The role of matrix stiffness in hepatic stellate cell activation and liver fibrosis

Engineering 3D Hydrogels for Personalized In Vitro Human Tissue Models

There is a growing interest in engineering hydrogels for 3D tissue and disease models. The major motivation is to better mimic the physiological microenvironment of the disease and human condition. 3D tissue models derived from patients' own cells can potentially revolutionize the way treatment and diagnostic alternatives are developed. This requires development of tissue mimetic hydrogels with user defined and tunable properties. In this review article, a recent summary of 3D hydrogel platforms for in vitro tissue and disease modeling is given. Hydrogel design considerations and available hydrogel systems are summarized, followed by the types of currently available hydrogel models, such as bulk hydrogels, porous scaffolds, fibrous scaffolds, hydrogel microspheres, hydrogel sandwich systems, microwells, and 3D bioprinted constructs. Although hydrogels are utilized for a wide range of tissue models, this article focuses on liver and cancer models. This article also provides a detailed section on current challenges and future perspectives of hydrogel-based tissue models.

Protective effects of Ampelopsis brevipedunculata against in vitro hepatic stellate cells system and thioacetamide-induced liver fibrosis rat model

CONTEXT

Ampelopsis brevipedunculata Maxim (Vitaceae) is a traditional medicinal herb used for treating liver disorders.

OBJECTIVE

The hepatoprotective effects of A. brevipedunculata ethanol extract (ABE) was investigated in experimental models of fibrosis.

MATERIALS AND METHODS

Hepatic stellate cells (HSCs) system in vitro and thioacetamide (TAA)-induced liver fibrosis rat model in vivo were used. Sprague-Dawley rats were divided into five groups of eight each (control, TAA, TAA with ABE 10 mg/kg, ABE 100 mg/kg and silymarin 50 mg/kg groups, respectively). Fibrosis was induced except to the control group by TAA (200 mg/kg, i.p.) twice per week for 13 weeks. ABE and silymarin was administered orally six times per week from the 7th week to the 13th week.

RESULTS

In HSC-T6 cells, ABE (0.1 mg/mL) and silymarin (0.05 mg/mL) significantly (p < 0.01) induced apoptosis (12.94 ± 5.72% and 14.9 ± 3.8%, respectively) compared with control group (7.51 ± 1.26%). The expression of fibrosis related genes (TGF-β, α-SMA and Col1A1) in HSC-T6 cells were significantly (p < 0.01) downregulated in ABE-treated groups compared with control group. In in vivo studies, ABE (10 and 100 mg/kg) treatment ameliorated the altered levels of serum biomarkers significantly (p < 0.01 and p < 0.001) in TAA-induced groups. Further, ABE (10 and 100 mg/kg) significantly (p < 0.01) attenuated the altered histopathological findings, glutathione content and the accumulation of hydroxyproline.

CONCLUSION

These results collectively indicate that ABE can potentially be developed as a therapeutic agent in the treatment of hepatic fibrosis.

Hepatoprotective effects of Yulangsan flavone against carbon tetrachloride (CCl4)-induced hepatic fibrosis in rats

BACKGROUND

Yulangsan flavone (YLSF) was extracted from the root of Millettia pulchra Kurz var-laxior (Dunn) Z. Wei, which has been widely used for liver disease treatment in the Guangxi province of China.

HYPOTHESIS/PURPOSE

The study was conducted to demonstrate the hepatoprotective effects of YLSF against CCl₄-induced hepatic fibrosis in rats, meanwhile revealing the potential mechanism.

STUDY DESIGN

Sprague-Dawley (SD) rats of both sexes were randomly divided into two groups: hepatic fibrosis group and normal control (NC) group. The rats in the hepatic fibrosis group were given 1 ml/kg 50% CCl₄ (1:1 mixed with peanut oil), while those in the NC group were given 1 ml/kg normal saline (NS), both via intragastric administration. The established experimental rat model from the hepatic fibrosis group was confirmed by pathological inspection and randomly divided into five groups: three YLSF groups (20 mg/kg, 40 mg/kg and 80 mg/kg), a colchicine group (0.20 mg/kg) and a model group (10 ml/kg NS). All rats were treated with corresponding drugs or NS once a day for four consecutive weeks. Twenty-four hours after the last administration, blood serum and hepatic tissue were collected.

METHODS

The activities of ALT and AST in the serum and the levels of SOD, MDA, GSH and GSH-Px in hepatic tissue were analysed, the indexes of liver, spleen and thymus were counted, the degree of hepatic injury was examined using HE and Masson staining, and the mRNA expression of Col-1, TIMP-1 and TGF-β1 in hepatic tissues was detected.

RESULTS

Compared with the model group, experimental results showed that YLSF and colchicine could reduce the levels of AST, ALT and MDA, increase the levels of SOD, GSH and GSH-Px, enhance rat survivability, decrease the liver, spleen and thymus index, significantly lessen collagen deposition and tissue damage and down-regulate the mRNA expression of Col-1, TIMP-1 and TGF-β1.

CONCLUSIONS

Our findings confirm that YLSF has a certain curative effect on rats with liver fibrosis induced by CCl₄, and its mechanism may include attenuating free radicals, inhibiting lipid peroxidation and accelerating extracellular matrix degradation by down-regulating expression of related genes.

Ethanol extracts collected from the Styela clava tunic alleviate hepatic injury induced by carbon tetrachloride (CCl4) through inhibition of hepatic apoptosis, inflammation, and fibrosis

The Styela clava tunic (SCT) is known as a good raw material for preparing anti-inflammatory compounds, wound healing films, guided bone regeneration, and food additives. To investigate whether ethanol extracts of the SCT (EtSCT) could protect against hepatic injury induced by carbon tetrachloride (CCl₄) in ICR mice, alterations in serum biochemical indicators, histopathology, hepatic apoptosis, inflammation, and fibrosis were observed in ICR mice pretreated with EtSCT for 5 days before CCl₄ injection. EtSCT contained 15.6 mg/g of flavonoid and 37.5 mg/g phenolic contents with high 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (93.3%) and metal chelation activity (46.5%). The EtSCT+CCl₄-treated groups showed decreased levels of ALT, LDH, and AST, indicating toxicity and a necrotic area in the liver, while the level of ALP remained constant. The formation of active caspase-3 and enhancement of Bax/Bcl-2 expression was effectively inhibited in the EtSCT+CCl₄-treated groups. Furthermore, the levels of pro- and anti-inflammatory cytokines and the phosphorylation of p38 in the TNF-α downstream signaling pathway rapidly recovered in the EtSCT+CCl₄-treated groups. The EtSCT+CCl₄-treated groups showed a significant decrease in hepatic fibrosis markers including collagen accumulation, MMP-2 expression, TGF-β1 concentration, and phosphorylation of Smad2/3. Moreover, a significant decline in malondialdehyde (MDA) concentration and enhancement of superoxide dismutase (SOD) expression were observed in the EtSCT+CCl₄-treated groups. Taken together, these results indicate that EtSCT can protect against hepatic injury induced by CCl₄-derived reactive intermediates through the suppression of hepatic apoptosis, inflammation, and fibrosis.

