Human Colorectal Cancer Infrastructure Constructed by the Glycocalyx

Endothelial Glycocalyx in the Peripheral Capillaries is Injured Under Oxaliplatin-Induced Neuropathy

Oxaliplatin, a platinum-based anticancer drug, is associated with peripheral neuropathy (oxaliplatin-induced peripheral neuropathy, OIPN), which can lead to worsening of quality of life and treatment interruption. The endothelial glycocalyx, a fragile carbohydrate-rich layer covering the luminal surface of endothelial cells, acts as an endothelial gatekeeper and has been suggested to protect nerves, astrocytes, and other cells from toxins and substances released from the capillary vessels. Mechanisms underlying OIPN and the role of the glycocalyx remain unclear. This study aimed to define changes in the three-dimensional ultrastructure of capillary endothelial glycocalyx near nerve fibers in the hind paws of mice with OIPN. The mouse model of OPIN revealed disruption of the endothelial glycocalyx in the peripheral nerve compartment, accompanied by vascular permeability, edema, and damage to the peripheral nerves. To investigate the potential treatment interventions, nafamostat mesilate, a glycocalyx protective agent was used in tumor-bearing male mice. Nafamostat mesilate suppressed mechanical allodynia associated with neuropathy. It also prevented intra-epidermal nerve fiber loss and improved vascular permeability in the peripheral paws. The disruption of endothelial glycocalyx in the capillaries that lie within peripheral nerve bundles is a novel finding in OPIN. Furthermore, these findings point toward the potential of a new treatment strategy targeting endothelial glycocalyx to prevent vascular injury as an effective treatment of neuropathy as well as of many other diseases. PERSPECTIVE: OIPN damages the endothelial glycocalyx in the peripheral capillaries, increasing vascular permeability. In order to prevent OIPN, this work offers a novel therapy approach that targets endothelial glycocalyx.

Glycocalyx analysis of bladder cancer: three-dimensional images in electron microscopy and vicia villosa lectin as a marker for invasiveness in frozen sections

Introduction: The abnormal glycocalyx (GCX) on the surface of cancer cells has been reported to be tall and aberrantly glycosylated and has been linked to the progression and spread of cancer-a finding also observed in bladder cancer. However, the characteristics of GCX in various types of human bladder cancer remain unknown, and herein, we aimed to provide information on the diversity of glycan components in the GCX of bladder cancers and to shed light on their characteristics. Methods: We used scanning electron microscopy and lanthanum staining to examine the surface GCX of human bladder carcinomas in three-dimensional images, showing the bulky GCX in some carcinomas. We also examined glycan alterations in early to progressive stages of bladder cancers using 20 distinct lectin stains on frozen sections from transurethral resection of bladder tumors. Results and discussion: Distinctive Vicia villosa lectin (VVL) staining was observed in invasive urothelial carcinomas, including those with muscle invasion and variant components. In the clinical setting, cancers with atypia of grades 2-3 had a significantly higher VVL scoring intensity than those with grade 1 atypia (p < 0.005). This study identified that a specific lectin, VVL, was more specific to invasive urothelial carcinomas. This lectin, which selectively binds to sites of cancer progression, is a promising target for drug delivery in future clinical investigations.

Mouse Brain Tissue Preparation for Scanning Electron Microscopy

Scanning electron microscopy (SEM) is used to observe the surface structure of an object by irradiating an electron beam onto the sample and detecting the reflected and emitted electrons. Because of its large depth of focus, SEM can provide the three-dimensional structure of small surfaces that cannot be observed using an optical microscope. Furthermore, the cross-sectional structure of the tissue can be observed by freeze-cracking. Observing the ultrastructure of organisms that contain large amounts of water in their bodies while maintaining high resolution is challenging; however, this has recently become possible. Here, we explain the fixation and freeze-cracking method for mouse brain samples.

