Stem Cell Rev and Rep DOI 10.1007/s12015-014-9502-7
Therapeutic Application of Adipose Derived Stem Cells in Acute Myocardial Infarction: Lessons from Animal Models B. A. Naaijkens & A. van Dijk & O. Kamp & P. A. J. Krijnen & H. W. M. Niessen & L. J. M. Juffermans
# Springer Science+Business Media New York 2014
Abstract The majority of patients survive an acute myocardial infarction (AMI). Their outcome is negatively influenced by post-AMI events, such as loss of viable cardiomyocytes due to a post-AMI inflammatory response, eventually resulting in heart failure and/or death. Recent pre-clinical animal studies indicate that mesenchymal stem cells derived from adipose tissue (ASC) are new promising candidates that may facilitate cardiovascular regeneration in the infarcted myocardium. In this review we have compared all animal studies in which ASC were used as a therapy post-AMI and have focused on aspects that might be important for future successful clinical application of ASC.
B. A. Naaijkens (*) : A. van Dijk : P. A. J. Krijnen : H. W. M. Niessen Department of Pathology, VU University Medical Center, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands e-mail: [email protected] H. W. M. Niessen Department of Cardiac Surgery, VU University Medical Center, Amsterdam, The Netherlands L. J. M. Juffermans Department of Physiology, VU University Medical Center, Amsterdam, The Netherlands O. Kamp : L. J. M. Juffermans Department of Cardiology, VU University Medical Center, Amsterdam, The Netherlands B. A. Naaijkens : A. van Dijk : O. Kamp : P. A. J. Krijnen : H. W. M. Niessen : L. J. M. Juffermans Institute of Cardiovascular Research (ICaR-VU), VU University Medical Center, Amsterdam, The Netherlands B. A. Naaijkens : O. Kamp : L. J. M. Juffermans Interuniversity Cardiology Institute of the Netherlands (ICIN), Utrecht, The Netherlands
Keywords Adipose derived stem cells . Acute myocardial infarction . Animal models . Cellular therapy
Abbreviations ASC Adipose derived stem cell AMI Acute myocardial infarction IV Intravenous injection IC Intracoronary injection IM Intramyocardial injection MSC Mesenchymal stem cell BMSC Bone marrow derived mesenchymal stem cell SVF Stromal vascular fraction LVEF Left ventricular ejection fraction I/R Ischemia/reperfusion
Introduction Coronary artery disease is a leading cause of morbidity and mortality in western society. Although the majority of patients that have suffered an acute myocardial infarction (AMI) survive this initial infarction, they may die due to long term complications [1–3]. Death of cardiomyocytes is not only induced by the ischemic event itself, but also by inflammation-induced necrosis post-AMI. These lost cardiomyocytes are then replaced by non-contractile scar tissue, facilitating cardiac function impairment, eventually resulting in heart failure. Although life-saving cardiovascular therapies, such as percutaneous coronary intervention, implantable defibrillators and pharmacotherapeutics, improved therapy post-AMI in the last decades, these current treatments do not actively restore or regenerate the damaged myocardial tissue [2–4]. Therefore, replenishing lost cardiomyocytes using stem cell therapy was hypothesized to be an ideal
Stem Cell Rev and Rep
solution to retain cardiac function and prevent heart failure development. The first adult mesenchymal stem cells used in therapy post-AMI in preclinical and clinical studies were isolated from bone marrow [5]. Zuk et al. showed in 2002 that adipose tissue is another interesting source of adult mesenchymal stem cells, which are now known as adipose derived stem cells (ASC) [6]. In general ASC have similar characteristics as bone marrow derived mesenchymal stem cells (BMSC). Both can differentiate towards cardiomyocytes and endothelial cells and are able to home to damaged tissues in vivo [7–10]. In addition, they secrete growth factors and cytokines of stem cells that can also stimulate cardiovascular repair, known as the paracrine effect. Similar to BMSC, ASC can be isolated and used autologously [8, 10, 11]. However, in contrast to bone marrow, adipose tissue can be obtained via a lesser invasive method, such as liposuction, resulting in lower patient discomfort and risks. More importantly, adipose tissue provides up to 100 times more stem cells per gram of tissue compared with bone marrow [12–14]. Recently, it was shown in two rat studies that ASC have a higher capacity to reduce the infarcted area post-AMI than BMSC [15, 16]. As such, this indicates that ASC have a high potential as an effective therapy post-AMI. In this review we have compared different aspects of animal AMI studies using ASC as therapy, and focused on features that could be important for future successful clinical application of ASC post-AMI.
