Cardiac cell therapies: the next generation

Intracellular Development of Resident Cardiac Stem Cells: An Overlooked Phenomenon in Myocardial Self-Renewal and Regeneration

At present, the approaches aimed at increasing myocardial regeneration after infarction are not available. The key question is the identity of cells capable of producing functional cardiac myocytes (CMs), replenishing those lost during ischemia. With identification of resident cardiac stem cells (CSCs), it has been supposed that this cell population may be crucial for myocardial self-renewal and regeneration. In the last few years, the focus has been shifted towards another concept, implying that new CMs are produced by dedifferentiation and proliferation of mature CMs. The observation that CSCs can undergo development inside immature cardiac cells by formation of “cell-in-cell structures” (CICSs) has enabled us to conclude that encapsulated CICSs are implicated in mammalian cardiomyogenesis over the entire lifespan. Earlier we demonstrated that new CMs are produced through formation of CSC-derived transitory amplifying cells (TACs) either in the CM colonies or inside encapsulated CICSs. In this study, we described the phenomenon of CSC penetration into mature CMs, resulting in the formation of vacuole-like CICSs (or non-encapsulated CICSs) containing proliferating CSCs with subsequent differentiation of CSC progeny into TACs and their release. In addition, we compared the phenotypes of TACs derived from encapsulated and non-encapsulated CICSs developing in immature and mature CMs, respectively.

Human Endomyocardial Biopsy Specimen-Derived Stromal Cells Modulate Angiotensin II-Induced Cardiac Remodeling

: Cardiac-derived adherent proliferating cells (CardAPs) are cells derived from human endomyocardial biopsy specimens; they share several properties with mesenchymal stromal cells. The aims of this study were to evaluate whether intramyocardial injection of CardAPs modulates cardiac fibrosis and hypertrophy in a mouse model of angiotensin II (Ang II)-induced systolic heart failure and to analyze underlying mechanisms. Intramyocardial application of 200,000 CardAPs improved left ventricular function. This was paralleled by a decline in left ventricular remodeling, as indicated by a reduction in cardiac fibrosis and hypertrophy. CardAPs reduced the ratio of the left ventricle to body weight and cardiac myosin expression (heavy chain), and decreased the Ang II-induced phosphorylation state of the cardiomyocyte hypertrophy mediators Akt, extracellular-signal regulated kinase (ERK) 1, and ERK2. In accordance with the antifibrotic and antihypertrophic effects of CardAPs shown in vivo, CardAP supplementation with cardiac fibroblasts decreased the Ang II-induced reactive oxygen species production, α-SMA expression, fibroblast proliferation, and collagen production. Coculture of CardAPs with HL-1 cardiomyocytes downregulated the Ang II-induced expression of myosin in HL-1. All antifibrotic and antihypertrophic features of CardAPs were mediated in a nitric oxide- and interleukin (IL)-10-dependent manner. Moreover, CardAPs induced a systemic immunomodulation, as indicated by a decrease in the activity of splenic mononuclear cells and an increase in splenic CD4CD25FoxP3, CD4-IL-10, and CD8-IL-10 T-regulatory cells in Ang II mice. Concomitantly, splenocytes from Ang II CardAPs mice induced less collagen in fibroblasts compared with splenocytes from Ang II mice. We conclude that CardAPs improve Ang II-induced cardiac remodeling involving antifibrotic and antihypertrophic effects via paracrine actions and immunomodulatory properties.

SIGNIFICANCE

Despite effective pharmacological treatment with angiotensin II type I receptor antagonists or angiotensin II-converting enzyme inhibitors, morbidity and mortality associated with heart failure are still substantial, prompting the search of novel therapeutic strategies. There is accumulating evidence supporting the use of cell therapy for cardiac repair. This study demonstrates that cells derived from human endomyocardial biopsies, cardiac-derived adherent proliferating cells (CardAPs), have the potential to reduce angiotensin II-induced cardiac remodeling and improve left ventricular function in angiotensin II mice. The mechanism involves antifibrotic and antihypertrophic effects via paracrine actions and immunomodulatory properties. These findings support the potential of CardAPs for the treatment of heart failure.

Adult stem cells and cardiac regeneration

There is worldwide demand for therapies to promote the robust repair and regeneration with maximum regain of function of particular tissues and organs damaged by disease or injury. The potential role of adult stem cells has been highlighted by an increasing number of in vitro and in vivo studies. Nowhere is this more evident than in adult stem cell-based therapies being explored to promote cardiac regeneration. In spite of encouraging advances, significant challenges remain.

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.

