A Japanese woman in her 70s is the first person
to receive tissue derived from induced pluripotent stem cells, a technology
that has created great expectations since it could offer the same regenerative
potential as embryo-derived cells but without some of the ethical and safety
concerns.
In a two-hour procedure starting at 14:20 local
time today, a team of three eye specialists lead by Yasuo Kurimoto of the Kobe
City Medical Center General Hospital implanted a 1.3 by 3.0 millimetre sheet of
retinal pigment epithelium cells into an eye of the Hyogo prefecture resident,
who suffers from age-related macular degeneration, a common eye condition that
can lead to blindness.
The procedure took place at the Institute for
Biomedical Research and Innovation, next to the RIKEN Center for Developmental
Biology (CDB), where ophthalmologist Masayo Takahashi had developed and tested
the epithelium sheets. Takahashi had reprogrammed some cells from the patient's
skin to produce induced pluripotent stem (iPS) cells. ('Pluripotent' means able
to differentiate into virtually any type of tissue in the body.) She then
coaxed those cells to differentiate into retinal pigment epithelium cells and
grow into a sheet for implantation.
The patient “took on all the risk that go with
the treatment as well as the surgery”, Kurimoto said in a statement released by
RIKEN. “I have utmost respect for the bravery she showed in resolving to go
through with it.”
He hit a sombre note in thanking Yoshiki Sasai,
a CDB researcher who recently committed suicide. “This project could not have
existed without the late Yoshiki Sasai’s research, which led the way to
differentiating retinal tissue from stem cells.”
Kurimoto also thanked Shinya Yamanaka, a
stem-cell scientist at Japan's Kyoto University “without whose discovery of iPS
cells, [such] clinical research would not be possible”. Yamanaka shared the
2012 Nobel Prize in Physiology or Medicine for that work.
Kurimoto performed the two-hour procedure a
mere four days after a health-ministry committee gave clearance for the human
trial (see 'Next-generation stem cells cleared for human trial').
To earn that, Takahashi and her collaborators
had done safety studies in both monkeys and mice. The animal tests found that
iPS cells were not rejected and did not lead to the growth of tumours (see
'Stem cells cruise to clinic').
Age-related macular degeneration results from
the breakdown of retinal epithelium, a layer of cells that support
photoreceptors needed for vision. The procedure Kurimoto performed is unlikely
to restore his patient's vision. However, researchers around the world will be
watching closely to see whether the cells are able to check the further
destruction of the retina while avoiding potential side effects, such as
bringing about an immune reaction or inducing cancerous growth.
“We've taken a momentous first step toward
regenerative medicine using iPS cells,” Takahashi said in a statement. “With
this as a starting point, I definitely want to bring [iPS cell-based
regenerative medicine] to as many people as possible.”