Biological properties and surgical applications of the human amniotic membrane

Abstract

The amniotic membrane (AM) is the inner part of the placenta. It has been used therapeutically for the last century. The biological proprieties of AM include immunomodulatory, anti-scarring, anti-microbial, pro or anti-angiogenic (surface dependent), and tissue growth promotion. Because of these, AM is a functional tissue for the treatment of different pathologies. The AM is today part of the treatment for various conditions such as wounds, ulcers, burns, adhesions, and skin injury, among others, with surgical resolution. This review focuses on the current surgical areas, including gynecology, plastic surgery, gastrointestinal, traumatology, neurosurgery, and ophthalmology, among others, that use AM as a therapeutic option to increase the success rate of surgical procedures. Currently there are articles describing the mechanisms of action of AM, some therapeutic implications and the use in surgeries of specific surgical areas, this prevents knowing the therapeutic response of AM when used in surgeries of different organs or tissues. Therefore, we described the use of AM in various surgical specialties along with the mechanisms of action, helping to improve the understanding of the therapeutic targets and achieving an adequate perspective of the surgical utility of AM with a particular emphasis on regenerative medicine.

Keywords: amniotic membrane; graft; placenta; regenerative medicine; surgery.

FIGURE 1

Components of the placenta and AM. The AM and the chorion are the two layers of the placenta. The epithelial layer, basal membrane, compact layer, fibroblast layer, and sponge layer are components of AM. The epithelial surface of AM is in con-tact with the fetus, and the chorionic layer is in contact with the maternal uterus.

FIGURE 2

Immunomodulatory function of the amniotic membrane. Amnion-derived cells (hAEC, human amniotic epithelial cells; hAMC, human amniotic mesenchymal cells) reduce the secretion of inflammatory cytokines (TNFα, IFNγ, IL-6, and 17) by monocytes and lymphocytes, favor the generation of Treg lymphocytes (trogocytosis process), induce the phenotypic switch of inflammatory macrophages M1 to M2, and inhibit macrophage migration and infiltration into tissues (Li et al., 2015; Tan et al., 2015).

FIGURE 3

Therapeutic effects of the amniotic membrane and the molecular mechanisms. Each disease has a specific pathophysiology; therefore, the therapeutic effects of AM are different for each of the pathologies. The molecular mechanisms involved are varied, but not all of them are involved in the resolution of the diseases. The figure reinforces the knowledge of the therapeutic effects of AM and also helps to understand future applications of this tissue. Lym, Lymphocyte; MØ, Macrophages; Neut, Neutrophils; MO, Monocytes; Treg, Lymphocyte regulator; NKs, Lymphocytes Natural Killers; CD, Cluster differentiation; αSMA, Smooth muscle actin; ERK, Extracellular signal-regulated kinase; Col, Collagen; FGF-R, Fibroblast growth factor receptor; ECM, Extra cellular matrix; MMP, Matrix metalloproteinases; BMP, Bone morphogenetic protein; THBS1, Thrombospondin 1; TIM, T cell immunoglobulin mucin; IL, Interleukin; VEGFA, Vascular endothelial growth factor A; ANG1, Angiopoietin 1; HGF, Hepatocyte Growth Factor; EGF, Epidermal growth factor; FGF, Fibroblast growth factors; eNOS, Endothelial nitric oxide synthase; PDEF, Pigment Epithelium-Derived Factor; PDGF, Platelet-derived growth factor; PLGF, Placental Growth Factor; KGF, Keratinocyte growth factor; NGF, Nerve growth factor; TGF, Transforming growth factor; TNF, Tumor necrosis factor; INF, Interferon; IGF, Insulin-like growth factor; IGFBP, Insulin-like growth factor-binding protein; NT, Neurotrophin; M-CSF, Macrophage-colony stimulating factor.

FIGURE 4

Impact of the amniotic membrane (AM) in different surgical procedures. The use of AM in surgeries in different surgical areas is used for different biological purposes, where the modification of pathophysiological processes impacts on the functionality, state and tissue condition of different organs, all of which is reflected in the postoperative clinical results. POFS, Post-operative fistulation and stenosis; POPF, Postoperative pancreatic fistulation; CSF, Cerebrospinal fluid.