[Cardiac progenitor cells-derived exosomes alleviate myocardial injury by regulating Treg cell differentiation through the mTOR pathway in mice with myocardial infarction].

OBJECTIVE: To investigate the effect of cardiac progenitor cells-derived exosomes (CPCs-Exo) on Treg differentiation in mice with myocardial infarction (MI). METHODS: Mouse models of MI established by ligation of the left anterior descending coronary artery (LAD) were treated with CPCs-Exos, and naive CD4+T cells were isolated from the spleen of the mice and divided into control group, CD4+T cell activation group (CD3+CD28), CPCs-Exos stimulation group (CD3+CD28+CPCs-Exos), mTOR activator group (CD3+CD28+CPCs-Exos+mTOR activator) and mTOR inhibitor group (CD3+CD28+CPCs-Exos+mTOR inhibitor). Western blotting was used to detect the expression levels of mTOR and p-mTOR in the treated cells. Flow cytometry was used to analyze the percentages of Treg and CD4+IL-10+T cells. The infarct size of the mice were measured with 2, 3, 5-triphenyltetrazole chloride (TTC) staining, and serum levels of LDH and CK-MB were detected using an automatic biochemical analyzer. RESULTS: Compared with the control group, the mouse models of MI showed significantly increased release of LDH (P<0.001) and CK-MB (P=0.0002) and increased percentages of Treg and CD4+IL-10+T cells. Treatment with CPC-Exos effectively reduced the MI area and lowered serum levels of LDH (P=0.003) and CK-MB (P=0.003) and the percentages of Tregs (P=0.001) and CD4+IL-10+T cells (P=0.004) in the MI mouse models. In the isolated CD4+T cells, CPCsExos treatment significantly up-regulated the percentages of Treg (P=0.01) and CD4+IL-10+ T cells (P=0.004) and increased the expression of mTOR (P=0.009) and p-mTOR (P=0.009), and these effects could be further enhanced by the mTOR activator but obviously attenuated by the mTOR inhibitor. CONCLUSION: CPCs-Exos promotes the differentiation of Treg in mice with MI by modulating the mTOR signaling pathway.

Cardiac Progenitor Cell Exosomal miR-935 Protects against Oxidative Stress.

Oxidative stress-induced myocardial apoptosis and necrosis are critically involved in ischemic infarction, and several sources of extracellular vesicles appear to be enriched in therapeutic activities. The central objective was to identify and validate the differential exosome miRNA repertoire in human cardiac progenitor cells (CPC). CPC exosomes were first analyzed by LC-MS/MS and compared by RNAseq with exomes of human mesenchymal stromal cells and human fibroblasts to define their differential exosome miRNA repertoire (exo-miRSEL). Proteomics demonstrated a highly significant representation of cardiovascular development functions and angiogenesis in CPC exosomes, and RNAseq analysis yielded about 350 different miRNAs; among the exo-miRSEL population, miR-935 was confirmed as the miRNA most significantly up-regulated; interestingly, miR-935 was also found to be preferentially expressed in mouse primary cardiac Bmi1+high CPC, a population highly enriched in progenitors. Furthermore, it was found that transfection of an miR-935 antagomiR combined with oxidative stress treatment provoked a significant increment both in apoptotic and necrotic populations, whereas transfection of a miR-935 mimic did not modify the response. Conclusion. miR-935 is a highly differentially expressed miRNA in exo-miRSEL, and its expression reduction promotes oxidative stress-associated apoptosis. MiR-935, together with other exosomal miRNA members, could counteract oxidative stress-related apoptosis, at least in CPC surroundings.

Intracoronary Delivery of Porcine Cardiac Progenitor Cells Overexpressing IGF-1 and HGF in a Pig Model of Sub-Acute Myocardial Infarction.

