Anne-Marie Lauzon

McGill University | McGill · Department of Medicine

The transcription factors (TFs) myocardin (MyoCD) and ETS Like-1 protein (Elk-1) competitively bind to serum response factor (SRF) and control myogenic- and mitogenic-related gene expression in smooth muscle, respectively. Their functions are therefore mutually inhibitory, which result in a contractile versus proliferative phenotype dichotomy. Airw...

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 functi...

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 musc...

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 in...

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. He...

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). Molecular...

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 path...

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 contro...

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 con...

The increased mass of airway smooth muscle (ASM) in the airways of asthmatic patients may contribute to the pathology of this disease by increasing the capacity for airway narrowing. Evidence for the airway epithelium as a participant in ASM remodeling is accruing. To investigate mechanisms by which airway epithelial cells induce ASM cell (ASMC) pr...

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. I...

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 is the result of increased ASM mass alone or also increased contractile force genera...

Cystic Fibrosis (CF) is a genetic disease that causes multiple pathologies in the airway. Two major respiratory symptoms of CF are airway hyperresponsiveness (AHR) and airway remodeling. Airway smooth muscle (ASM) is hypothesized to be responsible for these airway dysfunctions as their thickening is involved in remodeling and excessive contraction...

Significance The emergence of spatially distributed phenomena, such as traffic jams or disease outbreaks, results from spreading of local events to larger scale. We investigated spreading of local events in the simplified situation of a 1-dimensional system. In particular, we addressed perturbations in the mechanochemistry of groups of myosin molec...

Global changes in the state of spatially distributed systems can often be traced back to events resulting from local interactions. Whether the results of local interactions grow into global changes, however, depends (i) on the system geometry and (ii) the spatial spreading of the outcomes of local interactions. Here, we investigate how different sp...

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. A movement trace f...

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 o...

In vitro motility assays are a valuable tool in understanding and characterizing motor protein mechanics, but existing algorithms are not optimized for time resolved analyses. We propose an algorithm that combines trace detection with time resolved analysis. By tracking filament ends, we double the number of data points and minimize data loss from...

Rationale: 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 date no comprehensive study of cryopreservation protocols for isolated ASM has been performed. Met...

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 fib...

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

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 remodelling at the source of the mass increase is ongoing. We dissected human airway trees from asthmatic an...

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...

Background: Heaves is a naturally occurring equine disease that shares many similarities with human asthma including reversible antigen-induced bronchoconstriction, airway inflammation and remodeling. Objective: The purpose of this study was to determine whether the trachealis muscle is mechanically representative of the peripheral airway smooth...

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 surviv...

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 epi...

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 m...

In vitro motility and laser trap assays are commonly used for molecular mechanics measurements. However, chemicals cannot be added during 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. Biocompatibility of the compon...

Rationale: The latch-state describes the ability of tonic smooth muscle to maintain force at reduced ATP consumption and crossbridge cycling rate. In animal models this is evidenced by reduced unloaded shortening velocity (Vmax), presumably indicative of crossbridge cycling rate, and reduced myosin light chain phosphorylation (pMLC). In this study...

Asthma is an inflammatory disease of the airways characterized by airway hyperresponsiveness, an exaggerated bronchoconstrictive response of airway smooth muscle (ASM) to stimuli. However, whether asthmatic ASM is mechanically different from non-asthmatic ASM is still unclear. Most studies so far have been performed on the trachealis muscle but it...

Background: Studies conducted at the whole muscle level have shown that smooth muscle can maintain tension with low Adenosine triphosphate (ATP) consumption. Whereas it is generally accepted that this property (latch-state) is a consequence of the dephosphorylation of myosin during its attachment to actin, free dephosphorylated myosin can also bin...

Key points Activated CD4 ⁺ T cells enhance the contractility of airway smooth muscle. In order to enhance contractility, contact between CD4 ⁺ T cells and smooth muscle is required. The enhanced contractility is correlated with increased levels of fast myosin isoform. Our data suggest that inflammatory cells promote airway smooth muscle hypercontra...

