Repeated Vital Imaging Reveals Schwann Cells Induce and Guide Nerve Sprouting and Regeneration of Neuromuscular Junctions

The terminal Schwann cell processes that cover the neuromuscular junction sense neuromuscular transmission and modulate synaptic activities in normal muscles (Son et al., 1996; Robitaille, 1998). Recent researches show the terminal Schwann cell participates in the maintenance and repair of neuromuscular junctions. Reynolds and Woolf (1992) found that in response to muscle denervation, the terminal Schwann cell extends long processes. Based on static observations of rat neuromuscular junctions, Son and Thompson (1995) proposed that Schwann cell processes extended following nerve crush guide regenerating axons to grow beyond endplates, generating so called “escaped” fibers. Further, they found that some Schwann cell processes formed Schwann cell bridges interconnecting two endplates and these Schwann cell bridges guided escaped fibers to innervate adjacent endplates. These results however were from static observations; direct evidence is necessary to better understand Schwann cell functions during nerve regeneration. Repeated vital imaging developed by Lichtman and his colleagues (Lichtman et al., 1987) on double transgenic mice allows us to better study dynamic processes of this guidance and more Schwann cell functions during nerve regeneration through direct observation. In these