Tuft cell-derived acetylcholine promotes epithelial chloride secretion and intestinal helminth clearance.

Epithelial cells secrete chloride to regulate water release at mucosal barriers, supporting both homeostatic hydration and the "weep" response that is critical for type 2 immune defense against parasitic worms (helminths). Epithelial tuft cells in the small intestine sense helminths and release cytokines and lipids to activate type 2 immune cells, but whether they regulate epithelial secretion is unknown. Here, we found that tuft cell activation rapidly induced epithelial chloride secretion in the small intestine. This response required tuft cell sensory functions and tuft cell-derived acetylcholine (ACh), which acted directly on neighboring epithelial cells to stimulate chloride secretion, independent of neurons. Maximal tuft cell-induced chloride secretion coincided with immune restriction of helminths, and clearance was delayed in mice lacking tuft cell-derived ACh, despite normal type 2 inflammation. Thus, we have uncovered an epithelium-intrinsic response unit that uses ACh to couple tuft cell sensing to the secretory defenses of neighboring epithelial cells.

Distinct Epithelial-Innate Immune Cell Transcriptional Circuits Underlie Airway Hyperresponsiveness in Asthma.

Rationale: Indirect airway hyperresponsiveness (AHR) is a highly specific feature of asthma, but the underlying mechanisms responsible for driving indirect AHR remain incompletely understood. Objectives: To identify differences in gene expression in epithelial brushings obtained from individuals with asthma who were characterized for indirect AHR in the form of exercise-induced bronchoconstriction (EIB). Methods: RNA-sequencing analysis was performed on epithelial brushings obtained from individuals with asthma with EIB (n = 11) and without EIB (n = 9). Differentially expressed genes (DEGs) between the groups were correlated with measures of airway physiology, sputum inflammatory markers, and airway wall immunopathology. On the basis of these relationships, we examined the effects of primary airway epithelial cells (AECs) and specific epithelial cell-derived cytokines on both mast cells (MCs) and eosinophils (EOS). Measurements and Main Results: We identified 120 DEGs in individuals with and without EIB. Network analyses suggested critical roles for IL-33-, IL-18-, and IFN-γ-related signaling among these DEGs. IL1RL1 expression was positively correlated with the density of MCs in the epithelial compartment, and IL1RL1, IL18R1, and IFNG were positively correlated with the density of intraepithelial EOS. Subsequent ex vivo modeling demonstrated that AECs promote sustained type 2 (T2) inflammation in MCs and enhance IL-33-induced T2 gene expression. Furthermore, EOS increase the expression of IFNG and IL13 in response to both IL-18 and IL-33 as well as exposure to AECs. Conclusions: Circuits involving epithelial interactions with MCs and EOS are closely associated with indirect AHR. Ex vivo modeling indicates that epithelial-dependent regulation of these innate cells may be critical in indirect AHR and modulating T2 and non-T2 inflammation in asthma.

Type 2 inflammation reduces SARS-CoV-2 replication in the airway epithelium in allergic asthma through functional alteration of ciliated epithelial cells.

BACKGROUND: Despite well-known susceptibilities to other respiratory viral infections, individuals with allergic asthma have shown reduced susceptibility to severe coronavirus disease 2019 (COVID-19). OBJECTIVE: We sought to identify mechanisms whereby type 2 inflammation in the airway protects against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by using bronchial airway epithelial cells (AECs) from aeroallergen-sensitized children with asthma and healthy nonsensitized children. METHODS: We measured SARS-CoV-2 replication and ACE2 protein and performed bulk and single-cell RNA sequencing of ex vivo infected AEC samples with SARS-CoV-2 infection and with or without IL-13 treatment. RESULTS: We observed that viral replication was lower in AECs from children with allergic asthma than those from in healthy nonsensitized children and that IL-13 treatment reduced viral replication only in children with allergic asthma and not in healthy children. Lower viral transcript levels were associated with a downregulation of functional pathways of the ciliated epithelium related to differentiation as well as cilia and axoneme production and function, rather than lower ACE2 expression or increases in goblet cells or mucus secretion pathways. Moreover, single-cell RNA sequencing identified specific subsets of relatively undifferentiated ciliated epithelium (which are common in allergic asthma and highly responsive to IL-13) that directly accounted for impaired viral replication. CONCLUSION: Our results identify a novel mechanism of innate protection against SARS-CoV-2 in allergic asthma that provides important molecular and clinical insights during the ongoing COVID-19 pandemic.

