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Updated: May 1, 2026
Human Saphenous Vein Endothelial Cell Isolation and Exposure to Controlled Levels of Shear Stress and Stretch
Published on: April 21, 2023
Sox18 preserves the pulmonary endothelial barrier under conditions of increased shear stress
Christine M Gross1, Saurabh Aggarwal, Sanjiv Kumar
1Pulmonary Disease Program Vascular Biology Center, Georgia Regents University, Augusta, Georgia.
Insights
Increased pulmonary blood flow in congenital heart disease enhances endothelial barrier integrity. This protective effect is mediated by Sox18, which up-regulates Claudin-5, preventing pulmonary edema.
Area of Science:
- Cardiovascular Biology
- Endothelial Cell Biology
- Pulmonary Hypertension Research
Background:
- Children with congenital heart abnormalities often experience elevated pulmonary blood flow (PBF) and shear stress.
- Despite high permeability factors, pulmonary edema is not common in these patients, suggesting protective mechanisms.
- Laminar fluid shear stress is known to enhance pulmonary vascular barrier integrity, but the underlying mechanisms are unclear.
Purpose of the Study:
- To investigate the role of Sox18 in maintaining pulmonary vascular barrier integrity under increased shear stress.
- To elucidate the molecular mechanisms by which shear stress affects endothelial barrier function in the context of congenital heart disease.
Main Methods:
- Utilized an ovine model of congenital heart disease with increased PBF (shunt).
- Subjected ovine pulmonary arterial endothelial cells (PAEC) to laminar flow and analyzed trans-endothelial resistance (TER).
- Assessed Sox18 and Claudin-5 expression (mRNA and protein) in PAEC and lung tissue using microarray, gene manipulation, and biochemical assays.
Main Results:
- Laminar flow increased TER and Sox18 expression in PAEC.
- Sox18 overexpression enhanced TER, while Sox18 knockdown attenuated it, confirming Sox18's role in barrier integrity.
- Shear stress upregulated Claudin-5 in a Sox18-dependent manner; Claudin-5 depletion abolished the shear stress-induced increase in TER.
- Elevated Sox18 and Claudin-5 levels were observed in lung tissue of lambs with increased PBF.
Conclusions:
- Increased laminar flow protects endothelial barrier function through the Sox18-dependent upregulation of Claudin-5.
- Sox18 plays a critical role in maintaining pulmonary vascular barrier integrity in response to elevated shear stress.
- These findings offer insights into the mechanisms preventing pulmonary edema in pediatric congenital heart disease with increased PBF.
Abstract:
Shear stress secondary to increased pulmonary blood flow (PBF) is elevated in some children born with congenital cardiac abnormalities. However, the majority of these patients do not develop pulmonary edema, despite high levels of permeability inducing factors. Previous studies have suggested that laminar fluid shear stress can enhance pulmonary vascular barrier integrity. However, little is known about the mechanisms by which this occurs. Using microarray analysis, we have previously shown that Sox18, a transcription factor involved in blood vessel development and endothelial barrier integrity, is up-regulated in an ovine model of congenital heart disease with increased PBF (shunt). By subjecting ovine pulmonary arterial endothelial cells (PAEC) to laminar flow (20 dyn/cm(2) ), we identified an increase in trans-endothelial resistance (TER) across the PAEC monolayer that correlated with an increase in Sox18 expression. Further, the TER was also enhanced when Sox18 was over-expressed and attenuated when Sox18 expression was reduced, suggesting that Sox18 maintains the endothelial barrier integrity in response to shear stress. Further, we found that shear stress up-regulates the cellular tight junction protein, Claudin-5, in a Sox18 dependent manner, and Claudin-5 depletion abolished the Sox18 mediated increase in TER in response to shear stress. Finally, utilizing peripheral lung tissue of 4 week old shunt lambs with increased PBF, we found that both Sox18 and Claudin-5 mRNA and protein levels were elevated. In conclusion, these novel findings suggest that increased laminar flow protects endothelial barrier function via Sox18 dependent up-regulation of Claudin-5 expression.
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