A Practical Guide to the Automated Analysis of Vascular Growth, Maturation and Injury in the Brain

Hydrocortisone treatment as a tool to study conjunctival placode induction

BACKGROUND

Conjunctival placodes are a series of placodes that develop into the conjunctival (scleral) papillae and ultimately induce a series of scleral ossicles in the eyes of many vertebrates. This study establishes a hydrocortisone injection procedure (incl. dosage) that consistently inhibits all conjunctival papillae in the embryonic chicken eye. The effects of this hydrocortisone treatment on apoptosis, vasculature, and placode-related gene expression were assessed.

RESULTS

Hydrocortisone treatment does not increase apoptotic cell death or have a major effect on the ciliary artery or vascular plexus in the eye. β-catenin and Eda expression levels were not significantly altered following hydrocortisone treatment, despite the absence of conjunctival papillae. Notably, Fgf20 expression was significantly reduced following hydrocortisone treatment, and the distribution of β-catenin was altered.

CONCLUSIONS

Our study showed that conjunctival papillae induction begins as early as HH27.5 (E5.5). Hydrocortisone treatment reduces Fgf20 expression independently of β-catenin and Eda and may instead affect other members of the Wnt/β-catenin or Eda/Edar pathways, or it may affect the ability of morphogens to diffuse through the extracellular matrix. This study contributes to a growing profile of gene expression data during placode development and enhances our understanding of how some vertebrate eyes develop these fascinating bones.

Deep Learning for 3D Vascular Segmentation in Phase Contrast Tomography

Automated blood vessel segmentation is critical for biomedical image analysis, as vessel morphology changes are associated with numerous pathologies. Still, precise segmentation is difficult due to the complexity of vascular structures, anatomical variations across patients, the scarcity of annotated public datasets, and the quality of images. Our goal is to provide a foundation on the topic and identify a robust baseline model for application to vascular segmentation using a new imaging modality, Hierarchical Phase-Contrast Tomography (HiP-CT). We begin with an extensive review of current machine learning approaches for vascular segmentation across various organs. Our work introduces a meticulously curated training dataset, verified by double annotators, consisting of vascular data from three kidneys imaged using Hierarchical Phase-Contrast Tomography (HiP-CT) as part of the Human Organ Atlas Project. HiP-CT, pioneered at the European Synchrotron Radiation Facility in 2020, revolutionizes 3D organ imaging by offering resolution around 20μm/voxel, and enabling highly detailed localized zooms up to 1μm/voxel without physical sectioning. We leverage the nnU-Net framework to evaluate model performance on this high-resolution dataset, using both known and novel samples, and implementing metrics tailored for vascular structures. Our comprehensive review and empirical analysis on HiP-CT data sets a new standard for evaluating machine learning models in high-resolution organ imaging. Our three experiments yielded Dice scores of 0.9523 and 0.9410, and 0.8585, respectively. Nevertheless, DSC primarily assesses voxel-to-voxel concordance, overlooking several crucial characteristics of the vessels and should not be the sole metric for deciding the performance of vascular segmentation. Our results show that while segmentations yielded reasonably high scores-such as centerline Dice values ranging from 0.82 to 0.88, certain errors persisted. Specifically, large vessels that collapsed due to the lack of hydro-static pressure (HiP-CT is an ex vivo technique) were segmented poorly. Moreover, decreased connectivity in finer vessels and higher segmentation errors at vessel boundaries were observed. Such errors, particularly in significant vessels, obstruct the understanding of the structures by interrupting vascular tree connectivity. Through our review and outputs, we aim to set a benchmark for subsequent model evaluations using various modalities, especially with the HiP-CT imaging database.

Mesenchymal Stem Cell-Loaded Hydrogel Improves Surgical Treatment for Chronic Cerebral Ischemia

Chronic cerebral ischemia (CCI) results in a prolonged insufficient blood supply to the brain tissue, leading to impaired neuronal function and subsequent impairment of cognitive and motor abilities. Our previous research showed that in mice with bilateral carotid artery stenosis, the collateral neovascularization post Encephalo-myo-synangiosis (EMS) treatment could be facilitated by bone marrow mesenchymal stem cells (MSCs) transplantation. Considering the advantages of biomaterials, we synthesized and modified a gelatin hydrogel for MSCs encapsulation. We then applied this hydrogel on the brain surface during EMS operation in rats with CCI, and evaluated its impact on cognitive performance and collateral circulation. Consequently, MSCs encapsulated in hydrogel significantly augment the therapeutic effects of EMS, potentially by promoting neovascularization, facilitating neuronal differentiation, and suppressing neuroinflammation. Furthermore, taking advantage of multi-RNA-sequencing and in silico analysis, we revealed that MSCs loaded in hydrogel regulate PDCD4 and CASP2 through the overexpression of miR-183-5p and miR-96-5p, thereby downregulating the expression of apoptosis-related proteins and inhibiting early apoptosis. In conclusion, a gelatin hydrogel to enhance the functionality of MSCs has been developed, and its combination with EMS treatment can improve the therapeutic effect in rats with CCI, suggesting its potential clinical benefit.

