Acid Sphingomyelinase Deficiency Type B Patient-Derived Liver Organoids Reveals Altered Lysosomal Gene Expression and Lipid Homeostasis.

Acid sphingomyelinase deficiency (ASMD) or Niemann-Pick disease type A (NPA), type B (NPB) and type A/B (NPA/B), is a rare lysosomal storage disease characterized by progressive accumulation of sphingomyelin (SM) in the liver, lungs, bone marrow and, in severe cases, neurons. A disease model was established by generating liver organoids from a NPB patient carrying the p.Arg610del variant in the SMPD1 gene. Liver organoids were characterized by transcriptomic and lipidomic analysis. We observed altered lipid homeostasis in the patient-derived organoids showing the predictable increase in sphingomyelin (SM), together with cholesterol esters (CE) and triacylglycerides (TAG), and a reduction in phosphatidylcholine (PC) and cardiolipins (CL). Analysis of lysosomal gene expression pointed to 24 downregulated genes, including SMPD1, and 26 upregulated genes that reflect the lysosomal stress typical of the disease. Altered genes revealed reduced expression of enzymes that could be involved in the accumulation in the hepatocytes of sphyngoglycolipids and glycoproteins, as well as upregulated genes coding for different glycosidases and cathepsins. Lipidic and transcriptome changes support the use of hepatic organoids as ideal models for ASMD investigation.

Quantitative Lipid Profiling Reveals Major Differences between Liver Organoids with Normal Pi*M and Deficient Pi*Z Variants of Alpha-1-antitrypsin.

Different mutations in the SERPINA1 gene result in alpha-1 antitrypsin (AAT) deficiency and in an increased risk for the development of liver diseases. More than 90% of severe deficiency patients are homozygous for Z (Glu342Lys) mutation. This mutation causes Z-AAT polymerization and intrahepatic accumulation which can result in hepatic alterations leading to steatosis, fibrosis, cirrhosis, and/or hepatocarcinoma. We aimed to investigate lipid status in hepatocytes carrying Z and normal M alleles of the SERPINA1 gene. Hepatic organoids were developed to investigate lipid alterations. Lipid accumulation in HepG2 cells overexpressing Z-AAT, as well as in patient-derived hepatic organoids from Pi*MZ and Pi*ZZ individuals, was evaluated by Oil-Red staining in comparison to HepG2 cells expressing M-AAT and liver organoids from Pi*MM controls. Furthermore, mass spectrometry-based lipidomics analysis and transcriptomic profiling were assessed in Pi*MZ and Pi*ZZ organoids. HepG2 cells expressing Z-AAT and liver organoids from Pi*MZ and Pi*ZZ patients showed intracellular accumulation of AAT and high numbers of lipid droplets. These latter paralleled with augmented intrahepatic lipids, and in particular altered proportion of triglycerides, cholesterol esters, and cardiolipins. According to transcriptomic analysis, Pi*ZZ organoids possess many alterations in genes and cellular processes of lipid metabolism with a specific impact on the endoplasmic reticulum, mitochondria, and peroxisome dysfunction. Our data reveal a relationship between intrahepatic accumulation of Z-AAT and alterations in lipid homeostasis, which implies that liver organoids provide an excellent model to study liver diseases related to the mutation of the SERPINA1 gene.

NAFLD and AATD Are Two Diseases with Unbalanced Lipid Metabolism: Similarities and Differences.

Non-alcoholic fatty liver disease (NAFLD) is a type of steatosis commonly associated with obesity, dyslipidemia, hypertension, and diabetes. Other diseases such as inherited alpha-1 antitrypsin deficiency (AATD) have also been related to the development of liver steatosis. The primary reasons leading to hepatic lipid deposits can be genetic and epigenetic, and the outcomes range from benign steatosis to liver failure, as well as to extrahepatic diseases. Progressive hepatocellular damage and dysregulated systemic immune responses can affect extrahepatic organs, specifically the heart and lungs. In this review, we discuss the similarities and differences between the molecular pathways of NAFLD and AATD, and the putative value of hepatic organoids as novel models to investigate the physio pathological mechanisms of liver steatosis.

Mice inflammatory responses to inhaled aerosolized LPS: effects of various forms of human alpha1-antitrypsin.

