A hospital in Tokyo said it successfully transplanted liver cells derived from human embryonic stem (ES) cells to a baby with a potentially life-threatening disease, marking the first time ES cells have been used to treat human diseases in Japan.

The National Center for Child Health and Development (NCCHD) announced on May 21 that it carried out a clinical trial to transplant the cells into a baby with a severe liver disease. The transplant was a success, and the baby’s condition is now stable, according to the NCCHD.

The center said it was the world’s first transplant of liver cells derived from ES cells.

The baby developed a type of urea cycle disorder called citrullinemia type 1 in October 2019. The baby was just two days old.

The disease prevents the body from breaking down toxic ammonia due to a congenital lack of liver enzymes. An increase in the concentration of ammonia in the blood can cause permanent brain damage and may lead to death.

Citrullinemia type 1 is an intractable hereditary disease. About one in 530,000 people develop the disease. Fewer than 100 people are estimated to have the disease in Japan.

Treatment requires a liver transplant. But from a safety standpoint, it is difficult to transplant livers to babies until they reach the age of 3 to 5 months, when they weigh at least 6 kilograms.

The cellular transplant was conducted as a “bridge treatment” to improve liver function until the baby became old enough to receive a new liver.

The liver cell transplant procedure was performed when the baby was just six days old. Medical experts injected 190 million ES cell-derived liver cells into the baby’s abdomen over two days.

The baby was discharged from the hospital after the transplant. Then, around six months after birth, the baby underwent a living liver transplant from the father.

The administration of immunosuppressants prevented the baby’s body from rejecting the new liver, allowing the patient to be discharged from the hospital the following month.

The NCCHD aims to transplant ES-derived liver cells to five patients by 2022 to confirm the efficacy and safety of the treatment.

“Regenerative medicine will become a great blessing for patients with a liver disease,” said Mureo Kasahara, head of the Center for Organ Transplantation at the NCCHD.