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. 2015 Sep 8;5(3):392-404.
doi: 10.1016/j.stemcr.2015.07.013. Epub 2015 Aug 28.

Interleukin-25 Mediates Transcriptional Control of PD-L1 via STAT3 in Multipotent Human Mesenchymal Stromal Cells (hMSCs) to Suppress Th17 Responses

Wei-Bei Wang  1 , Men-Luh Yen  2 , Ko-Jiunn Liu  3 , Pei-Ju Hsu  1 , Ming-Hong Lin  4 , Pei-Min Chen  2 , Putty-Reddy Sudhir  5 , Chein-Hung Chen  5 , Chung-Hsuan Chen  5 , Huei-Kang Sytwu  4 , B Linju Yen  6
Affiliations

Interleukin-25 Mediates Transcriptional Control of PD-L1 via STAT3 in Multipotent Human Mesenchymal Stromal Cells (hMSCs) to Suppress Th17 Responses

Wei-Bei Wang et al. Stem Cell Reports. .

Abstract

Multipotent human mesenchymal stromal cells (hMSCs) harbor immunomodulatory properties that are therapeutically relevant. One of the most clinically important populations of leukocytes is the interleukin-17A (IL-17A)-secreting T (Th17) lymphocytes. However, mechanisms of hMSC and Th17 cell interactions are incompletely resolved. We found that, along with Th1 responses, hMSCs strongly suppressed Th17 responses and this required both IL-25--also known as IL--17E-as well as programmed death ligand-1 (PD-L1), a potent cell surface ligand for tolerance induction. Knockdown of IL-25 expression in hMSCs abrogated Th17 suppression in vitro and in vivo. However, IL-25 alone was insufficient to significantly suppress Th17 responses, which also required surface PD-L1 expression. Critically, IL-25 upregulated PD-L1 surface expression through the signaling pathways of JNK and STAT3, with STAT3 found to constitutively occupy the proximal region of the PD-L1 promoter. Our findings demonstrate the complexities of hMSC-mediated Th17 suppression, and highlight the IL-25/STAT3/PD-L1 axis as a candidate therapeutic target.

