Transplantation of embryonic stem cells improves the regeneration of periodontal furcation defects in a porcine model

Chronic Periodontal Infection and Not Iatrogenic Interference Is the Trigger of Medication-Related Osteonecrosis of the Jaw: Insights from a Large Animal Study (PerioBRONJ Pig Model)

Background and Objectives: Antiresorptive drugs are widely used in osteology and oncology. An important adverse effect of these drugs is medication-induced osteonecrosis of the jaw (MRONJ). There is scientific uncertainty about the underlying pathomechanism of MRONJ. A promising theory suspects infectious stimuli and local acidification with adverse effects on osteoclastic activity as crucial steps of MRONJ etiology. Clinical evidence showing a direct association between MRONJ and oral infections, such as periodontitis, without preceding surgical interventions is limited. Large animal models investigating the relationship between periodontitis and MRONJ have not been implemented. It is unclear whether the presence of infectious processes without surgical manipulation can trigger MRONJ. The following research question was formulated: is there a link between chronic oral infectious processes (periodontitis) and the occurrence of MRONJ in the absence of oral surgical procedures? Materials and Methods: A minipig large animal model for bisphosphonate-related ONJ (BRONJ) using 16 Göttingen minipigs divided into 2 groups (intervention/control) was designed and implemented. The intervention group included animals receiving i.v. bisphosphonates (zoledronate, n = 8, 0.05 mg/kg/week: ZOL group). The control group received no antiresorptive drug (n = 8: NON-ZOL group). Periodontitis lesions were induced by established procedures after 3 months of pretreatment (for the maxilla: the creation of an artificial gingival crevice and placement of a periodontal silk suture; for the mandible: the placement of a periodontal silk suture only). The outcomes were evaluated clinically and radiologically for 3 months postoperatively. After euthanasia a detailed histological evaluation was performed. Results: Periodontitis lesions could be induced successfully in all animals (both ZOL and NON-ZOL animals). MRONJ lesions of various stages developed around all periodontitis induction sites in the ZOL animals. The presence of MRONJ and periodontitis was proven clinically, radiologically and histologically. Conclusions: The results of this study provide further evidence that the infectious processes without prior dentoalveolar surgical interventions can trigger MRONJ. Therefore, iatrogenic disruption of the oral mucosa cannot be the decisive step in the pathogenesis of MRONJ.

Transplantation of Mature Adipocyte-Derived Dedifferentiated Fat Cells Facilitates Periodontal Tissue Regeneration of Class II Furcation Defects in Miniature Pigs

Adipose tissue is composed mostly of adipocytes that are in contact with capillaries. By using a ceiling culture method based on buoyancy, lipid-free fibroblast-like cells, also known as dedifferentiated fat (DFAT) cells, can be separated from mature adipocytes with a large single lipid droplet. DFAT cells can re-establish their active proliferation ability and transdifferentiate into various cell types under appropriate culture conditions. Herein, we sought to compare the regenerative potential of collagen matrix alone (control) with autologous DFAT cell-loaded collagen matrix transplantation in adult miniature pigs (microminipigs; MMPs). We established and transplanted DFAT cells into inflammation-inducing periodontal class II furcation defects. At 12 weeks after cell transplantation, a marked attachment gain was observed based on the clinical parameters of probing depth (PD) and clinical attachment level (CAL). Additionally, micro computed tomography (CT) revealed hard tissue formation in furcation defects of the second premolar. The cemento-enamel junction and alveolar bone crest distance was significantly shorter following transplantation. Moreover, newly formed cellular cementum, well-oriented periodontal ligament-like fibers, and alveolar bone formation were observed via histological analysis. No teratomas were found in the internal organs of recipient MMPs. Taken together, these findings suggest that DFAT cells can safely enhance periodontal tissue regeneration.

Stem cell therapies for periodontal tissue regeneration: a network meta-analysis of preclinical studies

Background

Periodontal tissue regeneration (PTR) is the ultimate goal of periodontal therapy. Currently, stem cell therapy is considered a promising strategy for achieving PTR. However, there is still no conclusive comparison that distinguishes clear hierarchies among different kinds of stem cells.

