Mechanisms of Endothelial-to-Mesenchymal Transition Induction by Extracellular Matrix Components in Pulmonary Fibrosis

Extracellular matrix in vascular homeostasis and disease

The extracellular matrix is an essential component and constitutes a dynamic microenvironment of the vessel wall with an indispensable role in vascular homeostasis and disease. From early development through to ageing, the vascular extracellular matrix undergoes various biochemical and biomechanical alterations in response to diverse environmental cues and exerts precise regulatory control over vessel remodelling. Advances in novel technologies that enable the comprehensive evaluation of extracellular matrix components and cell-matrix interactions have led to the emergence of therapeutic strategies that specifically target this fine-tuned network. In this Review, we explore various aspects of extracellular matrix biology in vascular development, disorders and ageing, emphasizing the effect of the extracellular matrix on disease initiation and progression. Additionally, we provide an overview of the potential therapeutic implications of targeting the extracellular matrix microenvironment in vascular diseases.

Modeling the profibrotic microenvironment in vitro: Model validation

Establishing the molecular and cellular mechanisms of fibrosis requires the development of validated and reproducible models. The complexity of in vivo models challenges the monitoring of an individual cell fate, in some cases making it impossible. However, the set of factors affecting cells in vitro culture systems differ significantly from in vivo conditions, insufficiently reproducing living systems. Thus, to model profibrotic conditions in vitro, usually the key profibrotic factor, transforming growth factor beta (TGFβ-1) is used as a single factor. TGFβ-1 stimulates the differentiation of fibroblasts into myofibroblasts, the main effector cells promoting the development and progression of fibrosis. However, except for soluble factors, the rigidity and composition of the extracellular matrix (ECM) play a critical role in the differentiation process. To develop the model of more complex profibrotic microenvironment in vitro, we used a combination of factors: decellularized ECM synthesized by human dermal fibroblasts in the presence of ascorbic acid if cultured as cell sheets and recombinant TGFβ-1 as a supplement. When culturing human mesenchymal stromal cells derived from adipose tissue (MSCs) under described conditions, we observed differentiation of MSCs into myofibroblasts due to increased number of cells with stress fibrils with alpha-smooth muscle actin (αSMA), and increased expression of myofibroblast marker genes such as collagen I, EDA-fibronectin and αSMA. Importantly, secretome of MSCs changed in these profibrotic microenvironment: the secretion of the profibrotic proteins SPARC and fibulin-2 increased, while the secretion of the antifibrotic hepatocyte growth factor (HGF) decreased. Analysis of transciptomic pattern of regulatory microRNAs in MSCs revealed 49 miRNAs with increased expression and 3 miRNAs with decreased expression under profibrotic stimuli. Bioinformatics analysis confirmed that at least 184 gene targets of the differently expressed miRNAs genes were associated with fibrosis. To further validate the developed model of profibrotic microenvironment, we cultured human dermal fibroblasts in these conditions and observed increased expression of fibroblast activation protein (FAPa) after 12 h of cultivation as well as increased level of αSMA and higher number of αSMA + stress fibrils after 72 h. The data obtained allow us to conclude that the conditions formed by the combination of profibrotic ECM and TGFβ-1 provide a complex profibrotic microenvironment in vitro. Thus, this model can be applicable in studying the mechanism of fibrosis development, as well as for the development of antifibrotic therapy.

Urban airborne PM2.5 induces pulmonary fibrosis through triggering glycolysis and subsequent modification of histone lactylation in macrophages

Airborne fine particulate matter (PM2.5) can cause pulmonary inflammation and even fibrosis, however, the underlying molecular mechanisms of the pathogenesis of PM2.5 exposure have not been fully appreciated. In the present study, we explored the dynamics of glycolysis and modification of histone lactylation in macrophages induced by PM2.5-exposure in both in vivo and in vitro models. Male C57BL/6 J mice were anesthetized and administrated with PM2.5 by intratracheal instillation once every other day for 4 weeks. Mouse RAW264.7 macrophages and alveolar epithelial MLE-12 cells were treated with PM2.5 for 24 h. We found that PM2.5 significantly increased lactate dehydrogenase (LDH) activities and lactate contents, and up-regulated the mRNA expression of key glycolytic enzymes in the lungs and bronchoalveolar lavage fluids of mice. Moreover, PM2.5 increased the levels of histone lactylation in both PM2.5-exposed lungs and RAW264.7 cells. The pro-fibrotic cytokines secreted from PM2.5-treated RAW264.7 cells triggered epithelial-mesenchymal transition (EMT) in MLE-12 cells through activating transforming growth factor-β (TGF-β)/Smad2/3 and VEGFA/ERK pathways. In contrast, LDHA inhibitor (GNE-140) pretreatment effectively alleviated PM2.5-induced pulmonary inflammation and fibrosis via inhibiting glycolysis and subsequent modification of histone lactylation in mice. Thus, our findings suggest that PM2.5-induced glycolysis and subsequent modification of histone lactylation play critical role in the PM2.5-associated pulmonary fibrosis.