Rhinovirus infection of the airway epithelium enhances mast cell immune responses via epithelial-derived interferons.

BACKGROUND: Mast cells (MCs) within the airway epithelium in asthma are closely related to airway dysfunction, but cross talk between airway epithelial cells (AECs) and MCs in asthma remains incompletely understood. Human rhinovirus (RV) infections are key triggers for asthma progression, and AECs from individuals with asthma may have dysregulated antiviral responses. OBJECTIVE: We utilized primary AECs in an ex vivo coculture model system to examine cross talk between AECs and MCs after epithelial rhinovirus infection. METHODS: Primary AECs were obtained from 11 children with asthma and 10 healthy children, differentiated at air-liquid interface, and cultured in the presence of laboratory of allergic diseases 2 (LAD2) MCs. AECs were infected with rhinovirus serogroup A 16 (RV16) for 48 hours. RNA isolated from both AECs and MCs underwent RNA sequencing. Direct effects of epithelial-derived interferons on LAD2 MCs were examined by real-time quantitative PCR. RESULTS: MCs increased expression of proinflammatory and antiviral genes in AECs. AECs demonstrated a robust antiviral response after RV16 infection that resulted in significant changes in MC gene expression, including upregulation of genes involved in antiviral responses, leukocyte activation, and type 2 inflammation. Subsequent ex vivo modeling demonstrated that IFN-ß induces MC type 2 gene expression. The effects of AEC donor phenotype were small relative to the effects of viral infection and the presence of MCs. CONCLUSIONS: There is significant cross talk between AECs and MCs, which are present in the epithelium in asthma. Epithelial-derived interferons not only play a role in viral suppression but also further alter MC immune responses including specific type 2 genes.

Loss of versican and production of hyaluronan in lung epithelial cells are associated with airway inflammation during RSV infection.

Airway inflammation is a critical feature of lower respiratory tract infections caused by viruses such as respiratory syncytial virus (RSV). A growing body of literature has demonstrated the importance of extracellular matrix changes such as the accumulation of hyaluronan (HA) and versican in the subepithelial space in promoting airway inflammation; however, whether these factors contribute to airway inflammation during RSV infection remains unknown. To test the hypothesis that RSV infection promotes inflammation via altered HA and versican production, we studied an ex vivo human bronchial epithelial cell (BEC)/human lung fibroblast (HLF) coculture model. RSV infection of BEC/HLF cocultures led to decreased hyaluronidase expression by HLFs, increased accumulation of HA, and enhanced adhesion of U937 cells as would be expected with increased HA. HLF production of versican was not altered following RSV infection; however, BEC production of versican was significantly downregulated following RSV infection. In vivo studies with epithelial-specific versican-deficient mice [SPC-Cre(+) Vcan-/-] demonstrated that RSV infection led to increased HA accumulation compared with control mice, which also coincided with decreased hyaluronidase expression in the lung. SPC-Cre(+) Vcan-/- mice demonstrated enhanced recruitment of monocytes and neutrophils in bronchoalveolar lavage fluid and increased neutrophils in the lung compared with SPC-Cre(-) RSV-infected littermates. Taken together, these data demonstrate that altered extracellular matrix accumulation of HA occurs following RSV infection and may contribute to airway inflammation. In addition, loss of epithelial expression of versican promotes airway inflammation during RSV infection further demonstrating that versican's role in inflammatory regulation is complex and dependent on the microenvironment.

