BDNF-Hyaluronic Acid Hydrogel Promotes Neuronal Differentiation of Neural Stem Cells in Aβ-Induced Injury and 5×FAD Mice

Objectives: Alzheimer’s disease (AD) is associated with impaired adult hippocampal neurogenesis (AHN). This study aimed to establish an in vitro model of Aβ1–42 oligomer-damaged neural stem cells (NSCs) and to employ the 5×FAD mouse model of AD in vivo, and to evaluate the therapeutic effects of brain-derived neurotrophic factor-loaded hyaluronic acid hydrogel (BDNF-HA gel) on AHN. Methods: In vitro, BDNF-HA gel was co-cultured with Aβ1–42 oligomer-impaired NSC spheres and evaluate NSC proliferation, migration, and differentiation. In vivo, BDNF-HA gel was infused intracerebroventricularly into 5×FAD mice. Using BrdU labeling, immunofluorescence, anterograde transsynaptic viral tracing, and behavioral tests, we assessed the effects of BDNF-HA gel on adult neurogenesis, newborn neuron integration into memory circuits, and cognitive function. Results: In vitro, BDNF-HA gel attenuated Aβ1–42-induced NSC apoptosis, restored proliferation and migration, promoted differentiation into neuroblasts, newborn neurons, and oligodendrocytes, and alleviated mitochondrial depolarization and loss of mitochondrial mass. In vivo, despite the absence of significant Aβ plaques reduction in 5×FAD mice, BDNF-HA gel markedly enhanced NSC proliferation and neurogenesis in the subventricular zone (SVZ) and subgranular zone (SGZ). Behavioral tests further revealed significant improvements in object recognition, spatial working memory, and spatial reference memory. Conclusions: BDNF-HA gel can effectively counteract the toxic microenvironment induced by Aβ oligomers, promoting NSC proliferation, migration, and differentiation into neurons. Without altering the Aβ burden, it significantly enhances adult neurogenesis and rescues cognitive deficits in AD mice.