There's something about human cloning that leaves a bad taste in my mouth.
Perhaps the primary issue I have with it is that we scientists really have no idea what is actually going on. That's a pretty crass statement. Let me back-pedal... we scientists don't really understand the mechanisms of differentiation nor the exact nature of a (pluripotent) stem cell. Because we don't know what's going on, I find it very difficult to see stem cells as the mechanism or therapy to solve issues of longevity.
The Speculist makes some very interesting and compelling arguments, but in the end, I think he misses the boat:
A few years from now, it may be possible to create an embryonic clone of myself. (Biology dictates that women are easier to clone than men, so it will be a while before I can do it.) Let's consider that embryo at four weeks. If I put it in the right environment, that blastocyst might grow into my identical twin brother. It isn't my twin brother now. It's just some growing tissue taken from my body and an egg I borrowed from somebody else. It would be an amazing little bud of life, similar to (genetically identical to) the amazing little bud of life that eventually grew into me. But we have a different developmental path for this bud. Rather than growing it into a separate human being, we're going to grow it back into me.
Emphasis mine. The fact is, that that growing tissue isn't just growing tissue... it is in fact a human-to-be... and note that the blastocyst in question is, as The Speculist points out, an entirely different being ("my twin brother"). The difference that he sees is that its his hunk of flesh. However it is not merely his genome. The moment it gained independence of him and began the process of division to give rise to "his twin brother" it really does become a seperate entity. It is not being grown as he says back into me. He goes on to say:
We aren't going to kill it; the whole idea is to produce a viable collection of ongoing cells. We will remove that part of it that makes it want to grow into a different person (satisfying Leon Kass to a certain extent, by the way) and otherwise, we will allow it to go on living indefinitely. If I am injured or get sick, part of this collection of cells will be reintroduced into the organism from which it came — that would be me — to help it recover. As I age, more of the cells might be introduced to help counteract the effects; still others might be put on a new developmental path towards being a finished "part": a heart or a set of lungs or a new pair of eyes.
Emphasis mine, again. This is more of that science fiction part of stem cells that make me chuckle. Certainly a stem cell, a true stem cell, is pluripotent, but the process of differentiation is not merely a result of genes turning on and off in the cell. There are a multitude of factors - external signals - that are responsible for creating tissues much less organs. While several homeotic genes have been discovered that direct differentiation signals other external signals dictate when a tissue forms. Thus in order to get a lung tissue or a heart tissue, the blastocyst move undergo many many divisions before a lung stem cell is formed, THEN even more divisions must occur before those tissues begin to differentiate into the cell types of interest or into whole organs. At this point the blastocyst is no longer just a blob of cells... it is in fact an embryo or potential human. One can not just stop the growth and differentiation signal to get the one tissue or organ one chooses. But I'll come back to this later.
Finally, The Speculist comes to this:
Each time one of these procedures was done, this living human tissue would grow into a human being. Why would anyone insist that it has to grow into a different human being? Says who? My twin brother can't demand that he has a right to exist. I never have to create a clone in the first place. And if I do create one, I assert that I have the right (before it grows into a separate and distinct human being) to decide that it will be me, rather than him, when it grows up.
This is why the hair on my neck sticks up. No longer does this blastocyst exist as a potential person, it is an object. A thing to be grown and discarded at the whim of the donor. The problem is, if the blastocyst could grow, it would develop into a completely seperate and unique individual. Genomically speaking, it would possess the same DNA, but over the course of multiple divisions with different stimuli and environs, an exact twin or copy could never be grown. The embryo in question would no similar to the donor than an identical twin is to its sibling. They may look the same (or maybe not), but they would be very distinct. In essence, what we have here is the promotion of human organ farming.
OK, so I promised to come back to tissues and organs. The answer to this question does lie in the exploitation and manipulation of tissue specific stem cells. A stem cell taken from the liver could be manipulated to give rise to harvestable tissue without the imposition of blastocyst destruction. Moreover, with microinjection, the cells in question could be manipulated then targetted to replace damaged tissue without having to destroy potential life. The problem is that our understanding of stem cells is in its infancy and in our race towards immortality, we take far too many short cuts.
As a scientist, I believe we need to proceed with caution. We've already moved beyond the point of proof-of-concept by cloning whole animals (albeit rather inefficiently) and using stem cells as experimental therapy. What needs to occur next is to determine what makes a stem cell a stem cell and what processes are required to initiate its differentiation. And if that means that an alveolar stem cell has different stem cell markers and initation signals than a hepatic stem cell, then we need to take the time and money to figure it out. Because the moment we stop recognizing the sanctity of life, potential or no, the moment we lose our own humanity.
