Closure of Fetoscopic Access Sites with Amniotic Extracellular Matrix Scaffolds in an In Vivo Model

Objective: The aim of our study was to develop an amniotic extracellular matrix scaffold for amnion cell in-growth and to evaluate its efficacy in healing a fetoscopic access site in the rabbit model. Material and Methods: Rabbit amnion from one donor doe were treated by enzymatic procedures in order to remove amnion cells from its collagenous extracellular matrix. The acellularity of the amniotic scaffold was investigated by light microcopy, histology and SEM. Fetoscopic access sites were closed with amniotic rabbit scaffolds at 23 days of gestation in 10 rabbit sacs. Additional 10 sacs served as positive controls and 61 unoperated fetuses were used as negative controls. At 30 days of gestation, a second look hysterotomy was performed. Outcome measures were presence of amniotic fluid, macroscopic membrane integrity evaluated by means of a methylene blue leakage test and histology/immunohistochemistry of the plugging site. Results: Manufactured amniotic matrix scaffolds of the rabbit demonstrated a cell-free collagen fiber network. Presence of amniotic fluid tended to be higher in the scaffold group (67%) compared with positive controls (17%¸ p=0.07). However, macroscopic membrane integrity was not different between the scaffold (56%) and positive control group (33%). Histological study of the membrane defect sites showed well integrated amniotic rabbit scaffolds in the surrounding tissues in all cases. All amniotic rabbit scaffolds showed cell in-growth and re-epithelialization, with an epithelialization rate of more than 50% in 44% of cases. Actually, integrity of the fetal membranes was restored by re-epithelialization of the amniotic rabbit scaffold in one case. Conclusion: Following induction of a membrane defect and sealing with a natural amniotic scaffold, there was consistent re-epithelialization within one week promising for closure of fetal membrane defects. Further studies should evaluate the mechanical properties of these reconstructed membranes.