Saving limbs by growing new blood vessels

A stem cell treatment developed by researchers in Japan avoids the need for limb amputation due to blocked blood flow. Preliminary clinical trials showed that the treatment reduced pain and eliminated the need for amputations¹ — but before being approved for clinical use, these results must be validated by randomized controlled trials.

In 2009, researchers at the Institute of Biomedical Research and Innovation, the Translational Research Informatics Center, and Kobe City Medical Center General Hospital conducted a clinical trial involving 17 patients with critical ischemia in their legs, a condition in which a thickening of the artery walls limits blood flow, causing pain while walking, skin ulcers and gangrene, and ultimately leading to amputation.

The researchers used a chemical treatment to release CD34⁺ stem cells, which can differentiate into the inner lining of blood vessels, from the patients’ bone marrow into their blood, then harvested them and transplanted them into the ischemic legs. The CD34⁺ stem cells also secrete cytokines, which can stimulate new blood vessel formation, explains Atsuhiko Kawamoto, lead author of the study.

The researchers measured several parameters to monitor the patients’ pain levels and walking ability during the 12 weeks after treatment. Ischemia symptoms gradually abated in all subjects, and no serious side-effects or adverse results relating to the cell therapy were reported. Even at the lowest dose of stem cells, no patients underwent amputations during the trial.

The patients were most gratified by the healing of ulcers and gangrene. “These are very painful, and patients often have to take care of wounds by themselves,” explains Kawamoto. “It's very tough, so the patients were very happy when the wounds completely healed.”

The researchers monitored the patients for four years. In a follow-up study, they reported that the improvements continued for four years, with no reports of adverse effects from the treatment. In about 85 per cent of patients, critical limb ischemia had disappeared four years after the trial, although four subjects died of unrelated cardiac complications².

CD34⁺ therapy has not yet been evaluated in a randomized controlled clinical trial — the gold standard of clinical evaluations.

Kawamoto plans to start such a trial soon, measuring the performance of the therapy against standard care over the course of one year. Data gathered in the preliminary trial and in a separate study³ have helped the researchers identify key factors to monitor during the randomized trial. “A randomized clinical trial is necessary for regulatory approval in Japan,” says Kawamoto. “If it’s successful, we can continue to commercialization.” 

1. Kawamoto, A., Katayama, M., Handa, N., Kinoshita, M., Takano, H., Horii, M. et al. Intramuscular transplantation of G-CSF-mobilized CD34⁺ cells in patients with critical limb ischemia: A phase I/IIa, multicenter, single-blinded, dose-escalation clinical trial. Stem Cells 27, 2857-2864 (2009). | article
2. Kinoshita, M., Fujita, Y., Katayama, M., Baba, R., Shibakawa, M., Yoshikawa, K. et al. Long-term clinical outcome after intramuscular transplantation of granulocyte colony stimulating factor-mobilized CD34 positive cells in patients with critical limb ischemia. Artherosclerosis 224, 440-445 (2012). | article
3. Fujita, Y., Kinoshita, M., Furukawa, Y., Nagano, T., Hashimoto, H., Hirami, Y., Kurimoto, Y. et al. Phase II clinical trial of CD34⁺ cell therapy to explore endpoint selection and timing in patients with critical limb ischemia. Circulation Journal 78, 490-501 (2014). | article