Three-dimensional structured illumination microscopy of liver sinusoidal endothelial cell fenestrations

The role of alpha-fetoprotein in the tumor microenvironment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a prevalent malignant cancer worldwide, characterized by high morbidity and mortality rates. Alpha-fetoprotein (AFP) is a glycoprotein synthesized by the liver and yolk sac during fetal development. However, the serum levels of AFP exhibit a significant correlation with the onset and progression of HCC in adults. Extensive research has demonstrated that the tumor microenvironment (TME) plays a crucial role in the malignant transformation of HCC, and AFP is a key factor in the TME, promoting HCC development. The objective of this review was to analyze the existing knowledge regarding the role of AFP in the TME. Specifically, this review focused on the effect of AFP on various cells in the TME, tumor immune evasion, and clinical application of AFP in the diagnosis and treatment of HCC. These findings offer valuable insights into the clinical treatment of HCC.

Liver sinusoidal endothelial cells show reduced scavenger function and downregulation of Fc gamma receptor IIb, yet maintain a preserved fenestration in the Glmpgt/gt mouse model of slowly progressing liver fibrosis

Liver sinusoidal endothelial cells (LSECs) are fenestrated endothelial cells with a unique, high endocytic clearance capacity for blood-borne waste macromolecules and colloids. This LSEC scavenger function has been insufficiently characterized in liver disease. The Glmpgt/gt mouse lacks expression of a subunit of the MFSD1/GLMP lysosomal membrane protein transporter complex, is born normal, but soon develops chronic, mild hepatocyte injury, leading to slowly progressing periportal liver fibrosis, and splenomegaly. This study examined how LSEC scavenger function and morphology are affected in the Glmpgt/gt model. FITC-labelled formaldehyde-treated serum albumin (FITC-FSA), a model ligand for LSEC scavenger receptors was administered intravenously into Glmpgt/gt mice, aged 4 months (peak of liver inflammation), 9-10 month, and age-matched Glmpwt/wt mice. Organs were harvested for light and electron microscopy, quantitative image analysis of ligand uptake, collagen accumulation, LSEC ultrastructure, and endocytosis receptor expression (also examined by qPCR and western blot). In both age groups, the Glmpgt/gt mice showed multifocal liver injury and fibrosis. The uptake of FITC-FSA in LSECs was significantly reduced in Glmpgt/gt compared to wild-type mice. Expression of LSEC receptors stabilin-1 (Stab1), and mannose receptor (Mcr1) was almost similar in liver of Glmpgt/gt mice and age-matched controls. At the same time, immunostaining revealed differences in the stabilin-1 expression pattern in sinusoids and accumulation of stabilin-1-positive macrophages in Glmpgt/gt liver. FcγRIIb (Fcgr2b), which mediates LSEC endocytosis of soluble immune complexes was widely and significantly downregulated in Glmpgt/gt liver. Despite increased collagen in space of Disse, LSECs of Glmpgt/gt mice showed well-preserved fenestrae organized in sieve plates but the frequency of holes >400 nm in diameter was increased, especially in areas with hepatocyte damage. In both genotypes, FITC-FSA also distributed to endothelial cells of spleen and bone marrow sinusoids, suggesting that these locations may function as possible compensatory sites of clearance of blood-borne scavenger receptor ligands in liver fibrosis.

Liver endothelial cells in NAFLD and transition to NASH and HCC

Non-alcoholic fatty liver disease (NAFLD) is considered as the hepatic manifestation of metabolic syndrome, which is characterised by obesity, insulin resistance, hypercholesterolemia and hypertension. NAFLD is the most frequent liver disease worldwide and more than 10% of NAFLD patients progress to the inflammatory and fibrotic stage of non-alcoholic steatohepatitis (NASH), which can lead to end-stage liver disease including hepatocellular carcinoma (HCC), the most frequent primary malignant liver tumor. Liver sinusoidal endothelial cells (LSEC) are strategically positioned at the interface between blood and hepatic parenchyma. LSECs are highly specialized cells, characterised by the presence of transcellular pores, called fenestrae, and exhibit anti-inflammatory and anti-fibrotic characteristics under physiological conditions. However, during NAFLD development they undergo capillarisation and acquire a phenotype similar to vascular endothelial cells, actively promoting all pathophysiological aspects of NAFLD, including steatosis, inflammation, and fibrosis. LSEC dysfunction is critical for the progression to NASH and HCC while restoring LSEC homeostasis appears to be a promising approach to prevent NAFLD progression and its complications and even reverse tissue damage. In this review we present current information on the role of LSEC throughout the progressive phases of NAFLD, summarising in vitro and in vivo experimental evidence and data from human studies.

The unique structural and functional characteristics of glomerular endothelial cell fenestrations and their potential as a therapeutic target in kidney disease

Glomerular endothelial cell (GEnC) fenestrations are a critical component of the glomerular filtration barrier. Their unique nondiaphragmed structure is key to their function in glomerular hydraulic permeability, and their aberration in disease can contribute to loss of glomerular filtration function. This review provides a comprehensive update of current understanding of the regulation and biogenesis of fenestrae. We consider diseases in which GEnC fenestration loss is recognized or may play a role and discuss methods with potential to facilitate the study of these critical structures. Literature is drawn from GEnCs as well as other fenestrated cell types such as liver sinusoidal endothelial cells that most closely parallel GEnCs.

Lactosylated Chitosan Nanoparticles Potentiate the Anticancer Effects of Telmisartan In Vitro and in a N-Nitrosodiethylamine-Induced Mice Model of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the leading cause of cancer-related mortality worldwide. Telmisartan (TLM), a BSC class II drug, has been reported to have antiproliferative activity in HCC. However, its therapeutic activity is limited by poor bioavailability and unpredictable distribution. This work aimed to enhance TLM's liver uptake for HCC management through passive and active targeting pathways utilizing chitosan nanoparticles decorated with lactose (LCH NPs) as a delivery system. In vitro cell cytotoxicity and cellular uptake studies indicated that TLM-LCH NPs significantly (p < 0.05) enhanced the antiproliferative activity and cellular uptake percentage of TLM. In vivo bioavailability and liver biodistribution studies indicated that TLM-LCH NPs significantly (p < 0.05) enhanced TLM concentrations in plasma and the liver. The relative liver uptake of TLM from TLM-LCH NPs was 2-fold higher than that of unmodified NPs and 5-fold higher than that of plain TLM suspension. In vivo studies of a N-nitrosodiethylamine-induced HCC model revealed that administration of TLM through LCH NPs improved liver histology and resulted in lower serum alpha-fetoprotein (AFP), matrix metalloproteinase 2 (MMP-2), vascular endothelial growth factor (VEGF) levels, and liver weight index compared to plain TLM and TLM-loaded unmodified NPs. These results reflected the high potentiality of LCH NPs as a liver-targeted delivery system for TLM in the treatment of HCC.

Three-dimensional structured illumination microscopy with enhanced axial resolution

The axial resolution of three-dimensional structured illumination microscopy (3D SIM) is limited to ∼300 nm. Here we present two distinct, complementary methods to improve axial resolution in 3D SIM with minimal or no modification to the optical system. We show that placing a mirror directly opposite the sample enables four-beam interference with higher spatial frequency content than 3D SIM illumination, offering near-isotropic imaging with ∼120-nm lateral and 160-nm axial resolution. We also developed a deep learning method achieving ∼120-nm isotropic resolution. This method can be combined with denoising to facilitate volumetric imaging spanning dozens of timepoints. We demonstrate the potential of these advances by imaging a variety of cellular samples, delineating the nanoscale distribution of vimentin and microtubule filaments, observing the relative positions of caveolar coat proteins and lysosomal markers and visualizing cytoskeletal dynamics within T cells in the early stages of immune synapse formation.

