Wanted! The best cell for cardiac regeneration**Editorials published in the Journal of the American College of Cardiologyreflect the views of the authors and do not necessarily represent the views of JACCor the American College of Cardiology

A brief review: adipose-derived stem cells and their therapeutic potential in cardiovascular diseases

Adipose-derived stem cells (ADSCs) are easily obtained and expanded, and have emerged as a novel source of adult stem cells for the treatment of cardiovascular diseases. These cells have been shown to have the capability of differentiating into cardiomyocytes, vascular smooth muscle cells, and endothelial cells. Furthermore, ADSCs secrete a series of paracrine factors to promote neovascularization, reduce apoptosis, and inhibit fibrosis, which contributes to cardiac regeneration. As a novel therapy in the regenerative field, ADSCs still face various limitations, such as low survival and engraftment. Thus, engineering and pharmacological studies have been conducted to solve these problems. Investigations have moved into phase I and II clinical trials examining the safety and efficacy of ADSCs in the setting of myocardial infarction. In this review, we discuss the differentiation and paracrine functions of ADSCs, the strategies promoting their therapeutic efficacy, and their clinical usage.

Reactive oxygen species and fibrosis: further evidence of a significant liaison

Age-related diseases such as obesity, diabetes, non-alcoholic fatty liver disease, chronic kidney disease and cardiomyopathy are frequently associated with fibrosis. Work within the last decade has improved our understanding of the pathophysiological mechanisms contributing to fibrosis development. In particular, oxidative stress and the antioxidant system appear to be crucial modulators of processes such as transforming growth factor-β1 (TGF-β1) signalling, metabolic homeostasis and chronic low-grade inflammation, all of which play important roles in fibrosis development and persistence. In the current review, we discuss the connections between reactive oxygen species, antioxidant enzymes and TGF-β1 signalling, together with functional consequences, reflecting a concept of redox-fibrosis that can be targeted in future therapies.

Graphical abstract

Redox-fibrosis: Impact of TGFβ1 on ROS generators, mediators and functional consequences

Fibrosis is one of the most prevalent features of age-related diseases like obesity, diabetes, non-alcoholic fatty liver disease, chronic kidney disease, or cardiomyopathy and affects millions of people in all countries. Although the understanding about the pathophysiology of fibrosis has improved a lot during the recent years, a number of mechanisms still remain unknown. Although TGF-β1 signaling, loss of metabolic homeostasis and chronic low-grade inflammation appear to play important roles in the pathogenesis of fibrosis, recent evidence indicates that oxidative stress and the antioxidant system may also be crucial for fibrosis development and persistence. These findings point to a concept of a redox-fibrosis where the cellular oxidant and antioxidant system could be potential therapeutic targets. The current review aims to summarize the existing links between TGF-β1 signaling, generation and action of reactive oxygen species, expression of antioxidative enzymes, and functional consequences including epigenetic redox-mediated responses during fibrosis.

Cellular mechanisms of tissue fibrosis. 1. Common and organ-specific mechanisms associated with tissue fibrosis

Fibrosis is a pathological scarring process that leads to destruction of organ architecture and impairment of organ function. Chronic loss of organ function in most organs, including bone marrow, heart, intestine, kidney, liver, lung, and skin, is associated with fibrosis, contributing to an estimated one third of natural deaths worldwide. Effective therapies to prevent or to even reverse existing fibrotic lesions are not yet available in any organ. There is hope that an understanding of common fibrosis pathways will lead to development of antifibrotic therapies that are effective in all of these tissues in the future. Here we review common and organ-specific pathways of tissue fibrosis.

Implantation of CD133+ stem cells in patients undergoing coronary bypass surgery: IMPACT-CABG pilot trial

BACKGROUND

The Implantation of Autologous CD133(+) Stem Cells in Patients Undergoing CABG (IMPACT-CABG) trial is investigating the feasibility, safety, and efficacy of intramyocardial injections of autologous CD133(+) stem cells during coronary artery bypass grafting (CABG) in patients with chronic ischemic cardiomyopathy. We are reporting the results of the first 5 open-label patients.

