A Novel Method for Floxed Gene Manipulation Using TAT-Cre Recombinase in Ex Vivo Precision-Cut Lung Slices (PCLS)

Precision-cut lung slices (PCLS), ex vivo 3D lung tissue models, have been widely used for various applications in lung research. PCLS serve as an excellent intermediary between in vitro and in vivo models because they retain all resident cell types within their natural niche while preserving the extracellular matrix environment. This protocol describes the TReATS (TAT-Cre recombinase-mediated floxed allele modification in tissue slices) method that enables rapid and efficient gene modification in PCLS derived from adult floxed animals. Here, we present detailed protocols for the TReATS method, consisting of two simple steps: PCLS generation and incubation in a TAT-Cre recombinase solution. Subsequent validation of gene modification involves live staining and imaging of PCLS, quantitative real-time PCR, and cell viability assessment. This four-day protocol eliminates the need for complex Cre-breeding, circumvents issues with premature lethality related to gene mutation, and significantly reduces the use of animals. The TReATS method offers a simple and reproducible solution for gene modification in complex ex vivo tissue-based models, accelerating the study of gene function, disease mechanisms, and the discovery of drug targets. Key features • Achieve permanent ex vivo gene modifications in complex tissue-based models within four days. • Highly adaptable gene modification method that can be applied to induce gene deletion or activation. • Allows simple Cre dosage testing in a controlled ex vivo setting with the advantage of using PCLS generated from the same animal as true controls. • With optimisation, this method can be applied to precision-cut tissue slices of other organs.

AChE reactivation in precision-cut lung slices following organophosphorus compound poisoning

Precision-cut lung slices (PCLS) are a suitable model for analyzing the acetylcholinesterase (AChE) activity and subsequent effects after exposure to organophosphorus (OP) compounds. In this study, the AChE activity was determined in intact PCLS for the first time. Since the current standard therapy for OP poisoning (atropine + oxime + benzodiazepine) lacks efficiency, reliable models to study novel therapeutic substances are needed. Models should depict pathophysiological mechanisms and help to evaluate the beneficial effects of new therapeutics. Here PCLS were exposed to three organophosphorus nerve agents (OPNAs): sarin (GB), cyclosarin (GF), and VX. They were then treated with three reactivators: HI-6, obidoxime (OBI), and a non-oxime (NOX-6). The endpoints investigated in this study were the AChE activity and the airway area (AA) change. OPNA exposure led to very low residual AChE activities. Depending on the reactivator properties different AChE reactivation results were measured. GB-inhibited PCLS-AChE was reactivated best, followed by VX and GF. To substantiate these findings and to understand the connection between the molecular and the functional levels in a more profound way the results were correlated to the AA changes. These investigations underline the importance of reactivator use and point to the possibilities for future improvements in the treatment of OPNA-exposed victims.

Precision-cut lung slices as an ex vivo model to study Pneumocystis murina survival and antimicrobial susceptibility

IMPORTANCE

Our study reveals the potential of precision-cut lung slices as an ex vivo platform to study the growth/survival of Pneumocystis spp. that can facilitate the development of new anti-fungal drugs.

Transcriptional Host Responses to Infection with Streptococcus suis in a Porcine Precision-Cut Lung Slice Model: Between-Strain Differences Suggest Association with Virulence Potential

Streptococcus suis is a porcine and zoonotic pathogen in the upper respiratory tract, expressing different capsular serotypes and virulence-associated factors. Given its genomic and phenotypic diversity, the virulence potential of S. suis cannot be attributed to a single factor. Since strong inflammatory response is a hallmark of S. suis infection, the objective of this study was to investigate the differences in transcriptional host responses to two serotype 2 and one serotype 9 strains. Both serotypes are frequently found in clinical isolates. We infected porcine precision-cut lung slices (PCLSs) with two serotype 2 strains of high (strain S10) and low (strain T15) virulence, and a serotype 9 strain 8067 of moderate virulence. We observed higher expression of inflammation-related genes during early infection with strains T15 and 8067, in contrast to infection with strain 10, whose expression peaked late. In addition, bacterial gene expression from infected PCLSs revealed differences, mainly of metabolism-related and certain virulence-associated bacterial genes amongst these strains. We conclude that the strain- and time-dependent induction of genes involved in innate immune response might reflect clinical outcomes of infection in vivo, implying rapid control of infection with less virulent strains compared to the highly virulent strain S10.

Inflammation plays a critical role in damage to the bronchiolar epithelium induced by Trueperella pyogenes in vitro and in vivo

Trueperella pyogenes can cause severe pulmonary disease in swine, but the mechanism of pathogenesis is not well defined. T. pyogenes-induced damage to porcine bronchial epithelial cells (PBECs), porcine precision-cut lung slices (PCLS), and respiratory epithelium of mice remains unknown. In this study, we used T. pyogenes 20121 to infect PBECs in air-liquid interface conditions and porcine PCLS. T. pyogenes could adhere to, colonize, and induce cytotoxic effect on PBECs and the luminal surface of bronchi in PCLS, which damaged the bronchiolar epithelium. Moreover, bronchiolar epithelial cells showed extensive degeneration in the lungs of infected mice. Furthermore, western blot showed that the NOD-like receptor (NLR)/C-terminal caspase recruitment domain (ASC)/caspase-1 axis and nuclear factor-kappa B pathway were involved in inflammation in PCLS and lungs of mice, which also confirms that porcine PCLS provide a platform to analyze the pulmonary immune response. Meanwhile, the levels of p-c-Jun N-terminal kinase, p-extracellular signal-regulated kinase, and p-protein kinase B (AKT) were increased significantly, which indicated the mitogen-activated protein kinase and Akt pathways were also involved in inflammation in T. pyogenes-infected mice. In addition, we used T. pyogenes 20121 to infect tumor necrosis factor-alpha (tnf-α-/-) mice, and the results indicated that apoptosis and injury in respiratory epithelium of infected tnf-α-/- mice were alleviated. Thus, the pro-inflammatory cytokine TNF-α played a role in apoptosis and the respiratory epithelium injury in mouse lungs. Collectively, our study provides insight into the inflammatory injury induced by T. pyogenes and suggests that blocking NLR may be a potential therapeutic strategy against T. pyogenes infection.

