Abstract
Human amniotic membrane (AM) has a long history of clinical use for wound treatment. AM serves as a wound protective barrier maintaining proper moisture. AM is anti-inflammatory, anti-microbial and antifibrotic, and supports angiogenesis, granulation tissue formation and wound re-epithelialization. These properties of AM are attributed to its native extracellular matrix, growth factors, and endogenous cells including mesenchymal stem cells. Advances in tissue preservation have helped to overcome the short shelf life of fresh AM and led to the development of AM products for clinical use. Viable cryopreserved amnion (VCAM), which retains all native components of fresh AM, has shown positive outcomes in clinical trials for wound management. However, cryopreservation requires ultra-low temperature storage and shipment that limits widespread use of VCAM. We have developed a lyopreservation technique to allow for ambient storage of living tissues. Here, we compared the structural, molecular, and functional properties of a viable lyopreserved human amniotic membrane (VLAM) with properties of VCAM using in vitro and in vivo wound models. We found that the structure, growth factors, and cell viability of VLAM is similar to that of VCAM and fresh AM. Both, VCAM and VLAM inhibited TNF-α secretion and upregulated VEGF expression in vitro under conditions designed to mimic inflammation and hypoxia in a wound microenvironment, and resulted in wound closure in a diabetic mouse chronic wound model. Taken together, these data demonstrate that VLAM structural and functional properties are equivalent to VCAM but without the constraints of ultra-low temperature storage.
Highlights
Human placental tissue, the amniotic membrane (AM), has a long history of use as a biological dressing for acute and chronic wounds [1,2,3,4]
Viable cryopreserved AM (VCAM) described in this study is a commercial placental product that is used for management of acute and chronic wounds and for a variety of surgical procedures [21,24,44]
VCAM retains all native components of fresh AM including viable cells and a full spectrum of biological activities associated with fresh tissue [17,20,45]
Summary
The amniotic membrane (AM), has a long history of use as a biological dressing for acute and chronic wounds [1,2,3,4]. AM maintains a moist environment in the wound, supports angiogenesis, granulation of the wound bed, and wound epithelialization [3,8]. These functional properties are attributed to the composition of tissue, including a collagen-rich structural extracellular matrix, growth factors and cytokines, and endogenous viable epithelial. While various preservation methods have been developed for placental tissue processing, most of these methods destroy native viable cells. Cryopreservation, a common method for long-term storage of viable cells and tissues, involves the cooling of samples to very low temperatures in the presence of cryoprotective agents followed by storage at ultra-low temperatures [12]. Recently has a cryopreservation method been developed to allow storage of AM for prolonged periods without compromising cell viability post-thaw [16,17,18]
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