myocardial infarction ( mi ) remains a leading cause of morbidity and mortality , resulting in 12.8% of deaths worldwide ( 1 , 2 ) . many therapeutic options , ranging from pharmaceutical therapeutics to mechanical procedures , are available for acute myocardial infarction ( 3 ) . reactive oxygen species ( ros ) play an important role in the pathogenesis of cardiovascular diseases . many studies have reported an association between such diseases and oxidative damage to cardiac cells . this association might be caused by an increased rate of free radical formation and/or weakening of the antioxidant defense system ( 4,5 ) . when the antioxidant defense system does not fully neutralize the effects of ros , ros can react with various cellular components , including phospholipids and proteins , resulting in lipid peroxidation and the oxidation of thiol groups . these oxidation reactions impair the normal functions of cell membranes and various cellular proteins , resulting in cardiac injury ( due to inflammation , apoptosis , and cell death ) ( 68 ) . cellular cardiomyoplasty is a new potential therapeutic approach that uses exogenous cells to repair regions of damaged myocardium . improved heart function following the transplantation of mesenchymal stem cells ( mscs ) has been reported in animal models of acute mi as well as in clinical studies on patients with heart failure ( 9 ) . various favorable characteristics , such as multilineage differentiation potential , ability to evade the host immune system , immunomodulatory capacities , and ease of proliferation in vitro , make mscs particularly attractive for cell therapy ( 10 ) . it has been well established that msc infusion improves the function of infarcted myocardium ( 11 ) . several mechanisms have been proposed to explain the ability of mscs to revive ischemic tissues . these mechanisms include the following : 1 ) secretion of antioxidant chemicals and free radical scavengers at the site of ischemia , 2 ) secretion of multiple angiogenic growth factors ( e.g. , vascular endothelial growth factor ( vegf ) and hepatocyte growth factor ( hgf ) ) with the potential to induce endothelial growth , migration , and tube formation , and 3 ) differentiation of transplanted mscs into myocytes , smooth muscle cells , and endothelial cells ( 12 ) . despite the several advantages of mscs , they have not shown satisfactory outcomes in many investigations , mostly due to their poor survival rate after transplantation ( 1317 ) . in fact , more than 99% of transplanted mscs die within one day after transplantation , there are no well - defined reasons for this low survival rate . however , it is worth noting that , during the isolation of mscs from their natural niche , they are inevitably exposed to harmful conditions , such as serum deprivation , hypoxia , and oxidative stress ( 18 ) . however , due to radiotherapy , chemotherapy , inflammation , and expression of pro - apoptotic factors , the microenvironment of the damaged tissues of recipients is not favorable for the survival of transplanted mscs ( 19 ) . hence , to develop an effective therapeutic modality , it is necessary to strengthen mscs so they can withstand such stresses ( 20 ) . it seems that higher survival rates of mscs can improve infarcted tissues through the secretion of protective factors and/or differentiation of the mscs . novel strategies are being developed to improve the biological and functional properties of mscs , such as preparation of the cells in special bioscaffolds ( 21 ) , preconditioning of the cells in cultures ( 14 , 15 ) , and genetic transformation ( 10 ) . nuclear factor e2-related factor 2 ( nrf2 ) is a potent transcription factor that is critical for the protection of cells against oxidative stresses . activation of nrf2 as a redox - sensor under stress conditions up - regulates the transcription of phase ii detoxification enzymes and antioxidant proteins , such as nad ( p)h : quinone oxidoreductase ( nqo1 ) , glutathione s - transferases ( gsts ) , glutamate - cysteine ligase , heme oxygenase-1(ho-1 ) , thioredoxin , and ferritin ( 22 , 23 ) . up - regulation of these factors in transplanted cells protects the cells against the ros produced in mi tissue . we recently showed that adenoviral - mediated nrf2 over - expression in mscs reduces oxidative stress - induced apoptosis and cytotoxicity . also , we showed that over - expression of nrf2 had no deleterious effect on the differentiation capability