Current progress in understanding the molecular pathogenesis of burn scar contracture

Abnormal wound healing is likely to induce scar formation, leading to dysfunction, deformity, and psychological trauma in burn patients. Despite the advancement of medical care treatment, scar contracture in burn patients remains a challenge. Myofibroblasts play a key role in scar contracture. It has been demonstrated that myofibroblasts, as well as inflammatory cells, fibroblasts, endothelial cells, and epithelial cells, secrete transforming growth factor-β1 (TGF-β1) and other cytokines, which can promote persistent myofibroblast activation via a positive regulation loop. In addition to the cellular contribution, the microenvironments, including the mechanical tension and integrin family, are also involved in scar contracture. Most recently, eukaryotic initiation factor 6 (eIF6), an upstream regulator of TGF-β1, has been demonstrated to be involved in myofibroblast differentiation and contraction in both in vitro fibroblast-populated collagen lattice (FPCL) and in vivo external mechanical stretch models. Moreover, the data showed that P311 could induce the transdifferentiation of epidermal stem cells to myofibroblasts by upregulating TGF-β1 expression, which mediated myofibroblast contraction. In this review, we briefly described the most current progress on the biological function of myofibroblasts in scar contracture and subsequently summarized the molecular events that initiated contracture. This would help us better understand the molecular basis of scar contracture as well as to find a comprehensive strategy for preventing/managing scar contracture.

Melatonin protects against lipid-induced mitochondrial dysfunction in hepatocytes and inhibits stellate cell activation during hepatic fibrosis in mice

Lipid generates reactive oxygen species (ROS) in consequence to mitochondrial fission followed by inflammation in propagating hepatic fibrosis. The interaction of SIRT1/Mitofusin2 is critical for maintaining mitochondrial integrity and functioning, which is disrupted upon excess lipid infiltration during the progression of steatohepatitis. The complex interplay between hepatic stellate cells and steatotic hepatocytes is critically regulated by extracellular factors including increased circulating free fatty acids during fibrogenesis. Melatonin, a potent antioxidant, protects against lipid-mediated mitochondrial ROS generation. Lipotoxicity induces disruption of SIRT1 and Mitofusin2 interaction leading to mitochondrial morphological disintegration in hepatocytes. Further, fragmented mitochondria leads to mitochondrial permeability transition pore opening, cell cycle arrest and apoptosis and melatonin protects against all these lipotoxicity-mediated dysfunctions. These impaired mitochondrial dynamics also enhances the cellular glycolytic flux and reduces mitochondrial oxygen consumption rate that potentiates ROS production. High glycolytic flux generates metabolically unfavorable milieu in hepatocytes leading to inflammation, which is abrogated by melatonin. The melatonin-mediated protection against mitochondrial dysfunction was also observed in high-fat diet (HFD)-fed mice through restoration of enzymatic activities associated with respiratory chain and TCA cycle. Subsequently, melatonin reduces hepatic fat deposition and inflammation in HFD-fed mice. Thus, melatonin disrupts the interaction between steatotic hepatocyte and stellate cells, leading to the activation of the latter to abrogate collagen deposition. Altogether, the results of the current study document that the pharmacological intervention with low dose of melatonin could abrogate lipotoxicity-mediated hepatic stellate cell activation and prevent the fibrosis progression.

Mathematical model of chronic pancreatitis

Chronic pancreatitis (CP) is a progressive inflammatory disease of the pancreas, leading to its fibrotic destruction. There are currently no drugs that can stop or slow the progression of the disease. The etiology of the disease is multifactorial, whereas recurrent attacks of acute pancreatitis are thought to precede the development of CP. A better understanding of the pathology of CP is needed to facilitate improved diagnosis and treatment strategies for this disease. The present paper develops a mathematical model of CP based on a dynamic network that includes macrophages, pancreatic stellate cells, and prominent cytokines that are present at high levels in the CP microenvironment. The model is represented by a system of partial differential equations. The model is used to explore in silico potential drugs that could slow the progression of the disease, for example infliximab (anti-TNF-[Formula: see text]) and tocilizumab or siltuximab (anti-IL-6/IL-6R).

Stiffness-Controlled Thermoresponsive Hydrogels for Cell Harvesting with Sustained Mechanical Memory

Most mechanobiological investigations focused on in situ mechanical regulation of cells on stiffness-controlled substrates with few downstream applications, as it is still challenging to harvest and expand mechanically primed cells by enzymatic digestion (e.g., trypsin) without interrupting cellular mechanical memory between passages. This study develops thermoresponsive hydrogels with controllable stiffness to generate mechanically primed cells with intact mechanical memory for augmented wound healing. No significant cellular property alteration of the fibroblasts primed on thermoresponsive hydrogels with varied stiffness has been observed through thermoresponsive harvesting. When reseeding the harvested cells for further evaluation, softer hydrogels are proven to better sustain the mechanical priming effects compared to rigid tissue culture plate, which indicates that both the stiffness-controlled substrate and thermoresponsive harvesting are required to sustain cellular mechanical memory between passages. Moreover, epigenetics analysis reveals that thermoresponsive harvesting could reduce the rearrangement and loss of chromatin proteins compared to that of trypsinization. In vivo wound healing using mechanically primed fibroblasts shows featured epithelium and sebaceous glands, which indicates augmented skin recovery compared with trypsinized fibroblasts. Thus, the thermoresponsive hydrogel-based cell harvesting system offers a powerful tool to investigate mechanobiology between cell passages and produces abundant cells with tailored mechanical priming properties for cell-based applications.

Mechanical Cell-Cell Communication in Fibrous Networks: The Importance of Network Geometry

Cells contracting in extracellular matrix (ECM) can transmit stress over long distances, communicating their position and orientation to cells many tens of micrometres away. Such phenomena are not observed when cells are seeded on substrates with linear elastic properties, such as polyacrylamide (PA) gel. The ability for fibrous substrates to support far reaching stress and strain fields has implications for many physiological processes, while the mechanical properties of ECM are central to several pathological processes, including tumour invasion and fibrosis. Theoretical models have investigated the properties of ECM in a variety of network geometries. However, the effects of network architecture on mechanical cell-cell communication have received little attention. This work investigates the effects of geometry on network mechanics, and thus the ability for cells to communicate mechanically through different networks. Cell-derived displacement fields are quantified for various network geometries while controlling for network topology, cross-link density and micromechanical properties. We find that the heterogeneity of response, fibre alignment, and substrate displacement fields are sensitive to network choice. Further, we show that certain geometries support mechanical communication over longer distances than others. As such, we predict that the choice of network geometry is important in fundamental modelling of cell-cell interactions in fibrous substrates, as well as in experimental settings, where mechanical signalling at the cellular scale plays an important role. This work thus informs the construction of theoretical models for substrate mechanics and experimental explorations of mechanical cell-cell communication.

SECs (Sinusoidal Endothelial Cells), Liver Microenvironment, and Fibrosis

Liver fibrosis is a wound-healing response to chronic liver injury such as alcoholic/nonalcoholic fatty liver disease and viral hepatitis with no FDA-approved treatments. Liver fibrosis results in a continual accumulation of extracellular matrix (ECM) proteins and paves the way for replacement of parenchyma with nonfunctional scar tissue. The fibrotic condition results in drastic changes in the local mechanical, chemical, and biological microenvironment of the tissue. Liver parenchyma is supported by an efficient network of vasculature lined by liver sinusoidal endothelial cells (LSECs). These nonparenchymal cells are highly specialized resident endothelial cell type with characteristic morphological and functional features. Alterations in LSECs phenotype including lack of LSEC fenestration, capillarization, and formation of an organized basement membrane have been shown to precede fibrosis and promote hepatic stellate cell activation. Here, we review the interplay of LSECs with the dynamic changes in the fibrotic liver microenvironment such as matrix rigidity, altered ECM protein profile, and cell-cell interactions to provide insight into the pivotal changes in LSEC physiology and the extent to which it mediates the progression of liver fibrosis. Establishing the molecular aspects of LSECs in the light of fibrotic microenvironment is valuable towards development of novel therapeutic and diagnostic targets of liver fibrosis.

