Cobalt protoporphyrin pretreatment protects human embryonic stem cell-derived cardiomyocytes from hypoxia/reoxygenation injury in vitro and increases graft size and vascularization in vivo

Nrf2/HO-1 as a therapeutic target in renal fibrosis

Chronic kidney disease (CKD) is one of the most prevalent chronic diseases and affects between 10 and 14 % of the world's population. The World Health Organization estimates that by 2040, the disease will be fifth in prevalence. End-stage CKD is characterized by renal fibrosis, which can eventually lead to kidney failure and death. Renal fibrosis develops due to multiple injuries and involves oxidative stress and inflammation. In the human body, nuclear factor erythroid 2-related factor 2 (Nrf2) plays an important role in the expression of antioxidant, anti-inflammatory, and cytoprotective genes, which prevents oxidative stress and inflammation damage. Heme oxygenase (HO-1) is an inducible homolog influenced by heme products and after exposure to cellular stress inducers such as oxidants, inflammatory chemokines/cytokines, and tissue damage as an outcome or downstream of Nrf2 activation. HO-1 is known for its antioxidative properties, which play an important role in regulating oxidative stress. In renal diseases-induced tissue fibrosis and xenobiotics-induced renal fibrosis, Nrf2/HO-1 has been targeted with promising results. This review summarizes these studies and highlights the interesting bioactive compounds that may assist in attenuating renal fibrosis mediated by HO-1 activation. In conclusion, Nrf2/HO-1 signal activation could have a renoprotective effect strategy against CKD caused by oxidative stress, inflammation, and consequent renal fibrosis.

Heterogeneous nuclear ribonucleoprotein U-actin complex derived from extracellular vesicles facilitates proliferation and migration of human coronary artery endothelial cells by promoting RNA polymerase II transcription

Coronary artery disease (CAD) represents a fatal public threat. The involvement of extracellular vesicles (EVs) in CAD has been documented. This study explored the regulation of embryonic stem cells (ESCs)-derived EVs-hnRNPU-actin complex in human coronary artery endothelial cell (HCAEC) growth. Firstly, in vitro HCAEC hypoxia models were established. EVs were extracted from ESCs by ultracentrifugation. HCAECs were treated with EVs and si-VEGF for 24 h under hypoxia, followed by assessment of cell proliferation, apoptosis, migration, and tube formation. Uptake of EVs by HCAECs was testified. Additionally, hnRNPU, VEGF, and RNA Pol II levels were determined using Western blotting and CHIP assays. Interaction between hnRNPU and actin was evaluated by Co-immunoprecipitation assay. HCAEC viability and proliferation were lowered, apoptosis was enhanced, wound fusion was decreased, and the number of tubular capillary structures was reduced under hypoxia, whereas ESC-EVs treatment counteracted these effects. Moreover, EVs transferred hnRNPU into HCAECs. EVs-hnRNPU-actin complex increased RNA Pol II level on the VEGF gene promoter and promoted VEGF expression in HCAECs. Inhibition of hnRNPU or VEGF both annulled the promotion of EVs on HCAEC growth. Collectively, ESC-EVs-hnRNPU-actin increased RNA Pol II phosphorylation and VEGF expression, thus promoting HCAEC growth.

Bisphosphonate of Zoledronate Has Antiapoptotic Effect on Hypoxia/Reoxygenation Injury in Human Embryonic Stem Cell-Derived Cardiomyocytes Through Trk Signaling Pathway