Rodent models of lipopolysaccharide (LPS)-induced pulmonary inflammation are used for anti-inflammatory drug testing. We aimed to characterize mice responses to aerosolized LPS alone or with intraperitoneal (i.p.) delivery of alpha1-antitrypsin (AAT). Balb/c mice were exposed to clean air or aerosolized LPS (0.21 mg/mL) for 10 min per day, for 3 d. One hour after each challenge, animals were treated i.p. with saline or with (4 mg/kg body weight) one of the AAT preparations: native (AAT), oxidized (oxAAT), recombinant (recAAT), or peptide of AAT (C-36). Experiments were terminated 6 h after the last dose of AATs. Transcriptome data of mice lungs exposed to clean air versus LPS revealed 656 differentially expressed genes and 155 significant gene ontology terms, including neutrophil migration and toll-like receptor signaling pathways. Concordantly, mice inhaling LPS showed higher bronchoalveolar lavage fluid neutrophil counts and levels of myeloperoxidase, inducible nitric oxide synthase, IL-1ß, TNFα, KC, IL-6, and granulocyte-macrophage colony-stimulating factor (GM-CSF). Plasma inflammatory markers did not increase. After i.p. application of AATs, about 1% to 2% of proteins reached the lungs but, except for GM-CSF, none of the proteins significantly influenced inflammatory markers. All AATs and C-36 significantly inhibited LPS-induced GM-CSF release. Surprisingly, only oxAAT decreased the expression of several LPS-induced inflammatory genes, such as Cxcl3, Cd14, Il1b, Nfkb1, and Nfkb2, in lung tissues. According to lung transcriptome data, oxAAT mostly affected genes related to transcriptional regulation while native AAT or recAAT affected genes of inflammatory pathways. Hence, we present a feasible mice model of local lung inflammation induced via aerosolized LPS that can be useful for systemic drug testing.

Loss of Serpina1 in Mice Leads to Altered Gene Expression in Inflammatory and Metabolic Pathways.

The SERPINA1 gene encodes alpha1-antitrypsin (AAT), an acute phase glycoprotein and serine protease inhibitor that is mainly (80-90%) produced in the liver. Point mutations in the SERPINA1 gene can lead to the misfolding, intracellular accumulation, and deficiency of circulating AAT protein, increasing the risk of developing chronic liver diseases or chronic obstructive pulmonary disease. Currently, siRNA technology can knock down the SERPINA1 gene and limit defective AAT production. How this latter affects other liver genes is unknown. Livers were taken from age- and sex-matched C57BL/6 wild-type (WT) and Serpina1 knockout mice (KO) aged from 8 to 14 weeks, all lacking the five serpin A1a-e paralogues. Total RNA was isolated and RNA sequencing, and transcriptome analysis was performed. The knockout of the Serpina1 gene in mice changed inflammatory, lipid metabolism, and cholesterol metabolism-related gene expression in the liver. Independent single-cell sequencing data of WT mice verified the involvement of Serpina1 in cholesterol metabolism. Our results from mice livers suggested that designing therapeutic strategies for the knockout of the SERPINA1 gene in humans must account for potential perturbations of key metabolic pathways and consequent mitigation of side effects.

DNA repair pathways are altered in neural cell models of frataxin deficiency.

Friedreich's ataxia (FRDA) is a hereditary and predominantly neurodegenerative disease caused by a deficiency of the protein frataxin (FXN). As part of the overall efforts to understand the molecular basis of neurodegeneration in FRDA, a new human neural cell line with doxycycline-induced FXN knockdown was established. This cell line, hereafter referred to as iFKD-SY, is derived from the human neuroblastoma SH-SY5Y and retains the ability to differentiate into mature neuron-like cells. In both proliferating and differentiated iFKD-SY cells, the induction of FXN deficiency is accompanied by increases in oxidative stress and DNA damage, reduced aconitase enzyme activity, higher levels of p53 and p21, activation of caspase-3, and subsequent apoptosis. More interestingly, FXN-deficient iFKD-SY cells exhibit an important transcriptional deregulation in many of the genes implicated in DNA repair pathways. The levels of some crucial proteins involved in DNA repair appear notably diminished. Furthermore, similar changes are found in two additional neural cell models of FXN deficit: primary cultures of FXN-deficient mouse neurons and human olfactory mucosa stem cells obtained from biopsies of FRDA patients. These results suggest that the deficiency of FXN leads to a down-regulation of DNA repair pathways that synergizes with oxidative stress to provoke DNA damage, which may be involved in the pathogenesis of FRDA. Thus, a failure in DNA repair may be considered a shared common molecular mechanism contributing to neurodegeneration in a number of hereditary ataxias including FRDA.

