Matrix regulation of idiopathic pulmonary fibrosis: the role of enzymes

Cell-type specific effects of mineralocorticoid receptor gene expression suggest intercellular communication regulating fibrosis in skeletal muscle disease

Introduction: Duchenne muscular dystrophy (DMD) is a fatal striated muscle degenerative disease. DMD is caused by loss of dystrophin protein, which results in sarcolemmal instability and cycles of myofiber degeneration and regeneration. Pathology is exacerbated by overactivation of infiltrating immune cells and fibroblasts, which leads to chronic inflammation and fibrosis. Mineralocorticoid receptors (MR), a type of nuclear steroid hormone receptors, are potential therapeutic targets for DMD. MR antagonists show clinical efficacy on DMD cardiomyopathy and preclinical efficacy on skeletal muscle in DMD models. Methods: We have previously generated myofiber and myeloid MR knockout mouse models to dissect cell-specific functions of MR within dystrophic muscles. Here, we compared skeletal muscle gene expression from both knockouts to further define cell-type specific signaling downstream from MR. Results: Myeloid MR knockout increased proinflammatory and profibrotic signaling, including numerous myofibroblast signature genes. Tenascin C was the most highly upregulated fibrotic gene in myeloid MR-knockout skeletal muscle and is a component of fibrosis in dystrophic skeletal muscle. Surprisingly, lysyl oxidase (Lox), canonically a collagen crosslinker, was increased in both MR knockouts, but did not localize to fibrotic regions of skeletal muscle. Lox localized within myofibers, including only a region of quadriceps muscles. Lysyl oxidase like 1 (Loxl1), another Lox family member, was increased only in myeloid MR knockout muscle and localized specifically to fibrotic regions. Discussion: This study suggests that MR signaling in the dystrophic muscle microenvironment involves communication between contributing cell types and modulates inflammatory and fibrotic pathways in muscle disease.

Emerging delivery approaches for targeted pulmonary fibrosis treatment

Pulmonary fibrosis (PF) is a progressive, and life-threatening interstitial lung disease which causes scarring in the lung parenchyma and thereby affects architecture and functioning of lung. It is an irreversible damage to lung functioning which is related to epithelial cell injury, immense accumulation of immune cells and inflammatory cytokines, and irregular recruitment of extracellular matrix. The inflammatory cytokines trigger the differentiation of fibroblasts into activated fibroblasts, also known as myofibroblasts, which further increase the production and deposition of collagen at the injury sites in the lung. Despite the significant morbidity and mortality associated with PF, there is no available treatment that efficiently and effectively treats the disease by reversing their underlying pathologies. In recent years, many therapeutic regimens, for instance, rho kinase inhibitors, Smad signaling pathway inhibitors, p38, BCL-xL/ BCL-2 and JNK pathway inhibitors, have been found to be potent and effective in treating PF, in preclinical stages. However, due to non-selectivity and non-specificity, the therapeutic molecules also result in toxicity mediated severe side effects. Hence, this review demonstrates recent advances on PF pathology, mechanism and targets related to PF, development of various drug delivery systems based on small molecules, RNAs, oligonucleotides, peptides, antibodies, exosomes, and stem cells for the treatment of PF and the progress of various therapeutic treatments in clinical trials to advance PF treatment.

Silicon dioxide-induced endoplasmic reticulum stress of alveolar macrophages and its role on the formation of silicosis fibrosis: a review article

Silicosis is a chronic lung inflammatory disease induced by long-term inhalation of high concentrations of silicon dioxide (SiO2), characterized by pulmonary fibrosis. Inhalation of silica invades alveolar macrophages (AMs) and changes the micro-environment of the cell, resulting in abnormal morphology and dysfunction of the endoplasmic reticulum (ER). Once beyond the range of cell regulation, the endoplasmic reticulum stress (ERS) will occur, which will lead to cell damage, necrosis, and apoptosis, eventually causing silicosis fibrosis through various mechanisms. This is a complex and delicate process accompanied by various macrophage-derived cytokines. Unfortunately, the details have not been systematically summarized yet. In this review, we systematically introduce the basic two processes: the process of inducing ERS by inhaling SiO2 and the process of inducing pulmonary fibrosis by ERS. Moreover, the underlying mechanism of the above two sequential events is also be discussed. We conclude that the ERS of alveolar macrophages caused by silica dust are involved deeply in the pathogenesis of silicosis. Therefore, changing the states of SiO2-induced ERS of macrophage may be an attractive therapeutic target for silicosis fibrosis.

The Regenerative Power of Stem Cells: Treating Bleomycin-Induced Lung Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive lung disease with no known cure, characterized by the formation of scar tissue in the lungs, leading to respiratory failure. Although the exact cause of IPF remains unclear, the condition is thought to result from a combination of genetic and environmental factors. One of the most widely used animal models to study IPF is the bleomycin-induced lung injury model in mice. In this model, the administration of the chemotherapeutic agent bleomycin causes pulmonary inflammation and fibrosis, which closely mimics the pathological features of human IPF. Numerous recent investigations have explored the functions of various categories of stem cells in the healing process of lung injury induced by bleomycin in mice, documenting the beneficial effects and challenges of this approach. Differentiation of stem cells into various cell types and their ability to modulate tissue microenvironment is an emerging aspect of the regenerative therapies. This review article aims to provide a comprehensive overview of the role of stem cells in repairing bleomycin-induced lung injury. It delves into the mechanisms through which various types of stem cells, including mesenchymal stem cells, embryonic stem cells, induced pluripotent stem cells, and lung resident stem cells, exert their therapeutic effects in this specific model. We have also discussed the unique set of intermediate markers and signaling factors that can influence the proliferation and differentiation of alveolar epithelial cells both during lung repair and homeostasis. Finally, we highlight the challenges and opportunities associated with translating stem cell therapy to the clinic for IPF patients. The novelty and implications of this review extend beyond the understanding of the potential of stem cells in treating IPF to the broader field of regenerative medicine. We believe that the review paves the way for further advancements in stem cell therapies, offering hope for patients suffering from this debilitating and currently incurable disease.

Asarinin attenuates bleomycin-induced pulmonary fibrosis by activating PPARγ

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive interstitial lung disease that lacks effective treatment modalities. Once patients are diagnosed with IPF, their median survival is approximately 3-5 years. PPARγ is an important target for the prevention and treatment of pulmonary fibrosis. Asarinin is a lignan compound that can be extracted from food plant Asarum heterotropoides. In this study, we investigated the therapeutic effects of asarinin in a pulmonary fibrosis model constructed using bleomycin in mice and explored the underlying mechanisms. Intraperitoneal administration of asarinin to mice with pulmonary fibrosis showed that asarinin effectively attenuated pulmonary fibrosis, and this effect was significantly inhibited by the PPARγ inhibitor GW9662. Asarinin inhibited TGF-β1-induced fibroblast-to-myofibroblast transition in vitro, while GW9662 and PPARγ gene silencing significantly inhibited this effect. In addition, asarinin inhibited not only the canonical Smad pathway of TGF-β but also the non-canonical AKT and MAPK pathways by activating PPARγ. Our study demonstrates that asarinin can be used as a therapeutic agent for pulmonary fibrosis, and that PPARγ is its key target.

Multifaced roles of desmoplastic reaction and fibrosis in pancreatic cancer progression: Current understanding and future directions

Desmoplastic reaction is a fibrosis reaction that is characterized by a large amount of dense extracellular matrix (ECM) and dense fibrous stroma. Fibrotic stroma around the tumor has several different components, including myofibroblasts, collagen, and other ECM molecules. This stromal reaction is a natural response to the tissue injury process, and fibrosis formation is a key factor in pancreatic cancer development. The fibrotic stroma of pancreatic cancer is associated with tumor progression, metastasis, and poor prognosis. Reportedly, multiple processes are involved in fibrosis, which is largely associated with the upregulation of various cytokines, chemokines, matrix metalloproteinases, and other growth factors that promote tumor growth and metastasis. Fibrosis is also associated with immunosuppressive cell recruitment, such as regulatory T cells (Tregs) with suppressing function to antitumor immunity. Further, dense fibrosis restricts the flow of nutrients and oxygen to the tumor cells, which can contribute to drug resistance. Furthermore, the dense collagen matrix can act as a physical barrier to block the entry of drugs into the tumor, thereby further contributing to drug resistance. Thus, understanding the mechanism of desmoplastic reaction and fibrosis in pancreatic cancer will open an avenue to innovative medicine and improve the prognosis of patients suffering from this disease.