METHODS

Bone marrow was harvested from iliac crests and stem cells were isolated using the CliniMACS CD133(+) Reagent System (Miltenyi Biotec, GmbH, Bergisch Gladbach, Germany). Patients received CABG, followed by CD133(+) cellular injection in the revascularized hypokinetic myocardium.

RESULTS

Five males New York Heart Association (NYHA) class III patients aged 64 ± 10 years were treated. Immunomagnetic cell processing allowed an average of 100 ± 48-fold enrichment in CD133(+) cells, with 92 ± 11% recovery after selection. Mean number of CD133(+) cells injected was 8.4 ± 1.2 million. There were no protocol-related complications during the 18-month follow-up and all patients improved to NYHA class I. Six-month echocardiography showed no significant improvement in left ventricular ejection fraction (34 ± 2% at baseline vs 38 ± 12%: P = 0.50). However, cardiac magnetic resonance showed that systolic wall thickening increased from 15.0 ± 10.5% to 29.0 ± 22.1% (P = 0.01). In addition, mean segmental wall thickness also improved in comparison with baseline (10.7 ± 2.7% to 12.1 ± 4.8%; P < 0.01).

CONCLUSIONS

This work represents the first Canadian experience with CD133(+) stem cells for the treatment of chronic ischemic cardiomyopathy. These results demonstrate the initial safety and feasibility of the IMPACT-CABG pilot trial. Subsequent patients are now being randomized to receive either CD133(+) stem cell or placebo.

Enhanced mobilization of the bone marrow-derived circulating progenitor cells by intracoronary freshly isolated bone marrow cells transplantation in patients with acute myocardial infarction

Autologous bone marrow cell transplantation (BMCs-Tx) is a promising novel option for treatment of cardiovascular disease. We analysed in a randomized controlled study the influence of the intracoronary autologous freshly isolated BMCs-Tx on the mobilization of bone marrow–derived circulating progenitor cells (BM-CPCs) in patients with acute myocardial infarction (AMI). Sixty-two patients with AMI were randomized to either freshly isolated BMCs-Tx or to a control group without cell therapy. Peripheral blood (PB) concentrations of CD34/45⁺- and CD133/45⁺-circulating progenitor cells were measured by flow cytometry in 42 AMI patients with cell therapy as well as in 20 AMI patients without cell therapy as a control group on days 1, 3, 5, 7, 8 and 3, 6 as well as 12 months after AMI. Global ejection fraction (EF) and the size of infarct area were determined by left ventriculography. We observed in patients with freshly isolated BMCs-Tx at 3 and 12 months follow up a significant reduction of infarct size and increase of global EF as well as infarct wall movement velocity. The mobilization of CD34/45⁺ and CD133/45⁺ BM-CPCs significantly increased with a peak on day 7 as compared to baseline after AMI in both groups (CD34/45⁺: P < 0.001, CD133/45⁺: P < 0.001). Moreover, this significant mobilization of BM-CPCs existed 3, 6 and 12 months after cell therapy compared to day 1 after AMI. In control group, there were no significant differences of CD34/45⁺ and CD133/45⁺ BM-CPCs mobilization between day 1 and 3, 6 and 12 months after AMI. Intracoronary transplantation of autologous freshly isolated BMCs by use of point of care system in patients with AMI may enhance and prolong the mobilization of CD34/45⁺ and CD133/45⁺ BM-CPCs in PB and this might increase the regenerative potency after AMI.

Bone marrow support of the heart in pressure overload is lost with aging

RATIONALE

Exogenous stem cell delivery is under investigation to prevent and treat cardiac dysfunction. It is less studied as to the extent endogenous bone marrow derived stem cells contribute to cardiac homeostais in response to stress and the affects of aging on this stress response.

OBJECTIVE

To determine the role of bone marrow (BM) derived stem cells on cardiac homeostasis in response to pressure overload (PO) and how this response is altered by aging.

METHODS AND RESULTS

Young (8 weeks) and old (>40 weeks) C57/b6 mice underwent homo- and heterochronic BM transplantation prior to transverse aortic constriction (TAC). We found that older BM is associated with decreased cardiac function following TAC. This decreased function is associated with decrease in BM cell engraftment, increased myocyte apoptosis, decreased myocyte hypertrophy, increased myocardial fibrosis and decreased cardiac function. Additionally, there is a decrease in activation of resident cells within the heart in response to PO in old mice. Interestingly, these effects are not due to alterations in vascular density or inflammation in response to PO or differences in ex vivo stem cell migration between young and old mice.

