Japanese researchers conducted the world's first surgery to implant induced pluripotent stem (iPS) cells into a human body

Japanese researchers conducted the world's first surgery to implant induced pluripotent stem (iPS) cells into a human body, representing a major step forward for regenerative medicine.

In the clinical test, a sheet of retinal pigment epithelium cells created from iPS cells was implanted into a female patient with age-related macular degeneration (AMD), an intractable disease that can lead to blindness in older people.

It is the first time that iPS cells have been implanted in a human body since they were first developed in 2007. The operation brings iPS cell technology closer to clinical application.

The patient is in a stable condition and is expected to leave the hospital in about a week, researchers from the two institutions involved in the project said.

The clinical trial, conducted on Sept. 12, was led by Masayo Takahashi, an ophthalmic researcher at Riken’s Center for Developmental Biology in Kobe. It was aimed at confirming the safety of iPS cell surgery. The team plans to conduct similar surgeries on five more patients.

“As I was observing the surgery, I became confident that the method has promising prospects,” Takahashi said at a news conference that day. “I'm determined to make every effort (to realize its clinical application).”

At a second news conference on Sept. 13, Yasuo Kurimoto, an ophthalmologist at the Institute of Biomedical Research and Innovation Hospital in Kobe, which conducted the operation, said the patient's condition already shows signs of improvement.

"My vision became brighter, and doctors' smocks look clean white now," the woman was quoted by Kurimoto as saying.

"We didn't anticipate the patient's condition would improve overnight," Kurimoto said. "It could be because the transplanted cells are working, or because the damaged area was removed. We must carefully evaluate the outcome," he said.

The patient is a Hyogo Prefecture resident in her 70s, according to Riken. She has been suffering from deteriorated vision due to AMD, which could not be alleviated by existing treatments.

The trial surgery was authorized by the health ministry in July 2013. The research team created iPS cells using skin cells taken from the patient last November. They then used the iPS cells to develop retinal pigment epithelium cells in sheet form in the following 10 months.

During the surgery, doctors removed damaged cells and non-essential blood vessels from behind the retina of the patient’s right eye. They then successfully implanted the sheet of retinal pigment epithelium cells, measuring 3 millimeters long and 1.3 millimeters wide, on the affected area.

The condition of the patient's eye and the implanted cell sheet will be periodically monitored over the next four years to assess whether there are any side effects from the operation. The researchers will also keep track of developments in her AMD symptoms and the quality of her vision.

As iPS cells can become cancerous or develop into unintended types of cells, the researchers used a method to exclude genes that could cause cancer in developing iPS cells. They also confirmed that the patient's genes used to develop the iPS cells have no abnormalities.

Kyoto University's Shinya Yamanaka, a Nobel Prize-winning iPS cell researcher who helped with the project, expressed confidence in the surgery’s outcome.

“We've reduced the potential risk as much as we could given the current level of medical science,” he said.

THE ASAHI SHIMBUN