Liver regeneration by oval cells employing bistability of stemness-senescence, Hippo signaling, EMT-MET, and polyploidy circuit

Liver hepatocytes possess remarkable regenerative capabilities, yet severe damage may compromise this process. Liver progenitor ("oval") cells exhibit the potential to differentiate into both hepatocytes and cholangiocytes, making them promising candidates for cell therapy. However, their mechanisms in liver regeneration are not clear. Here, on rat liver oval stem-like epithelial cells (WB-F344) a wound healing assay was performed. The scratched near-confluent monolayers (70% area removed) underwent the G1-arrest, bi-nucleation at 10-12 hours post-wounding, starting movement of epithelial to mesenchymal transition (EMT) cell portion into the wounded areas. Nanog nuclear upregulation, fragmentation, and transition as granules into cytoplasm and around, along with p16Ink4a nuclear intrusion from the cytoplasm, loss of epithelial markers, and YAP1/Hippo activation were seen near the wound edge. The replicative stress and proliferation boost followed, documented at 24 hours. Proliferation concluded at 40-48 hours, accomplished by reconstitution of epithelial tissue, the disappearance of Nanog granulation and p16Ink4a return to the cytoplasm, releasing excess. This investigation reveals novel regulatory facets in liver regeneration by oval cells. It accentuates the stemness-senescence bistable switch regulated by reciprocal nucleo-cytoplasmic transitions of opposite regulators, coordinated with Hippo-pathway switch, replicative stress, and boost, along with ploidy, EMT-MET and paracrine secretome circuits - enabling successfully resolving the massive injury. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=166 SRC="FIGDIR/small/586724v2_fig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@7dc56dorg.highwire.dtl.DTLVardef@12cabacorg.highwire.dtl.DTLVardef@1bacfc2org.highwire.dtl.DTLVardef@19dfbae_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFig 1.C_FLOATNO Graphical abstract. Bistable nuclear-cytoplasmic switch between stemness and senescence regulators in the wound healing process by oval liver cells: (1-2) Priming phase: (1) at the wound edge, (2) in the wound; (3) Proliferative phase, wound closure. Nanog - green; p16INK4A - red, EMT cell - with blue nucleus. C_FIG