miR-21 increases c-kit+ cardiac stem cell proliferation in vitro through PTEN/PI3K/Akt signaling

Effect of miR-21 in mesenchymal stem cells-derived extracellular vesicles behavior

BACKGROUND

A challenging new branch of research related to aging-associated diseases is the identification of miRNAs capable of modulating the senescence-associated secretory phenotype (SASP) which characterizes senescent cells and contributes to driving inflammation.

METHODS

Mesenchymal stem cells (MSC) from human umbilical cord stroma were stable modified using lentivirus transduction to inhibit miR-21-5p and shotgun proteomic analysis was performed in the MSC-derived extracellular vesicles (EV) to check the effect of miR-21 inhibition in their protein cargo. Besides, we studied the paracrine effect of those modified extracellular vesicles and also their effect on SASP.

RESULTS

Syndecan-1 (SDC1) was the most decreased protein in MSC-miR21--derived EV, and it was involved in inflammation and EV production. MSC-miR21--derived EV were found to produce a statistically significant inhibitory effect on SASP and inflammaging markers expression in receptor cells, and in the opposite way, these receptor cells increased their SASP and inflammaging expression statistically significantly when treated with MSC-miR-21+-derived EV.

CONCLUSION

This work demonstrates the importance of miR-21 in inflammaging and its role in SASP through SDC1.

MicroRNA-34a: A Novel Therapeutic Target in Fibrosis

Fibrosis can occur in many organs, and severe cases leading to organ failure and death. No specific treatment for fibrosis so far. In recent years, microRNA-34a (miR-34a) has been found to play a role in fibrotic diseases. MiR-34a is involved in the apoptosis, autophagy and cellular senescence, also regulates TGF-β1/Smad signal pathway, and negatively regulates the expression of multiple target genes to affect the deposition of extracellular matrix and regulate the process of fibrosis. Some studies have explored the efficacy of miR-34a-targeted therapies for fibrotic diseases. Therefore, miR-34a has specific potential for the treatment of fibrosis. This article reviews the important roles of miR-34a in fibrosis and provides the possibility for miR-34a as a novel therapeutic target in fibrosis.

hPMSCs-Derived Exosomal miRNA-21 Protects Against Aging-Related Oxidative Damage of CD4+ T Cells by Targeting the PTEN/PI3K-Nrf2 Axis

Mesenchymal stem cells (MSCs)-derived exosomes were considered a novel therapeutic approach in many aging-related diseases. This study aimed to clarify the protective effects of human placenta MSCs-derived exosomes (hPMSC-Exo) in aging-related CD4⁺ T cell senescence and identified the underlying mechanisms using a D-gal induced mouse aging model. Senescent T cells were detected SA-β-gal stain. The degree of DNA damage was evaluated by detecting the level of 8-OH-dG. The superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) activities were measured. The expression of aging-related proteins and senescence-associated secretory phenotype (SASP) were detected by Western blot and RT-PCR. We found that hPMSC-Exo treatment markedly decreased oxidative stress damage (ROS and 8-OH-dG), SA-β-gal positive cell number, aging-related protein expression (p53 and γ-H2AX), and SASP expression (IL-6 and OPN) in senescent CD4⁺ T cells. Additionally, hPMSC-Exo containing miR-21 effectively downregulated the expression of PTEN, increased p-PI3K and p-AKT expression, and Nrf2 nuclear translocation and the expression of downstream target genes (NQO1 and HO-1) in senescent CD4⁺ T cells. Furthermore, in vitro studies uncovered that hPMSC-Exo attenuated CD4⁺ T cell senescence by improving the PTEN/PI3K-Nrf2 axis by using the PTEN inhibitor bpV (HOpic). We also validated that PTEN was a target of miR-21 by using a luciferase reporter assay. Collectively, the obtained results suggested that hPMSC-Exo attenuates CD4⁺ T cells senescence via carrying miRNA-21 and activating PTEN/PI3K-Nrf2 axis mediated exogenous antioxidant defenses.

