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. 2011 Jan 7;6(1):e14497.
doi: 10.1371/journal.pone.0014497.

TWEAK Appears as a Modulator of Endometrial IL-18 Related Cytotoxic Activity of Uterine Natural Killers

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Free PMC article

TWEAK Appears as a Modulator of Endometrial IL-18 Related Cytotoxic Activity of Uterine Natural Killers

Marie Petitbarat et al. PLoS One. .
Free PMC article

Abstract

Background: TWEAK (Tumor necrosis factor like WEAK inducer of apoptosis) is highly expressed by different immune cells and triggers multiple cellular responses, including control of angiogenesis. Our objective was to investigate its role in the human endometrium during the implantation window, using an ex-vivo endometrial microhistoculture model. Indeed, previous results suggested that basic TWEAK expression influences the IL-18 related uNK recruitment and local cytotoxicity.

Methodology/principal findings: Endometrial biopsies were performed 7 to 9 days after the ovulation surge of women in monitored natural cycles. Biopsies were cut in micro-pieces and cultured on collagen sponge with appropriate medium. Morphology, functionality and cell death were analysed at different time of the culture. We used this ex vivo model to study mRNA expressions of NKp46 (a uNK cytotoxic receptor) and TGF-beta1 (protein which regulates uNK cytokine production) after adjunction of excess of recombinant IL-18 and either recombinant TWEAK or its antibody. NKp46 protein expression was also detailed by immunohistochemistry in selected patients with high basic mRNA level of IL-18 and either low or high mRNA level of TWEAK. The NKp46 immunostaining was stronger in patients with an IL-18 over-expression and a low TWEAK expression, when compared with patients with both IL-18 and TWEAK high expressions. We did not observe any difference for TWEAK expression when recombinant protein IL-18 or its antibody was added, or conversely, for IL-18 expression when TWEAK or its antibody was added in the culture medium. In a pro-inflammatory environment (obtained by an excess of IL-18), inhibition of TWEAK was able to increase significantly NKp46 and TGF-beta1 mRNA expressions.

Conclusions/significance: TWEAK doesn't act on IL-18 expression but seems to control IL-18 related cytotoxicity on uNK cells when IL-18 is over-expressed. Thus, TWEAK appears as a crucial physiological modulator to prevent endometrial uNK cytotoxicity in human.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Endometrium cells morphology providing from luteal phase.
Revealed by immunohistochemistry with cytokeratin (KL1) and vimentin antibodies (x 6,6). A–B: before culture, C–D: after 2 days of culture without hormones and without sponge, E–F: after 2 days of culture without hormones and with sponge, G–H: after 2 days of culture with hormones (50 nmol/l estradiol +50 nmol/l progesterone) and without sponge, I–J: after 2 days of culture with hormones (50 nmol estradiol +50 nmol progesterone) and with sponge.
Figure 2
Figure 2. Endometrium cells death revealed by FITC-Annexin V antibody.
A–D: after 2 days of culture, E–H: after 5 days of culture. A,E: without sponge and without hormones, B,F: without sponge and with hormones (50 nmol/l estradiol +50 nmol/l progesterone), C,G: with sponge and without hormones D,H: with sponge and with hormones (50 nmol/l estradiol +50 nmol/l progesterone).
Figure 3
Figure 3. Cytokine and growth factors measures in five different patients.
The culture medium was supplemented with 50 nmol/l of estradiol and progesterone. Proteins levels were measured on days 2 and 3. The graph represents for each protein the ratio of day 3 measure on day 2 measure, reported to the control condition. The control condition had no hormone addition. IL-1b and IL-Ra for patient 2 and PDGF for patient 5 were not detectable.
Figure 4
Figure 4. NKp46 immunostaining.
Patients with an overexpression of IL-18 and with low (A) or high level of TWEAK (B). Magnification is 20X (first column) and 40X (second column). ep: epithelium, s: stroma, gl: glands, sa: spiral arteries.
Figure 5
Figure 5. TWEAK (A) and IL-18 (B) mRNA expression.
From endometrial microhistoculture in 9 patients. The control medium was only supplemented with 50 nmol/l of hormones (estradiol and progesterone). Ethanolate was added to the medium as an inhibitor of Map Kinase pathway. Estradiol and progesterone were added in all media.
Figure 6
Figure 6. NKp46 (A) and TGF-β (B) expression.
From endometrial microhistoculture in 5 different patients. Recombinant human IL-18 (IL-18) alone or with anti-human TWEAK (IL-18 + AC TW) were added to the medium. Estradiol and progesterone were added in all media.

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