October 2017 Discover

LEFT: DAVID ZENTZ. RIGHT: STEVE ZYLIUS/UC-IRVINE COMMUNICATIONS

act like embryonic stem cells. Researchers called them
induced pluripotent cells, which are created by enticing
cells to turn on genes normally found in embryonic
stem cells. This process endows them with pluripotency,
or the ability to become any type of cell, including
neural stem cells. Just two years earlier, in 2004, Cali-
fornia voters bucked the White House and approved
Proposition 71, establishing the California Institute
for Regenerative Medicine. By 2006, the organization
issued its first batch of funding from the $3 billion war
chest the legislation allocated. With those two develop-
ments, research sputtered back to life.
Scientists then began to grapple with some funda-
mental issues. For starters, how could researchers turn

stem cells into mature cell types? Was there a chemical

or genetic signal that induced stem cells to create the

complex structures of the body and brain? And which

molecules and mechanisms were required to integrate

stem cells into an injured brain?

Figuring out the answers proved daunting. Over the

past decade, however, scientists have begun to decipher

how neurogenesis occurs and the anatomical location

where neural stem cells are born and maintained inside

the brain. “We now have the ability to culture and

isolate stem cells in a much more elegant and sophisti-

cated way,” says Gary Steinberg, a stem cell researcher

who heads the neurosurgery department at Stanford

University. “We now know much more about how the

cells work and how they best become integrated into

the circuits in the brain.”

DARKNESS TO LIGHT

“It was like someone was turning the lights on,” recalls

Kristin Macdonald, a 60-year-old from Beverly Hills,

Calif. Macdonald has retinitis pigmentosa, a genetic

disorder that causes a gradual decay of the photore-

ceptors — the rods and cones — in the retina. This thin

layer of tissue at the back of the eye detects light and

then converts it into nerve impulses that travel to the

brain’s vision centers to form images. As the rods and

cones die off, people with the disorder experience night

blindness and tunnel vision, and eventually become

legally or totally blind.

A gracious blonde with a dazzling smile, Macdonald

started losing her sight in her late 20s and was legally

blind by her 40s. In June 2015, she became the first

patient in North America to receive an eye injection

of about half a million retinal progenitor cells. The

aim was to repair and possibly replace damaged light-

sensing cells.

In the time since her treatment, she has noticed a

decided change. She can discern shapes and the faint

hue of colors, enabling her to recognize cars parked

Kristin Macdonald experienced improved vision after

a 2015 procedure to treat a degenerative eye condition.

Henry Klassen, a UC-Irvine ophthalmologist, is director

of a stem cell clinical project that included Macdonald.