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Age- and substrain-dependent sperm abnormalities in BALB/c mice and functional assessment of abnormal sperm by ICSI
Hiroshi Ohta1, Yuko Sakaide, Teruhiko Wakayama
1Laboratory for Genomic Reprogramming, Center for Developmental Biology, RIKEN, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe 650-0047, Japan. ohta@cdb.riken.jp
Background:
Male BALB/c mice produce a high proportion of morphologically abnormal sperm. Although the BALB/c male may be a useful model of human male infertility, it remains unclear whether the sperm abnormality rate (SAR) is affected by age or the BALB/c substrain.
Methods:
SARs (head shape) were assessed in three BALB/c substrains (A, AnN, ByJ) at 7 and 9 weeks and 6-10 months of age (c.100 sperm/male). The functional ability of abnormal sperm produced from 7-week-old and 6-10-month-old males was determined in BALB/c AnN mice by ICSI.
Results:
The SAR (quasi-normal plus abnormal sperm) was lower in BALB/c A than in the other two strains (P < 0.05). Further, the SARs of BALB/c AnN and ByJ strains at 7 weeks old were high and decreased rapidly by 9 weeks, suggesting that early spermatogenesis (i.e. the first wave of spermatogenesis) produced low-quality sperm. ICSI experiments indicated that 2-cell stage embryos which developed from morphologically abnormal sperm from both the first wave of spermatogenesis and the older mice (6-10 months) were similar to those from morphologically normal sperm in terms of producing progeny, although the number of 2-cell embryos was slightly lower (P < 0.05, chi(2) test) than with normal sperm.
Conclusions:
Although the SARs of BALB/c mice are affected by both age and substrain, the embryos that developed from morphologically abnormal sperm have normal genetic potential in terms of production of progeny.
Insights
BALB/c mice exhibit varying sperm abnormality rates (SAR) influenced by age and substrain. Despite morphological defects, abnormal sperm possess normal genetic potential for producing viable progeny.
Area of Science:
- Reproductive Biology
- Sperm Morphology
- Infertility Models
Background:
- Male BALB/c mice are a potential model for human male infertility due to high rates of morphologically abnormal sperm.
- The influence of age and specific BALB/c substrain on sperm abnormality rate (SAR) in these mice requires further investigation.
Purpose of the Study:
- To assess the impact of age and BALB/c substrain on sperm abnormality rates (SAR).
- To evaluate the functional capacity of morphologically abnormal sperm using intracytoplasmic sperm injection (ICSI).
Main Methods:
- Sperm abnormality rates (head shape) were quantified in three BALB/c substrains (A, AnN, ByJ) at different ages (7 weeks, 9 weeks, 6-10 months).
- Intracytoplasmic sperm injection (ICSI) was performed using sperm from 7-week-old and 6-10-month-old BALB/c AnN mice to assess embryo development.
Main Results:
- BALB/c A substrain showed significantly lower SAR compared to BALB/c AnN and ByJ strains.
- SAR in BALB/c AnN and ByJ strains decreased from 7 to 9 weeks of age, indicating reduced sperm quality during early spermatogenesis.
- Embryos developed from morphologically abnormal sperm via ICSI demonstrated similar genetic potential for progeny production as those from normal sperm, though with a slight reduction in 2-cell embryo numbers.
Conclusions:
- Sperm abnormality rates in BALB/c mice are significantly influenced by both the animal's age and its specific substrain.
- Morphologically abnormal sperm from BALB/c mice retain normal genetic potential for successful reproduction, suggesting their utility in infertility research.
