Alport syndrome is a rare genetic condition characterized by kidney disease, hearing loss, and eye abnormalities. The disease is caused by a mutation in the COLA3, COLA4, or COLA5 gene, which provide instructions to make a connective tissue protein called collagen type 4.
What are stem cells?
The human body consists of many different cell types. Most cells are specialized and carry out a specific function and cannot be converted into another cell type. Stem cells are cells whose fate is not yet determined, and they can still develop into different cell types.
Cells considered for stem cell therapy are either derived from embryos (embryonic stem cells) or adult tissues (adult stem cells). Embryonic stem cells, harvested from eggs fertilized outside the body, can develop into any cell type. Adult stem cells, on the other hand, can only develop into certain cell types, depending on their origin. The use of embryonic stem cells is tightly controlled due to ethical reasons. As a result, researchers try to alter adult stem cells in a way that they can produce a greater variety of cells and show properties of embryonic stem cells.
How stem cell therapy for Alport syndrome works
Alport syndrome patients tend to lose a type of specialized kidney cell called a podocyte. Podocytes surround the capillary blood vessels in the kidneys and are an essential component of the kidney’s filtration system. This loss appears to be involved in disease progression. Stem cell therapy approaches for Alport syndrome are aimed at replacing these cells. They involve transplanting stem cells from a healthy donor, whose collagen-type 4-encoding genes are intact, into patients.
Studies on stem cell therapy
Stem cell therapies for Alport syndrome have only been tested in mouse models, and they have not yet progressed to human clinical trials. Mouse studies are investigating what kind of stem cells are suitable and have the potential to become podocytes and to restore kidney function.
A study, published in the journal of the American Society of Nephrology in 2009, studied stem cell transplantation in mice that had mutations in the Col4A3 gene. The researchers tested different approaches and infused the mice with stem cells derived from the bone marrow of healthy mice, as well as embryonic stem cells from mice or humans. Infusion with either cell type improved kidney function and extended survival.
Another study was published in the journal Stem Cells and Development in 2016, in which researchers transplanted human chorionic stem cells taken from the membrane surrounding the fetus into mice lacking a functional Col4A3 gene. The transplant significantly improved kidney function.
In a further study published in Nature Scientific Reports in 2017, Alport syndrome mice were injected with amniotic fluid stem cells taken from the fluid surrounding the fetus. Before transplantation, the mice had increased levels of a protein called VEGF that promotes the growth of blood vessels in the glomeruli, which are the kidney’s filtering units. The abnormal growth of blood vessels in the kidneys is thought to cause kidney scarring and to contribute to kidney damage. In mice who received the stem cell transplant, VEGF levels normalized and disease progression was decreased.
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