NLRC5 Mediates IL-6 and IL-1β Secretion in LX-2 Cells and Modulated by the NF-κB/Smad3 Pathway

Recent data have shown that nucleotide-binding domain leucine-rich repeat proteins (NLRs), a class of innate immune receptors that respond to pathogen attack or cellular stress, have gained increasing attention. NLRC5 (NLR family, CARD domain containing 5) is the largest member of the NLR family, which has recently been identified as a critical regulator of immune responses. Until recently, the function of NLRC5 has been a matter of debate. In this study, we explore the role of NLRC5 in cytokine secretion and the role of the nuclear factor-κB (NF-κB) signaling pathway in tumor necrosis factor-alpha (TNF-α)-induced NLRC5 expression in LX-2 cells. We demonstrated that overexpression of NLRC5 results in an upregulation of IL-6 and IL-1β secretion. On the other hand, knockdown of NLRC5 by transfecting siRNA decreased IL-6 and IL-1β secretion in LX-2 cells. Meanwhile, the results showed that pyrrolidine dithiocarbamate (PDTC) (a specific inhibitor of the NF-κB signaling pathway) inhibited NLRC5 expression and NLRC5 silencing could increase the expression levels of p65 in cell nucleus accompanied with upregulated phosphorylation of Smad3 protein levels in response to TNF-α. These results indicated that NLRC5 plays a significant role in TNF-α-enhanced cytokine (IL-6 and IL-1β) secretion of LX-2 cells and the NF-κB/Smad3 signal pathway is involved in its induction of expression.

Hepatic sinusoids in liver injury, inflammation, and fibrosis: new pathophysiological insights

Changes of hepatic sinusoids are crucial in the pathogenesis of liver cirrhosis and portal hypertension. Liver injury leads to distinct morphological abnormalities such as loss of sinusoidal fenestration, vasoconstriction, and angiogenesis as well as molecular changes. Communication between the two key cells in this hepatic microenvironment-hepatic stellate cells (HSC) and sinusoidal endothelial cells (SEC)-has been studied for many years and several canonical pathways have been elucidated, such as decreased eNOS activity or increased PDGF and TGF-β production leading to activation and migration of HSC. In recent studies, alternative pathways of intercellular communication in liver diseases have been described such as cell-derived extracellular vesicles called exosomes, which deliver cell compounds to their target cells. Moreover, such extracellular vesicles may link injury to inflammation in alcoholic hepatitis. While inflammation leading to liver fibrosis has been studied in detail, in some circumstances pathways other than the known canonical inflammatory pathways may contribute to hepatic fibrogenesis. For example, in congestive hepatopathy, sinusoidal dilatation and fibrosis have been shown to be mediated by non-inflammatory mechanisms and associated with sinusoidal thrombi. A recently developed murine model further enables experimental studies of this disease entity. Increasing knowledge about these alternative disease pathways in liver injury, inflammation, and fibrosis may reveal possible target molecules for future therapies. This article builds upon a seminar given at the recent 3rd JSGE International Topic Conference in Sendai, Japan, and reviews the areas outlined above.

Versican: a novel modulator of hepatic fibrosis

Little is known about the deposition and turnover of proteoglycans in liver fibrosis, despite their abundance in the extracellular matrix. Versican plays diverse roles in modulating cell behavior in other fibroproliferative diseases, but remains poorly described in the liver. Hepatic fibrosis was induced by carbon tetrachloride treatment of C57BL/6 mice over 4 weeks followed by recovery over a 28-day period. Primary mouse hepatic stellate cells (HSCs) were activated in culture and versican was transiently knocked down in human (LX2) and mouse HSCs. Expression of versican, A Disintegrin-like and Metalloproteinase with Thrombospondin-1 motifs (ADAMTS)-1, -4, -5, -8, -9, -15, and -20, and markers of fibrogenesis were studied using immunohistochemistry, real-time quantitative PCR, and western blotting. Immunohistochemistry showed increased expression of versican in cirrhotic human livers and the mouse model of fibrosis. Carbon tetrachloride treatment led to significant increases in versican expression and the proteoglycanases ADAMTS-5, -9, -15, and -20, alongside TNF-α, α-smooth muscle actin (α-SMA), collagen-1, and TGF-β expression. During recovery, expression of many of these genes returned to control levels. However, expression of ADAMTS-5, -8, -9, and -15 showed delayed increases in expression at 28 days of recovery, which corresponded with decreases in versican V0 and V1 cleavage products (G1-DPEAAE(1401) and G1-DPEAAE(441)). Activation of primary HSCs in vitro significantly increased versican, α-SMA, and collagen-1 expression. Transient knockdown of versican in HSCs led to decreases in markers of fibrogenesis and reduced cell proliferation, without inducing apoptosis. Versican expression increases during HSC activation and liver fibrosis, and proteolytic processing occurs during the resolution of fibrosis. Knockdown studies in vitro suggest a possible role of versican in modulating hepatic fibrogenesis.

Protective Effect of Gallotannin-Enriched Extract Isolated from Galla Rhois against CCl₄-Induced Hepatotoxicity in ICR Mice

To investigate the toxicity, protective effects, and action mechanism of gallotannin-enriched extracts isolated from Galla Rhois (GEGR) against carbon tetrachloride (CCl₄)-induced hepatotoxicity in Institute for Cancer Research (ICR) mice, alterations in serum biochemical indicators, histopathological structure, antioxidative status, hepatic apoptosis-related proteins, and liver fibrosis regulating factors were measured in mice pretreated with GEGR for five days before CCl₄ injection. The GEGR/CCl₄ treated group showed decreased levels of three serum marker enzymes (ALP, AST, and ALT) representing liver toxicity, although LDH levels remained constant. Necrotic area indicating hepatic cell death significantly inhibited, while malondialdehyde (MDA) concentration and superoxide dismutase (SOD) expression were dramatically recovered in the GEGR preadministrated group. In mechanism analyses of GEGR, the formation of active caspase-3 and enhancement of Bax/Bcl-2 expression was effectively inhibited in the GEGR/CCl₄ treated group. The level of pro-inflammatory cytokines, TNF-α and IL-6, as well as the phosphorylation of p38 and JNK in the TNF-α downstream signaling pathway was rapidly recovered in the GEGR/CCl₄ treated group, while anti-inflammatory cytokine (IL-10) increased slightly in the same group. Furthermore, the GEGR/CCl₄ treated group showed a significant decrease in collagen accumulation results from alleviation of MMP-2 expression, TGF-β1 secretion and the phosphorylation of Smad2/3. Taken together, these results suggest that GEGR may induce remarkable protective effects against hepatic injury induced by CCl₄ treatment through upregulation of the anti-inflammatory and antioxidant system.

