Our organs too may have sexual identities

The organs in our body may have a sexual identity of their own, according to new research which may shed light on why some cancers are more common in women, and others in men.
The idea that our organs could be "male" or "female" raises the possibility that women and men may need different treatments as a result, researchers said.
"We wanted to ask a very basic question: whether it is just the cells of the sex organs of a fully developed organism that 'know' their sexual identity, or whether this is true of cells in other organs too - and whether that matters," said Irene Miguel-Aliaga from Clinical Sciences Centre (CSC), based at Imperial College London, who led the research.

The researchers examined stem cells in intestines of fruit flies. They used genetic tools that allow them to turn genes on and off specifically in these cells.
This allowed them to tailor the cells to be more female or more male. When the team feminised or masculinised the flies' gut stem cells this changed the extent to which the cells multiplied.
Female, or feminised cells were better able to proliferate. The researchers found that the effect of feminising adult gut stem cells was reversible.

"If we take a female fly and then in the adult we masculinise the stem cells in the intestine and wait, within three weeks the gut shrinks to the smaller, male-like size," said Bruno Hudry from CSC.

The team also found that the female intestine was more prone to tumours.
"We find it's a lot easier to create genetically-induced tumours in females than in males. So we suspect there is a trade-off going on," said Hudry.
"Females need this increased plasticity to cope with reproduction, but in certain circumstances that can be deleterious and make the female gut more prone to tumours," he said.
It was known that sex organs of vertebrates retain considerable plasticity: adult ovary and adult testis cells in mice can trans-differentiate into their counterparts following just a single genetic change, researchers said.
So these cells must have their sexual identity continuously reinforced throughout their postnatal life.

The team believes this to be the first time, however, that such plasticity has been demonstrated in adult cells outside the sex organs.
It may be obvious that males and females develop sex-specific organs as a foetus develops, but according to Miguel-Aliaga there has been an assumption that organs that are the same in both sexes function differently only because of different circulating hormones - for example, the oestrogen in women and testosterone in men that kick-in at puberty.
In some adult organs found in both sexes, such as the intestine, differences remain, and that these are not due to either developmental history or circulating hormones.

The study was published in the journal Nature.