Compensatory growth and recovery of cartilage cytoarchitecture after transient cell death in fetal mouse limbs.

A major question in developmental and regenerative biology is how organ size and architecture are controlled by progenitor cells. While limb bones exhibit catch-up growth (recovery of a normal growth trajectory after transient developmental perturbation), it is unclear how this emerges from the behaviour of chondroprogenitors, the cells sustaining the cartilage anlagen that are progressively replaced by bone. Here we show that transient sparse cell death in the mouse fetal cartilage is repaired postnatally, via a two-step process. During injury, progression of chondroprogenitors towards more differentiated states is delayed, leading to altered cartilage cytoarchitecture and impaired bone growth. Then, once cell death is over, chondroprogenitor differentiation is accelerated and cartilage structure recovered, including partial rescue of bone growth. At the molecular level, ectopic activation of mTORC1 correlates with, and is necessary for, part of the recovery, revealing a specific candidate to be explored during normal growth and in future therapies.

Does surgical companionship modify the learning curve for fenestrated and branched endovascular aortic repair?

OBJECTIVES: The goal of this study was to describe the learning curve of an operator trained in an aortic centre during the first years of performing fenestrated/branched endovascular aortic repairs independently. METHODS: Patients electively treated with fenestrated/branched stent grafts from January 2013 to March 2020 were included retrospectively. Groups were defined according to the treating operator: experienced operator (group 1), early-career operator (group 2) or both during a 14-month surgical companionship period (group 3). The early-career operator's learning curve was assessed using a cumulative sum analysis. A composite criterion including technical failure, death and/or any major adverse event was evaluated in a logistic regression model. RESULTS: Overall, 437 patients (93% male; median 69 (63, 77) years old) were included (group 1: n = 240; group 2: n = 173; group 3: n = 24). There were significantly more extended thoraco-abdominal aneurysms (extent I, II, III and V) in group 1 compared to group 2 [n = 68 (28%) vs 19 (11%), P<0.001]. The technical success rate was 94% (P=0.874). The 30-day mortality and/or major adverse event rates in juxta-/pararenal aneurysms or extent IV thoraco-abdominal aneurysms were 8.1% in group 1 and 9.7% in group 2 (P = 0.612), whereas they were 10% (group 1) and 0 (group 2) for extended thoraco-abdominal aneurysms (P=0.339). The adjusted cumulative sum analysis highlighted satisfactory results from the beginning of the experience. The operator's experience was not predictive of the composite criterion [adjusted OR 0.77; 95% (0.42, 1.40); P=0.40]. CONCLUSIONS: This study demonstrated favourable outcomes in patients treated with a fenestrated/branched aortic stent graft performed by an early-career operator trained in a high-volume centre from the beginning of independent practice.

Look who's TORking: mTOR-mediated integration of cell status and external signals during limb development and endochondral bone growth.

The balance of cell proliferation and size is key for the control of organ development and repair. Moreover, this balance has to be coordinated within tissues and between tissues to achieve robustness in the organ's pattern and size. The tetrapod limb has been used to study these topics during development and repair, and several conserved pathways have emerged. Among them, mechanistic target of rapamycin (mTOR) signaling, despite being active in several cell types and developmental stages, is one of the least understood in limb development, perhaps because of its multiple potential roles and interactions with other pathways. In the body of this review, we have collated and integrated what is known about the role of mTOR signaling in three aspects of tetrapod limb development: 1) limb outgrowth; 2) chondrocyte differentiation after mesenchymal condensation and 3) endochondral ossification-driven longitudinal bone growth. We conclude that, given its ability to interact with the most common signaling pathways, its presence in multiple cell types, and its ability to influence cell proliferation, size and differentiation, the mTOR pathway is a critical integrator of external stimuli and internal status, coordinating developmental transitions as complex as those taking place during limb development. This suggests that the study of the signaling pathways and transcription factors involved in limb patterning, morphogenesis and growth could benefit from probing the interaction of these pathways with mTOR components.

A New Pipeline to Automatically Segment and Semi-Automatically Measure Bone Length on 3D Models Obtained by Computed Tomography.

The characterization of developmental phenotypes often relies on the accurate linear measurement of structures that are small and require laborious preparation. This is tedious and prone to errors, especially when repeated for the multiple replicates that are required for statistical analysis, or when multiple distinct structures have to be analyzed. To address this issue, we have developed a pipeline for characterization of long-bone length using X-ray microtomography (XMT) scans. The pipeline involves semi-automated algorithms for automatic thresholding and fast interactive isolation and 3D-model generation of the main limb bones, using either the open-source ImageJ plugin BoneJ or the commercial Mimics Innovation Suite package. The tests showed the appropriate combination of scanning conditions and analysis parameters yields fast and comparable length results, highly correlated with the measurements obtained via ex vivo skeletal preparations. Moreover, since XMT is not destructive, the samples can be used afterward for histology or other applications. Our new pipelines will help developmental biologists and evolutionary researchers to achieve fast, reproducible and non-destructive length measurement of bone samples from multiple animal species.

