Vascular Architecture Research Articles

Morphometric Analysis of Placenta and Fetal Doppler Indices in Normal and High-Risk Pregnancies.

Background High-risk pregnancies, encompassing pregnancy-induced hypertension (PIH), gestational diabetes mellitus (GDM), preeclampsia toxemia (PET), and intrauterine growth restriction (IUGR), represent intricate medical challenges with potential repercussions for maternal and fetal health. This research undertakes a comprehensive comparative investigation into the variations of Doppler indices and placental parameters within the context of these high-risk conditions when juxtaposed against pregnancies characterized as normal. Methodology Employing a rigorous cross-sectional study design, a diverse cohort of pregnant individuals with gestational diabetes, IUGR, PIH, and preeclampsia was meticulously assembled. Additionally, a group of normal pregnant women served as the comparative reference. Doppler ultrasound assessments, viz, pulsatility index (PI), were carefully performed to estimate blood flow velocities within critical maternal and fetal vessels, while placental parameters were meticulously quantified, encompassing dimensions, vascular architecture, and morphological features. Results Except in the GDM group, all high-risk groups had reduced estimated placental weight and actual birth weight than normal pregnant women. All high-risk groups showed a highly significant elevation of the PI of the umbilical artery and PI of the middle cerebral artery (MCA) than normal but the PI of MCA was significantly reduced in the PET group than in normal individuals. The cerebro-placental ratio in the GDM and IUGR groups revealed markedly greater values, whereas PET showed lower values. IUGR and PIH groups showed a substantial reduction in the fetal birth weight. All high-risk groups (GDM, IUGR, PIH, and PET) showed a highly significant reduction in luminal area umbilical artery 1 than the normal pregnant women. In IUGR, marginal placental insertion was very high, followed by GDM and PET groups. Conclusions This study reveals that Doppler indices, placental parameters, newborn weight, and their related ratios may beutilizedto anticipate gestation difficulties and gain insight into the pathophysiology of problematic conceptions.

On the influence of the vascular architecture on Gradient Echo and Spin Echo BOLD fMRI signals across cortical depth: a simulation approach based on realistic 3D vascular networks.

GE-BOLD contrast stands out as the predominant technique in functional MRI experiments for its high sensitivity and straightforward implementation. GE-BOLD exhibits rather similar sensitivity to vessels independent of their size at submillimeter resolution studies like those examining cortical columns and laminae. However, the presence of nonspecific macrovascular contributions poses a challenge to accurately isolate neuronal activity. SE-BOLD increases specificity towards small vessels, thereby enhancing its specificity to neuronal activity, due to the effective suppression of extravascular contributions caused by macrovessels with its refocusing pulse. However, even SE-BOLD measurements may not completely remove these macrovascular contributions. By simulating hemodynamic signals across cortical depth, we gain insights into vascular contributions to the laminar BOLD signal. In this study, we employed four realistic 3D vascular models to simulate oxygen saturation states in various vascular compartments, aiming to characterize both intravascular and extravascular contributions to GE and SE signals, and corresponding BOLD signal changes, across cortical depth at 7T. Simulations suggest that SE-BOLD cannot completely reduce the macrovascular contribution near the pial surface. Simulations also show that both the specificity and signal amplitude of BOLD signals at 7T depend on the spatial arrangement of large vessels throughout cortical depth and on the pial surface.

Comparative assessment of liver tissue: from microstructural and mesoscale vascular architecture to macroscopic mechanics

Comparative assessment of liver tissue: from microstructural and mesoscale vascular architecture to macroscopic mechanics

Computational analysis of cancer cell adhesion in curved vessels affected by wall shear stress for prediction of metastatic spreading.