Amitriptyline inhibits bronchoconstriction and directly promotes dilatation of the airways

INTRODUCTION

The standard therapy for bronchial asthma consists of combinations of acute (short-acting ß2-sympathomimetics) and, depending on the severity of disease, additional long-term treatment (including inhaled glucocorticoids, long-acting ß2-sympathomimetics, anticholinergics, anti-IL-4R antibodies). The antidepressant amitriptyline has been identified as a relevant down-regulator of immunological TH2-phenotype in asthma, acting-at least partially-through inhibition of acid sphingomyelinase (ASM), an enzyme involved in sphingolipid metabolism. Here, we investigated the non-immunological role of amitriptyline on acute bronchoconstriction, a main feature of airway hyperresponsiveness in asthmatic disease.

METHODS

After stimulation of precision cut lung slices (PCLS) from mice (wildtype and ASM-knockout), rats, guinea pigs and human lungs with mediators of bronchoconstriction (endogenous and exogenous acetylcholine, methacholine, serotonin, endothelin, histamine, thromboxane-receptor agonist U46619 and leukotriene LTD4, airway area was monitored in the absence of or with rising concentrations of amitriptyline. Airway dilatation was also investigated in rat PCLS by prior contraction induced by methacholine. As bronchodilators for maximal relaxation, we used IBMX (PDE inhibitor) and salbutamol (ß2-adrenergic agonist) and compared these effects with the impact of amitriptyline treatment. Isolated perfused lungs (IPL) of wildtype mice were treated with amitriptyline, administered via the vascular system (perfusate) or intratracheally as an inhalation. To this end, amitriptyline was nebulized via pariboy in-vivo and mice were ventilated with the flexiVent setup immediately after inhalation of amitriptyline with monitoring of lung function.

RESULTS

Our results show amitriptyline to be a potential inhibitor of bronchoconstriction, induced by exogenous or endogenous (EFS) acetylcholine, serotonin and histamine, in PCLS from various species. The effects of endothelin, thromboxane and leukotrienes could not be blocked. In acute bronchoconstriction, amitriptyline seems to act ASM-independent, because ASM-deficiency (Smdp1-/-) did not change the effect of acetylcholine on airway contraction. Systemic as well as inhaled amitriptyline ameliorated the resistance of IPL after acetylcholine provocation. With the flexiVent setup, we demonstrated that the acetylcholine-induced rise in central and tissue resistance was much more marked in untreated animals than in amitriptyline-treated ones. Additionally, we provide clear evidence that amitriptyline dilatates pre-contracted airways as effectively as a combination of typical bronchodilators such as IBMX and salbutamol.

CONCLUSION

Amitriptyline is a drug of high potential, which inhibits acute bronchoconstriction and induces bronchodilatation in pre-contracted airways. It could be one of the first therapeutic agents in asthmatic disease to have powerful effects on the TH2-allergic phenotype and on acute airway hyperresponsiveness with bronchoconstriction, especially when inhaled.

Microphysiological Models of Lung Epithelium-Alveolar Macrophage Co-Cultures to Study Chronic Lung Disease

The interactions between immune cells and epithelial cells influence the progression of many respiratory diseases, such as chronic obstructive pulmonary disease (COPD). In vitro models allow for the examination of cells in controlled environments. However, these models lack the complex 3D architecture and vast multicellular interactions between the lung resident cells and infiltrating immune cells that can mediate cellular response to insults. In this study, three complementary microphysiological systems are presented to delineate the effects of cigarette smoke and respiratory disease on the lung epithelium. First, the Transwell system allows the co-culture of pulmonary immune and epithelial cells to evaluate cellular and monolayer phenotypic changes in response to cigarette smoke exposure. Next, the human and mouse precision-cut lung slices system provides a physiologically relevant model to study the effects of chronic insults like cigarette smoke with the dissection of specific interaction of immune cell subtypes within the structurally complex tissue environment. Finally, the lung-on-a-chip model provides an adaptable system for live imaging of polarized epithelial tissues that mimic the in vivo environment of the airways. Using a combination of these models, a complementary approach is provided to better address the intricate mechanisms of lung disease.

A new NRF2 activator for the treatment of human metabolic dysfunction-associated fatty liver disease

Background & Aims

Oxidative stress triggers metabolic-associated fatty liver disease (MAFLD) and fibrosis. Previous animal studies demonstrated that the transcription factor nuclear factor (erythroid-derived 2)-like 2 (NRF2), the master regulator of antioxidant response, protects against MAFLD and fibrosis. S217879, a next generation NRF2 activator has been recently shown to trigger diet-induced steatohepatitis resolution and to reduce established fibrosis in rodents. Our aim was to evaluate the therapeutic potential of S217879 in human MAFLD and its underlying mechanisms using the relevant experimental 3D model of patient-derived precision cut liver slices (PCLS).

Methods

We treated PCLS from 12 patients with varying stages of MAFLD with S217879 or elafibranor (peroxisome proliferator-activated receptor [PPAR]α/δ agonist used as a referent molecule) for 2 days. Safety and efficacy profiles, steatosis, liver injury, inflammation, and fibrosis were assessed as well as mechanisms involved in MAFLD pathophysiology, namely antioxidant response, autophagy, and endoplasmic reticulum-stress.

Results

Neither elafibranor nor S217879 had toxic effects at the tested concentrations on human PCLS with MAFLD. PPARα/δ and NRF2 target genes (pyruvate dehydrogenase kinase 4 [PDK4], fibroblast growth factor 21 [FGF21], and NAD(P)H quinone dehydrogenase 1 [NQO1], heme oxygenase 1 [HMOX1], respectively) were strongly upregulated in PCLS in response to elafibranor and S217879, respectively. Compared with untreated PCLS, elafibranor and S217879-treated slices displayed lower triglycerides and reduced inflammation (IL-1β, IL-6, chemokine (C-C motif) ligand 2 [CCL2]). Additional inflammatory markers (chemokine (C-C motif) ligand 5 [CCL5], stimulator of interferon genes [STING], intercellular adhesion molecule-1 [ICAM-1], vascular cell adhesion molecule-1 [VCAM-1]) were downregulated by S217879. S217879 but not elafibranor lowered DNA damage (phospho-Histone H2A.X [p-H2A.X], RAD51, X-ray repair cross complementing 1 [XRCC1]) and apoptosis (cleaved caspase-3), and inhibited fibrogenesis markers expression (alpha smooth muscle actin [α-SMA], collagen 1 alpha 1 [COL1A1], collagen 1 alpha 2 [COL1A2]). Such effects were mediated through an improvement of lipid metabolism, activated antioxidant response and enhanced autophagy, without effect on endoplasmic reticulum-stress.

