P2X7 receptor knockout does not alter renal function or prevent angiotensin II-induced kidney injury in F344 rats.

P2X7 receptors mediate immune and endothelial cell responses to extracellular ATP. Acute pharmacological blockade increases renal blood flow and filtration rate, suggesting that receptor activation promotes tonic vasoconstriction. P2X7 expression is increased in kidney disease and blockade/knockout is renoprotective. We generated a P2X7 knockout rat on F344 background, hypothesising enhanced renal blood flow and protection from angiotensin-II-induced renal injury. CRISPR/Cas9 introduced an early stop codon into exon 2 of P2rx7, abolishing P2X7 protein in kidney and reducing P2rx7 mRNA abundance by ~ 60% in bone-marrow derived macrophages. The M1 polarisation response to lipopolysaccharide was unaffected but P2X7 receptor knockout suppressed ATP-induced IL-1ß release. In male knockout rats, acetylcholine-induced dilation of the renal artery ex vivo was diminished but not the response to nitroprusside. Renal function in male and female knockout rats was not different from wild-type. Finally, in male rats infused with angiotensin-II for 6 weeks, P2X7 knockout did not reduce albuminuria, tubular injury, renal macrophage accrual, and renal perivascular fibrosis. Contrary to our hypothesis, global P2X7 knockout had no impact on in vivo renal hemodynamics. Our study does not indicate a major role for P2X7 receptor activation in renal vascular injury.

International Multi-Institutional Experience with Presentation and Management of Aortic Arch Laterality in Aberrant Subclavian Artery and Kommerell's Diverticulum.

BACKGROUND: Aberrant subclavian artery (ASA) with or without Kommerell's diverticulum (KD) is a rare anatomic aortic arch anomaly that can cause dysphagia and/or life-threatening rupture. The objective of this study is to compare outcomes of ASA/KD repair in patients with a left versus right aortic arch. METHODS: Using the Vascular Low Frequency Disease Consortium methodology, a retrospective review was performed of patients ≥18 years old with surgical treatment of ASA/KD from 2000 to 2020 at 20 institutions. RESULTS: 288 patients with ASA with or without KD were identified; 222 left-sided aortic arch (LAA), and 66 right-sided aortic arch (RAA). Mean age at repair was younger in LAA 54 vs. 58 years (P = 0.06). Patients in RAA were more likely to undergo repair due to symptoms (72.7% vs. 55.9%, P = 0.01), and more likely to present with dysphagia (57.6% vs. 39.1%, P < 0.01). The hybrid open/endovascular approach was the most common repair type in both groups. Rates of intraoperative complications, death within 30 days, return to the operating room, symptom relief and endoleaks were not significantly different. For patients with symptom status follow-up data, in LAA, 61.7% had complete relief, 34.0% had partial relief and 4.3% had no change. In RAA, 60.7% had complete relief, 34.4% had partial relief and 4.9% had no change. CONCLUSIONS: In patients with ASA/KD, RAA patients were less common than LAA, presented more frequently with dysphagia, had symptoms as an indication for intervention, and underwent treatment at a younger age. Open, endovascular and hybrid repair approaches appear equally effective, regardless of arch laterality.

Contemporary outcomes after treatment of aberrant subclavian artery and Kommerell's diverticulum.