In motility assays of muscle myosins, a distinct motile state emerges with increasing number of mechanically coupled myosin binding sites (N). This is explicable by coordinated myosin stepping (CMS): build-up of pre power stroke (PS) myosins is followed by a whole group PS and detachment cascade [1]. At low N, singular infrequent detachment cascade...

The proteins involved in smooth muscle's molecular contractile mechanism - the anti-parallel motion of actin and myosin filaments driven by myosin heads interacting with actin - are found as different isoforms. While their expression levels are altered in disease states, their relevance to the mechanical interaction of myosin with actin is not suff...

Naturally occurring groups of muscle myosin behave differently from individual myosins or small groups commonly assayed in vitro. Here, we investigate the emergence of myosin group behavior with increasing myosin group size. Assuming the number of myosin binding sites (N) is proportional to actin length (L) (N = L/35.5 nm), we resolve in vitro moti...

Background: Smooth muscle has the distinctive ability to maintain force for long periods of time and at low energy costs. While it is generally agreed that this property, called the latch-state, is due to the dephosphorylation of myosin while attached to actin, dephosphorylated-detached myosin can also attach to actin and may contribute to force m...

There is evidence that the actin-activated ATP kinetics and the mechanical work produced by muscle myosin molecules are regulated by two surface loops, located near the ATP binding pocket (loop 1), and in a region that interfaces with actin (loop 2). These loops regulate force and velocity of contraction, and have been investigated mostly in single...

Duchenne muscular dystrophy is a lethal disorder caused by defects in the dystrophin gene, which leads to respiratory or cardiac muscle failure. Lack of dystrophin predisposes the muscle cell sarcolemmal membrane to mechanical damage. However, the role of myosin in this muscle weakness has been poorly addressed. In the current study, in addition to...

Smooth muscle (SM) hyper-contractility is central to the pathophysiology of several diseases, including asthma. Inflammatory cells and/or their products may alter the expression of contractile proteins, thereby enhancing SM mechanics. The goal of the current study was to characterize the maximum unloaded shortening velocity (Vmax), stress (force/cr...

Molecular mechanical differences between actin isoforms remain elusive potentially because their sequence differences are limited to the actin regulatory protein binding sites[1]. We executed in vitro motility measurements of smooth muscle myosin with skeletal muscle α-actin (α-Act) and smooth muscle γ-actin (γ-Act) alone and in complexes with smoo...

Smooth muscle is unique in its capability to maintain force for long periods of time at low ATP (energy) consumption. This property, called the latch-state, is hypothesized to occur due to the dephosphorylation of myosin while attached to actin. Alternative theories have proposed that dephosphorylated-detached myosin can also re-attach to actin and...

It remains unclear whether airway smooth muscle (ASM) mechanics is altered in asthma. While efforts have originally focussed on contractile force, some evidence points to an increased velocity of shortening. A greater rate of airway renarrowing after a deep inspiration has been reported in asthmatics compared to controls, which could result from a...

Airway hyperresponsiveness (AHR), a characteristic of asthma that involves an excessive reduction in airway caliber, is a complex mechanism reflecting multiple processes that manifest over a large range of length and time scales. At one extreme, molecular interactions determine the force generated by airway smooth muscle (ASM). At the other, the sp...

Caffeine is sometimes used in cell physiological studies to release internally stored Ca(2+). We obtained evidence that caffeine may also act through a different mechanism that has not been previously described and sought to examine this in greater detail. We ruled out a role for phosphodiesterase (PDE) inhibition, since the effect was 1) not rever...

Patients with cystic fibrosis (CF) often suffer from gastrointestinal cramps and intestinal obstruction. The CF transmembrane conductance regulator (CFTR) channel has been shown to be expressed in vascular and airway smooth muscle (SM). We hypothesized that the absence of CFTR expression alters the gastrointestinal SM function and that these altera...

Background: Collective propulsion of actin by myosin motors is fundamental to most muscle contraction models. Single myosin load-dependent mechanochemistry as well as cooperative action of small numbers of motors are increasingly well-understood. Deducing macroscopic actin propulsion from microscopic actomyosin interaction would help to connect bot...

