Enhanced adipogenic differentiation and reduced collagen synthesis induced by human periodontal ligament stem cells might underlie the negative effect of recombinant human bone morphogenetic protein-2 on periodontal regeneration

Song D‐S, Park J‐C, Jung I‐H, Choi S‐H, Cho K‐S, Kim C‐K, Kim C‐S. Enhanced adipogenic differentiation and reduced collagen synthesis induced by human periodontal ligament stem cells might underlie the negative effect of recombinant human bone morphogenetic protein‐2 on periodontal regeneration. J Periodont Res 2011; 46: 193–203. © 2010 John Wiley & Sons A/S Background and Objective: Recombinant human bone morphogenetic protein‐2 (rhBMP‐2) is a potent inducer for the regeneration of mineralized tissue, but has a limited effect on the regeneration of cementum and periodontal ligament (PDL). The aim of the present study was to determine the effects of rhBMP‐2 on the in vitro and in vivo biologic activity of well‐characterized human PDL stem cells (hPDLSCs) and to elucidate the underlying mechanism of minimal periodontal regeneration by rhBMP‐2. Material and Methods: hPDLSCs were isolated and cultured, and then transplanted into an ectopic subcutaneous mouse model using a carrier treated either with or without rhBMP‐2. Comprehensive histologic, histometric and immunohistochemical analyses were performed after an 8‐wk healing period. The effects of rhBMP‐2 on the adipogenic and osteogenic/cementogenic differentiation of hPDLSCs were also evaluated. The effect of rhBMP‐2 on both soluble and insoluble collagen synthesis was analyzed, and the expression of mRNA and protein for collagen types I, II, III and V was assessed. Results: In the present study, rhBMP‐2 promoted both adipogenic and osteogenic/cementogenic differentiation of hPDLSCs in vitro, and the in vivo potential of hPDLSCs to form mineralized cementum and organized PDL tissue was down‐regulated following treatment with rhBMP‐2. Collagen synthesis, which plays a crucial role in the regeneration of cementum and the periodontal attachment, was significantly reduced, with associated modification of the relevant mRNA and protein expression profiles. Conclusion: In summary, the findings of the present study suggest that enhanced adipogenic differentiation and inhibition of collagen synthesis by hPDLSCs appear to be partly responsible for the minimal effect of rhBMP‐2 on cementum and PDL tissue regeneration by hPDLSCs.     

Apical tooth germ cell-conditioned medium enhances the differentiation of periodontal ligament stem cells into cementum/periodontal ligament-like tissues

Background and Objective: Limitations of current periodontal regeneration modalities in both predictability and extent of healing response, especially on new cementum and attachment formation, underscore the importance of restoring or providing a microenvironment that is capable of promoting the differentiatiation of periodontal ligament stem cells (PDLSCs) towards cementoblast‐like cells and the formation of cementum/periodontal ligament‐like tissues. The aim of this study was to investigate the biological effect of conditioned medium from developing apical tooth germ cells (APTG‐CM) on the differentiation and cementogenesis of PDLSCs both in vitro and in vivo. Material and Methods: Using the limiting dilution technique, single‐colony‐derived human PDLSCs were isolated and expanded to obtain homogeneous populations of PDLSCs. Morphological appearance, cell cycle analysis, bromodeoxyuridine incorporation, alkaline phosphatase (ALP) activity, mineralization behavior, gene expression of cementoblast phenotype and in vivo differentiation capacities of PDLSCs co‐cultured with APTG‐CM were evaluated. Results: The induced PDLSCs exhibited several characteristics of cementoblast lineages, as indicated by the morphological changes, increased proliferation, high ALP activity, and the expression of cementum‐related genes and calcified nodule formation in vitro. When transplanted into immunocompromised mice, the induced PDLSCs showed tissue‐regenerative capacity to produce cementum/periodontal ligament‐like structures, characterized by a layer of cementum‐like mineralized tissues and associated periodontal ligament‐like collagen fibers connecting with the newly formed cementum‐like deposits, whereas control, untreated PDLSCs transplants mainly formed connective tissues. Conclusion: Our findings suggest that APTG‐CM is able to provide a cementogenic microenvironment and induce differentiation of PDLSCs along the cementoblastic lineage. This has important implications for periodontal engineering.     