Differences in Acute Myocardial Infarction Models Four years after the initial description of ASC [6], Yamada et al. (2006) were the first to study the application of ASC as a putative therapy for AMI in a rat model [17]. In the following years, up to June 2013, 38 additional papers described the effects of ASC as a therapy post-AMI in various animal models (Fig. 1). These animal studies differed in 1) the animal model itself, i.e. the animal species used, animals with or
Number of publications
20 15 10 5 0 06-07
08-09
10-11
12-13*
Years Fig. 1 Number of pre-clinical studies analyzing the therapeutic effects of ASC administration in AMI. * = articles from Jan 2012 to October 2013
without an intact immune system and animals with or without reperfusion induction, and 2) ASC therapy specific aspects, such as the number of administered stem cells with or without culturing, the time point and the route of stem cell administration. In this paragraph, we will first discuss the different AMI animal models. Two points have to be noticed up front: 1) the number of studies that are described throughout this manuscript depends on whether or not a study analyzed a particular parameter, and may not always correspond to the number of studies shown in the Tables 2) the number of large animal studies is small (n=7), making a comparison somewhat more difficult. Immunodeficient Versus Immunocompetent Animals ASC therapy post-AMI was studied in both immunodeficient and immunocompetent animals: 9 studies used an immunodeficient model (depicted in Table 1), whilst 30 studies used an immunocompetent model (shown in Tables 2 and 3). These immunodeficient animals were all rodent studies, and only human ASC were applied in these studies (Table 1). It was found that human ASC did significantly reduce infarct size in 8 out of 9 (89 %) studies, significantly improved left ventricular ejection fraction (LVEF) in 9 out of 10 (90 %) studies as determined by echocardiography, and finally significantly enhanced the number of blood vessels in the infarcted area in 10 out of 10 (100 %) studies, as determined by counting blood vessels in the myocardium post-AMI (Table 1). Interestingly, 3 studies analyzed the differentiation capacity of human ASC and showed that they differentiated towards cardiomyocytes, microscopically shown by expression of the cardiomyocyte specific marker cardiac troponin T or connexin 43 [19, 23], or towards endothelial cells, as visualized by expression of the endothelial cell specific marker CD31 [26]. It is however known that the microenvironment of the infarcted myocardium in immunodeficient animals is strikingly different from immunocompetent animals and humans. In the widely used immunodeficient ‘severe combined immunodeficient’ (SCID) mice T and B-cells namely are absent, while a-thymic rats are depleted of T-cells [53, 54]. These T-cells not only play a role in the healing process post-AMI, by removing damaged and necrotic cells, but they may also jeopardize the administered ASC [55–57]. Thus, in an immunodeficient animal theoretically more stem cells are able to survive, which could positively influence the results. Indeed, in immunocompetent small animal models ASC had less beneficial effects. For example, in 9 out of 19 (47 %) immunocompetent small animal studies a significant reduction in infarct size was found versus in 8 out of 9 (89 %) immunodeficient animals. LVEF was found to be significantly improved in 14 out of 23 (61 %) studies in immunocompetent small animals versus a significant improvement in 9 out of 10 (90 %) immunodeficient animals. Finally, in 10 out of 18 (56 %) immunocompetent
Stem Cell Rev and Rep Table 1 ASC therapy in immunodeficient AMI models Study
Reference
Animal model
Reperfusion
Injection time
Cell type
Dose (*10^6)
Route
Infarct size
LVEF
Blood vessels
Bayes-Genis 2010 Bai 2010 Bai 2010
[18] [19] [19]
mouse NIH-Foxn1rnu Mouse (SCID) Mouse (SCID)
– – –
Therapeutic Application of Adipose Derived Stem Cells in Acute Myocardial Infarction: Lessons from Animal Models B. A. Naaijkens & A. van Dijk & O. Kamp & P. A. J. Krijnen & H. W. M. Niessen & L. J. M. Juffermans
# Springer Science+Business Media New York 2014
Abstract The majority of patients survive an acute myocardial infarction (AMI). Their outcome is negatively influenced by post-AMI events, such as loss of viable cardiomyocytes due to a post-AMI inflammatory response, eventually resulting in heart failure and/or death. Recent pre-clinical animal studies indicate that mesenchymal stem cells derived from adipose tissue (ASC) are new promising candidates that may facilitate cardiovascular regeneration in the infarcted myocardium. In this review we have compared all animal studies in which ASC were used as a therapy post-AMI and have focused on aspects that might be important for future successful clinical application of ASC.
