Applications of stripe assay in the study of CXCL12-mediated neural progenitor cell migration and polarization

The polarization and migration of neural progenitor cells (NPCs) are critical for embryonic brain development and neurogenesis after brain injury. Although stromal-derived factor-1α (SDF-1α, CXCL12) and its receptor CXCR4 are well-known to mediate the migration of NPCs in the developing brain, the dynamic cellular processes and structure-related molecular events remain elusive. Transwell and microfluidic-based assays are classical assays to effectively study cellular migration. However, both of them have limitations in the analysis of a single cell. In this study, we modified the stripe assay and extended its applications in the study of NPC polarization and intracellular molecular events associated with CXCL12-mediated migration. In response to localized CXCL12, NPCs formed lamellipodia in the stripe assay. Furthermore, CXCR4 and Rac1 quickly re-distributed to the area of lamellipodia, indicating their roles in NPC polarization upon CXCL12 stimulation. Although the chemokine stripes in the assay provided concentration gradients that can be best used to study cellular polarization and migration through immunocytochemistry, they can also generate live imaging data with comparable quality. In conclusion, stripe assay is a visual, dynamic and economical tool to study cellular mobility and its related molecule mechanisms.