Telmisartan-Loaded Lactosylated Chitosan Nanoparticles as a Liver Specific Delivery System: Synthesis, Optimization and Targeting Efficiency

Hepatocellular carcinoma (HCC) has a significant economic impact and a high mortality rate. Telmisartan (TLM) is a potential therapy for HCC, but it has a limited scope in drug delivery due to unpredictable distribution and poor bioavailability. The objective of this study was to prepare, design, and in vitro evaluate lactose-modified chitosan nanoparticles (LCH NPs) as a liver-targeted nanocarrier for TLM with the potential to offer a promising HCC therapy. The combination of chitosan with lactose was successfully attained using the Maillard reaction. TLM-LCH NPs were prepared, characterized, and optimized with the developed 2³ full factorial design. The optimized formulation (F1) was in vitro and in vivo characterized. LCH was synthesized with an acceptable yield of 43.8 ± 0.56%, a lactosylation degree of 14.34%, and a significantly higher aqueous solubility (6.28 ± 0.21 g/L) compared to native chitosan (0.25 ± 0.03 g/L). In vitro characterization demonstrated that, F1 had a particle size of 145.46 ± 0.7 nm, an entrapment efficiency of 90.21 ± 0.28%, and a surface charge of + 27.13 ± 0.21 mV. In vitro TLM release from F1 was most consistent with the Higuchi model and demonstrated significantly higher release at pH 5.5. Moreover, a significantly higher ratio of liver to plasma concentration was observed with TLM-LCH NPs compared to plain TLM and unmodified TLM-NPs. The obtained results nominate TLM-LCH NPs as a promising carrier for enhancing liver targeting of TLM in treatment of HCC.

Label-free superior contrast with c-band ultra-violet extinction microscopy

In 1934, Frits Zernike demonstrated that it is possible to exploit the sample's refractive index to obtain superior contrast images of biological cells. The refractive index contrast of a cell surrounded by media yields a change in the phase and intensity of the transmitted light wave. This change can be due to either scattering or absorption caused by the sample. Most cells are transparent at visible wavelengths, which means the imaginary component of their complex refractive index, also known as extinction coefficient k, is close to zero. Here, we explore the use of c-band ultra-violet (UVC) light for high-contrast high-resolution label-free microscopy, as k is naturally substantially higher in the UVC than at visible wavelengths. Using differential phase contrast illumination and associated processing, we achieve a 7- to 300-fold improvement in contrast compared to visible-wavelength and UVA differential interference contrast microscopy or holotomography, and quantify the extinction coefficient distribution within liver sinusoidal endothelial cells. With a resolution down to 215 nm, we are, for the first time in a far-field label-free method, able to image individual fenestrations within their sieve plates which normally requires electron or fluorescence superresolution microscopy. UVC illumination also matches the excitation peak of intrinsically fluorescent proteins and amino acids and thus allows us to utilize autofluorescence as an independent imaging modality on the same setup.

Lipid-based nucleic acid therapeutics with in vivo efficacy

Synthetic vectors for therapeutic nucleic acid delivery are currently competing significantly with their viral counter parts due to their reduced immunogenicity, large payload capacity, and ease of manufacture under GMP-compliant norms. The approval of Onpattro, a lipid-based siRNA therapeutic, and the proven clinical success of two lipid-based COVID-19 vaccines from Pfizer-BioNTech, and Moderna heralded the specific advantages of lipid-based systems among all other synthetic nucleic acid carriers. Lipid-based systems with diverse payloads-plasmid DNA (pDNA), antisense oligonucleotide (ASO), small interfering RNA (siRNA), microRNA (miRNA), small activating RNA (saRNA), and messenger RNA (mRNA)-are now becoming a mature technology, with growing impact in the clinic. Research over four decades identified the key factors determining the therapeutic success of these multi-component systems. Here, we discuss the main nucleic acid-based technologies, presenting their mechanism of action, delivery barriers facing them, the structural properties of the payload as well as the component lipids that regulate physicochemical properties, pharmacokinetics and biodistribution, efficacy, and toxicity of the resultant nanoparticles. We further detail on the formulation parameters, evolution of the manufacturing techniques that generate reproducible and scalable outputs, and key manufacturing aspects that enable control over physicochemical properties of the resultant particles. Preclinical applications of some of these formulations that were successfully translated from in vitro studies to animal models are subsequently discussed. Finally, clinical success and failure of these systems starting from 1993 to present are highlighted, in a holistic literature review focused on lipid-based nucleic acid delivery systems. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

[An update of understanding of the hepatic vascular system and new research strategies]

Although the portal vessels, liver sinusoids, and central vessels are known to contain microvessels with different structures and functions, their changes and roles in liver fibrogenesis have not been fully understood. Recent studies suggest that in mouse models of liver fibrogenesis, vascular changes can occur at a very early stage, and different liver vessels undergo different changes and play different roles, as shown by a decreased number of portal vessels, increased sinusoid capillarization and increased central vessels. The increase of portal vessels alleviates liver fibrosis, while the increase of central vessels and sinusoid capillarization aggravates liver fibrosis. A full understanding of the regulatory mechanisms of each of these vessels is vital for treatment of liver fibrosis. A combined regulation of different endothelial cell (EC) regulatory signaling pathways for vascular normalization may provide new strategies for liver fibrosis therapy. Further studies of the changes and functions of blood vessels in different liver diseases, liver development and regeneration may bring about important breakthroughs. This review summarizes the changes of 3 hepatic microvessels and their roles in liver fibrogenesis and propose the major directions of future studies in this field.

Transcytosis-enabled active extravasation of tumor nanomedicine

Extravasation is the first step for nanomedicines in circulation to reach targeted solid tumors. Traditional nanomedicines have been designed to extravasate into tumor interstitium through the interendothelial gaps previously assumed rich in tumor blood vessels, i.e., the enhanced permeability and retention (EPR) effect. While the EPR effect has been validated in animal xenograft tumor models, accumulating evidence implies that the EPR effect is very limited and highly heterogeneous in human tumors, leading to highly unpredictable and inefficient extravasation and thus limited therapeutic efficacy of nanomedicines, including those approved in clinics. Enabling EPR-independent extravasation is the key to develop new generation of nanomedicine with enhanced efficacy. Transcytosis of tumor endothelial cells can confer nanomedicines to actively extravasate into solid tumors without relying on the EPR effect. Here, we review and prospectthe development of transcytosis-inducing nanomedicines, in hope of providing instructive insights for design of nanomedicines that can undergo selective transcellular transport across tumor endothelial cells, and thus inspiring the development of next-generation nanomedicines for clinical translation.