CONCLUSIONS

BM derived stem cells are activated in response to cardiac PO, and the recruitment of BM derived cells are involved in cardiac myocyte hypertrophy and maintenance of function in response to PO which is lost with aging.

Impairment of human cell-based vasculogenesis in rats by hypercholesterolemia-induced endothelial dysfunction and rescue with L-arginine supplementation

OBJECTIVE

Clinical efficacy of cardiac cell therapy may be compromised by its target population, patients with endothelial dysfunction. In vivo inhibition by endothelial dysfunction has been demonstrated for protein angiogenesis but remains unclear for cell therapy. We examined whether hypercholesterolemia inhibits vasculogenic effects of transplanted human circulating progenitor cells in ischemic tissue and whether L-arginine, a nitric oxide donor, might prevent impairment.

METHODS

Athymic rats were fed either normal (group A) or high-cholesterol diets, the latter without (group B) or with (group C) oral L-arginine supplementation. Two weeks later, these rats underwent left femoral artery ligation followed by injection of 2 x 10(6) human circulating progenitor cells into left hind-limb muscle. A fourth group (group D) received supplemented high-cholesterol diets but no cells.

RESULTS

Group B had biochemical evidence of endothelial dysfunction and reduced tissue endothelial nitric oxide synthase expression, whereas group A levels were the same as in group C. By 21 postoperative days, left hind-limb perfusion had recovered fully in groups A and C, partially in D, and not at all in B (38% lower than group A, P < or = .004). Lower arteriolar densities were found in groups and B and D than in groups A and C (P < or = .02). Engrafted human cell numbers were equivalent in all cell-transplanted groups after 3 weeks.

CONCLUSIONS

Endothelial dysfunction inhibited effects of cell therapy, specifically vasculogenesis, suggesting a role for substrate modification to overcome this inhibition. Involved mechanisms appear related to use of cells but not engraftment and require further investigation.

Therapeutic potential of human adipose stem cells in a rat myocardial infarction model

PURPOSE

Stem cell transplantation is expected to have good effects in the treatment of myocardial infarction (MI). We tested the effect of the transplantation of human adipose-derived cells (ASCs) in Sprague-Dawley (SD) rats with myocardial infarctions.

MATERIALS AND METHODS

ASCs were isolated from the waste of elective abdominal surgery. The MI model was set up in SD rats by permanent ligation of the left anterior descending coronary artery. One week after MI, either 1 x 10(6) ASCs or an equal volume of phosphate-buffered saline (PBS) was injected into the infarct zone. Cardiac function was assessed by echocardiography, 1 day, 1 week, 2 weeks, and 4 weeks after treatment. Four weeks after transplantation, immunohistochemistry was performed.

RESULTS

Left ventricular function, including fractional shortening (FS), and ejection fraction (EF) showed a significant improvement in the ASCs transplantation group compared to the PBS group 4 weeks after treatment (p < 0.05). The anterior wall thickness of the left ventricle was significantly thicker in the ASCs transplantation group compared to the PBS group (p < 0.01). Multiple troponin T staining, and irregular, small amounts of connexin 43 expression also was observed in the ASCs transplantation group. Infarcted myocardium showed higher capillary density in the ASCs transplantation group than in the PBS injected group (p < 0.01).

CONCLUSION

This study provides encouraging evidence that transplantation of ASCs can improve cardiac function of infarct myocardium in rat models with a limitation of cardiac remodeling, improved wall thickness, and increased neovascularization.

