We have used in vitro scratch assays to examine the relative contribution of dermal
fibroblasts and keratinocytes in the wound repair process and to test the influence
of mesenchymal stem cell (MSC) secreted factors on both skin cell types. Scratch assays
were established using single cell and co-cultures of L929 fibroblasts and HaCaT keratinocytes,
with wound closure monitored via time-lapse microscopy. Both in serum supplemented
and serum free conditions, wound closure was faster in L929 fibroblast than HaCaT
keratinocyte scratch assays, and in co-culture the L929 fibroblasts lead the way in
closing the scratches. MSC-CM generated under serum free conditions significantly
enhanced the wound closure rate of both skin cell types separately and in co-culture,
whereas conditioned medium from L929 or HaCaT cultures had no significant effect.
This enhancement of wound closure in the presence of MSC-CM was due to accelerated
cell migration rather than increased cell proliferation. A number of wound healing
mediators were identified in MSC-CM, including TGF-beta1, the chemokines IL-6, IL-8,
MCP-1 and RANTES, and collagen type I, fibronectin, SPARC and IGFBP-7. This study
suggests that the trophic activity of MSC may play a role in skin wound closure by
affecting both dermal fibroblast and keratinocyte migration, along with a contribution
to the formation of extracellular matrix.
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