In silico model of the early effects of radiation therapy on the microcirculation and the surrounding tissues.

BACKGROUND: Radiation-induced organ dysfunction are frequently described by Normal Tissue Complication Probability models. The approximations of this radiobiological approach do not allow to consider the important role played by the microvasculature not only in the dose-response of the blood vessels but also of the organs where it is located. To this purpose, we presented a computational model that describes the fluid dynamics of microcirculation when the parameters of the network and the surrounding tissues are affected by radio-induced changes. MATERIALS AND METHODS: The effects of the ionizing radiation on the capillary bed are mediated by the inflammatory response. We derived from a literature search the possible morphological and functional variations of the network due to the process of the acute inflammation. Specifically, we considered vasodilation, increased membrane permeability with consequent fluid extravasation and increased wall elasticity. These perturbations to the system were included in a computational model, already able to describe the physics of the microcirculation and its exchanges with the surrounding tissues. RESULTS: Two computational descriptions were considered. In the first one, we changed a set of 4 parameters associated with the increased fluid exchange from the health scenario at the baseline to a seriously compromised scenario with the edema formation. The second study investigated the effect of a perturbation to the vessel wall elasticity. CONCLUSIONS: These simulations represent a first step towards the challenging objective of understanding and describing in a mechanistic way the effects of radiation on the vascular microenvironment.

Efficacy and Safety of the 532-nm KTP and Long-Pulsed 1064-nm Neodymium-doped Yttrium Aluminum Garnet Laser for Treatment of Vascular Malformations.

BACKGROUND: Pulsed dye lasers (PDLs) are well-established for treatment of capillary malformations but are unable to penetrate the depth needed to treat deeper vascular lesions. A combined approach using a deeper penetrating wavelength with a "superficial" wavelength could more comprehensively treat vascular malformations than PDL alone. OBJECTIVE: To evaluate the safety and efficacy of the long-pulsed 1064-nm neodymium:yttrium-aluminum-garnet (LP 1064-nm Nd:YAG) in conjunction with the 532-nm potassium titanyl phosphate (532-nm KTP) laser wavelengths for treatment of capillary venous and venous malformations. METHODS: In this retrospective single-center study, we queried patient records who underwent treatment with the 532-nm KTP and LP 1064-nm Nd:YAG laser wavelengths. A blinded panel of 3 physicians evaluated improvement in lesion color, elevation, texture, and overall architecture on a four-point scale: 0% to 25%; 26% to 50%, 51% to 75%, and 76% to 100%. RESULTS: Our cohort consisted of 23 cases. Sixteen cases had sufficient information for clinical assessment. Treatment number and parameters varied depending on lesion, skin type, and end point. Clinical assessment of treatment effectiveness revealed average scores of 51% to 75% improvement for color, elevation, texture, and overall architecture. CONCLUSION: This study illustrates that 2 wavelengths, 532-nm KTP to target superficial components and LP 1064-nm Nd:YAG for deeper components, can safely and effectively treat both capillary venous and venous malformations.

Nailfold Capillaroscopic Findings in an Orthopedic Surgeon: Reversible Abnormalities after the Cessation of Radiation Exposure.

Interventional fluoroscopy is a leading source of occupational ionizing radiation exposure for medical personnel. For example, orthopedic surgeons represent one occupation where the risk of exposure is large. This occupational hazard is the result of a cumulative dose of radiation over time. Adverse health effects induced by low-dose radiation exposure can arise from daily procedures performed over an entire career. Many of the radiation-induced effects that may develop are transient erythema, permanent epilation, dry desquamation, dermal necrosis and telangiectasia; these effects have occurred on the skin of fingers of interventionalists. Nailfold videocapillaroscopy (NVC) is a non-invasive technique useful for early detection of radiation-induced effects on microcirculation of fingernails. Here we report on a case of an orthopedic surgeon exposed to radiation for 30 years during his professional career. He performed NVC before and after the end of his professional career, and regression of the microcirculatory abnormalities were documented after cessation of radiation exposure. To our knowledge, this is the first published work in which the regression of chronic low-dose radiation-induced alterations of finger microvessels have been described and documented.