Introduction: The dynamics of circulating tumor cells (CTCs) within blood vessels play a pivotal role in predicting metastatic spreading of cancer within the body. However, the limited understanding and method to quantitatively investigate the influence of vascular architecture on CTC dynamics hinders our ability to predict metastatic process effectively. To address this limitation, the present study was conducted to investigate the influence of blood vessel tortuosity on the behaviour of CTCs, focusing specifically on establishing methods and examining the role of shear stress in CTC-vessel wall interactions and its subsequent impact on metastasis. Methods: We computationally simulated CTC behaviour under various shear stress conditions induced by vessel tortuosity. Our computational model, based on the lattice Boltzmann method (LBM) and a coarse-grained spectrin-link membrane model, efficiently simulates blood plasma dynamics and CTC deformability. The model incorporates fluid-structure interactions and receptor-ligand interactions crucial for CTC adhesion using the immersed boundary method (IBM). Results: Our findings reveal that uniform shear stress in straight vessels leads to predictable CTC-vessel interactions, whereas in curved vessels, asymmetrical flow patterns and altered shear stress create distinct adhesion dynamics, potentially influencing CTC extravasation. Quantitative analysis shows a 25% decrease in the wall shear stress in low-shear regions and a 58.5% increase in the high-shear region. We observed high-shear regions in curved vessels to be potential sites for increased CTC adhesion and extravasation, facilitated by elevated endothelial expression of adhesion molecules. This phenomenon correlates with the increased number of adhesion bonds, which rises to approximately 40 in high-shear regions, compared to around 12 for straight vessels and approximately 5-6 in low-shear regions. The findings also indicate an optimal cellular stiffness necessary for successful CTC extravasation in curved vessels. Discussion: By the quantitative assessment of the risk of CTC extravasation as a function of vessel tortuosity, our study offers a novel tool for the prediction of metastasis risk to support the development of personalized therapeutic interventions based on individual vascular characteristics and tumor cell properties.

Sildenafil Effect on Atrial Natriuretic Peptide Level in Pulmonary Hypertensive Rats.

Pulmonary Hypertension (PH) leads to changes in pulmonary vascular architecture, hypertrophy of the right ventricle, and heart failure. Sildenafil is a drug that can modulate PH by inducing smooth muscle relaxation and vasodilation. To investigate the ability of sildenafil to alleviate the monocritaline (MCT)-induced PH in rats and to estimate the role and its effect on the atrial natriuretic peptide (ANP) levels. 28 adult male rats were divided randomly into four groups: Group A (control group; n=7). Group B (MCT-treated group; n=7) was given a single dose of MCT 60 mg/kg subcutaneously. Group C (The reversal group; n=7) received a single dose of MCT 60 mg/kg subcutaneously for three weeks and then sildenafil at 50 mg/kg/day, given daily for another three weeks. Group D (The prevention group; n=7) simultaneously received a single dose of MCT 60 mg/kg subcutaneously and sildenafil daily at 50 mg/kg for three weeks. The animals in the prevention group showed a significant decrease in ANP levels compared to the reversal and MCT-treated groups. This decrease was associated with a significant reduction in the Fulton index ratio in the prevention group compared to the reversal group. The nitric oxide levels were also significantly higher in the reversal group than in the control group. Preventive sildenafil treatment was associated with a significant decrease in ANP levels and reduced MCT-induced cardiac hypertrophy in rats.

Ex Vivo Vascular Imaging and Perfusion Studies of Normal Kidney and Tumor Vasculature.

This work describes a comprehensive study of the vascular tree and perfusion characteristics of normal kidney and renal cell carcinoma. Methods: Nephrectomy specimens were perfused ex-vivo, and the regional blood flow was determined by infusion of radioactive microspheres. The vascular architecture was characterized by micronized barium sulphate infusion. Kidneys were subsequently sagitally sectioned, and autoradiograms were obtained to show the perfusate flow in relation to adjacent contact X-ray angiograms. Vascular resistance in defined tissue compartments was quantified, and finally, the tumor vasculature was 3D reconstructed via the micro-CT technique. Results show that the vascular tree of the kidney could be distinctly defined, and autoradiograms disclosed a high cortical flow. The peripheral resistance unit of the whole perfused specimen was 0.78 ± 0.40 (n = 26), while that of the renal cortex was 0.17 ± 0.07 (n = 15 with 114 samples). Micro-CT images from both cortex and medulla defined the vascular architecture. Angiograms from the renal tumors demonstrated a significant vascular heterogeneity within and between different tumors. A dense and irregular capillary network characterized peripheral tumor areas, whereas central parts of the tumors were less vascularized. Despite the dense capillarity, low perfusion through vessels with a diameter below 15 µm was seen on the autoradiograms. We conclude that micronized barium sulphate infusion may be used to demonstrate the vascular architecture in a complex organ. The vascular resistance was low, with little variation in the cortex of the normal kidney. Tumor tissue showed a considerable vascular structural heterogeneity with low perfusion through the peripheral nutritive capillaries and very poor perfusion of the central tumor, indicating intratumoral pressure exceeding the perfusion pressure. The merits and shortcomings of the various techniques used are discussed.

