I am doing wound healing assay by making a scratch with 200ul pipette tip on a 90% confluent culture of HCECs. The wound is closing up but it's been a week since I made the scratch. I expected it to close up completely within 4 days. I am using Keratinocyte Serum Free Media supplemented with EGF and Insulin for the cells. Where is it going wrong? Do I need to add something else in my media?Please let me know.