Fate of undifferentiated mouse embryonic stem cells within the rat heart: role of myocardial infarction and immune suppression

Injectable Hyaluronic Acid Hydrogel Loaded with Functionalized Human Mesenchymal Stem Cell Aggregates for Repairing Infarcted Myocardium

Conventional strategies of stem cell injection in treating myocardial infarction (MI) remain a challenge because of low retention rate and insufficient secretion of exogenous cytokines for efficiently improving the microenvironment in the infarcted myocardium, thus hampering the therapeutic effect. Herein, poly(lactic-co-glycolic acid) (PLGA) microparticles modified with human VE-cad-Fc fusion protein are fabricated and integrated with human mesenchymal stem cells (hMSCs) to construct functionalized MSC aggregates (FMAs). This fusion protein can effectively promote the paracrine activity of MSCs. The FMA is encapsulated with an injectable hyaluronic acid (HA)-based hydrogel, which is prepared by Schiff base reaction between oxidized HA (OHA) and hydrazided HA (HHA). The OHA@HHA hydrogel loading FMA is injected into the infarcted myocardium of rats, thereby efficiently improving the MI microenvironment in terms of decreased expressions of inflammatory cytokines and upregulated secretion of angiogenic factors compared to the plain hydrogel only and hydrogel encapsulating MSCs. The results of both echocardiography and histological analyses demonstrate the efficient reconstruction of cardiac function and structure and revascularization in the infarct myocardium. The delivery of functionalized stem cell aggregates with an injectable hydrogel offers a promising strategy for treating myocardial infarction and may be expanded to other tissue repair and reconstruction.

Cardiac Stem Cell-Loaded Delivery Systems: A New Challenge for Myocardial Tissue Regeneration

Cardiovascular disease (CVD) remains the leading cause of death in Western countries. Post-myocardial infarction heart failure can be considered a degenerative disease where myocyte loss outweighs any regenerative potential. In this scenario, regenerative biology and tissue engineering can provide effective solutions to repair the infarcted failing heart. The main strategies involve the use of stem and progenitor cells to regenerate/repair lost and dysfunctional tissue, administrated as a suspension or encapsulated in specific delivery systems. Several studies demonstrated that effectiveness of direct injection of cardiac stem cells (CSCs) is limited in humans by the hostile cardiac microenvironment and poor cell engraftment; therefore, the use of injectable hydrogel or pre-formed patches have been strongly advocated to obtain a better integration between delivered stem cells and host myocardial tissue. Several approaches were used to refine these types of constructs, trying to obtain an optimized functional scaffold. Despite the promising features of these stem cells’ delivery systems, few have reached the clinical practice. In this review, we summarize the advantages, and the novelty but also the current limitations of engineered patches and injectable hydrogels for tissue regenerative purposes, offering a perspective of how we believe tissue engineering should evolve to obtain the optimal delivery system applicable to the everyday clinical scenario.

Nano-Enabled Approaches for Stem Cell-Based Cardiac Tissue Engineering

Cardiac diseases are the most prevalent causes of mortality in the world, putting a major economic burden on global healthcare system. Tissue engineering strategies aim at developing efficient therapeutic approaches to overcome the current challenges in prolonging patients survival upon cardiac diseases. The integration of advanced biomaterials and stem cells has offered enormous promises for regeneration of damaged myocardium. Natural or synthetic biomaterials have been extensively used to deliver cells or bioactive molecules to the site of injury in heart. Additionally, nano-enabled approaches (e.g., nanomaterials, nanofeatured surfaces) have been instrumental in developing suitable scaffolding biomaterials and regulating stem cells microenvironment to achieve functional therapeutic outcomes. This review article explores tissue engineering strategies, which have emphasized on the use of nano-enabled approaches in combination with stem cells for regeneration and repair of injured myocardium upon myocardial infarction (MI). Primarily a wide range of biomaterials, along with different types of stem cells, which have utilized in cardiac tissue engineering will be presented. Then integration of nanomaterials and surface nanotopographies with biomaterials and stem cells for myocardial regeneration will be presented. The advantages and challenges of these approaches will be reviewed and future perspective will be discussed.

