Probabilistic cellular automata modelling of intercellular interactions in airways: complex pattern formation in patients with chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is a highly prevalent lung disease characterized by chronic inflammation and tissue remodeling possibly induced by unusual interactions between fibrocytes and CD8+ T lymphocytes in the peribronchial area. To investigate this phenomenon, we developed a probabilistic cellular automata type model where the two types of cells follow simple local interaction rules taking into account cell death, proliferation, migration and infiltration. We conducted a rigorous mathematical analysis using multiscale experimental data obtained in control and disease conditions to estimate the model's parameters accurately. The simulation of the model is straightforward to implement, and two distinct patterns emerged that we can analyse quantitatively. In particular, we show that the change in fibrocyte density in the COPD condition is mainly the consequence of their infiltration into the lung during exacerbations, suggesting possible explanations for experimental observations in normal and COPD tissue. Our integrated approach that combines a probabilistic cellular automata model and experimental findings will provide further insights into COPD in future studies.

Rhinovirus infection of bronchial epithelium induces specific bronchial smooth muscle cell migration of severe asthmatic patients.

BACKGROUND: Patients with severe asthma show an increase in both exacerbation frequency and bronchial smooth muscle (BSM) mass. Rhinovirus (RV) infection of the bronchial epithelium (BE) is the main trigger of asthma exacerbations. Histological analysis of biopsies shows that a close connection between BE and hypertrophic BSM is a criterion for severity of asthma. OBJECTIVE: We hypothesized that RV infection of BE specifically increases BSM-cell migration from patients with asthma. METHODS: Serum samples, biopsies, or BSM cells were obtained from 86 patients with severe asthma and 31 subjects without asthma. BE cells from subjects without asthma were cultured in an air-liquid interface and exposed to RV-16. Migration of BSM cells was assessed in response to BE supernatant using chemotaxis assays. Chemokine concentrations were analyzed by transcriptomics and ELISAs. Immunocytochemistry, western blotting, and flow cytometry were used to quantify CXCR3 isoform distribution. CXCR3 downstream signaling pathways were assessed by calcium imaging and western blots. RESULTS: BSM cells from patients with severe asthma specifically migrated toward RV-infected BE, whereas those from subjects without asthma did not. This specific migration is driven by BE C-X-C motif chemokine ligand 10, which was increased in vitro in response to RV infection as well as in vivo in serum from exacerbating patients with severe asthma. The mechanism is related to both decreased expression and activation of the CXCR3-B-specific isoform in BSM cells from those with severe asthma. CONCLUSIONS: We have demonstrated a novel mechanism of BSM remodeling in patients with severe asthma following RV exacerbation. This study highlights the C-X-C motif chemokine ligand 10/CXCR3-A axis as a potential therapeutic target in severe asthma.

Main Pathogenic Mechanisms and Recent Advances in COPD Peripheral Skeletal Muscle Wasting.

Chronic obstructive pulmonary disease (COPD) is a worldwide prevalent respiratory disease mainly caused by tobacco smoke exposure. COPD is now considered as a systemic disease with several comorbidities. Among them, skeletal muscle dysfunction affects around 20% of COPD patients and is associated with higher morbidity and mortality. Although the histological alterations are well characterized, including myofiber atrophy, a decreased proportion of slow-twitch myofibers, and a decreased capillarization and oxidative phosphorylation capacity, the molecular basis for muscle atrophy is complex and remains partly unknown. Major difficulties lie in patient heterogeneity, accessing patients' samples, and complex multifactorial process including extrinsic mechanisms, such as tobacco smoke or disuse, and intrinsic mechanisms, such as oxidative stress, hypoxia, or systemic inflammation. Muscle wasting is also a highly dynamic process whose investigation is hampered by the differential protein regulation according to the stage of atrophy. In this review, we report and discuss recent data regarding the molecular alterations in COPD leading to impaired muscle mass, including inflammation, hypoxia and hypercapnia, mitochondrial dysfunction, diverse metabolic changes such as oxidative and nitrosative stress and genetic and epigenetic modifications, all leading to an impaired anabolic/catabolic balance in the myocyte. We recapitulate data concerning skeletal muscle dysfunction obtained in the different rodent models of COPD. Finally, we propose several pathways that should be investigated in COPD skeletal muscle dysfunction in the future.

