Composition of Amnion Tissue
The amniotic sac is part of the placenta which encloses the unborn baby though term. It is composed of two types of tissue, amnion and chorion. Amnion is the inner most lining and consists of a single layer of epithelium cells, thin reticular fibers (basement membrane), a thick compact layer, and a fibroblast layer. The basement membrane contains collagen types III, IV, and V and cell-adhesion bioactive factors including fibronectin and laminins.
Historical Use of Amnion Tissue
The first recorded clinical use of amnion tissue was for use in skin transplantation in 19101. Shortly thereafter it was frequently used in the management of burns and those suffering from ulcerated skin conditions. For reasons unknown the use of amnion tissue generally ceased in the United States in the 1940s. In 1973 amnion tissue was reported being used in extraoral grafting applications such as temporary biologic dressings for full-thickness wounds2. In the years that followed it was used successfully in the reconstruction of vaginal malformed organs3, prevention of tissue adhesion4, and vestibuloplasty5.
The first clinical use of cyro-preserved amnion allograft in ophthalmic surgery was first reported in 19976. Today they are commonly used in ophthalmic surgery, and literature suggests suggests both cyro-preserved amnion allografts7 and dehydrated amnion allograft8 provide results equivalent to conjunctive autograft tissue. In 2009, an amnion allograft became available on a limited commercial basis for use as an adhesion barrier in spine and orthopedic procedures.
The Science of Amnion Tissue
Pre-clinical studies focused on the use of amnion tissue in oral mucosal tissue have demonstrated “excellent compatibility9, 10.” One of the reasons for this result is the composition of amnion tissue. Literature suggests the basement membrane of amnion tissue “closely mimics the basement membrane of human oral mucosa tissue11.” Of the laminins found in the basement membrane, Laminin-5 is the most prevalent. Laminin-5 possesses “a high affinity for cellular adhesion of gingival epithelial cells12.” In addition to its composition, the natural physical characteristics of amnion tissue form an early “physiologic seal” with the host tissue upon placement, thus precluding bacterial contamination13.
Amniotic tissue is derived from trophoblasts. These cells cover the developing embryo and only exhibit major histocompatibility complex (MHC) Class II antigens14. They do not possess MHC Class I antigens, which are present in all caderivic tissue and are responsible for rapid rejection of allografts14, 15.
References
1. Davis J.W. Skin transplantation of 550 cases at John Hopkins Hospital. John Hopkins Med. J. 1910; 15: 307.
2. Robson M.C., Krizek T.J. The effect of human amniotic membranes on the bacteria population of infected rat burns. Ann.Surg.1973; 177(2): 144-9.
3. Morton K.E., Dewhurst C.J. Human amnion in the treatment of vaginal malformations. Br. J. Obstet. Gynaecol. 1986; 93(1): 50-4.
4. Muralidharan S, Gu J, Laub G.W., Cichon R, Daloisio C, McGrath L.B. A new biological membrane for pericardial closure. J. Biomed. Mater. Res. 1991; 25(10): 1201-9.
5. R. Gtiler, M.T. Ercan, N. Ulutuncel, H. Devrim, N. Uran. Measurement of blood flow by the 133Xe clearance technique to grafts of amnion used in vestibuloplasty. Br. J. Oral Maxillo. Fac. Surg. 1997; 35: 280-283.
6. S.C. Tseng, P. Prabhasawat, S.H. Lee. Amniotic membrane transplantation for conjunctival surface reconstruction. Am J Ophthalmol. 1997; 124: 765-774.
7. Luanratanakorn P, Ratanapakorn T, Suwan-Apichon O, Chuck R.S. Randomised controlled study of conjunctival autograft versus amniotic membrane graft in pterygium excision. Br. J. Ophthal. 2006; 90(12): 1476-1480.
8. Memarzadeh F, Fahd A.K., Shamie N, Chuck R.S. Comparison of de-epithelialized amniotic membrane transplantation and conjunctival autograft after primary pterygium excision. Eye 2008; 22(1): 107-12.
9. M. Rinastiti, Harijadi, A. L. S. Santoso, W. Sosroseno. Histological evaluation of rabbit gingival wound healing transplanted with human amniotic membrane. Int. J. Oral Maxillofac. Surg. 2006; 35(3): 247–251.
10. M.G. Vilela-Goulart, R.T.S. Teixeira, D.C. Rangel, W. Niccoli-Filho, M. Gomes. Homogenous amniotic membrane as a biological dressing for oral mucositis in rats: Histomorphometric analysis. Archives of Oral Biology 2008; 53(12): 1163-1171.
11. Takashima S, Yasuo M, Sanzen N, Sekiguchi K, Okabe M, Yoshida T, Toda A, Nikaido T. Characterization of laminin isoforms in human amnion. Tissue and Cell 2008; 40(2): 75-81.
12. Pakkala T, Virtanen I, Oksanen J, Jones J C.R., Hormia M. Function of Laminins and Laminin-Binding Integrins in Gingival Epithelial Cell Adhesion. J. Periodontol 2002; 73(7): 709-19.
13. Talmi Y P., Sigler L, Inge E, Finkelstein Y, Zohar Y. Antibacterial Properties of Human Amniotic Membranes. Placenta 1991; 12(3): 285-88. 14. Aagaard-Tillery KM, Silver R, Dalton. J. Immunology of normal pregnancy. Semin Fetal Neonatal Med. 2006; 11(5): 279-95. 15. Veenstra van Nieuwenhoven AL, Heineman MJ, Faas MM. The immunology of successful pregnancy. Hum Reprod Update. 2003; 9(4): 347-57.
14. Aagaard-Tillery KM, Silver R, Dalton. J Immunology of normal pregnancy. Semin Fetal Neonatal Med. 2006; 11(5): 279-95.
15. Veenstra van Nieuwenhoven AL, Heineman MJ, Faas MM. The immunology of successful pregnancy. Hum Reprod Update. 2003; 9(4): 347-57.