A comparison of heat-induced hyperactivation in patients' sperm after colloid or pentoxifylline wash methods

OBJECTIVE: Our purpose was to compare kinematic parameters of human sperm after processing through two different wash methods and 40°C heat treatment. STUDY DESIGN: Sperm specimens (N = 169 cases) were washed by either colloid or pentoxifylline wash methods, and the motility parameters were measured at either 37°C or 40°C at baseline (0 hours) and after 4 hours. Five randomly selected washed specimens with matching 37°C (control) or 40°C heat treatments were assessed for changes in a sentinel gene. RESULTS: The percentage of sperm hyperactive motility was >5 times higher after the 40°C heat treatment, in comparison with the 37°C treatment, for both the colloid- and the pentoxifylline-washed sperm. The percentages of total motility and progression were equally enhanced in heated sperm for the two wash methods. No changes were detected in the sentinel gene with the heat treatment. CONCLUSION: Sperm cells mildly heated at 40°C responded with greater motility, progression, and hyper-activation. The data suggest that mild heat is a stimulus for sperm function because greater sperm hyperactivation is associated with increased sperm fertilizing capacity. The absence of change in the sentinel gene in heated sperm suggests that a temperature of 40°C is too low to initiate alterations in the highly condensed sperm chromatin. More studies are needed before mild heating of ejaculated sperm becomes acceptable for use in assisted reproductive technologies.