Best Explanation of Amniotic Membrane Layers and How to Place Amniotic Membrane on a Defect
A colleague asked me about Amniotic Membrane and how to place it on the eye.
Ammniotic membrane has multiple factors, such as collagen of various types, laminin, fibronectin, and proteoglycan that promote healing damaged cells. Amniotic membrane has a high tensile strength (its a pretty tough membrane) and induces reepithelialization through chemical mediators. It has multiple anti-inflammatory, antibacterial and antiviral properties acts as a scaffold in which cells can proliferate and differentiate as it has pluripotent cells among its layers. Amniotic membrane does not have any risk of tumor formation according to multiple publications.
When using amniotic membrane the goal is to face the stromal side towards the cornea and have the epithelial side facing up.
This sketch shows how the baby lies in relation to the exaggerated placental membranes: composed of the Amnion and the Chorion. We use only the amnion as this is a clear membrane with multiple healing factors. The chorion is filled with blood vessels that may not be as desirable in healing the cornea.
- Mamede AC, Carvalho MJ, Abrantes AM, Laranjo M, Maia CJ, et al. (2012) Amniotic membrane: from structure and functions to clinical applications. Cell Tissue Res 349: 447–458.
- Insausti CL, Alcaraz A, García-Vizcaíno EM, Mrowiec A, López-Martínez MC, et al. (2010) Amniotic membrane induces epithelialization in massive posttraumatic wounds. Wound Repair Regen 18: 368-77.
- Gruss JS, Jirsch DW (1978) Human amniotic membrane: a versatile wound dressing. Can Med Assoc J 118: 1237-1246.
- King AE, Paltoo A, Kelly RW, Sallenave JM, Bocking AD, et al. (2007) Expression of Natural Antimicrobials by Human Placenta and Fetal Membranes. Placenta 28: 161-169.
- Hartstein B, Gausche-Hill M, Cancio LC (2013) Burn Injuries in Children and the Use of Biological Dressings. PediatrEmerg Care 29: 939-94
Preparation of amniotic membrane for ocular surface reconstruction.
We describe the preparation and preservation of human amniotic membrane required for transplantation in the management of ocular surface diseases. Informed consent is obtained and the donor is screened to exclude risk of transmissible infections such as human immunodeficiency virus (HIV), hepatitis B virus, hepatitis C virus, and Treponema pallidum infections. Ideally, the media and washing solutions needed for the preparation of amniotic membrane are prepared only a week to 10 days prior to use and not stored in the freezer weeks ahead. The AM obtained under sterile conditions after elective caesarian section is washed free of blood clots and chorion. With the epithelial surface up, amniotic membrane is spread uniformly without folds or tears on individually sterilized 0.22 micron nitrocellulose membranes of the required sizes. The prepared filter membrane with the adherent amniotic membrane is placed in the preservative medium and stored at -80 degrees C. The membranes are released when the repeat serology for HIV after the window period has excluded virus infection in the donor. Depending on consumption they may be used up to 6 months after preparation, though many have recommended storage for an indefinite period. Since the amniotic membrane has only incomplete expression of HLA antigens and amniotic epithelial cells do not express them, it is not rejected after transplantation. The presence of several cytokines in the amniotic membrane promotes epithelialization with reduction of fibrosis during healing.