Ethics, stem cells and spinal cord repair.

Attempted repair of human spinal cord injury by transplantation of stem cells depends on complex biological interactions between the host and graft. Extrapolating results from experimental therapy in animals to humans with spinal cord injury requires great caution. There is great pressure on surgeons to transplant stem cells into humans with spinal cord injury. However, as the efficacy of and exact indications for this therapy are still uncertain, and morbidity (such as rejection or late tumour development) may result, only carefully designed studies based on sound experimental work which attempts to eliminate placebo effects should proceed. Premature application of stem cell transplantation in humans with spinal cord injury should be discouraged.