Inhibitory effects of Schisandrin C on collagen behavior in pulmonary fibrosis

Pulmonary fibrosis (PF) is a serious progressive fibrotic disease that is characterized by excessive accumulation of extracellular matrix (ECM), thus resulting in stiff lung tissues. Lysyl oxidase (LOX) is an enzyme involved in fibrosis by catalyzing collagen cross-linking. Studies found that the ingredients in schisandra ameliorated bleomycin (BLM)-induced PF, but it is unknown whether the anti-PF of schisandra is related to LOX. In this study, we established models of PF including a mouse model stimulated by BLM and a HFL1 cell model induced by transforming growth factor (TGF)-β1 to evaluate the inhibition effects of Schisandrin C (Sch C) on PF. We observed that Sch C treatment decreased pulmonary indexes compared to control group. Treatment of Sch C showed a significant reduction in the accumulation of ECM as evidenced by decreased expressions of α-SMA, FN, MMP2, MMP9, TIMP1 and collagen proteins such as Col 1A1, and Col 3A1. In addition, the expression of LOX in the lung tissue of mice after Sch C treatment was effectively decreased compared with the MOD group. The inhibition effects in vitro were consistent with those in vivo. Mechanistic studies revealed that Sch C significantly inhibited TGF-β1/Smad2/3 and TNF-α/JNK signaling pathways. In conclusion, our data demonstrated that Sch C significantly ameliorated PF in vivo and vitro, which may play an important role by reducing ECM deposition and inhibiting the production of LOX.

Targeted imaging of very late antigen-4 for noninvasive assessment of lung inflammation-fibrosis axis

BACKGROUND

The lack of noninvasive methods for assessment of dysregulated inflammation as a major driver of fibrosis (i.e., inflammation-fibrosis axis) has been a major challenge to precision management of fibrotic lung diseases. Here, we determined the potential of very late antigen-4 (VLA-4)-targeted positron emission tomography (PET) to detect inflammation in a mouse model of bleomycin-induced fibrotic lung injury.

METHOD

Single time-point and longitudinal VLA-4-targeted PET was performed using a high-affinity peptidomimetic radiotracer, 64Cu-LLP2A, at weeks 1, 2, and 4 after bleomycin-induced (2.5 units/kg) lung injury in C57BL/6J mice. The severity of fibrosis was determined by measuring the hydroxyproline content of the lungs and expression of markers of extracellular matrix remodeling. Flow cytometry and histology was performed to determine VLA-4 expression across different leukocyte subsets and their spatial distribution.

RESULTS

Lung uptake of 64Cu-LLP2A was significantly elevated throughout different stages of the progression of bleomycin-induced injury. High lung uptake of 64Cu-LLP2A at week-1 post-bleomycin was a predictor of poor survival over the 4-week follow up, supporting the prognostic potential of 64Cu-LLP2A PET during the early stage of the disease. Additionally, the progressive increase in 64Cu-LLP2A uptake from week-1 to week-4 post-bleomycin correlated with the ultimate extent of lung fibrosis and ECM remodeling. Flow cytometry revealed that LLP2A binding was restricted to leukocytes. A combination of increased expression of VLA-4 by alveolar macrophages and accumulation of VLA-4-expressing interstitial and monocyte-derived macrophages as well as dendritic cells was noted in bleomycin-injured, compared to control, lungs. Histology confirmed the increased expression of VLA-4 in bleomycin-injured lungs, particularly in inflamed and fibrotic regions.

CONCLUSIONS

VLA-4-targeted PET allows for assessment of the inflammation-fibrosis axis and prediction of disease progression in a murine model. The potential of 64Cu-LLP2A PET for assessment of the inflammation-fibrosis axis in human fibrotic lung diseases needs to be further investigated.

Extracellular matrix stiffness-The central cue for skin fibrosis

Skin fibrosis is a physiopathological process featuring the excessive deposition of extracellular matrix (ECM), which is the main architecture that provides structural support and constitutes the microenvironment for various cellular behaviors. Recently, increasing interest has been drawn to the relationship between the mechanical properties of the ECM and the initiation and modulation of skin fibrosis, with the engagement of a complex network of signaling pathways, the activation of mechanosensitive proteins, and changes in immunoregulation and metabolism. Simultaneous with the progression of skin fibrosis, the stiffness of ECM increases, which in turn perturbs mechanical and humoral homeostasis to drive cell fate toward an outcome that maintains and enhances the fibrosis process, thus forming a pro-fibrotic "positive feedback loop". In this review, we highlighted the central role of the ECM and its dynamic changes at both the molecular and cellular levels in skin fibrosis. We paid special attention to signaling pathways regulated by mechanical cues in ECM remodeling. We also systematically summarized antifibrotic interventions targeting the ECM, hopefully enlightening new strategies for fibrotic diseases.

Cell-Specific Response of NSIP- and IPF-Derived Fibroblasts to the Modification of the Elasticity, Biological Properties, and 3D Architecture of the Substrate

The fibrotic fibroblasts derived from idiopathic pulmonary fibrosis (IPF) and nonspecific interstitial pneumonia (NSIP) are surrounded by specific environments, characterized by increased stiffness, aberrant extracellular matrix (ECM) composition, and altered lung architecture. The presented research was aimed at investigating the effect of biological, physical, and topographical modification of the substrate on the properties of IPF- and NSIP-derived fibroblasts, and searching for the parameters enabling their identification. Soft and stiff polydimethylsiloxane (PDMS) was chosen for the basic substrates, the properties of which were subsequently tuned. To obtain the biological modification of the substrates, they were covered with ECM proteins, laminin, fibronectin, and collagen. The substrates that mimicked the 3D structure of the lungs were prepared using two approaches, resulting in porous structures that resemble natural lung architecture and honeycomb patterns, typical of IPF tissue. The growth of cells on soft and stiff PDMS covered with proteins, traced using fluorescence microscopy, confirmed an altered behavior of healthy and IPF- and NSIP-derived fibroblasts in response to the modified substrate properties, enabling their identification. In turn, differences in the mechanical properties of healthy and fibrotic fibroblasts, determined using atomic force microscopy working in force spectroscopy mode, as well as their growth on 3D-patterned substrates were not sufficient to discriminate between cell lines.

CD147 contributes to SARS-CoV-2-induced pulmonary fibrosis

COVID-19 patients can develop clinical and histopathological features associated with fibrosis, but the pathogenesis of fibrosis remains poorly understood. CD147 has been identified as a universal receptor for SARS-CoV-2 and its variants, which could initiate COVID-19-related cytokine storm. Here, we systemically analyzed lung pathogenesis in SARS-CoV-2- and its delta variant-infected humanized CD147 transgenic mice. Histopathology and Transmission Electron Microscopy revealed inflammation, fibroblast expansion and pronounced fibrotic remodeling in SARS-CoV-2-infected lungs. Consistently, RNA-sequencing identified a set of fibrosis signature genes. Furthermore, we identified CD147 as a crucial regulator for fibroblast activation induced by SARS-CoV-2. We found conditional knockout of CD147 in fibroblast suppressed activation of fibroblasts, decreasing susceptibility to bleomycin-induced pulmonary fibrosis. Meplazumab, a CD147 antibody, was able to inhibit the accumulation of activated fibroblasts and the production of ECM proteins, thus alleviating the progression of pulmonary fibrosis caused by SARS-CoV-2. In conclusion, we demonstrated that CD147 contributed to SARS-CoV-2-triggered progressive pulmonary fibrosis and identified CD147 as a potential therapeutic target for treating patients with post-COVID-19 pulmonary fibrosis.

Verbascoside and isoverbascoside ameliorate transforming growth factor β1-induced collagen expression by lung fibroblasts through Smad/non-Smad signaling pathways

AIMS

Pulmonary fibrosis (PF) is a chronic, irreversible, and debilitating lung disease that typically leads to respiratory failure, and is a major cause of morbidity and mortality. Few drugs are effective for the treatment of patients with PF or for reducing the rate of disease progression.

MAIN METHODS

Transforming growth factor-β1 (TGF-β1) is a profibrotic cytokine that signals through Smad and non-Smad pathways. Verbascoside (VB) and isoverbascoside (isoVB) exhibit anti-oxidative and anti-inflammatory activities, however, their anti-fibrotic effects remain unclear. This study evaluated the effects of VB and isoVB on TGF-β1-stimulated murine lung fibroblasts (MLg 2908) and also human lung fibroblasts (confirmed by immunostaining).

