Harmonizing the Generation and Pre-publication Stewardship of FAIR Image data

Together with the molecular knowledge of genes and proteins, biological images promise to significantly enhance the scientific understanding of complex cellular systems and to advance predictive and personalized therapeutic products for human health. For this potential to be realized, quality-assured image data must be shared among labs at a global scale to be compared, pooled, and reanalyzed, thus unleashing untold potential beyond the original purpose for which the data was generated. There are two broad sets of requirements to enable image data sharing in the life sciences. One set of requirements is articulated in the companion White Paper entitled "Enabling Global Image Data Sharing in the Life Sciences," which is published in parallel and addresses the need to build the cyberinfrastructure for sharing the digital array data (arXiv:2401.13023 [q-bio.OT], https://doi.org/10.48550/arXiv.2401.13023). In this White Paper, we detail a broad set of requirements, which involves collecting, managing, presenting, and propagating contextual information essential to assess the quality, understand the content, interpret the scientific implications, and reuse image data in the context of the experimental details. We start by providing an overview of the main lessons learned to date through international community activities, which have recently made considerable progress toward generating community standard practices for imaging Quality Control (QC) and metadata. We then provide a clear set of recommendations for amplifying this work. The driving goal is to address remaining challenges, and democratize access to common practices and tools for a spectrum of biomedical researchers, regardless of their expertise, access to resources, and geographical location.

Spatial transcriptomics reveals novel genes during the remodelling of the embryonic human arterial valves

Abnormalities of the arterial valves, including bicuspid aortic valve (BAV) are amongst the most common congenital defects and are a significant cause of morbidity as well as predisposition to disease in later life. Despite this, and compounded by their small size and relative inaccessibility, there is still much to understand about how the arterial valves form and remodel during embryogenesis, both at the morphological and genetic level. Here we set out to address this in human embryos, using Spatial Transcriptomics (ST). We show that ST can be used to investigate the transcriptome of the developing arterial valves, circumventing the problems of accurately dissecting out these tiny structures from the developing embryo. We show that the transcriptome of CS16 and CS19 arterial valves overlap considerably, despite being several days apart in terms of human gestation, and that expression data confirm that the great majority of the most differentially expressed genes are valve-specific. Moreover, we show that the transcriptome of the human arterial valves overlaps with that of mouse atrioventricular valves from a range of gestations, validating our dataset but also highlighting novel genes, including four that are not found in the mouse genome and have not previously been linked to valve development. Importantly, our data suggests that valve transcriptomes are under-represented when using commonly used databases to filter for genes important in cardiac development; this means that causative variants in valve-related genes may be excluded during filtering for genomic data analyses for, for example, BAV. Finally, we highlight "novel" pathways that likely play important roles in arterial valve development, showing that mouse knockouts of RBP1 have arterial valve defects. Thus, this study has confirmed the utility of ST for studies of the developing heart valves and broadens our knowledge of the genes and signalling pathways important in human valve development.

Detecting respiratory chain defects in osteoblasts from osteoarthritic patients using imaging mass cytometry

