Are hu­man space ba­bies con­ceiv­able?

China Daily (Hong Kong) - - FRONT PAGE -

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.”

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