of mscs . we hypothesized that over - expression of nrf2 in mscs ( nrf2-mscs ) , can effectively improve the efficiency of the transplantation of mscs , thereby enhancing cellular cardiomyoplasty . nrf2 over - expression can protect mscs against oxidative stresses encountered in the microenvironment of infarcted tissue . activation of the nrf2 signaling pathway is an important mechanism for protecting cells against oxidative stresses ( 24 ) . under non - stimulated conditions , nrf2 is retained in cytoplasm via interaction with the anchor protein , kelch - like ech - associated protein-1 ( keap1 ) , where it is maintained at a very low level by the keap1-dependent ubiquitination and proteasomal degradation systems ( 2528 ) . this interaction sequesters most of the nrf2 molecules in the cytoskeleton and keeps them away from the nucleus . the cysteine - rich surface of keap1 is oxidized in cases of oxidative and nitrosative stresses . this apparently produces a conformational change in keap1 , resulting in dissociation of nrf2 from keap1 . then , the released nrf2 is translocated to the nucleus , heterodimerizes with small maf proteins , and then binds to the antioxidant response element ( are ) , a common regulatory element found in the 5-flanking regions of the antioxidant and detoxification enzymes ( fig . 1 ) ( 2932 ) . further activation of nrf2 is mediated through phosphorylation of nrf2 by mitogen - activated protein kinases ( mapks ) , protein kinase c ( atypical isoform ) , and phosphoinositol-3-kinase ( pi3k ) . nrf2 effector genes that bear antioxidant response elements include a majority of the antioxidant proteins ( e.g. , gcl , ho-1 , and thioredoxin ) and phase ii detoxifying enzymes ( e.g. , nqo1 and gsts ) ( 26 ) . theoretically , the survival rate of the mscs will increase in stressful , oxidative environment of the infarcted myocardium by over - expression of nrf2 , resulting in higher potential of the mscs to repair the ischemic tissue . as mentioned earlier , we previously showed that over - expression of nrf2 in mscs protects them against various stresses . in addition , these engineered cells produce higher levels of antioxidants , such as sod and ho-1 . also , the nrf2-mscs showed less apoptosis when exposed to oxidative stresses ( 10 ) . furthermore , over - expression of nrf2 probably confers some additional benefits to mscs after they are transplanted . it has been shown that nrf2 has a role in the formation of blood vessels through the induction of the expression of vegf and hif-1 target genes ( 33 ) . the progression of angiogenesis is highly advantageous in the treatment of ischemic myocardium ( 34 ) . we could find no study that had been performed to evaluate the effect of nrf2 over - expression on differentiation of mscs into myocytes , smooth muscle cells , and endothelial cells . because of the importance of nrf2 signaling in anti - oxidative pathways , various studies have focused on the activation of nrf2 for cardio - protection . they have shown that the application of various factors , such as carbon monoxide , red wine , fumarate , hydrogen sulfide , and acute exercise , mediates cardio - protection through promotion of antioxidant mechanisms by activation of the nrf2 antioxidant pathway ( 3540 ) . to evaluate these hypotheses , next , nrf2 must be over - expressed in the authenticated mscs , and it is suggested that this be performed with the adenoviral expression system for transient over - expression of nrf2 , as described in our previous study ( 10 ) . then , after the evaluation of the safety concerns related to thenrf2 over - expression in mscs has been conducted , the mscs must be transplanted to the infarcted myocardium of mi patients via intramyocardial injection . then , biochemical and histological analyses must be performed to evaluate the effects of nrf2 over - expression in mscs on cardiac function . myocardial infarction ( mi ) remains a leading cause of morbidity and mortality , resulting in 12.8% of deaths worldwide ( 1 , 2 ) . many therapeutic options , ranging from pharmaceutical therapeutics to mechanical procedures , are available for acute myocardial infarction ( 3 ) . reactive oxygen species ( ros ) play an important role in the pathogenesis of cardiovascular diseases . many studies have reported an association between such diseases and oxidative damage to cardiac cells . this association might be caused by an increased rate of free radical formation and/or weakening