Alcohol-associated capillarization of sinusoids: A critique since the discovery by Schaffner and Popper in 1963

This article reviews the literature on capillarization of hepatic sinusoids since its discovery in 1963. Liver sinusoidal endothelial cells are uniquely fenestrated and lack an underlying basement membrane. In chronic liver disease, the sinusoids capillarize and transform into systemic capillaries, a process termed capillarization of sinusoids. The histopathology is marked by defenestration, basement membrane formation, and space of Disse fibrogenesis. Capillarized sinusoids compromise the bidirectional exchange of materials between sinusoids and hepatocytes, leading to hepatocellular dysfunction. Sinusoidal capillarization was first described in active cirrhosis of alcoholics in 1963. Since then, it has been found in early and progressive stages of alcoholic hepatic fibrosis before the onset of cirrhosis. The sinusoidal structure is not altered in alcoholic steatosis without fibrosis. Defenestration impairs the ability of the endothelium to filter chylomicron remnants from sinusoids into the Disse's space, contributing to alcohol-induced postprandial hyperlipidemia and possibly atherosclerosis. Ethanol also modulates the fenestration dynamics in animals. In baboons, chronic alcohol consumption diminishes endothelial porosity in concomitance with hepatic fibrogenesis and in rats defenestrates the endothelium in the absence of fibrosis, and sometimes capillarizes the sinusoids. Acute ethanol ingestion enlarges fenestrations in rats and contracts fenestrations in rabbits. In sinusoidal endothelial cell culture, ethanol elicits fenestration dilation, which is likely related to its interaction with fenestration-associated cytoskeleton. Ethanol potentiates sinusoidal injury caused by cocaine, acetaminophen or lipopolysaccharide in mice and rats. Understanding ethanol's mechanisms on pathogenesis of sinusoidal capillarization and fenestration dynamics will lead to development of methods to prevent risks for atherosclerosis in alcoholism.

The wHole Story About Fenestrations in LSEC

The porosity of liver sinusoidal endothelial cells (LSEC) ensures bidirectional passive transport of lipoproteins, drugs and solutes between the liver capillaries and the liver parenchyma. This porosity is realized via fenestrations - transcellular pores with diameters in the range of 50-300 nm - typically grouped together in sieve plates. Aging and several liver disorders severely reduce LSEC porosity, decreasing their filtration properties. Over the years, a variety of drugs, stimulants, and toxins have been investigated in the context of altered diameter or frequency of fenestrations. In fact, any change in the porosity, connected with the change in number and/or size of fenestrations is reflected in the overall liver-vascular system crosstalk. Recently, several commonly used medicines have been proposed to have a beneficial effect on LSEC re-fenestration in aging. These findings may be important for the aging populations of the world. In this review we collate the literature on medicines, recreational drugs, hormones and laboratory tools (including toxins) where the effect LSEC morphology was quantitatively analyzed. Moreover, different experimental models of liver pathology are discussed in the context of fenestrations. The second part of this review covers the cellular mechanisms of action to enable physicians and researchers to predict the effect of newly developed drugs on LSEC porosity. To achieve this, we discuss four existing hypotheses of regulation of fenestrations. Finally, we provide a summary of the cellular mechanisms which are demonstrated to tune the porosity of LSEC.

[Comparison and progress review of various super-resolution fluorescence imaging techniques]

&#x0201c;Seeing is believing&#x0201d; is the central philosophy of life science research, which runs through the continuous understanding of individual molecules, molecular complexes, molecular dynamic behavior, and the entire molecular network. Living and dynamic molecules are functional in nature; therefore, fluorescence microscopy has emerged as an irreplaceable tool in life science research. However, when fluorescence imaging is performed at the molecular level, some artificial signals may lead to erroneous experimental results. This obstacle is due to the limitation of the optical diffraction limit, and the fluorescence microscope cannot distinguish the target in the diffraction-limited space. Super-resolution fluorescence imaging technology breaks through the diffraction limit, allows visualization of biomolecules at the nanometer scale to the single-molecule level, and allows us to study the structure and dynamic processes of living cells with unprecedented spatial and temporal resolution. It has become a powerful tool for life science research and is gradually being applied to material science, catalytic reaction processes, and photolithography as well. The principle of super-resolution imaging technologies is different; therefore, it has different technical performances, thus limiting their specific technical characteristics and application scope. Current mainstream super-resolution imaging technologies can be classified into three types: structured illumination microscopy (SIM), stimulated emission depletion (STED), and single-molecule localization microscopy (SMLM). These microscopes use different complex technologies, but the strategy is the same and simple, i.e. two adjacent luminous points in a diffraction-limited space can be spatially resolved by time resolution. SIM has been used for three-dimensional real-time imaging in multicellular organisms; however, compared with other technologies, its lower horizontal and vertical resolutions need to be further optimized. STED is limited by its small imaging field of view and high photobleaching; however, the best time resolution can be considered at a high spatial resolution, and it has been proven that three-color STED imaging can be performed. In SMLM super-resolution imaging, the time resolution is affected by the time required to locate all fluorophores, which is closely related to the switching and luminescence properties of the fluorophore. With the improvement in horizontal and vertical resolution of imaging, the image acquisition speed, photobleaching characteristics, and the possibility of multi-color and dynamic imaging have increasingly become the key determinants of super-resolution fluorescence imaging. Thus far, the main use of super-resolution imaging technology has been focused on biological applications for studying structural changes less than 200 nm in dimension. In addition to the combination of structural and morphological characterization with biomolecular detection and identification, super-resolution imaging technology is rapidly expanding into the fields of interaction mapping, multi-target detection, and real-time imaging. In the latter applications, super-resolution imaging technology is particularly advantageous because of more flexible sample staining, higher labeling efficiency, faster and simpler readings, and gentler sample preparation procedures. In this article, we compare the principles of these three technologies and introduce their application progress in biology. We expect the results described herein will help researchers clarify the technical advantages and applicable application directions of different super-resolution imaging technologies, thus facilitating researchers in making reasonable choices in future research.

Composition of Intracellular Protein Corona around Nanoparticles during Internalization

It has been well established that the early-stage interactions of nanoparticles with cells are governed by the extracellular protein corona. However, after entering into the cells, the evolving protein corona is the key to subsequent processing of nanoparticles by cells. To identify the protein corona around intracellular nanoparticles, it is essential to maintain its original compositions during cell treatment. Herein, we develop a paraformaldehyde (PFA) cross-linking strategy to stabilize corona compositions when extracting protein coronas from cells, providing original information on protein coronas around intercellular gold nanoparticles (AuNPs). The stability of the protein corona after PFA cross-linking was carefully investigated with several characterization methods, and the results demonstrate that PFA cross-linking successfully prevents the dissociation and exchange of corona proteins. Then the recovered intracellular protein corona around AuNPs from living HepG2 cells with a PFA cross-linking strategy was subjected to nanoHPLC-MS/MS for proteomic analysis. It was found that the compositions of intracellular protein coronas are dominated by cell-derived proteins and undergo significant variation of protein species and amounts over time during internalization. Time-resolved analysis provides relevant proteins involved in nanoparticle cellular uptake and transportation, indicating that AuNPs are endocytosed mainly by a clathrin-mediated uptake mechanism and directed into an endolysosomal pathway toward their final destination. Such proteomic-based results are verified by pharmacological inhibition and TEM imaging analysis. This work provides a universal strategy to study compositions of protein corona around intercellular nanoparticles and could be a footstone to link the formation of protein corona around nanoparticles to their biological function in cells.

