Human cardiac explant-conditioned medium: soluble factors and cardiomyogenic effect on mesenchymal stem cells

Strategies for constructing pluripotent stem cell- and progenitor cell-derived three-dimensional cardiac micro-tissues

Three-dimensional (3D) cardiac micro-tissue is a promising model for simulating the structural and functional features of heart in vitro. This scientific achievement provides a platform for exploration about the mechanisms on the development, damage, and regeneration of tissue, hence, paving a way toward development of novel therapies for heart diseases. However, 3D micro-tissue technology is still in its infant stages faced with many challenges such as incompleteness of the tissue microarchitecture, loss of the resident immune cells, poor reproducibility, and deficiencies in continuously feeding the nutrients and removing wastes during micro-tissue culturing. There is an urgent need to optimize the construction of 3D cardiac micro-tissue and improve functions of the involved cells. Therefore, scaffolds and cell resources for building 3D cardiac micro-tissues, strategies for inducing the maturation and functionalization of pluripotent stem cell- or cardiac progenitor cell-derived cardiomyocytes, and the major challenges were reviewed in this writing to enable future fabrication of 3D cardiac micro-tissues or organoids for drug screening, disease modeling, regeneration treatment, and so on.

Cardiomyogenesis Modeling Using Pluripotent Stem Cells: The Role of Microenvironmental Signaling

Pluripotent stem cells (PSC) can be used as a model to study cardiomyogenic differentiation. In vitro modeling can reproduce cardiac development through modulation of some key signaling pathways. Therefore, many studies make use of this strategy to better understand cardiomyogenesis complexity and to determine possible ways to modulate cell fate. However, challenges remain regarding efficiency of differentiation protocols, cardiomyocyte (CM) maturation and therapeutic applications. Considering that the extracellular milieu is crucial for cellular behavior control, cardiac niche studies, such as those identifying secreted molecules from adult or neonatal tissues, allow the identification of extracellular factors that may contribute to CM differentiation and maturation. This review will focus on cardiomyogenesis modeling using PSC and the elements involved in cardiac microenvironmental signaling (the secretome - extracellular vesicles, extracellular matrix and soluble factors) that may contribute to CM specification and maturation.

Mesenchymal stem cells in cardiac regeneration: a detailed progress report of the last 6 years (2010-2015)

Mesenchymal stem cells have been used for cardiovascular regenerative therapy for decades. These cells have been established as one of the potential therapeutic agents, following several tests in animal models and clinical trials. In the process, various sources of mesenchymal stem cells have been identified which help in cardiac regeneration by either revitalizing the cardiac stem cells or revascularizing the arteries and veins of the heart. Although mesenchymal cell therapy has achieved considerable admiration, some challenges still remain that need to be overcome in order to establish it as a successful technique. This in-depth review is an attempt to summarize the major sources of mesenchymal stem cells involved in myocardial regeneration, the significant mechanisms involved in the process with a focus on studies (human and animal) conducted in the last 6 years and the challenges that remain to be addressed.

A cocktail method for promoting cardiomyocyte differentiation from bone marrow-derived mesenchymal stem cells

A growing body of evidence supports the argument that bone marrow-derived mesenchymal stem cells (MSCs) can differentiate into cardiomyocyte-like cells in an appropriate cellular environment, but the differentiation rate is low. A cocktail method was designed: we investigated the role of 5-azacytidine (5-aza), salvianolic acid B (SalB), and cardiomyocyte lysis medium (CLM) in inducing MSCs to acquire the phenotypical characteristics of cardiomyocytes. The fourth-passage MSCs were treated with 5-aza, SalB, CLM, 5-aza+salB, 5-aza+CLM, SalB+CLM, and 5-aza+SalB+CLM for 2 weeks. Immunofluorescence results showed that cTnT expression in the 5-aza+salB+CLM group was stronger than other groups. Real-time qPCR and Western blotting analyses showed that cTnT, alpha-cardiac actin, mef-2c, Cx43, and GSK-3beta expression increased while beta-catenin expression decreased. The salB+5-aza+CLM group had the most evident effects. SalB combined with 5-aza and CLM improved cardiomyocyte differentiation from MSCs. In the MSCs differentiation process, the Wnt/beta-catenin signaling pathway had been inhibited.