Conclusions

This study highlights the therapeutic potential of a new NRF2 activator for MAFLD using patient-derived PCLS supporting the evaluation of NRF2 activating strategies in clinical trials.

Impact and implications

Oxidative stress is a major driver of metabolic-associated fatty liver disease (MAFLD) development and progression. Nuclear factor (erythroid-derived 2)-like 2, the master regulator of the antioxidative stress response, is an attractive therapeutic target for the treatment of MAFLD. This study demonstrates that S217879, a new potent and selective nuclear factor (erythroid-derived 2)-like 2 activator, displays antisteatotic effects, lowers DNA damage, apoptosis, and inflammation and inhibits fibrogenesis in human PCLS in patients with MAFLD.

Mucosal Application of a Low-Energy Electron Inactivated Respiratory Syncytial Virus Vaccine Shows Protective Efficacy in an Animal Model

Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory tract infections in the elderly and in children, associated with pediatric hospitalizations. Recently, first vaccines have been approved for people over 60 years of age applied by intramuscular injection. However, a vaccination route via mucosal application holds great potential in the protection against respiratory pathogens like RSV. Mucosal vaccines induce local immune responses, resulting in a fast and efficient elimination of respiratory viruses after natural infection. Therefore, a low-energy electron irradiated RSV (LEEI-RSV) formulated with phosphatidylcholine-liposomes (PC-LEEI-RSV) was tested ex vivo in precision cut lung slices (PCLSs) for adverse effects. The immunogenicity and protective efficacy in vivo were analyzed in an RSV challenge model after intranasal vaccination using a homologous prime-boost immunization regimen. No side effects of PC-LEEI-RSV in PCLS and an efficient antibody induction in vivo could be observed. In contrast to unformulated LEEI-RSV, the mucosal vaccination of mice with PC formulated LEEI-RSV showed a statistically significant reduction in viral load after challenge. These results are a proof-of-principle for the use of LEEI-inactivated viruses formulated with liposomes to be administered intranasally to induce a mucosal immunity that could also be adapted for other respiratory viruses.

Drug-induced phospholipidosis is not correlated with the inhibition of SARS-CoV-2 - inhibition of SARS-CoV-2 is cell line-specific

Recently, Tummino et al. reported that 34 compounds, including Chloroquine and Fluoxetine, inhibit SARS-CoV-2 replication by inducing phospholipidosis, although Chloroquine failed to suppress viral replication in Calu-3 cells and patients. In contrast, Fluoxetine represses viral replication in human precision-cut lung slices (PCLS) and Calu-3 cells. Thus, it is unlikely that these compounds have similar mechanisms of action. Here, we analysed a subset of these compounds in the viral replication and phospholipidosis assays using the Calu-3 cells and PCLS as the patient-near system. Trimipramine and Chloroquine induced phospholipidosis but failed to inhibit SARS-CoV-2 replication in Calu-3 cells, which contradicts the reported findings and the proposed mechanism. Fluoxetine, only slightly induced phospholipidosis in Calu-3 cells but reduced viral replication by 2.7 orders of magnitude. Tilorone suppressed viral replication by 1.9 orders of magnitude in Calu-3 cells without causing phospholipidosis. Thus, induction of phospholipidosis is not correlated with the inhibition of SARS-CoV-2, and the compounds act via other mechanisms. However, we show that compounds, such as Amiodarone, Tamoxifen and Tilorone, with antiviral activity on Calu-3 cells, also inhibited viral replication in human PCLS. Our results indicate that antiviral assays against SARS-CoV-2 are cell-line specific. Data from Vero E6 can lead to non-transferable results, underlining the importance of an appropriate cell system for analysing antiviral compounds against SARS-CoV-2. We observed a correlation between the active compounds in Calu-3 cells and PCLS.

Perspectives on precision cut lung slices-powerful tools for investigation of mechanisms and therapeutic targets in lung diseases

Precision cut lung slices (PCLS) have emerged as powerful experimental tools for respiratory research. Pioneering studies using mouse PCLS to visualize intrapulmonary airway contractility have been extended to pulmonary arteries and for assessment of novel bronchodilators and vasodilators as therapeutics. Additional disease-relevant outcomes, including inflammatory, fibrotic, and regenerative responses, are now routinely measured in PCLS from multiple species, including humans. This review provides an overview of established and innovative uses of PCLS as an intermediary between cellular and organ-based studies and focuses on opportunities to increase their application to investigate mechanisms and therapeutic targets to oppose excessive airway contraction and fibrosis in lung diseases.

Menthol flavoring in e-cigarette condensate causes pulmonary dysfunction and cytotoxicity in precision cut lung slices

E-cigarette consumption is under scrutiny by regulatory authorities due to concerns about product toxicity, lack of manufacturing standards, and increasing reports of e-cigarette- or vaping-associated acute lung injury. In vitro studies have demonstrated cytotoxicity, mitochondrial dysfunction, and oxidative stress induced by unflavored e-cigarette aerosols and flavoring additives. However, e-cigarette effects on the complex lung parenchyma remain unclear. Herein, the impact of e-cigarette condensates with or without menthol flavoring on functional, structural, and cellular responses was investigated using mouse precision cut lung slices (PCLS). PCLS were exposed to e-cigarette condensates prepared from aerosolized vehicle, nicotine, nicotine + menthol, and menthol e-fluids at doses from 50 to 500 mM. Doses were normalized to the glycerin content of vehicle. Video-microscopy of PCLS revealed impaired contractile responsiveness of airways to methacholine and dampened ciliary beating following exposure to menthol-containing condensates at concentrations greater than 300 mM. Following 500 mM menthol-containing condensate exposure, epithelial exfoliation in intrabronchial airways was identified in histological sections of PCLS. Measurement of lactate dehydrogenase release, mitochondrial water-soluble-tetrazolium salt-1 conversion, and glutathione content supported earlier findings of nicotine or nicotine + menthol e-cigarette-induced dose-dependent cytotoxicity and oxidative stress responses. Evaluation of PCLS metabolic activity revealed dose-related impairment of mitochondrial oxidative phosphorylation and glycolysis after exposure to menthol-containing condensates. Taken together, these data demonstrate prominent menthol-induced pulmonary toxicity and impairment of essential physiological functions in the lung, which warrants concerns about e-cigarette consumer safety and emphasizes the need for further investigations of molecular mechanisms of toxicity and menthol effects in an experimental model of disease.

