Postnatal uterine development in Inverdale ewe lambs

Abstract

Postnatal development of the uterus involves, particularly, development of uterine glands. Studies with ovariectomized ewe lambs demonstrated a role for ovaries in uterine growth and endometrial gland development between postnatal days (PNDs) 14 and 56. The uterotrophic ovarian factor(s) is presumably derived from the large numbers of growing follicles in the neonatal ovary present after PND 14. The Inverdale gene mutation (FecXI) results in an increased ovulation rate in heterozygous ewes; however, homozygous ewes (II) are infertile and have 'streak' ovaries that lack normal developing of preantral and antral follicles. Uteri were obtained on PND 56 to determine whether postnatal uterine development differs between wild-type (CC) and II Inverdale ewes. When compared with wild-type ewes, uterine weight of II ewes was 52% lower, and uterine horn length tended to be shorter, resulting in a 68% reduction in uterine weight:length ratio in II ewes. Histomorphometrical analyses determined that endometria and myometria of II ewes were thinner and intercaruncular endometrium contained 38% fewer endometrial glands. Concentrations of estradiol in the neonatal ewes were low and not different between CC and II ewes, but II ewes had lower concentrations of testosterone and inhibin-a between PNDs 14 and 56. Receptors for androgen and activin were detected in the neonatal uteri of both CC and II ewes. These results support the concept that developing preantral and/or antral follicles of the ovary secrete uterotrophic factors, perhaps testosterone or inhibin-a, that acts in an endocrine manner to stimulate uterine growth and endometrial gland development in the neonatal ewes. Reproduction (2008) 135 357-365

Effects of immunization against androstenedione or bone morphogenetic protein 15 (BMP15) on reproductive performance in sheep1

“…In addition, altering androgen production has previously been linked to a reduced number of normal oocytes (Moor et al, 1980;Osborn et al, 1986). Androgen receptors have also been detected in the oviduct and uterus (Wilson and McPhaul, 1996;Okada et al, 2003;Hayashi et al, 2008). Furthermore, treatment of ewes with exogenous androgens between d 30 to 90 of pregnancy is known to have effects on multiple systems in the ewe including lowering the birth weight of the lamb (Padmanabhan et al, 2010).…”

Using sheep lines with mutations in single genes to better understand ovarian function

“…Adult ewes have a reproductive tract with morphology similar to that observed in a young lamb (Davis et al 1992, Nicol et al 2009). Analysis of the uterus of homozygous Inverdale animals showed suppression of uterine development (Hayashi et al 2008). However, it is important to note that the effects on gonadotrophin secretion and uterine development are thought to be indirect due to the absence of normal developing antral follicles.…”

Development of the Rete Ovarii in the Sheep Ovary.

“…Sex steroids have been implicated in the regulation of FST in the pituitary [85] but further study is required to see if this is true in the ovary. [88]. Oestrogens are essential for this growth as demonstrated in aromatase knockout mice [89].…”