Are human space babies conceivable?
As astronauts continue to break records for time spent in space, and manned Mars exploration is under discussion, scientists in China have begun a groundbreaking study to determine whether humans can reproduce in space.
Scientists will for the first time conduct an experiment to induce the differentiation of human embryonic stem cells into germ cells on China's first cargo spacecraft, Tianzhou 1.
The experiment aims to study the effects of the space environment on human reproduction, beginning with the study of microgravity on human stem cells and germ cells, said Kehkooi Kee, lead researcher for the project.
Kee, a Malaysian Chinese professor at China’s prestigious Tsinghua University, said the unprecedented experiment will study the basic development and maturation of germ cells in the microgravity environment, as well as the development potential of human embryonic stem cells.
The research is expected to provide a theoretical basis and technical support to solve the possible problems of human reproduction caused by the space environment, Kee said.
“It’s an important experiment because it is the first step toward directly understanding human reproduction during space exploration,” he said.
What kind of difficulties could people face in having children in space?
Experts say that in the known space environment, microgravity, radiation and magnetic fields could have a great impact on human reproduction. Among these factors, microgravity could be the largest challenge.
At the cellular level, microgravity might affect cell division or polarity. The cells of living organisms contain
many organic molecules. These molecules and cells are evolved to function under Earth’s gravitational force. But scientists are still not sure how microgravity could affect the physical force governing the molecular interactions and development of the cells, said Kee.
The United States, Russia and Europe have conducted many space experiments to examine whether microgravity is harmful to astronauts, especially the effects on muscles and bones. However, microgravity’s effect on human reproductive capacity has been rarely studied.
Previous research in this area mainly focused on monitoring the reproductive hormone levels of astronauts. Due to ethical and physical constraints, it has been very difficult to directly obtain and study their germ cells.
“If we aim to directly study human reproductive biology in space, we need to build an in-vitro platform to study the germ cells. So we chose to use human embryonic stem cells to differentiate into germ cells,” said Kee.
In 2009, he and his colleagues used human embryonic stem cells to create human primordial germ cells and spermlike cells for the first time.
Currently, the team has successfully obtained egglike cells from human embryonic stem cells and will be publishing this new finding soon.
Human embryonic stem cells can be induced into primordial germ cells and further differentiated into spermlike or egglike cells. But differentiating embryonic stem cells into spermlike or egglike cells is very difficult because it requires more developmental steps and more cellular factors, said Kee.
Although other scientists have conducted similar experiments, none has been able to differentiate human germ cells into such a mature state as Kee’s team has.
“We have compared the in-vitro cultured cells with in-vivo cells, and found they have many similar characteristics. But we can only call the in-vitro ones spermlike cells or egglike cells, because we still can’t prove they are exactly the same until we conduct functional experiments,” Kee said.
So far, all such experiments have been conducted on the ground, so scientists don’t know whether microgravity will affect the differentiation of human embryonic stem cells and the formation of germ cells.
“In the experiments on the ground, it usually takes six days to culture and obtain primordial germ cells, and about two weeks to form spermlike or egglike cells,” said Kee. “The experiment on Tianzhou 1 will last 30 days.”