Topical photodynamic therapy using different porphyrin precursors leads to differences in vascular photosensitization and vascular damage in normal mouse skin.

Different distributions of hexyl aminolevulinate (HAL), aminolevulinic acid (ALA) and methyl aminolevulinate (MAL) in the superficial vasculature are not well studied but they are hypothesized to play an important role in topical photodynamic therapy (PDT). The colocalization of fluorescent CD31 and protoporphyrin IX (PpIX) was calculated using confocal microscopy of mouse skin sections to investigate the vascular distribution after topical application. Vascular damage leads to disruption of the normal endothelial adherens junction complex, of which CD144 is an integral component. Therefore, normal CD31 combined with loss of normal fluorescent CD144 staining was visually scored to assess vascular damage. Both the vascular PpIX concentration and the vascular damage were highest for HAL, then ALA and then MAL. Vascular damage in MAL was not different from normal contralateral control skin. This pattern is consistent with literature data on vasoconstriction after PDT, and with the hypothesis that the vasculature plays a role in light fractionation that increases efficacy for HAL and ALA-PDT but not for MAL. These findings indicate that endothelial cells of superficial blood vessels synthesize biologically relevant PpIX concentrations, leading to vascular damage. Such vascular effects are expected to influence the oxygenation of tissue after PDT which can be important for treatment efficacy.

Monitoring blood volume and saturation using superficial fibre optic reflectance spectroscopy during PDT of actinic keratosis.

Optically monitoring the vascular physiology during photodynamic therapy (PDT) may help understand patient-specific treatment outcome. However, diffuse optical techniques have failed to observe changes herein, probably by optically sampling too deep. Therefore, we investigated using differential path-length spectroscopy (DPS) to obtain superficial measurements of vascular physiology in actinic keratosis (AK) skin. The AK-specific DPS interrogation depth was chosen up to 400 microns in depth, based on the thickness of AK histology samples. During light fractionated aminolevulinic acid-PDT, reflectance spectra were analyzed to yield quantitative estimates of blood volume and saturation. Blood volume showed significant lesion-specific changes during PDT without a general trend for all lesions and saturation remained high during PDT. This study shows that DPS allows optically monitoring the superficial blood volume and saturation during skin PDT. The patient-specific variability supports the need for dosimetric measurements. In DPS, the lesion-specific optimal interrogation depth can be varied based on lesion thickness.

Fractionated illumination at low fluence rate photodynamic therapy in mice.

Photodynamic therapy (PDT) for actinic field cancerization is effective but painful. Pain mechanisms remain unclear but fluence rate has been shown to be a critical factor. Lower fluence rates also utilize available oxygen more efficiently. We investigated PDT effect in normal SKH1-HR mice using low and high fluence rate aminolevulinic acid (ALA) PDT and a fractionated illumination scheme. Six groups of six mice with different light treatment parameters were studied. Visual skin damage was assessed up to 7days post-PDT. Fluorescence and reflectance spectroscopy during illuminations provided us with real-time information about protoporphyrin IX (PpIX) photobleaching. A novel dosing approach was introduced in that we used a photobleaching percentage instead of a preset fluence. Data show similar total and maximum damage scores in high and low fluence rate groups. Photobleaching of PpIX in the low fluence rate groups shows a trend toward more efficient photobleaching. Results indicate that low fluence rate PDT is as effective as and more efficient than high fluence rate PDT in normal mouse skin. Low fluence rate PDT light protocols need to be explored in human studies in search for an effective and well-tolerated treatment for actinic field cancerization.

[An extremely painful ulcer on the lower leg; Martorell arteriolosclerotic ulcer]. / Een zeer pijnlijk ulcus op het onderbeen: Ulcus arterioloscleroticum van Martorell.

A 63-year-old woman was referred to the dermatology outpatient department with extremely painful ulcers on the right lower leg. Medical history listed hypertension, diabetes mellitus and chronic obstructive pulmonary disease. Intensive analgesia was insufficient. Blood analysis, microbial cultures and venous ultrasound did not reveal a cause. At histopathologic examination of an ulcer, arteriolosclerosis was revealed. The patient was treated for Martorell arteriolosclerotic ulcer with nifedipine, acenocoumarol and split-thickness skin grafts followed by vacuum-assisted closure therapy. Two weeks postoperative, analgesia was discontinued and all ulcers were healed. Nifedipine and acenocoumarol were continued in the outpatient setting to prevent relapses. Patients with long-standing hypertension are particularly prone to cutaneous arteriolosclerosis. Thrombosis of the cutaneous arterioles results in painful ischemic ulcers. This disease probably frequently goes unrecognised.