5-Azacytidine-treated human mesenchymal stem/progenitor cells derived from umbilical cord, cord blood and bone marrow do not generate cardiomyocytes in vitro at high frequencies

The mechanical coupling of adult marrow stromal stem cells during cardiac regeneration assessed in a 2-D co-culture model

Postnatal cardiomyocytes undergo terminal differentiation and a restricted number of human cardiomyocytes retain the ability to divide and regenerate in response to ischemic injury. However, whether these neo-cardiomyocytes are derived from endogenous population of resident cardiac stem cells or from the exogenous double assurance population of resident bone marrow-derived stem cells that populate the damaged myocardium is unresolved and under intense investigation. The vital challenge is to ameliorate and/or regenerate the damaged myocardium. This can be achieved by stimulating proliferation of native quiescent cardiomyocytes and/or cardiac stem cell, or by recruiting exogenous autologous or allogeneic cells such as fetal or embryonic cardiomyocyte progenitors or bone marrow-derived stromal stem cells. The prerequisites are that these neo-cardiomyocytes must have the ability to integrate well within the native myocardium and must exhibit functional synchronization. Adult bone marrow stromal cells (BMSCs) have been shown to differentiate into cardiomyocyte-like cells both in vitro and in vivo. As a result, BMSCs may potentially play an essential role in cardiac repair and regeneration, but this concept requires further validation. In this report, we have provided compelling evidence that functioning cardiac tissue can be generated by the interaction of multipotent BMSCs with embryonic cardiac myocytes (ECMs) in two-dimensional (2-D) co-cultures. The differentiating BMSCs were induced to undergo cardiomyogenic differentiation pathway and were able to express unequivocal electromechanical coupling and functional synchronization with ECMs. Our 2-D co-culture system provides a useful in vitro model to elucidate various molecular mechanisms underpinning the integration and orderly maturation and differentiation of BMSCs into neo-cardiomyocytes during myocardial repair and regeneration.

Characterization of immortalized mesenchymal stem cells derived from foetal porcine pancreas

Islet replacement therapy is limited by shortage of donor islet cells. Usage of islet cells derived from porcine pancreatic stem cells (PSCs) is currently viewed as the most promising alternative for human islet transplantation. However, PSCs are rare and have a finite proliferative lifespan. In this study, we isolated and established an immortalized mesenchymal stem cell (MSC) line derived from foetal porcine pancreas, by transfecting human telomerase reverse transcriptase (hTERT) and called these immortalized pancreatic mesenchymal stem cells (iPMSCs). The iPMSCs have been cultured for more than 80 passages and have capacity to differentiate into neurons, cardiomyocytes, germ cells and islet-like cells, analysed by morphology, RT-PCR, western blotting, immunofluorescence, immunocytochemistry and transplantation assay. Islets derived from iPMSCs reversed hyperglycaemia in streptozotocin-induced diabetic mice and secreted insulin and C-peptide in vitro. These results demonstrated that iPMSCs might provide unlimited resources for islet replacement therapy and models for functional cell differentiation.

Therapeutic potential of adult bone marrow-derived mesenchymal stem cells in diseases of the skeleton

Mesenchymal stem cells (MSCs) are the most popular among the adult stem cells in tissue engineering and regenerative medicine. Since their discovery and functional characterization in the late 1960s and early 1970s, MSCs or MSC-like cells have been obtained from various mesodermal and non-mesodermal tissues, although majority of the therapeutic applications involved bone marrow-derived MSCs. Based on its mesenchymal origin, it was predicted earlier that MSCs only can differentiate into mesengenic lineages like bone, cartilage, fat or muscle. However, varied isolation and cell culturing methods identified subsets of MSCs in the bone marrow which not only differentiated into mesenchymal lineages, but also into ectodermal and endodermal derivatives. Although, true pluripotent status is yet to be established, MSCs have been successfully used in bone and cartilage regeneration in osteoporotic fracture and arthritis, respectively, and in the repair of cardiac tissue following myocardial infarction. Immunosuppressive properties of MSCs extend utility of MSCs to reduce complications of graft versus host disease and rheumatoid arthritis. Homing of MSCs to sites of tissue injury, including tumor, is well established. In addition to their ability in tissue regeneration, MSCs can be genetically engineered ex vivo for delivery of therapeutic molecule(s) to the sites of injury or tumorigenesis as cell therapy vehicles. MSCs tend to lose surface receptors for trafficking and have been reported to develop sarcoma in long-term culture. In this article, we reviewed the current status of MSCs with special emphasis to therapeutic application in bone-related diseases.

