A complication from stem cell therapy has led to the death of a patient with kidney disease. The patient suffered tissue damage and died from an infection after stem cells were injected into the kidney, according to a report by Canadian and Thai researchers in the Journal of the American Society of Nephrology.

The incident highlights the gap between stem cell research and treatment. Animal studies appeared to show that injecting stem cells directly into the kidney would be safe. Instead, it caused tissue damage -- called angiomyeloproliferative lesions -- at the injection sites.

Dr Duangpen Thirabanjasak, from Chulalongkorn University, who led the research, said: "This type of lesion has never been described before in patients, and we believe that this is either formed directly by the stem cells that were injected or that the stem cells caused these masses to form."

Andras Nagy, of Toronto's Mount Sinai Hospital, and Susan Quaggin, of the University of Toronto wrote in the journal that caution was needed with stem cell therapies - particularly if unregulated private clinics are offering them.

They wrote: "Premature enthusiasm and protocols that are not fully vetted are dangerous and result in negative publicity for the field of stem cell research, and more importantly, may result in disastrous outcomes with no benefit to the patient. Although there is promise, a large gap still exists between scientific knowledge and clinical translation for safe and effective stem cell-based therapies." ~BBC News, June 17