Scientific report on the analysis of the 2-year compulsory intensified monitoring of atypical scrapie.

The European Commission asked EFSA whether the scientific data on the 2-year intensified monitoring in atypical scrapie (AS) outbreaks (2013-2020) provide any evidence on the contagiousness of AS, and whether they added any new knowledge on the epidemiology of AS. An ad hoc data set from intensified monitoring in 22 countries with index case/s of AS in sheep and/or goats (742 flocks from 20 countries, 76 herds from 11 countries) was analysed. No secondary cases were confirmed in goat herds, while 35 secondary cases were confirmed in 28 sheep flocks from eight countries. The results of the calculated design prevalence and of a model simulation indicated that the intensified monitoring had limited ability to detect AS, with no difference between countries with or without secondary cases. A regression model showed an increased, but not statistically significant, prevalence (adjusted by surveillance stream) of secondary cases in infected flocks compared with that of index cases in the non-infected flocks (general population). A simulation model of within-flock transmission, comparing a contagious (i.e. transmissible between animals under natural conditions) with a non-contagious scenario, produced a better fit of the observed data with the non-contagious scenario, in which each sheep in a flock had the same probability of developing AS in the first year of life. Based on the analyses performed, and considering uncertainties and data limitations, it was concluded that there is no new evidence that AS can be transmitted between animals under natural conditions, and it is considered more likely (subjective probability range 50-66%) that AS is a non-contagious, rather than a contagious disease. The analysis of the data of the EU intensified monitoring in atypical scrapie infected flocks/herds confirmed some of the known epidemiological features of AS but identified that major knowledge gaps still remain.

An International Comparison of the Management of Gastrointestinal Surgical Emergencies in Octogenarians-England Versus United States: A National Population-based Cohort Study.

OBJECTIVE: To compare the United States and England for the utilization of surgical intervention and in-hospital mortality from 5 gastrointestinal emergencies in octogenarians. BACKGROUND: The proportion of older adults is growing and will represent a substantial challenge to clinicians in the next decade. METHODS: Between 2006 and 2012, the rate of surgical intervention and in-hospital mortality for 5 index conditions for octogenarians were compared between the United States and England: appendicitis, incarcerated/strangulated abdominal hernia, perforation of esophagus, small or large bowel, and peptic ulcer. Univariate and multivariate analyses were performed to adjust for underlying differences in patient demographics. RESULTS: Thirty-two thousand one hundred fifty-one admissions of octogenarians in England for 5 index surgical emergencies were compared with 162,142 admissions in the USA.Surgical intervention was significantly more common in the USA than in England for all 5 conditions: appendicitis [odds ratio (OR) 4.63, 95% confidence interval (95% CI) 4.21-5.09], abdominal hernia (OR 2.06, 95% CI 1.97-2.15), perforated esophagus (OR 1.71, 95% CI 1.31-2.24), small and large bowel perforation (OR 4.33, 95% CI 4.12-4.56), and peptic ulcer perforation (OR 4.63, 95% CI 4.27-5.02). In-hospital mortality was significantly more common in England than in the USA for all 5 conditions: appendicitis (OR 3.22, 95% CI 2.73-3.78), abdominal hernia (OR 3.49, 95% CI 3.29-3.70), perforated esophagus (OR 4.06, 95% CI 3.03-5.44), small and large bowel perforation (OR 6.97, 95% CI 6.60-7.37), and peptic ulcer perforation (OR 3.67, 95% CI 3.40-3.96). CONCLUSION: Surgery is used less commonly in England for emergency gastrointestinal conditions in octogenarians, which may be associated with a high rate of in-hospital mortality from these conditions compared with the USA.

Integrating levels of bone growth control: From stem cells to body proportions.