Semi-automated protocol to quantify and characterize fluorescent three-dimensional vascular images.

The microvasculature facilitates gas exchange, provides nutrients to cells, and regulates blood flow in response to stimuli. Vascular abnormalities are an indicator of pathology for various conditions, such as compromised vessel integrity in small vessel disease and angiogenesis in tumors. Traditional immunohistochemistry enables the visualization of tissue cross-sections containing exogenously labeled vasculature. Although this approach can be utilized to quantify vascular changes within small fields of view, it is not a practical way to study the vasculature on the scale of whole organs. Three-dimensional (3D) imaging presents a more appropriate method to visualize the vascular architecture in tissue. Here we describe the complete protocol that we use to characterize the vasculature of different organs in mice encompassing the methods to fluorescently label vessels, optically clear tissue, collect 3D vascular images, and quantify these vascular images with a semi-automated approach. To validate the automated segmentation of vascular images, one user manually segmented one hundred random regions of interest across different vascular images. The automated segmentation results had an average sensitivity of 83±11% and an average specificity of 91±6% when compared to manual segmentation. Applying this procedure of image analysis presents a method to reliably quantify and characterize vascular networks in a timely fashion. This procedure is also applicable to other methods of tissue clearing and vascular labels that generate 3D images of microvasculature.

The Art of Cerebral Revascularization: An Illustrative Case Series of Bypass Techniques for Complex Intracranial Aneurysms

Complex intracranial aneurysms (CIAs) comprise a subset of lesions with defiant vascular architecture, difficult access, and prior treatment. Surgical management of CIAs is often challenging and demands an assessment on a case-by-case basis. The generational evolution of bypass surgery has offered a long-standing potential for effective cerebral revascularization. Herein, we aim to illustrate a single-center experience treating CIAs. The authors conducted a retrospective analysis of clinical records of patients treated with cerebral revascularization techniques at Hospital Nacional Dos de Mayo, Lima, Peru, during 2018-2022. Relevant data were collected, including patient history, aneurysm features on imaging, preoperative complications, the intraoperative course, aneurysm occlusion rates, bypass patency, neurological function, and postoperative complications. Seventeen patients (70.59% female; median age: 53years) with 17 CIAs (64.7% saccular; 76.5% ruptured) were included. The most common clinical presentation included loss of consciousness (70.6%) and headaches (58.8%). Microsurgical treatment included first-, second-, and third-generation bypass. In 47.1% of cases, an anastomosis between the superficial temporal artery and the M3 segment was predominantly used, followed by an A3-A3 bypass (29.4%), a superficial temporal artery-M2 bypass (17.6%), and an external carotid artery to M2 bypass (5.9%). The intraoperative aneurysm rupture rate was 11.8%. Postoperative complications included ischemia (40%), cerebrospinal fluid fistulas (26.7%), and pneumonia (20%). At hospital discharge, the median Glasgow Coma Scale score was 14 (range: 10-15). At the 6-month follow-up, 82.4% of patients had a modified Rankin Scale score ≤2, bypass patency was present in all cases, and the morbidity rate was 17.6%. CIAs represent a spectrum of defiant vascular lesions with a poor natural history. Bypass surgery offers the potential for definitive treatment. Our case series illustrated the predominant role of cerebral revascularization of CIAs with a critical case-by-case approach to provide optimal outcomes in a limited-resource setting.

