Stem cell patents held by a University of Wisconsin organization are so restrictive that they create an impediment to research, according to a science journal published Friday.

The authors, California stem-cell researcher Jeanne F. Loring and patent attorney Cathryn Campbell, said the Wisconsin Alumni Research Foundation patented stem cells so broadly that other researchers can do little without infringing on the foundation's patents.

The article appears in Friday's issue of the journal Science.

Researchers value human embryonic stem cells because the generic cells hold promise for curing diseases such as diabetes, Alzheimer's and Parkinson's diseases.

The University of Wisconsin has owned patents on the cells ever since UW-Madison researcher James Thomson first figured out how to grow them in his lab in 1998.

The patents cover not only the cells but also the technique Thomson used to derive and grow them. That means most stem cell research across the country falls under the foundation's restrictions.

Carl Gulbrandsen, the foundation's executive director, said other universities would have also protected its rights to such a breakthrough.

"I'm not embarrassed at all to say that I hope the University of Wisconsin will make a whole lot of money from these patents," he said.

Initially, the foundation charged universities $5,000 to use the cells. Later, an agreement with the National Institutes of Health brought the price down to $500.

The foundation charges private labs up to $125,000 for the cells, plus an annual maintenance fee of up to $40,000. The fees vary depending on the size of the firms.

The fees also cover training to teach licensees how to maintain the finicky cells, Gulbrandsen added.

Loring and Campbell are not the first researchers to claim the dollar amounts impede research.

Doug Melton, who chairs Harvard University's department of molecular and cellular biology, agreed that the foundation's patents are too restrictive.

Harvard has its own stem-cell program and distributes its lines for free, but recipients are still bound by the foundation's restrictions.