It's pretty simple to extract a small number of living heart cells from a person and grow them in vitro. However that results in a lump of cells and is of limited utility. However if those same cells were grown on a silicon sheet, as was done in the OP, those new healthy heart cells could potentially be transplanted into a heart to replace damaged tissue. It would require a pacemaker to make the new tissue beat in rthymn, no nerves, with the rest of the heart but that is already being done.
This could then serve as a treatment for people with various heart disease issues that presently requires a transplant to treat. It's probably a generation or more from use in humans but it shows what may be possible in the relative short term.
Also I'm not seeing any indication there was any genetic modification going on.
It's more a bio-mechanic thing but still this type of thing has unlimited potential, stuff repairing a heart, build a new one and swap it out, and not just the heart, any organ and while your at it, I'd like a car that runs off food scraps and and heals when I have a fender bender!