The Activation of the RIG-I/MDA5 Signaling Pathway upon Influenza D Virus Infection Impairs the Pulmonary Proinflammatory Response Triggered by Mycoplasma bovis Superinfection

Concurrent infections with multiple pathogens are often described in cattle with respiratory illness. However, how the host-pathogen interactions influence the clinical outcome has been only partially explored in this species. Influenza D virus (IDV) was discovered in 2011. Since then, IDV has been detected worldwide in different hosts. A significant association between IDV and bacterial pathogens in sick cattle was shown in epidemiological studies, especially with Mycoplasma bovis. In an experimental challenge, IDV aggravated M. bovis-induced pneumonia. However, the mechanisms through which IDV drives an increased susceptibility to bacterial superinfections remain unknown. Here, we used the organotypic lung model precision-cut lung slices to study the interplay between IDV and M. bovis coinfection. Our results show that a primary IDV infection promotes M. bovis superinfection by increasing the bacterial replication and the ultrastructural damages in lung pneumocytes. In our model, IDV impaired the innate immune response triggered by M. bovis by decreasing the expression of several proinflammatory cytokines and chemokines that are important for immune cell recruitment and the bacterial clearance. Stimulations with agonists of cytosolic helicases and Toll-like receptors (TLRs) revealed that a primary activation of RIG-I/MDA5 desensitizes the TLR2 activation, similar to what was observed with IDV infection. The cross talk between these two pattern recognition receptors leads to a nonadditive response, which alters the TLR2-mediated cascade that controls the bacterial infection. These results highlight innate immune mechanisms that were not described for cattle so far and improve our understanding of the bovine host-microbe interactions and IDV pathogenesis. IMPORTANCE Since the spread of the respiratory influenza D virus (IDV) infection to the cattle population, the question about the impact of this virus on bovine respiratory disease (BRD) remains still unanswered. Animals affected by BRD are often coinfected with multiple pathogens, especially viruses and bacteria. In particular, viruses are suspected to enhance secondary bacterial superinfections. Here, we use an ex vivo model of lung tissue to study the effects of IDV infection on bacterial superinfections. Our results show that IDV increases the susceptibility to the respiratory pathogen Mycoplasma bovis. In particular, IDV seems to activate immune pathways that inhibit the innate immune response against the bacteria. This may allow M. bovis to increase its proliferation and to delay its clearance from lung tissue. These results suggest that IDV could have a negative impact on the respiratory pathology of cattle.

Electronic Cigarette Exposure Increases the Severity of Influenza a Virus Infection via TRAIL Dysregulation in Human Precision-Cut Lung Slices

The use of electronic nicotine dispensing systems (ENDS), also known as electronic cigarettes (ECs), is common among adolescents and young adults with limited knowledge about the detrimental effects on lung health such as respiratory viral infections and underlying mechanisms. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), a protein of the TNF family involved in cell apoptosis, is upregulated in COPD patients and during influenza A virus (IAV) infections, but its role in viral infection during EC exposures remains unclear. This study was aimed to investigate the effect of ECs on viral infection and TRAIL release in a human lung precision-cut lung slices (PCLS) model, and the role of TRAIL in regulating IAV infection. PCLS prepared from lungs of nonsmoker healthy human donors were exposed to EC juice (E-juice) and IAV for up to 3 days during which viral load, TRAIL, lactate dehydrogenase (LDH), and TNF-α in the tissue and supernatants were determined. TRAIL neutralizing antibody and recombinant TRAIL were utilized to determine the contribution of TRAIL to viral infection during EC exposures. E-juice increased viral load, TRAIL, TNF-α release and cytotoxicity in IAV-infected PCLS. TRAIL neutralizing antibody increased tissue viral load but reduced viral release into supernatants. Conversely, recombinant TRAIL decreased tissue viral load but increased viral release into supernatants. Further, recombinant TRAIL enhanced the expression of interferon-β and interferon-λ induced by E-juice exposure in IAV-infected PCLS. Our results suggest that EC exposure in human distal lungs amplifies viral infection and TRAIL release, and that TRAIL may serve as a mechanism to regulate viral infection. Appropriate levels of TRAIL may be important to control IAV infection in EC users.

Targeted GATA3 knockdown in activated T cells via pulmonary siRNA delivery as novel therapy for allergic asthma

GATA3 gene silencing in activated T cells displays a promising option to early-on undermine pathological pathways in the disease formation of allergic asthma. The central transcription factor of T helper 2 (Th2) cell cytokines IL-4, IL-5, and IL-13 plays a major role in immune and inflammatory cascades underlying asthmatic processes in the airways. Pulmonary delivery of small interfering RNAs (siRNA) to induce GATA3 knockdown within disease related T cells of asthmatic lungs via RNA interference (RNAi) presents an auspicious base to realize this strategy, however, still faces some major hurdles. Main obstacles for successful siRNA delivery in general comprise stability and targeting issues, while in addition the transfection of T cells presents a particularly challenging task itself. In previous studies, we have developed and advanced an eligible siRNA delivery system composed of polyethylenimine (PEI) as polycationic carrier, transferrin (Tf) as targeting ligand and melittin (Mel) as endosomolytic agent. Resulting Tf-Mel-PEI polyplexes exhibited ideal characteristics for targeted siRNA delivery to activated T cells and achieved efficient and sequence-specific gene knockdown in vitro. In this work, the therapeutic potential of this carrier system was evaluated in an optimized cellular model displaying the activated status of asthmatic T cells. Moreover, a suitable siRNA sequence combination was found for effective gene silencing of GATA3. To confirm the translatability of our findings, Tf-Mel-PEI polyplexes were additionally tested ex vivo in activated human precision-cut lung slices (PCLS). Here, the formulation showed a safe profile as well as successful delivery to the lung epithelium with 88% GATA3 silencing in lung explants. These findings support the feasibility of Tf-Mel-PEI as siRNA delivery system for targeted gene knockdown in activated T cells as a potential novel therapy for allergic asthma.

Functional changes in long-term incubated rat precision-cut lung slices

Background

Respiratory diseases represent a global health burden. Because research on therapeutic strategies of airway diseases is essential, the technique of precision-cut lung slices (PCLS) has been developed and widely studied. PCLS are an alternative ex vivo model and have the potential to replace and reduce in vivo animal models. So far, the majority of studies was conducted with short-term cultivated PCLS (≤ 72 h). As there is large interest in research of chronic diseases and chronic toxicity, feasibility of cultivating human PCLS long-term over 2 weeks and recently over 4 weeks was investigated by another research group with successful results. Our aim was to establish a model of long-term cultivated rat PCLS over a period of 29 days.

