Cytotoxic immune response after retroviral-mediated hepatic gene transfer in rat does not preclude expression from adeno-associated virus 1 transduced muscles

Revolutionary impact of nanodrug delivery on neuroscience

Brain research is the most expanding interdisciplinary research that is using the state of the art techniques to overcome limitations in order to conduct more accurate and effective experiments. Drug delivery to the target site in the central nervous system (CNS) is one of the most difficult steps in neuroscience researches and therapies. Taking advantage of the nanoscale structure of neural cells (both neurons and glia); nanodrug delivery (second generation of biotechnological products) has a potential revolutionary impact into the basic understanding, visualization and therapeutic applications of neuroscience. Current review article firstly provides an overview of preparation and characterization, purification and separation, loading and delivering of nanodrugs. Different types of nanoparticle bioproducts and a number of methods for their fabrication and delivery systems including (carbon) nanotubes are explained. In the second part, neuroscience and nervous system drugs are deeply investigated. Different mechanisms in which nanoparticles enhance the uptake and clearance of molecules form cerebrospinal fluid (CSF) are discussed. The focus is on nanodrugs that are being used or have potential to improve neural researches, diagnosis and therapy of neurodegenerative disorders.

In vitro and in vivo induction of bone formation based on adeno-associated virus-mediated BMP-7 gene therapy using human adipose-derived mesenchymal stem cells

AIM

To determine whether adeno-associated virus (AAV)-2-mediated, bone morphogenetic protein (BMP)-7-expressing human adipose-derived mesenchymal stem cells (ADMS) cells would induce bone formation in vitro and in vivo.

METHODS

ADMS cells were harvested from patients undergoing selective suction-assisted lipectomy and transduced with AAV carrying the human BMP-7 gene. Non-transduced cells and cells transduced with AAV serotype 2 carrying the enhanced green fluorescence protein gene served as controls. ADMS cells were qualitatively assessed for the production of BMP-7 and osteocalcin, and subjected to alkaline phosphatase (ALP) and Chinalizarin staining. A total of 2.5 x 10(6) cells mixed with type I collagen were implanted into the hind limb of severe combined immune-deficient (SCID) mice and subjected to a histological analysis 3 weeks post implantation.

RESULTS

Transfection of the ADMS cells achieved an efficiency of 99% at d 7. Transduction with AAV2-BMP-7 induced the expression of BMP-7 until d 56, which was markedly increased by d 7. The cells were positively stained for ALP. Osteocalcin production and matrix mineralization further confirmed that these cells differentiated into osteoblasts and induced bone formation in vitro. A histological examination demonstrated that implantation of BMP-7-expressing ADMS cells could induce new bone formation in vivo.

CONCLUSION

The present in vitro and in vivo study demonstrated that human ADMS cells would be a promising source of autologous mesenchymal stem cells for BMP gene therapy and tissue engineering.

Systemic correction of a fatty acid oxidation defect by intramuscular injection of a recombinant adeno-associated virus vector

Mitochondrial beta-oxidation of fatty acids is required to meet physiologic energy requirements during illness and periods of fasting or physiologic stress, and is most active in liver and striated muscle. Acyl-CoA dehydrogenases of varying chain-length specificities represent the first step in the mitochondria for each round of beta-oxidation, each of which removes two-carbon units as acetyl-CoA for entry into the tricarboxylic acid cycle. We have used recombinant adeno-associated virus (rAAV) vectors expressing short-chain acyl-CoA dehydrogenase (SCAD) to correct the accumulation of fatty acyl-CoA intermediates in deficient cell lines. The rAAV-SCAD vector was then packaged into either rAAV serotype 1 or 2 capsids and injected intramuscularly into SCAD-deficient mice. A systemic effect was observed as judged by restoration of circulating butyryl- carnitine levels to normal. Total lipid content at the injection site was also decreased as demonstrated by noninvasive magnetic resonance spectroscopy (MRS). SCAD enzyme activity in the injected muscle was found at necropsy to be above the normal control mouse level. This study is the first to demonstrate the systemic correction of a fatty acid oxidation disorder with rAAV and the utility of MRS as a noninvasive method to monitor SCAD correction after in vivo gene therapy.

Mixed hematopoietic molecular chimerism results in permanent transgene expression from retrovirally transduced hepatocytes in mice

BACKGROUND

Cytotoxic immune elimination of transduced hepatocytes may limit gene therapy for inherited liver diseases. Using beta-galactosidase as a marker gene, we studied whether creation of mixed beta-galactosidase molecular hematopoietic chimerism could induce tolerance to beta-galactosidase-transduced hepatocytes.

