Stem cell therapy represents the potential alteative effective strategy for some diseases that lack effective treatment currently.Correspondingly,it is crucial to establish high-sensitive and reliable quantification assay for tracing exogenous cell migration.In the present study,we first used both bioluminescence imaging (BLI) indirect labeling (human norepinephrine transporter-luciferase reporter system) and 89zirconium (89Zr)-hNSCs direct labeling combined with positron emission tomography/computer tomography (PET/CT) system for tracking human neural stem cells (hNSCs) migration into the brain via nasal administration in preclinical study.But the above two methods failed to give the biodistribution profile due to their low sensitivity.Considering its superior sensitivity and absolute quantitation capability,we developed and validated the droplet digital PCR (ddPCR) targeting species-specific gene in frozen and paraffin sections,slices,and whole blood with the sensitivity of 100-200 hNSCs.Accurate and high throughput quantification could be performed using ddPCR with the coefficient of variation (CVs) of lower quality control (LQC) below 30％.In combination with immunohistochemistry and ddPCR,we confirmed the migration of hNSCs into the brain via nasal administration,which supported the efficacy of hNSCs in MPTP-treated mice,an animal model of Parkinsons disease.In conclusion,the present study is the first to report the application of ddPCR in the pharmacokinetics profile description of tracking of hNSCs in preclinical studies.