Enhanced effectivity of an ALK5-inhibitor after cell-specific delivery to hepatic stellate cells in mice with liver injury

Cation-independent mannose 6-phosphate receptor: From roles and functions to targeted therapies

The cation-independent mannose 6-phosphate receptor (CI-M6PR) is a ubiquitous transmembrane receptor whose main intracellular role is to direct enzymes carrying mannose 6-phosphate moieties to lysosomal compartments. Recently, the small membrane-bound portion of this receptor has appeared to be implicated in numerous pathophysiological processes. This review presents an overview of the main ligand partners and the roles of CI-M6PR in lysosomal storage diseases, neurology, immunology and cancer fields. Moreover, this membrane receptor has already been noted for its strong potential in therapeutic applications thanks to its cellular internalization activity and its ability to address pathogenic factors to lysosomes for degradation. A number of therapeutic delivery approaches using CI-M6PR, in particular with enzymes, antibodies or nanoparticles, are currently being proposed.

Mechanism and Progress of Natural Products in the Treatment of NAFLD-Related Fibrosis

Nonalcoholic fatty liver disease (NAFLD) has emerged as the most prevalent chronic liver disorder worldwide, with liver fibrosis (LF) serving as a pivotal juncture in NAFLD progression. Natural products have demonstrated substantial antifibrotic properties, ushering in novel avenues for NAFLD treatment. This study provides a comprehensive review of the potential of natural products as antifibrotic agents, including flavonoids, polyphenol compounds, and terpenoids, with specific emphasis on the role of Baicalin in NAFLD-associated fibrosis. Mechanistically, these natural products have exhibited the capacity to target a multitude of signaling pathways, including Hedgehog, Wnt/β-catenin, TGF-β1, and NF-κB. Moreover, they can augment the activities of antioxidant enzymes, inhibit pro-fibrotic factors, and diminish fibrosis markers. In conclusion, this review underscores the considerable potential of natural products in addressing NAFLD-related liver fibrosis through multifaceted mechanisms. Nonetheless, it underscores the imperative need for further clinical investigation to authenticate their effectiveness, offering invaluable insights for future therapeutic advancements in this domain.

The progress of autoimmune hepatitis research and future challenges

Autoimmune hepatitis (AIH) is a chronic liver inflammatory disease with various immune system manifestations, showing a global trend of increased prevalence. AIH is diagnosed through histological abnormalities, clinical manifestations, and biochemical indicators. The biochemical markers involve interfacial hepatitis, transaminase abnormalities, positive autoantibodies, etc. Although AIH pathogenesis is unclear, gene mutations and immunological factors could be the leading factors. AIH usually presents as a chronic liver disease and sometimes as acute hepatitis, making it challenging to distinguish it from drug-related hepatitis due to similar clinical symptoms. Normalizing transaminases and serum IgG levels is essential in assessing the remission status of AIH treatment. Glucocorticoids and azathioprine are the first-line AIH treatment, with lifelong maintenance therapy in some patients. The quality of life and survival can be improved after appropriate treatment. However, certain limitations jeopardize the quality of treatment, including long treatment cycles, side effects, poor patient compliance, and inability to inhibit liver fibrosis and cirrhosis. Accurate AIH animal models will help us understand the pathophysiology of the disease while providing fresh perspectives for avoiding and treating AIH. This review will help us understand AIH better, from the cellular and molecular causes to the clinical features, and will provide insight into new therapy techniques with fewer side effects.

Liver Cell Type-Specific Targeting by Nanoformulations for Therapeutic Applications

