Lysophosphatidic acid accelerates lung fibrosis by inducing differentiation of mesenchymal stem cells into myofibroblasts

Involvement of lysophosphatidic acid-LPA1-YAP signaling in healthy and pathological FAPs migration

Skeletal muscle fibrosis is defined as the excessive accumulation of extracellular matrix (ECM) components and is a hallmark of muscular dystrophies. Fibro-adipogenic progenitors (FAPs) are the main source of ECM, and thus have been strongly implicated in fibrogenesis. In skeletal muscle fibrotic models, including muscular dystrophies, FAPs undergo dysregulations in terms of proliferation, differentiation, and apoptosis, however few studies have explored the impact of FAPs migration. Here, we studied fibroblast and FAPs migration and identified lysophosphatidic acid (LPA), a signaling lipid central to skeletal muscle fibrogenesis, as a significant migration inductor. We identified LPA receptor 1 (LPA1) mediated signaling as crucial for this effect through a mechanism dependent on the Hippo pathway, another pathway implicated in fibrosis across diverse tissues. This cross-talk favors the activation of the Yes-associated protein 1 (YAP) and Transcriptional coactivator with PDZ-binding motif (TAZ), leading to increased expression of fibrosis-associated genes. This study reveals the role of YAP in LPA-mediated fibrotic responses as inhibition of YAP transcriptional coactivator activity hinders LPA-induced migration in fibroblasts and FAPs. Moreover, we found that FAPs derived from the mdx4cv mice, a murine model of Duchenne muscular dystrophy, display a heightened migratory phenotype due to enhanced LPA signaling compared to wild-type FAPs. Remarkably, we found that the inhibition of LPA1 or YAP transcriptional coactivator activity in mdx4cv FAPs reverts this phenotype. In summary, the identified LPA-LPA1-YAP pathway emerges as a critical driver of skeletal muscle FAPs migration and provides insights into potential novel targets to mitigate fibrosis in muscular dystrophies.

Lysophosphatidic Acid-Mediated Inflammation at the Heart of Heart Failure

PURPOSE OF REVIEW

The primary aim of this review is to provide an in-depth examination of the role bioactive lipids-namely lysophosphatidic acid (LPA) and ceramides-play in inflammation-mediated cardiac remodeling during heart failure. With the global prevalence of heart failure on the rise, it is critical to understand the underlying molecular mechanisms contributing to its pathogenesis. Traditional studies have emphasized factors such as oxidative stress and neurohormonal activation, but emerging research has shed light on bioactive lipids as central mediators in heart failure pathology. By elucidating these intricacies, this review aims to: Bridge the gap between basic research and clinical practice by highlighting clinically relevant pathways contributing to the pathogenesis and prognosis of heart failure. Provide a foundation for the development of targeted therapies that could mitigate the effects of LPA and ceramides on heart failure. Serve as a comprehensive resource for clinicians and researchers interested in the molecular biology of heart failure, aiding in better diagnostic and therapeutic decisions.

RECENT FINDINGS

Recent findings have shed light on the central role of bioactive lipids, specifically lysophosphatidic acid (LPA) and ceramides, in heart failure pathology. Traditional studies have emphasized factors such as hypoxia-mediated cardiomyocyte loss and neurohormonal activation in the development of heart failure. Emerging research has elucidated the intricacies of bioactive lipid-mediated inflammation in cardiac remodeling and the development of heart failure. Studies have shown that LPA and ceramides contribute to the pathogenesis of heart failure by promoting inflammation, fibrosis, and apoptosis in cardiac cells. Additionally, recent studies have identified potential targeted therapies that could mitigate the effects of bioactive lipids on heart failure, including LPA receptor antagonists and ceramide synthase inhibitors. These recent findings provide a promising avenue for the development of targeted therapies that could improve the diagnosis and treatment of heart failure. In this review, we highlight the pivotal role of inflammation induced by bioactive lipid signaling and its influence on the pathogenesis of heart failure. By critically assessing the existing literature, we provide a comprehensive resource for clinicians and researchers interested in the molecular mechanisms of heart failure. Our review aims to bridge the gap between basic research and clinical practice by providing actionable insights and a foundation for the development of targeted therapies that could mitigate the effects of bioactive lipids on heart failure. We hope that this review will aid in better diagnostic and therapeutic decisions, further advancing our collective understanding and management of heart failure.

Pillar arene Se nanozyme therapeutic systems with dual drive power effectively penetrated mucus layer combined therapy acute lung injury

siRNA has demonstrated a promising paradigm for therapy of acute lung injury(ALI). However, the pulmonary mucus layer barrier powerfully hinders the therapeutic efficacy. Herein, we proposed to use dual drive power to enhance the mucus permeation of siRNA by constructing the neutral and targeted selenium nanozymes therapeutic system. The multifunctional selenium nanozymes (CWP-Se@Man) were synthesized by modifying with cationic water-soluble pillar arene (CWP) and mannose (Man). After loading CCR2-siRNA, the CWP-Se@Man reached electroneutrality that co-driven by electroneutrality and targeting, the mucus permeation capacity of CWP-Se@Man enhanced by ∼15 fold, thus effectively penetrate pulmonary mucus layer and deliver CCR2-siRNA into macrophages. Moreover, with optimizing the composition of CWP-Se@Man made of CWP (Slutsky, 2013) [5] or CWP (Ichikado et al., 2012) [6], the therapeutic system CWP (Ichikado et al., 2012) [6]-Se@Man showed better biological activities due to smaller size. In inflamed modes, the CWP-Se@Man nanotherapeutic systems loading CCR2-siRNA not only exerted pronounced anti-inflammatory effect through combining inhibit the chemotactic effect and ROS, but also effectively against ALI after blocking the circulatory effect of ROS and inflammatory cytokines. Therefore, this strategy of dual-driving force penetration mucus renders a unique approach for mediating trans-mucus nucleic acid delivery in lungs, and provide a promising treatment for the acute lung injury therapy.

Protective effects of natural compounds against paraquat-induced pulmonary toxicity: the role of the Nrf2/ARE signaling pathway

Paraquat (PQ) is a toxic herbicide to humans. Once absorbed, it accumulates in the lungs. PQ has been well documented that the generation of reactive oxygen species (ROS) is the main mechanism of its toxicity. Oxidative damage of PQ in lungs is represented as generation of cytotoxic and fibrotic mediators, interruption of epithelial and endothelial barriers, and inflammatory cell infiltration. No effective treatment for PQ toxicity is currently available. Several studies have shown that natural compounds (NCs) have the potential to alleviate PQ-induced pulmonary toxicity, due to their antioxidant and anti-inflammatory effects. NCs function as protective agents through stimulation of nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) signaling pathways. Elevation of Nrf2 levels leads to the expression of its downstream enzymes such as SOD, CAT, and HO-1. The hypothesized role of the Nrf2/ARE signaling pathway as the protective mechanism of NCs against PQ-induced pulmonary toxicity is reviewed.

Inhibition of LPA-LPAR1 and VEGF-VEGFR2 Signaling in IPF Treatment

Due to the complex mechanism and limited treatments available for pulmonary fibrosis, the development of targeted drugs or inhibitors based on their molecular mechanisms remains an important strategy for prevention and treatment. In this paper, the downstream signaling pathways mediated by VEGFR and LPAR1 in pulmonary cells and the role of these pathways in pulmonary fibrosis, as well as the current status of drug research on the targets of LPAR1 and VEGFR2, are described. The mechanism by which these two pathways regulate vascular leakage and collagen deposition leading to the development of pulmonary fibrosis are analyzed, and the mutual promotion of the two pathways is discussed. Here we propose the development of drugs that simultaneously target LPAR1 and VEGFR2, and discuss the important considerations in targeting and safety.

New therapeutic approaches against pulmonary fibrosis

Pulmonary fibrosis is the end-stage change of a large class of lung diseases characterized by the proliferation of fibroblasts and the accumulation of a large amount of extracellular matrix, accompanied by inflammatory damage and tissue structure destruction, which also shows the normal alveolar tissue is damaged and then abnormally repaired resulting in structural abnormalities (scarring). Pulmonary fibrosis has a serious impact on the respiratory function of the human body, and the clinical manifestation is progressive dyspnea. The incidence of pulmonary fibrosis-related diseases is increasing year by year, and no curative drugs have appeared so far. Nevertheless, research on pulmonary fibrosis have also increased in recent years, but there are no breakthrough results. Pathological changes of pulmonary fibrosis appear in the lungs of patients with coronavirus disease 2019 (COVID-19) that have not yet ended, and whether to improve the condition of patients with COVID-19 by means of the anti-fibrosis therapy, which are the questions we need to address now. This review systematically sheds light on the current state of research on fibrosis from multiple perspectives, hoping to provide some references for design and optimization of subsequent drugs and the selection of anti-fibrosis treatment plans and strategies.

