A simple solution for antibody signal enhancement in immunofluorescence and triple immunogold assays

Immuno-scanning electron microscopy of islet primary cilia

The definitive demonstration of protein localization on primary cilia has been a challenge for cilia biologists. Primary cilia are solitary thread-like projections that have a specialized protein composition, but as the ciliary structure overlays the cell membrane and other cell parts, the identity of ciliary proteins are difficult to ascertain by conventional imaging approaches like immunofluorescence microscopy. Surface scanning electron microscopy combined with immunolabeling (immuno-SEM) bypasses some of these indeterminacies by unambiguously showing protein expression in the context of the three-dimensional ultrastructure of the cilium. Here, we apply immuno-SEM to specifically identify proteins on the primary cilia of mouse and human pancreatic islets, including post-translationally modified tubulin, intraflagellar transport (IFT)88, the small GTPase Arl13b, as well as subunits of axonemal dynein. Key parameters in sample preparation, immunolabeling and imaging acquisition are discussed to facilitate similar studies by others in the cilia research community.

Immuno-Scanning Electron Microscopy of Islet Primary Cilia

The definitive demonstration of protein localization on primary cilia has been a challenge for cilia biologists. Primary cilia are solitary thread-like projections that contain specialized protein composition, but as the ciliary structure overlays the cell membrane and other cell parts, the identity of ciliary proteins are difficult to ascertain by conventional imaging approaches like immunofluorescence microscopy. Surface scanning electron microscopy combined with immuno-labeling (immuno-SEM) bypasses some of these indeterminacies by unambiguously showing protein expression in the context of the 3D ultrastructure of the cilium. Here we apply immuno-SEM to specifically identify proteins on the primary cilia of mouse and human pancreatic islets, including post-translationally modified tubulin, intraflagellar transport (IFT) 88, the small GTPase Arl13b, as well as subunits of axonemal dynein. Key parameters in sample preparation, immuno-labeling, and imaging acquisition are discussed to facilitate similar studies by others in the cilia research community.

Delineation of the healthy rabbit duodenum by immunohistochemistry - A short communication

The duodenum acts as a vital organ that performs fundamental physiological functions like digestion and nutrient absorption. Situated in the lower abdomen, the duodenum is located between the stomach and the jejunum. Usually, the duodenum is divided into four anatomical portions. We here compare paraffin embedded and cryosections of the healthy rabbit duodenum for research purposes. This analysis evaluates the differential outcomes resulting from the application of these fixation methodologies in conjunction with immunohistochemical assays targeting extracellular matrix markers collagen I, collagen III, fibronectin, α-smooth muscle actin (α-SMA), and proliferation marker ki67 as well as inflammatory marker PAR-2. Subsequent recommendations are provided based on our findings. Furthermore, the advantage of an antigen retrieval step in immunohistochemical labelling of paraffin sections was demonstrated and confirmed with an isotype negative control. Basic classical histological stainings as HE, GT and elastin were also performed. Comparison of different stainings and labellings was performed in serial sections, showing that adjacent to the circular muscle of the duodenum, the connective tissue was composed of collagen I and fibronectin, while the artery and vein walls were predominantly α-SMA positive. Moreover, PAR-2 immunohistochemical staining was performed, where particularly a type of gland adjacent to Brunner's glands showed prominent PAR-2 positive areas, while the Brunner's glands themselves were PAR-2 negative. Proliferating ki67 positive cells facing the lumen were highly abundant in all kinds of glands except for the Brunner's glands. This effort serves to furnish the research community with reference imagery pertinent to scientists opting for the rabbit duodenum model. The diversity of staining techniques employed herein establishes a foundational repository of images, primed for comparative analysis against pathological conditions. Furthermore, these images hold the potential to illustrate inter-species variations. For instance, they can be juxtaposed against murine or rat intestinal tracts, or even offer insights into the human context.

Delineation of the healthy rabbit tongue by immunohistochemistry - A technical note

In the oral cavity the tongue is an important muscular organ that supports the swallowing of food and liquids. It is responsible for the sense of taste, based on the many different taste buds it contains. Research in the field of tongue diseases demands for suitable preclinical models. The healthy rabbit tongue may therefore serve as baseline and reference for the pathological situation. With this consideration, we covered the fixation and histological stainings as well as the immunohistochemical labelling of the healthy rabbit tongue. In this technical note, initial choice of the fixative is discussed, with a comparison of formalin fixation and subsequent paraffin embedding versus cryopreservation. Moreover, we delineate the effect of an antigen retrieval step for formalin fixation by several examples. Finally, we provide ECM markers collagen I, collagen III, fibronectin, α-SMA and elastin staining as well as ki67 for proliferative status and PAR-2 protein expression as a marker for inflammatory status and nociception in tongue sections, mainly from the tongue body. Technically, we found superiority of paraffin sections for collagen I, collagen III, fibronectin, ki67 and α-SMA labelling, for selected detections systems. As for ECM components, the lamina propria was very rich in collagen and fibronectin, while the muscular body of the tongue showed only collagen and fibronectin positive areas between the muscle fibers. Moreover, α-SMA was clearly expressed in the walls of arteries and veins. The inflammatory marker PAR-2 on the other hand was prominently expressed in the salivary glands and to some extent in the walls of the vessels. Particular PAR-2 expression was found in the excretory ducts of the tongue. This technical note has the aim to provide baseline images that can be used to compare the pathological state of the diseased rabbit tongue as well as for inter-species comparison, such as mouse or rat tongue. Finally, it can be used for the comparison with the human situation.