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Figures

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Graphical abstract
Figure 1
Figure 1
Multipotent Human Mesenchymal Stromal Cells (hMSCs) Suppress Th17 Responses (A–D) Human peripheral blood CD3+ leukocytes (PBLs) (A, representative data; B, pooled data of 17 PBL donors co-cultured with all three hMSC donors) or CD3+ CD4 T cells (C, representative data; D, pooled data of 11 PBL donors co-cultured with all three hMSC donors) were co-cultured without (left) or with (right) hMSCs ex vivo, followed by PMA/ionomycin stimulation for 6 hr. (E–H) IL-17A production in ex-vivo-cultured CD3+ T cells was assessed by intracellular staining. IL-17A and IFN-γ production in CD3+ PBLs (E, representative data; F, pooled data) or CD3+ CD4 T cells (G, representative data; H, pooled data) without and with co-culture of hMSCs was analyzed by flow cytometry. Representative intracellular staining is shown for IL-17A+ IFN-γ−- CD3+ T cells (R3 region) and IL-17A+IFN-γ+ (R5 region) CD3+ T cells, and pooled data from PBLs (n = 4) or CD4 T cells (n = 4) co-cultured with two hMSC donors (donors A and B) are provided in (F) and (H), respectively. Gray bars represent the percentages of IL-17A+ IFN-γ−- CD3+ T cells, whereas white bars represent the percentages of IL-17A+IFN-γ+ T cells. (I and J) IL-22 production in four donors of CD3+ CD4 T cells (I, representative data; J, pooled data) without and with co-culture of two donors of hMSCs (donors A and B) was assessed by intracellular staining. Cell percentages are denoted in the dotplot quadrant of interest. Data are shown as mean ± SD. ∗p < 0.05, ∗∗p < 0.01.
Figure 2
Figure 2
hMSCs Constitutively Express IL-25 (A–D) Gene expression of IL-25 in placenta-derived hMSCs and fibroblast cell lines (MRC-5 and WS-1) (A), as well as three donors each of placental (left) and bone marrow (BM; right) hMSCs (B), was assessed by RT-PCR. Protein expression of IL-25 was determined by western blotting (C, K562 cell line and indicated amounts of recombinant human IL-25 [rhIL-25] as positive controls; tubulin as internal control) and intracellular staining for flow cytometric analysis (D; left, placental hMSC donor A; right, BM hMSC donor A). (E) Filled histograms represent isotype control; unfilled histograms represent IL-25 antibody staining, with pooled data (three donors each of placental and BM hMSCs). Ctrl, isotype control; MFI, mean fluorescence intensity; A.U., arbitrary units. (F) Secreted IL-25 by placental hMSCs (donor C, black bar), BM hMSCs (donor B, gray bar), MRC-5 (striped bar), or WS-1 (white bar) was assessed by collected conditioned medium of each cell type and analyzed by ELISA. Data are shown as mean ± SD of technical triplicates.
Figure 3
Figure 3
IL-25 Silencing in hMSCs Reverses Th17 Responses In Vitro and In Vivo (A–D) Freshly isolated human PBLs (A) or CD4 T cells (C) were co-cultured without (left) or with either siCtrl hMSCs (middle) or siIL-25 hMSCs (right) for 3 days, followed by PMA/ionomycin stimulation for 6 hr. IL-17A production in CD3+ T cells was assessed by intracellular staining. Numbers in the top right quadrants represent the percentages of IL-17A-producing CD3+ T cells. Pooled data from PBLs (n = 3) or CD4 T cells (n = 3) and two hMSC donors (donors A and B) are provided in (B) and (D), respectively. Data are shown as mean ± SD. ∗p < 0.05, ∗∗p < 0.01. (E) Experimental strategy for establishing in vivo inflammatory conditions in wild-type C57BL/6J mice with expansion of Th17 cells and adoptive transfer of hMSCs is shown. (F) On day 3 after LPS (100 μg/mouse) challenge, IL-17A production in activated CD4 T cells in splenocytes from control mice, PBS-treated mice, siCtrl-hMSC-treated mice, or siIL-25-hMSC-treated mice was assessed by intracellular staining. (G and H) Calculated (G) and relative (H) mean percentage of IL-17A-expressing CD4 T cells among control mice, PBS-treated mice, siCtrl-hMSC-treated mice, or siIL-25-hMSC-treated mice (n = 6). Data are shown as mean ± SD. ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.005.
Figure 4
Figure 4
Exogenous IL-25 Alone Is Insufficient to Significantly Suppress Th17 Responses, with Cell Contact Required as well for hMSC-Mediated Inhibition of Th17 Responses (A) Human CD4 T cells were treated with indicated doses of rhIL-25 for 18 hr, followed by PMA/ionomycin stimulation for 6 hr. IL-17A production in CD3+ T cells was assessed by intracellular staining. Numbers in the top right quadrants represent the percentages of IL-17A-producing CD3+ T cells. (B) Pooled data of five PBL donors are shown. (C) Human CD4 T cells (n = 4) were co-cultured without or with hMSCs (two donors, B and C) in the absence or presence of transwell barriers. (D) Pooled data from healthy donors are shown. Data are shown as mean ± SD. ∗∗p < 0.01; n.s., not significant.
Figure 5
Figure 5
IL-25 Induces PD-L1 Surface Expression on hMSCs and Human Monocytes (A) PD-L1 in siCtrl MSCs (left) and siPD-L1 MSCs (right) was analyzed by surface staining. (B) Freshly isolated human PBLs were co-cultured without (left) or with siCtrl MSCs (middle) or siPD-L1 MSCs (right) for 3 days, followed by PMA/ionomycin stimulation for 6 hr. IL-17A production in CD3+ T cells was assessed by intracellular staining. Representative data are shown with numbers in the top right quadrants representing the percentages of IL-17A-producing CD3+ T cells. (C) Pooled data from PBLs (n = 4) and two hMSC donors (donors A and B) are shown. (D) Folds of reversed phenotypes of siIL-25 and siPD-L1 are shown. (E) PD-L1 expression on siCtrl hMSCs (left) and siIL-25 hMSCs (right) was assessed by cell surface staining. Filled histograms represent isotype control; unfilled histograms represent PD-L1 antibody staining. (F) Pooled data of PD-L1 expression (indicated by fold change in MFI) on siIL-25 hMSCs and siPD-L1 hMSCs (all three donors) are shown. PD-L1 expression levels were compared between hMSCs silenced for the target gene (IL-25 or PD-L1) and the respective siCtrl. (G) hMSCs were treated with the indicated doses of rhIL-25 for 18 hr and assessed for cell surface PD-L1 expression by cell surface staining. Pooled data (all three donors) are shown in chart to the right with bars representing MFI. (H) Human PBLs were treated with the indicated doses of rhIL-25 for 18 hr and assessed for cell surface PD-L1 expression on monocytes, gated using FSC and SSC, by flow cytometric analysis. (I) Pooled data (ten PBL donors) are shown with bars representing MFI. ∗p < 0.05, ∗∗p < 0.01; n.s., not significant.
Figure 6
Figure 6
IL-25-Mediated PD-L1 Expression in Human Monocytes and hMSCs Is Mediated through JNK and STAT3, with STAT3 Involved in Transcriptional Control of PD-L1 (A) Human PBLs were pretreated with inhibitors of STAT3 (WP1066; 2.5 μM), JNK (SP600125; 25 μM), or MEK1 (PD98059; 20 μM) prior to 100 ng/ml rhIL-25 for 18 hr, with subsequent flow cytometric analysis for PD-L1 surface expression on monocytes, gated using FSC and SSC. Filled histograms represent isotype control; unfilled histograms represent PD-L1 antibody staining. (B–D) Pooled data (three donors) are shown (B) with bars representing MFI. hMSCs were treated with inhibitors of STAT3 (C; WP1066, 2.5 μM) and JNK (D; SP600125, 25 μM) for 6 hr, and subsequently assessed by flow cytometric analysis for PD-L1 surface expression. Pooled data (all three donors) for each respective inhibitor are provided (left charts) with bars representing MFI. (E) Putative GAS elements (STAT-binding sites) in the proximal promoter region of human PD-L1 gene (700 bp region upstream from the transcription start site), as determined with TFSearch web-based software. (F) Binding of STAT3 or IgG (negative control) in hMSCs was analyzed by chromatin immunoprecipitation (ChIP) with promoter-specific primers for region 1 and region 2. The input samples (positive control) represent 1% starting chromatin. (G) Schematic shows a model of hMSC-mediated suppression of Th17 responses involving the IL-25/STAT3/PD-L1 axis.
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