Chlamydia trachomatis promotes 3T3 cell differentiation into adipocytes

There is experimental and clinical evidence showing that some viral and bacterial pathogens are linked to the accumulation of excessive body fat and obesity.

The aim of the study was to investigate the ability of C. trachomatis to propagate in the pre-adipocyte cell line and induce its differentiation into fat cells.

3T3 L1 pre-adipocytes or McCoy cells were plated and infected with C. trachomatis. The cell monolayers were further studied by immunofluorescent and quantitative RT-PCR methods.

C. trachomatis can efficiently propagate in 3T3 L1 cells, a mouse pre-adipocyte cell line. The morphological characteristics of chlamydial growth revealed in 3T3 L1 cells with the monoclonal chlamydial MOMP-specific antibody resembled those seen in McCoy cells, a classic cell line used for chlamydial research. The number of chlamydial 16S rRNA copies detectable in the lysates of McCoy and 3T3 cells infected with C. trachomatis was almost identical, suggesting similar efficiency of pathogen propagation in both cell lines. Moreover, there was a significant increase in aP2 mRNA transcript levels as well as moderate induction of SCD-1 mRNA in the total RNA extracted from the infected 3T3 L1 cells 48 h following the pathogen inoculation. The increased expression of the adipogenic markers was also accompanied by lipid droplet accumulation in the C. trachomatis infected 3T3 L1 cells, suggesting their transformation into differentiated adipocytes.

The direct effect of the pathogen on fat cell progenitors observed in this work may explain abnormal fat deposition at the sites of chronic inflammation caused by C. trachomatis.