Constitutive and conditional deletion reveals distinct phenotypes driven by developmental versus neurotransmitter actions of the neuropeptide PACAP

Neuropeptides may exert trophic effects during development, and then neurotransmitter roles in the developed nervous system. One way to associate peptide-deficiency phenotypes with either role is first to assess potential phenotypes in so-called constitutive knockout mice, and then proceed to specify, regionally and temporally, where and when neuropeptide expression is required to prevent these phenotypes. We have previously demonstrated that the well-known constellation of behavioral and metabolic phenotypes associated with constitutive pituitary adenylate cyclase-activating peptide (PACAP) knockout mice are accompanied by transcriptomic alterations of two types: those that distinguish the PACAP-null phenotype from wild-type (WT) in otherwise quiescent mice (cPRGs), and gene induction that occurs in response to acute environmental perturbation in WT mice that do not occur in knockout mice (aPRGs). Comparing constitutive PACAP knockout mice to a variety of temporally and regionally specific PACAP knockouts, we show that the prominent hyperlocomotor phenotype is a consequence of early loss of PACAP expression, is associated with Fos overexpression in hippocampus and basal ganglia, and that a thermoregulatory effect previously shown to be mediated by PACAP-expressing neurons of medial preoptic hypothalamus is independent of PACAP expression in those neurons in adult mice. In contrast, PACAP dependence of weight loss/hypophagia triggered by restraint stress, seen in constitutive PACAP knockout mice, is phenocopied in mice in which PACAP is deleted after neuronal differentiation. Our results imply that PACAP has a prominent role as a trophic factor early in development determining global central nervous system characteristics, and in addition a second, discrete set of functions as a neurotransmitter in the fully developed nervous system that support physiological and psychological responses to stress.

In vivo retinal imaging is associated with cognitive decline, blood-brain barrier disruption and neuroinflammation in type 2 diabetic mice

Introduction

Type 2 diabetes (T2D) is associated with chronic inflammation and neurovascular changes that lead to functional impairment and atrophy in neural-derived tissue. A reduction in retinal thickness is an early indicator of diabetic retinopathy (DR), with progressive loss of neuroglia corresponding to DR severity. The brain undergoes similar pathophysiological events as the retina, which contribute to T2D-related cognitive decline.

Methods

This study explored the relationship between retinal thinning and cognitive decline in the LepR db/db model of T2D. Diabetic db/db and non-diabetic db/+ mice aged 14 and 28 weeks underwent cognitive testing in short and long-term memory domains and in vivo retinal imaging using optical coherence tomography (OCT), followed by plasma metabolic measures and ex vivo quantification of neuroinflammation, oxidative stress and microvascular leakage.

Results

At 28 weeks, mice exhibited retinal thinning in the ganglion cell complex and inner nuclear layer, concomitant with diabetic insulin resistance, memory deficits, increased expression of inflammation markers and cerebrovascular leakage. Interestingly, alterations in retinal thickness at both experimental timepoints were correlated with cognitive decline and elevated immune response in the brain and retina.

Discussion

These results suggest that changes in retinal thickness quantified with in vivo OCT imaging may be an indicator of diabetic cognitive dysfunction and neuroinflammation.

Delineation of the healthy rabbit tonsil by immunohistochemistry - A short communication

Situated in the oral cavity, the rabbit palatine tonsils are part of the mucosal immune system and help to defend the body against foreign pathogens. Expressed as two oval protrusions in the wall of the oropharynx, the rabbit palatine tonsils are characterized by excretory ducts and trabeculae. We here compare paraffin embedded and cryosections of the healthy rabbit tonsils. This analysis centers on evaluating the differential outcomes resulting from the application of these fixation methodologies in conjunction with immunohistochemical assays targeting collagen I, collagen III, fibronectin, α-smooth muscle actin (α-SMA), and ki67. Subsequent recommendations are provided based on our findings. Furthermore, we demonstrate the advantage of an antigen retrieval step in immunohistochemical labeling of paraffin sections. Basic classical histological stainings as HE, GT and elastin were also performed. Comparison of different stainings and labelings was furthermore performed in serial sections, showing that adjacent to the excretory ducts, the tonsillar tissue was particularly composed of collagen I and fibronectin, while the vessel walls were predominantly α-SMA positive. Moreover, PAR-2 immunohistochemical staining was performed, where a small fraction of the cells found in the tonsillar connective tissue were PAR-2 positive (probably a subpopulation of mast cells), as well as the lumen of some excretory ducts and trabeculae. Collagen III on the other hand was only weakly expressed in the tonsils. Proliferating ki67 positive cells were rare. This endeavor serves to furnish the scientific community with reference imagery pertinent to researchers opting for the rabbit palatine tonsil model. The diversity of staining techniques employed herein establishes a foundational repository of images, primed for comparative analysis against pathological conditions. Furthermore, these images hold the potential to illustrate inter-species variations. For instance, they can be juxtaposed against murine or rodent tonsils, or even offer insights into the human context.

