Hypoxia-preconditioned bone marrow-derived mesenchymal stem cells protect neurons from cardiac arrest-induced pyroptosis

Cardiac arrest can lead to severe neurological impairment as a result of inflammation,mitochondrial dysfunction,and post-cardiopulmonary resuscitation neurological damage.Hypoxic preconditioning has been shown to improve migration and survival of bone marrow–derived mesenchymal stem cells and reduce pyroptosis after cardiac arrest,but the specific mechanisms by which hypoxia-preconditioned bone marrow–derived mesenchymal stem cells protect against brain injury after cardiac arrest are unknown.To this end,we established an in vitro co-culture model of bone marrow–derived mesenchymal stem cells and oxygen–glucose deprived primary neurons and found that hypoxic preconditioning enhanced the protective effect of bone marrow stromal stem cells against neuronal pyroptosis,possibly through inhibition of the MAPK and nuclear factor κB pathways.Subsequently,we transplanted hypoxia-preconditioned bone marrow–derived mesenchymal stem cells into the lateral ventricle after the return of spontaneous circulation in an 8-minute cardiac arrest rat model induced by asphyxia.The results showed that hypoxia-preconditioned bone marrow–derived mesenchymal stem cells significantly reduced cardiac arrest–induced neuronal pyroptosis,oxidative stress,and mitochondrial damage,whereas knockdown of the liver isoform of phosphofructokinase in bone marrow–derived mesenchymal stem cells inhibited these effects.To conclude,hypoxia-preconditioned bone marrow–derived mesenchymal stem cells offer a promising therapeutic approach for neuronal injury following cardiac arrest,and their beneficial effects are potentially associated with increased expression of the liver isoform of phosphofructokinase following hypoxic preconditioning.

Cardiac differentiation is modulated by anti-apoptotic signals in murine embryonic stem cells

BACKGROUND Embryonic stem cells(ESCs)serve as a crucial ex vivo model,representing epiblast cells derived from the inner cell mass of blastocyst-stage embryos.ESCs exhibit a unique combination of self-renewal potency,unlimited proliferation,and pluripotency.The latter is evident by the ability of the isolated cells to differ-entiate spontaneously into multiple cell lineages,representing the three primary embryonic germ layers.Multiple regulatory networks guide ESCs,directing their self-renewal and lineage-specific differentiation.Apoptosis,or programmed cell death,emerges as a key event involved in sculpting and forming various organs and structures ensuring proper embryonic development.How-ever,the molecular mechanisms underlying the dynamic interplay between diffe-rentiation and apoptosis remain poorly understood.AIM To investigate the regulatory impact of apoptosis on the early differentiation of ESCs into cardiac cells,using mouse ESC(mESC)models-mESC-B-cell lym-phoma 2(BCL-2),mESC-PIM-2,and mESC-metallothionein-1(MET-1)-which overexpress the anti-apoptotic genes Bcl-2,Pim-2,and Met-1,respectively.METHODS mESC-T2(wild-type),mESC-BCL-2,mESC-PIM-2,and mESC-MET-1 have been used to assess the effect of potentiated apoptotic signals on cardiac differentiation.The hanging drop method was adopted to generate embryoid bodies(EBs)and induce terminal differentiation of mESCs.The size of the generated EBs was measured in each condition compared to the wild type.At the functional level,the percentage of cardiac differentiation was measured by calculating the number of beating cardiomyocytes in the manipulated mESCs compared to the control.At the molecular level,quantitative reverse transcription-polymerase chain reaction was used to assess the mRNA expression of three cardiac markers:Troponin T,GATA4,and NKX2.5.Additionally,troponin T protein expression was evaluated through immunofluorescence and western blot assays.RESULTS Our findings showed that the upregulation of Bcl-2,Pim-2,and Met-1 genes led to a reduction in the size of the EBs derived from the manipulated mESCs,in comparison with their wild-type counterpart.Additionally,a decrease in the count of beating cardiomyocytes among differentiated cells was observed.Furthermore,the mRNA expression of three cardiac markers-troponin T,GATA4,and NKX2.5-was diminished in mESCs overexpressing the three anti-apoptotic genes compared to the control cell line.Moreover,the overexpression of the anti-apoptotic genes resulted in a reduction in troponin T protein expression.CONCLUSION Our findings revealed that the upregulation of Bcl-2,Pim-2,and Met-1 genes altered cardiac differentiation,providing insight into the intricate interplay between apoptosis and ESC fate determination.

Could extracellular vesicles derived from mesenchymal stem cells be a potential therapy for acute pancreatitis-induced cardiac injury?

