Role of cholesterol, calcium, and mitochondrial activity in the susceptibility for cryodamage after a cycle of freezing and thawing

OBJECTIVE: To correlate the levels of two concrete sperm markers, cholesterol and Ca(+2), together with mitochondrial activity on raw semen samples with the post-thaw recovery of spermatozoa with progressive motility on human sperm samples as the first step to improve sperm cryostorage protocols. DESIGN: Controlled prospective research project. SETTING: Private and university-affiliated setting. PATIENT(S): Semen samples from 122 males attending our center for infertility (n = 47) or semen donation (n = 75) were studied. INTERVENTION(S): The mean basic semen parameters of the 122 semen samples studied before and after the freezing and thawing process. MAIN OUTCOME MEASURE(S): We determined Ca(+2) and cholesterol concentrations on seminal plasma by enzymoimmunoanalysis techniques, intracellular Ca(+2) concentrations, cholesterol concentrations in the sperm plasma membrane and mitochondrial activity by fluorometry. RESULT(S): Cholesterol concentration in seminal plasma and cholesterol contents in the sperm membrane and mitochondrial activity were studied. No correlations were initially found to be of statistical significance. Regarding seminal plasma and intracellular sperm Ca(+2) concentrations, a statistically significant negative correlation was found (P=.036 and P=.016). CONCLUSION(S): Higher cholesterol contents do not appear to protect sperm against cryodamage. Conversely, Ca(+2) equilibrium appears to be essential for a good post-thaw recovery. Mitochondrial activity is not reflecting the possibilities of sperm survival and is probably not a good indicator of the sperm metabolism.