In this work, we investigated the in vitro and in vivo functions of bisphosphonate of zoledronate (Zd) in hypoxia/reoxygenation (H/R) injured human embryonic stem cell-derived cardiomyocytes (hES-CMs). In the in vitro setting, the effects of Zd on hES-CM survival and differentiation were examined. We found that low and medium concentrations (<2 µm) of Zd did not induce cell death of hES-CMs. 0.5 µm Zd protected H/R-induced hES-CM apoptosis but did not affect key differentiation proteins, including hcTnl, PECM-1 Cnx43 and Pan-Cadherin. In addition, Zd-induced TrkA/B phosphorylation and promoted VEGF to counter the apoptotic effect of H/R injury. In the in vivo animal model of myocardial infarction, Zd treatment promoted the survival of hES-CMs by inducing PECAM1 and hcTnl. Thus, we concluded that Zd protected H/R-induced hES-CM apoptosis in vitro and promoted hES-CM survival in vivo. These data may facilitate the development of human embryonic stem cells into clinical applications for patients with ischemic heart disease.

Biodistribution studies for cell therapy products: Current status and issues

Information on the biodistribution (BD) of cell therapy products (CTPs) is essential for prediction and assessment of their efficacy and toxicity profiles in non-clinical and clinical studies. To conduct BD studies, it is necessary to understand regulatory requirements, implementation status, and analytical methods. This review aimed at surveying international and Japanese trends concerning the BD study for CTPs and the following subjects were investigated, which were considered particularly important: 1) comparison of guidelines to understand the regulatory status of BD studies in a global setting; 2) case studies of the BD study using databases to understand its current status in cell therapy; 3) case studies on quantitative polymerase chain reaction (qPCR) used primarily in non-clinical BD studies for CTPs; and 4) survey of imaging methods used for non-clinical and clinical BD studies. The results in this review will be a useful resource for implementing BD studies.

Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes, in Contrast to Adipose Tissue-Derived Stromal Cells, Efficiently Improve Heart Function in Murine Model of Myocardial Infarction

Cell therapies are extensively tested to restore heart function after myocardial infarction (MI). Survival of any cell type after intracardiac administration, however, may be limited due to unfavorable conditions of damaged tissue. Therefore, the aim of this study was to evaluate the therapeutic effect of adipose-derived stromal cells (ADSCs) and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) overexpressing either the proangiogenic SDF-1α or anti-inflammatory heme oxygenase-1 (HO-1) in a murine model of MI. ADSCs and hiPSCs were transduced with lentiviral vectors encoding luciferase (Luc), GFP and either HO-1 or SDF-1α. hiPSCs were then differentiated to hiPSC-CMs using small molecules modulating the WNT pathway. Genetically modified ADSCs were firstly administered via intracardiac injection after MI induction in Nude mice. Next, ADSCs-Luc-GFP and genetically modified hiPSC-CMs were injected into the hearts of the more receptive NOD/SCID strain to compare the therapeutic effect of both cell types. Ultrasonography, performed on days 7, 14, 28 and 42, revealed a significant decrease of left ventricular ejection fraction (LVEF) in all MI-induced groups. No improvement of LVEF was observed in ADSC-treated Nude and NOD/SCID mice. In contrast, administration of hiPSC-CMs resulted in a substantial increase of LVEF, occurring between 28 and 42 days after MI, and decreased fibrosis, regardless of genetic modification. Importantly, bioluminescence analysis, as well as immunofluorescent staining, confirmed the presence of hiPSC-CMs in murine tissue. Interestingly, the luminescence signal was strongest in hearts treated with hiPSC-CMs overexpressing HO-1. Performed experiments demonstrate that hiPSC-CMs, unlike ADSCs, are effective in improving heart function after MI. Additionally, long-term evaluation of heart function seems to be crucial for proper assessment of the effect of cell administration.