Acute pancreatitis(AP)often leads to a high incidence of cardiac injury,posing significant challenges in the treatment of severe AP and contributing to increased mortality rates.Mesenchymal stem cells(MSCs)release bioactive molecules that participate in various inflammatory diseases.Similarly,extracellular vesicles(EVs)secreted by MSCs have garnered extensive attention due to their comparable anti-inflammatory effects to MSCs and their potential to avoid risks associated with cell transplantation.Recently,the therapeutic potential of MSCs-EVs in various inflammatory diseases,including sepsis and AP,has gained increasing recognition.Although preclinical research on the utilization of MSCs-EVs in AP-induced cardiac injury is limited,several studies have demonstrated the positive effects of MSCs-EVs in regulating inflammation and immunity in sepsis-induced cardiac injury and cardiovascular diseases.Furthermore,clinical studies have been conducted on the therapeutic application of MSCs-EVs for some other diseases,wherein the contents of these EVs could be deliberately modified through prior modulation of MSCs.Consequently,we hypothesize that MSCs-EVs hold promise as a potential therapy for AP-induced cardiac injury.This paper aims to discuss this topic.However,additional research is essential to comprehensively elucidate the underlying mechanisms of MSCs-EVs in treating AP-induced cardiac injury,as well as to ascertain their safety and efficacy.

Wnt signaling pathway inhibitor promotes mesenchymal stem cells differentiation into cardiac progenitor cells in vitro and improves cardiomyopathy in vivo

BACKGROUND Cardiovascular diseases particularly myocardial infarction(MI)are the leading cause of mortality and morbidity around the globe.As cardiac tissue possesses very limited regeneration potential,therefore use of a potent small molecule,inhibitor Wnt production-4(IWP-4)for stem cell differentiation into cardiomyocytes could be a promising approach for cardiac regeneration.Wnt pathway inhibitors may help stem cells in their fate determination towards cardiomyogenic lineage and provide better homing and survival of cells in vivo.Mesenchymal stem cells(MSCs)derived from the human umbilical cord have the potential to regenerate cardiac tissue,as they are easy to isolate and possess multilineage differentiation capability.IWP-4 may promote the differentiation of MSCs into the cardiac lineage.AIM To evaluate the cardiac differentiation ability of IWP-4 and its subsequent in vivo effects.METHODS Umbilical cord tissue of human origin was utilized to isolate the MSCs which were characterized by their morphology,immunophenotyping of surface markers specific to MSCs,as well as by tri-lineage differentiation capability.Cytotoxicity analysis was performed to identify the optimal concentration of IWP-4.MSCs were treated with 5μM IWP-4 at two different time intervals.Differentiation of MSCs into cardiomyocytes was evaluated at DNA and protein levels.The MI ratmodel was developed.IWP-4 treated as well as untreated MSCs were implanted in the MI model,then the cardiac function was analyzed via echocardiography.MSCs were labeled with 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate(DiI)dye for tracking,while the regeneration of infarcted myocardium was examined by histology and immunohistochemistry.RESULTS MSCs were isolated and characterized.Cytotoxicity analysis showed that IWP-4 was non-cytotoxic at 5μM concentration.Cardiac specific gene and protein expression analyses exhibited more remarkable results in fourteen days treated group that was eventually selected for in vivo transplantation.Cardiac function was restored in the IWP-4 treated group in comparison to the MI group.Immunohistochemical analysis confirmed the homing of pre-differentiated MSCs that were labeled with DiI cell labeling dye.Histological analysis confirmed the significant reduction in fibrotic area,and improved left ventricular wall thickness in IWP-4 treated MSC group.CONCLUSION Treatment of MSCs with IWP-4 inhibits Wnt pathway and promotes cardiac differentiation.These pre-conditioned MSCs transplanted in vivo improved cardiac function by cell homing,survival,and differentiation at the infarcted region,increased left ventricular wall thickness,and reduced infarct size.

“Second-generation” stem cells for cardiac repair

Over the last years, stem cell therapy has emerged asan inspiring alternative to restore cardiac function after myocardial infarction. A large body of evidence has been obtained in this field but there is no conclusive data on the efficacy of these treatments. Preclinical studies and early reports in humans have been encouraging and have fostered a rapid clinical translation, but positive results have not been uniformly observed and when present, they have been modest. Several types of stem cells, manufacturing methods and delivery routes have been tested in different clinical settings but direct comparison between them is challenging and hinders further research. Despite enormous achievements, major barriers have been found and many fundamental issues remain to be resolved. A better knowledge of the molecular mechanisms implicated in cardiac development and myocardial regeneration is critically needed to overcome some of these hurdles. Genetic and pharmacological priming together with the discovery of new sources of cells have led to a "second generation" of cell products that holds an encouraging promise in cardiovascular regenerative medicine. In this report, we review recent advances in this field focusing on the new types of stem cells that are currently being tested in human beings and on the novel strategies employed to boost cell performance in order to improve cardiac function and outcomes after myocardial infarction.