Regenerative potential and healing dynamics of the periodontium: a critical‐size supra‐alveolar periodontal defect study

Objectives: The nature and characteristics of the newly formed periodontium obtained following regenerative procedures remain a matter of controversy. The objective of this study was to evaluate the regenerative potential of the periodontal attachment and healing dynamics as observed from the spatial distribution of newly formed cementum, periodontal ligament (PDL) and alveolar bone following optimal circumstances for wound healing/regeneration in a discriminating animal model. Material and Methods: Critical‐size, 6‐mm, supra‐alveolar, periodontal defects were surgically created in six young adult Beagle dogs. Space‐providing ePTFE devices with 300‐μm laser‐drilled pores were implanted to support wound stability and space provision in one jaw quadrant/animal. Treatments were alternated between left and right jaw quadrants in subsequent animals. The gingival flaps were advanced to submerge the defect sites for primary intention healing. Histometric analysis followed an 8‐week healing interval. Results: Healing was uneventful in all animals. The histometric analysis showed that cementum regeneration (2.99 ± 0.22 mm) was significantly greater than PDL (2.54 ± 0.18 mm, p=0.03) and bone regeneration (2.46 ± 0.26 mm, p=0.03). The wound area showed significant positive non‐linear effect on cementum (log β=1.25, p<0.001), PDL (log β=1.24, p<0.001) and new bone formation (log β=1.36, p<0.001). A high degree of concordance and significant linear relationship was observed between cementum, PDL and bone regeneration indicating that their formation virtually occurred in parallel. Conclusions: Cementum, PDL and alveolar bone virtually regenerate in parallel under optimal circumstances for periodontal wound healing/regeneration. Moreover, space provision positively influences the extent of periodontal regeneration.     

Periodontal ligament cell sheet promotes periodontal regeneration in athymic rats

Aim: The primary goal of periodontal treatment is regeneration of the periodontium. Current theories suggest that the periodontal ligament (PDL) cells have the capacity to participate in restoring connective and mineralized tissues, when appropriately triggered. We evaluated whether human PDL cell sheets could reconstruct periodontal tissue. Material and Methods: To obtain the cell sheet, human PDL cells were cultured on temperature‐responsive culture dishes with or without osteogenic differentiation medium. The cell sheets were transplanted on periodontal fenestration defects of immunodeficient rats. Forty rats were divided in two groups: in one group, cell sheets cultured with control medium were transplanted and in the other, cell sheets cultured with osteogenic differentiation medium were transplanted. The defects were analysed histologically and histomorphologically after healing. Results: Most of the experimental group exhibited a new cementum‐like layer and new attachment of collagen fibres to the layer. Histomorphological analyses indicated significant periodontal regeneration. The control group revealed dense extracellular matrix and fibre formation, but an obvious cementum layer was not observed. Conclusions: Transplanted PDL cell sheets cultured with osteogenic differentiation medium induced periodontal regeneration containing an obvious cementum layer and Sharpey's fibres. Thus, the method could be feasible as a new therapeutic approach for periodontal regeneration.     

Alveolar Bone Resorption Induced by CD4+CD45RB High‐Density T‐Cell Transfer in Immunocompromised Mice

