MicroRNA-regulated viral vectors for gene therapy

Safe and effective gene therapy approaches require targeted tissue-specific transfer of a therapeutic transgene.Besides traditional approaches, such as transcriptional and transductional targeting, micro RNA-dependent posttranscriptional suppression of transgene expression has been emerging as powerful new technology to increase the specificity of vector-mediated transgene expression. Micro RNAs are small non-coding RNAs and often expressed in a tissue-, lineage-, activation- or differentiation-specific pattern. They typically regulate gene expression by binding to imperfectly complementary sequences in the 3' untranslated region(UTR) of the m RNA. To control exogenous transgene expression, tandem repeats of artificial micro RNA target sites are usually incorporated into the 3' UTR of the transgene expression cassette, leading to subsequent degradation of transgene m RNA in cel s expressing the corresponding micro RNA. This targeting strategy, first shown for lentiviral vectors in antigen presenting cells, has now been used for tissue-specific expression of vector-encoded therapeutic transgenes, to reduce immune response against the transgene, to control virus tropism for oncolytic virotherapy, to increase safety of live attenuated virus vaccines and to identify and select cell subsets for pluripotent stem cell therapies, respectively. This review provides an introduction into the technical mechanism underlying micro RNA-regulation, highlights new developments in this field and gives an overview of applications of micro RNA-regulated viral vectors for cardiac, suicide gene cancer and hematopoietic stem cell therapy, as well as for treatment of neurological and eye diseases.

A RGD-Containing Oligopeptide (K)_(16)GRGBSPC: A Novel Vector for Integrin-Mediated Targeted Gene Belivery

A 23 amino acid, bifunctional integrin-targeted synthetic oligopeptide was evaluated for ex vivo gene delivery to rabbit bone marrow stromal cells （BMSCs）. Synthesis of the peptide （K）16GRGDSPC was performed on a solid-phase batch peptide synthesizer. BMSCs were transfected with plasmid DNA coding for luciferase by （K）j6GRGDSPC and the transfection efficiency was assayed. The influences of chloroquine and polyethyleneimine on the transfection efficiency were also examined. The target specificity of （K）16GRGDSPC to mediate exogenous gene into BMSCs was analyzed using cell attachment test and gene delivery inhibition test. The results showed that the transfection efficiency of the oligopeptide vector was lower than that of Lipofectamine. But in the presence of endosomal buffer chloroquine or endosomal disrupting agent polyethyleneimine, the transfection efficiency of the vector was greatly enhanced. In addition, RGD-containing peptides inhibited BMSCs＇ attachment to the 96-well plates pretreated with fibronectin or vitronecfin and significantly decreased the transfection efficiency of the oligopeptide vector. These studies demonstrated that oligopeptide （K）16GRGDSPC was an ideal novel targeted non-viral gene delivery vector, which was easy to be synthesized, high efficient and low cytotoxicity. The vector could effectively deliver exogenous gene into rat BMSCs.

Non-viral liposome-mediated transfer of brain-derived neurotrophic factor across the blood-brain barrier

Brain-derived neurotrophic factor（BDNF） plays an important role in the repair of central nervous system injury,but cannot directly traverse the blood-brain barrier.Liposomes are a new type of non-viral vector,able to carry macromolecules across the blood-brain barrier and into the brain.Here,we investigate whether BDNF could be transported across the blood-brain barrier by tail-vein injection of liposomes conjugated to transferrin（Tf） and polyethylene glycol（PEG）,and carrying BDNF modified with cytomegalovirus promoter（pC MV） or glial fibrillary acidic protein promoter（p GFAP）（Tf-p CMV-BDNF-PEG and Tf-p GFAP-BDNF-PEG,respectively）.Both liposomes were able to traverse the blood-brain barrier,and BDNF was mainly expressed in the cerebral cortex.BDNF expression in the cerebral cortex was higher in the Tf-p GFAP-BDNF-PEG group than in the Tf-p CMV-BDNF-PEG group.This study demonstrates the successful construction of a non-virus targeted liposome,Tf-p GFAP-BDNF-PEG,which crosses the blood-brain barrier and is distributed in the cerebral cortex.Our work provides an experimental basis for BDNF-related targeted drug delivery in the brain.

Passive tracking and size estimation of volume target based on acoustic vector intensity

The special sections of volume target are observed with acoustic vector intensity according to the difference among their radiated-noise characteristics, then three sections are tracked with Kalman filtering, and target size is estimated. Simulation results indicate that in ideal condition three sections of a ship can be tracked and ship's size can be estimated even though one of three sections can not be observed.