Serum Response Factor Expression in Excess Permits a Dual Contractile-Proliferative Phenotype of Airway Smooth Muscle.

The transcription factors (TFs) MyoCD (myocardin) and Elk-1 (ETS Like-1 protein) competitively bind to SRF (serum response factor) and control myogenic- and mitogenic-related gene expression in smooth muscle, respectively. Their functions are therefore mutually inhibitory, which results in a contractile-versus-proliferative phenotype dichotomy. Airway smooth muscle cell (ASMC) phenotype alterations occur in various inflammatory airway diseases, promoting pathological remodeling and contributing to airflow obstruction.

Induction of a memory-like CD4 T-cell phenotype by airway smooth muscle cells.

In asthma, CD4 T-cell interaction with airway smooth muscle (ASM) may enhance its contractile properties and promote its proliferation. However, less is known about the effects of this interaction on T cells. To explore the consequences of interaction of CD4 T cells with ASM we placed the cells in co-culture and analyzed the phenotypic and functional changes in the T cells.

A method for isolating contractile smooth muscle cells from cryopreserved tissue.

Multiple techniques have been developed to isolate contractile smooth muscle cells (SMCs) from tissues with varying degrees of success. However, most of these approaches rely on obtaining fresh tissue, which poses logistical challenges. In the present study, we introduce a novel protocol for isolating contractile SMCs from cryopreserved smooth muscle (SM) tissue, thereby enhancing experimental efficiency.

CD4 T cell-derived IFN-γ and LIGHT synergistically upregulate chemokine production from airway smooth muscle cells.

Airway smooth muscle (ASM) remodeling in asthmatic airways may contribute to persistent airflow limitation and airway hyperresponsiveness. CD4 T cells infiltrate the ASM layer where they may induce a proliferative and secretory ASM cell phenotype. We studied the interaction between activated CD4 T cells and ASM cells in co-culture in vitro and investigated the effects of CD4 T cells on chemokine production by ASM cells.

Automated, high temporal resolution mechanics measurements during incubation of contractile tissues.

Muscle tissue mechanics and contractility measurements have a great advantage over cultured cell level experiments as their mechanical and contractile properties are much closer to in vivo tissue properties. However, tissue level experiments cannot be combined with incubation with the same time resolution and consistency as cell culture studies. Here we present a system in which contractile tissues can be incubated for days while intermittently being tested for their mechanical and contractile properties.

Airway smooth muscle function in asthma.

Known to have affected around 340 million people across the world in 2018, asthma is a prevalent chronic inflammatory disease of the airways. The symptoms such as wheezing, dyspnea, chest tightness, and cough reflect episodes of reversible airway obstruction. Asthma is a heterogeneous disease that varies in clinical presentation, severity, and pathobiology, but consistently features airway hyperresponsiveness (AHR)-excessive airway narrowing due to an exaggerated response of the airways to various stimuli.

Molecular-level evidence of force maintenance by smooth muscle myosin during LC20 dephosphorylation.

Smooth muscle (SM) is found in most hollow organs of the body. Phasic SM, as found in the gut, contracts to propel content, whereas tonic SM, as found in most blood vessels, maintains tension. This force maintenance is referred to as the latch state and occurs at low levels of myosin activation (myosin light chain [LC20] phosphorylation).

System Identification and Two-Degree-of-Freedom Control of Nonlinear, Viscoelastic Tissues.

Objective: This paper presents a force control scheme for brief isotonic holds in an isometrically contracted muscle tissue, with minimal overshoot and settling time to measure its shortening velocity, a key parameter of muscle function.

Methods: A two-degree-of-freedom control configuration, formed by a feedback controller and a feedforward controller, is explored. The feedback controller is a proportional-integral controller and the feedforward controller is designed using the inverse of a control-oriented model of muscle tissue.

Interferon-γ amplifies airway smooth muscle-mediated CD4+ T cell recruitment by promoting the secretion of C-X-C-motif chemokine receptor 3 ligands.

