Studies by researchers at The Scripps Research Institute, La Jolla, showed that tiny molecules called miRNAs influence fertility of female mice, and also regulate the conversion of genetic information to proteins. These molecules are generated naturally by the body, in a complex process involving a protein called Dicer.

The study, lead by Dr Jiahuai Han and colleagues, demonstrated that female mice that had substantially lower levels of Dicer than normal mice were infertile. This infertility was caused by a malfunction of the corpus luteum, the structure formed where eggs are released and that is required to maintain early-stage pregnancies.

Having done detailed analysis, the researchers came to the conclusion that this impaired functioning of the corpus luteum was due to the body’s impediment to form new blood vessels, and that this was related with an increased expression of the protein TIMP1, which inhibits blood vessel formation.

By injecting miRNAs miR17-5p and let7b into the ovaries of mice that had low levels of Dicer, they showed a decrease of TIMP1 protein and an increase of blood vessels in the corpus luteum, which lead them to conclude that the development and function of the latter is regulated by miRNAs.