Targeting extracellular vesicles to injured tissue using membrane cloaking and surface display

BACKGROUND

Extracellular vesicles (EVs) and exosomes are nano-sized, membrane-bound vesicles shed by most eukaryotic cells studied to date. EVs play key signaling roles in cellular development, cancer metastasis, immune modulation and tissue regeneration. Attempts to modify exosomes to increase their targeting efficiency to specific tissue types are still in their infancy. Here we describe an EV membrane anchoring platform termed "cloaking" to directly embed tissue-specific antibodies or homing peptides on EV membrane surfaces ex vivo for enhanced vesicle uptake in cells of interest. The cloaking system consists of three components: DMPE phospholipid membrane anchor, polyethylene glycol spacer and a conjugated streptavidin platform molecule, to which any biotinylated molecule can be coupled for EV decoration.

RESULTS

We demonstrate the utility of membrane surface engineering and biodistribution tracking with this technology along with targeting EVs for enhanced uptake in cardiac fibroblasts, myoblasts and ischemic myocardium using combinations of fluorescent tags, tissue-targeting antibodies and homing peptide surface cloaks. We compare cloaking to a complementary approach, surface display, in which parental cells are engineered to secrete EVs with fusion surface targeting proteins.

CONCLUSIONS

EV targeting can be enhanced both by cloaking and by surface display; the former entails chemical modification of preformed EVs, while the latter requires genetic modification of the parent cells. Reduction to practice of the cloaking approach, using several different EV surface modifications to target distinct cells and tissues, supports the notion of cloaking as a platform technology.

Tumour necrosis factor alpha-induced neuronal loss is mediated by microglial phagocytosis

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TNF-α induces neuronal loss in culture without neuronal necrosis or apoptosis.

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TNF-α induces microglial phagocytosis, and the neuronal loss requires microglia.

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Neuronal loss requires the microglial vitronectin receptor, P2Y₆ receptor and MFG-E8.

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Blocking these phagocytic receptors leaves viable neurons.

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TNF-α induced phagoptosis might contribute to neuroinflammatory pathologies.

Tumour necrosis factor-α (TNF-α) is a pro-inflammatory cytokine, expressed in many brain pathologies and associated with neuronal loss. We show here that addition of TNF-α to neuronal–glial co-cultures increases microglial proliferation and phagocytosis, and results in neuronal loss that is prevented by eliminating microglia. Blocking microglial phagocytosis by inhibiting phagocytic vitronectin and P2Y₆ receptors, or genetically removing opsonin MFG-E8, prevented TNF-α induced loss of live neurons. Thus TNF-α appears to induce neuronal loss via microglial activation and phagocytosis of neurons, causing neuronal death by phagoptosis.

Detection and Characterization of Extracellular Vesicles by Transmission and Cryo-Transmission Electron Microscopy

Transmission electron microscopy (TEM) and transmission scanning electron Microscopy (TSEM), which denotes application of a scanning electron microscope (SEM) in the transmission mode, have been used to detect and characterize particles down to an imaging resolution of ~1 nm. In the field of EVs, TEM also has been valued for its capability to detect and characterize single EV. Furthermore, employing immunogold labeling in TEM could give information regarding biochemical properties of EV surface proteins. Significant shortcomings in TEM such as dehydration, chemical fixation, and/or staining of the biological specimens are eluded by the use of cryo-TEM. In cryo-TEM imaging, samples are directly applied onto an EM grid, vitrified and visualized, thus allowing for characterization of EVs near its native state. In this chapter, we describe a step-by-step guide for preparing EVs on the grid before TEM and cryo-TEM imaging. Finally, we provide a guide to an automated image-processing analysis to provide the size distribution of EVs.

Investigation of the phosphatidylserine binding properties of the lipid biosensor, Lactadherin C2 (LactC2), in different membrane environments