Human cardiac progenitor cells (hCPC) are considered a good candidate in cell therapy for ischemic heart disease, demonstrating capacity to improve functional recovery after myocardial infarction (MI), both in small and large preclinical animal models. However, improvements are required in terms of cell engraftment and efficacy. Based on previously published reports, insulin-growth factor 1 (IGF-1) and hepatocyte growth factor (HGF) have demonstrated substantial cardioprotective, repair and regeneration activities, so they are good candidates to be evaluated in large animal model of MI. We have validated porcine cardiac progenitor cells (pCPC) and lentiviral vectors to overexpress IGF-1 (co-expressing eGFP) and HGF (co-expressing mCherry). pCPC were transduced and IGF1-eGFPpos and HGF-mCherrypos populations were purified by cell sorting and further expanded. Overexpression of IGF-1 has a limited impact on pCPC expression profile, whereas results indicated that pCPC-HGF-mCherry cultures could be counter selecting high expresser cells. In addition, pCPC-IGF1-eGFP showed a higher cardiogenic response, evaluated in co-cultures with decellularized extracellular matrix, compared with native pCPC or pCPC-HGF-mCherry. In vivo intracoronary co-administration of pCPC-IGF1-eGFP and pCPC-HFG-mCherry (1:1; 40 × 106/animal), one week after the induction of an MI model in swine, revealed no significant improvement in cardiac function.

The Spatiotemporal Expression of Notch1 and Numb and Their Functional Interaction during Cardiac Morphogenesis.

Numb family proteins (NFPs), including Numb and Numblike (Numbl), are commonly known for their role as cell fate determinants for multiple types of progenitor cells, mainly due to their function as Notch inhibitors. Previous studies have shown that myocardial NFP double knockout (MDKO) hearts display an up-regulated Notch activation and various defects in cardiac progenitor cell differentiation and cardiac morphogenesis. Whether enhanced Notch activation causes these defects in MDKO is not fully clear. To answer the question, we examined the spatiotemporal patterns of Notch1 expression, Notch activation, and Numb expression in the murine embryonic hearts using multiple approaches including RNAScope, and Numb and Notch reporter mouse lines. To further interrogate the interaction between NFPs and Notch signaling activation, we deleted both Notch1 or RBPJk alleles in the MDKO. We examined and compared the phenotypes of Notch1 knockout, NFPs double knockout, Notch1; Numb; Numbl and RBPJk; Numb; Numbl triple knockouts. Our study showed that Notch1 is expressed and activated in the myocardium at several stages, and Numb is enriched in the epicardium and did not show the asymmetric distribution in the myocardium. Cardiac-specific Notch1 deletion causes multiple structural defects and embryonic lethality. Notch1 or RBPJk deletion in MDKO did not rescue the structural defects in the MDKO but partially rescued the defects of cardiac progenitor cell differentiation, cardiomyocyte proliferation, and trabecular morphogenesis. Our study concludes that NFPs regulate progenitor cell differentiation, cardiomyocyte proliferation, and trabecular morphogenesis partially through Notch1 and play more roles than inhibiting Notch1 signaling during cardiac morphogenesis.

DAND5 Inactivation Enhances Cardiac Differentiation in Mouse Embryonic Stem Cells.

Deciphering the clues of a regenerative mechanism for the mammalian adult heart would save millions of lives in the near future. Heart failure due to cardiomyocyte loss is still one of the significant health burdens worldwide. Here, we show the potential of a single molecule, DAND5, in mouse pluripotent stem cell-derived cardiomyocytes specification and proliferation. Dand5 loss-of-function generated the double of cardiac beating foci compared to the wild-type cells. The early formation of cardiac progenitor cells and the increased proliferative capacity of Dand5 KO mESC-derived cardiomyocytes contribute to the observed higher number of derived cardiac cells. Transcriptional profiling sequencing and quantitative RT-PCR assays showed an upregulation of early cardiac gene networks governing cardiomyocyte differentiation, cell cycling, and cardiac regenerative pathways but reduced levels of genes involved in cardiomyocyte maturation. These findings prompt DAND5 as a key driver for the generation and expansion of pluripotent stem cell-derived cardiomyocytes systems with further clinical application purposes.

Comparison of One and Three Intraventricular Injections of Cardiac Progenitor Cells in a Murine Model of Chronic Ischemic Cardiomyopathy.

