TGFB1 and Peritoneal Fibrosis: Furthermore, a few studies also found that direct co-culture of mesothelial cells with macrophages enhanced the protein expression of interleukin 1-beta (IL1β), TNFα, TGFβ1, and αSMA on mesothelial cells, indicating that interactions between mesothelial cells and macrophages were crucial in the development of peritoneal fibrosis [18,39].