Osteoporosis is a skeletal disease which is characterised by reduced bone mass and microarchitecture, with a subsequent loss of strength that predisposes to fragility and risk of fractures. The pathogenesis of falling bone mineral density, ultimately leading to a diagnosis of osteoporosis is incompletely understood but the disease is currently thought to be multifactorial. Humans are known to accumulate mitochondrial mutations and respiratory chain deficiency with age and mounting evidence suggests that this may indeed be the overarching cause intrinsic to the changing phenotype in advancing age and age-related disease. Mitochondrial mutations are detectable from the age of about 30 years onwards. Mitochondria contain their own genome which encodes 13 essential mitochondrial proteins and accumulates somatic variants at up to 10 times the rate of the nuclear genome. Once the concentration of any pathogenic mitochondrial genome variant exceeds a threshold, respiratory chain deficiency and cellular dysfunction occur. The Polg^D257A/D257A mouse model is a knock-in mutant that expresses a proof-reading-deficient version of PolgA, a nuclear encoded subunit of mtDNA polymerase. These mice are a useful model of age-related accumulation of mtDNA mutations in humans since their defective proof-reading mechanism leads to a mitochondrial DNA mutation rate 3-5 times higher than in wild-type mice. These mice showed enhanced levels of age-related osteoporosis along with respiratory chain deficiency in osteoblasts. To explore whether respiratory chain deficiency is also seen in human osteoblasts, we developed a protocol and analysis framework for imaging mass cytometry in bone tissue sections to analyse osteoblasts in situ. By comparing bone tissue sampled at one timepoint from femoral neck of 10 older healthy volunteers aged 40-85 with samples from young patients aged 1-19, we have identified complex I defect in osteoblasts from 6 out of 10 older volunteers, complex II defect in 2 out of 10 older volunteers, complex IV defect in 1 out of 10 older volunteers and complex V defect in 4 out of 10 older volunteers. These observations are consistent with findings from the Polg^D257A/D257A mouse model and suggest that respiratory chain deficiency, as a consequence of the accumulation of age-related pathogenic mitochondrial DNA mutations, may play a significant role in the pathogenesis of human age-related osteoporosis.

Towards community-driven metadata standards for light microscopy: tiered specifications extending the OME model

Rigorous record-keeping and quality control are required to ensure the quality, reproducibility and value of imaging data. The 4DN Initiative and BINA here propose light Microscopy Metadata specifications that extend the OME data model, scale with experimental intent and complexity, and make it possible for scientists to create comprehensive records of imaging experiments.

QUAREP-LiMi: A community-driven initiative to establish guidelines for quality assessment and reproducibility for instruments and images in light microscopy

A modern day light microscope has evolved from a tool devoted to making primarily empirical observations to what is now a sophisticated , quantitative device that is an integral part of both physical and life science research. Nowadays, microscopes are found in nearly every experimental laboratory. However, despite their prevalent use in capturing and quantifying scientific phenomena, neither a thorough understanding of the principles underlying quantitative imaging techniques nor appropriate knowledge of how to calibrate, operate and maintain microscopes can be taken for granted. This is clearly demonstrated by the well-documented and widespread difficulties that are routinely encountered in evaluating acquired data and reproducing scientific experiments. Indeed, studies have shown that more than 70% of researchers have tried and failed to repeat another scientist's experiments, while more than half have even failed to reproduce their own experiments. One factor behind the reproducibility crisis of experiments published in scientific journals is the frequent underreporting of imaging methods caused by a lack of awareness and/or a lack of knowledge of the applied technique. Whereas quality control procedures for some methods used in biomedical research, such as genomics (e.g. DNA sequencing, RNA-seq) or cytometry, have been introduced (e.g. ENCODE), this issue has not been tackled for optical microscopy instrumentation and images. Although many calibration standards and protocols have been published, there is a lack of awareness and agreement on common standards and guidelines for quality assessment and reproducibility. In April 2020, the QUality Assessment and REProducibility for instruments and images in Light Microscopy (QUAREP-LiMi) initiative was formed. This initiative comprises imaging scientists from academia and industry who share a common interest in achieving a better understanding of the performance and limitations of microscopes and improved quality control (QC) in light microscopy. The ultimate goal of the QUAREP-LiMi initiative is to establish a set of common QC standards, guidelines, metadata models and tools, including detailed protocols, with the ultimate aim of improving reproducible advances in scientific research. This White Paper (1) summarizes the major obstacles identified in the field that motivated the launch of the QUAREP-LiMi initiative; (2) identifies the urgent need to address these obstacles in a grassroots manner, through a community of stakeholders including, researchers, imaging scientists, bioimage analysts, bioimage informatics developers, corporate partners, funding agencies, standards organizations, scientific publishers and observers of such; (3) outlines the current actions of the QUAREP-LiMi initiative and (4) proposes future steps that can be taken to improve the dissemination and acceptance of the proposed guidelines to manage QC. To summarize, the principal goal of the QUAREP-LiMi initiative is to improve the overall quality and reproducibility of light microscope image data by introducing broadly accepted standard practices and accurately captured image data metrics.

