Sticky Science: Using Complex Coacervate Adhesives for Biomedical Applications.

Tissue adhesives are used for various medical applications, including wound closure, bleeding control, and bone healing. Currently available options often show weak adhesion or cause adverse effects. Recently, there has been an increasing interest in complex coacervates as medical adhesives. Complex coacervates are formed by mixing oppositely charged macromolecules that associate and undergo liquid-liquid phase separation, in which the dense bottom phase is the complex coacervate. Complex coacervates are strong and often biocompatible, and show strong underwater adhesion. The properties of the resulting materials are tunable by intrinsic factors such as polymer chemistry, molecular weight, charge density, and topology of the macromolecules, as well as extrinsic factors such as temperature, pH, and salt concentration. Therefore, complex coacervates are interesting new candidates for medical adhesives. In this review, it is described how complex coacervates form and how different factors influence their behavior. Next, an overview of recent studies on complex coacervates in the context of medical adhesives is presented. The application of complex coacervates as hemostatic or embolic agents, skin or bone repair adhesives, and soft tissue sealants is discussed. Lastly, additional possibilities for utilizing these materials in the future are discussed.

The soluble factor milieu in idiopathic pulmonary fibrosis dysregulates epithelial differentiation.

In idiopathic pulmonary fibrosis (IPF), epithelial abnormalities are present including bronchiolization and alveolar cell dysfunction. We hypothesized that the IPF microenvironment disrupts normal epithelial growth and differentiation. We mimicked the soluble factors within an IPF microenvironment using an IPF cocktail (IPFc), composed of nine factors which are increased in IPF lungs (CCL2, IL-1ß, IL-4, IL-8, IL-13, IL-33, TGF-ß, TNFα, and TSLP). Using IPFc, we asked whether the soluble factor milieu in IPF affects epithelial growth and differentiation and how IPFc compares to TGF-ß alone. Epithelial growth and differentiation were studied using mouse lung organoids (primary Epcam+ epithelial cells co-cultured with CCL206 fibroblasts). Organoids exposed to IPFc and TGF-ß were re-sorted into epithelial and fibroblast fractions and subjected to RNA sequencing. IPFc did not affect the number of organoids formed. However, pro-surfactant protein C expression was decreased. On these parameters, TGF-ß alone had similar effects. However, RNA sequencing of re-sorted organoids revealed that IPFc and TGF-ß had distinct effects on both epithelial cells and fibroblasts. IPFc upregulated goblet cell markers, whereas these were inhibited by TGF-ß. Although both IPFc and TGF-ß increased extracellular matrix gene expression, only TGF-ß increased myofibroblast markers. VEGF-C and Wnt signaling were among the most differentially regulated signaling pathways by IPFc versus TGF-ß. Interestingly, Wnt pathway activation rescued Sftpc downregulation induced by IPFc. In conclusion, IPFc alters epithelial differentiation in a way that is distinct from TGF-ß. Alterations in Wnt signaling contribute to these effects. IPFc may be a more comprehensive representation of the soluble factor microenvironment in IPF.

A 3D Epithelial-Mesenchymal Co-Culture Model of the Airway Wall Using Native Lung Extracellular Matrix.

Chronic obstructive pulmonary disease (COPD) is a chronic lung disease characterized by ongoing inflammation, impaired tissue repair, and aberrant interplay between airway epithelium and fibroblasts, resulting in an altered extracellular matrix (ECM) composition. The ECM is the three-dimensional (3D) scaffold that provides mechanical support and biochemical signals to cells, now recognized not only as a consequence but as a potential driver of disease progression. To elucidate how the ECM influences pathophysiological changes occurring in COPD, in vitro models are needed that incorporate the ECM. ECM hydrogels are a novel experimental tool for incorporating the ECM in experimental setups. We developed an airway wall model by combining lung-derived ECM hydrogels with a co-culture of primary human fibroblasts and epithelial cells at an air-liquid interface. Collagen IV and a mixture of collagen I, fibronectin, and bovine serum albumin were used as basement membrane-mimicking coatings. The model was initially assembled using porcine lung-derived ECM hydrogels and subsequently with COPD and non-COPD human lung-derived ECM hydrogels. The resulting 3D construct exhibited considerable contraction and supported co-culture, resulting in a differentiated epithelial layer. This multi-component 3D model allows the investigation of remodelling mechanisms, exploring ECM involvement in cellular crosstalk, and holds promise as a model for drug discovery studies exploring ECM involvement in cellular interactions.

