Primary ectocervical epithelial cells display lower permissivity to Chlamydia trachomatis than HeLa cells and a globally higher pro-inflammatory profile

Chongfa Tang,Chang Liu,Christine Louis-Sylvestre,Juliette Hugueny,Henri Cohen,Yael Levy-Zauberman,Benoit Maffei,Aminata Kane,Béatrice Niragire,Yongzheng Wu,Agathe Subtil,Anne-Claire Donnadieu,Thomas Vernay,Etienne Vincens

doi:10.1038/s41598-021-85123-7

Abstract

The tumoral origin and extensive passaging of HeLa cells, a most commonly used cervical epithelial cell line, raise concerns on their suitability to study the cell responses to infection. The present study was designed to isolate primary epithelial cells from human ectocervix explants and characterize their susceptibility to C. trachomatis infection. We achieved a high purity of isolation, assessed by the expression of E-cadherin and cytokeratin 14. The infectious progeny in these primary epithelial cells was lower than in HeLa cells. We showed that the difference in culture medium, and the addition of serum in HeLa cultures, accounted for a large part of these differences. However, all things considered the primary ectocervical epithelial cells remained less permissive than HeLa cells to C. trachomatis serovar L2 or D development. Finally, the basal level of transcription of genes coding for pro-inflammatory cytokines was globally higher in primary epithelial cells than in HeLa cells. Transcription of several pro-inflammatory genes was further induced by infection with C. trachomatis serovar L2 or serovar D. In conclusion, primary epithelial cells have a strong capacity to mount an inflammatory response to Chlamydia infection. Our simplified purification protocol from human explants should facilitate future studies to understand the contribution of this response to limiting the spread of the pathogen to the upper female genital tract.

Highlights

The tumoral origin and extensive passaging of HeLa cells, a most commonly used cervical epithelial cell line, raise concerns on their suitability to study the cell responses to infection
To limit contamination with fibroblasts, we introduced after digestion a mechanical separation of the mucosal layer, that is made of epithelial cells and mucus, from the stromal tissue (Fig. S1b)
We measured the efficacy of bacterial internalization, and again observed no difference between primary epithelial cells and HeLa cells (Fig. 2g, S3). These results indicate that the decrease in C. trachomatis infectivity in primary cells compared to HeLa cells were not due to defects in the attachment nor entry steps, but in failure, for about 75% to 90% of the bacteria, to initiate the development of a viable inclusion

Summary

Introduction

The tumoral origin and extensive passaging of HeLa cells, a most commonly used cervical epithelial cell line, raise concerns on their suitability to study the cell responses to infection. Due to its anatomy and hormonal regimen, the female genital tract (FGT) is two to three times more likely than the male’s to be infected by certain microorganisms such as Neisseria gonorrhea and Chlamydia trachomatis[2,3]. A better understanding of their intrinsic ability to limit C. trachomatis infection is required, and would be complementary to the data obtained from animal models For this purpose, HeLa cells, an epithelial cell line derived from a cervical cancer, have been widely used. Primary epithelial cells isolated from the human cervix have been used by different groups[10,11,12] They demonstrated, for instance, the expression of Toll-like receptors by these cells[13] and their capacity for antigen-presentation[14]. Studies on their response to Chlamydia infection remain scarce[10,15,16,17,18,19]

Methods

Results

Conclusion