Migration of human keratinocytes in plasma and serum and wound re-epithelialisation

When skin is wounded, human keratinocytes at the wound edge stop differentiating and start migrating to resurface the wound. How this change takes place is unclear. Because keratinocytes at the wound edge are for the first time surrounded by serum rather than plasma, serum could contain some migration-promoting factor or factors that is absent in plasma. We did standard computer-assisted in-vitro migration assays of human keratinocytes in the presence of either human plasma or serum. We also did a semiquantitative western blot analysis to determine if p38 mitogen-activated protein kinase (p38MAPK) was activated by either serum or plasma. Our results showed that keratinocytes migrating on collagen in the presence of serum produced migration indices in the range of 28, whereas those in the presence of plasma were about 12--the same level as control assays without either serum or plasma. We also showed that induced keratinocyte polarisation, activation of p38MAPK, and production of matrix metalloprotease 9 are possible mechanisms for promotion of re-epithelialisation of skin wounds by human serum.