An MRI study of the postnatal growth of the brain of the pig

Abstract

In all species the development of the brain will at some point go through a period of rapid growth. This period is called the ‘growth spurt’. During the growth spurt an enhanced vulnerability to nutritional factors or other growth restricting factors will occur in the brain. In different species the growth spurt can either take place prenatally, around the period of birth or postnatally, thus developmental levels at birth can differ strongly between species. An improved understanding of human brain growth could help determine for example when it is safe or unsafe to administer central nervous system altering drugs to pregnant/lactating women or very young children, and effects of perinatal adverse events like asphyxia on brain development. It is however not possible to do research on the human brain itself, because of various reasons. So finding a usable animal model for research on the developing human brain is important. When trying to find a suitable animal model the timing of the growth spurt should be taken into account. In 1966 Dickerson and Dobbing showed that the brain of the pig undergoes the growth spurt around the time of birth. Just like the human brain. Unlike the rat which has a growth spurt that takes place after birth, but is nevertheless much used as a model of developmental brain injury. Most of our knowledge of the developing pig brain is based on the research of Dickerson and Dobbing. Their methods were however imprecise. With the help of modern MRI techniques we have tried to determine a baseline for pig brain development by specifically looking at the development of brain volume, grey matter volume and white matter volume in ex vivo piglets at the ages of 1 day, 2 weeks and 4 weeks. Knowledge about the development of the pig brain will help us determine whether or not the pig is a good animal model for human brain development. Also, in the future we might use our knowledge of pig brain development to assess welfare in agricultural animals. From the MRI results it can be seen that piglets with a higher weight also seem to have a higher brain volume. All volumes increase over time, but the white matter increases at a higher rate than the other two volumes. Also the increase in volume over time follows a linear pattern for all measured volumes. We succeeded at establishing a baseline for brain development in the first four weeks of life of the piglet. The pig could still be a good animal model for research on the human brain. However, because we only looked at the first 4 weeks after birth more research will be needed. In the future in vivo or prenatal research might be done.