Micro-Meta App: an interactive tool for collecting microscopy metadata based on community specifications

For quality, interpretation, reproducibility and sharing value, microscopy images should be accompanied by detailed descriptions of the conditions that were used to produce them. Micro-Meta App is an intuitive, highly interoperable, open-source software tool that was developed in the context of the 4D Nucleome (4DN) consortium and is designed to facilitate the extraction and collection of relevant microscopy metadata as specified by the recent 4DN-BINA-OME tiered-system of Microscopy Metadata specifications. In addition to substantially lowering the burden of quality assurance, the visual nature of Micro-Meta App makes it particularly suited for training purposes.

Photo-isomerization of the Cyanine Dye Alexa-Fluor 647 (AF-647) in the Context of dSTORM Super-Resolution Microscopy

Cyanine dyes, as used in super-resolution fluorescence microscopy, undergo light-induced "blinking", enabling localization of fluorophores with spatial resolution beyond the optical diffraction limit. Despite a plethora of studies, the molecular origins of this blinking are not well understood. Here, we examine the photophysical properties of a bio-conjugate cyanine dye (AF-647), used extensively in dSTORM imaging. In the absence of a potent sacrificial reductant, light-induced electron transfer and intermediates formed via the metastable, triplet excited state are considered unlikely to play a significant role in the blinking events. Instead, it is found that, under conditions appropriate to dSTORM microscopy, AF-647 undergoes reversible photo-induced isomerization to at least two long-lived dark species. These photo-isomers are characterized spectroscopically and their interconversion probed by computational means. The first-formed isomer is light sensitive and transforms to a longer-lived species in modest yield that could be involved in dSTORM related blinking. Permanent photobleaching of AF-647 occurs with very low quantum yield and is partially suppressed by the anaerobic redox buffer.

Dynamics of single human embryonic stem cells and their pairs: a quantitative analysis

Numerous biological approaches are available to characterise the mechanisms which govern the formation of human embryonic stem cell (hESC) colonies. To understand how the kinematics of single and pairs of hESCs impact colony formation, we study their mobility characteristics using time-lapse imaging. We perform a detailed statistical analysis of their speed, survival, directionality, distance travelled and diffusivity. We confirm that single and pairs of cells migrate as a diffusive random walk for at least 7 hours of evolution. We show that the presence of Cell Tracer significantly reduces hESC mobility. Our results open the path to employ the theoretical framework of the diffusive random walk for the prognostic modelling and optimisation of the growth of hESC colonies. Indeed, we employ this random walk model to estimate the seeding density required to minimise the occurrence of hESC colonies arising from more than one founder cell and the minimal cell number needed for successful colony formation. Our prognostic model can be extended to investigate the kinematic behaviour of somatic cells emerging from hESC differentiation and to enable its wide application in phenotyping of pluripotent stem cells for large scale stem cell culture expansion and differentiation platforms.

Molecular determinants of transport function in zebrafish Slc34a Na-phosphate transporters

The epithelial Na⁺-coupled phosphate cotransporter family Slc34a (NaPi-II) is well conserved in vertebrates and plays an essential role in maintaining whole body levels of inorganic phosphate (P_i). A three-dimensional model of the transport protein has recently been proposed with defined substrate coordination sites. Zebrafish express two NaPi-II isoforms with high sequence identity but a 10-fold different apparent K_m for P_i ([Formula: see text]). We took advantage of the two zebrafish isoforms to investigate the contribution of specific amino acids to P_i coordination and transport. Mutations were introduced to gradually transform the low-affinity isoform into a high-affinity transporter. The constructs were expressed in Xenopus laevis oocytes and functionally characterized. Becaue the cotransport of P_i and Na involves multiple steps that could all influence [Formula: see text], we performed a detailed functional analysis to characterize the impact of the mutations on particular steps of the transport cycle. We used varying concentrations of the substrates P_i and its slightly larger analog, arsenate, as well as the cosubstrate, Na⁺ Moreover, electrogenic kinetics were performed to assess intramolecular movements of the transporter. All of the mutations were found to affect multiple transport steps, which suggested that the altered amino acids induced subtle structural changes rather than coordinating P_i directly. The likely positions of the critical residues were mapped to the model of human Slc34a, and their localization in relation to the proposed substrate binding pockets concurs well with the observed functional data.

