The Biological Effects And Repairing Function Of RhBMP-7 To Dental Pulp Cells And Dental Pulp Tissue

Bone morphogenetic protein (BMP) is one of the acidic proteins which is widespread in the bone tissues of animals. Recombinant human bone morphogenetic protein (rhBMP) has been used as pulp capping agent to promote the formation of reparative dentin, but we do not comprehensively understand the mechanism of that as yet. Research shows that the synthesis of alkaline phosphatase and Osteocalcin in fibroblast cells is up-regulated with the effect of BMP-7, and fibroblast cells can be calcified in vitro. Besides, fibroblast cells and myocardial cells induced by rhBMP-7 could form bone tissue ectopically in vivo. Then what effect of rhBMP-7 to the dental pulp cells will be? What is the mechanism? How is the prospect of the rhBMP-7 application as pulp capping agent to conserve vital pulp? To answer these questions preliminarily, we have done some experiments in vivo and vitro as following.1. Primary cultured human dental pulp cells to the fifth generation, and then added rhBMP-7 in different concentration to culture medium. MTT method and alkaline phosphatase activity assay was performed on human dental pulp cells. The results showed that rhBMP-7 could not only improve the proliferation ability but also enhance the alkaline phosphatase activity of human dental pulp cells when it's concentration was 60μg/L.2. Treated the rat's dental pulp tissue with rhBMP-7 in concentration of 60μg/L and then transplant it to somewhere under the renal capsule and head skin of other rats. Killed the rats some days after the transplantation, and observed the sections of the tissue transplanted. The results showed that the rat's dental pulp tissue treated with rhBMP-7 had calcified in different degrees, and the form of the calcification was punctate or small masses in shape aggregated together.3. The method was as same as 2. The tissue sections were obtained for immunohistochemical staining, and the expressions of OC, OPN and DSPP were observed. The results showed that the expressions of OC and OPN were significant in different degrees, but the expression of DSPP was not obvious. The results of this experiment mean that the dominant reason of the calcification in transplanted rat's dental pulp tissue treated with rhBMP-7 is osteogenesis effect of rhBMP-7, but the rhBMP-7 induction effect of immature mesenchymal cells differentiate into odontoblast cells is weak.4. Vital pulpotomy had been done in dogs, and capped the dental pulp with pulp capping agent which was made from chitosan thermosensitive hydrogel loading rhBMP-7. Calcium hydroxide was used as pulp capping agent in control group. Killed the dogs a few days after pulp-capping, and the dogs dental serial sections were demineralized and observed by HE staining. The results showed that the performance of pulp-capping with chitosan thermosensitive hydrogel loading rhBMP-7 was better than calcium hydroxide, besides, the osteoid dentin was formed more and faster. But the difference was not remarkable in aspect of inflammation control.