Correlation between spermatozoa chromatin condensation stability in vitro and chromatin decondensation after intracytoplasmic sperm injection (ICSI) (Preliminary results)

The ability of spermatozoa to fertilise oocytes depends on a sequence of ev ents ending ultimately in the decondensation of its chromatin. The purpose of this study was to identify the relationship between sperm chromatin deco ndensation after incubation with follicle fluid at various time intervals: chromatin stability within a definite time and chromatin decondensation aft er intracytoplasmic sperm injection and to determine whether chromatin deco ndensation in vitro could be used as a predictive test for fertilization ca pability of spermatozoa after ICSI. 15 infertile couples undergoing ICSI th erapy were included in this prospective study. The mean percentage of uncon densed chromatin of spermatozoa in the semen sample before the addition of follicular fluid as assessed by Acridine orange staining test was 3.46% +/- 4.0% (red stained). After semen incubation with follicular fluid for 30, 6 0, 120 minutes, the chromatin decondensation, the percentage of cells stain ed red with acridine orange was 6.8% +/- 5.7%, 8.6 +/- 5.4 and 7.8 +/- 8.4 after 120 minutes. 1.8% +/- 4.8% of spermatozoa chromatin decondensed in vi tro within 30 minutes after addition of follicular fluid and additionally 0 .73% +/- 5.6% decondensed in the following 60 minutes (red stained). On the other hand, among the 15 patients investigated 121 oocytes were collected (8.9 +/- 5.0) and 105 mature oocytes (MII) were injected (7.5 +/- 4.3). The fertilization rate was 63.3% (66/105) (this means that 66 Spermatozoa of 1 05 injected already decondensed) and the remaining 39 spermatozoa at first remain condensed or exhibited a decondensation later than 24 h. By analysin g the correlation between chromatin decondensation in vitro at various time intervals (30, 60, 120 min) as well as the degree of chromatin decondensat ion (chromatin stability) between 30 to 60 minutes, 60 to 120 minutes and f ertilization rate, no significant correlation was observed (r=-0.036, r=0.2 68, r=0.113, r=0.10 and r=0.043 respectively). In conclusion neither chroma tin decondensation in vitro (chromatin stability) after exposure to follicu lar fluid nor the chromatin condensation in a given time period could predi ct the fertilization capability of spermatozoa after ICSI technique.