Hypoxia‑induced miR‑210 contributes to apoptosis of mouse spermatocyte GC‑2 cells by targeting Kruppel‑like factor 7

Comprehensive Analysis and Reinforcement Learning of Hypoxic Genes Based on Four Machine Learning Algorithms for Estimating the Immune Landscape, Clinical Outcomes, and Therapeutic Implications in Patients With Lung Adenocarcinoma

Background

Patients with lung adenocarcinoma (LUAD) exhibit significant heterogeneity in therapeutic responses and overall survival (OS). In recent years, accumulating research has uncovered the critical roles of hypoxia in a variety of solid tumors, but its role in LUAD is not currently fully elucidated. This study aims to discover novel insights into the mechanistic and therapeutic implications of the hypoxia genes in LUAD cancers by exploring the potential association between hypoxia and LUAD.

Methods

Four machine learning approaches were implemented to screen out potential hypoxia-related genes for the prognosis of LUAD based on gene expression profile of LUAD samples obtained from The Cancer Genome Atlas (TCGA), then validated by six cohorts of validation datasets. The risk score derived from the hypoxia-related genes was proven to be an independent factor by using the univariate and multivariate Cox regression analyses and Kaplan-Meier survival analyses. Hypoxia-related mechanisms based on tumor mutational burden (TMB), the immune activity, and therapeutic value were also performed to adequately dig deeper into the clinical value of hypoxia-related genes. Finally, the expression level of hypoxia genes was validated at protein level and clinical samples from LUAD patients at transcript levels.

Results

All patients in TCGA and GEO-LUAD group were distinctly stratified into low- and high-risk groups based on the risk score. Survival analyses demonstrated that our risk score could serve as a powerful and independent risk factor for OS, and the nomogram also exhibited high accuracy. LUAD patients in high-risk group presented worse OS, lower TMB, and lower immune activity. We found that the model is highly sensitive to immune features. Moreover, we revealed that the hypoxia-related genes had potential therapeutic value for LUAD patients based on the drug sensitivity and chemotherapeutic response prediction. The protein and gene expression levels of 10 selected hypoxia gene also showed significant difference between LUAD tumors tissues and normal tissues. The validation experiment showed that the gene transcript levels of most of their genes were consistent with the levels of their translated proteins.

Conclusions

Our study might contribute to the optimization of risk stratification for survival and personalized management of LUAD patients by using the hypoxia genes, which will provide a valuable resource that will guide both mechanistic and therapeutic implications of the hypoxia genes in LUAD cancers.

Alterations of RNA Modification in Mouse Germ Cell-2 Spermatids Under Hypoxic Stress

Hypoxia is a known stress factor in mammals and has been shown to potentially impair male fertility, which manifests as spermatogenic dysfunction and decreased semen quality. Studies have shown that RNA modifications, the novel post-transcriptional regulators, are involved in spermatogenesis, and hypoxia-induced alterations in RNA modification in testes and sperm cells may be associated with impaired spermatogenesis in mice. However, the molecular mechanisms via which RNA modifications influence spermatogenesis under hypoxic stress conditions are unclear. In this study, we generated a mouse Germ Cell-2 spermatid (GC-2spd) hypoxia model by culturing cells in a 1% O2 incubator for 48 h or treating them with CoCl2 for 24 h. The hypoxia treatment significantly inhibited proliferation and induced apoptosis in GC-2spd cells. The RNA modification signatures of total RNAs (2 types) and differentially sized RNA fragments (7 types of approximately 80 nt-sized tRNAs; 9 types of 17–50 nt-sized sncRNAs) were altered, and tRNA stability was partially affected. Moreover, the expression profiles of sncRNAs, such as microRNAs, tsRNAs, rsRNAs, and ysRNAs, were significantly regulated, and this might be related to the alterations in RNA modification and subsequent transcriptomic changes. We comprehensively analyzed alterations in RNA modification signatures in total RNAs, tRNAs (approximately 80 nt), and small RNAs (17–50 nt) as well as the expression profiles of sncRNAs and transcriptomes in hypoxia-treated GC-2spd cells; our data suggested that RNA modifications may be involved in cellular responses under hypoxic stress conditions and could provide a basis for a better understanding of the molecular mechanisms underlying male infertility.

miRNA Pattern in Hypoxic Microenvironment of Kidney Cancer—Role of PTEN

MicroRNAs are post-transcriptional regulators of gene expression, and disturbances of their expression are the basis of many pathological states, including cancers. The miRNA pattern in the context of tumor microenvironment explains mechanisms related to cancer progression and provides a potential target of modern therapies. Here we show the miRNA pattern in renal cancer focusing on hypoxia as a characteristic feature of the tumor microenvironment and dysregulation of PTEN, being a major tumor suppressor. Methods comprised the CRSPR/Cas9 mediated PTEN knockout in the Renca kidney cancer cell line and global miRNA expression analysis in both in vivo and in vitro (in normoxic and hypoxic conditions). The results were validated on human cancer models with distinct PTEN status. The increase in miR-210-3p in hypoxia was universal; however, the hypoxia-induced decrease in PTEN was associated with an increase in miR-221-3p, the loss of PTEN affected the response to hypoxia differently by decreasing miR-10b-5p and increasing miR-206-3p. In turn, the complete loss of PTEN induces miR-155-5p, miR-100-5p. Upregulation of miR-342-3p in knockout PTEN occurred in the context of the whole tumor microenvironment. Thus, effective identification of miRNA patterns in cancers must consider the specificity of the tumor microenvironment together with the mutations of key suppressors.

