Chlamydia is the most frequently reported bacterial sexually transmitted infection worldwide and is a major sexual and reproductive health problem. To date, the research on chlamydial infections has primarily focused on females, despite similar incidence rates in both males and females. Recently, our group showed that Chlamydia reaches the testes despite bilateral vasectomy prior to infection, which eliminates the route of ascending cell-cell transmission in the male reproductive tract. Chlamydia achieves this by infecting penile macrophages at the primary infection site, which then disseminate to the testes via the hematogenous route, compromising the testes immune-privileged environment and dysregulating spermatogenesis. Ex vivo, we have shown that all key testicular cell types (Sertoli, Leydig, Spermatogonia, and resident testicular macrophages) are susceptible to infection and subsequent damage.
The mechanisms underlying Chlamydia’s ability to hijack penile macrophages and disseminate remains unknown. Therefore, to understand the direct effects of Chlamydia on macrophages, RNA sequencing and transcriptome analysis were performed on Chlamydia muridarum (Cmu) infected murine bone marrow-derived macrophages (BMDM) and the RAW264.7 macrophage cell line. We identified 735 and 3689 significantly upregulated, and 873 and 1091 downregulated genes in Cmu-infected BMDM and RAW264.7, respectively, when compared to uninfected controls. KEGG pathway analysis highlighted several biologically important, significantly altered canonical pathways, including cytokine-cytokine receptor interaction, focal adhesion, NFkB signaling pathway, and extracellular matrix-receptor interaction. Overall, the analysis of two types of Cmu-infected murine macrophages revealed that Chlamydia manipulates the host cell transcriptome to create an optimal environment for growth and maturation. Additionally, chlamydial infection likely influences macrophages to disseminate to distal sites and drive pathogenesis. This will be an important consideration for the downstream development of therapeutic intervention strategies to prevent infection and preserve male fertility.