KEY FINDINGS

Neither VB nor isoVB had a cytotoxic effect on MLg 2908 fibroblasts. Both compounds (10 μM) reduced intracellular reactive oxygen species and markedly attenuated collagen I expression in TGF-β1 (5 ng/ml)-induced MLg 2908 cells compared to TGF-β1 alone. Both compounds suppressed the TGF-β1-induced phosphorylation of Smad2/3 and ERK/p38 mitogen-activated protein kinases (MAPKs). VB and isoVB, but not pirfenidone and nintedanib, inhibited TGF-β1-induced pSmad2/3, ERK/p38 MAPK, and collagen I expression. VB and isoVB also decreased collagen I deposition in TGF-β1-induced MLg 2908 cells. Only isoVB significantly suppressed collagen I deposition in TGF-β1-induced human pulmonary cells. Our results indicated that VB and isoVB may exert antifibrotic effects by inhibiting TGF-β1-induced collagen I expression via inhibition of oxidative stress and downregulation of the Smad/non-Smad pathway.

SIGNIFICANCE

The present findings suggest that VB or isoVB may be used as a supplement to alleviate PF.

Functions of exogenous FGF signals in regulation of fibroblast to myofibroblast differentiation and extracellular matrix protein expression

Fibroblasts are widely distributed cells found in most tissues and upon tissue injury, they are able to differentiate into myofibroblasts, which express abundant extracellular matrix (ECM) proteins. Overexpression and unordered organization of ECM proteins cause tissue fibrosis in damaged tissue. Fibroblast growth factor (FGF) family proteins are well known to promote angiogenesis and tissue repair, but their activities in fibroblast differentiation and fibrosis have not been systematically reviewed. Here we summarize the effects of FGFs in fibroblast to myofibroblast differentiation and ECM protein expression and discuss the underlying potential regulatory mechanisms, to provide a basis for the clinical application of recombinant FGF protein drugs in treatment of tissue damage.

Specific epigenetic regulators serve as potential therapeutic targets in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF), a disorder observed mostly in older human beings, is characterised by chronic and progressive lung scarring leading to an irreversible decline in lung function. This health condition has a dismal prognosis and the currently available drugs only delay but fail to reverse the progression of lung damage. Consequently, it becomes imperative to discover improved therapeutic compounds and their cellular targets to cure IPF. In this regard, a number of recent studies have targeted the epigenetic regulation by histone deacetylases (HDACs) to develop and categorise antifibrotic drugs for lungs. Therefore, this review focuses on how aberrant expression or activity of Classes I, II and III HDACs alter TGF-β signalling to promote events such as epithelial-mesenchymal transition, differentiation of activated fibroblasts into myofibroblasts, and excess deposition of the extracellular matrix to propel lung fibrosis. Further, this study describes how certain chemical compounds or dietary changes modulate dysregulated HDACs to attenuate five faulty TGF-β-dependent profibrotic processes, both in animal models and cell lines replicating IPF, thereby identifying promising means to treat this lung disorder.

Targeting PI3K/AKT signaling for treatment of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive fibrotic interstitial pneumonia with unknown causes. The incidence rate increases year by year and the prognosis is poor without cure. Recently, phosphatidylinositol 3-kinase (PI3K)/protein kinase B (PKB/AKT) signaling pathway can be considered as a master regulator for IPF. The contribution of the PI3K/AKT in fibrotic processes is increasingly prominent, with PI3K/AKT inhibitors currently under clinical evaluation in IPF. Therefore, PI3K/AKT represents a critical signaling node during fibrogenesis with potential implications for the development of novel anti-fibrotic strategies. This review epitomizes the progress that is being made in understanding the complex interpretation of the cause of IPF, and demonstrates that PI3K/AKT can directly participate to the greatest extent in the formation of IPF or cooperate with other pathways to promote the development of fibrosis. We further summarize promising PI3K/AKT inhibitors with IPF treatment benefits, including inhibitors in clinical trials and pre-clinical studies and natural products, and discuss how these inhibitors mitigate fibrotic progression to explore possible potential agents, which will help to develop effective treatment strategies for IPF in the near future.

Skin biomechanics: a potential therapeutic intervention target to reduce scarring

Pathological scarring imposes a major clinical and social burden worldwide. Human cutaneous wounds are responsive to mechanical forces and convert mechanical cues to biochemical signals that eventually promote scarring. To understand the mechanotransduction pathways in cutaneous scarring and develop new mechanotherapy approaches to achieve optimal scarring, the current study highlights the mechanical behavior of unwounded and scarred skin as well as intra- and extracellular mechanisms behind keloid and hypertrophic scars. Additionally, the therapeutic interventions that promote optimal scar healing by mechanical means at the molecular, cellular or tissue level are extensively reviewed. The current literature highlights the significant role of fibroblasts in wound contraction and scar formation via differentiation into myofibroblasts. Thus, understanding myofibroblasts and their responses to mechanical loading allows the development of new scar therapeutics. A review of the current clinical and preclinical studies suggests that existing treatment strategies only reduce scarring on a small scale after wound closure and result in poor functional and aesthetic outcomes. Therefore, the perspective of mechanotherapies needs to consider the application of both mechanical forces and biochemical cues to achieve optimal scarring. Moreover, early intervention is critical in wound management; thus, mechanoregulation should be conducted during the healing process to avoid scar maturation. Future studies should either consider combining mechanical loading (pressure) therapies with tension offloading approaches for scar management or developing more effective early therapies based on contraction-blocking biomaterials for the prevention of pathological scarring.

The phosphodiesterase 4 inhibitor AA6216 suppresses activity of fibrosis-specific macrophages

Background

Idiopathic pulmonary fibrosis (IPF) is a form of chronic, progressive fibrosing interstitial pneumonia of unknown cause, with a poor prognosis. We previously showed the antifibrotic effects of a novel phosphodiesterase 4 (PDE4) inhibitor, AA6216. In this study, we examined the effect of AA6216 on the pulmonary accumulation of segregated-nucleus-containing atypical monocytes (SatMs), which produce tumor necrosis factor (TNF)-α and are involved in murine lung fibrosis.

Methods

Mice were treated with bleomycin intratracheally at day 0 and either 10 mg/kg AA6216, 100 mg/kg nintedanib, or vehicle orally once daily from day 0 to 8. On day 9, we isolated the bronchoalveolar lavage fluid and analyzed the SatM ratio. In addition, we evaluated the effect of AA6216 on TNF-α production from SatMs isolated from murine bone marrow.

Results

AA6216, and not the antifibrotic agent nintedanib, significantly suppressed the pulmonary accumulation of SatMs (AA6216: 68.3 ± 5.4%, Nintedanib: 129.8 ± 19.7%). Furthermore, AA6216 dose-dependently inhibited the production of TNF-α by SatMs.

Conclusions

AA6216 suppresses pathogenic SatMs in the lung, which contributes to its antifibrotic effects.

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Fibrosis-specific macrophages are critical for the development of lung fibrosis.

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The PDE4 inhibitor, AA6216, suppresses the pro-fibrotic activity of macrophages.

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AA6216 inhibits the pulmonary accumulation of fibrosis-specific macrophages.

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AA6216 inhibits the production of TNF-α by fibrosis-specific macrophages.

Expression of NF-κB-p65 and α-SMA in the Study of Capsules formed by Surface Textured Implants Versus Foam Covered Silicone Implants in a Rat Model

BACKGROUND

We aimed to compare inflammatory and intercellular transcription responses induced by surface textured (ST) implants versus foam covered (FC) silicone implants placed on the dorsal aspect of rats.

METHODS

We utilized 80 female rats of the Wistar lineage. The rats were divided into four subgroups of 20 with one type of implant placed in the dorsum per rat. Analysis was carried out on peri-implant capsules at 90 d and at 180 d post-surgery with microscopic evaluation of inflammatory and immuno-histochemical response of NF-κB-p65 and α-SMA in fibroblasts. This study was carried out at the Evangelical Faculty of Parana and at the Ivo Pitanguy Institute, Brazil in 2015.

RESULTS

The FC exhibited higher levels of acute and chronic inflammation on evaluation in both time frames. The capsule surrounding the ST implants was significantly thicker with well-organized collagen fibres. NFκB-p65 expression in the capsule surrounding the FC implant was more pronounced. There was higher and more significant α-SMA expression in the capsules of the surface textured (ST) silicone implants compared to the foam-covered (FC) silicone implants.

