Effects of flavonoid derivatives on human microvascular endothelial cells.

Some natural compounds, including flavonoids, are active in vasculature re-growth during hair follicle disruption, but their effects have not been yet evaluated directly on microvascular endothelial cells. Skin vascularisation regulates the physiological blood supply required for hair growth and its dysregulation is the basis of several human diseases. Follicle-derived vascular endothelial growth factor (VEGF) release from follicular keratinocytes promotes perifollicular vascularisation and increases follicle and hair size, while blockade of VEGF-mediated angiogenesis leads to impaired hair growth. Here, we tested three flavonoids, namely visnadin (VSD), hesperidin (HSP) and baicalin (BC), on cultured human microvascular endothelial cells (HMEC), comparing their effects with minoxidil (MXD), a synthetic drug broadly used in the treatment of androgenetic alopecia. The response to these compounds was assayed in terms of endothelial survival, proliferation, tubulogenesis and proangiogenic signalling. We show that BC promotes HMEC proliferation, while both VSD and MXD enhance tubulogenesis. Interestingly, only HSP increases VEGFR-2 phosphorylation.