Structural and Biological Comparison of Cryopreserved and Fresh Amniotic Membrane Tissues

The use of amniotic membrane (AM) to modulate wound healing and promote regeneration is increasing, but to date there has been no comprehensive study directly comparing the structural and biological properties of fresh and cryopreserved AM. Thus, in this study we compared fresh AM and fresh amniochorion to cryopreserved tissues. Histochemical staining confirmed that the cryopreservation process did not dramatically alter the tissue architecture nor collagen and glycosaminoglycan density. Biochemically, cryopreservation reduced total protein and human serum albumin contents, but retained high molecular weight hyaluronic acid species including the heavy chain-hyaluronic acid complex that is known to exert anti-inflammatory and anti-scarring effects. Cryopreserved and fresh AM extracts similarly suppressed viability and proliferation of RAW264.7 macrophages, and inhibited the transforming growth factor beta 1 promoter activity in corneal fibroblasts. These results collectively indicate that cryopreservation effectively preserves histological, biochemical, and functional properties of the AM tissue.