CONCLUSION

Activation of NFκB-p65 plays a key role in the evolution of capsule formation and maintenance of inflammation by regulating the healing process. Similarly, higher and more prolonged levels of inflammation (increased NF-κB-p65 results in increased inflammation) and lower α-SMA (higher α-SMA is protective against capsular contracture) did not directly translate to a thicker capsule and ultimately, capsular contracture in foam covered silicone implants.

The interplay of DAMPs, TLR4, and proinflammatory cytokines in pulmonary fibrosis

Pulmonary fibrosis is a chronic debilitating condition characterized by progressive deposition of connective tissue, leading to a steady restriction of lung elasticity, a decline in lung function, and a median survival of 4.5 years. The leading causes of pulmonary fibrosis are inhalation of foreign particles (such as silicosis and pneumoconiosis), infections (such as post COVID-19), autoimmune diseases (such as systemic autoimmune diseases of the connective tissue), and idiopathic pulmonary fibrosis. The therapeutics currently available for pulmonary fibrosis only modestly slow the progression of the disease. This review is centered on the interplay of damage-associated molecular pattern (DAMP) molecules, Toll-like receptor 4 (TLR4), and inflammatory cytokines (such as TNF-α, IL-1β, and IL-17) as they contribute to the pathogenesis of pulmonary fibrosis, and the possible avenues to develop effective therapeutics that disrupt this interplay.

Micellar Hyaluronidase and Spiperone as a Potential Treatment for Pulmonary Fibrosis

Concentration of hyaluronic acid (HA) in the lungs increases in idiopathic pulmonary fibrosis (IPF). HA is involved in the organization of fibrin, fibronectin, and collagen. HA has been proposed to be a biomarker of fibrosis and a potential target for antifibrotic therapy. Hyaluronidase (HD) breaks down HA into fragments, but is a subject of rapid hydrolysis. A conjugate of poloxamer hyaluronidase (pHD) was prepared using protein immobilization with ionizing radiation. In a model of bleomycin-induced pulmonary fibrosis, pHD decreased the level of tissue IL-1β and TGF-β, prevented the infiltration of the lung parenchyma by CD16⁺ cells, and reduced perivascular and peribronchial inflammation. Simultaneously, a decrease in the concentrations of HA, hydroxyproline, collagen 1, total soluble collagen, and the area of connective tissue in the lungs was observed. The effects of pHD were significantly stronger compared to native HD which can be attributed to the higher stability of pHD. Additional spiperone administration increased the anti-inflammatory and antifibrotic effects of pHD and accelerated the regeneration of the damaged lung. The potentiating effects of spiperone can be explained by the disruption of the dopamine-induced mobilization and migration of fibroblast progenitor cells into the lungs and differentiation of lung mesenchymal stem cells (MSC) into cells of stromal lines. Thus, a combination of pHD and spiperone may represent a promising approach for the treatment of IPF and lung regeneration.

Splicing factor SRSF6 mediates pleural fibrosis

Pleural fibrosis is defined as an excessive deposition of extracellular matrix that results in destruction of the normal pleural tissue architecture and compromised function. Tuberculous pleurisy, asbestos injury, and rheumatoid pleurisy are main causes of pleural fibrosis. Pleural mesothelial cells (PMCs) play a key role in pleural fibrosis. However, detailed mechanisms are poorly understood. Serine/arginine-rich protein SRSF6 belongs to a family of highly conserved RNA-binding splicing-factor proteins. Based on its known functions, SRSF6 should be expected to play a role in fibrotic diseases. However, the role of SRSF6 in pleural fibrosis remains unknown. In this study, SRSF6 protein was found to be increased in cells of tuberculous pleural effusions (TBPE) from patients, and decellularized TBPE, bleomycin, and TGF-β1 were confirmed to increase SRSF6 levels in PMCs. In vitro, SRSF6 mediated PMC proliferation and synthesis of the main fibrotic protein COL1A2. In vivo, SRSF6 inhibition prevented mouse experimental pleural fibrosis. Finally, activated SMAD2/3, increased SOX4, and depressed miRNA-506-3p were associated with SRSF6 upregulation in PMCs. These observations support a model in which SRSF6 induces pleural fibrosis through a cluster pathway, including SRSF6/WNT5A and SRSF6/SMAD1/5/9 signaling. In conclusion, we propose inhibition of the splicing factor SRSF6 as a strategy for treatment of pleural fibrosis.

Analysis of histology and long noncoding RNAs involved in the rabbit hair follicle density using RNA sequencing

BACKGROUND

Hair follicle density influences wool fibre production, which is one of the most important traits of the Wan Strain Angora rabbit. However, molecular mechanisms regulating hair follicle density have remained elusive.

RESULTS

In this study, hair follicle density at different body sites of Wan Strain Angora rabbits with high and low wool production (HWP and LWP) was investigated by histological analysis. Haematoxylin-eosin staining showed a higher hair follicle density in the skin of the HWP rabbits. The long noncoding RNA (lncRNA) profile was investigated by RNA sequencing, and 50 and 38 differentially expressed (DE) lncRNAs and genes, respectively, were screened between the HWP and LWP groups. A gene ontology analysis revealed that phospholipid, lipid metabolic, apoptotic, lipid biosynthetic, and lipid and fatty acid transport processes were significantly enriched. Potential functional lncRNAs that regulate lipid metabolism, amino acid synthesis, as well as the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) and hedgehog signalling pathways, were identified. Consequently, five lncRNAs (LNC_002171, LNC_000797, LNC_005567, LNC_013595, and LNC_020367) were considered to be potential regulators of hair follicle density and development. Three DE lncRNAs and genes were validated by quantitative real-time polymerase chain reaction (q-PCR).

CONCLUSIONS

LncRNA profiles provide information on lncRNA expression to improve the understanding of molecular mechanisms involved in the regulation of hair follicle density.

Elevated S100A9 expression in chronic rhinosinusitis coincides with elevated MMP production and proliferation in vitro

Chronic rhinosinusitis (CRS) is a common condition associated with inflammation and tissue remodeling of the nose and paranasal sinuses, frequently occurring with nasal polyps and allergies. Here we investigate inflammation and the protease profile in nasal tissues and plasma from control non-CRS patients and CRS patients. Gene expression for several cytokines, proteases, and antiproteases was quantified in nasal tissue from non-CRS and CRS subjects with nasal polyps. Elevated expression of S100A9, IL1A, MMP3, MMP7, MMP11, MMP25, MMP28, and CTSK was observed in tissue from CRS subjects with nasal polyps compared to control tissue. Tissue protein analysis confirmed elevated levels of these targets compared to controls, and increased MMP3 and MMP7 observed in CRS subjects with nasal polyps compared to CRS subjects without polyps. Plasma concentrations of MMP3 and MMP7 were elevated in the CRS groups compared to controls. The nasal cell line, CCL-30, was exposed to S100A9 protein, resulting in increased MMP3, MMP7, and CTSK gene expression and elevated proliferation. Silencing MMP3 significantly reduced S100A9-mediated cell proliferation. Therefore, the elevated expression of S100A9 and MMPs are observed in CRS nasal tissue and S100A9 stimulated MMP3 responses to contribute to elevated nasal cell proliferation.

A novel phosphodiesterase 4 inhibitor, AA6216, reduces macrophage activity and fibrosis in the lung

Idiopathic pulmonary fibrosis (IPF) is an intractable disease with poor prognosis, and therapeutic options are limited. While the pathogenic mechanism is unknown, cytokines, such as transforming growth factor (TGF)-β, and immune cells, such as monocytes and macrophages, that produce them, seem to be involved in fibrosis. Some phosphodiesterase 4 (PDE4) inhibitors reportedly have anti-fibrotic potential by acting on these disease-related factors. Therefore, we evaluated the effect of a novel PDE4 inhibitor, AA6216, on nonclinical IPF-related models and samples from IPF patients. First, we examined the inhibitory effect of AA6216 on the production of TGF-β1 from a human monocytic cell line, THP-1. Second, we analyzed the impact of AA6216 on TNF-α production by human alveolar macrophages collected from patients with IPF. Finally, we investigated the anti-fibrotic potency of AA6216 on bleomycin-induced lung fibrosis in mice. We found that AA6216 significantly inhibited TGF-β1 production by THP-1 cells. It also significantly suppressed TNF-α production by alveolar macrophages from patients with IPF. In the mouse model of bleomycin-induced pulmonary fibrosis, therapeutic administration of AA6216 significantly reduced fibrosis scores, collagen-stained areas, and TGF-β1 in bronchoalveolar lavage fluid. AA6216 may represent a new agent for the treatment of IPF with a distinct mechanism of action from that of conventional anti-fibrotic agents.

