Subacute intranasal administration of tissue plasminogen activator improves stroke recovery by inducing axonal remodeling in mice

Abstract

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

Targeted tPA overexpression in denervated spinal motor neurons promotes stroke recovery in mice

“…Thus, the RFP labeling in the pyramidal neurons represents that these neurons physically and functionally connect to the peripheral tissue where the PRV tracer was injected. Consistent with our previous data, 6,14 RFP labeling was found in the layer V pyramidal neurons of both rostral and caudal forelimb motor areas, primarily in the ipsilesional cortex (Figure 6(a) to (c)), while scattered RFP-positive neurons were detected in the contralesional hemisphere (e–g) in stroke mice treated with saline (a and e), AAV-RFP (b and f), or AAV-tPA (c and g). The data showed that AAV-tPA treatment significantly increased the number of RFP-positive neurons in both ipsilesional (d, p < 0.01 vs. saline, p < 0.001 vs. AAV-RFP) and contralesional (h, p < 0.05 vs. saline, p < 0.01 vs. AAV-RFP) cortices.…”

Protease-independent action of tissue plasminogen activator in brain plasticity and neurological recovery after ischemic stroke

“…In recent years, the long-term influence of tPA on CNS repair and plasticity after injury has begun to be elucidated. For example, tPA stimulates axonal sprouting at chronic stages after ischemic stroke (14), traumatic brain injury (15), and spinal cord injury (16,17), and these salutary effects correlate with improvements in neurological functions. However, whether tPA plays an indispensable role in poststroke functional recovery and the underlying mechanisms warrant further investigation.…”

Sequential Transcriptome Changes in the Penumbra after Ischemic Stroke

“…Several clinical studies reported that fiber tract integrity was significantly related to motor impairment in patients with stroke [5,6]. Moreover, a significant body of evidence supports the importance of axonal reorganization in recovery after stroke [7][8][9][10][11]. The interplay between growth factors and microvascular cells prompts axonal sprouting and facilitates functional recovery [12].…”