The research team has established the presence of stem cells in strawberry birthmarks (haemangiomas) that are proliferating. This has been determined by confirming the presence of proteins characteristic of these cells. However there is a family of three proteins called STATs that are associated with stem cells which are also known to have a role in the development of red blood cells – an activity known to occur in strawberry birthmarks. These STATs can be modified by the binding of phosphate groups. These phosphorylated proteins can promote the expansion and regulate the development of stem cells.
The role of these modified STAT proteins in strawberry birthmark development has been investigated. All three phosphorylated STATs studied were demonstrated in proliferating strawberry birthmarks but their expressions were reduced in the involuting (shrinking) haemangiomas. The STAT3 variant was the most abundant form. These reductions as the strawberry birthmark involutes reflect a depletion of the stem cells.