Hypoxia stimulates proliferation of rat neural stem/progenitor cells by regulating mir-21: an in vitro study

The Potential of miR-21 in Stem Cell Differentiation and its Application in Tissue Engineering and Regenerative Medicine

MicroRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are two important types of non-coding RNAs that are not translated into protein. These molecules can regulate various biological processes, including stem cell differentiation and self-renewal. One of the first known miRNAs in mammals is miR-21. Cancer-related studies have shown that this miRNA has proto-oncogene activity and is elevated in cancers. However, it is confirmed that miR-21 inhibits stem cell pluripotency and self-renewal and induces differentiation by targeting various genes. Regenerative medicine is a field of medical science that tries to regenerate and repair damaged tissues. Various studies have shown that miR-21 plays an essential role in regenerative medicine by affecting stem cell proliferation and differentiation. In this review, we will discuss the function of miR-21 in regenerative medicine of the liver, nerve, spinal cord, wound, bone, and dental tissues. In addition, the function of natural compounds and lncRNAs will be analyzed as potential regulators of miR-21 expression in regenerative medicine.

The role of hypoxia in stem cell regulation of the central nervous system: From embryonic development to adult proliferation

Hypoxia is involved in the regulation of various cell functions in the body, including the regulation of stem cells. The hypoxic microenvironment is indispensable from embryonic development to the regeneration and repair of adult cells. In addition to embryonic stem cells, which need to maintain their self-renewal properties and pluripotency in a hypoxic environment, adult stem cells, including neural stem cells (NSCs), also exist in a hypoxic microenvironment. The subventricular zone (SVZ) and hippocampal dentate gyrus (DG) are the main sites of adult neurogenesis in the brain. Hypoxia can promote the proliferation, migration, and maturation of NSCs in these regions. Also, because most neurons in the brain are non-regenerative, stem cell transplantation is considered as a promising strategy for treating central nervous system (CNS) diseases. Hypoxic treatment also increases the effectiveness of stem cell therapy. In this review, we firstly describe the role of hypoxia in different stem cells, such as embryonic stem cells, NSCs, and induced pluripotent stem cells, and discuss the role of hypoxia-treated stem cells in CNS diseases treatment. Furthermore, we highlight the role and mechanisms of hypoxia in regulating adult neurogenesis in the SVZ and DG and adult proliferation of other cells in the CNS.

MicroRNA124 and microRNA21-5p regulate migration, proliferation and differentiation of rat bone marrow mesenchymal stem cells

Mesenchymal stem cells (MSCs) are multipotent stromal cells that can be a useful source of cells for the treatment of many diseases, including neurologic diseases. The curative effect of MSCs relies mostly on cell’s capacity of migration, proliferation and differentiation. MicroRNAs (miRNAs) are small non-coding RNAs that play important roles on regulating various cell behaviors. Here, we report that miRNA-124 (miR124) and miRNA-21-5p (miR21-5p) display different regulatory roles on migration, proliferation and neuron differentiation of MSCs. MiR124 was shown greatly promoting MSCs migration and neuronal differentiation. MiR21-5p could significantly enhance the proliferation and neuronal differentiation ability of MSCs. MiR124 and miR21-5p synergistically promote differentiation of MSCs into neurons. Collectively, miR124 and miR21-5p can functionally regulate cell migration, proliferation and neuronal differentiation of MSCs. Therefore, miR124 and miR21-5p may be promising tools to improve transplantation efficiency for neural injury.

