The evolution of in vitro models of lung fibrosis: promising prospects for drug discovery

In silico screening and validation of natural compounds with fabrication and characterization of a lead compound-loaded chitosome for targeting lung fibrosis

Lung fibrosis (LF) is a serious complication with very limited therapeutic options. This study aimed to find a potential compound for targeting LF and develop a chitosome formulation to minimize any inherent drawbacks of the compound and achieve effective drug delivery. In total, 79 natural compounds were screened using an in silico approach against five targeted proteins (3HMG, 6B8Y, 2FAP, 3CQU, and 3DK9). Amongst these, quercetin (QER) exhibited the best efficacy (-14.725 kcal mol-1) and ΔG average (-86.45 ± 6.24) kcal mol-1 against the TGF-β receptor (PDB ID: 6B8Y). In vitro studies revealed that bleomycin-challenged A549 cells showed a fibrosis-like behaviour. Upon treatment with QER, the cell viability decreased owing to a reduction in the mitochondrial membrane potential and increased apoptosis. Furthermore, cell migration was inhibited with an improvement in cellular morphology. A QER-loaded chitosome formulation (QCF) was prepared through modified thin-film hydration. Variables were optimized using a response surface methodology Box-Behnken design. The QCF was further characterized on the basis of microscopic observation, zeta potential, entrapment efficiency, drug release and kinetics and by evaluating the effect of temperature on the QCF. Its zeta potential was +24.83 ± 0.32 mV, while microscopic observation showed that it had a spherical morphology with slightly rough surfaces after chitosan coating. Furthermore, the EE% was determined to be 81.75 ± 0.46%. The QCF also demonstrated a 74.23 ± 1.01% release of QER till 24 h, following Higuchi model kinetics. In conclusion, the in silico and in vitro cell line studies provided evidence for QER as a lead molecule for targeting LF. Moreover, the prepared QCF demonstrated sustained release with prospective QER targeted delivery. However, further extensive research is required to provide a promising strategy for the management of LF in the future.

Identification of early genes in the pathophysiology of fibrotic interstitial lung disease in a new model of pulmonary fibrosis

Some interstitial lung diseases involve pulmonary fibrosis, which is a process that is characterized by the excessive and abnormal accumulation of extracellular matrix in the pulmonary interalveolar space. Although the current anti-fibrotic therapy aims at slowing down the progression of pulmonary fibrosis, it does not reverse it, and many of the drugs that were identified in basic-research studies failed in clinical phases, mainly because of the lack of a model that can recapitulate the pathophysiological mechanisms of human pulmonary fibrosis. We developed a novel experimental model of pulmonary fibrosis induced by a cocktail of molecules on an air/liquid interface culture of mouse embryonic lung explants. Histological analyses revealed a pattern of usual interstitial pneumonia, the worst-prognosis form of pulmonary fibrosis. We performed a transcriptomics analysis at the single-cell level after the induction of fibrosis and before any histological signs of fibrosis could be observed. The results revealed increased expression of several gene families that are involved in early inflammation, fibrosis and iron homeostasis, as well as potential new genetic targets.

Modeling of lung organoid-based fibrosis for testing the sensitivity of anti-fibrotic drugs

BACKGROUND

Pulmonary fibrosis models play crucial roles in research of pulmonary fibrosis and anti-fibrosis drug screening. Despite the establishment of several pulmonary fibrosis models including lung fibrosis animals, stem cell differentiation, pulmospheres and so on, the one that mimic the personalized native lung lacks.

METHODS

We here developed a lung organoid-based fibrosis (LOF) model from native lung tissue, and the potential of the LOFs for the sensitivity test of anti-fibrotic drugs was evaluated.

RESULTS

Our results showed that the LOFs could be self-organized from the lung organoids and the fibroblasts derived from native lung tissue. Histochemical examination demonstrated that the LOFs were characteristic of pulmonary fibrosis in structure. Single-cell sequencing (SCS) further revealed that the cell clusters mimicked fibrotic process at cellular and molecular levels in the LOFs. Drug sensitivity test indicated that the LOFs could not only be used to evaluate the efficacy of anti-fibrotic drugs, but also display their toxicity.

CONCLUSIONS

We demonstrate that the LOFs represent an efficient fibrotic model that mimics faithfully the personalized characteristics of native lung tissue.

