Examination of the combined effects of chondroitinase ABC, growth factors and locomotor training following compressive spinal cord injury on neuroanatomical plasticity and kinematics.

While several cellular and pharmacological treatments have been evaluated following spinal cord injury (SCI) in animal models, it is increasingly recognized that approaches to address the glial scar, including the use of chondroitinase ABC (ChABC), can facilitate neuroanatomical plasticity. Moreover, increasing evidence suggests that combinatorial strategies are key to unlocking the plasticity that is enabled by ChABC. Given this, we evaluated the anatomical and functional consequences of ChABC in a combinatorial approach that also included growth factor (EGF, FGF2 and PDGF-AA) treatments and daily treadmill training on the recovery of hindlimb locomotion in rats with mid thoracic clip compression SCI. Using quantitative neuroanatomical and kinematic assessments, we demonstrate that the combined therapy significantly enhanced the neuroanatomical plasticity of major descending spinal tracts such as corticospinal and serotonergic-spinal pathways. Additionally, the pharmacological treatment attenuated chronic astrogliosis and inflammation at and adjacent to the lesion with the modest synergistic effects of treadmill training. We also observed a trend for earlier recovery of locomotion accompanied by an improvement of the overall angular excursions in rats treated with ChABC and growth factors in the first 4 weeks after SCI. At the end of the 7-week recovery period, rats from all groups exhibited an impressive spontaneous recovery of the kinematic parameters during locomotion on treadmill. However, although the combinatorial treatment led to clear chronic neuroanatomical plasticity, these structural changes did not translate to an additional long-term improvement of locomotor parameters studied including hindlimb-forelimb coupling. These findings demonstrate the beneficial effects of combined ChABC, growth factors and locomotor training on the plasticity of the injured spinal cord and the potential to induce earlier neurobehavioral recovery. However, additional approaches such as stem cell therapies or a more adapted treadmill training protocol may be required to optimize this repair strategy in order to induce sustained functional locomotor improvement

Limb coordination during locomotion.

<p>In <b>A</b> and <b>B</b>, coordination values plotted for each consecutive forelimb step cycle before and 7 weeks after SCI respectively. Usually the coordination measurement is expressed using polar coordinates. To simplify the representation of the coordination drift we converted these data to fit the Cartesian model by subtracting 1 to the polar values when two contacts of the forelimb with the treadmill belt occurred during one hindlimb step cycle (<i>i.e.</i> different stepping frequencies). This method renders an account of the intensity of the drift represented by the slope of the consecutive plots. (<b>C</b>) Hindlimbs coordination is expressed between 0 and 1 (<i>i.e.</i> theta) in a polar plot. The polar axis represents the delays from baseline (<i>i.e.</i> the innermost circle) to week 7 (<i>i.e.</i> the outermost) post-SCI. Circumference of the circles represent the normalized duration of right step cycle while the dots position on each circle represent the relative time position of the left foot contact averaged by group (see Alluin et al., 2011 for details). In addition, the size of each dot is proportional to the polar dispersion.</p

Combination of ChABC, GFs and training promotes plasticity of serotonergic fibers after SCI.

<p>(<b>A</b>) Transverse section of an uninjured spinal cord at mid-thoracic region demonstrates normal innervation pattern of serotonergic pathway (5-HT positive fibers) within the spinal cord. (<b>B</b>) Higher magnification of the boxed area in A shows the presence of serotonergic fibers in the gray matter areas representing of the signal that was quantified in our assessments. (C–G) At 7 weeks post-injury, 5-HT positive fibers in all experimental groups show significant changes in their localization (images shown for 1.5 mm rostral). In contrast to uninjured spinal cord, 5-HT immunoreactive fibers were sprouting in different regions of white matter in all injured groups. (<b>D</b>) Higher magnification of the boxed area in C shows the presence of serotonergic fibers in the white matter areas representing of the signal that was quantified in our assessments (H) Quantification of 5-HT immunointensity in the entire cross section of the spinal cord (traced areas in images) at various rostral and caudal distances revealed significantly increased level of 5-HT immunoreactivity in ChABC+GFs/trained group compared to both vehicle treated group at all examined rostral and caudal distances (*p<0.05, Two-way ANOVA, Holm-Sidak <i>post hoc</i>, n = 3–6). Interestingly, at the epicenter and 1.5 mm rostral and caudal distances, the ChABC+GFs/untrained group also showed a significantly higher expression of 5-HT-immunoreactivity compared to the vehicle treated groups (*p<0.05, Two-way ANOVA, Holm-Sidak <i>post hoc</i>).</p