Quercetin antagonizes imidacloprid-induced mitochondrial apoptosis through PTEN/PI3K/AKT in grass carp hepatocytes

Imidacloprid (IMI) is widely used in agriculture, and is toxic to non-target aquatic species. Quercetin (Que) is a flavonoid abundant in fruits and vegetables that exhibits anti-oxidant activity. In the present study, we treated grass carp hepatocytes (L8824) with 0.1 μM Que and/or 1 mM IMI for 24 h to explore the effect of Que on IMI-induced mitochondrial apoptosis. We found that IMI exposure enhanced reactive oxygen species (ROS) generation, inhibiting the activities of SOD, CAT and T-AOC, exacerbating the accumulation of MDA, aggravating the expression of mitochondrial apoptosis pathway (Cyt-C, BAX, Caspase9 and Caspase3) related genes and decreased the expression of anti-apoptosis gene B-cell lymphoma-2 (Bcl-2). In addition, Que and IMI co-treatment significantly restored the activity of anti-oxidant enzymes, downregulated ROS level and apoptosis rate, thereby alleviating the depletion of mitochondrial membrane potential (ΔΨm) and the expression of cytochrome c (Cyt-C), Bcl-2-associated X (BAX), and cysteinyl aspartate specific proteinases (Caspase9 and 3), increasing the Bcl-2 level. Furthermore, we elucidated that Que could inhibit the expression of phosphatase and tensin homolog deleted on chromosome 10 (PTEN), thus activating phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) pathway to attenuate IMI-induced apoptosis. Molecular docking provides assertive evidence for the interaction between Que ligand and PTEN receptor. Consequently, these results indicate that Que effectively antagonizes IMI-induced mitochondrial apoptosis in grass carp hepatocytes via regulating the PTEN/PI3K/AKT pathway.

MicroRNAs and exosomes: Cardiac stem cells in heart diseases

Treating cardiovascular diseases with cardiac stem cells (CSCs) is a valid treatment among various stem cell-based therapies. With supplying the physiological need for cardiovascular cells as their main function, under pathological circumstances, CSCs can also reproduce the myocardial cells. Although studies have identified many of CSCs' functions, our knowledge of molecular pathways that regulate these functions is not complete enough. Either physiological or pathological studies have shown, stem cells proliferation and differentiation could be regulated by microRNAs (miRNAs). How miRNAs regulate CSC behavior is an interesting area of research that can help us study and control the function of these cells in vitro; an achievement that may be beneficial for patients with cardiovascular diseases. The secretome of stem and progenitor cells has been studied and it has been determined that exosomes are the main source of their secretion which are very small vesicles at the nanoscale and originate from endosomes, which are secreted into the extracellular space and act as key signaling organelles in intercellular communication. Mesenchymal stem cells, cardiac-derived progenitor cells, embryonic stem cells, induced pluripotent stem cells (iPSCs), and iPSC-derived cardiomyocytes release exosomes that have been shown to have cardioprotective, immunomodulatory, and reparative effects. Herein, we summarize the regulation roles of miRNAs and exosomes in cardiac stem cells.

miR-21 in Human Cardiomyopathies

miR-21 is a 22-nucleotide long microRNA that matches target mRNAs in a complementary base pairing fashion and regulates gene expression by repressing or degrading target mRNAs. miR-21 is involved in various cardiomyopathies, including heart failure, dilated cardiomyopathy, myocardial infarction, and diabetic cardiomyopathy. Expression levels of miR-21 notably change in both heart and circulation and provide cardiac protection after heart injury. In the meantime, miR-21 also tightly links to cardiac dysfunctions such as cardiac hypertrophy and fibrosis. This review focuses on the miR-21 expression pattern and its functions in diseased-heart and further discusses the feasibility of miR-21 as a biomarker and therapeutic target in cardiomyopathies.

Effect of miRNA-136-targeted regulation of FGFR1 on proliferation and apoptosis of triple-negative breast cancer cells

PURPOSE

This study was designed to investigate the effect of micro RNA-targeted regulation of FGFR1 on the proliferation and apoptosis of triple-negative breast cancer (TNBC) cells.

METHODS

TNBC (MAD-MB-231), three types of breast cancer (MCF10A, MCF7, ZR751) cell lines, and normal breast tissue cell lines were extracted. Real-time PCR was used to detect the expression of miRNA-136 in different types of breast cells. The MAD-MB-231 cell lines were transfected with miRNA-136 mimic by lipofection. The effects of miRNA-136 on FGFR1 expression and apoptosis rate of MAD-MB-231 cell lines were determined using western blotting.

