Amniotic membrane as a substrate and delivery vehicle for stem cells

New therapeutic concepts and clinical strategies are emerging for the different kinds of human amniotic membranes (hAM). There are new commercial forms of hAM that are under investigation for old and new applications, from ocular surface epithelial persistent defects to the hAM extract eyedrops or the new use of hAM as a delivery platform and substrate for stem cells for ocular surface repair. Although there are more substrates used as support for growth, maintenance, and delivery of cultivated stem cells onto the ocular surface, hAM is still the most used universally, followed by fibrin‐based substrates. This is due to the notable biological properties of this live tissue. The only disadvantage may be that it must come from tissue banks and as such, there can be some shortages and the cost is not irrelevant. Several other types of synthetic substrates such as lotrafilcon A, siloxane hydrogels or poly lactide‐co‐glycolic acid (PLGA) polymers, have been used over the last years to facilitate cell culture and the subsequent transplantation onto the ocular surface. In addition, several polymeric biomaterials like polycaprolactone, polylactic glycolic acid, chitosan and gelatin membranes, collagen or elastin‐like polymers are being also used to support ocular epithelial cells in preclinical studies. However, none of those attempts to substitute hAM have been translated inti clinical use. We have successfully used hAM as substrate and delivery platform in preclinical research, both in vitro and in vivo models of stem cell deficiency, and in the two clinical trials that have been completed and published, with both cultivated epithelial cells from the limbal niche and bone marrow‐derived mesenchymal stem cells.