The world’s aging population suffers from an increasing incidence of coronary heart disease. Indeed, the World Health Organization reported that in 2016 ischemic heart disease is still the major cause of mortality worldwide, accounting for about 9.4 million cases of deaths p.a.. Despite different therapeutic approaches, in most cases heart transplantation (HTx) remains the only option for affected patients. Left ventricular assist devices offer an alternative to HTx but in most cases serve as only a temporary solution. The number of heart transplantations is limited by the number of available donor organs and thus many patients remain without adequate treatment.
Numerous stem cell (SC)-based approaches have been proposed for heart repair, but a multitude of experimental and clinical studies applying various adult stem cells have not achieved functional improvement, or showed only minor effects (Jiang, M., Expert opinion on biological therapy, 2010. 10: 667). More recently, however, patient-derived human induced pluripotent stem cells (hiPSCs), which, for the first time, provide a potential source of patient-derived cardiomyocytes (CMs) for heart repair, have become available. In order to generate these cells, easily accessible cell sources, e.g. blood cells, are reprogrammed into pluripotent stem cells in the laboratory. Intense research has driven forward dramatic progress in virtually all areas of iPSC technology relevant to the proposed project. This includes highly efficient reprogramming into iPS cells (Haase, A., Cell Stem Cell, 2009. 5: 434.; Lachmann, N., American journal of respiratory and critical care medicine, 2014. 189: 167), efficient genetic engineering of iPSCs (Merkert, S., Stem cell reports, 2014. 2: 107) as well as the development of technologies for the expansion and differentiation of iPSCs, e.g. CMs, at a clinically required large scale (Zweigerdt, R., Nat Protoc, 2011. 6: 689; Olmer, R., Tissue Eng Part C, 2012. 18: 772; Kempf, H., Stem cell reports, 2014. 6:1132). Intense research on safety issues concerning iPSC-based cell transplants, the most critical aspect for clinical applications, is ongoing. Importantly, the extremely low incidence of CM-derived tumours in human hearts suggests a low risk factor for a malignant transformation of terminally differentiated iPSC-derived CMs, and potential implant-related arrhythmias could be controlled through technical pacemaker devices.
A promising study (published in 2014) demonstrated, for the first time, the formation and functional coupling of large contractile human stem cell-derived heart muscle islands in a non-human primate (pig-tailed macaque, Macaca nemestrina) model of MI (Chong, J.J., Nature, 2014. 510: 273). In this case, embryonic stem cells were used instead of iPS cells. Within the iCARE consortium, in close collaboration with basic researchers, clinicians, veterinarians and experts from the German Primate Center, we will transplant human iPSC-based CMs into non-human primates (crab eating macaque or cynomolgus monkey; Macaca fascicularis) in order to examine their influence on the damaged heart. Cynomolgus monkeys belong to the family of Old Word monkeys and are frequently used in pharmaceutical industry, e.g. for safety and efficacy studies for certain drug approval.
Preclinical assessment of our cell therapy concept is crucial to cover both ethical and legal aspects. Based on the current state of research, these tests cannot be performed in small animals like mice or rats. Though these animals are well suited for many other animal studies, their hearts vary immensely from the human heart, especially concerning the beating rate. Compared to the human heart, the beating frequency is about 5-8 times higher in the rodent model. Thus, a functional integration of human CMs into the heart of mice or rats, including the required electrical and mechanical integration, seems impossible (Mummery, C.L., Sci Transl Med 2, 2010. 27: 29ps17; Garbern J.C., Cold Spring Harb Perspect Med 3, 2013. 4:a014019).
Heart size as well as physiology (including the beating frequency) of large animals like pigs more closely resemble the human heart (Garbern J.C., Cold Spring Harb Perspect Med 3, 2013. 4:a014019) and thus seem more suitable for the preclinical assessment of cell therapy concepts of heart diseases. Up to now, unfortunately, high quality iPSCs (and differentiated CMs) from pig or sheep have not been successfully generated, rendering it impossible to examine allogenic cardiomyocytes in this model. Our published results as well as data from other research groups additionally demonstrate the fact that survival of transplanted human cells in pigs is limited by an immunological barrier (Templin, C., Circulation 126, 2012. 4: 430; Kawamura, M., Circulation 127, 2012. 11 Suppl 1: S29). In contrast, recently published data (Chong, J.J., Nature, 2014. 510: 273) show that survival and functional integration of human CMs in NHPs is possible and might provide decisive information not only about the functionality of the desired therapy but also might demonstrate potential risks in a human-related animal model.
In conclusion, considering the current state of worldwide research, the use of NHPs is – from a scientific as well as from a clinical perspective - utterly necessary and in terms of urgently required novel therapeutic approaches, highly reasonable. From an ethical point of view, the stress for the animals caused by the experiments has to be weighed against the important clinical/practical insights gained for the treatment of patients with ischemic and, in many cases, lethal heart diseases. In view of the above points, we consider these animal experiments ethically justifiable. The principles of the 3R (Replacement, Reduction, Refinement) are of high priority and we will consider them in every experiment performed.
Here you can find further information regarding the importance of animal experiments with monkeys (German only):
Aims of the project
Generation and characterization of genetically enriched hiPSC derived CMs and transplantation in a preclinical non-human primate model.
Development of GMP compliant processes for the reprogramming and genetic modification of iPSCs as well as scale up of hiPSC-CM production for clinical use.
Enrichment of CM subtypes.
Development of an in vitro potency assay.
Discussion of the regulatory requirements for intramyocardial transplantation of autologous hiPSC-CMs in patients suffering from right-sided heart failure as a long-term consequence of a Mustard operation and submission of a first draft of an application protocol.
Updating the ‘Freedom to Operate (FtO)’ analysis and the business and exploitation plan.
Create a legal, ethical and commercial framework within which translation is facilitated.