Roles of Reactive Oxygen Species in Cardiac Differentiation, Reprogramming, and Regenerative Therapies

Reactive oxygen species (ROS) have been implicated in mechanisms of heart development and regenerative therapies such as the use of pluripotent stem cells. The roles of ROS mediating cell fate are dependent on the intensity of stimuli, cellular context, and metabolic status. ROS mainly act through several targets (such as kinases and transcription factors) and have diverse roles in different stages of cardiac differentiation, proliferation, and maturation. Therefore, further detailed investigation and characterization of redox signaling will help the understanding of the molecular mechanisms of ROS during different cellular processes and enable the design of targeted strategies to foster cardiac regeneration and functional recovery. In this review, we focus on the roles of ROS in cardiac differentiation as well as transdifferentiation (direct reprogramming). The potential mechanisms are discussed in regard to ROS generation pathways and regulation of downstream targets. Further methodological optimization is required for translational research in order to robustly enhance the generation efficiency of cardiac myocytes through metabolic modulations. Additionally, we highlight the deleterious effect of the host's ROS on graft (donor) cells in a paracrine manner during stem cell-based implantation. This knowledge is important for the development of antioxidant strategies to enhance cell survival and engraftment of tissue engineering-based technologies. Thus, proper timing and level of ROS generation after a myocardial injury need to be tailored to ensure the maximal efficacy of regenerative therapies and avoid undesired damage.

Deceleration of Liver Regeneration by Knockdown of Heme Oxygenase-1 is Associated With Impairment of Liver Injury Recovery After Reduced-Size Liver Transplantation in Rats

AIM

It has been reported that heme oxygenase-1 (HO-1) is upregulated during hepatocyte proliferation. Herein, we used a half-size liver transplantation (HSLT) model to study the impact of HO-1 on liver grafts proliferation. To the best of our knowledge, this is the first time that HO-1 has been characterized as a regulator of liver graft regeneration.

MATERIALS AND METHODS

Saline and tin protoporphyrin (SnPP, a HO-1 competitive inhibitor) were separately administered in vehicle and SnPP group before rats HSLT. Plasma samples were collected at 0, 1, 3, and 5 days after HSLT for liver function analysis. Liver tissues were obtained at 0, 1, 3, and 5 days after HSLT for analyses of histologic, apoptosis, and proliferation index by immunohistochemical, enzyme-linked immunosorbent assay, quantitative real-time polymerase chain reaction, and Western blotting.

RESULTS

HO-1 level was upregulated by the treatment of HSLT along with accelerated liver proliferation, which was reversed by SnPP. The reduced regeneration by SnPP lead to higher Suzuki's scores, alanine aminotransferase, and aspartate aminotransferase levels. The interleukin-6 levels, p-Stat3/t-Stat3, c-myc, and c-jun were decreased in the SnPP group than the vehicle group.

CONCLUSIONS

Our findings suggest that inhibition of HO-1 mitigates liver regeneration in part by downregulation of an interleukin-6/Stat3 axis. Targeted specific pharmacologic induction of HO-1 may be applicable in clinical practice.

Pro-apoptotic effect of haem oxygenase-1 in human colorectal carcinoma cells via endoplasmic reticular stress

Several biological effects of haem oxygenase (HO)‐1, including anti‐inflammatory, antiapoptotic and antioxidative properties were reported; however, the role of HO‐1 in apoptosis is still unclear. In the presence of stimulation by cobalt protoporphyrin (CoPP), an HO‐1 inducer, apoptotic characteristics were observed, including DNA laddering, hypodiploid cells, and cleavages of caspase (Casp)‐3 and poly(ADP) ribose polymerase (PARP) proteins in human colon carcinoma COLO205, HCT‐15, LOVO and HT‐29 cells in serum‐free (SF) conditions with increased HO‐1, but not heat shock protein 70 (HSP70) or HSP90. The addition of 10% foetal bovine serum (FBS) or 1% bovine serum albumin accordingly inhibited CoPP‐induced apoptosis and HO‐1 protein expression in human colon cancer cells. CoPP‐induced apoptosis of colon cancer cells was prevented by the addition of the pan‐caspase inhibitor, Z‐VAD‐FMK (VAD), and the Casp‐3 inhibitor, Z‐DEVD‐FMK (DEVD). N‐Acetyl cysteine inhibited reactive oxygen species‐generated H₂O₂‐induced cell death with reduced intracellular peroxide production, but did not affect CoPP‐induced apoptosis in human colorectal carcinoma (CRC) cells. Two CoPP analogs, ferric protoporphyrin and tin protoporphyrin, did not affect the viability of human CRC cells or HO‐1 expression by those cells, and knockdown of HO‐1 protein expression by HO‐1 small interfering (si)RNA reversed the cytotoxic effect elicited by CoPP. Furthermore, the carbon monoxide (CO) donor, CORM, but not FeSO₄ or biliverdin, induced DNA ladders, and cleavage of Casp‐3 and PARP proteins in human CRC cells. Increased phosphorylated levels of the endoplasmic reticular (ER) stress proteins, protein kinase R‐like ER kinase (PERK), and eukaryotic initiation factor 2α (eIF2α) by CORM and CoPP were identified, and the addition of the PERK inhibitor, GSK2606414, inhibited CORM‐ and CoPP‐induced apoptosis. Increased GRP78 level and formation of the HO‐1/GRP78 complex were detected in CORM‐ and CoPP‐treated human CRC cells. A pro‐apoptotic role of HO‐1 against the viability of human CRC cells via induction of CO and ER stress was firstly demonstrated herein.