Dysregulation of metabolic pathways in pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive disorder of unknown origin and the most common interstitial lung disease. It progresses with the recruitment of fibroblasts and myofibroblasts that contribute to the accumulation of extracellular matrix (ECM) proteins, leading to the loss of compliance and alveolar integrity, compromising the gas exchange capacity of the lung. Moreover, while there are therapeutics available, they do not offer a cure. Thus, there is a pressing need to identify better therapeutic targets. With the advent of transcriptomics, proteomics, and metabolomics, the cellular mechanisms underlying disease progression are better understood. Metabolic homeostasis is one such factor and its dysregulation has been shown to impact the outcome of IPF. Several metabolic pathways involved in the metabolism of lipids, protein and carbohydrates have been implicated in IPF. While metabolites are crucial for the generation of energy, it is now appreciated that metabolites have several non-metabolic roles in regulating cellular processes such as proliferation, signaling, and death among several other functions. Through this review, we succinctly elucidate the role of several metabolic pathways in IPF. Moreover, we also discuss potential therapeutics which target metabolism or metabolic pathways.

Activation of skeletal muscle FAPs by LPA requires the Hippo signaling via the FAK pathway

Lysophosphatidic acid (LPA) is a lysophospholipid that signals through six G-protein coupled receptors (LPARs), LPA₁ to LPA₆. LPA has been described as a potent modulator of fibrosis in different pathologies. In skeletal muscle, LPA increases fibrosis-related proteins and the number of fibro/adipogenic progenitors (FAPs). FAPs are the primary source of ECM-secreting myofibroblasts in acute and chronic damage. However, the effect of LPA on FAPs activation in vitro has not been explored. This study aimed to investigate FAPs' response to LPA and the downstream signaling mediators involved. Here, we demonstrated that LPA mediates FAPs activation by increasing their proliferation, expression of myofibroblasts markers, and upregulation of fibrosis-related proteins. Pretreatment with the LPA₁/LPA₃ antagonist Ki16425 or genetic deletion of LPA₁ attenuated the LPA-induced FAPs activation, resulting in decreased expression of cyclin e1, α-SMA, and fibronectin. We also evaluated the activation of the focal adhesion kinase (FAK) in response to LPA. Our results showed that LPA induces FAK phosphorylation in FAPs. Treatment with the P-FAK inhibitor PF-228 partially prevented the induction of cell responses involved in FAPs activation, suggesting that this pathway mediates LPA signaling. FAK activation controls downstream cell signaling within the cytoplasm, such as the Hippo pathway. LPA induced the dephosphorylation of the transcriptional coactivator YAP (Yes-associated protein) and promoted direct expression of target pathway genes such as Ctgf/Ccn2 and Ccn1. The blockage of YAP transcriptional activity with Super-TDU further confirmed the role of YAP in LPA-induced FAPs activation. Finally, we demonstrated that FAK is required for LPA-dependent YAP dephosphorylation and the induction of Hippo pathway target genes. In conclusion, LPA signals through LPA₁ to regulate FAPs activation by activating FAK to control the Hippo pathway.

Small-molecule-mediated OGG1 inhibition attenuates pulmonary inflammation and lung fibrosis in a murine lung fibrosis model

Interstitial lung diseases such as idiopathic pulmonary fibrosis (IPF) are caused by persistent micro-injuries to alveolar epithelial tissues accompanied by aberrant repair processes. IPF is currently treated with pirfenidone and nintedanib, compounds which slow the rate of disease progression but fail to target underlying pathophysiological mechanisms. The DNA repair protein 8-oxoguanine DNA glycosylase-1 (OGG1) has significant roles in the modulation of inflammation and metabolic syndromes. Currently, no pharmaceutical solutions targeting OGG1 have been utilized in the treatment of IPF. In this study we show Ogg1-targeting siRNA mitigates bleomycin-induced pulmonary fibrosis in male mice, highlighting OGG1 as a tractable target in lung fibrosis. The small molecule OGG1 inhibitor, TH5487, decreases myofibroblast transition and associated pro-fibrotic gene expressions in fibroblast cells. In addition, TH5487 decreases levels of pro-inflammatory mediators, inflammatory cell infiltration, and lung remodeling in a murine model of bleomycin-induced pulmonary fibrosis conducted in male C57BL6/J mice. OGG1 and SMAD7 interact to induce fibroblast proliferation and differentiation and display roles in fibrotic murine and IPF patient lung tissue. Taken together, these data suggest that TH5487 is a potentially clinically relevant treatment for IPF but further study in human trials is required.

Lung fibrogenic microenvironment in mouse reconstitutes human alveolar structure and lung tumor

A mesenchymal cell activation is a hallmark event of pulmonary fibrosis. Alveolar type 2 (AT2) cells are progenitor cells that maintain alveolar homeostasis, and their damage is assumed to be an initiating event for pulmonary fibrosis. However, the interaction between the lung fibrogenic microenvironment and AT2 cell dynamics remains to be elucidated. Here, we report a unique role of the lung fibrogenic microenvironment, where cell type-specific tissue reconstruction is achieved by exogenous cell transplantation. We found that in the lung fibrogenic microenvironment the AT2 cell pool was depleted, whereas mesenchymal cells could promote intact AT2 cell proliferation in vitro. Furthermore, exogenously transplanted AT2 cells formed alveolar colonies and ameliorated pulmonary fibrosis. Exogenous tumor cells formed tumor nests with relevant histological and transcriptional properties. Human primary cells were adaptable to this microenvironment, facilitating epithelial cell-targeted therapy in pulmonary fibrosis and the establishment of patient-derived xenografts for precision medicine in lung cancer.

•

Severe bleomycin-induced lung injury causes a significant AT2 cell loss

•

Mesenchymal cells in the fibrogenic lung supports AT2 cell proliferation

•

AT2 cell transplantation ameliorates bleomycin-induced pulmonary fibrosis

•

Novel orthotopic lung cancer models are established for patient-derived xenografts

Odontogenic Differentiation-Induced Tooth Regeneration by Psoralea corylifolia L

Psoralea corylifolia L. (P. corylifolia) has been used as an oriental phytomedicine to treat coldness of hands and feet in bone marrow injury. Hydroxyapatite is usually used for tooth regeneration. In this study, the role of P. corylifolia and bakuchiol, a compound originated from P. corylifolia as differentiation-inducing substances for tooth regeneration, was determined by monitoring odontogenic differentiation in human dental pulp stem cells (hDPSCs). We confirmed that P. corylifolia extracts and bakuchiol increased the odontogenic differentiation of hDPSCs. In addition, the expression of the odontogenic differentiation marker genes alkaline phosphatase (APL), Runt-related transcription factor 2 (RUNX-2), osteocalcin (OC), and dentin matrix acidic phosphoprotein-1 (DMP-1) was proved by real-time polymerase chain reaction, and protein expression of dentin matrix acidic phosphoprotein-1 (DMP-1) and dentin sialophosphoprotein (DSPP) was proved by western blotting. Further, by confirming the increase in small mothers against decapentaplegia (SMAD) 1/5/8 phosphorylation, the SMAD signaling pathway was found to increase the differentiation of odontoblasts. This study confirmed that P. corylifolia L. extracts and bakuchiol alone promote odontogenic differentiation in hDPSCs. These results suggest that bakuchiol from P. corylifolia is responsible for odontogenic differentiation, and they encourage future in vivo studies on dentin regeneration.

Extracellular Lipids in the Lung and Their Role in Pulmonary Fibrosis

Lipids are major actors and regulators of physiological processes within the lung. Initial research has described their critical role in tissue homeostasis and in orchestrating cellular communication to allow respiration. Over the past decades, a growing body of research has also emphasized how lipids and their metabolism may be altered, contributing to the development and progression of chronic lung diseases such as pulmonary fibrosis. In this review, we first describe the current working model of the mechanisms of lung fibrogenesis before introducing lipids and their cellular metabolism. We then summarize the evidence of altered lipid homeostasis during pulmonary fibrosis, focusing on their extracellular forms. Finally, we highlight how lipid targeting may open avenues to develop therapeutic options for patients with lung fibrosis.

