Changes in microcirculation and structural components of the skin under photodynamic effects

Abstract

Introduction . Distinctive features of microcirculation and their connection with structural disorders in the skin during photodynamic exposure using various photosensitizers (PS) are not well understood. Objective . Comparative analysis of the relationship between morphological abnormalities and changes in blood flow in the skin during photoactivation of PS, taking into consideration the influence on mast cells (MC), structural elements of the dermis and underlying muscle tissue. Materials and methods . In this work were used male Wistar rats (n=46). PS were administered intravenously: Radachlorin (RDC) (5 mg/kg) 3 hours, Coproporphyrin III (CPP) (10 mg/kg) 24 hours before irradiation. To control the accumulation of PS in the skin, methods of fluorescence videodermatoscopy and confocal scanning laser microscopy (CSLM) were used. Laser irradiation (662 and 635 nm) was performed with an energy density of 50 Jcm –2 , the irradiated surface area was 0,78 cm 2 . Laser Doppler flowmetry was used to assess microcirculation in the skin. Results . According to videodermatoscopy, fluorescence maximum values in the R channel were recorded 6-8 hours after administration, and amounted to 4901 [4190; 6732] a. u. for RDC and 2997 [2678; 3351] a. u. for CPP. Using the CSLM method, it was shown that CPP is poorly visualized in the walls of blood vessels. In experiments with RDC, the structures of areolar tissue of the hypodermis are determined. An hour after laser irradiation, in experiments with RDC, as well as with CPP, a significant decrease in blood flow was noted compared with the control to 3,61±0,7 and 4,27±1,4 PU, respectively. Structural changes when using both PS showed endothelial swelling, vasodilation and congestion, hemorrhages in the dermis, and underlying muscle tissue. The amount of MC was reduced. Conclusions . Laser irradiation with the parameters used in the work leads to a significant decrease in blood flow in the skin in experimental animals as a result of photoactivation of PS. CPP requires a higher radiation energy density. Morphological changes were revealed not only at the level of the epidermis, dermis and hypodermis, but also the underlying striated muscle tissue. In the early stages after exposure, massive degranulation of MC is noted with a decrease in their number.