The role of extracellular matrix hydrogels and adipose-derived stromal cells in soft tissue vascularization - A systematic review.

Decellularized extracellular matrix (dECM) hydrogels loaded with adipose-derived stromal cells (ASC) or their conditioned medium (ASC CM) present a promising and versatile treatment approach for tissue vascularization and regeneration. These hydrogels are easy to produce, store, personalize, manipulate, and deliver to the target tissue. This literature review aimed to investigate the applications of dECM hydrogels with ASC or ASC CM for in vivo tissue vascularization. Fourteen experimental studies have been reviewed using vessel density as the primary outcome parameter for in vivo vascularization. The studies consistently reported an increased efficacy in augmenting angiogenesis by the ASC or ASC CM-loaded hydrogels compared to untreated controls. However, this systematic review shows the need to standardize procedures and characterization, particularly of the final administered product(s). The findings from these experimental studies highlight the potential of dECM hydrogel with ASC or ASC CM in novel tissue regeneration and regenerative medicine applications.

The disruptive effects of COPD exacerbation-associated factors on epithelial repair responses.

Introduction: Exacerbations of chronic obstructive pulmonary disease (COPD) increase mortality risk and can lead to accelerated loss of lung function. The increased inflammatory response during exacerbations contributes to worsening of airflow limitation, but whether it also impacts epithelial repair is unclear. Therefore, we studied the effect of the soluble factor micro-environment during COPD exacerbations on epithelial repair using an exacerbation cocktail (EC), composed of four factors that are increased in COPD lungs during exacerbations (IL-1ß, IL-6, IL-8, TNF-α). Methods: Mouse organoids (primary CD31-CD45-Epcam+ cells co-cultured with CCL206 fibroblasts) were used to study epithelial progenitor behavior. Mature epithelial cell responses were evaluated using mouse precision cut lung slices (PCLS). The expression of epithelial supportive factors was assessed in CCL206 fibroblasts and primary human lung fibroblasts. Results: EC exposure increased the number and size of organoids formed, and upregulated Lamp3, Muc5ac and Muc5b expression in day 14 organoids. In PCLS, EC imparted no effect on epithelial marker expression. Pre-treatment of CCL206 fibroblasts with EC was sufficient to increase organoid formation. Additionally, the expression of Il33, Tgfa and Areg was increased in CCL206 fibroblasts from EC treated organoids, but these factors individually did not affect organoid formation or size. However, TGF-α downregulated Foxj1 expression and upregulated Aqp5 expression in day 14 organoids. Conclusions: EC exposure stimulates organoid formation and growth, but it alters epithelial differentiation. EC changes the epithelial progenitor support function of fibroblasts which contributes to observed effects on epithelial progenitors.

The lung extracellular matrix protein landscape in severe early-onset and moderate chronic obstructive pulmonary disease.

Extracellular matrix (ECM) remodeling has been implicated in the irreversible obstruction of airways and destruction of alveolar tissue in chronic obstructive pulmonary disease (COPD). Studies investigating differences in the lung ECM in COPD have mainly focused on some collagens and elastin, leaving an array of ECM components unexplored. We investigated the differences in the ECM landscape comparing severe-early onset (SEO)-COPD and moderate COPD to control lung tissue for collagen type I α chain 1 (COL1A1), collagen type VI α chain 1 (COL6A1); collagen type VI α chain 2 (COL6A2), collagen type XIV α chain 1 (COL14A1), fibulin 2 and 5 (FBLN2 and FBLN5), latent transforming growth factor ß binding protein 4 (LTBP4), lumican (LUM), versican (VCAN), decorin (DCN), and elastin (ELN) using image analysis and statistical modeling. Percentage area and/or mean intensity of expression of LUM in the parenchyma, and COL1A1, FBLN2, LTBP4, DCN, and VCAN in the airway walls, was proportionally lower in COPD compared to controls. Lowered levels of most ECM proteins were associated with decreasing forced expiratory volume in 1 s (FEV1) measurements, indicating a relationship with disease severity. Furthermore, we identified six unique ECM signatures where LUM and COL6A1 in parenchyma and COL1A1, FBLN5, DCN, and VCAN in airway walls appear essential in reflecting the presence and severity of COPD. These signatures emphasize the need to examine groups of proteins to represent an overall difference in the ECM landscape in COPD that are more likely to be related to functional effects than individual proteins. Our study revealed differences in the lung ECM landscape between control and COPD and between SEO and moderate COPD signifying distinct pathological processes in the different subgroups.NEW & NOTEWORTHY Our study identified chronic obstructive pulmonary disease (COPD)-associated differences in the lung extracellular matrix (ECM) composition. We highlight the compartmental differences in the ECM landscape in different subtypes of COPD. The most prominent differences were observed for severe-early onset COPD. Moreover, we identified unique ECM signatures that describe airway walls and parenchyma providing insight into the intertwined nature and complexity of ECM changes in COPD that together drive ECM remodeling and may contribute to disease pathogenesis.

