garnered significant attention for their potential to deliver targeted drugs and enable precise prostate cancer treatment. Herein, prostate cancer treatment with MSC-Exos drug-delivery systems is reviewed. This review provides a comprehensive introduction to the advantages of these systems, current research trends and progress, as well as an analysis of current challenges and future research directions. Moreover, this review lays a solid foundation for the continued development and application of MSC-Exos.

Selenoprotein P is a target for regulating extracellular vesicle biogenesis and secretion from activated microglia in vivo

Microglia, brain innate immune cells, participate in the spread of inflammatory signals and aggregated proteins through secretion of extracellular vesicles (EVs). Selenoprotein P (Sepp1) is a potential regulator of microglial EV secretion. Here, we investigate the effect of Sepp1 silencing on microglial transcriptomics to elucidate the Sepp1 regulatory mechanism of EV secretion and validate this effect in APPNL-G-F knockin mice. Silencing of Sepp1 significantly reduces EV secretion and CD63 loading to EVs from BV-2 microglia, as determined by single-vesicle flow cytometry and super-resolution microscopy. Sepp1 deficiency downregulates EV biogenesis machinery, accompanied by increased lysosomal activity and lipid metabolism. Silencing of Sepp1 in astrocytes but not neurons suppresses EV secretion in vitro. Finally, Sepp1 silencing reduces EV secretion from activated neurodegenerative microglia associated with amyloid plaques in APPNL-G-F mouse brains in vivo. Sepp1 is thus an emerging therapeutic target for ameliorating microglia-mediated disease spread through EV secretion in neurodegenerative disorders.

Research on the TSPAN6 regulating the secretion of ADSCs-Exos through syntenin-1 and promoting wound healing

BACKGROUND

Exosomes (Exos) from adipose-derived stem cells (ADSCs) have a high inclusion content and low immunogenicity, which helps to control inflammation and accelerate the healing of wounds. Unfortunately, the yield of exosomes is poor, which raises the expense and lengthens the treatment period in addition to impairing exosomes' therapeutic impact. Thus, one of the key problems that needs to be resolved in the current exosome study is increasing the exosome yield.

METHODS

Tetraspanin-6 (TSPAN6) overexpression and knockdown models of ADSCs were constructed to determine the number of exosomes secreted by each group of cells as well as the number of multivesicular bodies (MVBs) and intraluminal vesicles (ILVs) within the cells. Subsequently, the binding region of the interaction between TSPAN6 and syntenin-1 was identified using the yeast two-hybrid assay, and the interaction itself was identified by immunoprecipitation. Finally, cellular and animal studies were conducted to investigate the role of each class of exosomes.

RESULTS

When compared to the control group, the number of intracellular MVBs and ILVs was significantly larger, and the number of ADSCsTSPAN6+-Exos was more than three times higher. However, TSPAN6's ability to stimulate exosome secretion was reduced as a result of syntenin-1 knockdown. Additional yeast two-hybrid assay demonstrated that the critical structures for their interaction were the N-terminal, Postsynaptic density protein 95/Discs large protein/Zonula occludens 1 (PDZ1), and PDZ2 domains of syntenin-1, and the C-terminal of TSPAN6. In animal trials, the wound healing rate was best in the ADSCsTSPAN6+-Exos group, while cellular experiments demonstrated that ADSCsTSPAN6+-Exos better enhanced the proliferation and migration of human skin fibroblasts (HSFs) and human umbilical vein endothelial cells (HUVECs).

CONCLUSION

TSPAN6 stimulates exosome secretion and formation, as well as the creation of MVBs and ILVs in ADSCs. Syntenin-1 is essential for TSPAN6's stimulation of ADSCs-Exos secretion. Furthermore, ADSCsTSPAN6+-Exos has a greater ability to support wound healing, angiogenesis, and the proliferation and migration of a variety of cells.

Therapeutic application of mesenchymal stem cell-derived exosomes in skin wound healing

Wound healing is a complicated obstacle, especially for chronic wounds. Mesenchymal stem cell-derived exosomes may be a promising cell-free approach for treating skin wound healing. Exosomes can accelerate wound healing by attenuating inflammation, promoting angiogenesis, cell proliferation, extracellular matrix production and remodeling. However, many issues, such as off-target effects and high degradation of exosomes in wound sites need to be addressed before applying into clinical therapy. Therefore, the bioengineering technology has been introduced to modify exosomes with greater stability and specific therapeutic property. To prolong the function time and the local concentration of exosomes in the wound bed, the use of biomaterials to load exosomes emerges as a promising strategy. In this review, we summarize the biogenesis and characteristics of exosomes, the role of exosomes in wound healing, and the therapeutic applications of modified-exosomes in wound healing. The challenges and prospects of exosomes in wound healing are also discussed.

Composition, functions, and applications of exosomal membrane proteins

Exosomes play a crucial role in various biological processes, such as human development, immune responses, and disease occurrence. The membrane proteins on exosomes are pivotal factors for their biological functionality. Currently, numerous membrane proteins have been identified on exosome membranes, participating in intercellular communication, mediating target cell recognition, and regulating immune processes. Furthermore, membrane proteins from exosomes derived from cancer cells can serve as relevant biomarkers for early cancer diagnosis. This article provides a comprehensive review of the composition of exosome membrane proteins and their diverse functions in the organism's biological processes. Through in-depth exploration of exosome membrane proteins, it is expected to offer essential foundations for the future development of novel biomedical diagnostics and therapies.