Figure 11 - uploaded by Samir N Ghadiali
Content may be subject to copyright.
Cytoskeletal staining of A) actin filaments and B) tubulin filaments for EpC in high and low confluent monolayers. Green proteins represent actin filaments, red proteins represent tubulin and blue regions are nuclei of individual cells. The images were obtained with a 60X objective using an IX-71 inverted microscope.
Source publication
Recent advances in the ventilation of patients with acute respiratory distress syndrome (ARDS), including ventilation at low lung volumes, have resulted in a decreased mortality rate. However, even low-lung volume ventilation may exacerbate lung injury due to the cyclic opening and closing of fluid-occluded airways. Specifically, the hydrodynamic s...
Citations
... The limited number of patients of our study does not allow to draw definitive conclusions. In line with several studies, obese non-asthmatic children showed an asymptomatic increase in the more distal airway resistances, not detected by forced spirometry [22,23], but peripheral airways compression, could, over time, lead to a symptomatic reduced lung function, because of a local proinflammatory response related to a continuous damage of the airway epithelium [24]. ...
The existence of common inflammatory biomarkers linking obesity and asthma in children has been hypothesized. Nevertheless, laboratory and clinical characteristics of children with obesity and asthma are still poorly defined. The primary aim of the present study is to investigate the lung function and the cytokine profile, in children with obesity and asthma. In this prospective, cross-sectional pilot study, pulmonary function tests, biochemical parameters, and serum cytokines levels were compared in three groups of 28 children each, matched for age and sex. Obese children showed normal forced spirometry values except an increased distal airway resistance in subjects with obesity and no asthma. Both groups including obese children showed higher leptin and IL-10 levels and lower adiponectin and TNF-alpha levels compared to children with no obesity and asthma. IL-33 and TGF-beta1 levels were higher in children with obesity and asthma vs. children with normal weight and asthma. Finally, IL-6 was undetectable in approximately 70% of obese children with no asthma, in 57% obese asthmatic children and in 100% of children with normal-weight and asthma. Children with obesity and asthma show the most striking cytokine profile, suggesting a pro-inflammatory role of fat mass in asthma development.
... 24 Together, the change in airway mechanics leads to greater airway reactivity and air trapping with hyperinflation, and the mechanical changes may promote an inflammatory response in the airway as well. 25 Alveolar ventilation can also be affected by obesity since airway closure prevents gas exchange, causing ventilation-perfusion mismatch. 26 Distribution and degree of adiposity in the trunk, as opposed to other areas, may be a risk factor for why some obese individuals and not others develop late-onset non-atopic asthma with these mechanical changes. ...
The rates of asthma and obesity are increasing concurrently in the United States. Epidemiologic studies demonstrate that the incidence of asthma increases with obesity. Furthermore, obese individuals have asthma that is more severe, harder to control, and resistant to standard medications. In fact, specific asthma-obesity phenotypes have been identified. Various pathophysiologic mechanisms, including mechanical, inflammatory, metabolic and microbiome-associated, are at play in promulgating the obese-asthma phenotypes. While standard asthma medications, such as inhaled corticosteroids and biologics, are currently used to treat obese asthmatics, they may have limited effectiveness. Targeting the underlying aberrant processes, such as addressing steroid resistance, microbiome, metabolic and weight loss approaches, may be helpful.
... In addition, Yalcin et al. studied the effects of airway reopening speed and airway diameter on epithelial cell damage. In the process of reopening the airway by mechanical ventilation in acute respiratory distress syndrome, the distal area of the lung was more likely to be injured, and rapid inflation may have a cytoprotective effect [69]. Based on this, Huh et al. studied the mechanical damage of primary human small airway epithelial cells caused by the movement of a finite-length liquid plug in three-dimensional microfluidic system. ...
The pathogenesis of respiratory diseases is complex, and its occurrence and development also involve a series of pathological processes. The present research methods are have difficulty simulating the natural developing state of the disease in the body, and the results cannot reflect the real growth state and function in vivo. The development of microfluidic chip technology provides a technical platform for better research on respiratory diseases. The size of its microchannel can be similar to the space for cell growth in vivo. In addition, organ-on-a-chip can achieve long-term co-cultivation of multiple cells and produce precisely controllable fluid shear force, periodically changing mechanical force, and perfusate with varying solute concentration gradient. To sum up, the chip can be used to analyze the specific pathophysiological changes of organs meticulously, and it is widely used in scientific research on respiratory diseases. The focus of this review is to describe and discuss current studies of artificial respiratory systems based on organ-on-a-chip technology and to summarize their applications in the real world.
