Low‐Molecular‐Weight <i>Angelica sinensis</i> Polysaccharide Improves Neurological Function and Neuroplasticity Following Cerebral Ischemia–Reperfusion Injury

Neuroplasticity plays a pivotal role in post-stroke recovery, and <i>Angelica sinensis</i> polysaccharide has demonstrated neuroprotective properties. This study investigated the neuroprotective effects of low-molecular-weight <i>Angelica sinensis</i> polysaccharide (LMW-ASP) in a rat middle cerebral artery occlusion/reperfusion (MCAO/R) model. Structural characterization revealed that LMW-ASP (3.9 kDa), containing a pyranose ring and uronic acid, was a heteropolysaccharide that comprised fucose, galactosamine hydrochloride, rhamnose, arabinose, glucosamine hydrochloride, galactose, glucose, xylose, mannose, galacturonic acid, and glucuronic acid (0.007:0.003:0.057:0.209:0.009:0.284:0.303:0.006:0.032:0.083:0.007). Post-stroke administration of LMW-ASP (50 mg/kg) significantly improved body weight and neurological functions after MCAO/R. Moreover, microtubule-associated protein-2 expression was notably higher in the LMW-ASP group than in the model group (<i>p</i> < 0.01). Furthermore, Golgi-Cox staining confirmed that LMW-ASP increased the number of dendritic intersections (<i>p</i> < 0.05 for 90-120, 180, and 200 μm; <i>p</i> < 0.001 for 70 and 80 μm), the number of terminal branches (<i>p</i> < 0.01), the number of branch points (<i>p</i> < 0.01), and the density of basal dendritic spines (<i>p</i> < 0.05). Finally, transmission electron microscopy revealed an increase in the number of synapses (<i>p</i> < 0.001) and presynaptic vesicles (<i>p</i> < 0.001) in the LMW-ASP group. These results suggest that LMW-ASP is a potential pharmaceutical therapeutic approach for stroke recovery that enhances neuroplasticity.