The study of the mechanisms controlling organ size during development and regeneration is critical to understanding how complex life arises from cooperating single cells. Long bones are powerful models in this regard, as their size depends on a scaffold made from another tissue (cartilage, composed of chondrocytes), and both tissues interact during the growth period. Investigating long bone growth offers a valuable window into the processes that integrate internal and external cues to yield finely controlled size of organs. Within the cellular and molecular pathways that control bone growth, the regulation of stem-cell renewal, along with amplification and differentiation of their progeny, are key to understanding normal and perturbed long-bone development. The phenomenon of "catch-up" growth-where cellular hyperproliferation occurs following injury to restore a normal growth trajectory-reveals key aspects of this regulation, such as the fact that bone growth is target-seeking. The control mechanisms that lead to this behavior are either bottom-up or top-down, and the interaction between these modes is likely critical to achieve a highly nuanced, yet flexible, degree of control. The role of cartilage-intrinsic mechanisms has been well studied, establishing a very solid groundwork for this field. However, addressing the unanswered questions of bone growth arguably requires new hypotheses and approaches. Future research could for example address to what extent extrinsic signals and cells, as well as communication with other tissues, modulate intra-limb and inter-organ growth coordination. This article is categorized under: Adult Stem Cells, Tissue Renewal, and Regeneration > Tissue Stem Cells and Niches Establishment of Spatial and Temporal Patterns > Regulation of Size, Proportion, and Timing Vertebrate Organogenesis > Musculoskeletal and Vascular.

Proximo-distal positional information encoded by an Fgf-regulated gradient of homeodomain transcription factors in the vertebrate limb.

The positional information theory proposes that a coordinate system provides information to embryonic cells about their position and orientation along a patterning axis. Cells interpret this information to produce the appropriate pattern. During development, morphogens and interpreter transcription factors provide this information. We report a gradient of Meis homeodomain transcription factors along the mouse limb bud proximo-distal (PD) axis antiparallel to and shaped by the inhibitory action of distal fibroblast growth factor (FGF). Elimination of Meis results in premature limb distalization and HoxA expression, proximalization of PD segmental borders, and phocomelia. Our results show that Meis transcription factors interpret FGF signaling to convey positional information along the limb bud PD axis. These findings establish a new model for the generation of PD identities in the vertebrate limb and provide a molecular basis for the interpretation of FGF signal gradients during axial patterning.

Tablet and web-based audiometry to screen for hearing loss in adults with cystic fibrosis.

INTRODUCTION: Individuals with chronic lung disease (eg, cystic fibrosis (CF)) often receive antimicrobial therapy including aminoglycosides resulting in ototoxicity. Extended high-frequency audiometry has increased sensitivity for ototoxicity detection, but diagnostic audiometry in a sound-booth is costly, time-consuming and requires a trained audiologist. This cross-sectional study analysed tablet-based audiometry (Shoebox MD) performed by non-audiologists in an outpatient setting, alongside home web-based audiometry (3D Tune-In) to screen for hearing loss in adults with CF. METHODS: Hearing was analysed in 126 CF adults using validated questionnaires, a web self-hearing test (0.5 to 4 kHz), tablet (0.25 to 12 kHz) and sound-booth audiometry (0.25 to 12 kHz). A threshold of ≥25 dB hearing loss at ≥1 audiometric frequency was considered abnormal. Demographics and mitochondrial DNA sequencing were used to analyse risk factors, and accuracy and usability of hearing tests determined. RESULTS: Prevalence of hearing loss within any frequency band tested was 48%. Multivariate analysis showed age (OR 1.127; (95% CI: 1.07 to 1.18; p value<0.0001) per year older) and total intravenous antibiotic days over 10 years (OR 1.006; (95% CI: 1.002 to 1.010; p value=0.004) per further intravenous day) were significantly associated with increased risk of hearing loss. Tablet audiometry had good usability, was 93% sensitive, 88% specific with 94% negative predictive value to screen for hearing loss compared with web self-test audiometry and questionnaires which had poor sensitivity (17% and 13%, respectively). Intraclass correlation (ICC) of tablet versus sound-booth audiometry showed high correlation (ICC >0.9) at all frequencies ≥4 kHz. CONCLUSIONS: Adults with CF have a high prevalence of drug-related hearing loss and tablet-based audiometry can be a practical, accurate screening tool within integrated ototoxicity monitoring programmes for early detection.

A collection of genetic mouse lines and related tools for inducible and reversible intersectional mis-expression.

Thanks to many advances in genetic manipulation, mouse models have become very powerful in their ability to interrogate biological processes. In order to precisely target expression of a gene of interest to particular cell types, intersectional genetic approaches using two promoter/enhancers unique to a cell type are ideal. Within these methodologies, variants that add temporal control of gene expression are the most powerful. We describe the development, validation and application of an intersectional approach that involves three transgenes, requiring the intersection of two promoter/enhancers to target gene expression to precise cell types. Furthermore, the approach uses available lines expressing tTA/rTA to control the timing of gene expression based on whether doxycycline is absent or present, respectively. We also show that the approach can be extended to other animal models, using chicken embryos. We generated three mouse lines targeted at the Tigre (Igs7) locus with TRE-loxP-tdTomato-loxP upstream of three genes (p21, DTA and Ctgf), and combined them with Cre and tTA/rtTA lines that target expression to the cerebellum and limbs. Our tools will facilitate unraveling biological questions in multiple fields and organisms.