Magnetic resonance imaging tracing of transplanted bone marrow mesenchymal stem cells in a rat model of cardiac arrest-induced global brain ischemia

BACKGROUND： Numerous studies have shown that magnetic resonance imaging （MRI） can detect survival and migration of super paramagnetic iron oxide-labeled stem cells in models of focal cerebral infarction. OBJECTIVE： To observe distribution of bone marrow mesenchymal stem cells （BMSCs） in a rat model of global brain ischemia following cardiac arrest and resuscitation, and to investigate the feasibility of tracing iron oxide-labeled BMSCs using non-invasive MRI. DESIGN, TIME AND SETTING： The randomized, controlled, molecular imaging study was performed at the Linbaixin Medical Research Center, Second Affiliated Hospital, Sun Yat-sen University, and the Institute of Cardiopulmonary Cerebral Resuscitation, Sun Yat-sen University, China from October 2006 to February 2009. MATERIALS： A total of 40 clean, Sprague Dawley rats, aged 6 weeks and of either gender, were supplied by the Experimental Animal Center, Sun Yat-sen University, China, for isolation of BMSCs. Feridex （iron oxide）, Gyroscan Inetra 1.5T MRI system, and cardiopulmonary resuscitation device were used in this study. METHODS： A total of 30 healthy, male Sprague Dawiey rats, aged 6 months, were used to induce ventricular fibrillation using alternating current. After 8 minutes, the rats underwent 6-minute chest compression and mechanical ventilation, followed by electric defibrillation, to establish rat models of global brain ischemia due to cardiac arrest and resuscitation. A total of 24 successful models were randomly assigned to Feridex-labeled and non-labeled groups （n = 12 for each group）. At 2 hours after resuscitation, 5 ×10^8 Feridex-labeled BMSCs, with protamine sulfate as a carrier, and 5 ×10^6 non-labeled BMSCs were respectively transplanted into both groups of rats through the right carotid artery （cells were harvested in 1 mL phosphate buffered saline）. MAIN OUTCOME MEASURES： Feridex-labeled BMSCs were observed by Prussian blue staining and electron microscopy. Signal intensity, celluar viability, and proliferative capacity of BMSCs were measured using MRI, Trypan blue test, and M-IT assay, respectively. Distribution of transplanted cells was observed in rats utilizing MRI and Prussian blue staining prior to and 1, 3, 7, and 14 days after transplantation. RESULTS： Prussian blue staining displayed many blue granules in the Feridex-labeled BMSCs. High density of iron granules was observed in the cytoplasm under electron microscopy. According to MRI results, and compared with the non-labeled group, the signal intensity was decreased in the Feridex-labeled group （P 〈 0.05）. The decrease was most significant in the 50 pg/mL Feridex-labeled group （P 〈 0.01）. There were no significant differences in celluar viability and proliferation of BMSCs between the Feridex-labeled and non-labeled groups after 1 week （P 〉 0.05）. Low-signal lesions were detected in the rat hippocampus and temporal cortex at 3 days after transplantation. The low-signal lesions were still detectable at 14 days, and positively stained cells were observed in the hippocampus and temporal cortex using Prussian blue staining. There were no significant differences in signal intensity in the non-labeled group. CONCLUSION： BMSC transplantation traversed the blood-brain barrier and distributed into vulnerable zones in a rat model of cardiac arrest-induced global brain ischemia. MRI provided a non-invasive method to in vivo dynamically and spatially trace Feridex-labeled BMSCs after transplantation.

Fetal cardiac mesenchymal stem cells express embryonal markers and exhibit differentiation into cells of all three germ layers

AIM:To study the expression of embryonal markers by fetal cardiac mesenchymal stem cells(fC-MSC)and their differentiation into cells of all the germ layers. METHODS:Ten independent cultures of rat fCMSC were set up from cells derived from individual or pooled fetal hearts and studies given below were carried out at passages 3,6,15 and 21.The phenotypic markers CD29,CD31,CD34,CD45,CD73,CD90, CD105,CD166 and HLA-DR were analyzed by flow cytometry.The expression of embryonal markers Oct-4, Nanog,Sox-2,SSEA-1,SSEA-3,SSEA-4,TRA-1-60 and TRA 1-81 were studied by immunocytochemistry.The fC-MSC treated with specific induction medium were evaluated for their differentiation into(1)adipocytes and osteocytes(mesodermal cells)by Oil Red O and Alizarin Red staining,respectively,as well as by expression of lipoprotein lipase,PPARγ2 genes in adipocytes and osteopontin and RUNX2 genes in osteocytes by reverse-transcription polymerase chain reaction(RT- PCR);(2)neuronal(ectodermal)cells by expression of neuronal Filament-160 and Glial Fibrillar Acidic Protein by RT-PCR and immunocytochemistry;and(3)hepa- tocytic(endodermal)cells by expression of albumin by RT-PCR and immunocytochemistry,glycogen deposits by Periodic Acid Schiff staining and excretion of urea into the culture supernatant. RESULTS:The fC-MSC expressed CD29,CD73,CD90, CD105,CD166 but lacked expression of CD31,CD34, CD45 and HLA-DR.They expressed embryonal markers,viz.Oct-4,Nanog,Sox-2,SSEA-1,SSEA-3,SSEA-4, TRA-1-81 but not TRA-1-60.On treatment with specific induction media,they differentiated into adipocytes and osteocytes,neuronal cells and hepatocytic cells. CONCLUSION:Our results together suggest that fCMSC are primitive stem cell types with a high degree of plasticity and,in addition to their suitability for cardiovascular regenerative therapy,they may have a wide spectrum of therapeutic applications in regenerative medicine.