Crucial role of fatty acid oxidation in asthmatic bronchial smooth muscle remodelling.

BACKGROUND: Bronchial smooth muscle (BSM) remodelling in asthma is related to an increased mitochondrial biogenesis and enhanced BSM cell proliferation in asthma. Since mitochondria produce the highest levels of cellular energy and fatty acid ß-oxidation is the most powerful way to produce ATP, we hypothesised that, in asthmatic BSM cells, energetic metabolism is shifted towards the ß-oxidation of fatty acids. OBJECTIVES: We aimed to characterise BSM cell metabolism in asthma both in vitro and ex vivo to identify a novel target for reducing BSM cell proliferation. METHODS: 21 asthmatic and 31 non-asthmatic patients were enrolled. We used metabolomic and proteomic approaches to study BSM cells. Oxidative stress, ATP synthesis, fatty acid endocytosis, metabolite production, metabolic capabilities, mitochondrial networks, cell proliferation and apoptosis were assessed on BSM cells. Fatty acid content was assessed in vivo using matrix-assisted laser desorption/ionisation spectrometry imaging. RESULTS: Asthmatic BSM cells were characterised by an increased rate of mitochondrial respiration with a stimulated ATP production and mitochondrial ß-oxidation. Fatty acid consumption was increased in asthmatic BSM both in vitro and ex vivo. Proteome remodelling of asthmatic BSM occurred via two canonical mitochondrial pathways. The levels of carnitine palmitoyl transferase (CPT)2 and low-density lipoprotein (LDL) receptor, which internalise fatty acids through mitochondrial and cell membranes, respectively, were both increased in asthmatic BSM cells. Blocking CPT2 or LDL receptor drastically and specifically reduced asthmatic BSM cell proliferation. CONCLUSION: This study demonstrates a metabolic switch towards mitochondrial ß-oxidation in asthmatic BSM and identifies fatty acid metabolism as a new key target to reduce BSM remodelling in asthma.

Fibrocyte accumulation in the airway walls of COPD patients.

The remodelling mechanism and cellular players causing persistent airflow limitation in COPD remain largely elusive. We have recently demonstrated that circulating fibrocytes, a rare population of fibroblast-like cells produced by the bone marrow stroma, are increased in COPD patients during an exacerbation. We aimed to quantify fibrocyte density in situ in bronchial specimens from both control subjects and COPD patients, to define associations with relevant clinical, functional and computed tomography (CT) parameters, and to investigate the effect of the epithelial microenvironment on fibrocyte survival in vitro ("Fibrochir" study).A total of 17 COPD patients and 25 control subjects, all requiring thoracic surgery, were recruited. Using co-immunostaining and image analysis, we identified CD45+ FSP1+ cells as tissue fibrocytes, and quantified their density in distal and proximal bronchial specimens. Fibrocytes, cultured from the blood samples of six COPD patients, were exposed to primary bronchial epithelial cell secretions from control subjects or COPD patients.We demonstrate that fibrocytes are increased in both distal and proximal tissue specimens of COPD patients. The density of fibrocytes is negatively correlated with lung function parameters and positively correlated with bronchial wall thickness as assessed by CT scan. A high density of distal bronchial fibrocytes predicts the presence of COPD with a sensitivity of 83% and a specificity of 70%. Exposure of fibrocytes to COPD epithelial cell supernatant favours cell survival.Our results thus demonstrate an increased density of fibrocytes within the bronchi of COPD patients, which may be promoted by epithelial-derived survival-mediating factors.