Cardiomyocyte differentiation of rat bone marrow multipotent progenitor cells is associated with downregulation of Oct-4 expression

This study was to determine if bone marrow multipotent adult progenitor cells (MAPCs) underwent cardiac specification and Oct-4 expression during their cardiomyocyte differentiation in vitro. MAPCs were isolated from rat bone marrow, treated with 5-azacytidine (5-aza, 1μM) for 24h, and cultured in a serum-free medium for cardiac differentiation for up to 35 days. The cells started to express early cardiac-specific genes Nkx2.5 and GATA-4 with a significant increase in their mRNA level within 24h after 5-aza treatment. Western blotting analysis and immunofluorescence staining revealed that the cardiac-specific proteins connexin-43 and troponin I were expressed in the cells 7 days after 5-aza treatment. Flow cytometry analysis demonstrated that over 37% of the cells were positive for troponin I by 35 days of differentiation, although the cells did not display spontaneous contraction. On the other hand, the undifferentiated MAPCs expressed a significant level of the stem-cell-specific marker Oct-4 that was dramatically decreased in the cells shortly after the initiation of cardiomyocyte differentiation as evaluated using real-time (RT)-polymerase chain reaction, Western blotting, immunofluorescence staining, and flow cytometry. These data indicated that MAPCs were able to effectively differentiate into cardiomyocyte-like cells after 5-aza induction in association with downregulation of Oct-4 expression.

Prolongation of cardiac allograft survival by a novel population of autologous CD117+ bone marrow-derived progenitor cells

Autologous CD117(+) progenitor cells (PC) have been successfully utilized in myocardial infarction and ischemic injury, potentially through the replacement/repair of damaged vascular endothelium. To date, such cells have not been used to enhance solid organ transplant outcome. In this study, we determined whether autologous bone marrow-derived CD117(+) PC could benefit cardiac allograft survival, possibly by replacing donor vascular cells. Autologous, positively selected CD117(+) PC were administered posttransplantation and allografts were assessed for acute rejection. Although significant generation of recipient vascular cell chimerism was not observed, transferred PC disseminated both to the allograft and to peripheral lymphoid tissues and facilitated a significant, dose-dependent prolongation of allograft survival. While CD117(+) PC dramatically inhibited alloreactive T cell proliferation in vitro, this property did not differ from nonprotective CD117(-) bone marrow populations. In vivo, CD117(+) PC did not significantly inhibit T cell alloreactivity or increase peripheral regulatory T cell numbers. Thus, rather than inhibiting adaptive immunity to the allograft, CD117(+) PC may play a cytoprotective role in prolonging graft survival. Importantly, autologous CD117(+) PC appear to be distinct from bone marrow-derived mesenchymal stem cells (MSC) previously used to prolong allograft survival. As such, autologous CD117(+) PC represent a novel cellular therapy for promoting allograft survival.

Human endothelial stem/progenitor cells, angiogenic factors and vascular repair

Neovascularization or new blood vessel formation is of utmost importance not only for tissue and organ development and for tissue repair and regeneration, but also for pathological processes, such as tumour development. Despite this, the endothelial lineage, its origin, and the regulation of endothelial development and function either intrinsically from stem cells or extrinsically by proangiogenic supporting cells and other elements within local and specific microenvironmental niches are still not fully understood. There can be no doubt that for most tissues and organs, revascularization represents the holy grail for tissue repair, with autologous endothelial stem/progenitor cells, their proangiogenic counterparts and the products of these cells all being attractive targets for therapeutic intervention. Historically, a great deal of controversy has surrounded the identification and origin of cells and factors that contribute to revascularization, the use of such cells or their products as biomarkers to predict and monitor tissue damage and repair or tumour progression and therapeutic responses, and indeed their efficacy in revascularizing and repairing damaged tissues. Here, we will review the role of endothelial progenitor cells and of supporting proangiogenic cells and their products, principally in humans, as diagnostic and therapeutic agents for wound repair and tissue regeneration.

Human cardiac and bone marrow stromal cells exhibit distinctive properties related to their origin

AIMS

Bone marrow mesenchymal stromal cell (BMStC) transplantation into the infarcted heart improves left ventricular function and cardiac remodelling. However, it has been suggested that tissue-specific cells may be better for cardiac repair than cells from other sources. The objective of the present work has been the comparison of in vitro and in vivo properties of adult human cardiac stromal cells (CStC) to those of syngeneic BMStC.

METHODS AND RESULTS

Although CStC and BMStC exhibited a similar immunophenotype, their gene, microRNA, and protein expression profiles were remarkably different. Biologically, CStC, compared with BMStC, were less competent in acquiring the adipogenic and osteogenic phenotype but more efficiently expressed cardiovascular markers. When injected into the heart, in rat a model of chronic myocardial infarction, CStC persisted longer within the tissue, migrated into the scar, and differentiated into adult cardiomyocytes better than BMStC.

