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  • Application of Amniotic Tissue in Orthopedic Surgery


    The use of amniotic tissue in orthopedic surgery has increased in recent years. While more studies are needed to fully understand the therapeutic potential and define the appropriate applications of these tissues, basic science and clinical studies are available that indicate promising results. This review will highlight these studies as they relate to the musculoskeletal system.

    The amniotic membrane is a multilayer tissue forming the innermost layer of the amniotic sac that surrounds the developing fetus. It is comprised of 5 layers, from the inside out: a single layer of epithelial cells, a thick basement membrane, a compact layer, a fibroblast layer, and a spongy layer that abuts the surrounding chorion.1

    The amniotic membrane serves several functions, including synthesis of growth factors and cytokines, regulation of pH, transport of water and solutes, and provision of a permeable barrier to amniotic macromolecules.2
    Amniotic epithelial cells are derived from the pluripotent epiblast at approximately day 8 of gestation. This is well before gastrulation occurs at days 15 to 17, considered the “tipping point” when pluripotent cells differentiate into ectoderm, mesoderm, and endoderm.3 These cells express Oct-4 and Nanog, 2 molecular markers that are indicative of pluripotency.3 Two cell types have been identified in amniotic tissues that possess stem cell-like characteristics: human amniotic epithelial cells and human amniotic mesenchymal stromal cells.4 Both of these cell types have demonstrated the ability to differentiate into various cell lineages, including endothelial cells, adipocytes, myogenic cells, neurogenic cells, chondrocytes, tenocytes, and osteogenic cells.5-7 These previously reported findings indicate that amniotic cells and tissue have the capability to generate mesenchymal tissues.