Hematogenous dissemination of Chlamydia muridarum from the urethra in macrophages causes testicular infection and sperm DNA damage†

Abstract

The incidence of Chlamydia infection, in both females and males, is increasing worldwide. Male infections have been associated clinically with urethritis, epididymitis, and orchitis, believed to be caused by ascending infection, although the impact of infection on male fertility remains controversial. Using a mouse model of male chlamydial infection, we show that all the major testicular cell populations, germ cells, Sertoli cells, Leydig cells, and testicular macrophages can be productively infected. Furthermore, sperm isolated from vas deferens of infected mice also had increased levels of DNA damage as early as 4 weeks post-infection. Bilateral vasectomy, prior to infection, did not affect the chlamydial load recovered from testes at 2, 4, and 8 weeks post-infection, and Chlamydia-infected macrophages were detectable in blood and the testes as soon as 3 days post-infection. Partial depletion of macrophages with clodronate liposomes significantly reduced the testicular chlamydial burden, consistent with a hematogenous route of infection, with Chlamydia transported to the testes in infected macrophages. These data suggest that macrophages serve as Trojan horses, transporting Chlamydia from the penile urethra to the testes within 3 days of infection, bypassing the entire male reproductive tract. In the testes, infected macrophages likely transfer infection to Leydig, Sertoli, and germ cells, causing sperm DNA damage and impaired spermatogenesis.

Chlamydia muridarum Can Invade the Central Nervous System via the Olfactory and Trigeminal Nerves and Infect Peripheral Nerve Glial Cells

“…Since C. muridarum is an obligate intracellular bacterium with a lifecycle of~32-56 h (Ramsey et al, 2009;Bryan et al, 2019), the fact that C. muridarum invaded sites distant from the nasal epithelium so rapidly suggests that chlamydial EBs may rapidly "travel" (possibly by flow of extracellular fluid) via nerve fascicles into the CNS. It is also possible that localized C. muridarum infection in the nasal epithelium causes damage to the olfactory mucosa, allowing access to the underlying nerve fascicles.…”

DNA damage contributes to transcriptional and immunological dysregulation of testicular cells during Chlamydia infection

“…Mice were infected via the intrapenile route, and sperm was harvested from the vas deferens at six months post-infection as previously described. 10…”

“…Many factors negatively affect gene transcription and cell function, including DNA fragmentation and epigenetic modification. 11,12 DNA fragmentation in both sperm 10,13 and female reproductive tract cells 14 is induced by Chlamydia, and we hypothesize that the infection of male reproductive tract germ and somatic cells may cause similar DNA damage. Epigenetic modifications, in contrast, induce changes in gene expression without altering the genome sequence or stability, 15 for example addition or removal of methyl groups to DNA and/or histones.…”

“…blood-testis barrier and secrete anti-inflammatory and nutrient factors). 9 Each cell type is susceptible to 10 , and may be functionally compromised by Chlamydia infection, resulting in spermatogenesis dysregulation. There are numerous host and pathogen-derived mechanisms that could influence cell function; however, transcriptional and translational modifications are potent potential deregulators.…”

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“…Since C. muridarum is an obligate intracellular bacterium with a lifecycle of~32-56 h (Ramsey et al, 2009;Bryan et al, 2019), the fact that C. muridarum invaded sites distant from the nasal epithelium so rapidly suggests that chlamydial EBs may rapidly OECs and TgSCs also produced the regulatory cytokine (E) IL-6 while chemokines (F) CXCL-1, (G) MCP-1, (H) MIP-1a, and (I) MIP-1b were produced by TgSC, OECs, and macrophages. Cells that had not been infected (control cells) did not produce cytokines/chemokines at detectable levels.…”