title: Age- and substrain-dependent sperm abnormalities in BALB/c mice and functional assessment of abnormal sperm by ICSI.
abstract: 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.
authors.affiliation: Laboratory for Genomic Reprogramming, Center for Developmental Biology, RIKEN, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe 650-0047, Japan. ohta@cdb.riken.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ohta
authors.forename: Yuko
authors.initials: Y
authors.lastname: Sakaide
authors.forename: Teruhiko
authors.initials: T
authors.lastname: Wakayama
mesh_terms: D000375:Aging / Q000473:pathology / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D001755:Blastocyst / Q000166:cytology; D004195:Disease Models, Animal; D004624:Embryo Transfer; D047108:Embryonic Development; D005260:Female; D006801:Humans; D007248:Infertility, Male / Q000473:pathology / Q000503:physiopathology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C / Q000145:classification; D011247:Pregnancy; D013045:Species Specificity; D013077:Sperm Head / Q000473:pathology; D020554:Sperm Injections, Intracytoplasmic; D013091:Spermatogenesis; D013094:Spermatozoa / Q000002:abnormalities* / Q000502:physiology