Effects of straw direct vapor nitrogen method on the motility of post-thaw human sperm

Abstract

Objective To study the effects of two cryopreservation methods(direct vapor nitrogen method and program freezing method) on the motility of post-thaw human sperm. Methods The 25 semen samples were taken from 25 donors from Shanghai Human Sperm Bank during May to July 2011, using straw as a frozen carrier, the semen samples contained modified glycerol-yolk-citrate(GYC)（1∶1）as cryoprotectant, after the liquefaction, each semen sample was divided into 2 groups, and separately cryopreserved by direct vapor nitrogen method and program freezing method.According to the recommended standard of the World Health Organization, semen samples were analyzed before and after cryopreserving.Density, total motility, PR, motility parameters (including VAL, VSL, VCL, BCF) were determinated by the IVOS sperm analyzer.Semen samples were stained by modified papanicolaou stain and 200 sperms of each sample were counted under microscope by manual analysis to calculate the rate of normal morphology sperm.The paired t test was used to compare the above indictors before and after cryopreserving in one method and after thawing between two methods. Results Before cryopreserving, the total motility, PR, VAL, VSL, VCL, BCF were（91.36±4.96）%, （81.28±6.41）%, （59.29±9.30） μm/s, （49.80±8.40） μm/s, （83.39±15.70） μm/s, （16.68±3.36） Hz respectively, and after cryopreserving by direct vapor nitrogen method the results were (46.04±20.14)%, （40.22±18.42）%, （48.00±11.60）μm/s, （41.11±8.50） μm/s, （71.55±17.19） μm/s, （15.94±14.30） Hz respectively, the differences of the indictors above were observed with statistic significance except BCF （t=11.324, 11.958, 4.266, 3.964, 3.620, 0.258, P of BCF >0.05, P of others <0.05）; and after cryopreserving by program freezing method, the results were（48.05±18.27）%, （42.47±15.62）%, （45.30±6.51） μm/s, （38.08±4.99） μm/s, （64.23±11.75） μm/s，（14.00±2.99） Hz respectively, the differences of the indictors above showed statistic significance（t=10.337, 10.874, 7.154, 5.510, 6.494, 3.244, P＜0.05）.No significant differences were observed in the revival rate, total motility, PR and normal morphology sperm rate by using different methods（t=0.425, 0.364, 0.622, 1.106, P＞0.05）.The results of VAL, VSL, VCL, BCF in direct vapor nitrogen method were higher than that in program freezing method, when the differences of VSL and VCL were observed with statistic significance（t= 2.489, 2.822, P＜0.05）. Conclusions Using straw as carrier is practicable.Direct vapor nitrogen method is easier to operate than program freezing method.Post-thaw sperm cryopreseved by direct vapor nitrogen method has higher motility parameters, thus making this method an ideal one for fast freezing.(Chin J Lab Med, 2012，35：145-149) Key words: Sperm; Cryopreservation; Direct vapor nitrogen method; Program freezing method; Sperm motility