Mechanotransduction drives morphogenesis to develop folding during placental development in pigs.

INTRODUCTION

Our aim was to evaluate whether mechanical forces applied to the placenta of pigs correlate with morphological changes that coordinate the development of placental folds.

METHODS

We examined changes in the length of placental folds, expression of mechanotransduction-implicated molecules in placental tissues, changes in the size of subepithelial blood vessels within the endometrium, and effects of in vivo supplementation with arginine on fold development.

RESULTS

We observed that: 1) the length of folds increased 2) osteopontin, talin and focal adhesion kinase co-localized into aggregates at the maternal placental (uterine)-fetal placental interface; 3) filamin, actin related protein 2, and F-actin were enriched in the tops of maternal placental folds extending into fetal placental tissue; 4) maternal stromal fibroblasts acquired alpha smooth muscle actin; 5) endometrial blood vessels increased in size; and 6) supplementation with arginine increased fold length.

CONCLUSION

Results indicate that lengthening of folds associates with polymerization of actin that coincides with FA assembly, endometrial fibroblasts differentiate into myofibroblasts, and dilation of subepithelial blood vessels correlates with development of folds that is enhanced by arginine. We propose that dilation of subepithelial endometrial blood vessels delivers increased blood flow that pushes upward on the interface between the uterine luminal epithelium (LE) and the placental chorionic epithelium (CE), protrusive forces from growing uterine blood vessels trigger focal adhesion assembly and actin polymerization between the LE and CE, and endometrial fibroblasts differentiate into contractile myofibroblasts that pull connective tissue downward and inward to sculpt folds at the maternal placental-fetal placental interface.