Emerging therapeutic targets for the treatment of hepatic fibrosis

Fibrosis represents a response to chronic injury, aimed at maintaining organ integrity. Hepatic fibrosis is mainly related to chronic viral hepatitis B or C (HBV or HCV), alcoholic and nonalcoholic steatohepatitis (NASH), and biliary diseases. A deep understanding of the cellular and molecular mechanisms underlying liver fibrosis has enabled the development of 'pathogenetic tailored' therapeutic interventions. However, effective drugs to prevent or revert hepatic fibrosis are still lacking. In this review, we discuss the cellular populations and the molecular pathways involved in liver fibrogenesis as well as the novel approaches currently being tested in clinical trials.

Regulation of matrix metalloproteinase-1 and alpha-smooth muscle actin expression by interleukin-1 alpha and tumour necrosis factor alpha in hepatic stellate cells

Hepatic stellate cells (HSCs) are key players in liver fibrosis and regeneration via collagen degradation and synthesis. These phenomena involve inflammatory cytokines released from non-parenchymal liver cells such as Kupffer cells. Although the effects of individual cytokines on many cell types have been investigated in various conditions, such as inflammation and tissue fibrosis, investigating the effect of combined cytokines would further our understanding of the regulatory mechanisms in tissue fibrosis. Here, we report the effect of multiple cytokine combinations on primary HSCs. We first examined the effect of individual cytokines and then the simultaneous exposure of different cytokines, including interleukin-6 (IL-6), IL-1 alpha (IL-1α), platelet-derived growth factor (PDGF), tumour necrosis factor-alpha (TNF-α) and transforming growth factor-beta (TGF-β), on matrix metalloproteinase-1 (MMP1) gene expression in primary HSCs. We observed that the combination of all five cytokines induced higher levels of MMP1 gene expression. Of these cytokines, TNF-α and IL-1α were found to be the key cytokines for not only inducing MMP1 expression, but also increasing α-smooth muscle actin gene expression. In conclusion, the combined treatment of TNF-α and IL-1α on HSCs had an enhanced effect on the expression of the fibrotic genes, MMP1 and α-smooth muscle actin, so appears to be an important regulator for tissue regeneration. This finding suggests that stimulation with combined anti-fibrotic cytokines is a potential approach in the development of a novel therapy for the recovery of liver fibrosis.

Caspase-3/7-mediated Cleavage of β2-spectrin is Required for Acetaminophen-induced Liver Damage

The ubiquitously expressed β2-spectrin (β2SP, SPTBN1) is the most common non-erythrocytic member of the β-spectrin gene family. Loss of β2-spectrin leads to defects in liver development, and its haploinsufficiency spontaneously leads to chronic liver disease and the eventual development of hepatocellular cancer. However, the specific role of β2-spectrin in liver homeostasis remains to be elucidated. Here, we reported that β2-spectrin was cleaved by caspase-3/7 upon treatment with acetaminophen which is the main cause of acute liver injury. Blockage of β2-spectrin cleavage robustly attenuated β2-spectrin-specific functions, including regulation of the cell cycle, apoptosis, and transcription. Cleaved fragments of β2-spectrin were physiologically active, and the N- and C-terminal fragments retained discrete interaction partners and activity in transcriptional regulation and apoptosis, respectively. Cleavage of β2-spectrin facilitated the redistribution of the resulting fragments under conditions of liver damage induced by acetaminophen. In contrast, downregulation of β2-spectrin led to resistance to acetaminophen-induced cytotoxicity, and its insufficiency in the liver promoted suppression of acetaminophen-induced liver damage and enhancement of liver regeneration.

CONCLUSIONS

β2-Spectrin, a TGF-β mediator and signaling molecule, is cleaved and activated by caspase-3/7, consequently enhancing apoptosis and transcriptional control to determine cell fate upon liver damage. These findings have extended our knowledge on the spectrum of β2-spectrin functions from a scaffolding protein to a target and transmitter of TGF-β in liver damage.

Hepatic applications of endoscopic ultrasound: Current status and future directions

The diagnosis and staging of various gastrointestinal malignancies have been made possible with the use of endoscopic ultrasound, which is a relatively safe procedure. The field of endoscopic ultrasound is fast expanding due to advancements in therapeutic endoscopic ultrasound. Though various studies have established its role in gastrointestinal malignancies and pancreatic conditions, its potential in the field of hepatic lesions still remains vastly untapped. In this paper the authors attempt to review important and landmark trials, case series and case studies involving hepatic applications of endoscopic ultrasound, thus not only providing an overview of utilization of endoscopic ultrasound in various liver conditions but also speculating its future role.

Inhibition of IRF3 expression reduces TGF-β1-induced proliferation of hepatic stellate cells

Therapeutic management of liver fibrosis remains an unresolved clinical problem. Activation of hepatic stellate cell (HSC) is a pivotal event in the progression of liver fibrosis. Recent reports have showed that inhibition of activated HSC proliferation contributes to the reversal of liver fibrosis. Interferon regulatory factor 3 (IRF3), one member of the interferon regulatory factor (IRF) family, is recently proven to be a critical modulator in cardiac fibrosis. And accumulating evidence demonstrated that IRF3 plays a crucial role in liver diseases, such as hepatic steatosis, liver inflammation, and alcoholic liver injury. However, the understanding of the function of IRF3 in liver fibrosis remains limited. Our results identified the role of IRF3 in regulating human HSC (LX-2 cell) cell proliferation and apoptosis. The present study indicated that the expression of IRF3 was significantly increased in HSCs in response to TGF-β1 stimulation. Moreover, a stable and unlimited source of human HSC, the LX-2 cell line, transfected with IRF3-siRNA significantly decreases the expression level of type I collagen (Col1a1) and α-smooth muscle actin (α-SMA) in activated LX-2 cells. On the contrary, overexpression of IRF3 gives rise to an upregulation of Col1a1 and α-SMA in LX-2 cells, and further promoted HSC proliferation. Moreover, the inhibition of IRF3 significantly suppressed TGF-β1-induced HSC proliferation and increased its apoptosis. Of note, the present study indicated IRF3 may regulate LX-2 cell proliferation by via AKT signaling pathway. In summary, these observations suggest IRF3 may function as a novel regulator to modulate TGF-β1-induced LX-2 proliferation, at least in part, via AKT signaling pathway.

NLRC5 regulates TGF-β1-induced proliferation and activation of hepatic stellate cells during hepatic fibrosis

Therapeutic management of liver fibrosis remains an unsolved clinical problem. Hepatic accumulation of extracellular matrix, mainly collagen, is mediated by the production of transforming growth factor-β1 (TGF-β1) in hepatic stellate cells (HSCs). NLRC5, the largest member of the NLR protein family, has recently been identified as a critical regulator of immune responses. Novel evidence shows that NLRC5 is an important negative modulator of inflammatory pathways. Herein, we determined the regulation of NLRC5 in liver fibrogenesis and its underlying mechanisms. We have shown that NLRC5 was upregulated in human liver fibrotic tissues. Overexpression of NLRC5 resulted in an upregulation of collagen 1 and α-smooth muscle actin expression in HSC LX-2 cells, which was inhibited by NLRC5 knockdown with its siRNA. Furthermore, NLRC5 deficiency significantly suppressed TGF-β1-induced proliferation but increased apoptosis (i.e., increased caspases-3, DR4 and DR5) in LX-2 cells. In addition, knockdown of NLRC5 promoted the activation of NF-κB signaling pathways but abrogated phosphorylation of Smad2 and Smad3 proteins in response to TGF-β1. These results indicate that NLRC5 is a potent pro-fibrogenic molecule for HSC activation through TGF-β1/Smad and NF-κB signaling pathways. NLRC5 inhibition would be a promising therapeutic avenue for treating hepatic fibrosis.

