Human Neurons, Rat Brains

What does it mean to be made in the image of God? New research on human brain neurons implanted in rats forces us to ask this question.

The cells of adult humans can be reprogrammed to act as stem cells, and stem cells can then become any of the different cell types found throughout our bodies. Scientists have discovered how to induce stem cells to grow brain neurons that can then clump into three-dimensional neural tissue, called organoids – basically, little organs. While the neurons in these organoids show electrical activity like real human neurons, they do not grow to full size or make the type of connections brain neurons make because they lack the many other cells and supports found in a normal brain. However, organoids can give us insights into how the brain functions.

Opportunities & limitations

Since we can’t take a biopsy of brain tissue (like we can of a liver), neural organoids give us a model system to study brain dysfunctions. Suppose cells are taken from an individual with a specific genetic abnormality that results in a high risk of schizophrenia. These cells are reprogrammed to grow into neural organoids, and then these organoids are compared to organoids derived from a healthy individual. The schizophrenic patient’s derived organoids show abnormal electrical properties, which can be reversed with antipsychotic drugs used to treat schizophrenia. The effectiveness of these antipsychotic drugs suggests that organoids can be used to understand aspects of mental disorders. But organoid models are limited because they are still quite different from normal brain tissue.

This October, researchers reported that they implanted neural organoids into a developing rat brain. When put into three- to seven-day-old rats, these organoids receive physiological support from the rat, grow extensions and make active connections with rat neurons. They become part of the rat’s brain. If, after growing for about 150 days, these human brain neurons are stimulated, they influence rat learning. When implanted in this way, the organoids act very much like neurons in the human brain. Implantation gives us a better model to compare cells from healthy and mentally ill individuals, to see how their neurons differ and to discover how the illness can be corrected.

Ethical boundaries

This research raises ethical concerns about consciousness, what it means to be human, and, as suggested above, how we are made in the image of God. As a Christian, this research makes me wonder about the place of humans in God’s creation. While at the cellular level we may be intimately connected to animals, there is a profound border between humans and animals when considering us as individuals.

Scientists are aware of these issues. The United States Academies of Sciences, Engineering and Medicine in 2021 released a consensus report on this emerging field after consulting ethicists, religious scholars, scientists and lawyers. In one of its findings, the consensus report said they appreciated discussions with religious scholars of several faith traditions. But they bemoaned that there are currently few established forums for fostering this exchange.

As this is an exploding research area, Christians must stay aware of these developments. We have much to discuss about what this research means for theology – and for us as God’s children.