Endoplasmic reticulum stress-induced senescence in human lung fibroblasts.

Loss of proteostasis and cellular senescence have been previously established as characteristics of aging; however, their interaction in the context of lung aging and potential contributions to aging-associated lung remodeling remains understudied. In this study, we aimed to characterize endoplasmic reticulum (ER) stress response, cellular senescence, and their interaction in relation to extracellular matrix (ECM) production in lung fibroblasts from young (25-45 yr) and old (>60 yr) humans. Fibroblasts from young and old patients without significant preexisting lung disease were exposed to vehicle, MG132, etoposide, or salubrinal. Afterward, cells and cell lysates or supernatants were analyzed for ER stress, cellular senescence, and ECM changes using protein analysis, proliferation assay, and senescence-associated beta-galactosidase (SA-ß-Gal) staining. At baseline, fibroblasts from aging individuals showed increased levels of ER stress (ATF6 and PERK), senescence (p21 and McL-1), and ECM marker (COL1A1) compared to those from young individuals. Upon ER stress induction and etoposide exposure, fibroblasts showed an increase in senescence (SA-ß-Gal, p21, and Cav-1), ER stress (PERK), and ECM markers (COL1A1 and LUM) compared to vehicle. Additionally, IL-6 and IL-8 levels were increased in the supernatants of MG132- and etoposide-treated fibroblasts, respectively. Finally, the ER stress inhibitor salubrinal decreased the expression of p21 compared to vehicle and MG132 treatments; however, salubrinal inhibited COL1A1 but not p21 expression in MG132-treated fibroblasts. Our study suggests that ER stress response plays an important role in establishment and maintenance of a senescence phenotype in lung fibroblasts and therefore contributes to altered remodeling in the aging lung.NEW & NOTEWORTHY The current study establishes functional links between endoplasmic reticulum (ER) stress and cellular senescence per se in the specific context of aging human lung fibroblasts. Recognizing that the process of aging per se is complex, modulated by the myriad of lifelong and environmental exposures, it is striking to note that chronic ER stress may play a crucial role in the establishment and maintenance of cellular senescence in lung fibroblasts.

Stem cells, cell therapies, and bioengineering in lung biology and diseases 2023.

Repair and regeneration of a diseased lung using stem cells or bioengineered tissues is an exciting therapeutic approach for a variety of lung diseases and critical illnesses. Over the past decade, increasing evidence from preclinical models suggests that mesenchymal stromal cells, which are not normally resident in the lung, can be used to modulate immune responses after injury, but there have been challenges in translating these promising findings to the clinic. In parallel, there has been a surge in bioengineering studies investigating the use of artificial and acellular lung matrices as scaffolds for three-dimensional lung or airway regeneration, with some recent attempts of transplantation in large animal models. The combination of these studies with those involving stem cells, induced pluripotent stem cell derivatives, and/or cell therapies is a promising and rapidly developing research area. These studies have been further paralleled by significant increases in our understanding of the molecular and cellular events by which endogenous lung stem and/or progenitor cells arise during lung development and participate in normal and pathological remodeling after lung injury. For the 2023 Stem Cells, Cell Therapies, and Bioengineering in Lung Biology and Diseases Conference, scientific symposia were chosen to reflect the most cutting-edge advances in these fields. Sessions focused on the integration of "omics" technologies with function, the influence of immune cells on regeneration, and the role of the extracellular matrix in regeneration. The necessity for basic science studies to enhance fundamental understanding of lung regeneration and to design innovative translational studies was reinforced throughout the conference.

Mechanotransduction and the extracellular matrix: Key drivers of lung pathologies and drug responsiveness.

