Enhanced expression of heat shock protein 27 is correlated with axonal regeneration in mature retinal ganglion cells

The small heat shock protein, Hsp27, promotes axonal regeneration in peripheral neurons; however, an analogous role in the central nervous system has not been described. This study examined the relationship between Hsp27 expression and regeneration in mature retinal ganglion cells (RGCs). Adult rat optic nerves were transected and exposed to peripheral nerve autografts to stimulate regeneration of cut RGC axons. There was a five-fold increase in the Hsp27-positive fraction of RGCs that extended new axons into the graft when compared with those that survived injury but did not regenerate (30% versus 6% respectively, P = 0.001). Hsp27 protein was located throughout somata and neuritic processes, and there was a significant positive correlation between Hsp27 expression and axonal regeneration in injured neurons (R = 0.92, P < 0.0001). These findings are consistent with the growth-associated role of Hsp27 demonstrated in peripheral neurons and suggest that Hsp27 may mediate similar physiological functions in the central nervous system.