Adrenomedullin stimulation of cytokines and growth factor release in endothelial cells and skin fibroblasts: A possible role in wound healing
D Renshaw, JP Hinson & S Kapas
Cutaneous injury triggers a complex series of biological processes which lead to tissue repair and comprise the mechanism termed wound healing. Various growth factors and cytokines are involved in the multiple stages of wound healing. Keratinocyte growth factor (KGF) is secreted by skin fibroblasts and acts locally to induce cell proliferation. During wound healing KGF's role is as a re-epithelialising agent working in conjunction with pro-inflammatory cytokines such as interleukin 6 (IL-6) and IL-1 alpha to enable wound closure. Vascular endothelial growth factor (VEGF) is a 34-42 kDa heparin-binding glycoprotein with potent angiogenic as well as mitogenic properties. VEGF also displays vascular permeability-enhancing activity, specific for endothelial cells. Adrenomedullin (ADM), a multifunctional peptide first isolated in the adrenal gland is known to have a growth factor role in some tissues. The following in vitro experiments were designed to determine whether ADM is involved in wound healing, specifically by stimulating the secretion of growth factors and interleukins from endothelial cells and skin fibroblasts.
Cultured human micro-vascular endothelial cells (HMEC) and skin fibroblasts were grown to approximately 70 percent confluence in six well plates. Cells were serum starved for atleast 24 hours before being stimulated for a further 24 hours with adrenomedullin (10-7M). Media was assayed by ELISA for KGF, VEGF and IL-6. Statistical significance was determined at the 95% level by one-way ANOVA followed by a Tukey's test.
ADM caused a 2-2.5 fold increase in both IL-6 and VEGF secretion over controls from HMEC cells. In the skin fibroblast cell line ADM caused a significant increase in KGF secretion over control levels, but had no significant effect on either VEGF or IL-6. The above data suggests that ADM may be a major factor involved in the wound healing process.