Reproduction Abstracts

Introduction: Large within-litter variation in pig foetal weight may be associated with placental efficiency. Integrin receptors, including AVB6, are present at the attachment site between the foetal and uterine epithelium and may affect the efficiency of attachment. It is hypothesised that the expression of integrin receptors would differ between tissues supplying small foetuses compared to normal-sized littermates. This study compared the distribution and quantity of integrin AVB6 in placental and endometrial tissues supplying different sized foetuses.

Methods: Placental and endometrial tissues associated with the smallest and a normal-sized foetuses were collected from Large White X Landrace gilts at gestational day (GD) 30, and both sizes from both male and female foetuses at GD 60 and 90 (n=5, 7 and 5 respectively). Tissues were fixed in Bouin’s and immunohistochemistry for integrin AVB6 to estimate percentage staining was performed.

Results and Discussion: Integrin AVB6 was localised at blood vessels, luminal and glandular epithelium of the endometrium and at blood vessels and the trophectoderm of placenta at GD30, 60 and 90. Integrin AVB6 in the trophectoderm supplying male foetuses was higher than in females at GD30 (P=0.05). Integrin AVB6 expression per uterine gland of endometrium was increased from GD30 to GD60 and decreased from GD60 to GD90 (P<0.01). Within-females, but not males, integrin AVB6 expression per uterine gland was significantly decreased at GD60 compared to GD90. This temporal change was observed within both the small (P=0.04) and normal (P=0.01) female categories.

This is the first study showing that integrin AVB6 is present in porcine endometrial tissue, with interesting temporal changes in expression detected. Foetal size does not appear to alter the placental or endometrial expression of integrin AVB6. However, this study has highlighted intriguing differences between tissues supplying foetuses of different sex which warrant further investigation.

(Funding: Edinburgh University and BBSRC).