A Model of Indirect Cell Death Caused by Tumor Vascular Damage after High-Dose Radiotherapy.

There is increasing evidence that high doses of radiotherapy, like those delivered in stereotactic body radiotherapy (SBRT), trigger indirect mechanisms of cell death. Such effect seems to be two-fold. High doses may trigger an immune response and may cause vascular damage, leading to cell starvation and death. Development of mathematical response models, including indirect death, may help clinicians to design SBRT optimal schedules. Despite increasing experimental literature on indirect tumor cell death caused by vascular damage, efforts on modeling this effect have been limited. In this work, we present a biomathematical model of this effect. In our model, tumor oxygenation is obtained by solving the reaction-diffusion equation; radiotherapy kills tumor cells according to the linear-quadratic model, and also endothelial cells (EC), which can trigger loss of functionality of capillaries. Capillary death will affect tumor oxygenation, driving nearby tumor cells into severe hypoxia. Capillaries can recover functionality due to EC proliferation. Tumor cells entering a predetermined severe hypoxia status die according to a hypoxia-death model. This model fits recently published experimental data showing the effect of vascular damage on surviving fractions. It fits surviving fraction curves and qualitatively reproduces experimental values of percentages of functional capillaries 48 hours postirradiation, and hypoxic cells pre- and 48 hours postirradiation. This model is useful for exploring aspects of tumor and EC response to radiotherapy and constitutes a stepping stone toward modeling indirect tumor cell death caused by vascular damage and accounting for this effect during SBRT planning. SIGNIFICANCE: A novel biomathematical model of indirect tumor cell death caused by vascular radiation damage could potentially help clinicians interpret experimental data and design better radiotherapy schedules.

Patient-Side Appraisal of Late Radiation-Induced Oral Microvascular Changes.

PURPOSE: To determine the clinical feasibility of examining and measuring late irradiation changes in the oral microcirculation of head and neck (HN) cancer patients using the novel CytoCam video microscope system. METHODS AND MATERIALS: In 30 HN cancer patients and 30 age-matched controls, bilateral video images were recorded noninvasively of the oral microcirculation of the buccal mucosa and mandibular gingiva. Tissue perfusion parameters, such as functional capillary density (FCD), buccal blood vessel diameter, and microcirculatory flow index, were analyzed. RESULTS: No difference was observed for mean buccal mucosa FCD in irradiated versus healthy tissue, whereas a lower mean gingival FCD in irradiated versus healthy tissue was observed (34 ± 17 capillaries per millimeter squared [cpll/mm2] vs 68 ± 19 cpll/mm2; P < .001). A significant difference in mean buccal blood vessel diameter of 16 ± 3 µm was measured, compared with 14 ± 1 µm in control buccal mucosa (P < .001). No significant difference in microcirculatory flow index was observed between the 2 groups. CONCLUSIONS: Quantifying oral microcirculatory injury associated with late irradiation effects using the CytoCam was feasible in HN cancer patients. Results indicate that marked differences in tissue-specific microcirculatory measurements of angioarchitecture, diminished capillary density, and extensively dilated blood vessel diameters are associated with late irradiation effects in HN cancer patients.

Comparison of Emla cream and topical lidocaine tape for pain relief of V-beam laser treatment.

The authors compared the analgesic effects of two topical applications; Emla® cream (Sato Pharmaceutical Co. Ltd., Tokyo, Japan) and 60% lidocaine tape (Penles® tape; Maruho, Osaka, Japan). The authors examined 20 outpatients with capillary malformations. Emla® cream or Penles® tape was applied 1 h before laser irradiation using V-Beam. After V-Beam irradiation, pain intensity was measured using Pain Vision® (NIPRO, Osaka, Japan), while subjective pain was converted into numerical values using the VAS system. In the assessment using Pain Vision®, pain was significantly lower in patients who received Emla® cream (Welch test), whereas no difference was observed in VAS ratings between the two applications (student's t test). The objective system showed that Emla® cream had a significantly greater analgesic effect. We plan to evaluate the analgesic effects of these topical anesthetics by applying them to other anatomical areas.