Background: The aims of this study are to determine whether the antigen‐inexperienced (naive, CD45RB high‐density) T‐cell (CD4⁺CD45RB^High T‐cell) transfer model is associated with alveolar bone resorption, to elucidate the local osteogenic/adipogenic potential of alveolar bone marrow stromal cells (ABCs) from T‐cell–transferred animals, and to investigate the systemic osteogenic potential by transplanting human periodontal ligament stem cells (hPDLSCs) into these animals. Methods: CD4⁺CD45RB^High and CD4⁺CD45RB^Low (antigen‐experienced [memory, CD45RB low‐density]) T cells were sorted and transferred into severe combined immunodeficiency (SCID) mice to induce inflammatory bowel disease–like syndrome (n = 8). hPDLSCs were transplanted into T‐cell–transferred SCID mice to examine ectopic cementum formation 8 weeks after T‐cell transfer. The mandibles and tibias of these mice were retrieved for microcomputed tomography (micro‐CT), histomorphometric analysis, and isolation of ABCs 16 weeks after T‐cell transfer. The in vitro osteogenic and adipogenic potentials of the ABCs were evaluated. Results: Histologic and micro‐CT analysis revealed that the transfer of CD4⁺CD45RB^High T‐cell subset was sufficient for alveolar bone resorption and affected the osteogenic/adipogenic potential of ABCs. Furthermore, it was found that CD4⁺CD45RB^High T‐cell–transferred animals have decreased systemic osteogenic potential, as evidenced using the in vivo ectopic hPDLSC transplantation model. Conclusion: CD4⁺CD45RB^High T‐cell transfer induced both alveolar bone resorption and reduced systemic osteogenic potential, with a concomitant downregulation of the osteogenic potential of ABCs.     

Effect of humoral factors from hPDLSCs on the biologic activity of hABCs

Oral Diseases (2012) 18, 537–547 Objective: The human periodontal ligament stem cells (hPDLSCs) and human alveolar bone–derived stromal cells (hABCs) seem to be closely involved in the maintenance of alveolar bone in an anatomically indirect manner; however, there is little study on this matter. Therefore, the effect of hPDLSCs on the osteoclastogenic, osteogenic, and adipogenic differentiation of hABCs was evaluated, focusing on the humoral factors released by hPDLSCs. Materials and methods: Human periodontal ligament stem cells and hABCs were isolated and characterized. hPDLSCs were indirectly cocultured to observe the in vitro effect of humoral factors released from hPDLSCs on the osteoclastogenic, osteogenic, and adipogenic differentiation of hABCs. Human gingival fibroblasts (hGFs) were utilized as positive control. Results: Isolated cells demonstrated the presence of stem cells within. Indirect coculture of hPDLSCs greatly inhibited osteoclastogenesis by hABCs. Osteogenesis/adipogenesis of hABCs was also inhibited by indirect coculture with hPDLSC. The magnitude of regulatory effect from hPDLSCs was significantly greater than that of hGFs. Conclusions: Humoral factors released from hPDLSCs seemed to modulate the differentiation of hABCs, and the osteoclastogenic, osteogenic, and adipogenic differentiation of hABCs was all inhibited, suggesting the potential role of hPDLSCs in the maintenance of the alveolar bone.     

The structure of periodontal tissues formed following guided tissue regeneration therapy of intra-bony defects in the monkey

Objective: To describe the periodontal tissues formed following guided tissue regeneration (GTR) therapy of intra‐bony defects (IBD). Methods: Eight adult Macaca fascicularis monkeys were used. Proximal IBD were created at the mandibular second pre‐molars and second molars. After 3 months, GTR surgery was performed. The animals were euthanized at 6 months and 2 years after surgery. Block biopsies were harvested, and prepared for histological analysis. Results: At 6 months the defect had healed with new cementum (NC), periodontal ligament (PDL) and bone. The NC seemed to be firmly anchored to the dentin. Supra‐crestally, the NC consisted of a 10 μm thick layer of acellular extrinsic fibre cementum (AEFC). Sub‐crestally, the NC was considerably thicker and consisted of an inner layer of AEFC and an outer thicker layer of cellular mixed fibre cementum (CMFC). The extrinsic fibre density amounted to about 10 fibres per 100 μm. The PDL was wider than the pristine PDL and widened in coronal direction. After 2 years of healing, the thickness of the NC in the sub‐crestal compartment had increased by about 20 μm and the fibre density had increased by about 50%. Conclusion: After 2 years of healing the structure of the regenerated tissues resembled that of pristine periodontal tissues.     