Dataset on stroke infarct volume in rodents: A comparison of MRI and histological methods

This dataset offers images of mouse brains impacted by photothrombotic stroke in the sensorimotor cortex published by Weber et al. NeuroImage (2024). Data is gathered using two primary techniques: (1) whole-brain ex-vivo magnetic resonance imaging (MRI) and (2) 40 µm thick coronal histological sections that undergo immunofluorescence staining with NeuroTrace. Infarct areas and volumes are assessed through MRI at two distinct time frames-three days (acute) and 28 days (chronic) following photothrombotic stroke induction. Subsequently, the brains are sectioned into 40 µm thick coronal slices, stained with NeuroTrace, and imaged as whole sections. The dataset holds considerable value for reuse, particularly for researchers focused on stroke volume estimation methods as well as those interested in comparing the efficacy of MRI and histological techniques.

A Versatile Pipeline for High-fidelity Imaging and Analysis of Vascular Networks Across the Body

Structural and functional changes in vascular networks play a vital role during development, causing or contributing to the pathophysiology of injury and disease. Current methods to trace and image the vasculature in laboratory settings have proven inconsistent, inaccurate, and labor intensive, lacking the inherent three-dimensional structure of vasculature. Here, we provide a robust and highly reproducible method to image and quantify changes in vascular networks down to the capillary level. The method combines vasculature tracing, tissue clearing, and three-dimensional imaging techniques with vessel segmentation using AI-based convolutional reconstruction to rapidly process large, unsectioned tissue specimens throughout the body with high fidelity. The practicality and scalability of our protocol offer application across various fields of biomedical sciences. Obviating the need for sectioning of samples, this method will expedite qualitative and quantitative analyses of vascular networks. Preparation of the fluorescent gel perfusate takes < 30 min per study. Transcardiac perfusion and vasculature tracing takes approximately 20 min, while dissection of tissue samples ranges from 5 to 15 min depending on the tissue of interest. The tissue clearing protocol takes approximately 24-48 h per whole-tissue sample. Lastly, three-dimensional imaging and analysis can be completed in one day. The entire procedure can be carried out by a competent graduate student or experienced technician. Key features • This robust and highly reproducible method allows users to image and quantify changes in vascular networks down to the capillary level. • Three-dimensional imaging techniques with vessel segmentation enable rapid processing of large, unsectioned tissue specimens throughout the body. • It takes approximately 2-3 days for sample preparation, three-dimensional imaging, and analysis. • The user-friendly pipeline can be completed by experienced and non-experienced users.

A toolkit for stroke infarct volume estimation in rodents

Stroke volume is a key determinant of infarct severity and an important metric for evaluating treatments. However, accurate estimation of stroke volume can be challenging, due to the often confined 2-dimensional nature of available data. Here, we introduce a comprehensive semi-automated toolkit to reliably estimate stroke volumes based on (1) whole brains ex-vivo magnetic resonance imaging (MRI) and (2) brain sections that underwent immunofluorescence staining. We located and quantified infarct areas from MRI three days (acute) and 28 days (chronic) after photothrombotic stroke induction in whole mouse brains. MRI results were compared with measures obtained from immunofluorescent histologic sections of the same brains. We found that infarct volume determined by post-mortem MRI was highly correlated with a deviation of only 6.6 % (acute) and 4.9 % (chronic) to the measurements as determined in the histological brain sections indicating that both methods are capable of accurately assessing brain tissue damage (Pearson r > 0.9, p < 0.001). The Dice similarity coefficient (DC) showed a high degree of coherence (DC > 0.8) between MRI-delineated regions of interest (ROIs) and ROIs obtained from histologic sections at four to six pre-defined landmarks, with histology-based delineation demonstrating higher inter-operator similarity compared to MR images. We further investigated stroke-related scarring and post-ischemic angiogenesis in cortical peri‑infarct regions and described a negative correlation between GFAP+fluorescence intensity and MRI-obtained lesion size.

