Maternal dietary folate imbalance alters cerebellar astrocyte morphology and density in offspring

Maternal folate usage is essential for neurodevelopment, but its effects on cerebellar structure are unclear. Cerebellum undergoes a protracted period of development, making it sensitive to maternal nutritional imbalances. Astrocytes are necessary for cerebellar cortex structure and function. This study examined the impact of varying maternal dietary folate levels on the morphology and density of cerebellar astrocytes in rat offspring.

Twelve adult female rats (Rattus norvegicus) were randomly allocated to one of four premixed food groups: standard (2 mg/kg), folate-deficient (0 mg/kg), folate-supplemented (8 mg/kg), or folate supra-supplemented (40 mg/kg). The rats began their diets 14 days before mating and continued throughout pregnancy and lactation. On postnatal day 35, five pups from each group were sacrificed and their cerebellums were processed for immunohistochemical examination. The cerebellar astrocytes were labelled with an antibody against Glial Fibrillary Acid Protein (GFAP).

The offspring of the folate-deficient diet group exhibited few Bergmann and granule layer astrocytes. The Bergmann radial glial processes in this group were thinner, discontinuous, poorly organised, and had unclear end feet compared to controls. Conversely, the folate-supplemented group showed a predominance of well-organized Bergmann glia astrocytes with distinct, thicker, and densely packed processes, ending in clear conical pial foot processes. In the supra-supplemented group, there was evidence of astrogliosis in the form of large granule layer astrocytes with extended cytoplasmic projections. The Bergmann glia in this group were fewer and more varied in distribution and morphology. Some locations had many astrocytic processes, whereas others had none. Some processes were discontinuous and tortuous. The proportion of cerebellar cortical GFAP immunoreactive cells in folate-deficient diet, controls, folate-supplemented, and folate supra-supplemented groups were 2.09 ± 0.06 %, 4.69 ± 0.12 %, 10.14 ± 0.67 %, and 23.12 ± 3.48 %, respectively (p < 0.001).

These findings imply that both folate deficiency and excess supplementation in pregnancy can impair normal cerebellar astrocyte development, highlighting the importance of balanced folate levels during pregnancy for optimal neurodevelopmental outcomes.