Determination of reliable lung function parameters in intubated mice.

BACKGROUND: Animal models and, in particular, mice models, are important tools to investigate the pathogenesis of respiratory diseases and to test potential new therapeutic drugs. Lung function measurement is a key step in such investigation. In mice, it is usually performed using forced oscillation technique (FOT), negative pressure-driven forced expiratory (NPFE) and pressure-volume (PV) curve maneuvers. However, these techniques require a tracheostomy, which therefore only allows end-point measurements. Orotracheal intubation has been reported to be feasible and to give reproducible lung function measurements, but the agreement between intubation and tracheostomy generated-data remains to be tested. METHODS: Using the Flexivent system, we measured lung function parameters (in particular, forced vital capacity (FVC), forced expiratory volume in the first 0.1 s (FEV0.1), compliance (Crs) of the respiratory system, compliance (C) measured using PV loop and an estimate of inspiratory capacity (A)) in healthy intubated BALB/cJ mice and C57BL/6 J mice and compared the results with similar measurements performed in the same mice subsequently tracheostomized after intubation, by means of paired comparison method, correlation and Bland-Altman analysis. The feasibility of repetitive lung function measurements by intubation was also tested. RESULTS: We identified parameters that are accurately evaluated in intubated animals (i.e., FVC, FEV0.1, Crs, C and A in BALB/cJ and FVC, FEV0.1, and A in C57BL/6 J). Repetitive lung function measurements were obtained in C57BL/6 J mice. CONCLUSION: This subset of lung function parameters in orotracheally intubated mice is reliable, thereby allowing relevant longitudinal studies.

Chemokines in COPD: From Implication to Therapeutic Use.

: Chronic Obstructive Pulmonary Disease (COPD) represents the 3rd leading cause of death in the world. The underlying pathophysiological mechanisms have been the focus of extensive research in the past. The lung has a complex architecture, where structural cells interact continuously with immune cells that infiltrate into the pulmonary tissue. Both types of cells express chemokines and chemokine receptors, making them sensitive to modifications of concentration gradients. Cigarette smoke exposure and recurrent exacerbations, directly and indirectly, impact the expression of chemokines and chemokine receptors. Here, we provide an overview of the evidence regarding chemokines involvement in COPD, and we hypothesize that a dysregulation of this tightly regulated system is critical in COPD evolution, both at a stable state and during exacerbations. Targeting chemokines and chemokine receptors could be highly attractive as a mean to control both chronic inflammation and bronchial remodeling. We present a special focus on the CXCL8-CXCR1/2, CXCL9/10/11-CXCR3, CCL2-CCR2, and CXCL12-CXCR4 axes that seem particularly involved in the disease pathophysiology.

Fibrocytes in Asthma and Chronic Obstructive Pulmonary Disease: Variations on the Same Theme.

Fibrocytes are circulating cells that have fibroblast properties. They are produced by the bone marrow stroma, and they move from the blood to injured organs using multiple chemokine pathways. They exhibit marked functional and phenotypic plasticity in response to the local tissue microenvironment to ensure a proinflammatory or a more resolving phenotype. They can adopt immune cell properties and modulate conventional immune cell functions. Although their exact function is not always clear, they have emerged as key effector cells in several fibrotic diseases such as keloid, scleroderma, and idiopathic pulmonary fibrosis. Recent evidence suggests that fibrocytes could contribute to bronchial obstructive diseases such as asthma and chronic obstructive pulmonary disease. This review summarizes the reported roles of fibrocytes and their pathways into the lung in the context of asthma and chronic obstructive pulmonary disease, provides an overview of the different roles played by fibrocytes, and discusses their possible contributions to these obstructive diseases.

Bronchial Smooth Muscle Remodeling in Nonsevere Asthma.