Spatiotemporal signaling underlies progressive vascular rarefaction in myocardial infarction

Therapeutic angiogenesis represents a promising avenue to revascularize the ischemic heart. Its limited success is partly due to our poor understanding of the cardiac stroma, specifically mural cells, and their response to ischemic injury. Here, we combine single-cell and positional transcriptomics to assess the behavior of mural cells within the healing heart. In response to myocardial infarction, mural cells adopt an altered state closely associated with the infarct and retain a distinct lineage from fibroblasts. This response is concurrent with vascular rarefaction and reduced vascular coverage by mural cells. Positional transcriptomics reveals that the infarcted heart is governed by regional-dependent and temporally regulated programs. While the remote zone acts as an important source of pro-angiogenic signals, the infarct zone is accentuated by chronic activation of anti-angiogenic, pro-fibrotic, and inflammatory cues. Together, our work unveils the spatiotemporal programs underlying cardiac repair and establishes an association between vascular deterioration and mural cell dysfunction.

Leakage beyond the primary lesion: A temporal analysis of cerebrovascular dysregulation at sites of hippocampal secondary neurodegeneration following cortical photothrombotic stroke

We have previously demonstrated that a cortical stroke causes persistent impairment of hippocampal-dependent cognitive tasks concomitant with secondary neurodegenerative processes such as amyloid-β accumulation in the hippocampus, a region remote from the primary infarct. Interestingly, there is emerging evidence suggesting that deposition of amyloid-β around cerebral vessels may lead to cerebrovascular structural changes, neurovascular dysfunction, and disruption of blood-brain barrier integrity. However, there is limited knowledge about the temporal changes of hippocampal cerebrovasculature after cortical stroke. In the current study, we aimed to characterise the spatiotemporal cerebrovascular changes after cortical stroke. This was done using the photothrombotic stroke model targeting the motor and somatosensory cortices of mice. Cerebrovascular morphology as well as the co-localisation of amyloid-β with vasculature and blood-brain barrier integrity were assessed in the cortex and hippocampal regions at 7, 28 and 84 days post-stroke. Our findings showed transient cerebrovascular remodelling in the peri-infarct area up to 28 days post-stroke. Importantly, the cerebrovascular changes were extended beyond the peri-infarct region to the ipsilateral hippocampus and were sustained out to 84 days post-stroke. When investigating vessel diameter, we showed a decrease at 84 days in the peri-infarct and CA1 regions that were exacerbated in vessels with amyloid-β deposition. Lastly, we showed sustained vascular leakage in the peri-infarct and ipsilateral hippocampus, indicative of a compromised blood-brain-barrier. Our findings indicate that hippocampal vasculature may represent an important therapeutic target to mitigate the progression of post-stroke cognitive impairment.

Endothelial Cell APOE3 Regulates Neurovascular, Neuronal, and Behavioral Function

BACKGROUND

Specialized brain endothelial cells and human APOE3 are independently important for neurovascular function, yet whether APOE3 expression by endothelial cells contributes to brain function is currently unknown. In the present study, we determined whether the loss of endothelial cell APOE3 impacts brain vascular and neural function.

METHODS

We developed APOE3fl/fl/Cdh5(PAC)-CreERT2+/- (APOE3Cre+/-) and APOE3fl/fl/Cdh5(PAC)-CreERT2-/- (APOE3Cre-/-, control) mice and induced endothelial cell APOE3 knockdown with tamoxifen at ≈4 to 5 weeks of age. Neurovascular and neuronal function were evaluated by biochemistry, immunohistochemistry, behavioral testing, and electrophysiology at 9 months of age.

RESULTS

We found that the loss of endothelial APOE3 expression was sufficient to cause neurovascular dysfunction including higher permeability and lower vessel coverage in tandem with deficits in spatial memory and fear memory extinction and a disruption of cortical excitatory/inhibitory balance.

CONCLUSIONS

Our data collectively support the novel concept that endothelial APOE3 plays a critical role in the regulation of the neurovasculature, neural circuit function, and behavior.