Tumorigenesis of nuclear transfer-derived embryonic stem cells is reduced through differentiation and enrichment following transplantation in the infarcted rat heart

The aim of the present study was to evaluate the tumorigenic potential of nuclear transfer-derived (nt) mouse embryonic stem cells (mESCs) transplanted into infarcted rat hearts. The nt‑mESCs were cultured using a bioreactor system to develop embryoid bodies, which were induced with 1% ascorbic acid to differentiate into cardiomyocytes. The nt‑mESC‑derived cardiomyocytes (nt‑mESCs‑CMs) were enriched using Percoll density gradient separation to generate nt‑mESCs‑percoll‑enriched (PE)‑CMs. Ischemia was induced by ligating the left anterior descending coronary artery in female Sprague‑Dawley rats. Immunosuppressed rats (daily intraperitoneal injections of cyclosporine A and methylprednisolone) were randomly assigned to receive an injection containing 5x106 mESCs, nt‑mESCs, nt‑mESC‑CMs or nt‑mESC‑PE‑CMs. Analysis performed 8 weeks following transplantation revealed teratoma formation in 80, 86.67 and 33.33% of the rats administered with the mESCs, nt‑mESCs and nt‑mESC‑CMs, respectively, indicating no significant difference between the mESCs and nt‑mESCs; but significance (P<0.05) between the nt‑mESC‑CMs and nt‑mESCs. The mean tumor volumes were 82.72±6.52, 83.17±3.58 and 50.40±5.98 mm3, respectively (P>0.05 mESCs, vs. nt‑mESCs; P<0.05 nt‑mESC‑CMs, vs. nt‑mESCs). By contrast, no teratoma formation was detected in the rats, which received nt‑mESC‑PE‑CMs. Octamer‑binding transcription factor‑4, a specific marker of undifferentiated mESCs, was detected using polymerase chain reaction in the rats, which received nt‑mESCs and nt‑mESC‑CMs, but not in rats administered with nt‑mESC‑PE‑CMs. In conclusion, nt‑mESCs exhibited the same pluripotency as mESCs, and teratoma formation following nt‑mESC transplantation was reduced by cell differentiation and enrichment.

Role of spermatogonial stem cells extract in transdifferentiation of 5-Aza-2'-deoxycytidine-treated bone marrow mesenchymal stem cells into germ-like cells

As one of the induced pluripotent stem cells (iPSCs) methods, spermatogonial stem cells (SSCS ) extract is considered as new approach in stem cell therapy of infertility. 5-aza-2'-deoxycytidine (5-aza-dC) inhibits methyltransferase enzyme, and induces gene reprogramming; herein, the effects of SSCS extract incubation in 5-aza-dC-treated bone marrow mesenchymal stem cells (BMMSCs) has been surveyed. BMMSCs were isolated from femurs of three to four weeks old male NMRI mice, and the cells at passage three were treated with 2 µM 5-aza-dC for 72 hours. SSCs were isolated, cultured, and harvested at passage three to collect SSCS extract; BMMSCs were then incubated with SSCS extract in the three time periods: 72 hours, one week and two weeks. There were five groups: control, sham, extract, 5-aza-dC and extract-5-aza-dC. After one week of incubation, flow cytometry and real-time polymerase chain reaction (PCR) exhibited high levels of expression for β1- and α6-integrins and promyelocytic leukaemia zinc finger (PLZF) in extract and extract-5-aza-dC groups (P < 0.05 vs. control and 5-aza-dC), and cells in these two groups had two forms of morphology, round and fusiform, similar to germ-like cells. 5-aza-dC had no significant effects during the three time periods of evaluation. These data disclose the effectiveness of SSCs extract incubation in transdifferentiation of BMMSCs into germ-like cells; this strategy could introduce a new approach for treatment of male infertility in clinic.

