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Notes: Background  Microvascular abnormalities (capillary elongation, widening and tortuosity) are a characteristic feature of psoriasis and form one of the pathological diagnostic criteria. These changes occur early in the progression of a psoriatic plaque, before there is clinical or histological evidence of epidermal hyperplasia. Treatment of psoriatic microvessels with a pulsed dye laser (PDL) has been associated with both clinical improvement and clearance of lesions.Objectives  To quantify the structural vascular abnormalities in plaque skin using noninvasive techniques in vivo. Investigations were carried out before and after PDL treatment to determine the nature of laser-induced microvascular changes and the relationship between these changes and clinical improvement.Methods  Plaque microvessels were visualized using native capillaroscopy. Plaques were then treated three times with the PDL at 14-day intervals. Native capillaroscopy was repeated at 2 and 6 weeks after the final laser treatment. Images were analysed using a combination of nonstereological and stereological measurements.Results  Whole body disease was stable. Treated plaques showed a 48% reduction in plaque severity score (P 〈 0·01). Native studies showed that the PDL significantly reduced plaque microvessel density (P 〈 0·05), image area fraction (P 〈 0·01), microvessel length density (P 〈 0·01) and vessel image width (P 〈 0·01). The reduction in plaque severity score (which denoted clinical improvement) was related quantitatively to the reduction in microvessel area per unit area of plaque skin, i.e. the image area fraction (correlation coefficient = 0·772, P 〈 0·01). The greatest response of plaque microvessels was within 2 weeks after the final laser treatment, while the greatest reduction in plaque severity score occurred between 2 and 6 weeks after the final laser treatment, i.e. clinical improvement was preceded by microvascular improvement.Conclusions  These findings indicate that there is a close correlation between the state of the superficial vasculature and the clinical status of psoriasis. The expanded superficial microvascular bed in plaque skin is a necessary component for maintaining clinical lesions and these blood vessels are thus a legitimate target for treatment.

Notes: Background  Blood flow is substantially raised in psoriatic plaques. In addition, mechanisms of vasoconstriction and vasodilatation (locally and neurally mediated), although intact, are altered in magnitude. The elevated blood flow is considered to be a result of abnormalities (increase in vessel number, width and length) in the superficial capillary loops rather than changes in the deeper feeding vessels (arterioles).Objectives  To determine if selective thermolysis of psoriatic capillaries with a pulsed dye laser (PDL) leads to normalization of blood flow and also if the vasoconstrictor and vasodilator responses are returned to normal magnitude.Methods  Laser Doppler red cell flux was recorded from plaques on the forearm or elbow (untreated plaque site) and from clinically uninvolved skin at an equivalent site on the opposite limb. Plaques were treated on three occasions, at 2-weekly intervals, with a PDL. Laser Doppler red cell flux measurements were then repeated, 2 weeks after the final laser treatment was performed (treated plaque site).Results  There was significant clinical improvement in plaques after treatment (P = 0·02), but complete clearance of lesions did not occur. Blood flow in plaques under basal conditions remained significantly elevated above blood flow in clinically uninvolved skin, despite laser treatment (P 〈 0·001). The physiological tests of resistance vessel function showed that the laser did not impair the ability of psoriatic resistance vessels to constrict and dilate. However, there was only partial resolution of the percentage responses to the provocation tests towards the values recorded in clinically uninvolved skin.Conclusions  The results indicate that it is unlikely that the reduced resistance of the expanded superficial capillary bed is solely responsible for the massively elevated blood flow in plaque skin. It is more likely that the vascular abnormalities in psoriasis also extend to involve the deeper, larger resistance vessels (arterioles).

Notes: Background Elongated and tortuous capillary loops are distinctive features of psoriasis. The significance of these microvascular changes in the pathogenesis of plaques, however, remains unclear.Objectives To determine what part the expanded superficial capillary bed plays in the pathogenesis of clinical lesions by selectively thermolysing psoriatic capillaries with a pulsed dye laser (PDL).Methods Cutaneous lesions were biopsied before and after treatment and sections assessed by standard immunohistochemical techniques for changes in known indicators of angiogenesis, including endothelial surface area, endothelial cell proliferation and endothelial cell expression of adhesion molecules. We also measured lymphocytic infiltration and epidermal thickness, and quantified the presence of a marker of keratinocyte proliferation before and after treatment.Results The effect of the PDL was limited to the superficial capillary bed, with no changes in the microvessels (including venules and arterioles) of the upper reticular dermis. Although there was significant clinical improvement in plaques after treatment (P = 0·02), complete clearance of lesions was not achieved. Thermolysis of psoriatic capillaries caused a reduction in both endothelial surface area (P 〈 0·01) and endothelial cell proliferation in the superficial dermis (P = 0·04). Endothelial expression of surface adhesion molecules (integrins and E-selectin) important in angiogenesis was not, however, altered by treatment. The CD4+ and CD8+ T-cell infiltrate was significantly reduced in the superficial papillary dermis (P = 0·02 and P = 0·04, respectively), but not in the epidermis or upper reticular dermis. Laser treatment significantly reduced epidermal thickness (P = 0·001), but did not alter epidermal keratinocyte proliferation (P = 0·2).Conclusions The results demonstrate that dermal capillary changes alone are unlikely to be causal in psoriasis. They indicate that the expanded psoriatic capillaries may be important in facilitating the access of activated T cells to the skin and in maintaining the psoriatic plaque. These results do not refute the consensus view that plaque formation may be mediated by the release of growth factors/cytokines from activated epidermal T cells/keratinocytes.