Hepatic stellate cells--the pericytes in the liver

Therapeutic Application of Micellar Solubilized Xanthohumol in a Western-Type Diet-Induced Mouse Model of Obesity, Diabetes and Non-Alcoholic Fatty Liver Disease

Xanthohumol (XN), a prenylated chalcone from hops, has been reported to exhibit a variety of health-beneficial effects. However, poor bioavailability may limit its application in the prevention and therapy of diseases. The objective of this study was to determine whether a micellar solubilization of xanthohumol could enhance the bioavailability and biological efficacy of xanthohumol in a Western-type diet (WTD) induced model of obesity, diabetes and non-alcoholic fatty liver disease (NAFLD). After 3 weeks feeding with WTD, XN was additionally applied per oral gavage as micellar solubilizate (s-XN) or native extract (n-XN) at a daily dose of 2.5 mg/kg body weight for a further 8 weeks. Control mice received vehicle only in addition to the WTD. WTD-induced body weight-gain and glucose intolerance were significantly inhibited by s-XN application. Furthermore, WTD-induced hepatic steatosis, pro-inflammatory gene expression (MCP-1 and CXCL1) and immune cell infiltration as well as activation of hepatic stellate cells (HSC) and expression of collagen alpha I were significantly reduced in the livers of s-XN-treated mice compared to WTD controls. In contrast, application of n-XN had no or only slight effects on the WTD-induced pathological effects. In line with this, plasma XN concentration ranged between 100–330 nmol/L in the s-XN group while XN was not detectable in the serum samples of n-XN-treated mice. In conclusion, micellar solubilization enhanced the bioavailability and beneficial effects of xanthohumol on different components of the metabolic syndrome including all pathological steps of NAFLD. Notably, this was achieved in a dose more than 10-fold lower than effective beneficial doses of native xanthohumol reported in previous in vivo studies.

The Carcinogenic Role of the Notch Signaling Pathway in the Development of Hepatocellular Carcinoma

The Notch signaling pathway, known to be a highly conserved signaling pathway in embryonic development and adult tissue homeostasis, participates in cell fate decisions that include cellular differentiation, cell survival and cell death. However, other studies have shown that aberrant in Notch signaling is pro-tumorigenic, particularly in hepatocellular carcinoma (HCC). HCC is one of the most common malignant tumors in the world and has a high mortality rate. Growing evidence supports that Notch signaling plays a critical role in the development of HCC by regulating the tumor microenvironment, tumorigenesis, progression, angiogenesis, invasion and metastasis. Accordingly, overexpression of Notch is closely associated with poor prognosis in HCC. In this review, we focus on the pro-tumorigenic role of Notch signaling in HCC, summarize the current knowledge of Notch signaling and its role in HCC development, and outline the therapeutic potential of targeting Notch signaling in HCC.

Blockade of glycolysis-dependent contraction by oroxylin a via inhibition of lactate dehydrogenase-a in hepatic stellate cells

Background

Contraction of hepatic stellate cells (HSCs) plays an important role in the pathogenesis of liver fibrosis by regulating sinusoidal blood flow and extracellular matrix remodeling. Here, we investigated how HSC contraction was affected by the natural compound oroxylin A, and elucidated the underlying mechanism.

Methods

Cell contraction and glycolysis were examined in cultured human HSCs and mouse liver fibrosis model upon oroxylin A intervention using diversified cellular and molecular assays, as well as genetic approaches.

Results

Oroxylin A limited HSC contraction associated with inhibiting myosin light chain 2 phosphorylation. Oroxylin A blocked aerobic glycolysis in HSCs evidenced by reduction in glucose uptake and consumption and lactate production. Oroxylin A also decreased extracellular acidification rate and inhibited the expression and activity of glycolysis rate-limiting enzymes (hexose kinase 2, phosphofructokinase 1 and pyruvate kinas type M2) in HSCs. Then, we identified that oroxylin A blockade of aerobic glycolysis contributed to inhibition of HSC contraction. Furthermore, oroxylin A inhibited the expression and activity of lactate dehydrogenase-A (LDH-A) in HSCs, which was required for oroxylin A blockade of glycolysis and suppression of contraction. Oral administration of oroxylin A at 40 mg/kg reduced liver injury and fibrosis, and inhibited HSC glycolysis and contraction in mice with carbon tetrachloride-induced hepatic fibrosis. However, adenovirus-mediated overexpression of LDH-A significantly counteracted the oroxylin A’s effects in fibrotic mice.

Conclusions

Blockade of aerobic glycolysis by oroxylin A via inhibition of LDH-A reduced HSC contraction and attenuated liver fibrosis, suggesting LDH-A as a promising target for intervention of hepatic fibrosis.

Electronic supplementary material

The online version of this article (10.1186/s12964-019-0324-8) contains supplementary material, which is available to authorized users.

Pericytes in the Placenta: Role in Placental Development and Homeostasis

The placenta is the most variable organ, in terms of structure, among the species. Besides it, all placental types have the same function: production of viable offspring, independent of pregnancy length, litter number, or invasion level. The angiogenesis is a central mechanism for placental functionality, due to proper maternal-fetal communication and exchanges. Much is known about the vasculature structure, but little is known about vasculature development and cellular interactions. Pericytes are perivascular cells that were described to control vasculature stability and permeability. Nowadays there are several new functions discovered, such as lymphocyte modulation and activation, macrophage-like phagocytic properties, tissue regenerative and repair processes, and also the ability to modulate stem cells, majorly the hematopoietic. In parallel, placental tissues are known to be a particularly immune microenvironment and a rich stem cell niche. The pericyte function plethora could be similar in the placental microenvironment and could have a central role in placental development and homeostasis.

