Stem cell transplantation following traumatic brain injury (TBI) has been suggested as part of a therapeutic intervention to mitigate the severity of the injury. To date, preclinical studies of cel based therapeutics have focused on stereotactic injection of cells into, or adjacent to regions of injury. However, this delivery approach is problematic due to frequently limited and unpredictable migratory capacity of most of these cells. Coupled with variability in the cells ability to localize to the injury area, multiple injections are commonly performed. The cumulative effect of TBI, together with multiple penetrations/injections into the brain to delivery cells, increases the risk of bleeding/direct tissue injury counterproductive to the benefit the cells may offer. To address this issue, we propose to develop a practical and clinically applicable method to enhance the transplantation efficacy of stem cells following TBI. This approach involves loading stem cells, human neuroprogenitor cells (NPCs), with the ferromagnetic compound MION, combined with externally positioned magnets to 'pull' loaded stem cells towards the site of cortical injury. We propose to also enhance the ability of the cells to migrate through the brai by the use of transient metalloproteinase overexpression. One of the key advantages to our proposed stem cell migration strategy is that the stem cells can be delivered by injection either into the lateral ventricle or intra-arterially and directed towards the injured region. Currently tere are no technologies available to improve the migration, retention, and survival of stem cells transplanted into the central nervous system. Our hypothesis is that MION labeling and magnetic targeting and upregulation of Heat shock protein 70 (Hsp70) in stem cells will enhance their migration and survival into the lesion in an animal model of traumatic brain injury (TBI).
Specific Aim 1 A: To determine whether MION- labeled NPCs transfected with HSP-70 can be localized at the site of lesion in the ipsilateral cortex by injection into the ipsilateral lateral ventricle.
Specific Aim 1 B: To determine whether transplanted MION-labeled NPCs can be localized in the cerebral cortex at the site of lesion with intra-arterial injection of stem cells n TBI animals.
Specific Aim 1 C: To determine whether transplanted MION-labeled NPCs can be localized in the cerebral cortex at the site of lesion with intravenous injection of stem cells in BI animals.
Specific Aim 2) With these proof-of-principle experiments verifying our hypothesis that an applied magnetic field can target the migration of stem cells within the brain, we will use MIONRB-labeled NPCs in a rat model of TBI and determine whether we can localize SPIO- labeled NPCs at the sites of neuropathological changes using either form of injection. Functional outcome following transplantation will be evaluated with the Morris water maze test. Following the injury there will also be a significant increase in the number of activated microglia in the ara of the cortex adjacent to the site of the lesion. Treatment with NPCs will evaluate if the increase in the number of activated microglia is decreased following transplantation and no additional microgliosis occurs due to the procedure. Using magnets (neodymium) on one side of the cortex, the contralateral cortex will serve as the control side. We have already demonstrated that in non-TBI animals, MION-labeled NPCs are localized in the ipsilateral cortex following injection into the ipsilateral lateral ventricle. We will assess the retention of the NPCs at the lesion site over short intervals (hours) after transplantation and over longer intervals (days). In TBI, the brain blood barrier is compromised, thus as a sub aim, we will assess if the magnetic field will enhance the extravasation of stem cells. Under all these conditions, we will augment the survival of the stem cells migrating into the lesion, by their transfection with pro-survival gene, HSP70. The same studies will be carried out without HSP70 transfection. Using these techniques, we will optimize stem cell transplantation so that it will be a more effective targeted therapeutic method.
The incidence of traumatic brain injury (TBI) among the U.S. military veteran population is increasing and will impose a long-term care burden on the VA health care system. It is ever more important to develop new therapeutics that will facilitate the neurorestorative capacity of the central nervous system in TBI. Recent research has proposed using stem cell therapy. The lack of basic knowledge concerning stem cell migration following a transplant remains a bottleneck for attempting to design therapies. We have designed a method by using directed magnetic fields and labeling stem cells with MIONRB to deliver stem cells to cortical regions damaged in TBI. We will test our methods of targeting stem cells in an animal model of TBI. These results could shed further insight into using stem cell therapy as a neurorestorative therapy.
