Development of magnetic nanoparticle (MNP) based delivery system for gene transfer to multipotent neural precursor cells (NPCs)

The adult brain and spinal cord (together called the central nervous system or CNS) have a poor capacity to repair after injury. This leads to a poor prognosis for patients with severe spinal cord injuries and devastating consequences for their quality of life. Neural precursor cells or NPCs, have an enormous potential for increasing repair at injury sites in the CNS. As NPCs have the ability to migrate into areas of damage in the nervous system, an important application for these cells is as cellular vehicles to transport therapeutic genes (and other molecules) to the sites of injury in the CNS. Currently, the most widely used method of delivering genes to NPCs is to use modified viruses carrying genes, which infect cells and then transfer genes into the infected cells. However, this method has a number of drawbacks and is associated with major safety issues. New delivery systems using magnetic nanoparticles (MNPs) could be very useful in this regard, and have many benefits for delivery of genes. MNPs can be coated with genes and are taken up into cells. As they are magnetic,cells carrying MNPs can be targeted to particular areas of damage in the body by placing external magnetic fields over injury sites.Preliminary clinical trials shown that injecting MNPs into the body appears to be safe and do not seem to have toxic or carcinogenic effects. This study will establish if it is possible to use MNPs to deliver therapeutic genes to NPCs (that will then be used for transplantation into the spinal cord). We will assess methods to optimise the uptake of MNPs coated with genes into NPCs and establish if this procedure has any adverse effects on the survival and development of the cells.

Several studies demonstrate that multipotent neural precursor cells (NPCs) have key properties for delivery of therapeutic genes to the damaged CNS. NPCs can migrate long distances in the CNS especially to sites of nervous system pathology (a phenomenon termed 'pathotropism'). This makes them valuable 'cellular vehicles' for gene delivery to areas of neural trauma. Most studies use conventional, virus based delivery systems for gene transfer to NPCs. Although efficient, these have a number of drawbacks including safety issues and production limitations. This highlights a major need for the development of alternative, nonviral approaches for gene transfer to neural cells, for both basic research and therapeutic applications. Novel delivery systems employing MNPs could have important benefits in this context including (i) Safety as evidenced by a range of Phase I/II clinical trials (2) Flexibility as MNPs can be 'functionalised' with DNA, siRNA or anti-sense oligonucleotides (3) Long term trackability in vivo using MRI and fluorescence imaging (4) Targetability of MNP labelled cells to focal sites of pathology (including the spinal cord) using external magnetic field gradients over target sites. Our pilot studies show avid MNP uptake by NPCs with limited toxic effects. Furthermore, MNPs could be used reproducibly to deliver a reporter gene to NPCs. Taken together, these findings highlight a potentially major application of MNPs for gene transfer to NPCs.This study will use well characterised models to address a range of key issues that will be critical to MNP mediated gene transfer to NPCs (derived for transplanation). These include an evaluation of the safety of MNPs for NPC labelling, the ability of MNPs to deliver a therapeutic gene to NPCs and the ability of transfected NPCs to deliver a therapeutic protein to the spinal cord. Additionally, we will test if a novel, oscillating magnetic array system can be used to enhance MNP transfection efficacy.