Lysophosphatidic acid alters the expression profiles of angiogenic factors, cytokines, and chemokines in mouse liver sinusoidal endothelial cells

From outside to inside and back again: the lysophosphatidic acid-CCN axis in signal transduction

CCN1 and CCN2 are matricellular proteins that are transcriptionally induced by various stimuli, including growth factors. CCN proteins act to facilitate signaling events involving extracellular matrix proteins. Lysophosphatidic acid (LPA) is a lipid that activates G protein-coupled receptors (GPCRs), enhancing proliferation, adhesion, and migration in many types of cancer cells. Our group previously reported that LPA induces production of CCN1 protein in human prostate cancer cell lines within 2-4 h. In these cells, the mitogenic activity of LPA is mediated by LPA Receptor 1 (LPAR1), a GPCR. There are multiple examples of the induction of CCN proteins by LPA, and by the related lipid mediator sphingosine-1-phosphate (S1P), in various cellular models. The signaling pathways responsible for LPA/S1P-induced CCN1/2 typically involve activation of the small GTP-binding protein Rho and the transcription factor YAP. Inducible CCNs can potentially play roles in downstream signal transduction events required for LPA and S1P-induced responses. Specifically, CCNs secreted into the extracellular space can facilitate the activation of additional receptors and signal transduction pathways, contributing to the biphasic delayed responses typically seen in response to growth factors acting via GPCRs. In some model systems, CCN1 and CCN2 play key roles in LPA/S1P-induced cell migration and proliferation. In this way, an extracellular signal (LPA or S1P) can activate GPCR-mediated intracellular signaling to induce the production of extracellular modulators (CCN1 and CCN2) that in turn initiate another round of intracellular signaling.

Changes in gut microbiome correlate with intestinal barrier dysfunction and inflammation following a 3-day ethanol exposure in aged mice

Alcohol use among older adults is on the rise. This increase is clinically relevant as older adults are at risk for increased morbidity and mortality from many alcohol-related chronic diseases compared to younger patients. However, little is known regarding the synergistic effects of alcohol and age. There are intriguing data suggesting that aging may lead to impaired intestinal barrier integrity and dysbiosis of the intestinal microbiome, which could increase susceptibility to alcohol's negative effects. To study the effects of alcohol in age we exposed aged and young mice to 3 days of moderate ethanol and evaluated changes in gut parameters. We found that these levels of drinking do not have obvious effects in young mice but cause significant alcohol-induced gut barrier dysfunction and expression of the pro-inflammatory cytokine TNFα in aged mice. Ethanol-induced downregulation of expression of the gut-protective antimicrobial peptides Defa-rs1, Reg3b, and Reg3g was observed in aged, but not young mice. Analysis of the fecal microbiome revealed age-associated shifts in microbial taxa, which correlated with intestinal and hepatic inflammatory gene expression. Taken together, these data demonstrate that age drives microbiome dysbiosis, while ethanol exposure in aged mice induces changes in the expression of antimicrobial genes important for separating these potentially damaging microbes from the intestinal lumen. These changes highlight potential mechanistic targets for prevention of the age-related exacerbation of effects of ethanol on the gut.

Enrichment Methods for Murine Liver Non-Parenchymal Cells Differentially Affect Their Immunophenotype and Responsiveness towards Stimulation

Hepatocytes comprise the majority of the liver and largely exert metabolic functions, whereas non-parenchymal cells (NPCs)—comprising Kupffer cells, dendritic cells and liver sinusoidal endothelial cells—control the immunological state within this organ. Here, we compared the suitability of two isolation methods for murine liver NPCs. Liver perfusion (LP) with collagenase/DNase I applied via the portal vein leads to efficient liver digestion, whereas the modified liver dissociation (LD) method combines mechanical dissociation of the retrieved organ with enzymatic degradation of the extracellular matrix. In cases of both LP and LD, NPCs were enriched by subsequent gradient density centrifugation. Our results indicate that LP and LD are largely comparable with regards to the yield, purity, and composition of liver NPCs. However, LD-enriched liver NPCs displayed a higher degree of activation after overnight cultivation, and accordingly were less responsive towards stimulation with toll-like receptor ligands that are frequently used as adjuvants, e.g., in nano-vaccines. We conclude that LP is more suitable for obtaining liver NPCs for subsequent in vitro studies, whereas LD as the less laborious method, is more convenient for parallel isolation of larger numbers of samples for ex vivo analysis.

