Gene transfer in primary cultures of human hepatocytes

Glyco-poly-L-lysine is better than liposomal delivery of exogenous genes to rat of liver

AIM: To compare the effects of liposomes and glyco-poly-L-lysine on liver tar geted uptake and expression of plasmid in rat liver.

METHODS: After binding with lipofectamine or galactose-terminal glyco-poly-L-lysine, the plasmid could be expressed in eukaryotic cells when injected into Wistar rats by intravenous route. At different time intervals after the injection, the distribution and expression of the plasmid in liver of rats were observed and compared using in situ hybridization and immunohistochemistry.

RESULTS: The expression of the plasmid binding to liposomes or G-PLL could be markedly observed 24 h later, and began to decrease one week later, but it still could be observed up to three weeks. Both liposomes and G-PLL could deliver the plasmid to the liver effectively, but the effect of the latter was better than the former concerning the distribution and expression of the plasmid targeted uptake in the liver.

CONCLUSION: G-PLL is better than liposome as the targeted carrier for delivering exogenous genes to the liver.

Transcriptional regulation of stromelysin-1 gene expression is altered during progression of mouse mammary epithelial cells from functionally normal to malignant

The matrix metalloproteinase stromelysin-1 plays a central role during mammary gland development and tumor progression. To gain insight into the regulation of stromelysin-1 gene expression, the murine stromelysin-1 promoter was cloned and transfected into mouse mammary epithelial cells displaying various degrees of malignancy. A reconstituted basement membrane inhibited stromelysin-1 promoter activity in functionally normal cells, had little effect on moderately malignant cells and up-regulated the promoter in highly malignant cells. Spreading of normal and malignant cells was reduced by a reconstituted basement membrane, compared to a plastic substratum. Preventing spreading by maintenance of cells in suspension culture, regulated stromelysin-1 promoter activity in a manner similar to that on a reconstituted basement membrane. Conversely, increasing spreading by augmenting substratum adhesivity up-regulated stromelysin-1 promoter activity in tumor cells. In cells with reduced spreading in the presence of reconstituted basement membrane and in suspension culture, actin stress fibers were replaced by cortical actin bundles. In tumor cells, but not in functionally normal cells, treatment with phorbol diesters also resulted in accumulation of cortical actin and increased stromelysin-1 promoter activity. Consistent with an epithelial-to-mesenchymal conversion, regulation of stromelysin-1 gene expression in highly malignant cells was similar to its regulation in mammary fibroblasts. We conclude that the switch in transcriptional regulation of stromelysin-1 expression that occurs during epithelial-to-mesenchymal transition and conversion to tumorigenicity is related to altered regulation of signals from the cytoarchitecture.

Liposomes as a gene delivery system

Gene therapy is an active field that has progressed rapidly into clinical trials in a relatively short time. The key to success for any gene therapy strategy is to design a vector able to serve as a safe and efficient gene delivery vehicle. This has encouraged the development of nonviral DNA-mediated gene transfer techniques such as liposomes. Many liposome-based DNA delivery systems have been described, including molecular components for targeting given cell surface receptors or for escaping from the lysosomal compartment. Another recent technology using cationic lipids has been evaluated and has generated substantial interest in this approach to gene transfer.

alpha1 and alpha2 integrins mediate invasive activity of mouse mammary carcinoma cells through regulation of stromelysin-1 expression

Tumor cell invasion relies on cell migration and extracellular matrix proteolysis. We investigated the contribution of different integrins to the invasive activity of mouse mammary carcinoma cells. Antibodies against integrin subunits alpha6 and beta1, but not against alpha1 and alpha2, inhibited cell locomotion on a reconstituted basement membrane in two-dimensional cell migration assays, whereas antibodies against beta1, but not against alpha6 or alpha2, interfered with cell adhesion to basement membrane constituents. Blocking antibodies against alpha1 integrins impaired only cell adhesion to type IV collagen. Antibodies against alpha1, alpha2, alpha6, and beta1, but not alpha5, integrin subunits reduced invasion of a reconstituted basement membrane. Integrins alpha1 and alpha2, which contributed only marginally to motility and adhesion, regulated proteinase production. Antibodies against alpha1 and alpha2, but not alpha6 and beta1, integrin subunits inhibited both transcription and protein expression of the matrix metalloproteinase stromelysin-1. Inhibition of tumor cell invasion by antibodies against alpha1 and alpha2 was reversed by addition of recombinant stromelysin-1. In contrast, stromelysin-1 could not rescue invasion inhibited by anti-alpha6 antibodies. Our data indicate that alpha1 and alpha2 integrins confer invasive behavior by regulating stromelysin-1 expression, whereas alpha6 integrins regulate cell motility. These results provide new insights into the specific functions of integrins during tumor cell invasion.

