| PrefaceHeat Shock Response ( HSR) , also known as Stress Response (SR) , is a kind of protect strategy that cells developed to deal with adverse changes in their environment. This response is characterized by the extremely rapid increased expression of Heat Shock Proteins ( HSPs). One major family of the heat shock family is the HSP70 families that are consisted of two kinds of proteins, the constitutive HSP70 and the stress - inducible HSP70. The former continuously express and function as molecular chaperones for newly synthesized proteins. The later express only when cells are stressed, so their appearance is often diagnostic that the cell has experienced some type of trauma. More importantly, the levels of stress - inducible HSP70 have apparently direct correlation with the acquired thermotolerance of cells. Study the kinetics and the levels of HSP70 expression can give us some messages about the acquired theromotolerance of the stressed cell. The purpose of this study was to research the kinetics and the level of HSP70 in the dental pulps that have exposed to dental physical stress and then offer us the basis to put the theory of acquired thermotolerance into practice.Materials and Methods20 adult Sprague - Dawley male rats (280 -300g) were anesthetized , four were killed immediately after the anesthesia, the rest rats were fixed to the operation table and their maxillary first molars were injured by the dental drill for 1.5 minutes each. Four rats were killed immediately after the injury, four rats were killed 4 hours after, and four rats were killed 8 hours after the injury, the last four rats were killed 24 hours after the injury. The rats'first maxillary molars were extracted and put to the paraformaldehyde. 24 hours later, the molars were taken out and put to decalcification fluid. The specimens were taken out 20 days later, paraffin imbedded, made paraffin section, and then made HSP70 immunohistochemical ( IHC ) staining ( SP method) and HE staining. All the stained sections were studied under the light microscopy and under image pattern analysis; all the data (IOD average) were statistically analyzed.ResultsThe immunohistochemical staining of HSP70 suggested that HSP70 expressed in the non - injured and injured dental pulps. It is apparent that this immunoreactivity for HSP70 is present both within the odontoblasts and the odontoblast processes that occupy the dentin tables. The pulp cells (fibroblasts) appeared HSP70 immunoreactive too. The endothelial cells of the vessels, the smooth muscle cells all express HSP70 although their stain is less intense than that of the odontoblasts. The dental pulps obtained immediately after the physicalinjury expressed HSP70 as much as the pulps that were not injured. The pulps obtained four hours after the injury expressed more HSP70 than the non - injured pulps. The expression of HSP70 in pulps that recovered from injury for eight hours reached the maximum. HSP70 expressed in pulps that obtained twenty - four hours after injury went back to the normal standard.DiscussionThe constitutive HSP70 are continuously expressed and function as molecular chaperones for newly synthesized proteins, assisting in the folding and assembling of protein complexes and in translocation of proteins into organelles. Their degree of expression appears dependent on the metabolic activities of the cell. All cells in the dental pulp have physiological activities, so almost all cells in the pulp express HSP70. The odontoblasts have the ability to form dentin, this means that the odontoblasts exhibit higher secretary activities than the other pulp cells. So the odontoblast expressed more HSP70 than other cells.The other function of heat shock proteins is their ability to clear up the abnormally folded proteins accumulated in the cells. When the hard tissue of tooth was grinded and the dental pulp and odontoblasts were insulted, the synthesis of proteins in the odontoblasts was impacted , they cant experience their normal folding pathway and become abnormall...
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