Concise review: Engineering myocardial tissue: the convergence of stem cells biology and tissue engineering technology

Advanced heart failure represents a leading public health problem in the developed world. The clinical syndrome results from the loss of viable and/or fully functional myocardial tissue. Designing new approaches to augment the number of functioning human cardiac muscle cells in the failing heart serve as the foundation of modern regenerative cardiovascular medicine. A number of clinical trials have been performed in an attempt to increase the number of functional myocardial cells by the transplantation of a diverse group of stem or progenitor cells. Although there are some encouraging suggestions of a small early therapeutic benefit, to date, no evidence for robust cell or tissue engraftment has been shown, emphasizing the need for new approaches. Clinically meaningful cardiac regeneration requires the identification of the optimum cardiogenic cell types and their assembly into mature myocardial tissue that is functionally and electrically coupled to the native myocardium. We here review recent advances in stem cell biology and tissue engineering and describe how the convergence of these two fields may yield novel approaches for cardiac regeneration.

Oxytocin improves the expression of cardiac specific markers in porcine bone marrow stem cells differentiation

Bone marrow stem cells (BMSCs) treated with 5-azacytidine possess myogenic differentiation potential. Oxytocin (OT) induces cardiomyogenesis in murine embryonic and cardiac stem cells. We attempted to isolate, characterize, and induce OT-mediated cardiomyogenic differentiation of porcine pBMSCs. Cells were treated as: control, OT, and 5-azacytidine groups. During early passages, transcripts of Oct4, GATA4, OT receptor, and phospholamban were expressed. RT-PCR showed upregulation of GATA4 in OT and 5-azacytidine-induced groups. Immunocytochemistry revealed higher expressions of cardiac troponin T and myosin heavy chain in OT than in 5-azacytidine-induced groups (p < 0.01). Western blot analysis showed upregulation of cardiac troponin I in OT-induced pBMSCs (p < 0.01). We infer pBMSCs should be induced during early passages, when expressing transcription factors related to pluripotency and cardiomyogenesis, as well as OT receptor. The more abundant expression of cardiac specific proteins in OT-treated pBMSCs suggests OT could be a more potent cardiomyogenic inducer of pBMSC.

The role of tissue engineering and biomaterials in cardiac regenerative medicine

In recent years, the development of 3-dimensional engineered heart tissue (EHT) has made large strides forward because of advances in stem cell biology, materials science, prevascularization strategies, and nanotechnology. As a result, the role of tissue engineering in cardiac regenerative medicine has become multifaceted as new applications become feasible. Cardiac tissue engineering has long been established to have the potential to partially or fully restore cardiac function after cardiac injury. However, EHTs may also serve as surrogate human cardiac tissue for drug-related toxicity screening. Cardiotoxicity remains a major cause of drug withdrawal in the pharmaceutical industry. Unsafe drugs reach the market because preclinical evaluation is insufficient to weed out cardiotoxic drugs in all their forms. Bioengineering methods could provide functional and mature human myocardial tissues, ie, physiologically relevant platforms, for screening the cardiotoxic effects of pharmaceutical agents and facilitate the discovery of new therapeutic agents. Finally, advances in induced pluripotent stem cells have made patient-specific EHTs possible, which opens up the possibility of personalized medicine. Herein, we give an overview of the present state of the art in cardiac tissue engineering, the challenges to the field, and future perspectives.

