Deciphering the impacts of modulating the Wnt-planar cell polarity (PCP) pathway on alveolar repair

Many adult lung diseases involve dysregulated lung repair. Deciphering the molecular and cellular mechanisms that govern intrinsic lung repair is essential to develop new treatments to repair/regenerate the lungs. Aberrant Wnt signalling is associated with lung diseases including emphysema, idiopathic pulmonary fibrosis and pulmonary arterial hypertension but how Wnt signalling contributes to these diseases is still unclear. There are several alternative pathways that can be stimulated upon Wnt ligand binding, one of these is the Planar Cell Polarity (PCP) pathway which induces actin cytoskeleton remodelling. Wnt5a is known to stimulate the PCP pathway and this ligand is of particular interest in regenerative lung biology because of its association with lung diseases and its role in the alveolar stem cell niche. To decipher the cellular mechanisms through which Wnt5a and the PCP pathway affect alveolar repair we utilised a 3-D ex-vivo model of lung injury and repair, the AIR model. Our results show that Wnt5a specifically enhances the alveolar epithelial progenitor cell population following injury and surprisingly, this function is attenuated but not abolished in Looptail (Lp) mouse lungs in which the PCP pathway is dysfunctional. However, Lp tracheal epithelial cells show reduced stiffness and Lp alveolar epithelial cells are less migratory than wildtype (WT), indicating that Lp lung epithelial cells have a reduced capacity for repair. These findings provide important mechanistic insight into how Wnt5a and the PCP pathway contribute to lung repair and indicate that these components of Wnt signalling may be viable targets for the development of pro-repair treatments.

A method for TAT-Cre recombinase-mediated floxed allele modification in ex vivo tissue slices

Precision-cut lung slices (PCLS) are used for a variety of applications. However, methods to manipulate genes in PCLS are currently limited. We developed a new method, TAT-Cre recombinase-mediated floxed allele modification in tissue slices (TReATS), to induce highly effective and temporally controlled gene deletion or activation in ex vivo PCLS. Treatment of PCLS from Rosa26-flox-stop-flox-EYFP mice with cell-permeant TAT-Cre recombinase induced ubiquitous EYFP protein expression, indicating successful Cre-mediated excision of the upstream loxP-flanked stop sequence. Quantitative real-time PCR confirmed induction of EYFP. We successfully replicated the TReATS method in PCLS from Vangl2flox/flox mice, leading to the deletion of loxP-flanked exon 4 of the Vangl2 gene. Cre-treated Vangl2flox/flox PCLS exhibited cytoskeletal abnormalities, a known phenotype caused by VANGL2 dysfunction. We report a new method that bypasses conventional Cre-Lox breeding, allowing rapid and highly effective gene manipulation in ex vivo tissue models.

An Ex Vivo Acid Injury and Repair (AIR) Model Using Precision-Cut Lung Slices to Understand Lung Injury and Repair

Recent advances in cell culture models like air-liquid interface culture and ex vivo models such as organoids have advanced studies of lung biology; however, gaps exist between these models and tools that represent the complexity of the three-dimensional environment of the lung. Precision-cut lung slices (PCLS) mimic the in vivo environment and bridge the gap between in vitro and in vivo models. We have established the acid injury and repair (AIR) model where a spatially restricted area of tissue is injured using drops of HCl combined with Pluronic gel. Injury and repair are assessed by immunofluorescence using robust markers, including Ki67 for cell proliferation and prosurfactant protein C for alveolar type 2/progenitor cells. Importantly, the AIR model enables the study of injury and repair in mouse lung tissue without the need for an initial in vivo injury, and the results are highly reproducible. Here, we present detailed protocols for the generation of PCLS and the AIR model. We also describe methods to analyze and quantify injury in AIR-PCLS by immunostaining with established early repair markers and fluorescence imaging. This novel ex vivo model is a versatile tool for studying lung cell biology in acute lung injury and for semi-high-throughput screening of potential therapeutics. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Generation of precision-cut lung slices Basic Protocol 2: The acid injury and repair model Basic Protocol 3: Analysis of AIR-PCLS: Immunostaining and imaging.