... 221 Such damage increased with reduced airway compliance 222 and diameter. 218 The rupture of liquid plugs can also lead to epithelial cell injury caused by fluid mechanical stresses in the vicinity and downstream of plug rupture 216 with associated inflammatory response. 223 Different mechanical forces generated during interface propagation and acting on the epithelial cells lining opening airways include pressure and pressure gradients, shear stress, and shear stress gradients ( fig. ...
... Cyclic opening and closing of the small airways or alveolar ducts could generate shear stress, acting on the collapsed and surrounding lung. 215,218 Although frequently mentioned as a common cause of injury during repeated opening and closing, no studies directly assessed shear stress in vivo. During the propagation of gas-liquid interfaces in vitro, shear stress at the air bubble cap was estimated as far greater than that in the regions upstream or downstream of the bubble tip. ...
Pulmonary atelectasis is common in the perioperative period. Physiologically, it is produced when collapsing forces derived from positive pleural pressure and surface tension overcome expanding forces from alveolar pressure and parenchymal tethering. Atelectasis impairs blood oxygenation and reduces lung compliance. It is increasingly recognized that it can also induce local tissue biologic responses, such as inflammation, local immune dysfunction, and damage of the alveolar–capillary barrier, with potential loss of lung fluid clearance, increased lung protein permeability, and susceptibility to infection, factors that can initiate or exaggerate lung injury. Mechanical ventilation of a heterogeneously aerated lung (e.g., in the presence of atelectatic lung tissue) involves biomechanical processes that may precipitate further lung damage: concentration of mechanical forces, propagation of gas–liquid interfaces, and remote overdistension. Knowledge of such pathophysiologic mechanisms of atelectasis and their consequences in the healthy and diseased lung should guide optimal clinical management.
... It is concluded that cell death decreases as bubble speed and tube radius increase. These results also supported the previous experimental work by Yalcin et al. (Yalcin et al., 2007). The effects of wall flexibility when a semi-infinite bubble propagates in a collapsed fluid occluded channel have been investigated (Juel and Heap, 2007;Hazel and Heil, 2002;Jensen et al., 2002). ...
... Moreover, at low lung volume ventilation, there are repeatedly opening/closing events which further exacerbates the lung injury (Hubmayr, 2002;Pelosi and Rocco, 2007;Heil et al., 2008). Besides, experimental studies have shown that airway diameter, cell confluence, wall compliance, and cell morphology also play a key role in cell necrosis during mechanical ventilation (Yalcin et al., 2007;Dailey et al., 2009;Higuita-Castro et al., 2014). ...
... More specifically, this study aims to investigate the effects of n and Ca on the magnitude of the pressure gradient in the bifurcating daughter airway wall. Earlier studies have shown that slow viscous flow exists in distal lung airways (i.e., in generations 17, 18, and 19) where inertial effects may be neglected (Yalcin et al., 2007). We, therefore, solved the steady Stokes equations where the viscosity is not constant but obeys the power-law model, using FEM in COMSOL presented the results graphically. ...
Mucous fluid is non-Newtonian secretions in the lower lung airways that accumulates when the alveolar-capillary membrane ruptures during acute respiratory distress syndrome. The mucus fluid has, therefore, different types of non-Newtonian properties like shear-thinning, viscoelasticity, and non-zero yield stress. In this paper, we numerically solved the steady Stokes equations along with arbitrary Eulerian-Lagrangian moving mesh techniques to study the microbubble propagation in a two-dimensional asymmetric bifurcating airway filled with non-Newtonian fluid where the fluid has shear-thinning behavior described by the power-law model. Numerical results show that both shear-thinning and surface tension characterized by the behavior index (n) and Capillary number (Ca), respectively, had a significant impact on microbubble flow patterns and the magnitude of the pressure gradient. At low values of both n and Ca, the microbubble leaves a thin film-thickness with the airway wall while a large and sharp peak of the pressure gradient near the thin bubble tip. Interestingly, increasing both n and Ca, leads to an increase in film thickness and a decrease in the pressure gradient magnitude in both the daughter airway walls. It is observed the magnitude of the pressure gradient is more sensitive to Ca compared to n. We concluded that shear-thinning and surface tension not only significantly impact the patterns of microbubble propagation but also the hydrodynamic stress magnitudes at the airway wall.
