Expression of TGF-β, PDGF, Type I and II Collagen, and Osteonectin During Fracture Healing in Rat / 대한정형외과학회잡지

ABSTRACT

To define the basic sequential events of the healing process in normal fracture and evaluate the role of growth regulatory molecules and extracellular matrix components, the expression of transforming growth factor β(TGF-β), platelet-derived growth factor(PDGF), type I and II collagen, and chemistry during the healing process of an experimental fracture of tibia in 41 adult rats for 7 weeks using ABC methods. The phases of inflammation, reparation, and remodeling followed each other in sequence. The inflammatory phase was characterized by hemorrhage, edema, and infiltration of inflammatory cells on the first day. During the reparative phase, the undifferentiated mesenchyme undergoes rapid chondrogenesis, followed by endochondral ossification and supplemented by appositional bone formation. At day 3, the expression of TGF-β and PDGF was noted in the undifferentiated mesenchymal cells and from day 5, these two growth factors were detected in the osteoblasts and extracellular matrix in areas of endochondral ossification and newly formed periosteal bone. From day 3, the expression of type I collagen and osteonectin was noted in the osteoblasts and extracellular matrix in both endochondral ossification and appositional bone growth as a marker of ossification. From day 3, type III collagen was mainly expressed in the plump mesenchymal cells showing chondroid differentiation and chondroid matrix as a marker of cartilaginous reparative phase. From day 14, these growth factors and extracellular matrix components were decreased in staining intensity and at the 5th week, the histology and immunostaining pattern were similar to the mature bone.