The lung is a biomechanically active organ, with multiscale mechanical forces impacting the organ, tissue and cellular responses within this microenvironment. In chronic lung diseases, such as chronic obstructive pulmonary disease, pulmonary fibrosis and others, the structure of the lung is drastically altered impeding gas exchange. These changes are, in part, reflected in alterations in the composition, amount and organization of the extracellular matrix within the different lung compartments. The transmission of mechanical forces within lung tissue are broadcast by this complex mix of extracellular matrix components, in particular the collagens, elastin and proteoglycans and the crosslinking of these components. At both a macro and a micro level, the mechanical properties of the microenvironment have a key regulatory role in ascertaining cellular responses and the function of the lung. Cells adhere to, and receive signals from, the extracellular matrix through a number of different surface receptors and complexes which are important for mechanotransduction. This review summarizes the multiscale mechanics in the lung and how the mechanical environment changes in lung disease and aging. We then examine the role of mechanotransduction in driving cell signaling events in lung diseases and finish with a future perspective of the need to consider how such forces may impact pharmacological responsiveness in lung diseases.

Current evidence on the role of fibroblasts in large-vessel vasculitides: From pathogenesis to therapeutics.

Large-vessel vasculitides (LVV) comprise a group of chronic inflammatory diseases of the aorta and its major branches. The most common forms of LVV are giant cell arteritis (GCA) and Takayasu arteritis (TAK). Both GCA and TAK are characterized by granulomatous inflammation of the vessel wall accompanied by a maladaptive immune and vascular response that promotes vascular damage and remodeling. The inflammatory process in LVV starts in the adventitia where fibroblasts constitute the dominant cell population. Fibroblasts are traditionally recognized for synthesizing and renewing the extracellular matrix thereby being major players in maintenance of normal tissue architecture and in tissue repair. More recently, fibroblasts have emerged as a highly plastic cell population exerting various functions, including the regulation of local immune processes and organization of immune cells at the site of inflammation through production of cytokines, chemokines and growth factors as well as cell-cell interaction. In this review, we summarize and discuss the current knowledge on fibroblasts in LVV. Furthermore, we identify key questions that need to be addressed to fully understand the role of fibroblasts in the pathogenesis of LVV.

Physical Properties and Biochemical Composition of Extracellular Matrix-Derived Hydrogels Dictate Vascularization Potential in an Organ-Dependent Fashion.

The inherent extracellular matrix (ECM) originating from a specific tissue impacts the process of vascularization, specifically vascular network formation (VNF) orchestrated by endothelial cells (ECs). The specific contribution toward these processes of ECM from highly disparate organs such as the skin and lungs remains a relatively unexplored area. In this study, we compared VNF and ECM remodeling mediated by microvascular ECs within gel, lung, and combinations thereof (hybrid) ECM hydrogels. Irrespective of the EC source, the skin-derived ECM hydrogel exhibited a higher propensity to drive and support VNF compared to both lung and hybrid ECM hydrogels. There were distinct disparities in the physical properties of the three types of hydrogels, including viscoelastic properties and complex architectural configurations, including fiber diameter, pore area, and numbers among the fibers. The hybrid ECM hydrogel properties were unique and not the sum of the component ECM parts. Furthermore, cellular ECM remodeling responses varied with skin ECM hydrogels promoting matrix metalloproteinase 1 (MMP1) secretion, while hybrid ECM hydrogels exhibited increased MMP9, fibronectin, and collagen IV deposition. Principal component analysis (PCA) indicated that the influence of a gel's mechanical properties on VNF was stronger than the biochemical composition. These data indicate that the organ-specific properties of an ECM dictate its capacity to support VNF, while intriguingly showing that ECs respond to more than just the biochemical constituents of an ECM. The study suggests potential applications in regenerative medicine by strategically selecting ECM origin or combinations to manipulate vascularization, offering promising prospects for enhancing wound healing through pro-regenerative interventions.

Fibroblast alignment and matrix remodeling induced by a stiffness gradient in a skin-derived extracellular matrix hydrogel.