Development of passive CLARITY and immunofluorescent labelling of multiple proteins in human cerebellum: understanding mechanisms of neurodegeneration in mitochondrial disease

CLARITY enables immunofluorescent labelling and imaging of large volumes of tissue to provide a better insight into the three dimensional relationship between cellular morphology and spatial interactions between different cell types. In the current study, we optimise passive CLARITY and immunofluorescent labelling of neurons and mitochondrial proteins in mouse and human brain tissues to gain further insights into mechanisms of neurodegeneration occurring in mitochondrial disease. This is the first study to utilise human cerebellum fixed in paraformaldehyde and cryoprotected in conjunction with formalin-fixed tissues opening up further avenues for use of archived tissue. We optimised hydrogel-embedding and passive clearance of lipids from both mouse (n = 5) and human (n = 9) cerebellum as well as developing an immunofluorescent protocol that consistently labels different neuronal domains as well as blood vessels. In addition to visualising large structures, we were able to visualise mitochondrial proteins in passively cleared tissues to reveal respiratory chain deficiency associated with mitochondrial disease. We also demonstrate multiple use of tissues by stripping antibodies and re-probing the cerebellum. This technique allows interrogation of large volumes intact brain samples for better understanding of the complex pathological changes taking place in mitochondrial disease.

Investigating complex I deficiency in Purkinje cells and synapses in patients with mitochondrial disease

Aims

Cerebellar ataxia is common in patients with mitochondrial disease, and despite previous neuropathological investigations demonstrating vulnerability of the olivocerebellar pathway in patients with mitochondrial disease, the exact neurodegenerative mechanisms are still not clear. We use quantitative quadruple immunofluorescence to enable precise quantification of mitochondrial respiratory chain protein expression in Purkinje cell bodies and their synaptic terminals in the dentate nucleus.

Methods

We investigated NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 13 protein expression in 12 clinically and genetically defined patients with mitochondrial disease and ataxia and 10 age‐matched controls. Molecular genetic analysis was performed to determine heteroplasmy levels of mutated mitochondrial DNA in Purkinje cell bodies and inhibitory synapses.

Results

Our data reveal that complex I deficiency is present in both Purkinje cell bodies and their inhibitory synapses which surround dentate nucleus neurons. Inhibitory synapses are fewer and enlarged in patients which could represent a compensatory mechanism. Mitochondrial DNA heteroplasmy demonstrated similarly high levels of mutated mitochondrial DNA in cell bodies and synapses.

Conclusions

This is the first study to use a validated quantitative immunofluorescence technique to determine complex I expression in neurons and presynaptic terminals, evaluating the distribution of respiratory chain deficiencies and assessing the degree of morphological abnormalities affecting synapses. Respiratory chain deficiencies detected in Purkinje cell bodies and their synapses and structural synaptic changes are likely to contribute to altered cerebellar circuitry and progression of ataxia.

Extensive respiratory chain defects in inhibitory interneurones in patients with mitochondrial disease

Aims

Mitochondrial disorders are among the most frequently inherited cause of neurological disease and arise due to mutations in mitochondrial or nuclear DNA. Currently, we do not understand the specific involvement of certain brain regions or selective neuronal vulnerability in mitochondrial disease. Recent studies suggest γ‐aminobutyric acid (GABA)‐ergic interneurones are particularly susceptible to respiratory chain dysfunction. In this neuropathological study, we assess the impact of mitochondrial DNA defects on inhibitory interneurones in patients with mitochondrial disease.

Methods

Histochemical, immunohistochemical and immunofluorescent assays were performed on post‐mortem brain tissue from 10 patients and 10 age‐matched control individuals. We applied a quantitative immunofluorescent method to interrogate complex I and IV protein expression in mitochondria within GABAergic interneurone populations in the frontal, temporal and occipital cortices. We also evaluated the density of inhibitory interneurones in serial sections to determine if cell loss was occurring.

