Micro to macro scale analysis of the intact human renal arterial tree with Synchrotron Tomography

Background

The kidney vasculature is exquisitely structured to orchestrate renal function. Structural profiling of the vasculature in intact rodent kidneys, has provided insights into renal haemodynamics and oxygenation, but has never been extended to the human kidney beyond a few vascular generations. We hypothesised that synchrotron-based imaging of a human kidney would enable assessment of vasculature across the whole organ.

Methods

An intact kidney from a 63-year-old male was scanned using hierarchical phase-contrast tomography (HiP-CT), followed by semi-automated vessel segmentation and quantitative analysis. These data were compared to published micro-CT data of whole rat kidney.

Results

The intact human kidney vascular network was imaged with HiP-CT at 25 μm voxels, representing a 20-fold increase in resolution compared to clinical CT scanners. Our comparative quantitative analysis revealed the number of vessel generations, vascular asymmetry and a structural organisation optimised for minimal resistance to flow, are conserved between species, whereas the normalised radii are not. We further demonstrate regional heterogeneity in vessel geometry between renal cortex, medulla, and hilum, showing how the distance between vessels provides a structural basis for renal oxygenation and hypoxia.

Conclusions

Through the application of HiP-CT, we have provided the first quantification of the human renal arterial network, with a resolution comparable to that of light microscopy yet at a scale several orders of magnitude larger than that of a renal punch biopsy. Our findings bridge anatomical scales, profiling blood vessels across the intact human kidney, with implications for renal physiology, biophysical modelling, and tissue engineering.

Systemic gene therapy with thymosin β4 alleviates glomerular injury in mice

Plasma ultrafiltration in the kidney occurs across glomerular capillaries, which are surrounded by epithelial cells called podocytes. Podocytes have a unique shape maintained by a complex cytoskeleton, which becomes disrupted in glomerular disease resulting in defective filtration and albuminuria. Lack of endogenous thymosin β4 (TB4), an actin sequestering peptide, exacerbates glomerular injury and disrupts the organisation of the podocyte actin cytoskeleton, however, the potential of exogenous TB4 therapy to improve podocyte injury is unknown. Here, we have used Adriamycin (ADR), a toxin which injures podocytes and damages the glomerular filtration barrier leading to albuminuria in mice. Through interrogating single-cell RNA-sequencing data of isolated glomeruli we demonstrate that ADR injury results in reduced levels of podocyte TB4. Administration of an adeno-associated viral vector encoding TB4 increased the circulating level of TB4 and prevented ADR-induced podocyte loss and albuminuria. ADR injury was associated with disorganisation of the podocyte actin cytoskeleton in vitro, which was ameliorated by treatment with exogenous TB4. Collectively, we propose that systemic gene therapy with TB4 prevents podocyte injury and maintains glomerular filtration via protection of the podocyte cytoskeleton thus presenting a novel treatment strategy for glomerular disease.

The timing of auditory sensory deficits in Norrie disease has implications for therapeutic intervention

Norrie disease is caused by mutation of the NDP gene, presenting as congenital blindness followed by later onset of hearing loss. Protecting patients from hearing loss is critical for maintaining their quality of life. This study aimed to understand the onset of pathology in cochlear structure and function. By investigating patients and juvenile Ndp-mutant mice, we elucidated the sequence of onset of physiological changes (in auditory brainstem responses, distortion product otoacoustic emissions, endocochlear potential, blood-labyrinth barrier integrity) and determined the cellular, histological, and ultrastructural events leading to hearing loss. We found that cochlear vascular pathology occurs earlier than previously reported and precedes sensorineural hearing loss. The work defines a disease mechanism whereby early malformation of the cochlear microvasculature precedes loss of vessel integrity and decline of endocochlear potential, leading to hearing loss and hair cell death while sparing spiral ganglion cells. This provides essential information on events defining the optimal therapeutic window and indicates that early intervention is needed. In an era of advancing gene therapy and small-molecule technologies, this study establishes Ndp-mutant mice as a platform to test such interventions and has important implications for understanding the progression of hearing loss in Norrie disease.