Repeated doses of c-kit+ cardiac progenitor cells (CPCs) are superior to a single dose in improving LV function in rats with old myocardial infarction (MI). However, this concept needs testing in different species to determine whether it is generalizable. We used a new murine model of chronic ischemic cardiomyopathy whose unique feature is that cell therapy was started late (3 months) after MI. Mice received three echo-guided intraventricular infusions, 5 weeks apart, of vehicle, CPCs × 1, or CPCs × 3. Echocardiography demonstrated that the single-dose group exhibited improved LV ejection fraction (EF) after the 1st infusion (CPCs), but not after the 2nd and 3rd (vehicle). In contrast, in the multiple-dose group LVEF continued to improve, so that the final value was greater than in vehicle or single-dose groups (P < 0.05). Hemodynamic studies showed that compared with vehicle, both preload-dependent and preload-independent functional parameters were significantly increased in the multiple-dose group but not in the single-dose group. Thus, two independent methods of functional assessment (echocardiography and hemodynamic studies) consistently demonstrated the superiority of three doses of CPCs vs. one dose. Compared with the single-dose group, the multiple-dose group exhibited less LV hypertrophy, as evidenced by a greater reduction in LV/body weight ratio and cardiomyocyte cross-sectional area. Furthermore, unlike the single dose, three CPC doses reduced myocardial inflammatory cells in the risk region. This is the first study of echo-guided intraventricular infusion of CPCs in mice with chronic ischemic cardiomyopathy. The results demonstrate that the beneficial effects of three CPC doses are greater than those of one dose, supporting the concept that multiple treatments are necessary to properly evaluate cell therapy. Our findings indicate that this concept applies not only to rat models but also to murine models. The generalizability of this strategy greatly enhances its importance and provides a rationale for large animal studies. Graphical abstract.

After the storm: an objective appraisal of the efficacy of c-kit+ cardiac progenitor cells in preclinical models of heart disease.

The falsification of data related to c-kit+ cardiac progenitor cells (CPCs) by a Harvard laboratory has been a veritable tragedy. Does this fraud mean that CPCs are not beneficial in models of ischemic cardiomyopathy? At least 50 studies from 26 laboratories independent of the Harvard group have reported beneficial effects of CPCs in mice, rats, pigs, and cats. The mechanism of action remains unclear. Our group has shown that CPCs do not engraft in the diseased heart, do not differentiate into new cardiac myocytes, do not regenerate dead myocardium, and thus work via paracrine mechanisms. A casualty of the misconduct at Harvard has been the SCIPIO trial, a collaboration between the Harvard group and the group in Louisville. The retraction of the SCIPIO paper was caused exclusively by issues with data generated at Harvard, not those generated in Louisville. In the retraction notice, the Lancet editors stated: "Although we do not have any reservations about the clinical work in Louisville that used the preparations from Anversa's laboratory in good faith, the lack of reliability regarding the laboratory work at Harvard means that we are now retracting this paper". We must be careful not to dismiss all work on CPCs because of one laboratory's misconduct. An unbiased review of the literature supports the therapeutic potential of CPCs for heart failure at the preclinical level.

Heart Repair Induced by Cardiac Progenitor Cell Delivery within Polypyrrole-Loaded Cardiogel Post-ischemia.

Myocardial infarction (MI) irreversibly injures the heart tissue. Cardiovascular tissue engineering has been developed as a promising therapeutic approach for post-MI repair. Previously, we discovered the ability of a polypyrrole (PPy)-incorporated cardiogel (CG) for improvement of maturity and functional synchrony of rat neonatal cardiomyocytes. Here, we used the cross-linked form of PPy-incorporated CG (CG-PPy), in order to improve electromechanical properties of scaffold, for application in cardiac progenitor cell (CPC) transplantation on post-MI rat hearts. Improved mechanical property and electrical conductivity (sixfold) were evident in the cross-linked CG-PPy (P1) compared to cross-linked CG (C1) scaffolds. Transplantation of CPC-loaded P1 (P1-CPC) resulted in substantial improvement of cardiac functional properties. Furthermore, lower fibrotic tissue and higher CPC retention were observed. The grafted cells showed cardiomyocyte characteristics when stained with human cardiac troponin T and connexin43 antibodies, while neovessel formation was similarly prominent. These findings highlight the therapeutic promise of the P1 scaffold as a CPC carrier for functional restoration of the heart post-MI.

