Microvascular hyperpermeability and thrombosis induced by light/dye treatment

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

OBJECTIVE

S1P was found to protect the ESG by inhibiting MMP activity-dependent shedding of ESG in cultured endothelial cell studies. We aimed to further test that S1P contributes to the maintenance of normal vascular permeability by protecting the ESG in intact microvessels.

METHODS

We quantified the ESG in post-capillary venules of rat mesentery and measured the vascular permeability to albumin in the presence and absence of 1 μM S1P. We also measured permeability to albumin in the presence of MMP inhibitors and compared the measured permeability with those predicted by a transport model for the inter-endothelial cleft.

RESULTS

We found that in the absence of S1P, the fluorescence intensity of the FITC-anti-HS-labeled ESG was ~10% of that in the presence of S1P, whereas the measured permeability to albumin was ~6.5-fold of that in the presence of S1P. Similar results were observed with MMP inhibition. The predictions by the mathematical model further confirmed that S1P maintains microvascular permeability by preserving ESG.

CONCLUSIONS

Our results show that S1P contributes to the maintenance of normal vascular permeability by protecting the ESG in intact microvessels, consistent with parallel observation in cultured endothelial monolayers.

Adhesion of malignant mammary tumor cells MDA-MB-231 to microvessel wall increases microvascular permeability via degradation of endothelial surface glycocalyx

To investigate the effect of tumor cell adhesion on microvascular permeability (P) in intact microvessels, we measured the adhesion rate of human mammary carcinoma MDA-MB-231, the hydraulic conductivity (L(p)), the P, and reflection coefficient (σ) to albumin of the microvessels at the initial tumor cell adhesion and after ∼45 min cell perfusion in the postcapillary venules of rat mesentery in vivo. Rats (Sprague-Dawley, 250-300 g) were anesthetized with pentobarbital sodium given subcutaneously. A midline incision was made in the abdominal wall, and the mesentery was gently taken out and arranged on the surface of a glass coverslip for the measurement. An individual postcapillary venule was perfused with cells at a rate of ∼1 mm/s, which is the mean blood flow velocity in this type of microvessels. At the initial tumor cell adhesion, which was defined as one adherent cell in ∼100- to 145-μm vessel segment, L(p) was 1.5-fold and P was 2.3-fold of their controls, and σ decreased from 0.92 to 0.64; after ∼45-min perfusion, the adhesion increased to ∼5 adherent cells in ∼100- to 145-μm vessel segment, while L(p) increased to 2.8-fold, P to 5.7-fold of their controls, and σ decreased from 0.92 to 0.42. Combining these measured data with the predictions from a mathematical model for the interendothelial transport suggests that tumor cell adhesion to the microvessel wall degrades the endothelial surface glycocalyx (ESG) layer. This suggestion was confirmed by immunostaining of heparan sulfate of the ESG on the microvessel wall. Preserving of the ESG by a plasma glycoprotein orosomucoid decreased the P to albumin and reduced the tumor cell adhesion.