Imaging intact human organs with local resolution of cellular structures using hierarchical phase-contrast tomography

Imaging intact human organs from the organ to the cellular scale in three dimensions is a goal of biomedical imaging. To meet this challenge, we developed hierarchical phase-contrast tomography (HiP-CT), an X-ray phase propagation technique using the European Synchrotron Radiation Facility (ESRF)'s Extremely Brilliant Source (EBS). The spatial coherence of the ESRF-EBS combined with our beamline equipment, sample preparation and scanning developments enabled us to perform non-destructive, three-dimensional (3D) scans with hierarchically increasing resolution at any location in whole human organs. We applied HiP-CT to image five intact human organ types: brain, lung, heart, kidney and spleen. HiP-CT provided a structural overview of each whole organ followed by multiple higher-resolution volumes of interest, capturing organotypic functional units and certain individual specialized cells within intact human organs. We demonstrate the potential applications of HiP-CT through quantification and morphometry of glomeruli in an intact human kidney and identification of regional changes in the tissue architecture in a lung from a deceased donor with coronavirus disease 2019 (COVID-19).

Mechanisms and cell lineages in lymphatic vascular development

Lymphatic vessels have critical roles in both health and disease and their study is a rapidly evolving area of vascular biology. The consensus on how the first lymphatic vessels arise in the developing embryo has recently shifted. Originally, they were thought to solely derive by sprouting from veins. Since then, several studies have uncovered novel cellular mechanisms and a diversity of contributing cell lineages in the formation of organ lymphatic vasculature. Here, we review the key mechanisms and cell lineages contributing to lymphatic development, discuss the advantages and limitations of experimental techniques used for their study and highlight remaining knowledge gaps that require urgent attention. Emerging technologies should accelerate our understanding of how lymphatic vessels develop normally and how they contribute to disease.

The Biological Significance and Implications of Planar Cell Polarity for Nephrology

The orientation of cells in two-dimensional and three-dimensional space underpins how the kidney develops and responds to disease. The process by which cells orientate themselves within the plane of a tissue is termed planar cell polarity. In this Review, we discuss how planar cell polarity and the proteins that underpin it govern kidney organogenesis and pathology. The importance of planar cell polarity and its constituent proteins in multiple facets of kidney development is emphasised, including ureteric bud branching, tubular morphogenesis and nephron maturation. An overview is given of the relevance of planar cell polarity and its proteins for inherited human renal diseases, including congenital malformations with unknown aetiology and polycystic kidney disease. Finally, recent work is described outlining the influence of planar cell polarity proteins on glomerular diseases and highlight how this fundamental pathway could yield a new treatment paradigm for nephrology.

Multiscale three-dimensional imaging of intact human organs down to the cellular scale using hierarchical phase-contrast tomography

Human organs are complex, three-dimensional and multiscale systems. Spatially mapping the human body down through its hierarchy, from entire organs to their individual functional units and specialised cells, is a major obstacle to fully understanding health and disease. To meet this challenge, we developed hierarchical phase-contrast tomography (HiP-CT), an X-ray phase propagation technique utilising the European Synchrotron Radiation Facility's Extremely Brilliant Source: the world's first high-energy 4 th generation X-ray source. HiP-CT enabled three-dimensional and non-destructive imaging at near-micron resolution in soft tissues at one hundred thousand times the voxel size whilst maintaining the organ's structure. We applied HiP-CT to image five intact human parenchymal organs: brain, lung, heart, kidney and spleen. These were hierarchically assessed with HiP-CT, providing a structural overview of the whole organ alongside detail of the organ's individual functional units and cells. The potential applications of HiP-CT were demonstrated through quantification and morphometry of glomeruli in an intact human kidney, and identification of regional changes to the architecture of the air-tissue interface and alveolar morphology in the lung of a deceased COVID-19 patient. Overall, we show that HiP-CT is a powerful tool which can provide a comprehensive picture of structural information for whole intact human organs, encompassing precise details on functional units and their constituent cells to better understand human health and disease.

Beyond a Passive Conduit: Implications of Lymphatic Biology for Kidney Diseases

The kidney contains a network of lymphatic vessels that clear fluid, small molecules, and cells from the renal interstitium. Through modulating immune responses and via crosstalk with surrounding renal cells, lymphatic vessels have been implicated in the progression and maintenance of kidney disease. In this Review, we provide an overview of the development, structure, and function of lymphatic vessels in the healthy adult kidney. We then highlight the contributions of lymphatic vessels to multiple forms of renal pathology, emphasizing CKD, transplant rejection, and polycystic kidney disease and discuss strategies to target renal lymphatics using genetic and pharmacologic approaches. Overall, we argue the case for lymphatics playing a fundamental role in renal physiology and pathology and treatments modulating these vessels having therapeutic potential across the spectrum of kidney disease.

