First evidence of fetal DNA persisting in human brain tissue

The process, called fetal 'microchimerism (Mc)', is common in other tissues such as blood, but this is the first evidence of male Mc in the human female brain. Microchimerism can be both beneficial and harmful to maternal health, since it is associated with processes such as tissue repair, as well as to autoimmune diseases.

Testing for the presence of a particular region of the Y-chromosome in autopsied brain tissues, the research team discovered that 63% of their samples showed potentially long-lasting Mc in multiple brain regions. They also found that women with Alzheimer's disease (AD) had less Mc than women without the disease.

According to the authors, this result warrants further investigation because previous reports have suggested that AD may be more prevalent in women with a higher number of pregnancies compared to childless women. The researchers commented that changes to the blood-brain barrier that occur during pregnancy could facilitate the process by which Mc is acquired into the human brain.

"This is the first evidence that microchimerism can cross the blood-brain barrier to establish male fetal tissue in the human female brain" says Chan.