Decellularized diseased tissues: current state-of-the-art and future directions

Decellularized matrices derived from diseased tissues/organs have evolved in the most recent years, providing novel research perspectives for understanding disease occurrence and progression and providing accurate pseudo models for developing new disease treatments. Although decellularized matrix maintaining the native composition, ultrastructure, and biomechanical characteristics of extracellular matrix (ECM), alongside intact and perfusable vascular compartments, facilitates the construction of bioengineered organ explants in vitro and promotes angiogenesis and tissue/organ regeneration in vivo, the availability of healthy tissues and organs for the preparation of decellularized ECM materials is limited. In this paper, we review the research advancements in decellularized diseased matrices. Considering that current research focuses on the matrices derived from cancers and fibrotic organs (mainly fibrotic kidney, lungs, and liver), the pathological characterizations and the applications of these diseased matrices are mainly discussed. Additionally, a contrastive analysis between the decellularized diseased matrices and decellularized healthy matrices, along with the development in vitro 3D models, is discussed in this paper. And last, we have provided the challenges and future directions in this review. Deep and comprehensive research on decellularized diseased tissues and organs will promote in-depth exploration of source materials in tissue engineering field, thus providing new ideas for clinical transformation.

Phytohormones Affect Differentiation Status of Human Skin Fibroblasts via UPR Activation

Normalization of secretory activity and differentiation status of mesenchymal cells, including fibroblasts, is an important biomedical problem. One of the possible solutions is modulation of unfolded protein response (UPR) activated during fibroblast differentiation. Here, we investigated the effect of phytohormones on the secretory activity and differentiation of cultured human skin fibroblasts. Based on the analysis of expression of genes encoding UPR markers, abscisic acid (ABA) upregulated expression of the GRP78 and ATF4 genes, while gibberellic acid (GA) upregulated expression of CHOP. Evaluation of the biosynthetic activity of fibroblasts showed that ABA promoted secretion and synthesis of procollagen I and synthesis of fibronectin, as well as the total production of collagen and non-collagen proteins of the extracellular matrix (ECM). ABA also stimulated the synthesis of smooth muscle actin α (α-SMA), which is the marker of myofibroblasts, and increased the number of myofibroblasts in the cell population. On the contrary, GA increased the level of fibronectin secretion, but reduced procollagen I synthesis and the total production of the ECM collagen proteins. GA downregulated the synthesis of α-SMA and decreased the number of myofibroblasts in the cell population. Our results suggest that phytohormones modulate the biosynthetic activity of fibroblasts and affect their differentiation status.

Novel Potential Markers of Myofibroblast Differentiation Revealed by Single-Cell RNA Sequencing Analysis of Mesenchymal Stromal Cells in Profibrotic and Adipogenic Conditions

Mesenchymal stromal cells (MSCs) are the key regulators of tissue homeostasis and repair after damage. Accumulating evidence indicates the dual contribution of MSCs into the development of fibrosis induced by chronic injury: these cells can suppress the fibrotic process due to paracrine activity, but their promoting role in fibrosis by differentiating into myofibroblasts has also been demonstrated. Many model systems reproducing fibrosis have shown the ability of peroxisome proliferator-activated receptor (PPAR) agonists to reverse myofibroblast differentiation. Thus, the differentiation of multipotent cells into myofibroblasts and adipocytes can be considered as processes that require the activation of opposite patterns of gene expression. To test this hypothesis, we analyzed single cell RNA-Seq transcriptome of human adipose tissue MSCs after stimulation of the myofibroblast or adipogenic differentiation and revealed several genes that changed their expression in a reciprocal manner upon these conditions. We validated the expression of selected genes by RT-PCR, and evaluated the upregulation of several relevant proteins using immunocytochemistry, refining the results obtained by RNA-Seq analysis. We have shown, for the first time, the expression of neurotrimin (NTM), previously studied mainly in the nervous tissue, in human adipose tissue MSCs, and demonstrated its increased gene expression and clustering of membrane receptors upon the stimulation of myofibroblast differentiation. We also showed an increased level of CHD3 (Chromodomain-Helicase-DNA-binding protein 3) in MSCs under profibrotic conditions, while retinol dehydrogenase-10 (RDH10) was detected only in MSCs after adipogenic induction, which contradicted the data of transcriptomic analysis and again highlights the need to validate the data obtained by omics methods. Our findings suggest the further analysis of the potential contribution of neurotrimin and CHD3 in the regulation of myofibroblast differentiation and the development of fibrosis.