The novel ORFV protein ORFV113 activates LPA-p38 signaling

Viruses have evolved mechanisms to subvert critical cellular signaling pathways that regulate a wide range of cellular functions, including cell differentiation, proliferation and chemotaxis, and innate immune responses. Here, we describe a novel ORFV protein, ORFV113, that interacts with the G protein-coupled receptor Lysophosphatidic acid receptor 1 (LPA1). Consistent with its interaction with LPA1, ORFV113 enhances p38 kinase phosphorylation in ORFV infected cells in vitro and in vivo, and in cells transiently expressing ORFV113 or treated with soluble ORFV113. Infection of cells with virus lacking ORFV113 (OV-IA82Δ113) significantly decreased p38 phosphorylation and viral plaque size. Infection of cells with ORFV in the presence of a p38 kinase inhibitor markedly diminished ORFV replication, highlighting importance of p38 signaling during ORFV infection. ORFV113 enhancement of p38 activation was prevented in cells in which LPA1 expression was knocked down and in cells treated with LPA1 inhibitor. Infection of sheep with OV-IA82Δ113 led to a strikingly attenuated disease phenotype, indicating that ORFV113 is a major virulence determinant in the natural host. Notably, ORFV113 represents the first viral protein that modulates p38 signaling via interaction with LPA1 receptor.

Oxidized low-density lipoprotein activates extracellular signal-regulated kinase signaling to downregulate sortilin expression in liver sinusoidal endothelial cells

BACKGROUND AND AIM

Both type 2 diabetes mellitus and non-alcoholic fatty liver disease are closely associated with elevated levels of low-density lipoprotein cholesterol and its oxidized form (ox-LDL). This study aimed to investigate the regulation of sortilin in liver tissue and its potential implications for lipid metabolism.

METHODS

Sixty male Wistar rats were randomly divided into four groups: control group (n = 15), ox-LDL group (n = 15), PD98059 group (n = 15), and ox-LDL + PD98059 group (n = 15). Liver sinusoidal endothelial cells were extracted from liver tissue of the control group and were identified using an anti-CD31 antibody. Lipid droplet accumulation was observed by Oil red O and hematoxylin-eosin staining. The protein expression levels were detected by immunohistochemical staining, real-time reverse transcription-polymerase chain reaction, and western blot. Histopathologic examinations were performed by Gomori methenamine silver staining.

RESULTS

The ox-LDL group exhibited increased lipid droplet accumulation. Further, ox-LDL activated the extracellular signal-regulated kinase (ERK)-mediated downregulation of sortilin expression, whereas blocking of ERK signaling by PD98059 increased sortilin protein expression. Consistently, hematoxylin-eosin staining showed that the structure of the hepatocytes was loose and disordered in arrangement, with lipid droplets present in the cytoplasm of the ox-LDL group. However, PD98059 significantly improved the integration of the scaffold structure. Gomori methenamine silver staining showed that the ox-LDL group had darker and more obvious fragmented silver nitrate deposits in the basement membrane and sinus space.

CONCLUSIONS

Sortilin can protect liver sinusoidal endothelial cells from injury and maintain integration of the liver scaffold structure in ox-LDL-induced lipid-injured liver.

Dysregulation of the Lysophosphatidylcholine/Autotaxin/Lysophosphatidic Acid Axis in Acute-on-Chronic Liver Failure Is Associated With Mortality and Systemic Inflammation by Lysophosphatidic Acid-Dependent Monocyte Activation

BACKGROUND & AIMS

Acute-on-chronic liver failure (ACLF) is characterized by systemic inflammation, monocyte dysfunction, and susceptibility to infection. Lysophosphatidylcholines (LPCs) are immune-active lipids whose metabolic regulation and effect on monocyte function in ACLF is open for study.