Priming mesenchymal stem cells boosts stem cell therapy to treat myocardial infarction

Cardiovascular diseases are the number one cause of death globally and are projected to remain the single leading cause of death. Treatment options abounds, although efficacy is limited. Recent studies attribute discrete and ephemeral benefits to adult stem cell therapies, indicating the urge to improve stem cell based-therapy. In this study, we show that priming mesenchymal stem cells (MSC) towards cardiomyogenic lineage enhances their beneficial effects in vivo as treatment option for acute phase myocardial infarction. MSC were primed using cardiomyogenic media for 4 days, after which peak expression of key cardiomyogenic genes are reached and protein expression of Cx-43 and sarcomeric α-actinin are observed. MSC and primed MSC (pMSC) were characterized in vitro and used to treat infarcted rats immediately after left anterior descending (LAD) occlusion. Echocardiography analysis indicated that MSC-treated myocardium presented discrete improvement in function, but it also showed that pMSC treatment lead to superior beneficial results, compared with undifferentiated MSC. Seven days after cell injection, MSC and pMSC could still be detected in the myocardium. Connexin-43 expression was quantified through immunoblotting, and was superior in pMSC, indicating that this could be a possible explanation for the superior performance of pMSC therapy.

Injectable biodegradable hydrogels for embryonic stem cell transplantation: improved cardiac remodelling and function of myocardial infarction

In this study, an injectable, biodegradable hydrogel composite of oligo[poly(ethylene glycol) fumarate] (OPF) was investigated as a carrier of mouse embryonic stem cells (mESCs) for the treatment of myocardial infarction (MI). The OPF hydrogels were used to encapsulate mESCs. The cell differentiation in vitro over 14 days was determined via immunohistochemical examination. Then, mESCs encapsulated in OPF hydrogels were injected into the LV wall of a rat MI model. Detailed histological analysis and echocardiography were used to determine the structural and functional consequences after 4 weeks of transplantation. With ascorbic acid induction, mESCs could differentiate into cardiomyocytes and other cell types in all three lineages in the OPF hydrogel. After transplantation, both the 24-hr cell retention and 4-week graft size were significantly greater in the OPF + ESC group than that of the PBS + ESC group (P < 0.01). Four weeks after transplantation, OPF hydrogel alone significantly reduced the infarct size and collagen deposition and improved the cardiac function. The heart function and revascularization improved significantly, while the infarct size and fibrotic area decreased significantly in the OPF + ESC group compared with that of the PBS + ESC, OPF and PBS groups (P < 0.01). All treatments had significantly reduced MMP2 and MMP9 protein levels compared to the PBS control group, and the OPF + ESC group decreased most by Western blotting. Transplanted mESCs expressed cardiovascular markers. This study suggests the potential of a method for heart regeneration involving OPF hydrogels for stem cell encapsulation and transplantation.

Embryonic stem cell-based cardiopatches improve cardiac function in infarcted rats

Pluripotent stem cell-seeded cardiopatches hold promise for in situ regeneration of infarcted hearts. Here, we describe a novel cardiopatch based on bone morphogenetic protein 2-primed cardiac-committed mouse embryonic stem cells, embedded into biodegradable fibrin matrices and engrafted onto infarcted rat hearts. For in vivo tracking of the engrafted cardiac-committed cells, superparamagnetic iron oxide nanoparticles were magnetofected into the cells, thus enabling detection and functional evaluation by high-resolution magnetic resonance imaging. Six weeks after transplantation into infarcted rat hearts, both local (p < .04) and global (p < .015) heart function, as well as the left ventricular dilation (p < .0011), were significantly improved (p < .001) as compared with hearts receiving cardiopatches loaded with iron nanoparticles alone. Histological analysis revealed that the fibrin scaffolds had degraded over time and clusters of myocyte enhancer factor 2-positive cardiac-committed cells had colonized most of the infarcted myocardium, including the fibrotic area. De novo CD31-positive blood vessels were formed in the vicinity of the transplanted cardiopatch. Altogether, our data provide evidence that stem cell-based cardiopatches represent a promising therapeutic strategy to achieve efficient cell implantation and improved global and regional cardiac function after myocardial infarction.

