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Research Article | Open Access
Jian-Lan Zhao, Bo Tan, Gong Chen, Xiao-Ming Che, Zhuo-Ying Du, Qiang Yuan, Jian Yu, Yi-Rui Sun, Xiao-Mu Li, Jin Hu, Rong Xie, "Hypoxia-Induced Glioma-Derived Exosomal miRNA-199a-3p Promotes Ischemic Injury of Peritumoral Neurons by Inhibiting the mTOR Pathway", Oxidative Medicine and Cellular Longevity, vol. 2020, Article ID 5609637, 12 pages, 2020. https://doi.org/10.1155/2020/5609637
Hypoxia-Induced Glioma-Derived Exosomal miRNA-199a-3p Promotes Ischemic Injury of Peritumoral Neurons by Inhibiting the mTOR Pathway
The underlying molecular mechanisms that the hypoxic microenvironment could aggravate neuronal injury are still not clear. In this study, we hypothesized that the exosomes, exosomal miRNAs, and the mTOR signaling pathway might be involved in hypoxic peritumoral neuronal injury in glioma. Multimodal radiological images, HE, and HIF-1α staining of high-grade glioma (HGG) samples revealed that the peritumoral hypoxic area overlapped with the cytotoxic edema region and directly contacted with normal neurons. In either direct or indirect coculture system, hypoxia could promote normal mouse hippocampal neuronal cell (HT22) injury, and the growth of HT22 cells was suppressed by C6 glioma cells under hypoxic condition. For administrating hypoxia-induced glioma-derived exosomes (HIGDE) that could aggravate oxygen-glucose deprivation (OGD)/reperfusion neuronal injury, we identified that exosomes may be the communication medium between glioma cells and peritumoral neurons, and we furtherly found that exosomal miR-199a-3p mediated the OGD/reperfusion neuronal injury process by suppressing the mTOR signaling pathway. Moreover, the upregulation of miRNA-199a-3p in exosomes from glioma cells was induced by hypoxia-related HIF-1α activation. To sum up, hypoxia-induced glioma-derived exosomal miRNA-199a-3p can be upregulated by the activation of HIF-1α and is able to increase the ischemic injury of peritumoral neurons by inhibiting the mTOR pathway.
Glioblastoma multiforme (GBM) is the most common primary brain malignancy in adults with consistently very poor outcomes . Peritumoral hypoxia of solid tumors develops due to rapid tumor growth exceeding the vascular supply capabilities and/or tumor vasculature malfunctioning . Hypoxia is one of the most significant characteristics of GBM , and pseudopalisading necrosis with surrounding hypoxia is identified as a hallmark pathognomonic feature . It has been reported that the peritumoral hypoxic microenvironment could promote the growth of glioma cells ; however, its underlying molecular mechanisms are still not clear.
Exosomes are 40–100 nm nanosized vesicles released into the extracellular space from many cell types, including blood cells , and have been reported to play important roles in tumor progression . However, the mechanism of exosomes in the occurrence and/or regulation of hypoxia-induced glioma cell proliferation and neuronal injury remains unclear. MicroRNAs (miRNAs), small noncoding RNAs of 17~24 nucleotides, are able to regulate diverse biological processes through downregulation (sometimes upregulation) of the expression of target proteins . miRNAs have been confirmed to be altered by hypoxia to target crucial oncogenes and tumor suppressors, which are the hallmarks of tumorigenic processes . Valadi et al. reported the intercellular transfer of miRNAs via exosomes . Thus, it is reasonable to hypothesize that exosomal miRNAs participate in hypoxic exosomal phenomena. However, such phenomena have rarely been studied.
The mammalian target of rapamycin (mTOR) signaling pathway has been confirmed to play a central role in cell metabolism, growth, differentiation, development, and survival . The mTOR pathway was constructed by various components, including its upstream molecular Akt and its downstream factor S6K . The specific function of mTOR is regulated by different signal pathways . By applying an oxygen-glucose deprivation (OGD) model to mimic ischemic-reperfusion injury in vitro and using dMCAO rat models in vivo, we found that mTOR is a crucial signaling pathway in the protection against cerebral ischemia-reperfusion injury [14–16]. Thus, we hypothesized that the mTOR signaling pathway might be involved in hypoxic peritumoral neuronal injury in glioma and then induce the proliferation of glioma cells.