Intestinal Fibrosis in Inflammatory Bowel Disease and the Prospects of Mesenchymal Stem Cell Therapy

Intestinal fibrosis is an important complication of inflammatory bowel disease (IBD). In the course of the development of fibrosis, certain parts of the intestine become narrowed, significantly destroying the structure and function of the intestine and affecting the quality of life of patients. Chronic inflammation is an important initiating factor of fibrosis. Unfortunately, the existing anti-inflammatory drugs cannot effectively prevent and alleviate fibrosis, and there is no effective anti-fibrotic drug, which makes surgical treatment the mainstream treatment for intestinal fibrosis and stenosis. Mesenchymal stem cells (MSCs) are capable of tissue regeneration and repair through their self-differentiation, secretion of cytokines, and secretion of extracellular vesicles. MSCs have been shown to play an important therapeutic role in the fibrosis of many organs. However, the role of MSC in intestinal fibrosis largely remained unexplored. This review summarizes the mechanism of intestinal fibrosis, including the role of immune cells, TGF-β, and the gut microbiome and metabolites. Available treatment options for fibrosis, particularly, MSCs are also discussed.

Preventing the Increase in Lysophosphatidic Acids: A New Therapeutic Target in Pulmonary Hypertension?

Cardiovascular diseases (CVD) are the leading cause of premature death and disability in humans that are closely related to lipid metabolism and signaling. This study aimed to assess whether circulating lysophospholipids (LPL), lysophosphatidic acids (LPA) and monoacylglycerols (MAG) may be considered as potential therapeutic targets in CVD. For this objective, plasma levels of 22 compounds (13 LPL, 6 LPA and 3 MAG) were monitored by liquid chromatography coupled with tandem mass spectrometry (HPLC/MS²) in different rat models of CVD, i.e., angiotensin-II-induced hypertension (HTN), ischemic chronic heart failure (CHF) and sugen/hypoxia(SuHx)-induced pulmonary hypertension (PH). On one hand, there were modest changes on the monitored compounds in HTN (LPA 16:0, 18:1 and 20:4, LPC 16:1) and CHF (LPA 16:0, LPC 18:1 and LPE 16:0 and 18:0) models compared to control rats but these changes were no longer significant after multiple testing corrections. On the other hand, PH was associated with important changes in plasma LPA with a significant increase in LPA 16:0, 18:1, 18:2, 20:4 and 22:6 species. A deleterious impact of LPA was confirmed on cultured human pulmonary smooth muscle cells (PA-SMCs) with an increase in their proliferation. Finally, plasma level of LPA(16:0) was positively associated with the increase in pulmonary artery systolic pressure in patients with cardiac dysfunction. This study demonstrates that circulating LPA may contribute to the pathophysiology of PH. Additional experiments are needed to assess whether the modulation of LPA signaling in PH may be of interest.

Lysophosphatidic acid (LPA) receptor modulators: Structural features and recent development

Lysophosphatidic acid (LPA) activates six LPA receptors (LPAR_1-6) and regulates various cellular activities such as cell proliferation, cytoprotection, and wound healing. Many studies elucidated the pathological outcomes of LPA are due to the alteration in signaling pathways, which include migration and invasion of cancer cells, fibrosis, atherosclerosis, and inflammation. Current pathophysiological research on LPA and its receptors provides a means that LPA receptors are new therapeutic targets for disorders associated with LPA. Various chemical modulators are developed and are under investigation to treat a wide range of pathological complications. This review summarizes the physiological and pathological roles of LPA signaling, development of various LPA modulators, their structural features, patents, and their clinical outcomes.

Revisiting the role of lysophosphatidic acid in stem cell biology

Stem cells possess unique biological characteristics such as the ability to self-renew and to undergo multilineage differentiation into specialized cells. Whereas embryonic stem cells (ESC) can differentiate into all cell types of the body, somatic stem cells (SSC) are a population of stem cells located in distinct niches throughout the body that differentiate into the specific cell types of the tissue in which they reside in. SSC function mainly to restore cells as part of normal tissue homeostasis or to replenish cells that are damaged due to injury. Cancer stem-like cells (CSC) are said to be analogous to SSC in this manner where tumor growth and progression as well as metastasis are fueled by a small population of CSC that reside within the corresponding tumor. Moreover, emerging evidence indicates that CSC are inherently resistant to chemo- and radiotherapy that are often the cause of cancer relapse. Hence, major research efforts have been directed at identifying CSC populations in different cancer types and understanding their biology. Many factors are thought to regulate and maintain cell stemness, including bioactive lysophospholipids such as lysophosphatidic acid (LPA). In this review, we discuss some of the newly discovered functions of LPA not only in the regulation of CSC but also normal SSC, the similarities in these regulatory functions, and how these discoveries can pave way to the development of novel therapies in cancer and regenerative medicine.

The arachidonic acid metabolite 11,12-epoxyeicosatrienoic acid alleviates pulmonary fibrosis

Epoxyeicosatrienoic acids (EETs) are metabolites of arachidonic acid that are rapidly metabolized into diols by soluble epoxide hydrolase (sEH). sEH inhibition has been shown to increase the biological activity of EETs, which are known to have anti-inflammatory properties. However, the role of EETs in pulmonary fibrosis remains unexplored. Liquid chromatography with tandem mass spectrometry (LC-MS/MS) was used to analyze EETs in the lung tissues of patients with idiopathic pulmonary fibrosis (IPF, n = 29) and controls (n = 15), and the function of 11,12-EET was evaluated in in vitro and in vivo in pulmonary fibrosis models. EET levels in IPF lung tissues, including those of 8,9-EET, 11,12-EET, and 14,15-EET, were significantly lower than those in control tissues. The 11,12-EET/11,12-DHET ratio in human lung tissues also differentiated IPF from control tissues. 11,12-EET significantly decreased transforming growth factor (TGF)-β1-induced expression of α-smooth muscle actin (SMA) and collagen type-I in MRC-5 cells and primary fibroblasts from IPF patients. sEH-specific siRNA and 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU; sEH inhibitor) also decreased TGF-β1-induced expression of α-SMA and collagen type-I in fibroblasts. Moreover, 11,12-EET and TPPU decreased TGF-β1-induced p-Smad2/3 and extracellular-signal-regulated kinase (ERK) expression in primary fibroblasts from patients with IPF and fibronectin expression in Beas-2B cells. TPPU decreased the levels of hydroxyproline in the lungs of bleomycin-induced mice. 11,12-EET or sEH inhibitors could inhibit pulmonary fibrosis by regulating TGF-β1-induced profibrotic signaling, suggesting that 11,12-EET and the regulation of EETs could serve as potential therapeutic targets for IPF treatment.

Signaling molecules called eicosanoids, which are derived from fatty acids, can suppress lung damage in idiopathic pulmonary fibrosis (IPF), a chronic, progressive disease in which scar tissue builds up in the lungs, making it hard to breathe. The causes of IPF are unknown. Eicosanoids, which have anti-inflammatory properties, have been studied in various lung diseases. Jin Woo Song at the University of Ulsan College of Medicine in Seoul, South Korea, and co-workers investigated how they might affect IPF. They found that eicosanoid levels were lower in lung tissues from patients with IPF than in healthy tissues. Further investigation showed eicosanoid levels could be boosted by suppressing an enzyme called sEH that degrades them. Thus, suppression of sEH and boosting of eicosanoid levels show promise as therapeutic targets for IPF.

8-Oxoguanine DNA glycosylase modulates the cell transformation process in pulmonary fibrosis by inhibiting Smad2/3 and interacting with Smad7

The DNA repair enzyme 8-oxoguanine DNA glycosylase-1 (OGG1) is involved in early embryonic development, as well as in multiple conditions, including cardiac fibrosis, diabetes, and neurodegenerative diseases. But, function of OGG1 in pulmonary fibrosis was not entirely clear. In this study, we identified a novel function of OGG1 in the cell transformation process in pulmonary fibrosis. We demonstrated that OGG1 and Smad7 co-localize and interact in A549 cells. Bleomycin-induced pulmonary fibrosis was established in wild-type (WT) and Ogg1^-/- mice. Upon treatment with transforming growth factor (TGF)-β1, increased OGG1 expression was observed in WT mice with pulmonary fibrosis as well as in A549 cells, MRC-5 cells, and primary rat type II alveolar epithelial cells. The increased expression of OGG1 promoted cell migration, while OGG1 depletion decreased migration ability. Expression of the transformation-associated markers vimentin and alpha-smooth muscle actin were also affected by OGG1. We also observed that OGG1 promoted TGF-β1-induced cell transformation and activated Smad2/3 by interacting with Smad7. The interaction between OGG1 and the TGF-β/Smad axis modulates the cell transformation process in lung epithelial cells and fibroblasts. Moreover, we demonstrated that Ogg1 deficiency relieved pulmonary fibrosis in bleomycin-treated mice. Ogg1 knockout decreased the bleomycin-induced expression of Smad7 and phosphorylation of Smad2/3 in mice. These findings suggest that OGG1 has multiple biological functions in the pathogenesis of pulmonary fibrosis.

