High Toxicity, Low Receptor Density, and Low Integration Frequency Severely Impede the Use of Adenovirus Vectors for Production of Transgenic Mice

Albumin-Based Nanocarriers for the Simultaneous Delivery of Antioxidant Gene and Phytochemical to Combat Oxidative Stress

Human serum albumin (HSA) nanoparticles are promising biocompatible, nontoxic, and non-immunogenic platforms for biomedical applications such as bioimaging and drug and gene delivery. The development of nonviral gene delivery vectors is a great challenge for efficient and safe gene therapy. Sulforaphane (SF) can stimulate the expression of antioxidant genes via activation of a nuclear transcription factor, the erythroid-2 related factor 2 (Nrf-2). Here, we use polyethyleneimine (PEI)-stabilized HSA nanoparticles to stimulate endogenous antioxidant defense mechanisms in lung epithelial cells L-132 through the combinatorial effect of SF drug and antioxidant superoxide dismutase 1 gene (pSOD1 plasmid) delivered by HSA-PEI-SF-pSOD1 nanocomposites (NCs). The developed NCs demonstrated high biocompatibility (L-132 viability, >95%, MTT assay) and high antioxidant activity because of efficient entry of the SOD1 gene and SF-loaded NCs at a very low (3 μg) dose in L-132 cells. A high transfection efficiency of L-132 cells (∼66%, fluorescent microscopy) was obtained with the GFP-tagged transgene SOD1-GFP. We speculate that the antioxidant activity of HSA-PEI-SF-pSOD1 NCs in L-132 cells is due to the initial release of SF followed by subsequent SOD1 gene expression after three to four days of incubation. Hence, the developed HSA-based NCs can be efficient biocompatible nanocarriers for safe and effective drug and gene delivery applications to treat diseases with high oxidative stress due to combinatorial SF and SOD1 gene mechanisms.

Ligand-Modified Human Serum Albumin Nanoparticles for Enhanced Gene Delivery

The development of nonviral gene delivery systems is a great challenge to enable safe gene therapy. In this study, ligand-modified nanoparticles based on human serum albumin (HSA) were developed and optimized for an efficient gene therapy. Different glutaraldehyde cross-linking degrees were investigated to optimize the HSA nanoparticles for gene delivery. The peptide sequence arginine-glycine-aspartate (RGD) and the HIV-1 transactivator of transduction sequence (Tat) are well-known as promising targeting ligands. Plasmid DNA loaded HSA nanoparticles were covalently modified on their surface with these different ligands. The transfection potential of the obtained plasmid DNA loaded RGD- and Tat-modified nanoparticles was investigated in vitro, and optimal incubation conditions for these preparations were studied. It turned out that Tat-modified HSA nanoparticles with the lowest cross-linking degree of 20% showed the highest transfection potential. Taken together, ligand-functionalized HSA nanoparticles represent promising tools for efficient and safe gene therapy.

Genomic integration of adenoviral gene transfer vectors following transduction of fertilized mouse oocytes

Adenoviral vectors (AdV) are popular tools to deliver foreign genes into a wide range of cells. They have also been used in clinical gene therapy trials. Studies on AdV-mediated gene transfer to mammalian oocytes and transmission through the germ line have been reported controversially. In the present study we investigated whether AdV sequences integrate into the mouse genome by microinjecting AdV into the perivitelline space of fertilized oocytes. We applied a newly developed PCR technique (HiLo-PCR) for identification of chromosomal junctions next to the integrated AdV. We demonstrate that mouse oocytes can be transduced by different recombinant adenoviral vectors (first generation and gutless). In one transgenic mouse line using the first generation adenoviral vector, the genome has integrated into a highly repetitive cluster located on the Y chromosome. While the transgene (GFP) was expressed in early embryos, no expression was detected in adult transgenic mice. The use of gutless AdV resulted in expression of the transgene, albeit the vector was not transmitted to progeny. These results indicate that under optimized conditions fertilized mouse oocytes are transduced by AdV and give rise to transgenic founder animals. Therefore, adequate precautions should be taken in gene therapy protocols of reproductive patients since transduction of oocytes or early embryos and subsequent chromosomal integration cannot be ruled out entirely.

Kinetics of pronuclear development and the effects of vector type and timing of injection on the efficiency of gene transfer into rhesus macaque embryos

A series of experiments was performed to determine the dynamics of pronuclear development as well as the efficiency of either adenovirus-associated (AAV) or lentivirus-derived vectors to introduce a green fluorescent protein (GFP) reporter gene into rhesus macaque (Macaca mulatta) embryos. Assessment of pronuclear development at various times after fertilization revealed that the appearance of pronuclei was determined by the presence of the first and the timing of the second polar body. The dynamics of pronuclear formation was a significant determinant of whether an oocyte reached the blastocyst stage, however, when the percentage of blastocysts were based on the number of zygotes, the timing of the appearance of polar bodies did not appear to have any effect on subsequent development. Injection of different AAV-derived vectors showed that the serotype of the vector did not affect development or the proportion of transgenic embryos. Moreover, all putative transgenic embryos proved to be expression mosaics. Injection of embryos with lentiviral vectors showed that timing of injection (before or after fertilization) had no effect on subsequent transgene expression, but that the type of reporter gene determined post-injection development and rate of transgenesis. The transfer of embryos following injection of a lentiviral vector into three recipients resulted in one pregnancy which was lost during the second trimester. Analysis of fetal tissues showed ubiquitous presence of the transgene and GFP expression in all tissues examined. These results show that lentivirus-derived vectors can efficiently transform rhesus embryos and are suitable for the generation of transgenic rhesus monkeys.

Technologies for the study of epididymal-specific genes

Sperm maturation occurs during transit through the epididymis. Interactions between the epididymal epithelium and the sperm are crucial for the maturation process. Analyses of existing male-infertile mouse lines have begun to enumerate some of the genes involved. Recent advances in transgenic technologies to generate temporally and spatially restricted targeted gene disruptions show promise for progress in understanding sperm maturation. Gene silencing agents, such as RNAi, to manipulate gene expression may prove useful for the analysis of epididymal genes involved in the maturation process.