2. Materials and Methods
2.1. Glioma Samples and Image Data
Glioma samples were obtained from patients who were pathologically diagnosed with primary glioma at Huashan Hospital, Fudan University in 2017.1-2017.12. Image data, including MRI, were also retrospectively collected. This study strictly followed the Declaration of Helsinki and was approved by the Ethical Review Boards of Fudan University Huashan Hospital. Informed consent was obtained from all individual participants.
2.2. Hematoxylin-Eosin (HE) and Hypoxia-Induced Factor-1α (HIF-1α) Staining
2.3. Cell Line and Cell Culture
HT22 normal mouse hippocampal neuronal cells were obtained from David Schubert (Salk Institute, San Diego, CA). C6 glioma cells were obtained from the American Type Tissue Collection (Rockville, MD). HT22 and C6 glioma cells were normally cultured and are briefly described in Supplementary Methods 2. In our study, the HT22 and C6 cell lines were cocultured in either direct or indirect systems. Protocols for these coculture systems were previously described .
2.4. Primary Neuronal Cultures
This study strictly followed the ARRIVE guideline and was approved by the Ethical Review Boards of Fudan University Huashan Hospital. Primary neuronal cultures were prepared using timed-pregnant Sprague-Dawley rats (E18, Charles River Laboratories International, Wilmington, MA) as previously reported . This information is briefly described in Supplementary Methods 3.
2.5. Oxygen-Glucose Deprivation (OGD)/Reperfusion
2.6. 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium Bromide (MTT) Assay
2.7. Lactate Dehydrogenase (LDH) Release Assay
Cell viability was detected by LDH release using an LDH cytotoxicity assay kit (Cayman Chemical, Ann Arbor, MI) according to the manufacturer’s protocol. LDH activity was quantified by measuring absorbance at 490 nm with a microplate reader (Hangzhou, China). The ratio of released LDH to total LDH was calculated and presented as a relative LDH release compared to LDH release in nontreated cells.
2.8. Exosome Isolation and Identification
Exosomes were isolated from a postconditioned medium by successive centrifugation after 24 hours of culture in the presence of vesicle-depleted FBS (Wisent Inc.), as previously described . To determine whether exosomes were successfully isolated, transmission electron microscopy (TEM) (NanoSight Ltd., Amesbury, UK) and detection of the expression of CD81 by Western blotting (see below) were performed. For TEM, the protocol is briefly described in Supplementary Methods 6. Sizing of exosomes was performed by nanoparticle tracking analysis using the NanoSight LM10 instrument (NanoSight Ltd., Amesbury, UK) and ZetaView (Particle Metrix, Meerbusch, Germany).
2.9. Microarray Analysis
Total RNA was extracted using TRIzol reagent (Invitrogen, Carlsbad, CA, USA), and according to the manufacturer’s protocols, we conducted microarray analysis (Rat miRNA Microarray, Release 21.0, Aksomics, Shanghai, China) to detect the altered expression of miRNAs.
2.10. Lentiviral Vector Generation, Titration, and Gene Delivery
We used a lentiviral vector containing miR-199a-3p shRNA to inhibit miR-199a-3p expression (control: scramble shRNA). Moreover, we commercially constructed lentiviral vectors expressing S6K and HIF-1α. We used a 3-plasmid system for lentivirus packaging as detailed in our previous study . The virus particles were tittered with the TCID50 method as described previously . The protocols are briefly described in Supplementary Methods 7. The manufacturers and catalog numbers of the lentiviral vectors and lentiviral plasmid backbones used are listed in Supplementary Table S1.
2.11. Other Transfection Reagents
miR-199a-3p mimics and negative controls of miR-199a-3p mimic were purchased from Thermo Fisher Scientific Inc. (miR-199a-3p mimics: MC11779, negative control: 4464058). The miR-199a-3p mimics and negative controls (1 μg/ml) were directly added to the cell cultures at the indicated concentration 24 hours before OGD induction.
2.12. Protein Preparation and Western Blot Analysis
The protein levels of CD81 were examined by Western blotting. The harvested cells were homogenized in cold cell extraction buffer (Cat# FNN0001, Invitrogen, Carlsbad, CA, USA) containing 1 mM PMSF and protease inhibitor cocktail (1 : 20, Cat# P-2714, Sigma). The homogenates were centrifuged at 4°C for 20 min at 13000 rpm. The supernatant was used for Western blotting and is briefly described in Supplementary Methods 8. The manufacturers and catalog numbers of all primary antibodies used are listed in Supplementary Table S2.