In Vivo and In Vitro Evidence for an Interplay between the Glucocorticoid Receptor and the Vitamin D Receptor Signaling

Our previous work demonstrated that vitamin D (VitD) reduces experimental autoimmune encephalomyelitis (EAE) disease severity in wild-type (WT) but not in T cell-specific glucocorticoid (GC) receptor (GR)-deficient (GRlck) mice. This study aimed to investigate the interplay between the GR- and VitD receptor (VDR) signaling. In vivo, we confirmed the involvement of the GR in the VitD-induced effects in EAE using WT and GRlck mice. Furthermore, we observed that VitD-enhanced T cell apoptosis and T regulatory cell differentiation are diminished in vitro in CD3+ T cells of GRlck but not WT mice. Mechanistically, VitD does not appear to signal directly via the GR, as it does not bind to the GR, does not induce its nuclear translocation, and does not modulate the expression of two GR-induced genes. However, we observed that VitD enhances VDR protein expression in CD3+ T cells from WT but not GRlck mice in vitro, that the GR and the VDR spatially co-localize after VitD treatment, and that VitD does not modulate the expression of two VDR-induced genes in the absence of the GR. Our data suggest that a functional GR, specifically in T cells, is required for the VDR to signal appropriately to mediate the therapeutic effects of VitD.

Atrophic astrocytes in aged marmosets present tau hyperphosphorylation, RNA oxidation, and DNA fragmentation

Astrocytes perform multiple essential functions in the brain showing morphological changes. Hypertrophic astrocytes are commonly observed in cognitively healthy aged animals, implying a functional defense mechanism without losing neuronal support. In neurodegenerative diseases, astrocytes show morphological alterations, such as decreased process length and reduced number of branch points, known as astroglial atrophy, with detrimental effects on neuronal cells. The common marmoset (Callithrix jacchus) is a non-human primate that, with age, develops several features that resemble neurodegeneration. In this study, we characterize the morphological alterations in astrocytes of adolescent (mean 1.75 y), adult (mean 5.33 y), old (mean 11.25 y), and aged (mean 16.83 y) male marmosets. We observed a significantly reduced arborization in astrocytes of aged marmosets compared to younger animals in the hippocampus and entorhinal cortex. These astrocytes also show oxidative damage to RNA and increased nuclear plaques in the cortex and tau hyperphosphorylation (AT100). Astrocytes lacking S100A10 protein show a more severe atrophy and DNA fragmentation. Our results demonstrate the presence of atrophic astrocytes in the brains of aged marmosets.

Delineation of the healthy rabbit heart by immunohistochemistry - A technical note

Heart failure poses a big health problem and may result from obesity, smoking, alcohol and/or growing age. Studying pathological heart tissue demands accurate histological and immunohistochemical stainings in animal models, including chromogenic and fluorescent approaches. Moreover, a reliable set of healthy heart stainings and labeling are required, in order to provide a reference for the pathological situation. Heart and brain tissue of a healthy rabbit were collected, and different histological key steps were compared, such as paraffin embedding after formalin fixation versus cryopreservation; an antigen retrieval (AR) step in processing paraffin sections versus the same procedure without AR; or a chromogenic with a fluorescent detection system, respectively. Using serial sections, we stained the same morphological structure with classic approaches (HE, Masson Goldner Trichrome (GT) and Elastica van Gieson (EL)) and with different markers, including collagen I, collagen III, fibronectin, α-SMA, protease-activated receptor-2 (PAR-2) which is an inflammation-related marker, and ki67 for proliferating cells. Differences between conditions were quantitatively assessed by measuring the color intensity. Generally, cryosections exhibited a more prominent signal intensity in immunohistochemically labeled sections than in paraffin sections, but the strong staining was slurry, which sometimes impeded proper identification of morphological structures, particularly at higher magnifications. In addition, the advantage of an AR step was observed when compared to the condition without AR, where signal intensities were significantly lower. Different stainings of the heart arteries and the myocardium revealed a clear distribution of extracellular matrix components, with prominent collagen III in the artery wall, but an absence of collagen III in the myocardium. Moreover, paraffin-embedded sections provided more distinct structures compared to cryosections after collagen III, ki67, fibronectin, and α-SMA labeling. As for the Purkinje cells that were depicted in the heart and the cerebellum (Purkinje neurons), we found GT staining most suitable to depict them in the heart, while HE as well as EL staining was ideal to depict Purkinje neurons in the cerebellum. In sum, we provide useful reference images with different stainings for researchers using the rabbit heart or brain model. Such images can help to decide which of the immunohistochemical protocols are valuable to reach a specific aim. Recommendations are given for the best visualization of the target structures and specific (immunohistochemical) staining.

