Intriguing astrocyte responses in CA1 to reduced and rehabilitated masticatory function: Dorsal and ventral distinct perspectives in adult mice.

Objective: We sought to investigate the plasticity of diet-induced changes in astrocyte morphology of stratum lacunosum-moleculare (SLM) in CA1.

Design: Three diet regimes were adopted in 15 mice, from the 21st postnatal day to 6 months. The first diet regimen was pellet feed, called Hard Diet (HD). The second, with reduced masticatory, received a pellet-diet followed by a powdered-diet, and it was identified as Hard Diet/Soft Diet (HD/SD). Finally, the group with rehabilitated masticatory was named Hard Diet/Soft Diet/Hard Diet (HD/SD/HD). In the end, euthanasia and brain histological processing were performed, in which astrocytic immunoreactivity to glial-fibrillary-acidic-protein (GFAP) was tested. In reconstructed astrocytes, morphometric analysis was performed.

Results: Astrocyte morphometric revealed that changes in masticatory regimens impact astrocyte morphology. In the dorsal CA1, switching from a hard diet to a soft diet led to reductions in most variables, whereas in the ventral, fewer variables were affected, highlighting regional differences in astrocyte responses. Cluster analysis further showed that diet-induced changes in astrocyte morphology were reversible in the dorsal region, but not in the ventral region, indicating a persistent impact on astrocyte diversity and complexity in the ventral even after rehabilitation. Correlation tests between astrocyte morphology and behavioral performance demonstrated disrupted relationships under masticatory stress, with effects persisting after rehabilitation.

Conclusion: Changes in the diet result in significant alterations in astrocyte morphology, suggesting a direct link between dietary modulation and cellular structure. Morphometric analyses revealed distinct alterations in astrocyte morphology in response to changes in the masticatory regimen, with both dorsal/ventral regions displaying notable changes. Moreover, the regional differential effects on astrocytes underscore the complexity of mastication on neuroplasticity and cognitive function.