Lipid biosensors are robust tools used in both in vitro and in vivo applications of lipid imaging and lipid detection. Lactadherin C2 (LactC2) was described in 2000 as being a potent and specific sensor for phosphatidylserine (PS) (Andersen et al. Biochemistry 39:6200-6206, 2000). PS is an anionic phospholipid enriched in the inner leaflet of the plasma membrane and has paramount roles in apoptosis, cells signaling, and autophagy. The myriad roles PS plays in membrane dynamics make monitoring PS levels and function an important endeavor. LactC2 has functioned as a tantamount PS biosensor namely in the field of cellular imaging. While PS specificity and high affinity of LactC2 for PS containing membranes has been well established, much less is known regarding LactC2 selectivity for subcellular pools of PS or PS within different membrane environments (e.g., in the presence of cholesterol). Thus, there has been a lack of studies that have compared LactC2 PS sensitivity based upon the acyl chain length and saturation or the presence of other host lipids such as cholesterol. Here, we use surface plasmon resonance as a label-free method to quantitatively assess the apparent binding affinity of LactC2 for membranes containing PS with different acyl chains, different fluidity, as well as representative lipid vesicle mimetics of cellular membranes. Results demonstrate that LactC2 is an unbiased sensor for PS, and can sensitively interact with membranes containing PS with different acyl chain saturation and interact with PS species in a cholesterol-independent manner.

In Vivo Tracking of Extracellular Vesicles in Mice Using Fusion Protein Comprising Lactadherin and Gaussia Luciferase

Extracellular vesicles (EVs) are cell-derived vesicles comprising a lipid bilayer and are found in body fluids, such as blood, sweat, and urine. As EVs, especially exosomes, function as endogenous intercellular delivery tools, their roles in various biological events have been extensively investigated. In addition, they are expected to become safe and effective drug delivery systems (DDS) because of their intrinsic nature. In the development of EV-based DDS, as well as in the investigation of the biological functions of EVs, it is important to analyze the in vivo behavior of EVs by tracking them. Therefore, we have developed a sensitive EV-labeling method to track EVs in vivo by designing a fusion protein comprising lactadherin (LA) (alias milk fat globule-EGF factor 8), a protein that binds to EV membranes through interaction with phosphatidylserine, and Gaussia luciferase (gLuc), a chemiluminescent protein. gLuc-LA-labeled EVs are easily obtained by transfecting EV-producing cells with a gLuc-LA-encoding plasmid vector. Here, we describe methods to label EVs with the fusion protein and to track the labeled EVs in vivo.

Disorder in Milk Proteins: Lactadherin Multifunctionality and Structure

Milk fat globule membrane (MFGM) is one of the milk components that is produced by the lactating mammary glands and released to the milk in the form of vesicles. MFGM surrounds milk fat globule secreted by the milk producing cells and has a complex structure containing various lipids (e.g., triacylglycerides, phospholipids, and cholesterol), proteins and other macromolecules. Among the proteinaceous components of MFGM is lactadherin, also known as milk fat globule-EGF factor 8 protein (MFG-E8). Being one of the main proteins present in MFGM, lactadherin is related to milk secretion, has antimicrobial and antiviral effects, and plays important roles in the immune defense as one of the immune system molecules. Furthermore, lactadherin belongs to the family of secreted extracellular matrix proteins, and clearly can be considered as a multifunctional (or moonlighting) glycoprotein involved in regulation of many biological and physiological processes, such as angiogenesis, atherosclerosis, haemostasis, phagocytosis, and tissue remodeling. This review focuses on the similarities and differences of lactadherin among different species and describes the main functions of this protein, as well as its structure.

Brain-Derived Microparticles (BDMPs) Contribute to Neuroinflammation and Lactadherin Reduces BDMP Induced Neuroinflammation and Improves Outcome After Stroke