Cerebrovascular Blood Flow Design and Regulation; Vulnerability in Aging Brain

Nutrient delivery to the brain presents a unique challenge because the tissue functions as a computer system with in the order of 200,000 neurons/mm³. Penetrating arterioles bud from surface arteries of the brain and penetrate downward through the cortex. Capillary networks spread from penetrating arterioles through the surrounding tissue. Each penetrating arteriole forms a vascular unit, with little sharing of flow among vascular units (collateral flow). Unlike cells in other tissues, neurons have to be operationally isolated, interacting with other neurons through specific electrical connections. Neuronal activation typically involves only a few of the cells within a vascular unit, but the local increase in nutrient consumption is substantial. The metabolic response to activation is transmitted to the feeding arteriole through the endothelium of neighboring capillaries and alters calcium permeability of smooth muscle in the wall resulting in modulation of flow through the entire vascular unit. Many age and trauma related brain pathologies can be traced to vascular malfunction. This includes: 1. Physical damage such as in traumatic injury with imposed shear stress as soft tissue moves relative to the skull. Lack of collateral flow among vascular units results in death of the cells in that vascular unit and loss of brain tissue. 2. Age dependent changes lead to progressive increase in vascular resistance and decrease in tissue levels of oxygen and glucose. Chronic hypoxia/hypoglycemia compromises tissue energy metabolism and related regulatory processes. This alters stem cell proliferation and differentiation, undermines vascular integrity, and suppresses critical repair mechanisms such as oligodendrocyte generation and maturation. Reduced structural integrity results in local regions of acute hypoxia and microbleeds, while failure of oligodendrocytes to fully mature leads to poor axonal myelination and defective neuronal function. Understanding and treating age related pathologies, particularly in brain, requires better knowledge of why and how vasculature changes with age. That knowledge will, hopefully, make possible drugs/methods for protecting vascular function, substantially alleviating the negative health and cognitive deficits associated with growing old.

17β-Estradiol Protects Neural Stem/Progenitor Cells Against Ketamine-Induced Injury Through Estrogen Receptor β Pathway

Ketamine inhibits neural stem/progenitor cell (NSPC) proliferation and disrupts normal neurogenesis in the developing brain. 17β-Estradiol alleviates neurogenesis damage and enhances behavioral performance after ketamine administration. However, the receptor pathway of 17β-estradiol that protects NSPCs from ketamine-induced injury remains unknown. In the present study, we investigated the role of estrogen receptor α (ER-α) and estrogen receptor β (ER-β) in 17β-estradiol’s protection against ketamine-exposed NSPCs and explored its potential mechanism. The primary cultured NSPCs were identified by immunofluorescence and then treated with ketamine and varying doses of ER-α agonist 4,4′,4″-(4-propyl-[1H]-pyrazole-1,3,5-triyl) trisphenol (PPT) or ER-β agonist 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN) for 24 h. NSPC proliferation was analyzed by 5-bromo-2-deoxyuridine incorporation test. The expression of phosphorylated glycogen synthase kinase-3β (p-GSK-3β) was quantified by western blotting. It was found that treatment with different concentrations of PPT did not alter the inhibition of ketamine on NSPC proliferation. However, treatment with DPN attenuated the inhibition of ketamine on NSPC proliferation at 24 h after their exposure (P < 0.05). Furthermore, treatment with DPN increased p-GSK-3β expression in NSPCs exposed to ketamine. These findings indicated that ER-β mediates probably the protective effects of 17β-estradiol on ketamine-damaged NSPC proliferation and GSK-3β is involved in this process

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.

Hyperbaric oxygen toxicity in brain: A case of hyperoxia induced hypoglycemic brain syndrome

Hyperbaric oxygen exposure is a recent hazzard for higher animals that originated as humans began underwater construction, exploration, and sports. Exposure can lead to abnormal brain EEG, convulsions, and death, the time to onset of each stage of pathology decreasing with increase in oxygen pressure. We provide evidence that hyperoxia, through oxidative phosphorylation, increases the energy state ([ATP]/[ADP][Pi]) of cells critical to providing glucose to cells behind the blood brain barrier (BBB). Brain cells without an absolute dependence on glucose metabolism; i.e. those having sufficient ATP synthesis using lactate and glutamate as oxidizable substrates, are not themselves very adversely affected by hyperoxia. The increased energy state and decrease in free [AMP], however, suppress glucose transport through the blood brain barrier (BBB) and into cells behind the BBB. Glucose has to pass in sequence through three steps of transport by facilitated diffusion and transporter activity for each step is regulated in part by AMP dependent protein kinase. The physiological role of this regulation is to increase glucose transport in response to hypoxia and/or systemic hypoglycemia. Hyperoxia, however, through unphysiological decrease in free [AMP] suppresses 1) glucose transport through the BBB (endothelial GLUT1 transporters) into cerebrospinal fluid (CSF); 2) glucose transport from CSF into cells behind the BBB (GLUT3 transporters) and (GLUT4 transporters). Cumulative suppression of glucose transport results in local regions of hypoglycemia and induces hypoglycemic failure. It is suggested that failure is initiated at axons and synapses with insufficient mitochondria to meet their energy requirements.