Severe eosinophilic fasciitis: comparison of treatment with D-penicillamine plus corticosteroids vs. corticosteroids alone

OBJECTIVES

To compare the therapeutic effectiveness of corticosteroids (CS) alone vs. CS plus d-penicillamine (d-Pen) in severe eosinophilic fasciitis.

METHOD

A long-term prospective non-randomized trial of d-Pen plus CS vs. CS alone in patients with severe eosinophilic fasciitis, defined as clinically apparent cutaneous fibrotic involvement affecting more than 15% body surface area (BSA) or more than 10% BSA with joint flexion contractures.

RESULTS

Sixteen patients with severe eosinophilic fasciitis entered the study. Ten patients received d-Pen plus CS and six received CS alone. Affected BSA decreased from an average of 29% to 8.9% in the d-Pen plus CS group compared to a decrease in affected BSA from 28% to 22.83% in the CS-alone group. The reduction in affected BSA in the d-Pen plus CS group was significantly greater than in the CS-alone group (p = 0.038). Clinical improvement occurred in all d-Pen plus CS patients compared to only 33.3% of CS-alone patients (p = 0.008). There was no difference in overall frequency of adverse events between the groups (p = 0.60). The most common adverse event in the d-Pen plus CS group was proteinuria (33.3%). However, proteinuria also occurred in 16.6% in the CS-alone group.

CONCLUSIONS

Treatment with CS alone failed to induce clinical improvement in the majority of the severe eosinophilic fasciitis patients. By contrast, d-Pen plus CS resulted in significantly greater clinical improvement. These results suggest that initial treatment of severe eosinophilic fasciitis with CS alone is not sufficient for optimal therapeutic response and that addition of an antifibrotic agent results in an improved outcome.

Fibronectin fibrillogenesis facilitates mechano-dependent cell spreading, force generation, and nuclear size in human embryonic fibroblasts

Cells respond to mechanical cues from the substrate to which they are attached. These mechanical cues drive cell migration, proliferation, differentiation, and survival. Previous studies have highlighted three specific mechanisms through which substrate stiffness directly alters cell function: increasing stiffness drives (1) larger contractile forces; (2) increased cell spreading and size; and (3) altered nuclear deformation. While studies have shown that substrate mechanics are an important cue, the role of the extracellular matrix (ECM) has largely been ignored. The ECM is a crucial component of the mechanosensing system for two reasons: (1) many ECM fibrils are assembled by application of cell-generated forces, and (2) ECM proteins have unique mechanical properties that will undoubtedly alter the local stiffness sensed by a cell. We specifically focused on the role of the ECM protein fibronectin (FN), which plays a critical role in de novo tissue production. In this study, we first measured the effects of substrate stiffness on human embryonic fibroblasts by plating cells onto microfabricated pillar arrays (MPAs) of varying stiffness. Cells responded to increasing substrate stiffness by generating larger forces, spreading to larger sizes, and altering nuclear geometry. These cells also assembled FN fibrils across all stiffnesses, with optimal assembly occurring at approximately 6 kPa. We then inhibited FN assembly, which resulted in dramatic reductions in contractile force generation, cell spreading, and nuclear geometry across all stiffnesses. These findings suggest that FN fibrils play a critical role in facilitating cellular responses to substrate stiffness.

Extracellular matrix stiffness: An important regulatory factor in tumor invasion and metastasis

It has been well documented that biochemical factors of tumor microenvironment like stromal cells, immune cells, cytokines, and chemokines contribute to the regulation of tumor invasion and metastasis. However, the roles of physical factors, especially matrix rigidity or elasticity resulting from abundant matrix protein deposition and cross-linking, remain largely unexplored. Lately, with the establishment of a series of cell culturing platforms mirroring matrix stiffness, a giant leap has been witnessed in the research into mechanisms of matrix stiffness-mediated effects on tumor invasion and metastasis. This article reviews the impact of matrix stiffness on epithelial-mesenchymal transition (EMT), motility, integrin, invasion and metastasis genes, and stemness in tumors, to illustrate that matrix stiffness is also an important factor in the regulation of tumor invasion and metastasis.

Fibrosis Related Inflammatory Mediators: Role of the IL-10 Cytokine Family

Importance of chronic fibroproliferative diseases (FDs) including pulmonary fibrosis, chronic kidney diseases, inflammatory bowel disease, and cardiovascular or liver fibrosis is rapidly increasing and they have become a major public health problem. According to some estimates about 45% of all deaths are attributed to FDs in the developed world. Independently of their etiology the common hallmark of FDs is chronic inflammation. Infiltrating immune cells, endothelial, epithelial, and other resident cells of the injured organ release an orchestra of inflammatory mediators, which stimulate the proliferation and excessive extracellular matrix (ECM) production of myofibroblasts, the effector cells of organ fibrosis. Abnormal amount of ECM disturbs the original organ architecture leading to the decline of function. Although our knowledge is rapidly expanding, we still have neither a diagnostic tool to detect nor a drug to specifically target fibrosis. Therefore, there is an urgent need for the more comprehensive understanding of the pathomechanism of fibrosis and development of novel diagnostic and therapeutic strategies. In the present review we provide an overview of the common key mediators of organ fibrosis highlighting the role of interleukin-10 (IL-10) cytokine family members (IL-10, IL-19, IL-20, IL-22, IL-24, and IL-26), which recently came into focus as tissue remodeling-related inflammatory cytokines.

Varying RGD concentration and cell phenotype alters the expression of extracellular matrix genes in vocal fold fibroblasts

The impact of RGD integrin binding-peptide concentration and cell phenotype on directing extracellular matrix (ECM) gene expression in vocal fold fibroblasts is little understood. Less is known about cell response to RGD concentration on a biomaterial when fibroblasts are in a scar-like environment compared to a healthy environment. We investigated the effects of varying RGD integrin-binding peptide surface concentration on ECM gene expression of elastin, collagen type 3 alpha 1, decorin, fibronectin, hyaluronan synthase 2, and collagen type 1 alpha 2 in scarred and unscarred immortalized human vocal fold fibroblasts (I-HVFFs). Phenotype and RGD concentration affected ECM gene expression. Phenotype change from healthy to myofibroblast-like resulted in ECM gene up-regulation for all genes tested, except for decorin. Systematically altering RGD concentration affected the expression of elastin and collagen type 3 alpha 1 in a myofibroblast phenotype. Specifically greater up-regulation in gene expression was observed with higher RGD concentrations. This research demonstrates that controlling RGD concentration may influence ECM gene expression levels in fibroblasts. Such knowledge is critical in developing the next generation of bioactive materials that, when implanted into sites of tissue damage and scarring, will direct cells to regenerate healthy tissues with normal ECM ratios and morphologies.

