SPERM SELECTION WITH HYALURONAN AND BLASTOCYST DEVELOPMENT AFTER ICSI

Background. Selection of mature sperm for intracytoplasmic sperm injection (ICSI) has recently been made possible by hyaluronan, a naturally occurring substance found in the cumulus cells. Only fully mature sperm have the receptors on the head that effectively bind to the oocyte cumulus, or, to be more precise, to hyaluronan. The aim of this study was to evaluate the differences in fertilization rates and in embryo development to the blastocyst stage after ICSI performed either with sperm selected by hyaluronan or by standard morphological sperm appearance. Methods. This retrospective study involved 17 couples undergoing ICSI. One half of sibling oocytes were fertilized with sperm selected by hyaluronan (84 oocytes), and the other half with sperm selected on the basis of morphological appearance (89 oocytes). The comparison between the two groups involved fertilization rates and the percentages of arrested embryos, and delayed (morulae) and advanced blastocysts. Blastocysts were classified as early, developed and expanded. Results. In the group with hyaluronan-selected sperm 65 % of oocytes fertilized, and in the group with sperm selected by morphological appearance 70 % of oocytes. The fertilization rates did not statistically differ between the two groups, and neither did the percentages of arrested embryos (47 % vs. 62 %), morulae (11 % vs. 11 %), and blastocysts (42 % vs. 26 %). In the group with hyaluronan-selected sperm the shares of expanded and early blastocysts were significantly greater (P ≤ 0.04 and P ≤ 0.002, respectively) than in the group with sperm selected according to morphological appearance. Conclusions. The use of hyaluronan for sperm selection in ICSI does not affect fertilization rates. Hyaluronan-selected sperm improves subsequent development of embryos. A larger study sample is required for the assessment of hyaluronan-selected sperm on the achievement of pregnancies.