Iso-alpha acids from hops (Humulus lupulus) inhibit hepatic steatosis, inflammation, and fibrosis

Non-alcoholic fatty liver disease (NAFLD) is considered to be the hepatic manifestation of the metabolic syndrome. Iso-alpha acids (IAAs), hop-derived bitter compounds in beer, have been shown to beneficially affect different components of the metabolic syndrome such as insulin resistance and dyslipidemia. However, IAAs have not yet been studied in the context of chronic liver disease. Here we analyzed the effect of IAA on the pathogenesis of NAFLD. Once, we applied IAA to mice in combination with a NAFLD-inducing Western-type diet (WTD), and observed that IAA significantly inhibited WTD-induced body weight gain, glucose intolerance, and hepatic steatosis. Fitting to this, IAA dose-dependently inhibited cellular lipid accumulation in primary human hepatocytes (PHH) in vitro. Reduced expression of PPAR-gamma and key enzymes of lipid synthesis as well as increased expression of PPAR-alpha, indicative for increased lipid combustion, were identified as underlying mechanisms of reduced hepatocellular steatosis in vitro and in vivo. Analysis of hepatic HMOX1 expression indicated reduced oxidative stress in IAA-treated mice, which was paralleled by reduced activation of the JNK pathway and pro-inflammatory gene expression and immune cell infiltration. Furthermore, IAA reduced hepatic stellate cell (HSC) activation and pro-fibrogenic gene expression. Similarly, IAA also dose-dependently reduced oxidative stress and JNK activation in steatotic PHH, inhibited HSC activation, and reduced proliferation and pro-fibrogenic gene expression in already activated HSC in vitro. In conclusion, IAAs inhibit different pathophysiological steps of disease progression in NAFLD. Together with previous studies, which demonstrated the safety of even long-term application of IAA in humans, our data suggest IAA as promising therapeutic agent for the prevention and treatment of (non)alcoholic (fatty) liver disease.

Vitronectin from brain pericytes promotes adult forebrain neurogenesis by stimulating CNTF

Vitronectin (VTN) is a glycoprotein in the blood and affects hemostasis. VTN is also present in the extracellular matrix of various organs but little is known about its function in healthy adult tissues. We show, in adult mice, that VTN is uniquely expressed by approximately half of the pericytes of subventricular zone (SVZ) where neurogenesis continues throughout life. Intracerebral VTN antibody injection or VTN knockout reduced neurogenesis as well as expression of pro-neurogenic CNTF, and anti-neurogenic LIF and IL-6. Conversely, injections of VTN, or plasma from VTN+/+, but not VTN-/- mice, increased these cytokines. VTN promoted SVZ neurogenesis when LIF and IL-6 were suppressed by co-administration of a gp130 inhibitor. Unexpectedly, VTN inhibited FAK signaling and VTN-/- mice had increased FAK signaling in the SVZ. Further, an FAK inhibitor or VTN increased CNTF expression, but not in conditional astrocytic FAK knockout mice, suggesting that VTN increases CNTF through FAK inhibition in astrocytes. These results identify a novel role of pericyte-derived VTN in the brain, where it regulates SVZ neurogenesis through co-expression of CNTF, LIF and IL-6. VTN-integrin-FAK and gp130 signaling may provide novel targets to induce neurogenesis for cell replacement therapies.

Conditioned Medium from Human Amnion-Derived Mesenchymal Stem Cells Regulates Activation of Primary Hepatic Stellate Cells

Mesenchymal stem cells (MSCs), or multipotent mesenchymal stromal cells, are present in almost all organs and tissues, including the amnion. Human amnion-derived mesenchymal stem cell (hAMSC) transplantation has been reported to ameliorate liver fibrosis in animal models. However, the mechanism for the prevention of liver fibrosis is poorly understood. In this study, we investigated the effects, and underlying mechanisms, of a conditioned medium obtained from hAMSC cultures (hAMSC-CM) on a primary culture of rat hepatic stellate cells (HSCs). We observed that in routine culture, hAMSC-CM in HSCs significantly inhibited the expression of alpha-smooth muscle actin (α-SMA), an activation marker of HSCs, and the production of collagen type 1 (COL1), a dominant component of the extracellular matrix (ECM) in the culture medium. In addition, hAMSC-CM upregulated the expression of ECM degradation-related genes, such as metalloproteinase- (Mmp-) 2, Mmp-9, Mmp-13, and tissue inhibitor of metalloproteinase- (Timp-) 1; however, it did not affect the expression of collagen type 1α1 (Col1a1). These regulatory effects on HSCs were concentration-dependent. A cell proliferation assay indicated that hAMSC-CM significantly suppressed HSC proliferation and downregulated the expression of cyclin B (Ccnb), a proliferation-related gene. Transforming growth factor-beta (TGF-β) treatment further activated HSCs and hAMSC-CM significantly inhibited the upregulation of α-Sma and Col1a1 induced by TGF-β. These findings demonstrated that hAMSC-CM can modulate HSC function via secretory factors and provide a plausible explanation for the protective role of hAMSCs in liver fibrosis.

Effects of FGF21-secreting adipose-derived stem cells in thioacetamide-induced hepatic fibrosis

Mesenchymal stem cells (MSCs) have been investigated to treat liver diseases, but the efficiency of MSCs to treat chronic liver diseases is conflicting. FGF21 can reduce inflammation and fibrosis. We established FGF21‐secreting adipose derived stem cells (FGF21_ADSCs) to enhance the effects of ADSCs and transplanted them into thioacetamide (TAA)‐induced liver fibrosis mice via the tail vein. Transplantation of FGF21_ADSCs significantly improved liver fibrosis by decreasing serum hyaluronic acid and reducing the expression of fibrosis‐related factors such as α‐smooth muscle actin (α‐SMA), collagen and tissue inhibitor of metalloproteinase‐1 (TIMP‐1) compared with the Empty_ADSCs by inhibition of p‐JNK, NF‐κB and p‐Smad2/3 signalling. α‐lactoalbumin (LA) and lactotransferrin (LTF), secretory factors produced from FGF21_ADSCs inhibited TGF‐β1‐induced expression of α‐SMA and collagen in LX‐2 cells. These results suggest that transplantation of FGF21_ADSCs inhibited liver fibrosis more effectively than Empty_ADSCs, possibly via secretion of α‐LA and LTF.

Evaluation of Hepatoprotective Effect of Curcumin on Liver Cirrhosis Using a Combination of Biochemical Analysis and Magnetic Resonance-Based Electrical Conductivity Imaging

In oriental medicine, curcumin is used to treat inflammatory diseases, and its anti-inflammatory effect has been reported in recent research. In this feasibility study, the hepatoprotective effect of curcumin was investigated using a rat liver cirrhosis model, which was induced with dimethylnitrosamine (DMN). Together with biochemical analysis, we used a magnetic resonance-based electrical conductivity imaging method to evaluate tissue conditions associated with a protective effect. The effects of curcumin treatment and lactulose treatment on liver cirrhosis were compared. Electrical conductivity images indicated that liver tissues damaged by DMN showed decreased conductivity compared with normal liver tissues. In contrast, cirrhotic liver tissues treated with curcumin or lactulose showed increased conductivity than tissues in the DMN-only group. Specifically, conductivity of cirrhotic liver after curcumin treatment was similar to that of normal liver tissues. Histological staining and immunohistochemical examination showed significant levels of attenuated fibrosis and decreased inflammatory response after both curcumin and lactulose treatments compared with damaged liver tissues by DMN. The conductivity imaging and biochemical examination results indicate that curcumin's anti-inflammatory effect can prevent the progression of irreversible liver dysfunction.

