Modelling cardiac fibrosis through a mechanically active multi-chamber organ on chip device

Introduction Cardiac fibrosis (CF) is a pathological remodeling occurring, for instance, after myocardial infarction. The process is characterized by reduction in the number of cardiomyocytes (CMs), which are substituted by proliferating fibroblasts (FBs), assumption of a hypertrophic phenotype and increased deposition of extracellular matrix. To date, in vitro models of CF are still few, and seldom successfully mimic the native biomechanical microenvironment of the heart. In this study we propose an Organ-on-chip (OoC) model of CF that is mechanically active and, moreover, comprises multiple culture chambers to increase the experimental throughput. Device design and Experimental procedure The device incorporates 6 chambers for culturing 3D micro-constructs separated by normally closed doormat valves. Valves only open during cell injection to facilitate seeding operations and decrease experimental variability. A uniaxial mechanical strain is provided to the micro-constructs through underlaid actuation chambers. Different percentages of neonatal rat CMs and FBs were cocultured, moving from healthy control to pathological state. A population of 100% FBs was used as positive control of CF. Cells were laden into a fibrin hydrogel and exposed to profibrotic factors (i.e. Tgfb1-5ng/ml- and mechanical stretching-10%,1 Hz) for 5 days. Results and Discussion The percentage of cells expressing SMA (both CM and FB) generally enlarged with the ratio of FB in culture. Moreover, an increase in the number of FB resulted in augmented cell proliferation (Ki67+ cells), expression of CF linked genes (e.g. Fn, Col1a1, Col3a1, Mmp2, Mmp9), and deposition of extracellular matrix. Notably, however, the healthy control (80%CM) resulted resilient to the assumption of a fibrotic phenotype (both strain and Tgfb1). Furthermore, even reducing the percentage of CMs to 50% it was possible to rescue the pathological phenotype limiting CFs traits assumption and preserving constructs’ synchronous contraction capability. Conclusions We presented an OoC which, recapitulating some of the hallmarks of CF, could help in dissecting the specific role of the different cardiac populations in the pathology and in suggesting putative reparative strategies. Moreover, the presented platform integrates, for the first time, mechanical actuation and mid-throughput capability, thus possibly representing the base for higher yielding OoC based drug screening campaigns. Acknowledgments Fondazione Cariplo (Grant #2018-0551) MSCA IF (Grant #841975). PoliFab CleanRoom