Nucleophagy contributes to genome stability through degradation of type II topoisomerases A and B and nucleolar components

The nuclear architecture of mammalian cells can be altered as a consequence of anomalous accumulation of nuclear proteins or genomic alterations. Most of the knowledge about nuclear dynamics comes from studies on cancerous cells. How normal healthy cells maintain genome stability, avoiding accumulation of nuclear damaged material, is less understood. Here, we describe that primary mouse embryonic fibroblasts develop a basal level of nuclear buds and micronuclei, which increase after etoposide-induced DNA double-stranded breaks. Both basal and induced nuclear buds and micronuclei colocalize with the autophagic proteins BECN1 and LC3B (also known as MAP1LC3B) and with acidic vesicles, suggesting their clearance by nucleophagy. Some of the nuclear alterations also contain autophagic proteins and type II DNA topoisomerases (TOP2A and TOP2B), or the nucleolar protein fibrillarin, implying they are also targets of nucleophagy. We propose that basal nucleophagy contributes to genome and nuclear stability, as well as in response to DNA damage.

Colocalization of senescent biomarkers in deep, superficial, and ovarian endometriotic lesions: a pilot study

Endometriosis is a prevalent gynecological condition with deleterious effects on women's quality of life in terms of physical, emotional, and social compromise. It is an inflammatory disease characterized by the presence of endometrial-like tissue outside the uterus, and its presentation varies from superficial peritoneal lesions to deep infiltrative endometriosis and ovarian endometrioma. In our previous study, endometriotic lesions were implicated in cellular senescence as their inflammatory pattern could potentially compromise surrounding tissue integrity, thereby inducing a senescent state in cells. P16^Ink4a and lamin b1 are biomarkers used to assess cellular senescence. Indirect immunofluorescence staining is a broad technique used to assess cellular structure and behavior driven by protein-protein interactions that provide valuable information about cell functioning. The etiopathogeny of endometriosis is not completely understood and diagnostic approaches still rely on invasive methods; therefore, it is important to use validated methods to increase our understanding of the disease and the development of novel diagnostic tools. However, indirect immunofluorescence protocols are often tissue specific and, if neglected, can lead to misinterpretation of results. Moreover, no valid endometriotic tissue-specific colocalization immunofluorescence protocols have been established. Thus, we have validated a well-funded and suitable protocol to allow precise evaluation of the three presentations of endometriosis lesions using indirect immunofluorescence aiming to support further investigations in endometriosis lesions.

Dietary Fiber Modulates the Release of Gut Bacterial Products Preventing Cognitive Decline in an Alzheimer's Mouse Model

Fiber intake is associated with a lower risk for Alzheimer´s disease (AD) in older adults. Intake of plant-based diets rich in soluble fiber promotes the production of short-chain fatty acids (SCFAs: butyrate, acetate, propionate) by gut bacteria. Butyrate administration has antiinflammatory actions, but propionate promotes neuroinflammation. In AD patients, gut microbiota dysbiosis is a common feature even in the prodromal stages of the disease. It is unclear whether the neuroprotective effects of fiber intake rely on gut microbiota modifications and specific actions of SCFAs in brain cells. Here, we show that restoration of the gut microbiota dysbiosis through the intake of soluble fiber resulted in lower propionate and higher butyrate production, reduced astrocyte activation and improved cognitive function in 6-month-old male APP/PS1 mice. The neuroprotective effects were lost in antibiotic-treated mice. Moreover, propionate promoted higher glycolysis and mitochondrial respiration in astrocytes, while butyrate induced a more quiescent metabolism. Therefore, fiber intake neuroprotective action depends on the modulation of butyrate/propionate production by gut bacteria. Our data further support and provide a mechanism to explain the beneficial effects of dietary interventions rich in soluble fiber to prevent dementia and AD. Fiber intake restored the concentration of propionate and butyrate by modulating the composition of gut microbiota in male transgenic (Tg) mice with Alzheimer´s disease. Gut dysbiosis was associated with intestinal damage and high propionate levels in control diet fed-Tg mice. Fiber-rich diet restored intestinal integrity and promoted the abundance of butyrate-producing bacteria. Butyrate concentration was associated with better cognitive performance in fiber-fed Tg mice. A fiber-rich diet may prevent the development of a dysbiotic microbiome and the related cognitive dysfunction in people at risk of developing Alzheimer´s disease.

Aged mice ovaries harbor stem cells and germ cell nests but fail to form follicles

BACKGROUND

We recently published evidence to suggest that two populations of stem cells including very small embryonic-like stem cells (VSELs) and ovarian stem cells (OSCs) in ovary surface epithelium (OSE) undergo proliferation/differentiation, germ cell nests (GCN) formation, meiosis and eventually differentiate into oocytes that assemble as primordial follicles on regular basis during estrus cycle. Despite presence of stem cells, follicles get exhausted with advancing age in mice and result in senescence equivalent to menopause in women. Stem cells in aged ovaries can differentiate into oocytes upon transplantation into young ovaries, however, it is still not well understood why follicles get depleted with advancing age despite the presence of stem cells. The aim of the present study was to study stem cells and GCN in aged ovaries.

