A large part of the problem with creating organs using stem cells is getting them to turn into the tissues you want, such as muscle, rather than those you don't, such as bone. One line of research (I cannot find a link) into overcoming this has been to strip away the animal cells, leaving only the extracellular matrix , which would then be recolonised by human stem cells. The problem with this, of course, is that you stand a good chance of damaging the organ beyond repair, or else leaving animal cells which would trigger rejection of the organ or else risk diseases jumping the species barrier.
However, as homeopaths remind us, it is possible to repeatedly dilute a substance so much that the original substance no longer remains. So rather than try to get it right the first time, why not destroy most of the animal cells, repair it with human cells... and repeat the process until there is a sufficiently low chance that the animal cells will cause a problem?-- Selky, Aug 10 2017 We hate to have to say this, but there might - just might - be the germ of a good idea here ...-- 8th of 7, Aug 10 2017 It should , by [8th's] theory, strengthen the human immune system, given enough trials.-- wjt, Aug 11 2017 The answer is the type of stem cell. There exist "totipotent" stem cells that can yield any type of tissue, and there are "pluripotent" stem cells that can yield only a subset of types of tissue. I'm not sure just how limited they can be, but the logical thing to do is to seek the type of stem cell that can only yield the particular tissue desired.-- Vernon, Aug 15 2017 random, halfbakery