Overview of Amniotic Membrane Graft
A graft of the human amniotic membrane is used as an additional procedure in many areas of surgery and medical research focused on growing stem cells. The amniotic membrane is the protective covering of the sac where an unborn baby develops. It’s readily available and the methods to prepare and preserve it are not very costly.
Different medical specialists use this type of graft, including eye doctors, dentists, urinary system specialists, burn treatment experts, ear, nose, and throat surgeons, women’s health doctors, and scientists working on stem cell research. It’s a versatile tool in the medical field.
Anatomy and Physiology of Amniotic Membrane Graft
Amniotic Membrane Grafts (AMGs) are used by eye doctors for several purposes. They help in the growth of epithelial cells, which are found on the surface of the eye. They also provide structural support in cases where the cornea (the transparent front part of the eye) or sclera (the white part of the eye) are thinning or have small holes. Additionally, they can be used to cover large areas where the eye’s surface is damaged.
AMGs offer several benefits compared to other similar materials like heart tissue, connective tissue, and mucus membranes. For one, they can be easily acquired in large amounts. They are reasonably transparent, don’t usually cause immune reactions, and provide a good environment for cells to grow. Also, they go unnoticed when used in the eye and provide a smooth surface that can cover damaged areas.
However, AMGs do carry some drawbacks. Since they are a biological membrane, they don’t provide great structural strength, so they might not be suitable for certain cases. There also exists a risk of infection, and there is a small chance they could transmit diseases such as hepatitis, HIV, and COVID-19.
The human amniotic membrane, which makes up part of the placenta during pregnancy, exhibits several useful qualities. It promotes the growth of epithelial cells, doesn’t cause immune reactions, and has anti-inflammatory, anti-microbial, and anti-scarring properties. It’s currently being researched for its potential use in regenerative medicine. However, it lacks structural strength and carries a potential risk of infection, which may limit its usage.
The positive properties of AMGs are largely due to several factors they contain. These factors include TGF β, Fibroblast growth factor, and many others. These substances can reduce inflammation in the eye and promote healing.
Finally, AMGs also contain regulators of soft tissue healing, known as growth factors. These include bFGF, β-NGF, EGF and others, which all help in promoting the healing process.
Why do People Need Amniotic Membrane Graft
AMG, a medical treatment, is used widely in eye care, especially in treating conditions linked with the cornea, the clear front surface of the eye, the conjunctiva, the thin layer that covers the front of the eye, and the retina, the back part of the eye that allows us to see.
For corneal diseases, AMG can be very useful. If someone has damage to their cornea due to strong chemicals, AMG can help the cornea heal. It can also provide a base for other treatments in both acute and chronic cases. In conditions like Stevens-Johnson Syndrome, which often affects the skin and mucous membranes, including the eyes, AMG can help with healing. Diseases like bullous keratopathy, which can cause swelling and blurred vision, can also be relieved with AMG.
Similarly, for conjunctiva-related conditions, like injuries from chemicals or heat, AMG can assist in healing and reconstructing the damaged surface. For instance, in a procedure called trabeculectomy, which is usually done to treat glaucoma, AMG can help repair any leaks. It can also aid in healing after removal of eye growths known as pterygium or squamous neoplasia, and help reconstruct parts of the eye like the fornix and eyelid margin.
AMG can also be used in the reconstruction of the socket, the area where the eye is placed, and in growth of cells required for corneal health. It might also be applied for retinal disorders, where it can assist with the closure of macular holes, which affect our central vision, or support repair of breaks in the retina.
These potential uses of AMG just go to show how critical it can be in managing some severe eye conditions and helping individuals see better.
When a Person Should Avoid Amniotic Membrane Graft
For larger holes in the cornea (the transparent front part of your eye), a procedure known as AMG (Amniotic Membrane Grafting) won’t be able to provide the necessary structural support.
Sometimes, inflammation of the iris (the colored part of the eye) with some pus-like fluid accumulation, known as iritis with hypopyon, can occur after the AMG procedure. But don’t worry, this is often not infectious and can usually respond well to steroid eye drops.
Also, a repeat use of the amniotic membrane (a special type of tissue used for the grafting) from the same donor might cause allergic reactions in some people. So, if the AMG procedure has to be repeated, it’s generally better to use a membrane from a different donor to avoid this.
Equipment used for Amniotic Membrane Graft
The process of preparing and transporting Amniotic Membrane Grafts (AMG), a type of tissue transplant, requires certain items. Here are some of the needed things:
– ‘Dulbecco’s Modified Eagle’s Medium’: This is a nutrient-rich solution that helps the tissue to stay healthy during the preparation process.
– ‘Nitrocellulose paper’: This is a kind of paper used in laboratories which allows for the safe handling and storage of the tissue.
– ‘-80 degrees C refrigeration’: This is a very cold storage condition, necessary to keep the tissue in a stable and preserved state.
– ‘Human Placenta’: This is the organ that connects the developing baby to the mother’s uterine lining, it’s used as the source of the tissue for the graft.
Who is needed to perform Amniotic Membrane Graft?
The human amniotic membrane (a thin layer found inside the uterus where a baby grows) is carefully prepared by a special technician. This technician knows how to handle and prepare it. They do so under what known as a laminar flow hood or in a clean area like the operating room. This helps make sure no germs or foreign particles get in. The Amniotic Membrane Graft (AMG), which is the properly packaged and prepared amniotic membrane, is kept in a very cold refrigerator – around -80 degrees Celsius. This is done to ensure that it stays fresh and safe until it’s needed.