METHODS

OSE cells from aged mice (> 18 months equivalent to > 55 years old women) were enzymatically separated and used to study stem cells. Viable (7-AAD negative) VSELs in the size range of 2-6 µm with a surface phenotype of Lin-CD45-Sca-1+ were enumerated by flow cytometry. Immuno-fluorescence and RT-PCR analysis were done to study stem/progenitor cells (OCT-4, MVH, SCP3) and transcripts specific for VSELs (Oct-4A, Sox-2, Nanog), primordial germ cells (Stella), germ cells (Oct-4, Mvh), early meiosis (Mlh1, Scp1) and ring canals (Tex14).

RESULTS

Putative VSELs and OSCs were detected as darkly stained, spherical cells with high nucleo-cytoplasmic ratio along with germ cells nests (GCN) in Hematoxylin & Eosin stained OSE cells smears. Germ cells in GCN with distinct cytoplasmic continuity expressed OCT-4, MVH and SCP3. Transcripts specific for stem cells, early meiosis and ring canals were detected by RT-PCR studies.

CONCLUSION

Rather than resulting as a consequence of accelerated loss of primordial follicle and their subsequent depletion, ovarian senescence/menopause occurs as a result of stem cells dysfunction. VSELs and OSCs exist along with increased numbers of GCNs arrested in pre-meiotic or early meiotic stage in aged ovaries and primordial follicle assembly is blocked possibly due to age-related changes in their microenvironment.

POSTNATAL EXPOSURE TO LIPOPOLYSACCHARIDE COMBINED WITH HIGH-FAT DIET CONSUMPTION INDUCES IMMUNE TOLERANCE WITHOUT PREVENTION IN SPATIAL WORKING MEMORY IMPAIRMENT

High-fat diet (HFD) consumption has been related to metabolic alterations, such as obesity and cardiovascular problems, and has pronounced effects on brain plasticity and memory impairment. HFD exposure has a pro-inflammatory effect associated with microglial cell modifications in the hippocampus, a region involved in the working memory process. Immune tolerance can protect from inflammation in periphery induced by HFD consumption, when the immune response is desensitized in development period with lipopolysaccharide (LPS) exposure, maybe this previously state can change the course of the diseases associated to HFDs but is not known if can protect the hippocampus's inflammatory response. In the present study, male mice were injected with LPS (100μg.kg-1 body weight) on postnatal day 3 and fed with HFD for 16 weeks after weaning. Ours results indicated that postnatal exposure to LPS in the early postnatal developmental stage combined with HFD consumption prevented glycemia, insulin, HOMA-IR, microglial process, and increased pro-inflammatory cytokines mRNA expression, without changes in body weight gain and spatial working memory with respect vehicle + HFD group. These findings suggest that HFD consumption after postnatal LPS exposure induces hippocampal immune tolerance, without prevention in spatial working memory impairment on male mice.

Ten Approaches That Improve Immunostaining: A Review of the Latest Advances for the Optimization of Immunofluorescence

Immunostaining has emerged as one of the most common and valuable techniques that allow the localization of proteins at a quantitative level within cells and tissues using antibodies coupled to enzymes, fluorochromes, or colloidal nanogold particles. The application of fluorochromes during immunolabeling is referred to as immunofluorescence, a method coupled to widefield or confocal microscopy and extensively applied in basic research and clinical diagnosis. Notwithstanding, there are still disadvantages associated with the application of this technique due to technical challenges in the process, such as sample fixation, permeabilization, antibody incubation times, and fluid exchange, etc. These disadvantages call for continuous updates and improvements to the protocols extensively described in the literature. This review contributes to protocol optimization, outlining 10 current methods for improving sample processing in different stages of immunofluorescence, including a section with further recommendations. Additionally, we have extended our own antibody signal enhancer method, which was reported to significantly increase antibody signals and is useful for cervical cancer detection, to improve the signals of fluorochrome-conjugated staining reagents in fibrous tissues. In summary, this review is a valuable tool for experienced researchers and beginners when planning or troubleshooting the immunofluorescence assay.

Abnormalities in esophageal smooth muscle induced by mutations in collagen XIX

Collagen XIX is a nonfibrillar collagen that localizes in restricted tissues at very low amounts. A previous study on Col19a1 null mice revealed that collagen XIX is involved in esophageal muscle physiology and morphogenesis. Here, we use histological analysis to show that mice with a Col19a1 mutant lacking the NC3 domain and seven collagen triplets display abnormal transition of smooth to striated muscle in the abdominal segment of esophagus, and a widened esophagus with age. With two newly prepared antibodies, we analyzed the expression of collagen XIX in the mouse esophagus and show that collagen XIX colocalizes with α-smooth muscle actin. By immunoelectron microscopy, we confirmed the localization of collagen XIX in esophageal smooth muscle cells. Col19a1 mutant mice contained reduced levels of mutated Col19a1 mRNA. Interestingly, hepatocyte growth factor, which has an important role in esophageal striated muscle development, was reduced in the esophagus of the Col19a1 mutant mice. These findings suggest that collagen XIX may be critical for the function of esophageal smooth muscle cells as a scaffold for anteroposterior migration of esophagus-striated muscle cells.