RESULTS

miRNA-136 expression in TNBC cells was lower than that of controls, and was negatively correlated with TNM staging. miRNA-136 expression in MCF10A, MCF7, ZR751, and MAD-MB-231 cell lines was gradually decreased, and MCF10A expression in the other three cell lines was significantly higher than that of MAD-MB-231 cell line (P<0.05). Transfection with miRNA-136 significantly reduced the proliferation rate of MAD-MB-231, and a higher concentration and longer duration exhibited a more pronounced inhibitory effect on proliferation (P<0.05). Transfection with miRNA-136 significantly reduced FGFR1 expression in the MAD-MB-231 cell lines, without significantly affecting apoptosis.

CONCLUSION

miRNA-136 shows a very low expression level in TNBC cells. Transfection with miRNA-136 can significantly inhibit the proliferation of TNBC cells by external transfection, and has little effect on cell apoptosis. This may be related to miRNA-mediated changes in FGFR1 protein expression.

Hyperoside prevents sepsis-associated cardiac dysfunction through regulating cardiomyocyte viability and inflammation via inhibiting miR-21

BACKGROUND

Sepsis-associated cardiac dysfunction results in increased mortality. Hyperoside (Hyp) is a flavonoid, showing significant anti-inflammatory effects. However, its pharmacological effects on sepsis-induced cardiac dysfunction remain unknown. In this study, we attempted to explore whether Hyp could prevent cardiac dysfunction and its underlying mechanisms.

METHODS

We established a mice mode of sepsis by cecal ligation and puncture (CLP) treatment, and constructed a cell model of myocardial injury by lipopolysaccharide (LPS) stimulation. The cardiac function indicators and the inflammatory cytokine levels were measured. Effect of Hyp on cardiomyocyte viability was evaluated using MTT assay. The expression and functional role of microRNA-21 (miR-21), a documented molecule that regulated by Hyp, was evaluated in the constructed models, and the potential targets of miR-21 were predicted.

RESULTS

Hyp alleviated the impaired cardiac function and stimulated inflammation caused by CLP in the in vivo sepsis model, and alleviated the LPS-induced decrease in cell viability and increase in inflammation of cardiomyocytes. Additionally, Hyp significantly inhibited the expression of miR-21 in LPS-induced cardiomyocytes, and the increased cell viability and decreased inflammation caused by Hyp in the in vitro model could be reversed by miR-21 overexpression. In animal model of sepsis, the protective influence of Hyp against sepsis-induced cardiac dysfunction was attenuated by miR-21 upregulation.

CONCLUSION

Our findings demonstrated that Hyp may serve as a promising natural drug for the treatment of sepsis-associated cardiac dysfunction, and its protective role may exerted through regulating cardiomyocyte viability and inflammation by suppressing miR-21.

Double-Targeted Knockdown of miR-21 and CXCR4 Inhibits Malignant Glioma Progression by Suppression of the PI3K/AKT and Raf/MEK/ERK Pathways

Currently, miR-21 and CXCR4 are being extensively investigated as two key regulators in glioma malignancy. In this study, we investigated the combined effects of these two factors on glioma progression. Herein, the expression of miR-21 and CXCR4 was increased in tumor tissues and cell lines. Inhibition of miR-21, CXCR4, and miR-21 and CXCR4 together all reduced the migration, invasiveness, proliferation, and enhanced apoptosis in glioma cells, as well as reduced tumor volume and mass in xenograft model. The inhibition effect was strongest in double-targeted knockdown of miR-21 and CXCR4 group, whose downstream pathways involved in AKT axis and ERK axis activation. In conclusion, our findings reported that double-targeted knockdown of miR-21 and CXCR4 could more effectively inhibit the proliferation, migration, invasion, and growth of transplanted tumor and promote cell apoptosis, which were involved in the PI3K/AKT and Raf/MEK/ERK signaling pathways.