Lung Development Genes and Adult Lung Function

Rationale: Poor lung health in adult life may occur partly through suboptimal growth and development, as suggested by epidemiological evidence pointing to early life risk factors.

Objectives: To systematically investigate the effects of lung development genes on adult lung function.

Methods: Using UK Biobank data, we tested the association of 391 genes known to influence lung development with FVC and FEV₁/FVC. We split the dataset into two random subsets of 207,616 and 138,411 individuals, using the larger subset to select the most promising signals and the smaller subset for replication.

Measurements and Main Results: We identified 55 genes, of which 36 (16 for FVC, 19 for FEV₁/FVC, and one for both) had not been identified in the largest, most recent genome-wide study of lung function. Most of these 36 signals were intronic variants; expression data from blood and lung tissue showed that the majority affect the expression of the genes they lie within. Further testing of 34 of these 36 signals in the CHARGE and SpiroMeta consortia showed that 16 replicated after Bonferroni correction and another 12 replicated at nominal significance level. Of the 55 genes, 53 fell into four biological categories whose function is to regulate organ size and cell integrity (growth factors; transcriptional regulators; cell-to-cell adhesion; extracellular matrix), suggesting that these specific processes are important for adult lung health.

Conclusions: Our study demonstrates the importance of lung development genes in regulating adult lung function and influencing both restrictive and obstructive patterns. Further investigation of these developmental pathways could lead to druggable targets.

The Planar Polarity Component VANGL2 Is a Key Regulator of Mechanosignaling

VANGL2 is a component of the planar cell polarity (PCP) pathway, which regulates tissue polarity and patterning. The Vangl2 Lp mutation causes lung branching defects due to dysfunctional actomyosin-driven morphogenesis. Since the actomyosin network regulates cell mechanics, we speculated that mechanosignaling could be impaired when VANGL2 is disrupted. Here, we used live-imaging of precision-cut lung slices (PCLS) from Vangl2 Lp/+ mice to determine that alveologenesis is attenuated as a result of impaired epithelial cell migration. Vangl2 Lp/+ tracheal epithelial cells (TECs) and alveolar epithelial cells (AECs) exhibited highly disrupted actomyosin networks and focal adhesions (FAs). Functional assessment of cellular forces confirmed impaired traction force generation in Vangl2 Lp/+ TECs. YAP signaling in Vangl2 Lp airway epithelium was reduced, consistent with a role for VANGL2 in mechanotransduction. Furthermore, activation of RhoA signaling restored actomyosin organization in Vangl2 Lp/+ , confirming RhoA as an effector of VANGL2. This study identifies a pivotal role for VANGL2 in mechanosignaling, which underlies the key role of the PCP pathway in tissue morphogenesis.

The acid injury and repair (AIR) model: A novel ex-vivo tool to understand lung repair

Research into mechanisms underlying lung injury and subsequent repair responses is currently of paramount importance. There is a paucity of models that bridge the gap between in vitro and in vivo research. Such intermediate models are critical for researchers to decipher the mechanisms that drive repair and to test potential new treatments for lung repair and regeneration. Here we report the establishment of a new tool, the Acid Injury and Repair (AIR) model, that will facilitate studies of lung tissue repair. In this model, injury is applied to a restricted area of a precision-cut lung slice using hydrochloric acid, a clinically relevant driver. The surrounding area remains uninjured, thus mimicking the heterogeneous pattern of injury frequently observed in lung diseases. We show that in response to injury, the percentage of progenitor cells (pro surfactant protein C, proSP-C and TM4SF1 positive) significantly increases in the injured region. Whereas in the uninjured area, the percentage of proSP-C/TM4SF1 cells remains unchanged but proliferating cells (Ki67 positive) increase. These effects are modified in the presence of inhibitors of proliferation (Cytochalasin D) and Wnt secretion (C59) demonstrating that the AIR model is an important new tool for research into lung disease pathogenesis and potential regenerative medicine strategies.

