Two-dimensional, manually laborious, culturing systems for stem cells
may soon be relegated to history, thanks to A*STAR’s development of an
efficient bioreactor.
Inducing stem cells to become different cell types efficiently, and on a
large scale, is now possible using a three-dimensional platform
Induced pluripotent stem (iPS)
cells have the potential to form any cell type in the body, providing a
powerful tool for drug discovery and regenerative medicine. Yet coaxing these
cells to reliably take on a specific fate in the laboratory has proven
challenging on a large scale. Now, a team of A*STAR stem cell researchers has
developed a cell differentiation protocol in which iPS cells are propagated and
expanded in a three-dimensional (3D) bioreactor to efficiently create neural
progenitor cells1.
“Such a method will be a boon for
the nascent cell-therapy and drug-screening industry, as it will be able to
produce vast amounts of cells for transplantation and drug discovery in a
reproducible manner,” says Steve Oh at the A*STAR Bioprocessing Technology
Institute in Singapore, who led the research.
Oh and his co-workers started
with a so-called ‘microcarrier’ platform that they had previously developed for
culturing human embryonic stem cells on the surface of small solid particles in
a 3D suspension system2. They optimized the technology for human iPS cells,
demonstrating that protein-coated cylindrical microcarriers in stirred vessels,
known as spinner flasks, coupled with twice-daily culture medium exchange, can
support 20-fold expansion of reprogrammed stem cells. This yield was higher
than any other reported system for growing batches of such cells.
Normally, iPS cells would then
have to be painstakingly manipulated on a flat Petri plate to form more
specialized cells. But, with just a simple change of the growth medium in the
new 3D set-up, the researchers induced the cells to become neural precursors
with up to 85% efficiency. This integrated process of cell expansion and
differentiation produced 333 neural progenitor cells for each iPS cell seeded.
By comparison, the classic 2D tissue culture protocol, used by most scientists,
gave rise to just 53 neural precursors per initial stem cell.
“The 2D approach is manually
laborious, gives one-tenth of the yields and is variable from lab to lab,” says
Oh. “Microcarrier-based cultures provide larger surface areas for cell growth
and more of them can be added to the system to increase the aggregate sizes and
yields.”
Oh and his team also coaxed the
neural progenitors to further differentiate into many different types of brain
cells, including neurons, oligodendrocytes and astrocytes — the three primary
neural lineages. In the future, notes Oh, such neurons could be used to treat
Parkinson’s disease, for example; and, oligodendrocytes could be transplanted
to overcome spinal cord injuries.
The A*STAR-affiliated researchers
contributing to this research are from the Bioprocessing Technology Institute
References
- Bardy, J., Chen, A. K., Lim, Y. M., Wu, S., Wei,
S. et al. Microcarrier suspension cultures for high-density
expansion and differentiation of human pluripotent stem cells to neural
progenitor cells. Tissue Engineering Part C: Methods advance
online publication, 4 September 2012 (doi: 10.1089/ten.tec.2012.0146). | article
- Chen, A. K.-L., Chen, X., Choo, A. B. H.,
Reuveny, S. & Oh, S. K. W. Critical microcarrier properties affecting
the expansion of undifferentiated human embryonic stem cells. Stem
Cell Research 7, 97–111 (2011). | article
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