METHODS

Molecular hematopoietic chimerism was established in irradiated recipient mice by transplantation of either a mixture of wild-type and beta-galactosidase-transgenic bone marrow or autologous bone marrow stem cells that were transduced with beta-galactosidase lentiviral vectors. After transplantation, mice were hepatectomized and injected with beta-galactosidase recombinant retroviruses to transduce regenerating hepatocytes. We monitored the presence of beta-galactosidase-expressing hepatocytes as well as the appearance of anti-beta-galactosidase antibodies during the time.

RESULTS

In control animals, anti-beta-galactosidase antibodies and cytotoxic T-lymphocyte (CTL) response developed as early as 3 weeks after gene transfer. Transduced hepatocytes disappeared concomitantly. In bone marrow transplanted mice, tolerance could be observed in a significant proportion of animals. Tolerance resulted in permanent liver transgene expression and was absent unless a chimerism above 1% was achieved, demonstrating a threshold effect.

CONCLUSIONS

Creation of a molecular hematopoietic chimerism can result in transgene tolerance and evade immune rejection of retrovirally transduced hepatocytes. This strategy may be useful for hepatic inherited diseases in which the transgene product behaves as a non-self protein.

Adeno-associated virus-mediated bone morphogenetic protein-7 gene transfer induces C2C12 cell differentiation into osteoblast lineage cells

AIM

To investigate the effects of bone morphogenetic protein-7 (BMP7)-expressing recombinant adeno-associated virus (AAV) vector on the differentiation of C2C12 cells.

METHODS

AAV-BMP7 was packaged by infecting the stable cell clone BHK-21 (integrated with recombinant AAV vector plasmid pSNAV-BMP7) with recombinant herpes simplex virus type 1, which expresses AAV-2 Rep and Cap and possesses AAV packaging functions. Following infection with AAV-BMP7 at multiplicities of infection of 1 x 10(5) vector genomes per cell and subsequent culture, C2C12 cells were assessed qualitatively for BMP7 production, alkaline phosphatase activity, osteocalcin production and Cbfal and MyoD expression.

RESULTS

C2C12 cells transduced with AAV-BMP7 could produce BMP7 protein until d 28. Alkaline phosphatase in the cultured C2C12 cell lysate was elevated. Secreted osteocalcin in the culture medium was detectable at d 12 and Cbfal mRNA expression level was upregulated, coinciding with downregulation of MyoD in a temporal manner.

CONCLUSION

The present in vitro study demonstrated that AAV-BMP7 could infect and efficiently convert C2C12 cells from myoblasts into osteoblast lineage cells.

Long term phenobarbital administration does not promote the multiplication of hepatocytes replicating after single cyproterone acetate administration

Cyproterone acetate (CPA) is a synthetic antiandrogenic compound which is widely used in clinic but suspected to be hepatocarcinogenic. CPA is also mitogenic in rat liver. Using genetic labeling of dividing cells, we examined whether hepatocytes dividing in response to acute CPA administration could give rise to preneoplastic foci after administration of a tumor promoter: phenobarbital. CPA was administered orally to rats and dividing hepatocytes were genetically labeled using retroviral vectors carrying the beta-galactosidase gene. After labeling rats were given phenobarbital for 10 months and sacrificed. The presence of beta-galactosidase labeled hepatocytes as well as preneoplastic hepatocytes was assessed by immunohistochemistry. Genetic labeling of hepatocytes was obtained in all animals. At the end of phenobarbital administration, no hepatic tumors were observed. Preneoplastic foci were not increased in treated animals as compared to control rats. Moreover beta-galactosidase positive hepatocytes were never detected in preneoplastic foci. Finally, the size of the beta-galactosidase positive clusters was smaller in treated animals as compared to control rats. We conclude that acute CPA administration is not carcinogenic in rat liver and does not initiate preneoplastic hepatocytes capable to give rise to foci after phenobarbital promotion. Therefore the mitogenic property of CPA is distinct from its putative carcinogenic activity. Finally, analysis of the size of beta-galactosidase positive cells clusters demonstrate that phenobarbital does not induce hepatocyte proliferation in rats.

Recombinant adeno-associated viral (rAAV) vectors as therapeutic tools for Duchenne muscular dystrophy (DMD)

Duchenne muscular dystrophy (DMD) is a lethal genetic muscle disorder caused by recessive mutations in the dystrophin gene. The size of the gene (2.4 Mb) and mRNA (14 kb) in addition to immunogenicity problems and inefficient transduction of mature myofibres by currently available vector systems are formidable obstacles to the development of efficient gene therapy approaches. Adeno-associated viral (AAV) vectors overcome many of the problems associated with other vector systems (nonpathogenicity and minimal immunogenicity, extensive cell and tissue tropism) but accommodate limited transgene capacity (<5 kb). As a result of these observations, a number of laboratories worldwide have engineered a series of microdystrophin cDNAs based on genotype-phenotype relationship in Duchenne (DMD) and Becker (BMD) dystrophic patients, and transgenic studies in mdx mice. Recent progress in characterization of AAV serotypes from various species has demonstrated that alternative AAV serotypes are far more efficient in transducing muscle than the traditionally used AAV2. This article summarizes the current progress in the field of recombinant adeno-associated viral (rAAV) delivery for DMD, including optimization of recombinant AAV-microdystrophin vector systems/cassettes targeting the skeletal and cardiac musculature.

