#2144 Expression profile induced by TGF-β1 in senescent human peritoneal mesothelial cells is less pronounced than in young cells

Abstract

Abstract Background and Aims Transforming growth factor β1 (TGF-β1) is a recognized driver of both mesothelial-to-mesenchymal transition (MMT) and cellular senescence observed in vitro in human peritoneal mesothelial cells (HPMCs), and have a significant role in adverse peritoneal remodelling of patients treated with peritoneal dialysis (PD). We have previously shown that senescent HPMCs spontaneously acquire some phenotypic features of MMT which in young HPMCs are induced by TGF-β1. At the same time, senescent HPMCs appeared to be less responsive to TGF-β. It is not clear what determines which pathway is activated by TGF-β1. Here, we aimed to extend previous observations and used electron microscopy, transcriptomics, and proteomics to identify differences between young and senescent cells in their responsiveness to TGF-β. Method Replicative senescence of omentum-derived HPMCs isolated from 4 separate donors was induced by serial passages until cells ceased to grow and expressed senescence-associated β-galactosidase. Serum-starved young and senescent cells were treated in parallel with 1 ng/mL of TGF-β1 for 72 hours. Fixed cells were analyzed with a Jeol transmission electron microscope at 80 kV (Jeol, Tokyo, Japan). Cell lysates were analysed for global gene and protein expression using an integrated transcriptomic (Array-based) and proteomic (LC/MS-based) approach. Results Exposure to TGF-β1 led to phenotypic changes consistent with MMT in young, but not in senescent HPMCs (Fig. 1A). The omics analyses revealed that the response to TGF-β1 was associated with 89 genes being differentially expressed (55 down- and 34 up-upregulated) in young HPMCs and with 13 genes (5 down- and 8 up-regulated) in senescent HPMCs (Fig. 1B). In addition, TGF-β1 changed the expression of 131 proteins in young HPMCs (72 down- and 59 up-regulated) and 232 proteins in senescent HPMCs (127 down- and 105 up-regulated) (Fig. 1C). The responses to TGF-β identified at both the transcriptome and protein levels (Fig. 1D) and present in both young and senescent HPMCs included TGFBI (TGF-β-induced) and ITGB3 (β3 integrin), which were upregulated, and UPK1B (uroplakin 1B) and SEMA3B (semaphorin 3B), which were downregulated. Changes in response to TGF-β seen at the RNA and protein level included also VCAN (versican), ITGA11 (integrin α11), FN1 (fibronectin 1), CCNYL1 (Cyclin Y-like 1) and MYOZ2 (myozenin 2), however, these were observed only in young cells. A decrease in KLK7 (Kallikrein 7) gene expression after exposure to TGF-β was seen both in young and senescent HPMCs, with a decrease in KLK7 protein detected only in senescent cells. Finally, exposure to TGF-β led to an increase in THBS1 (thrombospondin 1) expression in young cells and at the protein level in senescent cells. Conclusion In conclusion, the profound morphological changes seen in senescent HPMCs are not significantly exacerbated by TGFβ. Likewise, changes in global gene and protein profiles in response to TGF-β appear to be less pronounced in senescent cells. Among the genes and proteins affected by TGF-β, those involved in angiogenesis and fibrosis deserve further attention as they may contribute to adverse peritoneal remodelling in PD patients.