RATIONALE: Increased bronchial smooth muscle (BSM) mass is a key feature of airway remodeling that classically distinguishes severe from nonsevere asthma. Proliferation of BSM cells involves a specific mitochondria-dependent pathway in individuals with severe asthma. However, BSM remodeling and mitochondrial biogenesis have not been examined in nonsevere asthma. OBJECTIVES: We aimed to assess whether an increase in BSM mass was also implicated in nonsevere asthma and its relationship with mitochondria and clinical outcomes. METHODS: We enrolled 34 never-smoker subjects with nonsevere asthma. In addition, we recruited 56 subjects with nonsevere asthma and 19 subjects with severe asthma as comparative groups (COBRA cohort [Cohorte Obstruction Bronchique et Asthme; Bronchial Obstruction and Asthma Cohort; sponsored by the French National Institute of Health and Medical Research, INSERM]). A phenotypic characterization was performed using questionnaires, atopy and pulmonary function testing, exhaled nitric oxide measurement, and blood collection. Bronchial biopsy specimens were processed for immunohistochemistry and electron microscopy analysis. After BSM remodeling assessment, subjects were monitored over a 12-month period. MEASUREMENTS AND MAIN RESULTS: We identified characteristic features of remodeling (BSM area >26.6%) and increased mitochondrial number within BSM in a subgroup of subjects with nonsevere asthma. The number of BSM mitochondria was positively correlated with BSM area (r = 0.78; P < 0.001). Follow-up analysis showed that subjects with asthma with high BSM had worse asthma control and a higher rate of exacerbations per year compared with subjects with low BSM. CONCLUSIONS: This study reveals that BSM remodeling and mitochondrial biogenesis may play a critical role in the natural history of nonsevere asthma (Mitasthme study). Clinical trial registered with www.clinicaltrials.gov (NCT00808730).

Blood fibrocytes are recruited during acute exacerbations of chronic obstructive pulmonary disease through a CXCR4-dependent pathway.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is characterized by peribronchial fibrosis. The chronic course of COPD is worsened by recurrent acute exacerbations. OBJECTIVE: The aim of the study was to evaluate the recruitment of blood fibrocytes in patients with COPD during exacerbations and, subsequently, to identify potential mechanisms implicated in such recruitment. METHODS: Using flow cytometry, we quantified circulating fibrocytes and characterized their chemokine receptor expression in 54 patients with COPD examined during an acute exacerbation (V1) and 2 months afterward (V2) and in 40 control subjects. The role of the chemokines CXCL12 and CCL11 in fibrocyte migration was investigated by using a chemotaxis assay. Patients were followed for up to 3 years after V1. RESULTS: We demonstrated a significantly increased number of circulating fibrocytes at V1 compared with control subjects. The number of circulating fibrocytes decreased at V2. A high percentage of circulating fibrocytes during exacerbation was associated with increased risk of death. The percentage of fibrocytes at V2 was negatively correlated with FEV1, forced vital capacity, FEV1/forced vital capacity ratio, transfer lung capacity of carbon monoxide, and Pao2. Fibrocytes highly expressed CXCR4 and CCR3, the chemokine receptors for CXCL12 and CCL11, respectively. Fibrocytes collected from patients with COPD at V1 had increased chemotactic migration in response to CXCL12 but not to CCL11 compared with those from control subjects. Plerixafor, a CXCR4 antagonist, decreased fibrocyte migration to plasma from patients with exacerbating COPD. CONCLUSION: Blood fibrocytes are recruited during COPD exacerbations and related to mortality and low lung function. The CXCL12/CXCR4 axis is involved in such fibrocyte recruitment (Firebrob study; ClinicalTrials NCT01196832).

Selective dysfunction of p53 for mitochondrial biogenesis induces cellular proliferation in bronchial smooth muscle from asthmatic patients.