Cardiac Progenitor Cells.

Cardiovascular diseases top the list of fatal illnesses worldwide. Cardiac tissues is known to be one of te least proliferative in the human body, with very limited regenraive capacity. Stem cell therapy has shown great potential for treatment of cardiovascular diseases in the experimental setting, but success in human trials has been limited. Applications of stem cell therapy for cardiovascular regeneration necessitate understamding of the complex and unique structure of the heart unit, and the embryologic development of the heart muscles and vessels. This chapter aims to provide an insight into cardiac progenitor cells and their potential applications in regenerative medicine. It also provides an overview of the embryological development of cardiac tissue, and the major findings on the development of cardiac stem cells, their characterization, and differentiation, and their regenerative potential. It concludes with clinical applications in treating cardiac disease using different approaches, and concludes with areas for future research.

Transcriptional Profiling of Single Cardiomyocytes in Health and Disease.

PURPOSE OF REVIEW: Cardiomyocytes are the chief cell type in the heart, and are central to the pathogenesis of many cardiac diseases. Increasing recognition of its cellular, molecular, and functional heterogeneity prompted us to review the latest advancements in cardiac health and disease at single-cell resolution. RECENT FINDINGS: Single-cell RNA profiling of cardiac lineage commitment events uncovered immense heterogeneity amongst ostensibly homogeneous cell populations. Classic cardiac transcription factors and new regulatory genes exhibit cell subtype-specific and temporally controlled expression patterns that serve the phenotypic changes in development, disease progression, and regeneration. Dissection of dynamically changing cell-cell communications and cardiac cell plasticity offers new opportunities in disease intervention and cardiac repair. Finally, updates in research models, platforms, and pipelines are continuously increasing the efficiency and reliability in data generation and interpretation. Transcriptional profiling of cardiac lineage cells, especially cardiomyocytes, has tremendously enriched our knowledge of the cellular milieu and the transcriptional network in the heart. Implementing technical standards and interrogating underexplored research areas will further our understanding of this organ and increase the likelihood of finding tractable therapeutic targets.

Engineered M13 Peptide Carrier Promotes Angiogenic Potential of Patient-Derived Human Cardiac Progenitor Cells and In Vivo Engraftment.

BACKGROUND: Despite promising advances in stem cell-based therapy, the treatment of ischemic cardiovascular diseases remains a big challenge due to both the insufficient in vivo viability of transplanted cells and poor angiogenic potential of stem cells. The goal of this study was to develop therapeutic human cardiac progenitor cells (hCPCs) for ischemic cardiovascular diseases with a novel M13 peptide carrier. METHOD: In this study, an engineered M13 peptide carrier was successfully generated using a QuikChange Kit. The cellular function of M13 peptide carrier-treated hCPCs was assessed using a tube formation assay and scratch wound healing assay. The in vivo engraftment and cell survival bioactivities of transplanted cells were demonstrated by immunohistochemistry after hCPC transplantation into a myocardial infarction animal model. RESULTS: The engineered M13RGD+SDKP peptide carrier, which expressed RGD peptide on PIII site and SDKP peptide on PVIII site, did not affect morphologic change and proliferation ability in hCPCs. In contrast, hCPCs treated with M13RGD+SDKP showed enhanced angiogenic capacity, including tube formation and migration capacity. Moreover, transplanted hCPCs with M13RGD+SDKP were engrafted into the ischemic region and promoted in vivo cell survival. CONCLUSION: Our present data provides a promising protocol for CPC-based cell therapy via short-term cell priming of hCPCs with engineered M13RGD+SDKP before cell transplantation for treatment of cardiovascular disease.

Coculture with noncardiac cells promoted maturation of human stem cell-derived cardiomyocyte microtissues.

