The Organ Tree
187
ing the proper current, and the ability of electrically injected silver ions
to dedifferentiate fibroblasts now gives us a possible method for produc-
ing an adequate blastema. We should now be able to supply the require-
ments for phase one in humans. Once this is done, the body itself can
probably take care of phase two, even though we don't understand the
process. Fingertip regrowth in children suggests that our bodies still
have the ability to redifferentiate the cells and organize the missing part,
as long as the electrical stimulus and the supply of sensitive cells are
sufficient.
Microsurgeons have performed wonders in reimplanting cleanly sev-
ered portions of arms, legs, and fingers, but these limbs are subject to
atrophy and obviously can't be grafted if they're too badly mangled or
riddled with disease. As one who has performed too many amputations
in his time, I find the prospect of being able to give a patient the real
thing instead of a prosthesis tremendously exciting. There's a good
chance that we'll eventually treat some nongenetic birth defects or old
injuries by cutting off the defective part and inducing a normal one to
grow. Perhaps, combined with gene splicing, such techniques could
even rectify genetic birth defects.
Since no one has yet achieved full regeneration in rats or any other
mammal,
these
dreams
won't
come
true
overnight.
They
aren't
chimerical, however. The remaining problems could probably be solved
in a decade or two of concerted basic research. Meanwhile, human capac-
ities for repair of certain tissues are greater than most people realize, and
there are already promising ways of enhancing some of them.
Cartilage
Fossils show that even the dinosaurs had arthritis, but unfortunately it
outlived them. Many varieties have been described, all of which result in
destruction of the hyaline (glassy) cartilage that lines the ends of the
bones. The remaining cartilage cells try to heal the defect by proliferat-
ing and making more cartilage. They're almost never equal to the task,
and scar tissue fills the rest of the hole. The result is pain, for scar tissue
is too spongy to bear much weight or keep the bones from grinding
against each other.
After our success at getting rat
legs to partially regenerate, we studied
this problem in 1973. We reasoned that, suite cartilage was
made by
only one kind of cell, getting it to regrow would be easier than working
with a whole limb.