Regenerating Tissue: Two Approaches
Snowcrash has an excellent posting on stem cells and how stem cells are turned into tissues. This is an incredibly important field of research which is a critical part of the SENS approach to rejuvenative therapies. Go check out the article, the good link, and the great graphic.
Singularity News points to an interesting article from Wired News dealing with regenerative therapies that do not rely upon stem cells.
When a worm is chopped in two, the missing part often re-grows. Researchers at several biotech companies are challenging the assumption that humans can't perform a similar feat by developing drugs that encourage self-regeneration.
Hydra Biosciences is working a regeneration drug that stimulates heart muscle-cell regrowth, and could lead to better recoveries for heart attack sufferers. The protein-based drug induces mature cells to become a little bit like stem cells.
It causes heart cells to "dedifferentiate" partially, reverting them to an earlier stage of development and activating their ability to generate more muscle cells. Stem cells, by contrast, are fully undifferentiated, meaning they're a clean slate and have the ability to turn into any type of tissue. But replacing damaged or diseased tissue by regenerating a patient's own tissue, advocates say, has a leg up on stem cell-based procedures because it eliminates many potential medical problems, like immune rejection.
"Stem cell therapy involves using cells from outside the body, so there's the potential for incompatibility," says Mark Keating, head of the human genetics division at the Novartis Institutes for Biomedical Research and an advisor to Hydra. "The cells can also divide too fast and become cancerous." He cautions, however, that it is too early to tell which of the two types of procedures will work best when tested in humans.
Of course autologous stem cells taken from the person himself are perfectly compatible, but those are generally adult stem cells (unless frozen stem cells from cord blood or embryonic clones are available). In general, what Mark Keating says is true.
The de-differentiation of mature cells is an interesting approach to creating quasi stem cells. Some of you may have read The Body Electric by Robert Becker. He is an orthopedist who pioneered the use of electromagnetic stimulation for healing difficult to heal bone fractures, and also pioneered the use of silver electrodes for healing chronic osteomyelitis infections that did not seem to heal with any other treatment. Anyway, Becker postulated that his electric stimulation was actually de-differentiating cells (either wbcs or fibrocytes) to form immature cells that then differentiated to osteoblasts, which then formed new bone to heal the fracture.
I doubt that is what actually happened, rather he was probably stimulating adult stem cells to become osteoblasts/osteocytes, but the concept of de-differentiation has always intrigued me, even after stem cell therapies became more practical.
Cancer is a form of de-differentiation that goes wildly out of control. Any modern therapies designed to regrow body parts will have to be carefully designed to avoid increased incidence of malignancies.