How cell therapy differs from gene therapy

Prof Anna David leads a team of scientists and clinicians at UCL that are finding new and fascinating ways to treat diseases in the unborn.

Brittle bone disease

One such disease is also known as brittle bone disease, also known as osteogenesis imperfecta, which sadly occurs in about one in 20,000 births.

Brittle bone disease can be devastating for young children because their bones are prone to fracture multiple times. Affected children may also present with shorter height, breathing problems, neurological abnormalities, hearing loss or other complications. The fractures can be very painful and there is often a stark reduction in quality of life.

The reason why some babies are born with brittle bone disease is that they have a problem forming the connective tissue that is essential for healthy bone growth and development. Most cases are caused by mutations in the COL1A1 and COL1A2 genes, both of which code for type I collagen.

For the moment, there is no cure. Treatment is limited and patients rely on painful physiotherapy and symptom control.

What is cell therapy?

Cell therapy is the transfer of cells into a patient in order to improve or even cure a disease. The origin of the cells depends on the treatment. The transplanted cells are often a type of adult or fetal stem cell which have the ability to divide and self renews as well as provide cells that mature into the relevant specialised cells of the tissue.

A common form of cell therapy is bone marrow transplantation, which has been performed for over 40 years.

Several investigative protocols of cell therapy involve the transfer of adult T lymphocytes that are genetically modified to increase their immune potency and can self renew and kill the disease-causing cells.

Stem cells from umbilical cord blood and other tissues are being developed to treat many genetic diseases and some acquired diseases. Stem cells from the fetus may be better than adult stem cells; they divide more and differentiate better into the definitive cell type, for example, fetal liver stem cells produce much more bone than adult liver stem cells.

How are gene therapy and cell therapy-related?

Both approaches have the potential to treat the underlying cause of both genetic and acquired diseases by replacing the missing proteins or cells, and they may suppress the expression of proteins that are toxic to cells.

Whereas gene therapy involves the transfer of genetic material into the appropriate cells, cell therapy is the transfer of cells to a patient. Gene therapy involves the transfer of genetic material usually in a carrier or vector, and the uptake of the gene into the appropriate cells of the body. Cell therapy involves the transfer of cells with the relevant function into the patient.

Risks of cell therapy

Risks of cell therapy also include the loss of tight control over cell division in the stem cells. Theoretically, the transplanted stem cells may gain a growth advantage and progress to a type of cancer or teratomas, but this is only rarely seen in stem cell transplantation and has not yet been seen in fetal stem cell transplantation.

Since each therapy has its potential risks, patients are strongly encouraged to ask questions of their investigators and clinicians until they fully understand the risks.

Stem cells can theoretically improve the disease condition for as long as the modified stem cells remain life, potentially the entire lifetime of the patient.

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