Ultrastructural characterization of hyperactive endothelial cells, pericytes and fibroblasts in hypertrophic and nodular port-wine stain lesions

Current clinical evidence is insufficient to support HMME-PDT as the first choice of treatment for young children with port wine birthmarks

BACKGROUND

Port wine birthmark (PWB) is a congenital vascular malformation of the skin. Pulsed dye laser (PDL) is the "gold standard" for the treatment of PWB globally. Hematoporphyrin monomethyl ether (HMME or hemoporfin)-mediated photodynamic therapy (HMME-PDT) has emerged as the first choice for PWB treatment, particularly for young children, in many major hospitals in China during the past several decades.

AIM

To evaluate whether HMME-PDT is superior to PDL by comparing the clinical efficacies of both modalities.

METHOD

PubMed records were searched for all relevant studies of PWB treatment using PDL (1988-2023) or HMME-PDT (2007-2023). Patient characteristics and clinical efficacies were extracted. Studies with a quartile percentage clearance or similar scale were included. A mean color clearance index (CI) per study was calculated and compared among groups. An overall CI (C0), with data weighted by cohort size, was used to evaluate the final efficacy for each modality.

RESULT

A total of 18 HMME-PDT studies with 3910 patients in China were eligible for inclusion in this analysis. Similarly, 40 PDL studies with 5094 patients from nine different countries were eligible for inclusion in this analysis. Over 58% of patients in the HMME-PDT studies were minors (<18 years old). A significant portion (21.3%) were young children (<3 years old). Similarly, 33.2% of patients in the PDL studies were minors. A small proportion (9.3%) was young children. The overall clearance rates for PDL were slightly, but not significantly, higher than those for HMME-PDT in cohorts with patients of all ages (C0, 0.54 vs. 0.48, p = 0.733), subpopulations with only minors (C0, 0.54 vs. 0.46, p = 0.714), and young children (C0, 0.67 vs. 0.50, p = 0.081). Regrettably, there was a lack of long-term data on follow-up evaluations for efficacy and impact of HMME-PDT on young children in general, and central nervous system development in particular, because their blood-brain barriers have a greater permeability as compared to adults.

CONCLUSION

PDL shows overall albeit insignificantly higher clearance rates than HMME-PDT in patients of all ages; particularly statistical significance is nearly achieved in young children. Collectively, current evidence is insufficient to support HMME-PDT as the first choice of treatment of PWBs in young children given: (1) overall inferior efficacy as compared to PDL; (2) risk of off-target exposure to meningeal vasculature during the procedure; (3) administration of steriods for mitigation of side effects; -and (4) lack of long-term data on the potential impact of HMME on central nervous system development in young children.

Pathogenesis of Port-Wine Stains: Directions for Future Therapies

Port-wine stains (PWSs) are congenital vascular malformations that involve the skin and mucosa. To date, the mechanisms underlying the pathogenesis and progression of PWSs are yet to be clearly elucidated. The potential reasons for dilated vessels are as follows: (1) somatic GNAQ (R183Q) mutations that form enlarged capillary malformation-like vessels through angiopoietin-2, (2) decreased perivascular nerve elements, (3) the coexistence of Eph receptor B1 and ephrin B2, and (4) the deficiency of αSMA expression in pericytes. In addition, ERK, c-JNK, P70S6K, AKT, PI3K, and PKC are assumed to be involved in PWS development. Although pulsed-dye laser (PDL) remains the gold standard for treating PWSs, the recurrence rate is high. Topical drugs, including imiquimod, axitinib, and rapamycin, combined with PDL treatments, are expected to alter the recurrence rate and reduce the number of PDL sessions for PWSs. For the deep vascular plexus, photosensitizers or photothermal transduction agents encapsulated by nanocarriers conjugated to surface markers (CD133/CD166/VEGFR-2) possess a promising therapeutic potential in photodynamic therapy or photothermal therapy for PWSs. The pathogenesis, progression, and treatment of PWSs should be extensively investigated.

