Stimulation of hippocampal neurogenesis by transcranial focused ultrasound and microbubbles in adult mice.

Transcranial focused ultrasound (FUS) and microbubble contrast agent, applied at parameters known to transiently increase blood-brain barrier permeability, were tested for the potential to stimulate hippocampal neurogenesis. In adult mice, FUS treatment significantly increased the number of proliferating cells and newborn neurons in the dentate gyrus of the dorsal hippocampus. This provides evidence that FUS with microbubbles can stimulate hippocampal neurogenesis, a process involved in learning and memory and affected in neurological disorders, such as Alzheimer's disease.

Amyloid-ß plaque reduction, endogenous antibody delivery and glial activation by brain-targeted, transcranial focused ultrasound.

Noninvasive, targeted drug delivery to the brain can be achieved using transcranial focused ultrasound (FUS), which transiently increases the permeability of the blood-brain barrier (BBB) for localized delivery of therapeutics from the blood to the brain. Previously, we have demonstrated that FUS can deliver intravenously-administered antibodies to the brain of a mouse model of Alzheimer's disease (AD) and rapidly reduce plaques composed of amyloid-ß peptides (Aß). Here, we investigated two potential effects of transcranial FUS itself that could contribute to a reduction of plaque pathology, namely the delivery of endogenous antibodies to the brain and the activation of glial cells. We demonstrate that transcranial FUS application leads to a significant reduction in plaque burden four days after a single treatment in the TgCRND8 mouse model of AD and that endogenous antibodies are found bound to Aß plaques. Immunohistochemical and western blot analyses showed an increase in endogenous immunoglobulins within the FUS-targeted cortex. Subsequently, microglia and astrocytes in FUS-treated cortical regions show signs of activation through increases in protein expression and changes in glial size, without changes in glial cell numbers. Enhanced activation of glia correlated with increased internalization of Aß in microglia and astrocytes. Together these data demonstrate that FUS improved the bioavailability of endogenous antibodies and led to a temporal activation of glial cells, providing evidence towards antibody- and glia-dependent mechanisms of FUS-mediated plaque reduction.

Targeted delivery of self-complementary adeno-associated virus serotype 9 to the brain, using magnetic resonance imaging-guided focused ultrasound.

Noninvasive drug delivery to the brain remains a major challenge for the treatment of neurological disorders. Transcranial focused ultrasound combined with lipid-coated gas microspheres injected into the bloodstream has been shown to increase the permeability of the blood-brain barrier locally and transiently. Coupled with magnetic resonance imaging, ultrasound can be guided to allow therapeutics administered in the blood to reach brain regions of interest. Using this approach, we perform gene transfer from the blood to specific regions of the mouse brain. Focused ultrasound was targeted to the right hemisphere, at multiple foci, or restricted to one focal point of the hippocampus or the striatum. Doses from 5 × 10(8) to 1.25 × 10(10) vector genomes per gram (VG/g) of self-complementary adeno-associated virus serotype 9 carrying the green fluorescent protein were injected into the tail vein. A dose of 2.5 × 10(9) VG/g was optimal to express the transgene, 12 days later, in neurons, astrocytes, and oligodendrocytes in brain regions targeted with ultrasound, while minimizing the infection of peripheral organs. In the hippocampus and striatum, predominantly neurons and astrocytes were infected, respectively. Transcranial focused ultrasound applications could fulfill a long-term goal of gene therapy: delivering vectors to diseased brain areas directly from the circulation, in a noninvasive manner.

Targeted delivery of neural stem cells to the brain using MRI-guided focused ultrasound to disrupt the blood-brain barrier.

Stem cell therapy is a promising strategy to treat neurodegenerative diseases, traumatic brain injury, and stroke. For stem cells to progress towards clinical use, the risks associated with invasive intracranial surgery used to deliver the cells to the brain, needs to be reduced. Here, we show that MRI-guided focused ultrasound (MRIgFUS) is a novel method for non-invasive delivery of stem cells from the blood to the brain by opening the blood brain barrier (BBB) in specific brain regions. We used MRI guidance to target the ultrasound beam thereby delivering the iron-labeled, green fluorescent protein (GFP)-expressing neural stem cells specifically to the striatum and the hippocampus of the rat brain. Detection of cellular iron using MRI established that the cells crossed the BBB to enter the brain. After sacrifice, 24 hours later, immunohistochemical analysis confirmed the presence of GFP-positive cells in the targeted brain regions. We determined that the neural stem cells expressed common stem cell markers (nestin and polysialic acid) suggesting they survived after transplantation with MRIgFUS. Furthermore, delivered stem cells expressed doublecortin in vivo indicating the stem cells were capable of differentiating into neurons. Together, we demonstrate that transient opening of the BBB with MRIgFUS is sufficient for transplantation of stem cells from the blood to targeted brain structures. These results suggest that MRIgFUS may be an effective alternative to invasive intracranial surgery for stem cell transplantation.

Antibodies targeted to the brain with image-guided focused ultrasound reduces amyloid-beta plaque load in the TgCRND8 mouse model of Alzheimer's disease.

Immunotherapy for Alzheimer's disease (AD) relies on antibodies directed against toxic amyloid-beta peptide (Abeta), which circulate in the bloodstream and remove Abeta from the brain. In mouse models of AD, the administration of anti-Abeta antibodies directly into the brain, in comparison to the bloodstream, was shown to be more efficient at reducing Abeta plaque pathology. Therefore, delivering anti-Abeta antibodies to the brain of AD patients may also improve treatment efficiency. Transcranial focused ultrasound (FUS) is known to transiently-enhance the permeability of the blood-brain barrier (BBB), allowing intravenously administered therapeutics to enter the brain. Our goal was to establish that anti-Abeta antibodies delivered to the brain using magnetic resonance imaging-guided FUS (MRIgFUS) can reduce plaque pathology. To test this, TgCRND8 mice received intravenous injections of MRI and FUS contrast agents, as well as anti-Abeta antibody, BAM-10. MRIgFUS was then applied transcranially. Within minutes, the MRI contrast agent entered the brain, and BAM-10 was later found bound to Abeta plaques in targeted cortical areas. Four days post-treatment, Abeta pathology was significantly reduced in TgCRND8 mice. In conclusion, this is the first report to demonstrate that MRIgFUS delivery of anti-Abeta antibodies provides the combined advantages of using a low dose of antibody and rapidly reducing plaque pathology.