Mechanism of lung development in the aetiology of adult congenital pulmonary airway malformations

Congenital pulmonary airway malformations (CPAMs) are rare lung abnormalities that result in cyst formation and are associated with respiratory distress in infants and malignant potential in adults. The pathogenesis of CPAMs remains unknown but data suggest disruption of the normal proximo-distal programme of airway branching and differentiation. Here, we demonstrate that adult human CPAM are lined with epithelium that retains SOX-2 and thyroid transcription factor-1 immunohistochemical markers, characteristic of the developing lung. However, RALDH-1, another key marker, is absent. This suggests a more complex aetiology for CPAM than complete focal arrest of lung development and may provide insight to the associated risk of malignancy.

Respiratory management in severe acute respiratory syndrome coronavirus 2 infection

The severe acute respiratory syndrome coronavirus 2 pandemic is to date affecting more than a million of patients and is challenging healthcare professionals around the world. Coronavirus disease 2019 may present with a wide range of clinical spectrum and severity, including severe interstitial pneumonia with high prevalence of hypoxic respiratory failure requiring intensive care admission. There has been increasing sharing experience regarding the patient's clinical features over the last weeks which has underlined the need for general guidance on treatment strategies. We summarise the evidence existing in the literature of oxygen and positive pressure treatments in patients at different stages of respiratory failure and over the course of the disease, including environment and ethical issues related to the ongoing coronavirus disease 2019 infection.

Time-lapse Imaging of Alveologenesis in Mouse Precision-cut Lung Slices

Alveoli are the gas-exchange units of lung. The process of alveolar development, alveologenesis, is regulated by a complex network of signaling pathways that act on various cell types including alveolar type I and II epithelial cells, fibroblasts and the vascular endothelium. Dysregulated alveologenesis results in bronchopulmonary dysplasia in neonates and in adults, disrupted alveolar regeneration is associated with chronic lung diseases including COPD and pulmonary fibrosis. Therefore, visualizing alveologenesis is critical to understand lung homeostasis and for the development of effective therapies for incurable lung diseases. We have developed a technique to visualize alveologenesis in real-time using a combination of widefield microscopy and image deconvolution of precision-cut lung slices. Here, we describe this live imaging technique in step-by-step detail. This time-lapse imaging technique can be used to capture the dynamics of individual cells within tissue slices over a long time period (up to 16 h), with minimal loss of fluorescence or cell toxicity.

Platypnoea-orthodeoxia syndrome: beware of investigations undertaken supine

Platypnoea-orthodeoxia syndrome (POS) is a rare disorder, manifesting as deoxygenation occurring when the patient is in the upright position. Four broad mechanisms for the condition have been described: intracardiac shunts, intrapulmonary shunts, hepatopulmonary syndrome and pulmonary ventilation-perfusion mismatch. Here, we present the first case of POS in a patient with a proven right to left intracardiac shunt occurring in the context of postural hypotension and normal right heart pressures. We highlight the need to carry out investigations in the upright position before discounting intracardiac shunting as a cause for the syndrome. Short-term improvement of the syndrome was obtained with medical management of the patient's orthostatic hypotension and as such suggests a conservative management strategy for similar patients, which may delay the need for invasive procedures to close the anatomical defect.

Regenerative pharmacology for COPD: breathing new life into old lungs

Chronic obstructive pulmonary disease (COPD) is a major global health concern with few effective treatments. Widespread destruction of alveolar tissue contributes to impaired gas exchange in severe COPD, and recent radiological evidence suggests that destruction of small airways is a major contributor to increased peripheral airway resistance in disease. This important finding might in part explain the failure of conventional anti-inflammatory treatments to restore lung function even in patients with mild disease. There is a clear need for alternative pharmacological strategies for patients with COPD/emphysema. Proposed regenerative strategies such as cell therapy and tissue engineering are hampered by poor availability of exogenous stem cells, discouraging trial results, and risks and cost associated with surgery. An alternative therapeutic approach is augmentation of lung regeneration and/or repair by biologically active factors, which have potential to be employed on a large scale. In favour of this strategy, the healthy adult lung is known to possess a remarkable endogenous regenerative capacity. Numerous preclinical studies have shown induction of regeneration in animal models of COPD/emphysema. Here, we argue that given the widespread and irreversible nature of COPD, serious consideration of regenerative pharmacology is necessary. However, for this approach to be feasible, a better understanding of the cell-specific molecular control of regeneration, the regenerative potential of the human lung and regenerative competencies of patients with COPD are required.