OBJECTIVE: Aberrant subclavian artery (ASA) and Kommerell's diverticulum (KD) are rare vascular anomalies that may be associated with lifestyle-limiting and life-threatening complications. The aim of this study is to report contemporary outcomes after invasive treatment of ASA/KD using a large international dataset. METHODS: Patients who underwent treatment for ASA/KD (2000-2020) were identified through the Vascular Low Frequency Disease Consortium, a multi-institutional collaboration to investigate uncommon vascular disorders. We report the early and mid-term clinical outcomes including stroke and mortality, technical success, and other operative outcomes including reintervention rates, patency, and endoleak. RESULTS: Overall, 285 patients were identified during the study period. The mean patient age was 57 years; 47% were female and 68% presented with symptoms. A right-sided arch was present in 23%. The mean KD diameter was 47.4 mm (range, 13.0-108.0 mm). The most common indication for treatment was symptoms (59%), followed by aneurysm size (38%). The most common symptom reported was dysphagia (44%). A ruptured KD was treated in 4.2% of cases, with a mean diameter of 43.9 mm (range, 18.0-100.0 mm). An open procedure was performed in 101 cases (36%); the most common approach was ASA ligation with subclavian transposition. An endovascular or hybrid approach was performed in 184 patients (64%); the most common approach was thoracic endograft and carotid-subclavian bypass. A staged operative strategy was employed more often than single setting repair (55% vs 45%). Compared with endovascular or hybrid approach, those in the open procedure group were more likely to be younger (49 years vs 61 years; P < .0001), female (64% vs 36%; P < .0001), and symptomatic (85% vs 59%; P < .0001). Complete or partial symptomatic relief at 1 year after intervention was 82.6%. There was no association between modality of treatment and symptom relief (open 87.2% vs endovascular or hybrid approach 78.9%; P = .13). After the intervention, 11 subclavian occlusions (4.5%) occurred; 3 were successfully thrombectomized resulting in a primary and secondary patency of 95% and 96%, respectively, at a median follow-up of 39 months. Among the 33 reinterventions (12%), the majority were performed for endoleak (36%), and more reinterventions occurred in the endovascular or hybrid approach than open procedure group (15% vs 6%; P = .02). The overall survival rate was 87.3% at a median follow-up of 41 months. The 30-day stroke and death rates were 4.2% and 4.9%, respectively. Urgent or emergent presentation was independently associated with increased risk of 30-day mortality (odds ratio [OR], 19.8; 95% confidence interval [CI], 3.3-116.6), overall mortality (OR, 3.6; 95% CI, 1.2-11.2) and intraoperative complications (OR, 8.3; 95% CI, 2.8-25.1). Females had a higher risk of reintervention (OR, 2.6; 95% CI, 1.0-6.5). At an aneurysm size of 44.4 mm, receiver operator characteristic curve analysis suggested that 60% of patients would have symptoms. CONCLUSIONS: Treatment of ASA/KD can be performed safely with low rates of mortality, stroke and reintervention and high rates of symptomatic relief, regardless of the repair strategy. Symptomatic and urgent operations were associated with worse outcomes in general, and female gender was associated with a higher likelihood of reintervention. Given the worse overall outcomes when symptomatic and the inherent risk of rupture, consideration of repair at 40 mm is reasonable in most patients. ASA/KD can be repaired in asymptomatic patients with excellent outcomes and young healthy patients may be considered better candidates for open approaches versus endovascular or hybrid modalities, given the lower likelihood of reintervention and lower early mortality rate.

Macrophages trigger cardiomyocyte proliferation by increasing epicardial vegfaa expression during larval zebrafish heart regeneration.

Cardiac injury leads to the loss of cardiomyocytes, which are rapidly replaced by the proliferation of the surviving cells in zebrafish, but not in mammals. In both the regenerative zebrafish and non-regenerative mammals, cardiac injury induces a sustained macrophage response. Macrophages are required for cardiomyocyte proliferation during zebrafish cardiac regeneration, but the mechanisms whereby macrophages facilitate this crucial process are fundamentally unknown. Using heartbeat-synchronized live imaging, RNA sequencing, and macrophage-null genotypes in the larval zebrafish cardiac injury model, we characterize macrophage function and reveal that these cells activate the epicardium, inducing cardiomyocyte proliferation. Mechanistically, macrophages are specifically recruited to the epicardial-myocardial niche, triggering the expansion of the epicardium, which upregulates vegfaa expression to induce cardiomyocyte proliferation. Our data suggest that epicardial Vegfaa augments a developmental cardiac growth pathway via increased endocardial notch signaling. The identification of this macrophage-dependent mechanism of cardiac regeneration highlights immunomodulation as a potential strategy for enhancing mammalian cardiac repair.

Comparative Studies of Renin-Null Zebrafish and Mice Provide New Functional Insights.

BACKGROUND: The renin-angiotensin system is highly conserved across vertebrates, including zebrafish, which possess orthologous genes coding for renin-angiotensin system proteins, and specialized mural cells of the kidney arterioles, capable of synthesising and secreting renin. METHODS: We generated zebrafish with CRISPR-Cas9-targeted knockout of renin (ren-/-) to investigate renin function in a low blood pressure environment. We used single-cell (10×) RNA sequencing analysis to compare the transcriptome profiles of renin lineage cells from mesonephric kidneys of ren-/- with ren+/+ zebrafish and with the metanephric kidneys of Ren1c-/- and Ren1c+/+ mice. RESULTS: The ren-/- larvae exhibited delays in larval growth, glomerular fusion and appearance of a swim bladder, but were viable and withstood low salinity during early larval stages. Optogenetic ablation of renin-expressing cells, located at the anterior mesenteric artery of 3-day-old larvae, caused a loss of tone, due to diminished contractility. The ren-/- mesonephric kidney exhibited vacuolated cells in the proximal tubule, which were also observed in Ren1c-/- mouse kidney. Fluorescent reporters for renin and smooth muscle actin (Tg(ren:LifeAct-RFP; acta2:EGFP)), revealed a dramatic recruitment of renin lineage cells along the renal vasculature of adult ren-/- fish, suggesting a continued requirement for renin, in the absence of detectable angiotensin metabolites, as seen in the Ren1YFP Ren1c-/- mouse. Both phenotypes were rescued by alleles lacking the potential for glycosylation at exon 2, suggesting that glycosylation is not essential for normal physiological function. CONCLUSIONS: Phenotypic similarities and transcriptional variations between mouse and zebrafish renin knockouts suggests evolution of renin cell function with terrestrial survival.