Cardiomyocytes derived from human pluripotent stem cells (hPSC-CM) provided a promising cell source for cell therapy, drug screening, and disease modeling. However, hPSC-CM are immature and phenotypically more similar to fetal rather than adult cardiomyocytes in vitro. We explored the impact of coculture of human embryonic stem cell-derived mesenchymal stem cells (hESC-MSC) and endothelial cells (ECs) with human embryonic stem cells-derived cardiac progenitor cells (hESC-CPC) on the gene expression and electrophysiological properties of hESC-CPC in 3D culture (microtissue spheroid). In this regard, hESC-CPC were cultured either alone (CM microtissue) or in coculture with EC and hESC-MSC (CMEM microtissue) on agar-coated 96-well round-bottomed plates for 1 week. Lumen-like structures were formed in CMEM but not in CM microtissue. Cardiac progenitor markers (TBX5, GATA4) were downregulated and cardiac sarcomeric transcripts (MLC2v and ß-MHC) were upregulated in CMEM compared with CM microtissue. Furthermore, beating frequencies, beating cycles, and field potential durations of CMEM resided in the range of adult cardiomyocytes rather than fetal like phenotypes observed in CM microtissue. These findings demonstrated that CPC spheroids in coculture with EC and hESC-MSC may undergo greater maturation toward an adult-like cardiomyocyte.

Population and Single-Cell Analysis of Human Cardiogenesis Reveals Unique LGR5 Ventricular Progenitors in Embryonic Outflow Tract.

The morphogenetic process of mammalian cardiac development is complex and highly regulated spatiotemporally by multipotent cardiac stem/progenitor cells (CPCs). Mouse studies have been informative for understanding mammalian cardiogenesis; however, similar insights have been poorly established in humans. Here, we report comprehensive gene expression profiles of human cardiac derivatives from multipotent CPCs to intermediates and mature cardiac cells by population and single-cell RNA-seq using human embryonic stem cell-derived and embryonic/fetal heart-derived cardiac cells micro-dissected from specific heart compartments. Importantly, we discover a uniquely human subset of cono-ventricular region-specific CPCs, marked by LGR5. At 4 to 5 weeks of fetal age, the LGR5+ population appears to emerge specifically in the proximal outflow tract of human embryonic hearts and thereafter promotes cardiac development and alignment through expansion of the ISL1+TNNT2+ intermediates. The current study contributes to a deeper understanding of human cardiogenesis, which may uncover the putative origins of certain human congenital cardiac malformations.

Modification of Cardiac Progenitor Cell-Derived Exosomes by miR-322 Provides Protection against Myocardial Infarction through Nox2-Dependent Angiogenesis.

Myocardial infarction (MI) is the primary cause of cardiovascular mortality, and therapeutic strategies to prevent or mitigate the consequences of MI are a high priority. Cardiac progenitor cells (CPCs) have been used to treat cardiac injury post-MI, and despite poor engraftment, they have been shown to inhibit apoptosis and to promote angiogenesis through poorly understood paracrine effects. We previously reported that the direct injection of exosomes derived from CPCs (CPCexo) into mouse hearts provides protection against apoptosis in a model of acute ischemia/reperfusion injury. Moreover, we and others have reported that reactive oxygen species (ROS) derived from NADPH oxidase (NOX) can enhance angiogenesis in endothelial cells (ECs). Here we examined whether bioengineered CPCexo transfected with a pro-angiogenic miR-322 (CPCexo-322) can improve therapeutic efficacy in a mouse model of MI as compared to CPCexo. Systemic administration of CPCexo-322 in mice after ischemic injury provided greater protection post-MI than control CPCexo, in part, through enhanced angiogenesis in the border zones of infarcted hearts. Mechanistically, the treatment of cultured human ECs with CPCexo-322 resulted in a greater angiogenic response, as determined by increased EC migration and capillary tube formation via increased Nox2-derived ROS. Our study reveals that the engineering of CPCexo via microRNA (miR) programing can enhance angiogenesis, and this may be an effective therapeutic strategy for the treatment of ischemic cardiovascular diseases.

Irisin promotes cardiac progenitor cell-induced myocardial repair and functional improvement in infarcted heart.