Multiscale and Multimodal Optical Imaging of the Ultrastructure of Human Liver Biopsies

The liver as the largest organ in the human body is composed of a complex macroscopic and microscopic architecture that supports its indispensable function to maintain physiological homeostasis. Optical imaging of the human liver is particularly challenging because of the need to cover length scales across 7 orders of magnitude (from the centimeter scale to the nanometer scale) in order to fully assess the ultrastructure of the entire organ down to the subcellular scale and probe its physiological function. This task becomes even more challenging the deeper within the organ one hopes to image, because of the strong absorption and scattering of visible light by the liver. Here, we demonstrate how optical imaging methods utilizing highly specific fluorescent labels, as well as label-free optical methods can seamlessly cover this entire size range in excised, fixed human liver tissue and we exemplify this by reconstructing the biliary tree in three-dimensional space. Imaging of tissue beyond approximately 0.5 mm length requires optical clearing of the human liver. We present the successful use of optical projection tomography and light-sheet fluorescence microscopy to derive information about the liver architecture on the millimeter scale. The intermediate size range is covered using label-free structural and chemically sensitive methods, such as second harmonic generation and coherent anti-Stokes Raman scattering microscopy. Laser-scanning confocal microscopy extends the resolution to the nanoscale, allowing us to ultimately image individual liver sinusoidal endothelial cells and their fenestrations by super-resolution structured illumination microscopy. This allowed us to visualize the human hepatobiliary system in 3D down to the cellular level, which indicates that reticular biliary networks communicate with portal bile ducts via single or a few ductuli. Non-linear optical microscopy enabled us to identify fibrotic regions extending from the portal field to the parenchyma, along with microvesicular steatosis in liver biopsies from an older patient. Lastly, super-resolution microscopy allowed us to visualize and determine the size distribution of fenestrations in human liver sinusoidal endothelial cells for the first time under aqueous conditions. Thus, this proof-of-concept study allows us to demonstrate, how, in combination, these techniques open up a new chapter in liver biopsy analysis.

Strategies for Delivering Nanoparticles across Tumor Blood Vessels

Nanoparticle transport across tumor blood vessels is a key step in nanoparticle delivery to solid tumors. However, the specific pathways and mechanisms of this nanoparticle delivery process are not fully understood. Here, the biological and physical characteristics of the tumor vasculature and the tumor microenvironment are explored and how these features affect nanoparticle transport across tumor blood vessels is discussed. The biological and physical methods to deliver nanoparticles into tumors are reviewed and paracellular and transcellular nanoparticle transport pathways are explored. Understanding the underlying pathways and mechanisms of nanoparticle tumor delivery will inform the engineering of safer and more effective nanomedicines for clinical translation.

A closer look at the role of insulin for the regulation of male reproductive function

While insulin demonstrates to have a considerable influence on the reproductive system, there are various unanswered questions regarding its precise sites, mechanisms of action, and roles for the developing and functioning of the adult male reproductive system. Apart from its effects on glucose level, insulin has an important role in the reproductive system directly by binding on insulin and IGF receptors in the brain and testis. To date, however, the effect of insulin or its alterations on blood-testis-barrier, as an important regulator of normal spermatogenesis and fertility, has not yet been studied. This review aimed to focus on the experimental and clinical studies to describe mechanisms by which insulin affects the hypothalamic-pituitary-gonadal (HPG) axis, testicular cells, spermatozoa, and sexual behavior. Moreover, we discussed the mechanism and impact of insulin changes in type 1 (insulin deficiency along with persisted or even increased sensitivity) and 2 (insulin resistance along with increased insulin level at the early stages of disease) diabetes and obesity on the male reproductive tract.

Applications of Nanobiomaterials in the Therapy and Imaging of Acute Liver Failure

This review focuses on the therapeutic mechanisms, targeting strategies of various nanomaterials in acute liver failure, and recent advances of diverse nanomaterials for acute liver failure therapy, diagnosis, and imaging. This review provides an outlook on the applications of nanomaterials, especially on the new horizons in acute liver failure therapy, and inspires broader interests across various disciplines. Acute liver failure (ALF), a fatal clinical disease featured with overwhelming hepatocyte necrosis, is a grand challenge in global health. However, a satisfactory therapeutic option for curing ALF is still absent, other than liver transplantation. Nanobiomaterials are currently being developed for the diagnosis and treatment of ALF. The liver can sequester most of nanoparticles from blood circulation, which becomes an intrinsic superiority for nanobiomaterials targeting hepatic diseases. Nanobiomaterials can enhance the bioavailability of free drugs, thereby significantly improving the therapeutic effects in ALF. Nanobiomaterials can also increase the liver accumulation of therapeutic agents and enable more effective targeting of the liver or specific liver cells. In addition, stimuli-responsive, optical, or magnetic nanomaterials exhibit great potential in the therapeutical, diagnostic, and imaging applications in ALF. Therefore, therapeutic agents in combination with nanobiomaterials increase the specificity of ALF therapy, diminish adverse systemic effects, and offer a multifunctional theranostic platform. Nanobiomaterial holds excellent significance and prospects in ALF theranostics. In this review, we summarize the therapeutic mechanisms and targeting strategies of various nanobiomaterials in ALF. We highlight recent developments of diverse nanomedicines for ALF therapy, diagnosis, and imaging. Furthermore, the challenges and future perspectives in the theranostics of ALF are also discussed.

Hepatic sinusoids versus central veins: Structures, markers, angiocrines, and roles in liver regeneration and homeostasis

The blood circulates through the hepatic sinusoids delivering nutrients and oxygen to the liver parenchyma and drains into the hepatic central vein, yet the structures and phenotypes of these vessels are distinctively different. Sinusoidal endothelial cells are uniquely fenestrated, lack basal lamina and possess organelles involved in endocytosis, pinocytosis, degradation, synthesis and secretion. Hepatic central veins are nonfenestrated but are also active in synthesis and secretion. Endothelial cells of sinusoids and central veins secrete angiocrines that play respective roles in hepatic regeneration and metabolic homeostasis. The list of markers for identifying sinusoidal endothelial cells is long and their terminologies are complex. Further, their uses vary in different investigations and, in some instances, could be confusing. Central vein markers are fewer but more distinctive. Here we analyze and categorize the molecular pathways/modules associated with the sinusoid-mediated liver regeneration in response to partial hepatectomy and chemical-induced acute or chronic injury. Similarly, we highlight the findings that central vein-derived angiocrines interact with Wnt/β-catenin in perivenous hepatocytes to direct gene expression and maintain pericentral metabolic zonation. The proposal that perivenous hepatocytes behave as stem/progenitor cells to provoke hepatic homeostatic cell renewal is reevaluated and newer concepts of broad zonal distribution of hepatocyte proliferation in liver homeostasis and regeneration are updated. Thus, this review integrates the structures, biology and physiology of liver sinusoids and central veins in mediating hepatic regeneration and metabolic homeostasis.