The vascular gene Apold1 is dispensable for normal development but controls angiogenesis under pathological conditions

The molecular mechanisms of angiogenesis have been intensely studied, but many genes that control endothelial behavior and fate still need to be described. Here, we characterize the role of Apold1 (Apolipoprotein L domain containing 1) in angiogenesis in vivo and in vitro. Single-cell analyses reveal that - across tissues - the expression of Apold1 is restricted to the vasculature and that Apold1 expression in endothelial cells (ECs) is highly sensitive to environmental factors. Using Apold1-/- mice, we find that Apold1 is dispensable for development and does not affect postnatal retinal angiogenesis nor alters the vascular network in adult brain and muscle. However, when exposed to ischemic conditions following photothrombotic stroke as well as femoral artery ligation, Apold1-/- mice display dramatic impairments in recovery and revascularization. We also find that human tumor endothelial cells express strikingly higher levels of Apold1 and that Apold1 deletion in mice stunts the growth of subcutaneous B16 melanoma tumors, which have smaller and poorly perfused vessels. Mechanistically, Apold1 is activated in ECs upon growth factor stimulation as well as in hypoxia, and Apold1 intrinsically controls EC proliferation but not migration. Our data demonstrate that Apold1 is a key regulator of angiogenesis in pathological settings, whereas it does not affect developmental angiogenesis, thus making it a promising candidate for clinical investigation.

Q-VAT: Quantitative Vascular Analysis Tool

As our imaging capability increase, so does our need for appropriate image quantification tools. Quantitative Vascular Analysis Tool (Q-VAT) is an open-source software, written for Fiji (ImageJ), that perform automated analysis and quantification on large two-dimensional images of whole tissue sections. Importantly, it allows separation of the vessel measurement based on diameter, allowing the macro- and microvasculature to be quantified separately. To enable analysis of entire tissue sections on regular laboratory computers, the vascular network of large samples is analyzed in a tile-wise manner, significantly reducing labor and bypassing several limitations related to manual quantification. Double or triple-stained slides can be analyzed, with a quantification of the percentage of vessels where the staining's overlap. To demonstrate the versatility, we applied Q-VAT to obtain morphological read-outs of the vasculature network in microscopy images of whole-mount immuno-stained sections of various mouse tissues.

Rapid and fully automated blood vasculature analysis in 3D light-sheet image volumes of different organs

Light-sheet fluorescence microscopy (LSFM) can produce high-resolution tomograms of tissue vasculature with high accuracy. However, data processing and analysis is laborious due to the size of the datasets. Here, we introduce VesselExpress, an automated software that reliably analyzes six characteristic vascular network parameters including vessel diameter in LSFM data on average computing hardware. VesselExpress is ∼100 times faster than other existing vessel analysis tools, requires no user interaction, and integrates batch processing and parallelization. Employing an innovative dual Frangi filter approach, we show that obesity induces a large-scale modulation of brain vasculature in mice and that seven other major organs differ strongly in their 3D vascular makeup. Hence, VesselExpress transforms LSFM from an observational to an analytical working tool.

Hyperglycemia with or without insulin resistance triggers different structural changes in brain microcirculation and perivascular matrix

Both type-1 and type-2 DM are related to an increased risk of cognitive impairment, neurovascular complications, and dementia. The primary triggers for complications are hyperglycemia and concomitant insulin resistance in type-2 DM. However, the diverse mechanisms in the pathogenesis of diabetes-related neurovascular complications and extracellular matrix (ECM) remodeling in type-1 and 2 have not been elucidated yet. Here, we investigated the high fat-high sucrose (HFHS) feeding model and streptozotocin-induced type-1 DM model to study the early effects of hyperglycemia with or without insulin resistance to demonstrate the brain microcirculatory changes, perivascular ECM alterations in histological sections and 3D-reconstructed cleared brain tissues. One of the main findings of this study was robust rarefaction in brain microvessels in both models. Interestingly, the HFHS model leads to widespread non-functional angiogenesis, but the type-1 DM model predominantly in the rostral brain. Rarefaction was accompanied by basement membrane thickening and perivascular collagen accumulation in type-1 DM; more severe blood-brain barrier leakage, and disruption of perivascular ECM organization, mainly of elastin and collagen fibers' structural integrity in the HFHS model. Our results point out that the downstream mechanisms of the long-term vascular complications of hyperglycemia models are structurally distinctive and may have implications for appropriate treatment options.

