Human sperm head vacuoles are physiological structures formed during the sperm development and maturation process

Human sperm head vacuoles have no effect on intracytoplasmic sperm injection outcomes because they are not abnormal structures but physiological changes occurring during the sperm development and maturation process.

Atsushi Tanaka, M.D., Motoi Nagayoshi, M.D., Izumi Tanaka, Phar.B., Hiroshi Kusunoki, Ph.D.

Volume 98, Issue 2, Pages 315-320, August 2012


To clarify whether human sperm vacuoles affected intracytoplasmic sperm injection (ICSI) success rates.

Retrospective study.

A private infertility clinic.

Spermatozoa and spermatids were obtained from 11 normozoospermic, 10 oligozoospermic or asthenozoospermic, 4 obstructive azoospermic, and 3 nonobstructive azoospermic men.

Differential interference contrast observation and intracytoplasmic injection of morphologically selected sperm.

Main Outcome Measure(s):
Incidence, size, and position of vacuoles of sperm cells were recorded. Ability of fertilization and blastocyst development were compared between cells with and without vacuoles.

More than 97.4% of ejaculated, 87.5% of epididymal, 87.5% of testicular spermatozoa, and more than 90.0% of Sc-Sd2 spermatids had vacuoles of various sizes. The incidence of vacuoles on ejaculated cells was significantly higher than that on the other types of cells, but there was no difference between sperm from normozoospermic men and those from the other donors. Removal of plasma membrane and/or acrosome did not affect the incidence of vacuoles. Although more than 60% of spermatozoa had small vacuoles in the acrosomal regions, 52.6% of Sb1-2 spermatids had large vacuoles. After injection of a motile spermatozoon with large and small vacuoles, 60.9% and 85.7% of metaphase II oocytes could be normally fertilized, respectively, and almost half of the zygotes developed to the blastocyst stage. When using sperm without vacuoles, the fertilization rate was 80.0%, but only 25% of them developed to the blastocyst stage.

Human sperm head vacuoles did not affect ICSI outcomes.

  • Sergio Gonçalves

    Do the authors consider, based upon the results of this study, that there is no indication for IMSI in current ART practice?

  • JamesS

    Are you suggesting that sperm without vacuoles are inferior to those with vacuoles. I ask this because your blastocyst rate as poorer in the ICSI with no vacuoles. This is contrary to other publications. Any suggestions as to why they form?

  • kivan

    Interesting study. Similarly designed, larger studies will be required to more definitively address the question of the effect of sperm vacuoles of varying sizes on fertilization potential and normal embryonic development. I’d love to hear some IMSI advocates chime in on the study.

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