Autologous precision-cut lung slice co-culture models for studying macrophage-driven fibrosis

Precision-cut lung slices (PCLS) are commonly used as an ex vivo model to study lung fibrosis; however, traditional models lack immune cell infiltration, including the recruitment of monocytes and macrophages, which are critical for inflammation and fibrosis. To address this limitation, we developed novel autologous PCLS-immune co-culture models that better replicate the processes of inflammation, repair, and immune cell recruitment associated with fibrosis. Fibrotic responses to nicotine, cigarette smoke extract (CSE), and a fibrosis-inducing cocktail (FC) were first evaluated in PCLS containing only tissue-resident macrophages, with upregulation of α-SMA-expressing fibroblasts confirmed by immunofluorescence and Western blotting, and collagen deposition quantified using Sirius Red staining. To study macrophage recruitment, we employed an indirect co-culture model using transwells to approximate blood vessel function. Chemotactic studies revealed increased migration of autologous bone marrow-derived macrophages (BMDMs) toward and infiltration into CSE-injured PCLS. In a direct co-culture model simulating the repair phase of fibrosis, PCLS exposed to CSE and FC showed further increased collagen deposition in the presence of autologous BMDMs, but not heterologous ones. These findings suggest that our novel PCLS-immune co-culture models provide a platform for studying macrophage involvement in fibrosis and offer potential for developing macrophage-targeted therapeutic strategies in pulmonary fibrosis.

Fibrosis in PCLS: comparing TGF-β and fibrotic cocktail

INTRODUCTION

Fibrotic cocktail (FC) is a combination of pro-fibrotic and pro-inflammatory mediators that induces early fibrotic changes in organotypic lung models. We hypothesised that transforming growth factor beta 1 (TGF-β1) alone induces a pro-fibrotic effect similar to FC. Our aim was to compare the pro-fibrotic effects of TGF-β1 with FC in human precision-cut lung slices (PCLS).

METHODS

PCLS from "healthy" lung tissue of cancer patients undergoing surgery (n = 7) were incubated with TGF-β1, FC or control for 72 h. Gene expression markers for myofibroblasts differentiation, extracellular matrix (ECM), as well as TGF-β receptors were assessed (RT-qPCR). ECM proteins expression in lysates and supernatant was assessed by ELISA and immunofluorescence.

RESULTS

We found that TGF-β1 significantly increased gene expression of ACTA2, COL1A1, CCN2, and VIM compared to control but also compared to FC. FC showed a significant increase of matrix metalloproteinase (MMP) 7 and 1 compared to control, while TGF-β receptor 2 was lower after FC compared to TGF-β1 or control. FC or TGF-β1 showed similar fibronectin protein expression in lysates and supernatants, while type I collagen protein expression in lysates was significantly greater with TGF-β1 compared to control.

CONCLUSIONS

Our findings show that TGF-β1 induces consistent pro-fibrotic changes in PCLS after 72 h. Compared to TGF-β1, FC treatment resulted in reduced gene expression of TGF-β receptor 2 and increased MMPs expression, potentially mitigating the early pro-fibrotic effects. Selecting specific pro-fibrotic stimuli may be preferable depending on the research question and time point of interest in lung fibrosis studies using PCLS.

Effect of ethyl acetate extract of the whole plant Clerodendrum phlomidis on improving bleomycin (BLM)-induced idiopathic pulmonary fibrosis (IPF) in Rats: In vitro and in vivo research

