Effects of PGs on intercellular communication between BMSCs and chondrocytes in a Transwell system. The Transwell system was used to coculture chondrocytes and BMSCs in the presence or absence of PGs. BMSCs, chondrocytes, and PGs were cultured separately or together in the Transwell system for 7 days. The gene expression of Col II, Sox9, and TGF-β1 in BMSCs in the lower chamber was detected (A). Chondrocytes were cultured separately or together with BMSCs and PGs in a Transwell system for 7 days, after which cells were treated with LY3200882, and Col II, PRG 4, and Smad2 gene expression in the BMS/Chon + PG/LY group was detected by PCR (B). The Smad2/3 protein was detected by cellular immunofluorescence staining (C–G). (H) Shows the difference in the number of positive cells. Chon: chondrocytes, LY: LY3200882. The letters a, b, c, and d indicate significant differences (p < 0.05) compared with the 1st, 2nd, 3rd, and 4th groups.