Evaluation of Cryoinjury of Sperm Chromatin According to Liquid Nitrogen Vapour Method (I)
Thitikan Ngamwuttiwong MD*, Somboon Kunathikom MD*
Affiliation : * Department of Obstetrics and Gynecology, Faculty of Medicine Siriraj Hospital, Mahidol University
Objective : To evaluate cryodamage on human sperm motility, cryosurvival rate, and sperm chromatin assessed
by acridine orange staining method (AO test) after a six-month freeze-thawing process using liquid nitrogen
vapor.
Study
Design : Experimental study.
Materials and Methods : Twenty normal semen samples were obtained from the male partner of infertile couples
attending the infertility unit, Siriraj Hospital. After semen analysis, each semen sample was frozen with liquid
nitrogen vapor. The acridine orange test was used for assessment of chromatin structures. After 6 months of
cryostorage, semen samples were thawed and the effects of cryopreservation on sperm chromatin integrity,
motility, morphology, vitality, and cryosurvival rate were evaluated.
Results : The mean percentage of normally condensed sperm chromatin in the native semen sample decreased
significantly (87.3 + 9.1 vs 47.9 + 26.2; p < 0.001) after the freeze-thawing process using liquid nitrogen
vapor. Furthermore, the mean percentage of sperm motility and vitality also decreased significantly after the
freeze-thawing process (52.6 + 1.9 vs 23.2 + 10.6 and 78.7 + 5.6 vs 30.3 + 8.8 respectively; p < 0.001). In
contrast, the numbers of sperm with normal morphology after cryopreservation were not different from those
before the procedure (21.4 + 4.3 vs 24.2 + 23.9; p = 0.606).
Conclusion : The freeze-thawing procedure using liquid nitrogen vapor had effects on chromatin, motility, and
vitality of human spermatozoa. The six-month cryopreservation of semen is a good method for avoiding the
window period of HIV; however, this can cause a lot of damage to spermatozoa, thus, limits their further use in
the treatment of infertility.
Keywords : Liquid nitrogen vapour, Sperm DNA integrity, Cryopreservation, AO test