Calcium-alginate hydrogel-encapsulated fibroblasts provide sustained release of vascular endothelial growth factor

Vascularization of engineered or damaged tissues is essential to maintain cell viability and proper tissue function. Revascularization of the left ventricle (LV) of the heart after myocardial infarction is particularly important, since hypoxia can give rise to chronic heart failure due to inappropriate remodeling of the LV after death of cardiomyocytes (CMs). Fibroblasts can express vascular endothelial growth factor (VEGF), which plays a major role in angiogenesis and also acts as a chemoattractant and survival factor for CMs and cardiac progenitors. In this in vitro model study, mouse NIH 3T3 fibroblasts encapsulated in 2% w/v Ca-alginate were shown to remain viable for 150 days. Semiquantitative reverse transcription-polymerase chain reaction and immunohistochemistry demonstrated that over 21 days of encapsulation, fibroblasts continued to express VEGF, while enzyme-linked immunosorbent assay showed that there was sustained release of VEGF from the Ca-alginate during this period. The scaffold degraded gradually over the 21 days, without reduction in volume. Cells released from the Ca-alginate at 7 and 21 days as a result of scaffold degradation were shown to retain viability, to adhere to fibronectin in a normal manner, and continue to express VEGF, demonstrating their potential to further contribute to maintenance of cardiac function after scaffold degradation. This model in vitro study therefore demonstrates that fibroblasts encapsulated in Ca-alginate provide sustained release of VEGF.

Intra coronary freshly isolated bone marrow cells transplantation improve cardiac function in patients with ischemic heart disease

Background

Autologous bone marrow cell transplantation (BMCs-Tx) is a promising novel option for treatment of cardiovascular disease. In this study we analyzed whether intracoronary autologous freshly isolated BMCs-Tx have beneficial effects on cardiac function in patients with ischemic heart disease (IHD).

Results

In this prospective nonrandomized study we treated 12 patients with IHD by freshly isolated BMCs-Tx by use of point of care system and compared them with a representative 12 control group without cell therapy. Global ejection fraction (EF) and infarct size area were determined by left ventriculography.

Intracoronary transplantation of autologous freshly isolated BMCs led to a significant reduction of infarct size (p < 0.001) and an increase of global EF (p = 0.003) as well as infarct wall movement velocity (p < 0.001) after 6 months follow-up compared to control group. In control group there were no significant differences of global EF, infarct size and infarct wall movement velocity between baseline and 6 months after coronary angiography. Furthermore, we found significant decrease in New York Heart Association (NYHA) as well as significant decrease of B-type natriuretic peptide (BNP) level 6 months after intracoronary cell therapy (p < 0.001), whereas there were no significant differences in control group 6 months after coronary angiography.

Conclusions

These results demonstrate that intracoronary transplantation of autologous freshly isolated BMCs by use of point of care system is safe and may lead to improvement of cardiac function in patients with IHD.

Trial registration

Registration number: ISRCTN54510226

From tendon to nerve: an MSC for all seasons

The potential of mesenchymal stem cells (MSCs) to regenerate damaged tissue is well documented, as this specialized progenitor cell type exhibits superior cellular properties, and would allow medical as well as ethical limitations to be overcome. By now, MSCs have been successfully introduced in manifold experimental approaches within the newly defined realm of Regenerative Medicine. Advanced methods for in vitro cell expansion, defined induction of distinct differentiation processes, 3-dimensional culture on specific scaffold material, and tissue engineering approaches have been designed, and many clinical trials not only have been launched, but recently could be completed. To date, most of the MSC-based therapeutic approaches have been executed to address bone, cartilage, or heart regeneration; further, prominent studies have shown the efficacy of ex vivo expanded and infused MSCs to countervail graft-versus-host disease. Yet more fields of application emerge in which MSCs unfold beneficial effects, and presently, therapies that effectively ameliorate nonhealing conditions after tendon or spinal cord injury are, courtesy of scientific research, forging ahead to the clinical trial stage.

Human amniotic fluid stem cell preconditioning improves their regenerative potential

Human amniotic fluid stem (hAFS) cells, a novel class of broadly multipotent stem cells that share characteristics of both embryonic and adult stem cells, have been regarded as promising candidate for cell therapy. Taking advantage by the well-established murine model of acute kidney injury (AKI), we studied the proregenerative effect of hAFS cells in immunodeficient mice injected with the nephrotoxic drug cisplatin. Infusion of hAFS cells in cisplatin mice improved renal function and limited tubular damage, although not to control level, and prolonged animal survival. Human AFS cells engrafted injured kidney predominantly in peritubular region without acquiring tubular epithelial markers. Human AFS cells exerted antiapoptotic effect, activated Akt, and stimulated proliferation of tubular cells possibly via local release of factors, including interleukin-6, vascular endothelial growth factor, and stromal cell-derived factor-1, which we documented in vitro to be produced by hAFS cells. The therapeutic potential of hAFS cells was enhanced by cell pretreatment with glial cell line-derived neurotrophic factor (GDNF), which markedly ameliorated renal function and tubular injury by increasing stem cell homing to the tubulointerstitial compartment. By in vitro studies, GDNF increased hAFS cell production of growth factors, motility, and expression of receptors involved in cell homing and survival. These findings indicate that hAFS cells can promote functional recovery and contribute to renal regeneration in AKI mice via local production of mitogenic and prosurvival factors. The effects of hAFS cells can be remarkably enhanced by GDNF preconditioning.

