Author: Mayuri Sinha Prasad, Laboratory for Stem Cell Research, Biomedicin,
Department of Health Science and Technology,
Aalborg University, Aalborg, Denmark
The potential use of stem cells in regenerative therapy is an exciting field of research, currently
undergoing tremendous development in order to bring the applications from the laboratory
benches to hospital bedsides. Both embryonic as well as adult stem cells have been shown to be
beneficial in the treatment of various debilitating disease in clinical trials around the world.
The main aim of this PhD dissertation is to gain a better understanding of the effect of low
oxygen tension on the differentiation, proliferation and ion channel function of human embryonic
stem cells (ESCs) and human adipose-derived stem cells (ASCs). For this purpose, the
investigation was divided into 3 sub-studies.
The first study focused on identifying the oxygen tension at which the ESCs would attain
optimal growth with minimal differentiation along with understanding the underlying molecular
pathway responsible for the effect. The results from the investigation indicate that culturing ESCs
at 5% oxygen tension can support long term undifferentiated propagation, without locking the
cells in a permanent state of pluripotency. Additionally we found that Notch-hypoxia cross talk
plays an important role in the maintenance of self-renewal.
The understanding gained from the first study was then taken further by investigating the
properties of human ESCs that were subjected to long term hypoxia to evaluate whether low
oxygen tension brought about any change in the ESC characteristics like proliferation, expression
of differentiation markers, karyotype, telomerase activity, differentiation capacity etc. This study
established that the ESCs exposed to long term hypoxia maintained features associated with
stable undifferentiated propagation and at the same time retained the capacity to differentiate into
the 3 germ layers.
The aim of the last study was to investigate the difference in the ion channel expression of the
embryonic and adipose-derived stem cell cultured in normoxic and 5% hypoxic conditions. The
results from this study detected a small but significant change in the level of some ion channel
gene expression in ESCs and further showed that hypoxic preconditioning influenced the
electrophysiological profile of ASCs on a population level.
Innumerable steps are involved in the transformation of the undifferentiated stem cells into
differentiated, functional cells. The understanding of molecular regulators that form a part of this
process is absolutely crucial for the development of the regenerative therapy. This dissertation is
a small part of the effort to unveil the molecular mechanisms underlying stem cells
differentiation, proliferation and ion channel function.
Molecular Mechanisms Underlying the Effect of Hypoxia on Stem Cell Growth and Differentiation