Methods

Rat PCLS were cultured for 29 days and analysed regarding viability, histopathology, reactivity and gene expression at different time points during cultivation.

Results

Cultivation of rat PCLS over a 29-day time period was successful with sustained viability. Furthermore, the ability of bronchoconstriction was maintained between 13 and 25 days, depending on the mediator. However, reduced relaxation, altered sensitivity and increased respiratory tone were observed. Regarding transcription, alteration in gene expression pattern of the investigated target genes was ascertained during long-term cultivation with mixed results. Furthermore, the preparation of PCLS seems to influence messenger ribonucleic acid (mRNA) expression of most target genes. Moreover, the addition of fetal bovine serum (FBS) to the culture medium did not improve viability of PCLS. In contrast to medium without FBS, FBS seems to affect measurements and resulted in marked cellular changes of metaplastic and/or regenerative origin.

Conclusions

Overall, a model of long-term cultivated rat PCLS which stays viable for 29 days and reactive for at least 13 days could be established. Before long-term cultivated PCLS can be used for in-depth study of chronic diseases and chronic toxicity, further investigations have to be made.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02169-5.

Improved Precision-Cut Liver Slice Cultures for Testing Drug-Induced Liver Fibrosis

In vitro models of human liver disease often fail to mimic the complex 3D structures and cellular organizations found in vivo. Precision cut liver slices (PCLS) retain the complex physiological architecture of the native liver and therefore could be an exceptional in vitro liver model. However, the production of PCLS induces a spontaneous culture-induced fibrogenic reaction, limiting the application of PCLS to anti-fibrotic compounds. Our aim was to improve PCLS cultures to allow compound-induced fibrosis induction. Hepatotoxicity in PCLS cultures was analyzed by lactate dehydrogenase leakage and albumin secretion, while fibrogenesis was analyzed by qRT-PCR and western blot for hepatic stellate cell (HSC) activation markers and collagen 6 secretion by enzyme-linked immunosorbent assays (ELISA). We demonstrate that supplementation of 3 mm mouse PCLS cultures with valproate strongly reduces fibrosis and improves cell viability in our PCLS cultures for up to 5 days. Fibrogenesis can still be induced both directly and indirectly through exposure to TGFβ and the hepatotoxin acetaminophen, respectively. Finally, human PCLS cultures showed similar but less robust results. In conclusion, we optimized PCLS cultures to allow for drug-induced liver fibrosis modeling.

Optimization of long-term cold storage of rat precision-cut lung slices with a tissue preservation solution

Precision-cut lung slices (PCLS) are used as ex vivo model of the lung to fill the gap between in vitro and in vivo experiments. To allow optimal utilization of PCLS, possibilities to prolong slice viability via cold storage using optimized storage solutions were evaluated. Rat PCLS were cold stored in DMEM/F-12 or two different preservation solutions for up to 28 days at 4°C. After rewarming in DMEM/F-12, metabolic activity, live/dead staining, and mitochondrial membrane potential was assessed to analyze overall tissue viability. Single-cell suspensions were prepared and proportions of CD45⁺, EpCAM⁺, CD31⁺, and CD90⁺ cells were analyzed. As functional parameters, TNF-α expression was analyzed to detect inflammatory activity and bronchoconstriction was evaluated after acetylcholine stimulus. After 14 days of cold storage, viability and mitochondrial membrane potential were significantly better preserved after storage in solution 1 (potassium chloride rich) and solution 2 (potassium- and lactobionate-rich analog) compared with DMEM/F-12. Analysis of cell populations revealed efficient preservation of EpCAM⁺, CD31⁺, and CD90⁺ cells. Proportion of CD45⁺ cells decreased during cold storage but was better preserved by both modified solutions than by DMEM/F-12. PCLS stored in solution 1 responded substantially longer to inflammatory stimulation than those stored in DMEM/F-12 or solution 2. Analysis of bronchoconstriction revealed total loss of function after 14 days of storage in DMEM/F-12 but, in contrast, a good response in PCLS stored in the optimized solutions. An improved base solution with a high potassium chloride concentration optimizes cold storage of PCLS and allows shipment between laboratories and stockpiling of tissue samples.

Organophosphorus pesticides exhibit compound specific effects in rat precision-cut lung slices (PCLS): mechanisms involved in airway response, cytotoxicity, inflammatory activation and antioxidative defense

Organophosphorus compound pesticides (OP) are widely used in pest control and might be misused for terrorist attacks. Although acetylcholinesterase (AChE) inhibition is the predominant toxic mechanism, OP may induce pneumonia and formation of lung edema after poisoning and during clinical treatment as life-threatening complication. To investigate the underlying mechanisms, rat precision-cut lung slices (PCLS) were exposed to the OP parathion, malathion and their biotransformation products paraoxon and malaoxon (100–2000 µmol/L). Airway response, metabolic activity, release of LDH, cytokine expression and oxidative stress response were analyzed. A concentration-dependent inhibition of airway relaxation was observed after exposure with the oxon but not with the thion-OP. In contrast, cytotoxic effects were observed for both forms in higher concentrations. Increased cytokine expression was observed after exposure to parathion and paraoxon (IL-6, GM-CSF, MIP-1α) and IL-6 expression was dependent on NFκB activation. Intracellular GSH levels were significantly reduced by all four tested OP but an increase in GSSG and HO-1 expression was predominantly observed after malaoxon exposure. Pretreatment with the antioxidant N-acetylcysteine reduced malaoxon but not paraoxon-induced cytotoxicity. PCLS as a 3D lung model system revealed OP-induced effects depending on the particular OP. The experimental data of this study contribute to a better understanding of OP toxicity on cellular targets and may be a possible explanation for the variety of clinical outcomes induced by different OP.

Decellularized Human Lung Scaffolds as Complex Three-Dimensional Tissue Culture Models to Study Functional Behavior of Fibroblasts

In vitro culturing of cells in two-dimensional (2D) environments is a widespread used methodology in biomedical research. Most commonly, cells are cultured on artificial plastic dish surfaces, which lead to abnormal functional behaviors, as plastic does not reflect the native microenvironment found in vivo or in situ. Therefore, a multitude of three-dimensional (3D) cell culture systems were developed in the past years, which aim to bridge the gap between 2D cell culture dishes and the in vivo situation. One of the more recent development in the field, the generation of viable precision-cut tissue slices from various organs emerged as an exciting approach to study complex interactions and biological processes ex vivo in 3D. Decellularization of such tissue slices leads to the removal of all functional cells, and leaves behind a scaffold of extracellular matrix (ECM), which closely recapitulates the molecular composition, mechanical properties, topology, and microarchitecture of native ECM. Subsequently, decellularized precision-cut lung slices (PCLS), also called 3D lung tissue culture (3D-LTCs), can be successfully reseeded with a variety of cell types, including fibroblasts, which attach to and engraft into the matrix. Here, we describe the generation of PCLS from resected human lung tissue and their decellularization and recellularization with primary human fibroblasts. This novel 3D tissue culture model allows for various functional studies of fibroblast behavior on native ECM composition and topology.

