BOSTON - For the first time, scientists have rebuilt a complex human organ,
the bladder, in seven young patients using live tissue grown in the lab ! a
breakthrough that could hold exciting promise for someday regenerating ailing
hearts and other organs.
A doctor at the
Institute for Regenerative Medicine at Wake Forest University School of
Medicine dips a specially constructed biodegradable mold, shaped like a
bladder, and seeded with human bladder cells, into a growth solution at
Wake Forest Uinversity in Winston-Salem, N.C., Thursday, March 30, 2006.
The laboratory-grown transplants are made from tissue samples from a
patient's diseased organs. [AP] |
Only simpler
tissues ! skin, bone, and cartilage ! have been lab-grown and transplanted in
the past. This is the first time that a more intricate organ has been mostly
replaced with tissue grown from the patient's own cells.
"This suggests that tissue engineering may one day be a solution to the
shortage of donor organs in this country for those needing transplants," said
Dr. Anthony Atala, the lead researcher. He said he believes the work provides a
model for growing other tissues and organs.
The bladder transplants, performed on seven patients ages 4 to 19, were being
reported online Tuesday in The Lancet medical journal. The research team at
Children's Hospital in Boston did the first procedure in 1999 but wanted to make
sure it would work on others. The results weren't announced while the doctors
did the other surgeries and followed the progress of the last patient for almost
two more years.
"It gives everyone in the field ... the evidence and encouragement they've
needed to say this can be done," said Dr. Stephen Badylak, a University of
Pittsburgh expert in tissue engineering.
Growing other organs will likely hold unforeseen challenges, however, since
organs are so specialized in their functions, scientists stress.
Even for people with bladder disease ! and there are an estimated 35 million
in the United States alone ! Atala's technique requires testing on more patients
and for longer times, researchers say. Replacing an entire bladder would pose
many more problems, including reconnecting urine tubes, blood supply, and nerve
signaling, according to Dr. Steve Y. Chung, an Illinois urologist who wrote a
commentary for The Lancet.
Still, he called the work "a tremendous, tremendous advance."
For the children and teenagers in the study, the transplants reduced leaking
from their bladders ! a potentially big gain in quality of life. For 16-year-old
Kaitlyne McNamara, the transplant has meant a new social life.
At the time of her surgery five years ago, her kidneys were close to failing
as a result of her weak bladder. Now, they are working again, and she no longer
wears a diaper. Instead, she was waiting for alternations on a low-cut
champagne-colored dress for her junior prom.
"Now that I've had the transplant, my body actually does what I want it to
do," she said last week near her home in Middletown, Conn. "Now I can go have
fun and not worry about having an accident."
Scientists, marveling at how animals like salamanders regenerate lost limbs,
have long toyed with the futuristic possibilities of regrowing worn-out or
injured human parts. Recent discoveries have transformed those hopes into an
emerging reality.
Over the past decade, researchers began fashioning better scaffold-like
platforms that hold growing cells and dissolve inside the body. The study of
stem cells, which can mature into all the body's other tissues, has also
supercharged progress in regenerative medicine.
The Boston researchers used a more mature cell type known as a progenitor.
They first operated on the patients to remove bad tissue that made up more than
half their bladders. They fished out muscle and bladder wall cells, seeded them
on cup-like bladder-shaped scaffolds of collagen, then let the cells reproduce
in the lab for seven weeks. Starting with tens of thousands, they ended up with
about 1.5 billion cells. The cell-bearing molds were then surgically sewn back
to the remnants of the patients' original and partly working bladders, where the
lab-nurtured cells kept maturing.
In undergoing the experimental procedure, the patients skirted the typical
side effects of grafts that would otherwise have been made with their own
intestinal tissue.
Atala, who has since moved to Wake Forest University, has already begun
commercializing his transplant techniques through Tengion, a company he helped
found in King of Prussia, Pa. It has licensing rights to patents on his work,
and some of his research collaborators have acted as consultants.
Some researchers were more cautious about the promise shown with the new
procedure, saying the study lacks any direct comparison group of patients
getting the traditional graft.
Dr. Joseph Zwischenberger, who edits the journal of the American Society of
Artificial Internal Organs, questioned how well the new bladders worked in the
first few patients and raised a "red flag" about two patients who left the study
for personal reasons and were ultimately omitted from the results. He also said
Atala's attempts to commercialize the technique should add some skepticism
toward the findings, which he nonetheless called "very interesting preliminary
data."
The patients in the study like Kaitlyne McNamara must still cope with the
ravages of spina bifida, the birth defect that caused their bladder problems.
Leaving the spine incompletely closed, spina bifida can turn off nerve signals
that keep the bladder healthy. The stiff, leathery bladder leaks frequently,
forcing the person to wear pads or diapers. What's worse, the weakened bladders
can flush urine back into the kidneys and damage them too.
The rebuilt bladders, though, were up to three times more elastic and better
at holding urine, the researchers report. In all seven patients, kidney function
was preserved, the study said. The patients must still empty their bladders
regularly with a tube but can avoid leaking in between.
"It's really science fiction at its best," marvels Tracy McNamara, the
transplant teenager's mother and a nurse.
She used to worry about her daughter dying from kidney damage or urinary
infections. That's all faded into the past. Now, she worries about all the time
her daughter fritters away on the telephone, talking to friends.