Human-derived feeder cells used to grow human stem cells

Researchers have for the first time successfully grown human stem cells without exposure to mouse feeder cells.

The breakthrough, reported today in the peer-reviewed journal Nature Biotechnology, is important because it brings the controversial science a step closer to therapeutic use.

Regulators, such as the Food and Drug Administration in the United States, have signalled that they would not grant approval for existing stem cell lines grown on a layer of mouse feeder cells to be used in human therapies because of the risk of cross infection.

But in a world-first experiment conducted at the National University of Singapore, researchers have used human-derived feeder cells to grow stem cells previously developed on rodent cells.

The group, headed by Prof Ariff Bongso and funded by Singapore company ES Cell International, also created a brand new human cell line, grown entirely without exposure to animal products.

Bongso said the research was an exciting example of scientific proof-of-principle that would help take the technology from bench to bedside.

"The new line will be used as a research tool and the methodology used to derive and develop it will be refined with the FDA for the creation of additional cell lines for clinical application," he said.

ES Cell's Melbourne-based CEO, Robert Klupacs, said the company, through its research bases outside Australia, would use the technology to derive new lines that would become the cornerstone of cell-based regenerative medicine.

"This latest research is a monumental breakthrough in overcoming the bottleneck existing in the progression of stem cell-based technology, and will reduce the lead-time to commencement of clinical trials," Klupacs said.

"Derivation of animal-free HES cell lines is the requisite standard for any future therapeutic product."

Work leading to this pioneering effort began about 18 months ago, with experiments continuing until about May this year to satisfy reviewers.

Up until now, scientists have created human cell lines by taking a bundle of cells from an aborted or left-over IVF embryo's inner cell mass, then growing them up on a layer of mouse feeder cells containing the required nutrients.

As the cells grow and expand, researchers put new mouse feeder layers on to support the cell line development.

In the Singapore experiment Bongso took two of ES Cell's existing cell lines, HES-3 and HES-4, which had been grown to date on mouse cells, and replaced the rodent feeder layer with a human feeder layer.

The human feeder was created using cultured fibroblasts from human foetal muscle and skin, taken from aborted 14-week old foetuses, and human adult fallopian tubes, taken from healthy hysterectomy patients.

Bongso also created a brand new human cell line using a frozen three-day-old human embryo donated by a couple undergoing fertility treatment and grown in vitro until it reached the blastocyst stage.

Once the inner cell mass was removed, these cells were also grown on a human feeder layer to generate a completely pure stem cell line.

The results showed the human embryonic cell lines grew as well, if not better, than they did using previous standard techniques and that they also retained the expected characteristics of stem cells.

Klupacs said that under existing laws, such an experiment would not have been permitted in Australia's southern states, although it might have been possible in QLD and NSW.

He said the experiment that showed cells grown on mouse feeders could be successfully switched to human feeders meant ES Cell could supply therapeutically useful lines to researchers under its agreement with the National Institutes of Health in the US.

But he said any new lines it derived would not be eligible because of US President George Bush's edict allowing research only of cell lines derived prior to August 2001.

Klupacs said that over the coming 12 months, ES Cell aimed to derive new cell lines and develop master cell banks for potential therapeutic use.