Influence of PHA Substrate Surface Characteristics on the Functional State of Endothelial Cells

The needs of modern regenerative medicine for biodegradable polymers are wide and varied. Restoration of the viability of the vascular tree is one of the most important components of the preservation of the usefulness of organs and tissues. The creation of vascular implants compatible with blood is an important task of vascular bioengineering. The function of the endothelial layer of the vessel, being largely responsible for the development of thrombotic complications, is of great importance for hemocompatibility. The development of surfaces with specific characteristics of biomaterials that are used in vascular technologies is one of the solutions for their correct endothelialization. Linear polyhydroxyalkanoates (PHAs) are biodegradable structural polymeric materials suitable for obtaining various types of implants and tissue engineering, having a wide range of structural and physicomechanical properties. The use of PHA of various monomeric compositions in endothelial cultivation makes it possible to evaluate the influence of material properties, especially surface characteristics, on the functional state of cells. It has been established that PHA samples with the inclusion of 3-hydroxyhexanoate have optimal characteristics for the formation of a human umbilical vein endothelial cell, HUVEC, monolayer in terms of cell morphology as well as the levels of expression of vinculin and VE-cadherin. The obtained results provide a rationale for the use of PHA copolymers as materials for direct contact with the endothelium in vascular implants.

TCF7/SNAI2/miR-4306 feedback loop promotes hypertrophy of ligamentum flavum

Background

Hypertrophy of ligamentum flavum (HLF) is the mainly cause of lumbar spinal stenosis (LSS), but the precise mechanism of HLF formation has not been fully elucidated. Emerging evidence indicates that transcription factor 7 (TCF7) is the key downstream functional molecule of Wnt/β-catenin signaling, which participated in regulating multiple biological processes. However, the role and underlying mechanism of TCF7 in HLF is still unclear.

Methods

We used mRNAs sequencing analysis of human LF and subsequent confirmation with RT-qPCR, western blot and immunohistochemistry to identified the TCF7 in HLF tissues and cells. Then effect of TCF7 on HLF progression was investigated both in vitro and in vivo. Mechanically, chromatin immunoprecipitation, dual-luciferase reporter assays, and rescue experiments were used to validate the regulation of TCF7/SNAI2/miR-4306 feedback loop.

Results

Our results identified for first time that the TCF7 expression was obviously elevated in HLF tissues and cells compared with control, and also found that TCF7 expression had significant positive correlation with LF thickness and fibrosis score. Notably, TCF7 inhibition suppressed the hyper-proliferation and fibrosis phenotype of HLF cells in vitro and ameliorated progression of HLF in mice in vivo, whereas TCF7 overexpression promoted hyper-proliferation and fibrosis phenotype of HLF cells in vitro. Our data further revealed that TCF7 interacted with SNAI2 promoter to transactivated the SNAI2 expression, thereby promoting hyper-proliferation and fibrosis phenotype of HLF cells in vitro. Furthermore, miR-4036 negatively regulated by SNAI2 could negatively feedback regulate TCF7 expression by directly binding to TCF7 mRNA 3’-UTR, thus inhibiting the hyper-proliferation and fibrosis phenotype of HLF cells in vitro.

Conclusions

Our study demonstrated that TCF7 inhibition could suppress HLF formation by modulating TCF7/SNAI2/miR-4306 feedback loop, which might be considered as a novel potential therapeutic target for HLF.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03677-0.

Epigallocatechin Gallate Relieved PM2.5-Induced Lung Fibrosis by Inhibiting Oxidative Damage and Epithelial-Mesenchymal Transition through AKT/mTOR Pathway

Oxidative damage and epithelial-mesenchymal transition (EMT) are main pathological processes leading to the development of PM2.5-induced lung fibrosis. Epigallocatechin gallate (EG), a natural polyphenol extracted from green tea, possesses the ability to combat oxidative stress and inflammation. However, the potential roles of EG in PM2.5-induced lung fibrosis have not been reported yet. In the present study, we investigated whether EG could relieve PM2.5-induced lung injury and fibrosis in vivo and in vitro. To mimic PM2.5-induced lung fibrosis, C57/BL6 mice were intranasally instilled with PM2.5 suspension, and MLE-12 lung epithelial cells were stimulated with PM2.5 (100 μg/mL) in vitro. The results showed that intragastric administration of EG (20 mg/kg/d or 80 mg/kg/d for 8 weeks) significantly prevented lung injury, inflammation, and oxidative stress in PM2.5-induced mice, apart from inhibiting collagen deposition. Additionally, EG treatment also suppressed the activation of AKT/mTOR signaling pathway in lung tissues challenged with PM2.5. In vitro experiments further demonstrated that EG treatment could enhance cell viability in a concentration-dependent manner in PM2.5-treated MLE-12 lung epithelial cells. Also, the overexpression of constitutively active AKT could offset the inhibitory effects of EG on EMT and oxidative stress in PM2.5-treated MLE-12 lung epithelial cells. Finally, AKT overexpression also blocked the inhibitory effect of EG on the phosphorylation of mTOR in PM2.5-treated MLE-12 lung epithelial cells. In conclusion, EG could improve PM2.5-induced lung fibrosis by decreasing oxidative damage and EMT through AKT/mTOR pathway, which might be a potential candidate for the treatment of PM2.5-induced lung fibrosis.