Stem Cells in Adult Mice Ovaries Form Germ Cell Nests, Undergo Meiosis, Neo-oogenesis and Follicle Assembly on Regular Basis During Estrus Cycle

Very small embryonic-like (VSELs) and ovarian (OSCs) stem cells are located in adult mammalian ovary surface epithelium (OSE). OSCs can expand long-term and differentiate into oocyte-like structures in vitro and have resulted in birth of fertile pups. Lineage tracing studies have provided evidence to suggest OSCs differentiation into oocytes in vivo. But how these stem cells function under normal physiological conditions has not yet been well worked out. Besides studying STRA-8 and SCP-3 expression in enzymatically isolated OSE cells smears, mice were injected BrdU to track mitosis, meiosis and follicle assembly. H&E stained OSE cells during late diestrus and proestrus showed VSELs undergoing asymmetrical cell divisions to give rise to slightly bigger OSCs which in turn underwent symmetrical cell divisions followed by clonal expansion (rapid expansion with incomplete cytokinesis) during early estrus to form germ cell nests (GCN). OCT-4, SSEA-1, MVH and DAZL positive cells in GCN expressed Erα, Erβ and FSHR, were interconnected by ring canals (TEX-14), showed mitochondrial aggregation (Cytochrome C) and Balbiani Body (TRAL). Apoptosis in 'nurse' cells was marked by PARP and putative oocytes were clearly visualized. BrdU was detected in cells undergoing mitosis/meiosis and also in an oocyte of secondary follicle. FACS sorted, green fluorescent protein (GFP) positive VSELs upon transplantation resulted in GFP positive GCN suggesting crucial role for VSELs in adult ovaries. Results suggest that various events described during oogenesis and follicle assembly in fetal ovaries are recapitulated on regular basis in adult ovary and result in the formation of follicles.

Postweaning Isolation Alters the Responses of Auditory Neurons to Serotonergic Modulation

Juvenile social experience, such as social isolation, has profound effects on communicative behavior, including signal production and reception. In the current study, we explored responsiveness to the neuromodulator serotonin as a potential mechanistic link between early life social isolation and auditory processing. The serotonergic system is sensitive to social isolation in many brain regions including the inferior colliculus (IC), an auditory midbrain nucleus. We investigated the effects of social experience on serotonergic responsiveness by measuring cFos, an immediate early gene product, in the IC of female mice. Serotonin was manipulated pharmacologically by administering fenfluramine, pCPA, or saline to mice that had undergone an extreme dichotomy in social experience after weaning: being housed in social groups versus individually. These mice were exposed to a 60-min recording of vocalizations from an opposite-sex interaction and perfused. Using immunohistochemistry, we measured the density of cFos-positive (cFos+) nuclei in the major subdivisions of the IC. Housing condition, drug treatment, and IC subregion all had a significant effect on cFos+ density. The central IC showed the highest density of cFos+ cells and also the most pronounced effects of housing condition and drug treatment. In the central IC, cFos+ density was higher following fenfluramine treatment than saline, and lower following pCPA treatment than fenfluramine. Individually housed mice showed a higher cFos+ density than socially housed mice in both of the pharmacological treatment groups, but not in the saline group. Drug treatment but not housing condition had strong effects on the behaviors of grooming, digging, rearing, and movement. Once the effects of drug condition were controlled, there were no across-individual correlations between cFos+ densities and behaviors. These findings suggest that the responses of auditory neurons to neuromodulation by serotonin are influenced by early life experience.

Automated Quantitative Analysis of ex vivo Blood-Brain Barrier Permeability Using Intellesis Machine-Learning

Background

An increase in blood brain barrier permeability commonly precedes neuro-inflammation and cognitive impairment in models of dementia. Common methods to estimate capillary permeability have potential confounders, or require laborious and subjective semi-manual analysis.

New method

Here we used snap frozen mouse and rat brain sections that were double-immunofluorescent labeled for immunoglobulin G (IgG; plasma protein) and laminin-α4 (capillary basement membrane). A Machine Learning Image Analysis program (Zeiss ZEN Intellisis) was trained to recognize and segment laminin-α4 to equivocally identify blood vessels in large sets of images. An IgG subclass based on a threshold intensity was segmented and quantitated only in extravascular regions. The residual parenchymal IgG fluorescence is indicative of blood-to-brain extravasation of IgG and was accurately quantitated.

Results

Automated machine-learning and threshold based segmentation of only parenchymal IgG extravasation accentuates otherwise indistinct capillary permeability, particularly frequent in minor BBB leakage. Comparison with Existing Methods: Large datasets can be processed and analyzed quickly and robustly to provide an overview of vascular permeability throughout the brain. All human bias or ambiguity involved in classifying and measuring leakage is removed.

Conclusion

Here we describe a fast and precise method of visualizing and quantitating BBB permeability in mouse and rat brain tissue, while avoiding the confounding influence of unphysiological conditions such as perfusion and eliminating any human related bias from analysis.