Irisin, a newly identified hormone and cardiokine, is critical for modulating body metabolism. New evidence indicates that irisin protects the heart against myocardial ischemic injury. However, whether irisin enhances cardiac progenitor cell (CPC)-induced cardiac repair remains unknown. This study examines the effect of irisin on CPC-induced cardiac repair when these cells are introduced into the infarcted myocardium. Nkx2.5+ CPC stable cells were isolated from mouse embryonic stem cells. Nkx2.5 + CPCs (0.5 × 10 6 ) were reintroduced into the infarcted myocardium using PEGlylated fibrin delivery. The mouse myocardial infarction model was created by permanent ligation of the left anterior descending (LAD) artery. Nkx2.5 + CPCs were pretreated with irisin at a concentration of 5 ng/ml in vitro for 24 hr before transplantation. Myocardial functions were evaluated by echocardiographic measurement. Eight weeks after engraftment, Nkx2.5 + CPCs improved ventricular function as evident by an increase in ejection fraction and fractional shortening. These findings are concomitant with the suppression of cardiac hypertrophy and attenuation of myocardial interstitial fibrosis. Transplantation of Nkx2.5 + CPCs promoted cardiac regeneration and neovascularization, which were increased with the pretreatment of Nkx2.5 + CPCs with irisin. Furthermore, irisin treatment promoted myocyte proliferation as indicated by proliferative markers Ki67 and phosphorylated histone 3 and decreased apoptosis. Additionally, irisin resulted in a marked reduction of histone deacetylase 4 and increased p38 acetylation in cultured CPCs. These results indicate that irisin promoted Nkx2.5 + CPC-induced cardiac regeneration and functional improvement and that irisin serves as a novel therapeutic approach for stem cells in cardiac repair.

Triggering Endogenous Cardiac Repair and Regeneration via Extracellular Vesicle-Mediated Communication.

A variety of paracrine signals create networks within the myocardium and mediate intercellular communications. Indeed, paracrine stimulation of the endogenous regenerative program of the heart, mainly based on resident cardiac progenitor cell (CPC) activation together with cardiomyocyte proliferation, has become increasingly relevant for future cardiac medicine. In the last years, it has been shown that extracellular vesicles (EV), including exosomes (Ex), are powerful conveyors of relevant biological effects. EV have been proposed not only as promising therapeutic tool for triggering cardiac regeneration and improving repair, but also as means of better understanding the physiological and pathological relationships between specific cardiac components, including cardiomyocytes and fibroblasts. Actually, EV from different kinds of exogenous stem cells have been shown to mediate beneficial effects on the injured myocardium. Moreover, endogenous cells, like CPC can instruct cardiovascular cell types, including cardiomyocytes, while cardiac stromal cells, especially fibroblasts, secrete EV that modulate relevant aspects of cardiomyocyte biology, such as hypertrophy and electrophysiological properties. Finally, cardiomyocytes too may release EV influencing the function of other cardiac cell types. Therefore, EV-based crosstalk is thought to be important in both physiology and pathology, being involved in the responses of the heart to noxious stimuli. In this review we will discuss the role of EV in both regulating cardiac homeostasis and driving heart regeneration. In particular, we will address their role in: (i) providing cardio-protection and enhancing cardiac repair mechanisms; (ii) CPC biology; and (iii) influencing adult cardiomyocyte behavior.

ALDH1A3 Is the Key Isoform That Contributes to Aldehyde Dehydrogenase Activity and Affects in Vitro Proliferation in Cardiac Atrial Appendage Progenitor Cells.