Microparticles (MPs, ~size between 0.1 and 1 mm) are lipid encased containers derived from intact cells which contain antigen from the parent cells. MPs are involved in intercellular communication and regulate inflammation. Stroke increases secretion of brain derived MP (BDMP) which activate macrophages/microglia and induce neuroinflammation. Lactadherin (Milk fat globule–EGF factor-8) binds to anionic phospholipids and extracellular matrices, promotes apoptotic cell clearance and limits pathogenic antigen cross presentation. In this study, we investigate whether BDMP affects stroke-induced neuroinflammation and whether Lactadherin treatment reduces stroke initiated BDMP-induced neuroinflammation, thereby improving functional outcome after stroke. Middle aged (8–9 months old) male C57BL/6J mice were subjected to distal middle cerebral artery occlusion (dMCAo) stroke, and BDMPs were extracted from ischemic brain 24 h after dMCAo by ultracentrifugation. Adult male C57BL/6J mice were subjected to dMCAo and treated via tail vein injection at 3 h after stroke with: (A) +PBS (n = 5/group); (B) +BDMPs (1.5 × 10⁸, n = 6/group); (C) +Lactadherin (400 μg/kg, n = 5/group); (D) +BDMP+Lactadherin (n = 6/group). A battery of neurological function tests were performed and mice sacrificed for immunostaining at 14 days after stroke. Blood plasma was used for Western blot assay. Our data indicate: (1) treatment of Stroke with BDMP significantly increases lesion volume, neurological deficits, blood brain barrier (BBB) leakage, microglial activation, inflammatory cell infiltration (CD45, microglia/macrophages, and neutrophils) into brain, inflammatory factor (TNFα, IL6, and IL1β) expression in brain, increases axon/white matter (WM) damage identified by decreased axon and myelin density, and increases inflammatory factor expression in the plasma when compared to PBS treated stroke mice; (2) when compared to PBS and BDMP treated stroke mice, Lactadherin and BDMP+Lactadherin treatment significantly improves neurological outcome, and decreases lesion volume, BBB leakage, axon/WM injury, inflammatory cell infiltration and inflammatory factor expression in the ischemic brain, respectively. Lactadherin treatment significantly increases anti-inflammatory factor (IL10) expression in ischemic brain and decreases IL1β expression in plasma compared to PBS and BDMP treated stroke mice, respectively. BDMP increases neuroinflammation and aggravates ischemic brain damage after stroke. Thus, Lactadherin exerts anti-inflammatory effects and improves the clearance of MPs to reduce stroke and BDMP induced neurological deficits.

Procoagulant Activity of Blood and Endothelial Cells via Phosphatidylserine Exposure and Microparticle Delivery in Patients with Diabetic Retinopathy

BACKGROUND/AIMS

The mechanisms for thrombosis in diabetic retinopathy (DR) are complex and need to be further elucidated. The purpose of this study was to test phosphatidylserine (PS) exposure on microparticles (MPs) and MP-origin cells from the circulation and to analyze cell-/MP-associated procoagulant activity (PCA) in DR patients.

METHODS

PS-positive MPs and cells from healthy controls (n = 20) and diabetic patients (n = 60) were analyzed by flow cytometry and confocal microscopy. Clotting time and purified coagulation complex assays were used to measure PCA.

RESULTS

PS exposure on platelets and monocytes was higher in proliferative DR (PDR) patients than in non-PDR patients or controls. The highest levels of MPs (derived from platelets [30%], erythrocytes [13%], leukocytes [28%], and endothelial cells [10%]) were found in patients with PDR. In addition, PS exposure on blood cells and shed MPs in DR patients led to significantly increased FXa and FIIa generation, fibrin formation, and markedly shortened coagulation time. Moreover, lactadherin reduced 70% of PCA by blocking PS, while an anti-tissue factor antibody had a smaller effect.

CONCLUSION

Our results confirmed that PCA in DR patients may be partly ascribed to PS exposure and MP release from blood and endothelial cells. Lactadherin may act as an efficient anticoagulant factor in this process.

Small extracellular vesicles from Ptpn1-deficient macrophages alleviate intestinal inflammation by reprogramming macrophage polarization via lactadherin enrichment

Tyrosine-protein phosphatase non-receptor type 1 (Ptpn1) is known to be involved in macrophage polarization. However, whether and how Ptpn1 regulates macrophage phenotype to affect intestinal epithelial barrier function remains largely unexplored. Herein, we investigated the impact of Ptpn1 and macrophage-derived small extracellular vesicles (sEVs) on macrophage-intestinal epithelial cell (IEC) interactions in the context of intestinal inflammation. We found that Ptpn1 knockdown shifts macrophages toward the anti-inflammatory M2 phenotype, thereby promoting intestinal barrier integrity and suppressing inflammatory response in the macrophage-IEC co-culture model. We further revealed that conditioned medium or sEVs isolated from Ptp1b knockdown macrophages are the primary factor driving the beneficial outcomes. Consistently, administration of the sEVs from Ptpn1-knockdown macrophages reduced disease severity and ameliorated intestinal inflammation in LPS-challenged mice. Furthermore, depletion of macrophages in mice abrogated the protective effect of Ptpn1-knockdown macrophage sEVs against Salmonella Typhimurium infection. Importantly, we found lactadherin to be highly enriched in the sEVs of Ptpn1-knockdown macrophages. Administration of recombinant lactadherin alleviated intestinal inflammation and barrier dysfunction by inducing macrophage M2 polarization. Interestingly, sEVs lactadherin was also internalized by macrophages and IECs, leading to macrophage M2 polarization and enhanced intestinal barrier integrity. Mechanistically, the anti-inflammatory and barrier-enhancing effect of lactadherin was achieved by reducing TNF-α and NF-κB activation. Thus, we demonstrated that sEVs from Ptpn1-knockdown macrophages mediate the communication between IECs and macrophages through enrichment of lactadherin. The outcome could potentially lead to the development of novel therapies for intestinal inflammatory disorders.