Pathology and prevention of brain microvascular and neuronal dysfunction induced by a high-fructose diet in rats

A high-fructose diet causes metabolic abnormalities in rats, and the cluster of complications points to microvascular and neuronal disorders of the brain. The aim of this study was to evaluate i) the involvement of microvascular disorders and neuronal plasticity in the deleterious effects of a high-fructose diet on the rat brain and ii) a comparative assessment of the effectiveness of Phytocollection therapy (with antidiabetic, antioxidant, and acetylcholinesterase inhibitory activities) compared to Galantamine as first-line therapy for dementia and Diabeton as first-line therapy for hyperglycemia. The calcium adenosine triphosphate non-injection histoangiological method was used to assess capillary network diameter and density. A high-fructose diet resulted in a significant decrease in the diameter and density of the capillary bed, and pharmacological manipulations had a modulatory effect on microcirculatory adaptive mechanisms. In vivo single-unit extracellular recording was used to investigate short-term plasticity in the medial prefrontal cortex. Differences in the parameters of spike background activity and expression of excitatory and inhibitory responses of cortical neurons have been discovered, allowing for flexibility and neuronal function stabilization in pathology and pharmacological prevention. Integration of the coupling mechanism between microvascular function and neuronal spike activity could delay the progressive decline in cognitive function in rats fed a high fructose diet.

Biomimicking Leaf-Vein Engraved Soft and Elastic Membrane Promotes Vascular Reconstruction

Hierarchical vasculature reconstruction is fundamental for tissue regeneration. The regeneration of functional vascular network requires a proper directional guidance, especially in case of large-size defects. To provide the "running track" for vasculature, a leaf-vein mimetic membrane using soft and elastic poly(lactide-co-propylene glycol-co-lactide) dimethacrylate is developed. Engraved with an interconnected and perfusable leaf-vein micropattern, the membrane can guide human umbilical vein endothelial cells (HUVECs) to form vasculature in vitro. In particular, the "running track" upregulates the angiogenesis-related gene expression and promotes the HUVECs to differentiate into tip cells and stalk cells via tuning vascular endothelial growth factor receptor 2 signaling transduction. As a proof of concept, its revascularization capability using a rat calvarial defect model in vivo is evaluated. The in vivo results demonstrate that the leaf-vein engraved membrane accelerates the formation and maturation of vasculature, leading to a hierarchical blood vessel network. With the superior pro-vasculature property, it is believed that the leaf-vein engraved membrane is not only an ideal candidate for the reconstruction of calvarial vasculature but also a promising solution for more complicated vasculature reconstruction, such as muscle, skin, and heart.

Deep learning-based behavioral profiling of rodent stroke recovery

Background

Stroke research heavily relies on rodent behavior when assessing underlying disease mechanisms and treatment efficacy. Although functional motor recovery is considered the primary targeted outcome, tests in rodents are still poorly reproducible and often unsuitable for unraveling the complex behavior after injury.

Results

Here, we provide a comprehensive 3D gait analysis of mice after focal cerebral ischemia based on the new deep learning-based software (DeepLabCut, DLC) that only requires basic behavioral equipment. We demonstrate a high precision 3D tracking of 10 body parts (including all relevant joints and reference landmarks) in several mouse strains. Building on this rigor motion tracking, a comprehensive post-analysis (with >100 parameters) unveils biologically relevant differences in locomotor profiles after a stroke over a time course of 3 weeks. We further refine the widely used ladder rung test using deep learning and compare its performance to human annotators. The generated DLC-assisted tests were then benchmarked to five widely used conventional behavioral set-ups (neurological scoring, rotarod, ladder rung walk, cylinder test, and single-pellet grasping) regarding sensitivity, accuracy, time use, and costs.

Conclusions

We conclude that deep learning-based motion tracking with comprehensive post-analysis provides accurate and sensitive data to describe the complex recovery of rodents following a stroke. The experimental set-up and analysis can also benefit a range of other neurological injuries that affect locomotion.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-022-01434-9.

Further Evidence of Neuroprotective Effects of Recombinant Human Erythropoietin and Growth Hormone in Hypoxic Brain Injury in Neonatal Mice

