Indian Hedgehog: A Mechanotransduction Mediator in Condylar Cartilage

TLDR

Indian hedgehog (Ihh) is a critical mediator that transduces mechanical signals to stimulate chondrocyte proliferation. The study aimed to delineate how mechanical signals are sensed and converted into tissue growth in the mandibular condyle by assessing Ihh expression and its association with mesenchymal cell proliferation during natural growth and mandibular advancement. Thirty‑five‑day‑old Sprague‑Dawley rats were fitted with functional appliances and, along with matched controls, were doubly labeled with iododeoxyuridine and bromodeoxyuridine to track proliferative mesenchymal cell cycles. Mandibular advancement induced Ihh expression, which correlated with increased replicating mesenchymal cells and reduced turnover time, indicating that Ihh mediates mechanotransduction to stimulate cellular proliferation in condylar cartilage.

Abstract

Indian hedgehog (Ihh) is a critical mediator transducing mechanical signals to stimulate chondrocyte proliferation. To clarify the cellular signal transduction pathway that senses and converts mechanical signals into tissue growth in mandibular condyle, we evaluated Ihh expression and its relation to the kinetics of replicating mesenchymal cells in condylar cartilage during natural growth and mandibular advancement. Thirty-five-day-old Sprague-Dawley rats were fitted with functional appliances. Experimental animals with matched controls were doubly labeled with iododeoxyuridine and bromodeoxyuridine so that we could evaluate the cycles of the proliferative mesenchymal cells. Mandibular advancement triggered Ihh expression in condylar cartilage. A higher level of Ihh expression coincided with the increase of the replicating mesenchymal cells’ population and the shortening of the turnover time. These findings suggested that Ihh acts as a mediator of mechanotransduction that converts mechanical signals resulting from anterior mandibular displacement to stimulate cellular proliferation in condylar cartilage.