FGF-17 from Hypoxic Human Wharton's Jelly-Derived Mesenchymal Stem Cells Is Responsible for Maintenance of Cell Proliferation at Late Passages

Background and Objectives

Although it is well known that hypoxic culture conditions enhance proliferation of human mesenchymal stem cells, the exact mechanism is not fully understood. In this study, we investigated the effect of fibroblast growth factor (FGF)-17 from hypoxic human Wharton's Jelly-derived mesenchymal stem cells (hWJ-MSCs) on cell proliferation at late passages.

Methods and Results

hWJ-MSCs were cultured in α-MEM medium supplemented with 10% fetal bovine serum (FBS) in normoxic (21% O₂) and hypoxic (1% O₂) conditions. Protein antibody array was performed to analyze secretory proteins in conditioned medium from normoxic and hypoxic hWJ-MSCs at passage 10. Cell proliferation of hypoxic hWJ-MSCs was increased compared with normoxic hWJ-MSCs from passage 7 to 10, and expression of secretory FGF-17 was highly increased in conditioned medium from hypoxic hWJ-MSCs at passage 10. Knockdown of FGF-17 in hypoxic and normoxic hWJ-MSCs decreased cell proliferation, whereas treatment of hypoxic and normoxic hWJ-MSCs with recombinant protein FGF-17 increased their proliferation. Signal transduction of FGF-17 in hypoxic and normoxic hWJ-MSCs involved the ERK1/2 pathway. Cell phenotypes were not changed under either condition. Differentiation-related genes adiponectin, Runx2, and chondroadherin were downregulated in normoxic hWJ-MSCs treated with rFGF-17, and upregulated by siFGF-17. Expression of alkaline phosphatase (ALP), Runx2, and chondroadherin was upregulated in hypoxic hWJ-MSCs, and this effect was rescued by transfection with siFGF-17. Only chondroadherin was upregulated in hypoxic hWJ-MSCs with rFGF-17.

Conclusions

In hypoxic culture conditions, FGF-17 from hypoxic hWJ-MSCs contributes to the maintenance of high proliferation at late passages through the ERK1/2 pathway.

RETRACTED: Gastrodin protects rat cardiomyocytes H9c2 from hypoxia-induced injury by up-regulation of microRNA-21

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief and Author. The journal contacted the authors for their response to the following remark from Dr Elisabeth Bik regarding this paper: ‘This paper belongs to a set of over 400 papers (as per February 2020) that share very similar Western blots with tadpole-like shaped bands, the same background pattern, and striking similarities in title structures, paper layout, bar graph design, and - in a subset - flow cytometry panels. Despite these similarities, these papers are authored by researchers from different departments and institutes, with almost no overlap in authors’. The authors failed to respond to this directly but instead requested the journal to retract the paper on the basis that the data were not represented accurately and new results have shown inconsistency with what has been reported in this paper. The authors apologise for any misconceptions that this paper may have resulted in.

MicroRNA-21 attenuates oxygen and glucose deprivation induced apoptotic death in human neural stem cells with inhibition of JNK and p38 MAPK signaling

Neural stem cells (NSCs) persist in the mammalian brain throughout life and protect against hypoxia-ischemia injury. NSCs are being increasingly recognized as a novel therapeutic target for various neurological disorders. Previous research indicates that miR-21 attenuates hypoxia-ischemia induced apoptotic death in various cell types. However, whether miR-21 plays a role in this protective effect mediated by NSCs is unknown, particularly in human NSCs (hNSCs). The present study investigated whether miR-21 could prevent hNSC injury induced by oxygen and glucose deprivation (OGD). Upon challenge with OGD treatment, loss of cell viability was observed in cultured hNSCs, as shown by CCK-8 assay. Moreover, quantitative real-time PCR (qRT-PCR) analysis indicated that expression of miR-21 increased in a time-dependent manner. TUNEL staining and Western blotting analysis showed that overexpression of miR-21 inhibited excessive hNSCs death induced by OGD treatment. Accordingly, knock down of miR-21 attenuated the neuroprotective effect observed in response to OGD treatment. Furthermore, JNK and p38 MAPKs inhibition was observed after overexpression of miR-21, and knock down of miR-21 had the opposite effect. We suggest that miR-21 prevents OGD-induced hNSCs death and apoptotic-associated protein activities through inhibiting JNK and p38 pathways in cultured hNSCs. Our findings may help to develop strategies for enhancing resident and transplanted NSCs survival after hypoxia-ischemic brain damage.