James McDonald can walk without
the aid of crutches again thanks to a promising new technology which uses
the intestines of hogs to strengthen weakened human knees. A March 9 Associated
Press story reported that McDonald was the first human being to receive the
still-experimental implant of small-intestinal submucos (SIS), derived
from the small intestines of hogs, into his knee. The intestine replaces
the kneeÂ’s anterior cruciate ligament (ACL).
In animal tests, SIS has shown
an ability to stimulate healing and growth of new blood vessels in damaged
tissue. “ItÂ’s exciting because it seems to have the capacity
to stimulate the bodyÂ’s healing response and to modify itself to
whatever environment itÂ’s being used in,” said Dr. Robert Hunter, who performed the surgery on McDonald.
McDonald and 11 other individuals
are being given the implants in Food and Drug Administration-approved
clinical trials to test their safety and efficacy in human beings. If
the trial prove successful, more comprehensive trials are likely and SIS
could have uses beyond mere knee replacement, including applications in
repairing tendons and ligaments and perhaps even replacing human arteries.
SIS avoids the thorny problem of
potential cross-species disease contamination by using a process which
ensures no individual hog cells are transferred to human beings. Animal rights activists have argued that the risk of spreading diseases through such xenotransplantation is unacceptable.