Hepatocytes exert pivotal roles in metabolism, protein synthesis and detoxification. Non-parenchymal liver cells (NPCs), largely comprising macrophages, dendritic cells, hepatic stellate cells and liver sinusoidal cells (LSECs), serve to induce immunological tolerance. Therefore, the liver is an important target for therapeutic approaches, in case of both (inflammatory) metabolic diseases and immunological disorders. This review aims to summarize current preclinical nanodrug-based approaches for the treatment of liver disorders. So far, nano-vaccines that aim to induce hepatitis virus-specific immune responses and nanoformulated adjuvants to overcome the default tolerogenic state of liver NPCs for the treatment of chronic hepatitis have been tested. Moreover, liver cancer may be treated using nanodrugs which specifically target and kill tumor cells. Alternatively, nanodrugs may target and reprogram or deplete immunosuppressive cells of the tumor microenvironment, such as tumor-associated macrophages. Here, combination therapies have been demonstrated to yield synergistic effects. In the case of autoimmune hepatitis and other inflammatory liver diseases, anti-inflammatory agents can be encapsulated into nanoparticles to dampen inflammatory processes specifically in the liver. Finally, the tolerance-promoting activity especially of LSECs has been exploited to induce antigen-specific tolerance for the treatment of allergic and autoimmune diseases.

Hepatic Stellate Cell Targeting Using Peptide-Modified Biologicals

Liver diseases are a leading cause of death worldwide and are rising exponentially due to increasing prevalence of metabolic disorders. Hepatic stellate cells (HSCs) are recognized as a key therapeutic target in liver diseases as these cells, upon activation during liver damage and ongoing liver inflammation, secrete excessive amounts of extracellular matrix that leads to liver tissue scarring (fibrosis) responsible for liver dysfunction (end-stage liver disease) and desmoplasia in hepatocellular carcinoma. Targeting of HSCs to reverse fibrosis progression has been realized by several experts in the field, including us. We have developed strategies to target activated HSCs by utilizing the receptors overexpressed on the surface of activated HSCs. One well-known receptor is platelet derived growth factor receptor-beta (PDGFR-β). Using PDGFR-β recognizing peptides (cyclic PPB or bicyclic PPB), we can deliver biologicals, e.g., interferon gamma (IFNγ) or IFNγ activity domain (mimetic IFNγ), to the activated HSCs that can inhibit their activation and reverse liver fibrosis. In this chapter, we provide the detailed methods and the principles involved in the synthesis of these targeted (mimetic) IFNγ constructs. These methods can be adapted for synthesizing constructs for targeted/cell-specific delivery of peptides/proteins, drugs, and imaging agents useful for various applications including diagnosis and treatment of inflammatory and fibrotic diseases and cancer.

Insulin-like Growth Factor-2 (IGF-2) in Fibrosis

The insulin family consists of insulin, insulin-like growth factor 1 (IGF-1), insulin-like growth factor 2 (IGF-2), their receptors (IR, IGF-1R and IGF-2R), and their binding proteins. All three ligands are involved in cell proliferation, apoptosis, protein synthesis and metabolism due to their homologous sequences and structural similarities. Insulin-like growth factor 2, a member of the insulin family, plays an important role in embryonic development, metabolic disorders, and tumorigenesis by combining with three receptors with different degrees of affinity. The main pathological feature of various fibrotic diseases is the excessive deposition of extracellular matrix (ECM) after tissue and organ damage, which eventually results in organic dysfunction because scar formation replaces tissue parenchyma. As a mitogenic factor, IGF-2 is overexpressed in many fibrotic diseases. It can promote the proliferation of fibroblasts significantly, as well as the production of ECM in a time- and dose-dependent manner. This review aims to describe the expression changes and fibrosis-promoting effects of IGF-2 in the skin, oral cavity, heart, lung, liver, and kidney fibrotic tissues.

Integrins as a drug target in liver fibrosis

As the worldwide prevalence of chronic liver diseases is high and continuing to increase, there is an urgent need for treatment to prevent cirrhosis-related morbidity and mortality. Integrins are heterodimeric cell-surface proteins that are promising targets for therapeutic intervention. αv integrins are central in the development of fibrosis as they activate latent TGFβ, a known profibrogenic cytokine. The αv subunit can form heterodimers with β1, β3, β5, β6 or β8 subunits and one or more of these integrins are central to the development of liver fibrosis, however, their relative importance is not understood. This review summarises the current knowledge of αv integrins and their respective β subunits in different organs, with a focus on liver fibrosis and the emerging preclinical and clinical data with regards to αv integrin inhibitors.