Idiopathic pulmonary fibrosis (IPF) is a prevalent chronic lung condition of unknown etiology characterized by fibrosis and inflammation. Lung scarring progresses owing to cytokines and immune cells that promote inflammation and fibrosis in idiopathic pulmonary fibrosis (IPF). The anti-inflammatory and anti-fibrotic properties of the ethyl acetate extract of Clerodendrum phlomidis (CPEA), derived from the Indian plant "agnimantha," are recognized in traditional Ayurvedic medicine. This study investigated the potential protective mechanisms of Clerodendrum phlomidis (CPEA), which have not been previously examined, and demonstrated how CPEA affects bleomycin (BLM)-induced lung fibrosis. Phytometabolomic analysis of Clerodendrum phlomidis was performed using UPLC-ESI-Q/TOF-MS. Free radical scavenging assays were also used to evaluate the antioxidant capacity of the plants using ABTS, DPPH, FRAP, and NO assays. Using ELISA and Griess reagent assays, we assessed the anti-inflammatory effects of CPEA in LPS-induced Jurkat, THP-1, and LL-29 cell lines. This study compared intratracheal injection of BLM-induced IPF in Wistar rats with oral administration of CPEA extract for its anti-fibrotic and anti-inflammatory properties. Multiple techniques were employed, including enzyme-linked immunosorbent assay (ELISA), hydroxyproline, histopathological, biochemical, antioxidant enzyme profiling, and hematological analyses. Polyphenolic compounds were identified using qualitative CPEA. Plant extracts demonstrated free radical-scavenging activity in vitro and exhibited antioxidant properties. CPEA extract reduced TNF-α, IL-1β, and NO levels in LPS-stimulated Jurkat, THP-1, and LL-29 cells. In response to BLM-induced lung and serum conditions in Wistar rats, the CPEA extract significantly reduced (p < 0.05) markers of inflammation and fibrosis (ALP, LDH, TNF-α, CXCL8-MIP2, MMP7, SP-A, SP-D, NO, TBARS, and MPO) and significantly restored antioxidant enzymes (p < 0.05) (GSH, GPx, and GST) and anti-inflammatory cytokines (IL10). Oral CPEA extract attenuates fibrosis, inflammation, oxidative stress, nitrosative stress, and lipid peroxidation in BLM-induced idiopathic pulmonary fibrosis (IPF). CPEA extract improved lung function and increased survival rates. Clinical trials are necessary, as this study indicated that the dietary flavonoid-rich component of CPEA extracts possesses anti-inflammatory and antioxidant properties. CPEA extract restored antioxidant enzyme levels and exerted anti-fibrotic and anti-inflammatory effects in rats with idiopathic lung fibrosis induced by BLM. CPEAs protect against lipopolysaccharide (LPS)-induced inflammation in vitro and bleomycin-induced idiopathic pulmonary fibrosis (IPF) in vivo. The findings of our investigation indicate that CPEA demonstrates therapeutic potential for IPF in human subjects, as evidenced by its capacity to enhance antioxidant, anti-inflammatory, and anti-fibrotic markers in preclinical disease models.

Developing human upper, lower, and deep lung airway models: Combining different scaffolds and developing complex co-cultures

Advanced in vitro models are crucial for studying human airway biology. Our objective was the development and optimization of 3D in vitro models representing diverse airway regions, including deep lung alveolar region. This initiative was aimed at assessing the influence of selective scaffold materials on distinct airway co-culture models. While PET membranes (30 µm thickness) were unsuitable for alveolar models due to their stiffness and relatively high Young's modulus, a combination of collagenous scaffolds seeded with Calu-3 cells and fibroblasts, showed increased mucus production going from week 1 to week 4 of air lift culture. Meanwhile standard electrospun polymer membrane (50-60 µm thick), which possesses a considerably low modulus of elasticity, offered higher flexibility and supported co-cultures of primary alveolar epithelial (huAEC) and endothelial cells (hEC) in concert with lung biopsy-derived fibroblasts which enhanced maturation of the tissue model. As published, designing human alveolar in vitro models require thin scaffold to mimic the required ultra-thin ECM, in addition to assuring right balanced AT1/AT2 ratio for biomimetic representation. We concluded that co-cultivation of primary/stem cells or cell lines has a higher influence on the function of the airway tissue models than the applied scaffolds.

Lactate activates ER stress to promote alveolar epithelial cells apoptosis in pulmonary fibrosis

Pulmonary fibrosis (PF) is a chronic, progressive lung disease characterized by fibroblast proliferation, extensive extracellular matrix and collagen deposition, accompanied by inflammatory damage, ultimately leading to death due to respiratory failure. Endoplasmic reticulum (ER) stress in pulmonary fibrotic tissue is indeed recognized as a significant factor exacerbating PF development. Emerging evidences indicated a potential association between ER stress induced by lactate and cellular apoptosis in PF. However, the mechanisms in this process need further elucidation. In this paper, pulmonary fibrosis model was induced by bleomycin (BLM) intratracheally in mice. In the cellular model, type II epithelial cells were treated by lactate and TGF-β to detect ER stress and apoptosis markers. Lactate could promote ER stress response and apoptosis. Mechanically, lactate activated Caspase-12 via ATF4-Chop axis to induce cell apoptosis and promote fibrosis. ER stress inhibitor could effectively suppress alveolar epithelial cells apoptosis and pulmonary fibrosis. We concluded that pro-fibrotic properties of lactate are associated with alveolar epithelial cells apoptosis by causing ER stress and thus provide new potential therapeutic targets for pulmonary fibrosis.

