The results obtained by researchers from the University of Washington University School of Medicine in St. Louis showed that the CRISPR/Cas9 technology may be promising as a treatment for diabetes, especially forms caused by a single gene mutation, and may also be used in the future for some patients with more common forms diabetes, such as type 1 and type 2.
To conduct the study, scientists transformed the skin cells from a patient with a rare genetic form of insulin-dependent diabetes, called Wolfram syndrome, into induced pluripotent stem cells (iPSCs). They were then differentiated into beta cells, in which the defect causing diabetes was corrected using the CRISPR/Cas9 gene editing tool, and the cells were implanted into mice.
The study was published April 22 in the journal Science Translational Medicine.
Wolfram syndrome is a serious hereditary disease with a progressive course, which includes 4 components: diabetes mellitus, diabetes insipidus, optic nerve atrophy and sensorineural hearing loss. Diabetes usually develops in childhood or adolescence, and patients are in dire need of insulin replacement therapy, which requires injections of insulin several times a day. Most patients have problems with vision and balance, as well as other complications. In many patients, this syndrome leads to early death.
«This is the first time CRISPR has been used to fix a patient’s diabetes-causing genetic defect and successfully reverse diabetes», – said co-senior investigator Jeffrey R. Millman, PhD, an assistant professor of medicine and of biomedical engineering at Washington University.
«For this study, we used cells from a patient with Wolfram syndrome because, conceptually, we knew it would be easier to correct a defect caused by a single gene. But we see this as a stepping stone toward applying gene therapy to a broader population of patients with diabetes».
Wolfram syndrome is caused by mutations in a single gene, which allows researchers to determine whether a combination of CRISPR using stem cells can correct a gene error and help cure diabetes.
A few years ago, Millman and his colleagues discovered a method for converting human stem cells into pancreatic beta cells, which regulate blood sugar by synthesizing insulin. Recently, the team has developed a new way to more efficiently convert human stem cells into insulin-producing cells that control blood sugar levels much better.
In a new study, scientists took additional steps to obtain cells from patients and use the CRISPR/Cas9 tool to correct the mutation in the gene that causes Wolfram syndrome (WFS1). Researchers then compared cells with the edited gene and beta cells from the same stem cell population that were not edited using CRISPR.
In laboratory conditions and after transplantation into mice with severe diabetes, the obtained beta cells edited with CRISPR secreted insulin more efficiently in response to glucose. Animals successfully cured diabetes, and blood sugar remained in the normal range for all six months of observation.
In the control group of mice, transplanted unedited beta cells produced insulin, which, however, was not enough to reverse diabetes.
«We basically were able to use these cells to cure the problem, making normal beta cells by correcting this mutation», – said co-senior investigator Fumihiko Urano, MD, PhD, Professor of medicine and a Professor of pathology and immunology. «It’s a proof of concept demonstrating that correcting gene defects that cause or contribute to diabetes — in this case, in the Wolfram syndrome gene — we can make beta cells that more effectively control blood sugar. It’s also possible that by correcting the genetic defects in these cells, we may correct other problems Wolfram syndrome patients experience, such as visual impairment and neurodegeneration».
In the future, using CRISPR to correct certain mutations in beta cells may help patients whose disease develops due to multiple genetic and environmental factors, such as type I diabetes, caused by the autoimmune process that destroys beta cells, and type II diabetes, which is closely associated with obesity and a systemic process called insulin resistance.
«We’re excited about the fact that we were able to combine these two technologies – growing beta cells from induced pluripotent stem cells and using CRISPR to correct genetic defects», – Millman said. «In fact, we found that corrected beta cells were indistinguishable from beta cells made from the stem cells of healthy people without diabetes».
In the future, the process of creating beta cells from stem cells should become easier, researchers say. For example, scientists have developed less intrusive methods for obtaining iPSCs from blood, and they are working on collecting stem cells from urine samples.
«In the future, we may be able to take a few milliliters of urine from a patient, make stem cells that we then can grow into beta cells, correct mutations in those cells with CRISPR, transplant them back into the patient, and cure their diabetes in our clinic. Genetic testing in patients with diabetes will guide us to identify genes that should be corrected, which will lead to a personalized regenerative gene therapy», – Urano said.