Endothelial-epithelial communication in polycystic kidney disease: Role of vascular endothelial growth factor signalling

Whereas targeting the cyst epithelium and its molecular machinery has been the prevailing clinical strategy for polycystic kidney disease, the endothelium, including blood vasculature and lymphatics, is emerging as an important player in this disorder. In this Review, we provide an overview of the structural and functional alterations to blood vasculature and lymphatic vessels in the polycystic kidney. We also discuss evidence for vascular endothelial growth factor signalling, otherwise critical for endothelial cell development and maintenance, as being a fundamental molecular pathway in polycystic kidney disease and a potential therapeutic target for modulating cyst expansion.

Tissue Clearing and Deep Imaging of the Kidney Using Confocal and Two-Photon Microscopy

Microscopic and macroscopic evaluation of biological tissues in three dimensions is becoming increasingly popular. This trend is coincident with the emergence of numerous tissue clearing strategies, and advancements in confocal and two-photon microscopy, enabling the study of intact organs and systems down to cellular and sub-cellular resolution. In this chapter, we describe a wholemount immunofluorescence technique for labeling structures in renal tissue. This technique combined with solvent-based tissue clearing and confocal imaging, with or without two-photon excitation, provides greater structural information than traditional sectioning and staining alone. Given the addition of paraffin embedding to our method, this hybrid protocol offers a powerful approach to combine confocal or two-photon findings with histological and further immunofluorescent analysis within the same tissue.

Spatiotemporal dynamics and heterogeneity of renal lymphatics in mammalian development and cystic kidney disease

Heterogeneity of lymphatic vessels during embryogenesis is critical for organ-specific lymphatic function. Little is known about lymphatics in the developing kidney, despite their established roles in pathology of the mature organ. We performed three-dimensional imaging to characterize lymphatic vessel formation in the mammalian embryonic kidney at single-cell resolution. In mouse, we visually and quantitatively assessed the development of kidney lymphatic vessels, remodeling from a ring-like anastomosis under the nascent renal pelvis; a site of VEGF-C expression, to form a patent vascular plexus. We identified a heterogenous population of lymphatic endothelial cell clusters in mouse and human embryonic kidneys. Exogenous VEGF-C expanded the lymphatic population in explanted mouse embryonic kidneys. Finally, we characterized complex kidney lymphatic abnormalities in a genetic mouse model of polycystic kidney disease. Our study provides novel insights into the development of kidney lymphatic vasculature; a system which likely has fundamental roles in renal development, physiology and disease.

In most organs in the body, fluid tends to build up in the spaces between cells, especially if the organs become inflamed. Each organ has a ‘waste disposal system’; a set of specialized tubes called lymphatic vessels, to clear away this excess fluid and keep a check on inflammation. Defects in these tubes have been linked to a wide range of diseases including heart attacks, obesity, dementia and cancer.

The kidneys are responsible for filtering blood and balancing many of the body’s chemical processes. Polycystic kidney disease (PKD) is the most common genetic kidney disorder and it results in cysts filled with fluid building up in the kidney. The growth of cysts in PKD may be due to a problem with the lymphatic vessels. However, compared to other organs, how lymphatic vessels first form within the kidney and what they do is not well understood.

Now, Jafree et al. have used three-dimensional imaging to study how lymphatic vessels form in the kidneys of mice and humans. The experiments showed that lymphatic vessels first appear when mouse kidneys are about half developed, and start to grow rapidly when the kidneys are thought to begin filtering blood. Clusters of cells that may help lymphatic vessels to grow were also found hidden deep within the kidneys of mouse embryos. Treating the kidneys with a factor that stimulates the growth of lymphatic vessels increased the numbers of these clusters. Jafree et al. found similar clusters of cells in human kidneys, suggesting that lymphatic vessels in the kidneys of different mammals may develop in the same way.

