Doctors have successfully transplanted insulin-producing cells from a mother to her diabetic daughter.
Many people with diabetes must have regular insulin shots
A team at Japan's Kyoto University Hospital removed islet cells from the healthy woman, and transplanted them into her 27-year-old daughter.
The breakthrough could be a much more effective way to treat type 1 diabetes.
Islet cells have previously been taken from dead organ donors and were often damaged from cold storage or by toxins in the blood after death.
The cells, found in the pancreas, produce a hormone called insulin which regulates sugar levels in the blood.
Type 1 diabetes - also known as insulin-dependent or immune-mediated diabetes - destroys these cells, and thus the body's ability to produce insulin.
People with the condition must regularly boost insulin levels, either by injection or by wearing a pump which dispenses the hormone under the skin.
If the hormone level is not properly controlled it can lead to complications such as blindness, or in extreme cases a coma, and death.
Transplant surgery can potentially solve the problem by providing patients with a fresh supply of insulin-producing islet cells.
Dr James Shapiro, of the University of Alberta, was one of the surgeons who led the Kyoto team.
He said the islet cells began to produce insulin minutes after being transplanted into the daughter.
Previously, she had experienced low blood sugar coma attacks, but following surgery her blood sugar control has been transformed.
Dr Shapiro said previous islet cells from brain dead donors were often severely damaged.
"Our expectation is that these islets from near-perfect organs will work better, although it's too early to tell.
"Living donor islet transplants could allow many more desperate patients with type 1 diabetes to get successful islet transplants.
"The donor operation is relatively safe, but is not entirely devoid of serious potential risk."
Jo Brodie, of the charity Diabetes UK, said: "The success of this groundbreaking operation is very exciting news for us.
"This could lead to many more people with Type 1 diabetes receiving islet cell transplants from living donors.
"It is also another step forward in finding a cure for diabetes. This is the first operation of its kind so we will be following the progress of the patient and any future operations very closely."