Quantitative phase microscopy with enhanced contrast and improved resolution through ultra-oblique illumination (UO-QPM)

Recent developments in phase contrast microscopy have enabled the label-free visualization of certain organelles due to their distinct morphological features, making this method an attractive alternative in the study of cellular dynamics. However tubular structures such as endoplasmic reticulum (ER) networks and complex dynamics such as the fusion and fission of mitochondria, due to their low phase contrast, still need fluorescent labeling to be adequately imaged. In this article, we report a quantitative phase microscope with ultra-oblique illumination that enables us to see those structures and their dynamics with high contrast for the first time without labeling. The imaging capability was validated through comparison to the fluorescence images with the same field-of-view. The high image resolution (~270 nm) was validated using both beads and cellular structures. Furthermore, we were able to record the vibration of ER networks at a frame rate of 250 Hz. We additionally show complex cellular processes such as remodeling of the mitochondria networks through fusion and fission and vesicle transportation along the ER without labels. Our high spatial and temporal resolution allowed us to observe mitochondria "spinning", which has not been reported before, further demonstrating the advantages of the proposed method.

Carvedilol attenuates carbon tetrachloride-induced liver fibrosis and hepatic sinusoidal capillarization in mice

Aim

To investigate the effect of carvedilol on liver fibrosis and hepatic sinusoidal capillarization in mice with carbon tetrachloride (CCl₄)-induced fibrosis.

Methods

A liver fibrosis mouse model was induced by intraperitoneal CCl₄ injection for 8 weeks. The mice were divided into five experimental groups: the normal group, the oil group, the CCl₄ group, the CCl₄+carvedilol (5 mg/kg/d) group, and the CCl₄+carvedilol (10 mg/kg/d) group. The extent of liver fibrosis was evaluated by histopathological staining, and the changes in fenestrations of hepatic sinus endothelial cells were observed by scanning electron microscope (SEM). The expression of α-smooth muscle actin (α-SMA) and vascular endothelial markers was detected by immunohistochemistry and Western blot assays. The effect of carvedilol on cell apoptosis was studied via Terminal deoxynucleotidyl Transferase Mediated dUTP Nick End Labeling (TUNEL) assay, and the serum levels of matrix metalloproteinase-8 (MMP-8), vascular endothelial growth factor (VEGF), and angiopoietin-2 were detected through a Luminex assay.

Results

Liver fibrosis in CCl₄-treated mice was attenuated by reduced accumulation of collagen and the reaction of inflammation with carvedilol treatment. Carvedilol reduced the activation of hepatic stellate cells (HSCs) and increased the number of apoptotic cells. The expression of α-SMA, CD31, CD34 and VWF (von Willebrand factor) was significantly decreased after carvedilol treatment. In addition, the number of fenestrae in the hepatic sinusoid showed notable differences between the groups, and the serum levels of MMP-8, VEGF and angiopoietin-2 were increased in the mice with liver fibrosis and reduced by carvedilol treatment.

Conclusion

The study demonstrated that carvedilol could prevent further development of liver fibrosis and hepatic sinusoidal capillarization in mice with CCl₄-induced fibrosis.

Manipulating fenestrations in young and old liver sinusoidal endothelial cells

Fenestrations are pores within liver sinusoidal endothelial cells (LSECs) that enable the transfer of substrates (particularly insulin and lipoproteins) between blood and hepatocytes. With increasing age, there are marked reductions in fenestrations, referred to as pseudocapillarization. Currently, fenestrations are thought to be regulated by vascular endothelial growth factor and nitric oxide (NO) pathways promoting remodeling of the actin cytoskeleton and cell membrane lipid rafts. We investigated the effects of drugs that act on these pathways on fenestrations in old (18-24 mo) and young mice (3-4 mo). Isolated LSECs were incubated with either cytochalasin 7-ketocholesterol, sildenafil, amlodipine, simvastatin, 2, 5-dimethoxy-4-iodoamphetamine (DOI), bosentan, TNF-related apoptosis-inducing ligand (TRAIL) or nicotinamide mononucleotide (NMN). LSECs were visualized under scanning electron microscopy to quantify fenestration porosity, diameter, and frequency, as well as direct stochastic optical reconstruction microscopy to examine actin and NO synthase. In young and old LSECs, fenestration porosity, diameter and frequency were increased by 7-ketocholesterol, while porosity and/or frequency were increased with NMN, sildenafil, amlodipine, TRAIL, and cytochalasin D. In old mice only, bosentan and DOI increased fenestration porosity and/or frequency. Modification of the actin cytoskeleton was observed with all agents that increased fenestrations, while NO synthase was only increased by sildenafil, amlodipine, and TRAIL. In conclusion, agents that target NO, actin, or lipid rafts promote changes in fenestrations in mice LSECs. Regulation of fenestrations occurs via both NO-dependent and independent pathways. This work indicates that age-related defenestration can be reversed pharmacologically, which has potential translational relevance for dyslipidemia and insulin resistance. NEW & NOTEWORTHY We demonstrate the effects of multiple nitric oxide-dependent and -independent pharmaceutical agents on fenestrations of the liver sinusoidal endothelium. Fenestrations are reorganized in response to nicotinamide mononucleotide, sildenafil, amlodipine, and TNF-related apoptosis-inducing ligand. This work indicates that age-related defenestration can be reversed pharmacologically, which has potential translational relevance for dyslipidemia and insulin resistance in old age.

Tunable-frequency three-dimensional structured illumination microscopy with reduced data-acquisition

The performance of a tunable three-dimensional (3D) structured illumination microscope (SIM) system and its ability to provide simultaneously super-resolution (SR) and optical-sectioning (OS) capabilities are investigated. Numerical results show that the performance of our 3D-SIM system is comparable with the one provided by a three-wave interference SIM, while requiring 40% fewer images for the reconstruction and providing frequency tunability in a cost-effective implementation. The performance of the system has been validated experimentally with images from test samples, which were also imaged with a commercial SIM based on incoherent-grid projection for comparison. Restored images from data acquired from an axially-thin fluorescent layer show a 1.6× improvement in OS capability compared to the commercial instrument while results from a fluorescent tilted USAF target show the OS and SR capabilities achieved by our system.

Cyp1b1 expression impacts the angiogenic and inflammatory properties of liver sinusoidal endothelial cells

Cytochrome P450 1B1 (CYP1B1) is a member of the cytochrome p450 family of enzymes that catalyze mono-oxygenase reactions. Although constitutive Cyp1b1 expression is limited in hepatocytes, its expression and function in liver sinusoidal endothelial cells (LSEC) remains unknown. Here we determined the impact of Cyp1b1 expression on LSEC properties prepared from Cyp1b1+/+ and Cyp1b1-/- mice. LSEC expressed PECAM-1, VE-cadherin, and B4 lectin similar to EC from other mouse tissues. Cyp1b1 +/+ LSEC constitutively expressed significant levels of Cyp1b1, while Cyp1b1-/- LSEC lacked Cyp1b1 expression. LSEC also expressed VEGFR3, PROX-1, and LYVE-1, VEGFR1 and VEGFR2, as well as other cell adhesion molecules including ICAM-1, ICAM-2, VCAM-1, and thrombospondin-1 (TSP1) receptors, CD36 and CD47. However, the expression of PV-1 and stabilin (fenestration markers), and endoglin were limited in these cells. The Cyp1b1-/- LSEC showed limited fenestration, and decreased levels of VEGF and BMP6. Cyp1b1-/- LSEC also showed a decrease in the levels of VE-cadherin and ZO-1 impacting adherens and gap junction formation. Cyp1b1-/- LSEC were significantly more apoptotic, proliferated at a faster rate, and were less adherent and more migratory. These changes were attributed, in part, to decreased amounts of TSP1 and increased AKT and ERK activation. The expressions of integrins were also altered by the lack of Cyp1b1, but the ability of these cells to undergo capillary morphogenesis was minimally affected. Furthermore, Cyp1b1-/- LSEC expressed lower levels of inflammatory mediators MCP-1 and TNF-α. Thus, Cyp1b1 expression has a significant impact on LSEC angiogenic and inflammatory functions.