Experimental in vivo data have recently shown complementary neuroprotective actions of rhEPO and growth hormone (rhGH) in a neonatal murine model of hypoxic brain injury. Here, we hypothesized that rhGH and rhEPO mediate stabilization of the blood−brain barrier (BBB) and regenerative vascular effects in hypoxic injury to the developing brain. Using an established model of neonatal hypoxia, neonatal mice (P7) were treated i.p. with rhGH (4000 µg/kg) or rhEPO (5000 IU/kg) 0/12/24 h after hypoxic exposure. After a regeneration period of 48 h or 7 d, cerebral mRNA expression of Vegf-A, its receptors and co-receptors, and selected tight junction proteins were determined using qRT-PCR and ELISA. Vessel structures were assessed by Pecam-1 and occludin (Ocln) IHC. While Vegf-A expression increased significantly with rhGH treatment (p < 0.01), expression of the Vegfr and TEK receptor tyrosine kinase (Tie-2) system remained unchanged. RhEPO increased Vegf-A (p < 0.05) and Angpt-2 (p < 0.05) expression. While hypoxia reduced the mean vessel area in the parietal cortex compared to controls (p < 0.05), rhGH and rhEPO prevented this reduction after 48 h of regeneration. Hypoxia significantly reduced the Ocln+ fraction of cortical vascular endothelial cells. Ocln signal intensity increased in the cortex in response to rhGH (p < 0.05) and in the cortex and hippocampus in response to rhEPO (p < 0.05). Our data indicate that rhGH and rhEPO have protective effects on hypoxia-induced BBB disruption and regenerative vascular effects during the post-hypoxic period in the developing brain.

Vascular network expansion, integrity of blood-brain interfaces, and cerebrospinal fluid cytokine concentration during postnatal development in the normal and jaundiced rat

BACKGROUND

Severe neonatal jaundice resulting from elevated levels of unconjugated bilirubin in the blood induces dramatic neurological impairment. Central oxidative stress and an inflammatory response have been associated with the pathophysiological mechanism. Cells forming the blood-brain barrier and the choroidal blood-CSF barrier are the first CNS cells exposed to increased plasma levels of unconjugated bilirubin. These barriers are key regulators of brain homeostasis and require active oxidative metabolism to fulfill their protective functions. The choroid plexus-CSF system is involved in neuroinflammatory processes. In this paper, we address the impact of neonatal hyperbilirubinemia on some aspects of brain barriers. We describe physiological changes in the neurovascular network, blood-brain/CSF barriers integrities, and CSF cytokine levels during the postnatal period in normobilirubinemic animals, and analyze these parameters in parallel in Gunn rats that are deficient in bilirubin catabolism and develop postnatal hyperbilirubinemia.

METHODS

Gunn rats bearing a mutation in UGT1a genes were used. The neurovascular network was analyzed by immunofluorescence stereomicroscopy. The integrity of the barriers was evaluated by [14C]-sucrose permeability measurement. CSF cytokine levels were measured by multiplex immunoassay. The choroid plexus-CSF system response to an inflammatory challenge was assessed by enumerating CSF leukocytes.

RESULTS

In normobilirubinemic animals, the neurovascular network expands postnatally and displays stage-specific regional variations in its complexity. Network expansion is not affected by hyperbilirubinemia. Permeability of the blood-brain and blood-CSF barriers to sucrose decreases between one- and 9-day-old animals, and does not differ between normobilirubinemic and hyperbilirubinemic rats. Cytokine profiles differ between CSF and plasma in all 1-, 9-, and 18-day-old animals. The CSF cytokine profile in 1-day-old animals is markedly different from that established in older animals. Hyperbilirubinemia perturbs these cytokine profiles only to a very limited extent, and reduces CSF immune cell infiltration triggered by systemic exposure to a bacterial lipopeptide.

CONCLUSION

The data highlight developmental specificities of the blood-brain barrier organization and of CSF cytokine content. They also indicate that a direct effect of bilirubin on the vascular system organization, brain barriers morphological integrity, and inflammatory response of the choroid plexus-CSF system is not involved in the alteration of brain functions induced by severe neonatal jaundice.

Orchestrating the Dermal/Epidermal Tissue Ratio during Wound Healing by Controlling the Moisture Content

A balanced and moist wound environment and surface increases the effect of various growth factors, cytokines, and chemokines, stimulating cell growth and wound healing. Considering this fact, we tested in vitro and in vivo water evaporation rates from the cellulose dressing epicite^hydro when combined with different secondary dressings as well as the resulting wound healing efficacy in a porcine donor site model. The aim of this study was to evaluate how the different rates of water evaporation affected wound healing efficacy. To this end, epicite^hydro primary dressing, in combination with different secondary dressing materials (cotton gauze, JELONET^◊, AQUACEL^® Extra ™, and OPSITE^◊ Flexifix), was placed on 3 × 3 cm-sized dermatome wounds with a depth of 1.2 mm on the flanks of domestic pigs. The healing process was analyzed histologically and quantified by morphometry. High water evaporation rates by using the correct secondary dressing, such as cotton gauze, favored a better re-epithelialization in comparison with the low water evaporation resulting from an occlusive secondary dressing, which favored the formation of a new and intact dermal tissue that nearly fully replaced all the dermis that was removed during wounding. This newly available evidence may be of great benefit to clinical wound management.