New models to study vascular mural cell embryonic origin: implications in vascular diseases

A key question in vascular biology is how the diversity of origin of vascular mural cells, namely smooth muscle cells (SMCs) and pericytes influences vessel properties, in particular the regional propensity to vascular diseases. This review therefore first describes the role and regulation of mural cells during vascular formation, with a focus on embryonic origin. We then consider the evidence that connects heterogeneities in SMC and pericyte origins with disease. Since this idea has major implications for understanding and modelling human disease, then there is a pressing need for new model systems to investigate mural cell development and the consequences of heterogeneity. Recent advances arising from in vitro strategies for deriving mural cells from human pluripotent stem cells as well as from the zebrafish model will be discussed and the medical relevance of these discoveries will be highlighted.

Ligand Activation of PPARγ by Ligustrazine Suppresses Pericyte Functions of Hepatic Stellate Cells via SMRT-Mediated Transrepression of HIF-1α

Rationale: Hepatic stellate cells (HSCs) are liver-specific pericytes regulating vascular remodeling during hepatic fibrosis. Here, we investigated how ligustrazine affects HSC pericyte functions.

Methods: Rat HSC-T6 and human HSC-LX2 cells were cultured, and multiple molecular experiments including real-time PCR, Western blot, flow cytometry, immunofluorescence, electrophoretic mobility shift assay and co-immunoprecipitation were used to elucidate the underlying mechanisms. Molecular simulation and site-directed mutagenesis were performed to uncover the target molecule of ligustrazine. Rats were intoxicated with CCl₄ for evaluating ligustrazine's effects in vivo.

Results: Ligustrazine inhibited angiogenic cytokine production, migration, adhesion and contraction in HSCs, and activated PPARγ. Selective PPARγ inhibitor GW9662 potently abrogated ligustrazine suppression of HSC pericyte functions. Additionally, HIF-1α inhibitor PX-478 repressed HSC pericyte functions, and ligustrazine inhibited the transcription of HIF-1α, which was diminished by GW9662. Moreover, ligustrazine downregulation of HIF-1α was rescued by knockdown of SMRT, and ligustrazine increased PPARγ physical interaction with SMRT, which was abolished by GW9662. These findings collectively indicated that activation of PPARγ by ligustrazine led to transrepression of HIF-1α via a SMRT-dependent mechanism. Furthermore, molecular docking evidence revealed that ligustrazine bound to PPARγ in a unique double-molecule manner via hydrogen bonding with the residues Ser289 and Ser342. Site-directed mutation of Ser289 and/or Ser342 resulted in the loss of ligustrazine transrepression of HIF-1α in HSCs, indicating that interactions with both the residues were indispensable for ligustrazine effects. Finally, ligustrazine improved hepatic injury, angiogenesis and vascular remodeling in CCl₄-induced liver fibrosis in rats.

Conclusions: We discovered a novel ligand activation pattern for PPARγ transrepression of the target gene with therapeutic implications in HSC pericyte biology and liver fibrosis.

Hepatic perivascular mesenchymal stem cells with myogenic properties

Pericytes are multipotent mesenchymal stem cells located on the walls of blood vessels in various organs and are characterized as CD146⁺ cells. In this study, we first immunohistochemically detected pericytes in the perivascular regions of liver from two mouse genotypes, namely wild-type (WT) and myostatin null (Mstn^-/- ). We further isolated pericytes using sorting as CD146⁺ CD34^- CD56^- CD45^- cells. The main finding of this study involves the contrasting fibrogenic vs. myogenic behaviour of liver pericytes from WT and Mstn^-/- mice, respectively. Sorted CD146⁺ liver pericytes (WT and Mstn^-/- ) expressed PDGFRβ, NG2, vimentin, adult stem cell markers CD73, CD105, CD44 and could be readily differentiated into adipogenic, osteogenic and chondrogenic lineages. Furthermore, these CD146⁺ cells from WT and Mstn^-/- livers did not express myostatin, in contrast to the total liver tissue of WT. The absence of αSMA and GFAP made these cells easily distinguishable from hepatic stellate cells. When subjected to standard myogenic differentiation with low serum the CD146⁺ cells from WT liver differentiated into myofibroblasts (fibrogenic) and the CD146⁺ cells from Mstn^-/- liver differentiated into multinucleated myotubes (myogenic). Finally, we transplanted CD146⁺ pericytes into tibialis anterior muscle of dystrophic mice and established the generation of novel myofibres, thereby proving their cell therapy potential. The liver tissue microenvironment with myostatin in WT and the absence of myostatin in Mstn^-/- conditions might exert a paracrine effect in determining the fate of pericyte-like cells in the liver.

FOXA2 alleviates CCl4-induced liver fibrosis by protecting hepatocytes in mice

The liver-enriched transcription factor Forkhead Box A2 (FOXA2) has been reported to be involved in bile acid homeostasis and bile duct development. However, the role of FOXA2 in liver fibrogenesis remains undefined. In this study, we found that the abundance of FOXA2 was significantly lower in fibrotic livers of patients and mice treated with CCl₄ than in controls. Interestingly, the expression level of FOXA2 decreased in hepatocytes, whereas FOXA2 was elevated in hepatic stellate cells (HSCs) of mouse fibrotic livers. Hepatocyte-specific ablation of FOXA2 in adult mice exacerbated liver fibrosis induced by CCl₄. Either lentivirus LV-CMV-FOXA2 mediated FOXA2 overexpression in the liver or adeno-associated virus AAV8-TBG-FOXA2-mediated hepatocyte-specific upregulation of FOXA2 alleviated hepatic fibrosis. Overexpression of FOXA2 in HSCs did not obviously affect hepatic fibrogenesis. Additionally, FOXA2 knockout in hepatocytes resulted in aberrant transcription of metabolic genes. Furthermore, hepatocyte-specific knockout of FOXA2 enhanced endoplasmic reticulum stress (ER stress) and the apoptosis of hepatocytes, whereas FOXA2 overexpression in hepatocytes suppressed ER stress and hepatocyte apoptosis in mouse fibrotic livers. In conclusion, our findings suggested that FOXA2-mediated hepatocyte protection has a therapeutic role in hepatic fibrosis, and thus may be a new, promising anti-fibrotic option for treating chronic liver diseases.

