If you heard about scientists growing body parts in a laboratory, you might assume that it's something out of science fiction. But such "regenerative medicine" is now occurring-and it will undoubtedly play an important role in the future of medical care.
Landmark breakthrough: Nine children and teenagers with a congenital defect that prevented their bladders from functioning properly received regenerated (laboratory-grown) bladders beginning in 1998. They have been followed for an average of seven years, and their bladders are continuing to function.
Anthony Atala, MD, director of Wake Forest University's Institute for Regenerative Medicine, one of the country's leading regenerative medicine research facilities, answered questions about this cutting-edge medical therapy.
- Where are we in the development of regenerative medicine? Much of the existing research has been conducted on animals, such as mice and rats. But we also know that there is a constant "turnover" of cells in the human body—that is, the growth of new cells and the regeneration of tissue after injury
For example, if a person's liver is damaged in a car accident and half of the organ must be surgically removed, the liver can regenerate. If you take an X-ray of the same patient nine months later, the liver is fully regrown. Since we know that many parts of the human body are able to regenerate, our goal is to enhance that function to treat certain injuries and diseases.
- What is unique about regenerative medicine's capacity for healing? Because the damaged or diseased body part is completely replaced, it has the potential to cure rather than manage illness, Regenerative medicine also will help solve organ shortages-the lengthy waiting period for a transplantable organ, such as a kidney, liver or heart, that sometimes ends in the patient's death if an organ does not become available. And because regenerated organs can be grown from a patient's own cells, there is less risk for organ rejection, a significant problem in transplants.
- Besides accident victims, what types of patients could potentially benefit most from regenerative medicine? People with diabetes or kidney, liver or heart failure are among the prime candidates. Others include patients who need replacement bone, muscle, ligament and tendon during surgery, and burn patients who don't have enough healthy skin for grafting
- How exactly are new organs and body tissues grown? Many methods are being tested and developed, but the most commonly used technique has already been utilized to create implantable bladders in humans (described earlier). This method is also being used in the laboratory to grow other organs, such as kidneys and livers, and structures, including the esophagus, blood vessels and heart valves.
For the regenerated bladders, the first step involved taking a small tissue sample-about half the size of a postage stamp-from the diseased organ. Cells from the sample were mixed with growth factors (naturally occurring substances capable of stimulating cell growth and reproduction) so that the cells would multiply in the lab.
Those cells were then layered onto a scaffold-like structure (or mold) that had the same shape as the diseased organ and was made out of materials that are compatible with the human body.
The cell-covered scaffold was then placed in an oven-like device or incubator that reproduced the conditions inside the human body-the same temperature and the same combination and concentration of biological elements. After approximately six to eight weeks, the cells had grown into tissue and the regenerated organ was ready to be implanted. It was removed from the incubator and placed in the patient by suturing it to the diseased organ. The scaffolding gradually degraded, and the new tissue integrated with the body.
- How is regenerative medicine currently being used? The process I just described was used to create the implantable bladders for children and teenagers with stiff, poorly functioning bladders. Previously, this defect was fixed by using a section of intestine to fashion a pouch to hold urine. But because intestinal tissue is not designed for such a use—but rather to absorb and excrete waste this procedure increased the risk for osteoporosis, kidney stones and cancer. The recipients of the regenerated bladders have fully functioning bladders without the side effects produced by the old procedure.
Clinical trials focusing on implantable bladder technology are now being conducted at about 10 US research centers. The next step will be to make the technology available for widespread use.
In another case, cells from ear cartilage were used to formulate an injectable gel to repair the bladder sphincter in women with a type of severe stress incontinence called intrinsic sphincter deficiency. This single injection was far more effective in producing continence than the existing procedure, which involves repeatedly injecting collagen (derived from cow carcasses) into the neck of the bladder.
- What are the greatest challenges scientists face in the development of regenerated organs and tissue? The least difficult processes involve flat organs, such as the skin and cartilage in some areas of the body. The next level of difficulty is a hollow organ, such as the bladder or stomach, which consists of many different cell types and must respond on demand (for example, the bladder must expand to hold urine, and the stomach expands when food is consumed).
The most difficult is a solid organ, such as a kidney or heart, which has the greatest number of cells and requires the most blood supply. Ensuring that a regenerated organ has a sufficient blood supply is a major challenge.
- Which human organs and tissues are being studied most for regeneration? At Wake Forest Institute, scientists are working on the regeneration of more than 20 different types of organs and tissues. For example, blood vessels for heart bypass surgery (which now are harvested from leg veins) and heart valves (which are currently replaced with the heart valves of pigs) are being engineered.
To treat battlefield injuries, we're developing new skin to repair burns and heal wounds without scarring. Meanwhile, attempts are being made to replace a human ear, engineer new muscle and grow fingers and limbs. Cellular therapies, such as the creation of cells from the pancreas that produce insulin to treat diabetes and the production of red blood cells to treat anemia, also are being investigated in the lab.
An exciting development in this area is the recent discovery of a new source of stem cells from amniotic fluid and placental tissue-a readily available, fast-growing stem cell that we have used in the laboratory to create muscle, bone, fat, blood vessel, nerve and liver cells. A "bank" of such cells could provide 99% of the US population with perfect genetic matches for organ transplantation.
- You haven't mentioned lungs or eyes are there any developments happening there? Yes. The Wake Forest laboratory is currently involved in efforts to engineer lung tissues and cornea tissues.
- How close are we to actually deriving the benefits of such treatments? Most of the developments in regenerative medicine are not yet ready for clinical use, but there may well be applicable results, such as engineered heart valves and blood vessels, during the next decade.
Blue to the Rescue?
Brilliant Blue, a food additive used to color foods such as blue M&Ms and Gatorade, interferes with the molecular events that cause spinal cord damage hours after an initial injury. This animal study finding may lead to new treatments for spinal cord injuries.
Clothes that Block Sun
When researchers dyed lightweight cotton fabrics different shades of blue, red and yellow and measured the amount of ultraviolet (UV) radiation that penetrated them, they found that darker, color-intense blue and red hues blocked more harmful UV rays than lighter yellow hues. This confirms past research that shows that dark colors such as black block harmful UV rays.
To protect skin from sun damage: Wear darker blue and red cottons.