CiRS-126 inhibits proliferation of ovarian granulosa cells through targeting the miR-21-PDCD4-ROS axis in a polycystic ovarian syndrome model

Polycystic ovarian syndrome (PCOS) is considered to be one of the most prevalent endocrine disorders affecting women of reproductive age. CiRS-126, an innovative circular microRNA, has previously been proven to be a promising miR-21 sponge. However, a proper understanding of the impact of ciRS-126 on PCOS is needed. Circular RNA (CiRS) profiles were initially evaluated in ovarian cortex samples obtained from 18 women with PCOS as well from 9 women without PCOS. Insulin-induced ovarian granulosa cells isolated from mice were utilized for the functional study. CiRS microarray analysis and quantitative real-time PCR indicated that ciRs-126 expression was downregulated while miR-21 expression was upregulated in PCOS samples and insulin-induced granulosa cells as compared with non-PCOS samples and non-insulin-induced granulosa cells. Furthermore, ectopic overexpression of ciRS-126 was associated with a reduction in proliferation and increased apoptosis in insulin-treated granulosa cells. Meanwhile, bioinformatic prediction and the results of the dual-luciferase reporter assay indicated the presence of consecutive binding in the ciRS-126-miR-21-programmed cell death protein 4 (PDCD4) axis. Moreover, overexpression of miR-21 blocked ciRS-126 repression of proliferation and triggered the death of insulin-induced granulosa cells. Excessive PDCD4 expression counteracted the influence of miR-21 on cell death and proliferation. The data indicated that PDCD4 played a regulatory role in ROS generation, which is reportedly involved in apoptosis. Therefore, ciRS-126 reduction in PCOS granulosa cells targeted the miR-21-PDCD4 axis to reduce proliferation and promote apoptosis. CiRS-126 shows potential as a promising predictor of clinical outcome as well as a therapeutic target in PCOS.

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.

An overview of the myocardial regeneration potential of cardiac c-Kit+ progenitor cells via PI3K and MAPK signaling pathways

In recent years, several studies have investigated cell transplantation as an innovative strategy to restore cardiac function following heart failure. Previous studies have also shown cardiac progenitor cells as suitable candidates for cardiac cell therapy compared with other stem cells. Cellular kit (c-kit) plays an important role in the survival and migration of cardiac progenitor cells. Like other types of cells, in the heart, cellular responses to various stimuli are mediated via coordinated pathways. Activation of c-kit⁺ cells leads to subsequent activation of several downstream mediators such as PI3K and the MAPK pathways. This review aims to outline current research findings on the role of PI3K/AKT and the MAPK pathways in myocardial regeneration potential of c-kit⁺.

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.

Curcumol inhibits colorectal cancer proliferation by targeting miR-21 and modulated PTEN/PI3K/Akt pathways

AIMS

The purpose of this study was to demonstrate how curcumol affected the expression of miR-21 and whether its effects on miR-21 was associated with the activation of PTEN/PI3K/Akt pathways in CRC cells.

MAIN METHODS

MTT and xenograft assay were used to examine how curcumol inhibits colorectal cancer (CRC) cells' growth. Q-PCR and western blot analysis were employed to test the role of miR-21 in the inhibition of curcumol on proliferation and PTEN/PI3K/Akt pathways of CRC cells.

KEY FINDINGS

We found that curcumol effectively inhibited CRC cells from proliferating via the PTEN/PI3K/Akt pathways and reduced expression of miR-21 both in vitro and in vivo. miR-21 mimics were found to decrease the protein level of PTEN and increase the expression of PI3K, phospho-Akt (p-Akt) and NF-κB, while miR-21 sponge (miR-21-SP) enhanced the expression of PTEN and reduced the activity of PI3K, Akt and NF-κB. Furthermore, miR-21-SP strengthened the role of curcumol in up-regulating PTEN and inhibiting PI3K/Akt pathways, but miR-21 reversed the effect of curcumol on the PTEN/PI3K/Akt pathways.

SIGNIFICANCE

Our research demonstrated that curcumol reduced the proliferation of CRC cells through PTEN/PI3K/Akt by targeting miR-21 and miR-21 could be a target molecule of curcumol for CRC treatment.