Interdependent and independent multidimensional role of tumor microenvironment on hepatocellular carcinoma

The novelty of an effective therapeutic targeting for hepatocellular carcinoma (HCC) is based on improved understanding of each component of tumor microenvironment (TME) and its correspondent interactions at biological and molecular levels. In this context, new expansions for the treatment against TME and its communication with HCC are under exploration. Despite of the fact that blockage of growth factor receptors has become a treatment of choice in late phases of HCC in clinical practice, still a precise targeted treatment should address all the components of TME. Targeting one specific element out of cellular (cancer associated fibroblasts, endothelial cells, hepatic stellate cells, Kupffer cells and lymphocytes) or non-cellular (extracellular matrix, growth factors, inflammatory cytokines, proteolytic enzymes) parts of TME may not be a successful remedy for the disease because of well-designed hindrances of each component and their functional alternativeness. Meanwhile there are some elements of TME like epithelial-mesenchymal transition and CAF, which are considerably important and need thorough investigations. Ascertaining the potential role of these elements, and a single or combinational drug therapy targeting these elements of TME simultaneously, may provide the appreciable considerations to eventually improve in clinical practices and may also minimize the chances of reoccurrence of HCC.

Analysis of molecular mechanisms of 5-fluorouracil-induced steatosis and inflammation in vitro and in mice

Chemotherapy-associated steatohepatitis is attracting increasing attention because it heralds an increased risk of morbidity and mortality in patients undergoing surgery because of liver metastases. The aim of this study was to develop in vitro and in vivo models to analyze the pathogenesis of 5-fluorouracil (5-FU)-induced steatohepatitis.

Therefore, primary human hepatocytes and HepG2 hepatoma cells were incubated with 5-FU at non-toxic concentrations up to 24 h. Furthermore, hepatic tissue of C57BL/6N mice was analyzed 24 h after application of a single 5-FU dose (200 mg/kg body weight). In vitro, incubation with 5-FU induced a significant increase of hepatocellular triglyceride levels. This was paralleled by an impairment of mitochondrial function and a dose- and time-dependently increased expression of fatty acid acyl-CoA oxidase 1 (ACOX1), which catalyzes the initial step for peroxisomal β-oxidation. The latter is known to generate reactive oxygen species, and consequently, expression of the antioxidant enzyme heme oxygenase 1 (HMOX1) was significantly upregulated in 5-FU-treated cells, indicative for oxidative stress. Furthermore, 5-FU significantly induced c-Jun N-terminal kinase (JNK) activation and the expression of pro-inflammatory genes IL-8 and ICAM-1. Also in vivo, 5-FU significantly induced hepatic ACOX1 and HMOX1 expression as well as JNK-activation, pro-inflammatory gene expression and immune cell infiltration. In summary, we identified molecular mechanisms by which 5-FU induces hepatocellular lipid accumulation and inflammation. Our newly developed models can be used to gain further insight into the pathogenesis of 5-FU-induced steatohepatitis and to develop therapeutic strategies to inhibit its development and progression.

Probing the unseen structure and function of liver cells through atomic force microscopy

With the arrival of atomic force microscopy (AFM) about thirty years ago, this new imaging tool opened up a new area for the exploration of biological samples, ranging from the tissue and cellular level down to the supramolecular scale. Commercial instruments of this new imaging technique began to appear in the five years following its discovery in 1986 by Binnig, Quate & Gerber. From that point onwards the AFM has attracted many liver biologists, and the number of publications describing structure-function relationships on the diverse set of liver cells has grown steadily ever since. It is therefore timely to reflect on the achievements of AFM in disclosing the cellular architecture of hepatocytes, liver sinusoidal endothelial cells, Kupffer cells, stellate cells and liver-associated natural killer cells. In this thematic paper, we present new data and provide an in-depth overview of the current AFM literature on liver cell biology. We furthermore include a future outlook on how this scanning probe imaging tool and its latest developments can contribute to clarify various structural and functional aspects of cells in liver health and disease.

Anti-fibrotic Effects of Synthetic Oligodeoxynucleotide for TGF-β1 and Smad in an Animal Model of Liver Cirrhosis

Liver fibrosis is characterized by changes in tissue architecture and extracellular matrix composition. Liver fibrosis affects not only hepatocytes but also the non-parenchymal cells such as hepatic stellate cells (HSCs), which are essential for maintaining an intact liver structure and function. Transforming growth factor β1 (TGF-β1) is a multifunctional cytokine that induces liver fibrosis through activation of Smad signaling pathways. To improve a new therapeutic approach, synthetic TGF-β1/Smad oligodeoxynucleotide (ODN) was used to suppress both TGF-β1 expression and Smad transcription factor using a combination of antisense ODN and decoy ODN. The aims of this study are to investigate the anti-fibrotic effects of TGF-β1/Smad ODN on simultaneous suppressions of both Smad transcription factor and TGF-β1 mRNA expression in the hepatic fibrosis model in vitro and in vivo. Synthetic TGF-β1/Smad ODN effectively inhibits Smad binding activity and TGF-β1 expression. TGF-β1/Smad ODN attenuated the epithelial mesenchymal transition (EMT) and activation of HSCs in TGF-β1-induced AML12 and HSC-T6 cells. TGF-β1/Smad ODN prevented the fibrogenesis and deposition of collagen in CCl₄-treated mouse model. Synthetic TGF-β1/Smad ODN demonstrates anti-fibrotic effects that are mediated by the suppression of fibrogenic protein and inflammatory cytokines. Therefore, synthetic TGF-β1/Smad ODN has substantial therapeutic feasibility for the treatment of liver fibrotic diseases.

MiR-122 modification enhances the therapeutic efficacy of adipose tissue-derived mesenchymal stem cells against liver fibrosis

Mesenchymal stem cell (MSC) transplantation alone may be insufficient for treatment of liver fibrosis because of complicated histopathological changes in the liver. Given that miR‐122 plays an essential role in liver fibrosis by negatively regulating the proliferation and transactivation of hepatic stellate cells (HSCs), this study investigated whether miR‐122 modification can improve the therapeutic efficacy of adipose tissue‐derived MSCs in treating liver fibrosis. MiR‐122‐modified AMSCs (AMSC‐122) were constructed through lentivirus‐mediated transfer of pre‐miR‐122. MiR‐122‐modified AMSCs expressed high level of miR‐122, while they retained their phenotype and differentiation potential as naïve AMSCs. AMSC‐122 more effectively suppressed the proliferation of and collagen maturation in HSCs than scramble miRNA‐modified AMSCs. In addition, AMSC‐derived exosomes mediated the miR‐122 communication between AMSCs and HSCs, further affecting the expression levels of miR‐122 target genes, such as insulin‐like growth factor receptor 1 (IGF1R), Cyclin G(1) (CCNG1) and prolyl‐4‐hydroxylase α1 (P4HA1), which are involved in proliferation of and collagen maturation in HSCs. Moreover, miR‐122 modification enhanced the therapeutic efficacy of AMSCs in the treatment of carbon tetrachloride (CCl₄)‐induced liver fibrosis by suppressing the activation of HSCs and alleviating collagen deposition. Results demonstrate that miR‐122 modification improves the therapeutic efficacy of AMSCs through exosome‐mediated miR‐122 communication; thus, miR‐122 modification is a new potential strategy for treatment of liver fibrosis.