... The EpCs were exposed to simulated shear stresses like those associated with airway reopening when mechanically ventilated in airway reopening conditions to test the effects of the selected anti-inflammatory steroidal agents in their efficacy to decrease cellular injuries during airway reopening. For this purpose, reopening conditions were generated using a parallel-plate microfluidic flow chamber system (Bioptechs-FCS2 chamber), as described in our previous work (57). The chamber consists of a rubber membrane sandwiched between an upper coverslip and a lower coverslip with EpCs. ...
Many patients who suffer from pulmonary diseases cannot inflate their lungs normally as they need Mechanical Ventilation (MV) to assist them. The stress associated with MV can damage delicate epithelium in small airways and alveoli which can cause complications in many cases resulting in Ventilation Induced Lungs injuries (VILI) especially in patients with Acute Respiratory Distress Syndrome (ARDS). Therefore, efforts have been used to developed safe modes for its use. In our work, we propose a different approach to decrease injuries of Epithelial Cells (EpCs) upon MV. We alter EpCs' cytoskeletal structure to increase their survival rate during airway reopening conditions associated with MV. We tested two anti-inflammatory drugs Dexamethasone (DEX) and Trans-Dehydroandrosterone (DHEA) to alter the cytoskeleton. Cultured rat L2 alveolar EpCs were exposed to airway reopening conditions using a parallel plate perfusion chamber. Cells were exposed to a single bubble propagation to simulate stresses associated with mechanical ventilation in both control and study groups. Cellular injury and cytoskeleton reorganization were assessed via fluorescent microscopy while cell topography was studied via Atomic Force Microscopy (AFM). Our results indicate that cells in cultured media, DEX, or DHEA solutions did not lead to cell death (static cultures). Bubble flows caused significant cell injury. Pre-exposure with DEX or DHEA decreased cell death significantly. The AFM verified cells' mechanics' alteration due to actin fibers depolymerization. These results suggest potential beneficial effects of DEX and DHEA for ARRDS treatment for COVID-19 patients. They are also critical for VILI and applicable to future clinical studies.
... Most studies focused on decreasing mechanical stresses during ventilation to decrease cellular injuries. Using an in-vitro system of airway reopening, we have exposed epithelial cell monolayers to bubble propagation and showed that decreasing flow-induced stresses over epithelial cells enhances cell viabilities (Dailey et al., 2007;Yalcin et al., 2007Yalcin et al., , 2009). As a result of similar efforts (Higuita-castro et al., 2014), safer ventilation strategies were adopted clinically. ...
Acute respiratory distress syndrome (ARDS) is an acute inflammatory lung condition. It is characterized by disruption of gas exchange inside the alveoli, accumulation of protein edema, and an increase in lung stiffness. One major cause of ARDS is a lung infection, such as SARS-COV-2 infection. Lungs of ARDS patients need to be mechanically ventilated for airway reopening. Consequently, ventilation might damage delicate lung tissue leading to excess edema, known as ventilator-induced lung injury (VILI). Mortality of COVID-19 patients under VILI seems to be higher than non-COVID patients, necessitating effective preventative therapies. VILI occurs when small air bubbles form in the alveoli, injuring epithelial cells (EPC) due to shear stress. Nitric oxide (NO) inhalation was suggested as a therapy for ARDS, however, it was shown that it is not effective because of the extremely short half-life of NO. In this study, NO-releasing nanoparticles were produced and tested in an in vitro model, representing airways in the deep lung. Cellular injuries were quantified via fluorescent live/dead assay. Atomic force microscopy (AFM) was used to assess cell morphology. qRT-PCR was performed to assess the expression of inflammatory markers, specifically IL6 and CCL2. ELISA was performed to assess IL6 and confirm qRT-PCR results at the protein level. Finally, ROS levels were assessed in all groups. Here, we show that NO delivery via nanoparticles enhanced EPC survival and recovery, AFM measurements revealed that NO exposure affect cell morphology, while qRT-PCR demonstrated a significant downregulation in IL6 and CCL2 expression when treating the cells to NO both before and after shear exposure. ELISA results for IL6 confirmed qRT-PCR data. ROS experiment results support our findings from previous experiments. These findings demonstrate that NO-releasing nanoparticles can be used as an effective delivery approach of NO to deep lung to prevent/reduce ARDS associated inflammation and cell injuries. This information is particularly useful to treat severe ARDS due to COVID-19 infection. These nanoparticles will be useful when clinically administrated to COVID-19 patients to reduce the symptoms originating from lung distress.