Human cardiac-derived adherent proliferating cells reduce murine acute Coxsackievirus B3-induced myocarditis

Background

Under conventional heart failure therapy, inflammatory cardiomyopathy typically has a progressive course, indicating a need for alternative therapeutic strategies to improve long-term outcomes. We recently isolated and identified novel cardiac-derived cells from human cardiac biopsies: cardiac-derived adherent proliferating cells (CAPs). They have similarities with mesenchymal stromal cells, which are known for their anti-apoptotic and immunomodulatory properties. We explored whether CAPs application could be a novel strategy to improve acute Coxsackievirus B3 (CVB3)-induced myocarditis.

Methodology/Principal Findings

To evaluate the safety of our approach, we first analyzed the expression of the coxsackie- and adenovirus receptor (CAR) and the co-receptor CD55 on CAPs, which are both required for effective CVB3 infectivity. We could demonstrate that CAPs only minimally express both receptors, which translates to minimal CVB3 copy numbers, and without viral particle release after CVB3 infection. Co-culture of CAPs with CVB3-infected HL-1 cardiomyocytes resulted in a reduction of CVB3-induced HL-1 apoptosis and viral progeny release. In addition, CAPs reduced CD4 and CD8 T cell proliferation. All CAPs-mediated protective effects were nitric oxide- and interleukin-10-dependent and required interferon-γ. In an acute murine model of CVB3-induced myocarditis, application of CAPs led to a decrease of cardiac apoptosis, cardiac CVB3 viral load and improved left ventricular contractility parameters. This was associated with a decline in cardiac mononuclear cell activity, an increase in T regulatory cells and T cell apoptosis, and an increase in left ventricular interleukin-10 and interferon-γ mRNA expression.

Conclusions

We conclude that CAPs are a unique type of cardiac-derived cells and promising tools to improve acute CVB3-induced myocarditis.

Pharmacological and biological antiviral therapeutics for cardiac coxsackievirus infections

Subtype B coxsackieviruses (CVB) represent the most commonly identified infectious agents associated with acute and chronic myocarditis, with CVB3 being the most common variant. Damage to the heart is induced both directly by virally mediated cell destruction and indirectly due to the immune and autoimmune processes reacting to virus infection. This review addresses antiviral therapeutics for cardiac coxsackievirus infections discovered over the last 25 years. One group represents pharmacologically active low molecular weight substances that inhibit virus uptake by binding to the virus capsid (e.g., pleconaril) or inactivate viral proteins (e.g., NO-metoprolol and ribavirin) or inhibit cellular proteins which are essential for viral replication (e.g., ubiquitination inhibitors). A second important group of substances are interferons. They have antiviral but also immunomodulating activities. The third and most recently discovered group includes biological and cellular therapeutics. Soluble receptor analogues (e.g., sCAR-Fc) bind to the virus capsid and block virus uptake. Small interfering RNAs, short hairpin RNAs and antisense oligonucleotides bind to and led to degradation of the viral RNA genome or cellular RNAs, thereby preventing their translation and viral replication. Most recently mesenchymal stem cell transplantation has been shown to possess antiviral activity in CVB3 infections. Taken together, a number of antiviral therapeutics has been developed for the treatment of myocardial CVB infection in recent years. In addition to low molecular weight inhibitors, biological therapeutics have become promising anti-viral agents.

Induced pluripotent stem cells in cardiovascular medicine

Induced pluripotent stem (iPS) cells are generated by reprogramming human somatic cells through the forced expression of several embryonic stem (ES) cell-specific transcription factors. The potential of iPS cells is having a significant impact on regenerative medicine, with the promise of infinite self-renewal, differentiation into multiple cell types, and no problems concerning ethics or immunological rejection. Human iPS cells are currently generated by transgene introduction principally through viral vectors, which integrate into host genomes, although the associated risk of tumorigenesis is driving research into nonintegration methods. Techniques for pluripotent stem cell differentiation and purification to yield cardiomyocytes are also advancing constantly. Although there remain some unsolved problems, cardiomyocyte transplantation may be a reality in the future. After those problems will be solved, applications of human iPS cells in human cardiovascular regenerative medicine will be envisaged for the future. Furthermore, iPS cell technology has generated new human disease models using disease-specific cells. This paper summarizes the progress of iPS cell technology in cardiovascular research.

In search of new therapeutic targets and strategies for heart failure: recent advances in basic science

Chronic heart failure continues to impose a substantial health-care burden, despite recent treatment advances. The key pathophysiological process that ultimately leads to chronic heart failure is cardiac remodelling in response to chronic disease stresses. Here, we review recent advances in our understanding of molecular and cellular mechanisms that play a part in the complex remodelling process, with a focus on key molecules and pathways that might be suitable targets for therapeutic manipulation. Such pathways include those that regulate cardiac myocyte hypertrophy, calcium homoeostasis, energetics, and cell survival, and processes that take place outside the cardiac myocyte--eg, in the myocardial vasculature and extracellular matrix. We also discuss major gaps in our current understanding, take a critical look at conventional approaches to target discovery that have been used to date, and consider new investigational avenues that might accelerate clinically relevant discovery.