TABLE 1.
Intact amniotic membrane biological and physical characteristics.
| Amniotic membrane features | Contributing factors | References |
| Biological properties | ||
| • Anti-inflammatory effect | Trapping inflammatory cells and driving them to apoptosis through its pro-apoptotic agents; production of anti-inflammatory factors by its epithelial cells; suppression the pro-inflammatory cytokines such as interleukin 1 alpha and 1 beta; production of MMP’s inhibitors; expression of migration inhibitory factor (MIF); expression of anti-inflammatory cytokines such as IL-1 receptor antagonist; secretion of anti-inflammatory factors such as PGE2, TGF-β, HGF, TNF-α, and MIF from mesenchymal and epithelial cells of AM | Mamede et al., 2012; Islam et al., 2015; Rocha and Baptista, 2015; Ilic et al., 2016 |
| • Antibacterial and antiviral effect | Expression of natural antibacterial molecules such as β-defensins, elafin, and cystatin E; adhesion to wound surface and to act as a barrier against bacterial infiltration | Mamede et al., 2012; Islam et al., 2015; Castellanos et al., 2017; Milan et al., 2020 |
| • Low antigenicity and non-immunogenicity | Lack of human leukocyte antigens A, B, C, and DR antigens, or β2-microglobulin on the surface of AM epithelial cells; absence of vessels, lymph, and nerves, in its structure | Mamede et al., 2012; Chopra and Thomas, 2013; Castellanos et al., 2017 |
| • Anti-scarring and anti-adhesive effect in wound healing | Reduction of proteases activity due to the secretion of tissue inhibitors of metalloproteinases (TIMPs); the decreased activity of fibroblasts through downregulation of TGF-β with AM hyaluronic acid content | Mamede et al., 2012; Castellanos et al., 2017 |
| • Angiogenesis and anti-angiogenesis properties (surface dependent) | Angiogenesis properties: secretion of VEGF, IL-8, angiogenin, interferon-γ, IL-6, bFGF, EGF, and PDGF by AM mesenchymal cells Anti-angiogenesis properties: secretion of IL-1, IL-2 receptor antagonist, IL-10, endostatin, TIMP-1, -2, -3, and -4, thrombospondin, and heparin sulfate proteoglycan by AM epithelial cells | Islam et al., 2015; Ilic et al., 2016 |
| • An anticancer agent with low tumorigenicity | Secretion of pro-apoptotic agents; secretion of IL-1, IL-2 receptor antagonist, IL-10, and endostatin which all inhibit tumor growth | Islam et al., 2015; Jafari et al., 2020 |
| • Promotion of epithelialization | Secretion of growth factors such as EGF, KGF, and HGF | Mamede et al., 2012; Islam et al., 2015; Ilic et al., 2016; Castellanos et al., 2017 |
| • Pain reliever | Mamede et al., 2012 | |
| • Support cell adhesion and growth | Its hyaluronic acid content and proteins such as fibronectin, laminin, collagens, and proteoglycans act as a ligand for integrin receptors | Ilic et al., 2016 |
| Mechanical properties (intact AM) | ||
| • Direct tensile mechanical properties | Placental: Force before rupture: 1.2 ± 0.2 N Strain at break: 19% ± 3% N Peripheral: Force before rupture: 0.68 ± 0.08 N Strain at break: 16% ± 1% N | Litwiniuk et al., 2017 |
| • Young’s modulus | 2.29–3.6 MPa | Niknejad et al., 2008 |
| • Tensile strength | 5.475 ± 0.135 MPa | Cai et al., 2015; Ramesh et al., 2017 |
| • Elastic modulus | 4.048 ± 1.702 MPa | |