Neuronal intermediate filament expression in rat dorsal root ganglia sensory neurons: an in vivo and in vitro study

Qualitative and quantitative examination was performed to evaluate the expression of peripherin and 200 kDa neurofilament in the sensory compartment of the peripheral nervous system of the rat both in vivo and in a new in vitro model. Under physiological conditions, these two neuronal intermediate filaments show different expression patterns in sensory neurons. To have a more complete comprehension of the role of these intermediate filaments and to fill in the blanks left in previously reported literature, we demonstrate in vivo using a morphological approach that peripherin and 200 kDa neurofilament define two distinct subpopulations within the dorsal root ganglia sensory neurons. Moreover, peripherin is specifically expressed in unmyelinated fibers while 200 kDa neurofilament is expressed in myelinated fibers. Additionally, in vitro analysis of RNA taken from dorsal root ganglia explants suggested that 200 kDa neurofilament is downregulated and peripherin is transiently expressed throughout sensory fiber regrowth. In particular, both neuronal intermediate filaments are downregulated immediately after sensory fiber axotomy thus suggesting that neither peripherin nor 200 kDa neurofilament has a role in the first steps of fiber regrowth. However, the upregulation of peripherin a few days after the beginning of fiber regrowth in vitro suggests that low levels of peripherin may be require to carry on the sequence of events involved in the correct regeneration and direction of sensory fibers.