Scientists
discover how to isolate stem cells from endometrium
Australian researchers
have discovered how to isolate probable stem cells from
the lining of women's wombs, thus providing a ready
source of stem cells for tissue engineering as well
as a possible route for understanding common conditions
such as endometriosis.
The finding opens up the possibility
of using the stem cells for tissue engineering applications
such as building up natural tissue to repair prolapsed
pelvic floors. Pelvic floor prolapse is a common condition,
affecting over 50% of women after childbirth; around
one in ten women have surgery and a third of these women
require repeated operations to correct the problem.
Dr Caroline Gargett describes how she and her PhD student,
Ms Kjiana Schwab, identified two markers, CD146 and
PDGF-Rß, which they were able to use to isolate
mesenchymal stem-like cells (MSC) from endometrial tissue
using a high speed cell sorting machine (fluorescence
activated cell sorting FACS). Only 1.5% of the
endometrial cells sorted in this way expressed both
markers and, therefore could be MSC.
They then investigated the properties of the MSC to
discover whether they really were stem cells, capable
of differentiating into a variety of different cell
types. They found the cells were able to produce clones
to form colonies of new cells at a rate that was 15
times greater than produced by the other endometrial
cells. Furthermore, the MSC were able to differentiate
into fat, bone, cartilage and smooth muscle cells in
the culture dish. The MSC also appeared to be located
around blood vessels in the endometrium (perivascular
region).
Dr Gargett, a senior scientist at the Centre for Women's
Health Research, Monash Institute of Medical Research,
Monash University, Victoria, Australia, explained: "Colony-forming
ability is a property of adult stem cells, as is the
ability to differentiate into different cell types.
The fact that the cells expressing the two markers were
located in the perivascular region strengthens our case
that we have isolated mesenchymal stem cells, because
mesenchymal stem cells from bone marrow and fat are
found around blood vessels too. It also gives us clues
as to how they might function in repairing and regenerating
new endometrium each month".
This is the first time that researchers have been able
to use markers to isolate MSC from the endometrium and
also the first study to show that the properties of
these cells mean they are highly likely to be stem cells.
Dr Gargett said: "We had previously detected that
MSC were present in the human endometrium but we were
unable to isolate the MSC, which was a big drawback
in studying their properties. The major finding of this
study was the identification of two markers which enabled
the prospective isolation of MSC-like cells from human
endometrial tissue. This allows us to characterise endometrial
MSC so we can understand their molecular and cellular
properties better, compare them to MSC from other sources,
such as bone marrow and fat, use them for tissue engineering
applications, such as making constructs with biological
scaffolds for pelvic floor prolapse surgery, and find
where they are located in endometrium (i.e. around blood
vessels); this gives us a clue as to how they might
function in growing new endometrium each menstrual cycle
and how they may have a role in gynaecological diseases
such as endometriosis".
The human endometrium is the only adult tissue that
contains a substantial amount of the connective tissue
framework (called stroma) that regularly regenerates
under normal conditions when a woman menstruates. Because
of its regenerative properties, Dr Gargett believed
that it might contain MSC that were responsible for
the monthly regeneration of the stroma and related blood
vessels, and which could be an easily available source
of MSC for stem cell therapy. However, until she identified
CD146 and PDGF-Rß as MSC markers, there were no
known markers and therefore no way of isolating the
endometrial MSC.
Her research, using tissue obtained from women aged
between 31-49 who were having hysterectomies, indicates
that the MSC are probably located mainly in the basalis
layer of the endometrium, which is the layer that is
not shed during a woman¹s period. "We think
that is where the MSC should be if they are responsible
for producing the functionalis layer, which grows each
month" said Dr Gargett.
This means that, although it might be possible to collect
MSC from menstrual blood, the most likely method of
collection would be curettage or biopsy.
" This would not be any more invasive than collecting
MSC from bone marrow or surgical removal (biopsy) of
fat tissue", said Dr Gargett. "MSC could also
be collected from postmenopausal women, whose endometrium
is very thin. If these women are given oestrogen replacement
therapy for a very short time (a week or two) their
endometrium will grow to the thickness of a reproductive
age woman and the MSC could be collected without harm
to the woman".
Dr Gargett believes that initial applications for endometrial
MSC would be to use them on the women that they had
been retrieved from (rather than on other people) for
gynaecological purposes such as pelvic floor prolapse.
"Pelvic floor prolapse is a common problem that
significantly impacts the lives of many women and they
find it embarrassing to talk about it is a hidden
disorder in need of an innovative therapy", she
explained.
"Clinicians have been using a synthetic mesh as
a reinforcement material to try and reduce the high
rate of recurrence of this condition. While these meshes
are often successful, a significant number of complications
arise due to erosion or rejection of the foreign material.
Increasingly clinicians have been trying biological
scaffold material, but this often fails as it lacks
cells and the body breaks it down faster than the body's
cells can infiltrate and strengthen the material. We
believe that using a combination of biological scaffold
and a woman's own MSC might provide a solution that
would ensure a longer lasting firm natural tissue that
would be a superior support for the prolapsed uterus.
" We also believe that the identification of the
MSC in human endometrium gives us the opportunity to
investigate their possible role in the development and
pathogenesis of common gynaecological disorders associated
with abnormal endometrial growth, such as endometriosis
and adenomyosis".
However, it will probably be at least ten years before
applications from Dr Gargett's findings will be used
in the clinic. The next stages of the research include
refining the technique by looking for further markers
and possibly a single marker that could do the same
job as two, and testing the possible tissue-engineering
applications in animal models before they are used in
humans.
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