Novel anti-tumour necrosis factor receptor-1 (TNFR1) domain antibody prevents pulmonary inflammation in experimental acute lung injury

BACKGROUND

Tumour necrosis factor alpha (TNF-α) is a pleiotropic cytokine with both injurious and protective functions, which are thought to diverge at the level of its two cell surface receptors, TNFR1 and TNFR2. In the setting of acute injury, selective inhibition of TNFR1 is predicted to attenuate the cell death and inflammation associated with TNF-α, while sparing or potentiating the protective effects of TNFR2 signalling. We developed a potent and selective antagonist of TNFR1 (GSK1995057) using a novel domain antibody (dAb) therapeutic and assessed its efficacy in vitro, in vivo and in a clinical trial involving healthy human subjects.

METHODS

We investigated the in vitro effects of GSK1995057 on human pulmonary microvascular endothelial cells (HMVEC-L) and then assessed the effects of pretreatment with nebulised GSK1995057 in a non-human primate model of acute lung injury. We then tested translation to humans by investigating the effects of a single nebulised dose of GSK1995057 in healthy humans (n=37) in a randomised controlled clinical trial in which subjects were subsequently exposed to inhaled endotoxin.

RESULTS

Selective inhibition of TNFR1 signalling potently inhibited cytokine and neutrophil adhesion molecule expression in activated HMVEC-L monolayers in vitro (P<0.01 and P<0.001, respectively), and also significantly attenuated inflammation and signs of lung injury in non-human primates (P<0.01 in all cases). In a randomised, placebo-controlled trial of nebulised GSK1995057 in 37 healthy humans challenged with a low dose of inhaled endotoxin, treatment with GSK1995057 attenuated pulmonary neutrophilia, inflammatory cytokine release (P<0.01 in all cases) and signs of endothelial injury (P<0.05) in bronchoalveolar lavage and serum samples.

CONCLUSION

These data support the potential for pulmonary delivery of a selective TNFR1 dAb as a novel therapeutic approach for the prevention of acute respiratory distress syndrome.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov NCT01587807.

AJRCCM: 100-Year Anniversary. Homeward Bound: A Centenary of Home Mechanical Ventilation

The evolution of home mechanical ventilation is an intertwined chronicle of negative and positive pressure modes and their role in managing ventilatory failure in neuromuscular diseases and other chronic disorders. The uptake of noninvasive positive pressure ventilation has resulted in widespread growth in home ventilation internationally and fewer patients being ventilated invasively. As with many applications of domiciliary medical technology, home ventilatory support has either led or run in parallel with acute hospital applications and has been influenced by medical and societal shifts in the approach to chronic care, the creation of community support teams, a preference of recipients to be treated at home, and economic imperatives. This review summarizes the trends and growing evidence base for ventilatory support outside the hospital.

Choking on a foreign body: a physiological study of the effectiveness of abdominal thrust manoeuvres to increase thoracic pressure

The Heimlich manoeuvre is a well-known intervention for the management of choking due to foreign body airway occlusion, but the evidence base for guidance on this topic is limited and guidelines differ. We measured pressures during abdominal thrusts in healthy volunteers. The angle at which thrusts were performed (upthrust vs circumferential) did not affect intrathoracic pressure. Self-administered abdominal thrusts produced similar pressures to those performed by another person. Chair thrusts, where the subject pushed their upper abdomen against a chair back, produced higher pressures than other manoeuvres. Both approaches should be included in basic life support teaching.