Primary rat LSECs preserve their characteristic phenotype after cryopreservation

Liver disease is a leading cause of morbidity and mortality worldwide. Recently, the liver non-parenchymal cells have gained increasing attention for their potential role in the development of liver disease. Liver sinusoidal endothelial cells (LSECs), a specialized type of endothelial cells that have unique morphology and function, play a fundamental role in maintaining liver homeostasis. Current protocols for LSEC isolation and cultivation rely on freshly isolated cells which can only be maintained differentiated in culture for a few days. This creates a limitation in the use of LSECs for research and a need for a consistent and reliable source of these cells. To date, no LSEC cryopreservation protocols have been reported that enable LSECs to retain their functional and morphological characteristics upon thawing and culturing. Here, we report a protocol to cryopreserve rat LSECs that, upon thawing, maintain full LSEC-signature features: fenestrations, scavenger receptor expression and endocytic function on par with freshly isolated cells. We have confirmed these features by a combination of biochemical and functional techniques, and super-resolution microscopy. Our findings offer a means to standardize research using LSECs, opening the prospects for designing pharmacological strategies for various liver diseases, and considering LSECs as a therapeutic target.

Novel targets for delaying aging: The importance of the liver and advances in drug delivery

Age-related changes in liver function have a significant impact on systemic aging and susceptibility to age-related diseases. Nutrient sensing pathways have emerged as important targets for the development of drugs that delay aging and the onset age-related diseases. This supports a central role for the hepatic regulation of metabolism in the association between nutrition and aging. Recently, a role for liver sinusoidal endothelial cells (LSECs) in the relationship between aging and metabolism has also been proposed. Age-related loss of fenestrations within LSECs impairs the transfer of substrates (such as lipoproteins and insulin) between sinusoidal blood and hepatocytes, resulting in post-prandial hyperlipidemia and insulin resistance. Targeted drug delivery methods such as nanoparticles and quantum dots will facilitate the direct delivery of drugs that regulate fenestrations in LSECs, providing an innovative approach to ameliorating age-related diseases and increasing healthspan.

STED microscopy: A simplified method for liver sinusoidal endothelial fenestrae analysis

BACKGROUND INFORMATION

Liver sinusoidal endothelial cells (LSECs) possess fenestrae, open transcellular pores with an average diameter of 100 nm. These fenestrae allow for the exchange between blood and hepatocytes. Alterations in their number or diameter in liver diseases have important implications for hepatic microcirculation and function. Although decades of studies, fenestrae are still observed into fixed cells and we have poor knowledge of their dynamics.

RESULTS

Using stimulated emission depletion (STED) super-resolution microscopy, we have established a faster and simplest method to observe and quantify fenestrae. Indeed, using cytochalasin D, an actin depolymerising agent known to promote fenestrae formation, we measure the increase of fenestrae number. We adapted this methodology to develop an automated method to study fenestrae dynamics. Moreover, with two-colour STED analysis, we have shown that this approach could be useful to study LSECs fenestrae molecular composition.

CONCLUSIONS

Our approach demonstrates that STED microscopy is suitable for LSEC fenestrae study.

SIGNIFICANCE

This new way of analysing LSEC fenestrae will allow for expedited investigation of their dynamics, molecular composition and functions to better understand their function in liver pathophysiology.

Endothelial insulin receptors differentially control insulin signaling kinetics in peripheral tissues and brain of mice

Insulin receptors (IRs) on endothelial cells may have a role in the regulation of transport of circulating insulin to its target tissues; however, how this impacts on insulin action in vivo is unclear. Using mice with endothelial-specific inactivation of the IR gene (EndoIRKO), we find that in response to systemic insulin stimulation, loss of endothelial IRs caused delayed onset of insulin signaling in skeletal muscle, brown fat, hypothalamus, hippocampus, and prefrontal cortex but not in liver or olfactory bulb. At the level of the brain, the delay of insulin signaling was associated with decreased levels of hypothalamic proopiomelanocortin, leading to increased food intake and obesity accompanied with hyperinsulinemia and hyperleptinemia. The loss of endothelial IRs also resulted in a delay in the acute hypoglycemic effect of systemic insulin administration and impaired glucose tolerance. In high-fat diet-treated mice, knockout of the endothelial IRs accelerated development of systemic insulin resistance but not food intake and obesity. Thus, IRs on endothelial cells have an important role in transendothelial insulin delivery in vivo which differentially regulates the kinetics of insulin signaling and insulin action in peripheral target tissues and different brain regions. Loss of this function predisposes animals to systemic insulin resistance, overeating, and obesity.

Single-molecule fluorescence microscopy review: shedding new light on old problems

Fluorescence microscopy is an invaluable tool in the biosciences, a genuine workhorse technique offering exceptional contrast in conjunction with high specificity of labelling with relatively minimal perturbation to biological samples compared with many competing biophysical techniques. Improvements in detector and dye technologies coupled to advances in image analysis methods have fuelled recent development towards single-molecule fluorescence microscopy, which can utilize light microscopy tools to enable the faithful detection and analysis of single fluorescent molecules used as reporter tags in biological samples. For example, the discovery of GFP, initiating the so-called 'green revolution', has pushed experimental tools in the biosciences to a completely new level of functional imaging of living samples, culminating in single fluorescent protein molecule detection. Today, fluorescence microscopy is an indispensable tool in single-molecule investigations, providing a high signal-to-noise ratio for visualization while still retaining the key features in the physiological context of native biological systems. In this review, we discuss some of the recent discoveries in the life sciences which have been enabled using single-molecule fluorescence microscopy, paying particular attention to the so-called 'super-resolution' fluorescence microscopy techniques in live cells, which are at the cutting-edge of these methods. In particular, how these tools can reveal new insights into long-standing puzzles in biology: old problems, which have been impossible to tackle using other more traditional tools until the emergence of new single-molecule fluorescence microscopy techniques.

Key role of liver sinusoidal endothelial cells in liver fibrosis

Because of the prevalence of viral hepatitis and nonalcoholic fatty liver disease (NAFLD), liver fibrosis has become a very common disease in Asia and elsewhere in the world, constantly increasing the burden of care borne by society. Hepatic sinusoidal capillarization, characterized by gradually shrinking fenestrae on the surface of liver sinusoidal endothelial cells (LSECs) and the formation of an organized basement membrane, is an initial pathologic change associated with liver fibrosis. Basic and clinical studies have indicated that LSECs play a key role in hepatic sinusoidal capillarization by affecting various aspects of the development and progression of liver fibrosis. Reviewing studies on the effect of LSECs on liver fibrosis is essential to better understanding the pathogenesis of liver fibrosis and its mechanism of progression. Moreover, such a review will provide a theoretical basis for identifying new methods to promote the regression or even inhibition of fibrosis. This review will focus on structural and functional changes in LSECs during hepatic sinusoidal capillarization and the interaction between the micro-environment of the liver and the body's immune system.