In vitro metabolism of lidocaine in subcellular post-mitochondrial fractions and precision cut slices from cattle liver

In vitro models are widely used to study the biotransformation of xenobiotics and to provide input parameters to physiologically based kinetic models required to predict the kinetic behavior in vivo. For farm animals this is not common practice yet. The use of slaughterhouse-derived tissue material may provide opportunities to study biotransformation reactions in farm animals. The goal of the present study was to explore the potential of slaughterhouse-derived bovine liver S9 (S9) and precision cut liver slices (PCLSs) to capture observed biotransformation reactions of lidocaine in cows. The in vitro data obtained with both S9 and PCLSs confirm in vivo findings that 2,6-dimethylaniline (DMA) is an important metabolite of lidocaine in cows, being for both PCLSs and S9 the end-product. In case of S9, also conversion of lidocaine to lidocaine-N-oxide and monoethylglycinexylidine (MEXG) was observed. MEGX is considered as intermediate for DMA formation, given that this metabolite was metabolized to DMA by both PLCSs and S9. In contrast to in vivo, no in vitro conversion of DMA to 4-OH-DMA was observed. Further work is needed to explain this lack of conversion and to further evaluate the use of slaughterhouse-derived tissue materials to predict the biotransformation of xenobiotics in farm animals.

A modified protocol for successful miRNA profiling in human precision-cut lung slices (PCLS)

Objective

Human precision cut lung slices (PCLS) are widely used as an ex vivo model system for drug discovery and development of new therapies. PCLS reflect the functional heterogeneity of lung tissue and possess relevant lung cell types. We thus determined the use of PCLS in studying non-coding RNAs notably miRNAs, which are important gene regulatory molecules. Since miRNAs play key role as mediators of respiratory diseases, they can serve as valuable prognostic or diagnostic biomarkers, and in therapeutic interventions, of lung diseases. A technical limitation though is the vast amount of agarose in PCLS which impedes (mi)RNA extraction by standard procedures. Here we modified our recently published protocol for RNA isolation from PCLS to enable miRNA readouts.

Results

The modified method relies on the separation of lysis and precipitation steps, and a clean-up procedure with specific magnetic beads. We obtained successfully quality miRNA amenable for downstream applications such as RTqPCR and whole transcriptome miRNA analysis. Comparison of miRNA profiles in PCLS with published data from human lung, identified all important miRNAs regulated in IPF, COPD, asthma or lung cancer. Therefore, this shows suitability of the method for analyzing miRNA targets and biomarkers in the valuable human PCLS model.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-021-05674-w.

Best Practices and Progress in Precision-Cut Liver Slice Cultures

Thirty-five years ago, precision-cut liver slices (PCLS) were described as a promising tool and were expected to become the standard in vitro model to study liver disease as they tick off all characteristics of a good in vitro model. In contrast to most in vitro models, PCLS retain the complex 3D liver structures found in vivo, including cell–cell and cell–matrix interactions, and therefore should constitute the most reliable tool to model and to investigate pathways underlying chronic liver disease in vitro. Nevertheless, the biggest disadvantage of the model is the initiation of a procedure-induced fibrotic response. In this review, we describe the parameters and potential of PCLS cultures and discuss whether the initially described limitations and pitfalls have been overcome. We summarize the latest advances in PCLS research and critically evaluate PCLS use and progress since its invention in 1985.

Determination of Senescent Myofibroblasts in Precision-Cut Lung Slices

Fibroblast-to-myofibroblast transdifferentiation and the acquisition of a senescent phenotype are hallmarks of fibrotic diseases. The study of the localization of senescent myofibroblasts as well as their interactions with other cell types in the fibrotic tissue has been hindered by the lack of methods to detect these cells in vivo. Here, we describe methods to detect tissue localization of senescent myofibroblasts in precision-cut lung slices (PCLS) by combining β-galactosidase staining with immunofluorescence techniques.

Applications and Approaches for Three-Dimensional Precision-Cut Lung Slices. Disease Modeling and Drug Discovery

Chronic lung diseases (CLDs), such as chronic obstructive pulmonary disease, interstitial lung disease, and lung cancer, are among the leading causes of morbidity globally and impose major health and financial burdens on patients and society. Effective treatments are scarce, and relevant human model systems to effectively study CLD pathomechanisms and thus discover and validate potential new targets and therapies are needed. Precision-cut lung slices (PCLS) from healthy and diseased human tissue represent one promising tool that can closely recapitulate the complexity of the lung's native environment, and recently, improved methodologies and accessibility to human tissue have led to an increased use of PCLS in CLD research. Here, we discuss approaches that use human PCLS to advance our understanding of CLD development, as well as drug discovery and validation for CLDs. PCLS enable investigators to study complex interactions among different cell types and the extracellular matrix in the native three-dimensional architecture of the lung. PCLS further allow for high-resolution (live) imaging of cellular functions in several dimensions. Importantly, PCLS can be derived from diseased lung tissue upon lung surgery or transplantation, thus allowing the study of CLDs in living human tissue. Moreover, CLDs can be modeled in PCLS derived from normal lung tissue to mimic the onset and progression of CLDs, complementing studies in end-stage diseased tissue. Altogether, PCLS are emerging as a remarkable tool to further bridge the gap between target identification and translation into clinical studies, and thus open novel avenues for future precision medicine approaches.

