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BACKGROUND We have recently demonstrated that injured patients in hemorrhagic shock shed syndecan-1 and that the early use of fresh frozen plasma (FFP) in these patients is correlated with improved clinical outcomes. As the lungs are frequently injured after trauma, we hypothesized that hemorrhagic shock-induced shedding of syndecan-1 exposes the underlying pulmonary vascular endothelium to injury resulting in inflammation and hyperpermeability, and that these effects would be mitigated by FFP. METHODS In vitro, pulmonary endothelial permeability, endothelial monolayer flux, transendothelial electrical resistance (TER), and leukocyte-endothelial binding were measured in pulmonary endothelial cells after incubation with equal volumes of FFP or lactated Ringers (LR). In vivo, using a coagulopathic mouse model of trauma and hemorrhagic shock, pulmonary hyperpermeability, neutrophil infiltration, and syndecan-1 expression and systemic shedding were assessed after three hours of resuscitation with either 1XFFP or 3XLR and compared to shock alone and shams. RESULTS In vitro, endothelial permeability and flux were decreased, TER was increased, and leukocyte-endothelial binding was inhibited by FFP compared to LR treated endothelial cells. In vivo, hemorrhagic shock was associated with systemic shedding of syndecan-1 which correlated with decreased pulmonary sydnecan-1 and increased pulmonary vascular hyperpermeability and inflammation. FFP resuscitation, compared to LR resuscitation, abrogated these injurious effects. CONCLUSIONS After hemorrhagic shock, FFP resuscitation inhibits endothelial cell hyperpermeability and inflammation and restores pulmonary syndecan-1 expression. Modulation of pulmonary syndecan-1 expression may mechanistically contribute to the beneficial effects FFP.

Abstract-In recent years, the endothelial cell surface glycocalyx has emerged as a structure of fundamental importance to a broad range of phenomena that determine cardiovascular health and disease. This new understanding of the functional significance of the glycocalyx has been made possible through recently developed experimental techniques using intravital microscopy that are capable of directly probing the glycocalyx in vivo. Using fluorescent microparticle image velocimetry in venules and endothelialized cylindrical collagen microchannels, we show that the hydrodynamically relevant endothelial cell glycocalyx surface layer observed in microvessels in vivo (0.52Ϯ0.28 m thickness), which is a fundamental determinant of the hydrodynamic and mechanical environment at the endothelial cell surface, is absent from human umbilical vein (0.03Ϯ0.04 m thickness) and bovine aortic (0.02Ϯ0.04 m thickness) endothelial cells grown and maintained under standard cell culture conditions in vitro. An endothelial surface-bound glycosaminoglycan layer, not necessarily indicative of but having similar hydrodynamic properties to the endothelial glycocalyx observed in vivo, was detected (0.21Ϯ0.27 m thickness) only after hyaluronan and chondroitin sulfate were added to the cell culture media at hyperphysiological concentrations (0.2 mg/mL perfused for 75 minutes). The implications of this glycocalyx deficiency under standard cell culture conditions in these pervasive in vitro models broadly impact a myriad of studies involving endothelial cell monolayers in which inferences are made that may depend on endothelial cell surface chemistry. In light of these findings, conclusions drawn from such studies in the areas of microvascular permeability, inflammation, mechanotransduction, and atherosclerosis must be carefully reconsidered. (Circ Res. 2008;102:770-776.)Key Words: cell culture Ⅲ glycocalyx Ⅲ mechanotransduction Ⅲ microcirculation Ⅲ vascular inflammation Ⅲ vascular permeability N umerous studies of endothelial cells (ECs) in culture have been undertaken in recent years that are intended to elucidate mechanisms of EC function spanning a broad range of fields in cardiovascular physiology and pathophysiology, including inflammation, vascular permeability, EC mechanotransduction, and atherosclerosis. [1][2][3][4][5][6][7][8][9] The scientific utility of these and many other studies involving ECs in culture is often critically dependent on cultured systems bearing close morphological, structural, and functional similarities to the tissues they are designed to emulate. Whether or not acknowledged, cell surface chemistry and, specifically, the state of the EC surface glycocalyx in vitro, is a fundamental determinant of the outcome of many of these studies.Over the past decade, it has become well established that the EC surface glycocalyx, a membrane-bound layer of carbohydrates and adsorbed plasma proteins, previously thought to be less than Ϸ50 nm in thickness, in fact extends Ϸ500 nm from the surface of the vascular endothelium in vi...

Abstract-Compelling evidence continues to emerge suggesting that the glycocalyx surface layer on vascular endothelial cells plays a determining role in numerous physiological processes including inflammation, microvascular permeability, and endothelial mechanotransduction. Previous research has shown that enzymes degrade the glycocalyx, whereas inflammation causes shedding of the layer. To track the endogenous recovery of the glycocalyx in vivo, we used fluorescent microparticle image velocimetry (-PIV) in mouse cremaster muscle venules to estimate the hydrodynamically relevant glycocalyx thickness 1, 3, 5, and 7 days after enzymatic or cytokine-mediated degradation of the layer. Results indicate that after acute degradation of the glycocalyx, 5 to 7 days are required for the layer to endogenously restore itself to its native hydrodynamically relevant thickness in vivo. In light of these findings, and because demonstrable evidence has emerged that standard cell culture conditions are not conducive to providing the environment and/or cellular conditions necessary to produce and maintain a physiologically relevant cell surface glycocalyx in vitro, we sought to determine whether merely the passage of time would be sufficient to promote the production of a hydrodynamically relevant glycocalyx on a confluent monolayer of human umbilical vein endothelial cells (HUVECs).Using -PIV, we found that the hydrodynamically relevant glycocalyx was substantially absent 7 days postconfluence on HUVEC-lined cylindrical collagen microchannels maintained under standard culture conditions. Thus, it remains to be determined how a hydrodynamically relevant glycocalyx surface layer can be synthesized and maintained in culture before the endothelial cell culture model can be used to elucidate glycocalyx-mediated mechanisms of endothelial cell function.

Both FFP and SDP similarly modulate pulmonary vascular integrity, permeability, and inflammation in vitro and in vivo in a murine model of HS and trauma.