Morphology and force probing of primary murine liver sinusoidal endothelial cells

Liver sinusoidal endothelial cells (LSECs) represent unique type of endothelial cells featured by their characteristic morphology, ie, lack of a basement membrane and presence of fenestrations-transmembrane pores acting as a dynamic filter between the vascular space and the liver parenchyma. Delicate structure of LSECs membrane combined with a submicron size of fenestrations hinders their visualization in live cells. In this work, we apply atomic force microscopy contact mode to characterize fenestrations in LSECs. We reveal the structure of fenestrations in live LSECs. Moreover, we show that the high-resolution imaging of fenestrations is possible for the glutaraldehyde-fixed LSECs. Finally, thorough information about the morphology of LSECs including great contrast in visualization of sieve plates and fenestrations is provided using Force Modulation mode. We show also the ability to precisely localize the cell nuclei in fixed LSECs. It can be helpful for more precise description of nanomechanical properties of cell nuclei using atomic force microscopy. Presented methodology combining high-quality imaging of fixed cells with an additional nanomechanical information of both live and fixed LSECs provides a unique approach to study LSECs morphology and nanomechanics that could foster understanding of the role of LSECs in maintaining liver homeostasis.

Deconvoluting hepatic processing of carbon nanotubes

Single-wall carbon nanotubes present unique opportunities for drug delivery, but have not advanced into the clinic. Differential nanotube accretion and clearance from critical organs have been observed, but the mechanism not fully elucidated. The liver has a complex cellular composition that regulates a range of metabolic functions and coincidently accumulates most particulate drugs. Here we provide the unexpected details of hepatic processing of covalently functionalized nanotubes including receptor-mediated endocytosis, cellular trafficking and biliary elimination. Ammonium-functionalized fibrillar nanocarbon is found to preferentially localize in the fenestrated sinusoidal endothelium of the liver but not resident macrophages. Stabilin receptors mediate the endocytic clearance of nanotubes. Biocompatibility is evidenced by the absence of cell death and no immune cell infiltration. Towards clinical application of this platform, nanotubes were evaluated for the first time in non-human primates. The pharmacologic profile in cynomolgus monkeys is equivalent to what was reported in mice and suggests that nanotubes should behave similarly in humans.

Application of carbon nanotubes as drug delivery carriers is stalled by uncertainties over their distribution and toxicity in vivo. Here, the authors use animal models to show that, while the bulk of nanotubes is renally cleared, a fraction can be eliminated through an alternative hepatobiliary pathway.

Intrahepatic regulation of antiviral T cell responses at initial stages of viral infection

It is generally accepted that the appropriate boost of early immune response will control viral replications and limit the immune-mediated pathology in viral hepatitis. However, poor immunity results in viral persistence, chronic inflammation and finally liver cirrhosis and carcinoma. As a peripheral non-lymphoid organ of immune surveillance, the liver continually encounters hundreds of molecules from the blood, including nutrients, toxins and pathogens. In this way, the liver maintains immune tolerance under healthy conditions, but responds quickly to the hepatotropic pathogens during the early stages of an infection. Although our knowledge of liver cell compositions and functions has been improved significantly in recent years, the intrahepatic immune regulation of antiviral T cells at the initial stage is complex and not well elucidated. Here, we summarize the role of liver cell subpopulations in regulating antiviral T cell response at the initial stages of viral infection. A better understanding of early hepatic immune regulation will pave the way for the development of novel therapies and vaccine design for human viral hepatitis.

Open-source image reconstruction of super-resolution structured illumination microscopy data in ImageJ

Super-resolved structured illumination microscopy (SR-SIM) is an important tool for fluorescence microscopy. SR-SIM microscopes perform multiple image acquisitions with varying illumination patterns, and reconstruct them to a super-resolved image. In its most frequent, linear implementation, SR-SIM doubles the spatial resolution. The reconstruction is performed numerically on the acquired wide-field image data, and thus relies on a software implementation of specific SR-SIM image reconstruction algorithms. We present fairSIM, an easy-to-use plugin that provides SR-SIM reconstructions for a wide range of SR-SIM platforms directly within ImageJ. For research groups developing their own implementations of super-resolution structured illumination microscopy, fairSIM takes away the hurdle of generating yet another implementation of the reconstruction algorithm. For users of commercial microscopes, it offers an additional, in-depth analysis option for their data independent of specific operating systems. As a modular, open-source solution, fairSIM can easily be adapted, automated and extended as the field of SR-SIM progresses.

Reconstruction of super resolution structured illumination microscopy (SR-SIM) datasets typically relies upon commercial software. Here Müller et al. present an open-source ImageJ plugin to facilitate reconstruction of SR-SIM data from a broad range of microscopy platforms.

Dietary macronutrients and the aging liver sinusoidal endothelial cell

Fenestrations are pores within the liver sinusoidal endothelial cells (LSECs) that line the sinusoids of the highly vascularized liver. Fenestrations facilitate the transfer of substrates between blood and hepatocytes. With pseudocapillarization of the hepatic sinusoid in old age, there is a loss of fenestrations. LSECs are uniquely exposed to gut-derived dietary and microbial substrates delivered by the portal circulation to the liver. Here we studied the effect of 25 diets varying in content of macronutrients and energy on LSEC fenestrations using the Geometric Framework method in a large cohort of mice aged 15 mo. Macronutrient distribution rather than total food or energy intake was associated with changes in fenestrations. Porosity and frequency were inversely associated with dietary fat intake, while fenestration diameter was inversely associated with protein or carbohydrate intake. Fenestrations were also linked to diet-induced changes in gut microbiome, with increased fenestrations associated with higher abundance of Firmicutes and reduced abundance of Bacteroidetes Diet-induced changes in levels of several fatty acids (C16:0, C19:0, and C20:4) were also significantly inversely associated with fenestrations, suggesting a link between dietary fat and modulation of lipid rafts in the LSECs. Diet influences fenestrations and these data reflect both the key role of the LSECs in clearing gut-derived molecules from the vascular circulation and the impact these molecules have on LSEC morphology.

Quantitative superresolution microscopy reveals differences in nuclear DNA organization of multiple myeloma and monoclonal gammopathy of undetermined significance

The mammalian nucleus has a distinct substructure that cannot be visualized directly by conventional microscopy. In this study, the organization of the DNA within the nucleus of multiple myeloma (MM) cells, their precursor cells (monoclonal gammopathy of undetermined significance; MGUS) and control lymphocytes of the representative patients is visualized and quantified by superresolution microscopy. Three‐dimensional structured illumination microscopy (3D‐SIM) increases the spatial resolution beyond the limits of conventional widefield fluorescence microscopy. 3D‐SIM reveals new insights into the nuclear architecture of cancer as we show for the first time that it resolves organizational differences in intranuclear DNA organization of myeloma cells in MGUS and in MM patients. In addition, we report a significant increase in nuclear submicron DNA structure and structure of the DNA‐free space in myeloma nuclei compared to normal lymphocyte nuclei. Our study provides previously unknown details of the nanoscopic DNA architecture of interphase nuclei of the normal lymphocytes, MGUS and MM cells. This study opens new avenues to understanding the disease progression from MGUS to MM. J. Cell. Biochem. 116: 704–710, 2015. © 2014 The Authors. Journal of Cellular Biochemistry published by Wiley Periodicals, Inc.