Liver slice culture as a model for lipid metabolism in fish

Hepatic lipid metabolism is traditionally investigated in vitro using hepatocyte monocultures lacking the complex three-dimensional structure and interacting cell types essential liver function. Precision cut liver slice (PCLS) culture represents an alternative in vitro system, which benefits from retention of tissue architecture. Here, we present the first comprehensive evaluation of the PCLS method in fish (Atlantic salmon, Salmo salar L.) and validate it in the context of lipid metabolism using feeding trials, extensive transcriptomic data, and fatty acid measurements. We observe an initial period of post-slicing global transcriptome adjustment, which plateaued after 3 days in major metabolic pathways and stabilized through 9 days. PCLS fed alpha-linolenic acid (ALA) and insulin responded in a liver-like manner, increasing lipid biosynthesis gene expression. We identify interactions between insulin and ALA, where two PUFA biosynthesis genes that were induced by insulin or ALA alone, were highly down-regulated when insulin and ALA were combined. We also find that transcriptomic profiles of liver slices are exceedingly more similar to whole liver than hepatocyte monocultures, both for lipid metabolism and liver marker genes. PCLS culture opens new avenues for high throughput experimentation on the effect of “novel feed composition” and represent a promising new strategy for studying genotype-specific molecular features of metabolism.

Host-Pathogen Interactions of Mycoplasma mycoides in Caprine and Bovine Precision-Cut Lung Slices (PCLS) Models

Respiratory infections caused by mycoplasma species in ruminants lead to considerable economic losses. Two important ruminant pathogens are Mycoplasma mycoides subsp. Mycoides (Mmm), the aetiological agent of contagious bovine pleuropneumonia and Mycoplasma mycoides subsp. capri (Mmc), which causes pneumonia, mastitis, arthritis, keratitis, and septicemia in goats. We established precision cut lung slices (PCLS) infection model for Mmm and Mmc to study host-pathogen interactions. We monitored infection over time using immunohistological analysis and electron microscopy. Moreover, infection burden was monitored by plating and quantitative real-time PCR. Results were compared with lungs from experimentally infected goats and cattle. Lungs from healthy goats and cattle were also included as controls. PCLS remained viable for up to two weeks. Both subspecies adhered to ciliated cells. However, the titer of Mmm in caprine PCLS decreased over time, indicating species specificity of Mmm. Mmc showed higher tropism to sub-bronchiolar tissue in caprine PCLS, which increased in a time-dependent manner. Moreover, Mmc was abundantly observed on pulmonary endothelial cells, indicating partially, how it causes systemic disease. Tissue destruction upon prolonged infection of slices was comparable to the in vivo samples. Therefore, PCLS represents a novel ex vivo model to study host-pathogen interaction in livestock mycoplasma.

COPD and asthma therapeutics for supportive treatment in organophosphate poisoning

Context: Nerve agents like sarin or VX have repeatedly been used in military conflicts or homicidal attacks, as seen in Syria or Malaysia 2017. Together with pesticides, nerve agents assort as organophosphorus compounds (OP), which inhibit the enzyme acetylcholinesterase. To counteract subsequent fatal symptoms due to acetylcholine (ACh) accumulation, oximes plus atropine are administered, a regimen that lacks efficacy in several cases of OP poisoning. New therapeutics are in development, but still need evaluation before clinical employment. Supportive treatment with already approved drugs presents an alternative, whereby compounds from COPD and asthma therapy are likely options. A recent pilot study by Chowdhury et al. included β2-agonist salbutamol in the treatment of OP-pesticide poisoned patients, yielding ambiguous results concerning the addition. Here, we provide experimental data for further investigations regarding the value of these drugs in OP poisoning. Methods: By video-microscopy, changes in airway area were analyzed in VX-poisoned rat precision cut lung slices (PCLS) after ACh-induced airway contraction and subsequent application of selected anticholinergics/β2-agonists. Results: Glycopyrrolate and ipratropium efficiently antagonized an ACh-induced airway contraction in VX-poisoned PCLS (EC₅₀ glycopyrrolate 15.8 nmol/L, EC₅₀ ipratropium 2.3 nmol/L). β2-agonists formoterol and salbutamol had only negligible effects when solely applied in the same setting. However, combination of formoterol or salbutamol with low dosed glycopyrrolate or atropine led to an additive effect compared to the sole application [50.6 ± 8.8% airway area increase after 10 nmol/L formoterol +1 nmol/L atropine versus 11.7 ± 9.2% (10 nmol/L formoterol) or 8.6 ± 5.9% (1 nmol/L atropine)]. Discussion: We showed antagonizing effects of anticholinergics and β2-agonists on ACh-induced airway contractions in VX-poisoned PCLS, thus providing experimental data to support a prospective comprehensive clinical study. Conclusions: Our results indicate that COPD and asthma therapeutics could be a valuable addition to the treatment of OP poisoning.

Differential effects of Nintedanib and Pirfenidone on lung alveolar epithelial cell function in ex vivo murine and human lung tissue cultures of pulmonary fibrosis

Background

Idiopathic pulmonary fibrosis (IPF) is a fatal interstitial lung disease. Repetitive injury and reprogramming of the lung epithelium are thought to be critical drivers of disease progression, contributing to fibroblast activation, extracellular matrix remodeling, and subsequently loss of lung architecture and function. To date, Pirfenidone and Nintedanib are the only approved drugs known to decelerate disease progression, however, if and how these drugs affect lung epithelial cell function, remains largely unexplored.

Methods

We treated murine and human 3D ex vivo lung tissue cultures (3D-LTCs; generated from precision cut lung slices (PCLS)) as well as primary murine alveolar epithelial type II (pmATII) cells with Pirfenidone or Nintedanib. Murine 3D-LTCs or pmATII cells were derived from the bleomycin model of fibrosis. Early fibrotic changes were induced in human 3D-LTCs by a mixture of profibrotic factors. Epithelial and mesenchymal cell function was determined by qPCR, Western blotting, Immunofluorescent staining, and ELISA.

Results

Low μM concentrations of Nintedanib (1 μM) and mM concentrations of Pirfenidone (2.5 mM) reduced fibrotic gene expression including Collagen 1a1 and Fibronectin in murine and human 3D-LTCs as well as pmATII cells. Notably, Nintedanib stabilized expression of distal lung epithelial cell markers, especially Surfactant Protein C in pmATII cells as well as in murine and human 3D-LTCs.

Conclusions

Pirfenidone and Nintedanib exhibit distinct effects on murine and human epithelial cells, which might contribute to their anti-fibrotic action. Human 3D-LTCs represent a valuable tool to assess anti-fibrotic mechanisms of potential drugs for the treatment of IPF patients.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0876-y) contains supplementary material, which is available to authorized users.