Inhibition of mast cells: a novel mechanism by which nintedanib may elicit anti-fibrotic effects

Background

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive lung disease which presents a grave prognosis for diagnosed patients. Nintedanib (a triple tyrosine kinase inhibitor) and pirfenidone (unclear mechanism of action) are the only approved therapies for IPF, but have limited efficacy. The pathogenic mechanisms of this disease are not fully elucidated; however, a role for mast cells (MCs) has been postulated.

Objectives

The aim of this work was to investigate a role for MCs in IPF and to understand whether nintedanib or pirfenidone could impact MC function.

Methods and results

MCs were significantly elevated in human IPF lung and negatively correlated with baseline lung function (FVC). Importantly, MCs were positively associated with the number of fibroblast foci, which has been linked to increased mortality. Furthermore, MCs were increased in the region immediately surrounding the fibroblast foci, and co-culture studies confirmed a role for MC–fibroblast crosstalk in fibrosis. Nintedanib but not pirfenidone inhibited recombinant stem cell factor (SCF)–induced MC survival. Further evaluation of nintedanib determined that it also inhibited human fibroblast-mediated MC survival. This was likely via a direct effect on ckit (SCF receptor) since nintedanib blocked SCF-stimulated ckit phosphorylation, as well as downstream effects on MC proliferation and cytokine release. In addition, nintedanib ablated the increase in lung MCs and impacted high tissue density frequency (HDFm) in a rat bleomycin model of lung fibrosis.

Conclusion

Nintedanib inhibits MC survival and activation and thus provides a novel additional mechanism by which this drug may exert anti-fibrotic effects in patients with IPF.

Gastrin-releasing peptide induces fibrotic response in MRC5s and proliferation in A549s

Idiopathic pulmonary fibrosis (IPF) is a complex lung disease, whose build-up scar tissue is induced by several molecules. Gastrin-releasing peptide (GRP) is released from pulmonary neuroendocrine cells, alveolar macrophages, and some nerve endings in the lung. A possible role of GRP in IPF is unclear. We aimed to investigate the fibrotic response to GRP, at the cellular level in MRC5 and A549 cell lines. The proliferative and fibrotic effects of GRP on these cells were evaluated by using BrdU, immunoblotting, immunofluorescence and qRT-PCR for molecules associated with myofibroblast differentiation, TGF-β and Wnt signalling. All doses of GRP increased the amount of BrdU incorporation in A549 cells. In contrast, the amount of BrdU increased in MRC5 cells in the first 24 h, though progressively decreased by 72 h. GRP did not stimulate epithelial-mesenchymal transition in A549 cells, rather, it stimulated the differentiation of MRC5 cells into myofibroblasts. Furthermore, GRP induced gene and protein expressions of p-Smad2/3 and Smad4, and reduced the levels of Smad7 in MRC5 cells. In addition, GRP decreased Wnt5a protein levels and stimulated β-catenin activation by increasing Wnt4, Wnt7a and β-catenin protein levels. GRP caused myofibroblast differentiation by inducing TGF-βand Wnt pathways via paracrine and autocrine signalling in MRC5 cells. In conclusion, GRP may lead to pulmonary fibrosis due to its proliferative and fibrotic effects on lung fibroblasts. The abrogation of GRP-mediated signal activation might be considered as a treatment modality for fibrotic lung diseases. Video Abstract.

Systemic Sclerosis Dermal Fibroblasts Induce Cutaneous Fibrosis Through Lysyl Oxidase-like 4: New Evidence From Three-Dimensional Skin-like Tissues

OBJECTIVE

Systemic sclerosis (SSc) is a clinically heterogeneous disease characterized by increased collagen accumulation and skin stiffness. Our previous work has demonstrated that transforming growth factor β (TGFβ) induces extracellular matrix (ECM) modifications through lysyl oxidase-like 4 (LOXL-4), a collagen crosslinking enzyme, in bioengineered human skin equivalents (HSEs) and self-assembled stromal tissues (SAS). We undertook this study to investigate cutaneous fibrosis and the role of LOXL-4 in SSc pathogenesis using HSEs and SAS.

METHODS

SSc-derived dermal fibroblasts (SScDFs; n = 8) and normal dermal fibroblasts (NDFs; n = 6) were incorporated into HSEs and SAS. These 3-dimensional skin-like microenvironments were used to study the effects of dysregulated LOXL-4 on ECM remodeling, fibroblast activation, and response to TGFβ stimulation.

RESULTS

SScDF-containing SAS showed increased stromal thickness, collagen deposition, and interleukin-6 secretion compared to NDF-containing SAS (P < 0.05). In HSE, SScDFs altered collagen as seen by a more mature and aligned fibrillar structure (P < 0.05). With SScDFs, enhanced stromal rigidity with increased collagen crosslinking (P < 0.05), up-regulation of LOXL4 expression (P < 0.01), and innate immune signaling genes were observed in both tissue models. Conversely, knockdown of LOXL4 suppressed rigidity, contraction, and α-smooth muscle actin expression in SScDFs in HSE, and TGFβ-induced ECM aggregation and collagen crosslinking in SAS.

CONCLUSION

A limitation to the development of effective therapeutics in SSc is the lack of in vitro human model systems that replicate human skin. Our findings demonstrate that SAS and HSE can serve as complementary in vitro skin-like models for investigation of the mechanisms and mediators that drive fibrosis in SSc and implicate a pivotal role for LOXL-4 in SSc pathogenesis.

YAP/TAZ are Activated by Mechanical and Hormonal Stimuli in Myometrium and Exhibit Increased Baseline Activation in Uterine Fibroids

Uterine fibroids (UFs) are benign myometrial neoplasms. The mechanical environment activates signaling through the Hippo pathway effectors Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding domain (TAZ) in other fibrotic disorders. Here, we assess the differences in YAP/TAZ responsiveness to signals in UF compared with myometrium (Myo). Matched samples of UF and Myo were collected. Atomic force microscopy (AFM) was used to determine in situ stiffness. Cells were plated sparsely on hydrogels or at confluence. Ten nanomolars of estradiol (E2) and 100 nM progesterone (P4) were used. Immunostaining for YAP/TAZ and extracellular matrix (ECM) proteins was performed. Cells were incubated with control or YAP1 (YAP)/WWTR1 (TAZ) small interfering RNA (siRNA). Real time qPCR was completed for connective tissue growth factor (CTGF). Cells were treated with verteporfin (a YAP inhibitor) or Y27632 (a ROCK inhibitor), and ECM gene expression was analyzed. Paired t test and Wilcoxon sign-rank test were used. AFM-measured tissue stiffness and YAP/TAZ nuclear localization in situ and in confluent cells were higher in UF compared with Myo (p < 0.05). Decreasing substrate stiffness reduced YAP/TAZ nuclear localization for both Myo and UF (p = 0.05). Stimulating cells with E2 or P4 increased YAP/TAZ nuclear localization, but only in Myo (p = 0.01). UFs had increased FN, COLI, and COLIII deposition. Following siRNA targeting, CTGF was found to be statistically decreased. Verteporfin treatment reduced cell survival and reduced FN deposition. Treatment with Y27632 demonstrated better cell tolerance and a reduction in ECM deposition. The mechanosensitive pathway may be linked to YAP/TAZ function and involved in transducing fibroid growth.

Idiopathic Pulmonary Fibrosis: Pathogenesis and the Emerging Role of Long Non-Coding RNAs

Idiopathic pulmonary fibrosis (IPF) is a progressive chronic disease characterized by excessing scarring of the lungs leading to irreversible decline in lung function. The aetiology and pathogenesis of the disease are still unclear, although lung fibroblast and epithelial cell activation, as well as the secretion of fibrotic and inflammatory mediators, have been strongly associated with the development and progression of IPF. Significantly, long non-coding RNAs (lncRNAs) are emerging as modulators of multiple biological processes, although their function and mechanism of action in IPF is poorly understood. LncRNAs have been shown to be important regulators of several diseases and their aberrant expression has been linked to the pathophysiology of fibrosis including IPF. This review will provide an overview of this emerging role of lncRNAs in the development of IPF.