Selective Cdk9 inhibition resolves neutrophilic inflammation and enhances cardiac regeneration in larval zebrafish.

Sustained neutrophilic inflammation is detrimental for cardiac repair and associated with adverse outcomes following myocardial infarction (MI). An attractive therapeutic strategy to treat MI is to reduce or remove infiltrating neutrophils to promote downstream reparative mechanisms. CDK9 inhibitor compounds enhance the resolution of neutrophilic inflammation; however, their effects on cardiac repair/regeneration are unknown. We have devised a cardiac injury model to investigate inflammatory and regenerative responses in larval zebrafish using heartbeat-synchronised light-sheet fluorescence microscopy. We used this model to test two clinically approved CDK9 inhibitors, AT7519 and flavopiridol, examining their effects on neutrophils, macrophages and cardiomyocyte regeneration. We found that AT7519 and flavopiridol resolve neutrophil infiltration by inducing reverse migration from the cardiac lesion. Although continuous exposure to AT7519 or flavopiridol caused adverse phenotypes, transient treatment accelerated neutrophil resolution while avoiding these effects. Transient treatment with AT7519, but not flavopiridol, augmented wound-associated macrophage polarisation, which enhanced macrophage-dependent cardiomyocyte number expansion and the rate of myocardial wound closure. Using cdk9-/- knockout mutants, we showed that AT7519 is a selective CDK9 inhibitor, revealing the potential of such treatments to promote cardiac repair/regeneration.

Loss of Adam10 Disrupts Ion Transport in Immortalized Kidney Collecting Duct Cells.

The kidney cortical collecting duct (CCD) comprises principal cells (PCs), intercalated cells (IC), and the recently discovered intermediate cell type. Kidney pathology in a mouse model of the syndrome of apparent aldosterone excess revealed plasticity of the CCD, with altered PC:intermediate cell:IC ratio. The self-immortalized mouse CCD cell line, mCCDcl1, shows functional characteristics of PCs, but displays a range of cell types, including intermediate cells, making it ideal to study plasticity. We knocked out Adam10, a key component of the Notch pathway, in mCCDcl1 cells, using CRISPR-Cas9 technology, and isolated independent clones, which exhibited severely affected sodium transport capacity and loss of aldosterone response. Single-cell RNA sequencing revealed significantly reduced expression of major PC-specific markers, such as Scnn1g (γ-ENaC) and Hsd11b2 (11ßHSD2), but no significant changes in transcription of components of the Notch pathway were observed. Immunostaining in the knockout clone confirmed the decrease in expression of γ-ENaC and importantly, showed an altered, diffuse distribution of PC and IC markers, suggesting altered trafficking in the Adam10 knockout clone as an explanation for the loss of polarization.

scRNA Transcription Profile of Adult Zebrafish Podocytes Using a Novel Reporter Strain.

BACKGROUND/AIMS: The role of podocytes is well conserved across species from drosophila to teleosts, and mammals. Identifying the molecular markers that actively maintain the integrity of the podocyte will enable a greater understanding of the changes that lead to damage. METHODS: We generated transgenic zebrafish, expressing fluorescent reporters driven by the podocin promoter, for the visualization and isolation of podocytes. We have conducted single cell RNA sequencing (scRNA-seq) on isolated podocytes from a zebrafish reporter line. RESULTS: We demonstrated that the LifeAct-TagRFP-T fluorescent reporter faithfully replicated podocin expression in vivo. We were also able to show spontaneous GCaMP6s fluorescence using light sheet (single plane illumination) microscopy. We identified many podocyte transcripts, encoding proteins related to calcium-binding and actin filament assembly, in common with those expressed in human and mouse mature podocytes. CONCLUSION: We describe the establishment of novel transgenic zebrafish and their use to identify and isolate podocyte cells for the preparation of a scRNA-seq library from normal podocytes. The scRNA-seq data identifies distinct populations of cells and potential gene switching between clusters. These data provide a foundation for future comparative studies and for exploiting the zebrafish as a model for kidney development, disease, injury and repair.