Paraquat induces pulmonary fibrosis through Wnt/β-catenin signaling pathway and myofibroblast differentiation

Paraquat (PQ) poisoning-induced pulmonary fibrosis always results in fatal harm to patients. Our study aimed to investigate the functions of the Wnt/β-catenin pathway in PQ-induced pulmonary fibrosis. By comparing the proteomic profiles of rat lung tissues using protein array in the absence or presence of PQ, the Wnt/β-catenin signaling, as a fibrosis-related pathway, was discovered to be profoundly activated by PQ. The protein levels of Wnt/β-catenin signaling components including MMP-2, β-catenin, Wnt3a, Wnt10b, Cyclin D1, and WISP1 were increased in PQ-treated rat lung tissues. Surprisingly, PQ was found to be able to promote lung epithelial cells and fibroblasts differentiating into myofibroblasts by activating Wnt/β-catenin signaling pathway. Dickkopf-1 (DKK1), an antagonist of Wnt/β-catenin signaling pathway, could inhibit the myofibroblast differentiation and attenuate PQ-induced pulmonary fibrogenesis in vitro and in vivo. The expression levels of fibroblasts markers Vimentin, α-smooth muscle actin (α-SMA) and Collagen I was detected and found to be increased when PQ treated and restored with additional DKK1 treatment. In summary, these assays indicated that Wnt/β-catenin signaling pathway played a regulatory role in the differentiation of lung epithelial cells and fibroblasts, and the pathogenesis of pulmonary fibrosis related to PQ. Inhibition of the Wnt/β-catenin signaling pathway may be investigated further as a potential fibrosis suppressor for pulmonary fibrosis therapy.

Lysophosphatidic Acid Receptors: Biochemical and Clinical Implications in Different Diseases

Lysophosphatidic acid (LPA, 1-acyl-2-hemolytic-sn-glycerol-3-phosphate) extracted from membrane phospholipid is a kind of simple bioactive glycophospholipid, which has many biological functions such as stimulating cell multiplication, cytoskeleton recombination, cell survival, drug-fast, synthesis of DNA and ion transport. Current studies have shown that six G-coupled protein receptors (LPAR1-6) can be activated by LPA. They stimulate a variety of signal transduction pathways through heterotrimeric G-proteins (such as Gα12/13, Gαq/11, Gαi/o and GαS). LPA and its receptors play vital roles in cancers, nervous system diseases, cardiovascular diseases, liver diseases, metabolic diseases, etc. In this article, we discussed the structure of LPA receptors and elucidated their functions in various diseases, in order to better understand them and point out new therapeutic schemes for them.

Identification and Modulation of Microenvironment Is Crucial for Effective Mesenchymal Stromal Cell Therapy in Acute Lung Injury

Rationale: There are controversial reports on applications of mesenchymal stromal cells (MSCs) in patients with acute respiratory distress syndrome (ARDS). Objectives: We hypothesized that lung microenvironment was the main determinant of beneficial versus detrimental effects of MSCs during ARDS. Methods: Lung proteome was profiled in three models of injury induced by acid instillation and/or mechanical ventilation in mice. Human gene of glutathione peroxidase-1 was delivered before MSC administration; or MSCs carrying human gene of IL-10 or hepatocyte growth factor were administered after lung injury. An inhibitory cocktail against IL-6, fibronectin, and oxidative stress was used in in vitro studies using human small airway epithelial cells and human MSCs after exposure to plasma of patients with ARDS. Measurements and Main Results: Distinct proteomic profiles were observed in three lung injury models. Administration of MSCs protected lung from ventilator-induced injury, whereas it worsened acid-primed lung injuries associated with fibrotic development in lung environment that had high levels of IL-6 and fibronectin along with low antioxidant capacity. Correction of microenvironment with glutathione peroxidase-1, or treatment with MSCs carrying human gene of IL-10 or hepatocyte growth factor after acid-primed injury, reversed the detrimental effects of native MSCs. Proteomic profiles obtained in the mouse models were also similarly observed in human ARDS. Treatment with the inhibitory cocktail in samples of patients with ARDS retained protective effects of MSCs in small airway epithelial cells. Conclusions: MSCs can be beneficial or detrimental depending on microenvironment at the time of administration. Identification of potential beneficiaries seems to be crucial to guide MSC therapy in ARDS.

Dynamic actin remodeling in response to lysophosphatidic acid

Lysophosphatidic acid (LPA) is a multifunctional regulator of actin cytoskeleton that exerts a dramatic impact on the actin cytoskeleton to build a platform for diverse cellular processes including growth cone guidance, neurite retraction and cell motility. It has been implicated in the formation and dissociation of complexes between actin and actin binding proteins, supporting its role in actin remodeling. Several studies point towards its ability to facilitate formation of special cellular structures including focal adhesions and actin stress fibres by phosphoregulation of several actin associated proteins and their multiple regulatory kinases and phosphatases. In addition, multiple levels of crosstalk among the signaling cascades activated by LPA, affect actin cytoskeleton-mediated cell migration and chemotaxis which in turn play a crucial role in cancer metastasis. In the current review, we have attempted to highlight the role of LPA as an actin modulator which functions by controlling activities of specific cellular proteins that underlie mechanisms employed in cytoskeletal and pathophysiological events within the cell. Further studies on the actin affecting/remodeling activity of LPA in different cell types will no doubt throw up many surprises essential to gain a full understanding of its contribution in physiological processes as well as in diseases.Communicated by Ramaswamy H. Sarma.

A Mini-Review: The Therapeutic Potential of Bone Marrow Mesenchymal Stem Cells and Relevant Signaling Cascades

Bone marrow mesenchymal stem cells (BMSCs) characterized multi-directional differentiation, low immunogenicity and high portability, serve as ideal "seed cells" in ophthalmological disease therapy. Therefore, in this mini-review, we examined the recent literature concerning the potential application of BMSCs for the treatment of ophthalmological disease, that includes: the cellular activity of BMSCs transplantation, migration and homing, as well as the immuno-modulatory and antiinflammatory effects of BMSCs and signaling involved. Each aspect is complementary to the others and together these aspects promoted further understanding of the potential use of BMSCs in treating ophthalmological diseases.

Oxidative stress and abnormal bioactive lipids in early cystic fibrosis lung disease

BACKGROUND

Clinical data indicate that airway inflammation in children with cystic fibrosis (CF) arises early, is associated with structural lung damage, and predicts progression. In bronchoalveolar lavage fluid (BALF) from CFTR mutant mice, several aspects of lipid metabolism are abnormal that contributes to lung disease. We aimed to determine whether lipid pathway dysregulation is also observed in BALF from children with CF, to identify biomarkers of early lung disease and potential therapeutic targets.

METHODS

A comprehensive panel of lipids that included Sphingolipids, oxylipins, isoprostanes and lysolipids, all bioactive lipid species known to be involved in inflammation and tissue remodeling, were measured in BALF from children with CF (1-6 years, N = 33) and age-matched non-CF patients with unexplained inflammatory disease (N = 16) by HPLC-MS/MS. Lipid data were correlated with chest CT scores and BALF inflammation biomarkers.

RESULTS

The ratio of long chain to very long chain ceramide species (LCC/VLCC) and lysolipid levels were enhanced in CF compared to non-CF patients, despite comparable neutrophil counts and bacterial load. In CF patients both LCC/VLCC and lysolipid levels correlated with inflammation and chest CT scores. The ceramide precursors Sphingosine, Sphinganine, Sphingomyelin, correlated with inflammation, whilst the oxidative stress marker isoprostane correlated with inflammation and chest CT scores. No correlation between lipids and current bacterial infection in CF (N = 5) was observed.

CONCLUSIONS

Several lipid biomarkers of early CF lung disease were identified, which point toward potential disease monitoring and therapeutic approaches that can be used to complement CFTR modulators.