Open-source analysis and visualization of segmented vasculature datasets with VesselVio

Vascular networks are fundamental components of biological systems. Quantitative analysis and observation of the features of these networks can improve our understanding of their roles in health and disease. Recent advancements in imaging technologies have enabled the generation of large-scale vasculature datasets, but barriers to analyzing these datasets remain. Modern analysis options are mainly limited to paid applications or open-source terminal-based software that requires programming knowledge with high learning curves. Here, we describe VesselVio, an open-source application developed to analyze and visualize pre-binarized vasculature datasets and pre-constructed vascular graphs. Vasculature datasets and graphs can be loaded with annotations and processed with custom parameters. Here, the program is tested on ground-truth datasets and is compared with current pipelines. The utility of VesselVio is demonstrated by the analysis of multiple formats of 2D and 3D datasets acquired with several imaging modalities, including annotated mouse whole-brain vasculature volumes.

Transcranial Direct Current Stimulation Alleviates Neurovascular Unit Dysfunction in Mice With Preclinical Alzheimer’s Disease

Neurons, glial cells and blood vessels are collectively referred to as the neurovascular unit (NVU). In the Alzheimer’s disease (AD) brain, the main components of the NVU undergo pathological changes. Transcranial direct current stimulation (tDCS) can protect neurons, induce changes in glial cells, regulate cerebral blood flow, and exert long-term neuroprotection. However, the mechanism by which tDCS improves NVU function is unclear. In this study, we explored the effect of tDCS on the NVU in mice with preclinical AD and the related mechanisms. 10 sessions of tDCS were given to six-month-old male APP/PS1 mice in the preclinical stage. The model group, sham stimulation group, and control group were made up of APP/PS1 mice and C57 mice of the same age. All mice were histologically evaluated two months after receiving tDCS. Protein content was measured using Western blotting and an enzyme-linked immunosorbent assay (ELISA). The link between glial cells and blood vessels was studied using immunofluorescence staining and lectin staining. The results showed that tDCS affected the metabolism of Aβ; the levels of Aβ, amyloid precursor protein (APP) and BACE1 were significantly reduced, and the levels of ADAM10 were significantly increased in the frontal cortex and hippocampus in the stimulation group. In the stimulation group, tDCS reduced the protein levels of Iba1 and GFAP and increased the protein levels of NeuN, LRP1 and PDGRFβ. This suggests that tDCS can improve NVU function in APP/PS1 mice in the preclinical stage. Increased blood vessel density and blood vessel length, decreased IgG extravasation, and increased the protein levels of occludin and coverage of astrocyte foot processes with blood vessels suggested that tDCS had a protective effect on the blood-brain barrier. Furthermore, the increased numbers of Vimentin, S100 expression and blood vessels (lectin-positive) around Aβ indicated that the effect of tDCS was mediated by astrocytes and blood vessels. There was no significant difference in these parameters between the model group and the sham stimulation group. In conclusion, our results show that tDCS can improve NVU function in APP/PS1 mice in the preclinical stage, providing further support for the use of tDCS as a treatment for AD.

Blood-brain barrier leakage and perivascular collagen accumulation precede microvessel rarefaction and memory impairment in a chronic hypertension animal model

Hypertension (HT) is one of the main causes of vascular dementia, lead to cognitive decline. Here, we investigated the relationship between cerebral microvessels, pericytes, extracellular matrix (ECM) accumulation, blood-brain barrier (BBB) breakdown, and memory impairment at mid-life in a chronic hypertension animal model. Spontaneously hypertensive rats (SHRs) (n = 20) are chosen for the model and age matched Wistar rats (n = 16) as controls. Changes in brain microvasculature and in vitro experiments are shown with immunofluorescence studies and cognition with open field, novel object recognition, and Y maze tests. There was a significant reduction in pericyte coverage in SHRs (p = 0.021), while the quantitative parameters of the cerebral microvascular network were not different between groups. On the other hand, parenchymal albumin leakage, as a Blood-brain barrier (BBB) breakdown marker, was prominent in SHRs (p = 0.023). Extracellular matrix (ECM) components, collagen type 1, 3 and 4 were significantly increased (accumulated) around microvasculature in SHRs (p = 0.011, p = 0.013, p = 0.037, respectively). Furthermore, in vitro experiments demonstrated that human brain vascular pericytes but not astrocytes and endothelial cells secreted type I collagen upon TGFβ1 exposure pointing out a possible role of pericytes in increased collagen accumulation around cerebral microvasculature due to HT. Furthermore, valsartan treatment decreased the amount of collagen type 1 secreted by pericytes after TGFβ1 exposure. At the time of evaluation, SHRs did not demonstrate cognitive decline and memory impairments. Our results showed that chronic HT causes ECM accumulation and BBB leakage before leading to memory impairments and therefore, pericytes could be a novel target for preventing vascular dementia.

