Læknaneminn - 01.04.2008, Page 104

aðeins hærra en sambærilegar erlendar rannsóknir.
Marktækur munur er á fj ölda karla og kvenna sem greinast
og mætti ætla að það sé vegna íjölda prólaktínóma sem er
algengari hjá konum en körlum. Niðurstöður sem valda
áhyggjum er hversu margir einstaklingar sem greinst hafa
með heiladingulsæxli eru ekki í eftirliti ásamt því sem þó
nokkri eru ekki í eftirliti hjá innkirtlaérfræðingi. Þetta er
eitthvað sem þyrfti að bæta.
Identification and localization of
trophoblast progenitor cells in the
mouse placenta
Elín Maríusdóttirl, Dr J. Cross2, Dr. D. Natale2, Dr. D.
Simmons2.
lDepartment of Medicine, University of Iceland,
2Department of Developmental Biology - University of
Calgary, Calgary Alberta.
Introduction:
The placenta has a critical role in transferring nutrients and
oxygen to the developing fetus. Nutrient transfer occurs
across the highly developed placenta villi that form to
create massive surface area. Problems concerning villous
development or function are the cause of many pregnancy
related diseases. Evidence suggests that abnormalities
in growth of the placental villi cause growth restriction
in the fetus. Low weight at birth is associated with a
spectrum of diseases both in childhood and later in life.
Studies of the normal growth of the mouse placental villi
(called the labyrinth in rodents) after embryonic day (E)
8.5, particularly identifying markers of trophoblast cell
progenitors that produce the villi should provide novel
insight into placental growth in general. Previous studies
suggested the presence of rapidly proliferating progenitor
cells that give rise to cells of the expanding labyrinth
between E8.5 and E12.5. Furthermore, when cells start to
differentiate they start to express Gcml, exit the cell cycle
and form syncytial cells that line the developing villi.
In this study we hypothesized that the homeobox gene
Ehox is a marker for trophoblast progenitor cells.
Materials and methods:
Histological sections of mouse placentas were selected
at random and using in situ hybridization we localized
Ehox mRNA expression and compared it with a known
marker of cell proliferation, phospho-histone H3 (PPH3
is expressed in cells in mitosis of the cell cycle). PPH3
positive cells were then quantified and also PPH3 positive
cells that express Ehox. To assess whether Ehox and Gcml
expression co-localized serial sections were compared.
Results:
Cell counting revealed that around 60% of PPH3 positive
cells also express Ehox. Furthermore comparison of serial
sections shows that Ehox and Gcml do not appear to co-
localize.
Conclusions:
Ehox and Gcml do not appear to co-localize, which
suggests that Ehox is not expressed in differentiated cells.
PPH3 is expressed in proliferating cells and a considerable
fraction of them express Ehox. We therefore conclude
based on expression patterns and cell counting that Ehox
mRNA expression is localized to trophoblast progenitor
cells in the placenta.
Culturing, differentiation and
subcloning of human embryonic stem
cells
Sólveig Helgadóttirl, Janne Jensen2, Jeonghoon Heo2,
Snorri S. Thorgeirsson2
lDepartment of Medicine of the University of Iceland,
2Lab of Experimental Carcinogenesis, National Insti-
tutes of Health
The unique features of embryonic stem cells (ESCs) are
their capacity to differentiate into all cell types comprising
the organism and their self-renewal potential. High
hopes are tied to possible utilization of ESCs, e.g. in drug
screening and replacement cell therapy.
In 1998 human ESCs (hESCs) were first isolated from the
inner cell mass (ICM) of blastocysts of preimplantation
embryos. Since then considerable knowledge has been
acquired in experimental procedures, including basic cell
culturing methods, growth factor treatment, transfection
and gene induction. Differentiation of hESCs can be
either spontaneous to form embryonic bodies (EBs)
or directed. Successful direction of differentiation of
hESCs into hematopoietic, neuronal and cardiomyocytic
lineages has been reported. Directed differentiation into
endoderm has been diíficult to achieve but is of great
interest owing to the lack of e.g. pancreatic fi cells and
liver cells for transplantation. There are however still
many challenges to improve culturing of undifferentiated
colonies, eíficiency of directed differentiation, isolation
and clonal expansion of homogenous populations of
committed cells.
The aim with our study was to optimize cell culture
conditions to maintain stable, undifferentiated H9
colonies. By revising established protocols we were able
to culture cells for multiple passages, both on a feeder cell
layer and in a feeder free environment using conditioned
media and high doses of basic FGF.
We aimed to improve the eíficiency of EB formation and
tried several approaches; suspension culturing of colonies
in FGF free media, spin down in 96 well non adherent plate
performed on single cells and hanging drop culturing of
colonies. Suspension culturing proved the most eíficient
method, but hanging drop culturing led to formation
of cell clusters we assumed to be cardiomyocytes. Spin
down culturing provided no viable colonies.
Cell differentiation was monitored by microscopic
inspection of cell morphology and gene expression.
RT-PCR was conducted for sox-17 (early endoderm
marker), brachyury (early mesoderm marker), AFP
(endoderm marker) and oct-4 (undifferentiated state