The amniotic membrane is a tissue of placental source. The amniotic membrane, in continuation to the chorion, is the inner layer of the amniotic sac that surrounds the embryo and, later, the fetus. The amniotic membrane at the end has an area ranging from about 700 to 1800 cm2, a weight of 15-35 grams, and a thickness ranging from 0.02 mm to 0.05 mm, depending on the pregnant women and of the different regions dell’amnios . It is a translucent membrane composed by three main layers: an epithelial layer, a thick basal membrane and a avascular mesenchyme. It does not contain nerves, muscles or lymph vessels and gets the nutrients and oxygen it needs directly from the amniotic fluid and from the fetal surface vessels.

A key feature of the amniotic membrane is support development of the embryo providing protection against infection and against  pressure of the surrounding structures. It also plays an important role during the birth: the amniotic epithelium is not only a major source of prostaglandins, especially prostaglandin E2, but also expresses the enzymes involved in their biosynthesis as a phospholipase, prostaglandin synthase and cyclooxygenase. From the epithelial layer of the amniotic membrane were isolated pluripotent stem cells.

Amniotic membrane properties

The chemical and biological properties up to now known of amniotic membrane are:

– Anti-inflammatory;

– antiangiogenetic

– antifibrotic

– scar over

– pro-regenerative

– antibacterial

– No tumorigenicity

– Lack of immunogenicity

Furthermore:

– Provides a matrix for cells migration and proliferation;

– Reduces pain on the application site;

– Provides a natural biological barrier. The “Banks of the amniotic membrane,” even in our country, are centers specializing in collection, storage, processing and distribution of donated amniotic membranes. The selection of donors abide by the regulations regards the safety of tissues. It should be noted that, from a legal point of view, the use of amniotic membrane does not have ethical limitations, as the removal occurs after delivery without any danger for mother and baby.

Clinical applications

The use of amniotic membrane in medicine has more than a century of history. Davis was the first to use it in 1910 in the skin graft. Later it has been employed in the treatment of burns and skin ulcers, in surgical reconstruction of various organs (bladder, urethra, vagina, tendons, eardrum, nasal mucosa, tongue, mouth), in prevention of post-surgical adhesions, especially abdominal and pelvic and in omphalocele repair. In ophthalmology its use was reported for the first time in 1940 by De Rotth, who employed fresh fetal membranes (amnion and chorion) on the ocular surface as biological dressings for the treatment of conjunctival defects. Later Sorby and colleagues used the preserved amniotic membrane as a temporary cover in the treatment of acute caustic eye damage. The use of amniotic membrane as a tissue, then, has a long history, but the renewed interest in last years is due to the discovery of its own stem cells. The amniotic cells are a valuable source of stem cells for cell graft and regenerative medicine. The epithelial layer of the amniotic membrane includes markers of pluripotent stem cells able to differentiate into all three germ layers (hepatocytes and pancreatic cells), mesoderm (cardiomyocytes, osteocytes, adipocytes and myocytes) and ectoderm (neurons and glial cells ). The amniotic membrane is a biomaterial easy to  obtain, process and transport. Moreover, thanks to the antimicrobial properties and low immunogenicity, it could bypass immunological complications biomaterials xenogeneic. For all these reasons it is an ideal candidate for the creation of scaffolds used in tissue engineering.

The scaffold properties of the amniotic membrane have been used by our groups in various fields of application:

– In the field of nerve regeneration, as a result of traumatic events that involve in a gap of the stumps of amputation; in this case we use the amniotic membrane as a regenerative scaffold. Clinical and in vitro studies show important results that let us  publication in international journals (Microsurgery, November 2014: DOI: 10.1002 / micr.22306)

– In chronic vascular ulcers of the lower limbs, both of artery and  blood vessel, in patients with long venous stasis or arterial disease of the lower limbs. Even in this case, the association of vascular surgery techniques  and plastic surgery techniques, associated with the use of amniotic membrane, leads to resolution long-term chronic wounds with stable results after time.

Michele Riccio; Elena Bondioli .