In vivo cardiac pacemaker function of differentiated human mesenchymal stem cells from adipose tissue transplanted into porcine hearts

BACKGROUND Mesenchymal stem cells(MSC)modified by gene transfer to express cardiac pacemaker channels such as HCN2 or HCN4 were shown to elicit pacemaker function after intracardiac transplantation in experimental animal models.Human MSC derived from adipose tissue(haMSC)differentiate into cells with pacemaker properties in vitro,but little is known about their behavior after intracardiac transplantation.AIM To investigate whether haMSC elicit biological pacemaker function in vivo after transplantation into pig hearts.METHODS haMSC under native conditions(nhaMSC)or after pre-conditioning by medium differentiation(dhaMSC)(n=6 pigs each,5×106 cells/animal)were injected into the porcine left ventricular free wall.Animals receiving PBS injection served as controls(n=6).Four weeks later,total atrioventricular(AV)-block was induced by radiofrequency catheter ablation,and electronic pacemaker devices were implanted for backup stimulation and heart rate monitoring.Ventricular rate and rhythm of pigs were evaluated during a follow-up of 15 d post ablation by 12-lead-ECG with heart rate assessment,24-h continuous rate monitoring recorded by electronic pacemaker,assessment of escape recovery time,and pharmacological challenge to address catecholaminergic rate response.Finally,hearts were analyzed by histological and immunohistochemical investigations.RESULTS In vivo transplantation of dhaMSC into the left ventricular free wall of pigs elicited spontaneous and regular rhythms that were pace-mapped to ventricular injection sites(mean heart rate 72.2±3.6 bpm;n=6)after experimental total AV block.Ventricular rhythms were stably detected over a 15-d period and were sensitive to catecholaminergic stimulation(mean maximum heart rate 131.0±6.2 bpm;n=6;P<0.001).Pigs,which received nhaMSC or PBS presented significantly lower ventricular rates(mean heart rates 47.2±2.5 bpm and 37.4±3.2 bpm,respectively;n=6 each;P<0.001)and exhibited little sensitivity towards catecholaminergic stimulation(mean maximum heart rates 76.4±3.1 bpm and 60.5±3.1 bpm,respectively;n=6 each;P<0.05).Histological and immunohistochemical evaluation of hearts treated with dhaMSC revealed local clusters of transplanted cells at the injection sites that lacked macrophage or lymphocyte infiltrations or tumor formation.Intense fluorescence signals at these sites indicated membrane expression of HCN4 and other pacemaker-specific proteins involved in cardiac automaticity and impulse propagation.CONCLUSION dhaMSC transplanted into pig left ventricles sustainably induced rate-responsive ventricular pacemaker activity after in vivo engraftment for four weeks.The data suggest that pre-conditioned MSC may further differentiate along a pacemakerrelated lineage after myocardial integration and may establish superior pacemaker properties in vivo.

Cardiac stem cells: Current knowledge and future prospects

Regenerative medicine is the field concerned with the repair and restoration of the integrity of damaged human tissues as well as whole organs.Since the inception of the field several decades ago,regenerative medicine therapies,namely stem cells,have received significant attention in preclinical studies and clinical trials.Apart from their known potential for differentiation into the various body cells,stem cells enhance the organ's intrinsic regenerative capacity by altering its environment,whether by exogenous injection or introducing their products that modulate endogenous stem cell function and fate for the sake of regeneration.Recently,research in cardiology has highlighted the evidence for the existence of cardiac stem and progenitor cells(CSCs/CPCs).The global burden of cardiovascular diseases’morbidity and mortality has demanded an in-depth understanding of the biology of CSCs/CPCs aiming at improving the outcome for an innovative therapeutic strategy.This review will discuss the nature of each of the CSCs/CPCs,their environment,their interplay with other cells,and their metabolism.In addition,important issues are tackled concerning the potency of CSCs/CPCs in relation to their secretome for mediating the ability to influence other cells.Moreover,the review will throw the light on the clinical trials and the preclinical studies using CSCs/CPCs and combined therapy for cardiac regeneration.Finally,the novel role of nanotechnology in cardiac regeneration will be explored.