Periodontal regeneration following implantation of cementum and periodontal ligament-derived cells

Nuñez J, Sanz‐Blasco S, Vignoletti F, Muñoz F, Arzate H, Villalobos C, Nuñez L, Caffesse RG, Sanz M. Periodontal regeneration following implantation of cementum and periodontal ligament‐derived cells. J Periodont Res 2012; 47: 33–44. © 2011 John Wiley & Sons A/S Background and Objective: The periodontal regeneration of bone defects is often unsatisfactory and could be largely improved by cell therapy. Therefore, the purpose of this study was to evaluate the regenerative potential of implanting canine cementum‐derived cells (CDCs) and canine periodontal ligament‐derived cells (PDLDCs) in experimentally created periodontal intrabony defects in beagle dogs. Material and Methods: Cells were obtained from premolars extracted from four beagle dogs. Three‐wall intrabony periodontal defects, 3 mm wide and 4 mm deep, were surgically created in their second and fourth premolars and plaque was allowed to accumulate. Once the defects were surgically debrided, periodontal regeneration was attempted by random implantation of collagen sponges embedded with 750,000 CDCs, 750,000 PDLDCs or culture medium. After 3 mo of healing, specimens were obtained and periodontal regenerative outcomes were assessed histologically and histometrically. Results: The histological analysis showed that a minimal amount of new cementum was formed in the control group (1.56 ± 0.39 mm), whereas in both test groups, significantly higher amounts of new cementum were formed (3.98 ± 0.59 mm in the CDC group and 4.07 ± 0.97 mm in the PDLDC group). The test groups also demonstrated a larger dimension of new connective tissue, resulting in a significantly more coronal level of histological attachment. Conclusion: This proof‐of‐principle study suggests that cellular therapy, in combination with a collagen sponge, promoted periodontal regeneration in experimental intrabony periodontal defects.     

Human cementoblasts express enamel‐associated molecules in vitro and in vivo

Nuñez J, Sanz M, Hoz‐Rodríguez L, Zeichner‐David M, Arzate H. Human cementoblasts express enamel‐associated molecules in vitro and in vivo. J Periodont Res 2010; 45: 809–814. © 2010 John Wiley & Sons A/S Background and Objective: Cementum is a mineralized tissue that facilitates the attachment of periodontal ligament to the root and surrounding alveolar bone and plays a key role in the regeneration of periodontal tissues. The molecular mechanisms that regulate the proliferation and differentiation of cementoblasts, however, have not been elucidated to date. Enamel molecules are believed to regulate cementoblast differentiation and to initiate the formation of acellular extrinsic fiber cementum. The purpose of this study was therefore to isolate and culture human root‐derived cells (HRDC) in order to determine whether they are able to express both cementum and specific enamel proteins and subsequently to confirm these findings in vivo. Material and Methods: Human root‐derived cells were isolated and expanded in vitro. Cells were characterized using RT‐PCR, immunostaining, western blotting and by examination of total mRNA to determine the expression of cementum and enamel markers. Human periodontal tissues were also examined for the expression of enamel‐related proteins by immunostaining. Results: We showed that HRDC express mRNA corresponding to ameloblastin (AMBN), amelogenin (AMEL), enamelin (ENAM), tuftelin (TUFT) and cementum‐associated molecules such as cementum protein 1 (CEMP1) and cementum attachment protein (CAP). Western blotting revealed that HRDC express both AMEL and AMBN gene products, as well as the cementum markers CEMP1 and CAP. In vivo, we have showed that AMBN and AMEL are expressed by cementoblasts lining cementum, paravascular cells and periodontal ligament cells. Conclusion: These results suggest that enamel‐associated and cementum‐associated proteins could act synergistically in regulating cementoblast differentiation and cementum deposition and offer new approaches on how the cementogenesis process is regulated.     