Drug Targeting and Nanomedicine: Lessons Learned from Liver Targeting and Opportunities for Drug Innovation

Drug targeting and nanomedicine are different strategies for improving the delivery of drugs to their target. Several antibodies, immuno-drug conjugates and nanomedicines are already approved and used in clinics, demonstrating the potential of such approaches, including the recent examples of the DNA- and RNA-based vaccines against COVID-19 infections. Nevertheless, targeting remains a major challenge in drug delivery and different aspects of how these objects are processed at organism and cell level still remain unclear, hampering the further development of efficient targeted drugs. In this review, we compare properties and advantages of smaller targeted drug constructs on the one hand, and larger nanomedicines carrying higher drug payload on the other hand. With examples from ongoing research in our Department and experiences from drug delivery to liver fibrosis, we illustrate opportunities in drug targeting and nanomedicine and current challenges that the field needs to address in order to further improve their success.

General sites of nanoparticle biodistribution as a novel opportunity for nanomedicine

The development of nanomedical devices has led to a considerable number of clinically applied nanotherapeutics. Yet, the overall poor translation of nanoparticular concepts into marketable systems has not met the initial expectations and led to increasing criticism in recent years. Most novel nano approaches thereby use highly refined formulations including a plethora of active targeting sequences, but ultimately fail to reach their target due to a generally high off-target deposition in organs such as the liver or kidney. In this context, we argue that initial nanoparticle (NP) development should not entirely become set on conventional formulation aspects. In contrast, we propose a change of focus towards a prior analysis of general sites of NP in vivo deposition and an assessment of how accumulation in these organs or tissues can be harnessed to develop therapies for site-related pathologies. We therefore give a comprehensive overview of existing nanotherapeutic targeting strategies for specific cell types within three of the usual suspects, i.e. the liver, kidney and the vascular system. We discuss the physiological surroundings and relevant pathologies of described tissues as well as the implications for NP-mediated drug delivery. Additionally, successful cell-selective NP concepts using active targeting strategies are assessed. By bringing together both (patho)physiological aspects and concepts for cell-selective NP formulations, we hope to show a novel opportunity for the development of more promising nanotherapeutic devices.

TGF-β signaling in liver metastasis

The presence of liver metastases drastically worsens the prognosis of cancer patients. The liver is the second most prevalent metastatic site in cancer patients, but systemic therapeutic opportunities that target liver metastases are still limited. To aid the discovery of novel treatment options for metastatic liver disease, we provide insight into the cellular and molecular steps required for liver colonization. For successful colonization in the liver, adaptation of tumor cells and surrounding stroma is essential. This includes the formation of a pre-metastatic niche, the creation of a fibrotic and immune suppressive environment, angiogenesis, and adaptation of tumor cells. We illustrate that transforming growth factor β (TGF-β) is a central cytokine in all these processes. At last, we devise that future research should focus on TGF-β inhibitory strategies, especially in combination with immunotherapy. This promising systemic treatment strategy has potential to eliminate distant metastases as the efficacy of immunotherapy will be enhanced.

Targeting Cancer Associated Fibroblasts in Liver Fibrosis and Liver Cancer Using Nanocarriers

