shRNA Used for Application in Gene Therapy

shRNA (full name is small hairpin RNA or short hairpin RNA) is a sequence of RNA with a tight hairpin turn that can be used to silence target gene expression by inducing RNA interference(RNAi ). shRNA is created in the cell from a DNA construct encoding a sequence of single stranded RNA and its complement, separated by a stuffer fragment, allowing the RNA molecule to fold back on itself, creating a dsRNA molecule with a hairpin loop.

shRNA has the ability to provide specific, long-lasting, gene silencing. Scientists ,therefore, have been considering about using it for gene therapy applications. Some shRNA-based therapies have already been put into trail now.

shRNA has been considered an advantageous mediator of RNAi because it has a relatively low rate of degradation and turnover. The disadvantage of using it lies in that its expression in cells needs the assistance of plasmids, viral or bacterial vectors, which may cause some safety concerns.

There are still many challenges in using shRNA expression. In the past, viral based gene therapy approaches have proved dangerous in clinical trials. Besides, If the shRNA is expressed at levels that are too high the cell might not be able to correctly process the endogenous RNA, which could cause significant problems. It is possible that the patient will generate an immune response against the therapy. And it is also probable that the shRNA could silence other unintended genes.

About RNA interference

RNAi is the best way to effectively knock down gene expression and study protein function in a wide range of cell types and it is a powerful genetic tool for conducting functional studies. This technique is usually mediated by the use of siRNAs or shRNAs. Previous studies have showed that vector-based shRNA expression strategy is capable of inducing RNAi in viable cells. And results have showed that using vectors to perform RNAi experiments can expand experimental possibilities beyond the traditional siRNA approach.

About Creative Biogene
Creative Biogene is a US based biotech product and service supplier for academic and governmental research institutes, pharmaceutical and biotechnology industry. The company provides a series of high quality shRNAs, which could be used for silencing target gene expression via RNA interference.


http://www.creative-biogene.com/Product/shRNA 

General Introduction of AAV, rAAV and rAAV Vector

Adeno-associated virus (AAV) is inherently replication-deficient virus that belongs to the family Parvoviridae. It is single-stranded DNA virus with very simple structure. Adeno-associated viral which has been artificially recombined called recombinant adeno-associated viral (rAAV). And recombinant adeno-associated viral used in scientific research is unusually called rAAV vector.

The rAAV vectors consist of a simple capsid with a single-stranded DNA genome and no viral coding sequences. Its limited ability to transduce dendritic cells results in its limited immune responses.They are nonimmunogenic and can transduce both dividing and nondividing cells. Different rAAV serotypes may transduce diverse cell types. All those features make rAAV vectors excellent tools to study the function of neuropeptides in local brain areas. And they can also be used to locally or systemically enhance or silence gene expression.

In recent years rAAV vectors have become increasingly valuable for in vivo studies in animals and are also currently being tested in human clinical trials. rAAV vector has proven to be very useful vector for efficient and long-term gene transfer in a variety of tissues including lung, muscle, brain, spinal cord, retina and liver, thus the use of rAAV vectors holds great promise for human gene therapy. Its advantages observed in numerous disease paradigms, such as, the broad host range, low level of immune response, and longevity of gene expression has enabled the initiation of a number of clinical trials.

In the past, rAAV was most often generated through the co-transfection of rAAV vector plasmid and wild-type AAV helper plasmid into Ad-infected cells. Now Ad-infected cells is no longer necessary due to the improvements in AAV helper design as well as construction of non-infectious mini-Ad plasmid helper, which has improved the yield of rAAV per transfected cell in a crude lysate. Scalable methods of rAAV production have been developed too, which means that rAAV production will no longer rely on DNA transfection. More scale-up production of rAAV has become possible in some laboratories.