Infection of Human Retinal Pigment Epithelium with Chlamydia trachomatis.

Little is known about the susceptibility of posterior segment tissues, particularly the human retinal pigment epithelium (hRPE), to Chlamydia trachomatis. The purpose of the study was to investigate the possibility of infecting the hRPE with Chlamydia trachomatis, and to examine the infectivity of different Chlamydia trachomatis clinical isolates for hRPE cells and the hRPE cell response to the infection.Cultured hRPE and McCoy cells were inoculated with eight Chlamydia trachomatis (serovar E) clinical isolates at multiplicity of infection (MOI) of 2.0 or 0.3. To detect Chlamydia trachomatis, samples were stained immunohistochemically with anti-major outer membrane protein antibodies at 24h, 48h, and 72h postinoculation (PI). The changes in the expression of signaling molecules and proteins of cytoskeleton and extracellular matrix in hRPE cells were examined immunohistochemically.All eight clinical isolates demonstrated ability to infect hRPE cells. At equal MOI of 0.3, the infectivity of Chlamydia trachomatis clinical isolates for RPE culture was found to be at least as high as that for McCoy cell culture. At 24h PI, the percentage of inclusion-containing cells varied from 1.5 ± 0.52 to 14.6 ± 3.3% in hRPE cell culture infected at MOI of 2.0 against 0.37 ± 0.34 to 8.9 ± 0.2% in McCoy cell culture infected at MOI of 0.3. Collagen type I, collagen type IV, basic fibroblast growth factor, transforming growth factor-beta and interleukin-8 expression at 48h PI were maximally increased, by 2.1-, 1.3-, 1.5-, 1.5- and 1.6-fold, respectively, in the Chlamydia trachomatis-infected compared with control hRPE cell culture specimens (P < 0.05).This study, for the first time, proved the possibility of infecting hRPE cultured cells with Chlamydia trachomatis, which leads to proproliferative and proinflammatory changes in the expression of signaling molecules and extracellular matrix components

Immunohistochemistry and direct immunofluorescent staining of hRPE and McCoy cell cultures at different time-points postinoculation with <i>Chlamydia trachomatis</i> (clinical isolate No.24032).

<p>In both types of cultures, both techniques reveal highly immunoreactive inclusions (arrowheads). Twenty-four to 72 h postinoculation, a reduction in the number of intracellular inclusions is observed due to the release of a new generation of EBs to the extracellular environment. Scale bar: 50 μm.</p

Primary Antibodies Used to Detect <i>C</i>. <i>trachomatis</i> Antigens, Signaling, Cytoskeleton and Extracellular Matrix Molecules.

<p><i>MOMP</i>, major outer membrane protein; <i>VEGF</i>, vascular endothelial growth factor; <i>TNF–α</i>, tumor necrosis factors–α; <i>α-SMA</i>, smooth muscle actin; <i>MMP–9</i>, matrix metalloproteinase 9; <i>bFGF</i>, basic fibroblast growth factor; <i>TGF–β</i>, transforming growth factor β; <i>RFU</i>, ready for use</p

Changes in the percentage of inclusion-containing cells in hRPE and McCoy cell cultures following inoculation with <i>Chlamydia trachomatis</i> (clinical isolate No.24032).

<p>Changes in the percentage of inclusion-containing cells in hRPE and McCoy cell cultures following inoculation with <i>Chlamydia trachomatis</i> (clinical isolate No.24032).</p

Immunohistochemistry micrographs of hRPE cell culture at 72 hours postinoculation with <i>Chlamydia trachomatis</i> clinical isolate No.24032.

<p>(A) Intracellular inclusions (arrowhead) exhibiting weak immune responsiveness (due to release of EBs to extracellular environment). (B) Numerous EBs (arrowheads) in microscopy projection of cells without inclusions. Scale bar: 10 μm.</p

Clinical Isolates of <i>C</i>. <i>trachomatis</i>, the Doses Used to Infect Cell Cultures and Multiplicities of Infection Corresponding to the Doses and to the Isolates.

<p><i>IFU</i>, inclusion forming units; <i>MOI</i>, multiplicity of infection</p

Changes in the expression of signaling molecules and proteins of cytoskeleton and extracellular matrix of hRPE cells grown in culture following inoculation with <i>Chlamydia trachomatis</i> (clinical isolates Nos. 24032 and 27692).

<p>Changes in the expression of signaling molecules and proteins of cytoskeleton and extracellular matrix of hRPE cells grown in culture following inoculation with <i>Chlamydia trachomatis</i> (clinical isolates Nos. 24032 and 27692).</p