Injury responses and repair mechanisms of the injured growth plate.

The growth plate is responsible for longitudinal growth of children's long bones. However, being a cartilaginous tissue, the growth plate has a limited ability for regeneration and thus injured growth plate is often repaired by bony tissue resulting in bone growth defects of the involved limb. Understanding the pathophysiology of growth plate bony repair and developing preventative treatments remain a challenge. This review discusses previous and recent studies investigating growth plate injury responses and repair mechanisms in a rat tibial growth plate injury model. Following an injury, inflammatory, fibrogenic, osteogenic and bone-bridge maturation repair phases have been observed on days 1-3, 3-7, 7-14 and 10 onwards, respectively. Important roles of several growth factors and cytokines (such as PDGF-BB, FGF-2, TNF-alpha? and IL-1beta) have been highlighted, regulating different phases of growth plate injury repair. Studies have also shown that while intramembranous ossification is the major mechanism responsible for the bony repair, endochondral ossification, to a lesser extent, also plays a role. Further understanding of the growth plate injury responses and bony repair mechanisms is still required.