Too many migrated cells — packed solid, can't count (Transwell Migration / Invasion Assay)

Question

Accepted Answer

Lower surface is densely covered with cells that fuse together; individual cells cannot be counted. Common causes: 1) Seeded too many cells 2) Incubation time was too long 3) Matrigel concentration was too low (for invasion assay) 4) Cells are unusually adherent to each other Solutions: 1) Reduce cell seeding number; run a density gradient 2) Shorten incubation time 3) For invasion: use appropriate Matrigel concentration (typically 1:8 – 1:10 dilution) 4) Pipette cells gently to avoid clumping in suspension