APPROACHES & RESULTS

Three hundred forty-two subjects were recruited and characterized for blood lipid, cytokines, phospholipase (PLA), and autotaxin (ATX) concentration. Peripheral blood mononuclear cells and CD14⁺ monocytes were cultured with LPC, or its autotaxin (ATX)-derived product, lysophosphatidic acid (LPA), with or without lipopolysaccharide stimulation and assessed for surface marker phenotype, cytokines production, ATX and LPA-receptor expression, and phagocytosis. Hepatic ATX expression was determined by immunohistochemistry. Healthy volunteers and patients with sepsis or acute liver failure served as controls. ACLF serum was depleted in LPCs with up-regulated LPA levels. Patients who died had lower LPC levels than survivors (area under the receiver operating characteristic curve, 0.94; P < 0.001). Patients with high-grade ACLF had the lowest LPC concentrations and these rose over the first 3 days of admission. ATX concentrations were higher in patients with AD and ACLF and correlated with Model for End-Stage Liver Disease, Consortium on Chronic Liver Failure-Sequential Organ Failure Assessment, and LPC/LPA concentrations. Reduction in LPC correlated with higher monocyte Mer-tyrosine-kinase (MerTK) and CD163 expression. Plasma ATX concentrations rose dynamically during ACLF evolution, correlating with IL-6 and TNF-α, and were associated with increased hepatocyte ATX expression. ACLF patients had lower human leukocyte antigen-DR isotype and higher CD163/MerTK monocyte expression than controls; both CD163/MerTK expression levels were reduced in ACLF ex vivo following LPA, but not LPC, treatment. LPA induced up-regulation of proinflammatory cytokines by CD14⁺ cells without increasing phagocytic capacity.

CONCLUSIONS

ATX up-regulation in ACLF promotes LPA production from LPC. LPA suppresses MerTK/CD163 expression and increases monocyte proinflammatory cytokine production. This metabolic pathway could be investigated to therapeutically reprogram monocytes in ACLF.

Long non-coding RNA Meg3 deficiency impairs glucose homeostasis and insulin signaling by inducing cellular senescence of hepatic endothelium in obesity

Obesity-induced insulin resistance is a risk factor for diabetes and cardiovascular disease. However, the mechanisms underlying endothelial senescence in obesity, and how it impacts obesity-induced insulin resistance remain incompletely understood. In this study, transcriptome analysis revealed that the long non-coding RNA (lncRNA) Maternally expressed gene 3 (Meg3) is one of the top differentially expressed lncRNAs in the vascular endothelium in diet-induced obese mice. Meg3 knockdown induces cellular senescence of endothelial cells characterized by increased senescence-associated β–galactosidase activity, increased levels of endogenous superoxide, impaired mitochondrial structure and function, and impaired autophagy. Moreover, Meg3 knockdown causes cellular senescence of hepatic endothelium in diet-induced obese mice. Furthermore, Meg3 expression is elevated in human nonalcoholic fatty livers and nonalcoholic steatohepatitis livers, which positively correlates with the expression of CDKN2A encoding p16, an important hallmark of cellular senescence. Meg3 knockdown potentiates obesity-induced insulin resistance and impairs glucose homeostasis. Insulin signaling is reduced by Meg3 knockdown in the liver and, to a lesser extent, in the skeletal muscle, but not in the visceral fat of obese mice. We found that the attenuation of cellular senescence of hepatic endothelium by ablating p53 expression in vascular endothelium can restore impaired glucose homeostasis and insulin signaling in obesity. In conclusion, our data demonstrate that cellular senescence of hepatic endothelium promotes obesity-induced insulin resistance, which is tightly regulated by the expression of Meg3. Our results suggest that manipulation of Meg3 expression may represent a novel approach to managing obesity-associated hepatic endothelial senescence and insulin resistance.