Location of eosinophils in the airway wall is critical for specific features of airway hyperresponsiveness and T2 inflammation in asthma.

BACKGROUND: Eosinophils are implicated as effector cells in asthma, but the functional implications of the precise location of eosinophils in the airway wall is poorly understood. We aimed to quantify eosinophils in the different compartments of the airway wall and associate these findings with clinical features of asthma and markers of airway inflammation. METHODS: In this cross-sectional study, we utilised design-based stereology to accurately partition the numerical density of eosinophils in both the epithelial compartment and the subepithelial space (airway wall area below the basal lamina including the submucosa) in individuals with and without asthma and related these findings to airway hyperresponsiveness (AHR) and features of airway inflammation. RESULTS: Intraepithelial eosinophils were linked to the presence of asthma and endogenous AHR, the type that is most specific for asthma. In contrast, both intraepithelial and subepithelial eosinophils were associated with type 2 (T2) inflammation, with the strongest association between IL5 expression and intraepithelial eosinophils. Eosinophil infiltration of the airway wall was linked to a specific mast cell phenotype that has been described in asthma. We found that interleukin (IL)-33 and IL-5 additively increased cysteinyl leukotriene (CysLT) production by eosinophils and that the CysLT LTC4 along with IL-33 increased IL13 expression in mast cells and altered their protease profile. CONCLUSIONS: We conclude that intraepithelial eosinophils are associated with endogenous AHR and T2 inflammation and may interact with intraepithelial mast cells via CysLTs to regulate airway inflammation.

Juvenile, but Not Adult, Mice Display Increased Myeloid Recruitment and Extracellular Matrix Remodeling during Respiratory Syncytial Virus Infection.

Early life respiratory syncytial virus (RSV) infection has been linked to the onset of asthma. Despite this association, our knowledge of the progression of the initial viral infection is limited, and no safe or effective vaccine currently exists. Bronchioalveolar lavage, whole-lung cellular isolation, and gene expression analysis were performed on 3-wk- (juvenile) and 8-wk-old (adult) RSV-infected C57BL/6 mice to investigate age-related differences in immunologic responses; juvenile mice displayed a sustained myeloid infiltrate (including monocytes and neutrophils) with increased RNA expression of Ccl2, Ccl3, and Ccl4, when compared with adult mice, at 72 h postinfection. Juvenile mice demonstrated αSma expression (indicative of myofibroblast activity), increased hyaluronan deposition in the lung parenchyma (attributed to asthma progression), and a lack of CD64 upregulation on the surface of monocytes (which, in conjunction with serum amyloid P, is responsible for clearing residual hyaluronan and cellular debris). RSV infection of human airway epithelial cell, human lung fibroblast, and U937 monocyte cocultures (at air-liquid interface) displayed similar CCL expression and suggested matrix metalloproteinase-7 and MMP9 as possible extracellular matrix modifiers. These mouse data, in conjunction with our findings in human monocytes, suggest that the sustained influx of myeloid cells in the lungs of juvenile mice during acute RSV infection could potentiate extracellular matrix remodeling, facilitating conditions that support the development of asthma.

Use of Fractional Exhaled Nitric Oxide to Guide the Treatment of Asthma: An Official American Thoracic Society Clinical Practice Guideline.

Background: The fractional exhaled nitric oxide (FENO) test is a point-of-care test that is used in the assessment of asthma. Objective: To provide evidence-based clinical guidance on whether FENO testing is indicated to optimize asthma treatment in patients with asthma in whom treatment is being considered. Methods: An international, multidisciplinary panel of experts was convened to form a consensus document regarding a single question relevant to the use of FENO. The question was selected from three potential questions based on the greatest perceived impact on clinical practice and the unmet need for evidence-based answers related to this question. The panel performed systematic reviews of published randomized controlled trials between 2004 and 2019 and followed the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) evidence-to-decision framework to develop recommendations. All panel members evaluated and approved the recommendations. Main Results: After considering the overall low quality of the evidence, the panel made a conditional recommendation for FENO-based care. In patients with asthma in whom treatment is being considered, we suggest that FENO is beneficial and should be used in addition to usual care. This judgment is based on a balance of effects that probably favors the intervention; the moderate costs and availability of resources, which probably favors the intervention; and the perceived acceptability and feasibility of the intervention in daily practice. Conclusions: Clinicians should consider this recommendation to measure FENO in patients with asthma in whom treatment is being considered based on current best available evidence.

