Chinese scientists and doctors began a landmark clinical trial using a collagen complex and stem cells to repair damaged human spinal cord.

Six patients have signed up for the trial and the first surgery was completed on Friday, said a statement from the Chinese Academy of Sciences (CAS) said.

The research was led by Dai Jianwu, a research fellow with the Institute of Genetics and Development Biology of CAS.

The surgery done a patient on Friday went smoothly and he is in a good condition, Dai said.

The patient was implanted with mesenchymal stem cells and a collagen complex made up of collagen scaffold fibers, also described as collagen tubes, with collagen binding brain-derived neurotrophic factor (BDNF), a protein to support and encourage the growth of neurons, Dai was quoted by state-run Xinhua news agency.

The collagen complex acts as a bridge for nerves to reconnect and mesenchymal stem cells help tissue recovery, Dai said.

"Previous tests on rats and dogs showed positive results," he said.

In this stage, scientists aim to test the safety of surgery?and perfect its design, he said.

In the next stage, about 20 to 30 more patients will be involved, he added.

The trial is the first in China and probably the first across the world. 

"We hope the research can shed light on this clinical challenge," Dai said.