Sequential process in brain‐derived neurotrophic factor‐induced functional periodontal tissue regeneration

We recently demonstrated that brain‐derived neurotrophic factor (BDNF) promotes periodontal tissue regeneration. The purpose of this study was to establish an essential component of a rational approach for the clinical application of BDNF in periodontal regenerative therapy. Here, we assessed the sequence of early events in BDNF‐induced periodontal tissue regeneration, especially from the aspect of cementum regeneration. Brain‐derived neurotrophic factor was applied into experimental periodontal defects in Beagle dogs. The localization of cells positive for neurotrophic tyrosine kinase, receptor, type 2, proliferating cell nuclear antigen, osteopontin, integrin αVβ3, and integrin α2β1 was evaluated by immunohistochemistry. The effects of BDNF on adhesion of cultured human periodontal ligament cells was examined by an in vitro study. The results suggest that BDNF could induce rapid cementum regeneration by stimulating adhesion, proliferation, and differentiation of periodontal ligament cells in the early regenerative phase, resulting in enhancement of periodontal tissue regeneration.     

Redefining the induction of periodontal tissue regeneration in primates by the osteogenic proteins of the transforming growth factor‐β supergene family

The molecular bases of periodontal tissue induction and regeneration are the osteogenic proteins of the transforming growth factor‐β (TGF‐β) supergene family. These morphogens act as soluble mediators for the induction of tissues morphogenesis sculpting the multicellular mineralized structures of the periodontal tissues with functionally oriented ligament fibers into newly formed cementum. Human TGF‐β₃ (hTGF‐β₃) in growth factor‐reduced Matrigel^® matrix induces cementogenesis when implanted in class II mandibular furcation defects surgically prepared in the non‐human primate Chacma baboon, Papio ursinus. The newly formed periodontal ligament space is characterized by running fibers tightly attached to the cementoid surface penetrating as mineralized constructs within the newly formed cementum assembling and initiating within the mineralized dentine. Angiogenesis heralds the newly formed periodontal ligament space, and newly sprouting capillaries are lined by cellular elements with condensed chromatin interpreted as angioblasts responsible for the rapid and sustained induction of angiogenesis. The inductive activity of hTGF‐β₃ in Matrigel^® matrix is enhanced by the addition of autogenous morcellated fragments of the rectus abdominis muscle potentially providing myoblastic, pericytic/perivascular stem cells for continuous tissue induction and morphogenesis. The striated rectus abdominis muscle is endowed with stem cell niches in para/perivascular location, which can be dominant, thus imposing stem cell features or stemness to the surrounding cells. This capacity to impose stemness is morphologically shown by greater alveolar bone induction and cementogenesis when hTGF‐β₃ in Matrigel^® matrix is combined with morcellated fragments of autogenous rectus abdominis muscle. The induction of periodontal tissue morphogenesis develops as a mosaic structure in which the osteogenic proteins of the TGF‐β supergene family singly, synergistically and synchronously initiate and maintain tissue induction and morphogenesis. In primates, the presence of several homologous yet molecularly different isoforms with osteogenic activity highlights the biological significance of this apparent redundancy and indicates multiple interactions during embryonic development and bone regeneration in postnatal life. Molecular redundancy with associated different biological functionalities in primate tissues may simply represent the fine‐tuning of speciation‐related molecular evolution in anthropoid apes at the early Pliocene boundary, which resulted in finer tuning of the bone induction cascade.     