Editor's Choice - Assessment of Correlation Between Mean Size of Infrarenal Abdominal Aortic Aneurysm at Time of Intact Repair Against Repair and Rupture Rate in Nine Countries.

OBJECTIVE: This study aimed to analyse the mean abdominal aortic aneurysm (AAA) diameter for repair in nine countries, and to determine variation in mean AAA diameter for elective AAA repair and its relationship to rupture AAA repair rates and aneurysm related mortality in corresponding populations. METHODS: Data on intact (iAAA) and ruptured infrarenal AAA (rAAA) repair for the years 2010-2012 were collected from Denmark, England, Finland, Germany, Hungary, New Zealand, Norway, Sweden, and the USA. The rate of iAAA repair and rAAA per 100 000 inhabitants above 59 years old, mean AAA diameter for iAAA repair and rAAA repair, and the national rates of rAAA were assessed. National cause of death statistics were used to estimate aneurysm related mortality. Direct standardisation methods were applied to the national mortality data. Logistic regression and analysis of variance model adjustments were made for age groups, sex, and year. RESULTS: There was a variation in the mean diameter of iAAA repair (n = 34 566; range Germany = 57 mm, Denmark = 68 mm). The standardised iAAA repair rate per 100000 inhabitants varied from 10.4 (Hungary) to 66.5 (Norway), p<.01, and the standardised rAAA repair rate per 100 000 from 5.8 (USA) to 16.9 (England), p<.01. Overall, there was no significant correlation between mean diameter of iAAA repair and standardised iAAA rate (r2 = 0.04, p = .3). There was no significant correlation between rAAA repair rate (n = 12 628) with mean diameter of iAAA repair (r2 = 0.2, p = .1). CONCLUSION: Despite recommendations from learned society guidelines, data indicate variations in mean diameter for AAA repair. There was no significant correlation between mean diameter of AAA repair and rates of iAAA repair and rAAA repair. These analyses are subject to differences in disease prevalence, uncertainties in rupture rates, validations of vascular registries, causes of death and registrations.

An international comparison of the utilisation of and outcomes from minimal access surgery for the treatment of common abdominal surgical emergencies.

BACKGROUND: Minimal access surgery (MAS) has suggested improvements in clinical outcomes compared to open surgery in several abdominal elective and emergency surgeries. The aims of this study were to compare England with the United States in the utilisation of MAS and mortality from four common abdominal surgical emergencies. METHODS: Between 2006 and 2012, the rate of MAS and in-hospital mortality for appendicitis, incarcerated or strangulated abdominal hernia, small or large bowel and peptic ulcer perforation were compared between England and the United States. Univariate and multivariate analyses were performed to adjust for differences in baseline patient demographics. RESULTS: 132,364 admissions in England were compared to an estimated 1,811,136 admissions in the United States. Minimal access surgery was used less commonly in England for appendicitis (odds ratio (OR) 0.27, 95% CI 0.267-0.278), abdominal hernia (OR 0.16, 95% CI 0.15-0.17), small or large bowel perforation (OR 0.33, 95% CI 0.32-0.35) and peptic ulcer perforation (OR 0.93, 95% CI 0.87-0.99). In-hospital mortality was increased in England compared to the United States for all four conditions: appendicitis (OR 2.11, 95% CI 1.66-2.68), abdominal hernia (OR 3.25, 95% CI 3.10-3.40), small or large bowel perforation (OR 3.88, 95% CI 3.76-3.99) and peptic ulcer perforation (OR 3.09, 95% CI 2.94-3.25). In England, after adjustment for patient demographics, open surgery was associated with increased in-hospital mortality for abdominal hernia (OR 1.80, 95% CI 1.26-2.71), small or large bowel perforation (OR 1.59, 95% CI 1.37-1.87) and peptic ulcer perforation (OR 2.31, 95% CI 1.91-2.82). CONCLUSIONS: Minimal access surgery was performed less commonly and in-hospital mortality was increased in England compared to the United States for common abdominal surgical conditions. Therefore, strategies to enhance adoption of MAS in emergency conditions in England need to be optimised and include appropriate patient selection and improved surgeon MAS training.