2.13. Reverse Transcription-Quantitative Polymerase Chain Reaction (RT-qPCR)
2.14. Statistical Analysis
All results obtained from at least 3 independent experiments were performed, /group. GraphPad Prism 6.0 software was used for statistical analyses. One-way or 2-way ANOVA was used followed by the Fisher least significant difference post hoc test. Tests were considered significant at values < 0.05. Data are presented as the (SE).
3.1. Evidence of Hypoxia Was Observed in Both Glioma and Its Surrounding Parenchyma
Multimodal radiological assessments were performed for patients with glioma to verify whether hypoxia occurred in glioma and its surrounding parenchyma as previously reported. In MRI, the tumor lesion is best defined on contrast-enhanced T1W sequence, while paratumoral vasogenic and/or cytotoxic edema can be clearly identified as hyperintense signals on T2 and Flair sequences (Figure 1(a)). Further 18F-FDG and 18F-FMISO PET/CT scannings were performed in this glioma patient and clearly showed that the regions of paratumoral hypoxia were the same as the regions of edema identified on T2 and Flair MRI images, which demonstrated a close relationship between paratumoral edema and the occurrence of hypoxia (Figure 1(b)). Regions of edema showed low perfusion features on MR PW studies (Figure 1(c)).
Tumor samples from surgical resection were processed by HE and HIF-1α staining (Figures 1(d) and 1(e)). Normal neurons mixed with high-grade glioma (HGG) cells within the paratumoral area were observed by HE staining, indicating the invasive growth of glioma cells. In addition, microthrombi were also observed. The density of positive HIF-1α staining was higher in tumoral areas than in normal parenchyma, which confirmed the existence of hypoxia in glioma and its surrounding parenchyma (Figures 1(f) and 1(g)) and also suggested that glioma cells were growing within and around hypoxic environments.
3.2. Hypoxia Promoted C6 Cell Proliferation and HT22 Neuron Injury via Exosomes and Exosomal miR-199a-3p
In a direct coculture system, the ratio of C6/HT22 cells was significantly increased after hypoxia treatment (Figure 2(a)). C6 and HT22 cells were further cultured separately in both monoculture and indirect coculture systems. The proliferation ability of HT22 cells was decreased after hypoxia treatment in the monoculture system but was significantly further suppressed in the indirect coculture system with C6 cells. In addition, the MTT of C6 cells in hypoxia condition were higher than those in none hypoxia environment (Figure 2(b)). However, the question remained of what caused the phenotype that in either the direct or indirect coculture system, the growth of HT22 cells was suppressed by C6 cells under hypoxic conditions. In the study, we identified exosomes and exosomal miRNA as the potential underlying mechanism.
First, exosomes were isolated from the medium of C6 cells cultured with or without hypoxia (1% oxygen) treatment (hypoxia-induced glioma-derived exosomes (HIGDE) and non-hypoxia-induced glioma-derived exosomes (NHIGDE)). Their size and morphology were identified by TEM (Figure 3(a)). The presence of CD81 (a specific marker of exosomes) in isolated exosomes was confirmed using Western blotting (Figure 3(b)). LDH release after OGD/reperfusion injury in HT22 cells was significantly increased with HIGDE treatment but remained the same after NHIGDE treatment (Figure 3(c)). These results suggest that HIGDE might aggravate hypoxia-induced neuronal injury.
Then, RNase was used to degrade RNA components in exosomes to further investigate the potential mechanism of HIGDE-induced OGD/reperfusion injury in HT22 cells. The level of LDH release in HT22 cells with HIGDE treatment was significantly lower after RNase treatment compared with that in the non-RNase-treated (vehicle) group and was similar to that in the NHIGDE group (Figure 3(d)). The microRNA microarray analysis revealed sixteen highly expressed miRNAs in HIGDE than NHIGDE (Figure 3(e)). Among them, miRNA-199a-3p was the most highly expressed, with approximately 3 times the 1level in HIGDE. This was also confirmed by RT-qPCR (Figure 3(f)).
