Irreversible damage to membrane integrity caused by chilling during the lipid phase transition is directly related to the quantity of lipids present [3]. Cholesterol is a major structural lipid constituent of the membrane and regulates its function. Therefore, the cholesterol/phospholipid ratio is a vital determinant of plasma membrane fluidity and stability during cryopreservation [10]. Membranes with high concentrations

of cholesterol are more fluid at low temperatures and consequently more resistant to damage during cooling [40] and [41]. To increase membrane fluidity and permeability at low temperatures, cholesterol can be added to the plasma membrane, thereby providing an alternative method for increasing oocyte tolerance for cryopreservation. Selleckchem Proteasome inhibitor Cyclodextrins can act as carrier molecules for the incorporation of cholesterol into plasma membranes [1], [10] and [25]. Cyclodextrins are water-soluble cyclic oligosaccharides consisting of glucose units (α-d-glucopyranoside) joined by connections typeα-1,4 that contain a hydrophobic center capable of integrating lipids. Due to its structure, free cyclodextrin can selectively deplete cholesterol from isolated or intact membranes from a variety of cells, including spermatozoa and oocytes [23], whereas

cyclodextrins preloaded with cholesterol deliver cholesterol to the plasma membrane. Therefore, this simple approach can be used prior to cryopreservation to change the membrane composition and minimize membrane damage. Methyl-β-cyclodextrin (MβCD) is the most potent BIBW2992 solubility dmso cyclodextrin family member with respect to its affinity for cholesterol binding. Moreover, it was showed that cholesterol improve bovine [1] and [25] and equine [20] sperm viability Farnesyltransferase after cryopreservation [23]. One study demonstrated that cholesterol carried by cyclodextrin entered cumulus cells and oocytes, which improved the survival of vitrified mature bovine oocytes [10]. No further studies have investigated this simple approach to reduce oocyte

cold sensitivity. In the present study, we used MβCD to load cholesterol from fetal calf serum (FCS) and deliver it to the oocyte plasma membrane. The purpose of this study was to investigate the effect of MβCD exposure on the in vitro maturation rates and developmental ability of cold-stressed as well as vitrified immature bovine oocytes. Unless otherwise indicated, chemicals were purchased from Sigma (St. Louis, MO, USA). Cryotop devices were purchased from Ingámed (Maringá, PR, Brazil). Ovaries from crossbred cows (Bos indicus × Bos taurus) were collected immediately after slaughter and transported to the laboratory in saline solution (0.9% NaCl) supplemented with penicillin G (100 IU/mL) and streptomycin sulfate (100 g/mL) at 35 °C. Cumulus oocyte complexes (COCs) were aspirated from 3- to 8-mm diameter follicles with an 18-gauge needle and pooled in a 15-mL conical tube.