2008 EN.pdf

In addition to thrombolysis, tissue plasminogen activator (tPA) can evoke neurorestorative processes. We<br>therefore investigated the therapeutic effect of subacute intranasal administration of tPA post stroke on neurological<br>recovery and on corticospinal innervation in mice. A transgenic mouse line, in which the pyramidal<br>neurons and corticospinal tract (CST) axons are specifically labeled by yellow fluorescent protein (YFP) was<br>employed. Adult CST-YFP mice were subjected to right unilateral middle cerebral artery occlusion (MCAo), and<br>were randomly divided into groups treated with saline or tPA intranasally in the subacute phase. Pseudorabies<br>virus (PRV)-614-monomeric red fluorescent protein (RFP) was injected into the left forelimb. The cervical spinal<br>cord and brain were processed for fluorescent microscopy to detect YFP and RFP labeling. Primary embryonic<br>neurons were cultured with tPA at different concentrations. Neurite length and branch numbers were then<br>measured. In vivo, subacute tPA treatment significantly enhanced functional recovery (p < 0.05), and increased<br>CST density in the denervated gray matter, and in the numbers of PRV-labeled neurons in bilateral cortices. The<br>behavioral performance was significantly correlated with axonal density in the denervated spinal cord. In vitro,<br>both neurite length and branch numbers significantly increased with concentration of tPA (p < 0.05). Our<br>results demonstrate that tPA dose-dependently increases neurite outgrowth and branching of cultured cortical<br>neurons. Subacute intranasal administration of tPA may provide enhance neurological recovery after stroke by<br>promoting CST axonal remodeling.