Cancer associated fibroblasts (CAF) and the extracellular matrix (ECM) produced by them have been recognized as key players in cancer biology and emerged as important targets for cancer treatment and drug discovery. Apart from their presence in stroma rich tumors, such as biliary, pancreatic and subtypes of hepatocellular cancer (HCC), both CAF and certain ECM components are also present in cancers without an overt intra-tumoral desmoplastic reaction. They support cancer development, growth, metastasis and resistance to chemo- or checkpoint inhibitor therapy by a multitude of mechanisms, including angiogenesis, ECM remodeling and active immunosuppression by secretion of tumor promoting and immune suppressive cytokines, chemokines and growth factors. CAF resemble activated hepatic stellate cells (HSC)/myofibroblasts, expressing α-smooth muscle actin and especially fibroblast activation protein (FAP). Apart from FAP, CAF also upregulate other functional cell surface proteins like platelet-derived growth factor receptor β (PDGFRβ) or the insulin-like growth factor receptor II (IGFRII). Notably, if formulated with adequate size and zeta potential, injected nanoparticles home preferentially to the liver. Several nanoparticular formulations were tested successfully to deliver dugs to activated HSC/myofibroblasts. Thus, surface modified nanocarriers with a cyclic peptide binding to the PDGFRβ or with mannose-6-phosphate binding to the IGFRII, effectively directed drug delivery to activated HSC/CAF in vivo. Even unguided nanohydrogel particles and lipoplexes loaded with siRNA demonstrated a high in vivo uptake and functional siRNA delivery in activated HSC, indicating that liver CAF/HSC are also addressed specifically by well-devised nanocarriers with optimized physicochemical properties. Therefore, CAF have become an attractive target for the development of stroma-based cancer therapies, especially in the liver.

P311, Friend, or Foe of Tissue Fibrosis?

P311 was first identified by the group of Studler et al. (1993) in the developing brain. In healthy, but mainly in pathological tissues, P311 is implicated in cell migration and proliferation. Furthermore, evidence in models of tissue fibrosis points to the colocalization with and the stimulation of transforming growth factor β1 by P311. This review provides a comprehensive overview on P311 and discusses its potential as an anti-fibrotic target.

Liver fibrosis: Direct antifibrotic agents and targeted therapies

Liver fibrosis and in particular cirrhosis are the major causes of morbidity and mortality of patients with chronic liver disease. Their prevention or reversal have become major endpoints in clinical trials with novel liver specific drugs. Remarkable progress has been made with therapies that efficiently address the cause of the underlying liver disease, as in chronic hepatitis B and C. Highly effective antiviral therapy can prevent progression or even induce reversal in the majority of patients, but such treatment remains elusive for the majority of liver patients with advanced alcoholic or nonalcoholic steatohepatitis, genetic or autoimmune liver diseases. Moreover, drugs that would speed up fibrosis reversal are needed for patients with cirrhosis, since even with effective causal therapy reversal is slow or the disease may further progress. Therefore, highly efficient and specific antifibrotic agents are needed that can address advanced fibrosis, i.e., the detrimental downstream result of all chronic liver diseases. This review discusses targeted antifibrotic therapies that address molecules and mechanisms that are central to fibrogenesis or fibrolysis, including strategies that allow targeting of activated hepatic stellate cells and myofibroblasts and other fibrogenic effector cells. Focus is on collagen synthesis, integrins and cells and mechanisms specific including specific downregulation of TGFbeta signaling, major extracellular matrix (ECM) components, ECM-crosslinking, and ECM-receptors such as integrins and discoidin domain receptors, ECM-crosslinking and methods for targeted delivery of small interfering RNA, antisense oligonucleotides and small molecules to increase potency and reduce side effects. With an increased understanding of the biology of the ECM and liver fibrosis and an improved preclinical validation, the translation of these approaches to the clinic is currently ongoing. Application to patients with liver fibrosis and a personalized treatment is tightly linked to the development of noninvasive biomarkers of fibrosis, fibrogenesis and fibrolysis.

Drug targeting to myofibroblasts: Implications for fibrosis and cancer

Myofibroblasts are the key players in extracellular matrix remodeling, a core phenomenon in numerous devastating fibrotic diseases. Not only in organ fibrosis, but also the pivotal role of myofibroblasts in tumor progression, invasion and metastasis has recently been highlighted. Myofibroblast targeting has gained tremendous attention in order to inhibit the progression of incurable fibrotic diseases, or to limit the myofibroblast-induced tumor progression and metastasis. In this review, we outline the origin of myofibroblasts, their general characteristics and functions during fibrosis progression in three major organs: liver, kidneys and lungs as well as in cancer. We will then discuss the state-of-the art drug targeting technologies to myofibroblasts in context of the above-mentioned organs and tumor microenvironment. The overall objective of this review is therefore to advance our understanding in drug targeting to myofibroblasts, and concurrently identify opportunities and challenges for designing new strategies to develop novel diagnostics and therapeutics against fibrosis and cancer.

