TeachableMedicalNews article 01152023

Teachable moment in classrooms:

  1. special senses chapter – tunics/layers of the eye
  2. special senses chapter – structure of the cornea
  3. tissues chapter – collagen is found in the extracellular matrix of many connective tissues
  4. immune system chapter – recognition of non-self antigens
  5. immune system chapter – role of lymphocytes for immune functions

The news item:  Recently this news item was online:

Eye implant made from pig protein restored sight in 14 blind people

Twenty people with diseased or damaged corneas saw improvements to their vision after receiving implants engineered out of protein from pigskin.

The article states that collagen from pig skin was helpful in restoring vision to people with the disorder called keratoconus, that this disease represents a bulging of the front of the eye, that about 50-200 from 100,000 people have this disease, and that the treatment includes injection of this collagen into the cornea.

So, Why Do I Care??  Our vision is the most precious sense, so, any loss of visual capacity has a major effect on our quality of life. The misshaped cornea causes loss of sharp vision.  As the article states keratoconus is a relatively rare disorder, nonetheless it is important to keep an account of any remedy that restores vision.

Plain English, Please!!! First, let’s talk about what keratoconus is. At the front of the eyeball there is a transparent sheet called cornea. From the side it looks like a flat bubble. The cornea focuses light into the eye. In some people the cornea has a pointy shape like a small ice cream cone. This keratoconus condition prevents the focusing of light, so, blurred, cloudy vision is the result.

Second, let’s talk about the injection into the cornea. While the cornea is a very thin sheet of tissue, it is possible to inject materials into the sheet.  Because the cornea is flexible, injection of the proper amount of liquid can change the shape from an ice cream cone to the flat bubble shape.

Third, let’s talk about the pig collagen used in this treatment. While it is our primary goal is to restore the normal shape to the cornea, it is important to keep in mind that the cornea must remain transparent after the injection, because light can not be focused with an opaque cornea. This why collagen is the right material for injection. The normal cornea is rich in collagen, so, it is the expectation that injecting a collagen solution into the cornea will retain transparency. Collagen has another advantage, because collagen protein is not easily recognized by the immune system as foreign material. A pig kidney is rejected by a human recipient because the pig cells are recognized as non-self by the lymphocytes of the human immune system. Our lymphocytes can read molecular shapes of antigens just like we read name tags in a meeting. Lymphocytes can distinguish millions of non-self name tags (indicating foreign material) from self name tags that are normal part of our bodies. As it turns out, pig collagen has so few non-self name tags that the human immune system tolerates pig collagen. In other words, our lymphocytes will not attack the pig collagen.

 

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