Cryopreservation of preantral ovarian follicles in situ from domestic cats (Felis catus) using different cryoprotective agents.

The objective of this investigation was to verify the structural characteristics of preantral follicles (PAF) of cat ovarian tissue after cryopreservation in 1.5 M glycerol or ethylene glycol, using a slow-freezing procedure. Ovaries (n = 10) from domestic cats were divided into fragments. One fragment was immediately preserved for classical histology (fresh control), and additional fragments were immersed in minimum essential medium plus 10% bovine fetal serum (MEM+BFS), or MEM+BFS supplemented with 1.5 M glycerol or ethylene glycol. The samples were frozen and plunged into liquid nitrogen. After 1 wk, the samples were thawed. A total of 600 PAF were evaluated. In the fresh control, there were 71.3% normal PAF. After thawing, the rates of normal PAF were 26.0, 39.3 and 58.0% for samples without cryoprotectant or with glycerol or ethylene glycol, respectively. We concluded that ethylene glycol was useful for the cryopreservation of feline PAF in situ.