... For better understanding the effects of bubble flow-induced damage caused by mechanical ventilation, we have previously developed an in vitro model of airway reopening [14,15]. In the developed model, the simulation of reopening dynamics was manifested through air bubble propagations inside an adjustable height parallel plate flow chamber, as shown in Figure 1. ...
... Here, bubble propagation was created with a syringe pump, and a variety of fluids can be tested on confluent or sub-confluent monolayers of EpCs. For the calculation of levels of normal and shear stresses in such a configuration, please refer to our previous studies [14,15]. In this paper, we present our protocol for the generation of a bubble flow-induced stress wave on cell monolayers. ...
... We have realized that more cells die in the regions close to side walls. Also, cell confluency is an important factor in cell injury for this type of perfusion experiment [14]. Therefore, to compare different experimental groups, it is advised to culture cells to the same confluency level. ...
Parallel plate flow chambers are widely used to expose cultured cells to physiological flows for the investigation of a variety of diseases. These applications usually involve the generation of continuous and steady fluid flow over cell monolayers for extended durations, usually a few days. Another technique is to generate a fast high-stress wave over the cells to see the immediate effect of flow-induced stresses. This can be achieved by propagating an air/liquid interface, in other words, a bubble, over cell monolayers. The approach is relevant to the reopening event of fluid-filled lung bronchioles and alveoli during mechanical ventilation therapy of Acute Respiratory Distress Syndrome. This article explains how we generate a stress wave using a parallel plate flow chamber and presents representative results of this wave on cultured lung epithelial cells.
... Rezidüel hacim ve toplam akciğer kapasitesi üzerindeki nispeten küçük etkinin aksine, obezitenin fonksiyonel rezidüel kapasite ve ekspiratuar rezerv hacmi (ERV) üzerindeki etkisi, net bir doz-cevap ilişkisi ile çok daha büyük bulunmuştur (25) . Yapılan çalışmalar, ERV'deki bu dramatik azalmanın, morbid obez bireyleri, çok düşük akciğer hacimlerinde tidal solunuma yol açarak bronkokonstriksiyon sırasında hiperinflasyon geliştirmeye daha yatkın hale getirdiği (26) ve ayrıca oluşan bu sekellerin, hava yolu epiteline zarar vererek hava yollarında proinflamatuvar bir tepki oluşturabileceğini göstermiştir (27) . Obezitenin oluşturduğu mekanik etki ile ayrıca, hava yolu direnci ve solunum sistemi kas hasarı da artmaktadır. ...
... 16 In addition, Yalcin HC et al, in an in vitro model of airway reopening showed significant epithelial cell injury. 17 Moreover, Zerah-Lancner et al, found a significant decrease in the FEV 1 /FVC ratio, in the V 50 and V 25 , as the severity of OSAHS increases, in 170 patients undergoing a sleep study. 18 Baydur et al, showed expiratory flow limitation in COPD and OSAHS patients, but their results could not distinguish the two cohorts. ...
Introduction and objectives
Most of the studies of the pathophysiology of Obstructive Sleep Apnea-Hypopnea Syndrome (OSAHS) focus on the collapsibility and obstruction of the upper airways. The aim of our study was the investigation of small airways’ function in patients with OSAHS.
Materials and methods
We studied 23 patients (mean age, 51.6 years) diagnosed with mild to severe OSAHS, without comorbidities and 8 controls (mean age, 45.9 years). All subjects underwent full polysomnography sleep study; spirometry and maximum flow/volume curves while breathing room air and a mixture of 80%He-20%O2. The volume of equal flows (VisoV⋅) of the two curves and the difference of flows at 50% of FVC (ΔV˙max50) were calculated, as indicates of small airways’ function.
Results
The results showed that VisoV⋅ was significantly increased in patients with OSAHS compared with controls (18.79 ± 9.39 vs. 4.72 ± 4.68, p = 0.004). No statistically significantly difference was found in ΔV˙max50% (p = 0.551); or the maximum Expiratory flow at 25–75% of FVC (p = 0.067) and the maximum expiratory flow at 50% of FVC (p = 0.174) breathing air.
Conclusions
We conclude that at the time of the diagnosis of OSAHS, the function of the small airways is affected. This could be due to breathing at low lung volumes and the cyclic closure/opening of the small airways and may affect the natural history of OSAHS. The findings could lead to new therapeutic implications, targeting directly the small airways.
