BEIJING (XINHUA) - Chinese researchers are studying the use of stem cell technology in the treatment of people critically ill with the coronavirus, the Science and Technology Daily reported.

Four Covid-19 patients who received stem cell treatment while in a serious condition have been discharged from hospital after recovering, and the clinical trial of the therapy will be further expanded, Vice-Minister of Science and Technology Xu Nanping, was cited by the paper as saying.

Stem cells can self-renew or multiply while maintaining the potential to develop into other types of cells. They can become cells of the blood, heart, lungs or other body parts.

Stem cells also have a strong secretory function, promoting the formation of new blood vessels, cell proliferation and differentiation, and inhibiting inflammatory response, experts say.

Stem cell therapy has also been used in treating H7N9 avian flu and showed good results.

According to the Ministry of Science and Technology, the Chinese Academy of Sciences has developed a new stem cell drug, CAStem, which has shown promising results in treating Covid-19 in animal experiments.

The research team has applied for urgent assessment by the National Medical Products Administration. Approvals by the ethics committee, and clinical observation and evaluation are in progress.

Another research team from the fifth medical centre of the Chinese PLA General Hospital is cooperating with hospitals and institutions in Wuhan - the epicentre of the epidemic - and northern China's Tianjin municipality to conduct clinical research on the safety and effectiveness of mesenchymal stem cell therapy in treating Covid-19 patients.

A research team at the School of Medicine of the Tongji University is studying universal lung stem cell therapy that can be widely used in the epidemic control. The therapy is expected to enter the clinical stage soon.

Professor Zuo Wei, head of the research team and the chief scientist of a national key research project on stem cells, said that the research now mainly focuses on improving the condition of critically ill Covid-19 patients.

He explained that when the patients are in a severe condition, the cause of deterioration and even death is the "inflammatory storm", when the human immune system is over-activated by the infection.

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That will damage the lungs and impair breathing. Some severe patients may have respiratory failure.

"Lung inflammation and injury are the focus of the treatment of severe patients," Prof Zuo said.

The damage to lung tissue can be fatal, and stem cell therapy is expected to help repair the damage, Prof Zuo added.

Currently, three kinds of stem cells - mesenchymal, lung and embryonic stem cells - are used in treatments. Researchers usually inject stem cell products into the lungs.

Stem cells can improve the immune microenvironment in the lungs and reduce the risk of pulmonary failure caused by inflammation.

Stem cells have the potential of self-renewal and differentiation, and can develop into corresponding functional cells and alveoli, and then repair the damaged tissue, Prof Zuo said.

However, the wider use of stem cell technology to treat Covid-19 is still some time away.

The safety and effectiveness of a new drug or therapy need to be verified with sufficient clinical trials, Prof Zuo stressed.