Vascular architecture regulates mesenchymal stromal cell heterogeneity via P53-PDGF signaling in the mouse incisor

Mesenchymal stem cells (MSCs) reside in niches to maintain tissue homeostasis and contribute to repair and regeneration. Although the physiological functions of blood and lymphatic vasculature are well studied, their regulation of MSCs as niche components remains largely unknown. Using adult mouse incisors as a model, we uncover the role of Trp53 in regulating vascular composition through THBS2 to maintain mesenchymal tissue homeostasis. Loss of Trp53 in GLI1+ progeny increases arteries and decreases other vessel types. Platelet-derived growth factors from arteries deposit in the MSC region and interact with PDGFRA and PDGFRB. Significantly, PDGFRA+ and PDGFRB+ cells differentially contribute to defined cell lineages in the adult mouse incisor. Collectively, our results highlight Trp53's importance in regulating the vascular niche for MSCs. They also shed light on how different arterial cells provide unique cues to regulate MSC subpopulations and maintain their heterogeneity. Furthermore, they provide mechanistic insight into MSC-vasculature crosstalk.

Vascular Organization: Lessons from Development and Disease.

Organ formation requires tight coordination with vascular growth. Intricate networks of blood vessels course through all organs and tissues and are composed of both endothelial cells (ECs) and associated mural cells. Despite decades of research into the biology of blood vessel formation and homeostasis, little is known about how the vasculature ensures its properly coordinated growth and intimate development with the cells of different organs. Even more mystifying is how a highly dynamic endothelium quiesces to differentiate into mature vessels, and how disruption of this mature quiescence results in pathological conditions. Interestingly, both intra- and interorgan vascular architecture hold critical importance to the maintenance of blood vessels, as the rate of flow and supply of supportive angiogenic factors can be altered with deleterious effects. In this article, we review the basic mechanisms of blood vessel formation and maintenance with an emphasis on organ-specific vascular development, and we examine the case of transient pulmonary arteriovenous malformations as a case study of vascular homeostatic mechanisms.

Vascular flow design and predicting evolution

Porous materials are usually thought of as amorphous mixtures of two or more things, solids, fluids, and voids. I was drawn to the nature absent from the amorphous: the structure, flow, configuration, design, purpose, and evolution. This article is a pictorial review of the work. It begins with defining the terms: design, freedom, evolution, and prediction (theory). Vascular (tree shaped) architectures offer greater flow access than channels with only one length scale (diameter, slit, wall to wall spacing). The tendency to evolve with freedom toward flow configurations that provide greater access is everywhere in nature, bio, and non-bio. This universal phenomenon is summarized as the Constructal Law of evolution everywhere, which empowers us to predict evolution, miniaturization, high density of fluid flow and heat transfer, and scaling up (or down) of existing designs. Vascular designs are icons of the multiscale design called hierarchy. Vasculatures occur naturally because they flow more easily—they offer greater access—than one-scale designs. All movement in society is hierarchical, from city traffic to global air traffic, fuel consumption, and wealth. The future of evolutionary design everywhere points toward vascular, hierarchical flow architectures that will continue to morph with freedom and directionality.

Vascular damage and excessive proliferation compromise liver function after extended hepatectomy in mice.

Surgical resection remains the gold standard for liver tumor treatment, yet the emergence of post-operative liver failure, known as the small for size syndrome (SFSS), poses a significant challenge. The activation of hypoxia sensors in a SFSS liver remnant initiated early angiogenesis, improving vascular architecture, safeguarding against liver failure and reducing mortality. The study aimed to elucidate vascular remodeling mechanisms in SFSS, its impact on hepatocyte function and subsequent liver failure. Mice underwent extended partial hepatectomy to induce SFSS, with a subset exposed to hypoxia immediately after surgery. Hypoxia bolstered post-hepatectomy survival rates. Early proliferation of liver sinusoidal cells, coupled with recruitment of putative endothelial progenitor cells (EPC), increased vascular density, improved lobular perfusion, and limited hemorrhagic events in the regenerating liver under hypoxia. Administration of granulocyte colony stimulating factor (G-CSF) in hepatectomized mice mimicked the effects of hypoxia on vascular remodeling and EPC recruitment, but failed to rescue survival. Compared to normoxia, hypoxia favored hepatocyte function over proliferation, promoting functional preservation in the regenerating remnant. Injection of AAV8-TBG-HNF4α virus for hepatocyte-specific overexpression of HNF4α, the master regulator of hepatocyte function, enforced functionality in proliferating hepatocytes but did not rescue survival. The combination of HNF4α overexpression and G-CSF treatment rescued survival after SFSS-setting hepatectomy. In summary, SFSS arises from an imbalance and desynchronized interplay between functional regeneration and vascular restructuring. To improve survival following SFSS-hepatectomy, it is essential to adopt a two-pronged strategy aimed at preserving the function of proliferating parenchymal cells and simultaneously attenuating vascular damage.