CONCLUSION

Our findings demonstrate that although CStC and BMStC share a common stromal phenotype, CStC present cardiovascular-associated features and may represent an important cell source for more efficient cardiac repair.

Mesenchymal stromal cells from human perinatal tissues: From biology to cell therapy

Cell-based regenerative medicine is of growing interest in biomedical research. The role of stem cells in this context is under intense scrutiny and may help to define principles of organ regeneration and develop innovative therapeutics for organ failure. Utilizing stem and progenitor cells for organ replacement has been conducted for many years when performing hematopoietic stem cell transplantation. Since the first successful transplantation of umbilical cord blood to treat hematological malignancies, non-hematopoietic stem and progenitor cell populations have recently been identified within umbilical cord blood and other perinatal and fetal tissues. A cell population entitled mesenchymal stromal cells (MSCs) emerged as one of the most intensely studied as it subsumes a variety of capacities: MSCs can differentiate into various subtypes of the mesodermal lineage, they secrete a large array of trophic factors suitable of recruiting endogenous repair processes and they are immunomodulatory.Focusing on perinatal tissues to isolate MSCs, we will discuss some of the challenges associated with these cell types concentrating on concepts of isolation and expansion, the comparison with cells derived from other tissue sources, regarding phenotype and differentiation capacity and finally their therapeutic potential.

Differential effect of myocardial matrix and integrins on cardiac differentiation of human mesenchymal stem cells

Dysregulation of matrix synthesis during myocardial fibrosis in post-infarct ventricular remodeling contributes to ventricular dysfunction. Bone marrow stem cell transplantation prevents functional deterioration following myocardial infarction. However, effect of myocardial extracellular matrix (ECM) on stem cell differentiation is poorly understood. We investigate the role of collagen matrices and integrin system in cardiac differentiation and engraftment of stem cells in infarcted myocardium. Sternum-derived bone marrow mesenchymal stem cells (MSCs) were differentiated into cardiomyocyte-like cells (CLCs). They were characterized using RT-PCR, immunofluorescence, flow cytometry and functional integrin neutralization assays. CLCs were injected into peri-infarct borders of injured myocardium of Wistar rats one week following left anterior descending (LAD) artery ligation. Cardiac function was analyzed via pressure-volume relationships. Cardiac differentiated CLCs displayed collagen V specificity, which was absent in undifferentiated MSCs. Collagen V, but not collagen I matrix, promoted attachment, proliferation and cardiac differentiation of CLCs. In contrast to beta(1), alpha(v) integrin contributed minimally in the attachment of CLCs on collagen matrices. However, inhibition of alpha(v)beta(3,) but not alpha(2)beta(1) integrin, selectively attenuated troponin T, sarcomeric alpha-actin and ryanodine 2 receptor gene expression in CLCs. Both MSC and CLC transplantation prevented chamber dilatation and improved contractile function. However, systolic activity in MSC transplanted animals was accompanied by heightened wall stress as demonstrated by elevated myocardial end-diastolic pressure and prolonged tissue relaxation time. Localization of CLCs in the vicinity of collagen V-expressing myofibers promoted their integration into cardiac syncytium. CLCs may facilitate hemodynamic recovery by preserving tissue elasticity in the peri-infarct borders that sustains contractile efficiency for functional recovery in an actively remodeling infarcted myocardium.

A 3-D cardiac muscle construct for exploring adult marrow stem cell based myocardial regeneration

Adult bone marrow stromal cells (BMSCs) are capable of differentiating into cardiomyocyte-like cells in vitro and contribute to myocardial regeneration in vivo. Consequently, BMSCs may potentially play a vital role in cardiac repair and regeneration. However, this concept has been limited by inadequate and inconsistent differentiation of BMSCs into cardiomyocytes along with poor survival and integration of neo-cardiomyocytes after implantation into ischemic myocardium. In order to overcome these barriers and to explore adult stem cell based myocardial regeneration, we have developed an in vitro model of three-dimensional (3-D) cardiac muscle using rat ventricular embryonic cardiomyocytes (ECMs) and BMSCs. When ECMs and BMSCs were seeded sequentially onto a 3-D tubular scaffold engineered from topographically aligned type I collagen-fibers and cultured in basal medium for 7, 14, 21, or 28 days, the maturation and co-differentiation into a cardiomyocyte lineage was observed. Phenotypic induction was characterized at morphological, immunological, biochemical and molecular levels. The observed expression of transcripts coding for cardiomyocyte phenotypic markers and the immunolocalization of cardiomyogenic lineage-associated proteins revealed typical expression patterns of neo-cardiomyogenesis. At the biochemical level differentiating cells exhibited appropriate metabolic activity and at the ultrastructural level myofibrillar and sarcomeric organization were indicative of an immature phenotype. Our 3-D co-culture system sustains the ECMs in vitro continuum of differentiation process and simultaneously induces the maturation and differentiation of BMSCs into cardiomyocyte-like cells. Thus, this novel 3-D co-culture system provides a useful in vitro model to investigate the functional role and interplay of developing ECMs and BMSCs during cardiomyogenic differentiation.

