Strand of human hair at 200x magnification. Credit:
And, as a team of University of
Wisconsin-Madison researchers show in a study of
rhesus monkeys, published in the April 2014 edition of the journal Pediatric
Research, it can also reveal the womb environment in which an infant formed.
It's the first time researchers have used infant
hair to examine the hormonal environment to which the fetus was exposed during
development and it promises to yield a wealth of new information. The findings
have significant implications for several fields, from neonatology to
psychology, social science to neurology.
"We had this 'Aha!' realization that we could use
hair in newborns, because it starts growing one to two months before birth,"
says Christopher Coe, UW-Madison professor of psychology and director of the
Harlow Center for Biological Psychology. "It provides a glimpse of the prenatal
Hair closest to the scalp reveals the most recent
information but moving down the shaft effectively transits an individual's
For the noninvasive study, researchers took small
samples of hair from mother rhesus monkeys and their infants using common hair
clippers. The hair was cleaned and pulverized into a fine powder using a
high-speed grinder. The hormonal signature was then read using a new mass
The researchers were interested in whether there
were differences in the hormones of infants born to younger, first-time mothers
versus more experienced mothers. To test their question, they compared monkey
mothers equivalent in age to 15-year-old humans to older monkeys, similar in age
to pregnant young adults.
"It provided a model of teenage pregnancy," says
Coe. "You're still growing yourself and if you're 15 and pregnant, mom and
developing baby are more in competition with each other."
The researchers used rhesus monkeys because they are
an ideal model species for humans.
It's well known that maternal age plays a role in
pregnancy and delivery outcomes, and a growing body of evidence shows that
levels of some hormones – such as the stress
hormone cortisol and female-typical hormones like estrogen – are higher in
young mothers and younger women pregnant for the first time.
Prior studies have shown high levels of cortisol and
drugs that act like it can have a lasting impact on the developing brain,
including impairment in reflexes and attention, and an increased incidence of
emotional and learning problems.
In the monkey study, researchers found that
cortisone, an inactive form of cortisol, was higher in young mothers and in
their babies than in hair of the
older mothers and their infants.
Babies born to
young mothers also had higher levels of estrone (a form of estrogen) and
testosterone in their hair than did babies born to older mothers. Levels of both
these hormones were surprisingly similar between male and female infants.
Both Coe and Amita Kapoor, first author of the study
and former postdoctoral researcher in Coe's lab, are particularly interested in
whether these differences impact "maleness and femaleness" of the babies:
whether higher exposure to these steroid hormones during fetal development leads
to more pronounced gender differences in behavior later in life.
The findings raise questions about everything from
the significance of birth order to stereotypical "boy" and "girl" behaviors in
Additionally, what happens to a developing fetus
while in the womb may impact its risk for chronic disease later in life, says
"Type 2 diabetes, metabolic disease, coronary artery
disease, psychiatric disorders – there [may be] a whole host of long-term
repercussions of stress in utero," says Kapoor, now an assistant researcher at
the Wisconsin National Primate Research Center's Assay Services.
She referred to a theory proposed by the
epidemiologist David Barker, which suggests the developing fetus may be
"programmed" in response to the womb environment.
Those who study people are "really excited because
it's so noninvasive," Kapoor says, although getting enough hair from humans is a
challenge researchers have nearly, but not quite, figured out. Most human babies
aren't as hairy other primates.
For the rhesus study, Kapoor – working with
colleague Curtis Hedman, of the Wisconsin State Laboratory of Hygiene – was able
to refine a new method for looking at multiple hormones at a time.
She was able to analyze eight hormones
simultaneously and is now working to increase that number.
For Coe, this "proof-of-concept" study provides a
new world of opportunity.
hair is non-toxic and stable at room temperature, it's easy to store and
easy to transport.
"How does the prenatal environment set the stage for
risk or for resilience?" he asks. "The new collaborations are an unexpected
gift. It's more than just cool technology or a cool idea."
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