Long-term influence of sialoadenectomy on the liver of male albino rat

Epidermal growth factor is an endocrine product of the submandibular gland; the liver is an important target of its action and is affected by sialoadenectomy. Thirty rats were used in this study and divided into group I (sham-operated animals), group II (sialoadenectomy after 4 weeks), and group III (sialoadenectomy after 10 weeks). Liver samples were processed for light and electron microscope examination. Sialoadenectomy induced mild-to-moderate liver damage which persists up to 10 weeks after the operation. This damage is manifested morphologically rather than functionally, affecting the general structure, hepatocytes, hepatic stellate cells, and hepatic sinusoids.

Embrionary way to create a fatty liver in portal hypertension

Portal hypertension in the rat by triple partial portal vein ligation produces an array of splanchnic and systemic disorders, including hepatic steatosis. In the current review these alterations are considered components of a systemic inflammatory response that would develop through three overlapping phenotypes: The neurogenic, the immune and the endocrine. These three inflammatory phenotypes could resemble the functions expressed during embryonic development of mammals. In turn, the inflammatory phenotypes would be represented in the embryo by two functional axes, that is, a coelomic-amniotic axis and a trophoblastic yolk-sac or vitelline axis. In this sense, the inflammatory response developed after triple partial portal vein ligation in the rat would integrate both functional embryonic axes on the liver interstitial space of Disse. If so, this fact would favor the successive development of steatosis, steatohepatitis and fibrosis. Firstly, these recapitulated embryonic functions would produce the evolution of liver steatosis. In this way, this fat liver could represent a yolk-sac-like in portal hypertensive rats. After that, the systemic recapitulation of these embryonic functions in experimental prehepatic portal hypertension would consequently induce a gastrulation-like response in which a hepatic wound healing reaction or fibrosis occur. In conclusion, studying the mechanisms involved in embryonic development could provide key results for a better understanding of the nonalcoholic fatty liver disease etiopathogeny.

Discovering cardiac pericyte biology: From physiopathological mechanisms to potential therapeutic applications in ischemic heart disease

Microvascular pericytes and the more recently discovered adventitial pericyte-like progenitor cells are a subpopulation of vascular stem cells closely associated with small and large blood vessels respectively. These populations of perivascular cells are remarkably abundant in the heart. Pericytes control important physiological processes such as angiogenesis, blood flow and vascular permeability. In the heart, this pleiotropic activity makes pericytes extremely interesting for applications in regenerative medicine. On the other hand, dysfunction of pericytes could participate in the pathogenesis of cardiovascular disease, such as arterial hypertension, fibro-calcific cardiovascular remodeling, myocardial edema and post-ischemic coronary no-reflow. On a therapeutic standpoint, preclinical studies in small animal models of myocardial infarction have demonstrated the healing potential of pericytes transplantation, which has been ascribed to direct vascular incorporation and paracrine pro-angiogenic and anti-apoptotic activities. These promising findings open the door to the clinical use of pericytes for the treatment of cardiovascular diseases.

Effects of Melatonin on Differentiation Potential of Ito Cells in Mice with Induced Fibrosis of the Liver

We studied the effects of melatonin on differentiation potential of Ito cells during atypical regeneration of mouse liver under conditions of CCl₄-induced fibrosis. The dynamics of fibrosis was traced at the histological level and the effects of melatonin on the differentiation potential of mouse Ito cells were evaluated. Melatonin alleviated fibrotic changes in the liver tissue and reduced differentiation of Ito cells into myofibroblasts under conditions of atypical regeneration of the liver in induced fibrosis. The hepatoprotective role of melatonin was shown.

Fibronectin Extra Domain A Promotes Liver Sinusoid Repair following Hepatectomy

Liver sinusoidal endothelial cells (LSECs) are the main endothelial cells in the liver and are important for maintaining liver homeostasis as well as responding to injury. LSECs express cellular fibronectin containing the alternatively spliced extra domain A (EIIIA-cFN) and increase expression of this isoform after liver injury, although its function is not well understood. Here, we examined the role of EIIIA-cFN in liver regeneration following partial hepatectomy. We carried out two-thirds partial hepatectomies in mice lacking EIIIA-cFN and in their wild type littermates, studied liver endothelial cell adhesion on decellularized, EIIIA-cFN-containing matrices and investigated the role of cellular fibronectins in liver endothelial cell tubulogenesis. We found that liver weight recovery following hepatectomy was significantly delayed and that sinusoidal repair was impaired in EIIIA-cFN null mice, especially females, as was the lipid accumulation typical of the post-hepatectomy liver. In vitro, we found that liver endothelial cells were more adhesive to cell-deposited matrices containing the EIIIA domain and that cellular fibronectin enhanced tubulogenesis and vascular cord formation. The integrin α₉β₁, which specifically binds EIIIA-cFN, promoted tubulogenesis and adhesion of liver endothelial cells to EIIIA-cFN. Our findings identify a role for EIIIA-cFN in liver regeneration and tubulogenesis. We suggest that sinusoidal repair is enhanced by increased LSEC adhesion, which is mediated by EIIIA-cFN.

Prophylactic role of coenzyme Q10 and Cynara scolymus L on doxorubicin-induced toxicity in rats: Biochemical and immunohistochemical study

Objective:

The study aims to evaluate the protective effects of coenzyme Q10 (CoQ10) and Cynara scolymus L (CS) on doxorubicin (dox)-induced toxicity.

Materials and Methods:

Sixty male rats were divided into six groups. Group 1 as a control. Group 2 received dox (10 mg/kg) intraperitoneally. Group 3 received CoQ10 (200 mg/kg). Group 4 received CS (500 mg/kg). Group 5 received CoQ10 (200 mg/kg) and dox (10 mg/kg). Group 6 received CS (500 mg/kg) and dox (10 mg/kg). The rats were then evaluated biochemically and immunohistochemically.