of the antioxidant defense system ( 4,5 ) . when the antioxidant defense system does not fully neutralize the effects of ros , ros can react with various cellular components , including phospholipids and proteins , resulting in lipid peroxidation and the oxidation of thiol groups . these oxidation reactions impair the normal functions of cell membranes and various cellular proteins , resulting in cardiac injury ( due to inflammation , apoptosis , and cell death ) ( 68 ) . cellular cardiomyoplasty is a new potential therapeutic approach that uses exogenous cells to repair regions of damaged myocardium . improved heart function following the transplantation of mesenchymal stem cells ( mscs ) has been reported in animal models of acute mi as well as in clinical studies on patients with heart failure ( 9 ) . various favorable characteristics , such as multilineage differentiation potential , ability to evade the host immune system , immunomodulatory capacities , and ease of proliferation in vitro , make mscs particularly attractive for cell therapy ( 10 ) . it has been well established that msc infusion improves the function of infarcted myocardium ( 11 ) . several mechanisms have been proposed to explain the ability of mscs to revive ischemic tissues . these mechanisms include the following : 1 ) secretion of antioxidant chemicals and free radical scavengers at the site of ischemia , 2 ) secretion of multiple angiogenic growth factors ( e.g. , vascular endothelial growth factor ( vegf ) and hepatocyte growth factor ( hgf ) ) with the potential to induce endothelial growth , migration , and tube formation , and 3 ) differentiation of transplanted mscs into myocytes , smooth muscle cells , and endothelial cells ( 12 ) . despite the several advantages of mscs , they have not shown satisfactory outcomes in many investigations , mostly due to their poor survival rate after transplantation ( 1317 ) . in fact , more than 99% of transplanted mscs die within one day after transplantation , there are no well - defined reasons for this low survival rate . however , it is worth noting that , during the isolation of mscs from their natural niche , they are inevitably exposed to harmful conditions , such as serum deprivation , hypoxia , and oxidative stress ( 18 ) . however , due to radiotherapy , chemotherapy , inflammation , and expression of pro - apoptotic factors , the microenvironment of the damaged tissues of recipients is not favorable for the survival of transplanted mscs ( 19 ) . hence , to develop an effective therapeutic modality , it is necessary to strengthen mscs so they can withstand such stresses ( 20 ) . it seems that higher survival rates of mscs can improve infarcted tissues through the secretion of protective factors and/or differentiation of the mscs . novel strategies are being developed to improve the biological and functional properties of mscs , such as preparation of the cells in special bioscaffolds ( 21 ) , preconditioning of the cells in cultures ( 14 , 15 ) , and genetic transformation ( 10 ) . nuclear factor e2-related factor 2 ( nrf2 ) is a potent transcription factor that is critical for the protection of cells against oxidative stresses . activation of nrf2 as a redox - sensor under stress conditions up - regulates the transcription of phase ii detoxification enzymes and antioxidant proteins , such as nad ( p)h : quinone oxidoreductase ( nqo1 ) , glutathione s - transferases ( gsts ) , glutamate - cysteine ligase , heme oxygenase-1(ho-1 ) , thioredoxin , and ferritin ( 22 , 23 ) . up - regulation of these factors in transplanted cells protects the cells against the ros produced in mi tissue . we recently showed that adenoviral - mediated nrf2 over - expression in mscs reduces oxidative stress - induced apoptosis and cytotoxicity . also , we showed that over - expression of nrf2 had no deleterious effect on the differentiation capability of mscs . we hypothesized that over - expression of nrf2 in mscs ( nrf2-mscs ) , can effectively improve the efficiency of the transplantation of mscs , thereby enhancing cellular cardiomyoplasty . nrf2 over - expression can protect mscs against oxidative stresses encountered in the microenvironment of infarcted tissue . activation of the nrf2 signaling pathway is an important mechanism for protecting cells against oxidative stresses ( 24 ) . under non - stimulated conditions , nrf2 is retained in cytoplasm via interaction with the anchor protein , kelch - like ech - associated