Modeling Progressive Fibrosis with Pluripotent Stem Cells Identifies an Anti-fibrotic Small Molecule

Progressive organ fibrosis accounts for one-third of all deaths worldwide, yet preclinical models that mimic the complex, progressive nature of the disease are lacking, and hence, there are no curative therapies. Progressive fibrosis across organs shares common cellular and molecular pathways involving chronic injury, inflammation, and aberrant repair resulting in deposition of extracellular matrix, organ remodeling, and ultimately organ failure. We describe the generation and characterization of an in vitro progressive fibrosis model that uses cell types derived from induced pluripotent stem cells. Our model produces endogenous activated transforming growth factor β (TGF-β) and contains activated fibroblastic aggregates that progressively increase in size and stiffness with activation of known fibrotic molecular and cellular changes. We used this model as a phenotypic drug discovery platform for modulators of fibrosis. We validated this platform by identifying a compound that promotes resolution of fibrosis in in vivo and ex vivo models of ocular and lung fibrosis.

Fibulin-1c regulates transforming growth factor-β activation in pulmonary tissue fibrosis

Tissue remodeling/fibrosis is a major feature of all fibrotic diseases, including idiopathic pulmonary fibrosis (IPF). It is underpinned by accumulating extracellular matrix (ECM) proteins. Fibulin-1c (Fbln1c) is a matricellular ECM protein associated with lung fibrosis in both humans and mice, and stabilizes collagen formation. Here we discovered that Fbln1c was increased in the lung tissues of IPF patients and experimental bleomycin-induced pulmonary fibrosis. Fbln1c-deficient (-/-) mice had reduced pulmonary remodeling/fibrosis and improved lung function after bleomycin challenge. Fbln1c interacted with fibronectin, periostin and tenascin-c in collagen deposits following bleomycin challenge. In a novel mechanism of fibrosis Fbln1c bound to latent transforming growth factor (TGF)-β binding protein-1 (LTBP1) to induce TGF-β activation, and mediated downstream Smad3 phosphorylation/signaling. This process increased myofibroblast numbers and collagen deposition. Fbln1 and LTBP1 co-localized in lung tissues from IPF patients. Thus, Fbln1c may be a novel driver of TGF-β-induced fibrosis involving LTBP1 and may be an upstream therapeutic target.

Lysyl oxidase enzymes mediate TGF-β1-induced fibrotic phenotypes in human skin-like tissues

Cutaneous fibrosis is a common complication seen in mixed connective tissue diseases. It often occurs as a result of TGF-β-induced deposition of excessive amounts of collagen in the skin. Lysyl oxidases (LOXs), a family of extracellular matrix (ECM)-modifying enzymes responsible for collagen cross-linking, are known to be increased in dermal fibroblasts from patients with fibrotic diseases, denoting a possible role of LOXs in fibrosis. To directly study this, we have developed two bioengineered, in vitro skin-like models: human skin equivalents (hSEs), and self-assembled stromal tissues (SASs) that contain either normal or systemic sclerosis (SSc; scleroderma) patient-derived fibroblasts. These tissues provide an organ-level structure that could be combined with non-invasive, label-free, multiphoton microscopy (SHG/TPEF) to reveal alterations in the organization and cross-linking levels of collagen fibers during the development of cutaneous fibrosis, which demonstrated increased stromal rigidity and activation of dermal fibroblasts in response to TGF-β1. Specifically, inhibition of specific LOXs isoforms, LOX and LOXL4, in foreskin fibroblasts (HFFs) resulted in antagonistic effects on TGF-β1-induced fibrogenic hallmarks in both hSEs and SASs. In addition, a translational relevance of these models was seen as similar antifibrogenic phenotypes were achieved upon knocking down LOXL4 in tissues containing SSc patient-derived-dermal fibroblasts (SScDFs). These findings point to a pivotal role of LOXs in TGF-β1-induced cutaneous fibrosis through impaired ECM homeostasis in skin-like tissues, and show the value of these tissue platforms in accelerating the discovery of antifibrosis therapeutics.

Precision-cut lung slices from bleomycin treated animals as a model for testing potential therapies for idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a complex lung disease with incompletely understood pathophysiology. Effectiveness of available medicines is limited and the need for new and improved therapies remains. Due to complexity of the disease, it is difficult to develop predictable in vitro models. In this study we have described precision-cut lung slices (PCLS) prepared from bleomycin treated mice as an in vitro model for testing of novel compounds with antifibrotic activity. We have shown that PCLS during in vitro incubation retain characteristics of bleomycin model with increased expression of fibrosis related genes ACTA2 (α-smooth muscle actin), COL1A1 (collagen 1), FN1 (fibronectin 1), MMP12 (matrix metalloproteinase 12) and TIMP1 (tissue inhibitor of metalloproteinases). To further evaluate PCLS as an in vitro model, we have tested ALK5 inhibitor SB525334 which was previously shown to attenuate fibrosis in in vivo bleomycin model and nintedanib which is the FDA approved treatment for IPF. SB525334 and nintedanib inhibited expression of fibrosis related genes in PCLS from bleomycin treated mice. In addition, comparable activity profile of SB525334 was achieved in PCLS and in vivo model. Altogether these results suggest that PCLS may be a suitable in vitro model for compound testing during drug development process.

Cadherin-11-mediated adhesion of macrophages to myofibroblasts establishes a profibrotic niche of active TGF-β

Macrophages contribute to the activation of fibroblastic cells into myofibroblasts, which secrete collagen and contract the collagen matrix to acutely repair injured tissue. Persistent myofibroblast activation leads to the accumulation of fibrotic scar tissue that impairs organ function. We investigated the key processes that turn acute beneficial repair into destructive progressive fibrosis. We showed that homotypic cadherin-11 interactions promoted the specific binding of macrophages to and persistent activation of profibrotic myofibroblasts. Cadherin-11 was highly abundant at contacts between macrophages and myofibroblasts in mouse and human fibrotic lung tissues. In attachment assays, cadherin-11 junctions mediated specific recognition and strong adhesion between macrophages and myofibroblasts. One functional outcome of cadherin-11-mediated adhesion was locally restricted activation of latent transforming growth factor-β (TGF-β) between macrophage-myofibroblast pairs that was not observed in cocultures of macrophages and myofibroblasts that were not in contact with one another. Our data suggest that cadherin-11 junctions maintain latent TGF-β-producing macrophages and TGF-β-activating myofibroblasts in close proximity to one another. Inhibition of homotypic cadherin-11 interactions could be used to cause macrophage-myofibroblast separation, thereby destabilizing the profibrotic niche.

Lysyl oxidases regulate fibrillar collagen remodelling in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive scarring disease of the lung with few effective therapeutic options. Structural remodelling of the extracellular matrix [i.e. collagen cross-linking mediated by the lysyl oxidase (LO) family of enzymes (LOX, LOXL1-4)] might contribute to disease pathogenesis and represent a therapeutic target. This study aimed to further our understanding of the mechanisms by which LO inhibitors might improve lung fibrosis. Lung tissues from IPF and non-IPF subjects were examined for collagen structure (second harmonic generation imaging) and LO gene (microarray analysis) and protein (immunohistochemistry and western blotting) levels. Functional effects (collagen structure and tissue stiffness using atomic force microscopy) of LO inhibitors on collagen remodelling were examined in two models, collagen hydrogels and decellularized human lung matrices. LOXL1/LOXL2 gene expression and protein levels were increased in IPF versus non-IPF. Increased collagen fibril thickness in IPF versus non-IPF lung tissues correlated with increased LOXL1/LOXL2, and decreased LOX, protein expression. β-Aminoproprionitrile (β-APN; pan-LO inhibitor) but not Compound A (LOXL2-specific inhibitor) interfered with transforming growth factor-β-induced collagen remodelling in both models. The β-APN treatment group was tested further, and β-APN was found to interfere with stiffening in the decellularized matrix model. LOXL1 activity might drive collagen remodelling in IPF lungs. The interrelationship between collagen structural remodelling and LOs is disrupted in IPF lungs. Inhibition of LO activity alleviates fibrosis by limiting fibrillar collagen cross-linking, thereby potentially impeding the formation of a pathological microenvironment in IPF.

Summary: Transforming growth factor-β-induced collagen remodelling is driven by enhanced lysyl oxidase expression in idiopathic pulmonary fibrosis.