3.3. Exosomal miR-199a-3p Mediated HIGDE-Induced OGD/Reperfusion Injury in Primary Neurons
To elucidate the effects of miRNA-199a-3p on ischemic-reperfusion injury of neurons, we transfected primary cultured neurons with miRNA-199a-3p mimic or control miRNA (Figure 4(a)). The LDH assay showed that primary cultured neurons with NHIGDE+miRNA-199a-3p mimics suffered more severe OGD/reperfusion injury, which was similar to the effects of HIGDE (Figure 4(b)). In addition, miRNA-199a-3p shRNA was used to knock down the expression of miRNA-199a-3p in neuronal cells (Figure 4(c)). LDH release levels suggested that the ischemia injury caused by HIGDE was blocked by miRNA-199a-3p shRNA (Figure 4(d)).
3.4. miRNA-199a-3p Aggravated Neuronal Injury with HIGDE Administration by Suppressing the mTOR Signal
NHIGDE and HIGDE from C6 cells were isolated and administered to the medium of primary cultured neurons. After the OGD/reperfusion treatment, the expression of pmTOR, mTOR, and pS6K was clearly decreased in comparison to that in non-OGD neurons (Figure 5(a)). The mRNA level of total mTOR in primary cultured neurons was also significantly lower with HIGDE administration than with NHIGDE administration, but the mRNA level of total S6K remained stable (Figure 5(b)). After OGD/reperfusion injury, LDH released from the neurons treated with phosphatidic acid (PA) plus HIGDE, similar to the neurons treated with NHIGDE+vehicle, was lower than that in the neurons treated only with HIGDE+vehicle (Figure 5(c)). Moreover, when S6K was overexpressed, the OGD/reperfusion injury of primary neurons treated with HIGDE was significantly decreased in comparison to that in neurons treated with HIGDE without S6K overexpression (Figure 5(d)).
Next, we transfected isolated NHIGDE with miRNA-199a-3p mimics. mTOR mRNA expression after OGD/reperfusion injury was significantly decreased in primary neurons treated with NHIGDE plus miRNA-199a-3p mimics, as well as HIGDE (Figure 6(a)). In addition, mTOR, pmTOR, and pS6K expression in primary neurons treated with NHIGDE plus miRNA-199a-3p mimics was obviously decreased, as indicated by Western blotting (Figure 6(b), Supplementary Figure IA). Moreover, after OGD/reperfusion injury, the mRNA level of mTOR did not decrease in primary neurons cultured with HIGDE from these C6 cells treated with miRNA-199a-3p shRNA compared with neurons cultured with NHIGDE but was much higher than that in neurons cultured with HIGDE treated only with scramble shRNA (Figure 6(c)). Finally, when primary neurons were cultured with NHIGDE or HIGDE plus miRNA-199a-3p shRNA, the expression of pmTOR, mTOR, and pS6K was clearly higher than that in neurons treated with HIGDE plus scramble shRNA (Figure 6(d), Supplementary Figure IB).
3.5. The Upregulation of miRNA-199a-3p in Exosomes from C6 Glioma Cells Was Induced by Hypoxia-Related HIF-1α Activation
HIF-1α is a crucial regulatory factor in the oxygen balance of mammalian cells. Our bioinformatics analysis identified HIF-1α reacting element (HRE) sequences in the upstream area of miRNA-199a1 (Figure 7(a)). Western blotting further confirmed the upregulated expression of HIF-1α in C6 cells cultured in hypoxic environments (Figure 7(b)). These findings suggested that HIF-1α might be activated by hypoxia and was related to miRNA-199a.
When HIF-1α was overexpressed in C6 cells, the expression of miRNA-199a-3p RNA in NHIGDE was remarkably higher than that in NHIGDE without HIF-1α overexpression (Lenti GFP) (Figure 7(c)). Conversely, when the expression of HIF-1α in C6 cells was knocked down (HIF-1α shRNA), the expression of miRNA-199a-3p in HIGDE decreased significantly in comparison to that in HIGDE without HIF-1α suppression (Figure 7(d)).
In this study, we found that exosomal miRNA-199a-3p could be upregulated in a hypoxic microenvironment; via suppressing the mTOR signaling pathway, HIGDE were able to exacerbate the ischemic injury of peritumoral neurons. Although the role of miR-199a-3p in glioma progression was previously investigated, the ischemic injury mechanism of peritumoral neurons, involving miR-199a-3p, exosomes, and the mTOR signaling pathway, has rarely been studied. For in ischemic stroke, infarcted brain parenchyma also characterized by hypoxia as glioma, it was reasonable that exosomes released from ischemia brain could have the same effects as HIGDE and thus can aggravate hypoxia injury in neurons around the infarcted brain. This is a novel ischemic neuronal injury mechanism.
