Cryopreservation of human amniotic membrane for ocular surface reconstruction: a comparison between protocols.

Purpose: To compare the effects on adhesive and structural properties of newer preservation conditions to those obtained with an established, standardized protocol (dimethyl sulfoxide at -180 °C). In attempt to simplify and enhance the safety of the procedure, we tested dextran-based freezing medium and a dry condition (no medium) at temperatures of -80 °C.

Methods: Five patches of human amniotic membrane were obtained from three different donors. For each donor, five preservation condition were tested: dimethyl sulfoxide at -180 °C, dimethyl sulfoxide at -80 °C, dextran-based medium at -180 °C, dextran-based medium at -80 °C and dry freezing at -80 °C (no medium). At the end of four months storage period, adhesive properties and structure were analyzed.

Results: None of the newer preservation protocols showed differences in adhesive and structural properties of the tissues. The stromal layer always kept its adhesiveness, while both structure and basement membrane were not altered by any the preservation protocol.

Conclusions: Switching from liquid nitrogen cryopreservation to -80 °C would reduce manipulation, simplify the procedure, making it also cheaper. The use of dextran-based freezing medium or no medium at all (dry condition) would avoid the potential toxicity of the dimethyl sulfoxide-based freezing media.