Simplified Preparation of αvβ3 Integrin-Targeted Microbubbles Based on a Clinically Available Ultrasound Contrast Agent: Validation in a Tumor-Bearing Mouse Model

The usefulness of ultrasound molecular imaging with α_vβ₃ integrin-targeted microbubbles for detecting tumor angiogenesis has been demonstrated. Recently, we developed α_vβ₃ integrin-targeted microbubbles by modifying clinically available microbubbles (Sonazoid, Daiichi-Sankyo Pharmaceuticals, Tokyo, Japan) with a secreted glycoprotein (lactadherin). The aims of our present study were to simplify the preparation of lactadherin-bearing Sonazoid and to examine the diagnostic utility of lactadherin-bearing Sonazoid for α_vβ₃ integrin-expressing tumor vessels by using SK-OV-3-tumor-bearing mice. By incubating 1.2 × 10⁷ Sonazoid microbubbles with 1.0 µg lactadherin, the complicated washing and centrifugation steps during the microbubble preparation could be omitted with no significant reduction in labeling ratio of lactadherin-bearing Sonazoid. In addition, the number of Sonazoid microbubbles accumulated in the SK-OV-3 tumor was significantly increased by modifying Sonazoid with lactadherin. Our data suggest that the lactadherin-bearing Sonazoid is an easily prepared and potentially clinically translatable targeted microbubble for α_vβ₃ integrin-expressing vessels.

Imaging the myocardium at risk with ⁹⁹mTc-lactadherin administered after reperfusion in a porcine model

INTRODUCTION

Phosphatidylserine is translocated from the inner to the outer leaflet of the plasma membrane in the early stages of apoptosis and necrosis and in reversibly injured cells. In rabbit hearts, ischemia followed by reperfusion results in exposure of phosphatidylserine on myocytes unaffected by apoptosis or necrosis. Lactadherin was recently introduced as a highly sensitive phosphatidylserine ligand. We hypothesized that ischemic myocardial cell damage can be identified by radio-labeled lactadherin and that the ischemic area at risk (AAR) can be visualized retrospectively after reperfusion.

METHODS

Left anterior descending coronary artery in pigs was occluded for 20 minutes, 45 minutes or 45 minutes preceded by ischemic preconditioning. In all three groups, (99m)Tc-lactadherin was injected intravenously 30 minutes after reperfusion. The AAR was demarcated by Evans blue and the infarct size by 2,3,5,-triphenyltetrazodium chloride staining.

RESULTS

The regional myocardial uptake of (99m)Tc-lactadherin closely correlated with the AAR (r=.83, P = .001). The area of (99m)Tc-lactadherin uptake was unaltered by a shorter duration of ischemia and ischemic preconditioning (P=.23) despite significantly different infarct development (P=.001).

CONCLUSION

The results suggest that (99m)Tc-lactadherin can be used as a sensitive marker for AAR imaging when injected 30 minutes after reperfusion following acute ischemia.

Cell injury after ischemia and reperfusion in the porcine kidney evaluated by radiolabelled microspheres, sestamibi, and lactadherin

Background

The purpose of the present study was to quantify renal cell injury after ischemia and reperfusion in a pig model using ^99mTc-lactadherin as a marker of apoptosis and ^99mTc-sestamibi as a marker of mitochondrial dysfunction.

Methods

Thirty-four pigs were randomized into unilateral renal warm ischemia of 120 (WI₁₂₀) or 240 min (WI₂₄₀). The glomerular filtration rate (GFR) was calculated by renal clearance of ⁵¹Cr-ethylenediaminetetraacetic acid, and apoptosis was quantified by immunohistochemical detection of caspase-3. After 240 min of reperfusion, intravenous ^99mTc-lactadherin or ^99mTc-sestamibi was injected simultaneously with ¹⁵³Gd microspheres into the aorta. Ex-vivo static planar images of the kidneys were acquired for determination of the differential renal function of tracer distribution using a gamma camera.