4.1. Peritumor Hypoxia Is the Microenvironment That May Aggravate Ischemic Injury in Peritumoral Neurons and Promote the Invasive Growth of Tumor Cells
Hypoxia frequently occurs in solid tumors due to erratic tumor neovascularization resulting from rapid cell proliferation, which leads to poor oxygen diffusion . Consistent with previous studies , our multimodal examinations found that areas of peritumoral edema were the same as areas of hypoxia. Because high HIF-1α was regarded as a biomarker of the existence of hypoxia , hypoxia was detected in the parenchyma surrounding glioma lesions in our study. In addition to evidence of the existence of hypoxia, the results of HE-stained surgical samples also suggested the invasive growth of glioma cells. We confirmed the existence of hypoxia in the peritumoral region. Moreover, these findings also indicated that glioma cells grew within or around hypoxic environments. Thus, we mainly focused on peritumoral neuron injury understimulated hypoxic conditions in this study.
It is widely accepted that oxygen deficiency is a major factor associated with neuronal damage and promotion of invasive growth of glioma cells . In this study, we found that the proliferation ability of glioma cells was significantly higher than that of normal neuronal cells under hypoxic conditions in either a direct or indirect coculture system. These results further confirmed that the hypoxic microenvironment might be a potential factor that promotes glioma cell proliferation and, especially, exacerbates the injury of peritumoral normal neurons. But concerning that neurons do not proliferate in vivo, the ratio between C6 and HT22 may be due to a reduced number of neurons rather than an increased proliferation of glioma cell. We admitted this may be a potential explanation to the phenotype, but as shown in Figure 2(b), the MTT of C6 was statistically higher in hypoxia condition than none hypoxia environment either in mono- or cocultured system, which suggested that the ratio also may be affected by increasing C6 glioma cell proliferation ability in hypoxia. However, in this study, exosomes and exosomal miRNA were assumed as the potential underlying mechanism.
To clarify this underlying mechanism, we aimed to explore the interactions between hypoxia injury and exosomes/exosomal miRNA. Our in vitro results showed that hypoxia neuronal injury could be aggravated by the administration of HIGDE, and RNAs in exosomes were closely related to ischemic injury in normal neurons. Such exosomes (HIGDE) were different from the exosomes secreted by tumor cells under normal conditions (NHIGDE), and such differences were induced by miRNA-199a-3p. Moreover, we also verified that the upregulation of miRNA-199a-3p exacerbated hypoxic injury. On the other hand, hypoxic injury could be obviously relieved once miRNA-199a-3p was silenced. In addition, our study verified a positive relationship between the level of HIF-1α and miRNA-199a-3p. We concluded that HIF-1α could be activated by hypoxia and thus could upregulate the expression of miRNA-199a-3p, then induce ischemic injury in peritumoral normal neurons.
4.2. Exosomes May Be a Communication Medium between Glioma Cells and Peritumoral Neurons
Exosomes are a type of extracellular vesicles that are able to facilitate intercellular communication and crosstalk within the tumor environment. Exosomes secreted by tumor cells are now recognized to be involved in a variety of processes underlying tumor progression, including oncogenic genes and miRNAs . It was confirmed that exosomes can pass the blood-brain barrier and deliver RNAs within brain tissue .
Our results also showed that after applying OGD to glioma cells, HIGDE, containing upregulated miRNA-199a-3p, were able to exacerbate the injury of normal neurons. In contrast, when oxygen was sufficient in C6 cells, the hypoxic injury of neuron cells treated with NHIGDE was significantly less severe, and in addition, the level of miRNA-199a-3p in NHIGDE was also lower. These findings suggested that HIGDE could be released from glioma cells into the extracellular space and enter peritumoral normal neurons under a hypoxic environment.
It was indicated that exosomes may be the connecting medium between glioma cells and normal neurons and are the pivotal factor that induces the peritumoral hypoxia neuronal injury.
4.3. A Novel Ischemic Injury Mechanism: miRNA-199a-3p, Exosomes, and the mTOR Signaling Pathway
As mentioned above, the upregulation of miRNA-199a-3p in exosomes of glioma cells induced by peritumoral hypoxia and HIF-1α activation might be the core molecular mechanism underlying the aggravated hypoxic injury of peritumoral neurons. However, the specific pathway is not clear.
