Human embryonic stem cells – famed for their capability to transform themselves into any type of specialized cell – are a prissy bunch, as any scientist who has tried to grow them in the lab can tell you. The slightest offense causes them to disavow their almighty abilities, or pluripotency in science lingo, and start differentiating into whatever cell type they feel like.
Travis Berggren knows this all too well. He spent five years analyzing the needs of temperamental human embryonic stem cells at WiCell, a private, non-profit stem cell institute headed by scientific director James Thomson after the University of Wisconsin researcher created the first human embryonic stem cell lines nearly 10 years ago.
"Pluripotent stem cells are balanced on a pinnacle and it doesn't take much to have them to roll off on either side," says Berggren, Salk's new staff scientist who joined the Institute in September to lead the new stem cell core facility.
Just like any other cell type, stem cells are grown in plastic laboratory culture dishes that contain a nutrient-rich broth known as culture medium – with one important difference: The surface of the dish is typically first coated with so-called feeder cells that provide additional nutrients and signaling factors for the stem cells.
For some experiments and therapeutic applications, however, stem cells need to be grown without the company of feeder cells, which can skew results or contaminate the stem cell sample. Berggren would later help solve this problem with a key discovery at WiCell.
Berggren had just finished his doctorate degree in Chemistry at the University of Wisconsin when WiCell was looking for somebody who could set up a mass spectrometry proteomics program for human embryonic stem cells – his area of expertise. Mass spectrometry is used to identify and, increasingly, to precisely quantify thousands of proteins from complex samples.
"In the beginning I naively assumed that the stem cell work would be done by others, but I quickly realized that if you need things to get done, you needed to do it yourself," Berggren remembers.
But that was easier said then done. While mouse stem cells had been around for two decades and the technical details had been all worked out, human embryonic stem cells turned out to be a different breed altogether.
"The defined factors that allowed mouse stem cells to grow in culture didn't work for human cells," says Berggren. "And, somewhat ironically, the feeder cells that are used to grow mouse embryonic stem cells support both types of cells although they signal through different pathways."
So, the young stem cell researcher started by identifying the signal molecules from feeder cells that are directly involved in allowing human embryonic stem cells to grow. Aided by this research, WiCell researchers successfully developed the first chemically defined media for human embryonic stem cells. Other scientists have since developed specially formulated culture media that allow them to grow stem cells without the support provided by non-stem cells.
"While removing a lot of biological variability and inconsistencies, growing cells without feeder cells makes it a lot more challenging. But I have a lot of experience and I am looking forward to establishing this expertise at the Salk," says Berggren.
"On behalf of the Institute's Stem Cell Committee, which includes Salk researchers Fred H. Gage, Chris Kintner, Leanne Jones, Inder Verma and Sam Pfaff, we are delighted to have Travis on board to share his expertise in stem cells so that all of our scientists can take this knowledge into new directions in research," says Juan Carlos Izpisúa Belmonte, chair of the committee.
A San Diego native, Berggren is no stranger to the Institute. After finishing his undergraduate studies at UCSD and a short stint as a commercial fisherman, he worked in professor Wylie Vale's lab at Salk. "Originally, I wanted to do synthetic organic chemistry but it sounded better on paper and I was glad to get a chance to work in a lab with a biological focus," says Berggren with a laugh.
For his graduate studies, he exchanged the eternal sunshine of Southern California for icy winters along the shores of lake Michigan. "I was just amazed how much your face can hurt," he says, "but the novelty factor wore off quickly and I am very happy to be back."