Retinal Pigment Treated with Stem Cells

Retinitis pigmentosa is a rare disease that develops with a frequency of 1: 4000. The cause of the disease is atrophy of photoreceptors, that is, cells that can process visual signals into electrical signals that are transmitted to the brain. There are two types of photoreceptors – rods and cones. Atrophy begins with rods, that is, the cells responsible for vision at dawn and in the dark. As the next cells disappear, the patient’s field of vision narrows to preserve the central vision zone, consisting mainly of cones. Cones are photoreceptors that allow us to see details, colors, read and perform precise actions. In most patients with retinitis pigmentosa, cones begin to fade at an older age. An exception is a certain type of retinitis pigmentosa called “cone-rod dystrophy,” in which the cones atrophy first and then the rods.

In addition to atrophy of photoreceptors, with retinitis pigmentosa, posterior subcapsular cataracts occur in 39-72% of cases, and hearing impairments that have nothing to do with Usher’s syndrome in 30% of cases.

Due to the nature of the disease, the first difficulties appear in childhood, especially at dawn and at night. Parents notice that the child is unable to find or complete certain tasks in low light conditions. For example, a child cannot go to the toilet at night in an unfamiliar place.

The most severe type of retinits pigmentosa is Leber’s hereditary optic neuropathy LHON, in which both types of photoreceptors, i.e., cones and rods, are affected.

Inheritance routes

Retinitis pigmentosa is a group of diseases that are inherited, although there may be cases in which no one in the family has had this disease before. Sometimes retinitis pigmentosa can be part of disease syndromes, that is, a situation in which visual impairment is accompanied by other diseases. The most common syndromes of diseases involving retinitis pigmentosa are Ascher’s syndrome (visual impairment occurs along with hearing impairment), Laurence-Moon-Biedl syndrome or Refsum’s syndrome.

There are 4 routes of inheritance, and all of them can be found in retinitis pigmentosa:

To understand how difficult it is to diagnose and treat this disease, it is worth noting that so far 150 genetic mutations have been discovered in retinitis pigmentosa.

Such a large variability in the mode of inheritance creates enormous difficulties in diagnosis, since even a genetic examination does not guarantee answers to all questions. This is partly due to the cost of examining a huge number of genes, and partly due to the inability to isolate all damaged genes, since, as mentioned earlier, sudden gene mutations are possible in retinitis.

What are stem cells?

Many myths and inaccuracies have emerged around stem cells. First of all, it’s worth noting that stem cells are not just one type of cell, but many types. Among them, there are both undifferentiated stem cells and mesenchymal cells, which are currently being intensively researched and are mainly used in clinical research and scientific experiments. Mesenchymal stem cells can be obtained from three sources: bone marrow, adipose tissue, or the umbilical cord, namely the connective tissue that surrounds blood vessels called gelatin of Wharton.

Regardless of the type of tissue from which we want to obtain stem cells, all methods are to isolate and then stimulate the stem cells to multiply. For example, it takes about two months to obtain stem cells from gelatin of Wharton from the moment of harvesting the umbilical cord to receiving the finished product.

It is worth emphasizing that in the case of mesenchymal stem cells, there are no ethical problems, as in the case of undifferentiated stem cells of human embryos.

It is also possible to transplant cells from another person without the risk of transplant rejection. This is because stem cells are almost invisible to the body’s immune system.

How can stem cell therapy help patients with retinitis pigmentosa?

Mesenchymal stem cells should be considered as an additional secretory gland, which, under certain conditions, produces substances that improve blood supply, have an anti-inflammatory effect, and promote regeneration. Mesenchymal stem cells have an anti-carcinogenic effect. In addition to the therapeutic effect, which consists in changing the cellular environment and transferring damaged cells to a mode of proper functioning, stem cells can also be transformed into other cells. It is worth emphasizing that the number of cells that are to be transformed into missing cells is small. In animal studies, it was revealed that the cells that have arisen have the properties of missing nerve cells, they are able to secrete substances specific to them. However, it is not known whether the newly formed cells are capable of developing synapsis or connections between nerve cells. In the case of complex tissues, such as the retina, the creation of new cell layers at this stage of the development of science is impossible.