Reintervention After Antireflux Surgery for Gastroesophageal Reflux Disease in England.

BACKGROUND: After antireflux surgery, highly variable rates of recurrent gastroesophageal reflux disease (GERD) have been reported. OBJECTIVE: To identify the occurrence and risk factors of recurrent GERD requiring surgical reintervention or medication. METHODS: The Hospital Episode Statistics database was used to identify adults in England receiving primary antireflux surgery for GERD in 2000 to 2012 with follow-up through 2014, and the outcome was surgical reintervention. In a subset of participants, the Clinical Practice Research Datalink was additionally used to assess proton pump inhibitor therapy for at least 6 months (medical reintervention). Risk factors were assessed using multivariable Cox regression providing adjusted hazard ratios (HRs) with 95% confidence intervals (95% CIs). RESULTS: Among 22,377 patients who underwent primary antireflux surgery in the Hospital Episode Statistics dataset, 811 (3.6%) had surgical reintervention, with risk factors being age 41 to 60 years (HR = 1.22, 95% CI 1.03-1.44), female sex (HR = 1.5; 95% CI 1.3-1.74), white ethnicity (HR = 1.71, 95% CI 1.06-2.77), and low hospital annual volume of antireflux surgery (HR = 1.32, 95% CI 1.04-1.67). Among 2005 patients who underwent primary antireflux surgery in the Clinical Practice Research Datalink dataset, 189 (9.4%) had surgical reintervention and 1192 (59.5%) used proton pump inhibitor therapy, with risk factors for the combined outcome being age >60 years (HR = 2.38, 95% CI 1.81-3.13) and preoperative psychiatric morbidity (HR = 1.58, 95% CI 1.25-1.99). CONCLUSION: At least 3.6% of patients may require surgical reintervention and 59.5% medical therapy following antireflux surgery in England. The influence of patient characteristics and hospital volume highlights the need for patient selection and surgical experience in successful antireflux surgery.

Cerebellar nuclei excitatory neurons regulate developmental scaling of presynaptic Purkinje cell number and organ growth.

For neural systems to function effectively, the numbers of each cell type must be proportioned properly during development. We found that conditional knockout of the mouse homeobox genes En1 and En2 in the excitatory cerebellar nuclei neurons (eCN) leads to reduced postnatal growth of the cerebellar cortex. A subset of medial and intermediate eCN are lost in the mutants, with an associated cell non-autonomous loss of their presynaptic partner Purkinje cells by birth leading to proportional scaling down of neuron production in the postnatal cerebellar cortex. Genetic killing of embryonic eCN throughout the cerebellum also leads to loss of Purkinje cells and reduced postnatal growth but throughout the cerebellar cortex. Thus, the eCN play a key role in scaling the size of the cerebellum by influencing the survival of their Purkinje cell partners, which in turn regulate production of granule cells and interneurons via the amount of sonic hedgehog secreted.

Comparison of Surgical Intervention and Mortality for Seven Surgical Emergencies in England and the United States.

OBJECTIVE: To examine differences between England and the USA in the rate of surgical intervention and in-hospital mortality for 7 index surgical emergencies. BACKGROUND: Considerable international variation exists in the configuration, provision, and outcomes of emergency healthcare. METHODS: Patients aged <80 years hospitalized with 1 of 7 surgical emergencies (ruptured abdominal aortic aneurysm, aortic dissection, appendicitis, perforated esophagus, peptic ulcer, small bowel or large bowel, and incarcerated or strangulated hernias) were identified from English Hospital Episode Statistics and the USA Nationwide Inpatient Sample (2006-2012) and classified by whether they received a corrective surgical intervention. The rates of surgical intervention and population mortality were compared between England and the USA after adjustment for patient demographic factors. RESULTS: From 2006 to 2012, there were 136,047 admissions in English hospitals and 1,863,626 admissions in US hospitals due to the index surgical emergencies.Proportion of patients receiving no surgical intervention, for all 7 conditions was greater in the England (OR 4.25, 1.55, 8.53, 1.92, 2.06, 2.42, 1.75) and population in-hospital mortality was greater in England (OR 1.34, 1.67, 2.22, 1.65, 2.7, 4.46, 3.22) for ruptured abdominal aortic aneurysm, aortic dissection, appendicitis, perforated esophagus, peptic ulcer, small bowel or large bowel, and incarcerated or strangulated hernias respectively.In England (where follow-up was available), lack of utilization of surgery was also associated with increased in-hospital and long-term mortality for all conditions. CONCLUSION: England and US hospitals differ in the threshold for surgical intervention, which may be associated with increases in mortality in England for these 7 general surgical emergencies.