This one is fairly impressive. In M.S. the body's immune system fails and attacks the body's nervous system. The solution seems to be to extract some stem cells from the victim, use cancer drugs to obliterate the existing immune system, then put the stem cells back where they replace the missing system. The new system does not seem to have the flaws of the one its replacing.
This has some implications for other diseases involving the immune system. We can now either reprogram the system or completely replace it.
At the same time some debate continues on the topic of mixing human and animal genes. We already do this to give lab mice human-like organs on which we test new drugs and/or therapies. The problem comes in when it is noted that mice with human analog organs also seem to be noticeably smarter. Growing a replacement heart and liver inside a pig may sound like a good idea, but what if when you come to harvest the organs, the pig has a pistol and want's to keep them? Intelligence we now understand does not come from one gene or even a small handful but from a rather large collection of widely scattered markers.