Methods

A systematic review and network meta-analysis (NMA) was performed using MEDLINE (via PubMed), EMBASE, and Web of Science up to February 2020. Preclinical studies assessing five types of stem cells for PTR were included; the five types of stem cells included periodontal ligament-derived stem cells (PDLSCs), bone marrow-derived stem cells (BMSCs), adipose tissue-derived stem cells (ADSCs), dental pulp-derived stem cells (DPSCs), and gingival-derived stem cells (GMSCs). The primary outcomes were three histological indicators with continuous variables: newly formed alveolar bone (NB), newly formed cementum (NC), and newly formed periodontal ligament (NPDL). We performed pairwise meta-analyses using a random-effects model and then performed a random-effects NMA using a multivariate meta-analysis model.

Results

Sixty preclinical studies assessing five different stem cell-based therapies were identified. The NMA showed that in terms of NB, PDLSCs (standardized mean difference 1.87, 95% credible interval 1.24 to 2.51), BMSCs (1.88, 1.17 to 2.59), and DPSCs (1.69, 0.64 to 2.75) were statistically more efficacious than cell carriers (CCs). In addition, PDLSCs were superior to GMSCs (1.49, 0.04 to 2.94). For NC, PDLSCs (2.18, 1.48 to 2.87), BMSCs (2.11, 1.28 to 2.94), and ADSCs (1.55, 0.18 to 2.91) were superior to CCs. For NPDL, PDLSCs (1.69, 0.92 to 2.47) and BMSCs (1.41, 0.56 to 2.26) were more efficacious than CCs, and PDLSCs (1.26, 0.11 to 2.42) were superior to GMSCs. The results of treatment hierarchies also demonstrated that the two highest-ranked interventions were PDLSCs and BMSCs.

Conclusion

PDLSCs and BMSCs were the most effective and well-documented stem cells for PTR among the five kinds of stem cells evaluated in this study, and there was no statistical significance between them. To translate the stem cell therapies for PTR successfully in the clinic, future studies should utilize robust experimental designs and reports.

Periodontal regenerative medicine using mesenchymal stem cells and biomaterials: A systematic review of pre-clinical studies

The aim of the systematic review was to analyze the use of mesenchymal stem cells (MSC) and biomaterial for periodontal regeneration from preclinical animal models and human. Electronic databases were searched and additional hand-search in leading journals was performed. The research strategy was achieved according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The including criteria were as follows: MSC, biomaterial, in vivo studies, with histologic and radiologic analysis and written in English. The risk of bias was assessed for individual studies. A total of 50 articles were selected and investigated in the systematic review. These results indicate that MSC and scaffold provide beneficial effects on periodontal regeneration, with no adverse effects of such interventions. Future studies need to identify the suitable association of MSC and biomaterial and to characterize the type of new cementum and the organization of the periodontal ligament fiber regeneration.

Porcine-induced pluripotent stem cell-derived osteoblast-like cells ameliorate trabecular bone mass of osteoporotic rats

AIM

We created rat models of osteoporosis and verified a novel idea to recover bone mass via local cell transplantation.

MATERIALS & METHODS

The rats were treated with ovariectomy, 0.1% calcium diet or 3 mg/kg body weight/day of prednisolone and porcine-induced pluripotent stem cell (piPSC)-derived osteoblast-like cells were transplanted into the medullary cavity of the left femurs.

RESULTS

The piPSC-derived osteoblast-like cells exerted therapeutic potential on prednisolone treatment group, which confirmed by improvements in trabecular bone volume (15.93 ± 2.20%), bone surface/volume ratio (27.82 ± 1.40 1/mm), thickness (1.40 ± 0.01 mm), separation (0.99 ± 0.10 mm), number (1.13 ± 0.13 1/mm) and total porosity (84.06 ± 2.20%).

CONCLUSION

These results first uncovered therapeutic potential of xenotransplantation with piPSCs for glucocorticoid-induced osteoporosis treatment in the rat models.

Comparative study of periodontal differentiation propensity of induced pluripotent stem cells from different tissue origins

BACKGROUND

Despite being almost identical to embryonic stem cells, induced pluripotent stem cells (iPSCs) have been shown to possess a residual somatic memory that favors their differentiation propensity into donor tissue. To further confirm this assumption, we compare for the first time the periodontal differentiation tendency of human gingival fibroblast-derived iPSCs (G-iPSCs) and human neonatal skin fibroblast-derived iPSCs (S-iPSCs) to assess whether G-iPSCs could be more efficiently induced toward periodontal cells.

