牵张成骨的细胞力学效应和新骨生物力学特性的研究

(1)、To establish an animal model in goats for lengthening mandible by distraction osteogenesis.(2)、To study the mode of bone formation and biomechanical properties of the regenerated bone resulting from mandibular distraction osteogenesis.(3)、To observe the expression of bone growth factors during mandibular distraction osteognesis..(4)、To study the changes in the inferior alveolar nerve and temporomandibular joint after mandibular osteodistraction..(5)、To observe the effects of mechanical stretching on the proliferation and biological behavior changes in cultured human osteoblast-like cells.Materials：.Young adult goats and rabbits；costom-made distractors；Flexcercell 3000 stretching unit；Human osteoblast-like cells (Saos-2 and MG-63 osteoblasts).etc.Methods:.X-ray examination；histology；Electronic microscopy ；Biomechanical testing instrument；immunohistochemistry；RIA and Northern blot analysis, etc.Results and Conclusions:(1)、The new bone was mainly formed by intramembranous ossification following mandibular lengthening by distraction osteogenesis in goats..(2)、The compressive strength and bending stiffiness of the new bone reached the normal level at 4 and 8 weeks after completion of mandibular distraction, respectively.but the shearing strength remained significantly weaker than that of the normal bone at 8 weeks after distraction.(3)、The increased expression of BMP、 TGF-β 、IGF-Ⅰ and bFGF in the newly formed bone were observed after mandibular distraction osteogenesis in goats.(4)、Mild or moderate Wallerain degeneration was seen in the inferior alveolar nerve following mandibular osteodistraction at a rate of 1mm/day, but higher rate(2 mm/d) may cause serious injury in nerve tissue. The degenerated nerve fibers could recover totally via a complicated repair mechanism. Schwann cells and S-100 protein may play important roles in axon regeneration of the distracted nerves after mandibular lengthening. Unilateral mandibular lengthening can create adaptive remodeling in temporomandibular joints of goats，but rapid distraction may result in degenerative change in the joints..(5)、Mechanical strain can stimulate the proliferation of the human osteoblast-like cells，the effect might be related to the magnitude of mechanical loading. Additionally, mechanical strain can increase PGE2 synthesis, and TGF-β and IGF-Ⅰ mRNA expression. These cytokines and growth factors may play critical roles in cellular response to mechanical stimulation.

牵张成骨是目前复颌骨畸形或缺损的新技术。牵张成骨的细胞力学效应和新骨功能特性是一个急待解决的重要课题。本研究通过下颌牵张动物实验模型和力学刺激一细胞培养系统，从大体及细胞生物力学角度研究牵张后新骨组织力学特性及成骨细胞的应力应变关系，为阐明牵张成骨分子机制，采取有效措施加速新骨形成和防止畸形复发提供科学依据。