Results:

Dox produced a significant deterioration of hepatic and renal functional parameters. Moreover, an upsurge of oxidative stress and nitrosative stress markers. The expression of alpha-smooth muscle actin (α-SMA) was increased and proliferating cell nuclear antigen (PCNA) expression was decreased. Administration of CoQ10 and CS resulted in a significant improvement of hepatic and renal functional parameters, and an improvement of both α-SMA and PCNA.

Conclusion:

It is concluded that pretreatment with CoQ10 and CS is associated with up-regulation of favorable protective enzymes and down-regulation of oxidative stress. That can be advised as a supplement to dox-treated patients.

Hedgehog regulates yes-associated protein 1 in regenerating mouse liver

Adult liver regeneration requires induction and suppression of proliferative activity in multiple types of liver cells. The mechanisms that orchestrate the global changes in gene expression that are required for proliferative activity to change within individual liver cells, and that coordinate proliferative activity among different types of liver cells, are not well understood. Morphogenic signaling pathways that are active during fetal development, including Hedgehog and Hippo/Yes-associated protein 1 (Yap1), regulate liver regeneration in adulthood. Cirrhosis and liver cancer result when these pathways become dysregulated, but relatively little is known about the mechanisms that coordinate and control morphogenic signaling during effective liver regeneration. We evaluated the hypothesis that the Hedgehog pathway controls Yap1 activation during liver regeneration by studying intact mice and cultured liver cells. In cultured hepatic stellate cells (HSCs), disrupting Hedgehog signaling blocked activation of Yap1, and knocking down Yap1 inhibited induction of both Yap1- and Hedgehog-regulated genes that enable HSC to become myofibroblasts (MFs). In mice, disrupting Hedgehog signaling in MFs inhibited liver regeneration after partial hepactectomy (PH). Reduced proliferative activity in the liver epithelial compartment resulted from loss of stroma-derived paracrine signals that activate Yap1 and the Hedgehog pathway in hepatocytes. This prevented hepatocytes from up-regulating Yap1- and Hedgehog-regulated transcription factors that normally promote their proliferation.

CONCLUSIONS

Morphogenic signaling in HSCs is necessary to reprogram hepatocytes to regenerate the liver epithelial compartment post-PH. This discovery identifies novel molecules that might be targeted to correct defective repair during cirrhosis and liver cancer. (Hepatology 2016;64:232-244).

Mechanisms of adaptation of the hepatic vasculature to the deteriorating conditions of blood circulation in liver cirrhosis

PubMed, EMBASE, Orphanet, MIDLINE, Google Scholar and Cochrane Library were searched for articles published between 1983 and 2015. Relevant articles were selected by using the following terms: “Liver cirrhosis”, “Endothelial dysfunction”, “Sinusoidal remodeling”, “Intrahepatic angiogenesis” and “Pathogenesis of portal hypertension”. Then the reference lists of identified articles were searched for other relevant publications as well. Besides gross hepatic structural disorders related to diffuse fibrosis and formation of regenerative nodules, the complex morphofunctional rearrangement of the hepatic microvascular bed and intrahepatic angiogenesis also play important roles in hemodynamic disturbances in liver cirrhosis. It is characterized by endothelial dysfunction and impaired paracrine interaction between activated stellate hepatocytes and sinusoidal endotheliocytes, sinusoidal remodeling and capillarization, as well as development of the collateral microcirculation. In spite of the fact that complex morphofunctional rearrangement of the hepatic microvascular bed and intrahepatic angiogenesis in liver cirrhosis are the compensatory-adaptive reaction to the deteriorating conditions of blood circulation, they contribute to progression of disease and development of serious complications, in particular, related to portal hypertension.

Cryptolepine derivative-6h inhibits liver fibrosis in TGF-β1-induced HSC-T6 cells by targeting the Shh pathway

Liver fibrosis is a worldwide problem with a significant morbidity and mortality. Cryptolepis sanguinolenta (family Periplocaceae) is widely used in West African countries for the treatment of malaria, as well as for some other diseases. However, the role of C. sanguinolenta in hepatic fibrosis is still unknown. It has been reported that Methyl-CpG binding protein 2 (MeCP2) had a high expression in liver fibrosis and played a central role in its pathobiology. Interestingly, we found that a cryptolepine derivative (HZ-6h) could inhibit liver fibrosis by reducing MeCP2 expression, as evidenced by the dramatic downregulation of α-smooth muscle actin (α-SMA) and type I collagen alpha-1 (Col1α1) in protein levels in vitro. Meanwhile, we also found that HZ-6h could reduce the cell viability and promote apoptosis of hepatic stellate cells (HSCs) treated with transforming growth factor beta 1(TGF-β1). Then, we investigated the potential molecular mechanisms and found that HZ-6h blocked Shh signaling in HSC-T6 cells, resulting in the decreased protein expression of Patched-1 (PTCH-1), Sonic hedgehog (Shh), and glioma-associated oncogene homolog 1 (GLI1). In short, these results indicate that HZ-6h inhibits liver fibrosis by downregulating MeCP2 through the Shh pathway in TGF-β1-induced HSC-T6 cells.

Differential Roles of Angiogenesis in the Induction of Fibrogenesis and the Resolution of Fibrosis in Liver

Liver fibrosis is a wound healing process that includes inflammation, deposition of extracellular matrix molecules, and pathological neovascularization. Angiogenesis, which is defined by the formation of new blood vessels from pre-existing vessels, is a complex and dynamic process under both physiological and pathological conditions. Although whether angiogenesis can induce or occur in parallel with the progression of hepatic fibrosis has not yet been determined, intrahepatic sinusoidal formation and remodeling are key features of liver fibrosis. Some recent evidence has suggested that experimental inhibition of angiogenesis ameliorates the development of liver fibrosis, while other recent studies indicate that neutralization or genetic ablation of vascular endothelial growth factor (VEGF) in myeloid cells can delay tissue repair and fibrosis resolution in damaged liver. In this review, we briefly summarize the current knowledge about the differential roles of angiogenesis in the induction of fibrogenesis and the resolution of fibrosis in damaged livers. Possible strategies for the prevention and treatment of liver fibrosis are also discussed.