Gene therapy for central nervous system injury: the use of cationic liposomes: an invited review

This paper briefly reviews general principles of gene therapy with emphasis on the therapeutic potential of cationic liposome-mediated neurotrophin gene transfer to treat central nervous system (CNS) injury. Current developments in studies of gene therapy for CNS injury are both impressive and promising. Ex vivo gene transfer into the CNS is relatively mature in animal studies following more than a decade of experimental studies. In vivo gene transfer into the CNS has gained more attention recently. Although progress has been made using viral vectors, rapid advances in transfection technologies employing cationic liposomes, together with the relatively low toxicity of these nonviral vector systems, suggest that liposomes may have significant potential for clinical applications. Although many investigators have recognized that gene therapy may be useful for treatment of certain genetic defect diseases or cancer, gene therapy for CNS injury is relatively novel. In contrast to genetic defect disorders, temporary induction of transgenes may have therapeutic applications for CNS injuries such as stroke and trauma. Employing gene transfer techniques to achieve therapeutically useful levels of expression of neurotrophins in the CNS could provide a new strategy for treatment of the traumatically injured CNS.

Effects of fusogenic and DNA-binding amphiphilic compounds on the receptor-mediated gene transfer into hepatic cells by asialofetuin-labeled liposomes

Effects of fusogenic and DNA-binding amphiphilic compounds on the receptor-mediated gene transfer using asialofetuin-labeled liposomes (AF-liposomes) were examined with HepG2 cells and rat hepatocytes in primary culture. AF-liposomes were sufficiently taken up by both types of cells through the asialoglycoprotein receptor-mediated endocytosis. In HepG2 cells, bacterial beta-galactosidase (beta-Gal) gene expression was observed by transfection using AF-liposomes encapsulating plasmid pCMV beta DNA (AF-liposome-pCMV beta). By addition of dioleoylphosphatidylethanolamine (DOPE) to the liposomal lipid composition (AF-liposome(DOPE)-pCMV beta), the transfection efficiency was clearly increased. The effects of DOPE were more conspicuous in the presence of chloroquine in the medium throughout the transfection. When pCMV beta complexed with gramicidin S (pCMV beta (GrS)) was encapsulated (AF-liposome(DOPE)-pCMV beta (GrS) and was transfected to HepG2 cells, an significantly high beta-Gal activity in the cells was observed as compared with that in the cells transfected with AF-liposome(DOPE)-pCMV beta. No effects of GrS were found in the transfection using AF-non-labeled control liposomes. In primary culture of rat hepatocytes, no beta-Gal gene expression was observed even though AF-liposome(DOPE)-pCMV beta was introduced into the cells prepared from adult rats. However, following the transfection with AF-liposome(DOPE)-pCMV beta, the beta-Gal activity was expressed in the cells from immature rats cultured in the medium supplemented with epidermal growth factor and insulin, and the transfection efficiency was 2-fold higher than that transfected with pCMV beta encapsulated in AF-non-labeled control liposomes. By the complex formation of pCMV beta with GrS, the transfection efficiency of AF-liposome(DOPE)-pCMV beta (GrS) increased according to the increase of GrS in the complex. It was shown that AF-liposome(DOPE)-pCMV beta (GrS) did efficiently introduce and express beta-Gal gene in both HepG2 cells and primary hepatocytes in the receptor mediated manner.

Cytoskeletal derangements following central nervous system injury: modulation by neurotrophic gene transfection

This paper reviews important new evidence indicating that traumatic brain injury can produce more widespread derangements to the neuronal cytoskeleton than previously recognized. Although cytoskeletal derangements in axons have long been documented, recent data suggest that traumatic brain injury can produce structural derangements to dendrites and cell bodies as well. Many of these investigations have employed in vivo models to provide important insights into mechanisms possibly mediating the acute loss of cytoskeletal proteins, including disturbances in calcium homeostasis and activation of calcium-dependent proteolytic enzymes. However, we have little understanding of processes mediating the recovery of cytoskeletal proteins following injury. This paper provides recent evidence from in vitro models of central nervous system injury that neurotrophic proteins can enhance the recovery of the neuronal cytoskeleton. Neurotrophin-based therapy could employ either administration of exogenous neurotrophic proteins and/or transfection of cDNA for appropriate neurotrophins.

Rescue of injury-induced neurofilament loss by BDNF gene transfection in primary septo-hippocampal cell cultures

We employed primary septo-hippocampal cell cultures to determine the ability of liposome-mediated BDNF gene transfection to facilitate recovery of neurofilament loss caused by depolarization injury. After BDNF gene transfection in uninjured cultures, RT-PCR and immunohistochemical staining confirmed increases in BDNF mRNA and protein in transfected cells. Three days after depolarization injury, Western blot and immunohistochemical analyses detected significant loss of neurofilament proteins in non-transfected cultures, while BDNF transfection produced marked increases in neurofilament proteins following either pre-injury transfection or transfection 24 h following injury. Immunohistochemical studies also detected enhanced immunolabeling of BDNF and total neurofilament protein (phosphorylated and non-phosphorylated) in injured neurons following BDNF transfection or administration of exogenous BDNF protein, compared to untransfected, injured controls.