Cardioprotective effects of omega-3 fatty acids and ascorbic acid improve regenerative capacity of embryonic stem cell-derived cardiac lineage cells

One of the major issues in cell therapy of myocardial infarction (MI) is early death of engrafted cells in a harsh oxidative stress environment, which limits the potential therapeutic utility of this strategy in the clinical setting. Increasing evidence implicates beneficial effects of omega-3 fatty acids including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and ascorbic acid (AA) in cardiovascular diseases, in particular their role in ameliorating fibrosis. In the current study, we aim to assess the cytoprotective role of EPA + DHA and AA in protecting embryonic stem cell (ESC)-derived cardiac lineage cells and amelioration of fibrosis. Herein, we have shown that preincubation of the cells with EPA + DHA + AA prior to H₂ O₂ treatment attenuated generation of reactive oxygen species (ROS) and enhanced cell viability. Gene expression analysis revealed that preincubation with EPA + DHA + AA followed by H₂ O₂ treatment, upregulated heme oxygenase-1 (HO-1) along with cardiac markers (GATA4, myosin heavy chain, α isoform [MYH6]), connexin 43 [CX43]) and attenuated oxidative stress-induced upregulation of fibroblast markers (vimentin and collagen type 1 [Col1]). Alterations in gene expression patterns were followed by marked elevation of cardiac troponin (TNNT2) positive cells and reduced numbers of vimentin positive cells. An injection of EPA + DHA + AA-pretreated ESC-derived cardiac lineage cells into the ischemic myocardium of a rat model of MI significantly reduced fibrosis compared to the vehicle group. This study provided evidence that EPA + DHA + AA may be an appropriate preincubation regimen for regenerative purposes. © 2019 BioFactors, 45(3):427-438, 2019.

Discovery of Novel Small-Molecule Inducers of Heme Oxygenase-1 That Protect Human iPSC-Derived Cardiomyocytes from Oxidative Stress

Oxidative injury to cardiomyocytes plays a critical role in cardiac pathogenesis following myocardial infarction. Transplantation of stem cell-derived cardiomyocytes has recently progressed as a novel treatment to repair damaged cardiac tissue but its efficacy has been limited by poor survival of transplanted cells owing to oxidative stress in the post-transplantation environment. Identification of small molecules that activate cardioprotective pathways to prevent oxidative damage and increase survival of stem cells post-transplantation is therefore of great interest for improving the efficacy of stem cell therapies. This report describes a chemical biology phenotypic screening approach to identify and validate small molecules that protect human-induced pluripotent stem cell cardiomyocytes (hiPSC-CMs) from oxidative stress. A luminescence-based high-throughput assay for cell viability was used to screen a diverse collection of 48,640 small molecules for protection of hiPSC-CMs from peroxide-induced cell death. Cardioprotective activity of "hit" compounds was confirmed using impedance-based detection of cardiomyocyte monolayer integrity and contractile function. Structure-activity relationship studies led to the identification of a potent class of compounds with 4-(pyridine-2-yl)thiazole scaffold. Examination of gene expression in hiPSC-CMs revealed that the hit compound, designated cardioprotectant 312 (CP-312), induces robust upregulation of heme oxygenase-1, a marker of the antioxidant response network that has been strongly correlated with protection of cardiomyocytes from oxidative stress. CP-312 therefore represents a novel chemical scaffold identified by phenotypic high-throughput screening using hiPSC-CMs that activates the antioxidant defense response and may lead to improved pharmacological cardioprotective therapies.