METHODS

We induced G- and S-iPSCs under the treatment of growth/differentiation factor-5 and connective tissue growth factor, respectively, for 14 days. Immunofluorescence staining and real-time polymerase chain reaction were used to compare their expression levels of related markers. Furthermore, a hydrogel carrier was developed to seed these periodontal progenitors for subcutaneous implantation in non-obese diabetic-severe combined immunodeficiency disease mice. Their differentiated periodontal phenotype maintenance was further assayed by HE observation, immunohistochemical staining and immunofluorescence co-localization with pre-labeled PKH67.

RESULTS

As expected, both iPSCs were inclined to differentiate back into their original lineage by expressing higher markers at both gene and protein levels in vitro. HE observation of G-iPSCs-seeded hydrogel constructs present more mineralized structure formation than S-iPSCs-seeded ones. Immunohistochemical staining and immunofluorescence analysis also showed stronger positive staining for periodontal related markers in G-iPSCs-seeded hydrogel constructs.

CONCLUSIONS

Our results preliminarily confirmed that both G- and S-iPSCs were inclined to differentiate back into their original tissue in vitro. Animal study further confirmed the phenotype maintenance of periodontal differentiated G-iPSCs, which highlighted their significant implications for therapeutic use in periodontal regeneration.

Effects of Klf4 and c-Myc Knockdown on Pluripotency Maintenance in Porcine Induced Pluripotent Stem Cell

Objective

The importance of Oct4 and Sox2 in maintaining pluripotency and self-renewal is well-understood, but the functions of Klf4 and c-Myc has not been fully investigated. In the present study, we attempted to determine the roles of Klf4 and c-Myc on pluripotency maintenance of porcine induced pluripotent stem (piPS) cells.

Materials and Methods

In this experimental study, we performed short hairpin RNA (shRNA) to knock down the Klf4 and c-Myc functions of piPS cells and examined pluripotency markers and teratoma formation to evaluate piPS cell pluripotency. The shRNA-Klf4 and shRNA-c-Myc vectors containing a reporter gene, TagFP635, were transfected into piPS cells by lentivirus infection. The piPS cells fully expressing infrared fluorescence were selected to confirm gene knockdown of Klf4 and c-Myc reverse transcription-polymerase chain reaction (RT-PCR). Next, for pluripotency evaluation, expression of pluripotency markers was detected by immunocytochemical staining, and capability of teratoma formation was investigated by piPS cell transplantation into nonobese diabetic-severe combined immunodeficiency (NOD-SCID) mice.

Results

Our findings indicated that Klf4 and c-Myc functions of piPS cells were knocked down by shRNA transfection, and knockdown of Klf4 and c-Myc functions impaired expression of pluripotency markers such as Oct4, AP, SSEA-3, SSEA-4, TRA-1-6, and TRA-1-81. Furthermore, piPS cells without Klf4 and c-Myc expression failed to form teratomas.

Conclusion

The pluripotency of piPS cells are crucially dependent upon Klf4 and c-Myc expression. These findings, suggesting potential mechanisms of Klf4 and c-Myc contribution to piPS cell formation, have important implications for application, regulation, and tumorigenesis of piPS cells.

Efficacy of stem cells on periodontal regeneration: Systematic review of pre-clinical studies

This systematic review aims to evaluate mesenchymal stem cells (MSC) periodontal regenerative potential in animal models. MEDLINE, EMBASE and LILACS databases were searched for quantitative pre-clinical controlled animal model studies that evaluated the effect of local administration of MSC on periodontal regeneration. The systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement guidelines. Twenty-two studies met the inclusion criteria. Periodontal defects were surgically created in all studies. In seven studies, periodontal inflammation was experimentally induced following surgical defect creation. Differences in defect morphology were identified among the studies. Autogenous, alogenous and xenogenous MSC were used to promote periodontal regeneration. These included bone marrow-derived MSC, periodontal ligament (PDL)-derived MSC, dental pulp-derived MSC, gingival margin-derived MSC, foreskin-derived induced pluripotent stem cells, adipose tissue-derived MSC, cementum-derived MSC, periapical follicular MSC and alveolar periosteal cells. Meta-analysis was not possible due to heterogeneities in study designs. In most of the studies, local MSC implantation was not associated with adverse effects. The use of bone marrow-derived MSC for periodontal regeneration yielded conflicting results. In contrast, PDL-MSC consistently promoted increased PDL and cementum regeneration. Finally, the adjunct use of MSC improved the regenerative outcomes of periodontal defects treated with membranes or bone substitutes. Despite the quality level of the existing evidence, the current data indicate that the use of MSC may provide beneficial effects on periodontal regeneration. The various degrees of success of MSC in periodontal regeneration are likely to be related to the use of heterogeneous cells. Thus, future studies need to identify phenotypic profiles of highly regenerative MSC populations.

