Researchers have recently expanded our knowledge of the biological bond between mother and child. The deep psychological and physical connection begins during pregnancy, when the mother’s body provides everything the fetus needs to develop and grow. The placenta is comprised of cells from both the mother and fetus, and serves as a conduit through which the two exchange nutrients, gasses and wastes. In some cases, cells actually migrate through the placenta. They become part of the organs of the body, including lungs, thyroid, muscle, liver, heart, kidney and skin, contributing to tissue repair and cancer prevention. On the negative side, they sometimes cause immune disorders.
The scientific name for the presence of a small number of genetically distinct cells in an organism is microchimerism. Scientists have known for many years that cells containing the male “Y” chromosome sometimes circulate in the blood of women following pregnancy. These cells are male, so they cannot belong to the women, and the likely explanation is that they came from babies during gestation.
This new study found microchimeric cells not only in the blood, but also imbedded in the brain. The scientists studied the brains of deceased women, and found the male cells embedded in the multiple brain regions of over 60 percent of the women. For some reason, there were many fewer such cells in the brains of women who had had Alzheimer’s disease.
Researchers speculate that the microchimeric cells usually result from a cross-placenta exchange, but there is some evidence cells may be transferred from mother to child through breastfeeding. There are also exchanges of cells between twins in utero, and cells from an older sibling may remain in the mother’s body, then migrate through the placenta to an infant. Cells from the grandmother may be inside the woman’s body, and they, too, could enter the body of an infant.
The activity of the microchimeric cells in women’s bodies is unknown, but scientists have theories. Fetal microchimeric cells are like stem cells, as they develop into different types of tissue and probably aid in tissue repair. A number of researchers have been doing animal studies to learn more, and they found that when the heart of a female rat was injured, the fetal cells in her body migrated to the heart and developed into cardiac tissue to repair the damage. In other animal studies, microchimeric cells differentiated into nerve cells
Because these cells belong partly to the mother, her body recognizes the relationship, but also recognizes they are partly foreign. This recognition may stimulate the immune system to be alert for cells that are partly similar to and partly different from the self, possibly providing protection against cancer. Conversely, microchimerism is more comment in patients with Multiple Sclerosis than in their healthy siblings indicating these cells may provoke an autoimmune attack.
Science has much still to learn about microchimerism, and the answers it finds may open the door to new cures for disease. Meanwhile, the phenomenon is a reminder that we human beings are interconnected in mysterious ways.