Ovarian tissue vitrification: the use of a novel metal closed system for clinical grade cryopreservation.

OBJECTIVE

To investigate whether a metal chamber is an appropriate system for vitrification of ovarian tissue under clinical grade.

METHODS

Experimental study, control versus treatment. Bovine ovarian cortices cut in 1x1x1 mm fragments were vitrified using ethylene glycol and dimethyl sulfoxide inside steel cryovials, whose bases were in touch with Liquid Nitrogen (LN2). Screw caps closed the cryovials before plunging into LN2. Primordial (n=356) and primary (n=327) follicles and the stroma were analyzed after histological preparation using light microscopy.

RESULTS

High rate of primordial (93%) and primary (80%) follicles presented normal morphology in the rewarmed fragments. There was not a significant difference between controls and primordial follicles morphology (P=0.1519). Significant difference was observed for the primary follicles (P=0.0097). Important to point out that stromal cells and collagen fibers presented a remarkable integrity, without major alterations in the cryopreserved tissues.

CONCLUSIONS

The steel cryovial seems to be a safe means of vitrification under clinical grade conditions, with very fast cooling rates and no direct contact of the biological material with the liquid nitrogen (LN2). Ovarian reserve represented by primordial and primary follicles and stroma are very well preserved in this vitrification system.