Temporal dynamics of diffusion kurtosis imaging parallels astroglial GFAP expression in a non-traumatic spinal cord injury animal model of ischemia-reperfusion.

OBJECTIVES

Spinal cord ischemia-reperfusion (I/R) injury triggers rapid secondary degeneration, yet sensitive noninvasive markers that reflect early astroglial and microstructural alterations remain scarce. This study aimed to delineate the temporal changes in GFAP immunoreactivity as an indicator of astroglial response following spinal cord I/R and to determine how these pathological dynamics correspond to diffusion kurtosis imaging (DKI) metrics in a rabbit model.

METHODS

Forty-five male New Zealand White rabbits were randomized into a Sham group or four I/R groups with reperfusion durations of 6 h, 24 h, 72 h, and 7 d (n = 9/group). DKI (b = 0, 1,000, 2000 s/mm2) was performed on a 3.0 T scanner to obtain fractional anisotropy (FA), mean diffusivity (MD), and mean kurtosis (MK) maps. Motor function was assessed using the modified Tarlov score. Histopathology, GFAP immunohistochemistry with optical density (OD), and Western blot analysis of L3-L5 segments were performed immediately after imaging. Group comparisons were conducted using ANOVA, and correlations between DKI parameters, GFAP expression, and Tarlov scores were evaluated using Pearson analyses.

RESULTS

Following I/R, GFAP immunoreactivity increased progressively and reached its highest mean value at 72 h, and this temporal pattern was confirmed by Western blot analysis (p < 0.001 vs. Sham). This peak coincided with the most pronounced reductions in FA and MK (both p < 0.01) and the maximal increase in MD. FA showed a moderate negative correlation with GFAP expression (r = -0.547, p < 0.01) and with motor function, while MK demonstrated a comparatively weaker negative association. MD correlated weakly and positively with GFAP. Functional deficits paralleled imaging and pathological deterioration, with partial improvement from 72 h and further recovery by 7 d, although not to baseline.

CONCLUSION

GFAP immunoreactivity after spinal cord I/R follows a well-defined temporal trajectory that closely parallels DKI-derived microstructural alterations, supporting the utility of DKI parameters as noninvasive biomarkers that reflect astroglial response dynamics during early spinal cord I/R injury.