Satellite Cell Expression of RAGE (Receptor for Advanced Glycation end Products) Is Important for Collateral Vessel Formation

Background The growth and remodeling of vascular networks is an important component of the prognosis for patients with peripheral artery disease. One protein that has been previously implicated to play a role in this process is RAGE (receptor for advanced glycation end products). This study sought to determine the cellular source of RAGE in the ischemic hind limb and the role of RAGE signaling in this cell type. Methods and Results Using a hind limb ischemia model of vascular growth, this study found skeletal muscle satellite cells to be a novel major cellular source of RAGE in ischemic tissue by both staining and cellular sorting. Although wild-type satellite cells increased tumor necrosis factor-α and monocyte chemoattractant protein-1 production in response to ischemia in vivo and a RAGE ligand in vitro, satellite cells from RAGE knockout mice lacked the increase in cytokine production both in vivo in response to ischemia and in vitro after stimuli with the RAGE ligand high-mobility group box 1. Furthermore, encapsulated wild-type satellite cells improved perfusion after hind limb ischemia surgery by both perfusion staining and vessel quantification, but RAGE knockout satellite cells provided no improvement over empty capsules. Conclusions Thus, RAGE expression and signaling in satellite cells is crucial for their response to stimuli and angiogenic and arteriogenic functions.

Characterization of the Blood Brain Barrier Disruption in the Photothrombotic Stroke Model

Blood brain barrier (BBB) damage is an important pathophysiological feature of ischemic stroke which significantly contributes to development of severe brain injury and therefore is an interesting target for therapeutic intervention. A popular permanent occlusion model to study long term recovery following stroke is the photothrombotic model, which so far has not been anatomically characterized for BBB leakage beyond the acute phase. Here, we observed enhanced BBB permeability over a time course of 3 weeks in peri-infarct and core regions of the ischemic cortex. Slight increases in BBB permeability could also be seen in the contralesional cortex, hippocampus and the cerebellum at different time points, regions where lesion-induced degeneration of pathways is prominent. Severe damage of tight and adherens junctions and loss of pericytes was observed within the peri-infarct region. Overall, the photothrombotic stroke model reproduces a variety of features observed in human stroke and thus, represents a suitable model to study BBB damage and therapeutic approaches interfering with this process.

Distinct changes in all major components of the neurovascular unit across different neuropathological stages of Alzheimer's disease

In the brain capillaries, endothelial cells, pericytes, astrocytes and microglia form a structural and functional complex called neurovascular unit (NVU) which is critically involved in maintaining neuronal homeostasis. In the present study, we applied a comprehensive immunohistochemical approach to investigate the structural alterations in the NVU across different Alzheimer's disease (AD) neuropathological stages. Post-mortem human cortical and hippocampal samples derived from AD patients and non-demented elderly control individuals were immunostained using a panel of markers representing specific components of the NVU including Collagen IV (basement membrane), PDGFR-β (pericytes), GFAP (astrocytes), Iba1 (microglia), MRC1 (perivascular macrophages) and lectin as an endothelial cell label. Astrocytes (GFAP) and microglia (Iba1) were quantified both in the whole visual-field and specifically within the NVU, and the sample set was additionally analyzed using anti-tau (AT8) and three different anti-Aβ (clones G2-10, G2-11, 4G8) antibodies. Analyses of lectin labeled sections showed an altered vascular distribution in AD patients as revealed by a reduced nearest distance between capillaries. Within the NVU, a Braak-stage dependent reduction in pericyte coverage was identified as the earliest structural alteration during AD progression. In comparison to non-demented elderly controls, AD patients showed a significantly higher astrocyte coverage within the NVU, which was paralleled by a reduced microglial coverage around capillaries. Assessment of perivascular macrophages moreover demonstrated a relocation of these cells from leptomeningeal arteries to penetrating parenchymal vessels in AD patients. Collectively, the results of our study represent a comprehensive first in-depth analysis of AD-related structural changes in the NVU and suggest distinct alterations in all components of the NVU during AD progression.