Enhanced radiation dose and DNA damage associated with iodinated contrast media in diagnostic X-ray imaging.

A review was undertaken of studies reporting increased DNA damage in circulating blood cells and increased organ doses, for X-ray exposures enhanced by iodinated contrast media (ICM), compared to unenhanced imaging. This effect may be due to ICM molecules acting as a source of secondary radiation (Auger/photoelectrons, fluorescence X-rays) following absorption of primary X-ray photons. It is unclear if the reported increase in DNA damage to blood cells necessarily implies an increased risk of developing cancer. Upon ICM-enhancement, the attenuation properties of blood differ substantially from surrounding tissues. Increased energy deposition is likely to occur within very close proximity to ICM molecules (within a few tens of micrometres). Consequently, in many situations, damage and dose enhancement may be restricted to the blood and vessel wall only. Increased cancer risks may be possible, in cases where ICM molecules are given sufficient time to reach the capillary network and interstitial fluid at the time of exposure. In all situations, the extrapolation of blood cell damage to other tissues requires caution where contrast media are involved. Future research is needed to determine the impact of ICM on dose to cells outside the blood itself and vessel walls, and to determine the concentration of ICM in blood vessels and interstitial fluid at the time of exposure.

Ionizing radiation reduces ADAM10 expression in brain microvascular endothelial cells undergoing stress-induced senescence.

Cellular senescence is associated with aging and is considered a potential contributor to age-associated neurodegenerative disease. Exposure to ionizing radiation increases the risk of developing premature neurovascular degeneration and dementia but also induces premature senescence. As cells of the cerebrovascular endothelium are particularly susceptible to radiation and play an important role in brain homeostasis, we investigated radiation-induced senescence in brain microvascular endothelial cells (EC). Using biotinylation to label surface proteins, streptavidin enrichment and proteomic analysis, we analyzed the surface proteome of stress-induced senescent EC in culture. An array of both recognized and novel senescence-associated proteins were identified. Most notably, we identified and validated the novel radiation-stimulated down-regulation of the protease, a disintegrin and metalloprotease 10 (ADAM10). ADAM10 is an important modulator of amyloid beta protein production, accumulation of which is central to the pathologies of Alzheimer's disease and cerebral amyloid angiopathy. Concurrently, we identified and validated increased surface expression of ADAM10 proteolytic targets with roles in neural proliferation and survival, inflammation and immune activation (L1CAM, NEO1, NEST, TLR2, DDX58). ADAM10 may be a key molecule linking radiation, senescence and endothelial dysfunction with increased risk of premature neurodegenerative diseases normally associated with aging.

Low-dose ionizing radiation induces therapeutic neovascularization in a pre-clinical model of hindlimb ischemia.

AIMS: We have previously shown that low-dose ionizing radiation (LDIR) induces angiogenesis but there is no evidence that it induces neovascularization in the setting of peripheral arterial disease. Here, we investigated the use of LDIR as an innovative and non-invasive strategy to stimulate therapeutic neovascularization using a model of experimentally induced hindlimb ischemia (HLI). METHODS AND RESULTS: After surgical induction of unilateral HLI, both hindlimbs of female C57BL/6 mice were sham-irradiated or irradiated with four daily fractions of 0.3 Gy, in consecutive days and allowed to recover. We demonstrate that LDIR, significantly improved blood perfusion in the murine ischemic limb by stimulating neovascularization, as assessed by laser Doppler flow, capillary density, and collateral vessel formation. LDIR significantly increased the circulating levels of VEGF, PlGF, and G-CSF, as well as the number of circulating endothelial progenitor cells (EPCs) mediating their incorporation to ischemic muscles. These effects were dependent upon LDIR exposition on the ischemic niche (thigh and shank regions). In irradiated ischemic muscles, these effects were independent of the recruitment of monocytes and macrophages. Importantly, LDIR induced a durable and simultaneous up-regulation of a repertoire of pro-angiogenic factors and their receptors in endothelial cells (ECs), as evident in ECs isolated from the irradiated gastrocnemius muscles by laser capture microdissection. This specific mechanism was mediated via vascular endothelial growth factor (VEGF) receptor signaling, since VEGF receptor inhibition abrogated the LDIR-mediated gene up-regulation and impeded the increase in capillary density. Finally, the vasculature in an irradiated non-ischemic bed was not affected and after 52 week of LDIR exposure no differences in the incidence of morbidity and mortality were seen. CONCLUSIONS: These findings disclose an innovative, non-invasive strategy to induce therapeutic neovascularization in a mouse model of HLI, emerging as a novel approach in the treatment of critical limb ischemia patients.

