Serglycin in Quiescent and Proliferating Primary Endothelial Cells.

Trine M Reine,Astri J Meen,Trond G Jenssen,Arkady Rutkovskiy,Svein O Kolset,Tram T Vuong,Jarle Vaage,Peter Chen

doi:10.1371/journal.pone.0145584

Trine M Reine, Astri J Meen + Show 6 more

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https://doi.org/10.1371/journal.pone.0145584

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Abstract

Proteoglycans are fundamental components of the endothelial barrier, but the functions of the proteoglycan serglycin in endothelium are less described. Our aim was to describe the roles of serglycin in processes relevant for endothelial dysfunction. Primary human umbilical vein endothelial cells (HUVEC) were cultured in vitro and the expression of proteoglycans was investigated. Dense cell cultures representing the quiescent endothelium coating the vasculature was compared to sparse activated cell cultures, relevant for diabetes, cancer and cardiovascular disease. Secretion of 35S- proteoglycans increased in sparse cultures, and we showed that serglycin is a major component of the cell-density sensitive proteoglycan population. In contrast to the other proteoglycans, serglycin expression and secretion was higher in proliferating compared to quiescent HUVEC. RNAi silencing of serglycin inhibited proliferation and wound healing, and serglycin expression and secretion was augmented by hypoxia, mechanical strain and IL-1β induced inflammation. Notably, the secretion of the angiogenic chemokine CCL2 resulting from IL-1β activation, was increased in serglycin knockdown cells, while angiopoietin was not affected. Both serglycin and CCL2 were secreted predominantly to the apical side of polarized HUVEC, and serglycin and CCL2 co-localized both in perinuclear areas and in vesicles. These results suggest functions for serglycin in endothelial cells trough interactions with partner molecules, in biological processes with relevance for diabetic complications, cardiovascular disease and cancer development.

Highlights

We identified the upper band as predominately heparan sulfate proteoglycans by its susceptibility to HNO2 depolymerization, while the 250–300 kDa and the 100 kDa bands were of the Chondroitin sulfate (CS)/dermatan sulfate (DS) type, as they were susceptible to chondroitin ABC lyase (cABC) digestion
In this study we observe a 9-fold increase in 35S-proteoglycan secretion in proliferating endothelial cells compared to quiescent cultures, and we identify serglycin as an important component of the celldensity sensitive proteoglycan population
Most previous studies have focused on serglycin in hematopoietic cells [22], serglycin is expressed by other cells including smooth muscle cells [48], cancer cells [25, 26], endothelial cells [35] and adipose tissue [49]

Summary

Introduction

35S-proteoglycan secretion increased ~ 9 times (± 3.7) in sparse compared to dense cell cultures (Fig 2A). Cellular density had no significant effect on the distribution of 35S- proteoglycans between the medium and the cell fractions, the medium contained 67 and 62% of the total 35Sproteoglycans in sparse and dense cultures, respectively (Fig 2B). In contrast to all other proteoglycans investigated; only expression of serglycin mRNA increased with decreasing cell density.

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