CCN1-Mediated Signaling in Placental Villous Tissues after SARS-CoV-2 Infection in Term Pregnant Women: Implications for Dysregulated Angiogenesis.

The global spread of SARS-CoV-2 has increased infections among pregnant women. This study aimed to explore placental pathology alterations and angiogenic factor levels in term pregnant women after SARS-CoV-2 infection in a retrospective single-center study. Additionally, we investigated the role and underlying mechanism of the vascular inflammation-promoting, cysteine-rich protein 61 (CYR61/CCN1) in this context. All analyses were performed in term pregnant women infected with or without SARS-CoV-2. The sFlt-1, PlGF, and sEng serum levels were quantified using ELISA. Placental protein expressions were examined by immunoblot and immunostaining. Additionally, the effect of CCN1 protein on SGHPL-5 trophoblast cells was examined. We found that SARS-CoV-2 activated the inflammatory response in pregnant women, leading to pronounced vascular alterations in placental villous tissues. Elevated serum anti-angiogenic factors (sFlt-1, sEng) upon SARS-CoV-2 infection may directly contribute to these pathological changes. Upregulated CCN1 and pNF-κB in placental villous tissues of infected patients are identified as crucial factors in placental alterations. As a conclusion, CCN1 was significantly elevated in the placentas of term pregnant women infected with SARS-CoV-2. By activating a cascade of inflammatory responses, CCN1 induced the production of the anti-angiogenic factors sFlt-1 and sEng, which may lead to abnormal placental vascular architecture.

Expert consensus on multidisciplinary diagnosis and treatment of brain arteriovenous malformation

Brain arteriovenous malformation (BAVM) is a cerebral vasculature disorder caused by gene mutation. Current available treatment measures include surgical resection, interventional embolization and stereotactic radiosurgery. The three therapeutic methods have their own advantages for different vascular structures.However, due to the complex vascular architecture of the lesion and its close anatomical relationship with brain tissue, any single treatment can not safely and effectively treat all BAVM cases. Therefore, in order to better regulate and guide the clinical diagnosis and treatment of BAVM patients in China, the National Medical School for Neurological Diseases, the Professional Committee of Neurointervention of the Chinese Medical Doctor Association and the radio-neurosurgery Expert Committee of the World Chinese Neurosurgeons Association jointly discussed and formulated this expert consensus. After in-depth analysis of the evidence of evidence-based medicine at home and abroad, the expert group combined with the specific situation of China, and gave 33 recommendations on specific clinical diagnosis and treatment issues such as predictive factors of cerebral arteriovenous malformation hemorrhage, clinical risks during pregnancy, imaging diagnosis measures, and clinical treatment strategies, in order to provide guidance for the diagnosis and treatment of BAVM nationwide.

Topological insight of immune-vascular distribution in peri-implantitis lesions.