Angiotensin II receptor blocker valsartan ameliorates cardiac fibrosis partly by inhibiting miR-21 expression in diabetic nephropathy mice

Cardiac fibrosis with diabetic nephropathy (DN) is one of major diabetic complications. miR-21 and MMP-9 were closely associated with fibrosis diseases. Angiotensin II receptor blockers (ARB) have cardioprotective effects. However, it remains unclear whether miR-21 was involved in the mechanism of cardiac fibrosis with DN by target MMP-9 and ARB ameliorates cardiac fibrosis partly by inhibiting miR-21 expression. In this study, In Situ Hybridization(ISH), RT-PCR, cell transfection, western blotting and laser confocal telescope were used, respectively. ISH showed that miR-21, concentrated in cytoplasmic foci in the proximity of the nucleus, was mainly localized in cardiac fibroblasts and at relatively low levels in cardiomyocytes within cardiac tissue with DN. RT-PCR showed that miR-21 expression was significantly enhanced in cardiac tissue with DN, accompanied by the increase of col-IV, FN, CVF, PVCA, LVMI, HWI and NT-pro-BNP (p < 0.05). Bioinformatics analysis and Luciferase reporter gene assays showed that MMP-9 was a validated target of miR-21. Furthermore, cell transfection experiments showed that miR-21 overexpression directly decreased MMP-9 expression. Interestingly, miR-21 levels in cardiac tissue was positively correlated with ACR (r = -0.870, P = 0.003), whereas, uncorrelated with SBP, HbA1C and T-Cho (p > 0.05). More importantly, ARB can significantly decrease miR-21 expression in cardiac tissue, cardiac fibroblasts and serum. Overall, our results suggested that miR-21 may contribute to the pathogenesis of cardiac fibrosis with DN by target MMP-9, and that miR-21 may be a new possible therapeutic target for ARB in cardiac fibrosis with DN.

Hydrogen sulfide ameliorates rat myocardial fibrosis induced by thyroxine through PI3K/AKT signaling pathway

This study aims to investigate the role and regulatory mechanism of the Hydrogen sulfide (H₂S) in amelioration of rat myocardial fibrosis induced by thyroxine through interfering the autophagy via regulating the activity of PI3K/AKT1 signaling pathway and the expression of relative miRNA. 40 adult male SD rats were randomly divided into 4 groups (n = 10): the control group, the thyroxine model group (TH group), the model group with H₂S intervention (TH + H₂S group) and the normal group with H₂S intervention (H₂S group). Pathological changes were observed via H&E staining and Masson staining, Expressions of MMPs/TIMPs, PI3K/AKT, autophagy-related proteins in myocardial tissues were detected via Western blotting, and the expressions of miR-21, miR-34a, miR-214 and miR-221 were detected via RT-qPCR. Compared with the control group, in the TH group, myocardial fibrosis was more significant, the expressions of proteins in PI3K/AKT and autophagy-related proteins were significantly decreased, as well as the expression of miR-221; while the expressions of miR-21, miR-34a and miR-214 were significantly elevated. By contrast, all above-mentioned changes were obviously reversed with H₂S treatment, which demonstrated the positive function of H₂S in amelioration of rat myocardial fibrosis induced by thyroxine. The mechanism of such amelioration may be correlated with autophagy activated by the upregulation of expression of PI3K/AKT signaling pathway and downregulation of expressions of miR-21, miR-34a and miR-214.

microRNAs and cardiac stem cells in heart development and disease

Cumulative evidence has proven that proliferation, differentiation and migration of cardiac stem cells (CSCs) dominate early heart development and contribute to the later occurrence of heart disease. Among other mechanisms, microRNAs work as the 'fine-tuning' to modulate the levels of target genes in a specific cell type. The distinct microRNA signatures in CSCs reveal the stages and functions of CSCs. The focus of this review is to summarize recent knowledge advances in CSC proliferation, differentiation and migration and to discuss how microRNAs regulate these processes during heart development and in heart disease. Better understanding of microRNA regulation on CSCs under different situations will enable the unveiling of the mechanisms of heart disease and open new avenues in the therapeutic potentials of microRNA modulation to treat heart disease.

Beyond cardiomyocyte loss: Role of Notch in cardiac aging

The knowledge of the cellular events occurring in the aging heart has dramatically expanded in the last decade and is expected to further grow in years to come. It is now clear that impaired function and loss of cardiomyocytes are major features of cardiac aging, but other events are likewise important. In particular, accumulating experimental evidence highlights the importance of fibroblast and cardiac progenitor cell (CPC) dysfunction. The Notch pathway regulates cardiomyocyte, fibroblast, and CPC activity and, thus, may be critically involved in heart disease associated with advanced age, especially heart failure. In a translational perspective, thorough investigation of the Notch system in the aging myocardium may lead to the identification of molecular targets for novel therapies for age-related cardiac disease.