Antifibrotic effects of 2-carba cyclic phosphatidic acid (2ccPA) in systemic sclerosis: contribution to the novel treatment

Background

Cyclic phosphatidic acid (cPA) has an inhibitory effect on the autotaxin (ATX)/lysophosphatidic acid (LPA) axis, which has been implicated to play an important role in the progression of fibrosis in systemic sclerosis (SSc). The purpose of this study is to assess the antifibrotic activity of cPA for the treatment of SSc using SSc skin fibroblasts and an animal model of bleomycin-induced skin fibrosis.

Methods

We used a chemically stable derivative of cPA (2ccPA). First, we investigated the effect of 2ccPA on extracellular matrix (ECM) expression in skin fibroblasts. Next, the effect of 2ccPA on the intracellular cAMP levels was determined to investigate the mechanisms of the antifibrotic activity of 2ccPA. Finally, we administered 2ccPA to bleomycin-induced SSc model mice to evaluate whether 2ccPA prevented the progression of skin fibrosis.

Results

2ccPA decreased ECM expression in SSc skin fibroblasts and TGF-β1-treated healthy skin fibroblasts without LPA stimulation. 2ccPA increased the intracellular cAMP levels in skin fibroblasts, suggesting that the antifibrotic effect of 2ccPA was the consequence of the increase in the intracellular cAMP levels. Administration of 2ccPA also ameliorated the progression of bleomycin-induced skin fibrosis in mice.

Conclusions

Our data indicated that 2ccPA had inhibitory effects on the progression of skin fibrosis by abrogating ECM production from activated skin fibroblasts. These cells were repressed, at least in part, by increased intracellular cAMP levels. 2ccPA may be able to be used to treat fibrotic lesions in SSc.

Lipids - two sides of the same coin in lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by progressive extracellular matrix deposition in the lung parenchyma leading to the destruction of lung structure, respiratory failure and premature death. Recent studies revealed that the pathogenesis of IPF is associated with alterations in the synthesis and the activity of lipids, lipid regulating proteins and cell membrane lipid transporters and receptors in different lung cells. Furthermore, deregulated lipid metabolism was found to contribute to the profibrotic phenotypes of lung fibroblasts and alveolar epithelial cells. Consequently, several pharmacological agents, targeting lipids, lipid mediators, and lipoprotein receptors, was successfully tested in the animal models of lung fibrosis and entered early phase clinical trials. In this review, we highlight new therapeutic options to counteract disturbed lipid hemostasis in the maladaptive lung remodeling.

Inhibition of mesenchymal stromal cells' chemotactic effect to ameliorate paraquat-induced pulmonary fibrosis

BACKGROUND

Paraquat (PQ) poisoning is one of the leading causes of suicide attempts in China signature by acute onset of respiratory distress with massive matrix production resulting in progressive pulmonary fibrosis. There is no specific antidote and mortality remains high without effective treatment available. The cellular mechanisms underlying PQ-induced pulmonary fibrosis remain largely unknown.

OBJECTIVES

To determine the origin of mesenchymal stem cells (MSCs) migrated to the lung after PQ exposure and their roles in PQ-induced pulmonary fibrosis, to further explore the possible mechanisms involved in these processes, and to help finding novel therapies.

METHODS

We used a combination of lineage tracking techniques to investigate the contributions of several cells of MSCs, marked by Nestin or CXCL12, and traced their co-expression of α-smooth muscle actin (α-SMA), a marker for fibrosis, or their co-location with matrix production, marked by collagen-1 production (Col1-GFP) following PQ exposure. Then, we used a CXCL12flox/flox; Prx1-Cre mice and a pharmacologic agent AMD3100 to selectively deplete chemotactic mechanism of the MSCs, and tested pro-fibrotic pathways, fibrotic processes and survival of mice after PQ exposure.

RESULTS

Our results showed that after paraquat exposure, the residential Nestin + MSCs were quickly expanded and contributed to extracellular matrix production. Moreover, when we used a CXCL12flox/flox; Prx1-Cre mice to selectively deplete chemotactic mechanism of the MSC, we found that PQ exposure in these mice failed to activate pro-fibrotic pathways including TGF-β, Wnt and EGFR signaling. Furthermore, when the chemotactic effect of MSCs via CXCL12 was blocked by a pharmacologic agent, AMD3100, it alleviated the development of the fibrotic process and improved survival rate in mice exposed to PQ.

CONCLUSION

Collectively, our data suggest paraquat intoxication rapidly activated Nestin + MSCs and that blocking chemotactic effects of MSCs by perivascular CXCL12 inhibition may effectively protect pulmonary injury following paraquat exposure. Our results revealed a novel mechanism for post-PQ lung injury and indicated a novel therapeutic option to attenuate fibrosis induced by paraquat.

Airway remodeling disease: primary human structural cells and phenotypic and pathway assays to identify targets with potential to prevent or reverse remodeling

Airway remodeling is a characteristic of many chronic respiratory diseases and occurs when there are significant changes to the architecture of the small and large airways leading to progressive loss of lung function. Some common features include airway smooth muscle and goblet cell hyperplasia, basement membrane thickening and subepithelial fibrosis. To explore the mechanisms driving airway remodeling and identify novel targets to treat this aspect of respiratory disease, appropriate models must be used that will accurately predict the pathology of disease. Phenotypic assays can be used in primary human lung cells to measure changes in cell behavior that are associated with particular disease pathology. This is becoming increasingly popular when targeting chronic pathologies such as airway remodeling, where phenotypic assays are likely to model disease in vitro more accurately than traditional second messenger assays. Here we review the use of primary human lung structural cells in a range of disease-relevant chronic phenotypic assays, and how they may be used in target identification/validation and drug discovery.

Inhibitory effect of tranilast on the myofibroblast differentiation of rat mesenchymal stem cells induced by transforming growth factor‑β1 in vitro

Mesenchymal stem cell (MSC) transplantation is able to attenuate organ fibrosis; however, increasing evidence has indicated that MSCs may be an important cell source of myofibroblasts, which are vital pathogenic cells in fibrotic diseases. The results of the present study revealed that co‑culturing with exogenous transforming growth factor (TGF)‑β1 can induce the transdifferentiation of cultured rat MSCs into myofibroblasts in vitro. Treatment of the MSCs with tranilast [N‑(3',4'‑dimethoxycinnamoyl)‑anthranilic acid] attenuated this fibrotic process. Immunocytochemical staining, western blot analysis, reverse transcription‑quantitative polymerase chain reaction analysis and cell viability assays were performed in order to evaluate the molecular mechanisms underlying the effects of tranilast on TGF‑β1‑mediated MSC‑to‑myofibroblast activation. The results demonstrated that TGF‑β1 upregulated the expression of α‑smooth muscle actin (α‑SMA) and collagen type I, and increased the phosphorylation of mothers against decapentaplegic homolog 3 (Smad3) and extracellular signal‑regulated kinase 1/2 (ERK1/2) in the rat MSCs; by contrast, tranilast pretreatment downregulated their expression. Furthermore, the proliferation of MSCs induced by TGF‑β1 was decreased by pretreatment with tranilast. In conclusion, the results of the present study demonstrated that tranilast treatment markedly suppressed the TGF‑β1‑induced differentiation of cultured rat MSCs into myofibroblasts, potentially by inhibiting the Smad3 and ERK1/2 signaling pathways. Therefore, this may be a potential antifibrotic therapeutic strategy, serving as an adjuvant treatment following transplantation of MSCs.

Roles of lysophosphatidic acid and sphingosine-1-phosphate in stem cell biology

Stem cells are unique in their ability to self-renew and differentiate into various cell types. Because of these features, stem cells are key to the formation of organisms and play fundamental roles in tissue regeneration and repair. Mechanisms controlling their fate are thus fundamental to the development and homeostasis of tissues and organs. Lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) are bioactive phospholipids that play a wide range of roles in multiple cell types, during developmental and pathophysiological events. Considerable evidence now demonstrates the potent roles of LPA and S1P in the biology of pluripotent and adult stem cells, from maintenance to repair. Here we review their roles for each main category of stem cells and explore how those effects impact development and physiopathology.

Ras homolog family member A/Rho-associated protein kinase 1 signaling modulates lineage commitment of mesenchymal stem cells in asthmatic patients through lymphoid enhancer-binding factor 1

BACKGROUND

Numbers of mesenchymal stem cells (MSCs) are increased in the airways after allergen challenge. Ras homolog family member A (RhoA)/Rho-associated protein kinase 1 (ROCK) signaling is critical in determining the lineage fate of MSCs in tissue repair/remodeling.