Heterozygous Vangl2Looptail mice reveal novel roles for the planar cell polarity pathway in adult lung homeostasis and repair

Lung diseases impose a huge economic and health burden worldwide. A key aspect of several adult lung diseases, such as idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD), including emphysema, is aberrant tissue repair, which leads to an accumulation of damage and impaired respiratory function. Currently, there are few effective treatments available for these diseases and their incidence is rising. The planar cell polarity (PCP) pathway is critical for the embryonic development of many organs, including kidney and lung. We have previously shown that perturbation of the PCP pathway impairs tissue morphogenesis, which disrupts the number and shape of epithelial tubes formed within these organs during embryogenesis. However, very little is known about the role of the PCP pathway beyond birth, partly because of the perinatal lethality of many PCP mouse mutant lines. Here, we investigate heterozygous Looptail (Lp) mice, in which a single copy of the core PCP gene, Vangl2, is disrupted. We show that these mice are viable but display severe airspace enlargement and impaired adult lung function. Underlying these defects, we find that Vangl2^Lp/+ lungs exhibit altered distribution of actin microfilaments and abnormal regulation of the actin-modifying protein cofilin. In addition, we show that Vangl2^Lp/+ lungs exhibit many of the hallmarks of tissue damage, including an altered macrophage population, abnormal elastin deposition and elevated levels of the elastin-modifying enzyme, Mmp12, all of which are observed in emphysema. In vitro, disruption of VANGL2 impairs directed cell migration and reduces the rate of repair following scratch wounding of human alveolar epithelial cells. Moreover, using population data from a birth cohort of young adults, all aged 31, we found evidence of an interactive effect between VANGL2 and smoking on lung function. Finally, we show that PCP genes VANGL2 and SCRIB are significantly downregulated in lung tissue from patients with emphysema. Our data reveal an important novel role for the PCP pathway in adult lung homeostasis and repair and shed new light on the genetic factors which may modify destructive lung diseases such as emphysema.

Summary: Manipulating the PCP pathway may provide new approaches to treat damaged lung tissue.

Association of Forced Vital Capacity with the Developmental Gene NCOR2

Background

Forced Vital Capacity (FVC) is an important predictor of all-cause mortality in the absence of chronic respiratory conditions. Epidemiological evidence highlights the role of early life factors on adult FVC, pointing to environmental exposures and genes affecting lung development as risk factors for low FVC later in life. Although highly heritable, a small number of genes have been found associated with FVC, and we aimed at identifying further genetic variants by focusing on lung development genes.

Methods

Per-allele effects of 24,728 SNPs in 403 genes involved in lung development were tested in 7,749 adults from three studies (NFBC1966, ECRHS, EGEA). The most significant SNP for the top 25 genes was followed-up in 46,103 adults (CHARGE and SpiroMeta consortia) and 5,062 children (ALSPAC). Associations were considered replicated if the replication p-value survived Bonferroni correction (p<0.002; 0.05/25), with a nominal p-value considered as suggestive evidence. For SNPs with evidence of replication, effects on the expression levels of nearby genes in lung tissue were tested in 1,111 lung samples (Lung eQTL consortium), with further functional investigation performed using public epigenomic profiling data (ENCODE).

Results

NCOR2-rs12708369 showed strong replication in children (p = 0.0002), with replication unavailable in adults due to low imputation quality. This intronic variant is in a strong transcriptional enhancer element in lung fibroblasts, but its eQTL effects could not be tested due to low imputation quality in the eQTL dataset. SERPINE2-rs6754561 replicated at nominal level in both adults (p = 0.036) and children (p = 0.045), while WNT16-rs2707469 replicated at nominal level only in adults (p = 0.026). The eQTL analyses showed association of WNT16-rs2707469 with expression levels of the nearby gene CPED1. We found no statistically significant eQTL effects for SERPINE2-rs6754561.

Conclusions

We have identified a new gene, NCOR2, in the retinoic acid signalling pathway pointing to a role of vitamin A metabolism in the regulation of FVC. Our findings also support SERPINE2, a COPD gene with weak previous evidence of association with FVC, and suggest WNT16 as a further promising candidate.

Biomarkers of acute lung injury: worth their salt?

The validation of biomarkers has become a key goal of translational biomedical research. The purpose of this article is to discuss the role of biomarkers in the management of acute lung injury (ALI) and related research. Biomarkers should be sensitive and specific indicators of clinically important processes and should change in a relevant timeframe to affect recruitment to trials or clinical management. We do not believe that they necessarily need to reflect pathogenic processes. We critically examined current strategies used to identify biomarkers and which, owing to expedience, have been dominated by reanalysis of blood derived markers from large multicenter Phase 3 studies. Combining new and existing validated biomarkers with physiological and other data may add predictive power and facilitate the development of important aids to research and therapy.

