Progranulin Promotes Regeneration Of Inflammatory Periodontal Bone Defect In Rats

Background and PurposesPeriodontitis which was caused by the initial factor,oral plaque biofilm,is a chronic infectious inflammatory disease which leads to destroy periodontal soft and hard tissues.Therefore,it is important for periodontal tissue engineering to restore periodontal soft and hard tissue.It is well known that periodontal ligament stem cells(PDLSCs)are treated as seed cells in periodontal tissue engineering.However,the proliferation and differentiation abilities of PDLSCs were easily affected by many periodontal microenvironments,such as many inflammatory factors,tumor necrosis factor α(TNF-α),which was regarded as the major regulation factor during the pathogenesis of periodontitis.TNF-a played the negative effect on the osteogenic differentiation of stem cells.Hence,the essential goal in the field of periodontal regeneration is to search biologically active factors which could not only promote the osteogenic differentiation of stem cells,but also antagonize the inflammatory response to promote the regeneration and repair of periodontal tissues.Progranulin(PGRN)has been proved to play a crucial role in anti-inflammation and osteogenesis promotion.Unfortunately,the effect of PGRN on regeneration of inflammatory periodontal bone defect remains unclear.In present study,the therapeutic effect of PGRN on regeneration of inflammatory periodontal bone defect was evaluated and provide the new treatment ideas for periodontal regeneration in an inflammatory environment.Materials and Methods54 Wistar rats were randomly assigned into two groups which were named as periodontitis group and healthy group.In the periodontitis group,rats were anesthetized by using intraperitoneal injection with pentobarbital(35 mg/kg)and placed on the operation table with horizontal supine position,which allowed an access to place 0.3 mm orthodontic ligature into the gingival sulci embracing the cervical margin of the left mandibular first molar.Rats were fed with standard rat feed and 10%sucrose solution drinking.In the healthy group,the rats were fed w:ith standard rat feed and sterilized water without orthodontic ligature.After 2 weeks,the rats were sacrificed and the mandibular specimens were harvested.The specimens were prepared for hematoxylin and eosin staining.Rats with periodontitis were randomly divided into three groups:(1)PBS;(2)recombinant human PGRN(rhPGRN 8 μg):(3)anti-TNF-α(Lenalidomide,3μg).Periodontal bone defect model was made at the left of the mandible in the buccal side of the first and second molars in the range of 3x2x1 mm.Then,the collagen membranes were implanted into bone defects respectively.The rats were sacrificed at 1,4,6 weeks after operation and the mandibular specimens were harvested.Volume of new bone was assessed by radiological and histomorphometric analysis.Expression of osteogenesis-related markers and tumor necrosis factor-α(TNF-a)was evaluated using immunohistochemistry.Tartrate-resistant acid phosphatase(TRAP)staining was also performed to determine the number of osteoclasts.Immunofluorescence(IF)staining was performed to explore the interaction between rhPGRN and tumor necrosis factor receptors(TNFRs).ResultsThe results showed that compared with the PBS group and the anti-TNF-a group,the rhPGRN group had significantly superior quantity and quality of newly formed bone higher expression of alkaline phosphatase(ALP),runt-related TNFR2 and transcription factor 2(Runx2).Similar to the anti-TNF-a group,the rhPGRN group also exhibited the significant inhibitory effect on the expression of TNF-a and the number of TRAP positive cells compared with the PBS group.ConclusionHence,our experiment suggests that PGRN promotes regeneration of inflammatory periodontal bone defect in rats via anti-inflammation,osteoclastogenic inhibition and osteogenic promotion.Local administration of PGRN may provide a new therapeutic strategy for periodontal bone regeneration.