title: Comparison of sperm quality and DNA integrity in mouse sperm exposed to various cooling velocities and osmotic stress.
abstract: The first objective was to compare sperm quality following conventional manual sperm freezing (cryovials held 1, 2, 3, and 4 cm, respectively, above liquid nitrogen (LN(2)) for 10 min, resulting in cooling velocities of approximately -14.9, -10.1, -6.6, and -5.1 °C/min, respectively), and cooling velocities of -5, -20, -40, and -100 °C/min in a programmed automated freezer, for sperm recovered from CD-1, B6129SF1, and C57BL/6NCrlBR mice. Furthermore, using these strains, as well as 129S/SvPaslco, and DBA/2NCrlBR mice, the second objective was to determine the effects on DNA integrity of sperm exposed to hyposmotic (1 mOsm/L) and hyperosmotic (2400 mOsm/L) solutions, compared to an isosmotic control (300 mOsm/L). For freezing above LN(2) or in an automated freezer, 2 cm above LN(2) and -100 °C/min, respectively, were optimal (P < 0.05-0.01), with no significant differences between these two approaches for post-thaw progressive motility, DNA integrity, and in vitro rates of fertilization and blastocyst formation. Both manual and automated freezing techniques increased post-thaw sperm DNA fragmentation (P < 0.01); the DNA integrity of post-thaw sperm was significantly affected by cooling velocity and strain background. Relative to isosmotic controls, a hyposmotic solution was more deleterious (P < 0.05-0.01) to sperm DNA integrity than a hyperosmotic solution for CD-1, B6129SF1, C57BL/6, and DBA mice (there were strain-dependent differences). In conclusion, optimization of freezing distance and cooling velocity (manual and automated freezing, respectively) were significant factors for efficient cryopreservation and re-derivation of mice from frozen-thawed sperm. Additionally, osmotically-driven volume changes in mouse sperm increased DNA fragmentation, with susceptibility affected by background strain.
authors: Physiology and Experimental Medicine Research Program, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors: Cengiz
authors: C
authors: Yildiz
authors: Napoleon
authors: N
authors: Law
authors: Palma
authors: P
authors: Ottaviani
authors: Keith
authors: K
authors: Jarvi
authors: Colin
authors: C
authors: McKerlie
mesh_terms: D000818:Animals; D015925:Cryopreservation / Q000379:methods / Q000662:veterinary*; D053938:DNA Fragmentation; D005307:Fertilization in Vitro / Q000662:veterinary; D005615:Freezing; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains / Q000235:genetics*; D009997:Osmotic Pressure; D013081:Sperm Motility; D013094:Spermatozoa / Q000502:physiology*