Human fertilization with round and elongated spermatids

Area of Science:

• Reproductive Medicine
• Andrology
• Assisted Reproductive Technology

Background:

• Human spermatids from ejaculate and testicular tissue are potential sources for intracytoplasmic sperm injection (ICSI).
• Previous studies have explored the efficacy of using spermatids for fertilization, but direct comparisons with spermatozoa are crucial.

Purpose of the Study:

• To evaluate and compare the fertilization rates of human spermatids (round and elongated) and spermatozoa when used for ICSI.
• To assess the potential benefit of testicular biopsy for obtaining spermatozoa when only spermatids are available in ejaculate.

Main Methods:

• Spermatids and spermatozoa were isolated from ejaculate and testicular biopsies.
• Subzonal insemination needles (SUZI) and ICSI needles of varying diameters were used for cell isolation and injection.
• Metaphase II oocytes were injected with round spermatids, elongated spermatids, or spermatozoa.

Main Results:

• Overall fertilization rates were 30% for round spermatids, 24% for elongated spermatids, and 67% for spermatozoa.
• Fertilization rates using spermatozoa were significantly higher (P < 0.001) than using spermatids.
• When comparing ejaculate spermatids with testicular spermatozoa in sibling oocytes, fertilization rates were 24% and 79%, respectively.

Conclusions:

• Testicular spermatozoa demonstrate superior fertilization capacity compared to both ejaculated and testicular spermatids via ICSI.
• The findings suggest that a testicular biopsy to retrieve spermatozoa is a viable option if only spermatids are present in the ejaculate.