Cromolyn sodium and masitinib combination inhibits fibroblast-myofibroblast transition and exerts additive cell-protective and antioxidant effects on a bleomycin-induced in vitro fibrosis model

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal fibrotic lung disease. While recent studies have suggested the potential efficacy of tyrosine kinase inhibitors in managing IPF, masitinib, a clinically used tyrosine kinase inhibitor, has not yet been investigated for its efficacy in fibrotic lung diseases. In a previous study on an in vitro neurodegenerative model, we demonstrated the synergistic antitoxic and antioxidant effects of masitinib combined with cromolyn sodium, an FDA-approved mast cell stabilizer. This study aims to investigate the anti-fibrotic and antioxidant effects of the masitinib-cromolyn sodium combination in an in vitro model of pulmonary fibrosis. Fibroblast cell cultures treated with bleomycin and/or hydrogen peroxide (H2O2) were subjected to masitinib and/or cromolyn sodium, followed by assessments of cell viability, morphological and apoptotic nuclear changes, triple-immunofluorescence labeling, and total oxidant/antioxidant capacities, besides ratio of Bax and Bcl-2 mRNA expressions as an indication of apoptosis. The combined treatment of masitinib and cromolyn sodium effectively prevented the fibroblast myofibroblast transition, a hallmark of fibrosis, and significantly reduced bleomycin / H2O2-induced apoptosis and oxidative stress. This study is the first to demonstrate the additive anti-fibrotic, cell-protective, and antioxidant effects of the masitinib-cromolyn sodium combination in an in vitro fibrosis model, suggesting its potential as an innovative therapeutic approach for pulmonary fibrosis. Combination therapy may be more advantageous in that both drugs could be administered in lower doses, exerting less side effects, and at the same time providing diverse mechanisms of action simultaneously.

CSF3 aggravates acute exacerbation of pulmonary fibrosis by disrupting alveolar epithelial barrier integrity

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive respiratory disorder characterized by poor prognosis, often presenting with acute exacerbation. The primary cause of death associated with IPF is acute exacerbation of IPF (AE-IPF). However, the pathophysiology of acute exacerbation has not been clearly elucidated yet. This study aims to investigate the underlying pathophysiological molecular mechanism in a mouse AE-PF model. C57BL/6J mice were intratracheally administered bleomycin (BLM, 5 mg/kg) to induce pulmonary fibrosis. After 14 days, lipopolysaccharide (LPS, 2 mg/kg) was injected via the trachea route. Histological assessments, including H&E and Masson staining, as well as inflammatory indicators, were included to evaluate the induction of AE-PF by BLM and LPS in mice. Transcriptomic profiling of pulmonary tissues identified CSF3 as one of the top 10 upregulated DEGs in AE-PF mice. Indeed, administration of exogenous CSF3 protein exacerbated AE-PF in mice. Mechanistically, CSF3 disrupted alveolar epithelial barrier integrity and permeability by regulating specialized cell adhesion complexes such as tight junctions (TJs) and adherens junctions (AJs) via PI3K/p-Akt/Snail pathway, contributing to the aggravation of AE-PF in mice. Moreover, the discovery of elevated sera CSF3 indicated a notable increase in IPF patients during the exacerbation of the disease. Pearson correlation analysis in IPF patients revealed significant positive associations between CSF3 levels and KL-6 levels, LDH levels, CRP levels, respectively. These results provide mechanistic insights into the role of CSF3 in exacerbating of lung fibrotic disease and indicate monitoring CSF3 levels may aid in early clinical decisions for alternative therapy in the management of rapidly progressing IPF.

Novel air-liquid interface culture model to investigate stiffness-dependent behaviors of alveolar epithelial cells

Pulmonary alveoli are functional units in gas exchange in the lung, and their dysfunctions in lung diseases such as interstitial pneumonia are accompanied by fibrotic changes in structure, elevating the stiffness of extracellular matrix components. The present study aimed to test the hypothesis that such changes in alveoli stiffness induce functional alteration of epithelial cell functions, exacerbating lung diseases. For this, we have developed a novel method of culturing alveolar epithelial cells on polyacrylamide gel with different elastic modulus at an air-liquid interface. It was demonstrated that A549 cells on soft gels, mimicking the modulus of a healthy lung, upregulated mRNA expression and protein synthesis of surfactant protein C (SFTPC). By contrast, the cells on stiff gels, mimicking the modulus of the fibrotic lung, exhibited upregulation of SFTPC gene expression but not at the protein level. Cell morphology, as well as cell nucleus volume, were also different between the two types of gels.