Large skin injuries heal as scars. Stiffness gradually increases from normal skin to scar tissue (20x higher), due to excessive deposition and crosslinking of extracellular matrix (ECM) mostly produced by (myo)fibroblasts. Using a custom mold, skin-derived ECM hydrogels (dECM) were UV crosslinked after diffusion of ruthenium (Ru) to produce a Ru-dECM gradient hydrogel. The Ru diffusion gradient equates to a stiffness gradient and models physiology of the scarred skin. Crosslinking in Ru-dECM hydrogels results in a 23-fold increase in stiffness from a stiffness similar to that of normal skin. Collagen fiber density increases in a stiffness-dependent fashion while stress relaxation also alters, with one additional Maxwell element necessary for characterizing Ru-dECM. Alignment of fibroblasts encapsulated in hydrogels suggests that the stiffness gradient directs fibroblasts to orientate at ∼45 ° in regions below 120 kPa. In areas above 120 kPa, fibroblasts decrease the stiffness prior to adjusting their orientation. Furthermore, fibroblasts remodel their surrounding ECM in a gradient-dependent fashion, with rearrangement of cell-surrounding ECM in high-stiffness areas, and formation of interlaced collagen bundles in low-stiffness areas. Overall, this study shows that fibroblasts remodel their local environment to generate an optimal ECM mechanical and topographical environment. STATEMENT OF SIGNIFICANCE: This study developed a versatile in vitro model with a gradient stiffness using skin-derived ECM hydrogel with unchanged biochemical environment. Using Ruthenium crosslinking, a 20-fold stiffness increase was achieved as observed in fibrotic skin. The interaction between fibroblasts and matrix depends on changes in the matrix stiffness. The stiffness gradient directed the alignment of fibroblasts with ∼45° in regions with≤ 120 kPa. The cells in regions with the higher stiffness decreased stiffness first and then oriented themselves. Furthermore, fibroblasts remodeled surrounding ECM and regulated its mechanics in a gradient-dependent fashion to reach an optimal condition. Our study highlights the dynamic interplay between cells and surrounding matrix, shedding light on potential mechanisms and strategies to target scar formation and remodeling.

Neo-epitope detection identifies extracellular matrix turnover in systemic inflammation and sepsis: an exploratory study.

BACKGROUND: Sepsis is associated with high morbidity and mortality, primarily due to systemic inflammation-induced tissue damage, resulting organ failure, and impaired recovery. Regulated extracellular matrix (ECM) turnover is crucial for maintaining tissue homeostasis in health and in response to disease-related changes in the tissue microenvironment. Conversely, uncontrolled turnover can contribute to tissue damage. Systemic Inflammation is implicated to play a role in the regulation of ECM turnover, but the relationship between the two is largely unclear. METHODS: We performed an exploratory study in 10 healthy male volunteers who were intravenously challenged with 2 ng/kg lipopolysaccharide (LPS, derived from Escherichia coli) to induce systemic inflammation. Plasma samples were collected before (T0) and after (T 1 h, 3 h, 6 h and 24 h) the LPS challenge. Furthermore, plasma was collected from 43 patients with septic shock on day 1 of ICU admission. Circulating neo-epitopes of extracellular matrix turnover, including ECM degradation neo-epitopes of collagen type I (C1M), type III (C3M), type IV (C4Ma3), and type VI (C6M), elastin (ELP-3) and fibrin (X-FIB), as well as the ECM synthesis neo-epitopes of collagen type III (PRO-C3), collagen type IV (PRO-C4) and collagen type VI (PRO-C6) were measured by ELISA. Patient outcome data were obtained from electronic patient records. RESULTS: Twenty-four hours after LPS administration, all measured ECM turnover neo-epitopes, except ELP-3, were increased compared to baseline levels. In septic shock patients, concentrations of all measured ECM neo-epitopes were higher compared to healthy controls. In addition, concentrations of C6M, ELP-3 and X-FIB were higher in patients with septic shock who ultimately did not survive (N = 7) compared to those who recovered (N = 36). CONCLUSION: ECM turnover is induced in a model of systemic inflammation in healthy volunteers and was observed in patients with septic shock. Understanding interactions between systemic inflammation and ECM turnover may provide further insight into mechanisms underlying acute and persistent organ failure in sepsis.

Three dimensional fibrotic extracellular matrix directs microenvironment fiber remodeling by fibroblasts.