In Vitro Study on Mesenchymal Stem Cells:Anti-apoptotic Effects on Cardiac Myocytes

Objectives To investigate the anti-apoptotic effects of mesenchymal stem cells （MSCs） on hypoxic injured cardiac myocytes in vitro. Methods MSCs were isolated from bone marrow of Sprague-Dawley （SD） rats, and cardiac myocytes from neonatal rats. The rat cardiac myocytes were co-cultured with MSCs or MSC-conditioned media in anoxia （95% N2 ±5% CO2） for 72 hours. Cell apoptosis was measured by Hoechst 33258 staining. The expression of Bcl-2 and Bax in cardiac myocytes was tested by Western Blot. Results The apoptotic rate was 51.6% ± 2.4% when cardiac myocytes were cultured in continuous hypoxia and was significantly decreased when cardiac myocytes were cocultured with MSCs or MSC-conditioned media （ 15.1% ± 5.4% and 24. 0% ± 4.2% respectively, P 〈 0. 001 ）. The decreased expression of Bax in the cardiac myocytes was greatly related to the decreasing of apoptosis, but there was no difference in Bcl-2 expression among these groups. Conclusions Co-cultured MSCs showed significant anti-apoptotic effects on cardiac myocytes in continuous hypoxia. The mechanism may be the interact of cell to cell and paracrine of cytokines which effected the expression of Bax in the cardiac myocytes.

Intravenously Injected Mesenchymal Stem Cells Home to Infarcted Myocardium Without Altering Cardiac Function

Background:Systemic delivery of mesenchymal stem cells (MSCs) to the infarcted myocardium is an attractive noninvasive strategy, but therapeutic effect of this strategy remain highly controversial. Methods: Myocardial infarction was induced in female Sprague-Dawley rats by transient ligation of the left anterior descending coronary artery for 60 min. Either 2.5×106 DiI-labeled MSCs or equivalent saline was injected into the tail vein at 24 h after infarction.Results: Three days later, MSCs localized predominantly in the infarct region of heart rather than in the remote region. MSCs were also observed in spleen, lung and liver. At 4 weeks after infarction, echocardiographic parameters, including ejection fraction, fractional shortening, left ventricular end-diastolic and end-systolic diameters, were not significantly different between MSCs and saline groups. Hemodynamic examination showed that ±dp/dtmax were similar between MSCs and saline-treated animals. Histological evaluation revealed that infarct size and vessel density were not significantly changed by MSCs infusion.Conclusion: Intravenously injected MSCs can home to infarcted myocardium, but plays a limited role in cardiac repair following myocardial infarction.

Therapeutic effect of Cistanche deserticola on defecation in senile constipation rat model through stem cell factor/C-kit signaling pathway

BACKGROUND Constipation is one of the chronic gastrointestinal functional diseases.It seriously affects the quality of life.Cistanche deserticola(C.deserticola)can treat constipation obviously,but its mechanism has not been clarified.We supposed that mechanism of it improved the intestinal motility by stimulating interstitial Cajal cells(ICC).Activation of the C-kit receptor on the surface of ICC is closely related to ICC function,and the stem cell factor(SCF)/C-kit signaling pathways plays an important role on it.To investigate the mechanism of how C.deserticola treats constipation,this study aimed to establish a constipation model in rats and explore the role of SCF/C-kit signaling pathway in the treatment.AIM To explore the SCF/C-kit signaling pathways in the role of C.deserticola for treatment of constipation by a constipation rat model.METHODS Forty-eight 8-mo-old Sprague–Dawley rats were divided into 4 groups by random weight method:Normal group(n=12),model group(n=12),C.deserticola group(n=12)and blocker group(n=12).The normal group received normal saline by gavage;the model group received loperamide by gavage;the blocker group received loperamide and C.deserticola by gavage,and STI571 was injected by intraperitoneally.During treatment,the weight,fecal granules and fecal quality were recorded every 10 d.On day 20 after model induction,the colon tissues of each group were removed.Hematoxylin and eosin staining was used to observe pathological changes.Expression levels of SCF,C-kit and Aquaporin genes were detected by immunohistochemistry,western blotting,and real-time-quantitative polymerase chain reaction.The colonic epithelial mitochondria and goblet cells were observed by transmission electron microscopy.RESULTS Compared with the normal group,as treatment progressed,the weight of rats in the model and blocker groups decreased significantly,the stool weight decreased,and the stool quality was dry(P<0.05).C.deserticola reversed the decrease in body weight and stool weight and improved stool quality.Histopathological analysis indicated that the colonic mucosal epithelium in the model group was incomplete,and the arrangement of the glands was irregular or damaged.Treatment with C.deserticola improved the integrity and continuity of the epithelial cells and regular arrangement of the glands.The blocking agents inhibited the effects of C.deserticola Immunohistochemistry and real-timequantitative polymerase chain reaction showed that expression of SCF and C-kit protein or genes in the colonic tissue of the model group was decreased(P<0.05),while treatment with C.deserticola increased protein or gene expression(P<0.05).Western blotting showed that expression of aquaporin APQ3 was increased,while the expression of Cx43 decreased in the model group.Treatment with C.deserticola inhibited expression of APQ3 and promoted expression of Cx43.Transmission electron microscopy showed that the mitochondria of the colonic epithelium in the model group were swollen and arranged disorderly,and microvilli were sparse.The condition was better in the C.deserticola group.Mice treated with STI571 blocker confirmed that blocking the SCF/C-kit pathway inhibited the improvement of constipation by C.deserticola.CONCLUSION C.deserticola improved defecation in rats with constipation,and the SCF/C-kit signaling pathway,which is a key link of ICC function,played an important role of the treatment.

