Characterization of cardiac progenitor cell activity in engineered heart muscle

by Elif Levent
Doctoral thesis
Date of Examination:2016-06-13
Date of issue:2016-06-21
Advisor:Prof. Dr. Wolfram-Hubertus Zimmermann
Referee:Prof. Dr. Dörthe Katschinski
Referee:Prof. Dr. Susanne Lutz
Persistent Address: http://dx.doi.org/10.53846/goediss-5706

 

 

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Abstract

English

The heart has been considered a post-mitotic organ incapable of regeneration upon injury. Recent findings suggest that the heart contains cardiac progenitor cells (CPCs) with the potential to give rise to cardiovascular cells. CPCs are currently under clinical investigation aiming at cell-based induction of heart regeneration in patients with myocardial infarction related injury. The mechanisms of action underlying the reported beneficial effects of CPCs remain for the most part elusive. This study was designed to enhance our knowledge on CPC biological activity. By making use of engineered heart muscle (EHM) constructed from cardiomyocytes, fibroblasts and CPCs in a collagen type 1 hydrogel the aim was to simulate a three-dimensional heart muscle environment as closely as possible. Different types of mouse and human CPCs were investigated and found to be mesenchymal cells distinct from fibroblasts. Transcriptome profiling suggested a pericyte phenotype within the human CPC population. Despite the apparent differences in cell phenotype, CPCs and fibroblast supported the assembly of cardiomyocytes into macroscopically contracting EHM. Evidence for CPC transdifferentiation in EHM could not be obtained. Novel EHM models of hypoxia/reoxygenation and chronic hypoxia damage were developed and used to study potential cardio-protective effects of CPCs. Surprisingly, these experiments revealed that hypoxia/reoxygenation damage could be attenuated by fibroblasts, but not by CPCs. This effect appeared to be mediated by the release of cell protective growth factors and cytokines from fibroblasts. Conversely, transcriptome profiling suggested angiogeneic and immune modulatory activity in CPCs, which may not be effective in a vascular and leukocyte-free EHM. The cell context specific biological activity of CPCs was further exemplified by studies in EHM tri-cultures composed of cardiomyocytes, fibroblasts and CPCs. Only tricultures with CPCs were protected from chonic hypoxia. Finally, to in the future be able to visualize the oxygenation level in cardiomyocytes, a transgenic hypoxia reporter was established. In summary, CPCs exhibited a distinct phenotype from fibroblasts. It appeared that CPCs require a specific mutlicellular context to exhibit protective effects upon hypoxia. EHM-hypoxia injury tools and a transgenic hypoxia reporter were developed to facilitate future organoid studies on cardio-protection.
Keywords: Cardiac progenitor cells
 
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