Immunological barriers to stem-cell based cardiac repair

Repair of damaged myocardium with pluripotent stem cell derived cardiomyocytes is becoming increasingly more feasible. Developments in stem cell research emphasize the need to address the foreseeable problem of immune rejection following transplantation. Pluripotent stem cell (PSC) derived cardiomyocytes have unique immune characteristics, some of which are not advantageous for transplantation. Here we review the possible mechanisms of PSC-derived cardiomyocytes rejection, summarize the current knowledge pertaining to immunogenicity of such cells and describe the existing controversies. Myocardial graft rejection can be reduced by modifying PSCs prior to their differentiation into cardiomyocytes. Overall, this approach facilitates the development of universal donor stem cells suitable for the regeneration of many different tissue types.

In vitro cardiomyogenic potential of human amniotic fluid stem cells

Stem cell therapy for damaged cardiac tissue is currently limited by a number of factors, including inability to obtain sufficient cell numbers, the potential tumorigenicity of certain types of stem cells and the possible link between stem cell therapy and the development of malignant arrhythmias. In this study, we investigated whether human amniotic fluid-derived stem (hAFS) cells could be a potential source of cells for cardiac cell therapy, by testing the in vitro differentiation capabilities. Undifferentiated hAFS cells express several cardiac genes, including the transcription factor mef2, the gap junction connexin43, and H- and N-cadherin. A 24 h incubation with 5-aza-2'-deoxycytidine (5-AZA-dC) induced hAFS cell differentiation along the cardiac lineage. Evidence for this differentiation included morphological changes, upregulation of cardiac-specific genes (cardiac troponin I and cardiac troponin T) and redistribution of connexin43, as well as downregulation of the stem cell marker SRY-box 2 (sox2). When co-cultured with neonatal rat cardiomyocytes (NRCs), hAFS cells formed both mechanical and electrical connections with the NRCs. Dye transfer experiments showed that calcein dye could be transferred from NRCs to hAFS cells through cellular connections. The gap junction connexin43 likely involved in the communication between the two cell types, because 12-O-tetradecanoylphorbol 13-acetate (TPA) could partially block cellular crosstalk. We conclude that hAFS cells can be differentiated into a cardiomyocyte-like phenotype and can establish functional communication with NRCs. Thus, hAFS cells may potentially be used for cardiac cell therapy.

Electrospun biocomposite nanofibrous patch for cardiac tissue engineering

A bioengineered construct that matches the chemical, mechanical, biological properties and extracellular matrix morphology of native tissue could be suitable as a cardiac patch for supporting the heart after myocardial infarction. The potential of utilizing a composite nanofibrous scaffold of poly(dl-lactide-co-glycolide)/gelatin (PLGA/Gel) as a biomimetic cardiac patch is studied by culturing a population of cardiomyocyte containing cells on the electrospun scaffolds. The chemical characterization and mechanical properties of the electrospun PLGA and PLGA/Gel nanofibers were studied by Fourier transform infrared spectroscopy, scanning electron microscopy and tensile measurements. The biocompatibility of the scaffolds was also studied and the cardiomyocytes seeded on PLGA/Gel nanofibers were found to express the typical functional cardiac proteins such as alpha-actinin and troponin I, showing the easy integration of cardiomyocytes on PLGA/Gel scaffolds. Our studies strengthen the application of electrospun PLGA/Gel nanofibers as a bio-mechanical support for injured myocardium and as a potential substrate for induction of endogenous cardiomyocyte proliferation, ultimately reducing the cardiac dysfunction and improving cardiac remodeling.

Transplantation of mouse embryonic stem cells induces hematopoietic and tissue chimerism in rats

Embryonic stem cells (ESC) can differentiate into all cell lineages, and ESC-like cells were shown to induce hematopoietic chimerism and tolerance in allogeneic models. The aim of our study was to test the capacity of mouse ESC (mESC) to engraft in rats in a xenotransplantation setting. Forty-six rats were transplanted intravenously with 1 million mESC, without immunosuppression (group 1, n = 23) or with cyclosporine (group 2, n = 23). Three months after mESC transplantation, skin grafts were performed from allogeneic, xenogeneic identical to mESC, or xenogeneic third party donors. At day 27 post-transplant, we detected circulating mouse cells in the blood of 4/23 and 5/23 animals of group 1 and group 2, respectively. Chimerism was confirmed by PCR. We also identified long-term surviving murine cells within livers of chimeric animals. Skin grafts showed no difference in survival between allogeneic and xenogeneic donors. Transplantation of xenogeneic mouse ESC induced short-term chimerism in the blood and persistent tissue chimerism in the liver of recipient rats, but did not induce tolerance to skin grafts. Improved immunosuppressive protocols should be tested to prolong chimerism and allow tolerance.