Abnormal neonatal sodium handling in skin precedes hypertension in the SAME rat.

We discovered high Na+ and water content in the skin of newborn Sprague-Dawley rats, which reduced ~ 2.5-fold by 7 days of age, indicating rapid changes in extracellular volume (ECV). Equivalent changes in ECV post birth were also observed in C57Bl/6 J mice, with a fourfold reduction over 7 days, to approximately adult levels. This established the generality of increased ECV at birth. We investigated early sodium and water handling in neonates from a second rat strain, Fischer, and an Hsd11b2-knockout rat modelling the syndrome of apparent mineralocorticoid excess (SAME). Despite Hsd11b2-/- animals exhibiting lower skin Na+ and water levels than controls at birth, they retained ~ 30% higher Na+ content in their pelts at the expense of K+ thereafter. Hsd11b2-/- neonates exhibited incipient hypokalaemia from 15 days of age and became increasingly polydipsic and polyuric from weaning. As with adults, they excreted a high proportion of ingested Na+ through the kidney, (56.15 ± 8.21% versus control 34.15 ± 8.23%; n = 4; P < 0.0001), suggesting that changes in nephron electrolyte transporters identified in adults, by RNA-seq analysis, occur by 4 weeks of age. Our data reveal that Na+ imbalance in the Hsd11b2-/- neonate leads to excess Na+ storage in skin and incipient hypokalaemia, which, together with increased, glucocorticoid-induced Na+ uptake in the kidney, then contribute to progressive, volume contracted, salt-sensitive hypertension. Skin Na+ plays an important role in the development of SAME but, equally, may play a key physiological role at birth, supporting post-natal growth, as an innate barrier to infection or as a rudimentary kidney.

Role of Pericytes in the Development of the Renin/Angiotensin System: Induction of Functional Renin in Cultures of Pericytes.

Renal pericytes have a critical importance for angiogenesis and vascular remodeling, medullary blood flow regulation, and development of fibrosis. An emerging role for kidney pericytes is their ability to induce renin expression and synthesis. Here, we present methods for purification of human renal pericytes, their primary culture, and differentiation into renin-producing cells. Possible applications of these protocols include investigations into (1) renin cell recruitment mechanisms, (2) modulation of renin expression/secretion by small molecules, and (3) renin expression/secretion in nonrenal pericytes. A potential therapeutic application of this work is the identification of new players regulating the renin-angiotensin system.

Transcription Factor Pit-1 Affects Transcriptional Timing in the Dual-Promoter Human Prolactin Gene.

Gene transcription occurs in short bursts interspersed with silent periods, and these kinetics can be altered by promoter structure. The effect of alternate promoter architecture on transcription bursting is not known. We studied the human prolactin (hPRL) gene that contains 2 promoters, a pituitary-specific promoter that requires the transcription factor Pit-1 and displays dramatic transcriptional bursting activity and an alternate upstream promoter that is active in nonpituitary tissues. We studied large hPRL genomic fragments with luciferase reporters, and used bacterial artificial chromosome recombineering to manipulate critical promoter regions. Stochastic switch mathematical modelling of single-cell time-lapse luminescence image data revealed that the Pit-1-dependent promoter showed longer, higher-amplitude transcriptional bursts. Knockdown studies confirmed that the presence of Pit-1 stabilized and prolonged periods of active transcription. Pit-1 therefore plays an active role in establishing the timing of transcription cycles, in addition to its cell-specific functions.

Live Imaging of Heart Injury in Larval Zebrafish Reveals a Multi-Stage Model of Neutrophil and Macrophage Migration.

