Fecundity is impaired in a mouse model of osteogenesis imperfecta

Osteogenesis imperfecta (OI), or brittle bone disease, is most often caused by mutations in genes encoding type I collagen or proteins that process it. Women with OI have a small, but significant increase in risk of serious pregnancy complications including uterine rupture. Here, the OI mouse, Col1a2(oim/oim), was used to examine the effects of collagen mutation on establishment and maintenance of pregnancy. Picrosirius birefringence was faint in Col1a2(oim/oim)uteri, indicating diminished collagen in the myometrium and endometrium. There was some evidence of increased uterine gland number (p = .055) and size (p = .12) in (p = .055) virgin uteri, though the they were not significantly different than controls. There were no differences in the number of corpora lutea, or the time from pairing to delivery of pups between Col1a2(oim/oim)and control dams, suggesting that ovulation and conception occur normally. However, when examined at Gestation Day 6.5 (postimplantation), gestation Day 10.5 (midpregnancy), and Postnatal Days 1-2, Col1a2(oim/oim)dams had significantly fewer viable pups than controls overall. In pairwise comparisons, the loss was only significant in the postnatal group, suggesting the gradual loss of pups over time. Overall, the Col1a2(oim/oim)mouse data suggest that OI impairs uterine function in pregnancy in a way that affects a small but significant number of fetuses.