Side dependent effects of the human amnion on angiogenesis

Amnion (AM), the innermost layer of human placenta, has a variety of functions such as capability to reduce scarring and inflammation, as well as anti-microbial and immunoregulatory properties. However, there are challenging reports about angiogenic and anti-angiogenic effects of the AM. The aim of this study was to evaluate whether the angiogenesis is dependent on epithelial or mesenchymal sides of this membrane.

Dorsal skinfold chamber model was performed on male rats. A layer of dorsal skin of rats was removed and the AM was implanted in either epithelial side up or mesenchymal side up position. Intra-vital microscopy was done one week after tissue transplantation. In vitro evaluation of angiogenesis was also performed using rat aortic ring assay on the AM.

The number of vessel sprouts and their lengths were increased more significantly in epithelial side up group comparing to the control group. Inhibitory effect of epithelial side of the AM on angiogenesis was clearly seen in mesenchymal side up group. Both number and length of sprouts in mesenchymal up group were decreased in comparison to epithelial side up group. In aortic ring assay, angiogenesis was detected on the AM after removal of the amniotic epithelial cells.

This study showed that the AM has both angiogenic and anti-angiogenic properties, which is surface dependent. Therefore, the AM can have a vast application in both ischemic organs through inducing angiogenesis and pathological situations such as cancer in which angiogenesis must be inhibited.