Showing papers by "James P. Butler published in 2016"

Collective migration and cell jamming in asthma, cancer and development

Abstract: Collective cellular migration within the epithelial layer impacts upon development, wound healing and cancer invasion, but remains poorly understood. Prevailing conceptual frameworks tend to focus on the isolated role of each particular underlying factor - taken one at a time or at most a few at a time - and thus might not be tailored to describe a cellular collective that embodies a wide palette of physical and molecular interactions that are both strong and complex. To bridge this gap, we shift the spotlight to the emerging concept of cell jamming, which points to only a small set of parameters that govern when a cellular collective might jam and rigidify like a solid, or instead unjam and flow like a fluid. As gateways to cellular migration, the unjamming transition (UJT) and the epithelial-to-mesenchymal transition (EMT) share certain superficial similarities, but their congruence - or lack thereof - remains unclear. In this Commentary, we discuss aspects of cell jamming, its established role in human epithelial cell layers derived from the airways of non-asthmatic and asthmatic donors, and its speculative but emerging roles in development and cancer cell invasion.

Kisspeptin Responsiveness Signals Emergence of Reproductive Endocrine Activity: Implications for Human Puberty.

Abstract: Context: Some patients with idiopathic hypogonadotropic hypogonadism (IHH) undergo spontaneous activation of their hypothalamic-pituitary-gonadal axis resulting in normalization of steroidogenesis and/or gametogenesis, a phenomenon termed reversal. Objective: To assess the responsiveness of the GnRH neuronal network to exogenous kisspeptin administration in IHH patients who have undergone reversal. Participants: Six men with congenital IHH and evidence for reversal. Intervention: Subjects underwent q10 min blood sampling to measure GnRH-induced LH secretion at baseline and in response to iv boluses of kisspeptin (0.24–2.4 nmol/kg) and GnRH (75 ng/kg). Results: Individuals with sustained reversal of their hypogonadotropism (spontaneous LH pulses) responded to exogenous kisspeptin with a GnRH-induced LH pulse. Individuals who had reversal but then subsequently suffered relapse of their IHH (loss of spontaneous LH pulsatility) did not respond to kisspeptin. Conclusions: The ability of kisspeptin to stimulate...

Tube Law of the Pharyngeal Airway in Sleeping Patients with Obstructive Sleep Apnea.

Abstract: STUDY OBJECTIVES Obstructive sleep apnea (OSA) is characterized by repetitive pharyngeal collapse during sleep. However, the dynamics of pharyngeal narrowing and re-expansion during flow-limited breathing are not well described. The static pharyngeal tube law (end-expiratory area versus luminal pressure) has demonstrated increasing pharyngeal compliance as luminal pressure decreases, indicating that the airway would be sucked closed with sufficient inspiratory effort. On the contrary, the airway is rarely sucked closed during inspiratory flow limitation, suggesting that the airway is getting stiffer. Therefore, we hypothesized that during inspiratory flow limitation, as opposed to static conditions, the pharynx becomes stiffer as luminal pressure decreases. METHODS Upper airway endoscopy and simultaneous measurements of airflow and epiglottic pressure were performed during natural nonrapid eye movement sleep. Continuous positive (or negative) airway pressure was used to induce flow limitation. Flow-limited breaths were selected for airway cross-sectional area measurements. Relative airway area was quantified as a percentage of end-expiratory area. Inspiratory airway radial compliance was calculated at each quintile of epiglottic pressure versus airway area plot (tube law). RESULTS Eighteen subjects (14 males) with OSA (apnea-hypopnea index = 57 ± 27 events/h), aged 49 ± 8 y, with a body mass index of 35 ± 6 kg/m(2) were studied. A total of 163 flow limited breaths were analyzed (9 ± 3 breaths per subject). Compliances at the fourth (2.0 ± 4.7 % area/cmH2O) and fifth (0.0 ± 1.7 % area/cmH2O) quintiles were significantly lower than the first (12.2 ± 5.5 % area/cmH2O) pressure quintile (P < 0.05). CONCLUSIONS The pharyngeal tube law is concave (airway gets stiffer as luminal pressure decreases) during respiratory cycles under inspiratory flow limitation.

