Cell Mobility after Laser Axotomy Figure 3. Soma motility response to axonal injury quantitative analysis. A. Instantaneous velocity and B. trajectory of the cell shown in Supplemental Video S4. Transection occurred at t = 0. The horizontal line in A shows the mean baseline velocity of control cells. Point were acquired every 5 minutes approximatelly. doi:10.1371/journal.pone.0026832.g003 correlation between the regenerative response of cells and their motility. The regenerative response of RGC-5 to axotomy correlates with axon length Whether a cell regenerated its axon after axotomy was inversely dependent on the baseline length of the axon. The mean axon length of cells that regenerated their axons (group A) was 60616 mm, compared to 90635 mm for group B of cells that did not regenerate their axons (p = 0.0007); (Fig. 5A). These data imply that RGC-5 cells with longer axons were less likely to initiate a regenerative program after axotomy compared with those with shorter axons. RGC-5 soma motility is directly related to the length of the severed axon The motility of axotomized RGC-5 somas was lesser when the axon regeneration program was initiated (Fig. 3). Furthermore, the likelihood of regeneration was greater when the axon length was shorter (Fig. 5). We therefore predicted that RGC-5 soma motility Figure 4. Soma motility response to axonal injury group comparisons. A. Initial reaction and B. long-term response. Cell motility changes were correlated to the regenerative response. Cell group labels are inj for injured cells, cont for control cells, A for that cells that either regrowth new axons or repaired injured one and, B represents cells that were not able either to regenerate or replace injured axons. doi:10.1371/journal.pone.0026832.g004 would be directly correlated with axon length, and this was indeed the case. In Fig. 5B the mean velocity is plotted as a function of the axon length, with cell motility increasing with greater axon lengths. RGC-5 cell migration correlates with the likelihood of regeneration A surprising observation that arose from analyzing multiple cells in parallel was that axotomized cells tended to migrate towards the injury site (see Supplemental Videos S2 , S3 and S4). To quantify this phenomenon, we measured the minimum distance between the cell body and the injury site (dm) during the migration, and compared it to the initial distance d0. Cells that approached the injury site therefore tended to have the ratio dm/d0,1 (see Supplemental Videos S2 and S3) and cells that moved away dm/ d0 = 1 (see Supplemental Video S4). The migration of the soma towards the injury site also correlated with the regenerative response (Fig. 6), with cells that regenerated their axons being (A) PLoS ONE | www.plosone.org 4 November 2011 | Volume 6 | Issue 11 | e26832