Ultrasound-Mediated Kallidinogenase-Loaded Microbubble Targeted Therapy for Acute Cerebral Infarction

The neuroprotective effects of kallidinogenase against acute cerebral infarction have been demonstrated, and the use of microbubbles has been suggested as a therapeutic mechanism for drug delivery. This study was designed to investigate the optimal parameters for preparing kallidinogenase-loaded microbubbles (KLMs) and to evaluate the effects of KLM-targeted therapy on neurogenesis and angiogenesis following experimental acute cerebral infarction in rats.

KLMs were prepared by mechanical shaking. Male Wistar rats were randomly divided into an ultrasound-mediated KLM-treated group and 4 control groups. Treatments were administered via daily tail vein injection on 6 consecutive days, starting at 24 hours after middle cerebral artery occlusion (MCAO). The ultrasound-treated groups were subjected to a 2-MHz pulse of ultrasonic irradiation on the lateral skull of the ischemic side for 10 minutes during injection. Cell proliferation was examined using a 5-bromo-2-deoxyuridine assay. Infarct volume and neurological function were evaluated on days 3 and 7 after MCAO.

The ultrasound-mediated KLM and kallidinogenase treatments significantly increased the numbers of doublecortin-immunoreactive cells in the subventricular zone (SVZ) and laminin⁺ cells in the peri-infarction region on day 7 after MCAO, compared with the other 3 groups (all P <.05). The neurological function scores of the ultrasound-mediated KLM-treated group were significantly better than those of rats treated with kallidinogenase alone or with the other treatments (all P <.05).

Treatment with the ultrasound-mediated KLMs promoted the proliferation of SVZ neuroblasts and vascular regeneration, which contributed to functional improvement after stroke. These findings provide a novel therapy for ischemic stroke.