Results

In WI₁₂₀, there was no significant difference in the uptake of microspheres in the ischemic and contralateral normal kidney indicating adequate perfusion (uptake in ischemic kidney relative to the sum of uptake in both kidneys; 46% ± 12% and 51% ± 5%). In WI₂₄₀, the uptake of microspheres was severely reduced in both groups (17% ± 11% and 27% ± 17%). GFR was severely reduced in the post ischemic kidney in both groups.

In both groups, the uptake of lactadherin was reduced (41% ± 8%, 17% ± 13%) but not different from the uptake of ¹⁵³Gd microspheres. Caspase-3-positive cell profiles were increased in the post-ischemic kidneys (p < 0.001) and increased as the length of ischemia increased (p = 0.003). In both WI₁₂₀ and WI₂₄₀, the amount of ^99mTc-sestamibi in the ischemic kidney was significantly lower than the amount of ¹⁵³Gd microspheres (40 ± 5 versus 51 ± 5 and 20 ± 11 versus 27 ± 17; p < 0.05).

Conclusions

In an established pig model with unilateral renal warm ischemia, we found significantly reduced ^99mTc-sestamibi uptake relative to perfusion in the kidneys exposed to ischemia indicating a potential ability to detect renal ischemic and reperfusion injuries. However, apoptosis was not detected using ^99mTc-lactadherin in the post-ischemic kidneys despite increased number of caspase-3-positive cell profiles.

Trial registration

This study is approved by the Danish Inspectorate of Animal Experiments (2010/561-1837).

Identification and functional characterization of lactadherin, an agglutinating glycoprotein from the chordate Styela clava

Lactadherin is an extracellular matrix glycoprotein with stimulating agglutination ability that plays crucial roles in animal immunology. In the present study, a novel lactadherin, Sc-lactadherin, was identified from the marine invertebrate chordate, Styela clava. Its full-length cDNA consisted of 579 bps, encoding 193 amino acids with a coagulation FA58C domain. Recombinant Sc-lactadherin via a prokaryotic expression system showed strong hemocyte fusion activity. Therefore, we further examined its effects on cell behaviors using human umbilical vein endothelial cells (HUVECs) and human cervical cancer (HeLa) cells. Recombinant Sc-lactadherin significantly increased the proliferation rate of HUVECs and HeLa cells and improved the cell migration rate of HUVECs. These results demonstrated that the lactadherin identified from the marine ascidian displayed the agglutinating activity. Functional characterization of the recombinant protein showed that it promoted cell proliferation and migration, indicating the potential roles of Sc-lactadherin in immunology and organogenesis in marine ascidians.

Using a lactadherin-immobilized silicon surface for capturing and monitoring plasma microvesicles as a foundation for diagnostic device development

Microvesicles (MVs) are found in several types of body fluids and are promising disease biomarkers and therapeutic targets. This study aimed to develop a novel biofunctionalized surface for binding plasma microvesicles (PMVs) based on a lab-on-a-chip (LOC) approach. A new lactadherin (LACT)-functionalized surface was prepared and examined for monitoring PMVs. Moreover, two different strategies of LACT immobilization on a silicon surface were applied to compare different LACT orientations. A higher PMV to LACT binding efficiency was observed for LACT bonded to an αvβ3 integrin-functionalized surface compared with that for LACT directly bonded to a glutaraldehyde-modified surface. Effective binding of PMVs and its components for both LACT immobilization strategies was confirmed using spectral ellipsometry and time-of-flight secondary ion mass spectrometry methods. The proposed PMV capturing system can be used as a foundation to design novel point-of-care (POC) diagnostic devices to detect and characterize PMVs in clinical samples. Graphical Abstract.

Brain-derived extracellular vesicles mediate traumatic brain injury associated multi-organ damage

Traumatic brain injury (TBI) can negatively impact systemic organs, which can lead to more death and disability. However, the mechanism underlying the effect of TBI on systemic organs remains unclear. In previous work, we found that brain-derived extracellular vesicles (BDEVs) released from the injured brain can induce systemic coagulation with a widespread fibrin deposition in the microvasculature of the lungs, kidney, and heart in a mouse model of TBI. In this study, we investigated whether BDEVs can induce heart, lung, liver, and kidney injury in TBI mice. The results of pathological staining and related biomarkers indicated that BDEVs can induce histological damage and systematic dysfunction. In vivo imaging system demonstrated that BDEVs can gather in systemic organs. We also found that BDEVs could induce cell apoptosis in the lung, liver, heart, and kidney. Furthermore, we discovered that BDEVs could cause multi-organ endothelial cell damage. Finally, this secondary multi-organ damage could be relieved by removing circulating BDEVs. Our research provides a novel perspective and potential mechanism of TBI-associated multi-organ damage.