•LncRNA Meg3 is a top differentially expressed lncRNA in the vascular endothelium in obese mice.

•Meg3 knockdown causes cellular senescence of HUVECs and of hepatic endothelium in obese mice.

•Meg3 expression is elevated in human NAFLD and NASH Nlivers, and correlates with CDKN2A expression -a senescent marker.

•Meg3 knockdown impairs glucose homeostasis and insulin signaling in obese mice.

•Attenuation of hepatic endothelial senescence improves glucose homeostasis and insulin signaling in obese mice.

The Role of Lysophosphatidic Acid in Adult Stem Cells

Stem cells are undifferentiated multipotent precursor cells that are capable both of perpetuating themselves as stem cells (self-renewal) and of undergoing differentiation into one or more specialized types of cells. And these stem cells have been reported to reside within distinct anatomic locations termed “niches”. The long-term goals of stem cell biology range from an understanding of cell-lineage determination and tissue organization to cellular therapeutics for degenerative diseases. Stem cells maintain tissue function throughout an organism’s lifespan by replacing differentiated cells. To perform this function, stem cells provide a unique combination of multilineage developmental potential and the capacity to undergo self-renewing divisions. The loss of self-renewal capacity in stem cells underlies certain degenerative diseases and the aging process. This self-renewal regulation must balance the regenerative needs of tissues that persist throughout life. Recent evidence suggests lysophosphatidic acid (LPA) signaling pathway plays an important role in the regulation of a variety of stem cells. In this review, we summarize the evidence linking between LPA and stem cell regulation. The LPA-induced signaling pathway regulates the proliferation and survival of stem cells and progenitors, and thus are likely to play a role in the maintenance of stem cell population in the body. This lipid mediator regulatory system can be a novel potential therapeutics for stem cell maintenance.

An evidence for surface expression of an immunogenic epitope of sarcoplasmic/endoplasmic reticulum calcium-ATPase2a on antigen-presenting cells from naive mice in the mediation of autoimmune myocarditis

We recently reported identification of sarcoplasmic/endoplasmic reticulum calcium-ATPase2a (SERCA2a) 971-990, which induces atrial myocarditis by generating autoreactive T cells in A/J mice. However, it was unknown how antigen-sensitized T cells could recognize SERCA2a 971-990, since SERCA2a-expression is confined to an intracellular compartment. In this report, we present evidence that antigen-presenting cells (APCs) from lymphoid and non-lymphoid organs in naïve animals present SERCA2a 971-990 and stimulate antigen-specific T cells. Using major histocompatibility complex (MHC) class II dextramers for SERCA2a 971-990, we created a panel of T cell hybridomas and demonstrated that splenocytes from naïve A/J mice stimulated the hybridoma cells without exogenous supplementation of SERCA2a 971-990. We then recapitulated this phenomenon by using SERCA2a 971-990 -specific primary T cells, verifying that the T cell responses were MHC-restricted. Furthermore, SERCA2a 971-990 -sensitzed T cells exposed to APCs from naïve mice were found to produce the inflammatory cytokines interferon-γ, granulocyte macrophage colony stimulating factor, and interleukin-17A, which are implicated in the induction of myocarditis. Finally, while T cells exposed to mononuclear cells (MNCs) obtained from heart and liver also responded similarly to splenocytes, endothelial cells (ECs) generated from the corresponding organs displayed opposing effects, in that the proliferative responses were suppressed with the heart ECs, but not with the liver ECs. Taken together, our data suggest that the surface expression of SERCA2a 971-990 by naïve APCs can potentially trigger pathogenic autoreactive T cell responses under conditions of autoimmunity, which may have implications in endothelial dysfunction.