High aldehyde dehydrogenase (ALDHhi) activity has been reported in normal and cancer stem cells. We and others have shown previously that human ALDHhi cardiac atrial appendage cells are enriched with stem/progenitor cells. The role of ALDH in these cells is poorly understood but it may come down to the specific ALDH isoform(s) expressed. This study aimed to compare ALDHhi and ALDHlo atrial cells and to identify the isoform(s) that contribute to ALDH activity, and their functional role. Methods and Results: Cells were isolated from atrial appendage specimens from patients with ischemic and/or valvular heart disease undergoing heart surgery. ALDHhi activity assessed with the Aldefluor reagent coincided with primitive surface marker expression (CD34+). Depending on their ALDH activity, RT-PCR analysis of ALDHhi and ALDHlo cells demonstrated a differential pattern of pluripotency genes (Oct 4, Nanog) and genes for more established cardiac lineages (Nkx2.5, Tbx5, Mef2c, GATA4). ALDHhi cells, but not ALDHlo cells, formed clones and were culture-expanded. When cultured under cardiac differentiation conditions, ALDHhi cells gave rise to a higher number of cardiomyocytes compared with ALDHlo cells. Among 19 ALDH isoforms known in human, ALDH1A3 was most highly expressed in ALDHhi atrial cells. Knocking down ALDH1A3, but not ALDH1A1, ALDH1A2, ALDH2, ALDH4A1, or ALDH8A1 using siRNA decreased ALDH activity and cell proliferation in ALDHhi cells. Conversely, overexpressing ALDH1A3 with a retroviral vector increased proliferation in ALDHlo cells. Conclusions: ALDH1A3 is the key isoform responsible for ALDH activity in ALDHhi atrial appendage cells, which have a propensity to differentiate into cardiomyocytes. ALDH1A3 affects in vitro proliferation of these cells.

Evaluation of Hydrogels Presenting Extracellular Matrix-Derived Adhesion Peptides and Encapsulating Cardiac Progenitor Cells for Cardiac Repair.

Cell therapy is an emerging paradigm for the treatment of heart disease. In spite of the exciting and promising preclinical results, the benefits of cell therapy for cardiac repair in patients have been modest at best. Biomaterials-based approaches may overcome the barriers of poor differentiation and retention of transplanted cells. In this study, we prepared and tested hydrogels presenting extracellular matrix (ECM)-derived adhesion peptides as delivery vehicles for c-kit+ cardiac progenitor cells (CPCs). We assessed their effects on cell behavior in vitro as well as cardiac repair in rats undergoing ischemia reperfusion. Hydrogels presenting the collagen-derived GFOGER peptide induced cardiomyocyte differentiation of CPCs as demonstrated by increased expression of cardiomyocyte structural proteins. However, conditioned media obtained from GFOGER hydrogels showed lower levels of secreted reparative factors. Interestingly, following injection in rats undergoing ischemia-reperfusion, treatment with CPCs encapsulated in nonadhesive RDG-presenting hydrogels resulted in the preservation of cardiac contractility and attenuation of postinfarct remodeling whereas the adhesion peptide-presenting hydrogels did not induce any functional improvement. Retention of cells was significantly higher when delivered with nonadhesive hydrogels compared to ECM-derived peptide gels. These data suggest that factors including cell differentiation state, paracrine factors and interaction with biomaterials influence the effectiveness of biomaterials-based cell therapy. A holistic consideration of these multiple variables should be included in cell-biomaterial combination therapy designs.

The epicardium as a source of multipotent adult cardiac progenitor cells: Their origin, role and fate.

Since the regenerative capacity of the adult mammalian heart is limited, cardiac injury leads to the formation of scar tissue and thereby increases the risk of developing compensatory heart failure. Stem cell therapy is a promising therapeutic approach but is facing problems with engraftment and clinical feasibility. Targeting an endogenous stem cell population could circumvent these limitations. The epicardium, a membranous layer covering the outside of the myocardium, is an accessible cell population which plays a key role in the developing heart. Epicardial cells undergo epithelial to mesenchymal transition (EMT), thus providing epicardial derived cells (EPDCs) that migrate into the myocardium and cooperate in myocardial vascularisation and compaction. In the adult heart, injury activates the epicardium, and an embryonic-like response is observed which includes EMT and differentiation of the EPDCs into cardiac cell types. Furthermore, paracrine communication between the epicardium and myocardium improves the regenerative response. The significant role of the epicardium has been shown in both the developing and the regenerating heart. Interestingly, the epicardial contribution to cardiac repair can be improved in several ways. In this review, an overview of the epicardial origin and fate will be given and potential therapeutic approaches will be discussed.