5-Azacytidine induces changes in electrophysiological properties of human mesenchymal stem cells

Previously, mouse bone marrow-derived stem cells （MSC） treated with the unspecific DNA methyltransferase inhibitor 5-azacytidine were reported to differentiate into cardiomyocytes. The aim of the present study was to investigate the efficiency of a similar differentiation strategy in human mononuclear cells obtained from healthy bone marrow donors. After 1-3 passages, cultures were exposed for 24 h to 5-azacytidine （3 μM） followed by 6 weeks of further culture. Drug treatment did not induce expression of myogenic marker MyoD or cardiac markers Nkx2.5 and GATA-4 and did not yield beating cells during follow-up. In patch clamp experiments, approximately 10-15% of treated and untreated cells exhibited L-type Ca^2＋ currents. Almost all cells showed outwardly rectifying K^＋ currents of rapid or slow activation kinetics. Mean current amplitude at ＋60 mV doubled after 6 weeks of treatment compared with time-matched controls. Membrane capacitance of treated cells was significantly larger than in controls 2 weeks after treatment and remained high after 6 weeks, Expression levels of mRNAs for the K^＋ channels Kv 1,1, Kv 1,5, Kv2,1, Kv4,3 and KCNMA 1 and for the Ca^2＋ channel Cav 1.2 were not affected by 5-azacytidine. Treatment with potassium channel blockers tetraethylammonium and clofilium at concentrations shown previously to inhibit rapid or slowly activating K^＋ currents of hMSC inhibited proliferation of these cells. Our results suggest that despite the absence of differentiation ofhMSC into cardiomyocytes, treatme.nt with 5-azacytidine caused profound changes in current density.

How do resident stem cells repair the damaged myocardium?

It has been a decade since the monumental discovery of resident stem cells in the mammalian heart, and the following studies witnessed the continuous turnover of cardiomyocytes and vascular cells, maintaining the homeostasis of the organ. Recently, the autologous administration of c-kit-positive cardiac stem cells in patients with ischemic heart failure has led to an incredible outcome; the left ventricular ejection fraction of the celltreated group improved from 30% at the baseline to 38% after one year and to 42% after two years of cell injection. The potential underlying mechanisms, before and after cell infusion, are explored and discussed in this article. Some of them are related to the intrinsic property of the resident stem cells, such as direct differentiation, paracrine action, and immunomodulatory function, whereas others involve environmental factors, leading to cellular reverse remodeling and to the natural selection of "juvenile" cells. It has now been demonstrated that cardiac stem cells for therapeutic purposes can be prepared from tiny biopsied specimens of the failing heart as well as from frozen tissues, which may remarkably expand the repertoire of the strategy against various cardiovascular disorders, including non-ischemic cardiomyopathy and congenital heart diseases. Further translational investigations are needed to explore these possibilities.

Cardiogenic differentiation of mesenchymal stem cells on elastomeric poly (glycerol sebacate)/collagen core/shell fibers