Fast-track preparation of lung specimens for electron microscope observations of the pulmonary endothelial glycocalyx

The glycocalyx (GCX) covers the luminal surface of blood vessels and regulates vascular permeability. As GCX degradation predicts various types of vasculopathy, confirming the presence of this structure is useful for diagnosis. Since the GCX layer is very fragile, careful fixation is necessary to preserve its structure. We explored appropriate and feasible methodologies for visualizing the GCX layer using lung tissue specimens excised from anesthetized mice. Each specimen was degassed and immersed in Alcian blue (ALB) fixative solution, and then observed using electron microscopy. Specimens from septic mice were prepared as negative GCX controls. Using these immersion-fixed specimens, the GCX layer was successfully observed using both transmission and scanning electron microscopy; these observations were similar to those obtained using the conventional method of lanthanum perfusion fixation. Spherical aggregates of GCX were observed in the septic mouse specimens, and the GCX density was lower in the septic specimens than in the non-septic specimens. Of note, the presently reported methodology reduced the specimen preparation time from 6 to 2 days. We, therefore, concluded that our novel method could be applied to human lung specimens and could potentially contribute to the further elucidation of vasculopathies.

Development of extrahepatic bile ducts and mechanisms of tumorigenesis: Lessons from mouse models

The biliary system is a highly branched tubular network consisting of intrahepatic bile ducts (IHBDs) and extrahepatic bile ducts (EHBDs). IHBDs are derived from hepatic progenitor cells, while EHBDs originate directly from the endoderm through a separate branching morphogenetic process. Traits that are important for cancer are often found to overlap in developmental and other processes. Therefore, it has been suggested that intrahepatic cholangiocarcinomas (iCCAs) and extrahepatic cholangiocarcinomas (eCCAs) have different developmental mechanisms. While much evidence is being gathered on the mechanism of iCCAs, the evidence for eCCA is still very limited. The main reason for this is that there are very few appropriate animal models for eCCA. We can gain important insights from these animal models, particularly genetically engineered mouse models (GEMMs). GEMMs are immunocompetent and mimic human CCA subtypes with a specific mutational pattern, allowing the development of precancerous lesions, that is, biliary intraepithelial neoplasia (BilIN) and intraductal papillary neoplasm of the bile duct (IPNB). This review provides a summary of the pathogenesis and mechanisms of eCCA that can be revealed by GEMMs. Furthermore, we discuss several clinical questions, such as whether BilIN and IPNB really become malignant, whether the peribiliary gland is the origin of eCCAs, and others.

Form follows function: The endothelial glycocalyx

Three types of capillaries, namely continuous, fenestrated, and sinusoidal, form the microvascular system; each type has a specialized structure and function to respond to the demands of the organs they supply. The endothelial glycocalyx, a gel-like layer of glycoproteins that covers the luminal surface of the capillary endothelium, is also thought to maintain organ and vascular homeostasis by exhibiting different morphologies based on the functions of the organs and capillaries in which it is found. Recent advances in analytical technology have enabled more detailed observations of the endothelial glycocalyx, revealing that it indeed differs in structure across various organs. Furthermore, differences in the lectin staining patterns suggest the presence of different endothelial glycocalyx components across various organs. Interestingly, injury to the endothelial glycocalyx due to various pathologic and physiological stimuli causes the release of these components into the blood. Thus, circulating glycocalyx components may be useful biomarkers of organ dysfunction and disease severity. Moreover, a recent study suggested that chronic injury to the glycocalyx reduces the production of these glycocalyx components and changes their structure, leading it to become more vulnerable to external stimuli. In this review, we have summarized the various endothelial glycocalyx structures and their functions.

Microbial metabolite deoxycholic acid promotes vasculogenic mimicry formation in intestinal carcinogenesis

A high-fat diet (HFD) leads to long-term exposure to gut microbial metabolite secondary bile acids, such as deoxycholic acid (DCA), in the intestine, which is closely linked to colorectal cancer (CRC). Evidence reveals that vasculogenic mimicry (VM) is a critical event for the malignant transformation of cancer. Therefore, this study investigated the crucial roles of DCA in the regulation of VM and the progression of intestinal carcinogenesis. The effects of an HFD on VM formation and epithelial-mesenchymal transition (EMT) in human CRC tissues were investigated. The fecal DCA level was detected in HFD-treated Apc^min/+ mice. Then the effects of DCA on VM formation, EMT, and vascular endothelial growth factor receptor 2 (VEGFR2) signaling were evaluated in vitro and in vivo. Here we demonstrated that compared with a normal diet, an HFD exacerbated VM formation and EMT in CRC patients. An HFD could alter the composition of the gut microbiota and significantly increase the fecal DCA level in Apc^min/+ mice. More importantly, DCA promoted tumor cell proliferation, induced EMT, increased VM formation, and activated VEGFR2, which led to intestinal carcinogenesis. In addition, DCA enhanced the proliferation and migration of HCT-116 cells, and induced EMT process and vitro tube formation. Furthermore, the silence of VEGFR2 reduced DCA-induced EMT, VM formation, and migration. Collectively, our results indicated that microbial metabolite DCA promoted VM formation and EMT through VEGFR2 activation, which further exacerbated intestinal carcinogenesis.