Cardiomyocyte marker expression in a human lymphocyte cell line using mouse cardiomyocyte extract

Cell transplantation shows potential for the treatment of cardiac diseases. Embryonic stem cells, cord blood and mesenchymal stem cells have been suggested as sources for transplantation therapy. Because of some technical limitations with the use of stem cells, transdifferentiation of fully differentiated cells is a potentially useful alternative. We investigated whether human peripheral blood cells could transdifferentiate into cardiomyocyte. Transdifferentiation was induced in a human B lymphocyte cell line (Raji). Cardiomyocyte extract was prepared from adult mouse cardiomyocytes. The cells were treated with 5-aza-2-deoxycytidine and trichostatin A, permeabilized with streptolysin O, and exposed to the mouse cardiomyocyte extract. They were cultured for 10 days, 3 weeks and 4 weeks. Cardiomyocyte markers were detected with immunohistochemistry and flow cytometry. Immunocytochemistry revealed that some cells expressed myosin heavy chain, α-actinin and cardiac troponin T after 3 and 4 weeks. Flow cytometry confirmed these data. In cells exposed to trichostatin A and 5-aza-2-deoxycytidine and permeabilized in the presence of the cardiomyocyte extract, troponin T expression was seen in 3.53% of the cells and 3.11% of them expressed α-actinin. After exposure to the cardiomyocyte extract, some permeabilized cells adhered to the plate loosely; however, the morphology did not change significantly, and they continued to show a rounded shape after 4 weeks. Our treated lymphocytes expressed cardiomyocyte markers. Our results suggest that lymphocytes may be useful in future research as a source of cells for reprogramming procedures.

Tumourigenesis in the infarcted rat heart is eliminated through differentiation and enrichment of the transplanted embryonic stem cells

AIMS

The therapeutic potential of embryonic stem cells (ESCs) in ischaemic heart disease has been widely explored. However, tumourigenesis upon implantation interferes with the clinical application of ESC transplantation. This study aims to evaluate the influence of differentiation and enrichment of transplanted ESCs on tumourigenesis in infarcted rat hearts.

METHODS AND RESULTS

Mouse ESCs (mESCs) were cultured using a bioreactor system to develop embryoid bodies, which were then induced with 1% ascorbic acid to differentiate into cardiomyocytes. The mESCs-derived cardiomyocytes (mESCs-CMs) were enriched by Percoll density gradient separation. The specific markers (OCT-4, Sox2, and Nanog) of undifferentiated ESCs were detected by PCR both in mESCs and in mESCs-CMs, but not in the mESC-derived Percoll-enriched cardiomyocytes (mESC-PE-CMs). Immunosuppressed rats with infarcted hearts were randomly injected with the mESCs, mESC-CMs, or mESC-PE-CMs. Eight weeks after cell transplantation, histological and immunohistochemical analysis showed that the transplantation of both mESCs and mESC-CMs caused the formation of teratomas. The incidence of teratoma was markedly lower (P < 0.05) in the mESC-CMs group than in the mESCs group. The average tumour volume was significantly lower (P < 0.05) in the mESC-CMs group than in the mESCs group. Tumour formation was absent in the mESC-PE-CMs group.

CONCLUSION

Enrichment of the mESC-differentiated cardiomyocytes inhibited the development of teratoma after cell transplantation in the infarcted rat hearts. These findings offer a new strategy for eliminating teratoma formation in ESCs transplantation and could be a step forward in the development of human ESCs transplantation therapy in ischaemic heart disease.

