One, two, three steps toward cell therapy for stroke.

Many clinical trials have failed despite positive laboratory findings. Stroke clinical trials are no exception, with tissue plasminogen activator (tPA) still the only effective drug for stroke with limited therapeutic window. In order to enhance the successful outcome of novel therapies in the clinic, initiatives for translational research guidelines have been pursued. In particular, the advancement of stem cell therapy for stroke from the laboratory to the clinic has now been guided by a set of recommendations called Stem cell Therapeutics as an Emerging Paradigm for Stroke or STEPS. We review here the major criteria for preclinical studies of stem cells arising from the three STEPS meetings in an effort to further emphasize the need for careful and rigorous assessment of the safety, efficacy, and mechanism of action associated with stem cell therapy for stroke. Learning from our previous mistakes and identifying gaps in knowledge will likely prevent stem cell therapy from becoming yet another statistic of failed clinical trial in stroke.