( ose to look solely at embryonic stem ce...)Researchers devise way to mass-produce embryonic stem cells

"There's more of a demand for an unlimited supply of embryonic stem cells," Yang said. Also, embryonic stem cells are pluripotent ?they can become any kind of cell in the body, while adult stem cells usually develop into a type of cell based on the kind of tissue that they originated from.

The bioreactor has a chamber that holds the polymer threads on which the stem cells grow and another chamber that holds fluid, or medium. This medium delivers chemical messengers, called cytokines, to the stem cells. The cytokines essentially tell the stem cells to stay in their undifferentiated state.

The difference between growing stem cells in a flask vs. the bioreactor is that the cells grown in the bioreactor could grow in three dimensions, while cells growing on a flat surface ?the bottom of the flask ?could not.

"Cells grown on a flat surface don't act like they would in the body," Yang said. "The growing surface affects how a cell forms, what it looks like and even how it expresses genes."

Cells grown in the bioreactor could grow for a much longer period of time than they could in the flask, as cells had more room to grow in the bioreactor.

"In the same amount of time we could grow up to a billion stem cells per milliliter in the bioreactor, compared to tens of millions of cells per milliliter with conventional systems," Yang said.

Also, it seems that embryonic stem cells grown by conventional methods are more likely to spontaneously differentiate, or change. Researchers aren't sure why or how some stem cells differentiate without prompting.

Yang and Ouyang tested both sets of cells ?the ones grown in a flask and those grown in the bioreactor ?for two key proteins. The presence of these proteins indicates that a stem cell has not differentiated. In the bioreactor experiment, 94 percent of the stem cells tested positive for these proteins, compared
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Source:Ohio State University