Injectable cardiac tissue engineering for the treatment of myocardial infarction

Heart disease is a leading cause of morbidity and mortality worldwide. Myocardial infarction leads to permanent loss of cardiac tissue and ultimately heart failure. However, current therapies could only stall the progression of the disease. Thus, new therapies are needed to regenerate damaged hearts to overcome poor prognosis of patients with heart failure. The shortage of heart donors is also a factor for innovating new therapies. Although the cardiac performance by cell-based therapy has improved, unsatisfactory cell retention and transplant survival still plague this technique. Because biomaterials can improve the cell retention, survival and differentiation, cardiac tissue engineering is now being explored as an approach to support cell-based therapies and enhance their efficacy for cardiac disease. In the last decade, cardiac tissue engineering has made considerable progress. Among different kinds of approaches in the cardiac tissue engineering, the approach of injectable cardiac tissue engineering is more minimally invasive than that of in vitro engineered tissue or epicardial patch implantation. It is therefore clinically appealing. In this review, we strive to describe the major progress in the flied of injectable cardiac tissue engineering, including seeding cell sources, biomaterials and novel findings in preclinical studies and clinical applications. The remaining problems will also be discussed.

Embryonic stem cell-derived endothelial cells engraft into the ischemic hindlimb and restore perfusion

OBJECTIVE

We examined the effect of delivery modality on the survival, localization, and functional effects of exogenously administered embryonic stem cells (ESCs) or endothelial cells derived from them (ESC-ECs) in the ischemic hindlimb.

METHODS AND RESULTS

Murine ESCs or ESC-ECs were stably transduced with a construct for bioluminescence imaging (BLI) and fluorescent detection. In a syngeneic murine model of limb ischemia, ESCs or ESC-ECs were delivered by intramuscular (IM), intrafemoral artery (IA), or intrafemoral vein injections (n=5 in each group). For 2 weeks, cell survival and localization were tracked by BLI and confirmed by immunohistochemistry, and functional improvement was assessed by laser Doppler perfusion. BLI showed that ESCs localized to the ischemic limb after IM or IA, but not after intrafemoral vein administration. Regardless of the route of administration, ESCs were detected outside the hindlimb circulation in the spleen or lungs. ESCs did not improve limb perfusion and generated teratomas. In contrast, ESC-ECs delivered by all 3 modalities localized to the ischemic limb, as assessed by BLI. Most surprisingly, ESC-EC injected intrafemoral vein eventually localized to the ischemic limb after initially lodging in the pulmonary circulation. Immunohistochemical studies confirmed the engraftment of ESC-ECs into the limb vasculature after 2 weeks. Notably, ESC-ECs were not detected in the spleen or lungs after 2 weeks, regardless of route of administration. Furthermore, ESC-ECs significantly improved limb perfusion and neovascularization compared with the parental ESCs or the vehicle control group.

CONCLUSION

In contrast to parental ESCs, ESC-ECs preferentially localized in the ischemic hindlimb by IA, IM, and intrafemoral vein delivery. ESC-ECs engrafted into the ischemic microvasculature, enhanced neovascularization, and improved limb perfusion.

Stem cell therapy for chronic myocardial infarction

Although recent advances for the treatment of myocardial infarction have dramatically increased the rate of survival after the ischemic event, this has also led to a rise in the number of chronic patients, making the finding of a suitable therapy a compulsory subject for modern medicine. Over the last decade, stem cells have been a promise for the cure of several diseases not only due to their plasticity but also to their capacity to act in a paracrine manner and influence the affected tissue, prompting the launching of several clinical trials. In spite of the knowledge already acquired, stem cell application to chronically infarcted hearts has been much less approached than its acute counterpart. Through this review, we will focus in stem cell therapy in animal models of chronic myocardial infarction: cell types employed, functional results, mechanisms analyzed, and questions raised.