Embryonic and adult stem cell therapy

There are many types of stem cells. All share the characteristics of being able to self-renew and to give rise to differentiated progeny. Over the last decades, great excitement has been generated by the prospect of being able to exploit these properties for the repair, improvement, and/or replacement of damaged organs. However, many hurdles, both scientific and ethical, remain in the path of using human embryonic stem cells for tissue-engineering purposes. In this report we review current strategies for isolating, enriching, and, most recently, inducing the development of human pluripotent stem cells. In so doing, we discuss the scientific and ethical issues associated with this endeavor. Finally, progress in the use of stem cells as therapies for type 1 diabetes mellitus, congestive heart failure, and various neurologic and immunohematologic disorders, and as vehicles for the delivery of gene therapy, is briefly discussed.

Efficient expansion of mesenchymal stromal cells from umbilical cord under low serum conditions

BACKGROUND

Mesenchymal stromal cells (MSC) are of clinical interest for their potential use in regenerative medicine and immunotherapy. Originally derived from bone marrow (BM), MSC have now been isolated from most tissues, including umbilical cord (UC) and UC blood (UCB). If MSC from UC are biologically equivalent to those from BM, they would be attractive as a readily available and non-invasive source for cellular therapies.

METHODS

Sections of UC were separated into vascular and Wharton's jelly (WJ) fractions, which were then digested individually to release MSC that were isolated by plastic adherence in a 10% fetal calf serum (FCS) medium, or a low serum medium designed for multipotent adult progenitor cells (MAPC). The resulting perivascular (PV) and WJ MSC lines were assayed for expression of characteristic markers and differentiation and immunosuppressive properties.

RESULTS

MSC lines were readily derived from most UC tested. Cells grown in MAPC medium (MM) tended to be smaller and more elongated and expressed more nestin, but did not differ substantially in their growth rate, expression of other markers and differentiation capacity. All UC lines tested were adipogenic but poorly osteogenic, and were equivalent in their ability to suppress T-cell proliferation induced by phytohemagglutinin (PHA), activation beads and allostimulation.

CONCLUSIONS

UC is a convenient, efficient source of MSC that can be expanded under low serum conditions for application on future studies of tissue regeneration and immunosuppression.

Delayed enrichment of mesenchymal cells promotes cardiac lineage and calcium transient development

Bone marrow-derived mesenchymal stem cells (BM-MSCs) can be induced to differentiate into myogenic cells. Despite their potential, previous studies have not been successful in producing a high percentage of cardiac-like cells with a muscle phenotype. We hypothesized that cardiac lineage development in BM-MSC is related to cell passage, culture milieu, and enrichment for specific cell subtypes before and during differentiation. Our study demonstrated that Lin(-) BM-MSC at an intermediate passage (IP; P8-P12) expressed cardiac troponin T (cTnT) after 21 days in culture. Cardiac TnT expression was similar whether IP cells were differentiated in media containing 5-azacytidine+2% FBS (AZA; 14%) or 2% FBS alone (LS; 12%) and both were significantly higher than AZA+5% FBS. This expression was potentiated by first enriching for CD117/Sca-1 cells followed by differentiation (AZA, 39% and LS, 28%). A second sequential enrichment for the dihydropyridine receptor subunit alpha2delta1 (DHPR-alpha2) resulted in cardiac TnT expressed in 54% of cultured cells compared to 28% of cells after CD117/Sca-1(+) enrichment. Cells enriched for CD117/Sca-1 and subjected to differentiation displayed spontaneous intracellular Ca(2+) transients with an increase in transient frequency and a 60% decrease in the transient duration amplitude between days 14 and 29. In conclusion, IP CD117/Sca-1(+) murine BM-MSCs display robust cardiac muscle lineage development that can be induced independent of AZA but is diminished under higher serum concentrations. Furthermore, temporal changes in calcium kinetics commensurate with increased cTnT expression suggest progressive maturation of a cardiac muscle lineage. Enrichment with CD117/Sca-1 to establish lineage commitment followed by DHPR-alpha2 in lineage developing cells may enhance the therapeutic potential of these cells for transplantation.

