Brain cells from a rare New Zealand pig will be used in an attempt to regrow dying human brain cells in Parkinson's patients.

The world first trial on four New Zealanders with Parkinson's disease will take brain cells from the Auckland Island species of pig and inject them into the human brains.

The cells will be directed towards the damaged parts of the patients' brains.

Parkinson's disease causes tremors, loss of movement and cognitive impairment and occurs when nerve cells in the brain die or are damaged.

Scientists hope a growth factor hormone released by the pig brain cells will cause the dying human cells to grow back and reconnect to existing cells.

The Auckland Island species has been selected for the trial because it is free of viruses usually carried by pigs.

Neurologist Dr Barry Snow says animal studies have shown the "remarkable regrowth" of damaged cells.

The human trial will kick off in September with the first patient, while the other three will be injected at a later date.

There is currently no cure for Parkinson's disease and treatments become ineffective after a few years.