Phosphatidylserine induce thrombotic tendency and liver damage in obstructive jaundice

INTRODUCTION

Hypercoagulability contributes to the majority of deaths and organ failure associated with obstructive jaundice (OJ). However, the exact mechanism of the coagulopathy in OJ remains elusive. Our objectives were to demonstrate whether phosphatidylserine (PS) exposure on blood cells (BCs), microparticles (MPs), and endothelial cells (ECs) can account for the hypercoagulability and liver damage in OJ patients.

METHODS

We evaluated OJ patients at two time point, which before (Day 0) and 7 days (Day 7) after the endoscopic retrograde cholangiopancreatography procedure (ERCP), and compared with healthy controls. Lactadherin was used to quantify PS exposure on BCs, MPs and ECs. Human umbilical vein endothelial cells (HUVECs) were incubated with serum of OJ patients and the expression of PS were evaluated. Meanwhile, healthy BCs and HUVECs were treated with 0, 25, 50 or 100µM unconjugated bilirubin (UCB) and PS exposure on cells were evaluated. Procoagulant activity was evaluated by purified coagulation complex assays, clotting time, and fibrin turbidity. In addition, we established a cholestatic mouse model by bile duct ligation to determine the potential role of PS in intrahepatic coagulation and liver damage.

RESULTS

Using flow cytometry, we found that OJ patients exhibited elevated levels of PS + BCs and associated MPs compared to the controls. Furthermore, the number of PS + BCs and MPs in patients at Day 0 were significantly higher than in patients at Day 7. Similarly, we observed markedly elevated PS exposure on HUVECs cultured with serum from patients at Day 0 versus serum from patients at Day 7. In vitro assays, PS exposure on BCs and HUVECs progressively increased with the concentration of UCB. Moreover, PS + BCs and MPs contributed to greatly shortened coagulation time and markedly enhanced coagulation factor Xa, thrombin, and fibrin generation. This procoagulant activity could be blocked approximately 80%, by the addition of lactadherin. Moreover, cholestatic mice exhibited significantly increased levels of liver tissue necrosis, fibrin deposition, and thrombophilia compared to sham mice. The enhanced intrahepatic coagulation and liver injury could be reversed by inhibiting PS with lactadherin.

CONCLUSIONS

These results highlight the pathogenic activity of PS + cells and MPs in promoting a prothrombotic environment and liver damage in OJ. As such, lactadherin, a PS blockade, may be a viable therapeutic strategy for treating such patients.

Lactadherin immunoblockade in small extracellular vesicles inhibits sEV-mediated increase of pro-metastatic capacities

BACKGROUND

Tumor-derived small extracellular vesicles (sEVs) can promote tumorigenic and metastatic capacities in less aggressive recipient cells mainly through the biomolecules in their cargo. However, despite recent advances, the specific molecules orchestrating these changes are not completely defined. Lactadherin is a secreted glycoprotein typically found in the milk fat globule membrane. Its overexpression has been associated with increased tumorigenesis and metastasis in breast cancer (BC) and other tumors. However, neither its presence in sEVs secreted by BC cells, nor its role in sEV-mediated intercellular communication have been described. The present study focused on the role of lactadherin-containing sEVs from metastatic MDA-MB-231 triple-negative BC (TNBC) cells (sEV-MDA231) in the promotion of pro-metastatic capacities in non-tumorigenic and non-metastatic recipient cells in vitro, as well as their pro-metastatic role in a murine model of peritoneal carcinomatosis.

RESULTS

We show that lactadherin is present in sEVs secreted by BC cells and it is higher in sEV-MDA231 compared with the other BC cell-secreted sEVs measured through ELISA. Incubation of non-metastatic recipient cells with sEV-MDA231 increases their migration and, to some extent, their tumoroid formation capacity but not their anchorage-independent growth. Remarkably, lactadherin blockade in sEV-MDA231 results in a significant decrease of those sEV-mediated changes in vitro. Similarly, intraperitoneally treatment of mice with MDA-MB-231 BC cells and sEV-MDA231 greatly increase the formation of malignant ascites and tumor micronodules, effects that were significantly inhibited when lactadherin was previously blocked in those sEV-MDA231.