Irradiation as a hazard for mucociliary clearance.

OBJECTIVES: In this paper we study effects of irradiation to pulmonary tissue on a micro and ultrastructural level to get insights into the dynamics of morphological changes and associated post-radiative physiological conditions. METHODS: Animal and human pulmonary tissue with and without radiation damage was subject to light, transmission, scanning and polarization microscopy and morphometric evaluation. RESULTS: The present investigations on the influence of irradiation on experimental and human lung tissue demonstrate that complex changes are induced in the cells which are essential for mucociliary clearance. These changes are a shortage of alveolar macrophages, cell apoptosis, proliferation of collagen ligament in the barrier of gaseous exchange, retraction of endothelial lining of capillaries and significant broadening of the gaseous exchange barrier, resulting in serious damage for the O2 and CO2 exchange. CONCLUSIONS: These changes at microscopic, cellular, and ciliary level trigger conditions for various diseases of the respiratory system, which is further assessed by a simultaneous computer aided estimation of ciliary function. With the concurrent world-wide increase of respiratory diseases, these findings are important knowledge for the clinical practice.

Microvascular injury in persistent gastric ulcers after yttrium-90 microsphere radioembolization for liver malignancies.

Yttrium-90 microsphere radioembolization ((90)Y MRE) is a therapy for liver malignancies by permanently implanting (90)Y-containing microspheres into tumors via hepatic artery. The etiology of persistent gastric ulcerations in patients presenting months after treatment remains unclear. Three patients who presented with gastric ulceration 4 to 13 months after (90)Y MRE were examined by esophagogastroduodenoscopy and biopsies. Pathological examinations showed multiple (90)Y microspheres scattered within the lamina propria and submucosa. Most of the microspheres were distributed in a linear fashion, consistent with an intravascular location; however, the vascular lumen and endothelial cells were not present. The microspheres were surrounded by fibrotic tissue infiltrated by chronic inflammatory cells and rare neutrophils. Epithelial granulation without pititis and miniaturized glands with intervening fibrosis were noted, compatible with chronic ischemic changes. These findings suggest that the persistent gastric ulceration is a result of localized ischemic injury in response to (90)Y MRE-induced vascular damage.

Sestrin2 protects the myocardium against radiation-induced damage.

The purpose of this study was to investigate the role of Sestrin2 in response to radiation-induced injury to the heart and on the cardiomyopathy development in the mouse. Mice with genetic deletion of the Sestrin2 (Sestrin2 knockout mice [Sestrin2 KO]) and treatment with irradiation (22 or 15 Gy) were used as independent approaches to determine the role of Sestrin2. Echocardiography (before and after isoproterenol challenge) and left ventricular (LV) catheterization were performed to evaluate changes in LV dimensions and function. Masson's trichrome was used to assess myocardial fibrosis. Immunohistochemistry and Western blot were used to detect the capillary density. After 22 or 15 Gy irradiation, the LV ejection fraction (EF) was impaired in wt mice at 1 week and 4 months after irradiation when compared with sham irradiation. Compared to wt mice, Sestrin2 KO mice had significant reduction in reduced LVEF at 1 week and 4 months after irradiation. A significant increase in LV end-diastolic pressure and myocardial fibrosis and a significant decrease in capillary density were observed in irradiation-wt mice, as well as in irradiation-Sestrin2 KO mice. Sestrin2 involved in the regulation of cardiomyopathy (such as myocardial fibrosis) after irradiation. Overexpression of Sestrin2 might be useful in limiting radiation-induced myocardial injury.