Identification of multipotent stem cells from adult dog periodontal ligament

Periodontal diseases, which are characterized by destruction of the connective tissues responsible for restraining the teeth within the jaw, are the main cause of tooth loss. Periodontal regeneration mediated by human periodontal ligament stem cells (hPDLSCs) may offer an alternative strategy for the treatment of periodontal disease. Dogs are a widely used large-animal model for the study of periodontal-disease progression, tissue regeneration, and dental implants, but little attention has been paid to the identification of the cells involved in this species. This study aimed to characterize stem cells isolated from canine periodontal ligament (cPDLSCs). The cPDLSCs, like hPDLSCs, showed clonogenic capability and expressed the mesenchymal stem cell markers STRO-1, CD146, and CD105, but not CD34. After induction of osteogenesis, cPDLSCs showed calcium accumulation in vitro. Moreover, cPDLSCs also showed both adipogenic and chondrogenic potential. Compared with cell-free controls, more cementum/periodontal ligament-like structures were observed in CB-17/SCID mice into which cPDLSCs had been transplanted. These results suggest that cPDLSCs are clonogenic, highly proliferative, and have multidifferentiation potential, and that they could be used as a new cellular therapeutic approach to facilitate successful and more predictable regeneration of periodontal tissue using a canine model of periodontal disease.     

Effects of heparin-binding epidermal growth factor-like growth factor on cell repopulation and signal transduction in periodontal ligament cells after scratch wounding in vitro

Background and Objective: A growing amount of attention has been placed on periodontal regeneration and wound healing for periodontal therapy. This study was conducted in an effort to determine the effects of heparin‐binding epidermal growth factor‐like growth factor on cell repopulation and signal transduction in periodontal ligament cells after scratch wounding in vitro. Material and Methods: Human periodontal ligament cells were acquired from explant tissue of human healthy periodontal ligament. After the wounding of periodontal ligament cells, the change in expression of heparin‐binding epidermal growth factor‐like growth factor and epidermal growth factor receptors 1–4 mRNA was assessed. The effects of heparin‐binding epidermal growth factor‐like growth factor on periodontal ligament cell proliferation and repopulation were assessed in vitro via the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay and by photographing the injuries, respectively. Extracellular signal‐regulated kinase (Erk)1/2, p38 and Akt phosphorylation was characterized via western blotting. Results: Scratch wounding resulted in a significant up‐regulation of heparin‐binding epidermal growth factor‐like growth factor mRNA expression, whereas wounding had no effect on the expression levels of epidermal growth factor receptors 1–4. Interestingly, no expression of epidermal growth factor receptors 2 and 4 was detectable prior to or after wounding. Heparin‐binding epidermal growth factor‐like growth factor treatment promoted the proliferation and repopulation of periodontal ligament cells. The scratch wounding also stimulated the phosphorylation of Erk1/2 and p38, but not of Akt, in periodontal ligament cells, and heparin‐binding epidermal growth factor‐like growth factor treatment applied after wounding amplified and extended the activations of Erk1/2 and p38, but not of Akt. Furthermore, Erk1/2 inhibition blocked the process of cell repopulation induced by heparin‐binding epidermal growth factor‐like growth factor, whereas the inhibition of p38 delayed the process. Conclusion: These results indicate that heparin‐binding epidermal growth factor‐like growth factor may constitute a critical factor in the wound healing of human periodontal ligament cells by a mechanism that requires the activation of Erk1/2 via specific interaction with epidermal growth factor receptor 1.     

Attachment formation after transplantation of teeth cultured with enamel matrix derivative in dogs

Background: Implantation of cultured cells may be applied for periodontal regeneration in the future. However, a donor is essential in each case and tooth extraction is required to obtain the periodontal ligament–derived cell. We developed a novel regenerative technique combining tissue culture and transplantation of teeth. The purpose of this study is to evaluate the effect of enamel matrix derivative (EMD) on periodontal healing using this technique in dogs. Methods: A total of 32 incisors from seven beagle dogs were used. The periodontal ligament and cementum 5 mm from the coronal part of the roots were removed, whereas those in the apical part were preserved. Teeth were transplanted after the following treatments: 1) culture with application of EMD to the root surface for 6 weeks (n = 11); 2) culture without application of EMD for 6 weeks (n = 11); and 3) immediately transplanted without culture as control (n = 10). Eight weeks after transplantation, periodontal healing was analyzed. Results: The downgrowth of junctional epithelium on the roots of the EMD and culture groups was significantly smaller than that in the control group (P <0.01). Most of the root‐planed surfaces in the EMD group were covered with new cementum (72.2% ± 8.6%). This was significantly greater than that in the culture (29.1% ± 22.9%) and control groups (0.3% ± 1.1%). Conclusions: Transplantation of tissue‐cultured teeth decreased epithelial downgrowth and increased connective tissue attachment on the root‐planed surface. Furthermore, EMD could remarkably increase the new connective tissue attachment in this periodontal regenerative technique.     