Cellular extracts from post-mortem human cardiac tissue direct cardiomyogenic differentiation of human adipose tissue-derived stem cells

BACKGROUND AIMS

Human adipose tissue-derived stem cells (hASCs) can be easily (and inexpensively) expanded in culture, and their high plasticity allows their conversion to different cell types. We study the potential capacity of postmortem cardiac tissue to direct cardiac differentiation of hASCs in vitro.

METHODS

Cardiac tissue collected from autopsies was used to obtain cell extracts and conditioned medium, and both approaches were tested for cardiac induction.

RESULTS

Gene expression analyses proved that post-mortem human cardiac tissue maintains genetic integrity. hASCs exposed to the cell extracts or conditioned medium for 2 weeks achieved the appearance of myotube-like structures and were positive for cardiac markers such as sarcomeric α-actinin, cardiac troponin I and T and desmin as proved by immunofluorescence. In addition, differentiated cells showed increased expression of cardiomyocyte-related genes analyzed by reverse transcriptase polymerase chain reaction (GATA-4, myocyte-enhancer factor-2c, α-cardiac actin and cardiac troponin I).

CONCLUSIONS

For the first time, post-mortem human cardiac tissue was used to induce hASC differentiation into myocardial-like cells. The methodology described here would serve as a useful model to obtain cardiomyocyte-like cells in vitro.

Cardiomyocyte-like cells differentiation from non β-catenin expression mesenchymal stem cells

Recent studies have shown that block wnt/β-catenin signaling pathway is integrant for cardiomyocytes differentiation from bone marrow mesenchymal stem cells (MSCs). By transducing the MSCs with lentivirus which contain β-catenin interference RNA, we screened out the non β-catenin expression clone. In the establishment of knockdown β-catenin in MSCs, we investigated the role of 5-azacytidine (5-aza), salvianolic acid B (salB), and cardiomyocytes lysis medium (CLM) in inducing MSCs to differentiate into cardiomyocyte-like cells. A method for culturing MSCs and cardiomyocytes was established. Purified MSCs were investigated by flow cytometry. The MSCs were positive for CD90 and CD29, but negative for CD34 and CD45. Meanwhile, the cardiomyocytes contracted spontaneously after 24 h of seeding into the plates. The fourth-passage non-β-catenin expression MSCs were divided into eight groups: control group, 5-aza, salB, CLM, 5-aza + salB, 5-aza + CLM, salB + CLM, and 5-aza + salB + CLM. The gene and protein expression of cTnT, α-actin, β-myosin, β-catenin, and GSK-3β were detected by quantitative real-time PCR and Western blotting. Our results showed that cTnT expression in 5-aza + salB + CLM group was ninefold higher than in the control group in the non-β-catenin MSCs model, implying that cardiomyocytes differentiation from MSCs is an extremely complicated process and it is necessary to consider the internal and external environmental conditions, such as suitable pharmaceutical inducers, cardiomyocytes microenvironments, inhibition of the negative signaling pathway and so on.

Endometrial regenerative cells for treatment of heart failure: a new stem cell enters the clinic

Heart failure is one of the key causes of morbidity and mortality world-wide. The recent findings that regeneration is possible in the heart have made stem cell therapeutics the Holy Grail of modern cardiovascular medicine. The success of cardiac regenerative therapies hinges on the combination of an effective allogeneic “off the shelf” cell product with a practical delivery system. In 2007 Medistem discovered the Endometrial Regenerative Cell (ERC), a new mesenchymal-like stem cell. Medistem and subsequently independent groups have demonstrated that ERC are superior to bone marrow mesenchymal stem cells (MSC), the most widely used stem cell source in development. ERC possess robust expansion capability (one donor can generate 20,000 patients doses), key growth factor production and high levels of angiogenic activity. ERC have been published in the peer reviewed literature to be significantly more effect at treating animal models of heart failure (Hida et al. Stem Cells 2008).