Neutrophils and macrophages are crucial effectors and modulators of repair and regeneration following myocardial infarction, but they cannot be easily observed in vivo in mammalian models. Hence many studies have utilized larval zebrafish injury models to examine neutrophils and macrophages in their tissue of interest. However, to date the migratory patterns and ontogeny of these recruited cells is unknown. In this study, we address this need by comparing our larval zebrafish model of cardiac injury to the archetypal tail fin injury model. Our in vivo imaging allowed comprehensive mapping of neutrophil and macrophage migration from primary hematopoietic sites, to the wound. Early following injury there is an acute phase of neutrophil recruitment that is followed by sustained macrophage recruitment. Both cell types are initially recruited locally and subsequently from distal sites, primarily the caudal hematopoietic tissue (CHT). Once liberated from the CHT, some neutrophils and macrophages enter circulation, but most use abluminal vascular endothelium to crawl through the larva. In both injury models the innate immune response resolves by reverse migration, with very little apoptosis or efferocytosis of neutrophils. Furthermore, our in vivo imaging led to the finding of a novel wound responsive mpeg1+ neutrophil subset, highlighting previously unrecognized heterogeneity in neutrophils. Our study provides a detailed analysis of the modes of immune cell migration in larval zebrafish, paving the way for future studies examining tissue injury and inflammation.

Author Correction: Adaptive prospective optical gating enables day-long 3D time-lapse imaging of the beating embryonic zebrafish heart.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Are your cash-flow tools recession ready?

In good times like those most businesses have enjoyed for the past decade, business owners have typically watched their income statements with pleasure, as year-to-year performance gains have fattened their dividend payouts and increased the valuation of the companies they own and run. All too often in such times, scant attention is paid to what's between the top line and the bottom line of the income statement. Worse, most business owners, in my experience, give little more than a cursory nod to the balance sheet. Why does this matter? When a recession lands on their doorstep with a sudden thud, as it apparently just has, many of these same people will find themselves having sailed too close to the wind, with cash running out and a dearth of tools to help them weather the storm and understand what has gone wrong. But it need not be so, for there are four simple tools to help any business owner answer these four important questions: (1) Where is cash going in my business, and where is it coming from? (2) To what extent are my profit margins improving or declining, and why? (3) To what extent am I effectively managing the cash-flow relationships with my customers and my suppliers? (4) What, if anything, can I do to better manage the cash that flows into and out of my business? If your business is threatened by the COVID-19 pandemic, here are some tools to help it survive.

Endothelin-1 Mediates the Systemic and Renal Hemodynamic Effects of GPR81 Activation.

GPR81 (G-protein-coupled receptor 81) is highly expressed in adipocytes, and activation by the endogenous ligand lactate inhibits lipolysis. GPR81 is also expressed in the heart, liver, and kidney, but roles in nonadipose tissues are poorly defined. GPR81 agonists, developed to improve blood lipid profile, might also provide insights into GPR81 physiology. Here, we assessed the blood pressure and renal hemodynamic responses to the GPR81 agonist, AZ'5538. In male wild-type mice, intravenous AZ'5538 infusion caused a rapid and sustained increase in systolic and diastolic blood pressure. Renal artery blood flow, intrarenal tissue perfusion, and glomerular filtration rate were all significantly reduced. AZ'5538 had no effect on blood pressure or renal hemodynamics in Gpr81-/- mice. Gpr81 mRNA was expressed in renal artery vascular smooth muscle, in the afferent arteriole, in glomerular and medullary perivascular cells, and in pericyte-like cells isolated from kidney. Intravenous AZ'5538 increased plasma ET-1 (endothelin 1), and pretreatment with BQ123 (endothelin-A receptor antagonist) prevented the pressor effects of GPR81 activation, whereas BQ788 (endothelin-B receptor antagonist) did not. Renal ischemia-reperfusion injury, which increases renal extracellular lactate, increased the renal expression of genes encoding ET-1, KIM-1 (Kidney Injury Molecule 1), collagen type 1-α1, TNF-α (tumor necrosis factor-α), and F4/80 in wild-type mice but not in Gpr81-/- mice. In summary, activation of GPR81 in vascular smooth muscle and perivascular cells regulates renal hemodynamics, mediated by release of the potent vasoconstrictor ET-1. This suggests that lactate may be a paracrine regulator of renal blood flow, particularly relevant when extracellular lactate is high as occurs during ischemic renal disease.

Cellular plasticity: A mechanism for homeostasis in the kidney.

Cellular plasticity is a topical subject with interest spanning a wide range of fields from developmental biology to regenerative medicine. Even the nomenclature is a subject of debate, and the underlying mechanisms are still under investigation. On top of injury repair, cell plasticity is a constant physiological process in adult organisms and tissues, in response to homeostatic challenges. In this review we discuss two examples of plasticity for the maintenance of homeostasis in the renal system-namely the renin-producing juxtaglomerular cells (JG cells) and cortical collecting duct (CCD) cells. JG cells show plasticity through recruitment mechanisms, answering the demand for an increase in renin production. In the CCD, cells appear to have the ability to transdifferentiate between principal and intercalated cells to help maintain the highly regulated solute transport levels of that segment. These two cases highlight the complexity of plasticity processes and the role they can play in the kidney.

