Growth kinetics of Chlamydia trachomatis in primary human Sertoli cells

Simone Filardo,Marisa Di Pietro,Ian N Clarke,Rosa Sessa,Rachel J Skilton,Colette E O’Neill

doi:10.1038/s41598-019-42396-3

Simone Filardo, Marisa Di Pietro + Show 4 more

Open Access

https://doi.org/10.1038/s41598-019-42396-3

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Abstract

Chlamydia trachomatis (Ct) is the leading cause of bacterial sexually transmitted infections worldwide and has been associated with male infertility. Recently, it was hypothesized that Ct may infect the epithelium of the seminiferous tubule, formed by Sertoli cells, thus leading to impaired spermatogenesis. To date, there is a lack of data on Ct infection of the seminiferous epithelium; therefore, we aimed to characterize, for the first time, an in vitro infection model of primary human Sertoli cells. We compared Ct inclusion size, morphology and growth kinetics with those in McCoy cells and we studied F-actin fibres, Vimentin-based intermediate filaments and α-tubulin microtubules in Sertoli and McCoy cells. Our main finding highlighted the ability of Ct to infect Sertoli cells, although with a unique growth profile and the inability to exit host cells. Furthermore, we observed alterations in the cytoskeletal fibres of infected Sertoli cells. Our results suggest that Ct struggles to generate a productive infection in Sertoli cells, limiting its dissemination in the host. Nevertheless, the adverse effect on the cytoskeleton supports the notion that Ct may compromise the blood-testis barrier, impairing spermatogenesis.

Highlights

C. trachomatis is an obligate intracellular pathogen characterized by a distinctive developmental cycle, alternating between two morphologically and functionally distinct forms, the elementary body (EB), the extracellular infectious form, and the replicative body (RB), the intracellular replicative form[1,2]
Several potential pathophysiological mechanisms have been investigated and, amongst them, one theory postulates that the infection of the seminiferous tubule epithelium by C. trachomatis might lead to inflammatory damage and, result in impaired spermatogenesis[8,9]
Primary human Sertoli cells grown on coverslips possess a thin and wide cytoplasm with irregular morphology and are approximately ten times the size of McCoy cells

Summary

Introduction

C. trachomatis is an obligate intracellular pathogen characterized by a distinctive developmental cycle, alternating between two morphologically and functionally distinct forms, the elementary body (EB), the extracellular infectious form, and the replicative body (RB), the intracellular replicative form[1,2]. In more than half of all cases, the aetiology is unknown, and amongst all the potential risk factors, C. trachomatis has been the target of several studies that suggested an association between this pathogen and male infertility[8,9,10,11,12,13,14,15]. A report analysing a model of C. muridarum infection in male C57BL/6 mice demonstrated that this pathogen severely affects the seminiferous tubules, formed by Sertoli cells, leading to compromised spermatogenesis with reduced sperm count, motility and altered morphology of mature spermatozoa[16]. The restructuring of the BTB is a complex process that is mainly supported by the Sertoli cell cytoskeleton, and, as such, the maintenance of its structural integrity is essential for the generation of mature functional spermatozoa[17,19,20]

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