Effects Of Different Magnitudes Of Hydraulic Pressure On Alkaline Phosphatase Activity And Apoptosis In Human Periodontal Ligament Fibroblasts In Vitro

The periodontal membrane is located between alveolar bone and cementum. When the mechanical forces are exerted upon teeth, all sorts of pressure that the teeth bear will be transferred from periodontal membrane to alveolar bone, so the main cellular content -human periodontal ligament fibroblast (HPLF) is often under a pressure circumstance in vivo. HPLF has the potential to differentiate cementoblast and osteoblast, and secretes the important active substances to adjust metabolism of periodontal tissue. So HPLF plays an important role at the reconstruction of periodontal tissue. HPLF has the higher Alkaline Phosphatase (ALPase) activity; it is commonly considered that ALPase is an important parameter that represents local tissue and cell's calcification tendency and ossific ability, so HPLF also plays important role at calcification process of periodontal tissue. Thus it can be seen, by studying the relation between activity of ALPase and mechanical forces, we can know more about activity of HPLF. But when teeth are exerted excessive pressure, whether or not it can influence the activity of ALPase of HPLF's , and the extent of such influence, we know little about it. At present, it also has few researching report about whether Apoptosis will be induced to happen and furthermore influence the calcification of periodontal tissue when mechanical forces are exerted upon HPLF.To counter above problems, the study was conducted by using hydraulic pressure controlled cellular strain unit that was designed by us. It can exert accurate, adjustable, identical hydraulic pressure upon cell and can fairly good imitate circumstance in vivo, so it has certain leading advantages. HPLF were cultured using tissue explant culture techniques. After cells grew 3-6 passages, we examined the change of ALPase activities and investigated the influences on Apoptosis when cells were exerted different pressure and different pressure times by using cytobiological detection methods. From all those experiments, we investigatedaction mechanism that excessive pressure causes teeth loosen. It can provide experimental bases and theoretical bases for clinic work how to control mechanical forces exerted on teeth correctly. The main results are:1 The results reveal that pressure of lOOKpa and 200Kpa have none influence on ALPase activities of HPLF. But when the pressure is 300Kpa, and the pressure time is prolonged to 720min, it will decrease ALPase activities obviously.2 Northern blotting hybridization reveals that the decrease of ALPase activities is caused by lower of its mRNA's expression level.3 When the pressure is lOOKpa, SOOKpa and 500Kpa, Apoptosis is not detected in both experimental groups and control groups, and pressure time has no influence on Apoptosis. It reveals when teeth are exerted excessive pressure, ALPase activities decrease and influence reconstruction of periodontal tissue, but Apoptosis don't participate in this process.