Photodynamic Therapy Using HMME for Port-Wine Stains: Clinical Effectiveness and Sonographic Appearance

This study aims at exploring the clinical efficacy and sonographic changes of photodynamic therapy (PDT) using Hematoporphyrin Monomethyl Ether (HMME) for the treatment of port-wine stains (PWS). Forty-five patients with PWS were recruited between March 2017 and June 2018 from the Department of Dermatology of The Third Affiliated Hospital of Soochow University. Five cases were of the pink type, thirty-nine cases were of the purple-red type, and one case was of the thickened type. All patients received three treatment sessions of PDT. After covering normal skin outside the treated area, patients received an intravenous injection of 5 mg/kg HMME within 20 minutes. The affected areas were exposed to a 532 nm LED light and were kept vertically at a distance of 10 cm. The irradiation energy density was set between 80 and 110 J/cm² in 15-minute sessions. Intermittent power density adjustment was performed at a rate of 5 mW/cm², and the treatment was withheld when the endpoint reaction appeared. Three follow-ups were performed before and after treatment, respectively, and the efficacy, thickness, and density of skin before and after treatment were evaluated with high-frequency ultrasound. The overall efficacy rate was 97.78% in forty-five cases after treatment for three sessions. Efficacy was related to age (P = 0.029) and lesion severity (P < 0.001). There were significant differences in the efficacy between the groups of <18 years old, 18-29 years old, and >29 years old (P = 0.029). A marked decrease in the numbers of distorted enlarged blood vessels per unit of the lesion was observed under high-frequency ultrasound. There were significant differences in skin thickness and skin density before and after treatment (F = 14.528, 5.428, P < 0.001). The swelling was reported to varying degrees in the treated areas in 23 patients with cheek lesion and in 6 frontal lesions. Hyperpigmentation after inflammation was observed in four patients that faded spontaneously after two months. In conclusion, photodynamic therapy for the treatment of PWS using HMME is effective and safe with few adverse reactions. Moreover, monitoring the changes in skin thickness and density of lesion tissue using high-frequency ultrasound can objectively evaluate the clinical efficacy of HMME photodynamic therapy and provide the basis for the formulation of individualized photodynamic therapy.

The Pathogenesis of Port Wine Stain and Sturge Weber Syndrome: Complex Interactions between Genetic Alterations and Aberrant MAPK and PI3K Activation

Port wine stain (PWS) is a congenital vascular malformation involving human skin. Approximately 15-20% of children a facial PWS involving the ophthalmic (V1) trigeminal dermatome are at risk for Sturge Weber syndrome (SWS), a neurocutaneous disorder with vascular malformations in the cerebral cortex on the same side of the facial PWS lesions. Recently, evidence has surfaced that advanced our understanding of the pathogenesis of PWS/SWS, including discoveries of somatic genetic mutations (GNAQ, PI3K), MAPK and PI3K aberrant activations, and molecular phenotypes of PWS endothelial cells. In this review, we summarize current knowledge on the etiology and pathology of PWS/SWS based on evidence that the activation of MAPK and/or PI3K contributes to the malformations, as well as potential futuristic treatment approaches targeting these aberrantly dysregulated signaling pathways. Current data support that: (1) PWS is a multifactorial malformation involving the entire physiological structure of human skin; (2) PWS should be pathoanatomically re-defined as "a malformation resulting from differentiation-impaired endothelial cells with a progressive dilatation of immature venule-like vasculatures"; (3) dysregulation of vascular MAPK and/or PI3K signaling during human embryonic development plays a part in the pathogenesis and progression of PWS/SWS; and (4) sporadic low frequency somatic mutations, such as GNAQ, PI3K, work as team players but not as a lone wolf, contributing to the development of vascular phenotypes. We also address many crucial questions yet to be answered in the future research investigations.

Membrane trafficking and exocytosis are upregulated in port wine stain blood vessels

INTRODUCTION

Port wine stain (PWS) is characterized as a progressive dilatation of immature venule-like vasculatures which result from differentiation-impaired endothelial cells. In this study, we aimed to identify the major biological pathways accounting for the pathogenesis of PWS.

METHODS

Sequential windowed acquisition of all theoretical fragment ion mass spectra (SWATH-MS) was used to identify differentially expressed proteins in PWS lesions, followed by confirmative studies with immunohistochemistry, immunoblot and transmission electron microscopy (TEM).

RESULTS

107 out of 299 identified proteins showed differential expressions in PWS lesions as compared to normal skin, mainly involving the functions of biosynthesis, membrane trafficking, cytoskeleton and cell adhesion/migration. The confirmative studies showed that expressions of membrane trafficking/exocytosis related proteins such as VAT1, IQGAP1, HSC70, clathrin, perlecan, spectrin α1 and GDIR1 were significantly increased in PWS blood vessels as compared to normal ones; while collagen subtypes 6A1 and 6A3 were decreased in PWS skin. Furthermore, TEM studies showed there is a significant upregulation of extracellular vesicle exocytosis from PWS blood vessels as compared to control.

CONCLUSIONS

The biological process of membrane trafficking and exocytosis is enhanced in PWS blood vessels. Our results imply that the extracellular vesicles released by lesional endothelial cells may act as potential intercellular signaling mediators to contribute to the pathogenesis of PWS.