Hes1, an important gene for activation of hepatic stellate cells, is regulated by Notch1 and TGF-β/BMP signaling

AIM: To determine the role of Notch1 and Hes1 in regulating the activation of hepatic stellate cells (HSCs) and whether Hes1 is regulated by transforming growth factor (TGF)/bone morphogenetic protein (BMP) signaling.

METHODS: Immunofluorescence staining was used to detect the expression of desmin, glial fibrillary acidic protein and the myofibroblastic marker α-smooth muscle actin (α-SMA) after freshly isolated, normal rat HSCs had been activated in culture for different numbers of days (0, 1, 3, 7 and 10 d). The expression of α-SMA, collagen1α2 (COL1α2), Notch receptors (Notch1-4), and the Notch target genes Hes1 and Hey1 were analyzed by reverse transcriptase-polymerase chain reaction. Luciferase reporter assays and Western blot were used to study the regulation of α-SMA, COL1α1, COL1α2 and Hes1 by NICD1, Hes1, CA-ALK3, and CA-ALK5 in HSC-T6 cells. Moreover, the effects of inhibiting Hes1 function in HSC-T6 cells using a Hes1 decoy were also investigated.

RESULTS: The expression of Notch1 and Hes1 mRNAs was significantly down-regulated during the culture of freshly isolated HSCs. In HSC-T6 cells, Notch1 inhibited the promoter activities of α-SMA, COL1α1 and COL1α2. On the other hand, Hes1 enhanced the promoter activities of α-SMA and COL1α2, and this effect could be blocked by inhibiting Hes1 function with a Hes1 decoy. Furthermore, co-transfection of pcDNA3-CA-ALK3 (BMP signaling activin receptor-like kinase 3) and pcDNA3.1-NICD1 further increased the expression of Hes1 compared with transfection of either vector alone in HSC-T6 cells, while pcDNA3-CA-ALK5 (TGF-β signaling activin receptor-like kinase 5) reduced the effect of NICD1 on Hes1 expression.

CONCLUSION: Selective interruption of Hes1 or maintenance of Hes1 at a reasonable level decreases the promoter activities of α-SMA and COL1α2, and these conditions may provide an anti-fibrotic strategy against hepatic fibrosis.

Hepatic stellate cells and liver fibrosis

Hepatic stellate cells are resident perisinusoidal cells distributed throughout the liver, with a remarkable range of functions in normal and injured liver. Derived embryologically from septum transversum mesenchyme, their precursors include submesothelial cells that invade the liver parenchyma from the hepatic capsule. In normal adult liver, their most characteristic feature is the presence of cytoplasmic perinuclear droplets that are laden with retinyl (vitamin A) esters. Normal stellate cells display several patterns of intermediate filaments expression (e.g., desmin, vimentin, and/or glial fibrillary acidic protein) suggesting that there are subpopulations within this parental cell type. In the normal liver, stellate cells participate in retinoid storage, vasoregulation through endothelial cell interactions, extracellular matrix homeostasis, drug detoxification, immunotolerance, and possibly the preservation of hepatocyte mass through secretion of mitogens including hepatocyte growth factor. During liver injury, stellate cells activate into alpha smooth muscle actin-expressing contractile myofibroblasts, which contribute to vascular distortion and increased vascular resistance, thereby promoting portal hypertension. Other features of stellate cell activation include mitogen-mediated proliferation, increased fibrogenesis driven by connective tissue growth factor, and transforming growth factor beta 1, amplified inflammation and immunoregulation, and altered matrix degradation. Evolving areas of interest in stellate cell biology seek to understand mechanisms of their clearance during fibrosis resolution by either apoptosis, senescence, or reversion, and their contribution to hepatic stem cell amplification, regeneration, and hepatocellular cancer.

Endoplasmic reticulum stress is the crossroads of autophagy, inflammation, and apoptosis signaling pathways and participates in liver fibrosis

OBJECTIVE

The objective of the review is to examine the crossroads of autophagy, inflammation, and apoptosis signaling pathways and their participation in liver fibrosis.

INTRODUCTION

Endoplasmic reticulum (ER) stress was emerged as a common feature relevant to the pathogenesis of diseases associated with organ fibrosis. However, the functional consequences of these alterations on ER stress and the possible involvement in liver fibrosis were currently largely unexplored. Here, we will survey the recent literature in the field and discuss recent insights focusing on some cellular models expressing mutant proteins involved in liver fibrosis.

METHODS

A computer-based online search with PubMed, Scopus and Web of Science databases was performed for articles published, concerning ER stress, adaptation, inflammation and apoptosis with relevance to liver fibrosis.

RESULTS AND CONCLUSIONS

Progression of liver fibrosis requires sustained inflammation leading to hepatocytes apoptosis through ER stress, whereas associated with activation of hepatic stellate cells (HSCs) into a fibrogenic and proliferative cell type. Faced with persistent and massive ER stress, HSCs adaptation starts to fail and apoptosis occurs in reversal of liver fibrosis, possibly mediated through calcium perturbations, unfolded protein response, and the pro-apoptotic transcription factor CHOP. Although limited in scope, current studies underscored that ER stress is tightly linked to adaptation, inflammation and apoptosis, and recent evidences suggested that these processes are related to the pathogenesis of liver fibrosis and its recovery.

Delivery and targeting of miRNAs for treating liver fibrosis

Liver fibrosis is a pathological condition originating from liver damage that leads to excess accumulation of extracellular matrix (ECM) proteins in the liver. Viral infection, chronic injury, local inflammatory responses and oxidative stress are the major factors contributing to the onset and progression of liver fibrosis. Multiple cell types and various growth factors and inflammatory cytokines are involved in the induction and progression of this disease. Various strategies currently being tried to attenuate liver fibrosis include the inhibition of HSC activation or induction of their apoptosis, reduction of collagen production and deposition, decrease in inflammation, and liver transplantation. Liver fibrosis treatment approaches are mainly based on small drug molecules, antibodies, oligonucleotides (ODNs), siRNA and miRNAs. MicroRNAs (miRNA or miR) are endogenous noncoding RNA of ~22 nucleotides that regulate gene expression at post transcription level. There are several miRNAs having aberrant expressions and play a key role in the pathogenesis of liver fibrosis. Single miRNA can target multiple mRNAs, and we can predict its targets based on seed region pairing, thermodynamic stability of pairing and species conservation. For in vivo delivery, we need some additional chemical modification in their structure, and suitable delivery systems like micelles, liposomes and conjugation with targeting or stabilizing the moiety. Here, we discuss the role of miRNAs in fibrogenesis and current approaches of utilizing these miRNAs for treating liver fibrosis.

Liver bioengineering: from the stage of liver decellularized matrix to the multiple cellular actors and bioreactor special effects

Liver bioengineering has been a field of intense research and popular excitement in the past decades. It experiences great interest since the introduction of whole liver acellular scaffolds generated by perfusion decellularization (1-3). Nevertheless, the different strategies developed so far have failed to generate hepatic tissue in vitro bioequivalent to native liver tissue. Even notable novel strategies that rely on iPSC-derived liver progenitor cells potential to self-organize in association with endothelial cells in hepatic organoids are lacking critical components of the native tissue (e.g., bile ducts, functional vascular network, hepatic microarchitecture, etc) (4). Hence, it is vital to understand the strengths and short comes of our current strategies in this quest to re-create liver organogenesis in vitro. To shed some light into these issues, this review describes the different actors that play crucial roles in liver organogenesis and highlights the steps still missing to successfully generate whole livers and hepatic organoids in vitro for multiple applications.

