Abstract

Cilia, microtubule-based organelles that project from the apical luminal surface of endothelial cells (ECs), are widely regarded as low-flow sensors. Previous reports suggest that upon high shear stress, cilia on the EC surface are lost, and more recent evidence suggests that deciliation—the physical removal of cilia from the cell surface—is a predominant mechanism for cilia loss in mammalian cells. Thus, we hypothesized that EC deciliation facilitated by changes in shear stress would manifest in increased abundance of cilia-related proteins in circulation. To test this hypothesis, we performed shear stress experiments that mimicked flow conditions from low to high shear stress in human primary cells and a zebrafish model system. In the primary cells, we showed that upon shear stress induction, indeed, ciliary fragments were observed in the effluent in vitro, and effluents contained ciliary proteins normally expressed in both endothelial and epithelial cells. In zebrafish, upon shear stress induction, fewer cilia-expressing ECs were observed. To test the translational relevance of these findings, we investigated our hypothesis using patient blood samples from sickle cell disease and found that plasma levels of ciliary proteins were elevated compared with healthy controls. Further, sickled red blood cells demonstrated high levels of ciliary protein (ARL13b) on their surface after adhesion to brain ECs. Brain ECs postinteraction with sickle RBCs showed high reactive oxygen species (ROS) levels. Attenuating ROS levels in brain ECs decreased cilia protein levels on RBCs and rescued ciliary protein levels in brain ECs. Collectively, these data suggest that cilia and ciliary proteins in circulation are detectable under various altered-flow conditions, which could serve as a surrogate biomarker of the damaged endothelium.

Highlights

  • Cilia are microtubule-based organelles that are present in most eukaryotic cells [1] and are distinguished based on the arrangement of 9 outer microtubule doublets enclosing a central doublet (9+2) or not (9+0). 9+0 cilia are often referred to as primary nonmotile cilia and 9+2 cilia as motile cilia [2]

  • Attenuating reactive oxygen species (ROS) levels in brain endothelial cells (ECs) decreased cilia protein levels on RBCs and rescued ciliary protein levels in brain ECs. These data suggest that cilia and ciliary proteins in circulation are detectable under various altered-flow conditions, which could serve as a surrogate biomarker of the damaged endothelium

  • Our present study reveals that cilia-specific proteins can be quantified in the plasma and should be explored as biomarkers of endothelial damage or dysfunction

Read more

Summary

Introduction

Cilia are microtubule-based organelles that are present in most eukaryotic cells [1] and are distinguished based on the arrangement of 9 outer microtubule doublets enclosing a central doublet (9+2) or not (9+0). 9+0 cilia are often referred to as primary nonmotile cilia and 9+2 cilia as motile cilia [2]. Ciliary length is often correlated with mechanosensory action in blood vessels, with cells experiencing low shear stress having longer cilia and cells in blood vessels with high shear stress having shorter cilia or no cilia [12, 13]. In both zebrafish and mammals, primary cilia are considered enriched in regions of low shear stress [11, 14]. In the mammalian retinal vasculature, primary cilia are suggested to act in concert with bone morphogenetic protein 9 to minimize vessel regression before onset of high shear stress–mediated vascular remodeling [15]. EC cilia are widely considered as low shear stress sensors

Methods
Results
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call