On Sat, 4 Sep 1999 GBurch1@aol.com wrote:
> In a message dated 99-08-30 03:43:28 EDT, I wrote:
> > Re: organ cloning
> > I'm of the opinion that one of the major problems is the
> > cell division rate. How long does it take you to grow
> > a 5 kg (?) liver from a single cell with a 24 hour
> > doubling time?
> To date, I've been thinking this will be the
> numero uno biotech breakthrough within the next ten to 15 years.
Yep. Its going to fall tissue by tissue. They can do skin and cartilage and probably most blood cell types now. A couple of others like liver and heart may be on the horizon. Kidney may be one of the tougher due to its much more complex microarchitecture.
> Have you worked through the question regarding time you pose here to a
> next-order approximation, Robert?
Well, to a first order approximation you could look at the growth in a child. You get a first-order organ in 9 months. Given the constraints on the mothers glucose level, I suspect you can go much faster than that. Someone else did a second order approximation and said about 1 month. That may be reasonable.
> Do you know if anyone's working specifically on these issues?
There are a number of groups working on it from various approaches. I think at this time, we are probably limited by the problem of not knowing all of the growth hormones and development switches. Once those are become available (3-5 years, after the genome is finished), things will move much quicker. The real limit may be whether for some organs, you don't have any stem cells (real or inducible) in your body from which the organ can be generated. If that turns out to be the case, then growing replacements will require engineering cell lines to serve as the seed(s). That will take some time. However the ability of growth factors to induce cell type switching or even drive them in reverse (from the perspective of maturity) seems to be much greater than people would have expected 10 years ago.
Ultimately you will be limited by an infrastructure problem. You have to build the organ factories. This may be *iffy* if the xenotransplant people show significant progress. On the other hand there will always be a market for human organs as compared with the xenotransplants (for safety reasons, concerns for the poor pigs, etc.).
When I get a chance someday I'll pull the organ masses out of NM and do a complete set of calculations.