Biological Differences between Cryopreserved and Dehydrated Amniotic Membrane Tissue Grafts

Abstract

Purpose: Amniotic membrane (AM) processing methods can dramatically impair both the structural integrity, and biological activity, of critical matrix cell signaling factors essential for the intended use of the product. To analyze the effect of different AM available commercially for the ophthalmology market on conserving the therapeutic potential of the tissue, we compared cryopreserved (CryoTek™) and dehydrated (Purion®) processed tissue grafts in physical and biochemical assays.

Methods: Cryopreserved thin (CT-Thin) and thick (CT-Thick) tissues were compared to dehydrated, (EF) and (AF) AM tissue grafts. Structural properties of cryopreserved and dehydrated AM were assessed by histological staining while biochemical properties were measured in soluble tissue extracts by comparing hyaluronan (HA) content and molecular weight (MW) spectrum; and critical proteoglycan (HC-HA) and protein (PTX3) signaling factors.

Results: Histochemical staining demonstrated dehydrated tissues having a more compact extracellular matrix compared to the cryopreserved tissues even after the prescribed hydration duration. HA quantity was highest in CT-Thick, and although content was relatively similar in CT-Thin and EF/AF, the MW analysis revealed all cryopreserved samples contained high MW HA, while the dehydrated samples contained low MW HA. Essential signaling proteins, HC-HA and PTX3 detected by western blots were present in cryopreserved samples but were either compromised, or completely absent, in dehydrated tissues.

Conclusions: The cryopreservation process better preserves the structural integrity and biochemistry of AM tissue grafts in comparison to dehydrated grafts, and suggests the therapeutic benefit of dehydrated AM may be compromised as a result.

Keywords: 765 wound healing • 687 regeneration • 490 cytokines/chemokines