CONCLUSIONS

As to our knowledge, our study provides the first evidence on the role of lactadherin in metastatic BC cell-secreted sEVs as promoter of: (i) metastatic capacities in less aggressive recipient cells, and ii) the formation of malignant ascites and metastatic tumor nodules. These results increase our understanding on the role of lactadherin in sEVs as promoter of metastatic capacities which can be used as a therapeutic option for BC and other malignancies.

Milk Fat Globules: 2024 Updates

Milk fat globules (MFGs) are a remarkable example of nature's ingenuity. Human milk (HM) carries contains 3-5% fat, 0.8-0.9% protein, 6.9-7.2% carbohydrate calculated as lactose, and 0.2% mineral constituents. Most of these nutrients are carried in these MFGs, which are composed of an energy-rich triacylglycerol (TAG) core surrounded by a triple membrane structure. The membrane contains polar lipids, specialized proteins, glycoproteins, and cholesterol. Each of these bioactive components serves important nutritional, immunological, neurological, and digestive functions. These MFGs are designed to release energy rapidly in the upper gastrointestinal tract and then persist for some time in the gut lumen so that the protective bioactive molecules are conveyed to the colon. These properties may shape the microbial colonization and innate immune properties of the developing gastrointestinal tract. Milk fat globules in milk from humans and ruminants may resemble in structure but there are considerable differences in size, profile, composition, and specific constituents. There are possibilities to not only enhance the nutritional composition in a goal-oriented fashion to correct specific deficiencies in the infant but also to use these fat globules as a nutraceutical in infants who require specific treatments. To mention a few, there might be possibilities in enhancing neurodevelopment, in defense against gastrointestinal and respiratory tract infections, improving insulin sensitivity, treating chronic inflammation, and altering plasma lipids. This review provides an overview of the composition, structure, and biological activities of the various components of the MFGs. We have assimilated research findings from our own laboratory with an extensive review of the literature utilizing key terms in multiple databases including PubMed, EMBASE, and Science Direct. To avoid bias in the identification of studies, keywords were short-listed a priori from anecdotal experience and PubMed's Medical Subject Heading (MeSH) thesaurus.

Common proteins analysis of different mammals' mature milk by 4D-Label-Free

The milk proteins from samples of 13 different animals were identified utilizing 4D-Label-Free proteomics technology, leading to the identification of a substantial number of proteins. Among the various samples, Chinese people (CHP) milk proteins exhibited the highest count, with 1149 distinct proteins. Simultaneously, we identified common proteins present in these animal milk. It's notable presence in goat milk contributes to enhancing infant infection resistance, showcasing the beneficial role of lactoperoxidase. Galectin-3 binding protein (Gal-3BP) and tetraspanin in human milk are significantly higher than those in other animals, which determine the prominent antiviral effect of human milk and the important processes related to cell transduction. Furthermore, human milk, camel milk, goat milk and sheep milk proved to be rich sources of milk fat globule membrane (MFGM) proteins. The insights obtained from this study can serve as a foundational framework for exploring the role of different animal milk proteins in disease treatment and the composition of infant formula.

Lactadherin adjusts secretion and expression of interleukin-2, interleukin-4 and interferon-γ in EEI-10 cells

AIM: To define the function that lactadherin adjusts lymphocytes of gut-associated lymphoid tissue (GALT) cytokines secretion and expression.

METHODS: We extracted mRNA from human mammary cancer MCF-7 cells, and amplified the target gene from cDNA. The lactadherin was cloned into PET28 vector by digestion, ligation then transformation into DH5α cells to check positive clones. The cDNA encoding the desired polypeptide was transformed into BL-21 cells. The expression of recombinant protein was induced by isopropyl-β-D-thiogalactopyranoside (IPTG). The protein was purified with a nickel column. We detected the proliferation of EEI-10 cells after treated by different concentration of lactadherin using H³-Tdr assay. Then we checked the secretion of IL-2, IL-4 and IFN-g in treated EEI-10 cells using enzyme-linked immunosorbent assay (ELISA) and the cytokines mRNA expression using reverse transcription polymerase chain reaction (RT-PCR).

