Free Radicals - Michael Brooks [68]
For instance, Alan Trounson, a stem cell researcher at Monash University in Melbourne, has grown cells from testes in a liquid broth, then used that broth to aid the growth of mouse embryonic stem cells. The growth of testes cells certainly seemed to release useful growth factors into the liquid: the stem cells steeped in it developed into something akin to egg-carrying follicles. Renee Reijo Pera, a researcher at the University of California at San Francisco, added bone proteins to her stem cell mix and found that this boosted the number of stem cells that became proto-eggs. Teresa Woodruff of Northwestern University, Illinois, has pushed the texture side of things: she made capsules of gel from a chemical found in seaweed and injected natural harvested mouse follicles into them. The gel provided a perfect supporting medium: when Woodruff stimulates ovulation with a hormone injection, fertile eggs are released from the follicles.
Woodruff has managed to fertilise these eggs, and produce live young. In 2009 her team managed to incubate human follicles to the point where they looked like mature eggs that produced all the standard hormones, such as oestrogen and progesterone. The law still forbids the fertilisation of human eggs for research purposes, but Woodruff is amazed that progress has been so quick that they are now bumping up against this barrier. Ten years ago, she told Wired magazine, it looked as though where they are now was more than fifty years away. The procedures involved have ‘turned out to be much simpler than we ever dreamed’, Woodruff says.
There is still the spectre – as with IVF – of producing babies with abnormalities. The one serious difficulty in creating a new life from scratch lies in a process called imprinting. The DNA contained in every cell in the body is, essentially, one long molecule. Within that molecule are the genes that carry the instructions for making proteins and other molecules essential to the processes of life. In mammals, those genes are ‘imprinted’ with a chemical tag that switches certain sets of genes on or off, and it is this imprinting that, when a male and female’s DNA is combined in an embryo, determines what qualities it will have. So, when creating sperm and eggs from stem cells, imprinting the DNA with the right tags is crucial. Any existing chemical tags have to be removed and the correct new tags have to be put in their place. Get this wrong, and foetal abnormalities are inevitable. At the moment, we have yet to get a proper handle on the imprinting process: what chemical environment creates the right tags in the cultured cells, for example, remains a mystery. But if the history of assisted reproduction teaches us anything, it is that there is no reason why we should not be able to solve that mystery.
The artificial womb is coming too: financial issues aside, it is now seen simply as an engineering problem. Hung-Ching Liu, a researcher at Cornell University’s Center for Reproductive Medicine and Infertility, is building a womb from a few cells taken from the endometria, the womb linings, of women visiting the clinic. The clinic’s considerable IVF success rate, Liu figured, might be improved by giving the embryo a few home comforts – even if they were contained in a Petri dish.
In Liu’s first attempts, the endometrial tissue was too thin for the embryo to implant onto. It kept breaking through and hitting glass, like a tree root hitting bedrock, and contact with a hard surface is enough to stunt the development of any embryo. Then Liu borrowed an idea from skin grafting: she grew the tissue on a biodegradable scaffold woven from collagen and chondroitin, a major component of the body’s cartilaginous tissue. The scaffold was bowl-shaped, but gradually disappeared over time, leaving a bowl of endometrial tissue. Liu then took embryos left over from IVF treatments in the clinic, placed them in the layers of cultivated tissue, and stood back to watch. For ten days