ROCK2 Regulates Monocyte Migration and Cell to Cell Adhesion in Vascular Endothelial Cells

The small GTPase Rho and its downstream effector, Rho-kinase (ROCK), regulate various cellular functions, including organization of the actin cytoskeleton, cell adhesion and migration. A pro-inflammatory lipid mediator, lysophosphatidic acid (LPA), is a potent activator of the Rho/ROCK signalling pathway and has been shown to induce the expression of chemokines and cell adhesion molecules (CAMs). In the present study, we aimed to elucidate the precise mechanism by which ROCK regulates LPA-induced expressions and functions of chemokines and CAMs. We observed that ROCK blockade reduced LPA-induced phosphorylation of IκBα and inhibited NF-κB RelA/p65 phosphorylation, leading to attenuation of RelA/p65 nuclear translocation. Furthermore, small interfering RNA-mediated ROCK isoform knockdown experiments revealed that LPA induces the expression of monocyte chemoattractant protein-1 (MCP-1) and E-selectin via ROCK2 in human aortic endothelial cells (HAECs). Importantly, we found that ROCK2 but not ROCK1 controls LPA-induced monocytic migration and monocyte adhesion toward endothelial cells. These findings demonstrate that ROCK2 is a key regulator of endothelial inflammation. We conclude that targeting endothelial ROCK2 is potentially effective in attenuation of atherosclerosis.

CXC Motif Ligand 16 Promotes Nonalcoholic Fatty Liver Disease Progression via Hepatocyte-Stellate Cell Crosstalk

CONTEXT

Nonalcoholic fatty liver disease (NAFLD) is a focus of attention because of its prevalence. CXC motif ligand 16 (CXCL16) has been studied in inflammatory and metabolic diseases.

OBJECTIVE

To investigate the role of CXCL16 in steatosis and fibrosis in patients with NAFLD.

DESIGN

Liver specimens and sera of patients with NAFLD were collected from 2012 to 2017.

SETTING

Beijing 302 Hospital.

PARTICIPANTS

117 patients with NAFLD and 15 healthy controls.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

The main outcome measures were CXCL16 levels in sera and biopsy specimens of patients with NAFLD.

RESULTS

CXCL16 serum level was markedly elevated in patients with NAFLD, especially in those at the S3 steatosis level according to the steatosis, activity, and fibrosis (SAF) scoring system. The different serum levels of CXCL16 between groups were due to data in patients with A or F scores ≥2, according to the SAF scoring system. CXCL16 accumulated around steatotic hepatocytes in biopsy specimens. In vitro, CXCL16 treatment led to severe steatosis of hepatocytes in the hepatocyte-stellate cell coculture system and suppressed the respiration rate of hepatocytes. Lipogenic gene expression and hepatic stellate cell activation indexes were increased in a CXCL16 overexpression system. In addition, ligands in the Hedgehog pathway cascade were downregulated in hepatocytes.

CONCLUSIONS

CXCL16 was highly expressed in patients with NAFLD, suggesting that it may contribute to steatotic and fibrotic progression. CXCL16 may be a potential noninvasive marker of NAFLD and a future potential therapeutic target to treat NAFLD.

Recurrent aphthous stomatitis may be a precursor or risk factor for specific cancers: A case-control frequency-matched study

BACKGROUND

Recurrent aphthous stomatitis (RAS) is considered a prophase symptom in patients with specific cancers. This study assessed the association between RAS and subsequent onset of cancer based on a nationwide population-based database in Taiwan.

MATERIALS AND METHODS

We selected study participants from the National Health Insurance Research Database from January 2000 to December 2008. Patients in the non-RAS cohort were matched to case study patients at a 1:1 ratio through frequency matching. All participants were followed up for at least 5 years, and those who received cancer diagnoses during follow-up were identified.