Statins in nonsurgical and surgical periodontal therapy. A systematic review and meta‐analysis of preclinical in vivo trials

The cholesterol‐lowering drugs, statins, possess anti‐inflammatory, antimicrobial and pro‐osteogenic properties, and thus have been tested as an adjunct to periodontal treatment. The present systematic review aimed to answer the following focused research question: What is the effect of local and/or systemic statin use on periodontal tissues in preclinical in vivo studies of experimentally induced periodontitis (EIP ) and/or acute/chronified periodontal defect (ACP ) models? A literature search (of Medline/PubMed, Embase/Ovid, CENTRAL /Ovid) using the following main eligibility criteria was performed: (i) English or German language; (ii) controlled preclinical in vivo trials; (iii) local and/or systemic statin use in EIP and/or ACP models; and (iv) quantitative evaluation of periodontal tissues (i.e., alveolar bone level/amount, attachment level, cementum formation, periodontal ligament formation). Sixteen studies in EIP models and 7 studies in ACP models evaluated simvastatin, atorvastatin or rosuvastatin. Thirteen of the EIP (81%) and 2 of the ACP (29%) studies presented significantly better results in terms of alveolar bone level/amount in favor of statins. Meta‐analysis based on 14 EIP trials confirmed a significant benefit of local and systemic statin use (P  < .001) in terms of alveolar bone level/amount; meta‐regression revealed that statin type exhibited a significant effect (P  = .014) in favor of atorvastatin. Three studies reported a significantly higher periodontal attachment level in favor of statin use (P  < .001). Complete periodontal regeneration was never observed; furthermore, statins did not exert any apparent effect on cementum formation. Neither local nor systemic use of statins resulted in severe adverse effects. Statin use in periodontal indications has a positive effect on periodontal tissue parameters, supporting the positive results already observed in clinical trials. Nevertheless, not all statins available have been tested so far, and further research is needed to identify the maximum effective concentration/dose and optimal carrier.     

基质细胞衍生因子-1对炎症和正常来源的 人牙周膜干细胞成骨分化能力的影响

目的 通过体外培养炎症来源的人牙周膜干细胞（iPDLSCs）和正常来源的人牙周膜干细胞（hPDLSCs）,比较基质细胞衍生因子-1（SDF-1）对于两种来源细胞的成骨分化作用。方法 采用组织块酶消化法原代培养iPDLSCs 和hPDLSCs,经有限稀释法纯化,通过流式细胞仪对干细胞表面标记物检测鉴定后,对其进行成骨诱导;MTT法检测并比较SDF-1对两种来源的细胞增殖能力的影响;茜素红染色检测SDF-1作用于两种来源的细胞后钙化骨量的表达;碱性磷酸酶法比较SDF-1作用于两者的成骨分化能力;逆转录聚合酶链反应（RT-PCR）法检测SDF-1作用于两种牙周膜干细胞前后成骨相关基因表达水平的变化。结果 两种来源的牙周膜细胞经纯化后均阳性表达干细胞标记物。hPDLSCs较iPDLSCs增殖能力高;两种细胞经SDF-1成骨诱导培养后,成骨相关基因的表达水平均较诱导前明显上调（P<0.05）,SDF-1在50、200 ng·mL ^-1时分别对iPDLSCs和hPDLSCs细胞成骨分化作用最明显（P<0.05）。结论 正常来源和炎症来源的人牙周膜干细胞均具有成骨分化能力,SDF-1可增强两种来源的牙周膜干细胞的成骨分化能力。