| PrefaceExtracellular matrix is an intercellular matter that forms a micro - environment for cells to live in and has the effects of support, join, nutrition, defense and protection. . The matrix metalloproteinstes (MMPs) belongs to the endopeptidase family which participates in multiple physiological and pathological processes by degrading extracellular matrix . The matrix metalloproteinste - 8 ( MMP - 8 ) is one of MMPs, whose active substrates are Type I , II , III, VII and X col-lagens. Collagen is closely related with the differentiation, maturity and injury repair of cells in the body tissue. The main function of MMP - 8 is to degrade collagen. The immature permanent tooth is an important stage of development. Therefore it is necessary to make a study of the expression of MMP - 8 and collagen in the dental pulp in the period. But study on the expression and distribution of MMP - 8 in pulps of immature perment teeth has not been reported. The purpose of this experimental research is to study the expression and effect of MMP - 8 in the tooth development.For the first time, by use of immunohistochemical and image a-nalysis techniques, we presented the expression and distribution pat-tern of type I collagen and MMP - 8 in pulps of permanent teeth at different root development stage.Materials and MethodsDental pulps were obtained from healthy caries - free permanent teeth in need of extraction. All subjects had no systematic disease and didnt take any immune - inhibited drugs within three months. Based on the root development status, the pulp tissue was classified into three groups-, root just starting development, root being in development and root finishing development. After extracted, the dental pulp was rapidly removed, then fixed in 0.4% paraformaladehyde (PH7. 4) at 4^ for 48 hours. Tissue blocks were dehydrated in ascending series of ethanol, cleared in xylene and embedded in paraffin. Serial sections were cut 5jjtm thick. Anti - human polyclone antibody was used for staining. The sampies were observed under light microscope. Meta Morph/coolsnapfx/AX70 image analysis software was used to detect the gray value of type I collagen and MMP - 8 positive stained in dental pulp. The data were statistically analyzed by use of SPSS.ResultsStaining of immunohistochemistry for type I collagen in dental pulps revealed that there were positive reactions in the cytoplasm of fi-beroblast, odontoblast, and epithelial cells in blood vessel wall in immature and mature permanent teeth, especially at the stage of root just starting development.Image analysis of type I collagen indicated the with the development of root formation, the gray value of the positive reaction in three groups were higher and higher and were significantly different whenroot finishing development (P < 0.01). For all groups, there were no staisticaldifference between gray values in different parts.Staining of immunohistochemistry for MMP - 8 in dental pulps revealed that there were positive reactions in the cytoplasm of fiber-oblast, odontoblast, and epithelial cells in blood .vessel wall and immature permanent teeth, especially at the stage of root just starting development.Image analysis of MMP - 8 indicated the with the development of root formation, the gray value of the positive reaction in three groups were higher and were significantly different when root finishing development (P<0.05).MMP - 8 is positively related with the expression of Type I collagen in the pulp. ( 0 < r < 1)DisscussionIn this experiment each group of odontoblast is positive for Type I collagen by immunohistochemistry stain. With the development of the root of tooth, the stain is weakened, signifying the odontoblast is capable to secrete Type I collagen. With the development of the root of tooth, the ability of the odontoblast to secrete Type I collagen is weakened and the synthesis of Type I collagen is reduced.In this experiment it is found that in the pulp of immature and mature permanent teeth, the expression of Type...
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