| PURPOSE:Matrix extracellular phosphoglycoprotein(MEPE) is a member of the SIBLING(Small Integrin-Binding Ligand, N-linked Glycoprotein) family. This family member also includes: osteopontin, bone sialoprotein, tooth matrix protein-1, dentin salivary phosphorylation protein and enamelin. Proteins of SIBLING family play a very important role in matrix calcification, regulation of osteoblasts and function of osteoclasts. Matrix extracellular phosphoglycoprotein is a kind of phosphorus-regulating factor that has important function in phosphate metabolic disorder and proliferation of osteoblast in bone tissue diseases and periodontal tissue physiological connection.In order to provide theoretical basis for further studies of molecular mechanism of tooth development and periodontal regeneration, this study is objective to observe the expressions in tooth germs and periodontal tissues in continuous process of development after tooth eruption, and explore the role of matrix extracellular phosphoglycoprotein may play in the formation of mice tooth hard tissues and periodontal tissues. By observe MEPE expression in the process of periodontal wound healing, the study could provide theoretical basis for therapies of periodontitis, alveolar atrophy, alveolar bone deformity and jaw fracture by using matrix extracellular phosphoglycoprotein.METHODS:Postnatal BALB/c mice (Research Animal Center Shandong University) of different development stages were used. Anesthetized animals were sacrificed by vascular perfusion through the left ventricle and into the aorta. The vasculature was pre-rinsed with 0.9% physiological saline for 30s followed by perfusion for 30min with 4% paraformaldehyde (pH 7.0). The mandible were dissected and immersed in the same fixative solution for an additional 24h at 4℃. After decalcificated with 10% EDTA for 30-60 days, dehydrated through graded ethanol, cleared with xylene and embedded in paraffin, and 5μm thick continuous slices were made.Following surgery to create a bony window on the buccal aspects of mandibular molar roots, 24 Wistar rats were randomly divided into two groups. One group animals were sacrificed after 14 days and the other group animals were sacrificed after 28 days. Anesthetized animals were sacrificed by vascular perfusion through the left ventricle and into the aorta. The vasculature was pre-rinsed with 0.9% physiological saline for 30s followed by perfusion for 30min with 4% paraformaldehyde (pH 7.0). The mandibles were dissected and immersed in the same fixative solution for an additional 24h at 4℃. After decalcificated with 10% EDTA for 90 days, dehydrated through graded ethanol, cleared with xylene and embedded in paraffin, and 5μm thick continuous slices were made.The sections were stained with hematoxylin and eosin (H.E.) and observed by light microscopy.RESULTS:Expression of MEPE during the development process after tooth eruption: in the early growth stage of mouse tooth germ, MEPE expression was observed in enamel organ, dental pulp and odontoblasts. MEPE expression decreased following the development of tooth germ, meanwhile, it gradually increased in periodontal membrane and was present in predentin. MEPE showed high expression in mature osteocytes embedded in bone lacuna. Expression of MEPE in the healing course of periodontal defects: on the 14th day, part of new alveolar bone formed in the operation area and periodontal fibers attached to root dentin occurred; on the 28th day, the operation area was covered by new alveolar bone, periodontal fiber and part of cementum was observed between new alveolar bone and dentin, most periodontal membrane adhered to root surface; During the healing process, MEPE expressed in alveolar bone and periodontal membrane.CONCLUSION:1. Matrix extracellular phosphoglycoprotein (MEPE) may play an important role in promoting formation of dental hard tissues and dentinal tubules.2. Matrix extracellular phosphoglycoprotein (MEPE) may effects on the formation of periodontal membrane,maintenance of the width of periodontal membrane and stabilized internal environment.3. Matrix extracellular phosphoglycoprotein (MEPE) may contribute to promote formation of alveolar bone and periodontal membrane in the progress of periodontal tissue regeneration.
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