Non-equilibrium cytoquake dynamics in cytoskeletal remodeling and stabilization

Abstract: The cytoskeleton (CSK) is a tensed fiber framework that supports, shapes and stabilizes the cell. The CSK is in a constant state of remodeling, moreover, which is an active non-equilibrium thermodynamic process. We report here that cytoskeletal remodeling involves reconfigurations that are not only sudden but also are transmitted to great distances within the cell in a fashion reminiscent of quakes in the Earth's crust. Remarkably, these events in the cell conform both qualitatively and quantitatively to empirical laws typical of earthquakes, including hierarchical fault structures, cumulative energy distributions following the Gutenberg–Richter law, and rate of after-shocks following Omori's law. While it is well-established that remodeling and stabilization of the cytoskeleton are non-equilibrium process, these new unanticipated observations establish that these processes are also remarkably non-local and strongly cooperative.

Airway and Parenchymal Strains during Bronchoconstriction in the Precision Cut Lung Slice.

Abstract: The precision-cut lung slice (PCLS) is a powerful tool for studying airway reactivity, but biomechanical measurements to date have largely focused on changes in airway caliber. Here we describe an image processing tool that reveals the associated spatio-temporal changes in airway and parenchymal strains. Displacements of sub-regions within the PCLS are tracked in phase-contrast movies acquired after addition of contractile and relaxing drugs. From displacement maps, strains are determined across the entire PCLS or along user-specified directions. In a representative mouse PCLS challenged with 10−4M methacholine, as lumen area decreased, compressive circumferential strains were highest in the 50 μm closest to the airway lumen while expansive radial strains were highest in the region 50–100 μm from the lumen. However, at any given distance from the airway the strain distribution varied substantially in the vicinity of neighboring small airways and blood vessels. Upon challenge with the relaxant agonist chloroquine, although most strains disappeared, residual positive strains remained a long time after addition of chloroquine, predominantly in the radial direction. Taken together, these findings establish strain mapping as a new tool to elucidate local dynamic mechanical events within the constricting airway and its supporting parenchyma.

Compressive Stress Causes an Unjamming Transition and an Epithelial–Mesenchymal Transition in the Airway Epithelium in Asthma

Abstract: One of the major characteristics of asthma is bronchospasm, which is caused by excessively contracted smooth muscle and results in buckling of the airway epithelium. Buckling of the epithelium imposes compressive mechanical stress on the airway epithelial cells. We previously reported that compressive mechanical stress, which is similar to stress that occurs during bronchospasm, induces airway remodeling in well-differentiated primary human bronchial epithelial (HBE) cells maintained in air–liquid interface culture. In this study, we investigated the physical behavior of HBE cells cultured from normal donors and donors with asthma to gain a better understanding of the mechanobiology of airway epithelial cells. We captured time-lapse images of HBE cells and quantified cellular motions. In normal cells, the transition from an unjammed state, in which cells flow like a fluid and rearrange with neighbors frequently, to a jammed state, in which cells move little, like a solid, and rearrange infrequently, occurred between Days 6 and 8 in air–liquid interface culture, but in asthmatic cells the transition was delayed until Day 14 (1). Also, in cell lysates from Days 6 through 14, the existence of vimentin was temporally correlated with the onset of the jamming transition. Treatment of asthmatic cells with SB431542, a transforming growth factor-b receptor inhibitor, accelerated the jamming transition and the disappearance of vimentin. Furthermore, compressive stress caused the jammed cells to transition to an unjammed state, but pretreatment with SB431542 attenuated the compressive stress-induced unjamming transition. Repeated applications of compressive stress induced the expression of vimentin and slug (epithelial–mesenchymal transition marker proteins) but reduced claudin-1 (a tight junction protein). Maturation of unjammed HBE cells causes a jamming transition, whereas compression of the jammed HBE cells causes an unjamming transition. Importantly, transforming growth factor-b controls the jamming transition and associated vimentin expression, and compressive stress induces EMT. These findings suggest that the jamming–unjamming transition is a novel physical feature that captures injury-repair processes and differentiates the normal epithelium from the asthmatic epithelium. Author disclosures are available with the text of this article at www.atsjournals.org.