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Release: April 16, 2002

UI researcher receives funding to study skin stem cells

A University of Iowa researcher has received a five-year, $750,000 grant from the National Institute on Aging (NIA) to investigate whether skin stem cells age.

These stem cells are found in the outer layer of the skin, or epidermis, which forms a vital barrier between us and the world. Diseases that disrupt the integrity of the epidermis are usually fatal.

Like other adult stem cells, skin stem cells are unspecialized self-renewing cells found in a specialized tissue. Continuous renewal of the epidermis is maintained by epidermal stem cells.

Although it has been assumed that cells in the skin do age, studies examining how long skin stem cells continue to grow and divide in culture have found little difference between stem cells from a 90-year old human and stem cells from 20-year old. Furthermore, these cell cultures proliferated for many more cell-population doublings than would ever happen in a human lifetime.

"So the question is, do stem cells age?" said Jackie Bickenbach, Ph.D., UI associate professor of anatomy and cell biology and dermatology. "If it turns out that these stem cells don't age, it may be possible to use cells from our skin to repopulate bone marrow or maybe repair organs."

Skin stem cells are easier to harvest than other adult stem cells, requiring only a simple biopsy. Researchers have found that cells obtained from this sample can be grown in culture and the cell population can be expanded to some extent.

Bickenbach and her team have developed a method for isolating skin stem cells from the epidermis. They also have shown that these cells, taken from newborn mice, and injected into a mouse blastocyst (early-stage embryo) can develop into many other tissue types that are found throughout the mouse born from that embryo. This was not true for other proliferating cells from the mouse epidermis.

Bickenbach and her team plan to use the NIA grant to find out whether skin stem cells from old adult mice and young adult mice have the same potential to develop into multiple tissue types.

"We will do the same set of experiments with these older stem cells, injecting labeled skin stem cells into blastocysts and investigating which mouse tissues contain the label, indicating that skin stem cells have transformed into that cell type," Bickenbach said.

The UI team also will compare the life span of mice derived from blastocysts injected with old stem cells and those from blastocysts injected with young stem cells.

If older skin stem cells can be transformed in the blastocyst into other cell types, that finding might have important implications for developing tissue renewal and repair therapies to treat human diseases.

In addition to the studies using blastocysts, the researchers also will perform long-term proliferative studies of young and old skin stem cells from both mice and humans to compare the growth of these cells in culture. One thing the UI team plans to investigate is whether growing stem cells in culture changes the nature of the cells in any way. The team also plans to analyze responses of skin stem cells of varying ages to environmental factors introduced in culture.

The researchers hope that their experiments will help determine whether the age of the stem cell has an effect on its response to the environment or extrinsic factors in determining its fate.

In addition to the NIA grant, Bickenbach also has received a "focused giving" award from Johnson and Johnson, which will provide $80,000 each year for three years to further study environmental effects on skin stem cells. These studies could pave the way to developing therapies whereby skin stem cells are used to deliver therapeutic genes to a patient in a controlled manner. For example, they might be possible to grow a skin patch that delivers insulin. Bickenbach noted that any such medical applications were likely many years away.

In addition to Bickenbach, UI researchers involve in these studies include Luchuan Liang, Ph.D., and Sathivel Chinnathambi, Ph.D.

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