Adipose-derived cells

Heart failure is by far the most common cause of hospitalization in Western countries, with onerous economic consequences. Cell therapy holds great promise for use in tissue regeneration and is increasingly used in an effort to improve outcomes in cardiac disease. Recently it has been shown that adipose tissue, in addition to committed adipogenic, endothelial progenitor cells and pluripotent vascular progenitor cells, also contains multipotent cell types (adipose-derived stem cells, ADSCs) that, in cell culture conditions, have shown to have an impressive developmental plasticity including the ability to undergo multilineage differentiation and self-renewal. ADSCs express multiple CD marker antigens similar to those observed on MSCs and are also capable of secreting a large number of angiogenesis-related cytokines, including vascular endothelial growth factor, granulocyte/macrophage colony stimulating factor, stromal-derived factor-1alpha, and hepatocyte growth factor. Adipose tissue can be harvested in large quantities with minimal morbidity in several regions of the body and, on average, 100 ml of human adipose tissue yields about 1 x 10(6) stem cells. Studies conducted in porcine AMI models have shown a significant LV functional improvement, with no report of any potentially fatal arrhythmias. The APOLLO trial, a prospective, double blind, randomized, placebo-controlled trial currently in the recruiting phase, is a "first-in-man" study that explores the safety and feasibility of ADSC transplantation in patients with acute MI.

Pilot study to evaluate the safety and feasibility of intracoronary CD133(+) and CD133(-) CD34(+) cell therapy in patients with nonviable anterior myocardial infarction

OBJECTIVES

The long-term effect of intracoronary infusion of progenitor cells in patients with chronic ischemic cardiomyopathy.

BACKGROUND

Bone marrow stem-cell administration in patients with myocardial infarction improved myocardial performance and in some studies contributed to favorable left ventricular remodeling.

METHODS

We report on the results of a pilot, single center, controlled safety, and feasibility study, including 24 patients with old, nonviable anterior myocardial infarction. Twelve patients underwent intracoronary administration of selected CD133(+) and CD133(-)CD34(+) progenitor cells and 12 were followed up on medical therapy. Left ventricular volumes and ejection fraction, at rest and during low-dose dobutamine, and myocardial viability, using TL-201 reinjection scintigraphy, were analyzed at baseline and long-term follow-up.

RESULTS

Patients in the treatment group experienced a sustained decrease in left ventricular end-diastolic and end-systolic resting volumes (P = 0.008 and P = 0.002, respectively), as well as an improvement in global ejection fraction at rest [from (27.2 +/- 6.8)% to (29.7 +/- 7.3)%, P = 0.016]. Segmental anterior and apical wall perfusion, during TL-201 reinjection, were similarly improved (P = 0.005 and P < 0.001, respectively). One patient developed restenosis at the cell delivery site and one progression of atherosclerosis. During 28.0 +/- 8.7 months of clinical follow-up, only one patient experienced deterioration of heart failure. In the control group, we observed stability in the perfusion defect and deterioration in end-diastolic and end-systolic volumes (P= 0.002 and P = 0.003, respectively) and a nonsignificant decrease in ejection fraction (P = 0.11).

CONCLUSION

Intracoronary infusion of selected CD133(+) and CD133(-)CD34(+) progenitor cells to a previously infarcted and nonviable anterior wall is safe, and results in sustained improvement in segmental myocardial perfusion and in favorable left ventricular remodeling.

Regenerative medicine for cardiovascular disorders-new milestones: adult stem cells

Cardiovascular disorders are the leading causes of mortality and morbidity in the developed world. Cell-based modalities have received considerable scientific attention over the last decade for their potential use in this clinical arena. This review was intended as a brief overview on the subject of therapeutic potential of adult stem cells in cardiovascular medicine with basic science findings and the current status of clinical applications. The historical perspective and basic concepts are reviewed and a description of current applications and potential adverse effects in cardiovascular medicine is given. Future improvements on cell-based therapies will likely provide remarkable improvement in survival and quality of life for millions of patients with cardiovascular disorders.

Tissue-engineered injectable collagen-based matrices for improved cell delivery and vascularization of ischemic tissue using CD133+ progenitors expanded from the peripheral blood

BACKGROUND

The use of stem and/or progenitor cells to achieve potent vasculogenesis in humans has been hindered by low cell numbers, implant capacity, and survival. This study investigated the expansion of CD133+ cells and the use of an injectable collagen-based tissue engineered matrix to support cell delivery and implantation within target ischemic tissue.