Bone marrow mesenchymal stem cell-derived exosomal miR-21 protects C-kit+ cardiac stem cells from oxidative injury through the PTEN/PI3K/Akt axis

Stem cell (SC) therapy for ischemic cardiomyopathy is hampered by poor survival of the implanted cells. Recently, SC-derived exosomes have been shown to facilitate cell proliferation and survival by transporting various proteins and non-coding RNAs (such as microRNAs and lncRNAs). In this study, miR-21 was highly enriched in exosomes derived from bone marrow mesenchymal stem cells (MSCs). Interestingly, exosomes collected from hydrogen peroxide (H₂O₂)-treated MSCs (H-Exo) contained higher levels of miR-21 than exosomes released from MSCs under normal conditions (N-Exo). The pre-treatment of C-kit⁺ cardiac stem cells (CSCs) with H-Exos resulted in significantly increased levels of miR-21 and phosphor-Akt (pAkt) and decreased levels of PTEN, which is a known target of miR-21. AnnexinV-FITC/PI analysis further demonstrated that the degree of oxidative stress-induced apoptosis was markedly lower in H-Exo-treated C-kit⁺ CSCs than that in N-Exo-treated cells. These protective effects could be blocked by both a miR-21 inhibitor and the PI3K/Akt inhibitor LY294002. Therefore, exosomal miR-21 derived from H₂O₂-treated MSCs could be transported to C-kit⁺ cardiac stem cells to functionally inhibit PTEN expression, thereby activating PI3K/AKT signaling and leading to protection against oxidative stress-triggered cell death. Thus, exosomes derived from MSCs could be used as a new therapeutic vehicle to facilitate C-kit⁺ CSC therapies in the ischemic myocardium.

The microRNA miR-21 conditions the brain to protect against ischemic and traumatic injuries

Ischemic and traumatic injuries to CNS remain leading causes of death and disability worldwide, despite decades of research into risk factors, therapies, and preventative measures. Recent studies showed that CNS injuries significantly alter the cerebral microRNAome that impact the secondary brain damage as well as plasticity and recovery. Many microRNA based therapies are currently in various clinical trials for different pathologic conditions indicating their therapeutic potential. In the present review, we discuss the role of miR-21 in acute CNS injuries which is currently thought to be a potent neuroprotective microRNA. We emphasize on the potential of miR-21 in promoting cell and tissue survival and preventing inflammation and apoptosis. We also discussed the role of miR-21 in conditioning the brain to promote ischemic tolerance. Finally, we discussed some of the challenges and difficulties to develop miR-21 as a neuroprotective therapy in humans.

Endothelial and cardiac progenitor cells for cardiovascular repair: A controversial paradigm in cell therapy

Stem cells have the potential to differentiate into cardiovascular cell lineages and to stimulate tissue regeneration in a paracrine/autocrine manner; thus, they have been extensively studied as candidate cell sources for cardiovascular regeneration. Several preclinical and clinical studies addressing the therapeutic potential of endothelial progenitor cells (EPCs) and cardiac progenitor cells (CPCs) in cardiovascular diseases have been performed. For instance, autologous EPC transplantation and EPC mobilization through pharmacological agents contributed to vascular repair and neovascularization in different animal models of limb ischemia and myocardial infarction. Also, CPC administration and in situ stimulation of resident CPCs have been shown to improve myocardial survival and function in experimental models of ischemic heart disease. However, clinical studies using EPC- and CPC-based therapeutic approaches have produced mixed results. In this regard, intracoronary, intra-myocardial or intramuscular injection of either bone marrow-derived or peripheral blood progenitor cells has improved pathological features of tissue ischemia in humans, despite modest or no clinical benefit has been observed in most cases. Also, the intriguing scientific background surrounding the potential clinical applications of EPC capture stenting is still waiting for a confirmatory proof. Moreover, clinical findings on the efficacy of CPC-based cell therapy in heart diseases are still very preliminary and based on small-size studies. Despite promising evidence, widespread clinical application of both EPCs and CPCs remains delayed due to several unresolved issues. The present review provides a summary of the different applications of EPCs and CPCs for cardiovascular cell therapy and underlies their advantages and limitations.