Altered Secretome and ROS Production in Olfactory Mucosa Stem Cells Derived from Friedreich's Ataxia Patients.

Friedreich's ataxia is the most common hereditary ataxia for which there is no cure or approved treatment at present. However, therapeutic developments based on the understanding of pathological mechanisms underlying the disease have advanced considerably, with the implementation of cellular models that mimic the disease playing a crucial role. Human olfactory ecto-mesenchymal stem cells represent a novel model that could prove useful due to their accessibility and neurogenic capacity. Here, we isolated and cultured these stem cells from Friedreich´s ataxia patients and healthy donors, characterizing their phenotype and describing disease-specific features such as reduced cell viability, impaired aconitase activity, increased ROS production and the release of cytokines involved in neuroinflammation. Importantly, we observed a positive effect on patient-derived cells, when frataxin levels were restored, confirming the utility of this in vitro model to study the disease. This model will improve our understanding of Friedreich´s ataxia pathogenesis and will help in developing rationally designed therapeutic strategies.

Analysis of Putative Epigenetic Regulatory Elements in the FXN Genomic Locus.

Friedreich´s ataxia (FRDA) is an autosomal recessive disease caused by an abnormally expanded Guanine-Adenine-Adenine (GAA) repeat sequence within the first intron of the frataxin gene (FXN). The molecular mechanisms associated with FRDA are still poorly understood and most studies on FXN gene regulation have been focused on the region around the minimal promoter and the region in which triplet expansion occurs. Nevertheless, since there could be more epigenetic changes involved in the reduced levels of FXN transcripts, the aim of this study was to obtain a more detailed view of the possible regulatory elements by analyzing data from ENCODE and Roadmap consortia databases. This bioinformatic analysis indicated new putative regulatory regions within the FXN genomic locus, including exons, introns, and upstream and downstream regions. Moreover, the region next to the end of intron 4 is of special interest, since the enhancer signals in FRDA-affected tissues are weak or absent in this region, whilst they are strong in the rest of the analyzed tissues. Therefore, these results suggest that there could be a direct relationship between the absence of enhancer sequences in this specific region and their predisposition to be affected in this pathology.

Enhanced Production of Herpes Simplex Virus 1 Amplicon Vectors by Gene Modification and Optimization of Packaging Cell Growth Medium.

Herpes simplex virus 1 (HSV-1)-derived amplicon vectors are unique in their ability to accommodate large DNA molecules allowing whole genomic loci to be included with all of their regulatory elements. Additional advantages of these amplicons include their minimal toxicity and ability to persist as episomes, with negligible risk of insertional mutagenesis, being particularly well-suited for gene therapy of neurological disorders due to their outstanding ability to deliver genes into neurons and other neural cells. However, extensive gene therapy application has been hindered by difficulties in vector production. This work improved HSV-1 amplicons production by genetic modification of the packaging cell line and optimization of the culture medium. A stably-transfected Vero 2-2 cell line overexpressing the anti-apoptotic Bcl-2 protein was generated, exhibiting an increased resistance to apoptosis, prolonged culture duration, and a significant improvement in viral vector production. Additionally, supplementation of the growth medium with antioxidants, polyamines, amino acids, and reduced glutathione further increased the yield of packaged amplicon vectors. With these modifications, HSV-1 amplicons could be isolated from culture supernatants instead of cell lysates, leading to vector preparations with higher titer and purity and paving the way for generation of stable cell lines that are capable of continuous herpesviral vector production.

Prospects for the use of artificial chromosomes and minichromosome-like episomes in gene therapy.

