Characterization and Clinical Applications of Amniotic Membranes

Abstract

During pregnancy, every vertebrate has layers of extraembryonic tissue surrounding the developing fetus called placental membranes, or fetal membranes. The two fetal membranes which immediately surround the amniotic cavity are the chorion (outer membrane) and the amnion (inner membrane). The chorion is an opaque membrane which lies on the outer layer of the amniotic sac, whereas the amnion is a more translucent structure which lies on the inner layer, adjacent to the amniotic fluid [1]. These membranes have a composition of extracellular connective tissue components, making them a promising biomaterial for a variety of therapies. Additionally, the cells of these fetal membranes are a potential source of material for stem cell therapies. Transmission electron microscopy (TEM) comparisons of the ultrastructure of chorion vs. amnion stromal cells show that chorion stromal cells are similar to hematopoietic progenitor cells, while amnion stromal cells are more like mesenchymal and epithelial cells, suggesting multi-potentiality [2]. Due to the composition of extracellular connective tissue components and the stem cell properties of their epithelial and mesenchymal cells, the amnion has become highly attractive for cell-based repair and regenerative medicine, despite being traditionally considered a waste material or byproduct of pregnancy (Figure 1)