Human models of acute lung injury

Acute lung injury (ALI) is a syndrome that is characterised by acute inflammation and tissue injury that affects normal gas exchange in the lungs. Hallmarks of ALI include dysfunction of the alveolar-capillary membrane resulting in increased vascular permeability, an influx of inflammatory cells into the lung and a local pro-coagulant state. Patients with ALI present with severe hypoxaemia and radiological evidence of bilateral pulmonary oedema. The syndrome has a mortality rate of approximately 35% and usually requires invasive mechanical ventilation. ALI can follow direct pulmonary insults, such as pneumonia, or occur indirectly as a result of blood-borne insults, commonly severe bacterial sepsis. Although animal models of ALI have been developed, none of them fully recapitulate the human disease. The differences between the human syndrome and the phenotype observed in animal models might, in part, explain why interventions that are successful in models have failed to translate into novel therapies. Improved animal models and the development of human in vivo and ex vivo models are therefore required. In this article, we consider the clinical features of ALI, discuss the limitations of current animal models and highlight how emerging human models of ALI might help to answer outstanding questions about this syndrome.

Is a regenerative approach viable for the treatment of COPD?

Degenerative lung diseases such as chronic obstructive pulmonary disease (COPD) are common with huge worldwide morbidity. Anti-inflammatory drug development strategies have proved disappointing and current treatment is aimed at symptomatic relief. Only lung transplantation with all its attendant difficulties offers hope of cure and the outlook for affected patients is bleak. Lung regeneration therapies aim to reverse the structural and functional deficits in COPD either by delivery of exogenous lung cells to replace lost tissue, delivery of exogenous stem cells to induce a local paracrine effect probably through an anti-inflammatory action or by the administration of small molecules to stimulate the endogenous regenerative ability of lung cells. In animal models of emphysema and disrupted alveolar development each of these strategies has shown some success but there are potential tumour-inducing dangers with a cellular approach. Small molecules such as all-trans retinoic acid have been successful in animal models although the mechanism is not completely understood. There are currently two Pharma-sponsored trials in progress concerning patients with COPD, one of a specific retinoic acid receptor gamma agonist and another using mesenchymal stem cells.

Palovarotene, a novel retinoic acid receptor gamma agonist for the treatment of emphysema

Emphysema is characterized by the destruction of alveoli and alveolar ducts within the lungs. Retinoid signaling is believed to play a role in alveologenesis, with the retinoic acid receptor gamma thought to be required for alveolar formation. Based on this hypothesis, Roche Holding AG is developing palovarotene (R-667, RO-3300074), a selective retinoic acid receptor gamma agonist for the treatment of emphysema. In small animal studies, palovarotene was claimed to reverse the structural, functional and inflammatory features of cigarette smoke-induced emphysema. Phase I clinical trials of palovarotene in patients with emphysema demonstrated that the drug is well tolerated, with improvements observed in markers of emphysema progression. Unlike all-trans retinoic acid, the pharmacokinetic profile of palovarotene appears to be dose-proportional. At the time of publication, a phase II, placebo-controlled trial was ongoing, and was expected to report prospective measurements of exercise, gas transfer and lung densitometry endpoints. The development of a selective retinoic acid receptor gamma agonist for the treatment of emphysema represents the first of a new class of small-molecule regenerative therapies that may prove useful for the treatment of destructive or age-related lung disease.

Retinoid induction of alveolar regeneration: from mice to man?

The use of retinoids to induce human lung regeneration is under investigation in a number of studies in patients with chronic obstructive pulmonary disease (COPD). Retinoic acid (RA) has complex pleiotropic functions during vertebrate patterning and development and can induce regeneration in a number of different organ systems. Studies of retinoid signalling during lung development might provide a molecular basis to explain pharmacological induction of alveolar regeneration in adult models of lung disease. In this review the role of endogenous RA signalling during alveologenesis is explored and data suggesting that a number of exogenous retinoids can induce regeneration in the adult lung are discussed. Current controversies in this area are highlighted and a hypothesis of lung regeneration is put forward. Understanding the cellular and molecular mechanisms of induction of regeneration will be central for effective translation into patients with lung disease and may reveal novel insights into the pathogenesis of alveolar disease and senescence.