AIM: To facilitate engineering of suitable biomaterials to meet the challenges associated with myocardial infarction. METHODS: Poly (glycerol sebacate)/collagen (PGS/ collagen) core/shell fibers were fabricated by core/ shell electrospinning technique, with core as PGS and shell as collagen polymer; and the scaffolds were characterized by scanning electron microscope (SEM), fourier transform infrared spectroscopy (FTIR), contact angle and tensile testing for cardiac tissue engineering. Collagen nanofibers were also fabricated by electrospinning for comparison with core/shell fibers. Studies on cell-scaffold interaction were carriedout using cardiac cells and mesenchymal stem cells (MSCs) co-culture system with cardiac cells and MSCs separately serving as positive and negative controls respectively. The co-culture system was characterized for cell proliferation and differentiation of MSCs into cardiomyogenic lineage in the co-culture environment using dual immunocytochemistry. The co-culture cells were stained with cardiac specific marker proteins like actinin and troponin and MSC specific marker protein CD 105 for proving the cardiogenic differentiation of MSCs. Further the morphology of cells was analyzed using SEM.RESULTS: PGS/collagen core/shell fibers, core is PGS polymer having an elastic modulus related to that of cardiac fibers and shell as collagen, providing natural environment for cellular activities like cell adhesion, proliferation and differentiation. SEM micrographs of electrospun fibrous scaffolds revealed porous, beadless, uniform fibers with a fiber diameter in the range of 380 ± 77 nm and 1192 ± 277 nm for collagen fibers and PGS/collagen core/shell fibers respectively. The obtained PGS/collagen core/shell fibrous scaffolds were hydrophilic having a water contact angle of 17.9 ± 4.6° compared to collagen nanofibers which had a contact angle value of 30 ± 3.2°. The PGS/collagen core/shell fibers had mechanical properties comparable to that of native heart muscle with a young's modulus of 4.24 ± 0.7 MPa, while that of collagen nanofibers was comparatively higher around 30.11 ± 1.68 MPa. FTIR spectrum was performed to confirm the functional groups present in the electrospun scaffolds. Amide Ⅰ and amide Ⅱ of collagen were detected at 1638.95 cm -1 and 1551.64 cm -1 in the electrospun collagen fibers and at 1646.22 cm -1 and 1540.73 cm -1 for PGS/collagen core/shell fibers respectively. Cell culture studies performed using MSCs and cardiac cells co-culture environment, indicated that the cellproliferation significantly increased on PGS/collagen core/shell scaffolds compared to collagen fibers and the cardiac marker proteins actinin and troponin were expressed more on PGS/collagen core/shell scaffolds compared to collagen fibers alone. Dual immunofluorescent staining was performed to further confirm the cardiogenic differentiation of MSCs by employing MSC specific marker protein, CD 105 and cardiac specific marker protein, actinin. SEM observations of cardiac cells showed normal morphology on PGS/collagen fibers and providing adequate tensile strength for the regeneration of myocardial infarction. CONCLUSION: Combination of PGS/collagen fibers and cardiac cells/MSCs co-culture system providing natural microenvironments to improve cell survival and differentiation, could bring cardiac tissue engineering to clinical application.

Cardiac disease modeling using induced pluripotent stem cell-derived human cardiomyocytes

Causative mutations and variants associated with cardiac diseases have been found in genes encoding cardiac ion channels, accessory proteins, cytoskeletal components, junctional proteins, and signaling molecules. In most cases the functional evaluation of the genetic alterationhas been carried out by expressing the mutated proteins in in-vitro heterologous systems. While these studies have provided a wealth of functional details that have greatly enhanced the understanding of the pathological mechanisms, it has always been clear that heterologous expression of the mutant protein bears the intrinsic limitation of the lack of a proper intracellular environment and the lack of pathological remodeling. The results obtained from the application of the next generation sequencing technique to patients suffering from cardiac diseases have identified several loci, mostly in non-coding DNA regions, which still await functional analysis. The isolation and culture of human embryonic stem cells has initially provided a constant source of cells from which cardiomyocytes(CMs) can be obtained by differentiation. Furthermore, the possibility to reprogram cellular fate to a pluripotent state, has opened this process to the study of genetic diseases. Thus induced pluripotent stem cells(i PSCs) represent a completely new cellular model that overcomes the limitations of heterologous studies. Importantly, due to the possibility to keep spontaneously beating CMs in culture for several months, during which they show a certain degree of maturation/aging, this approach will also provide a system in which to address the effect of long-term expression of the mutated proteins or any other DNA mutation, in terms of electrophysiological remodeling. Moreover, since i PSC preserve the entire patients' genetic context, the system will help the physicians in identifying the most appropriate pharmacological intervention to correct the functional alteration. This article summarizes the current knowledge of cardiac genetic diseases modelled with i PSC.

Cardiotrophin-1 promotes cardiomyocyte differentiation from mouse induced pluripotent stem cells via JAK2/STAT3/Pim-1 signaling pathway

Background The induced pluripotent stem cell （iPSC） has shown great potential in cellular therapy of myocardial infarction （MI）, while its application is hampered by the low efficiency of cardiomyocyte differentiation. The present study was designed to investigate the effects of cardiotrophin-1 （CT-1） on cardiomyocyte differentiation from mouse induced pluripotent stem cells （miPSCs） and the underlying mechanisms involved. Methods The optimal treatment condition for cardiomyocyte differentiation from miPSCs was established with ideal concentration （10 ng/mL） and duration （from day 3 to day 14） of CT-1 administration. Up-regulated expression of cardiac specific genes that accounted for embryonic cardiogenesis was observed by quantitative RT-PCR. Elevated amount of a-myosin heavy chain （ct-MHC） and cardiac troponin I （cTn I） positive cells were detected by immunofluorescence staining and flow cytometry analysis in CT- 1 group. Results Transmission electron microscopic analysis revealed that cells treated with CT- 1 showed better organized sacromeric structure and more mitochondria, which are morphological characteristic of matured cardiomyocytes. Western blot demonstrated that CT-1 promotes cardiomyocyte differentiation from miPSCs partly via JAK2/STAT3/Pim-1 pathway as compared with control group. Conclusions These findings suggested that CT-1 could enhance the cardiomyocyte differentiation as well as the maturation of mouse induced pluripotent stem cell derived cardiomyocytes by regulating JAK2/STAT3/Pim-1 signaling pathway.