Chronic hepatitis B virus and liver fibrosis: A mathematical model

Hepatitis B virus (HBV) infection is a liver disorder that can result in cirrhosis, liver failure and hepatocellular carcinoma. HBV infection remains a major global health problem, as it affects more 350 million people chronically and kills roughly 600,000 people annually. Drugs currently used against HBV include IFN-α that decreases viremia, inflammation and the growth of liver fibrosis, and adefovir that decreases the viral load. Each of these drugs can have severe side-effects. In the present paper, we consider the treatment of chronic HBV by a combination of IFN-α and adefovir, and raise the following question: What should be the optimal ratio between IFN-α and adefovir in order to achieve the best 'efficacy' under constraints on the total amount of the drugs; here the efficacy is measured by the reduction of the levels of inflammation and of fibrosis? We develop a mathematical model of HBV pathogenesis by a system of partial differential equations (PDEs) and use the model to simulate a 'synergy map' which addresses the above question.

Engineered cell and tissue models of pulmonary fibrosis

Pulmonary fibrosis includes several lung disorders characterized by scar formation and Idiopathic Pulmonary Fibrosis (IPF) is a particularly severe form of pulmonary fibrosis of unknown etiology with a mean life expectancy of 3years' post-diagnosis. Treatments for IPF are limited to two FDA approved drugs, pirfenidone and nintedanib. Most lead candidate drugs that are identified in pre-clinical animal studies fail in human clinical trials. Thus, there is a need for advanced humanized in vitro models of the lung to improve candidate treatments prior to moving to human clinical trials. The development of 3D tissue models has created systems capable of emulating human lung structure, function, and cell and matrix interactions. The specific models accomplish these features and preliminary studies conducted using some of these systems have shown potential for in vitro anti-fibrotic drug testing. Further characterization and improvements will enable these tissue models to extend their utility for in vitro drug testing, to help identify signaling pathways and mechanisms for new drug targets, and potentially reduce animal models as standard pre-clinical models of study. In the current review, we contrast different in vitro models based on increasing dimensionality (2D, 2.5D and 3D), with added focus on contemporary 3D pulmonary models of fibrosis.

Matrix stiffness and tumor-associated macrophages modulate epithelial to mesenchymal transition of human adenocarcinoma cells

The tumor microenvironment (TME) is gaining increasing attention in oncology, as it is recognized to be functionally important during tumor development and progression. Tumors are heterogeneous tissues that, in addition to tumor cells, contain tumor-associated cell types such as immune cells, fibroblasts, and endothelial cells. These other cells, together with the specific extracellular matrix (ECM), create a permissive environment for tumor growth. While the influence of tumor-infiltrating cells and mechanical properties of the ECM in tumor invasion and progression have been studied separately, their interaction within the complex TME and the epithelial -to-mesenchymal transition (EMT) is still unclear. In this work, we develop a 3D co-culture model of lung adenocarcinoma cells and macrophages in an interpenetrating network hydrogel, to investigate the influence of the macrophage phenotype and ECM stiffness in the induction of EMT. Rising ECM stiffness increases both tumor cell proliferation and invasiveness. The presence of tumor-associated macrophages and the ECM stiffness jointly contribute to an invasive phenotype, and modulate the expression of key EMT-related markers. Overall, these findings support the utility of in vitro 3D cancer models that allow one to study interactions among key components of the TME.

Petroleum coke exposure leads to altered secretome profiles in human lung models

Petroleum coke (PC) is a coal-like product that is produced during the refinement of crude oil and bituminous sand. Fugitive dust from open storage of PC in urban areas is a potential human health concern. Animal inhalation studies suggest that PC leads to an adverse pulmonary histopathology, including areas of fibrosis and chronic inflammation; however, little is known about its impact on human health. In order to identify biomarkers and cellular pathways that are associated with exposure, we performed two-dimensional liquid chromatography-mass spectrometric analyses on secreted proteins from two human lung culture models. A total of 2795 proteins were identified and relatively quantified from an immortalized cell line and 2406 proteins from primary cultures that were either mock treated or exposed to particulate matter with a diameter of 2.5-10 μm PC or filtered urban air particulates for 16 h. Pathway analysis on secretomes from primary lung cultures indicated that PC exposure suppressed the secretion of proteins involved in the organization of the extracellular matrix and epithelial differentiation. Because these cellular processes could facilitate fibrosis, we performed chronic 12-day exposure studies on three-dimensional human lung cultures consisting of epithelia and stromal fibroblasts. Relative to mock-treated cells, matrix metallopeptidase 9 levels in the conditioned media were lower by 4 days postexposure and remained suppressed for the duration of the experiment. Immunocytochemical staining of collagen III, a marker associated with fibrosis, showed increased accumulation in the epithelial layer and at the air-liquid interface.

Treprostinil inhibits proliferation and extracellular matrix deposition by fibroblasts through cAMP activation

Idiopathic pulmonary fibrosis (IPF) is characterized by peripheral lung fibrosis and increased interstitial extracellular matrix (ECM) deposition. In IPF, tumor growth factor (TGF)-β1 which is the major stimulus of ECM deposition, and platelet derived growth factor (PDGF)-BB is a potent stimulus of fibrosis. Thus, the effect of Treprostinil on TGF-ß1 and PDGF-induced fibroblast proliferation and ECM deposition was investigated. Human peripheral lung fibroblasts of seven IPF patients and five lung donors were stimulated by PDGF, or TGF-β1, or the combination. Cells were pre-incubated (30 min) with either Treprostinil, forskolin, di-deoxyadenosine (DDA), or vehicle. Treprostinil time dependently activated cAMP thereby preventing PDGF-BB induced proliferation and TGF-β1 secretion. Cell counts indicated proliferation; α-smooth muscle actin (α-SMA) indicted differentiation, and collagen type-1 or fibronectin deposition remodeling. Myo-fibroblast indicating α-SMA expression was significantly reduced and its formation was altered by Treprostinil. Collagen type-I and fibronectin deposition were also reduced by Treprostinil. The effect of Treprostinil on collagen type-I deposition was cAMP sensitive as it was counteracted by DDA, while the effect on fibronectin was not cAMP mediated. Treprostinil antagonized the pro-fibrotic effects of both PDGF-BB and TGF-β1 in primary human lung fibroblasts. The data presented propose a therapeutic relevant anti-fibrotic effect of Treprostinil in IPF.

Pirfenidone reduces subchondral bone loss and fibrosis after murine knee cartilage injury

Pirfenidone is an anti-inflammatory and anti-fibrotic drug that has shown efficacy in lung and kidney fibrosis. Because inflammation and fibrosis have been linked to the progression of osteoarthritis, we investigated the effects of oral Pirfenidone in a mouse model of cartilage injury, which results in chronic inflammation and joint-wide fibrosis in mice that lack hyaluronan synthase 1 (Has1^-/- ) in comparison to wild-type. Femoral cartilage was surgically injured in wild-type and Has1^-/- mice, and Pirfenidone was administered in food starting after 3 days. At 4 weeks, Pirfenidone reduced the appearance, on micro-computed tomography, of pitting in subchondral bone at, and cortical bone surrounding, the site of cartilage injury. This corresponded with a reduction in fibrotic tissue deposits as observed with gross joint surface photography. Pirfenidone resulted in significant recovery of trabecular bone parameters affected by joint injury in Has1^-/- mice, although the effect in wild-type was less pronounced. Pirfenidone also increased Safranin-O staining of growth plate cartilage after cartilage injury and sham operation in both genotypes. Taken together with the expression of selected extracellular matrix, inflammation, and fibrosis genes, these results indicate that Pirfenidone may confer chondrogenic and bone-protective effects, although the well-known anti-fibrotic effects of Pirfenidone may occur earlier in the wound-healing response than the time point examined in this study. Further investigations to identify the specific cell populations in the joint and signaling pathways that are responsive to Pirfenidone are warranted, as Pirfenidone and other anti-fibrotic drugs may encourage tissue repair and prevent progression of post-traumatic osteoarthritis. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:365-376, 2018.

Activated human T lymphocytes inhibit TGFβ-induced fibroblast to myofibroblast differentiation via prostaglandins D2 and E2

In pulmonary fibrosis (PF), fibroblasts and myofibroblasts proliferate and deposit excessive extracellular matrix in the interstitium, impairing normal lung function. Because most forms of PF have a poor prognosis and limited treatment options, PF represents an urgent unmet need for novel, effective therapeutics. Although the role of immune cells in lung fibrosis is unclear, recent studies suggest that T lymphocyte (T cell) activation may be impaired in PF patients. Furthermore, we have previously shown that activated T cells can produce prostaglandins with anti-scarring potential. Here, we test the hypothesis that activated T cells directly inhibit myofibroblast differentiation using a coculture system. Coculture with activated primary blood-derived T cells, from both healthy human donors and PF patients, inhibited transforming growth factor β-induced myofibroblast differentiation in primary human lung fibroblasts isolated from either normal or PF lung tissue. Coculture supernatants contained anti-fibrotic prostaglandins D₂ and E₂, and the inhibitory effect of coculture on myofibroblast differentiation was largely reversed when prostaglandin production was abrogated either by resting the T cells before coculture or via specific pharmacological inhibitors. Moreover, coculture conditions induced COX-2 in HLFs but not in T cells, suggesting that T cells deliver an activating signal to HLFs, which in turn produce anti-fibrotic prostaglandins. We show for the first time that coculture with activated primary human T lymphocytes strongly inhibits myofibroblast differentiation, revealing a novel cell-to-cell communication network with therapeutic implications for fibrotic lung diseases.