Preparing for Amniotic Membrane Graft
The placenta, which is a crucial organ of pregnancy, is collected from mothers who have had a planned C-section. But only if the mothers have tested negative for certain diseases like HIV, Hepatitis B and C and syphilis. Also, in light of the ongoing pandemic, they must not have the SARS-CoV-2 virus, which causes COVID-19. While extracting the placenta, all necessary steps are taken to ensure that the process is sterile. Any blood clots present are washed off with a balanced salt solution. A gentle dissection process is then used to separate the amniotic membrane (a thin layer that surrounds the baby) from the thicker part of the placenta called the chorion.
The separated membrane is then placed on a special paper. It is cut into small pieces and then stored in sterile containers. These containers have a special medium, prepared in a laboratory, that helps preserve the membranes. They are stored at a temperature of -80 degrees Celsius.
There are other ways of preparing the placenta too. You can also use physiological saline or a solution called phosphate-buffered saline to wash the membrane. This is followed by additional washing using a compound called Dimethyl Sulfoxide (DMSO), which is dissolved in the saline solution.
There are also different methods to preserve the amniotic membrane such as freezing it (cryopreservation), drying after freezing (freeze-drying), or using gamma rays (gamma irradiation). These processes ensure the integrity of the amniotic membrane for future use. All of this is carried out with extreme caution to ensure safety and effectiveness.
How is Amniotic Membrane Graft performed
Amniotic membrane graft is a type of treatment where a thin, protective layer (called the amniotic membrane) is laid over the eye’s surface, including the cornea (the clear front surface of the eye). You can tell which side of the membrane is the stromal side (the one that should go against the eye surface) because it feels sticky. This membrane can be used to fill in areas where the cornea has become too thin, either as a single layer or several layers stacked together. It can also be used as a kind of bandage to cover areas where the cornea’s outer layer (the epithelium) is damaged.
In some severe cases, like when a person has suffered a chemical injury to the eye, the amniotic membrane can be spread out over the entire front of the eye and neatly tucked under the edges of the eyelids. This is done using a device called a conformer. The amniotic membrane can also serve as a base for placing limbal stem cells. These cells are special cells from the border of the cornea that can help repair it.
No matter what the procedure, the amniotic membrane is attached to the eye surface using tiny stitches, made either with 10-0 nylon or 8-0 polyglactin 910, which are two types of suture materials. In some cases, a type of medical adhesive known as fibrin glue may also be used to secure the membrane.
Possible Complications of Amniotic Membrane Graft
If the amniotic membrane, which is a layer of tissue, is not correctly anchored during grafting (a type of surgery), it may be lost early. Another possible issue is keratitis, an inflammation of the eye’s cornea, that could be caused by the membrane getting contaminated. In rare cases, a sterile hypopyon might develop after the grafting procedure. Hypopyon is a condition where there is a buildup of white blood cells in the front part of the eye.
One patient with a specific kind of corneal swelling, known as pseudophakic bullous keratopathy, experienced hypopyon after receiving an amniotic membrane graft. However, they responded well to treatment with steroids, which were injected around the eye.
Generally, severe complications are not known to occur with this type of grafting. But, there’s a small chance that infectious diseases such as HIV, Hepatitis B, or Hepatitis C could be passed to the patient during the procedure.
What Else Should I Know About Amniotic Membrane Graft?
Scientists have found a special way to treat certain eye conditions by using the thin layer that covers a developing baby in the uterus, known as the amniotic membrane. These membranes are carefully stored for use and have to be thawed out carefully before they can be used. They are usually moist rather than dry, coming in different forms like freeze-dried, treated with radiation, or preserved in a very cool state.
The process of using the amniotic membrane involves attaching it to the surface of the eye, either using a special sort of glue or with stitches. To keep it in place, a contact lens bandage can be used. The amniotic membrane slowly breaks down and becomes part of the surface of the eye, aiding in healing by reducing scars, slowing the growth of new blood vessels, and reducing inflammation.
In certain situations, the amniotic membrane can be applied in multiple layers to seal deeper injuries, or laid over the eye’s surface for persistent corneal epithelial defects, which is an issue where the clear front part of the eye doesn’t heal appropriately.
In advanced medicine, the amniotic membrane is also used as a foundation to grow stem cells in labs. These cells can be grown from the patient’s own cells (autologous) or from a different person (allogenic). These cells can be taken from the edge of the cornea (limbal stem cells) or from cells in the mouth (oral mucosal cells).
In the cases of chemical burns, certain diseases, and other causes of damage to these limbal stem cells, the amniotic membrane is placed onto the eyeball and either glued down or sutured.
A number of studies showed that amniotic membrane grafts help the eye heal quickly, offer relief from pain, result in an improvement in vision, and help to improve the function of the limbal stem cells.
These membranes have also been put to use to seal small perforations in the cornea and to aid in healing conditions where the cornea doesn’t heal properly.
One study placed stem cells onto an amniotic membrane and then transplanted them into the patient’s eye and noted the eye healed in most patients, regardless of whether the source of stem cells was a living donor or from a dead person.
In another study, the cells were grown outside of the body using the discarded parts of the cornea from a different procedure. Significant improvement in both visual clarity and the condition leading to the problem was seen in the majority of the patients, and vision improved in almost half.
Cells grown from the patient’s own mouth or from donor cells obtained from the margin of the cornea, showed generally comparable improvements. The cell technique avoids the need for suppression of the immune system because the cells are from the patient’s own body, but might have a slightly higher chance of graft failure and ongoing corneal healing problems than with donor cells from the cornea.
Recently, a simpler method has been developed to grow limbal stem cells in the body, which can be used in cases of unilateral limbal stem cell deficiency (a condition where the eye can’t repair). This makes a stem cell lab unnecessary and avoids their expense. It has a high success rate in allowing the area to re-heal, restoring the transparency of the cornea, and improving patient’s vision.