Tenascin-C promotes migration of hepatic stellate cells and production of type I collagen

Tenascin-C (TN-C) is an extracellular matrix glycoprotein markedly upregulated during liver fibrosis. The study is performed to explore the role of TN-C during the growth and activation of hepatic stellate cells (HSCs). We found that TN-C was accumulated accompanying with the HSC activation. Our data on cell migration assay revealed that the rTN-C treatment enhanced HSC migration in a dose- and time-dependent manner, but did not influence their proliferation. HSCs transfected with pTARGET-TN-C overexpression vector displayed increased the type I collagen (Col I) production. TN-C overexpression enhanced the process of HSC activation through TGF-β1 signaling. Moreover, the anti-α9β1 integrin antibody treatment blocked the TN-C-driven Col I increase in rat HSCs. Collectively, TN-C had a positive role in activation of HSCs mediated by TGF-β1 and α9β1 integrin, manifesting elevation of Col I production and promotion of cell migration. Our results provide a potential insight for the therapy of hepatic fibrosis.

Role of fibroblast growth factors in organ regeneration and repair

In its broad sense, regeneration refers to the renewal of lost cells, tissues or organs as part of the normal life cycle (skin, hair, endometrium etc.) or as part of an adaptive mechanism that organisms have developed throughout evolution. For example, worms, starfish and amphibians have developed remarkable regenerative capabilities allowing them to voluntarily shed body parts, in a process called autotomy, only to replace the lost parts afterwards. The bizarre myth of the fireproof homicidal salamander that can survive fire and poison apple trees has persisted until the 20th century. Salamanders possess one of the most robust regenerative machineries in vertebrates and attempting to draw lessons from limb regeneration in these animals and extrapolate the knowledge to mammals is a never-ending endeavor. Fibroblast growth factors are potent morphogens and mitogens that are highly conserved among the animal kingdom. These growth factors play key roles in organogenesis during embryonic development as well as homeostatic balance during postnatal life. In this review, we provide a summary about the current knowledge regarding the involvement of fibroblast growth factor signaling in organ regeneration and repair. We also shed light on the use of these growth factors in previous and current clinical trials in a wide array of human diseases.

Hepatic stellate cells promote upregulation of epithelial cell adhesion molecule and epithelial-mesenchymal transition in hepatic cancer cells

Microenvironment plays an important role in epithelial-mesenchymal transition (EMT) and stemness of cells in hepatocellular carcinoma (HCC). Epithelial cell adhesion molecule (EpCAM) is known as a tumor stemness marker of HCC. To investigate the relationship between microenvironment and stemness, we performed an in vitro co-culture assay. Four HCC cell lines (HepG2, Hep3B, HuH-7 and PLC/PRF/5) were co-cultured with the TWNT-1 immortalized hepatic stellate cells (HSCs), which create a microenvironment with HCC. Cell proliferation ability was analyzed by flow cytometry (FCM) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, while migration ability was assessed by a wound healing assay. Expression of EpCAM was analyzed by immunoblotting and FCM. HCC cell lines were co-cultured with TWNT-1 treated with small interfering RNA (siRNA) for TGF-β and HB-EGF; we then analyzed proliferation, migration ability and protein expression using the methods described above. Proliferation ability was unchanged in HCC cell lines co-cultured with TWNT-1. Migration ability was increased in HCC cell lines (HepG2, Hep3B, HuH-7 and PLC/PRF/5) directly (216.2±67.0, 61.0±22.0, 124.0±66.2 and 51.5±40.3%) and indirectly (102.5±22.0, 84.6±30.9, 86.1±25.7 and 73.9±29.7%) co-cultured with TWNT-1 compared with the HCC uni-culture. Immunoblot analysis revealed increased EpCAM expression in the HCC cell lines co-cultured with TWNT-1. Flow cytometry revealed that the population of E-cadherin-/N-cadherin+ and EpCAM-positive cells increased and accordingly, EMT and stemness in the HCC cell line were activated. These results were similar in the directly and indirectly co-cultured samples, indicating that humoral factors were at play. Conversely, HCC cell lines co-cultured with siRNA‑treated TWNT-1 showed decreased migration ability, a decreased population of EpCAM-positive and E-cadherin-/N-cadherin+ cells. Taken together, humoral factors secreted from TWNT-1 promote upregulation of EpCAM and EMT in hepatic cancer cells.

Causal Modeling of Cancer-Stromal Communication Identifies PAPPA as a Novel Stroma-Secreted Factor Activating NFκB Signaling in Hepatocellular Carcinoma

Inter-cellular communication with stromal cells is vital for cancer cells. Molecules involved in the communication are potential drug targets. To identify them systematically, we applied a systems level analysis that combined reverse network engineering with causal effect estimation. Using only observational transcriptome profiles we searched for paracrine factors sending messages from activated hepatic stellate cells (HSC) to hepatocellular carcinoma (HCC) cells. We condensed these messages to predict ten proteins that, acting in concert, cause the majority of the gene expression changes observed in HCC cells. Among the 10 paracrine factors were both known and unknown cancer promoting stromal factors, the former including Placental Growth Factor (PGF) and Periostin (POSTN), while Pregnancy-Associated Plasma Protein A (PAPPA) was among the latter. Further support for the predicted effect of PAPPA on HCC cells came from both in vitro studies that showed PAPPA to contribute to the activation of NFκB signaling, and clinical data, which linked higher expression levels of PAPPA to advanced stage HCC. In summary, this study demonstrates the potential of causal modeling in combination with a condensation step borrowed from gene set analysis [Model-based Gene Set Analysis (MGSA)] in the identification of stromal signaling molecules influencing the cancer phenotype.

All living cells rely on communication with other cells to ensure their function and survival. Molecular signals are sent among cells of the same cell type and from cells of one cell type to another. In cancer, not only the cancer cells themselves are responsible for the malignancy, but also stromal (non-cancerous) cells and the molecular signals they send to cancer cells are important factors that determine the severity and outcome of the disease. Therefore, the identification of stromal signals and their influence on cancer cells is important for the development of novel treatment strategies. With a computational systems biology model of stroma-cancer cell communication, we have compiled a set of ten proteins secreted by stromal cells that shape the cancer phenotype. Most importantly, our causal analysis uncovered Pregnancy-Associated Plasma Protein A (PAPPA) as a novel paracrine inducer of the pro-tumorigenic NFκB signaling pathway. In liver cancer patients, higher levels of PAPPA protein indicate a more progressed tumor stage, confirming its clinical relevance.