BACKGROUND: Increase of bronchial smooth muscle (BSM) mass is a crucial feature of asthma remodeling. The mechanisms of such an increased BSM mass are complex but involve enhanced mitochondrial biogenesis, leading to increased proliferation of BSM cells in asthmatic patients. The major tumor suppressor protein p53 is a key cell regulator involved in cell proliferation and has also been implicated in mitochondrial biogenesis. However, the role of p53 in BSM cell proliferation and mitochondrial biogenesis has not been investigated thus far. OBJECTIVE: We sought to evaluate the role of p53 in proliferation of BSM cells in asthmatic patients and mitochondrial biogenesis. METHODS: The expression of p53 was assessed both in vitro by using flow cytometry and Western blotting and ex vivo by using RT-PCR after laser microdissection. The role of p53 was assessed with small hairpin RNA lentivirus in both asthmatic patients and control subjects with BSM cell proliferation by using 5-bromo-2'-deoxyuridine and cell counting and in the expression of p21, BCL2-associated X protein, mitochondrial transcription factor A (TFAM), and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α). RESULTS: Twenty-nine patients with moderate-to-severe asthma and 26 control subjects were enrolled in the study. p53 expression was increased in BSM from asthmatic patients both ex vivo and in vitro, with a decreased interaction with mouse double minute 2 homolog (Mdm2) and an increased phosphorylation of serine 20. p53 did not inhibit the transcription of both TFAM and PGC-1α in BSM cells from asthmatic patients. As a consequence, p53 is unable to slow the increased mitochondrial biogenesis and hence the subsequent increased proliferation of BSM cells in asthmatic patients. CONCLUSION: This study suggests that p53 might act as a new potential therapeutic target against BSM remodeling in asthmatic patients.

House dust mites induce proliferation of severe asthmatic smooth muscle cells via an epithelium-dependent pathway.

RATIONALE: Asthma is a frequent airway disease, and asthma control determinants have been associated with indoor allergen sensitization. The most frequent allergens are house dust mites (HDM), which act in vivo on the bronchial epithelial layer. Severe asthma has also been associated with bronchial remodeling and more specifically with increased mass of bronchial smooth muscle (BSM). However, the relationship between HDM stimulation of the bronchial epithelial layer and BSM remodeling is unknown. OBJECTIVES: To evaluate whether epithelial stimulation with HDM induces BSM cell proliferation in subjects with severe asthma. METHODS: A total of 22 subjects with severe asthma and 27 subjects with no asthma were recruited. We have developed an in vitro culture model combining an epithelium layer in air-liquid interface (ALI) interacting with BSM. We assessed BSM proliferation using BrdU incorporation. We explored the role of epithelium-derived mediators using reverse-transcriptase polymerase chain reaction (RT-PCR) and ELISA in vitro and in vivo. Finally, leukotrienes receptor expression was assessed in vitro by flow cytometry and RT-PCR and ex vivo by laser microdissection and RT-PCR. MEASUREMENTS AND MAIN RESULTS: We found that epithelial stimulation by HDM selectively increased the proliferation of asthmatic BSM cells and not that of nonasthmatic cells. The mechanism involved epithelial protease-activated receptor-2-dependent production of leukotrienes C4 associated with an overexpression of leukotrienes receptor CysLTR1 by asthmatic BSM cells in vitro and ex vivo. CONCLUSIONS: This work demonstrates the selective role of HDM on BSM remodeling in patients with severe asthma and points out different therapeutic targets at epithelial and smooth muscle levels.

Calcium channel blocker reduces airway remodeling in severe asthma. A proof-of-concept study.

