Clone and Grow

William Saletan of Slate, who is in favor of embryonic stem cell research, discusses a study where researchers removed animal embryos from their mothers and injected the area where their kidneys were developing with adult stem cells. They then grew the embryos in-vitro for a couple days before they died. They removed the rudimentary kidneys from the animals and the kidney tissue continued to grow.

The authors called this "an in vitro organ factory." Technically, that was correct, since the factory was in a lab dish. But the factory itself was a rat. The human cells were inside a living organ inside a living being inside a dish. The distinction between in vivo and in vitro had collapsed. So had the barrier to making transplantable tissue. The report's final sentence said it all: "Here, we have demonstrated a system that might provide the means to generate self-organs … by using the inherent developmental system of an immunocompromised xenogeneic host."

Inherent developmental system. That's the key: a 9-day rat, a 4-week pig, a 6-week calf. But those are all foreign species—"xenogeneic," in the language of the Japanese study. They have to be "immunocompromised"—deprived of the ability to reject your cells—because their DNA doesn't match yours. The only developmental system that doesn't have to be immunocompromised is your clone.

Don't be scared. We don't have to grow a whole new you. Judging from the studies we looked at yesterday, an embryo cloned from one of your cells would need just six or seven weeks to grow many of the tissues you need. We already condone harvesting of cells from cloned human embryos for the first two weeks. Why stop there? We'll tackle that question tomorrow.

I guess we'll have to wait and see if Saletan is in favor of cloning human embryos, implanting them in women for 6 or 7 weeks and then removing them to get mini-organs.

We already condone? Who's the "we?" The Slate staff? Pro-cloning-for-research groups?