Dynamic contrast-enhanced MRI reveals glymphatic dysfunction in mice with depressive-like behavior.

OBJECTIVE

This study aimed to investigate glymphatic system dysfunction in chronic unpredictable mild stress (CUMS)-induced depressive-like mice and its association with aquaporin-4 (AQP4) and astrocyte alterations using dynamic contrast-enhanced MRI (DCE-MRI).

METHODS

Thirty-eight C57BL/6 mice were randomized into CUMS (28-day stress protocol) and control groups. Behavioral tests (sucrose preference, forced swim, tail suspension) assessed depressive phenotypes. DCE-MRI with Gd-DTPA cisterna magna injection was performed to evaluate glymphatic dynamics via hierarchical and k-means clustering of time-signal curves. Ex vivo Texas Red-dextran-3 tracer imaging quantified cerebrospinal fluid (CSF) influx. Immunofluorescence measured AQP4 polarization and GFAP expression in the hippocampus, prefrontal cortex, and hypothalamic regions. Statistical analyses included independent t-tests.

RESULTS

CUMS mice exhibited reduced sucrose preference (0.71 vs. 0.81, t = 2.113, P = 0.0418) and prolonged immobility in forced swim tests (176.6 vs. 156.4 s, t = 2.200, P = 0.0343). DCE-MRI revealed a statistically significant intergroup difference in contrast agent signal intensity distribution within the Right Cortical Amygdala(Cortical amygdalar-R), (t = 2.641, P = 0.0247, P < 0.05). Simultaneously, CUMS mice exhibited significant contrast agent accumulation in the thalamus. Hierarchical clustering identified enhanced Gd-DTPA influx but delayed peak timing in CUMS clusters, while k-means analysis showed reduced efflux in CSF-dense regions (P < 0.01). Ex vivo tracer influx was reduced in CUMS (24.64 %vs.39.09 %, t = 5.440, P = 0.0003). Immunofluorescence revealed reduced AQP4 expression in CUMS hippocampus (t = 2.697, P = 0.027) and prefrontal cortex (t = 4.543, P = 0.0007), decreased polarization (t = 2.308, P = 0.0396), and diminished GFAP expression (t = 10.08, P < 0.0001).

CONCLUSIONS

CUMS-induced depressive-like behavior is linked to glymphatic dysfunction, characterized by impaired CSF influx/efflux and AQP4/astrocyte downregulation. DCE-MRI clustering analysis provides novel insights into spatiotemporal glymphatic abnormalities, highlighting potential therapeutic targets for depression.