Retinoic acid in alveolar development, maintenance and regeneration

Recent data suggest that exogenous retinoic acid (RA), the biologically active derivative of vitamin A, can induce alveolar regeneration in a rat model of experimental emphysema. Here, we describe a mouse model of disrupted alveolar development using dexamethasone administered postnatally. We show that the effects of dexamethasone are concentration dependent, dose dependent, long lasting and result in a severe loss of alveolar surface area. When RA is administered to these animals as adults, lung architecture and the surface area per unit of body weight are completely restored to normal. This remarkable effect may be because RA is required during normal alveolar development and administering RA re-awakens gene cascades used during development. We provide evidence that RA is required during alveologenesis in the mouse by showing that the levels of the retinoid binding proteins, the RA receptors and two RA synthesizing enzymes peak postnatally. Furthermore, an inhibitor of RA synthesis, disulphiram, disrupts alveologenesis. We also show that RA is required throughout life for the maintenance of lung alveoli because when rats are deprived of dietary retinol they lose alveoli and show the features of emphysema. Alveolar regeneration with RA may therefore be an important novel therapeutic approach to the treatment of respiratory diseases characterized by a reduced gas-exchanging surface area such as bronchopulmonary dysplasia and emphysema for which there are currently no treatments.

Retinoic acid induces alveolar regeneration in the adult mouse lung

Recent data suggests that exogenous retinoic acid (RA) can induce alveolar regeneration in a mouse and a rat model of experimental emphysema and disrupted alveolar development. This may be because RA is required during normal alveolar development and the subsequent provision of RA reawakens the gene cascades used during development. Here, additional evidence that RA is required during alveologenesis in the mouse is provided by showing that disulphiram disrupts this process. A further model of disrupted alveolar development using dexamethasone administered postnatally is then described, and it is further shown that RA administered to these adult mice restores the lung architecture to normal. Alveolar regeneration with retinoic acid may therefore be an important novel therapeutic approach to the treatment of respiratory diseases characterised by a reduced gas-exchanging surface area, such as bronchopulmonary dysplasia and emphysema.

Retinoic acid, a regeneration-inducing molecule

Retinoic acid (RA) is the biologically active metabolite of vitamin A. It is a low molecular weight, lipophilic molecule that acts on the nucleus to induce gene transcription. In amphibians and mammals, it induces the regeneration of several tissues and organs and these examples are reviewed here. RA induces the "super-regeneration" of organs that can already regenerate such as the urodele amphibian limb by respecifying positional information in the limb. In organs that cannot normally regenerate such as the adult mammalian lung, RA induces the complete regeneration of alveoli that have been destroyed by various noxious treatments. In the mammalian central nervous system (CNS), which is another tissue that cannot regenerate, RA does not induce neurite outgrowth as it does in the embryonic CNS, because one of the retinoic acid receptors, RAR beta 2, is not up-regulated. When RAR beta 2 is transfected into the adult spinal cord in vitro, then neurite outgrowth is stimulated. In all these cases, RA is required for the development of the organ, in the first place suggesting that the same gene pathways are likely to be used for both development and regeneration. This suggestion, therefore, might serve as a strategy for identifying potential tissue or organ targets that have the capacity to be stimulated to regenerate.

Temporal/spatial expression of retinoid binding proteins and RAR isoforms in the postnatal lung

Endogenous retinoids have been implicated in alveologenesis in both the rat and the mouse, and exogenous retinoic acid (RA) can reverse or partially reverse experimental emphysema in adult rat and mouse models by an unknown mechanism. In this study, we examine the cellular and molecular biology of retinoid signaling during alveologenesis in the mouse. We describe the temporal and spatial expression of the retinoid binding proteins CRBP-I, CRBP-II, and CRABP-I using RT-PCR and immunohistochemistry. We identify the retinoic acid receptor isoforms RAR-alpha 1, RAR-beta 2, RAR-beta 4, and RAR-gamma 2 and describe their temporal and spatial expression using RT-PCR and in situ hybridization. We demonstrate that both retinoid binding proteins and RAR isoforms are temporally regulated and found within the alveolar septal regions during alveologenesis. These data support a role of dynamic endogenous RA signaling during alveolar formation.