METHODS AND RESULTS

Adult human CD133+ progenitor cells from the peripheral blood were generated and expanded by successive removal and culture of CD133- cell fractions, and delivered within an injectable collagen-based matrix into the ischemic hindlimb of athymic rats. Controls received injections of phosphate-buffered saline, matrix, or CD133+ cells alone. Immunohistochemistry of hindlimb muscle 2 weeks after treatment revealed that the number of CD133+ cells retained within the target site was >2-fold greater when delivered by matrix than when delivered alone (P<0.01). The transplanted CD133+ cells incorporated into vascular structures, and the matrix itself also was vascularized. Rats that received matrix and CD133+ cells demonstrated greater intramuscular arteriole and capillary density than other treatment groups (P<0.05 and P<0.01, respectively).

CONCLUSIONS

Compared with other experimental approaches, treatment of ischemic muscle tissue with generated CD133+ progenitor cells delivered in an injectable collagen-based matrix significantly improved the restoration of a vascular network. This work demonstrates a novel approach for the expansion and delivery of blood CD133+ cells with resultant improvement of their implantation and vasculogenic capacity.

Intracoronary injection of CD133-positive enriched bone marrow progenitor cells promotes cardiac recovery after recent myocardial infarction: feasibility and safety

BACKGROUND

Bone marrow CD133-positive (CD133+) cells possess high hematopoietic and angiogenic capacity. We tested the feasibility, safety, and functional effects of the use of enriched CD133+ progenitor cells after intracoronary administration in patients with recent myocardial infarction.

METHODS AND RESULTS

Among 35 patients with acute myocardial infarction treated with stenting, 19 underwent intracoronary administration of CD133+ progenitor cells (12.6+/-2.2 x 10(6) cells) 11.6+/-1.4 days later (group 1) and 16 did not (group 2). At 4 months, left ventricular ejection fraction increased significantly in group 1 (from 45.0+/-2.6% to 52.1+/-3.5%, P<0.05), but only tended to increase in case-matched group 2 patients (from 44.3+/-3.1% to 48.6+/-3.6%, P=NS). Likewise, left ventricular regional chordae shortening increased in group 1 (from 11.5+/-1.0% to 16.1+/-1.3%, P<0.05) but remained unchanged in group 2 patients (from 11.1+/-1.1% to 12.7+/-1.3%, P=NS). This was paralleled by reduction in the perfusion defect in group 1 (from 28.0+/-4.1% to 22.5+/-4.1%, P<0.05) and no change in group 2 (from 25.0+/-3.0% to 22.6+/-4.1%, P=NS). In group 1, two patients developed in-stent reocclusion, 7 developed in-stent restenosis, and 2 developed significant de novo lesion of the infarct-related artery. In group 2, four patients showed in-stent restenosis. In group 1 patients without reocclusion, glucose uptake shown by positron emission tomography with 18fluorodeoxyglucose in the infarct-related territory increased from 51.2+/-2.6% to 57.5+/-3.5% (P<0.05). No stem cell-related arrhythmias were noted, either clinically or during programmed stimulation studies at 4 months.

CONCLUSIONS

In patients with recent myocardial infarction, intracoronary administration of enriched CD133+ cells is feasible but was associated with increased incidence of coronary events. Nevertheless, it seems to be associated with improved left ventricular performance paralleled with increased myocardial perfusion and viability.

Muscle-derived stem cells: Implications for effective myoblast transfer therapy

Stem cells have been proposed as a wonder solution for tissue repair in many situations and have attracted much attention in the media for both their therapeutic potential and ethical implications. In addition to the excitement generated by embryonic stem cells, research has now identified a number of stem cells within adult tissues which pose much more realistic targets for therapeutic interventions. Myoblast transfer therapy (MTT) has long been viewed as a potential therapy for the debilitating muscle-wasting disorder Duchenne Muscular Dystrophy. This technique relies on the transplantation of committed muscle precursor cells directly into the muscle fibres but has had little success in clinical trials. The recent discovery of a population of cells within adult muscle with stem cell-like characteristics has interesting implications for the future of such putative cell transplantation therapies. This review focuses on the characterization and application of these potential muscle-derived stem cells (MDSC) to MTT.

Stem cells as future therapy in cardiology

This article focuses on the key studies relevant to the clinical application of stem-cell research in cardiovascular disease. The authors also discuss current and future directions in clinical cardiovascular stem-cell research, including the potential problems and pitfalls that must be addressed to ensure the safety, as well as the efficacy, of treatment regimens in this rapidly evolving therapeutic field.