Further experiments showed that the lymphatic vessels of kidneys in mice with PKD become distorted early on in the disease, when cysts are still small and before the mice develop symptoms. In the future, identifying drugs that target kidney lymphatic vessels may lead to more effective treatments for patients with PKD and other kidney diseases.

Accuracy of the painDETECT screening questionnaire for detection of neuropathic components in hospital-based patients with orofacial pain: a prospective cohort study

Background

Better tools are required for the earlier identification and management of orofacial pain with different aetiologies. The painDETECT questionnaire is a patient-completed screening tool with utility for identification of neuropathic pain in a range of contexts. 254 patients, referred from primary care for management of orofacial pain and attending a secondary care centre, were prospectively recruited, and completed the painDETECT prior to consultation. The aim of this study was to determine the accuracy of the painDETECT to detect neuropathic components of orofacial pain, when compared to a reference standard of clinical diagnosis by experienced physicians, in a cohort of hospital-based patients.

Results

For the 251 patients included in the analysis, the painDETECT had a modest ability to detect neuropathic components of orofacial pain (AUROC, 0.63; 95% CI, 0.58–0.70; p = 0.001). Patients with orofacial pain diagnoses associated with neuropathic components had higher painDETECT scores than those with non-neuropathic components. However, the painDETECT was weaker at distinguishing patients with mixed pain types, and multiple diagnoses were associated with poor accuracy of the painDETECT.

Conclusion

In secondary care settings, the painDETECT performed modestly at identifying neuropathic components, and underestimates the complexity of orofacial pain in its mixed presentations and with multiple diagnoses. Prior to clinical applications or research use, the painDETECT and other generic screening tools must be adapted and revalidated for orofacial pain patients, and separately in primary care, where orofacial pain is considerably less common.

Electronic supplementary material

The online version of this article (10.1186/s10194-018-0932-5) contains supplementary material, which is available to authorized users.

Describing the first 2000 registrations to the Research Registry®: A study protocol

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Research Registry offers a venue for the registration of research involving human participants;

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It is now imperative to register all studies (not just trials) involving human participants;

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This protocol outlines the analysis to examine the first 2000 registrations received.

Background

In 2013, the Declaration of Helsinki was updated and required the registration of all research studies involving human participants. Prior registries focussed on the registration of clinical trials and systematic reviews, and we estimate that only 10% of observational research is registered in a publically accessible registry. The Research Registry® was established to provide a venue of registration for any study, prospectively or retrospectively, involving human participants. This protocol describes the analysis for the first 2000 registrations received to the Research Registry®.

Methods and analysis

Data for each registration to the Research Registry® (www.researchregistry.com), adapted from the World Health Organisation minimum data set, has been collected since the launch of the registry in 2015. A weekly curation process ensures that inappropriate registrations, such as duplicate studies or those not involving human participants, are removed from the registry. We will present the characteristics of the first 2000 registrations and how they have changed overtime. A quality score will be calculated for each registration by two independent teams, and inter-rater reliability will be calculated. Funding sources of work registered will also be presented. This process will also be performed for the systematic review portion of the registry (‘The Review Registry’), which will be considered separately.

Ethics and dissemination

Ethical approval is not required for this study as it involves no human participants. The findings will be presented at international conferences and published in a peer reviewed journal.

Surveying opinions of 149 registrants to the Research Registry: Awareness of and attitudes towards research registration

BACKGROUND

Research registration is an important ethical principle in the Declaration of Helsinki, however, progress to increase registration has been slow. Understanding the attitudes of users towards registries may provide insights into increase research registration. In this survey-based study, we sought to gain insight from users of a single global research registry, the Research Registry^® (www.researchregistry.com).

METHODS

A Google Forms survey was created and emailed to all users of the Research Registry^® (n = 1432). Multiple choice and free-text answers were analyzed using descriptive statistics and thematic analysis respectively.

RESULTS

From 925 contactable registrations, 149 (16.1%) completed the survey. The most commonly registered study type was retrospective cohort (32.2%). 23 registrations (15.4%) were made during the planning or conception of the study, whereas 67 (45.0%) registered at the time of journal submission, or during the peer review process. Of those that declared whether they had performed unregistered research or not, 51 (45.5%) participants had previously performed unregistered research. Registrants were most commonly made aware of the Research Registry^® through submission to the International Journal of Surgery (IJS) family of journals (n = 57, 47.5%). Survey participants identified the most important features of registration to be its convenience, including the ease, time and cost of registration. Thematic analysis revealed the most common motive for registration to be as a mandatory requirement of journal submission, and that registration can be improved by simplification of the registration process.