Alveolar proliferation, retinoid synthesizing enzymes, and endogenous retinoids in the postnatal mouse lung. Different roles for Aldh-1 and Raldh-2

Alveoli are formed postnatally in the rat, mouse, and human. The molecular signals controlling the patterning of this developmental process are not well understood. Here we describe immunohistochemical studies that label proliferating alveolar wall cells which suggest two distinct patterns of alveologenesis: (1) a low grade, peripheral subpleural parenchymal process which occurs from P1 through to P15; and (2) a dramatic increase in central cell proliferation from P4 which is complete by P15, corresponding to the well described period of alveolar septation. We describe the temporal and spatial expression of the retinoid-synthesizing enzymes Aldh-1 and Raldh-2 in the postnatal mouse lung. Both enzymes are upregulated during the period of maximal alveolar wall cell proliferation. Aldh-1 is located in the bronchial epithelium and alveolar parenchyma, and Raldh-2 is restricted to the bronchial epithelium and pleural mesothelial cells. High-pressure liquid chromatography (HPLC) reveals that rapidly septating lungs have relatively simple chromatographic profiles; in contrast, the adult lungs have a complex profile that includes many novel retinoids. These data suggest two patterns of alveolar proliferation with temporal and spatial association of the enzymes Aldh-1 and Raldh-2 and a dynamic role for different retinoids in both the septating and adult mouse lung.

Healthcare support workers and the scrubbed role

The scrubbed role is highly valued amongst many theatre nurses. A survey by Roberts (1989) found that 61.9% of 147 nurses stated that they preferred the scrubbed role to an anaesthetic role (4.8%). There is more recent evidence that nursing still dominates the scrubbed role, with over 50% of 108 nurses surveyed stating that they only worked in the scrubbed area of the operating department (Hind 1997).

Interprofessional working and learning in a UK operating department

This study explores the issues of working and training together for nurses and operating department assistants and practitioners (ODAs/ODPs), based on experiences in an operating department. Interviews and focus groups with nurses, ODAs/ODPs and medical staff were the means of collecting data.

Health care support workers in the critical care setting

The 1999/2000 winter demands on the NHS have once again highlighted deficits in UK critical care provision (Daily Telegraph, 2000; London Evening Standard, 2000) Recent years have seen the development of the role of health care support workers in the NHS; some critical care units now employ health care support workers This research examined the views of critical care unit staff on the introduction of health care support workers into the critical care unit It is concluded that the role is viable within the setting of this study A framework is outlined that could form the basis for a critical care health care support worker training programme

Exploring the expanded role of nurses in critical care

This paper reports on a small research study that explored the perceptions of staff in an intensive/coronary/high-dependency care unit on the expanded role of nurses in critical care. The research was undertaken in two phases. In the first phase, focus groups and interviews of nursing and medical staff were used as methods to explore their perceptions. Data were analysed by thematic content analysis and generated four categories: specialized skills; maintaining competence; how far nurses can go; and training and education. Using verbatim examples from the participants, these categories are described. In summary, it was found that both doctors and nurses were in favour of nursing role developments, and for the nurses this was driven by their desire to meet the patients' needs. In a smaller second phase, a questionnaire was developed based on information gained in the first phase. It was utilized to seek the views of all the nursing staff on specific role-expansion activities. Findings revealed substantial support for developing the role of critical care nurses in a number of activities: cannulation; venepuncture; ordering blood tests and X-rays; performing physiotherapy; inserting arterial lines; performing elective cardioversion; thrombolysis treatment and intubation. This research study has yielded important information. However, it is recognized that, whilst these roles may be new to this particular critical care unit, there are many other units where they may already be common practice. Whenever new roles are developed, it is important to evaluate their effectiveness in measurable terms and regular audit is advisable. Further research is therefore recommended on both the development and evaluation of new roles in critical care.