OBJECTIVES

We sought to investigate the role of RhoA/ROCK signaling in lineage commitment of MSCs during allergen-induced airway remodeling and delineate the underlying mechanisms.

METHODS

Active RhoA expression in lung tissues of asthmatic patients and its role in cockroach allergen-induced airway inflammation and remodeling were investigated. RhoA/ROCK signaling-mediated MSC lineage commitment was assessed in an asthma mouse model by using MSC lineage tracing mice (nestin-Cre; ROSA26-EYFP). The role of RhoA/ROCK in MSC lineage commitment was also examined by using MSCs expressing constitutively active RhoA (RhoA-L63) or dominant negative RhoA (RhoA-N19). Downstream RhoA-regulated genes were identified by using the Stem Cell Signaling Array.

RESULTS

Lung tissues from asthmatic mice showed increased expression of active RhoA when compared with those from control mice. Inhibition of RhoA/ROCK signaling with fasudil, a RhoA/ROCK inhibitor, reversed established cockroach allergen-induced airway inflammation and remodeling, as assessed based on greater collagen deposition/fibrosis. Furthermore, fasudil inhibited MSC differentiation into fibroblasts/myofibroblasts but promoted MSC differentiation into epithelial cells in asthmatic nestin-Cre; ROSA26-EYFP mice. Consistently, expression of RhoA-L63 facilitated differentiation of MSCs into fibroblasts/myofibroblasts, whereas expression of RhoA-19 switched the differentiation toward epithelial cells. The gene array identified the Wnt signaling effector lymphoid enhancer-binding factor 1 (Lef1) as the most upregulated gene in RhoA-L63-transfected MSCs. Knockdown of Lef1 induced MSC differentiation away from fibroblasts/myofibroblasts but toward epithelial cells.

CONCLUSIONS

These findings uncover a previously unrecognized role of RhoA/ROCK signaling in MSC-involved airway repair/remodeling in the setting of asthma.

Identification of compounds acting as negative allosteric modulators of the LPA1 receptor

The Lysophosphatidic Acid 1 Receptor (LPA₁ receptor) has been linked to the initiation and progression of a variety of poorly treated fibrotic conditions. Several compounds that have been described as LPA₁ receptor antagonists have progressed into clinical trials: 1-(4-{4-[3-methyl-4-({[(1R)-1-phenylethoxy]carbonyl}amino)-1,2-oxazol-5-yl]phenyl}phenyl)cyclopropane-1-carboxylic acid (BMS-986202) and 2-{4-methoxy-3-[2-(3-methylphenyl)ethoxy]benzamido}-2,3-dihydro-1H-indene-2-carboxylic acid (SAR-100842). We considered that as LPA₁ receptor function is involved in many normal physiological processes, inhibition of specific signalling pathways associated with fibrosis may be therapeutically advantageous. We compared the binding and functional effects of a novel compound; 4-({(Cyclopropylmethyl)[4-(2-fluorophenoxy)benzoyl]amino}methyl}benzoic acid (TAK-615) with BMS-986202 and SAR-100842. Back-scattering interferometry (BSI) was used to show that the apparent affinity of TAK-615 was enhanced in the presence of LPA. The binding signal for BMS-986202 was not detected in the presence of LPA suggesting competition but interestingly the apparent affinity of SAR-100842 was also enhanced in the presence of LPA. Only BMS-986202 was able to fully inhibit the response to LPA in calcium mobilisation, β-arrestin, cAMP, GTPγS and RhoA functional assays. TAK-615 and SAR-100842 showed different inhibitory profiles in the same functional assays. Further binding studies indicated that TAK-615 is not competitive with either SAR-100842 or BMS-986202, suggesting a different site of binding. The results generated with this set of experiments demonstrate that TAK-615 acts as a negative allosteric modulator (NAM) of the LPA₁ receptor. Surprisingly we find that SAR-100842 also behaves like a NAM. BMS-986202 on the other hand behaves like an orthosteric antagonist.

Type I collagen induces mesenchymal cell differentiation into myofibroblasts through YAP-induced TGF-β1 activation

In organ fibrosis, mechanical stress and transforming growth factor beta-1 (TGF-β1) promote differentiation into myofibroblast from mesenchymal cells, leading to extracellular matrix (ECM) remodeling or active synthesis, deposition or degradation of ECM components. A major component of ECM, type I collagen (col I) triple helical molecules assemble into fibrils or are denatured to gelatin without triple-helicity in remodeling. However, whether changes of ECM components in remodeling have influence on mesenchymal cell differentiation remains elusive. This study adopted three states of collagen I existing in ECM remodeling: molecular collagen, fibrillar collagen and gelatin to see what are characteristics in the effects on two cell lines of mesenchymal origin, murine 3T3-L1 embryonic fibroblast and murine C2C12 myoblasts. The results showed that all three forms of collagen I were capable of inducing these two cells to differentiate into myofibroblasts characterized by increased expression of alpha-smooth muscle actin (α-SMA) mRNA. The expression of α-SMA is positively regulated by TGF-β1. Nuclear translocation of Yes-associated protein (YAP) is involved in this process. Focal adhesion kinase (FAK) is activated in the cells cultured on molecular collagen-coated plates, contributing to YAP activation. On the other hand, in the cells cultured on fibrillar collagen gel or gelatin-coated plates, oxidative stress but not FAK induce YAP activation. In conclusion, the three physicochemically distinct forms of col I induce the differentiation of mesenchymal cells into myofibroblasts through different pathways.

Targeting the RhoA-ROCK pathway to regulate T-cell homeostasis in hypoxia-induced pulmonary arterial hypertension

BACKGROUND

Hypoxic pulmonary arterial hypertension (PAH) is a crippling disease with limited therapeutic methods. The imbalance of T helper 17 cell (Th17)/regulatory T cell (Treg) plays an important role in the development of Hypoxic PAH. However, whether targeting the ras homolog family member A-Rho kinase (RhoA-ROCK) pathway (activation and inhibition) by lysophosphatidic acid (LPA) and fasudil (FSD) regulate T-cell homeostasis in Hypoxic PAH remain unknown.

OBJECTIVE

To examine the effects of LPA and FSD on hypoxic pulmonary vascular remodeling and homeostasis of Th17/Treg cells in Hypoxic PAH.

METHODS

Rats were exposed to hypoxia (10 ± 0.5% O₂) to induce Hypoxic PAH. The experiments consists of two parts. Forty rats were randomly divided into four groups (n = 10): normoxia group, normoxia + LPA group, hypoxia group and hypoxia + LPA group. Thirty rats were randomly divided into another three groups (n = 10): normoxia group, hypoxia group, and hypoxia + FSD group. Rats in normoxia + LPA group and hypoxia + LPA group were intraperitoneally injected 40 μg/kg LPA daily. Rats in hypoxia + FSD group were intraperitoneally injected 30 mg/kg fasudil daily. The effects of LPA and FSD on the development of hypoxic PAH and right ventricle (RV) hypertrophy, on pulmonary vascular remodeling, and on changes of Th17/Treg cells and levels of interleukin-17 (IL-17) and IL-10 were examined.

RESULTS

PAH and RV hypertrophy occurred in rats exposed to hypoxia. LPA exacerbated hypoxic pulmonary vascular remodeling and FSD inhibited it. LPA increased Th17/Treg imbalance in peripheral blood and spleen. However, after treatment with FSD, hypoxic PAH rats showed an obvious reduction of Th17 cells as well as an increase of Treg cells. LPA increased the expression of phosphorylated-signal transducer and activator of transcription 3 (p-STAT3) and reduced the p-STAT5 in peripheral blood and spleen in hypoxic PAH rats. The expression of p-STAT3 and p-STAT5 in hypoxic PAH rats treated with FSD showed opposite changes. LPA increased the expression of IL-17 and reduced the IL-10 in small intrapulmonary arteries and serum in hypoxic PAH. However, the expression of IL-17 and IL-10 in hypoxic PAH rats treated with FSD showed opposite changes.

CONCLUSIONS

Activation and inhibition of RhoA-ROCK pathway by LPA and FSD modulated the homeostasis of Th17/Treg cells via regulating STAT3/STAT5 phosphorylation in hypoxic PAH. Thus, Apart from influence of pulmonary vascular remodeling, regulation of Th17/Treg homeostasis by RhoA-ROCK pathway play a key role in hypoxic PAH.

