Editing genes a possible way to cure sickle cell disease

A single gene mutation can hinder the flow of oxygen in the body and make millions sick world over. Now scientists at Stanford University might have found a potential cure for this life-threatening blood condition, the sickle cell disease.

It is more common in people of sub-Saharan, South American, Caribbean, Central American, Saudi Arabian, Indian, Turkish, Italian and Greek descent, according to the Center for Disease Control and Prevention in America. A change in the shape of red blood cells causes people to suffer from anaemia, organ damage, episodic pain and hypertension which can cause heart failure.

Scientists at Stanford University School of Medicine have used a gene editing tool to repair the gene that causes sickle cell disease. "What we've finally shown is that we can do it. It's not just on the chalkboard," said Dr Matthew Porteus, the senior author of the study published in the journal Nature.

Known as the CRISPR-Cas9 editing tool, the scientists used stem cells in patients with sickle cell disease to correct the genetic mutation. With the study and unpublished findings from his lab, Porteus believes his team has amassed enough proof to start planning the first human clinical trial.

"We think we have a complete data set to present to the FDA (Food and Drug Administration) to say we've done all pre-clinical experiments to show this is ready for a clinical trial," Porteus told Reuters by phone.

How does gene editing work?

CRISPR works as a type of molecular scissors that can selectively trim away unwanted parts of the genome, and replace it with new stretches of DNA.

Porteus' team tried a new technique used a harmless virus to introduce the repair mechanism into cells.

After a series of tests in healthy cells, the team tested the gene editing system in blood-forming cells from four patients with sickle cell disease. They showed they could correct the mutation in 30 to 50 percent of these diseased cells.

Porteus said the findings were very encouraging because prior studies have shown that if you can correct mutations in 10 percent of cells, that should create enough to cure the disease.

Stanford is now scaling up its laboratory processes to support human trials.

The process will involve using chemotherapy to wipe out a patient's blood system but not their immune system, as is done in a stem cell transplant. Then, the team would inject the patient's own corrected stem cells, which the researchers hope would engraft into the bone marrow and produce healthy blood cells.

At present, the only potential long-term treatment option is a bone marrow transplant which is costly and complicated.

What happens in sickle cell disease?

In sickle cell disease, the body makes mutant, sickle-shaped haemoglobin, the protein in red blood cells that carries oxygen to the body's tissues.

Unlike healthy red blood cells which are round and mobile, in sickle cell patients, the cells change shape, harden and become sticky. This causes the cells to die early—resulting in a shortage of red blood cells—and they can clog smaller blood vessels.

Symptoms often don't appear until an infant is at least four months old and include infections, pain, and swollen abdomen, hands and feet. Sickle cell can also delay puberty and impede growth.