From Bench to Market: Preparing Human Pluripotent Stem Cells Derived Cardiomyocytes for Various Applications

Human cardiomyocytes (CMs) cease to proliferate and remain terminally differentiated thereafter, when humans reach the mid-20s. Thus, any damages sustained by myocardium tissue are irreversible, and they require medical interventions to regain functionality. To date, new surgical procedures and drugs have been developed, albeit with limited success, to treat various heart diseases including myocardial infarction. Hence, there is a pressing need to develop more effective treatment methods to address the increasing mortality rate of the heart diseases. Functional CMs are not only an important in vitro cellular tool to model various types of heart diseases for drug development, but they are also a promising therapeutic agent for cell therapy. However, the limited proliferative capacity entails difficulties in acquiring functional CMs in the scale that is required for pathological studies and cell therapy development. Stem cells, human pluripotent stem cells (hPSCs) in particular, have been considered as an unlimited cellular source for providing functional CMs for various applications. Notable progress has already been made: the first clinical trials of hPSCs derived CMs (hPSC-CMs) for treating myocardial infarction was approved in 2015, and their potential use in disease modeling and drug discovery is being fully explored. This concise review gives an account of current development of differentiation, purification and maturation techniques for hPSC-CMs, and their application in cell therapy development and pharmaceutical industries will be discussed with the latest experimental evidence.

Keap1 knockdown in melanocytes induces cell proliferation and survival via HO-1-associated β-catenin signaling

BACKGROUND

Nrf2-Keap1 signaling pathway protects cells against photo-oxidative stress. Yet in recent works, its role in melanogenesis together with cell protection functions against oxidative stress has been gaining interest. However, its effect on melanogenesis still has contradictory results from different studies.

OBJECTIVE

The aims of our study were to investigate the effect of Keap1 silencing in melanocyte on melanogenesis and its associated mechanism.

METHODS

Primary human epidermal melanocytes and melan-a cell line were used for this experiment. RNA sequencing was done to identify genes involved in melanocyte biology using Keap1 knockdown through siRNA techniques. And melanogenesis and the expression of melanogenesis-associated molecules were evaluated in Keap1 silenced melanocyte to examine the effects of Keap1 on melanogenesis, melanocyte growth, and related pathways.

RESULTS

RNA-sequencing data revealed that Keap1 knockdown in primary human epidermal melanocytes (PHEMs) induced cell survival-related gene expression. Additionally, siRNA-mediated inhibition of Keap1 led to upregulation of MITF and melanogenesis-associated molecules along with Nrf2 activation in PHEMs. HO-1, a major gene that is upregulated in RNA-sequencing using Keap1-silenced PHEMs, protected melanocytes against H₂O₂-induced cell death and upregulated MITF and β-catenin expression. Further, increased expression of melanogenesis-associated molecules after Keap1 silencing was validated to occur through HO-1-associated β-catenin activation in a Keap1 and HO-1 double knockdown experiment.

CONCLUSION

This work suggests that Keap1 silencing in melanocytes induced melanogenesis and the expression of melanogenesis-associated molecules through HO-1-associated β-catenin activation. Keap1 downregulation in melanocytes is important for cell proliferation and survival.