Results

We observed significant, global reductions in complex I expression within GABAergic interneurones in frontal, temporal and occipital cortices in the majority of patients. While complex IV expression is more variable, there is reduced expression in patients harbouring m.8344A>G point mutations and POLG mutations. In addition to the severe respiratory chain deficiencies observed in remaining interneurones, quantification of GABAergic cell density showed a dramatic reduction in cell density suggesting interneurone loss.

Conclusions

We propose that the combined loss of interneurones and severe respiratory deficiency in remaining interneurones contributes to impaired neuronal network oscillations and could underlie development of neurological deficits, such as cognitive impairment and epilepsy, in mitochondrial disease.

Polypoidal choroidal vasculopathy: an angiographic discussion

The understanding of polypoidal choroidal vasculopathy has evolved rapidly in the past three decades. The hallmark of the disease is the presence of typical hyperfluorescent nodules in the early phase of indocyanine green angiography. Although the classical clinical presentation is recurrent serosanguinous detachment of the retinal pigment epithelium, it may present with clinical features indistinguishable from exudative age-related macular degeneration secondary to choroidal neovascularization. Some cases may present initially with submacular haemorrhage, but later with features of exudative age-related macular degeneration. Studying the associated network of vessels using confocal scanning laser ophthalmoscopy indocyanine green dynamic angiography revealed in many cases feeder vessels, branching pattern, and leakage similar to choroidal neovascularization. Owing to the overlap of clinical and angiographic features, it may be considered as a vascular subtype of exudative age-related macular degeneration. However, having seemingly better natural history, better response to photodynamic therapy, and incomplete response to anti-vascular endothelial growth factor therapy suggests that it should be studied as a separate entity from choroidal neovascularization. Combining angio-occlusion of the polyps using photodynamic therapy and anti-permeability effect of anti-vascular endothelial growth factor therapy on the branching vascular network may provide a synergistic effect. We await the result of EVEREST trial, a multi-centre randomized controlled trial comparing photodynamic therapy, with or without ranibizumab, with ranibizumab monotherapy.

Knowledge of visual experience during cataract surgery under local anaesthesia: a nationwide survey of UK ophthalmologists

AIM

To evaluate the knowledge and practices of UK ophthalmologists regarding patients' subjective visual experience during cataract surgery under local anaesthesia.

METHODS

A nationwide postal survey was conducted on UK ophthalmologists using a standardised questionnaire.

RESULTS

The proportion of surgeons who operated under regional anaesthesia who thought that patients could experience the following visual sensations were: no light perception (54%); light perception (95%); one or more colours (93%); flashes of light (81%); movement (87%); instruments (61%); surgeon's hands or fingers (53%); surgeon (43%); and changes in light brightness (88%). Fifty-eight per cent of them thought that patients might be frightened by this, and 77% thought that preoperative counselling could help alleviate this fear. The proportion of surgeons who operated under topical anaesthesia who thought that patients could experience the following visual sensations were: no light perception (10%); light perception (94%); one or more colours (97%); flashes of light (86%); movement (96%); instruments (81%); surgeon's hands or fingers (65%); surgeon (51%); changes in light brightness (95%). Fifty-nine per cent of them thought that patients might be frightened by this, and 80% thought that preoperative counselling could help alleviate this fear.

CONCLUSION

Most UK surgeons believed that during cataract surgery under local anaesthesia, patients might experience various visual sensations which could cause fear and that such fear could be alleviated by preoperative counselling.

[Cogan syndrome or sarcoidosis?]

INTRODUCTION

The Cogan's syndrome is characterized by the association of vestibulo-auditory dysfunction, non syphilitic interstitial keratitis or another significant inflammatory eye lesion. Some authors consider this disease as a vasculitis, because it is frequently associated with systemic manifestations. Based on Cogan's diagnostic criteria, Cogan's syndrome may be part of other systemic diseases, as polyarteritis nodosa or Wegener's granulomatosis.

EXEGESIS

We report the case of a patient who presented with a Cogan's syndrome and developed further sarcoidosis.

CONCLUSION

If Cogan's syndrome is characterized as systemic disease because of its association with aortitis or other vasculitis, on the other hand, clinical presentation may be part of many other systemic diseases.