Stem cell-related therapies for vascular diseases

The therapeutic potential of 'adult' or at least non-embryonic stem cells and their progeny has developed gradually over the past half century as a consequence of the wealth of knowledge derived from stem cell research. Translational research coupled with clinical trials and derived from basic research has led the way to the clinic. This commenced with the use of haematopoietic stem cell transplantation (HSCT), to treat haematological malignancies, to be followed by the most recent clinical trials to treat a variety of coronary and peripheral artery diseases. Stem cells and their progeny isolated from bone marrow or blood appear to exert an ameliorating effect in certain vascular disorders. Although promising, some of these treatments remain controversial and further research and, where indicated, appropriately powered trials are required to confirm the safety and determine the efficacy of these novel therapies.

Route of delivery and baseline left ventricular ejection fraction, key factors of bone-marrow-derived cell therapy for ischaemic heart disease

AIMS

Previous evaluation of autologous bone-marrow stem-cell (BMSC) therapy following acute myocardial infarction (AMI) suggests that cell dose and timing of stem-cell administration post-MI are important factors in the efficacy of cellular therapy. This study aimed to assess whether route of delivery and baseline left ventricular ejection fraction (LVEF) of the participants may also affect the outcome of BMSC treatment in patients with AMI and ischaemic heart disease (IHD).

METHODS AND RESULTS

Randomized controlled trials of BMSCs as treatment for AMI and IHD were identified by searching MEDLINE, EMBASE, the Cochrane Library, and the Current Controlled Trials Register through to November 2008. Twenty-one trials (25 comparisons) with a total of 1091 participants were eligible. Data were analysed using a random-effects model. Improvement in LVEF in favour of the control was observed when BMSC were administered by intracoronary infusion [-0.19% (95% CI, -0.24 to -0.14; P < 0.00001)] in IHD patients. However, the effect on LVEF was statistically significant and in favour of BMSC when cells were delivered by intra-myocardial injection [5.85% (95% CI, 2.50-9.19; P = 0.0006)]. The significant improvement in LVEF observed in AMI patients was independent from the baseline LVEF of the participants. However, in patients suffering from chronic IHD, increase in LVEF was significant only in the group with lower LVEF at baseline [4.42% (CI, 1.87-6.96; P = 0.0007)].

CONCLUSION

Clinical evidence suggests that route of delivery and baseline LVEF influence the effect of BMSC therapy in treating AMI and chronic IHD.

Effect of human umbilical cord blood cells on Ang-II-induced hypertrophy in mice

We have assessed the capacity of human umbilical cord blood (hUCB)-derived stem cells to differentiate into cardiomyocytes and repair angiotensin II induced insult in culture and in mouse hearts when injected. hUCB were able to differentiate into cardiomyocyte-like cells, when induced with 5-azacytidine or co-cultured with rat neonatal cardiomyocytes (NRCM). When co-cultured, hUCB reversed the pathological effects induced by angiotensin II (Ang-II) in NRCM and in mice injected after Ang-II infusion. As assessed by increased heart weight to body mass ratio and Ang-II-induced fibrosis, cardiac hypertrophy was also reduced after hUCB were injected. hUCB also reversed the pathological heart failure markers induced by Ang-II in mice. Further, we observed a shift from pathological hypertrophy towards physiological hypertrophy by hUCB in Ang-II-challenged mice. Our findings support hUCB as a feasible model for experimentation in stem cell therapy and emphasize the relevance of the hUCB in reversing heart failure conditions.

Human embryonic stem cells and cardiac cell fate

Human embryonic stem (HES) cells are pluripotent and give rise to any cell lineage. More specifically, how the first embryonic lineage (i.e., cardiac lineage) is acquired remains in many aspects questionable. Herein, we summarize the protocols that have been used to direct the fate of HES cells toward the cardiomyocytic lineage. We further discuss the regulation of transcriptional pathways underlying this process of differentiation. Finally, we propose perspectives of this research in the near future.

Mesenchymal stem cells and cardiac repair

Accumulating clinical and experimental evidence indicates that mesenchymal stem cells (MSCs) are promising cell types in the treatment of cardiac dysfunction. They may trigger production of reparative growth factors, replace damaged cells and create an environment that favours endogenous cardiac repair. However, identifying mechanisms which regulate the role of MSCs in cardiac repair is still at work. To achieve the maximal clinical benefits, ex vivo manipulation can further enhance MSC therapeutic potential. This review focuses on the mechanism of MSCs in cardiac repair, with emphasis on ex vivo manipulation.