Hepatic stellate cell-targeted therapy for hepatic fibrosis

Hepatic fibrosis is the ultimate pathological feature of all forms of chronic hepatic damage. There is currently no clinical cure for advanced liver fibrosis. Activation and proliferation of hepatic stellate cells (HSCs) is a key step in the development of liver fibrosis, and therefore, HSCs are target cells for hepatic fibrosis treatment. Targeted delivery of drugs to activated HSCs would increase the drug concentration in the liver at the sites of active fibrogenesis and avoid undesirable systemic effects. Mannose 6-phosphate modified human serum albumin, vitamin A, and hyaluronic acid are three kinds of the most investigated carriers that deliver drugs to the activated HSCs specifically. Conjugation of these carriers with molecules with anti-fibrosis activity such as angiotensin receptor blockers, activin-like kinase 5 inhibitors, Rho-kinase inhibitors, small interfering RNAs, hepatocyte growth factor gene, or nitrogen monoxide can lead to specific distribution and effects in HSCs. This review will focus on these preclinical developments of HSCs-targeted drug conjugates for the treatment of liver fibrosis.

Nanotechnology in Glycomics: Applications in Diagnostics, Therapy, Imaging, and Separation Processes

This review comprehensively covers the most recent achievements (from 2013) in the successful integration of nanomaterials in the field of glycomics. The first part of the paper addresses the beneficial properties of nanomaterials for the construction of biosensors, bioanalytical devices, and protocols for the detection of various analytes, including viruses and whole cells, together with their key characteristics. The second part of the review focuses on the application of nanomaterials integrated with glycans for various biomedical applications, that is, vaccines against viral and bacterial infections and cancer cells, as therapeutic agents, for in vivo imaging and nuclear magnetic resonance imaging, and for selective drug delivery. The final part of the review describes various ways in which glycan enrichment can be effectively done using nanomaterials, molecularly imprinted polymers with polymer thickness controlled at the nanoscale, with a subsequent analysis of glycans by mass spectrometry. A short section describing an active glycoprofiling by microengines (microrockets) is covered as well.

Impact of TGF-β inhibition during acute exercise on Achilles tendon extracellular matrix

The purpose of this study was to evaluate the role of TGF-β₁ in regulating tendon extracellular matrix after acute exercise. Wistar rats exercised (n = 15) on a treadmill for four consecutive days (60 min/day) or maintained normal cage activity. After each exercise bout, the peritendinous space of each Achilles tendon was injected with a TGF-β₁ receptor inhibitor or sham. Independent of group, tendons injected with inhibitor exhibited ~50% lower Smad 3 (Ser^423/425) (P < 0.05) and 2.5-fold greater ERK1/2 phosphorylation (P < 0.05) when compared with sham (P < 0.05). Injection of the inhibitor did not alter collagen content in either group (P > 0.05). In exercised rats, hydroxylyslpyridinoline content and collagen III expression were lower (P < 0.05) in tendons injected with inhibitor when compared with sham. In nonexercised rats, collagen I and lysyl oxidase (LOX) expression was lower (P < 0.05) in tendons injected with inhibitor when compared with sham. Decorin expression was not altered by inhibitor in either group (P > 0.05). On the basis of evaluation of hematoxylin and eosin (H&E) stained cross sections, cell numbers were not altered by inhibitor treatment in either group (P > 0.05). Evaluation of H&E-stained sections revealed no effect of inhibitor on collagen fibril morphology. In contrast, scores for regional variation in cellularity decreased in exercised rats (P < 0.05). No differences in fiber arrangement, structure, and nuclei form were noted in either group (P > 0.05). Our findings suggest that TGF-β₁ signaling is necessary for the regulation of tendon cross-link formation, as well as collagen and LOX gene transcription in an exercise-dependent manner.