B. A. Naaijkens (*) : A. van Dijk : P. A. J. Krijnen : H. W. M. Niessen Department of Pathology, VU University Medical Center, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands e-mail: [email protected] H. W. M. Niessen Department of Cardiac Surgery, VU University Medical Center, Amsterdam, The Netherlands L. J. M. Juffermans Department of Physiology, VU University Medical Center, Amsterdam, The Netherlands O. Kamp : L. J. M. Juffermans Department of Cardiology, VU University Medical Center, Amsterdam, The Netherlands B. A. Naaijkens : A. van Dijk : O. Kamp : P. A. J. Krijnen : H. W. M. Niessen : L. J. M. Juffermans Institute of Cardiovascular Research (ICaR-VU), VU University Medical Center, Amsterdam, The Netherlands B. A. Naaijkens : O. Kamp : L. J. M. Juffermans Interuniversity Cardiology Institute of the Netherlands (ICIN), Utrecht, The Netherlands
Keywords Adipose derived stem cells . Acute myocardial infarction . Animal models . Cellular therapy
Abbreviations ASC Adipose derived stem cell AMI Acute myocardial infarction IV Intravenous injection IC Intracoronary injection IM Intramyocardial injection MSC Mesenchymal stem cell BMSC Bone marrow derived mesenchymal stem cell SVF Stromal vascular fraction LVEF Left ventricular ejection fraction I/R Ischemia/reperfusion
Introduction Coronary artery disease is a leading cause of morbidity and mortality in western society. Although the majority of patients that have suffered an acute myocardial infarction (AMI) survive this initial infarction, they may die due to long term complications [1–3]. Death of cardiomyocytes is not only induced by the ischemic event itself, but also by inflammation-induced necrosis post-AMI. These lost cardiomyocytes are then replaced by non-contractile scar tissue, facilitating cardiac function impairment, eventually resulting in heart failure. Although life-saving cardiovascular therapies, such as percutaneous coronary intervention, implantable defibrillators and pharmacotherapeutics, improved therapy post-AMI in the last decades, these current treatments do not actively restore or regenerate the damaged myocardial tissue [2–4]. Therefore, replenishing lost cardiomyocytes using stem cell therapy was hypothesized to be an ideal
Stem Cell Rev and Rep
solution to retain cardiac function and prevent heart failure development. The first adult mesenchymal stem cells used in therapy post-AMI in preclinical and clinical studies were isolated from bone marrow [5]. Zuk et al. showed in 2002 that adipose tissue is another interesting source of adult mesenchymal stem cells, which are now known as adipose derived stem cells (ASC) [6]. In general ASC have similar characteristics as bone marrow derived mesenchymal stem cells (BMSC). Both can differentiate towards cardiomyocytes and endothelial cells and are able to home to damaged tissues in vivo [7–10]. In addition, they secrete growth factors and cytokines of stem cells that can also stimulate cardiovascular repair, known as the paracrine effect. Similar to BMSC, ASC can be isolated and used autologously [8, 10, 11]. However, in contrast to bone marrow, adipose tissue can be obtained via a lesser invasive method, such as liposuction, resulting in lower patient discomfort and risks. More importantly, adipose tissue provides up to 100 times more stem cells per gram of tissue compared with bone marrow [12–14]. Recently, it was shown in two rat studies that ASC have a higher capacity to reduce the infarcted area post-AMI than BMSC [15, 16]. As such, this indicates that ASC have a high potential as an effective therapy post-AMI. In this review we have compared different aspects of animal AMI studies using ASC as therapy, and focused on features that could be important for future successful clinical application of ASC post-AMI.
