Scientists at Cold Spring Harbor Laboratory (CSHL) have identified a potential link between inflammation during pregnancy and the development of autism-like traits in male mice. The study, published by the laboratory, indicates that disruptions in the placenta may play a critical role in early neurodevelopment, offering new insights into the origins of autism spectrum disorder.
Early Placental Damage in Male Fetuses
The research team, led by CSHL Associate Professor Lucas Cheadle, investigated how maternal immune responses affect fetal development. To simulate the effects of a viral infection without introducing an actual virus, the scientists triggered an immune response in pregnant mice at various stages of gestation. They found that fetuses were most vulnerable when inflammation occurred 12.5 days into pregnancy.
According to Irene Sanchez Martin, a postdoctoral researcher in Cheadle’s laboratory, approximately one-third of the fetuses showed developmental abnormalities within just 24 hours of the inflammatory trigger. This rapid onset of abnormalities suggests that the window for such developmental disruptions is narrower than previously understood.
The study revealed a stark contrast between male and female offspring. Across all experiments, autism-like traits appeared exclusively in male fetuses, while female fetuses continued to develop normally. This sex-specific vulnerability emerged before the typical hormonal surges or sexual differentiation in the brain, a timing that surprised the researchers.
“It’s really fascinating, because we’re looking at an age which precedes hormonal surges. It precedes sexual differentiation in the brain and many other regions. So, it’s surprising there would be a sex-based difference this early,” Cheadle said.
Role of Spongiotrophoblasts in Immune Tolerance
To understand why male fetuses were affected while females were not, the researchers examined the placenta, specifically a region where maternal and fetal cells interact. They focused on specialized cells called spongiotrophoblasts, which help the mother’s immune system tolerate the developing fetus.
In normally developing fetuses, these cells remained healthy. However, male fetuses exhibiting developmental abnormalities showed visible damage to the spongiotrophoblasts. These cells are essential for preventing the mother’s immune system from attacking the fetus, which carries genetic material from both parents.
The findings suggest that maternal immune activation can interfere with this protective function. When spongiotrophoblasts are damaged, the mother’s immune response may begin to affect the developing fetus in harmful ways. This disruption appears to be a gateway to autism for some individuals, according to Cheadle.
“To truly understand autism spectrum disorder, we have to look beyond the brain,” Cheadle said. “Our work suggests that maternal immune activation and changes within the placenta are a gateway to autism for some unique individuals.”
Sex Differences and Future Research Directions
The study raises questions about why male embryos are more susceptible to these inflammatory effects. One possibility is that male embryos produce distinctive proteins that trigger an unfavorable maternal immune response following a viral infection. Another explanation is that female embryos possess a protective mechanism that helps them withstand inflammation during this sensitive developmental period.
Cheadle noted that these biological pathways may differ significantly between sexes. “A protective mechanism may exist within the female that could be harnessed to help the male. We’re trying to understand how autism emerges in both sexes,” he explained. “The evidence says that there are potentially different mechanisms.”
The research team plans to investigate both male and female mice more closely to uncover the specific mechanisms responsible for these contrasting responses. While the findings come from experiments in mice and do not establish that the same mechanisms cause autism in humans, they highlight the placenta as a potential site for early intervention strategies.
Understanding these differences could help researchers identify why some individuals are more vulnerable to environmental influences during pregnancy. The work could eventually lead to new targets for treatments and strategies for intervening earlier in the developmental processes associated with autism.
Source: ScienceDaily