Our study focused on the role of the mTOR pathway due to its well-known protective ability against damage to neurons and other tissues [15, 30]. The specific role of the mTOR pathway in neuronal cells is still under debate. Some studies have also found that mTOR activation might even be harmful after neuronal injury [31, 32]. However, our previous studies showed that the mTOR pathway played protective roles in ischemic rats [16, 33]. The relationship or interplay between mTOR and miRNA-199a-3p has been studied in cholangiocarcinoma , gastric cancer , and nonneoplastic C2C12 muscle cells . Shen et al. found that miR-199a-3p in glioma cell lines can be the tumor suppressor gene on cellular proliferation via the AKT/mTOR signaling pathway . Moreover, in spinal cord injury rats, activity-dependent plasticity can be modulated by miRNA-199a-3p via the PTEN/mTOR pathway . It is suggested that the activities of the mTOR pathway may be regulated by miRNA-199a-3p after stroke-related ischemic injury, but to the best of our knowledge, the molecular mechanism involving mTOR and miRNA-199a-3p has rarely been investigated in the hypoxic injury of neurons.
In the current study, mTOR showed protective effects against the injury of neurons subjected to a hypoxic environment. In other words, activating the mTOR pathway might relieve the hypoxic injury of peritumoral normal neuronal cells induced by glioma cells and might inhibit the invasive growth of glioma cells in a hypoxic microenvironment.
We used PA and overexpression of S6K to verify this mechanism. As indicated by the LDH levels, activating the mTOR signaling pathway alleviated the injury of neuronal cells under hypoxic conditions similar to peritumoral conditions in vivo, which suggested that the mechanism of the protective effects of mTOR activation against the hypoxic injury of neuronal cells was induced by HIGDE. Then, we interfered with the expression of miRNA-199a-3p. These findings suggested that miRNA-199a-3p was able to suppress the mTOR signaling pathway and thus aggravate the hypoxic injury of normal neurons induced by HIGDE (Figure 8).
There are still several limitations in this study. First, an in vivo or animal study is required to confirm our in vitro results. Moreover, a further study is required to elucidate whether the effect of miRNA-199a-3p in suppressing mTOR signaling is direct or mediated indirectly by additional factors. Finally, the molecular mechanism should be verified in other models.
As hypoxia worsens, hypoxia-induced glioma-derived exosomal miRNA-199a-3p can be upregulated by the activation of HIF-1α and is able to increase the ischemic injury of neurons by inhibiting the mTOR pathway.
|HER:||HIF-1α reacting element|
|HIGDE:||Hypoxia-induced glioma-derived exosomes|
|mTOR:||Mammalian target of rapamycin|
|MRI:||Magnetic resonance imaging|
|NHIGDE:||None hypoxia-induced glioma-derived exosomes|
|OGD:||Oxygen glucose deprivation|
|TEM:||Transmission electron microscopy.|
The data used to support the findings of this study are included within the article and the supplementary information file.
Conflicts of Interest
The authors declare that they have no conflicts of interest with the contents of this article.
Jian-Lan Zhao designed the study, performed the experiments, collected data, and wrote the manuscript. Bo Tan, Gong Chen, Qiang Yuan, Jian-Yu, and Yi-Rui Sun performed the experiments and data collection. Xiao-Ming Che and Zhuo-Ying Du helped in data collection and analyzation. Xiao-Mu Li performed the experiments, analyzed the data, and revised the manuscript. Jin Hu and Rong Xie designed the study, analyzed the data, revised the manuscript, and did the final approval. Jian-Lan Zhao, Bo Tan, and Gong Chen contributed equally to this work.
This study was supported by the National Natural Science Foundation of China (NSFC) (81701206, 81671200, 81870968, 81770770, 81970695 and 81870909) and the National Key R&D Program of China (2018YFA0107900). We are grateful to everyone in the Department of Neurosurgery, Huashan Hospital, Fudan University.
Table S1: lentiviral plasmid backbones, lentiviral vectors, and miRNA mimics. Table S2: antibodies, their concentrations, and manufacturers in the present studies. Table S3: primers used for RT-qPCR. Supplementary Figure I: quantification of the expression of pmTOR, mTOR, and pS6K when primary cultured neurons were treated with NHIGDE, HIGDE, miR-199a-3p mimics, or miR-199a-3p shRNA. (Supplementary Materials)
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