RATIONALE: Severe asthma is a major public health issue throughout the world. Increased bronchial smooth muscle (BSM) mass, a characteristic feature of airway remodeling in severe asthma, is associated with resistance to high-intensity treatment and poor prognosis. In vitro, the Ca(2+)-channel blocker gallopamil decreased the proliferation of BSM cells from patients with severe asthma. OBJECTIVES: We conducted a double-blind, randomized, placebo-controlled study to evaluate the effect of gallopamil on airway remodeling in patients with severe asthma. METHODS: Subjects received either gallopamil (n = 16) or placebo (n = 15) for 1 year and were monitored for an additional 3-month period. Airway remodeling was analyzed at baseline and after treatment phase using both fiberoptic bronchoscopy and computed tomography scan. The primary end point was the BSM area. Secondary end points included normalized BSM thickness and frequency of asthma exacerbations. MEASUREMENTS AND MAIN RESULTS: BSM area was reduced in the gallopamil group (baseline vs. end of treatment) but was unchanged in the placebo group. Between-group differences in BSM area were not significantly different in gallopamil versus placebo groups. By contrast, between-group differences in normalized BSM thickness were significantly different between the two groups. The mean number of exacerbations per month was not different during the treatment phase in gallopamil versus placebo group but was significantly lower in patients previously treated with gallopamil during the follow-up period. There were no differences between the groups with respect to overall side effects. CONCLUSIONS: Gallopamil treatment for 12 months reduces BSM remodeling and prevents the occurrence of asthma exacerbations. Clinical trial registered with www.clinicaltrials.gov (NCT 00896428).

Investigating axonal guidance with microdevice-based approaches.

The precise wiring of the nervous system relies on processes by which axons navigate in a complex environment and are guided by a concerted action of attractive and repulsive factors to reach their target. Investigating these guidance processes depends critically on our ability to control in space and time the microenvironment of neurons. The implementation of microfabrication techniques in cell biology now enables a precise control of the extracellular physical and chemical environment of cultured cells. However, microtechnology is only beginning to be applied in the field of axon guidance due to specific requirements of neuronal cultures. Here we review microdevices specifically designed to study axonal guidance and compare them with the conventional assays used to probe gradient sensing in cell biology. We also discuss how innovative microdevice-based approaches will enable the investigation of important systems-level questions on the gradient sensing properties of nerve cells, such as the sensitivity and robustness in the detection of directional signals or the combinatorial response to multiple cues.

Cytoplasmic intermediate filaments mediate actin-driven positioning of the nucleus.

The localization of the nucleus is precisely regulated, and defects in nuclear positioning are observed in diseases such as lissencephaly, cerebellar ataxia and dysplasia. We show here that cytoplasmic intermediate filaments are essential players in actin-dependent positioning of the nucleus. The actin retrograde flow is relayed by a flow of intermediate filaments that accumulate asymmetrically around the nuclear envelope. Perturbations of the intermediate filament network alter positioning of the nucleus in both migrating and immobile astrocytes. This function of intermediate filaments might be crucial for regulating cell motility, in particular in tumor cells expressing high levels of cytoplasmic intermediate filaments.

Cellular interplay in skeletal muscle regeneration and wasting: insights from animal models.

Skeletal muscle wasting, whether related to physiological ageing, muscle disuse or to an underlying chronic disease, is a key determinant to quality of life and mortality. However, cellular basis responsible for increased catabolism in myocytes often remains unclear. Although myocytes represent the vast majority of skeletal muscle cellular population, they are surrounded by numerous cells with various functions. Animal models, mostly rodents, can help to decipher the mechanisms behind this highly dynamic process, by allowing access to every muscle as well as time-course studies. Satellite cells (SCs) play a crucial role in muscle regeneration, within a niche also composed of fibroblasts and vascular and immune cells. Their proliferation and differentiation is altered in several models of muscle wasting such as cancer, chronic kidney disease or chronic obstructive pulmonary disease (COPD). Fibro-adipogenic progenitor cells are also responsible for functional muscle growth and repair and are associated in disease to muscle fibrosis such as in chronic kidney disease. Other cells have recently proven to have direct myogenic potential, such as pericytes. Outside their role in angiogenesis, endothelial cells and pericytes also participate to healthy muscle homoeostasis by promoting SC pool maintenance (so-called myogenesis-angiogenesis coupling). Their role in chronic diseases muscle wasting has been less studied. Immune cells are pivotal for muscle repair after injury: Macrophages undergo a transition from the M1 to the M2 state along with the transition between the inflammatory and resolutive phase of muscle repair. T regulatory lymphocytes promote and regulate this transition and are also able to activate SC proliferation and differentiation. Neural cells such as terminal Schwann cells, motor neurons and kranocytes are notably implicated in age-related sarcopenia. Last, newly identified cells in skeletal muscle, such as telocytes or interstitial tenocytes could play a role in tissular homoeostasis. We also put a special focus on cellular alterations occurring in COPD, a chronic and highly prevalent respiratory disease mainly linked to tobacco smoke exposure, where muscle wasting is strongly associated with increased mortality, and discuss the pros and cons of animal models versus human studies in this context. Finally, we discuss resident cells metabolism and present future promising leads for research, including the use of muscle organoids.