Multimodal super-resolution optical microscopy visualizes the close connection between membrane and the cytoskeleton in liver sinusoidal endothelial cell fenestrations

Liver sinusoidal endothelial cells (LSECs) act as a filter between blood and the hepatocytes. LSECs are highly fenestrated cells; they contain transcellular pores with diameters between 50 to 200 nm. The small sizes of the fenestrae have so far prohibited any functional analysis with standard and advanced light microscopy techniques. Only the advent of super-resolution optical fluorescence microscopy now permits the recording of such small cellular structures. Here, we demonstrate the complementary use of two different super-resolution optical microscopy modalities, 3D structured illumination microscopy (3D-SIM) and single molecule localization microscopy in a common optical platform to obtain new insights into the association between the cytoskeleton and the plasma membrane that supports the formation of fenestrations. We applied 3D-SIM to multi-color stained LSECs to acquire highly resolved overviews of large sample areas. We then further increased the spatial resolution for imaging fenestrations by single molecule localization microscopy applied to select small locations of interest in the same sample on the same microscope setup. We optimized the use of fluorescent membrane stains for these imaging conditions. The combination of these techniques offers a unique opportunity to significantly improve studies of subcellular ultrastructures such as LSEC fenestrations.

Constitutive and ghrelin-dependent GHSR1a activation impairs CaV2.1 and CaV2.2 currents in hypothalamic neurons

Constitutive and ligand-dependent GHSR1a activity attenuates Ca_V2 current and hypothalamic GABA release through distinct mechanisms and signaling pathways.

The growth hormone secretagogue receptor type 1a (GHSR1a) has the highest known constitutive activity of any G protein–coupled receptor (GPCR). GHSR1a mediates the action of the hormone ghrelin, and its activation increases transcriptional and electrical activity in hypothalamic neurons. Although GHSR1a is present at GABAergic presynaptic terminals, its effect on neurotransmitter release remains unclear. The activities of the voltage-gated calcium channels, Ca_V2.1 and Ca_V2.2, which mediate neurotransmitter release at presynaptic terminals, are modulated by many GPCRs. Here, we show that both constitutive and agonist-dependent GHSR1a activity elicit a strong impairment of Ca_V2.1 and Ca_V2.2 currents in rat and mouse hypothalamic neurons and in a heterologous expression system. Constitutive GHSR1a activity reduces Ca_V2 currents by a G_i/o-dependent mechanism that involves persistent reduction in channel density at the plasma membrane, whereas ghrelin-dependent GHSR1a inhibition is reversible and involves altered Ca_V2 gating via a G_q-dependent pathway. Thus, GHSR1a differentially inhibits Ca_V2 channels by G_i/o or G_q protein pathways depending on its mode of activation. Moreover, we present evidence suggesting that GHSR1a-mediated inhibition of Ca_V2 attenuates GABA release in hypothalamic neurons, a mechanism that could contribute to neuronal activation through the disinhibition of postsynaptic neurons.

Nanoparticles as Nonfluorescent Analogues of Fluorophores for Optical Nanoscopy

Optical microscopy modalities that achieve spatial resolution beyond the resolution limit have opened up new opportunities in the biomedical sciences to reveal the structure and kinetics of biological processes on the nanoscale. These methods are, however, mostly restricted to fluorescence as contrast mechanism, which limits the ultimate spatial resolution and observation time that can be achieved by photobleaching of the fluorescent probes. Here, we demonstrate that Raman scattering provides a valuable contrast mechanism for optical nanoscopy in the form of super-resolution structured illumination microscopy. We find that nanotags, i.e., gold and silver nanoparticles that are capable of surface-enhanced Raman scattering (SERS), can be imaged with a spatial resolution beyond the diffraction limit in four dimensions alongside and with similar excitation power as fluorescent probes. The highly polarized nature of super-resolution structured illumination microscopy renders these nanotags elliptical in the reconstructed super-resolved images, which enables us to determine their orientation within the sample. The robustness of nanotags against photobleaching allows us to image these particles for unlimited periods of time. We demonstrate this by imaging isolated nanotags in a dense layer of fluorophores, as well as on the surface of and after internalization by osteosarcoma cells, always in the presence of fluorescent probes. Our results show that SERS nanotags have the potential to become highly multiplexed and chemically sensitive optical probes for optical nanoscopy that can replace fluorophores in applications where fluorescence photobleaching is prohibitive for following the evolution of biological processes for extended times.

A standardized method for the analysis of liver sinusoidal endothelial cells and their fenestrations by scanning electron microscopy

Liver sinusoidal endothelial cells are the gateway to the liver, their transcellular fenestrations allow the unimpeded transfer of small and dissolved substances from the blood into the liver parenchyma for metabolism and processing. Fenestrations are dynamic structures--both their size and/or number can be altered in response to various physiological states, drugs, and disease, making them an important target for modulation. An understanding of how LSEC morphology is influenced by various disease, toxic, and physiological states and how these changes impact on liver function requires accurate measurement of the size and number of fenestrations. In this paper, we describe scanning electron microscopy fixation and processing techniques used in our laboratory to ensure reproducible specimen preparation and accurate interpretation. The methods include perfusion fixation, secondary fixation and dehydration, preparation for the scanning electron microscope and analysis. Finally, we provide a step by step method for standardized image analysis which will benefit all researchers in the field.

Extravasated platelet aggregation in liver zone 3 may correlate with the progression of sinusoidal obstruction syndrome following living donor liver transplantation: A case report

Sinusoidal obstruction syndrome (SOS), previously known as veno-occlusive disease, is relatively rare subsequent to liver transplantation (LT). SOS refractory to medical therapy, however, can result in centrilobular fibrosis, portal hypertension and liver failure. Although sinusoidal endothelial cell damage around central venules (zone 3) occurs early in the development of SOS, the detailed mechanism of SOS development and its association with thrombocytopenia are not yet completely understood. The present report describes a patient who experienced SOS with unexplained thrombocytopenia following living donor LT. The progression of SOS resulted in graft dysfunction and the patient succumbed. The presence of platelets in the liver allograft was assayed immunohistochemically using antibody to the platelet marker cluster of differentiation 42b (platelet glycoprotein Ib). Platelet aggregates were found attached to hepatocytes along the sinusoid and within the cytoplasm of hepatocytes, particularly in zone 3. By contrast, no staining was observed in zone 1. These findings suggested that extravasated platelet aggregation in the space of Disse and the phagocytosis of platelets by hepatocytes were initiated by sinusoidal endothelial cell damage due to the toxicity of the immunosuppressant tacrolimus or a corticosteroid pulse, and that platelet activation and degranulation may be at least partially involved in the mechanism responsible for SOS.

QSIM: quantitative structured illumination microscopy image processing in ImageJ

BACKGROUND

Structured illumination microscopy has been extensively used in biological imaging due to its low cost and easy implementation. However, the lack of quantitative imaging capability limits its application in absolute irradiance measurements.

METHOD

We have developed a quantitative structured illumination microscopy image processing algorithm (QSIM) as a plugin for the widely used ImageJ software. QSIM can work with the raw images acquired by a traditional structured illumination microscope and can quantitatively measure photon numbers, with noise estimates for both wide-field images and sectioned images.

RESULTS AND CONCLUSION

We demonstrated the quantitative image processing capability of QSIM by imaging a mouse kidney section in 3D. The results show that QSIM can transform structured illumination microscopy from qualitative to quantitative, which is essential for demanding fluorescence imaging applications.