Peter B. Noble’s research while affiliated with University of Western Australia and other places

From the results of well‐performed population health studies, we now have excellent data demonstrating that deficits in adult lung function may be present early in life, possibly as a result of developmental disorders, incurring a lifelong risk of obstructive airway diseases such as asthma and chronic obstructive pulmonary disease. Suboptimal fetal development results in intrauterine growth restriction and low birth weight at term (an outcome distinct from preterm complications), which are associated with subsequent obstructive disease. Numerous prenatal exposures and disorders compromise fetal development and these are summarized herein. Various physiological, structural, and mechanical abnormalities may result from prenatal disruption, including changes to airway smooth muscle structure–function, goblet cell biology, airway stiffness, geometry of the bronchial tree, lung parenchymal structure and mechanics, respiratory skeletal muscle contraction, and pulmonary inflammation. The literature therefore supports the need for early life intervention to prevent or correct growth defects, which may include simple nutritional or antioxidant therapy. © 2024 American Physiological Society. Compr Physiol 14:5729‐5762, 2024.

Purpose Bronchial thermoplasty (BT) is a bronchoscopic intervention for the treatment of severe asthma. Despite demonstrated symptomatic benefit, the underlying mechanisms by which this is achieved remain uncertain. We hypothesize that the effects of BT are driven by improvements in ventilation heterogeneity as assessed using functional respiratory imaging (FRI). Patient and Methods Eighteen consecutive patients with severe asthma who underwent clinically indicated BT were recruited. Patients were assessed at baseline, 4-week after treatment of the left lung, and 12-month after treatment of the right lung. Data collected included short-acting beta-agonist (SABA) and oral prednisolone (OCS) use, asthma control questionnaire (ACQ-5) and exacerbation history. Patients also underwent lung function tests and chest computed tomography. Ventilation parameters including interquartile distance (IQD; measure of ventilation heterogeneity) were derived using FRI. Results 12 months after BT, significant improvements were seen in SABA and OCS use, ACQ-5, and number of OCS-requiring exacerbations. Apart from pre-bronchodilator FEV1, no other significant changes were observed in lung function. Ventilation heterogeneity significantly improved after treatment of the left lung (0.18 ± 0.04 vs 0.20 ± 0.04, p=0.045), with treatment effect persisting up to 12 months later (0.18 ± 0.05 vs 0.20 ± 0.04, p=0.028). Ventilation heterogeneity also improved after treatment of the right lung, although this did not reach statistical significance (0.18 ± 0.05 vs 0.19 ± 0.04, p=0.06). Conclusion Clinical benefits after BT are accompanied by improvements in ventilation heterogeneity, advancing our understanding of its mechanism of action. Beyond BT, FRI has the potential to be expanded into other clinical applications.

In obstructive airway diseases such as asthma and chronic obstructive pulmonary disease (COPD), the extracellular matrix (ECM) protein amount and composition of the airway smooth muscle (ASM) is often remodelled, likely altering tissue stiffness. The underlying mechanism of how human ASM cell (hASMC) mechanosenses the aberrant microenvironment is not well understood. Physiological stiffnesses of the ASM were measured by uniaxial compression tester using porcine ASM layers under 0, 5 and 10% longitudinal stretch above in situ length. Linear stiffness gradient hydrogels (230 kPa range) were fabricated and functionalized with ECM proteins, collagen I (ColI), fibronectin (Fn) and laminin (Ln), to recapitulate the above‐measured range of stiffnesses. Overall, hASMC mechanosensation exhibited a clear correlation with the underlying hydrogel stiffness. Cell size, nuclear size and contractile marker alpha‐smooth muscle actin (αSMA) expression showed a strong correlation to substrate stiffness. Mechanosensation, assessed by Lamin‐A intensity and nuc/cyto YAP, exhibited stiffness‐mediated behaviour only on ColI and Fn‐coated hydrogels. Inhibition studies using blebbistatin or Y27632 attenuated most mechanotransduction‐derived cell morphological responses, αSMA and Lamin‐A expression and nuc/cyto YAP (blebbistatin only). This study highlights the interplay and complexities between stiffness and ECM protein type on hASMC mechanosensation, relevant to airway remodelling in obstructive airway diseases.

Quantifying airway smooth muscle (ASM) in patients with asthma raises the possibility of improved and personalized disease management. Endobronchial polarization-sensitive optical coherence tomography (PS-OCT) is a promising quantitative imaging approach that is in the early stages of clinical translation. To date, only animal tissues have been used to assess the accuracy of PS-OCT to quantify absolute (rather than relative) ASM in cross-sections with directly matched histological cross-sections as validation. We report the use of whole fresh human and pig airways to perform a detailed side-by-side qualitative and quantitative validation of PS-OCT against gold standard histology. We matched and quantified 120 sections from five human and seven pig (small and large) airways and linked PS-OCT signatures of ASM to the tissue structural appearance in histology. Notably, we found that human cartilage perichondrium can share with ASM the properties of birefringence and circumferential alignment of fibers, making it a significant confounder for ASM detection. Measurements not corrected for perichondrium overestimated ASM content several-fold (p<0.001, paired t-test). After careful exclusion of perichondrium, we found a strong positive correlation (r=0.96, p<0.00001) of ASM area measured by PS-OCT and histology, supporting the method's application in human subjects. Matching human histology further indicated that PS-OCT allows conclusions on the intra-layer composition and in turn potential contractile capacity of ASM bands. Together these results form a reliable basis for future clinical studies.

Background: Lung inflammation and impaired alveolarization precede bronchopulmonary dysplasia (BPD). Glucocorticoids are anti-inflammatory and reduce ventilator requirements in preterm infants. However, high-dose glucocorticoids inhibit alveolarization. The effect of glucocorticoids on lung function and structure in preterm newborns exposed to antenatal inflammation is unknown. We hypothesise that postnatal low-dose dexamethasone reduces ventilator requirements, prevents inflammation and BPD-like lung pathology, following antenatal inflammation. Methods: Pregnant ewes received intra-amniotic LPS (E.coli, 4 mg/mL) or saline at 126 days gestation; preterm lambs were delivered 48 h later. Lambs were randomised to receive either tapered intravenous dexamethasone (LPS/Dex, n = 9) or saline (LPS/Sal, n = 10; Sal/Sal, n = 9) commencing <3 h after birth. Respiratory support was gradually de-escalated, using a standardised protocol aimed at weaning from ventilation towards unassisted respiration. Tissues were collected at day 7. Results: Lung morphology and mRNA levels for inflammatory mediators were measured. Respiratory support requirements were not different between groups. Histological analyses revealed higher tissue content and unchanged alveolarization in LPS/Sal compared to other groups. LPS/Dex lambs exhibited decreased markers of pulmonary inflammation compared to LPS/Sal. Conclusion: Tapered low-dose dexamethasone reduces the impact of antenatal LPS on ventilation requirements throughout the first week of life and reduces inflammation and pathological thickening of the preterm lung IMPACT: We are the first to investigate the combination of antenatal inflammation and postnatal dexamethasone therapy in a pragmatic study design, akin to contemporary neonatal care. We show that antenatal inflammation with postnatal dexamethasone therapy does not reduce ventilator requirements, but has beneficial maturational impacts on the lungs of preterm lambs at 7 days of life. Appropriate tapered postnatal dexamethasone dosing should be explored for extuabtion of oxygen-dependant neonates.