Anti-Müllerian hormone and its receptor are detected in most gonadotropin-releasing-hormone cell bodies and fibers in heifer brains

Circulating concentrations of Anti-Müllerian hormone (AMH) can indicate fertility in various animals, but the physiological mechanisms underlying the effect of AMH on fertility remain unknown. We recently discovered that AMH has extragonadal functions via its main receptor, AMH receptor type 2 (AMHR2). Specifically, AMH stimulates the secretion of luteinizing hormone and follicle-stimulating hormone from bovine gonadotrophs. Moreover, gonadotrophs themselves express AMH to exert paracrine/autocrine functions, and AMH can activate gonadotropin-releasing-hormone (GnRH) neurons in mice. This study aimed to evaluate whether AMH and AMHR2 are detected in areas of the brain relevant to neuroendocrine control of reproduction: the preoptic area (POA), arcuate nucleus (ARC), and median eminence (ME), and in particular within GnRH neurons. Reverse transcription-polymerase chain reaction detected both AMH and AMHR2 mRNA in tissues containing POA, as well as in those containing both ARC and ME, collected from postpubertal heifers. Western blotting detected AMH and AMHR2 protein in the collected tissues. Triple fluorescence immunohistochemistry revealed that most cell bodies or fibers of GnRH neurons were AMHR2-positive and AMH-positive, although some were negative. Immunohistochemistry revealed that 75% to 85% of cell bodies and fibers of GnRH neurons were positive for both AMH and AMHR2 in the POA, ARC, and both the internal and external zones of the ME. The cell bodies of GnRH neurons were situated around other AMH-positive cell bodies or fibers of GnRH and non-GNRH neurons. Our findings thus indicate that AMH and AMHR2 are detected in most cell bodies or fibers of GnRH neurons in the POA, ARC, and ME of heifer brains. These data support the need for further study as to how AMH and AMHR2 act within the hypothalamus to influence GnRH and gonadotropin secretion.

Amelioration of elastase-induced lung emphysema and reversal of pulmonary hypertension by pharmacological iNOS inhibition in mice

BACKGROUND AND PURPOSE

Chronic obstructive pulmonary disease, encompassing chronic airway obstruction and lung emphysema, is a major worldwide health problem and a severe socio-economic burden. Evidence previously provided by our group has shown that inhibition of inducible NOS (iNOS) prevents development of mild emphysema in a mouse model of chronic tobacco smoke exposure and can even trigger lung regeneration. Moreover, we could demonstrate that pulmonary hypertension is not only abolished in cigarette smoke-exposed iNOS^-/- mice but also precedes emphysema development. Possible regenerative effects of pharmacological iNOS inhibition in more severe models of emphysema not dependent on tobacco smoke, however, are hitherto unknown.

EXPERIMENTAL APPROACH

We have established a mouse model using a single dose of porcine pancreatic elastase or saline, intratracheally instilled in C57BL/6J mice. Emphysema, as well as pulmonary hypertension development was determined by both structural and functional measurements.

KEY RESULTS

Our data revealed that (i) emphysema is fully established after 21 days, with the same degree of emphysema after 21 and 28 days post instillation, (ii) emphysema is stable for at least 12 weeks and (iii) pulmonary hypertension is evident, in contrast to smoke models, only after emphysema development. Oral treatment with the iNOS inhibitor N(6)-(1-iminoethyl)-l-lysine (L-NIL) was started after emphysema establishment and continued for 12 weeks. This resulted in significant lung regeneration, evident in the improvement of emphysema and reversal of pulmonary hypertension.

CONCLUSION AND IMPLICATIONS

Our data indicate that iNOS is a potential new therapeutic target to treat severe emphysema and associated pulmonary hypertension.

LINKED ARTICLES

This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.1/issuetoc.

Increased oxidative stress, hyperphosphorylation of tau, and dystrophic microglia in the hippocampus of aged Tupaia belangeri

Aging is a major risk factor for the development of neurodegenerative diseases. Alzheimer's disease and other neurodegenerative diseases are characterized by abnormal and prominent protein aggregation in the brain, partially due to deficiency in protein clearance. It has been proposed that alterations in microglia phagocytosis and debris clearance hasten the onset of neurodegeneration. Dystrophic microglia are abundant in aged humans, and it has been associated with the onset of disease. Furthermore, alterations in microglia containing ferritin are associated with neurodegenerative conditions. To further understand the process of microglia dysfunction during the aging process, we used hippocampal sections from Tupaia belangeri (tree shrews). Adult (mean age 3.8 years), old (mean age 6 years), and aged (mean age 7.5 years) tree shrews were used for histochemical and immunostaining techniques to determine ferritin and Iba1 positive microglia, iron tissue content, tau hyperphosphorylation and oxidized-RNA in dentate gyrus, subiculum, and CA1-CA3 hippocampal regions. Our results indicated that aged tree shrews presented an increased number of activated microglia containing ferritin, but microglia labeled with Iba1 with a dystrophic phenotype was more abundant in aged individuals. With aging, oxidative damage to RNA (8OHG) increased significantly in all hippocampal regions, while tau hyperphosphorylation (AT100) was enhanced in DG, CA3, and SUB in aged animals. Phagocytic inclusions of 8OHG- and AT100-damaged cells were observed in activated M2 microglia in old and aged animals. These data indicate that aged tree shrew may be a suitable model for translational research to study brain and microglia alterations during the aging process.