Artificial chromosomes and minichromosome-like episomes are large DNA molecules capable of containing whole genomic loci, and be maintained as nonintegrating, replicating molecules in proliferating human somatic cells. Authentic human artificial chromosomes are very difficult to engineer because of the difficulties associated with centromere structure, so they are not widely used for gene-therapy applications. However, OriP/EBNA1-based episomes, which they lack true centromeres, can be maintained stably in dividing cells as they bind to mitotic chromosomes and segregate into daughter cells. These episomes are more easily engineered than true human artificial chromosomes and can carry entire genes along with all their regulatory sequences. Thus, these constructs may facilitate the long-term persistence and physiological regulation of the expression of therapeutic genes, which is crucial for some gene therapy applications. In particular, they are promising vectors for gene therapy in inherited diseases that are caused by recessive mutations, for example haemophilia A and Friedreich's ataxia. Interestingly, the episome carrying the frataxin gene (deficient in Friedreich's ataxia) has been demonstrated to rescue the susceptibility to oxidative stress which is typical of fibroblasts from Friedreich's ataxia patients. This provides evidence of their potential to treat genetic diseases linked to recessive mutations through gene therapy.

Factor VIII mRNA expression from a BAC carrying the intact locus made by homologous recombination.

Hemophilia A is caused by mutations in the gene encoding factor VIII (F8) and is an important target for gene therapy. The F8 gene contains 26 exons spread over approximately 186 kb and no work using the intact genomic locus has been carried out. We have constructed a 250-kb BAC carrying all 26 exons, the introns, and more than 40 kb of upstream and 20 kb of downstream DNA. This F8 BAC was further retrofitted with either the oriP/EBNA-1 elements from Epstein-Barr virus, which allow episomal maintenance in mammalian cells, or alphoid DNA, which allows human artificial chromosome formation in some human cell lines. Lipofection of the oriP/EBNA-1-containing version into mouse Hepa1-6 cells resulted in expression of F8 mRNA spanning the F8 gene. The >300-kb BAC carrying alphoid DNA was successfully delivered to 293A and HT1080 cells using bacterial delivery, resulting in greater than endogenous levels of F8 mRNA expression.

Construction of human artificial chromosome vectors by recombineering.

Human artificial chromosomes (HACs) can be formed de novo by transfection of large fragments of cloned alphoid DNA into human HT1080 cells in tissue culture. In order to generate HACs carrying a gene of interest, one can either co-transfect the alphoid DNA and the gene of interest, or one can clone both into a single vector prior to transfection. Here we describe linking approximately 70 kb of alphoid DNA onto a 156-kb BAC carrying the human HPRT gene using Red homologous recombination in the EL350 Escherichia coli host [Lee et al., Genomics 73 (2001) 56-65]. A selectable marker and EGFP marker were then added by loxP/Cre recombination using the arabinose inducible cre gene in the EL350 bacteria. The final construct generates minichromosomes in HT1080 cells and the HPRT gene is expressed. The retrofitting vector can be used to add the approximately 70 kb of alphoid DNA to any BAC carrying a gene of interest to generate a HAC vector. The method can also be used to link any unrelated BAC or PAC insert onto another BAC clone. The EL350 bacteria are an excellent host for building up complex vectors by a combination of homologous and loxP/Cre recombination.

Sequence diversity of the internal transcribed spacer (ITS) region of the rRNA operons among different serogroups of Legionella pneumophila isolates.

The genus Legionella is represented by 48 species and Legionella pneumophila includes 15 serogroups. In this work, we have studied the intergenic 16S-23S spacer region (ITS) in L. pneumophila to determine the feasability of using amplification polymorphisms in this region, to establish intraspecies differences and to discriminate Legionella species. The amplification of this region, using 16S14F and 23S0R primers, and the analysis of amplicons by the analysis of fragments technique showed that all the L. pneumophila serogroups studied presented the same electrophoretic pattern. Moreover, the analysis of different Legionella species showed that the amplification polymorphisms obtained were species-specific. In order to study the sequence variability of this region, the existence in L. pneumophila of three ribosomal operons was determined by pulsed field gel eletrophoresis (PFGE). Two of the 16S-23S rRNA ITS presented a tRNA Ala and the third one a tRNA Ile. Nevertheless, the variability expected in this region of the operon was not found and the rest of the ITS contained only punctual mutations.