MicroRNA Let-7i Is a Promising Serum Biomarker for Post-stroke Cognitive Impairment and Alleviated OGD-Induced Cell Damage in vitro by Regulating Bcl-2

Three major problems with this research:

1. It is in vitro 

2. It is only biomarkers and prediction, NOT RECOVERY

3. No statement on how this knowledge can be used for recovery.

 

MicroRNA Let-7i Is a Promising Serum Biomarker for Post-stroke Cognitive Impairment and Alleviated OGD-Induced Cell Damage in vitro by Regulating Bcl-2

Zhan-Qiang Wang^1,2, Kuo Li^1,3, Jie Huang², Tian-Tian Huo¹ and Pei-Yuan Lv^1*

• ¹Department of Neurology, Hebei General Hospital, Shijiazhuang, China
• ²Department of Neurology, Cangzhou People’s Hospital, Cangzhou, China
• ³Department of Neurology, Cangzhou Central Hospital, Cangzhou, China

Background: The mechanism of post-stroke cognitive impairment (PSCI) has not been explained. We aimed to investigate whether miR-let-7i participates in the PSCI and illuminates its underlying role in oxygen–glucose deprivation (OGD)-induced cell apoptosis.

Methods: Blood samples from 36 subjects with PSCI and 38 with post-stroke cognitive normality (Non-PSCI) were collected to evaluate the differential expression of miR-let-7 family members, using qRT-PCT analysis. Spearman correlation was performed to estimate the correlation between the miR-1et-7i level and Montreal Cognitive Assessment (MoCA) score. Treatment of SH-SY5Y cells with OGD was used to induce cell apoptosis in vitro. Effects of miR-let-7i on OGD-induced cell apoptosis was estimated after transfection. The target gene of miR-let-7i was analyzed by dual luciferase reporter gene assay.

Results: The expression of miR-let-7i was up-regulated in PSCI patients compared with Non-PSCI (p < 0.001) and negatively correlated with MoCA score (r = −0.643, p < 0.001). When exposed to OGD, SH-SY5Y cells showed significant apoptosis accompanied by miR-let-7i up-regulation. In OGD-treated cells, miR-let-7i up-regulation was accompanied by cell apoptosis, while down-regulation showed the opposite effect. Luciferase reporter assay showed that Bcl-2 was a target gene of miR-let-7i. Western blot showed that miR-let-7i up-regulation promoted Bcl-2 expression, while qRT-PCR showed that miR-let-7i had no effect on Bcl-2 expression.

Conclusion: miR-let-7i was overexpressed in PSCI patients and it could be used as a diagnostic biomarker for PSCI. We illuminated the potential mechanism that miR-let-7i alleviated OGD-induced cell damage by targeting Bcl-2 at the post-transcriptional level.

Introduction

Stroke is a major cause of cognitive impairment and dementia and has been reported to increase the risk of cognitive impairment at least five to eight times (Merino, 2002; Srikanth et al., 2003; Qu et al., 2015). At present, the prevalence of post-stroke cognitive impairment (PSCI) is increasing because of the aging population and a rise in the number of stroke survivors (Jacquin et al., 2014). The prevalence of PSCI in various countries was varied from 17% to 92%, and it has also reached 80.97% in China (Pasi et al., 2012; Qu et al., 2015). PSCI occur immediately after a stroke or after a certain period, but it is often overlooked at onset (Chi et al., 2019). Consequently, the timely diagnosis and prevention of PSCI are critical at present. However, there is a lack of biomarkers that could accurately predict PSCI. Previously, the pathogenesis of PSCI has been shown that due to the paucity of energy or oxygen to the brain, the region-specific neural damage occurred, ultimately leading to a progressive cognitive impairment (Wahul et al., 2018). Even so, the pathogenesis of PSCI remains unclear.

MicroRNAs (miRNAs) are a class of small endogenous RNA molecules that regulate gene expression in many biological processes (Brown and Naldini, 2009; Keasey et al., 2016). MiRNAs presented in human serum in a highly stable form that could be resistant to repeated freeze–thaw cycles and endogenous enzymatic degradation (Scholer et al., 2010). Meanwhile, miRNA expression levels are consistent across individuals of the same species (Reid et al., 2011). Because of these properties, miRNAs have become a popular diagnostic marker. Previously, miR-132 was demonstrated to be a risk marker of PSCI and could be used as a diagnostic biomarker for PSCI (Huang et al., 2016). Recently, Balakathiresan et al. (2012) analyzed the expression of various candidate miRNAs in the serum of animals post-blast overpressure injury. Among these, miR-let-7i was reported to be highly enriched in the brain of rats with traumatic brain injury (TBI). In experimental brain injury, miR-let-7i is up-regulated in cerebrospinal fluid as early as 3 h post-injury and has been used as a diagnostic biomarker for TBI (Bhomia et al., 2016). Thus, we speculated that miR-let-7i may be used as an alternative biomarker for PSCI. However, the role of miR-let-7i in the pathogenesis of PSCI has not yet been elaborated, especially its molecular mechanism. It is well acknowledged that hypoxia could induce oxidative stress, which is involved in neuronal cell death, which is one of the leading causes of neurodegenerative diseases, such as cerebral ischemia reperfusion after stroke (Bains and Shaw, 1997; Tabner et al., 2005). Thus, investigating the role of miR-let-7i in the prevention of neuronal cell death has the potential to prevent PSCI.

The aim of present study was to investigate whether miR-let-7i participates in the pathogenesis of PSCI and illuminates its underlying role in oxygen–glucose deprivation (OGD)-induced cell apoptosis in vitro. In present study, we collected blood samples from 36 subjects with PSCI and 38 with Non-PSCI to detect the differential expression of miR-let-7 family members and evaluate the relationship between miR-let-7 and PSCI. Importantly, we induced apoptosis by OGD treatment in vitro to simulate brain injury, expecting to elucidate the molecular mechanism of miR-let-7 in PSCI.

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