Notch suppresses angiogenesis and progression of hepatic metastases

The Notch pathway plays multiple key roles in tumorigenesis, and its signaling components have therefore aroused great interest as targets for emerging therapies. Here, we show that inhibition of Notch, using a soluble receptor Notch1 decoy, unexpectedly caused a remarkable increase in liver metastases from neuroblastoma and breast cancer cells. Increased liver metastases were also seen after treatment with the γ-secretase inhibitor PF-03084014. Transgenic mice with heterozygous loss of Notch1 demonstrated a marked increase in hepatic metastases, indicating that Notch1 signaling acts as metastatic suppressor in the liver microenvironment. Inhibition of DLL1/4 with ligand-specific Notch1 decoys increased sprouting of sinusoidal endothelial cells into micrometastases, thereby supporting early metastatic angiogenic growth. Inhibition of tumor-derived JAG1 signaling activated hepatic stellate cells, increasing their recruitment to vasculature of micrometastases, thereby supporting progression to macrometastases. These results demonstrate that inhibition of Notch causes pathologic activation of liver stromal cells, promoting angiogenesis and growth of hepatic metastases. Our findings have potentially serious implications for Notch inhibition therapy.

The role of miRNAs in the regulation of inflammatory processes during hepatofibrogenesis

Liver cirrhosis represents the end stage of most chronic inflammatory liver diseases and is a major global health burden. Despite the enormous relevance of cirrhotic disease, pharmacological strategies for prevention or treatment of hepatic fibrosis are still limited, underlining the need to establish a better understanding of the molecular mechanisms underlying the pathogenesis of hepatic cirrhosis. Recently, miRNAs have emerged as a new class of RNAs that do not withhold the information to encode for proteins but regulate whole gene expression networks during different physiological and pathological processes. Various authors demonstrated that miRNA species are functionally involved in the regulation of chronic liver damage and development of liver cirrhosis in inflamed livers. Moreover, circulating miRNA patterns were suggested to serve as blood-based biomarkers indicating liver injury and progression to hepatic cirrhosis and cancer. Here we summarize current findings on a potential role of miRNAs in the cascade leading from liver inflammation to liver fibrosis and finally hepatocellular carcinoma. We compare data from animal models with findings on miRNAs dysregulated in human patients and finally highlight a potential use of miRNAs as biomarkers for liver injury, fibrosis and cancer.

Targeting pericytes for angiogenic therapies

In pathological scenarios, such as tumor growth and diabetic retinopathy, blocking angiogenesis would be beneficial. In others, such as myocardial infarction and hypertension, promoting angiogenesis might be desirable. Due to their putative influence on endothelial cells, vascular pericytes have become a topic of growing interest and are increasingly being evaluated as a potential target for angioregulatory therapies. The strategy of manipulating pericyte recruitment to capillaries could result in anti- or proangiogenic effects. Our current understanding of pericytes, however, is limited by knowledge gaps regarding pericyte identity and lineage. To use a music analogy, this review is a "mash-up" that attempts to integrate what we know about pericyte functionality and expression with what is beginning to be elucidated regarding their regenerative potential. We explore the lingering questions regarding pericyte phenotypic identity and lineage. The expression of different pericyte markers (e.g., SMA, Desmin, NG2, and PDGFR-β) varies for different subpopulations and tissues. Previous use of these markers to identify pericytes has suggested potential phenotypic overlaps and plasticity toward other cell phenotypes. Our review chronicles the state of the literature, identifies critical unanswered questions, and motivates future research aimed at understanding this intriguing cell type and harnessing its therapeutic potential.

Pericytes at the intersection between tissue regeneration and pathology

Perivascular multipotent cells, pericytes, contribute to the generation and repair of various tissues in response to injury. They are heterogeneous in their morphology, distribution, origin and markers, and elucidating their molecular and cellular differences may inform novel treatments for disorders in which tissue regeneration is either impaired or excessive. Moreover, these discoveries offer novel cellular targets for therapeutic approaches to many diseases. This review discusses recent studies that support the concept that pericyte subtypes play a distinctive role in myogenesis, neurogenesis, adipogenesis, fibrogenesis and angiogenesis.

Update on implications and mechanisms of angiogenesis in liver fibrosis

Liver fibrosis occurs as a compensatory response to the process of tissue repair in a wide range of chronic liver injures. It is characterized by excessive deposition of extracellular matrix in liver tissues. As the pathogenesis progresses without effective management, it will lead to formation of liver fiber nodules and disruption of normal liver structure and function, finally culminating in cirrhosis and hepatocellular carcinoma. A new discovery shows that liver angiogenesis is strictly associated with, and may even favor fibrogenic progression of chronic liver diseases. Recent basic and clinical investigations also demonstrate that liver fibrogenesis is accompanied by pathological angiogenesis and sinusoidal remodeling, which critically determine the pathogenesis and prognosis of liver fibrosis. Inhibition of pathological angiogenesis is considered to be a new strategy for the treatment of liver fibrosis. This review summarizes current knowledge on the process of angiogenesis, the relationships between angiogenesis and liver fibrosis, and on the molecular mechanisms of liver angiogenesis. On the other hand, it also presents the different strategies that have been used in experimental models to counteract excessive angiogenesis and the role of angiogenesis in the prevention and treatment of liver fibrosis.

Molecular control of capillary morphogenesis and maturation by recognition and remodeling of the extracellular matrix: functional roles of endothelial cells and pericytes in health and disease

This review addresses fundamental mechanisms underlying how capillaries form in three-dimensional extracellular matrices and how endothelial cells (ECs) and pericytes co-assemble to form capillary networks. In addition to playing a critical role in supplying oxygen and nutrients to tissues, recent work suggests that blood vessels supply important signals to facilitate tissue development. Here, we hypothesize that another major function of capillaries is to supply signals to suppress major disease mechanisms including inflammation, infection, thrombosis, hemorrhage, edema, ischemic injury, fibrosis, autoimmune disease and tumor growth/progression. Capillary dysfunction plays a key pathogenic role in many human diseases, and thus, this suppressing function may be attenuated and central toward the initiation and progression of disease. We describe how capillaries form through creation of EC-lined tube networks and vascular guidance tunnels in 3D extracellular matrices. Pericytes recruit to the abluminal EC tube surface within these tunnel spaces, and work together to assemble the vascular basement membrane matrix. These processes occur under serum-free conditions in 3D collagen or fibrin matrices and in response to five key growth factors which are stem cell factor, interleukin-3, stromal-derived factor-1α, fibroblast growth factor-2 and insulin. In addition, we identified a key role for EC-derived platelet-derived growth factor-BB and heparin-binding epidermal growth factor in pericyte recruitment and proliferation to promote EC-pericyte tube co-assembly and vascular basement membrane matrix deposition. A molecular understanding of capillary morphogenesis and maturation should lead to novel therapeutic strategies to repair capillary dysfunction in major human disease contexts including cancer and diabetes.