Idiopathic pulmonary fibrosis (IPF), for which effective treatments are limited, results in excessive and disorganized deposition of aberrant extracellular matrix (ECM). An altered ECM microenvironment is postulated to contribute to disease progression through inducing profibrotic behavior of lung fibroblasts, the main producers and regulators of ECM. Here, we examined this hypothesis in a 3D in vitro model system by growing primary human lung fibroblasts in ECM-derived hydrogels from non-fibrotic (control) or IPF lung tissue. Using this model, we compared how control and IPF lung-derived fibroblasts responded in control and fibrotic microenvironments in a combinatorial manner. Culture of fibroblasts in fibrotic hydrogels did not alter in the overall amount of collagen or glycosaminoglycans but did cause a drastic change in fiber organization compared to culture in control hydrogels. High-density collagen percentage was increased by control fibroblasts in IPF hydrogels at day 7, but decreased at day 14. In contrast, IPF fibroblasts only decreased the high-density collagen percentage at day 14, which was accompanied by enhanced fiber alignment in IPF hydrogels. Similarly, stiffness of fibrotic hydrogels was increased only by control fibroblasts by day 14 while those of control hydrogels were not altered by fibroblasts. These data highlight how the ECM-remodeling responses of fibroblasts are influenced by the origin of both the cells and the ECM. Moreover, by showing how the 3D microenvironment plays a crucial role in directing cells, our study paves the way in guiding future investigations examining fibrotic processes with respect to ECM remodeling responses of fibroblasts. STATEMENT OF SIGNIFICANCE: In this study, we investigated the influence of the altered extracellular matrix (ECM) in Idiopathic Pulmonary Fibrosis (IPF), using a 3D in vitro model system composed of ECM-derived hydrogels from both IPF and control lungs, seeded with human IPF and control lung fibroblasts. While our results indicated that fibrotic microenvironment did not change the overall collagen or glycosaminoglycan content, it resulted in a dramatically alteration of fiber organization and mechanical properties. Control fibroblasts responded differently from IPF fibroblasts, highlighting the unique instructive role of the fibrotic ECM and the interplay with fibroblast origin. These results underscore the importance of 3D microenvironments in guiding pro-fibrotic responses, offering potential insights for future IPF therapies as well as other fibrotic diseases and cancer.

Extracellular Matrix as a Driver of Chronic Lung Diseases.

The extracellular matrix (ECM) is not just a three-dimensional scaffold that provides stable support for all cells in the lungs, but also an important component of chronic fibrotic airway, vascular, and interstitial diseases. It is a bioactive entity that is dynamically modulated during tissue homeostasis and disease, that controls structural and immune cell functions and drug responses, and that can release fragments that have biological activity and that can be used to monitor disease activity. There is a growing recognition of the importance of considering ECM changes in chronic airway, vascular, and interstitial diseases, including 1) compositional changes, 2) structural and organizational changes, and 3) mechanical changes and how these affect disease pathogenesis. As altered ECM biology is an important component of many lung diseases, disease models must incorporate this factor to fully recapitulate disease-driver pathways and to study potential novel therapeutic interventions. Although novel models are evolving that capture some or all of the elements of the altered ECM microenvironment in lung diseases, opportunities exist to more fully understand cell-ECM interactions that will help devise future therapeutic targets to restore function in chronic lung diseases. In this perspective article, we review evolving knowledge about the ECM's role in homeostasis and disease in the lung.

3-D culture of human lung fibroblasts decreases proliferative and increases extracellular matrix remodeling genes.

Fibroblasts are the main producers of extracellular matrix (ECM) responsible for ECM maintenance and repair, a process often disrupted in chronic lung diseases. The accompanying mechanical changes adversely affect resident cells and overall lung function. Numerous models have been used to elucidate fibroblast behavior that are now evolving toward complex three-dimensional (3-D) models incorporating ECM, aiming to replicate the cells' native environment. Little is known about the cellular changes that occur when moving from two-dimensional (2-D) to 3-D cell culture. This study compared the gene expression profiles of primary human lung fibroblasts from seven subjects with normal lung function, that were cultured for 24 h on 2-D collagen I-coated tissue culture plastic and in 3-D collagen I hydrogels, which are commonly used to mimic ECM in various models, from contraction assays to intricate organ-on-a-chip models. Comparing 3-D with 2-D cell culture, 6,771 differentially expressed genes (2,896 up, 3,875 down) were found; enriched gene sets within the downregulated genes, identified through Gene Set Enrichment Analysis and Ingenuity Pathway Analysis, were involved in the initiation of DNA replication which implied downregulation of fibroblast proliferation in 3-D. Observation of cells for 72 h in 2-D and 3-D environments confirmed the reduced progression through the cell cycle in 3-D. A focused analysis, examining the Hippo pathway and ECM-associated genes, showed differential patterns of gene expression in the 3-D versus 2-D culture. Altogether, the transcriptional response of fibroblasts cultured in 3-D indicated inhibition of proliferation, and alterations in Hippo and ECM pathways indicating a complete switch from proliferation to ECM remodeling.NEW & NOTEWORTHY With the introduction of complex three-dimensional (3-D) lung models, comes a need for understanding cellular behavior in these models. We compared gene expression profiles of human lung fibroblasts grown on two-dimensional (2-D) collagen I-coated surfaces with those in 3-D collagen I hydrogels. RNA sequencing and subsequent pathway analyses showed decreased proliferation, increased extracellular matrix (ECM) remodeling, and altered Hippo signaling and ECM deposition-related gene signatures. These findings highlight unique responses of fibroblasts in 3-D models.

