Fig. 4: PGCCs facilitate transformation of CAFs and stimulate production of collagen I by fibroblasts dominantly via IL-6 pathway.

A Coculture of PGCCs or IL-6 with normal fibroblasts (for 72 h) enriched the population of CAFs (indicated as α-SMA positivity), which can be inhibited by IL-6R antibody and apigenin. Positive percentage of α-SMA in test groups of fibroblasts: Control, 2.3 ± 1.5%; paclitaxel (PTX), 37.3 ± 3.2%; Reg Sup, 19.0 ± 2.1%; PGCCs Sup, 78.0 ± 3.0%; IL-6, 72.7 ± 2.5%; IL-6R antibody, 23.0 ± 3.6%; apigenin, 15.0 ± 4.6%. Bars, 50 µm. B Level of procollagen I in fibroblasts (cocultured for 72 h) was significantly triggered by PGCCs Sup (554.3 ± 29.7 pg/ml) and IL-6 protein (394.3 ± 23.1 pg/ml) and reduced by blocking with IL-6R antibody (167.3 ± 10.7 pg/ml) and apigenin (126.5 ± 6.4 pg/ml). C LOX level and phosphorylation of STAT3 in fibroblasts (cocultured for 72 h) was increased when exposed to PGCCs, IL-6, and PTX and was inhibited by IL-6 knockdown, IL-6R antibody, and apigenin. D Cross-linking and deposition of collagen I outside fibroblasts (cocultured for 72 h) were significantly apparent and web-like when cocultured with PGCCs or treated by IL-6 protein alone. This cross-linking was attenuated by IL-6R blockage and apigenin. When treated with PTX only, the collagen is cluster- or spot-like. Panel corners show higher magnification of the squared areas to clearly show the morphology of collagen. Bars, 50 µm.