RESULTS

Among 52 307 patients with and 52 304 patients without RAS, the combined hazard ratio (HR) of all subsequent cancer cases was 1.3 (95% confidence interval [CI]: 1.25-1.35, P = 0). RAS diagnosis was associated with risk for cancers of the head and neck (aHR = 2, 95% CI: 1.8-2.3), colon (aHR = 1.2, 95% CI: 1.1-1.4), liver (aHR = 1.1, 95% CI: 1-1.3), pancreas (aHR = 1.4, 95% CI: 1.1-1.7), skin (aHR = 1.4, 95% CI: 1.2-1.7), breast (aHR = 1.2, 95% CI: 1.1-1.4), and prostate (aHR = 1.5, 95% CI: 1.3-1.8), as well as hematologic cancers (aHR = 1.6, 95% CI: 1.3-1.9). A higher risk was observed for male patients (aHR = 1.35, 95% CI: 1.28-1.42) than for female patients (aHR = 1.25, 95% CI: 1.18-1.31) with RAS.

CONCLUSIONS

RAS was associated with specific cancers. Susceptible RAS patients should be screened for specific cancers.

Lysophosphatidic acid protects against acetaminophen-induced acute liver injury

We investigated the effect of lysophosphatidic acid (LPA) in experimental acetaminophen (APAP)-induced acute liver injury. LPA administration significantly reduced APAP-challenged acute liver injury, showing attenuated liver damage, liver cell death and aspartate aminotransferase and alanine aminotransferase levels. APAP overdose-induced mortality was also significantly decreased by LPA administration. Regarding the mechanism involved in LPA-induced protection against acute liver injury, LPA administration significantly increased the glutathione level, which was markedly decreased in APAP challenge-induced acute liver injury. LPA administration also strongly blocked the APAP challenge-elicited phosphorylation of JNK, ERK and GSK3β, which are involved in the pathogenesis of acute liver injury. Furthermore, LPA administration decreased the production of TNF-α and IL-1β in an experimental drug-induced liver injury animal model. Mouse primary hepatocytes express LPA1,3-6, and injection of the LPA receptor antagonist KI16425 (an LPA1,3-selective inhibitor) or H2L 5765834 (an LPA1,3,5-selective inhibitor) did not reverse the LPA-induced protective effects against acute liver injury. The therapeutic administration of LPA also blocked APAP-induced liver damage, leading to an increased survival rate. Collectively, these results indicate that the well-known bioactive lipid LPA can block the pathogenesis of APAP-induced acute liver injury by increasing the glutathione level but decreasing inflammatory cytokines in an LPA1,3,5-independent manner. Our results suggest that LPA might be an important therapeutic agent for drug-induced liver injury.

Diet-induced obesity links to ER positive breast cancer progression via LPA/PKD-1-CD36 signaling-mediated microvascular remodeling

Obesity increases cancer risk including breast cancer (BC). However, the direct regulatory mechanisms by which obesity promotes BC progression remain largely unknown. We show that lysophosphatidic acid/protein kinase D1 (LPA/PKD-1)-CD36 signaling is a bona fide breast cancer promoter via stimulating microvascular remodeling in chronic diet-induced obesity (DIO). We observed that the growth of an estrogen receptor (ER) positive breast cancer was markedly increased when compared to the lean control, and specifically accompanied by increased microvascular remodeling in a syngeneic BC model in female DIO mice. The tumor neovessels in DIO mice demonstrated elevated levels of alpha smooth muscle actin (α-SMA), vascular endothelial growth factor receptor 2 (VEGFR 2) and endothelial differentiation gene 2/LPA receptor1 (Edg2/LPA1), enhanced PKD-1 phosphorylation, and reduced CD36 expression. Tumor associated endothelial cells (TAECs) exposed to LPA demonstrated sustained nuclear PKD-1 phosphorylation, and elevated mRNA levels of ephrin B2, and reduced mRNA expression of CD36. TAEC proliferation also increased in response to LPA/PKD-1 signaling. These studies suggest that the LPA/PKD-1-CD36 signaling axis links DIO to malignant progression of BC via stimulation of de novo tumor arteriogenesis through arteriolar remodeling of microvasculature in the tumor microenvironment. Targeting this signaling axis could provide an additional novel therapeutic strategy.