To characterize the distribution of macrophages, neutrophils, NK cells, and blood vessels in peri-implantitis compared to healthy aged gingiva samples. This observational study included eight gingival samples from peri-implantitis and eight from periodontally healthy individuals. By immunofluorescence were identified neutrophils, NK cells, macrophages, and their pro-inflammatory or pro-healing phenotypes, and blood vessels. Two ROIs were designated as zone 1, connective tissue closest to the epithelium and zone 2, connective tissue over 200 microns from the rete ridges. Immune cells and vascular structures were quantified and characterized according to their distribution in both zones. Two peri-implantitis zones were characterized by unique macrophage phenotypes and blood vessel architecture. Blood vessels were larger in zone 2 in peri-implantitis. A greater number of NK cells and macrophages were found in peri-implantitis compared to healthy aged samples. A higher presence of pro-inflammatory macrophages was found in zone 1 compared to zone 2. A similar proportion of pro-inflammatory and pro-healing macrophages were found in zone 2. A specific distribution for pro-inflammatory macrophages and vascular architecture is observed in peri-implantitis. TNF-α colocalizes with macrophages in the connective tissue near rete ridges. NK cells are more abundant in peri-implantitis than in healthy samples.

Abstract 6763: A human-relevant vascularized organ-on-a chip platform for anti-tumor drug efficacy and liver injury assessment

Abstract Cancer global burden accounts for 19.3 million new cases and 10 million deaths in 2020. Despite advances on the understanding of disease progression and efforts to find successful therapeutic strategies, most drugs fail in clinical stages. Lack of models with clinical mimicry recapitulating the in vivo pathophysiology and the organ microenvironment where the tumor forms is a key driver reducing the success rate of anti-cancer drugs. Animal models remain the gold standard for preclinical research but fail to recapitulate the complex human tumor microenvironment, a critical component determining tumor development, progression, and response to treatments. Organ-on-a-chip models allow to control the environment and organization of cells in an in vivo-like arrangement by culturing multiple cell types to better replicate human conditions, and by implementing different biochemical and physical stimuli, such as fluid shear stress, chemical/nutrient gradients, and perfusion/flow to recapitulate the human vascular system physiology. We leverage our 3D bioprinting technologies to develop complex vascularized organ-on-a-chip models aimed to recapitulate the tumor and liver niche. Both organ-systems are interconnected by our h-VIOS™ platform, allowing dynamic perfusion for 21 days and enabling the simultaneous assessment of anti-tumor therapeutic efficacy and drug-induced liver injury. Our hydrogels feature a complex perfusable vasculature that interfaces with an interstitial chamber where tissues of interest are grown. The vasculature allows for continued and controlled delivery of nutrients, oxygen, and small molecule drugs. Dextran diffusion studies revealed diffusion coefficients ranging from 43.2 μm2/s (4kDa) to 8 μm2/s (70kDa). Vascular architectures are lined with endothelial cells forming a functional barrier expressing the junctional markers ZO-1 and PECAM-1. Moreover, we can modulate the permeability of our vasculature architecture, allowing the extravasation of immune and cancer cells. PBMC-derived T cells and Jurkat cells undergo transendothelial migration in response to a CXCL12 gradient, highlighting the applicability of our model for immunotherapeutic efficacy studies. The tumor interstitial chamber incorporates co-culture of cancer spheroids or tumoroids, fibroblasts, endothelial and immune cells. Colon carcinoma spheroids effectively integrate into the tumor niche with no growth arrest. The liver model consists of an interstitial chamber with a lobular microstructure supporting the monoculture of primary human hepatocytes, and sustaining their viability and function for 9 days as demonstrated by high albumin production, urea synthesis and CYP activity. Our organ-on-a-chip models are fully customizable and anticipated to contribute to advance personalized medicine and improve clinical translation rates. Citation Format: Juliana Navarro-Yepes, Queeny Dasgupta, Purboja Purkayastha, Kevin Janson, Cassio Mello, Ameya Narkar, Soon Seng Ng, Taci Pereira. A human-relevant vascularized organ-on-a chip platform for anti-tumor drug efficacy and liver injury assessment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6763.

Variations of the submental artery: A series of cases

This article aims to educate surgeons about the variations in the course of the submental artery that exist and are encountered when performing routine head and neck dissection. Vascular architecture is critical for ensuring the success of regenerative and reconstructive procedures. The authors briefly describe variations in the submental artery that were identified and documented in relation to the mylohyoid muscle during routine neck dissection. It is imperative to understand Submental Artery: its branches, distribution, course and variations that are reported. A clear understanding of the variations will help surgeons maintain the vascularity of flaps.

