Authors: Angela C C Jochems, Gordon W Blair, Michael S Stringer...

Background and Purpose- Perivascular spaces (PVS) around venules may help drain interstitial fluid from the brain. We examined relationships between suspected venules and PVS visible on brain magnetic resonance imaging. Methods- We developed a visual venular quantification method to examine the spatial relationship between venules and PVS. We recruited patients with lacunar stroke or minor nondisabling ischemic stroke and performed brain magnetic resonance imaging and retinal imaging. We quantified venules on gradient echo or susceptibility-weighted imaging and PVS on T2-weighted magnetic resonance imaging in the centrum semiovale and then determined overlap between venules and PVS. We assessed associations between venular count and patient demographic characteristics, vascular risk factors, small vessel disease features, retinal vessels, and venous sinus pulsatility. Results- Among 67 patients (69% men, 69.0±9.8 years), only 4.6% (range, 0%-18%) of venules overlapped with PVS. Total venular count increased with total centrum semiovale PVS count in 55 patients after accounting for venule-PVS overlap (β=0.468 [95% CI, 0.187-0.750]) and transverse sinus pulsatility (β=0.547 [95% CI, 0.309-0.786]) and adjusting for age, sex, and systolic blood pressure. Conclusions- Despite increases in both visible PVS and suspected venules, we found minimal spatial overlap between them in patients with sporadic small vessel disease, suggesting that most magnetic resonance imaging-visible centrum semiovale PVS are periarteriolar rather than perivenular.

Topics: Aged; Brain; Brain Ischemia; Cerebral Small Vessel Diseases; Female; Glymphatic System; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Stroke; Stroke, Lacunar; Transverse Sinuses; Venules

PubMed: 32264759
DOI: 10.1161/STROKEAHA.120.029163

Review

Authors: Gerlanda Vella, Sophie Guelfi, Gabriele Bergers...

High endothelial venules (HEVs) are specialized postcapillary venules composed of cuboidal blood endothelial cells that express high levels of sulfated sialomucins to bind L-Selectin/CD62L on lymphocytes, thereby facilitating their transmigration from the blood into the lymph nodes (LN) and other secondary lymphoid organs (SLO). HEVs have also been identified in human and murine tumors in predominantly CD3T cell-enriched areas with fewer CD20B-cell aggregates that are reminiscent of tertiary lymphoid-like structures (TLS). While HEV/TLS areas in human tumors are predominantly associated with increased survival, tumoral HEVs (TU-HEV) in mice have shown to foster lymphocyte-enriched immune centers and boost an immune response combined with different immunotherapies. Here, we discuss the current insight into TU-HEV formation, function, and regulation in tumors and elaborate on the functional implication, opportunities, and challenges of TU-HEV formation for cancer immunotherapy.

Topics: Animals; Endothelial Cells; Humans; Immunotherapy; L-Selectin; Lymphocytes; Neoplasms; Sialomucins; Signal Transduction; Tertiary Lymphoid Structures; Transendothelial and Transepithelial Migration; Tumor Microenvironment; Venules

PubMed: 34484246
DOI: 10.3389/fimmu.2021.736670

Authors: Unal Mutlu, Sonja A Swanson, Caroline C W Klaver...

A potential mechanism by which smoking affects ischemic stroke is through wider venules, but this mediating role of wider venules has never been quantified. Here, we aimed to estimate to what extent the effect of smoking on ischemic stroke is possibly mediated by the venules via the recently developed four-way effect decomposition. This study was part of a population-based study including 9109 stroke-free persons participated in the study in 1990, 2004, or 2006 (mean age: 63.7 years; 58% women). Smoking behavior (smoking versus non-smoking) was identified by interview. Retinal venular calibers were measured semi-automatically on retinal photographs. Incident strokes were assessed until January 2016. A regression-based approach was used with venular calibers as mediator to decompose the total effect of smoking compared to non-smoking into four components: controlled direct effect (neither mediation nor interaction), pure indirect effect (mediation only), reference interaction effect (interaction only) and mediated interaction effect (both mediation and interaction). During a mean follow-up of 12.5 years, 665 persons suffered an ischemic stroke. Smoking increased the risk of developing ischemic stroke compared to non-smoking with an excess risk of 0.41 (95% confidence interval 0.10; 0.67). With retinal venules as a potential mediator, the excess relative risk could be decomposed into 77% controlled direct effect, 4% mediation only, 4% interaction only, and 15% mediated interaction. To conclude, in the pathophysiology of ischemic stroke, the effect of smoking on ischemic stroke may partly explained by changes in the venules, where there is both pure mediation and mediated interaction.

