Abstract TMP113: Conditional Expression Of Mir-20a-3p In Neurons Versus Astrocytes And Its Impact On Acute Stroke Outcomes

Abstract

Introduction: MiR-20a-3p was found to be upregulated in the brains of adult female rats, who typically sustain smaller infarcts, compared to that of middle-aged rats, who typically sustain larger infarcts. In fact, qRT-PCR analysis shows that miR-20a-3p is profoundly upregulated (>240,000-fold elevation) in adult astrocytes post-stroke, while ischemic neurons do not exhibit this upregulation. Intravenous injections of miR-20a-3p mimic, given 4h after stroke, reduced infarct size and improved sensory motor function in middle-aged rats, and surprisingly exogenous miR-20a-3p was preferentially taken up by neurons . To better understand the cellular target of this miRNA, we compared the efficacy of conditional expression of miR-20a-3p in neurons versus astrocytes in improving acute stroke outcomes. Methods: Two viral vectors to conditionally express miR-20a-3p in neurons (rAAV5-TetOn-NSE-miR-20a-3p-mCherry) and astrocytes (rAAV5-TetOn-GFAP-miR-20a-3p-mCherry) were injected into the striatum of middle-aged female rats.Control subjects were given an identical vector minus miR-20a-3p. After 6 weeks, the rats were subjected to middle cerebral artery occlusion, and the virus was activated by i.p. doxycycline 4h post-stroke. Behavioral assessments were performed at 2d and 5d. Animals were terminated at 5d, and infarct size was assessed. Results: Astrocytic miR-20a-3p improved survival compared to control (p=0.0372), and neuronal miR-20a-3p showed a trend for improved survival (p=0.0805). Neuronal miR-20a-3p reduced latency on the adhesive removal task at 2d and 5d, while astrocytic miR-20a-3p demonstrated modest improvement only at 5d. Moreover, neuronal miR-20a-3p significantly reduced infarct size relative to control (p=0.0087), while astrocytic miR-20a-3p did not improve infarct size(p=0.1117). Conclusions: Both rAAVs resulted in improvement in stroke outcomes; however, the results from the neuronal vector were much more robust. The fact that astrocytes upregulate miR-20a-3p after stroke yet neurons more efficiently use the miRNA to improve stroke outcome suggest that this miRNA may be transferred from astrocytes to neurons to confer neuroprotection. Supported by RFAG042189 to FS and 1F31NS118970-01A to TEB.