BACKGROUND: Cryopreservation of immature testicular tissue could be considered as a major step in fertility preservation for young boys with cancer. In the present study, eight different freezing protocols were evaluated in immature mice testis. METHODS: Testis from six-day-old mice were frozen using either 1,2-propanediol (PROH) or dimethylsulphoxide (DMSO: D) at 1.5 M. Different cooling rate curves were tested: (i) controlled slow protocol with seeding (CS1) or (ii) without seeding (CS2), (iii) controlled rapid protocol and (iv) non-controlled protocol. Cryodamage of seminiferous cords was semi-quantitatively determined, establishing a scoring of alterations. Cell viability and apoptosis induction were assessed on testicular cell suspensions immediately after digestion (D0) and after a 20-h culture period (D1). Cells recovered after digestion of 100 mg tissue and the rate of living and non-apoptotic cells were quantified at D0 and D1. A long-term culture (9 days) of testis pieces was carried out for the protocol offering the best survival. Testosterone production, intratubular cell proliferation and tubule growth were assessed. RESULTS: DMSO produced optimal results in the different cooling rate curves tested when compared with PROH. Optimal results were obtained for the DCS2 procedure (P < 0.05). Testosterone production, tubule growth and cell proliferation of post-thaw pieces were similar to fresh samples. CONCLUSIONS: Testis freezing with 1.5 M DMSO in a CS2 procedure was found to maintain not only immature testicular tissue architecture, but also viability of testicular cells, endocrine and partial exocrine functions of the testis. Semi-quantitative evaluation of seminiferous cord cryodamage can be effectively used to rapidly screen optimal freezing conditions and as a possible quality control in a human application.

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These data show that NT-proBNP can be stored for at least two years at -20 degrees C before measurement without a substantial loss of immunoreactivity.