Topics: Brain; Brain Ischemia; Female; Humans; Male; Middle Aged; Risk Factors; Smoking; Stroke; Venules

PubMed: 30182323
DOI: 10.1007/s10654-018-0436-2

Authors: Yen-Lin Chen, Robert H Rosa, Lih Kuo...

Purpose

Endothelin-1 (ET-1) is a potent vasoactive factor implicated in development of diabetic retinopathy, which is commonly associated with retinal edema and hyperglycemia. Although the vasomotor activity of venules contributes to the regulation of tissue fluid homeostasis, responses of human retinal venules to ET-1 under euglycemia and hyperglycemia remain unknown and the ET-1 receptor subtype corresponding to vasomotor function has not been determined. Herein, we addressed these issues by examining the reactivity of isolated human retinal venules to ET-1, and results from porcine retinal venules were compared.

Methods

Retinal tissues were obtained from patients undergoing enucleation. Human and porcine retinal venules were isolated and pressurized to assess diameter changes in response to ET-1 after exposure to 5 mM control glucose or 25 mM high glucose for 2 hours.

Results

Both human and porcine retinal venules exposed to control glucose developed similar basal tone and constricted comparably to ET-1 in a concentration-dependent manner. ET-1-induced constrictions of human and porcine retinal venules were abolished by ET receptor antagonist BQ123. During high glucose exposure, basal tone of human and porcine retinal venules was unaltered but ET-1-induced vasoconstrictions were enhanced.

Conclusions

ET-1 elicits comparable constriction of human and porcine retinal venules by activation of ET receptors. In vitro hyperglycemia augments human and porcine retinal venular responses to ET-1.

Translational Relevance

Similarities in vasoconstriction to ET-1 between human and porcine retinal venules support the latter as an effective model of the human retinal microcirculation to help identify vascular targets for the treatment of retinal complications in patients with diabetes.

Topics: Animals; Constriction; Endothelin-1; Humans; Hyperglycemia; Swine; Vasoconstriction; Venules

PubMed: 32879758
DOI: 10.1167/tvst.9.9.1

Authors: Krzysztof Kucharz, Kasper Kristensen, Kasper Bendix Johnsen...

Effective treatments of neurodegenerative diseases require drugs to be actively transported across the blood-brain barrier (BBB). However, nanoparticle drug carriers explored for this purpose show negligible brain uptake, and the lack of basic understanding of nanoparticle-BBB interactions underlies many translational failures. Here, using two-photon microscopy in mice, we characterize the receptor-mediated transcytosis of nanoparticles at all steps of delivery to the brain in vivo. We show that transferrin receptor-targeted liposome nanoparticles are sequestered by the endothelium at capillaries and venules, but not at arterioles. The nanoparticles move unobstructed within endothelium, but transcytosis-mediated brain entry occurs mainly at post-capillary venules, and is negligible in capillaries. The vascular location of nanoparticle brain entry corresponds to the presence of perivascular space, which facilitates nanoparticle movement after transcytosis. Thus, post-capillary venules are the point-of-least resistance at the BBB, and compared to capillaries, provide a more feasible route for nanoparticle drug carriers into the brain.

Topics: Animals; Arterioles; Biological Transport; Blood-Brain Barrier; Brain; Capillaries; Drug Carriers; Endothelium; Kinetics; Liposomes; Mice; Nanoparticles; Receptors, Transferrin; Transcytosis; Venules

PubMed: 34226541
DOI: 10.1038/s41467-021-24323-1

Authors: Britt Roosenboom, Ellen G van Lochem, Jos Meijer...

PNAd and MAdCAM-1 addressins on venules are of importance in T-cell homing and potential therapeutic targets in ulcerative colitis (UC). Normally, PNAd high endothelial venules (HEVs) are only present in lymphoid organs, whereas small numbers of MAdCAM-1 venules can be seen in non-lymphoid tissue. We aimed to study their presence in the intestinal mucosa of UC patients at diagnosis and during follow-up, and their correlation with disease activity. Colonic biopsy specimens of 378 UC patients were analyzed by immunohistochemistry for CD3, CD20, ERG, MECA-79 (PNAd) and MECA-376 (MAdCAM-1) and compared to healthy controls (HC). The proportion of PNAdHEVs in UC at diagnosis was 4.9% (IQR 2.0%-8.3%), while none were detected in HC. During follow-up, PNAdHEVs completely disappeared in remission ( = 93), whereas the proportion in active disease was similar to baseline ( = 285, = 0.39). The proportion of MAdCAM-1venules in UC at baseline was 5.8% (IQR 2.6-10.0). During follow-up, the proportion in remission was comparable to diagnosis, but upregulated (7.5% (IQR 4.4-10.9), = 0.001) in active disease. In conclusion, PNAdHEVs appear in UC during active inflammation which could thus serve as a marker for disease activity, whereas MAdCAM-1venules remain present after inflammation is resolved and increase after subsequent flares, reflecting chronicity and potentially serving as a therapeutic target.