SwabExpress: An End-to-End Protocol for Extraction-Free COVID-19 Testing.

BACKGROUND: The urgent need for massively scaled clinical testing for SARS-CoV-2, along with global shortages of critical reagents and supplies, has necessitated development of streamlined laboratory testing protocols. Conventional nucleic acid testing for SARS-CoV-2 involves collection of a clinical specimen with a nasopharyngeal swab in transport medium, nucleic acid extraction, and quantitative reverse-transcription PCR (RT-qPCR). As testing has scaled across the world, the global supply chain has buckled, rendering testing reagents and materials scarce. To address shortages, we developed SwabExpress, an end-to-end protocol developed to employ mass produced anterior nares swabs and bypass the requirement for transport media and nucleic acid extraction. METHODS: We evaluated anterior nares swabs, transported dry and eluted in low-TE buffer as a direct-to-RT-qPCR alternative to extraction-dependent viral transport media. We validated our protocol of using heat treatment for viral inactivation and added a proteinase K digestion step to reduce amplification interference. We tested this protocol across archived and prospectively collected swab specimens to fine-tune test performance. RESULTS: After optimization, SwabExpress has a low limit of detection at 2-4 molecules/µL, 100% sensitivity, and 99.4% specificity when compared side by side with a traditional RT-qPCR protocol employing extraction. On real-world specimens, SwabExpress outperforms an automated extraction system while simultaneously reducing cost and hands-on time. CONCLUSION: SwabExpress is a simplified workflow that facilitates scaled testing for COVID-19 without sacrificing test performance. It may serve as a template for the simplification of PCR-based clinical laboratory tests, particularly in times of critical shortages during pandemics.

Infants with evolving bronchopulmonary dysplasia demonstrate monocyte-specific expression of IL-1 in tracheal aspirates.

Bronchopulmonary dysplasia (BPD) remains a devastating consequence of prematurity. Repeated inflammatory insults worsen lung injury, but there are no predictors for BPD-related respiratory outcomes or targeted therapies. We sought to understand inflammatory mechanisms in evolving BPD through molecular characterization of monocytes in tracheal aspirates from infants at risk for developing BPD. We performed flow cytometry targeting myeloid cell populations on prospectively collected tracheal aspirates from intubated patients born before 29 wk of gestation and <30 days old. We identified CD14+CD16+ (double-positive) and CD14+CD16- (single-positive) monocytes and characterized their gene expression profiles by RNA sequencing and quantitative PCR. We further analyzed differential gene expression between time points to evaluate changes in monocyte function over the first weeks of life. Expression of IL-1A, IL-1B, and IL-1 receptor antagonist mRNA was increased in monocytes collected at day of life (DOL) 7, DOL 14, and DOL 28 compared with those collected at DOL 3. This study suggests that early changes in monocyte-specific IL-1 cytokine pathways may be associated with evolving BPD.

Interferon response to respiratory syncytial virus by bronchial epithelium from children with asthma is inversely correlated with pulmonary function.