Current methods of delivering stem cells into the heart suffer several limitations in addition to poor delivery efficiency. Surgical methods are highly invasive, and the classical catheter based techniques are limited by need for sophisticated cardiac mapping systems and risk of myocardial perforation. Medistem together with Dr. Amit Patel Director of Clinical Regenerative Medicine at University of Utah have developed a novel minimally invasive delivery method that has been demonstrated safe and effective for delivery of stem cells (Tuma et al. J Transl Med 2012). Medistem is evaluating the combination of ERC, together with our retrograde delivery procedure in a 60 heart failure patient, double blind, placebo controlled phase II trial. To date 17 patients have been dosed and preliminary analysis by the Data Safety Monitoring Board has allowed for trial continuation.

The combined use of a novel “off the shelf” cell together with a minimally invasive 30 minute delivery method provides a potentially paradigm-shifting approach to cardiac regenerative therapy.

Cardiac stem cell therapy: stemness or commitment?

Cardiac stem cell therapy to promote engraftment of de novo beating cardiac muscle cells in cardiomyopathies could potentially improve clinical outcomes for many patients with congestive heart failure. Clinical trials carried out over the last decade for cardiac regeneration have revealed inadequacy of current approaches in cell therapy. Chief among them is the choice of stem cells to achieve the desired outcomes. Initial enthusiasm of adult bone marrow stems cells for myocyte regeneration has largely been relegated to paracrine-driven, donor cell-independent, endogenous cardiac repair. However, true functional restoration in heart failure is likely to require considerable myocyte replacement. In order to match stem cell application to various clinical scenarios, we review the necessity to preprime stem cells towards cardiac fate before myocardial transplantation and if these differentiated stem cells could confer added advantage over current choice of undifferentiated stem cells. We explore differentiation ability of various stem cells to cardiac progenitors/cardiomyocytes and compare their applicability in providing targeted recovery in light of current clinical challenges of cell therapy.

Heart cells with regenerative potential from pediatric patients with end stage heart failure: a translatable method to enrich and propagate

Background. Human cardiac-derived progenitor cells (hCPCs) have shown promise in treating heart failure (HF) in adults. The purpose of this study was to describe derivation of hCPCs from pediatric patients with end-stage HF. Methods. At surgery, discarded right atrial tissues (hAA) were obtained from HF patients (n = 25; hAA-CHF). Minced tissues were suspended in complete (serum-containing) DMEM. Cells were selected for their tissue migration and expression of stem cell factor receptor (hc-kit). Characterization of hc-kit(positive) cells included immunohistochemical screening with a panel of monoclonal antibodies. Results. Cells, including phase-bright cells identified as hc-kit(positive), spontaneously emigrated from hAA-CHF in suspended explant cultures (SEC) after Day 7. When cocultured with tissue, emigrated hc-kit(positive) cells proliferated, first as loosely attached clones and later as multicellular clusters. At Day 21~5% of cells were hc-kit(positive). Between Days 14 and 28 hc-kit(positive) cells exhibited mesodermal commitment (GATA-4(positive) and NKX2.5(positive)); then after Day 28 cardiac lineages (flk-1(positive), smooth muscle actin(positive), troponin-I(positive), and myosin light chain(positive)). Conclusions. C-kit(positive) hCPCs can be derived from atrial tissue of pediatric patients with end-stage HF. SEC is a novel culture method for derivation of migratory hc-kit(positive) cells that favors clinical translation by reducing the need for exogenously added factors to expand hCPCs in vitro.

