The evolution of the distal nerve stump. As Wallerian degeneration proceeds, factors that promote regeneration, laminin and growth factors, are upregulated. MAG, an inhibitor of regeneration, is cleared within the first week, and the inhibitory CSPGs are upregulated transiently. The net effect (dotted line) is an initially inhibitory environment that becomes progressively more supportive of regeneration. The relative changes within each factor are derived from experimental data (see DISCUSSION); the relative impact of each factor in relation to the others is hypothetical .