Heme Oxygenase-1 and Carbon Monoxide in the Heart: The Balancing Act Between Danger Signaling and Pro-Survival

Understanding the processes governing the ability of the heart to repair and regenerate after injury is crucial for developing translational medical solutions. New avenues of exploration include cardiac cell therapy and cellular reprogramming targeting cell death and regeneration. An attractive possibility is the exploitation of cytoprotective genes that exist solely for self-preservation processes and serve to promote and support cell survival. Although the antioxidant and heat-shock proteins are included in this category, one enzyme that has received a great deal of attention as a master protective sentinel is heme oxygenase-1 (HO-1), the rate-limiting step in the catabolism of heme into the bioactive signaling molecules carbon monoxide, biliverdin, and iron. The remarkable cardioprotective effects ascribed to heme oxygenase-1 are best evidenced by its ability to regulate inflammatory processes, cellular signaling, and mitochondrial function ultimately mitigating myocardial tissue injury and the progression of vascular-proliferative disease. We discuss here new insights into the role of heme oxygenase-1 and heme on cardiovascular health, and importantly, how they might be leveraged to promote heart repair after injury.

Human pluripotent stem cells: Prospects and challenges as a source of cardiomyocytes for in vitro modeling and cell-based cardiac repair

Human pluripotent stem cells (PSCs) represent an attractive source of cardiomyocytes with potential applications including disease modeling, drug discovery and safety screening, and novel cell-based cardiac therapies. Insights from embryology have contributed to the development of efficient, reliable methods capable of generating large quantities of human PSC-cardiomyocytes with cardiac purities ranging up to 90%. However, for human PSCs to meet their full potential, the field must identify methods to generate cardiomyocyte populations that are uniform in subtype (e.g. homogeneous ventricular cardiomyocytes) and have more mature structural and functional properties. For in vivo applications, cardiomyocyte production must be highly scalable and clinical grade, and we will need to overcome challenges including graft cell death, immune rejection, arrhythmogenesis, and tumorigenic potential. Here we discuss the types of human PSCs, commonly used methods to guide their differentiation into cardiomyocytes, the phenotype of the resultant cardiomyocytes, and the remaining obstacles to their successful translation.

Can Cytoprotective Cobalt Protoporphyrin Protect Skeletal Muscle and Muscle-derived Stem Cells From Ischemic Injury?

BACKGROUND

Extremity trauma is the most common injury seen in combat hospitals as well as in civilian trauma centers. Major skeletal muscle injuries that are complicated by ischemia often result in substantial muscle loss, residual disability, or even amputation, yet few treatment options are available. A therapy that would increase skeletal muscle tolerance to hypoxic damage could reduce acute myocyte loss and enhance preservation of muscle mass in these situations.

QUESTIONS/PURPOSES

In these experiments, we investigated (1) whether cobalt protoporphyrin (CoPP), a pharmacologic inducer of cytoprotective heme oxygenase-1 (HO-1), would upregulate HO-1 expression and activity in skeletal muscle, tested in muscle-derived stem cells (MDSCs); and (2) whether CoPP exposure would protect MDSCs from cell death during in vitro hypoxia/reoxygenation. Then, using an in vivo mouse model of hindlimb ischemia/reperfusion injury, we examined (3) whether CoPP pharmacotherapy would reduce skeletal muscle damage when delivered after injury; and (4) whether it would alter the host inflammatory response to injury.

