Microvascular hyperpermeability and thrombosis induced by light/dye treatment

Abstract

To investigate microvascular hyperpermeability and thrombosis induced by photodynamic therapy or light/dye treatment, we quantified the initiation time for thrombus formation, thrombus growth rate, and the time for the microvessel occlusion in post-capillary venules of rat mesenteries. Under similar light/dye treatments, we also measured the microvessel hydraulic conductivity (Lp) and solute permeability (P) to TRITC-BSA (bovine serum albumin), respectively, in the same type of microvessels as for thrombosis. Under an irradiation power of 0.37 mW/mm(2), thrombus was initiated in 3.8 ± 0.4 min, its growth rate was 3.9 ± 0.3% of the vessel mid-plane area/min, and the microvessels were completely occluded in 29.3 ± 2.2 min (SE, n = 8). Under the same irradiation power, Lp and P increased gradually, reaching a plateau in 3-5 min. At the plateau, Lp had increased to 2.2 ± 0.2 times (n = 11), while P had increased to 4.1 ± 0.7 (n = 7) times their baseline values, respectively. Neither Lp nor P increased further after longer time exposure (up to 30 min). Comparison of the measured Lp and P data with predictions from a mathematical model for the inter-endothelial cleft suggests that an almost complete depletion of the glycocalyx layer at the luminal surface of the endothelium might be one of the structural mechanisms by which the light/dye increases microvascular permeability and induces thrombosis.

Sphingosine‐1‐phosphate Maintains Normal Vascular Permeability by Preserving Endothelial Surface Glycocalyx in Intact Microvessels

“…To further quantitatively investigate the underlying structural mechanisms by which S1P maintains microvessel permeability, we adapted the mathematical model for inter‐endothelial transport developed by Fu et al . . Figure A shows a 3‐D model geometry for the inter‐endothelial cleft in the wall of a rat mesenteric microvessel (revised from Fu et al .…”

“…These concentrations were the optimized concentrations used in for the S1P and inhibitor effects on the endothelial permeability in vivo and in vitro . The detailed method using a theta pipette for P measurement has been previously described in . Briefly, a post‐capillary venule was cannulated with a θ pipette.…”

“…Concentrations of 0.75 and 0.1 mg/mL were used in the experiment, respectively, for AlexFluor 555‐BSA and SF. These concentrations were in the linear range under our imaging settings according to our in vitro calibrations .…”

Sphingosine-1-phosphate reduces adhesion of malignant mammary tumor cells MDA-MB-231 to microvessel walls by protecting endothelial surface glycocalyx

“…These concentrations were the optimized concentrations used in (20,23,25,29) for the S1P and inhibitor effects on the endothelial permeability in vivo and in vitro. The detailed method for P measurement has been previously described in (32,33,38). Briefly, a post-capillary venule was cannulated with a theta pipette.…”

“…The assumption for using the above equation for determining the P was that the fluorescence intensity is linearly related to the fluorescence concentration. AlexFluor 555-BSA was at the concentration of 0.75 mg/ml, which was in the linear range under the imaging settings according to in vitro calibrations (28,32,38).…”