Tibiopedal arterial minimally invasive retrograde revascularization (TAMI) in patients with peripheral arterial disease and critical limb ischemia. On behalf of the Peripheral Registry of Endovascular Clinical Outcomes (PRIME).

OBJECTIVES AND BACKGROUND: Complex peripheral arterial disease (PAD) and critical limb ischemia (CLI) are associated with high morbidity and mortality. Endovascular techniques have become prevalent in treatment of advanced PAD and CLI, and use of techniques such as tibiopedal minimally invasive revascularization (TAMI), have been proven safe in small, single-center series. However, its use has not been systematically compared to traditional approaches. METHODS AND RESULTS: This is a retrospective, multicenter analysis which enrolled 744 patients with advanced PAD and CLI who underwent 1,195 endovascular interventions between January 2013 and April 2018. Data was analyzed based on access used for revascularization: 840 performed via femoral access, 254 via dual access, and 101 via TAMI. The dual access group had the highest median Rutherford Class and lowest number of patent tibial vessels. Median fluoroscopy time, procedure time, hospital stay, and contrast volume were significantly lower in the TAMI access group when compared to both femoral/dual access groups. There was also a significant difference between all groups regarding location of target lesions: Femoropopliteal lesions were most commonly treated via femoral access; infrapopliteal lesions, via TAMI, and multilevel lesions via dual access. CONCLUSIONS: Stand-alone TAMI or tibial access as an integral part of a dual access treatment strategy, is safe and efficacious in the treatment of patients with advanced PAD and CLI who have infrapopliteal lesions. Larger prospective and randomized studies may be useful to further validate this approach.

The utility of abdominopelvic CT in pregnant patients with abdominal pain and a negative or inconclusive abdominal MRI.

Pregnant women with abdominal pain can pose a diagnostic dilemma due to the nonspecific nature of symptoms and the desire to avoid radiation to the conceptus. Many algorithms will suggest ultrasound (US) or Magnetic Resonance Imaging (MRI) as the first-line imaging choice in pregnant women with abdominal pain due to the lack of ionizing radiation. However, these studies can have limitations as well. Abdominopelvic MRI is susceptible to respiratory motion that could cause a study to be nondiagnostic (Zaitsev et al., 2015 [1]). In the current case series, we present 8 pregnant patients with abdominal pain who underwent CT abdomen and pelvis after negative or inconclusive abdominal MRI exams. To our knowledge, this is the only case series that describes CT findings in the pregnant population after negative or inconclusive MRI.

Adaptive prospective optical gating enables day-long 3D time-lapse imaging of the beating embryonic zebrafish heart.

Three-dimensional fluorescence time-lapse imaging of the beating heart is extremely challenging, due to the heart's constant motion and a need to avoid pharmacological or phototoxic damage. Although real-time triggered imaging can computationally "freeze" the heart for 3D imaging, no previous algorithm has been able to maintain phase-lock across developmental timescales. We report a new algorithm capable of maintaining day-long phase-lock, permitting routine acquisition of synchronised 3D + time video time-lapse datasets of the beating zebrafish heart. This approach has enabled us for the first time to directly observe detailed developmental and cellular processes in the beating heart, revealing the dynamics of the immune response to injury and witnessing intriguing proliferative events that challenge the established literature on cardiac trabeculation. Our approach opens up exciting new opportunities for direct time-lapse imaging studies over a 24-hour time course, to understand the cellular mechanisms underlying cardiac development, repair and regeneration.

Animal Models of Hypertension: A Scientific Statement From the American Heart Association.

Hypertension is the most common chronic disease in the world, yet the precise cause of elevated blood pressure often cannot be determined. Animal models have been useful for unraveling the pathogenesis of hypertension and for testing novel therapeutic strategies. The utility of animal models for improving the understanding of the pathogenesis, prevention, and treatment of hypertension and its comorbidities depends on their validity for representing human forms of hypertension, including responses to therapy, and on the quality of studies in those models (such as reproducibility and experimental design). Important unmet needs in this field include the development of models that mimic the discrete hypertensive syndromes that now populate the clinic, resolution of ongoing controversies in the pathogenesis of hypertension, and the development of new avenues for preventing and treating hypertension and its complications. Animal models may indeed be useful for addressing these unmet needs.