Stretch-induced hepatic endothelial mechanocrine and hepatocyte proliferation

The study focuses on how mechanical stretching of liver sinusoidal endothelial cells (LSECs) after partial hepatectomy (surgical removal of a part of the liver) triggers liver regeneration by promoting hepatocyte (liver cell) proliferation. When part of the liver is removed, blood flow per unit of liver volume increases, causing the liver's tiny blood vessels (sinusoids) to stretch. This stretch acts as a signal for regeneration.

A key finding was the role of a protein called HB-EGF (heparin-binding EGF-like growth factor), which is crucial for hepatocyte proliferation. The mechanical stretch of LSECs causes them to produce HB-EGF through a process called "mechanotransduction," where physical forces are converted into biochemical signals. This process depends on YAP (Yes-associated protein), which moves into the cell nucleus and activates genes like Hbegf that promote HB-EGF production.

YAP's nuclear entry happens via two mechanisms: 1) passive entry through expanded nuclear pores due to F-actin polymerization, and 2) active transport assisted by a protein called BAG3. β1-integrin, a receptor on LSECs, acts as the key mechanosensor that detects the stretch and starts this signaling cascade.

The HB-EGF secreted by stretched LSECs activates EGFR signaling in hepatocytes, stimulating their proliferation and aiding liver recovery. This "mechanocrine" process—mechanical forces triggering biochemical signals—links blood flow changes to liver regeneration, highlighting a novel pathway for understanding liver repair.