Mammalian MSC from selected species: Features and applications

Mesenchymal stromal/stem cells (MSC) are promising candidates for cellular therapy of different diseases in humans and in animals. Following the guidelines of the International Society for Cell Therapy, human MSC may be identified by expression of a specific panel of cell surface markers (CD105+, CD73+, CD90+, CD34-, CD14-, or CD11b-, CD79- or CD19-, HLA-DR-). In addition, multiple differentiation potential into at least the osteogenic, adipogenic, and chondrogenic lineage is a main criterion for MSC definition. Human MSC and MSC of a variety of mammals isolated from different tissues meet these criteria. In addition to the abovementioned, they express many more cell surface markers. Yet, these are not uniquely expressed by MSC. The gross phenotypic appearance like marker expression and differentiation potential is similar albeit not identical for MSC from different tissues and species. Similarly, MSC may feature different biological characteristics depending on the tissue source and the isolation and culture procedures. Their versatile biological qualities comprising immunomodulatory, anti-inflammatory, and proregenerative capacities rely largely on the migratory and secretory capabilities of MSC. They are attracted to sites of tissue lesion and secrete factors to promote self-repair of the injured tissue. This is a big perspective for clinical MSC applications in both veterinary and human medicine. Phase I/II clinical trials have been initiated to assess safety and feasibility of MSC therapies in acute and chronic disease settings. Yet, since the mode of MSC action in a specific disease environment is still unknown at large, it is mandatory to unravel the response of MSC from a given source onto a specific disease environment in suitable animal models prior to clinical applications. © 2017 International Society for Advancement of Cytometry.

Role of TAZ in Lysophosphatidic Acid-Induced Migration and Proliferation of Human Adipose-Derived Mesenchymal Stem Cells

Transcriptional co-activator with a PDZ-binding motif (TAZ) is an important factor in lysophosphatidic acid (LPA)-induced promotion of migration and proliferation of human mesenchymal stem cells (MSCs). The expression of TAZ significantly increased at 6 h after LPA treatment, and TAZ knockdown inhibited the LPA-induced migration and proliferation of MSCs. In addition, embryonic fibroblasts from TAZ knockout mice exhibited the reduction in LPA-induced migration and proliferation. The LPA1 receptor inhibitor Ki16425 blocked LPA responses in MSCs. Although TAZ knockdown or knockout did not reduce LPA-induced phosphorylation of ERK and AKT, the MEK inhibitor U0126 or the ROCK inhibitor Y27632 blocked LPA-induced TAZ expression along with the reduction in the proliferation and migration of MSCs. Our data suggest that TAZ is an important mediator of LPA signaling in MSCs in the downstream of MEK and ROCK signaling.

Mesenchymal stem cells in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a major cause of respiratory failure in critically ill patients and common outcome of various lung interstitial diseases. Its mortality remains high, and no effective pharmacotherapy, in addition to artificial ventilation and transplantation, exists. As such, the administration of mesenchymal stem or stromal cells (MSCs) is currently investigated as a new therapeutic method for pulmonary fibrosis. Clinical trials on MSC-based therapy as a potential treatment for lung injury and fibrosis are also performed. MSCs can migrate to injured sites and secrete multiple paracrine factors and then regulate endothelial and epithelial permeability, decrease inflammation, enhance tissue repair, and inhibit bacterial growth. In this review, recent studies on stem cells, particularly MSCs, involved in alleviating lung inflammation and fibrosis and their potential MSC-induced mechanisms, including migration and differentiation, soluble factor and extracellular vesicle secretion, and endogenous regulatory functions, were summarized.

Regulatory mechanisms of TGF-β1-induced fibrogenesis of human alveolar epithelial cells

Pulmonary fibrosis is characterized by an extensive activation of fibrogenic cells and deposition of extracellular matrix (ECM). Transforming growth factor (TGF)‐β1 plays a pivotal role in the pathogenesis of pulmonary fibrosis, probably through the epithelial‐ to‐mesenchymal transition (EMT) and ECM production. The present study investigates potential mechanism by which TGF‐β1 induces EMT and ECM production in the fibrogenesis of human lung epithelial cells during pulmonary fibrosis. The expression of EMT phenotype and other proteins relevant to fibrogenesis were measured and the cell bio‐behaviours were assessed using Cell‐IQ Alive Image Monitoring System. We found that TGF‐β1‐induced EMT was accompanied with increased collagen I deposition, which may be involved in the regulation of connective tissue growth factor (CTGF) and phosphoinositide 3‐kinase (PI3K) signalling pathway. Treatment with PI3K inhibitors significantly attenuated the TGF‐β1‐ induced EMT, CTGF expression and collagen I synthesis in lung epithelial cells. The interference of CTGF expression impaired the basal and TGF‐β1‐stimulated collagen I deposition, but did not affect the process of EMT. Our data indicate that the signal pathway of TGF‐β1/PI3K/CTGF plays an important role in the fibrogenesis of human lung epithelial cells, which may be a novel therapeutic approach to prevent and treat pulmonary fibrosis.

Lysophosphatidic Acid Receptor Is a Functional Marker of Adult Hippocampal Precursor Cells

Here, we show that the lysophosphatidic acid receptor 1 (LPA₁) is expressed by a defined population of type 1 stem cells and type 2a precursor cells in the adult mouse dentate gyrus. LPA₁, in contrast to Nestin, also marks the quiescent stem cell population. Combining LPA₁-GFP with EGFR and prominin-1 expression, we have enabled the prospective separation of both proliferative and non-proliferative precursor cell populations. Transcriptional profiling of the isolated proliferative precursor cells suggested immune mechanisms and cytokine signaling as molecular regulators of adult hippocampal precursor cell proliferation. In addition to LPA₁ being a marker of this important stem cell population, we also show that the corresponding ligand LPA is directly involved in the regulation of adult hippocampal precursor cell proliferation and neurogenesis, an effect that can be attributed to LPA signaling via the AKT and MAPK pathways.

•

LPA₁-GFP⁺ allows the prospective isolation of hippocampal precursor cells

•

Method for separation of proliferative from non-proliferative precursor cells

•

Proliferative precursor cells have a unique immune-cell-like transcriptional profile

•

LPA increases in vivo hippocampal neurogenesis via the LPA₁-AKT and MAPK pathways

Epigenetic regulation of diacylglycerol kinase alpha promotes radiation-induced fibrosis

Radiotherapy is a fundamental part of cancer treatment but its use is limited by the onset of late adverse effects in the normal tissue, especially radiation-induced fibrosis. Since the molecular causes for fibrosis are largely unknown, we analyse if epigenetic regulation might explain inter-individual differences in fibrosis risk. DNA methylation profiling of dermal fibroblasts obtained from breast cancer patients prior to irradiation identifies differences associated with fibrosis. One region is characterized as a differentially methylated enhancer of diacylglycerol kinase alpha (DGKA). Decreased DNA methylation at this enhancer enables recruitment of the profibrotic transcription factor early growth response 1 (EGR1) and facilitates radiation-induced DGKA transcription in cells from patients later developing fibrosis. Conversely, inhibition of DGKA has pronounced effects on diacylglycerol-mediated lipid homeostasis and reduces profibrotic fibroblast activation. Collectively, DGKA is an epigenetically deregulated kinase involved in radiation response and may serve as a marker and therapeutic target for personalized radiotherapy.

Radiotherapy can induce fibrosis in cancer patients, limiting its use in clinical settings. Here, the authors identify a differentially methylated enhancer of the lipid kinase DGKA in fibroblasts from breast cancer patients developing fibrosis after radiotherapy and they show that DGKA inhibition affects lipid homeostasis and reduces pro-fibrotic fibroblast activation.

Integrated long non-coding RNA analyses identify novel regulators of epithelial-mesenchymal transition in the mouse model of pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic fatal lung disease characterized by aberrant accumulation of fibroblast population and deposition of extra cellular matrix. Increasing evidence support that epithelial‐mesenchymal transition (EMT) of alveolar epithelial cells is a critical process in the pathogenesis of IPF. Although delivery of bleomycin to induce acute lung injury is the most well‐studied animal model of pulmonary fibrosis, there is considerable interest to pursue other models to understand the common and/or specific pathological mechanisms. In this study, we established a mouse model of pulmonary injury and progressive interstitial fibrosis via intraperitoneal injection of paraquat, a widely used herbicide known to cause pulmonary fibrosis in human. Using transcriptome sequencing and microarray analysis, we profiled expression of long non‐coding RNAs (lncRNAs) and identified 513 up‐regulated and 204 down‐regulated lncRNAs in paraquat‐induced fibrotic lung tissues. Gene ontology analysis revealed that the differentially expressed lncRNAs are implicated in cell differentiation, epithelium morphogenesis and wound healing, pathways closely associated with EMT. Furthermore, we identified the evolutionally conserved target genes of two up‐regulated lncRNAs, uc.77 and 2700086A05Rik, as Zeb2 and Hoxa3, respectively, both of which are important modulators of EMT. Consistently, overexpression of uc.77 or 2700086A05Rik in human lung epithelial cells induced EMT as demonstrated by changes in gene and protein expression of various EMT markers and cell morphology. Collectively, our results uncovered a crucial role of lncRNA in the regulation of EMT during lung fibrosis and provide potential avenues for the discovery of novel molecular markers and therapeutic targets for IPF.

