When the virus was injected into a region of the hearts of seven guinea pigs, five later had heartbeats which originated from their new pacemaker.

BBC: Virus rebuilds heart's own pacemaker in animal tests

The scientists mixed it with the VEGF and injected the combination into the hearts of two groups of test animals, rats and pigs, in which they had induced heart attacks. (Pig hearts bear significant similarities to human ones.) In both cases, instead of being washed away, the VEGF stayed on the lattice and slowly got released over several weeks.

WSJ: Nanotechnology Holds Promise for Heart Patients

And some surgeons think they have found a way to make that dream come true: by husbanding pigs not for their chops but for their hearts, livers, lungs and even their neurons.

ECONOMIST: Pigged out

But the alternative is to implant livers, hearts, and skin taken from cows and pigs, or human cadavers into people.

FORBES: Advanced Tissue Sciences Founder Wins Inventor Award