Liver gene therapy: advances and hurdles

Liver gene therapy is being developed as an alternative to orthotopic liver transplantation, which is the only effective therapy for many liver diseases. The liver has unique features that make it attractive for in vivo and ex vivo gene transfer. In vivo approach is far less invasive than ex vivo approach, although in most cases, host immune response directed against the transgene product and/or vector particles severely impairs the efficiency of gene transfer, and precludes long-term transgene expression after in vivo gene delivery. Ex vivo approach allows for an elective targeting of the hepatocytes, avoiding that the transgene be expressed in professional antigen-presenting, but is faced with the low in vitro proliferative ability of hepatocytes, and to the low in vivo liver repopulating ability of transplanted cells. In some specific situations where immune response was controlled or transplanted cells had a strong growth advantage over host hepatocytes, gene transfer resulted in long-term and complete correction of a liver genetic defect. In this review, we will outline the liver diseases that may benefit from gene therapy, the vector technology under investigation, the advances and the problems to be overcome.

Genetic manipulation in nutrition, metabolism, and obesity research

We summarize the current standard methods for overexpressing, inactivating, or manipulating genes, with special focus on nutritional and obesity research. These molecular biology procedures can be carried out with the maintenance of the genetic information to subsequent generations (transgenic technology) or devised to exclusively transfer the genetic material to a given target animal, which cannot be transmitted to the future progeny (gene therapy). On the other hand, the RNA interference (RNAi) approach allows for the creation of new experimental models by transient ablation of gene expression by degrading specific mRNA, which can be applied to assess different biological functions and mechanisms. The combination of these technologies contributes to the study of the function and regulation of different metabolism- and obesity-related genes as well as the identification of new pharmacologic targets for nutritional and therapeutic approaches.

Long term transgene expression by hepatocytes transduced with retroviral vectors requires induction of immune tolerance to the transgene

BACKGROUND/AIMS

Gene therapy for inherited liver diseases requires permanent expression of the therapeutic gene. However, in vivo liver transduction with retroviral vectors triggers an immune elimination of transduced hepatocytes. Here we investigated whether immune response could be prevented by treatment with compounds known to induce tolerance in organ transplantation: CTLA4Ig and LF-15-0195.

METHODS

CTLA4Ig was administered either via i.p. injection of the drug or by i.m. injection of recombinant adenoviruses encoding CTLA4Ig. LF-15-0195 was administered i.p. All animals were subjected to partial hepatectomy and received beta-galactosidase retroviral vectors intravenously. Appearance of anti-beta-galactosidase antibodies was monitored and the number of positive hepatocytes was assessed at day 7 and at sacrifice.

RESULTS

No beta-galactosidase antibodies were detected as long as CTLA4Ig was detectable in serum. Short-term treatment with CTLA4Ig induced tolerance in a significant proportion of animals only at high dose (1 mg/kg). Administration of CTLA4Ig adenovectors resulted in prolonged secretion of CTLA4Ig and permanent absence of anti-beta-galactosidase antibodies. LF-15-0915 administration achieved tolerance in some animals.

CONCLUSIONS

In conclusion, manipulation of the immune system at the time of virus delivery using clinically relevant tolerance-inducing protocols is a promising approach to achieve long term expression after retrovirus-mediated gene transfer to the liver.

AAV gene transfer to the retina does not protect retrovirally transduced hepatocytes from the immune response

Gene therapy of inherited hepatic disease relies on sustained expression of the therapeutic transgene. In many instances, such expression will require immune tolerization to the non-self therapeutic transgene product. We previously demonstrated that a cytotoxic immune response eliminated hepatocytes after in vivo transduction using recombinant retroviral vectors. In the present study we investigated whether prior gene transfer to the retina, which is suspected to induce immune tolerance, could alleviate the immune response occurring after retrovirus mediated gene transfer to the liver. Retinal cells were transduced using adeno-associated viral vectors harbouring a beta-galactosidase transgene. Sixty days later, regenerating hepatocytes were transduced after partial hepatectomy using a recombinant retrovirus carrying the transgene. Three weeks later, anti beta-galactosidase antibodies were present in all animals. Elimination of the transduced hepatocytes eventually occurred in all animals by 2 months after liver gene transfer, although sustained beta-galactosidase expression was still present in the retina in 66% of the animals. We conclude that although the retina behaves as an immunoprivileged site, gene expression in the subretinal space is not sufficient to induce immune tolerance to a transgene product expressed in the liver.