Bcl-2 protection of axotomized Purkinje cells in organotypic culture is age dependent and not associated with an enhancement of axonal regeneration

Abstract

Organotypic cerebellar cultures offer a good model to determine whether experimentally induced changes in Purkinje cell death vulnerability could be correlated with changes in their regenerative capability. This chapter describes that bcl-2 protection of Purkinje cell from axotomy is not constant, but age dependent, and does not enhance Purkinje cell axonal regeneration. The occurrence of a partial temporal overlapping between the sensitivity of neurons to die after axotomy and their ability to regenerate has suggested that cell death and axonal regeneration might be regulated by common signaling pathways. To determine whether an increase in cell death vulnerability is correlated with increased regenerative capability, hu-bcl-2 overexpressing mice have been used, in which overexpression of hu-bcl-2—an anti-apoptotic molecule—prevents the massive Purkinje cell death in P3 organotypic cultures. The chapter shows that this hu-bcl-2 overexpression is not enough to prevent the cell death induced by axotomy, at least in cerebellar explants taken from P0 to P5 mouse pups, suggesting that the Purkinje cell death following either organotypic culture or axotomy are different; among the few hu-bcl-2 overexpressing Purkinje cells that survive axotomy, the percentage able to regenerate their axons decreases with time. The results, thus, confirm that Purkinje cell death and axonal regeneration are differentially regulated and that the intracellular signaling pathways implied in these two cell decisions do not overlap.