A Monte Carlo approach to small-scale dosimetry of solid tumour microvasculature for nuclear medicine therapies with (223)Ra-, (131)I-, (177)Lu- and (111)In-labelled radiopharmaceuticals.

The small-scale dosimetry of radionuclides in solid-tumours is directly related to the intra-tumoral distribution of the administered radiopharmaceutical, which is affected by its egress from the vasculature and dispersion within the tumour. The aim of the present study was to evaluate the combined dosimetric effects of radiopharmaceutical distribution and range of the emitted radiation in a model of tumour microvasculature. We developed a computational model of solid-tumour microenvironment around a blood capillary vessel, and we simulated the transport of radiation emitted by (223)Ra, (111)In, (131)I and (177)Lu using the GEANT4 Monte Carlo. For each nuclide, several models of radiopharmaceutical dispersion throughout the capillary vessel were considered. Radial dose profiles around the capillary vessel, the Initial Radioactivity (IR) necessary to deposit 100 Gy of dose at the edge of the viable tumour-cell region, the Endothelial Cell Mean Dose (ECMD) and the Tumour Edge Mean Dose (TEMD), i.e. the mean dose imparted at the 250-µm layer of tissue, were computed. The results for beta and Auger emitters demonstrate that the photon dose is about three to four orders of magnitude lower than that deposited by electrons. For (223)Ra, the beta emissions of its progeny deliver a dose about three orders of magnitude lower than that delivered by the alpha emissions. Such results may help to characterize the dose inhomogeneities in solid tumour therapies with radiopharmaceuticals, taking into account the interplay between drug distribution from vasculature and range of ionizing radiations.

Late inflammatory and thrombotic changes in irradiated hearts of C57BL/6 wild-type and atherosclerosis-prone ApoE-deficient mice.

BACKGROUND AND PURPOSE: Radiation-induced heart disease represents a late complication of thoracic radiotherapy. We investigated the inflammatory and thrombotic response after local heart irradiation in wild-type and atherosclerosis-prone mice. MATERIAL AND METHODS: Atherosclerosis-prone ApoE(-/-) and C57BL/6 wild-type mice were sacrificed 20, 40, and 60 weeks after irradiation with 0.2, 2, 8, or 16 Gy. The expression of CD31, vascular cell adhesion molecule-1 (VCAM-1), thrombomodulin (TM), and CD45 were quantified by immunofluorescence staining of heart tissue sections. RESULTS: Microvascular density decreased at 40 weeks after 16 Gy in C57BL/6 but not in ApoE(-/-) mice. CD31 expression declined in C57BL/6 mice at 40 weeks (8 Gy), but increased in ApoE(-/-) mice at 20 (2/8/16 Gy) and 60 weeks (16 Gy). Capillary area decreased in C57BL/6 at 40 weeks (8/16 Gy) but increased in ApoE(-/-) mice at 20 weeks (16 Gy). Endocardial VCAM-1 expression remained unchanged. TM-positive capillaries decreased at 40 weeks (8/16 Gy) in C57BL/6 and at 60 weeks (2/16 Gy) in ApoE(-/-) mice. Leukocyte infiltration transiently rose 40 weeks after 8 Gy (only ApoE(-/-)) and 16 Gy. After receiving a low irradiation dose of 0.2 Gy, no significant changes were observed in any of the mouse models. CONCLUSION: This study demonstrated that local heart irradiation affects microvascular structure and induces inflammatory/thrombotic responses in mice in a dose- and time-dependent manner. Thereby, significant prothrombotic changes were found in both strains, although they were progressive in ApoE(-/-) mice only. Proinflammatory responses, like the increase of adhesion molecules and leukocyte infiltration, were more pronounced and occurred at lower doses in ApoE(-/-) vs. C57BL/6 mice. These findings indicate that metabolic risk factors, such as decreased ApoE lipoproteins, may lead to an enhanced proinflammatory and prothrombotic late response in locally irradiated hearts.

Cell and Tissue Damage after Skin Exposure to Ionizing Radiation: Short- and Long-Term Effects after a Single and Fractional Doses.