Combination of mesenchymal stem cells and three-dimensional collagen scaffold preserves ventricular remodeling in rat myocardial infarction model

BACKGROUND Cardiovascular diseases are the major cause of mortality worldwide.Regeneration of the damaged myocardium remains a challenge due to mechanical constraints and limited healing ability of the adult heart tissue.Cardiac tissue engineering using biomaterial scaffolds combined with stem cells and bioactive molecules could be a highly promising approach for cardiac repair.Use of biomaterials can provide suitable microenvironment to the cells and can solve cell engraftment problems associated with cell transplantation alone.Mesenchymal stem cells(MSCs)are potential candidates in cardiac tissue engineering because of their multilineage differentiation potential and ease of isolation.Use of DNA methyl transferase inhibitor,such as zebularine,in combination with three-dimensional(3D)scaffold can promote efficient MSC differentiation into cardiac lineage,as epigenetic modifications play a fundamental role in determining cell fate and lineage specific gene expression.AIM To investigate the role of collagen scaffold and zebularine in the differentiation of rat bone marrow(BM)-MSCs and their subsequent in vivo effects.METHODS MSCs were isolated from rat BM and characterized morphologically,immunophenotypically and by multilineage differentiation potential.MSCs were seeded in collagen scaffold and treated with 3μmol/L zebularine in three different ways.Cytotoxicity analysis was done and cardiac differentiation was analyzed at the gene and protein levels.Treated and untreated MSC-seeded scaffolds were transplanted in the rat myocardial infarction(MI)model and cardiac function was assessed by echocardiography.Cell tracking was performed by DiI dye labeling,while regeneration and neovascularization were evaluated by histological and immunohistochemical analysis,respectively.RESULTS MSCs were successfully isolated and seeded in collagen scaffold.Cytotoxicity analysis revealed that zebularine was not cytotoxic in any of the treatment groups.Cardiac differentiation analysis showed more pronounced results in the type 3 treatment group which was subsequently chosen for the transplantation in the in vivo MI model.Significant improvement in cardiac function was observed in the zebularine treated MSC-seeded scaffold group as compared to the MI control.Histological analysis also showed reduction in fibrotic scar,improvement in left ventricular wall thickness and preservation of ventricular remodeling in the zebularine treated MSC-seeded scaffold group.Immunohistochemical analysis revealed significant expression of cardiac proteins in DiI labeled transplanted cells and a significant increase in the number of blood vessels in the zebularine treated MSC-seeded collagen scaffold transplanted group.CONCLUSION Combination of 3D collagen scaffold and zebularine treatment enhances cardiac differentiation potential of MSCs,improves cell engraftment at the infarcted region,reduces infarct size and improves cardiac function.

Stem cell therapies in cardiac diseases: Current status and future possibilities

Cardiovascular diseases represent the world’s leading cause of death. In thisheterogeneous group of diseases, ischemic cardiomyopathies are the mostdevastating and prevalent, estimated to cause 17.9 million deaths per year.Despite all biomedical efforts, there are no effective treatments that can replacethe myocytes lost during an ischemic event or progression of the disease to heartfailure. In this context, cell therapy is an emerging therapeutic alternative to treatcardiovascular diseases by cell administration, aimed at cardiac regeneration andrepair. In this review, we will cover more than 30 years of cell therapy in cardiology,presenting the main milestones and drawbacks in the field and signalingfuture challenges and perspectives. The outcomes of cardiac cell therapies arediscussed in three distinct aspects: The search for remuscularization byreplacement of lost cells by exogenous adult cells, the endogenous stem cell era,which pursued the isolation of a progenitor with the ability to induce heart repair,and the utilization of pluripotent stem cells as a rich and reliable source ofcardiomyocytes. Acellular therapies using cell derivatives, such as microvesiclesand exosomes, are presented as a promising cell-free therapeutic alternative.

New directions in cardiac stem cell therapy: An update for clinicians

The emergence of cardiac stem cell therapy can be traced to late 2001, when studies in small animal models of myocardial infarction suggested that stem cells could engraft, proliferate, and regenerate myo-cardium. Subsequent animal laboratory studies showed improved cardiac function, perfusion and survival compared to controls (Figure 1). Within two years, the first clinical trials of stem cell therapy began to appear, and we now have several trials of intracoronary infusion of bone marrow cells with more than one year follow-up. Although this clinical therapy has proven to be safe, the magnitude of improvement in objective measures like ejection fraction has been modest, and the therapy has not entered clinical practice. In the absence of a large prospective randomized trial, the field has moved back to the laboratory. This manuscript aims to provide clinicians with a broad overview of this complex field by briefly reviewing the existing status of clinical myocardial regeneration therapy, then describing selected examples from the laboratory research approaches that may provide a platform for new and potentially increasingly effective clinical strategies.