Fig. 6: hUC-MSC-derived CHI3L1 inhibits T cells through PPARδ/STAT1/3.

A GSEA showing that the IL6-JAK-STAT3 pathway is enriched in T cells co-cultured with MSC^shCHI3L1 compared with T + MSC^shNTC group. B GSEA showing that the IL6-JAK-STAT3 pathway is repressed in T cells co-cultured with MSC^shNTC compared to activated T cells. C–D Heatmap of RNA-sequencing data showing the expression level of genes involved in IL6-JAK-STAT3 pathway in indicated samples. E Western blot for phosphorylated and total STAT1 and STAT3 in T cells with indicated treatments for 2 days. F Western blot for phosphorylated and total STAT1 and STAT3 in T cells cultured with or without rCHI3L1 (100 ng/mL). G Heatmap of RNA-sequencing data showing the expression level of PPARD in activated T cells (T cells), T cells co-cultured with MSC^shNTC (+ MSC^shNTC), and T cells co-cultured with MSC^shCHI3L1 (+ MSC ^shCHI3L1). H RT-qPCR for PPARD in T cells cultured alone or co-cultured with hUC-MSCs with or without CHI3L1 knockdown. I Western blot and corresponding densitometry analysis (J) for PPARδ in T cells culture alone, or co-cultured with MSC^shNTC or MSC^shCHI3L1. K Western blot for phosphorylated and total STAT1 and STAT3 in liver MNCs in indicated groups. L Representative western blot for testing phosphorylated-STAT1 (p-STAT1), total STAT1, phosphorylated-STAT3 (p-STAT3), and total STAT3 in human naïve CD3⁺ T cells, CD3⁺ T cells activated by PHA, activated CD3⁺ T cells co-cultured with MSCs, and activated CD3⁺ T cells co-cultured with MSCs in the presence of PPARδ inhibitor (GSK3787, S8025, Selleck). GSK3787 was added simultaneously with PHA at a concentration of 1 μM for 48 h. M Western blot for phosphorylated and total STAT1 and STAT3 in T cells stimulated with PHA in the absence or presence of PPARδ agonist GW501516 (10 μM). N Representative flow cytometry plots and quantification (O) of IFN-γ (upper) and TNF-α (lower)-producing CD3⁺ T cells treated with GW501516. DMSO was used as a control in (L–O).