The Effect Of Platelet-rich Fibrin On Schwann Cells

Objective and background：Osseointergrated implants have been widely used in clinics to repair themissing teeth. Periodontal ligament contains a large number of Ruffini endings,which are the main mechanical receptors of the natural teeth. Compared tonatural teeth, implants have no periodontal ligament around them. A smallnumber of sensory nerve endings in the peri-implant environment serve as amain source of sensory response. Therefore, the sensory thresholds of theimplant are10-100times higher than thoses of natural teeth. That means whensuffered with excessive force, the peri-implant bone will be absorbed and theimplant may even be damaged. The dentists usually design theimplant-supported restorations with ‘lighter’ occlusal contacts to solve thisproblem. This not only reduces the efficiency of implant-supported restorations,but also can not completely avoid the risk of implant failure. How to promoteimplant peripheral nerve regeneration has become the key to solve thisproblem.Peripheral nerve is composed of axons and Schwann cells, which wraparound the axons. The proliferation of Schwann cells plays an important role inperipheral nerve regeneration. Cell proliferation requires the participation of avariety of growth factors. Studies have shown that VEGF （vascular endothelialgrowth factor）, FGF-b （fibroblast growth factor-basic）, and IGF-I （insulin-likegrowth factor-I） can promote the proliferation of Schwann cells. Choukroun’sPRF is rich of growth factors, including those mentioned above. Thisexperiment studies the effect of Choukroun’s PRF on proliferation and functionof Schwann cells, in order to provide experimental data for peri-implant nerveregeneration. Methods：Bilateral sciatic nerves of New Zealand white rabbit （1.5².0kg） were cutunder sterile conditions. Use trypsin and collagenase to digest the nerves toobtain Schwann cells. The growth characteristics of the cells were observed.Schwann cells were identified by S-100immunofluorescence staining method.Choukroun’s PRF was made of the blood taken from the animal’s heart. Theexperiment contains two groups. Experimental groups: cells were cultured instandard conditions with Choukroun’s PRF. Control group: cells were culturedin standard conditions. Each group has three samples. MTT values, cell cycle,and nerve growth factor expression were tested in the experimental and controlgroups at each time point.Results；1. Culture and identification of Schwann cells（1） Schwann cells are small, most of them are spindle, a few of them aretriangular or irregular in shape. The nucleus is apparent in the side of the cellbody.（2）96hours after the digestion and passage, the Schwann cells began togrow quickly. There is a significant increase in cell number. The morphologyand grow condition of them became similar with the primary cells.（3） Schwann cells express S-100protein, which is green after processed byimmunofluorescent staining method.2. The effect of Choukroun’s PRF on the proliferation of Schwann cells（1） Cell growth curve showed that cells in the control group grew slowlyduring1-3days after the passage, during4-9days cells came into a rapidgrowth period, after9days cells came into the platform period. The cells in theexperimental group grew slowly during1-2days after the passage, during3-7days cells came into a rapid growth period, after7days cells came into theplatform period. （2） MTT results showed that: at1^st,3^rd,5^th,7^th and9^th day, the absorbancevalues of the experimental group were significantly higher than the controlgroup （p <0.05）.（3） Flow cytometry tested that: on the3^rd and5^th day, the percent of cellsin the S+G₂M phase in the experimental group is significantly higher than thatin the control group.3. ELISA results showed that on the3rd,5^th, and7thday Schwann cells inthe experimental group secreted much more NGF than those in the controlgroup （p <0.05）.Conclusion：1. Choukroun’s PRF can promote proliferation of Schwann cells.2. Choukroun’s PRF can promote Schwann cells to secrete NGF （nervegrowth factor）.