BACKGROUND: Respiratory viral infection in early childhood, including that from respiratory syncytial virus (RSV), has been previously associated with the development of asthma. OBJECTIVE: We aimed to determine whether ex vivo RSV infection of bronchial epithelial cells (BECs) from children with asthma would induce specific gene expression patterns and whether such patterns were associated with lung function among BEC donors. METHODS: Primary BECs from carefully characterized children with asthma (n = 18) and matched healthy children without asthma (n = 8) were differentiated at an air-liquid interface for 21 days. Air-liquid interface cultures were infected with RSV for 96 hours and RNA was subsequently isolated from BECs. In each case, we analyzed gene expression using RNA sequencing and assessed differences between conditions by linear modeling of the data. BEC donors completed spirometry to measure lung function. RESULTS: RSV infection of BECs from subjects with asthma, compared with uninfected BECs from subjects with asthma, led to a significant increase in expression of 6199 genes. There was significantly greater expression of 195 genes in BECs from children with asthma and airway obstruction (FEV1/forced vital capacity < 0.85 and FEV1 < 100% predicted) than in BECs from children with asthma without obstruction, or in BECs from healthy children. These specific genes were found to be highly enriched for viral response genes induced in parallel with types I and III interferons. CONCLUSIONS: BECs from children with asthma and with obstructive physiology exhibit greater expression of types I and III interferons and interferon-stimulated genes than do cells from children with normal lung function, and expression of interferon-associated genes correlates with the degree of airway obstruction. These findings suggest that an exaggerated interferon response to viral infection by airway epithelial cells may be a mechanism leading to lung function decline in a subset of children with asthma.

Deficient Follistatin-like 3 Secretion by Asthmatic Airway Epithelium Impairs Fibroblast Regulation and Fibroblast-to-Myofibroblast Transition.

Bronchial epithelial cells (BECs) from healthy children inhibit human lung fibroblast (HLF) expression of collagen and fibroblast-to-myofibroblast transition (FMT), whereas asthmatic BECs do so less effectively, suggesting that diminished epithelial-derived regulatory factors contribute to airway remodeling. Preliminary data demonstrated that secretion of the activin A inhibitor follistatin-like 3 (FSTL3) by healthy BECs was greater than that by asthmatic BECs. We sought to determine the relative secretion of FSTL3 and activin A by asthmatic and healthy BECs, and whether FSTL3 inhibits FMT. To quantify the abundance of the total proteome FSTL3 and activin A in supernatants of differentiated BEC cultures from healthy children and children with asthma, we performed mass spectrometry and ELISA. HLFs were cocultured with primary BECs and then HLF expression of collagen I and α-smooth muscle actin (α-SMA) was quantified by qPCR, and FMT was quantified by flow cytometry. Loss-of-function studies were conducted using lentivirus-delivered shRNA. Using mass spectrometry and ELISA results from larger cohorts, we found that FSTL3 concentrations were greater in media conditioned by healthy BECs compared with asthmatic BECs (4,012 vs. 2,553 pg/ml; P = 0.002), and in media conditioned by asthmatic BECs from children with normal lung function relative to those with airflow obstruction (FEV1/FVC ratio < 0.8; n = 9; 3,026 vs. 1,922 pg/ml; P = 0.04). shRNA depletion of FSTL3 in BECs (n = 8) increased HLF collagen I expression by 92% (P = 0.001) and α-SMA expression by 88% (P = 0.02), and increased FMT by flow cytometry in cocultured HLFs, whereas shRNA depletion of activin A (n = 6) resulted in decreased α-SMA (22%; P = 0.01) expression and decreased FMT. Together, these results indicate that deficient FSTL3 expression by asthmatic BECs impairs epithelial regulation of HLFs and FMT.

Asthmatic bronchial epithelial cells promote the establishment of a Hyaluronan-enriched, leukocyte-adhesive extracellular matrix by lung fibroblasts.