Airway wall extracellular matrix changes induced by bronchial thermoplasty in severe asthma.

BACKGROUND: Airway remodeling is a prominent feature of asthma, which involves increased airway smooth muscle mass and altered extracellular matrix composition. Bronchial thermoplasty (BT), a bronchoscopic treatment for severe asthma, targets airway remodeling. OBJECTIVE: We sought to investigate the effect of BT on extracellular matrix composition and its association with clinical outcomes. METHODS: This is a substudy of the TASMA trial. Thirty patients with severe asthma were BT-treated, of whom 13 patients were treated for 6 months with standard therapy (control group) before BT. Demographic data, clinical data including pulmonary function, and bronchial biopsies were collected. Biopsies at BT-treated and nontreated locations were analyzed by histological and immunohistochemical staining. Associations between histology and clinical outcomes were explored. RESULTS: Six months after treatment, it was found that the reticular basement membrane thickness was reduced from 7.28 µm to 5.74 µm (21% relative reduction) and the percentage area of tissue positive for collagen increased from 26.3% to 29.8% (13% relative increase). Collagen structure analysis revealed a reduction in the curvature frequency of fibers. The percentage area positive for fibulin-1 and fibronectin increased by 2.5% and 5.9%, respectively (relative increase of 124% and 15%). No changes were found for elastin. The changes in collagen and fibulin-1 negatively associated with changes in FEV1 reversibility. CONCLUSIONS: Besides reduction of airway smooth muscle mass, BT has an impact on reticular basement membrane thickness and the extracellular matrix arrangement characterized by an increase in tissue area occupied by collagen with a less dense fiber organization. Both collagen and fibulin-1 are negatively associated with the change in FEV1 reversibility.

Collagen type XIV is proportionally lower in the lung tissue of patients with IPF.

Abnormal deposition of extracellular matrix (ECM) in lung tissue is a characteristic of idiopathic pulmonary fibrosis (IPF). Increased collagen deposition is also accompanied by altered collagen organization. Collagen type XIV, a fibril-associated collagen, supports collagen fibril organization. Its status in IPF has not been described at the protein level yet. In this study, we utilized publicly available datasets for single-cell RNA-sequencing for characterizing collagen type XIV expression at the gene level. For protein level comparison, we applied immunohistochemical staining for collagen type XIV on lung tissue sections from IPF patients and compared it to lung tissue sections from never smoking and ex-smoking donors. Analyzing the relative amounts of collagen type XIV at the whole tissue level, as well as in parenchyma, airway wall and bronchial epithelium, we found consistently lower proportions of collagen type XIV in all lung tissue compartments across IPF samples. Our study suggests proportionally lower collagen type XIV in IPF lung tissues may have implications for the assembly of the ECM fibers potentially contributing to progression of fibrosis.

Fibroblasts alter the physical properties of dermal ECM-derived hydrogels to create a pro-angiogenic microenvironment.

This study aimed to investigate the impact of fibroblasts (MRC-5) on the extracellular matrix (ECM) microenvironment of endothelial cells (ECs) during the vascularization of skin-derived ECM hydrogel in vitro. Two types of ECs were studied: human dermal microvascular endothelial cells (HMEC) and human pulmonary microvascular endothelial cells (HPMEC). Results showed that the presence of MRC-5 fibroblasts increased the stiffness of the hydrogel and led to larger fiber diameters and increased porosity. Extensive collagen fiber remodeling occurred in the ECM hydrogel with MRC-5 fibroblasts. Additionally, higher levels of fibulin-1 and fibronectin were deposited in the hydrogel when co-cultured with MRC-5 fibroblasts. These findings suggest that MRC-5 fibroblasts play a role in modifying the ECM microenvironment, promoting vascularization through dynamic ECM remodeling.