α7 integrin mediates neurite outgrowth of distinct populations of adult sensory neurons

The successful regeneration of peripheral branches of sensory neurons following injury is attributed to the presence of neurotrophins and interaction of regenerating axons with the extracellular matrix. Here, we show that the laminin receptor, α7β1 integrin is a crucial mediator of neurite outgrowth from distinct populations of sensory neurons. Following sciatic nerve crush, α7 integrin is expressed by medium-large diameter, NF200-immunoreactive (IR), and medium diameter, CGRP-IR, neurons, but very few small diameter non-peptidergic neurons. The functional significance of α7 integrin expression following injury was addressed using dissociated adult rat and mouse sensory neurons. By using function-blocking antibodies and neurons isolated from α7 integrin null mice, we demonstrate that NGF- and NT-3-stimulated neurite outgrowth is reduced in the absence of α7 integrin signaling. In contrast, GDNF-stimulated neurite outgrowth is less dependent on α7 integrin. These results define an essential interaction between α7 integrin and laminin for mediating neurite outgrowth of subpopulations of injured adult sensory neurons.