Extracellular Vesicle–Mediated Delivery of Circular RNA SCMH1 Promotes Functional Recovery in Rodent and Nonhuman Primate Ischemic Stroke Models

Abstract

Background: Stroke is a leading cause of adult disability that can severely compromise patients' quality of life, yet no effective medication currently exists to accelerate rehabilitation. A variety of circular RNA (circRNAs) molecules are known to function in ischemic brain injury. Lentivirus-based expression systems have been widely used in basic studies of circRNAs, but safety issues with such delivery systems have limited exploration of potential therapeutic roles for circRNAs. Methods: Circular RNA SCMH1 (circSCMH1) was screened from the plasma of acute ischemic stroke (AIS) patients using circRNA microarrays. Engineered RVG-circSCMH1-extracellular vesicles (RVG-circSCMH1-EVs) were generated to selectively deliver circSCMH1 to the brain. Nissl staining was used to examine infarct size. Behavioral tasks were performed to evaluate motor functions in both rodent and nonhuman primate ischemic stroke models. Golgi staining and immunostaining were used to examine neuroplasticity and glial activation. Proteomic assays and RNA-seq data combined with transcriptional profiling were used to identify downstream targets of circSCMH1. Results: CircSCMH1 levels were significantly decreased in plasma of AIS patients, offering significant power in predicting stroke outcomes. The decreased levels of circSCMH1 were further confirmed in the plasma and peri-infarct cortex of photothrombotic (PT) stroke mice. Beyond demonstrating proof-of-concept for an RNA drug delivery technology, we observed that circSCMH1 treatment improved functional recovery post stroke in both mice and monkeys, and discovered that circSCMH1 enhanced the neuronal plasticity and also inhibited glial activation and peripheral immune cell infiltration. Mechanistically, circSCMH1 binds to the transcription factor MeCP2, thereby releasing repression of MeCP2 target gene transcription. Conclusions: RVG-circSCMH1-EVs afford protection by promoting functional recovery in the rodent and the nonhuman primate ischemic stroke models. Our study presents a potentially widely applicable nucleotide drug delivery technology and demonstrates the basic mechanism of how circRNAs can be therapeutically exploited to improve post-stroke outcomes.

RETRACTED: Overexpression of circRNA circUCK2 Attenuates Cell Apoptosis in Cerebral Ischemia-Reperfusion Injury via miR-125b-5p/GDF11 Signaling

“…A previous circRNAs microarray study in an established MCAO stroke model revealed that circUCK2 is one of the circRNAs downregulated during ischemic stroke. 27 Considering that circUCK2 plays a critical role in stroke, further experiments were needed to dissect the detailed mechanisms. In this study, we first detected the expression of circUCK2 in a murine ischemic stroke model (MCAO) using quantitative reverse transcription PCR (qRT-PCR), and the results showed that circUCK2 expression was decreased in the brain tissue of mice subjected to the MCAO model and in oxygen glucose deprivation (OGD)-induced HT-22 neurons ( Figures 1 A and 1B).…”

“…A recent study showed that circUCK2 was significantly downregulated in patients with ischemic stroke. 27 The overexpression of circUCK2 demonstrated substantial protective effects on neurons. As expected, our results elucidated the role of the circUCK2/miR-125b-5p/SIRT1 axis in stroke-associated neuronal injury and neurological deficits.…”

EV-origin: Enumerating the tissue-cellular origin of circulating extracellular vesicles using exLR profile

“…In particular, plasma EVs originate from host cells mediate their mutual regulation locally or remotely, these EVs have cell type-specific biomolecules and could be exploited as predictive biomarkers for disease treatment [7] , [8] , [9] , [10] , [11] , [12] , [13] , [14] . The brain cell originated EVs could also be detected in CSF reflect the physiological and pathological changes taking place in the originated brain tissue [15] , [16] , [17] . Meanwhile, EVs encapsulate RNAs reflect the phenotype and functional states of their parent cells [18] .…”

Circular RNA: metabolism, functions and interactions with proteins

“…CircHuR inhibits gastric cancer (GC) proliferation, invasion and metastasis by sequestering CCHC-type zinc finger nucleic acid binding protein (CNBP) from the human antigen R (HuR) promoter, thus downregulating HuR and repressing tumor [ 102 ]. Similarly, circSCMH1 delivered by EVs improves neuronal plasticity, and inhibits glial activation and immune cell infiltration post-stroke by sequestering methyl-CpG binding protein 2 (MeCP2) and compromising its role in transcriptional repression [ 103 ]. CircSamd4 [ 104 ] and autophagy-related circRNA (ACR) [ 105 ] also conform to this type.…”