Lynn Allen-Hoffman was wrapping up a routine experiment on the aging of human skin when a colleague noticed something peculiar. Skin cells die within a few weeks, but there in the middle of a sea of dead cells was a small "colony" of living cells.

And they were thriving.

"What is this?" the University of Wisconsin pathologist murmured to Sandy Schlosser, manager of her lab, who had first noticed the colony.

All the other cells in a series of petri dishes, grown from a circumcised tissue sample from an infant, had clearly died, yet here was a group of cells that were going merrily along their way. The experiment was essentially the same one that Allen- Hoffman has been carrying on for years, yet, as she says, "I had never seen anything like this."

Four Years And Counting

That was four years ago, and the cells are still alive today, continuing to reproduce and filling jars with cells that can form human skin.

And Allen-Hoffman is coming to grips with an astonishing development. Somehow, quite by accident, her lab has produced what appears to be immortal human tissue. The discovery may lead to essentially an inexhaustible source of human skin for everything from treatment of burn victims, to testing of anti-cancer agents, to better cosmetics.

Word of the finding swept across the University of Wisconsin's campus like a prairie fire, leading to a collaborative effort involving experts from a wide range of disciplines, and the formation of a university-related company to develop commercial uses for the cells. It will be years before all the testing can be done to see if the process can be tried out on humans, but that is Allen-Hoffman's ultimate goal.

It took the university only one year to patent the cells, a process that normally takes several years. But Allen- Hoffman still isn't sure exactly what she did.

Natural Growth

The researchers had been testing a number of "agents" to see if they could somehow slow down the aging process of human skin cells. They were using tissue from the circumcision of an infant -- which is normally discarded -- because young cells reproduce very efficiently.

The cells had been placed in a series of tissue culture dishes. Under such circumstances, cells join together to form a thin skin, which Allen-Hoffman calls a "wound
heal." It only takes a few weeks for the cells to go through an entire life span, dividing into new cells, building up layers the same way that skin is layered on the human body.

Skin sheds continuously, taking away harmful bacteria and viruses in a "simple but elegant" way of protecting the organism, Allen-Hoffman says. During a normal lifetime, we each shed about 90 pounds of human skin, accounting for a sizable amount of the dust and microscopic creatures in our homes.

Allen-Hoffman says she can't take credit for everything that happened on that eventful day in 1996. She has gone through the same experiment over and over, using other cells from the original sample, thinking that perhaps they did something to cause the "spontaneous immortality" of a handful of cells. But it has never happened again. But fortunately, when the colony was first discovered she isolated the cells and put them in a series of petri dishes, where they continued to grow and multiply.

Then she preserved some of the cells through freezing, making sure that she would have a continuous supply for further experimentation. What, she wondered, could have caused all this?

Magical Chromosome

She feared initially that the cells were "tumorigenic," meaning they could produce cancerous tumors, thus accounting for their unorthodox life style. But laboratory
experiments ruled out the possibility. The cells were implanted in animals and tissues where tumors would be expected if indeed the cells were precancerous.

"Not a single tumor formed," she says.

But what could account for the fact that they refused to die?

The answer, the researchers found, rested in a single strand of one chromosome. Chromosomes are the tiny strands of genetic material that contain the DNA that determines the characteristics of the entire cell, and chromosome 8 had a duplicate string of DNA. "The cells just have a double dose, so to speak, of the genes that are on that section of chromosome 8," Allen-Hoffman says.

That appears to be the only difference in the cells, and the reason for their "immortality." In all other ways, she says, they are exactly the same as the "normal" cells from the original sample. But, she insists, she did nothing that might have caused that mutation.

It apparently happened, she adds, while the cells were in the petri dish, but at this point no one knows why the mutation occurred, or why it should have affected the life span. The research moved beyond the excitement of finding something new earlier this year when she met with Michael Schurr, a surgeon in the university's burn center. Schurr asked her to sit in on an operation.

The patient was a farmer who suffered burns over 98 percent of his body when a propane tank exploded last year. "The only part of him that wasn't burned was the part covered by his boots," Allen-Hoffman says.

She watched as Schurr attempted to spread thin sheets of skin, the best that could be obtained from the victim's feet, over various parts of his body. The sheets were about the texture of "wet tissue paper," she says, illustrating just how difficult the surgeon's task was.

Skin Factory Possibility

It was an electrifying moment for Allen-Hoffman, who realized that if the immortal cells she has in her lab can be used for human skin graphs, Schurr someday will have a ready supply of disease-free human skin that could improve a burn victim's chances of survival immeasurably.

Schurr is now a member of the research team, gearing up for tests that could lead to human trials. It remains to be seen whether the cells will be rejected by the victim's body, and whether the new skin will, indeed, perform as expected.

It's all a bit mind-numbing, Allen-Hoffman says, since she is convinced she did nothing to cause the cells to become immortal. What she did, however, was exactly the right thing.

"Our contribution to this whole thing is a very humble one," she says. "And that was we recognized what we had," and took the necessary steps to protect and preserve it.

Bravo, no matter how it eventually turns out.