**5.3 miRNA biomarkers in stroke**

The multi-targeting potential of miRNAs places them in a powerful position in the diagnosis and prognosis of heterogeneous conditions such as stroke, where early diagnosis has significant implications for prognosis. A number of miRNAs have been shown to demonstrate diagnostic and prognostic value in acute stroke, and a recent systemic review and bioinformatic analysis has highlighted and identified the most promising candidates [147]. miR-16 has been identified as significantly upregulated in the plasma of acute ischemic stroke (AIS) patients, and upregulation of miR-16 is associated with poorer prognosis (mRS 3–6)[148, 149]. Independent studies have identified the downregulation of miR-126 in plasma from AIS patients as a biomarker of disease severity. Circulating levels of miR-126 negatively correlated with pro-inflammatory cytokine levels and National Institute of Health Stroke Scale (NIHSS) scores [150–152]. Similarly, downregulation of circulating miR-355 has also been reported as having high sensitivity as a biomarker of acute ischaemic stroke and to correlate negatively with NIHSS scores in AIS patients [153].

Upregulation of miR-130a has been reported as a potential biomarker in the diagnosis of brain oedema and prognosis in haemorrhagic stroke, positively correlating with NIHSS and mRS scores [154]. Moreover, antagonism of miR-130a expression in *in vivo* and *in vitro* models of ischaemia demonstrated attenuation of brain oedema and reduced blood-brain barrier permeability.
