Despite many concerns about stem cell therapies, Japan has just approved stem cell therapy for spinal cord injury. However, according to the experts asked for comments by Nature – ten specialists in the science of stem cells or spinal cord injuries who were not involved in the work – evidence that the treatment work is insufficient. In addition, they suggest that the clinical trial on which the approval was based was too small and poorly designed.

The Japanese stem cell therapy, called Stemirac, consists of isolating the patient's mesenchymal stem cells, a type of "adult" stem cells – from their bone marrow, to extend them in large numbers to the laboratory and to reinject them intravenously patient. within 40 days after a spinal cord injury. Expanded stem cells should restore damaged nerve cells and improve paralysis by reducing inflammation and protecting existing neurons. Researchers involved in the development of Stemirac even suggest that some stem cells could turn into neurons to replace those lost as a result of the injury. However, independent scientists claim that, although MSCs may have certain characteristics, their neuronal function has not been demonstrated.

The safety of various types of autologous stem cell infusions – derived from a patient's own cells – has not been fully established. Previously, trials on stem cell therapies had reported blood clots and dangerous lesions (1). In addition, stem cells are often trapped in the lungs where they can not provide any therapeutic benefit.

The Health Ministry committee gave the company the go-ahead last November to commercialize stem cell therapy developed jointly with Professor Osamu Honmo of the Sapporo Medical University. Since Jan. 24, the company is now authorized to market and sell the treatment as long as it collects data from participants over the next seven years to demonstrate its effectiveness.

The recent approval departs from established probate procedures to ensure patient safety by conducting valid clinical trials. Many other countries require rigorous clinical trials with hundreds of patients before they can sell new treatments. Japan has put in place a program to accelerate regenerative medicine treatments with minimal evidence of effectiveness, based on the collection of monitoring data.

Stemirac's approval is based on the results of an unpublished clinical trial involving only 13 patients with spinal cord injuries. According to the results, 12 out of 13 patients improved from at least one level of the deficiency scale of the American Spinal Injury Association after six months. In other words, patients have regained some degree of sensation and movement. However, the trial was not double-blind – the gold standard for the evaluation of new treatments – making it difficult to determine the long-term effectiveness of treatment. Without double blind, it remains to be determined whether patients would have recovered naturally.

Masanori Fukushima, a Japanese oncologist involved in the work, says the results are "unprecedented" and that most patients have been too badly injured to recover naturally.

(1) Thirabanjasak, D., Tantiwongse, K. and Thorner, P.S. Angiomyeloproliferative Lesions After Autologous Stem Cell Therapy. Journal of the American Society of Nephrology (2010) DOI: 10.1681 / ASN.2009111156

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