Clinical Advancements in the Targeted Therapies against Liver Fibrosis

Hepatic fibrosis, characterized by excessive accumulation of extracellular matrix (ECM) proteins leading to liver dysfunction, is a growing cause of mortality worldwide. Hepatocellular damage owing to liver injury leads to the release of profibrotic factors from infiltrating inflammatory cells that results in the activation of hepatic stellate cells (HSCs). Upon activation, HSCs undergo characteristic morphological and functional changes and are transformed into proliferative and contractile ECM-producing myofibroblasts. Over recent years, a number of therapeutic strategies have been developed to inhibit hepatocyte apoptosis, inflammatory responses, and HSCs proliferation and activation. Preclinical studies have yielded numerous targets for the development of antifibrotic therapies, some of which have entered clinical trials and showed improved therapeutic efficacy and desirable safety profiles. Furthermore, advancements have been made in the development of noninvasive markers and techniques for the accurate disease assessment and therapy responses. Here, we focus on the clinical developments attained in the field of targeted antifibrotics for the treatment of liver fibrosis, for example, small molecule drugs, antibodies, and targeted drug conjugate. We further briefly highlight different noninvasive diagnostic technologies and will provide an overview about different therapeutic targets, clinical trials, endpoints, and translational efforts that have been made to halt or reverse the progression of liver fibrosis.

Glucocorticoids Have Opposing Effects on Liver Fibrosis in Hepatic Stellate and Immune Cells

Liver fibrosis is a reversible wound-healing process that is protective in the short term, but prolonged fibrotic responses lead to excessive accumulation of extracellular matrix components that suppresses hepatocyte regeneration, resulting in permanent liver damage. Upon liver damage, nonparenchymal cells including immune cells and hepatic stellate cells (HSCs) have crucial roles in the progression and regression of liver fibrosis. Here, we report differential roles of the glucocorticoid receptor (GR), acting in immune cells and HSCs, in liver fibrosis. In the carbon tetrachloride hepatotoxin-induced fibrosis model, both steroidal and nonsteroidal GR ligands suppressed expression of fibrotic genes and decreased extracellular matrix deposition but also inhibited immune cell infiltration and exacerbated liver injury. These counteracting effects of GR ligands were dissociated in mice with conditional GR knockout in immune cells (GR(LysM)) or HSC (GR(hGFAP)): the impacts of dexamethasone on immune cell infiltration and liver injury were totally blunted in GR(LysM) mice, whereas the suppression of fibrotic gene expression was diminished in GR(hGFAP) mice. The effect of GR activation in HSC was further confirmed in the LX-2 HSC cell line, in which antifibrotic effects were mediated by GR ligand inhibition of Sma and mad-related protein 3 (SMAD3) expression. We conclude that GR has differential roles in immune cells and HSCs to modulate liver injury and liver fibrosis. Specific activation of HSC-GR without alteration of GR activity in immune cells provides a potential therapeutic approach to treatment of hepatic fibrosis.

Alk5 inhibition increases delivery of macromolecular and protein-bound contrast agents to tumors

Limited transendothelial permeability across tumor microvessels represents a significant bottleneck in the development of tumor-specific diagnostic agents and theranostic drugs. Here, we show an approach to increase transendothelial permeability of macromolecular and nanoparticle-based contrast agents via inhibition of the type I TGF-β receptor, activin-like kinase 5 (Alk5), in tumors. Alk5 inhibition significantly increased tumor contrast agent delivery and enhancement on imaging studies, while healthy organs remained relatively unaffected. Imaging data correlated with significantly decreased tumor interstitial fluid pressure, while tumor vascular density remained unchanged. This immediately clinically translatable concept involving Alk5 inhibitor pretreatment prior to an imaging study could be leveraged for improved tumor delivery of macromolecular and nanoparticle-based imaging probes and, thereby, facilitate development of more sensitive imaging tests for cancer diagnosis, enhanced tumor characterization, and personalized, image-guided therapies.