METHODS

MDSCs were exposed in vitro to a single dose of 25 μΜ CoPP and harvested over 24 to 96 hours, assessing HO-1 protein expression by Western blot densitometry and HO-1 enzyme activity by cGMP levels. To generate hypoxia/reoxygenation stress, MDSCs were treated in vitro with phosphate-buffered saline (vehicle), CoPP, or CoPP plus an HO-1 inhibitor, tin protoporphyrin (SnPP), and then subjected to 5 hours of hypoxia (< 0.5% O2) followed by 24 hours of reoxygenation and evaluated for apoptosis. In vivo, hindlimb ischemia/reperfusion injury was produced in mice by unilateral 2-hour tourniquet application followed by 24 hours of reperfusion. In three postinjury treatment groups (n = 7 mice/group), CoPP was administered intraperitoneally during ischemia, at the onset of reperfusion, or 1 hour later. Two control groups of mice with the same injury received phosphate-buffered saline (vehicle) or the HO-1 inhibitor, SnPP. Myocyte damage in the gastrocnemius and tibialis anterior muscles was determined by uptake of intraperitoneally delivered Evans blue dye (EBD), quantified by image analysis. On serial sections, inflammation was gauged by the mean myeloperoxidase staining intensity per unit area over the entirety of each muscle.

RESULTS

In MDSCs, a single exposure to CoPP increased HO-1 protein expression and enzyme activity, both of which were sustained for 96 hours. CoPP treatment of MDSCs reduced apoptotic cell populations by 55% after in vitro hypoxia/reoxygenation injury (from a mean of 57.3% apoptotic cells in vehicle-treated controls to 25.7% in CoPP-treated cells, mean difference 31.6%; confidence interval [CI], 28.1-35.0; p < 0.001). In the hindlimb ischemia/reperfusion model, CoPP delivered during ischemia produced a 38% reduction in myocyte damage in the gastrocnemius muscle (from 86.4% ± 7% EBD(+) myofibers in vehicle-treated, injured controls to 53.2% EBD(+) in CoPP-treated muscle, mean difference 33.2%; 95% CI, 18.3, 48.4; p < 0.001). A 30% reduction in injury to the gastrocnemius was seen with drug delivery at the onset of reperfusion (to 60.6% ± 13% EBD(+) with CoPP treatment, mean difference 25.8%; CI, 12.2-39.4; p < 0.001). In the tibialis anterior, however, myocyte damage was decreased only when CoPP was given at the onset of reperfusion, resulting in a 27% reduction in injury (from 78.8% ± 8% EBD(+) myofibers in injured controls to 58.3% ± 14% with CoPP treatment, mean difference 20.5%; CI, 6.1-35.0; p = 0.004). Delaying CoPP delivery until 1 hour after tourniquet release obviated the protective effect in both muscles. Mean MPO staining intensity per unit area, indicating the host inflammatory response, decreased by 27-34% across both the gastrocnemius and tibialis anterior muscles when CoPP was given either during ischemia or at the time of reperfusion. Delaying drug delivery until 1 hour after the start of reperfusion abrogated this antiinflammatory effect.

CONCLUSIONS

CoPP can decrease skeletal muscle damage when given early in the course of ischemia/reperfusion injury and also provide protection for regenerative stem cell populations.

CLINICAL RELEVANCE

Pharmacotherapy with HO-1 inducers, delivered in the field, on hospital arrival, or during trauma surgery, may improve preservation of muscle mass and muscle-inherent stem cells after severe ischemic limb injury.

Cobalt alleviates GA-induced programmed cell death in wheat aleurone layers via the regulation of H2O2 production and heme oxygenase-1 expression

Heme oxygenase-1 (HO-1) and hydrogen peroxide (H2O2) are key signaling molecules that are produced in response to various environmental stimuli. Here, we demonstrate that cobalt is able to delay gibberellic acid (GA)-induced programmed cell death (PCD) in wheat aleurone layers. A similar response was observed when samples were pretreated with carbon monoxide (CO) or bilirubin (BR), two end-products of HO catalysis. We further observed that increased HO-1 expression played a role in the cobalt-induced alleviation of PCD. The application of HO-1-specific inhibitor, zinc protoporphyrin-IX (ZnPPIX), substantially prevented the increases of HO-1 activity and the alleviation of PCD triggered by cobalt. The stimulation of HO-1 expression, and alleviation of PCD might be caused by the initial H2O2 production induced by cobalt. qRT-PCR and enzymatic assays revealed that cobalt-induced gene expression and the corresponding activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), three enzymes that metabolize reactive oxygen species, were consistent with the H2O2 accumulation during GA treatment. These cobalt responses were differentially blocked by co-treatment with ZnPPIX. We therefore suggest that HO-1 functions in the cobalt-triggered alleviation of PCD in wheat aleurone layers, which is also dependent on the enhancement of the activities of antioxidant enzymes.