Asthmatic airways feature increased ASM mass that is largely attributable to hyperplasia, and which potentially contributes to excessive airway narrowing. T cells induce ASMC proliferation via contact-dependent mechanisms in vitro that may have importance for asthmatic ASM growth, as CD4+ T cells infiltrate ASM bundles in asthmatic human airways. In this study, we used an in vitro migration assay to investigate the pathways responsible for the trafficking of human CD4+ T cells to ASM.

Intrapulmonary airway smooth muscle is hyperreactive with a distinct proteome in asthma.

Constriction of airways during asthmatic exacerbation is the result of airway smooth muscle (ASM) contraction. Although it is generally accepted that ASM is hypercontractile in asthma, this has not been unambiguously demonstrated. Whether airway hyperresponsiveness (AHR) is the result of increased ASM mass alone or also increased contractile force generation per unit of muscle directly determines the potential avenues for treatment.

Characterization of cystic fibrosis airway smooth muscle cell proliferative and contractile activities.

Cystic fibrosis (CF) is a genetic disease that causes multiple airway abnormalities. Two major respiratory consequences of CF are airway hyperresponsiveness (AHR) and airway remodeling. Airway smooth muscle (ASM) is hypothesized to be responsible for the airway dysfunction, since their thickening is involved in remodeling, and excessive contraction by the ASM may cause AHR.

Spreading of perturbations in myosin group kinetics along actin filaments.

Global changes in the state of spatially distributed systems can often be traced back to perturbations that arise locally. Whether such local perturbations grow into global changes depends on the system geometry and the spatial spreading of these perturbations. Here, we investigate how different spreading behaviors of local perturbations determine their global impact in 1-dimensional systems of different size.

Rapid time-stamped analysis of filament motility.

The in vitro motility assay is a valuable tool to understand motor protein mechanics, but existing algorithms are not optimized for accurate time resolution. We propose an algorithm that combines trace detection with a time-stamped analysis. By tracking filament ends, we minimize data loss from overlapping and crossing filaments.

Contractile Properties of Intrapulmonary Airway Smooth Muscle in Cystic Fibrosis.

Cystic fibrosis (CF) is an autosomal-recessive disease caused by mutations in the CF transmembrane conductance regulator gene. Many patients with CF have asthma-like symptoms and airway hyperresponsiveness, which are potentially associated with altered airway smooth muscle (ASM) contractility. Our goal in this study was to assess the contractility of the CF intrapulmonary ASM.

Maintenance of contractile function of isolated airway smooth muscle after cryopreservation.

Isolated human airway smooth muscle (ASM) tissue contractility studies are essential for understanding the role of ASM in respiratory disease, but limited availability and cost render storage options necessary for optimal use. However, to our knowledge, no comprehensive study of cryopreservation protocols for isolated ASM has been performed to date. We tested several cryostorage protocols on equine trachealis ASM using different cryostorage media [1.

Basic Fibroblast Growth Factor 2 Is a Determinant of CD4 T Cell-Airway Smooth Muscle Cell Communication through Membrane Conduits.

Activated CD4 T cells connect to airway smooth muscle cells (ASMCs) in vitro via lymphocyte-derived membrane conduits (LMCs) structurally similar to membrane nanotubes with unknown intercellular signals triggering their formation. We examined the structure and function of CD4 T cell-derived LMCs, and we established a role for ASMC-derived basic fibroblast growth factor 2 (FGF2b) and FGF receptor (FGFR)1 in LMC formation. Blocking FGF2b's synthesis and FGFR1 function reduced LMC formation.

Epithelial Cells Induce a Cyclo-Oxygenase-1-Dependent Endogenous Reduction in Airway Smooth Muscle Contractile Phenotype.

Airway smooth muscle cells (ASMCs) are phenotypically regulated to exist in either a proliferative or a contractile state. However, the influence of other airway structural cell types on ASMC phenotype is largely unknown. Although epithelial cells are known to drive ASM proliferation, their effects on the contractile phenotype are uncertain.

Directional preference of airway smooth muscle mass increase in human asthmatic airways.

