Midbody plays an active role in fibroblast-myofibroblast transition by mediating TGF-β signaling

The transition of fibroblasts into myofibroblasts is a crucial step in kidney fibrosis. However, the biological processes involved in this transdifferentiation are incompletely understood. In this study, we discovered that the midbody plays a role in the fibroblast-myofibroblast transition by mediating TGF-β/Smad signaling. Combining bulk RNA-seq, histology, and the western blot of unilateral ureteral obstruction kidneys, we demonstrated that the pathway related to microtubules is implicated in kidney fibrosis, and the blocking of microtubule dynamics by colchicine improved kidney fibrosis. Subsequently, to explore microtubule-based organelles in detail, we cultured NRK-49F (rat kidney fibroblast cell line) and HKC-8 (human proximal tubule cell line) under transforming growth factor-β1 (TGF-β1) stimulation, which caused deciliation in both cell lines during epithelial-mesenchymal and fibroblast-myofibroblast transition. We identified another microtubule-based organelle, the midbody, whose formation is promoted by TGF-β1 in fibroblasts as a result of proliferation in contrast to tubular cells. Notably, TGF-β receptors were present in the midbody of both cell lines. In TGF-β1-treated fibroblasts, colchicine or Hedgehog pathway inhibitor 4 impaired the midbody formation, and attenuated the upregulation of canonical TGF-β/Smad signaling and α-SMA expression. These findings offer novel insight into the midbody as an active organelle involved in fibroblast-myofibroblast transition by mediating TGF-β/Smad signaling, which could be a potential therapeutic target.