The gut microbiota metabolite indole alleviates liver inflammation in mice

The gut microbiota regulates key hepatic functions, notably through the production of bacterial metabolites that are transported via the portal circulation. We evaluated the effects of metabolites produced by the gut microbiota from aromatic amino acids (phenylacetate, benzoate, p-cresol, and indole) on liver inflammation induced by bacterial endotoxin. Precision-cut liver slices prepared from control mice, Kupffer cell (KC)-depleted mice, and obese mice ( ob/ ob) were treated with or without LPS and bacterial metabolites. We observed beneficial effects of indole that dose-dependently reduced the LPS-induced up-regulation of proinflammatory mediators at both mRNA and protein levels in precision-cut liver slices prepared from control or ob/ ob mice. KC depletion partly prevented the antiinflammatory effects of indole, notably through a reduction of nucleotide-binding domain and leucine-rich repeat containing (NLR) family pyrin domain-containing 3 (NLRP3) pathway activation. In vivo, the oral administration of indole before an LPS injection reduced the expression of key proteins of the NF-κB pathway and downstream proinflammatory gene up-regulation. Indole also prevented LPS-induced alterations of cholesterol metabolism through a transcriptional regulation associated with increased 4β-hydroxycholesterol hepatic levels. In summary, indole appears as a bacterial metabolite produced from tryptophan that is able to counteract the detrimental effects of LPS in the liver. Indole could be a new target to develop innovative strategies to decrease hepatic inflammation.-Beaumont, M., Neyrinck, A. M., Olivares, M., Rodriguez, J., de Rocca Serra, A., Roumain, M., Bindels, L. B., Cani, P. D., Evenepoel, P., Muccioli, G. G., Demoulin, J.-B., Delzenne, N. M. The gut microbiota metabolite indole alleviates liver inflammation in mice.

Assessment of long-term cultivated human precision-cut lung slices as an ex vivo system for evaluation of chronic cytotoxicity and functionality

Background

Investigation of basic chronic inflammatory mechanisms and development of new therapeutics targeting the respiratory tract requires appropriate testing systems, including those to monitor long- persistence. Human precision-cut lung slices (PCLS) have been demonstrated to mimic the human respiratory tract and have potential of an alternative, ex-vivo system to replace or augment in-vitro testing and animal models. So far, most research on PCLS has been conducted for short cultivation periods (≤72 h), while analyses of slowly metabolized therapeutics require long-term survival of PCLS in culture. In the present study, we evaluated viability, physiology and structural integrity of PCLS cultured for up to 15 days.

Methods

PCLS were cultured for 15 days and various parameters were assessed at different time points.

Results

Structural integrity and viability of cultured PCLS remained constant for 15 days. Moreover, bronchoconstriction was inducible over the whole period of cultivation, though with decreased sensitivity (EC₅₀1d = 4 × 10⁻⁸ M vs. EC₅₀15d = 4 × 10⁻⁶ M) and reduced maximum of initial airway area (1d = 0.5% vs. 15d = 18.7%). In contrast, even though still clearly inducible compared to medium control, LPS-induced TNF-α secretion decreased significantly from day 1 to day 15 of culture.

Conclusions

Overall, though long-term cultivation of PCLS need further investigation for cytokine secretion, possibly on a cellular level, PCLS are feasible for bronchoconstriction studies and toxicity assays.

Electronic supplementary material

The online version of this article (doi:10.1186/s12995-017-0158-5) contains supplementary material, which is available to authorized users.

Corrigendum: Airway and Parenchymal Strains during Bronchoconstriction in the Precision Cut Lung Slice

[This corrects the article on p. 309 in vol. 7, PMID: 27559314.].

Airway and Parenchymal Strains during Bronchoconstriction in the Precision Cut Lung Slice

The precision-cut lung slice (PCLS) is a powerful tool for studying airway reactivity, but biomechanical measurements to date have largely focused on changes in airway caliber. Here we describe an image processing tool that reveals the associated spatio-temporal changes in airway and parenchymal strains. Displacements of sub-regions within the PCLS are tracked in phase-contrast movies acquired after addition of contractile and relaxing drugs. From displacement maps, strains are determined across the entire PCLS or along user-specified directions. In a representative mouse PCLS challenged with 10(-4)M methacholine, as lumen area decreased, compressive circumferential strains were highest in the 50 μm closest to the airway lumen while expansive radial strains were highest in the region 50-100 μm from the lumen. However, at any given distance from the airway the strain distribution varied substantially in the vicinity of neighboring small airways and blood vessels. Upon challenge with the relaxant agonist chloroquine, although most strains disappeared, residual positive strains remained a long time after addition of chloroquine, predominantly in the radial direction. Taken together, these findings establish strain mapping as a new tool to elucidate local dynamic mechanical events within the constricting airway and its supporting parenchyma.

Cell-specific PPARγ deficiency establishes anti-inflammatory and anti-fibrogenic properties for this nuclear receptor in non-parenchymal liver cells

BACKGROUND & AIMS

PPARγ plays an essential role in the transcriptional regulation of genes involved in lipid and glucose metabolism, insulin sensitivity, and inflammation. We recently demonstrated that PPARγ plays a causative role in hepatocyte lipid deposition, contributing to the pathogenesis of hepatic steatosis. In this study, we investigated the role of PPARγ in the inflammatory and fibrogenic response of the liver.

METHODS

Heterozygous floxed/null Cre/LoxP mice with targeted deletion of PPARγ in either hepatocytes (Alb-Cre), macrophages (LysM-Cre) or hepatic stellate cells (HSCs) (aP2-Cre) were submitted to carbon tetrachloride (CCl4) liver injury. Further analyses were performed in precision-cut liver slices (PCLS) and primary cultures of hepatocytes, macrophages, and HSCs.

RESULTS

LysM-Cre mice displayed an exacerbated response to chronic CCl4 injury and showed higher necroinflammatory injury, lipid peroxidation, inflammatory infiltrate, cleaved-caspase-3 and caspase 3/7 activity, and COX-2, TNF-α, CXCL2, and IL-1β expression than Alb-Cre and control mice. The deleterious effects of PPARγ disruption in liver macrophages were confirmed in an acute model of CCl4 injury as well as in PCLS incubated with LPS. Moreover, LysM-Cre mice showed an aggravated fibrogenic response to CCl4, as revealed by more prominent Sirius Red and Masson's trichrome staining, elevated hydroxyproline content and induced α-SMA and TIMP-1 expression. Importantly, aP2-Cre mice with specific disruption of PPARγ in HSCs, as confirmed by immunocytochemical analysis of individual liver cells, also showed exacerbated liver damage and fibrogenic response to CCl4.

CONCLUSIONS

These data unveil anti-inflammatory and anti-fibrogenic roles for PPARγ in non-parenchymal liver cells.