Topics: Adult; Colitis, Ulcerative; Disease Progression; Female; Humans; Immunoglobulins; Intestinal Mucosa; Male; Middle Aged; Venules

PubMed: 32268498
DOI: 10.3390/cells9040891

The Early Innate Immune Response to, and Phagocyte-Dependent Entry of, Cryptococcus neoformans Map to the Perivascular Space of Cortical Post-Capillary Venules in Neurocryptococcosis.

Authors: Keren Kaufman-Francis, Julianne T Djordjevic, Pierre-Georges Juillard...

The innate immune system is the primary defense against cryptococcal infection, but paradoxically it promotes infection of the central nervous system. We performed a detailed longitudinal study of neurocryptococcosis in normal, chimeric, green fluorescent protein phagocyte-positive mice and phagocyte-depleted mice and interrogated the central nervous system innate immune response to Cryptococcus neoformans H99 using confocal microscopy, histology, flow cytometry, and quantification of brain cytokine/chemokines and fungal burdens. C. neoformans was present in the perivascular space (PVS) of post-capillary venules. This was associated with a massive influx of blood-derived monocytes, neutrophils, and T lymphocytes into the PVS and a predominantly proinflammatory cytokine/chemokine response. Phagocytes containing cryptococci were present only in the lumen and corresponding PVS of post-capillary venules. Free cryptococci were observed breaching the glia limitans, the protective barrier between the PVS and the cerebral parenchyma. Parenchymal cryptococcomas were typically in direct contact with post-capillary venules and lacked surrounding immune cell infiltrates. Phagocyte depletion abrogated cryptococcoma formation and PVS infiltrates. Together, these observations suggest that cryptococcomas can originate via phagocyte-dependent transport across post-capillary venular endothelium into the PVS and thence via passage of free cryptococci into the brain. In conclusion, we demonstrate for the first time that the PVS of cortical post-capillary venules is the major site of the early innate immune response to, and phagocyte-dependent entry of, C. neoformans.

Topics: Animals; Brain; Cryptococcus neoformans; Disease Models, Animal; Female; Immunity, Innate; Meningitis, Cryptococcal; Mice; Mice, Inbred C57BL; Monocytes; Phagocytes; T-Lymphocytes; Venules

PubMed: 29929915
DOI: 10.1016/j.ajpath.2018.03.015

Authors: Angie De La Cruz, Aubrey Hargrave, Sri Magadi...

Platelet extravasation during inflammation is under-appreciated. In wild-type (WT) mice, a central corneal epithelial abrasion initiates neutrophil (PMN) and platelet extravasation from peripheral limbal venules. The same injury in mice expressing low levels of the β-integrin, CD18 (CD18 mice) shows reduced platelet extravasation with PMN extravasation apparently unaffected. To better define the role of CD18 on platelet extravasation, we focused on two relevant cell types expressing CD18: PMNs and mast cells. Following corneal abrasion in WT mice, we observed not only extravasated PMNs and platelets but also extravasated erythrocytes (RBCs). Ultrastructural observations of engorged limbal venules showed platelets and RBCs passing through endothelial pores. In contrast, injured CD18 mice showed significantly less venule engorgement and markedly reduced platelet and RBC extravasation; mast cell degranulation was also reduced compared to WT mice. Corneal abrasion in mast cell-deficient (Kit) mice showed less venule engorgement, delayed PMN extravasation, reduced platelet and RBC extravasation and delayed wound healing compared to WT mice. Finally, antibody-induced depletion of circulating PMNs prior to corneal abrasion reduced mast cell degranulation, venule engorgement, and extravasation of PMNs, platelets, and RBCs. In summary, in the injured cornea, platelet and RBC extravasation depends on CD18, PMNs, and mast cell degranulation.

Topics: Animals; Blood Platelets; CD18 Antigens; Cell Degranulation; Cell Movement; Chemotaxis, Leukocyte; Cornea; Corneal Injuries; Epithelium, Corneal; Erythrocytes; Female; Hyperemia; Macrophages; Male; Mast Cells; Mice; Mice, Inbred C57BL; Microcirculation; Microscopy, Electron; Models, Animal; Neutrophils; Phagocytosis; Regeneration; Transendothelial and Transepithelial Migration; Vasculitis; Venules; Wound Healing

PubMed: 34298979
DOI: 10.3390/ijms22147360

Authors: Yen-Lin Chen, Yi Ren, Wenjuan Xu...

