Stroke is an age-related disease. Recovery after stroke is associated with axonal sprouting in cortex adjacent to the infarct. The molecular program that induces a mature cortical neuron to sprout a new connection after stroke is not known. We selectively isolated neurons that sprout a new connection in cortex after stroke and compared their whole-genome expression profile to that of adjacent, non-sprouting neurons. This ‘sprouting transcriptome’ identified a neuronal growth program that consists of growth factor, cell adhesion, axonal guidance and cytoskeletal modifying molecules that differed by age and time point. Gain and loss of function in three distinct functional classes showed new roles for these proteins in epigenetic regulation of axonal sprouting, growth factor–dependent survival of neurons and, in the aged mouse, paradoxical upregulation of myelin and ephrin receptors in sprouting neurons. This neuronal growth program may provide new therapeutic targets and suggest mechanisms for age-related differences in functional recovery.

Background and Purpose-Stroke produces diaschisis in adjacent and connected regions. The sequential changes in diaschisis over time and the relationship of regions of diaschisis to functional cortical areas and regions of poststroke neuroplasticity have not been determined. Methods-Small cortical strokes were produced in the barrel cortex of rats. Relative glucose metabolism was determined in vivo over time with

Cell-derived microvesicles (MVs), recognized as important components of cell-cell communication, contain mRNAs, miRNAs, proteins and lipids and transfer their bioactive contents from parent cells to cells of other origins. We have studied the effect that MVs released from embryonic stem cells (ESMVs) have on retinal progenitor Müller cells. Cultured human Müller cells were exposed to mouse ESMVs every 48 hours for a total of 9 treatments. Morphological changes were observed by light microscopy in the treated cells, which grew as individual heterogeneous cells, compared to the uniform, spindle-like adherent cellular sheets of untreated cells. ESMVs transferred to Müller cells embryonic stem cell (ESC) mRNAs involved in the maintenance of pluripotency, including Oct4 and Sox2, and the miRNAs of the 290 cluster, important regulators of the ESC-specific cell cycle. Moreover, ESMV exposure induced up-regulation of the basal levels of endogenous human Oct4 mRNA in Müller cells. mRNA and miRNA microarrays of ESMV-treated vs. untreated Müller cells revealed the up-regulation of genes and miRNAs involved in the induction of pluripotency, cellular proliferation, early ocular genes and genes important for retinal protection and remodeling, as well as the down-regulation of inhibitory and scar-related genes and miRNAs involved in differentiation and cell cycle arrest. To further characterize the heterogeneous cell population of ESMV-treated Müller cells, their expression of retinal cell markers was compared to that in untreated control cells by immunocytochemistry. Markers for amacrine, ganglion and rod photoreceptors were present in treated but not in control Müller cells. Together, our findings indicate that ESMs induce de-differentiation and pluripotency in their target Müller cells, which may turn on an early retinogenic program of differentiation.

Stroke produces a region of complete cell death and areas of partial damage, injury, and gliosis. The spatial relationship of these regions of damage to the infarct core and within spared neuronal circuits has not been identified. A model of cortical stroke was developed within functional subsets of the somatosensory cortex. Infarct size, regions of apoptosis, oxidative DNA damage, heat shock protein induction, and subtypes of reactive gliosis were precisely mapped with the somatosensory body map, quantified, and interrelated. Three tissue microenvironments were recognized: zones of partial ischemic damage, heat shock protein induction, and distributed gliosis. These three zones involved progressively more distant cortical regions, each larger than the infarct core. The zone of partial ischemic damage represents an overlap region of apoptotic cell death, oxidative DNA damage, loss of synaptic connections, and local reactive gliosis. The zone of distributed gliosis occupies distinct functional areas of the somatosensory cortex. The tissue reorganization induced by stroke is much larger than the stroke site itself. Adjacent tissue microenvironments are sites of distinct reactive cellular signaling and may serve as a link between the processes of acute cell death and delayed neuronal plasticity after focal stroke.