Rex Reyes traveled four hours daily this summer between a lab at the UC Davis Institute for Regenerative Cures in Sacramento and his home in Vallejo.

The commute by train and bus was well worth it for the experience of participating in stem cell research, the incoming Vallejo High School senior said.

Reyes was one of four area teens interning this summer at the institute as part of a pilot program sponsored by the California Institute for Regenerative Medicine.

The other three were Thomas Gepts and Kalani Ratnasiri of Davis High and Jaskaran Dhillon of Sheldon High.

They received certificates Wednesday for successfully meeting requirements for ultraclean preparation of stem cells.

Program directors selected the students based on their award-winning presentations of biotechnology concepts on websites they designed for UCD's 2011 Teen Biotech Challenge.

The four took a course in the procedures and techniques of stem cell production with master's-degree students from California State University, Sacramento, and worked on individual projects with scientist mentors.

The Good Manufacturing Practice lab was a highlight for Reyes.

"It was challenging for us kids because we were so nervous," said Reyes, describing the head-to-toe sterile gowns and exacting cleanliness of the facility. "When you get it right, it feels really good, like you've really accomplished something."

Reyes completed construction of a custom-designed DNA tool for stem cell research with his mentor, Karen Pepper. The tool helps researchers identify cells with desired traits by making the cells glow green.

The students presented their summer work with posters and oral explanations at a conference in Oakland last week.

Gepts, who will be a senior this fall, was impressed by the chance to meet scientists in non-traditional careers at the conference.

The son of a UC Davis biologist, Gepts would like to combine his enthusiasm for biology with his interests in foreign policy and politics.

Ratnasiri, entering her junior year, is considering whether there will be more research in her future. This summer, she learned to respect the precision and repetition required for stem cell research.

"It takes a lot time and a lot of monotony, but the end result is pretty cool," she said.

Ratnasiri's mentor, Whitney Cary, has a personal interest in Huntington's disease, a degenerative dementia that results, in part, from the destruction of spiny neurons in the brain.

Ratnasiri helped Cary grow embryonic stem cells and coax them to become spiny neurons, and got to see video of her neuron charges moving and connecting with each other under a microscope.

Ratnasiri said her interest in biology leans toward sports medicine.

Encouraging proper healing of athletes' broken bones, or helping people with fragile bones build the strength to play games like soccer, are distant applications of the research Dhillon worked on this summer.

An incoming senior, Dhillon digested a large volume of scientific literature to help plan his summer experiment. This was Dhillon's second summer in biological research.

In 2010, he worked at the UC Davis Center for Biophotonics, and the combined experience has made him turn from a direct path to medicine to aim instead at a career in clinical research.

But that's in the future. As for Reyes, he said he's looking forward to senior outings and college applications – and the prom.

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