Psoriasis is a chronic inflammatory
skin disease in which epidermal proliferation is closely associated with excessive microvascular expansion within the papillary dermis.
Angiopoietins have recently been identified as the major
ligands of the endothelial- specific
receptor Tie2.
Angiopoietin 1 induces Tie2 signaling as a receptor activator and maintains blood vessel formation, whereas
angiopoietin 2 destabilizes vessels by blocking Tie2 signaling as an antagonist of
angiopoietin 1 and acts with
vascular endothelial growth factor to initiate angiogenesis. In this study we examined the potential role of
angiopoietins and the
Tie2 receptor in vascular changes of
psoriasis.
Angiopoietin 1,
angiopoietin 2, and Tie2 were upregulated in involved
psoriasis skin compared to uninvolved
psoriasis skin, healthy skin, and chronic spongiotic
dermatitis skin.
Angiopoietin 1 was expressed by stromal cells in the highly vascularized papillary dermis of involved
psoriasis skin.
Angiopoietin 2 was expressed by endothelial cells in the vicinity of the proliferating epidermis that abundantly expressed
vascular endothelial growth factor.
Vascular endothelial growth factor and
basic fibroblast growth factor, which were overexpressed in involved
psoriasis skin, enhanced
angiopoietin 2 and Tie2 expression in dermal microvascular endothelial cell cultures. Thus, our findings suggest that upregulation of
angiopoietin 1,
angiopoietin 2, and Tie2 is closely associated with the development of microvascular proliferation in
psoriasis, and that the angiopoietin-Tie2 system may act coordinately with
vascular endothelial growth factor and
basic fibroblast growth factor to promote neovascularization in
psoriasis. Moreover, successful antipsoriatic treatment was accompanied by noticeable reduction of
angiopoietin 2 expression, suggesting that alteration of
angiopoietin 2 expression may be particularly important in controlling vascular proliferation in the treatment of
psoriasis.