No tumors were found over 2–4 years in four patients with complete cervical spinal cord injury after neural progenitor transplantation
No tumors were found over 2–4 years in four patients with complete cervical spinal cord injury after neural progenitor transplantation
Nature Medicine has published the results of the first human trial of this type of transplant. Four men received two million cells each, 14–28 days after injury. The purpose of this phase 1 trial was to assess the safety of the procedure.
After a complete cervical spinal cord injury, signals from the brain cannot reach the body below the damaged area. In the double neural bypass, implants detected the intention to move an arm, then bypassed the interruption by electrically stimulating the muscles and spinal cord. In this trial, surgeons injected cells directly into the damaged area of the spinal cord.
The transplant consisted of neural progenitors, which are cells that can develop into neurons and into cells that cover nerve fibers with the protective sheath called myelin. The progenitors were grown from iPSC, which are reprogrammed cells from donated umbilical cord blood that have regained the ability to develop into different tissues. A single cell line can be used to manufacture standardized batches in advance for several patients.
Before transplantation, the laboratory tested the cells for genetic changes and guided them toward a more mature state to reduce the risk of excessive growth. The patients then received tacrolimus for nine months. This drug suppresses the immune system and helps prevent the body from rejecting the donor cells.
During the first year, physicians recorded 84 adverse events. These included two moderate surgical complications and 22 mild or moderate reactions associated with tacrolimus. MRI and positron emission tomography (PET), which measures metabolic activity in tissues, showed no evidence of tumor growth at the transplant site. Over 2–4 years of follow-up, none of the four patients developed a severe reaction related to the cell product, and none experienced deterioration in neurological function.
All participants had higher scores for movement and independence in daily activities after one year. Two regained voluntary movement below the injury.
These improvements cannot be attributed to the transplant without comparison with similar patients who did not receive the cells. Some function returns naturally during the first months after injury. The next study will need to distinguish this natural recovery from any effect of the transplanted cells. The current study addressed a different question: whether a standardized cell product could be prepared, injected into an injured spinal cord, and followed for several years without signs of tumor growth.