Airway smooth muscle (ASM) orientation and morphology determine the ability of the muscle to constrict the airway. In asthma, ASM mass is increased, but it is unknown whether ASM orientation and morphology are altered as well or whether the remodeling at the source of the mass increase is ongoing. We dissected human airway trees from asthmatic and control lungs.

Airway hyperresponsiveness; smooth muscle as the principal actor.

Airway hyperresponsiveness (AHR) is a defining characteristic of asthma that refers to the capacity of the airways to undergo exaggerated narrowing in response to stimuli that do not result in comparable degrees of airway narrowing in healthy subjects. Airway smooth muscle (ASM) contraction mediates airway narrowing, but it remains uncertain as to whether the smooth muscle is intrinsically altered in asthmatic subjects or is responding abnormally as a result of the milieu in which it sits. ASM in the trachea or major bronchi does not differ in its contractile characteristics in asthmatics, but the more pertinent peripheral airways await complete exploration.

Peripheral Airway Smooth Muscle, but Not the Trachealis, Is Hypercontractile in an Equine Model of Asthma.

Heaves is a naturally occurring equine disease that shares many similarities with human asthma, including reversible antigen-induced bronchoconstriction, airway inflammation, and remodeling. The purpose of this study was to determine whether the trachealis muscle is mechanically representative of the peripheral airway smooth muscle (ASM) in an equine model of asthma. Tracheal and peripheral ASM of heaves-affected horses under exacerbation, or under clinical remission of the disease, and control horses were dissected and freed of epithelium to measure unloaded shortening velocity (Vmax), stress (force/cross-sectional area), methacholine effective concentration at which 50% of the maximum response is obtained, and stiffness.

Nanotubes connect CD4+ T cells to airway smooth muscle cells: novel mechanism of T cell survival.

Contact between airway smooth muscle (ASM) cells and activated CD4(+) T cells, a key interaction in diseases such as asthma, triggers ASM cell proliferation and enhances T cell survival. We hypothesized that direct contact between ASM and CD4(+) T cells facilitated the transfer of anti-apoptotic proteins via nanotubes, resulting in increased survival of activated CD4(+) T cells. CD4(+) T cells, isolated from PBMCs of healthy subjects, when activated and cocultured with ASM cells for 24 h, formed nanotubes that were visualized by immunofluorescence and atomic force microscopy.

Human trachealis and main bronchi smooth muscle are normoresponsive in asthma.

Rationale: Airway smooth muscle (ASM) plays a key role in airway hyperresponsiveness (AHR) but it is unclear whether its contractility is intrinsically changed in asthma.

Objectives: To investigate whether key parameters of ASM contractility are altered in subjects with asthma.

Methods: Human trachea and main bronchi were dissected free of epithelium and connective tissues and suspended in a force-length measurement set-up.

Phosphate and ADP differently inhibit coordinated smooth muscle myosin groups.

Actin filaments propelled in vitro by groups of skeletal muscle myosin motors exhibit distinct phases of active sliding or arrest, whose occurrence depends on actin length (L) within a range of up to 1.0 μm. Smooth muscle myosin filaments are exponentially distributed with ≈150 nm average length in vivo--suggesting relevance of the L-dependence of myosin group kinetics.

A microfluidic chamber to study the dynamics of muscle-contraction-specific molecular interactions.

In vitro motility and laser trap assays are commonly used for molecular mechanics measurements. However, chemicals cannot be added during these measurements, because they create flows that alter the molecular mechanics. Thus, we designed a microfluidic device that allows the addition of chemicals without creating bulk flows.

Inhaled corticosteroids modulate the (+)insert smooth muscle myosin heavy chain in the equine asthmatic airways.

Rationale: Overexpression of the (+)insert smooth muscle myosin heavy chain (SMMHC) isoform could contribute to airway bronchospasm by increasing the velocity of contraction. Whether the (+)insert isoform is present in the small airways and its expression is reversible in asthma are unknown.

Objectives: To determine the anatomical location and the expression kinetics of the (+)insert SMMHC isoform in airways of horses with heaves and to evaluate its modulation in response to disease status.