RESULTS: Lactadherin protein was successfully obtained and confirmed by SDS-PAGE electrophoresis and specific antibody verification. When treated with 250 mg/L lactadherin, EEI-10 cells showed a significant increase in proliferation. The levels of IL-2 and IFN-γ secretion enhanced significantly in the cells with lactadherin functional peptide in comparison with those in the untreated cells (P = 0.0394, P = 0.0082, respectively), but IL-4 secretion had no marked change. The expression of IL-2 and IFN-γ mRNA, especially IFN-γ mRNA, were also higher in the lactadherin-treated cells than those in the untreated cells.

CONCLUSION: Lactadherin can up-regulated the secretion and expression of IL-2 and IFN-γ in EEI-10 cells.

Brain-derived extracellular vesicles mediate systemic coagulopathy and inflammation after traumatic brain injury

Traumatic brain injury (TBI) can induce systemic coagulopathy and inflammation, thereby increasing the risk of mortality and disability. However, the mechanism causing systemic coagulopathy and inflammation following TBI remains unclear. In prior research, we discovered that brain-derived extracellular vesicles (BDEVs), originating from the injured brain, can activate the coagulation cascade and inflammatory cells. In this study, we primarily investigated how BDEVs affect systemic coagulopathy and inflammation in peripheral circulation. The results of cytokines and coagulation function indicated that BDEVs can lead to systemic coagulopathy and inflammation by influencing inflammatory factors and chemokines within 24 h. Furthermore, according to flow cytometry and blood cell counter results, we found that BDEVs induced changes in the blood count such as a reduced number of platelets and leukocytes and an increased percentage of neutrophils, macrophages, activated platelets, circulating platelet-EVs, and leukocyte-derived EVs. We also discovered that eliminating circulating BDEVs with lactadherin helped improve coagulopathy and inflammation, relieved blood cell dysfunction, and decreased the circulating platelet-EVs and leukocyte-derived EVs. Our research provides a novel viewpoint and potential mechanism of TBI-associated secondary damage.

Genetically encoded phosphatidylserine biosensor for in vitro, ex vivo and in vivo labelling

BACKGROUND

The dynamics of phosphatidylserine in the plasma membrane is a tightly regulated feature of eukaryotic cells. Phosphatidylserine (PS) is found preferentially in the inner leaflet of the plasma membrane. Disruption of this asymmetry leads to the exposure of phosphatidylserine on the cell surface and is associated with cell death, synaptic pruning, blood clotting and other cellular processes. Due to the role of phosphatidylserine in widespread cellular functions, an efficient phosphatidylserine probe is needed to study them. Currently, a few different phosphatidylserine labelling tools are available; however, these labels have unfavourable signal-to-noise ratios and are difficult to use in tissues due to limited permeability. Their application in living tissue requires injection procedures that damage the tissue and release damage-associated molecular patterns, which in turn stimulates phosphatidylserine exposure.

METHODS

For this reason, we developed a novel genetically encoded phosphatidylserine probe based on the C2 domain of the lactadherin (MFG-E8) protein, suitable for labelling exposed phosphatidylserine in various research models. We tested the C2 probe specificity to phosphatidylserine on hybrid bilayer lipid membranes by observing surface plasmon resonance angle shift. Then, we analysed purified fused C2 proteins on different cell culture lines or engineered AAVs encoding C2 probes on tissue cultures after apoptosis induction. For in vivo experiments, neurotropic AAVs were intravenously injected into perinatal mice, and after 2 weeks, brain slices were collected to observe C2-SNAP expression.

RESULTS

The biophysical analysis revealed the high specificity of the C2 probe for phosphatidylserine. The fused recombinant C2 proteins were suitable for labelling phosphatidylserine on the surface of apoptotic cells in various cell lines. We engineered AAVs and validated them in organotypic brain tissue cultures for non-invasive delivery of the genetically encoded C2 probe and showed that these probes were expressed in the brain in vivo after intravenous AAV delivery to mice.

CONCLUSIONS

We have demonstrated that the developed genetically encoded PS biosensor can be utilised in a variety of assays as a two-component system of C2 and C2m2 fusion proteins. This system allows for precise quantification and PS visualisation at directly specified threshold levels, enabling the evaluation of PS exposure in both physiological and cell death processes.