Calcium chelation promotes microtubule regrowth and axonal recovery after laser-induced axonal injury

Axons that are damaged locally due to stretch or crush injury often undergo widespread and irrecoverable damage. Transient elevation of cytosolic free calcium across extended regions of the axon, and calcium mediated disintegration of cytoskeletal elements is one of the main causes of this neurodegeneration. When axonal damage involves complete transection of axons, any recovery has to be driven by the formation of fresh motile tips (growth-cones). However, axons could also undergo partial damage where the axonal plasma membrane retains its continuity while cytoskeletal elements undergo extensive disintegration triggered by elevated free calcium. We invoke such a condition using a partial laser ablation technique, and we show that complete axonal recovery, mainly mediated by microtubule regrowth, is possible in such cases when extracellular calcium is depleted. This method allows us to explore the dynamics of cytoskeletal damage after injury and the modes of recovery of microtubules and actin filaments. Apart from understanding the mechanisms of cytoskeletal damage and recovery, our results can have significant impact on devising treatment strategies for crush injuries to nerves.