Follicular fluid exosomes act on the bovine oocyte to improve oocyte competence to support development and survival to heat shock.

Addition of follicular fluid to oocyte maturation medium can affect cumulus cell function, increase competence of the oocytes to be fertilised and develop to the blastocyst stage and protect the oocyte from heat shock. Here, it was tested whether exosomes in follicular fluid are responsible for the effects of follicular fluid on the function of the cumulus-oocyte complex (COC). This was accomplished by culturing COCs during oocyte maturation at 38.5°C (body temperature of the cow) or 41°C (heat shock) with follicular fluid or exosomes derived from follicular fluid and evaluating various aspects of function of the oocyte and the embryo derived from it. Negative effects of heat shock on cleavage and blastocyst development, but not cumulus expansion, were reduced by follicular fluid and exosomes. The results support the idea that exosomes in follicular fluid play important roles during oocyte maturation to enhance oocyte function and protect it from stress.