Indications for and Uses of Amniotic Membrane: Clinic

Key Concepts

Amniotic membrane (AM) promotes epithelialization, inhibits inflammation, and has antimicrobial properties with negligible immunologic response.
As a patch, the AM acts as a biologic contact lens that reduces inflammation and promotes epithelialization beneath.
In partial limbal deficiencies, AM helps to reestablish the environment for stem cells (SC) at the corneoscleral limbus, reduces inflammation, and stimulates the proliferation of limbal SCs.
There are several options of AM as a patch graft for clinical use. We review the various types of patch grafts and their most common uses in the clinical setting.

The Amniotic Membrane: Histology, Biologic Properties, and Clinical Effects

The amniotic membrane (AM) is the innermost layer of the fetal membranes and is composed of three layers: the epithelium, the basement membrane (BM), and the stroma. It is an avascular fetal membrane that lies deep to the chorion and which does not trigger any immunologic response despite expressing human leukocyte antigen (HLA) I and HLA II. ^, After donors are screened for transmittable diseases, the AM is harvested in a sterile environment during elective cesarean section. The AM epithelium has a monolayer of cuboidal cells attached to the basal lamina by numerous hemidesmosomes; the BM is composed of collagen IV and VII, fibronectin, and laminin 1 and 5; the loose connective tissue of the stroma confers tensile strength, a similar stroma composition also found in the conjunctival and corneal BMs.

AM is a rich course of biologically active growth factors and promotes healing and acts as an effective material for wound dressing in ocular and nonocular structures. Studies on human AM preserved at -80°C for 1 month revealed the presence of growth factors (epidermal growth factor (EGF), transforming growth factor-α (TGF-α), keratinocyte growth factor (KGF), hepatocyte growth factor (HGF), basic fibroblast growth factor (bFGF), TGF-β1, and TGF-β2), which were found in higher levels in AM. The epithelium of the AM also provides cytokines that maintain the microenvironment of the stem cells (SCs) of the corneal epithelium. The BM facilitates migration of epithelial cells, reinforces adhesion of basal epithelial cells, and prevents apoptosis. Finally, a component of the stroma suppresses signaling via TGF-β, which modulates the proliferation of normal corneal, conjunctival, and limbal fibroblasts, and reduces subconjunctival fibrosis. The stroma also contains antiinflammatory and antiangiogenic proteins and protease inhibitors that reduce stromal inflammation and ulceration.

AM promotes healing of the ocular surface by several mechanisms. It acts as a physical barrier to protect conjunctival and corneal epithelium from friction from the eyelids, and promotes epithelial growth through cell migration, adhesion, and differentiation, while simultaneously inhibiting cell death. ^,

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