34 Cellular effects of antifreeze proteins type I and III in extender for sheep semen cryopreservation
Authors: Correia L. F. L. , Espírito-Santo C. G. , Braga R. F. , Brair V. L. , de Paula C. J. C. , da Silva A. A. , Brandão F. Z. , Freitas V. J. F. , Ungerfeld R. , Souza-Fabjan J. M. G. 
Published: January 2021

Antifreeze proteins (AFP) have been included in extenders for sperm cryopreservation to prevent ice crystal formation. Thus, this study assessed the effects of supplementing semen extender with two concentrations of AFP types I and III on the quality of frozen–thawed ram sperm. The hypothesis is that various types and concentrations of AFP enhance cryopreservation of ram sperm. Semen was collected from 4 rams, pooled in 6 replicates, and allocated into 1 of 5 treatments: Control (CONT, without AFP); AFP type I [0.1 (AFPI-0.1) or 0.5 (AFPI-0.5) µg±mL−1]; or AFP type III [0.1 (AFPIII-0.1) or 0.5 (AFPIII-0.5) µg±mL−1]. Straws were placed on a metal wire net frame at 37°C and placed in a refrigerator for 2h to cool them to 5°C (−0.25°C/min). After 2h for stabilisation, straws were cooled in liquid nitrogen vapor (−15.3°C/min) and subsequently immersed (−196°C). After thawing, samples from each treatment were evaluated microscopically (sperm kinetics, plasma membrane integrity, capacitation, hypoosmotic test, acrosome status and mitochondrial activity, chromatin condensation, morphology, binding to egg perivitelline membrane, and lipoperoxidation quantification). The normal distribution of residuals was determined by Shapiro-Wilk test and homoscedasticity by Levene’s test. Normally distributed variables were analysed with one-way analysis of variance (ANOVA), followed by Tukey’s test. The non-normally distributed were analysed by Kruskal–Wallis and Dunn’s test. The repeated-measures ANOVA in general linear model (GLM) was used to effects of concentration for each AFP type in paired samples. The Greenhouse-Geisser test was applied when sphericity was not considered, followed by the Sidak test. Values of P&lt;0.05 were considered significant. Treatments affected (P&lt;0.05) kinetic parameters, plasma membrane integrity, and morphology. Linearity was greater in AFPI-0.1 (56.6±3.1%, mean±s.e.m.), AFPI-0.5 (56.9±2.2%), and AFPIII-0.5 (64.7±6.2%) than in CONT (36.8±3.0%). Straightness was greater in all AFP-supplemented extenders (overall mean, 78.6±2.8%) than in CONT (63.2±0.8%). Plasma membrane integrity was greater in AFPI-0.1 (49.1±4.6%) and AFPI-0.5 (36.6±7.3%) compared with CONT (13.0±4.4%). All AFP groups had a greater percentage of normal sperm (overall mean: 74.3±1.3%) than CONT (65.3±1.9%). There were no significant differences in percentage of sperm with functional membrane (overall mean: 16.1±3.3%), normal acrosome (11.5±4.5%), mitochondrial activity (24.5±6.5%), chromatin condensation (98.8±0.4%), perivitelline membrane binding rate (194.0±44.5 sperm/mm2), and lipoperoxidation (556.7±20.5 TBARS ng±mL−1). In conclusion, the use of AFP, predominantly type I, had potential as a cryoprotectant for ram sperm, increasing sperm cell protection, with no adverse effects on potential fertilization capacity and did not increase reactive oxygen species.
This research was funded by FAPERJ, CNPq, and CAPES (Finance Code 001).