Telokin is a smooth muscle (SM)-specific protein identical to the C-terminal domain of myosin light chain kinase (MLCK). Telokin retards myosin phosphorylation and accelerates its dephosphorylation, but not by simple competition with MLCK. Telokin also prevents myosin's folded conformation. This study explores the effect of telokin on the mechanics...

Smooth muscle is unique in its ability to maintain force for long periods of time at low energy consumption. This property, called the latch-state, has been postulated to be a consequence of the dephosphorylation of myosin molecules when attached to the actin thin filament. Alternatively, unphosphorylated (unPHOS) myosin could potentially attach to...

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Despite the emerging use of bronchial thermoplasty in asthma therapy, the response of airway smooth muscle (ASM) to extreme temperatures is unknown. We investigated the immediate effects of exposing ASM to supraphysiologic temperatures. Isometric contractions were studied in bovine ASM before and after exposure to various thermal loads and/or pharm...

Although the active properties of airway smooth muscle (ASM) have garnered much modeling attention, the passive mechanical properties are not as well studied. In particular, there are important dynamic effects observed in passive ASM, particularly strain-induced fluidization, which have been observed both experimentally and in models; however, to d...

We present a multiscale, spatially distributed model of lung and airway behaviour with the goal of furthering the understanding of airway hyper-responsiveness and asthma. The model provides an initial computational framework for linking events at the cellular and molecular levels, such as Ca(2+) and crossbridge dynamics, to events at the level of t...

Airway hyperresponsiveness (AHR) is a characteristic feature of asthma. It has been proposed that an increase in the shortening velocity of airway smooth muscle (ASM) could contribute to AHR. To address this possibility, we tested whether an increase in the isotonic shortening velocity of ASM is associated with an increase in the rate and total amo...

Airway smooth muscle (ASM) is cyclically stretched during breathing, even in the active state, yet the factors determining its dynamic force-length behavior remain incompletely understood. We developed a model of the activated ASM strip and compared its behavior to that observed in strips of rat trachealis muscle stimulated with methacholine. The m...

The effects of remodeling of airway smooth muscle (SM) by hyperplasia on airway SM contractility in vivo are poorly explored. The aim of this study was to investigate the relationship between allergen-induced airway SM hyperplasia and its contractile phenotype. Brown Norway rats were sensitized with ovalbumin (OVA) or saline on day 0 and then eithe...

Airway smooth muscle (ASM) exhibits complex contractile dynamics and has a highly disordered structure. This contrasts with skeletal muscle which contains ordered arrays of contractile filaments aligned with the long axes of the cells. Models of ASM, however, are often based on Huxley's cross-bridge model, which was developed for skeletal muscle an...

Smooth muscle (SM) is unique in its ability to maintain force for long periods of time at low energy cost. This property is called the latch-state. One of the assumptions of the latch state model of Hai and Murphy is that myosin must first be phosphorylated in order to attach to the thin filament. However, we previously demonstrated that unphosphor...

Airway smooth muscle (SM) of patients with asthma exhibits a greater velocity of shortening (Vmax) than that of normal subjects, and this is thought to contribute to airway hyperresponsiveness. A greater Vmax can result from increased myosin activation. This has been reported in sensitized human airway SM and in models of asthma. A faster Vmax can...

Smooth muscle is unique in its ability to maintain force at low MgATP consumption. This property, called the latch state, is more prominent in tonic than phasic smooth muscle. Studies performed at the muscle strip level have suggested that myosin from tonic muscle has a greater affinity for MgADP and therefore remains attached to actin longer than...

Airway hyperresponsiveness (AH) is a hallmark of asthma. The dynamics of the airway smooth muscle (SM) contraction, rather than its force-generating capacity, have been postulated to be key features of AH. Two mechanisms were proposed whereby an increased velocity of shortening (Vmax) of the airway SM leads to excessive bronchoconstriction. The fir...

Excessive airway obstruction is the cause of symptoms and abnormal lung function in asthma. As airway smooth muscle (ASM) is the effecter controlling airway calibre, it is suspected that dysfunction of ASM contributes to the pathophysiology of asthma. However, the precise role of ASM in the ser