BACKGROUND: Airway inflammation is a hallmark of asthma. Alterations in extracellular matrix (ECM) hyaluronan (HA) content have been shown to modulate the recruitment and retention of inflammatory cells. Bronchial epithelial cells (BECs) regulate the activity of human lung fibroblasts (HLFs); however, their contribution in regulating HLF production of HA in asthma is unknown. In this study, we tested the hypothesis that BECs from asthmatic children promote the generation of a pro-inflammatory, HA-enriched ECM by HLFs, which promotes the retention of leukocytes. METHODS: BECs were obtained from well-characterized asthmatic and healthy children ages 6-18 years. HLFs were co-cultured with BECs for 96 h and samples were harvested for analysis of gene expression, synthesis and accumulation of HA, and subjected to a leukocyte adhesion assay with U937 monocytes. RESULTS: We observed increased expression of HA synthases HAS2 and HAS3 in HLFs co-cultured with asthmatic BECs. Furthermore, we demonstrated greater total accumulation and increased synthesis of HA by HLFs co-cultured with asthmatic BECs compared to healthy BEC/HLF co-cultures. ECM generated by HLFs co-cultured with asthmatic BECs displayed increased HA-dependent adhesion of leukocytes in a separate in vitro binding assay. CONCLUSIONS: Our findings demonstrate that BEC regulation of HA production by HLFs is altered in asthma, which may in turn promote the establishment of a more leukocyte-permissive ECM promoting airway inflammation in this disease.

Stability of gene expression by primary bronchial epithelial cells over increasing passage number.

BACKGROUND: An increasing number of studies using primary human bronchial epithelial cells (BECs) have reported intrinsic differences in the expression of several genes between cells from asthmatic and non-asthmatic donors. The stability of gene expression by primary BECs with increasing cell passage number has not been well characterized. METHODS: To determine if expression by primary BECs from asthmatic and non-asthmatic children of selected genes associated with airway remodeling, innate immune response, immunomodulatory factors, and markers of differentiated airway epithelium, are stable over increasing cell passage number, we studied gene expression patterns in passages 1, 2, 3, 4, and 5 BECs from asthmatic (n = 6) and healthy (n = 6) subjects that were differentiated at an air-liquid interface. RNA was harvested from BECs and RT-PCR was performed for TGFß1, TGFß2, activin A, FSTL3, MUC5AC, TSLP, IL-33, CXCL10, IFIH1, p63, KT5, TUBB4A, TJP1, OCLN, and FOXJ1. RESULTS: Expression of TGFß1, TGFß2, activin A, FSTL3, MUC5AC, CXCL10, IFIH1, p63, KT5, TUBB4A, TJP1, OCLN, and FOXJ1 by primary BECs from asthmatic and healthy children was stable with no significant differences between passages 1, 2 and 3; however, gene expression at cell passages 4 and 5 was significantly greater and more variable compared to passage 1 BECs for many of these genes. IL-33 and FOXJ1 expression was also stable between passages 1 through 3, however, expression at passages 4 and 5 was significantly lower than by passage 1 BECs. TSLP, p63, and KRT5 expression was stable across BEC passages 1 through 5 for both asthmatic and healthy BECs. CONCLUSIONS: These observations illustrate the importance of using BECs from passage ≤3 when studying gene expression by asthmatic and non-asthmatic primary BECs and characterizing the expression pattern across increasing cell passage number for each new gene studied, as beyond passage 3 genes expressed by primary BECs appear to less accurately model in vivo airway epithelial gene expression.

Interplay of extracellular matrix and leukocytes in lung inflammation.

During inflammation, leukocytes influx into lung compartments and interact with extracellular matrix (ECM). Two ECM components, versican and hyaluronan, increase in a range of lung diseases. The interaction of leukocytes with these ECM components controls leukocyte retention and accumulation, proliferation, migration, differentiation, and activation as part of the inflammatory phase of lung disease. In addition, bronchial epithelial cells from asthmatic children co-cultured with human lung fibroblasts generate an ECM that is adherent for monocytes/macrophages. Macrophages are present in both early and late lung inflammation. Matrix metalloproteinase 10 (MMP10) is induced in alveolar macrophages with injury and infection and modulates macrophage phenotype and their ability to degrade collagenous ECM components. Collectively, studies outlined in this review highlight the importance of specific ECM components in the regulation of inflammatory events in lung disease. The widespread involvement of these ECM components in the pathogenesis of lung inflammation make them attractive candidates for therapeutic intervention.

