Stem Cell Breakthrough: Mass-Production Of 'Embryonic' Stem Cells From A Human H

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Stem Cell Breakthrough: Mass-Production Of 'Embryonic' Stem Cells

From A Human Hair

http://medicalnewscenter.com/out/out.cgi?

http://www.sciencedaily.com/releases/2008/10/081017164917.htm

The first reports of the successful reprogramming of adult human

cells back into so-called induced pluripotent stem (iPS) cells, which

by all appearances looked and acted like embryonic stem cells,

created a media stir. But the process was woefully inefficient: Only

one out of 10,000 cells could be persuaded to turn back the clock.

Now, a team of researchers led by Izpisúa Belmonte at the

Salk Institute for Biological Studies, succeeded in boosting the

reprogramming efficiency more than 100-fold, while cutting the time

it takes in half. In fact, they repeatedly generated iPS cells from

the tiny number of keratinocytes attached to a single hair plucked

from a human scalp.

Their method, published ahead of print in the Oct. 17, 2008 online

edition of Nature Biotechnology, not only provides a practical and

simple alternative for the generation of patient- and disease-

specific stem cells, which had been hampered by the low efficiency of

the reprogramming process, but also spares patients invasive

procedures to collect suitable starting material, since the process

only requires a single human hair.

" Having a very efficient and practical way of generating patient-

specific stem cells, which unlike human embryonic stem cells,

wouldn't be rejected by the patient's immune system after

transplantation brings us a step closer to the clinical application

of stem cell therapy, " says Belmonte, PhD., a professor in the Gene

Expression Laboratory and director of the Center of Regenerative

Medicine in Barcelona, Spain.

Keratinocytes form the uppermost layer of skin and produce keratin, a

tough protein that is the primary constituent of hair, nails and

skin. They originate in the basal layer of the epidermis, from where

they move up through the different layers of the epidermis and are

eventually shed.

While scientists have successfully reprogrammed different types of

mouse cells (fibroblasts, liver and intestinal cells), skin

fibroblasts were the only human cell type they had ever tried their

hands on. Fibroblasts help make the connective tissue in the body and

are the primary cell type in the deeper layers of the skin, where

they are responsible for wound healing and the secretion of proteins

that form collagen.

For the first set of experiments, first author Trond Aasen, Ph.D., a

postdoctoral researcher at the Center of Regenerative Medicine in

Barcelona, used viral vectors to slip the genes for the master

regulators Oct4, Sox2, as well as Klf4 and c-Myc into keratinocytes

cultured from human skin explants. After only 10 days — instead of

the more typical three to four weeks — one out of 100 hundred cells

grew into a tiny colony with all the markings of a typical human

embryonic stem cell colony.

The researchers then successfully prodded what they call keratinocyte-

derived iPS cells or KiPS cells to distinguish them from fibroblast-

derived iPS cells into becoming all the cell types in the human body,

including heart muscle cells and dopamine-producing neurons, which

are affected by Parkinson's disease.

Taking advantage of the high efficiency of the keratinocyte

reprogramming process, Aasen decided to test whether he could

establish KiPS cells from minute amounts of biological samples. " We

plucked a single hair from a co-worker's scalp and cultured the

keratinocytes, which are found in the outer root sheet area, " recalls

Aasen. He then successfully reprogrammed these cells into bona fide

KiPS cells.

Just why keratinocytes appear to be much more malleable than other

cell types is still an open question. " We checked a whole rainbow of

cells and found keratinocytes to be the easiest to be reprogrammed, "

says Belmonte. " It is still not clear exactly why that is and knowing

it will be very important for the technology to develop fully, " he

speculates.

They researchers did find one hint, though. When they compared the

expression profiles of genes related to stem cell identity, growth or

differentiation between keratinocytes, fibroblasts, human embryonic

stem cells (hESC) and KiPS cells, keratinocytes had more in common

with hESCs and KiPS cells than with fibroblasts.

Researchers who also contributed to the study include Angel Raya,

Ph.D., J. Barrero, Ph.D., Elena Garreta, Ph.D., Antonella

Consiglio Ph.D., Federico , Ph.D., Rita Vassena, Ph.D.,

Josipa Bilic, Ph.D., Vladimir Pekarik, Ph.D., Gustavo Tiscornia,

Ph.D., Edel, Ph.D., and Stéphanie Boué, Ph.D., at the Center

of Regenerative Medicine in Barcelona, Spain.