Ionizing radiation is often used to treat progressive neoplasms. However, the consequences of long-term radiation exposure to healthy skin tissue are poorly understood. We aimed to evaluate the short- and long-term radiation damage to healthy skin of the same irradiation given either as single or fractional doses. C57BL/J6 mice were randomly assigned to one of three groups: a control and two exposure groups (5 Gy ×2 or 10 Gy ×1). The inguinal area was irradiated (6-MeV beam) 1 week after depilation in the treatment groups. Skin samples were evaluated macroscopically and histologically for up to 6 months after the final exposure. After anagen hair follicle injury by irradiation, hair cycling resumed in both groups, but hair graying was observed in the 10 Gy ×1 group but not in the 5 Gy ×2 group, suggesting the dose of each fractional exposure is more relevant to melanocyte stem cell damage than the total dose. On the other hand, in the long term, the fractional double exposures induced more severe atrophy and capillary reduction in the dermis and subcutis, suggesting fractional exposure may cause more depletion of tissue stem cells and endothelial cells in the tissue. Thus, our results indicated that there were differences between the degrees of damage that occurred as a result of a single exposure compared with fractional exposures to ionizing radiation: the former induces more severe acute injury to the skin with irreversible depigmentation of hairs, while the latter induces long-term damage to the dermis and subcutis.

Antiangiogenic effect of methotrexate and PUVA on psoriasis.

Vascular endothelial growth factor (VEGF) is important factor for angiogenesis in psoriasis. Methotrexate and psoralen and ultraviolet light A (PUVA) mainly target the T cell-mediated immunopathology of psoriasis. Our work aimed at estimating VEGF mRNA in psoriatic patients and investigating whether the standard therapeutic modalities (methotrexate and PUVA) exert their antiangiogenic activity through altering VEGF levels. Twenty-four chronic plaque psoriasis patients were enrolled. Patients were divided into two groups (12 patients each); group A received intramuscular methotrexate and group B was treated by PUVA three times/week in a PUVA 1000 cabin for 10 weeks each. Twelve healthy volunteers served as controls. A skin biopsy was taken from lesional skin before and after treatment for RT-PCR detection of VEGF mRNA. Capillary perfusion scanning using LASER Doppler perfusion imaging was performed on the same psoriatic plaque before and after treatment and was also done for the controls. Following both methotrexate and PUVA, a significant reduction in the amount of VEGF mRNA (P < 0.001 and P = 0.002, respectively) and capillary perfusion (P = 0.002) occurred. These reductions were significantly higher in the methotrexate group (P < 0.001 and  P = 0.001, respectively) than in the PUVA group. The percentage of clinical improvement in the examined psoriatic plaque was significantly positively correlated with the percentage of reduction in the amount of VEGF mRNA (r = 0.850, P < 0.001) and the percentage of reduction in the capillary perfusion (r = 0.684, P < 0.001). Both modalities may exert an antiangiogenic effect. Methotrexate appears to have possibly a more potent antiangiogenic effect than PUVA.

Transient repetitive exposure to low level light therapy enhances collateral blood vessel growth in the ischemic hindlimb of the tight skin mouse.

The tight skin mouse (Tsk(-/+)) is a model of scleroderma characterized by impaired vasoreactivity, increased oxidative stress, attenuated angiogenic response to VEGF and production of the angiogenesis inhibitor angiostatin. Low-level light therapy (LLLT) stimulates angiogenesis in myocardial infarction and chemotherapy-induced mucositis. We hypothesize that repetitive LLLT restores vessel growth in the ischemic hindlimb of Tsk(-/+) mice by attenuating angiostatin and enhancing angiomotin effects in vivo. C57Bl/6J and Tsk(-/+) mice underwent ligation of the femoral artery. Relative blood flow to the foot was measured using a laser Doppler imager. Tsk(-/+) mice received LLLT (670 nm, 50 mW cm(-2), 30 J cm(-2)) for 10 min per day for 14 days. Vascular density was determined using lycopersicom lectin staining. Immunofluorescent labeling, Western blot analysis and immunoprecipitation were used to determine angiostatin and angiomotin expression. Recovery of blood flow to the ischemic limb was reduced in Tsk(-/+) compared with C57Bl/6 mice 2 weeks after surgery. LLLT treatment of Tsk(-/+) mice restored blood flow to levels observed in C57Bl/6 mice. Vascular density was decreased, angiostatin expression was enhanced and angiomotin depressed in the ischemic hindlimb of Tsk(-/+) mice. LLLT treatment reversed these abnormalities. LLLT stimulates angiogenesis by increasing angiomotin and decreasing angiostatin expression in the ischemic hindlimb of Tsk(-/+) mice.

