The use of an adeno-associated viral vector for efficient bicistronic expression of two genes in the central nervous system

Overexpression of the Fibroblast Growth Factor Receptor 1 (FGFR1) in a Model of Spinal Cord Injury in Rats

Spinal cord injury (SCI) is a severe condition that affects many people and results in high health care costs. Therefore, it is essential to find new targets for treatment. The fibroblast growth factor receptor 1 (FGFR1) signalling pathway has a history of being explored for SCI treatment. Several groups have examined the effect of high availability of different FGFR1 ligands at the injury site and reported corticospinal tract (CST) regeneration as well as improved motor functions. In this study, we investigated overexpression of the FGFR1 in rat corticospinal neurons in vivo after injury (unilateral pyramidotomy) and in cerebellar granule neurons (CGNs) in vitro. We show that overexpression of FGFR1 using AAV1 intracortical injections did not increase sprouting of the treated corticospinal tract and did not improve dexterity or walking in a rat model of SCI. Furthermore, we show that overexpression of FGFR1 in vitro resulted in decreased neurite outgrowth compared to control. Thus, our results suggest that the FGFR1 is not a suitable therapeutic target after SCI.

Trans-neuronal transduction of spinal neurons following cortical injection and anterograde axonal transport of a bicistronic AAV1 vector

Adeno-associated viral (AAV) vectors are one of the most promising gene delivery systems to the central nervous system. We now report, that AAV1 can be used to express transgenes trans-neuronally in neurons distant from the injection site. Specifically, intracortical injection of a bicistronic AAV1 vector trans-neuronally transduced spinal neurons as shown by fluorescence microscopy, the presence of AAV genome and AAV transcript in the contralateral spinal cord. Prior pyramidotomy abolished spinal transduction, confirming anterograde axonal transport of AAV1 in the corticospinal tract. These observations demonstrate the potential of bicistronic AAV1 for trans-neuronal expression of therapeutic transgenes in neurological disorders or reporter genes in connectivity studies.

Anti-apoptotic potency of TNFR:Fc gene in ischemia/ reperfusion-induced myocardial cell injury

The aim of the study was to investigate the anti-apoptotic potency of TNFR:Fc gene in ischemia/reperfusion-induced myocardial cell injury and hypoxia/reoxygenation-induced H9c2 rat cardiomyocytes injury. Rats were randomly divided into the following groups (n=8): (1) sham operation group; (2) ischemia-reperfusion (I/R) rats treated with rAAV-EGFP; (3) I/R rats treated with rAAV-TNFR:Fc group. rAAV-EGFP or rAAV-TNFR:Fc was injected intra-myocardial at four sites on the anterior and posterior walls of left ventricle immediately after the construction of I/R-induced AMI model in rats. The effects of TNFR:Fc on apoptosis and cardiacfunction were observed after 72 h of coronary reperfusion. In the in vitro study, apoptosis was analyzed in H9c2 rat cardiomyocytes treated either with nomoxia alone, or hypoxia/reoxygenation in the presence of rAAV-GFP or rAAV-TNFR:Fc. We found that (1) TNFR:Fc gene improved cardiac function (EF, LVESP, LVEDP and dp/dt max) post I/R-induced AMI; (2) TNFR:Fc gene inhibited I/R-induced apoptosis and attenuated the level of TNF-α in serum and cardiac tissue; (3) TNFR:Fc gene prevented apoptosis in hypoxia/reoxygenation-induced H9c2 rat cardiomyocytes associated with inhibition of caspase-3 activation and normalization of ratio of the Bcl-2/Bax. We concluded that TNFR:Fc gene transfection has anti-apoptotic potency in ischemia/reperfusion-induced myocardial cell injury.

Gene delivery strategies to promote spinal cord repair

Gene therapies hold great promise for the treatment of many neurodegenerative disorders and traumatic injuries in the central nervous system. However, development of effective methods to deliver such therapies in a controlled manner to the spinal cord is a necessity for their translation to the clinic. Although essential progress has been made to improve efficiency of transgene delivery and reduce the immunogenicity of genetic vectors, there is still much work to be done to achieve clinical strategies capable of reversing neurodegeneration and mediating tissue regeneration. In particular, strategies to achieve localized, robust expression of therapeutic transgenes by target cell types, at controlled levels over defined time periods, will be necessary to fully regenerate functional spinal cord tissues. This review summarizes the progress over the last decade toward the development of effective gene therapies in the spinal cord, including identification of appropriate target genes, improvements to design of genetic vectors, advances in delivery methods, and strategies for delivery of multiple transgenes with synergistic actions. The potential of biomaterials to mediate gene delivery while simultaneously providing inductive scaffolding to facilitate tissue regeneration is also discussed.