Krüppel-like factor 7 attenuates hippocampal neuronal injury after traumatic brain injury

Our previous study has shown that the transcription factor Krüppel-like factor 7 (KLF7) promotes peripheral nerve regeneration and motor function recovery after spinal cord injury. KLF7 also participates in traumatic brain injury, but its regulatory mechanisms remain poorly understood. In the present study, an HT22 cell model of traumatic brain injury was established by stretch injury and oxygen-glucose deprivation. These cells were then transfected with an adeno-associated virus carrying KLF7 (AAV-KLF7). The results revealed that, after stretch injury and oxygen-glucose deprivation, KLF7 greatly reduced apoptosis, activated caspase-3 and lactate dehydrogenase, downregulated the expression of the apoptotic markers B-cell lymphoma 2 (Bcl-2)-associated X protein (Bax) and cleaved caspase-3, and increased the expression of βIII-tubulin and the antiapoptotic marker Bcl-2. Furthermore, KLF7 overexpression upregulated Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3) phosphorylation in HT22 cells treated by stretch injury and oxygen-glucose deprivation. Immunoprecipitation assays revealed that KLF7 directly participated in the phosphorylation of STAT3. In addition, treatment with AG490, a selective inhibitor of JAK2/STAT3, weakened the protective effects of KLF7. A mouse controlled cortical impact model of traumatic brain injury was then established. At 30 minutes before modeling, AAV-KLF7 was injected into the ipsilateral lateral ventricle. The protein and mRNA levels of KLF7 in the hippocampus were increased at 1 day after injury and recovered to normal levels at 3 days after injury. KLF7 reduced ipsilateral hippocampal atrophy, decreased the injured cortex volume, downregulated Bax and cleaved caspase-3 expression, and increased the number of 5-bromo-2'-deoxyuridine-positive neurons and Bcl-2 protein expression. Moreover, KLF7 transfection greatly enhanced the phosphorylation of JAK2 and STAT3 in the ipsilateral hippocampus. These results suggest that KLF7 may protect hippocampal neurons after traumatic brain injury through activation of the JAK2/STAT3 signaling pathway. The study was approved by the Institutional Review Board of Mudanjiang Medical University, China (approval No. mdjyxy-2018-0012) on March 6, 2018.

miR-210 Regulates Apoptotic Cell Death during Cellular Hypoxia and Reoxygenation in a Diametrically Opposite Manner

Apoptotic cell death of cardiomyocytes is a characteristic hallmark of ischemia-reperfusion (I/R) injury. The master hypoxamiR, microRNA-210 (miR-210), is considered the primary driver of the cellular response to hypoxic stress. However, to date, no consensus has emerged with regards to the polarity of the miR-210-elicited cellular response, as miR-210 has been shown to exacerbate as well as attenuate hypoxia-driven apoptotic cell death. Herein, in AC-16 cardiomyocytes subjected to hypoxia-reoxygenation (H-R) stress, we unravel novel facets of miR-210 biology and resolve the biological response mediated by miR-210 into the hypoxia and reoxygenation temporal components. Using transient overexpression and decoy/inhibition vectors to modulate miR-210 expression, we elucidated a Janus role miR-210 in the cellular response to H-R stress, wherein miR-210 mitigated the hypoxia-induced apoptotic cell death but exacerbated apoptotic cell death during cellular reoxygenation. We further delineated the underlying cellular mechanisms that confer this diametrically opposite effect of miR-210 on apoptotic cell death. Our exhaustive biochemical assays cogently demonstrate that miR-210 attenuates the hypoxia-driven intrinsic apoptosis pathway, while significantly augmenting the reoxygenation-induced caspase-8-mediated extrinsic apoptosis pathway. Our study is the first to unveil this Janus role of miR-210 and to substantiate the cellular mechanisms that underlie this functional duality.

Effects of Environmental and Pathological Hypoxia on Male Fertility

Male infertility is a widespread health problem affecting approximately 6%-8% of the male population, and hypoxia may be a causative factor. In mammals, two types of hypoxia are known, including environmental and pathological hypoxia. Studies looking at the effects of hypoxia on male infertility have linked both types of hypoxia to poor sperm quality and pregnancy outcomes. Hypoxia damages testicular seminiferous tubule directly, leading to the disorder of seminiferous epithelium and shedding of spermatogenic cells. Hypoxia can also disrupt the balance between oxidative phosphorylation and glycolysis of spermatogenic cells, resulting in impaired self-renewal and differentiation of spermatogonia, and failure of meiosis. In addition, hypoxia disrupts the secretion of reproductive hormones, causing spermatogenic arrest and erectile dysfunction. The possible mechanisms involved in hypoxia on male reproductive toxicity mainly include excessive ROS mediated oxidative stress, HIF-1α mediated germ cell apoptosis and proliferation inhibition, systematic inflammation and epigenetic changes. In this review, we discuss the correlations between hypoxia and male infertility based on epidemiological, clinical and animal studies and enumerate the hypoxic factors causing male infertility in detail. Demonstration of the causal association between hypoxia and male infertility will provide more options for the treatment of male infertility.