Purpose

Endothelin-1 (ET-1) is a potent vasoconstrictor peptide implicated in retinal venous pathologies such as diabetic retinopathy and retinal vein occlusion. However, underlying mechanisms contributing to venular constriction remain unknown. Thus, we examined the roles of ET-1 receptors, extracellular calcium (Ca2+), L-type voltage-operated calcium channels (L-VOCCs), Rho kinase (ROCK), and protein kinase C (PKC) in ET-1-induced constriction of retinal venules.

Methods

Porcine retinal venules were isolated and pressurized for vasoreactivity study using videomicroscopic techniques. Protein and mRNA were analyzed using molecular tools.

Results

Retinal venules developed basal tone and constricted concentration-dependently to ET-1. The ETA receptor (ETAR) antagonist BQ123 abolished venular constriction to ET-1, but ETB receptor (ETBR) antagonist BQ788 had no effect on vasoconstriction. The ETBR agonist sarafotoxin S6c did not elicit vasomotor activity. In the absence of extracellular Ca2+, venules lost basal tone and ET-1-induced constriction was nearly abolished. Although L-VOCC inhibitor nifedipine also reduced basal tone and blocked vasoconstriction to L-VOCC activator Bay K8644, constriction of venules to ET-1 remained. The ROCK inhibitor H-1152 but not PKC inhibitor Gö 6983 prevented ET-1-induced vasoconstriction. Protein and mRNA expressions of ETARs and ETBRs, along with ROCK1 and ROCK2 isoforms, were detected in retinal venules.

Conclusions

Extracellular Ca2+ entry via L-VOCCs is essential for developing and maintaining basal tone of porcine retinal venules. ET-1 causes significant constriction of retinal venules by activating ETARs and extracellular Ca2+ entry independent of L-VOCCs. Activation of ROCK signaling, without involvement of PKC, appears to mediate venular constriction to ET-1 in the porcine retina.

Topics: Animals; Blotting, Western; Calcium; Calcium Channels, L-Type; Endothelin B Receptor Antagonists; Endothelin Receptor Antagonists; Endothelin-1; Female; Male; Oligopeptides; Peptides, Cyclic; Piperidines; Protein Kinase C; RNA, Messenger; Real-Time Polymerase Chain Reaction; Receptor, Endothelin A; Retinal Vein; Sus scrofa; Vasoconstriction; Venules; rho-Associated Kinases

PubMed: 30372743
DOI: 10.1167/iovs.18-25369

Authors: Junko Sawada, Carole Y Perrot, Linyuan Chen...

Recruitment of naive T cells to lymph nodes is essential for the development of adaptive immunity. Upon pathogen infection, lymph nodes promptly increase the influx of naive T cells from the circulation in order to screen and prime the T cells. The precise contribution of the lymph node vasculature to the regulation of this process remains unclear. Here we show a role for the Ras GTPase, R-Ras, in the functional adaptation of high endothelial venules to increase naive T cell trafficking to the lymph nodes. R-Ras is transiently up-regulated in the endothelium of high endothelial venules by the inflammatory cytokine tumor necrosis factor (TNF) within 24 hours of pathogen inoculation. TNF induces R-Ras upregulation in endothelial cells via JNK and p38 mitogen-activated protein kinase but not NF-κB. Studies of T cell trafficking found that the loss of function of endothelial R-Ras impairs the rapid acceleration of naive T cell recruitment to the lymph nodes upon inflammation. This defect diminished the ability of naive OT-1 T cells to develop antitumor activity against ovalbumin-expressing melanoma. Proteomic analyses suggest that endothelial R-Ras facilitates TNF-dependent transendothelial migration (diapedesis) of naive T cells by modulating molecular assembly the at T cell-endothelial cell interface. These findings give new mechanistic insights into the functional adaptation of high endothelial venules to accelerate naive T cell recruitment to the lymph nodes.

Topics: Animals; Chemotaxis, Leukocyte; Endothelial Cells; Humans; Lymph Nodes; Mice; T-Lymphocytes; Transendothelial and Transepithelial Migration; Tumor Necrosis Factor-alpha; Up-Regulation; Venules; ras Proteins

PubMed: 33159887
DOI: 10.1016/j.ajpath.2020.10.009