| Dental eruption and succession of deciduous teeth are complex physiological processes, whose mechanisms are not fully clarified. At present, it has been proved that OC and OD are two important functional cells involved in the physiological absorption of deciduous tooth root and the formation of the tooth eruption passage.Histologically similar to OC, OD is the cell which absorb tooth hard tissue. The study on OC and OD is an important aspect of the reaserch about the succession of deciduous teeth mechanism.SHIP, that is SH2-containing inositol 5 ' -phosphatase , whose peculiarity is expressed in the hematopoietic lineage and spermatids of the testis,is one of the negative regulators of cell signal transduction.SHIP is tyrosine-phosphorylated and translocates in hematopoietic cells after stimulated by any of a broad number of cytokines and growth factors. As a kind of phosphatase, SHIP can hydrolyze the phosphate group from the 5' position of both phosphatidylinositol 3,4,5- trisphosphate [PI (3, 4, 5) P3 ]and inositol-1,3,4,5- tetrakisphosphates[ Ins(1 3 4, 5)P4] Resulting in inhibiting many activating signaling pathways such as PI-3K,Ras-MAPK,PLCr signaling pathway and negatively regulating theactivation and proliferation of myeloid hematopoietic cells.Up to now, there has no literature on the expression of SHIP in OC at home and abroad. According to the fact that OC derives from hematopoietic cells and forms through mononuclear precurosor fusing, it is deduced that SHIP may express in OC. Takeshita et al found that in SHIP-/- mice, the number of OC is increased two-fold. Similar to Pagetic OC, SHIP-/- OC was enlarged, containing over 100 nuclei and exhibited enhanced absorptive activity, resulting in a 22% loss of bone-mineral density and a 49% decrease in fracture energy. Their investigation indicated that SHIP may be expressed in OC and negatively regulated OC formation and function. In order to approach whether SHIP is expressed or not in OC and OD during the succession of deciduou teeth, this investigation, on the one hand, divided the process of the succession of deciduous teeth into three phases: stable phase of deciduous root, absorptive phase of deciduous root and permanent dentition phase. By IHC and ISH, the expression of SHIP in deciduous teeth pulp, root, periodontal tissues and permanent tooth germ and tissues around dental sac was detected at protein and mRNA level respectively and then the role of SHIP during the succession of deciduous teeth was analysed. On the other hand, this investigation, referring to some documents on OC culture in vitro, cultured PBMC, separated from human peripheral blood cells with lymphocyte separating medium ,with cell medium mixed with la,25(OH)2D3,DEX,M-CSF and RANKL. By IHC and ISH, the expression of SHIP in OLC, which appeared after 14 days of culture, was detected at protein and mRNA level respectively and then the role of SHIP in OC formation and function was analysed.The main experimental results are as follows:Part One: The expression of SHIP during dogs' succession ofdeciduous teeth1 Stable phase of dogs' deciduous tooth rootIn this phase, the deciduous teeth roots were not absorbed physiologically and were integrial. There were no OD in deciduous tooth pulp and no alveolar absorption lacunae around deciduous tooth root. The succeeded permanent teeth germs were in developing phase, whose coronal dentin and enamel had partly formed and odontoblasts and ameloblasts aligned along dentin and enamel orderly. The alveolar around permanent teeth germs was in rebuilding phase and osteoclasts located in the alveolar absorbed lacunae. In this phase, IHC and ISH staining of SHIP in deciduous tooth pulp, root and periodontal tissue were negative, which probably was due to the expression of SHIP was severely restricted to hematopoietic cells and very little blood cells remained in sections when samples were perfused through blood vessel; IHC and ISH staining of SHIP in OC in alveolar absorption lacunae were positive, which indicated that SH... |
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