Hepatocyte autotaxin expression promotes liver fibrosis and cancer

Autotaxin (ATX) is a secreted lysophospholipase D that catalyzes the production of lysophosphatidic acid (LPA), a pleiotropic growth-factor-like lysophospholipid. Increased ATX expression has been detected in various chronic inflammatory disorders and different types of cancer; however, little is known about its role and mode of action in liver fibrosis and cancer. Here, increased ATX expression was detected in chronic liver disease (CLD) patients of different etiologies, associated with shorter overall survival. In mice, different hepatotoxic stimuli linked with the development of different forms of CLDs were shown to stimulate hepatocyte ATX expression, leading to increased LPA levels, activation of hepatic stellate cells (HSCs), and amplification of profibrotic signals. Hepatocyte-specific, conditional genetic deletion and/or transgenic overexpression of ATX established a liver profibrotic role for ATX/LPA, whereas pharmacological ATX inhibition studies suggested ATX as a possible therapeutic target in CLDs. In addition, hepatocyte ATX ablation and the consequent deregulation of lipid homeostasis was also shown to attenuate hepatocellular carcinoma (HCC) development, thus implicating ATX/LPA in the causative link of cirrhosis and HCC.

CONCLUSION

ATX is a novel player in the pathogenesis of liver fibrosis and cancer and a promising therapeutic target. (Hepatology 2017;65:1369-1383).

An optimized method for mouse liver sinusoidal endothelial cell isolation

The objective of the present study was to develop an accurate and reproducible method for liver sinusoidal endothelial cell (LSEC) isolation in mice. Non-parenchymal cells were isolated using a modified two-step collagenase digestion combined with Optiprep density gradient centrifugation. LSEC were further purified using two prevalent methods, short-term selective adherence and CD146+ magnetic-activated cell sorting (MACS), and compared in terms of cell yield, viability and purity to our purification technique using CD11b cell depletion combined with long-term selective adherence. LSEC purification using our technique allowed to obtain 7.07±3.80 million LSEC per liver, while CD146+ MACS and short-term selective adherence yielded 2.94±1.28 and 0.99±0.66 million LSEC, respectively. Purity of the final cell preparation reached 95.10±2.58% when using our method. In contrast, CD146+ MACS and short-term selective adherence gave purities of 86.75±3.26% and 47.95±9.82%, respectively. Similarly, contamination by non-LSEC was the lowest when purification was performed using our technique, with a proportion of contaminating macrophages of only 1.87±0.77%. Further, isolated cells analysed by scanning electron microscopy presented typical LSEC fenestrations organized in sieve plates, demonstrating that the technique allowed to isolate bona fide LSEC. In conclusion, we described a reliable and reproducible technique for the isolation of high yields of pure LSEC in mice. This protocol provides an efficient method to prepare LSEC for studying their biological functions.

Inhibition of lysophosphatidic acid receptors 1 and 3 attenuates atherosclerosis development in LDL-receptor deficient mice

Lysophosphatidic acid (LPA) is a natural lysophospholipid present at high concentrations within lipid-rich atherosclerotic plaques. Upon local accumulation in the damaged vessels, LPA can act as a potent activator for various types of immune cells through its specific membrane receptors LPA_1/3. LPA elicits chemotactic, pro-inflammatory and apoptotic effects that lead to atherosclerotic plaque progression. In this study we aimed to inhibit LPA signaling by means of LPA_1/3 antagonism using the small molecule Ki16425. We show that LPA_1/3 inhibition significantly impaired atherosclerosis progression. Treatment with Ki16425 also resulted in reduced CCL2 production and secretion, which led to less monocyte and neutrophil infiltration. Furthermore, we provide evidence that LPA_1/3 blockade enhanced the percentage of non-inflammatory, Ly6C^low monocytes and CD4⁺ CD25⁺ FoxP3⁺ T-regulatory cells. Finally, we demonstrate that LPA_1/3 antagonism mildly reduced plasma LDL cholesterol levels. Therefore, pharmacological inhibition of LPA_1/3 receptors may prove a promising approach to diminish atherosclerosis development.

