Tissue differentiation and cytokine synthesis during strain-related bone formation in distraction osteogenesis

To investigate the contributions of various cytokines that are involved in mechanically related bone formation, we applied defined uniaxial strains in a rabbit model of mandibular elongation and examined the regenerating bone during early stages of distraction osteogenesis by histomorphometry. We al so measured serum concentrations of various cytokines during the distractio n. Cell proliferation and differentiation indices correlated significantly (P < 0.001) with the extent of load application, Serum concentrations of insul in-like growth factor-1 (IGF-1) decreased after osteotomy whereas transform ing growth factor <beta>1 (TGF beta1) showed a postoperative increase. Pros taglandin E2 (PGE2) concentrations were constant throughout the experimenta l period. Collagen degradation decreased slightly postoperatively and incre ased in samples exposed to higher magnitudes of strain. Our data show that it is the magnitude of mechanical strain that decides tissue response by a characteristic cell proliferation and differentiation. The operative trauma leads to inverse changes in serum concentrations of TGF beta1 and IGF-1, t hereby promoting the recruitment of osteoblastic precursor cells as well as collagen matrix synthesis. (C) 2001 The British Association of Oral and Ma xillofacial Surgeons.