Innovative three-dimensional models for understanding mechanisms underlying lung diseases: powerful tools for translational research.

Chronic lung diseases result from alteration and/or destruction of lung tissue, inevitably causing decreased breathing capacity and quality of life for patients. While animal models have paved the way for our understanding of pathobiology and the development of therapeutic strategies for disease management, their translational capacity is limited. There is, therefore, a well-recognised need for innovative in vitro models to reflect chronic lung diseases, which will facilitate mechanism investigation and the advancement of new treatment strategies. In the last decades, lungs have been modelled in healthy and diseased conditions using precision-cut lung slices, organoids, extracellular matrix-derived hydrogels and lung-on-chip systems. These three-dimensional models together provide a wide spectrum of applicability and mimicry of the lung microenvironment. While each system has its own limitations, their advantages over traditional two-dimensional culture systems, or even over animal models, increases the value of in vitro models. Generating new and advanced models with increased translational capacity will not only benefit our understanding of the pathobiology of lung diseases but should also shorten the timelines required for discovery and generation of new therapeutics. This article summarises and provides an outline of the European Respiratory Society research seminar "Innovative 3D models for understanding mechanisms underlying lung diseases: powerful tools for translational research", held in Lisbon, Portugal, in April 2022. Current in vitro models developed for recapitulating healthy and diseased lungs are outlined and discussed with respect to the challenges associated with them, efforts to develop best practices for model generation, characterisation and utilisation of models and state-of-the-art translational potential.

Short-range interactions between fibrocytes and CD8+ T cells in COPD bronchial inflammatory response.

Bronchi of chronic obstructive pulmonary disease (COPD) are the site of extensive cell infiltration, allowing persistent contact between resident cells and immune cells. Tissue fibrocytes interaction with CD8+ T cells and its consequences were investigated using a combination of in situ, in vitro experiments and mathematical modeling. We show that fibrocytes and CD8+ T cells are found in the vicinity of distal airways and that potential interactions are more frequent in tissues from COPD patients compared to those of control subjects. Increased proximity and clusterization between CD8+ T cells and fibrocytes are associated with altered lung function. Tissular CD8+ T cells from COPD patients promote fibrocyte chemotaxis via the CXCL8-CXCR1/2 axis. Live imaging shows that CD8+ T cells establish short-term interactions with fibrocytes, that trigger CD8+ T cell proliferation in a CD54- and CD86-dependent manner, pro-inflammatory cytokines production, CD8+ T cell cytotoxic activity against bronchial epithelial cells and fibrocyte immunomodulatory properties. We defined a computational model describing these intercellular interactions and calibrated the parameters based on our experimental measurements. We show the model's ability to reproduce histological ex vivo characteristics, and observe an important contribution of fibrocyte-mediated CD8+ T cell proliferation in COPD development. Using the model to test therapeutic scenarios, we predict a recovery time of several years, and the failure of targeting chemotaxis or interacting processes. Altogether, our study reveals that local interactions between fibrocytes and CD8+ T cells could jeopardize the balance between protective immunity and chronic inflammation in the bronchi of COPD patients.