Autotaxin-LPA axis regulates hMSC migration by adherent junction disruption and cytoskeletal rearrangement via LPAR1/3-dependent PKC/GSK3β/β-catenin and PKC/Rho GTPase pathways

Bioactive molecules and stem cell-based regenerative engineering is emerging a promising approach for regenerating tissues. Autotaxin (ATX) is a key enzyme that regulates lysophosphatidic acid (LPA) levels in biological fluids, which exerts a wide range of cellular functions. However, the biological role of ATX in human umbilical cord blood-derived mesenchymal stem cells (hMSCs) migration remains to be fully elucidated. In this study, we observed that hMSCs, which were stimulated with LPA, accelerated wound healing, and LPA increased the migration of hMSCs into a wound site in a mouse skin wound healing model. In an experiment to investigate the effect of LPA on hMSC migration, ATX and LPA increased hMSC migration in a dose-dependent manner, and LPA receptor 1/3 siRNA transfections inhibited the ATX-induced cell migration. Furthermore, LPA increased Ca(2+) influx and PKC phosphorylation, which were blocked by Gαi and Gαq knockdown as well as by Ptx pretreatment. LPA increased GSK3β phosphorylation and β-catenin activation. LPA induced the cytosol to nuclear translocation of β-catenin, which was inhibited by PKC inhibitors. LPA stimulated the binding of β-catenin on the E-box located in the promoter of the CDH-1 gene and decreased CDH-1 promoter activity. In addition, the ATX and LPA-induced increase in hMSC migration was blocked by β-catenin siRNA transfection. LPA-induced PKC phosphorylation is also involved in Rac1 and CDC42 activation, and Rac1 and CDC42 knockdown abolished LPA-induced F-actin reorganization. In conclusion, ATX/LPA stimulates the migration of hMSCs through LPAR1/3-dependent E-cadherin reduction and cytoskeletal rearrangement via PKC/GSK3β/β-catenin and PKC/Rho GTPase pathways.

Mesenchymal Stromal Cells in Animal Bleomycin Pulmonary Fibrosis Models: A Systematic Review

Idiopathic pulmonary fibrosis is an inexorably progressive lung disease with few available treatments. New therapeutic options are needed. Stem cells have generated much enthusiasm for the treatment of several conditions, including lung diseases. Human trials of mesenchymal stromal cell (MSC) therapy for pulmonary fibrosis are under way. To shed light on the potential usefulness of MSCs for human disease, we aimed to systematically review the preclinical literature to determine if MSCs are beneficial in animal bleomycin pulmonary fibrosis models. The MEDLINE and Embase databases were searched for original studies of stem cell therapy in animal bleomycin models of pulmonary fibrosis. Studies using embryonic stem cells or induced pluripotent stem cells were excluded. Seventeen studies were selected, all of which used MSCs in rodents. MSC therapy led to an improvement in bleomycin-induced lung collagen deposition in animal lungs and in the pulmonary fibrosis Ashcroft score in most studies. MSC therapy improved histopathology in almost all studies in which it was evaluated qualitatively. Furthermore, MSC therapy was found to improve 14-day survival in animals with bleomycin-induced pulmonary fibrosis. Bronchoalveolar lavage total and neutrophil counts, as well as transforming growth factor-β levels, were also reduced by MSCs. MSCs are beneficial in rodent bleomycin pulmonary fibrosis models. Since most studies examined the initial inflammatory phase rather than the chronic fibrotic phase, preclinical data offer better support for human trials of MSCs in acute exacerbations of pulmonary fibrosis rather than the chronic phase of the disease.

SIGNIFICANCE

There has been increased interest in mesenchymal stromal cell therapy for lung diseases. A few small clinical trials are under way in idiopathic pulmonary fibrosis. Preclinical evidence was assessed in a systematic review, as is often done for clinical studies. The existing studies offer better support for efficacy in the initial inflammatory phase rather than the fibrotic phase that human trials are targeting.

XL413, a cell division cycle 7 kinase inhibitor enhanced the anti-fibrotic effect of pirfenidone on TGF-β1-stimulated C3H10T1/2 cells via Smad2/4

Pirfenidone is an orally bioavailable synthetic compound with therapeutic potential for idiopathic pulmonary fibrosis. It is thought to act through antioxidant and anti-fibrotic pathways. Pirfenidone inhibits proliferation and/or myofibroblast differentiation of a wide range of cell types, however, little studies have analyzed the effect of pirfenidone on the mesenchymal stem cells, which play an important role on the origin of myofibroblasts. We recently found that pirfenidone had anti-proliferative activity via G1 phase arrest and cell division cycle 7 (Cdc7) kinase expression decrease in transforming growth factor-β1 (TGF-β1)-stimulated murine mesenchymal stem C3H10T1/2 cells. Pirfenidone also had inhibiting effect on the migration and α-SMA expression. Moreover, in this study we showed for the first time that Cdc7 inhibitor XL413 enhanced the anti-fibrotic activity of pirfenidone via depressed the expression of Smad2/4 proteins, and also prevented the nuclear accumulation and translocation of Smad2 protein. In conclusion, we demonstrated that pirfenidone inhibited proliferation, migration and differentiation of TGF-β1-stimulated C3H10T1/2 cells, which could be enhanced by Cdc7 inhibitor XL413, via Smad2/4. Combination with pirfenidone and XL413 might provide a potential candidate for the treatment of TGF-β1 associated fibrosis. It needs in vivo studies to further validate its therapeutic function and safety in the future.

The Role of Lysophosphatidic Acid on Airway Epithelial Cell Denudation in a Murine Heterotopic Tracheal Transplant Model

Supplemental digital content is available in the text.

Background

Chronic rejection is the major leading cause of morbidity and mortality after lung transplantation. Obliterative bronchiolitis (OB), a fibroproliferative disorder of the small airways, is the main manifestation of chronic lung allograft rejection. However, there is currently no treatment for the disease. We hypothesized that lysophosphatidic acid (LPA) participates in the progression of OB. The aim of this study was to reveal the involvement of LPA on the lesion of OB.

Methods

Ki16198, an antagonist specifically for LPA₁ and LPA₃, was daily administered into the heterotopic tracheal transplant model mice at the day of transplantation. At days 10 and 28, the allografts were isolated and evaluated histologically. The messenger RNA levels of LPAR in microdissected mouse airway regions were assessed to reveal localization of lysophosphatidic acid receptors. The human airway epithelial cell was used to evaluate the mechanism of LPA-induced suppression of cell adhesion to the extracellular matrix (ECM).

Results

The administration of Ki16198 attenuated airway epithelial cell loss in the allograft at day 10. Messenger RNAs of LPA₁ and LPA₃ were detected in the airway epithelial cells of the mice. Lysophosphatidic acid inhibited the attachment of human airway epithelial cells to the ECM and induced cell detachment from the ECM, which was mediated by LPA₁ and Rho-kinase pathway. However, Ki16198 did not prevent obliteration of allograft at day 28.

Conclusions

The LPA signaling is involved in the status of epithelial cells by distinct contribution in 2 different phases of the OB lesion. This finding suggests a role of LPA in the pathogenesis of OB.

Autotaxin-LPA receptor axis in the pathogenesis of lung diseases

Lysophosphatidic acid (LPA) is a small lipid which mediates a variety of cellular functions via the activation of LPA receptors. LPA is generated from lysophosphatidylcholine by the extracellular enzyme, autotaxin (ATX). Elevated ATX expression, LPA production and their signaling pathways have been reported in multiple pathological conditions of lung tissue, including inflammation, fibrosis and cancer. Emerging evidence has highlighted the importance of ATX and LPA receptors in the pathogenesis of lung diseases. Here, we briefly review the current knowledge of different roles of the ATX-LPA receptor axis in lung diseases focusing on inflammation, fibrosis and cancer.