The fact is the neither the potential of adult nor embryonic stem cells have been explored enough to weigh in definitively on which would be preferable, or even feasible, for sundry indications. One would think the entire point of doing research on stem cells would be to figure those sorts of things out. It’s really a rather straightforward approach: Try out your options, see which works best.
Bush’s prohibition has effectively destroyed that investigative paradigm in the USA. I can put it no more plainly. Industry simply cannot absorb the financial risks involved in such development of such speculative technologies alone. I can think of no precedent for such a massively expensive endeavor being born by private interests alone. It’s more than naive to think “industry” will somehow pool its collective resources in some munificent collaborative effort to fill the gap left by the lack of public funds of the amounts usually applied to such exciting and promising new fields. It’s a market fundamentalist fantasy, nothing more. Such a consortium would be borderline anticompetitive, quite frankly, and what biotech and pharma does is compete. There are the occasional strategic partnerships, but nothing of this scale. Not even close. So money is a really, really big problem.
The other is the chilling effect of not only present regulatory restrictions, but the threat of them in the future. What’s the point of sinking massive amounts of R&D money into something that could be made illegal for all you know? Nobody will outlaw adult stem cells, because nobody could imagine some damn fool bishop comparing adult stem cell research to Mengele’s Holocaust attrocities. In this sort of political climate, what CEO in his right mind is going to stake the future of his outfit on something the “moral majority” thinks is a cardinal sin? Not in this country. Not without support from academia.
America will cede its preeminance in biotech if this trend continues. It’s really quite plain. Europe, to a lesser degree, and Asia, to a greater degree, will be the new powerhouses, because if embryonic stem cells can do a tenth of what researchers hope they can do, they will absolutely revolutionize medicine. It’ll be as big as vaccines, or anti-cancer therapies, or organ transplants. For some adult tissues, the use of adult stem cells might be sufficient; but for others, like the heart (check out this brilliant paper from Ken Chien’s lab) it’s difficult to harvest more than hundreds or maybe a few thousand of resident stem cells that can differentiate into what you want from the entire organ. You can’t take an entire heart out of a human being to extract a paltry thousand cardiac stem cells when you need millions to repair an infarct. An acceptable biopsy might yield less than ten, if you’re exceedingly lucky. It would require more than twenty doublings to expand such a pool, and threatening changes in culture from what is virtually a clonal expansion are no less a potential problem with adult cells as ebryonal ones. Without active telomerase, senescence is also in issue with such a program, a potential problem embryonal stem cells do not have. Forced expression of telomerase components has been shown to increase the proliferative capacity of stem cells in culture, but in adult cells, active telomerase is a hallmark of cancer, and must be very carefully and completely abrogated before engrafting. Telomerase shuts off naturally when embryonal stem cells differentiate. ES cells can be expanded almost as much as you like while in a virtually totipotent state up until differentiation is triggered, so numbers of cells that can be produced of a wide variety of tissue types is potentially limitless. Hematopoietic and stromal stem cells can’t even come close to this natural versatility, and their potential is proving more limited than was earlier hoped in the hands of some investigators. There’s talk of getting all sorts of cell types out of fat, but those findings, or the potential of that approach, remains controversial.
Like I said, it would be great to give any and all promising candiates a fair shot at success. Right now, I’d say the focus on adult stem cells in this country is largely a reflection of the moral quandry, as created by the religious right. There’s no reason why what was done in Korea couldn’t have been done here. People have been talking about the very things they’ve accomplished for years. Why didn’t we do it instead? Well, why do you think? Because nobody thought autologous cell grafts derived from cloned embryos might be an approach of enormous promise? Fuck no. It’s because the theocrats have largely derailed the effort.