Differences in Acute Myocardial Infarction Models Four years after the initial description of ASC [6], Yamada et al. (2006) were the first to study the application of ASC as a putative therapy for AMI in a rat model [17]. In the following years, up to June 2013, 38 additional papers described the effects of ASC as a therapy post-AMI in various animal models (Fig. 1). These animal studies differed in 1) the animal model itself, i.e. the animal species used, animals with or
Number of publications
20 15 10 5 0 06-07
08-09
10-11
12-13*
Years Fig. 1 Number of pre-clinical studies analyzing the therapeutic effects of ASC administration in AMI. * = articles from Jan 2012 to October 2013
without an intact immune system and animals with or without reperfusion induction, and 2) ASC therapy specific aspects, such as the number of administered stem cells with or without culturing, the time point and the route of stem cell administration. In this paragraph, we will first discuss the different AMI animal models. Two points have to be noticed up front: 1) the number of studies that are described throughout this manuscript depends on whether or not a study analyzed a particular parameter, and may not always correspond to the number of studies shown in the Tables 2) the number of large animal studies is small (n=7), making a comparison somewhat more difficult. Immunodeficient Versus Immunocompetent Animals ASC therapy post-AMI was studied in both immunodeficient and immunocompetent animals: 9 studies used an immunodeficient model (depicted in Table 1), whilst 30 studies used an immunocompetent model (shown in Tables 2 and 3). These immunodeficient animals were all rodent studies, and only human ASC were applied in these studies (Table 1). It was found that human ASC did significantly reduce infarct size in 8 out of 9 (89 %) studies, significantly improved left ventricular ejection fraction (LVEF) in 9 out of 10 (90 %) studies as determined by echocardiography, and finally significantly enhanced the number of blood vessels in the infarcted area in 10 out of 10 (100 %) studies, as determined by counting blood vessels in the myocardium post-AMI (Table 1). Interestingly, 3 studies analyzed the differentiation capacity of human ASC and showed that they differentiated towards cardiomyocytes, microscopically shown by expression of the cardiomyocyte specific marker cardiac troponin T or connexin 43 [19, 23], or towards endothelial cells, as visualized by expression of the endothelial cell specific marker CD31 [26]. It is however known that the microenvironment of the infarcted myocardium in immunodeficient animals is strikingly different from immunocompetent animals and humans. In the widely used immunodeficient ‘severe combined immunodeficient’ (SCID) mice T and B-cells namely are absent, while a-thymic rats are depleted of T-cells [53, 54]. These T-cells not only play a role in the healing process post-AMI, by removing damaged and necrotic cells, but they may also jeopardize the administered ASC [55–57]. Thus, in an immunodeficient animal theoretically more stem cells are able to survive, which could positively influence the results. Indeed, in immunocompetent small animal models ASC had less beneficial effects. For example, in 9 out of 19 (47 %) immunocompetent small animal studies a significant reduction in infarct size was found versus in 8 out of 9 (89 %) immunodeficient animals. LVEF was found to be significantly improved in 14 out of 23 (61 %) studies in immunocompetent small animals versus a significant improvement in 9 out of 10 (90 %) immunodeficient animals. Finally, in 10 out of 18 (56 %) immunocompetent
Stem Cell Rev and Rep Table 1 ASC therapy in immunodeficient AMI models Study
Reference
Animal model
Reperfusion
Injection time
Cell type
Dose (*10^6)
Route
Infarct size
LVEF
Blood vessels
Bayes-Genis 2010 Bai 2010 Bai 2010
[18] [19] [19]
mouse NIH-Foxn1rnu Mouse (SCID) Mouse (SCID)
– – –
