Background: Amniotic membranes collected from the placenta have attracted attention as a tissue/cell source in regenerative medicine. It is beginning to be used clinically as a wound dressing. The fetal membranes, which consist of two layers of amniotic membrane and chorion, and decellularized amnion, obtained by removing amnion epithelial cells, are also promising materials. There are reports that these amniotic membrane-related tissues contribute to peripheral nerve repair and are expected to be used as nerve repair materials or protective agents. However, detailed analysis of amniotic tissues for clinical use has not progressed. Therefore, it is necessary to elucidate which part of the amnion-related tissues should be used and how.
Method: The sciatic nerves of rats were cut and then sutured, and the intervention groups were wrapped with either amniotic membranes, fetal membranes or decellularized amniotic membranes. The amniotic membrane-related tissues were used immediately after being collected from the human placenta without undergoing any processing, such as freezing or drying. Nerve function was evaluated using SFI (Sciatic Function Index) and NCS (Nerve Conduction Study), and the subjects were observed for 16 weeks.
Results: Based on the NCS results, statistically significant electrophysiological recovery was observed in the amniotic group compared to the control group in the middle of the observation period (5-8 weeks). However, the control group converged to almost the same value in the late period (16 weeks). In the fetal membranes group, when we analyzed the changes over the entire observation period from pre-surgery to 16 weeks, we found that electrophysiological improvements exceeded those in the control group. There were no differences regarding SFI results among three groups.
Conclusion: Both the use of amniotic membranes and fetal membranes promoted electrophysiological improvement of peripheral nerves after injury. On the other hand, no apparent effects on improving motor functions were observed. In this experiment, we verified the effects of fetal and decellularized amniotic membranes in addition to human amnion. However, we did not find that decellularized amniotic membranes had a healing-promoting effect. Therefore, it was hypothesized that factors that promote healing exist in amniotic epithelial cells or the chorion.