Regulation of proximal tubular cell differentiation and proliferation in primary culture by matrix stiffness and ECM components

To explore whether matrix stiffness affects cell differentiation, proliferation, and transforming growth factor (TGF)-β1-induced epithelial-mesenchymal transition (EMT) in primary cultures of mouse proximal tubular epithelial cells (mPTECs), we used a soft matrix made from monomeric collagen type I-coated polyacrylamide gel or matrigel (MG). Both kinds of soft matrix benefited primary mPTECs to retain tubular-like morphology with differentiation and growth arrest and to evade TGF-β1-induced EMT. However, the potent effect of MG on mPTEC differentiation was suppressed by glutaraldehyde-induced cross-linking and subsequently stiffening MG or by an increasing ratio of collagen in the soft mixed gel. Culture media supplemented with MG also helped mPTECs to retain tubular-like morphology and a differentiated phenotype on stiff culture dishes as soft MG did. We further found that the protein level and activity of ERK were scaled with the matrix stiffness. U-0126, a MEK inhibitor, abolished the stiff matrix-induced dedifferentiation and proliferation. These data suggest that the ERK signaling pathway plays a vital role in matrix stiffness-regulated cell growth and differentiation. Taken together, both compliant property and specific MG signals from the matrix are required for the regulation of epithelial differentiation and proliferation. This study provides a basic understanding of how physical and chemical cues derived from the extracellular matrix regulate the physiological function of proximal tubules and the pathological development of renal fibrosis.

Characterization of animal models for primary sclerosing cholangitis (PSC)

Primary sclerosing cholangitis (PSC) is a chronic cholangiopathy characterized by biliary fibrosis, development of cholestasis and end stage liver disease, high risk of malignancy, and frequent need for liver transplantation. The poor understanding of its pathogenesis is also reflected in the lack of effective medical treatment. Well-characterized animal models are utterly needed to develop novel pathogenetic concepts and study new treatment strategies. Currently there is no consensus on how to evaluate and characterize potential PSC models, which makes direct comparison of experimental results and effective exchange of study material between research groups difficult. The International Primary Sclerosing Cholangitis Study Group (IPSCSG) has therefore summarized these key issues in a position paper proposing standard requirements for the study of animal models of PSC.

Matrix biology of idiopathic pulmonary fibrosis: a workshop report of the national heart, lung, and blood institute

A hallmark of idiopathic pulmonary fibrosis (IPF) is excessive and disordered deposition of extracellular matrix. Although the lung extracellular matrix normally plays an essential role in development and maintenance of lung tissue through reciprocal interactions with resident cells, the disordered matrix in the diseased lung is increasingly recognized as an active and important contributor to IPF pathogenesis. This working group summary from a recently conducted National Heart, Lung, and Blood Institute strategic planning workshop for IPF research highlights recent advances, challenges, and opportunities in the study of matrix biology in IPF. Particular attention is given to the composition and mechanical properties of the matrix in normal and diseased lungs, and the biochemical and biomechanical influences exerted by pathological matrix. Recently developed model systems are also summarized as key tools for advancing our understanding of matrix biology in IPF. Emerging approaches to therapeutically target the matrix in preclinical and clinical settings are discussed, as are important concepts, such as alterations of the matrix with aging and the potential for the resolution of fibrosis. Specific recommendations for future studies in matrix biology of IPF are also proposed.

Future directions in idiopathic pulmonary fibrosis research. An NHLBI workshop report

The median survival of patients with idiopathic pulmonary fibrosis (IPF) continues to be approximately 3 years from the time of diagnosis, underscoring the lack of effective medical therapies for this disease. In the United States alone, approximately 40,000 patients die of this disease annually. In November 2012, the NHLBI held a workshop aimed at coordinating research efforts and accelerating the development of IPF therapies. Basic, translational, and clinical researchers gathered with representatives from the NHLBI, patient advocacy groups, pharmaceutical companies, and the U.S. Food and Drug Administration to review the current state of IPF research and identify priority areas, opportunities for collaborations, and directions for future research. The workshop was organized into groups that were tasked with assessing and making recommendations to promote progress in one of the following six critical areas of research: (1) biology of alveolar epithelial injury and aberrant repair; (2) role of extracellular matrix; (3) preclinical modeling; (4) role of inflammation and immunity; (5) genetic, epigenetic, and environmental determinants; (6) translation of discoveries into diagnostics and therapeutics. The workshop recommendations provide a basis for directing future research and strategic planning by scientific, professional, and patient communities and the NHLBI.

Multiscale mechanical simulations of cell compacted collagen gels

Engineered tissues are commonly stretched or compressed (i.e., conditioned) during culture to stimulate extracellular matrix (ECM) production and to improve the mechanical properties of the growing construct. The relationships between mechanical stimulation and ECM remodeling, however, are complex, interdependent, and dynamic. Thus, theoretical models are required for understanding the underlying phenomena so that the conditioning process can be optimized to produce functional engineered tissues. Here, we continue our development of multiscale mechanical models by simulating the effect of cell tractions on developing isometric tension and redistributing forces in the surrounding fibers of a collagen gel embedded with explants. The model predicted patterns of fiber reorganization that were similar to those observed experimentally. Furthermore, the inclusion of cell compaction also changed the distribution of fiber strains in the gel compared to the acellular case, particularly in the regions around the cells where the highest strains were found.

Vitamin B12 supplement alleviates N'-nitrosodimethylamine-induced hepatic fibrosis in rats

Abstract Context: Altered vitamin B12 levels have been correlated with hepatotoxicity; however, further evidence is required to establish its protective role. Objective: To evaluate the effects of vitamin B12 supplement in protecting N'-nitrosodimethylamine (NDMA)-induced hepatic fibrosis in Wistar rats. Materials and methods: Hepatic fibrosis was induced by administering NDMA in doses of 10 mg/kg body weight thrice a week for 21 days. Another group received equal doses (10 mg/kg body weight) of vitamin B12 subsequent to NDMA treatment. Animals from either group were sacrificed weekly from the start of the treatment along with their respective controls. Progression of hepatic fibrosis, in addition to the effect of vitamin B12, was assessed biochemically for liver function biomarkers, liver glycogen, hydroxyproline (HP) and B12 reserves along with histopathologically by hematoxylin and eosin (H & E) as well immunohistochemical staining for α-SMA expression. Results and discussion: Elevation in the levels of aminotransferases, SALP, total bilirubin and HP was observed in NDMA treated rats, which was concomitant with remarkable depletion in liver glycogen and B12 reserves (p < 0.05). Liver biopsies also demonstrated disrupted lobular architecture, collagen amassing and intense fibrosis by NDMA treatment. Immunohistochemical staining showed the presence of activated stellate cells that was dramatically increased up to day 21 in fibrotic rats. Following vitamin B12 treatment, liver function biomarkers, glycogen contents and hepatic vitamin B12 reserves were restored in fibrotic rats, significantly. Vitamin B12 administration also facilitated restoration of normal liver architecture. Conclusion: These findings provide interesting new evidence in favor of protective role for vitamin B12 against NDMA-induced hepatic fibrosis in rats.