The effectiveness of alprostadil in treating coronary microcirculation dysfunction following ST-segment elevation myocardial infarction in a pig model

Though alprostadil has been reported to improve the impaired microcirculation of patients with pulmonary arterial hypertension, its effectiveness as a treatment for coronary microvasculature dysfunction (CMD) following ST-segment elevation myocardial infarction (STEMI) is unknown. A total of 18 miniature pigs with CMD following STEMI were randomized into three groups that received an intracoronary injection of 5 ml of normal saline, 2 mg of nicorandil or 10 µg of alprostadil immediately after measurement of the index of microcirculatory resistance (IMR) and then an intravenous drip containing 5 ml of normal saline, 2 mg of nicorandil or 10 µg of alprostadil once a day for 6 days. The IMR, cardiac function using ultrasound, infarct areas and heparanase levels in infarct areas were measured and compared between the three groups. The IMR decreased markedly 10 min after alprostadil or nicorandil intracoronary injection (both P<0.05) but not following saline injection (P>0.05). After 7 days, the IMR was substantially lower in the alprostadil and nicorandil groups compared with the saline group (both P<0.05) and the ejection fraction was considerably higher in the alprostadil and nicorandil groups compared with the saline group (both P<0.05). Differences in infarct areas and the relative heparanase expression levels among the 3 groups were similar to the differences in the ejection fraction. No significant differences in the above assessment indexes were identified in the alprostadil and nicorandil groups. Alprostadil infusion improved coronary microcirculation function, reduced the infarct area and limited left ventricular dilatation in a pig coronary microvasculature dysfunction model following STEMI.

Update on the Role of the Endothelial Glycocalyx in Angiogenesis and Vascular Inflammation

The endothelial glycocalyx is a negatively charged, carbohydrate-rich structure that arises from the luminal surface of the vascular endothelium and is comprised of proteoglycans, glycoproteins, and glycolipids. The glycocalyx, which sits at the interface between the endothelium and the blood, is involved in a wide array of physiological and pathophysiological processes, including as a mechanotransducer and as a regulator of inflammation. Most recently, components of the glycocalyx have been shown to play a key role in controlling angiogenesis. In this review, we briefly summarize the structure and function of the endothelial glycocalyx. We focus on its role and functions in vascular inflammation and angiogenesis and discuss the important unanswered questions in this field.

Three-dimensional electron microscopy for endothelial glycocalyx observation using Alcian blue with silver enhancement

Glycocalyx (GCX) is a thin layer of negatively charged glycoproteins that covers the vascular endothelial surface and regulates various biological processes. Because of the delicate and fragile properties of this structure, it is difficult to detect GCX morphologically. We established a simple method for a three-dimensional visualization of endothelial GCX using low-vacuum scanning electron microscopy (LVSEM) on formalin-fixed paraffin-embedded (FFPE) sections. Mouse kidney tissue was fixed with 10% buffered formalin containing 1% Alcian blue (ALB) via perfusion and immersion. FFPE sections were observed by light microscopy (LM) and LVSEM, and formalin-fixed epoxy resin-embedded ultrathin sections were observed by transmission electron microscopy (TEM). The endothelial GCX from various levels of kidney blood vessels was stained blue in LM and confirmed as a thin osmiophilic layer in TEM. In LVSEM, the sections stained by periodic acid methenamine silver (PAM) revealed the endothelial GCX as a layer of dense silver-enhanced particles, in both the samples fixed via perfusion and immersion. Correlative light and electron microscopy (CLEM) revealed the fine visible structure of endothelial GCX. This simple method using FFPE samples with ALB will enable the three-dimensional evaluation of endothelial GCX alterations in various human diseases associated with endothelial injury in future studies.