Lysocardiolipin acyltransferase regulates TGF-β mediated lung fibroblast differentiation

Lysocardiolipin acyltransferase (LYCAT), a cardiolipin remodeling enzyme, plays a key role in mitochondrial function and vascular development. We previously reported that reduced LYCAT mRNA levels in peripheral blood mononuclear cells correlated with poor pulmonary function outcomes and decreased survival in IPF patients. Further LYCAT overexpression reduced lung fibrosis, and LYCAT knockdown accentuated experimental pulmonary fibrosis. NADPH Oxidase 4 (NOX4) expression and oxidative stress are known to contribute to lung fibroblast differentiation and progression of fibrosis. In this study, we investigated the role of LYCAT in TGF-β mediated differentiation of human lung fibroblasts to myofibroblasts, and whether this occurred through mitochondrial superoxide and NOX4 mediated hydrogen peroxide (H₂O₂) generation. Our data indicated that LYCAT expression was up-regulated in primary lung fibroblasts isolated from IPF patients and bleomycin-challenged mice, compared to controls. In vitro, siRNA-mediated SMAD3 depletion inhibited TGF-β stimulated LYCAT expression in human lung fibroblasts. ChIP immunoprecipitation assay revealed TGF-β stimulated SMAD2/3 binding to the endogenous LYCAT promoter, and mutation of the SMAD2/3 binding sites (-179/-183 and -540/-544) reduced TGF-β-stimulated LYCAT promoter activity. Overexpression of LYCAT attenuated TGF-β-induced mitochondrial and intracellular oxidative stress, NOX4 expression and differentiation of human lung fibroblasts. Further, pretreatment with Mito-TEMPO, a mitochondrial superoxide scavenger, blocked TGF-β-induced mitochondrial superoxide_, NOX4 expression and differentiation of human lung fibroblasts. Treatment of human lung fibroblast with NOX1/NOX4 inhibitor, GKT137831, also attenuated TGF-β induced fibroblast differentiation and mitochondrial oxidative stress. Collectively, these results suggest that LYCAT is a negative regulator of TGF-β-induced lung fibroblast differentiation by modulation of mitochondrial superoxide and NOX4 dependent H₂O₂ generation, and this may serve as a potential therapeutic target for human lung fibrosis.

The effects of collagen-rich extracellular matrix on the intracellular delivery of glycol chitosan nanoparticles in human lung fibroblasts

Recent progress in nanomedicine has shown a strong possibility of targeted therapy for obstinate chronic lung diseases including idiopathic pulmonary fibrosis (IPF). IPF is a fatal lung disease characterized by persistent fibrotic fibroblasts in response to type I collagen-rich extracellular matrix. As a pathological microenvironment is important in understanding the biological behavior of nanoparticles, in vitro cellular uptake of glycol chitosan nanoparticles (CNPs) in human lung fibroblasts was comparatively studied in the presence or absence of type I collagen matrix. Primary human lung fibroblasts from non-IPF and IPF patients (n=6/group) showed significantly increased cellular uptake of CNPs (>33.6-78.1 times) when they were cultured on collagen matrix. To elucidate the underlying mechanism of enhanced cellular delivery of CNPs in lung fibroblasts on collagen, cells were pretreated with chlorpromazine, genistein, and amiloride to inhibit clathrin-mediated endocytosis, caveolae-mediated endocytosis, and macropinocytosis, respectively. Amiloride pretreatment remarkably reduced the cellular uptake of CNPs, suggesting that lung fibroblasts mainly utilize the macropinocytosis-dependent mechanism when interacted with collagen. In addition, the internalization of CNPs was predominantly suppressed by a phosphoinositide 3-kinase (PI3K) inhibitor in IPF fibroblasts, indicating that enhanced PI3K activity associated with late-stage macropinocytosis can be particularly important for the enhanced cellular delivery of CNPs in IPF fibroblasts. Our study strongly supports the concept that a pathological microenvironment which surrounds lung fibroblasts has a significant impact on the intracellular delivery of nanoparticles. Based on the property of enhanced intracellular delivery of CNPs when fibroblasts are made to interact with a collagen-rich matrix, we suggest that CNPs may have great potential as a drug-carrier system for targeting fibrotic lung fibroblasts.

Role of Rho-Associated Coiled-Coil Forming Kinase Isoforms in Regulation of Stiffness-Induced Myofibroblast Differentiation in Lung Fibrosis

Fibrosis is a major cause of progressive organ dysfunction in several chronic pulmonary diseases. Rho-associated coiled-coil forming kinase (ROCK) has been shown to be involved in myofibroblast differentiation driven by altered matrix stiffness in a fibrotic state. There are two known ROCK isoforms in humans, ROCK1 and ROCK2, but the specific role of each isoform in myofibroblast differentiation in lung fibrosis remains unknown. To study this, we developed a gelatin methacryloyl hydrogel-based culture system with different stiffness levels relevant to healthy and fibrotic lungs. We have shown that stiff matrix, but not soft matrix, can induce myofibroblast differentiation with high smooth muscle actin isoform (αSMA) expression. Furthermore, our data confirmed that the inhibition of ROCK signaling by a pharmacological inhibitor (i.e., Y27632) attenuates stiffness-induced αSMA expression and fiber assembly in myofibroblasts. To assess the role of ROCK isoforms in this process, we used short interfering RNA to knock down the expression of each isoform. Our data showed that knocking down either ROCK1 or ROCK2 did not result in a reduction in αSMA expression in myofibroblasts on stiff matrix, as opposed to soft matrix, where αSMA expression was reduced significantly. Paradoxically, on stiff matrix, the absence of one isoform (particularly ROCK2) exaggerated αSMA expression and led to thick fiber assembly. Moreover, complete loss of αSMA fiber assembly was seen only in the absence of both ROCK isoforms, suggesting that both isoforms are implicated in this process. Overall, our results indicate the differential role of ROCK isoforms in myofibroblast differentiation on soft and stiff matrices.

Heart regeneration in the salamander relies on macrophage-mediated control of fibroblast activation and the extracellular landscape

In dramatic contrast to the poor repair outcomes for humans and rodent models such as mice, salamanders and some fish species are able to completely regenerate heart tissue following tissue injury, at any life stage. This capacity for complete cardiac repair provides a template for understanding the process of regeneration and for developing strategies to improve human cardiac repair outcomes. Using a cardiac cryo-injury model we show that heart regeneration is dependent on the innate immune system, as macrophage depletion during early time points post-injury results in regeneration failure. In contrast to the transient extracellular matrix that normally accompanies regeneration, this intervention resulted in a permanent, highly cross-linked extracellular matrix scar derived from alternative fibroblast activation and lysyl-oxidase enzyme synthesis. The activation of cardiomyocyte proliferation was not affected by macrophage depletion, indicating that cardiomyocyte replacement is an independent feature of the regenerative process, and is not sufficient to prevent fibrotic progression. These findings highlight the interplay between macrophages and fibroblasts as an important component of cardiac regeneration, and the prevention of fibrosis as a key therapeutic target in the promotion of cardiac repair in mammals.

Heart regeneration in salamanders is dependent on the activation of immune cells. James Godwin of The Jackson Laboratory and MDI Biological Laboratory in the US and colleagues depleted all major organs of a group of Mexican salamanders of macrophages, an immune cell responsible for removing cellular debris. They then injured the salamanders’ heart wall with a liquid nitrogen-cooled probe. Unlike adult mammals, zebrafish and salamanders can normally regenerate their hearts after injury. The team found that macrophage-depleted salamanders were unable to regenerate their hearts compared to a control group. Macrophage depletion led to the formation of a permanent fibrotic extracellular matrix scar. But it did not affect the proliferation of heart muscle cells, indicating that their function is not sufficient to prevent the progression of injury toward fibrosis instead of regeneration.