Mothers And Offspring Can Share Cells Throughout Life
ScienceDaily (May 2, 2008) — Cutting the umbilical cord doesn't
necessarily sever the physical link between mother and child. Many
cells pass back and forth between the mother and fetus during
pregnancy and can be detected in the tissues and organs of both even
decades later. This mixing of cells from two genetically distinct
individuals is called microchimerism. The phenomenon is the focus of
an increasing number of scientists who wonder what role these cells
play in the body.
A potentially significant one, it turns out. Research implicates that
maternal and fetal microchimerism plays both adverse and beneficial
roles in some autoimmune diseases as well as the prevention of at
least one cancer. This double-edged sword in turn has opened new
avenues of study of the body's immune system and the possibility of
developing new tests and therapies.
Two of the world's leading researchers in microchimerism are J. Lee
Nelson, M.D., of Fred Hutchinson Cancer Research Center's Clinical
Research Division; and V.K. Gadi, M.D., Ph.D., assistant professor of
medicine at the University of Washington. Nelson also is a professor
of medicine at the University of Washington. Gadi is also a research
associate in the Hutchinson Center's Clinical Research Division.
In 2007, they were the first to report these potentially beneficial
effects of microchimerism:
In January, Nelson reported the first discovery that cells passed
from mother to child during pregnancy can differentiate into
functioning islet beta cells that produce insulin in the child. The
same study also found maternal DNA in greater amounts in the blood of
children and young adults with Type 1 diabetes than their healthy
siblings and a control group, implying that the cells may be
attempting to repair damaged tissue. There was no evidence that the
mother's cells were attacking the child's insulin cells and no
evidence that the maternal cells were targets of an immune response
from the child's immune system. The findings could lead to new
approaches to treating Type 1 diabetes. For example, if maternal
microchimerism results in cells that make insulin, a mother's stem
cells might be harvested and used to treat her diabetic child. Such
cells would have a genetic edge over donated islet cells from a
cadaver that are usually completely genetically mismatched.
Last October, a research paper by Gadi and Nelson described findings
that suggest fetal cells that persist in a woman's body long after
pregnancy in some cases may reduce the woman's risk of breast cancer.
The scientists examined the blood of 82 women post-pregnancy, 35 of
whom had had breast cancer. They looked for male DNA in the blood,
presuming it was present due to a prior pregnancy with a male. Fetal
microchimerism (FMc) was found significantly more often in healthy
women than women with a history of breast cancer, 43 percent versus
14 percent respectively. The scientists concluded that FMc may
contribute to the reduction of breast cancer based on the hypothesis
that residual fetal cells may provide immune surveillance of
malignant cells in the mother. They caution that further studies are
needed to confirm the theory.
Microchimerism reveals its Jekyll and Hyde personality in the case of
autoimmune diseases. In the late 1990s, Nelson's group was the first
to investigate microchimerism in an autoimmune disease:
In 1996 Nelson's lab proposed that fetal microchimerism might in part
explain the female predilection to autoimmune disease and they
subsequently discovered elevated levels of fetal microchimerism in
the blood of women with scleroderma compared to healthy women.
Subsequent studies found fetal microchimerism in internal organs and
in skin affected by scleroderma.
In 1999 Nelson's group found that maternal microchimerism persists
into adult life in individuals who have normal immune systems. They
presumed this is due to engraftment with maternal stem cells. Stem
cells can become multiple different types of cells. Researchers
wondered whether maternal cells can become part of the cells that
make up tissues. Scientists found maternal cells in the hearts of
infants who died from heart block due to neonatal lupus and
identified that most of the maternal cells were cardiac myocytes
(heart muscle cells). They theorized that the maternal cells are the
target of an immune attack.
On the other hand, women with rheumatoid arthritis often have their
disease improve or even disappear during pregnancy. A beneficial role
of fetal microchimerism was suggested by the research finding that
elevated levels of fetal microchimerism significantly correlated with
pregnancy-induced amelioration of rheumatoid arthritis.
The Nelson lab has expanded its study of microchimerism into the
fields of reproduction, HIV/AIDS and transplantation. For example,
scientists are investigating microchimerism in complications of
pregnancy, especially preeclampsia, a disorder characterized by high
blood pressure in women in their third trimester of pregnancy, and in
recurrent pregnancy loss.
Nelson's group also is investigating maternal microchimerism in
patients with HIV and is looking at whether maternal microchimerism
levels correlate with whether there is progression or non-progression
to AIDS.
Transplantation of stem cells to treat some cancers results in
chimerism. Graft-vs.-host disease occurs more often if the cell donor
is a woman with prior pregnancies. Tests of female donor cells found
they contained male microchimerism, consistent with the
interpretation that fetal microchimerism contributes to graft-vs.-
host disease. In kidney, pancreas and islet transplantation, Gadi,
Nelson and collaborators tested serial serum samples and found that
donor-specific microchimerism detection may become a useful non-
invasive test for early rejection. This has led to work by several
other research groups to therapeutically exploit the principles of
naturally-acquired microchimerism in their selection of donors for
transplantation.
The discovery that a mother's cells can turn up in her adult progeny
and that fetal cells can occur in women who were once pregnant
heralds the emergence of microchimerism as an important new theme in
biology.
Adapted from materials provided by Fred Hutchinson Cancer Research
Center.
Need to cite this story in your essay, paper, or report? Use one of
the following formats:
APA
MLA Fred Hutchinson Cancer Research Center (2008, May 2). Mothers
And Offspring Can Share Cells Throughout Life. ScienceDaily.
Retrieved May 4, 2008, from http://www.scienced
/releases/2008/
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