Microbeam radiation-induced tissue damage depends on the stage of vascular maturation.

PURPOSE: To explore the effects of microbeam radiation (MR) on vascular biology, we used the chick chorioallantoic membrane (CAM) model of an almost pure vascular system with immature vessels (lacking periendothelial coverage) at Day 8 and mature vessels (with coverage) at Day 12 of development. METHODS AND MATERIALS: CAMs were irradiated with microplanar beams (width, ∼25 µm; interbeam spacing, ∼200 µm) at entrance doses of 200 or 300 Gy and, for comparison, with a broad beam (seamless radiation [SLR]), with entrance doses of 5 to 40 Gy. RESULTS: In vivo monitoring of Day-8 CAM vasculature 6 h after 200 Gy MR revealed a near total destruction of the immature capillary plexus. Conversely, 200 Gy MR barely affected Day-12 CAM mature microvasculature. Morphological evaluation of Day-12 CAMs after the dose was increased to 300 Gy revealed opened interendothelial junctions, which could explain the transient mesenchymal edema immediately after irradiation. Electron micrographs revealed cytoplasmic vacuolization of endothelial cells in the beam path, with disrupted luminal surfaces; often the lumen was engorged with erythrocytes and leukocytes. After 30 min, the capillary plexus adopted a striated metronomic pattern, with alternating destroyed and intact zones, corresponding to the beam and the interbeam paths within the array. SLR at a dose of 10 Gy caused growth retardation, resulting in a remarkable reduction in the vascular endpoint density 24 h postirradiation. A dose of 40 Gy damaged the entire CAM vasculature. CONCLUSIONS: The effects of MR are mediated by capillary damage, with tissue injury caused by insufficient blood supply. Vascular toxicity and physiological effects of MR depend on the stage of capillary maturation and appear in the first 15 to 60 min after irradiation. Conversely, the effects of SLR, due to the arrest of cell proliferation, persist for a longer time.

Pulsed dye laser double-pass treatment of patients with resistant capillary malformations.

The pulsed dye laser is an effective and established treatment for port-wine stains and has become the generally accepted standard of care. However, in many cases, complete clearance cannot be achieved as a significant proportion of lesions become resistant to treatment. Multiple passes or pulse-stacking techniques have been used to improve the extent and rate of fading, but concerns over increased adverse effects have limited this clinical approach. In this work, a double-pass technique with the pulsed dye laser has been described, which may allow for increased depth of vascular injury, greater efficacy, and an acceptable risk profile. Our aim was to determine the efficacy and the rate of side-effects for a double-pass protocol with a pulsed dye laser (PDL) to treat patients previously treated with PDL and/or other laser modalities. A retrospective chart review was conducted of 26 patients treated with a minimum of three double-pass treatments alone, or in combination, with single pass conventional PDL. Almost half of the patients (n = 12) showed either a moderate or significant improvement in fading compared to pre-treatment photographs with the double-pass technique. In a further 12 patients, there was a mild improvement. In two patients, there was no change. Sixteen patients developed mild side-effects: blisters (n = 5), dry scabs (n = 11) and transient hyperpigmentation (n = 4). This preliminary experience suggests that a double-pass technique at defined intervals between the first and second treatment with PDL can further lighten some port-wine stains, which are resistant to conventional single-pass treatments. This technique may be a useful addition to the laser treatment of PWS and deserves further scrutiny with randomized prospective studies and histological analysis to confirm the increased depth of vascular injury.