Seminal plasma miR-210-3p induces spermatogenic cell apoptosis by activating caspase-3 in patients with varicocele

The aim of this study was to investigate the role of seminal plasma miR-210-3p in the impairment of semen quality caused by varicocele. This study included 102 patients whose semen quality was normal when they were diagnosed with varicocele. A 2-year follow-up for included patients was performed, and they were divided into Group A (semen quality became abnormal) and Group B (semen quality remained normal) according to the results of semen analysis during the follow-up. Semen parameters and seminal plasma miR-210-3p expression were investigated by semen analysis and quantitative real-time polymerase chain reaction, respectively. In vitro experiments with GC-2 cells were performed to explore the role of miR-210-3p in spermatogenic cells. The results of quantitative real-time polymerase chain reaction showed that the level of seminal plasma miR-210-3p in Group A was higher than that in Group B both after 2-year follow-up and when they were diagnosed with varicocele (both P < 0.01). Apoptosis and proliferation assays showed that miR-210-3p induces apoptosis of spermatogenic cells by promoting caspase-3 activation. In conclusion, our study indicated that seminal plasma miR-210-3p induces spermatogenic cell apoptosis by activating caspase-3 in patients with varicocele. Seminal plasma miR-210-3p may be a potential biomarker for predicting impaired semen quality caused by varicocele.

Hypoxia-challenged MSC-derived exosomes deliver miR-210 to attenuate post-infarction cardiac apoptosis

BACKGROUND

Myocardial infarction (MI) is a major cause of death worldwide. Although percutaneous coronary intervention and coronary artery bypass grafting can prolong life, cardiac damage persists. In particular, cardiomyocytes have no regenerative capacity. Mesenchymal stem cells (MSCs) are attractive candidates for the treatment of MI. The manner by which MSCs exert a beneficial effect upon injured cells is a source of continued study.

METHODS

After the isolation and identification of exosomes from MSCs, the expression of miR-210 was determined by microarray chip. Subsequently, gain- and loss-function approaches were conducted to detect the role of exosomes and exosomal-miR-210 in cell proliferation and apoptosis of cardiomyocytes, as well as the MI in vivo. Dual-Luciferase Report Gene System was used to demonstrate the target gene of miR-210.

RESULTS

We tested the hypothesis that MSC-derived exosomes transfer specific miRNA to protect cardiomyocytes from apoptotic cell death. Interestingly, direct cardiac injection of MSC exosomes reduced infarct size and improved heart function after coronary ligation. In vitro, the MSC exosomes enhanced cardiomyocyte survival to hypoxia. Confirmation of exosome uptake in myocytes was confirmed. Dual-luciferase reporter assay implicated miR-210 as a mediator of the therapeutic effect and AIFM3 as a downstream target. Treatment with miR-210 overexpressing MSC exosomes improved myocyte protection to both in vitro and in vivo stress. Furthermore, the endogenous and exogenous miR-210 had the same therapeutic effects.

CONCLUSION

These results demonstrated that the beneficial effects offered by MSC-exosomes transplantation after MI are at least partially because of excreted exosome containing mainly miR-210.

Fetal Hypoxia Impacts on Proliferation and Differentiation of Sca-1+ Cardiac Progenitor Cells and Maturation of Cardiomyocytes: A Role of MicroRNA-210

Hypoxia is one of the most frequent and severe stresses to an organism’s homeostatic mechanisms, and hypoxia during gestation has profound adverse effects on the heart development increasing the occurrence of congenital heart defects (CHDs). Cardiac progenitor cells (CPCs) are responsible for early heart development and the later occurrence of heart disease. However, the mechanism of how hypoxic stress affects CPC fate decisions and contributes to CHDs remains a topic of debate. Here we examined the effect of hypoxic stress on the regulations of CPC fate decisions and the potential mechanism. We found that experimental induction of hypoxic responses compromised CPC function by regulating CPC proliferation and differentiation and restraining cardiomyocyte maturation. In addition, echocardiography indicated that fetal hypoxia reduced interventricular septum thickness at diastole and the ejection time, but increased the heart rate, in mouse young adult offspring with a gender-related difference. Further study revealed that hypoxia upregulated microRNA-210 expression in Sca-1⁺ CPCs and impeded the cell differentiation. Blockage of microRNA-210 with LNA-anti-microRNA-210 significantly promoted differentiation of Sca-1⁺ CPCs into cardiomyocytes. Thus, the present findings provide clear evidence that hypoxia alters CPC fate decisions and reveal a novel mechanism of microRNA-210 in the hypoxic effect, raising the possibility of microRNA-210 as a potential therapeutic target for heart disease.