Rapid generation of functional hepatocyte-like cells from human adipose-derived stem cells

BACKGROUND

Liver disease is a major cause of death worldwide. Orthotropic liver transplantation (OLT) represents the only effective treatment for patients with liver failure, but the increasing demand for organs is unfortunately so great that its application is limited. Hepatocyte transplantation is a promising alternative to OLT for the treatment of some liver-based metabolic disorders or acute liver failure. Unfortunately, the lack of donor livers also makes it difficult to obtain enough viable hepatocytes for hepatocyte-based therapies. Currently, a fundamental solution to this key problem is still lacking. Here we show a novel non-transgenic protocol that facilitates the rapid generation of functional induced hepatocytes (iHeps) from human adipose-derived stem cells (hADSCs), providing a source of available cells for autologous hepatocytes to treat liver disease.

METHODS

We used collagenase digestion to isolate hADSCs. The surface marker was detected by flow cytometry. The multipotential differentiation potency was detected by induction into adipocytes, osteocytes, and chondrocytes. Passage 3-7 hADSCs were induced into iHeps using an induction culture system composed of small molecule compounds and cell factors.

RESULTS

Primary cultured hADSCs presented a fusiform or polygon appearance that became fibroblast-like after passage 3. More than 95 % of the cells expressed the mesenchymal cell markers CD29, CD44, CD166, CD105, and CD90. hADSCs possessed multipotential differentiation towards adipocytes, osteocytes, and chondrocytes. We rapidly induced hADSCs into iHeps within 10 days in vitro; the cellular morphology changed from fusiform to close-connected cubiform, which was similar to hepatocytes. After induction, most of the iHeps co-expressed albumin and alpha-1 antitrypsin; they also expressed mature hepatocyte special genes and achieved the basic functions of hepatocyte. Moreover, iHep transplantation could improve the liver function of acute liver-injured NPG mice and prolong life.

CONCLUSIONS

We isolated highly purified hADSCs and rapidly induced them into functional hepatocyte-like cells within 10 days. These results provide a source of available cells for autologous hepatocytes to treat liver disease.

Methods for Isolation and Purification of Murine Liver Sinusoidal Endothelial Cells: A Systematic Review

To study the biological functions of liver sinusoidal endothelial cells (LSEC) and to identify their interplay with blood or liver cells, techniques allowing for the isolation and purification of LSEC have been developed over the last decades. The objective of the present review is to summarize and to compare the efficiency of existing methods for isolating murine LSEC. Toward this end, the MEDLINE database was searched for all original articles describing LSEC isolation from rat and mouse livers. Out of the 489 publications identified, 23 reported the main steps and outcomes of the procedure and were included in our review. Here, we report and analyse the technical details of the essential steps of the techniques used for LSEC isolation. The correlations between the prevalence of some steps and the efficiency of LSEC isolation were also identified. We found that centrifugal elutriation, selective adherence and, more recently, magnetic-activated cell sorting were used for LSEC purification. Centrifugal elutriation procured high yields of pure LSEC (for rats 30-141.9 million cells for 85-98% purities; for mice 9-9.25 million cells for >95% purities), but the use of this method remained limited due to its high technical requirements. Selective adherence showed inconsistent results in terms of cell yields and purities in rats (5-100 million cells for 73.7-95% purities). In contrast, magnetic-activated cell sorting allowed for the isolation of highly pure LSEC, but overall lower cell yields were reported (for rats 10.7 million cells with 97.6% purity; for mice 0.5-9 million cells with 90-98% purities). Notably, the controversies regarding the accuracy of several phenotypic markers for LSEC should be considered and their use for both magnetic sorting and characterization remain doubtful. It appears that more effort is needed to refine and standardize the procedure for LSEC isolation, with a focus on the identification of specific antigens. Such a procedure is required to identify the molecular mechanisms regulating the function of LSEC and to improve our understanding of their role in complex cellular processes in the liver.