Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8464433 | Cryobiology | 2017 | 7 Pages |
Abstract
In order to protect sperm chromosomes against degradation when they are being stored for relatively high temperatures, we investigated the optimal pH of the freeze-drying solution, EGTA/Tris-HCl buffered solution alkalinized by NaOH (Na-ETBS) or KOH (K-ETBS). Mouse spermatozoa suspended in Na-ETBS or K-ETBS were freeze-dried at pH 5.0-8.4 and stored at 4 °C or 50 °C for 3 days. Some freeze-dried samples were stored at 25 °C for 3 days or 1 month. After storage, samples injected into oocytes using intracytoplasmic sperm injection were assessed for chromosome damage in resulting zygotes. Irrespective of freeze-drying solutions and storage temperatures, almost all the zygotes (97-100%) produced using the spermatozoa freeze-dried at pH 5.0 had structural chromosome aberrations of sperm origin. When freeze-drying was conducted at pH 8.0-8.4 using Na-ETBS, the incidence of chromosome damage decreased to 14-17% in 4 °C storage and 24-26% in 50 °C storage. When freeze-dried in K-ETBS, the lowest level of chromosome damage occurred at pH levels of 7.7-8.4 at 4 °C storage (13-15%) and at pH 7.7-8.0 at 50 °C storage (16-23%). Spermatozoa freeze-dried in Na-ETBS at pH 8.2 and K-ETBS at pH 7.7 showed no significant increase in chromosome damage during 25 °C storage from 3 days to 1 month (11%-20% in Na-ETBS; 13%-18% in K-ETBS). Thus, use of the solutions optimized for short-term storage at high temperature (50 °C, 3 days) permits prolonged storage (1 month) of freeze-dried spermatozoa at room temperature.
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Authors
Hirokazu Kusakabe, Hiroyuki Tateno,