Potential Use of Biological Proteins for Liver Failure Therapy

Biological proteins have unlimited potential for use as pharmaceutical products due to their various biological activities, which include non-toxicity, biocompatibility, and biodegradability. Recent scientific advances allow for the development of novel innovative protein-based products that draw on the quality of their innate biological activities. Some of them hold promising potential for novel therapeutic agents/devices for addressing hepatic diseases such as hepatitis, fibrosis, and hepatocarcinomas. This review attempts to provide an overview of the development of protein-based products that take advantage of their biological activity for medication, and discusses possibilities for the therapeutic potential of protein-based products produced through different approaches to specifically target the liver (or hepatic cells: hepatocytes, hepatic stellate cells, liver sinusoidal endothelial cells, and Kupffer cells) in the treatment of hepatic diseases.

Diverse origins of the myofibroblast—implications for kidney fibrosis

Fibrosis is the common end point of chronic kidney disease. The persistent production of inflammatory cytokines and growth factors leads to an ongoing process of extracellular matrix production that eventually disrupts the normal functioning of the organ. During fibrosis, the myofibroblast is commonly regarded as the predominant effector cell. Accumulating evidence has demonstrated a diverse origin of myofibroblasts in kidney fibrosis. Proposed major contributors of myofibroblasts include bone marrow-derived fibroblasts, tubular epithelial cells, endothelial cells, pericytes and interstitial fibroblasts; the published data, however, have not yet clearly defined the relative contribution of these different cellular sources. Myofibroblasts have been reported to originate from various sources, irrespective of the nature of the initial damage responsible for the induction of kidney fibrosis. Here, we review the possible relevance of the diversity of myofibroblast progenitors in kidney fibrosis and the implications for the development of novel therapeutic approaches. Specifically, we discuss the current status of preclinical and clinical antifibrotic therapy and describe targeting strategies that might help support resident and circulating cells to maintain or regain their original functional differentiation state. Such strategies might help these cells resist their transition to a myofibroblast phenotype to prevent, or even reverse, the fibrotic state.

Angiotensin II stimulates canonical TGF-β signaling pathway through angiotensin type 1 receptor to induce granulation tissue contraction

Hypertrophic scar contraction (HSc) is caused by granulation tissue contraction propagated by myofibroblast and fibroblast migration and contractility. Identifying the stimulants that promote migration and contractility is key to mitigating HSc. Angiotensin II (AngII) promotes migration and contractility of heart, liver, and lung fibroblasts; thus, we investigated the mechanisms of AngII in HSc. Human scar and unwounded dermis were immunostained for AngII receptors angiotensin type 1 receptor (AT1 receptor) and angiotensin type 2 receptor (AT2 receptor) and analyzed for AT1 receptor expression using Western blot. In vitro assays of fibroblast contraction and migration under AngII stimulation were conducted with AT1 receptor, AT2 receptor, p38, Jun N-terminal kinase (JNK), MEK, and activin receptor-like kinase 5 (ALK5) antagonism. Excisional wounds were created on AT1 receptor KO and wild-type (WT) mice treated with AngII ± losartan and ALK5 and JNK inhibitors SB-431542 and SP-600125, respectively. Granulation tissue contraction was quantified, and wounds were analyzed by immunohistochemistry. AT1 receptor expression was increased in scar, but not unwounded tissue. AngII induced fibroblast contraction and migration through AT1 receptor. Cell migration was inhibited by ALK5 and JNK, but not p38 or MEK blockade. In vivo experiments determined that absence of AT1 receptor and chemical AT1 receptor antagonism diminished granulation tissue contraction while AngII stimulated wound contraction. AngII granulation tissue contraction was diminished by ALK5 inhibition, but not JNK. AngII promotes granulation tissue contraction through AT1 receptor and downstream canonical transforming growth factor (TGF)-β signaling pathway, ALK5. Further understanding the pathogenesis of HSc as an integrated signaling mechanism could improve our approach to establishing effective therapeutic interventions.

KEY MESSAGE

AT1 receptor expression is increased in scar tissue compared to unwounded tissue. AngII stimulates expression of proteins that confer cell migration and contraction. AngII stimulates fibroblast migration and contraction through AT1 receptor, ALK5, and JNK. AngII-stimulated in vivo granulation tissue contraction is AT1 receptor and ALK5 dependent.