Derivation of injury-responsive dendritic cells for acute brain targeting and therapeutic protein delivery in the stroke-injured rat.

Research with experimental stroke models has identified a wide range of therapeutic proteins that can prevent the brain damage caused by this form of acute neurological injury. Despite this, we do not yet have safe and effective ways to deliver therapeutic proteins to the injured brain, and this remains a major obstacle for clinical translation. Current targeted strategies typically involve invasive neurosurgery, whereas systemic approaches produce the undesirable outcome of non-specific protein delivery to the entire brain, rather than solely to the injury site. As a potential way to address this, we developed a protein delivery system modeled after the endogenous immune cell response to brain injury. Using ex-vivo-engineered dendritic cells (DCs), we find that these cells can transiently home to brain injury in a rat model of stroke with both temporal and spatial selectivity. We present a standardized method to derive injury-responsive DCs from bone marrow and show that injury targeting is dependent on culture conditions that maintain an immature DC phenotype. Further, we find evidence that when loaded with therapeutic cargo, cultured DCs can suppress initial neuron death caused by an ischemic injury. These results demonstrate a non-invasive method to target ischemic brain injury and may ultimately provide a way to selectively deliver therapeutic compounds to the injured brain.

Neurogenesis and alterations of neural stem cells in mouse models of cerebral amyloidosis.

The hippocampus in Alzheimer's disease is burdened with amyloid plaques and is one of the few locations where neurogenesis continues throughout adult life. To evaluate the impact of amyloid-beta deposition on neural stem cells, hippocampal neurogenesis was assessed using bromodeoxyuridine incorporation and doublecortin staining in two amyloid precursor protein (APP) transgenic mouse models. In 5-month-old APP23 mice prior to amyloid deposition, neurogenesis showed no robust difference relative to wild-type control mice, but 25-month-old amyloid-depositing APP23 mice showed significant increases in neurogenesis compared to controls. In contrast, 8-month-old amyloid-depositing APPPS1 mice revealed decreases in neurogenesis compared to controls. To study whether alterations in neurogenesis are the result of amyloid-induced changes at the level of neural stem cells, APPPS1 mice were crossed with mice expressing green fluorescence protein (GFP) under a central nervous system-specific nestin promoter. Eight-month-old nestin-GFP x APPPS1 mice exhibited decreases in quiescent nestin-positive astrocyte-like stem cells, while transient amplifying progenitor cells did not change in number. Strikingly, both astrocyte-like and transient-amplifying progenitor cells revealed an aberrant morphologic reaction toward congophilic amyloid-deposits. A similar reaction toward the amyloid was no longer observed in doublecortin-positive immature neurons. Results provide evidence for a disruption of neural stem cell biology in an amyloidogenic environment and support findings that neurogenesis is differently affected among various transgenic mouse models of Alzheimer's disease.