Sustained expression of functional nerve growth factor in primary septo-hippocampal cell cultures by liposome-mediated gene transfer

We examined liposome-mediated gene transfection of nerve growth factor (NGF) in primary central nervous system cultures. RT-PCR analyses detected increased expression of NGF mRNA one day after liposome-mediated NGF gene transfection. ELISA studies detected large increases in NGF protein in cells and in culture medium after NGF gene transfection. Cells continued to secrete NGF into the medium for at least 2 weeks. NGF bioassays confirmed that the NGF secreted after gene transfection was biologically active.

Optimizing liposome-mediated gene transfer in primary rat septo-hippocampal cell cultures

Although liposomes have been widely employed to transfect DNA into a variety of cell types, no previous studies have systematically examined conditions producing optimal liposomal-mediated transfection of DNA into central nervous system (CNS) cells. Thus, we used the beta-galactosidase (beta-gal) reporter gene to examine factors influencing the efficiency of liposome-mediated gene transfection in CNS cell cultures. Our results indicate that without increasing the amounts of DNA, increased liposome concentrations within certain limits enhanced transfection efficiency. However, higher liposome levels could produce cell lysis. Without increasing liposome concentrations, increased amounts of DNA did not improve transfection efficiency. Employing the optimal concentration (1 microgram DNA/3 microliters liposomes/well), beta-gal gene expression was sustained for at least two weeks after transfection in primary septo-hippocampal cultures.

Culturing of primary hepatocytes as entrapped aggregates in a packed bed bioreactor: a potential bioartificial liver

Conventional culture systems for hepatocytes generally involve cells cultured as flat, monolayer cells, with limited cell-cell contact, in a static pool of medium, unlike the liver in vivo where the parenchymal cells are cuboidal, with extensive cell-cell contact, and are continuously perfused with blood. We report here a novel bioreactor system for the culturing of primary hepatocytes with cuboidal cell shape, extensive cell-cell contact, and perfusing medium. The hepatocytes were inoculated into the bioreactor and allowed to recirculate at a rate optimal for them to collide and form aggregates. These newly-formed aggregates were subsequently entrapped in a packed bed of glass beads. The bioreactor was perfused with oxygenated nutrient medium, with controlled oxygen tension, pH, and medium perfusion rate. The hepatocytes were viable for up to the longest time point studied of 15 days in culture based on urea synthesis, albumin synthesis and cell morphology. Light microscopy studies of hepatocytes cultured for 15 days in the bioreactor showed interconnecting three-dimensional structures resembling the hepatic cell plate in the liver organ. Electron microscopy studies on the same cells revealed ultrastructure similar to the hepatocytes in vivo, including the presence of plentiful mitochondria, rough and smooth endoplasmic reticulum, glycogen granules, peroxisomes, and desmosomes. We believe that our hepatocyte bioreactor is a major improvement over conventional culture systems, with important industrial applications including toxicology, drug metabolism, and protein/peptide synthesis. The hepatocyte bioreactor concept may also be used as the basis for the development of a bioartificial liver to provide extracorporeal hepatic support to patients with hepatic failure.

A simplified method for the culturing of primary adult rat and human hepatocytes as multicellular spheroids

A simple and highly reproducible method was established for the culturing of adult rat and human hepatocytes as multicellular aggregates (spheroids). Purified rat and human liver parenchymal cells were cultured on nontissue culture (bacteriological) polystyrene petri dishes on a rotating platform. After an overnight incubation, the cells were found to form multicellular aggregates. The aggregates became spheroidal in shape after several days in culture. Histological sections of the spheroids showed an organized structure consisting of squamated cells on the outermost layer and cuboidal cells in the interior. Cellular structures characteristic of hepatocytes in the liver in vivo including bile canaliculi, peroxisomes, Golgi bodies, abundant mitochondria, and rough and smooth endoplasmic reticulum were observed with electron microscopy. The spheroids were found to be viable up to the longest time studied of approx. 1 month in culture as demonstrated by their adherence and growth on collagen-coated substratum. The morphological resemblance between hepatocytes cultured as spheroids and the liver in vivo suggests that the spheroids may be a useful in vitro experimental model of the liver. Our simple method should allow hepatocytes to be cultured as spheroids easily in any laboratory equipped for cell culture. Our study here also is the first to report the culturing of human hepatocytes as spheroids.