Platelet-derived growth factor signaling in porcine testicular tubular somatic cells

Mechanisms governing somatic cell interactions in the testis are not well defined. The platelet-derived growth factor (PDGF) pathway mediates epithelial-mesenchymal interactions and is involved in testicular morphogenesis in rodents. However, its roles in the testis of higher mammals remain largely unknown. Here, we investigated how PDGF signaling inhibition affects immature (1-week-old) porcine testicular tubular somatic cells (TTSCs), including cell-cell communication and morphogenesis. From scRNA-seq data, we established the PDGF pathway signatures in crosstalk between testicular cells, identifying Sertoli cells as the primary source and peritubular myoid cells as the main recipients of PDGF. Further, we demonstrated that PDGF inhibition by CP673451 affects TTSC functions, proliferation and cytoskeleton, with reduced cell area, focal adhesion size and fibronectin production, and decreased expression of peritubular myoid cell-specific genes. PDGF inhibition did not impair testicular organoid formation and tubule morphogenesis in vitro, but it correlated with ablation of cytoplasmic extensions from the tubule surface, potentially related to interactions between TTSCs and the extracellular matrix. PDGF signaling can be transduced by primary cilia, sensory organelles that respond to environmental stimuli, and PDGF inhibition increased the percentage of ciliated cells and ciliary length in TTSCs. Comprehensive morphological characterization of primary cilia in the porcine testis indicated that these remain submerged in the cytoplasm. In conclusion, the PDGF signaling pathway is active in the immature pig testis and may influence testis morphogenesis by affecting cell-extracellular matrix interaction, cytoskeleton and primary cilia. However, the role of primary cilia-modulated PDGF signaling in the testis remains to be determined.