protein-1 ( keap1 ) , where it is maintained at a very low level by the keap1-dependent ubiquitination and proteasomal degradation systems ( 2528 ) . this interaction sequesters most of the nrf2 molecules in the cytoskeleton and keeps them away from the nucleus . the cysteine - rich surface of keap1 is oxidized in cases of oxidative and nitrosative stresses . this apparently produces a conformational change in keap1 , resulting in dissociation of nrf2 from keap1 . then , the released nrf2 is translocated to the nucleus , heterodimerizes with small maf proteins , and then binds to the antioxidant response element ( are ) , a common regulatory element found in the 5-flanking regions of the antioxidant and detoxification enzymes ( fig . 1 ) ( 2932 ) . further activation of nrf2 is mediated through phosphorylation of nrf2 by mitogen - activated protein kinases ( mapks ) , protein kinase c ( atypical isoform ) , and phosphoinositol-3-kinase ( pi3k ) . nrf2 effector genes that bear antioxidant response elements include a majority of the antioxidant proteins ( e.g. , gcl , ho-1 , and thioredoxin ) and phase ii detoxifying enzymes ( e.g. , nqo1 and gsts ) ( 26 ) . theoretically , the survival rate of the mscs will increase in stressful , oxidative environment of the infarcted myocardium by over - expression of nrf2 , resulting in higher potential of the mscs to repair the ischemic tissue . as mentioned earlier , we previously showed that over - expression of nrf2 in mscs protects them against various stresses . in addition , these engineered cells produce higher levels of antioxidants , such as sod and ho-1 . also , the nrf2-mscs showed less apoptosis when exposed to oxidative stresses ( 10 ) . furthermore , over - expression of nrf2 probably confers some additional benefits to mscs after they are transplanted . it has been shown that nrf2 has a role in the formation of blood vessels through the induction of the expression of vegf and hif-1 target genes ( 33 ) . the progression of angiogenesis is highly advantageous in the treatment of ischemic myocardium ( 34 ) . we could find no study that had been performed to evaluate the effect of nrf2 over - expression on differentiation of mscs into myocytes , smooth muscle cells , and endothelial cells . because of the importance of nrf2 signaling in anti - oxidative pathways , various studies have focused on the activation of nrf2 for cardio - protection . they have shown that the application of various factors , such as carbon monoxide , red wine , fumarate , hydrogen sulfide , and acute exercise , mediates cardio - protection through promotion of antioxidant mechanisms by activation of the nrf2 antioxidant pathway ( 3540 ) . to evaluate these hypotheses , next , nrf2 must be over - expressed in the authenticated mscs , and it is suggested that this be performed with the adenoviral expression system for transient over - expression of nrf2 , as described in our previous study ( 10 ) . then , after the evaluation of the safety concerns related to thenrf2 over - expression in mscs has been conducted , the mscs must be transplanted to the infarcted myocardium of mi patients via intramyocardial injection . then , biochemical and histological analyses must be performed to evaluate the effects of nrf2 over - expression in mscs on cardiac function . it is expected that the over - expression of nrf2 in mscs will protect the mscs against the unfavorable conditions of the infarcted tissue ( such as oxidative stresses ) , increase their survival rate in the infarcted tissue , and improve their function in repairing the injured tissue .
myocardial infarction ( mi ) is the leading cause of death worldwide . 
 various therapeutic strategies have been introduced for mi treatment . in recent years , 
 interest in utilizing mesenchymal stem cells ( mscs ) for mi therapy has increased . 
 in fact , the use of mscs for mi treatment , known as cellular cardiomyoplasty , is in the clinical trial stage . 
 however , despite promising results , most mscs die after transplantation as a result of exposure to various stresses . 
 nuclear factor ( erythroid - derived 2)-like 2 ( nrf2 ) , a well - known cytoprotective transcription factor , protects mscs against some stresses . over - expression of nrf2 in mscs 
 decreases their apoptosis in vitro without any adverse effects on their differentiation capacity . 
 therefore , we hypothesized that over - expression of nrf2 in mscs can improve cellular cardiomyoplasty .