Bone marrow-derived human mesenchymal stem cells express cardiomyogenic proteins but do not exhibit functional cardiomyogenic differentiation potential

Despite their paracrine activites, cardiomyogenic differentiation of bone marrow (BM)-derived mesenchymal stem cells (MSCs) is thought to contribute to cardiac regeneration. To systematically evaluate the role of differentiation in MSC-mediated cardiac regeneration, the cardiomyogenic differentiation potential of human MSCs (hMSCs) and murine MSCs (mMSCs) was investigated in vitro and in vivo by inducing cardiomyogenic and noncardiomyogenic differentiation. Untreated hMSCs showed upregulation of cardiac tropopin I, cardiac actin, and myosin light chain mRNA and protein, and treatment of hMSCs with various cardiomyogenic differentiation media led to an enhanced expression of cardiomyogenic genes and proteins; however, no functional cardiomyogenic differentiation of hMSCs was observed. Moreover, co-culturing of hMSCs with cardiomyocytes derived from murine pluripotent cells (mcP19) or with murine fetal cardiomyocytes (mfCMCs) did not result in functional cardiomyogenic differentiation of hMSCs. Despite direct contact to beating mfCMCs, hMSCs could be effectively differentiated into cells of only the adipogenic and osteogenic lineage. After intramyocardial transplantation into a mouse model of myocardial infarction, Sca-1(+) mMSCs migrated to the infarcted area and survived at least 14 days but showed inconsistent evidence of functional cardiomyogenic differentiation. Neither in vitro treatment nor intramyocardial transplantation of MSCs reliably generated MSC-derived cardiomyocytes, indicating that functional cardiomyogenic differentiation of BM-derived MSCs is a rare event and, therefore, may not be the main contributor to cardiac regeneration.

Soluble factors from multipotent mesenchymal stromal cells have antinecrotic effect on cardiomyocytes in vitro and improve cardiac function in infarcted rat hearts

The mechanisms underlying the functional improvement after injection of multipotent mesenchymal stromal cells (MSCs) in infarcted hearts remain incompletely understood. The aim of this study was to investigate if soluble factors secreted by MSCs promote cardioprotection. For this purpose, conditioned medium (CM) was obtained after three passages from MSC cultures submitted to 72 h of conditioning in serum-free DMEM under normoxia (NCM) or hypoxia (HCM) conditions. CM was concentrated 25-fold before use (NCM-25X, concentrated normoxia conditioned medium; HCM-25X, concentrated hypoxia conditioned medium). The in vitro cardioprotection was evaluated in neonatal ventricular cardiomyocytes by quantifying apoptosis after 24 h of serum deprivation associated with hypoxia (1% O(2)) in the absence or presence of NCM and HCM (nonconcentrated and 25-fold concentrated). The in vivo cardioprotection of HCM was tested in a model of myocardial infarction (MI) induced in Wistar male rats by permanent left coronary occlusion. Intramyocardial injection of HCM-25X (n = 14) or nonconditioned DMEM (n = 16) was performed 3 h after coronary occlusion and cardiac function was evaluated 19-21 days after medium injection. Cardiac function was evaluated by electro- and echocardiogram, left ventricular catheterization, and treadmill test. The in vitro results showed that HCM was able to decrease cardiomyocyte necrosis. The in vivo results showed that HCM-25X administered 3 h after AMI was able to promote a significant reduction (35%) in left ventricular end-diastolic pressure and improvement of cardiac contractility (15%) and relaxation (12%). These results suggest that soluble factors released in vitro by MSCs are able to promote cardioprotection in vitro and improve cardiac function in vivo.

Integration potential of mouse and human bone marrow-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) are a multipotent cell population which has been described to exert renoprotective and regenerative effects in experimental models of kidney injury. Several lines of evidence indicate that MSCs also have the ability to contribute to nephrogenesis, suggesting that the cells can be employed in stem cell-based applications aimed at de novo renal tissue generation. In this study we re-evaluate the capacity of mouse and human bone marrow-derived MSCs to contribute to the development of renal tissue using a novel method of embryonic kidney culture. Although MSCs show expression of some genes involved in renal development, their contribution to nephrogenesis is very limited in comparison to other stem cell types tested. Furthermore, we found that both mouse and human MSCs have a detrimental effect on the ex vivo development of mouse embryonic kidney, this effect being mediated through a paracrine action. Stimulation with conditioned medium from a mouse renal progenitor population increases the ability of mouse MSCs to integrate into developing renal tissue and prevents the negative effects on kidney development, but does not appear to enhance their ability to undergo nephrogenesis.