Comparative evaluation of trypsin and elastase digestion techniques for isolation of murine retinal vasculature

Dysfunctional pericytes and disruption of adherens or tight junctions are related to many microvascular diseases, including diabetic retinopathy. In this context, visualizing retinal vascular architecture becomes essential for understanding retinal vascular disease pathophysiology. Although flat mounts provide a demonstration of the retinal blood vasculature, they often lack a clear view of microaneurysms and capillary architecture. Trypsin and elastase digestion are the two techniques for isolating retinal vasculatures in rats, mice, and other animal models. Our observations in the present study reveal that trypsin digestion impacts the association between pericytes and endothelial cells. In contrast, elastase digestion effectively preserves these features in the blood vessels. Furthermore, trypsin digestion disrupts endothelial adherens and tight junctions that elastase digestion does not. Therefore, elastase digestion emerges as a superior technique for isolating retinal vessels, which can be utilized to collect reliable and consistent data to comprehend the pathophysiology of disorders involving microvascular structures.

β1 integrins play a critical role maintaining vascular integrity in the hypoxic spinal cord, particularly in white matter

Interactions between extracellular matrix (ECM) proteins and β1 integrins play an essential role maintaining vascular integrity in the brain, particularly under vascular remodeling conditions. As blood vessels in the spinal cord are reported to have distinct properties from those in the brain, here we examined the impact of β1 integrin inhibition on spinal cord vascular integrity, both under normoxic conditions, when blood vessels are stable, and during exposure to chronic mild hypoxia (CMH), when extensive vascular remodeling occurs. We found that a function-blocking β1 integrin antibody triggered a small degree of vascular disruption in the spinal cord under normoxic conditions, but under hypoxic conditions, it greatly enhanced (20-fold) vascular disruption, preferentially in spinal cord white matter (WM). This resulted in elevated microglial activation as well as marked loss of myelin integrity and reduced density of oligodendroglial cells. To understand why vascular breakdown is localized to WM, we compared expression levels of major BBB components of WM and grey matter (GM) blood vessels, but this revealed no obvious differences. Interestingly however, hypoxyprobe staining demonstrated that the most severe levels of spinal cord hypoxia induced by CMH occurred in the WM. Analysis of brain tissue revealed a similar preferential vulnerability of WM tracts to show vascular disruption under these conditions. Taken together, these findings demonstrate an essential role for β1 integrins in maintaining vascular integrity in the spinal cord, and unexpectedly, reveal a novel and fundamental difference between WM and GM blood vessels in their dependence on β1 integrin function during hypoxic exposure. Our data support the concept that the preferential WM vulnerability described may be less a result of intrinsic differences in vascular barrier properties between WM and GM, and more a consequence of differences in vascular density and architecture.

Distinct cellular microenvironment with cytotypic effects regulates orderly regeneration of vascular tissues

Regeneration of the architecturally complex blood vascular system requires precise temporal and spatial control of cell behaviours. Additional components must be integrated into the structure to achieve clinical success for in situ tissue engineering. Consequently, this study proposed a universal method for including any substrate type in vascular cell extracellular matrices (VCEM) via regulating selective adhesion to promote vascular tissue regeneration. The results uncovered that the VCEM worked as cell adhesion substrates, exhibited cell type specificity, and functioned as an address signal for recognition by vascular cells, which resulted in matching with the determined cells. The qPCR and immunofluorescence results revealed that a cell type-specific VCEM could be designed to promote or inhibit cell adhesion, consistenting with the expression patterns of eyes absent 3 (Eya3). In addition, a 3D vascular graft combined with VCEM which could recapitulate the vascular cell-like microenvironment was fabricated. The vascular graft revealed a prospective role for cellular microenvironment in the establishment of vascular cell distribution and tissue architecture, and potentiated the orderly regeneration and functional recovery of vascular tissues in vivo. The findings demonstrate that differential adhesion between cell types due to the cellular microenvironment is sufficient to drive the complex assembly of engineered blood vessel functional units, and underlies hierarchical organization during vascular regeneration.