Cobalt alleviates GA-induced programmed cell death in wheat aleurone layers via the regulation of H2O2 production and heme oxygenase-1 expression

Heme oxygenase-1 (HO-1) and hydrogen peroxide (H₂O₂) are key signaling molecules that are produced in response to various environmental stimuli. Here, we demonstrate that cobalt is able to delay gibberellic acid (GA)-induced programmed cell death (PCD) in wheat aleurone layers. A similar response was observed when samples were pretreated with carbon monoxide (CO) or bilirubin (BR), two end-products of HO catalysis. We further observed that increased HO-1 expression played a role in the cobalt-induced alleviation of PCD. The application of HO-1-specific inhibitor, zinc protoporphyrin-IX (ZnPPIX), substantially prevented the increases of HO-1 activity and the alleviation of PCD triggered by cobalt. The stimulation of HO-1 expression, and alleviation of PCD might be caused by the initial H₂O₂ production induced by cobalt. qRT-PCR and enzymatic assays revealed that cobalt-induced gene expression and the corresponding activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), three enzymes that metabolize reactive oxygen species, were consistent with the H₂O₂ accumulation during GA treatment. These cobalt responses were differentially blocked by co-treatment with ZnPPIX. We therefore suggest that HO-1 functions in the cobalt-triggered alleviation of PCD in wheat aleurone layers, which is also dependent on the enhancement of the activities of antioxidant enzymes.

Targeting survival pathways to create infarct-spanning bridges of human embryonic stem cell-derived cardiomyocytes

OBJECTIVE

Generating myocyte grafts that bridge across infarcts could maximize their functional impact and best utilize small numbers of stem cells. To date, however, graft survival within acute infarcts has not been feasible. To enhance intrainfarct graft viability, human embryonic stem cell-derived cardiomyocytes (hESC-CMs) were pretreated before implantation with cobalt protoporphyrin (CoPP), a pharmacologic inducer of cytoprotective heme oxygenase-1.

METHODS

After preculturing with CoPP (vs phosphate-buffered saline), hESC-CMs were injected intramyocardially into acutely infarcted rat hearts, using directed injections to span the infarct. A further group received CoPP-pretreated hESC-CMs plus 4 weekly doses of systemic CoPP to prolong exposure to cytoprotectants. Two control groups with infarcts received vehicle-only intramyocardial injections or weekly systemic CoPP without cell therapy. Postinfarct ventricular function was gauged by echocardiography and graft size quantified at 8 weeks by histomorphometry.

RESULTS

CoPP-preconditioned hESC-CMs formed stable grafts deep within infarcted myocardium, while grafts without CoPP exposure survived mainly at the infarct periphery. Fractional shortening was improved at 4 and 8 weeks in all hearts receiving cell therapies (P < .01 vs vehicle-only injections). CoPP treatment of both graft hESC-CMs and recipient animals resulted in the largest grafts, highest fractional shortening, preserved wall thickness, and reduced infarct dimensions.

CONCLUSIONS

Cellular therapy delivered acutely after infarction significantly improved postinfarct ventricular function at 1 and 2 months. CoPP pretreatment of cells resulted in stable hESC-CM grafts within infarcted myocardium. This design enables construction of directionally oriented, infarct-spanning bands of new cardiomyocytes that might further improve functional restoration as engrafted myocytes proliferate and mature.