Novel stem cell technology develops a new cell for repairing spinal cord injuries

Transplanting immature support cells called astrocytes, which were first generated in tissue culture from stem cell-like cells called glial restricted precursors, resulted in much better outcomes for spinal cord repair than just transplanting stem cells alone. This result challenges current ideas of how to use stem cells to promote tissue repair.

The research team led by Stephen Davies from Baylor College of Medicine, Houston, USA and colleagues from the University of Rochester Medical Center, New York, USA took embryonic glial precursor cells and induced them to differentiate in culture into a specific type of embryonic astrocyte known to be highly supportive of nerve fibre growth. They hoped these cells would have the repair capabilities of the embryonic spinal cord, which is lost in adults. Davies et al. transplanted these cells into cuts in the spinal cord of adult rats and measured the growth of nerve fibres by labelling them with a dye. They then compared healing and recovery in these rats with the recovery in spinal cord injured rats that received either undifferentiated glial precursor cells or no treatment at all.

Davies et al.’s results show that transplants of the precursor-derived astrocytes promoted the rapid growth of 40% of sensory nerve fibres across the cuts. The transplanted cells also suppressed the formation of scar tissue and aligned damaged tissue at the injury site. Furthermore, neurons in the brain that normally degenerate if their nerve fibres are severed in the spinal cord, were rescued when their cut nerve fibres interacted with the astrocytes transplanted into spinal cord injuries. In contrast, transplanted precursor cells failed to suppress scar formation or promote the growth of any nerve fibres across the injury site. Importantly, in a sensitive test of limb placement during walking, rats that received the astrocyte transplants recovered and were able to walk normally within two weeks, whereas the other rats that received undifferentiated precursor cells did not recover at all and still had difficulties with walking four weeks after the surgery.

These studies make important advances in both stem cell technology and identification of the right cell types for repairing the injured adult nervous system.