Official American Thoracic Society Clinical Practice Guidelines: Diagnostic Evaluation of Infants with Recurrent or Persistent Wheezing.

BACKGROUND: Infantile wheezing is a common problem, but there are no guidelines for the evaluation of infants with recurrent or persistent wheezing that is not relieved or prevented by standard therapies. METHODS: An American Thoracic Society-sanctioned guideline development committee selected clinical questions related to uncertainties or controversies in the diagnostic evaluation of wheezing infants. Members of the committee conducted pragmatic evidence syntheses, which followed the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach. The evidence syntheses were used to inform the formulation and grading of recommendations. RESULTS: The pragmatic evidence syntheses identified few studies that addressed the clinical questions. The studies that were identified constituted very low-quality evidence, consisting almost exclusively of case series with risk of selection bias, indirect patient populations, and imprecise estimates. The committee made conditional recommendations to perform bronchoscopic airway survey, bronchoalveolar lavage, esophageal pH monitoring, and a swallowing study. It also made conditional recommendations against empiric food avoidance, upper gastrointestinal radiography, and gastrointestinal scintigraphy. Finally, the committee recommended additional research about the roles of infant pulmonary function testing and food avoidance or dietary changes, based on allergy testing. CONCLUSIONS: Although infantile wheezing is common, there is a paucity of evidence to guide clinicians in selecting diagnostic tests for recurrent or persistent wheezing. Our committee made several conditional recommendations to guide clinicians; however, additional research that measures clinical outcomes is needed to improve our confidence in the effects of various diagnostic interventions and to allow advice to be provided with greater confidence.

Fibroblast-myofibroblast transition is differentially regulated by bronchial epithelial cells from asthmatic children.

BACKGROUND: Airway remodeling is a proposed mechanism that underlies the persistent loss of lung function associated with childhood asthma. Previous studies have demonstrated that human lung fibroblasts (HLFs) co-cultured with primary human bronchial epithelial cells (BECs) from asthmatic children exhibit greater expression of extracellular matrix (ECM) components compared to co-culture with BECs derived from healthy children. Myofibroblasts represent a population of differentiated fibroblasts that have greater synthetic activity. We hypothesized co-culture with asthmatic BECs would lead to greater fibroblast to myofibroblast transition (FMT) compared to co-culture with healthy BECs. METHODS: BECs were obtained from well-characterized asthmatic and healthy children and were proliferated and differentiated at an air-liquid interface (ALI). BEC-ALI cultures were co-cultured with HLFs for 96 hours. RT-PCR was performed in HLFs for alpha smooth muscle actin (α-SMA) and flow cytometry was used to assay for α-SMA antibody labeling of HLFs. RT-PCR was also preformed for the expression of tropomyosin-I as an additional marker of myofibroblast phenotype. In separate experiments, we investigated the role of TGFß2 in BEC-HLF co-cultures using monoclonal antibody inhibition. RESULTS: Expression of α-SMA by HLFs alone was greater than by HLFs co-cultured with healthy BECs, but not different than α-SMA expression by HLFs co-cultured with asthmatic BECs. Flow cytometry also revealed significantly less α-SMA expression by healthy co-co-cultures compared to asthmatic co-cultures or HLF alone. Monoclonal antibody inhibition of TGFß2 led to similar expression of α-SMA between healthy and asthmatic BEC-HLF co-cultures. Expression of topomyosin-I was also significantly increased in HLF co-cultured with asthmatic BECs compared to healthy BEC-HLF co-cultures or HLF cultured alone. CONCLUSION: These findings suggest dysregulation of FMT in HLF co-cultured with asthmatic as compared to healthy BECs. Our results suggest TGFß2 may be involved in the differential regulation of FMT by asthmatic BECs. These findings further illustrate the importance of BEC-HLF cross-talk in asthmatic airway remodeling.