SiGNATURE project started with developing a maturation culture system for hiPSC-CMs, consisting in 3D microtissues composed by hiPSC- CMs, -fibroblasts and -vascular cells. The interaction between the different cell types was shown to promote maturation in different important aspects: structure, function, gene expression and metabolism. Strikingly, maturation of hiPSC-CMs was maintained even after they were dissociated from the tissue. The microtissues are composed by only 5000 cells which are able to auto-aggregate into spheric spontaneously beating structures, meaning the model is simple to produce and very cost-effective. The model also demonstrated to be very flexible: the three composing cell types can be derived by either healthy individuals or cardiac patients, with different possible combinations. These results were disseminated with two publications in high-impact scientific journals (Giacomelli, Meraviglia, Campostrini al. Cell Stem Cell, 2020; Campostrini et al. Nature Protocols, 2021) and advertised via press release and social media (Facebook, Linkedin).
The microtissue model was then used to demonstrate its utility to study heart disease. We used hiPSC-CMs from two patients, carrying a mutation in SCN5A and KCNQ1 gene, respectively. These genes encode for two important ion channels determining the electrical activity of cardiomyocytes that are subjected to complex regulation of their expression during development. SCN5A mutation was in a form only expressed postnatally, whereas the mutation of KCNQ1 inherited from the father is initially silenced in embryonic development. For these reasons, both mutations were not detectable in immature hiPSC-CMs. When we included patient hiPSC-CMs in microtissues, the expression of both mutations was significantly increased and the functional impact on the electrical activity could be evaluated. Thanks to the flexibility of the microtissue system, we further demonstrated that a specific factor MBNL1 was necessary for the expression of a postnatal form of SCN5A, since maturation effect on SCN5A was absent in hiPSC-CMs lacking MBNL1. These results are now in press in a specialized scientific journal (Campostrini et al. Cardiovascular Research, 2022).