Participation of miR-200a in TGF-β1-mediated hepatic stellate cell activation

Hepatic stellate cell (HSC) activation is a pivotal event in the initiation and progression of hepatic fibrosis since it mediates transforming growth factor beta 1 (TGF-β1)-driven extracellular matrix (ECM) deposition. MicroRNAs (miRNAs), small non-coding RNAs modulating messenger RNA (mRNA) and protein expression, have emerged as key factors to regulate cell proliferation, differentiation, and apoptosis. Although the function of miR-200a has been discussed in many cancers and fibrotic diseases, its role in hepatic fibrosis is still poorly understood. The aim of this study is to investigate whether miR-200a could attenuate hepatic fibrosis partly through Wnt/β-catenin and TGF-β-dependant mechanisms. Our study found that the expression of endogenous miR-200a was decreased in vitro in TGF-β1-induced HSC activation as well as in vivo in CCl4-induced rat liver fibrosis. Overexpression of miR-200a significantly inhibited α-SMA activity and further affected the proliferation of TGF-β1-dependent activation of HSC. In addition, we identified β-catenin and TGF-β2 as two functional downstream targets for miR-200a. Interestingly, miR-200a specifically suppressed β-catenin in the protein level, whereas miR-200a-mediated suppression of TGF-β2 was shown on both mRNA and protein levels. Our results revealed the critical regulatory role of miR-200a in HSC activation and implied miR-200a as a potential candidate for therapy by deregulation of Wnt/β-catenin and TGFβ signaling pathways, at least in part, via decreasing the expression of β-catenin and TGF-β2.

Effects of non-linearity on cell-ECM interactions

Filamentous biopolymers such as F-actin, vimentin, fibrin and collagen that form networks within the cytoskeleton or the extracellular matrix have unusual rheological properties not present in most synthetic soft materials that are used as cell substrates or scaffolds for tissue engineering. Gels formed by purified filamentous biopolymers are often strain stiffening, with an elastic modulus that can increase an order of magnitude at moderate strains that are relevant to cell and tissue deformation in vivo. This review summarizes some experimental studies of non-linear rheology in biopolymer gels, discusses possible molecular mechanisms that account for strain stiffening, and explores the possible relevance of non-linear rheology to the interactions between cell and extracellular matrices.

Regulation and Relevance of Myofibroblast Responses in Idiopathic Pulmonary Fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is a chronic, progressive, incurable lung disease of unknown etiology with only limited treatment options. Current paradigms of disease pathogenesis feature recurrent or prolonged epithelial injury and an ensuing inflammatory response that culminates in the appearance of activated myofibroblasts. These cells are believed central to the excessive deposition of extracellular matrix that eventually obliterates the alveolar space to cause respiratory failure. Because the factors driving the accumulation of myofibroblasts remain poorly understood, effective therapies remain elusive. This review focuses on recent understanding of myofibroblasts including their seemingly uncontrolled proliferation and survival, their controversial origin in pathological IPF tissues, and the local biochemical and biomechanical matrix factors that drive their behavior. In addition, novel antifibrotics under development for the treatment of lung disease will be discussed. As our understanding of fibroblast and myofibroblast biology regulation expands, these cells may prove to be effective therapeutic targets.

Alleviation of Dimethylnitrosamine-Induced Liver Injury and Fibrosis by Supplementation of Anabasis articulata Extract in Rats

Anabasis articulata (Forssk) Moq. (Chenopodiaceae) is an herb, grows in Egypt, and used in folk medicine to treat diabetes, fever, and kidney infections. The protective and therapeutic effects of the ethanol extract of A. articulata aerial parts were evaluated against dimethylnitrosamine (DMN)-induced liver fibrosis, compared with the standard drug, silymarin. Hepatic hydroxyproline content, serum transforming growth factor-β1 (TGF-β1), interleukin 10 (IL-10) and fructosamine were measured as liver fibrosis markers. Hepatic malondialdehyde (MDA), nitric oxide (NO), catalase (CAT), glutathione reductase (GR) and glutathione content (GSH) were measured as oxidant/antioxidant markers. Parallel histopathological investigations were also performed. Protective and therapeutic administration of A. articulata (100 mg/kg daily for 4 weeks), markedly prevented DMN-induced loss in body and liver weights. The extract significantly inhibited the elevation of hepatic hydroxyproline, NO and MDA (P < 0.05), as well as serum fructosamine, and TGF-β1 (P < 0.05) induced by DMN while it restored IL-10 to normal level in both protective and therapeutic groups. Furthermore, A. articulata prevented the depletion in CAT, GR, and GSH levels (P ≤ 0.05). In addition, oral administration of A. articulata extract and silymarin to both protective and therapeutic groups reduced the increase in liver function enzyme activities; alanine and aspartate amintransferases, gamma-glutamyl transferase in addition to alkaline phosphatase, and caused significant increase in serum albumin concentration as compared to DMN group. These data corresponded closely with those obtained for the drug silymarin. Histopathological studies confirmed the biochemical data and revealed remarkable improvement in liver architecture. Thus, it could be concluded that, A. articulata extract exhibited in vivo hepatoprotective and therapeutic effects against DMN-induced liver injury and may act as a useful agent in controlling the progression of hepatic fibrosis through reduction of oxidative stress and improving liver function.

The mechanical environment modulates intracellular calcium oscillation activities of myofibroblasts

Myofibroblast contraction is fundamental in the excessive tissue remodeling that is characteristic of fibrotic tissue contractures. Tissue remodeling during development of fibrosis leads to gradually increasing stiffness of the extracellular matrix. We propose that this increased stiffness positively feeds back on the contractile activities of myofibroblasts. We have previously shown that cycles of contraction directly correlate with periodic intracellular calcium oscillations in cultured myofibroblasts. We analyze cytosolic calcium dynamics using fluorescent calcium indicators to evaluate the possible impact of mechanical stress on myofibroblast contractile activity. To modulate extracellular mechanics, we seeded primary rat subcutaneous myofibroblasts on silicone substrates and into collagen gels of different elastic modulus. We modulated cell stress by cell growth on differently adhesive culture substrates, by restricting cell spreading area on micro-printed adhesive islands, and depolymerizing actin with Cytochalasin D. In general, calcium oscillation frequencies in myofibroblasts increased with increasing mechanical challenge. These results provide new insight on how changing mechanical conditions for myofibroblasts are encoded in calcium oscillations and possibly explain how reparative cells adapt their contractile behavior to the stresses occurring in normal and pathological tissue repair.

Evolving therapies for liver fibrosis

Fibrosis is an intrinsic response to chronic injury, maintaining organ integrity when extensive necrosis or apoptosis occurs. With protracted damage, fibrosis can progress toward excessive scarring and organ failure, as in liver cirrhosis. To date, antifibrotic treatment of fibrosis represents an unconquered area for drug development, with enormous potential but also high risks. Preclinical research has yielded numerous targets for antifibrotic agents, some of which have entered early-phase clinical studies, but progress has been hampered due to the relative lack of sensitive and specific biomarkers to measure fibrosis progression or reversal. Here we focus on antifibrotic approaches for liver that address specific cell types and functional units that orchestrate fibrotic wound healing responses and have a sound preclinical database or antifibrotic activity in early clinical trials. We also touch upon relevant clinical study endpoints, optimal study design, and developments in fibrosis imaging and biomarkers.