Federal regulators have cleared Geron, a California biotechnology company, to proceed with the world’s first test of embryonic stem cell treatment on patients with spinal cord injuries.

The Food and Drug Administration (FDA) revoked a clinical hold on the study that was put in place last summer when Geron revealed that mice had developed cysts during the experiment. FDA officials declined to comment on why they decided to lift their hold on the study.

With patient recruitment could begin as early as next month, many of the ethical questions—that initially delayed Geron’s study—remain unanswered.

If part of the study’s intention is to test the safety of stem cell treatment, how would the informed consent be structured? How can Geron address ethical issues raised by the use of embryonic stem cells? How might this research affect peer organizations that are also working toward similar goals? How might the roles and responsibilities of institutional review boards (IRBs) and embryonic stem cell research oversight (ESCRO) committees change if this type of research becomes more mainstream?