Vitrification preserves proliferation capacity in human spermatogonia

Area of Science:

• Reproductive Biology
• Cryobiology
• Oncology

Background:

• Current clinical practice for immature testicular tissue (ITT) cryobanking uses slow-freezing.
• Vitrification is a promising alternative for long-term ITT storage, aiming to preserve spermatogonial stem cells (SSCs) for fertility restoration in young cancer patients.
• Previous studies demonstrated in vitro SSC survival post-vitrification, but functionality remained unevaluated.

Purpose of the Study:

• To assess the potential benefits of vitrifying human ITT for future fertility preservation.
• To evaluate the efficacy of vitrified human ITT in an in vivo murine xenotransplantation model.

Main Methods:

• Ten ITT samples from patients aged 2-12 years were used.
• Fragments were xenografted into nude mice for 6 months (fresh, slow-frozen, and vitrified-warmed groups).
• Histological and immunohistochemical analyses assessed spermatogonia, proliferation, and Leydig cells.

Main Results:

• Seminiferous tubules maintained integrity across all groups post-cryopreservation and xenografting.
• Spermatogonia (SG) survival and proliferation were confirmed in all xenografted groups.
• While SG initiated spermatogenesis, a blockage at the pachytene stage was observed; recovery rates were 3.4% (fresh), 4.1% (slow-frozen), and 7.3% (vitrified-warmed).

Conclusions:

• Vitrification maintains SSC proliferation capacity in xenografted ITT for up to six months.
• The study highlights the need to optimize ITT vitrification for SSC preservation and improve xenotransplantation models for studying human spermatogenesis.
• While not yet justifying a change from current slow-freezing practices, vitrification warrants further research as a viable fertility preservation alternative.