CONCLUSION

Registries must focus on engaging their network of users to ensure that research registration is a dynamic process. They need to adopt a user-centered and agile approach to their development, with a strong focus on "customer service". Moreover, by working in partnership with journals, it is possible to improve compliance with registration.

The First 500 Registrations to the Research Registry®: Advancing Registration of Under-Registered Study Types

Introduction

The Declaration of Helsinki 2013 encourages the registration of all research studies involving human participants. However, emphasis has been placed on prospective clinical trials, and it is estimated that only 10% of observational studies are registered. In response, Research Registry^®1 was launched in February 2015; a retrospectively curated registry that is free and easy to use. Research Registry^® enables prospective or retrospective registration of studies, including those study types that cannot be registered on existing registries. In this study, we describe the first 500 registrations on Research Registry^®.

Methods

Since the launch of Research Registry^® in February 2015, data of registrations have been collected, including type of studies registered, country of origin, and data curation activity. Inappropriate registrations, such as duplicates, were identified by the data curation process. These were removed from the database or modified as required. A quality score was assigned for each registration, based on Sir Austin Bradford Hill’s criteria on what research studies should convey. Changes in quality scores over time were assessed.

Results

A total of 500 studies were registered on Research Registry^® from February 2015 to October 2015, with a total of 1.7 million patients enrolled. The most common study types were retrospective cohort studies (37.2%), case series (14.8%), and first-in-man case reports (10.4%). Registrations were received from 57 different countries; the most submissions were received from Turkey, followed by China and the United Kingdom. Retrospective data curation identified 80 studies that were initially registered as the incorrect study type, and were subsequently correct. The Kruskal–Wallis test identified a significant improvement in quality scores for registrations from February 2015 to October 2015 (p < 0.0001).

Conclusions

Since its conception in February 2015, Research Registry^® has established itself as a new registry that is free, easy to use, and enables the registration of various study types, including observational studies and first-in-man case reports. Going forward, our plan is to continue developing Research Registry^® in line with user feedback and usability studies. We plan to further promote Research Registry^® to advance the cause of registration of research, to increase compliance with the Declaration of Helsinki 2013.

An assessment of the compliance of systematic review articles published in craniofacial surgery with the PRISMA statement guidelines: A systematic review

CONTEXT

Systematic review evidence is increasing within craniofacial surgery. Compliance with recognised reporting guidelines for systematic review evidence has not been assessed.

OBJECTIVE

To assess the compliance of systematic reviews published in craniofacial journals with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting criteria.

DATA SOURCES, SEARCH TERMS AND STUDY SELECTION

Thomson Reuters impact factor was used to identify three top craniofacial journals. A search for all systematic review articles published in these journals from 1st May 2010 to 30th April 2015 was conducted using MEDLINE PubMed.

DATA EXTRACTION

Two independent researchers assessed each study for inclusion and performed the data extraction. Data included the article reference information; the pathology and interventions examined and compliance of each review article with the PRISMA checklist.

DATA SYNTHESIS AND RESULTS

97 studies were returned by the search. 62 studies proceeded to data extraction. The mean percentage of applicable PRISMA items that were met across all studies was 72.5% (range 28.6-96.2%). The area of poorest compliance was with the declaration of a study protocol (19.4% of studies). Only 37.1% of studies declared their source of funding.

CONCLUSIONS

Compliance of systematic review articles within craniofacial surgery with areas of the PRISMA checklist could be improved.

How to approach supervisors for research opportunities

In this article, we use our experiences to provide tips for contacting potential supervisors, what to expect from them and how to approach them for research opportunities. With appropriate planning, you will be surprised by the number of prestigious academics who would be willing for you to join their research group, and to get you involved in a research project.

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Contacting potential supervisors is a time consuming process that requires a great deal of organisation.

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Be proactive in your approach.

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The first email is very important, as is the meeting that may follow.

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Choose carefully and take a holistic approach when choosing your supervisor to ensure you have the best possible research experience.