The child was born with hyperammonaemia and required a liver transplant. However, this is unsafe for newborns, and babies born with the condition have to wait several months before they are able to have the operation. The clinical trial was for a 'bridge-treatment', designed to minimise the effects of the disease until a transplant became possible.
'It was often the case that babies with this condition died from seizures or suffered brain damage before the liver transplant could take place,' said the trial's leader Dr Mureo Kasahara, head of the transplant unit in the National Centre for Child Health and Development in Tokyo, Japan. 'The latest case is hugely significant in that we have proved the effectiveness of the method'.
Hyperammonaemia affects one in 8000 to 44,000 people, not always from birth. Ammonia is not converted to urea by the liver and excreted, but instead builds up to toxic levels in the blood.
The researchers used human embryonic stem cells from fertilised eggs to make liver cells and delivered them to a single infant patient with hyperammonaemia. This is the first human stem cell therapy trial in Japan and the first case in the world to apply liver cells derived from stem cells.
The baby in this study was injected with 190,000 stem-cell-derived liver cells six days after birth. The toxic ammonia concentration in the infant's blood stopped rising, confirming that the injected liver cells had reached their destination in the liver. The baby subsequently received a liver transplant after reaching the safe weight of six kilograms and was able to be discharged from hospital.
In Europe, the US and occasionally in Japan, the alternative bridge-treatment for managing this condition is to use liver cells from dead donors. These, once injected into the newborn babies with the condition, can keep the liver functioning until liver transplantation can be performed. However, securing donor liver cells readily and steadily is not always feasible and stem-cell-derived liver cells can potentially solve this problem.
The fertilised eggs used to generate the stem cells were donated with the consent of families who have completed fertility treatment.