In vivo imaging: a dynamic imaging approach to study spinal cord regeneration.

Upon spinal cord injury, severed axons and the surrounding tissue undergo a series of pathological changes, including retraction of proximal axon ends, degeneration of distal axon ends and formation of a dense fibrotic scar that inhibits regenerative axonal growth. Until recently it was technically challenging to study these dynamic events in the mammalian central nervous system. Here, we describe and discuss the recently established genetic tract tracing approach of in vivo imaging. This technique allows studying acute pathological events following a spinal cord lesion. In addition, the novel development of chronic spinal cord preparations such as the implanted spinal chamber now also enables long-term imaging studies. Hence, in vivo imaging allows the direct observation of acute and chronic dynamic degenerative and regenerative events of individual neurons after traumatic injury in the living animal.