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在线翻译:
szdaily -> In depth
Tianzhou-1 extends scientific research into space
    2017-April-25  08:53    Shenzhen Daily

Tianzhou-1 extends scientific research into space

CHINA’S first cargo spacecraft, Tianzhou-1, has docked with the country’s Tiangong II space laboratory. The docking took place Saturday afternoon and the two spacecraft will stay in combined orbit for about two months. During this period of time, the Tianzhou-1 will resupply fuel to Tiangong II and conduct scientific experiments, according to the China Manned Space Agency.

Can we grow human organs in space?

Scientists around the world are looking for the “keys” to enable humans to regrow tissues or organs lost due to illness or injury, just like gecko regrowing a tail. Their quest now extends into space.

Scientists from the Institute of Zoology of the Chinese Academy of Sciences (CAS) are conducting experiments on Tianzhou-1 to study the effects of micro-gravity on embryonic stem cell proliferation and differentiation.

The spacecraft is carrying embryonic stem cells and embryoid bodies of mice. Scientists will observe the process of their proliferation and differentiation in space through microscope images. Parallel experiments will be conducted on the ground to compare the results, says lead researcher Duan Enkui.

“We hope to get an initial understanding about the space micro-gravity effects on stem cell proliferation and differentiation,” said Duan.

Embryonic stem cells are pluripotent cells that have the potential to become any type of cell in the body. One of the main characteristics of stem cells is their ability to self-renew or multiply while maintaining the potential to develop into other types of cells. Stem cells can become cells of the blood, heart, bones, skin, muscles, brain or other body parts. They are valuable as research tools and might, in the future, be used to treat a wide range of ailments.

The study of micro-gravity’s effects on the proliferation and differentiation of stem cells is a hot topic in the field of spacelife science.

“In ground experiments simulating micro-gravity conditions, we found the differentiation ability of mouse embryonic stem cells is enhanced. We also discovered the key gene responsible for this change and the molecular signaling pathway,” says Lei Xiaohua, a member of the research team. “Can we use micro-gravity conditions to realize large-scale proliferation of stem cells and tissue engineering construction? That’s what we want to find out,” says Lei.

Are human space babies conceivable?

Chinese scientists will for the first time conduct an experiment to induce the differentiation of human embryonic stem cells into germ cells on 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, says Kehkooi Kee, lead researcher on the project.

Kee, a Malaysia Chinese professor at China’s prestigious Tsinghua University, says the unprecedented experiment will study the basic development and maturation of germ cells in the micro-gravity environment, and the developmental 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 towards directly understanding human reproduction during space exploration,” he says.

What kind of difficulties could people face by having children in space?

Experts say that in the known space environment, micro-gravity, radiation and magnetic fields could have a great impact on human reproduction. Among these factors, micro-gravity could be the largest challenge.

At the cellular level, micro-gravity might affect cell division or polarity. The cells of living organisms contain many organic molecules. These molecules and cells are evolved to function under the earth’s gravitational force. But scientists are still not clear how micro-gravity could affect the physical force governing the molecular interactions and developments of the cells, says Kee.

The United States, Russia and Europe have conducted many space experiments to examine if micro-gravity is harmful to astronauts, especially the effects on the muscle and bones. However, microgravity effect on human reproductive capacity has rarely been studied.

Previous research in this area mainly focused on monitoring the reproductive hormone levels of astronauts. Due to the 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,” says Kee.

In 2009, he and his colleagues used human embryonic stem cells to create human primordial germ cells and sperm-like cells for the first time. They published their research in the academic journal Nature. Currently, the team has successfully obtained egg-like cells from human embryonic stem cells and will be publishing this novel finding soon.

Human embryonic stem cells can be induced into primordial germ cells and further differentiate into sperm-like or egg-like cells. But differentiating embryonic stem cells into sperm-like or egg-like cells is very difficult because they require more developmental steps and more cellular factors, says Kee.

So far, all such experiments have been conducted on the ground, so scientists do not know whether micro-gravity will affect the differentiation of human embryonic stem cells and the formation of germ cells.

Medicine for bone loss to be tested

Scientists will test a medicine to treat bone loss during the maiden voyage of Tianzhou-1. The medicine has been specially developed for astronauts, but they hope it will benefit ordinary people too.

Chinese scientists will use the micro-gravity environment to test the effect of 3-hydroxybutyric acid (3HB) in preventing osteoporosis, said research leader Chen Guoqiang, who is also director of the Center for Synthetic and Systems Biology at Tsinghua University.

Normally, the solid structure of bone tissue is stimulated and maintained by gravity and physical exercise. But the micro-gravity environment in space eases the load on bones, causing rapid bone loss and osteoporosis, Chen said.

“One day of bone loss in space is equivalent to a year on earth,” he said.

Research shows astronauts suffer average monthly bone loss of 0.5 percent to 2 percent in space, especially in weight-bearing bones such as the tibia, femur and vertebrae.

Back on earth, they can take double or triple the time of their flight period to recover. Sometimes bone loss is permanent.

Micro-gravity mainly inhibits the differentiation of osteoblasts (bone-forming cells), which is accompanied by the mass growth of osteoclasts (bone-resorbing cells), causing bone structure to change, said Chen.

Standard drug treatments for osteoporosis have a range of side effects, including tumors or cardiovascular diseases. The medicines are also relatively ineffective for treating osteoporosis caused by micro-gravity.

Chen said 3HB is one of the main components of ketone bodies, which occur naturally in mammals. It had been used to treat epilepsy for many years. “We found that 3HB can promote bone formation,” said Chen.

Unlike the chemical synthetic 3HB for treating epilepsy, Chen’s team used microbial fermentation to produce 3HB, which has entirely the same structure as the 3HB naturally existing in the human body. So it’s safer than chemical synthetic drugs, Chen said.

Experiments simulating the micro-gravity environment have been conducted on the ground. “We hope to test the effect of the medicine in a real space micro-gravity environment,” Chen said.

Since Tianzhou-1 cannot carry animals, scientists will compare the osteoblast cell samples treated and not treated with 3HB. Microscope images of the samples will be transmitted to earth.

(Xinhua)

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