Cortical neurons develop a senescence-like phenotype promoted by dysfunctional autophagy

Senescent cells accumulate in various tissues and organs with aging altering surrounding tissue due to an active secretome, and at least in mice their elimination extends healthy lifespan and ameliorates several chronic diseases. Whether all cell types senesce, including post-mitotic cells, has been poorly described mainly because cellular senescence was defined as a permanent cell cycle arrest. Nevertheless, neurons with features of senescence have been described in old rodent and human brains. In this study we characterized an in vitro model useful to study the molecular basis of senescence of primary rat cortical cells that recapitulates senescent features described in brain aging. We found that in long-term cultures, rat primary cortical neurons displayed features of cellular senescence before glial cells did, and developed a functional senescence-associated secretory phenotype able to induce paracrine premature senescence of mouse embryonic fibroblasts but proliferation of rat glial cells. Functional autophagy seems to prevent neuronal senescence, as we observed an autophagic flux reduction in senescent neurons both in vitro and in vivo, and autophagy impairment induced cortical cell senescence while autophagy stimulation inhibited it. Our findings suggest that aging-associated dysfunctional autophagy contributes to senescence transition also in neuronal cells.

Invasion of a murine in vitro blood-brain barrier co-culture model by dengue virus serotypes 1 to 4

The blood-brain barrier (BBB) is a physical barrier that restricts the passage of cells and molecules as well as pathogens into the central nervous system (CNS). Some viruses enter the CNS by disrupting the BBB, while others can reach the CNS without altering the integrity of the BBB. Even though dengue virus (DENV) is not a distinctive neurotropic virus, the virus is considered to be one of the leading causes of neurological manifestations. In this study, we found that DENV is able to compromise the integrity of a murine in vitro blood-brain barrier (BBB) model, resulting in hyperpermeability, as shown by a significant increase in sucrose and albumin permeability. Infection of brain endothelial cells (ECs) was facilitated by the presence of glycans, in particular, mannose and N-acetyl glucosamine residues, on cell surfaces and viral envelope proteins, and the requirement for glycan moieties for cell infection was serotype-specific. Direct viral disruption of brain ECs was observed, leading to a significant decrease in tight-junction protein expression and peripheral localization, which contributed to the changes in BBB permeability. In conclusion, the hyperpermeability and breaching mechanism of BBB by DENV are primarily due to direct consequences of viral infection of ECs, as shown in this in vitro study.

Regenerative capacity in the lamprey spinal cord is not altered after a repeated transection

The resilience of regeneration in vertebrates is not very well understood. Yet understanding if tissues can regenerate after repeated insults, and identifying limitations, is important for elucidating the underlying mechanisms of tissue plasticity. This is particularly challenging in tissues, such as the nervous system, which possess a large number of terminally differentiated cells and often exhibit limited regeneration in the first place. However, unlike mammals, which exhibit very limited regeneration of spinal cord tissues, many non-mammalian vertebrates, including lampreys, bony fishes, amphibians, and reptiles, regenerate their spinal cords and functionally recover even after a complete spinal cord transection. It is well established that lampreys undergo full functional recovery of swimming behaviors after a single spinal cord transection, which is accompanied by tissue repair at the lesion site, as well as axon and synapse regeneration. Here we begin to explore the resilience of spinal cord regeneration in lampreys after a second spinal transection (re-transection). We report that by all functional and anatomical measures tested, lampreys regenerate after spinal re-transection just as robustly as after single transections. Recovery of swimming, synapse and cytoskeletal distributions, axon regeneration, and neuronal survival were nearly identical after spinal transection or re-transection. Only minor differences in tissue repair at the lesion site were observed in re-transected spinal cords. Thus, regenerative potential in the lamprey spinal cord is largely unaffected by spinal re-transection, indicating a greater persistent regenerative potential than exists in some other highly regenerative models. These findings establish a new path for uncovering pro-regenerative targets that could be deployed in non-regenerative conditions.

We also CanFly! The 2nd MexFly drosophila research conference

The 2nd Mexican Drosophila Research Conference (MexFly) took place on June 30th and July 1st, 2016 in Mexico City, at the Center for Research and Advanced Studies of the National Polytechnic Institute (Cinvestav). Principal investigators, postdocs, students, and technicians from Drosophila labs across Mexico attended. The guest speaker was Chris Rushlow from New York University, who presented work on Zelda, a key transcriptional activator of the early zygotic genome. Here we provide a brief report of the meeting, which sketches the present landscape of Drosophila research in Mexico. We also provide a brief historical note on one of the pioneers of the field in this country, Victor Salceda, personally trained by Theodosius Dobzhansky. Salceda presented at the meeting an update of his collaborative project with Dobzhansky on the distribution of Drosophila pseudoobscura chromosomal inversions, initiated over forty years ago.