MicroRNA-22 Promoted Osteogenic Differentiation of Human Periodontal Ligament Stem Cells by Targeting HDAC6

Stem cells transplantation is a promising therapy strategy for accelerating periodontal regeneration and reconstruction. Genetic modification could induce stem cells directional differentiation to facilitate recovery of physiological functions. In this study, we investigated the role and mechanism of miR-22 on human periodontal ligament stem cells (PDLSCs). First, a cellular model of osteogenic differentiation was first established by osteogenic inductive cocktail. Real-time PCR determined that expression of miR-22 was significantly increased during PDLSCs osteogenic differentiation. Alizirin red staining showed that overexpression of miR-22 in PDLSCs induced better mineralized nodule formation. Real-time PCR and Western blot further confirmed up-regulation of osteogenic genes Runx2 and OPN in miR-22-overexpressing PDLSCs. Conversely, inhibition of miR-22 delayed the process of PDLSCs osteogenic differentiation. Furthermore, Histone deacetylase 6 (HDAC6) was identified as a target gene of miR-22. Overexpression of miR-22 not only reduced the luciferase activity of the reporter containing the 3' untranslated region of HDAC6 mRNA, but also suppressed the endogenous protein expression of HDAC6. Rescue experiment showed that the promotion role of miR-22 in osteogenic differentiation could be relieved by overexpression of HDAC6. Meanwhile, overexpression of HDAC6 alone could also delay the osteogenic differentiation process. The results demonstrated that miR-22 promoted PDLSCs osteogenic differentiation by inhibiting HDAC6 expression, suggesting that miR-22 might be developed as a target of genetic modified stem cells therapy for periodontal diseases. J. Cell. Biochem. 118: 1653-1658, 2017. © 2017 Wiley Periodicals, Inc.

Emerging regenerative approaches for periodontal reconstruction: a systematic review from the AAP Regeneration Workshop

More than 30 years have passed since the first successful application of regenerative therapy for treatment of periodontal diseases. Despite being feasible, periodontal regeneration still faces numerous challenges, and complete restoration of structure and function of the diseased periodontium is often considered an unpredictable task. This review highlights developing basic science and technologies for potential application to achieve reconstruction of the periodontium. A comprehensive search of the electronic bibliographic database PubMed was conducted to identify different emerging therapeutic approaches reported to influence either biologic pathways and/or tissues involved in periodontal regeneration. Each citation was assessed based on its abstract, and the full text of potentially eligible reports was retrieved. Based on the review of the full papers, their suitability for inclusion in this report was determined. In principle, only reports from scientifically well-designed studies that presented preclinical in vivo (animal studies) or clinical (human studies) evidence for successful periodontal regeneration were included. Hence, in vitro studies, namely those conducted in laboratories without any live animals, were excluded. In case of especially recent and relevant reviews with a narrow focus on specific regenerative approaches, they were identified as such, and thereby the option of referring to them to summarize the status of a specific approach, in addition to or instead of listing each separately, was preserved. Admittedly, the presence of subjectivity in the selection of studies to include in this overview cannot be excluded. However, it is believed that the contemporary approaches described in this review collectively represent the current efforts that have reported preclinical or clinical methods to successfully enhance regeneration of the periodontium. Today's challenges facing periodontal regenerative therapy continue to stimulate important research and clinical development, which, in turn, shapes the current concept of periodontal tissue engineering. Emerging technologies--such as stem cell therapy, bone anabolic agents, genetic approaches, and nanomaterials--also offer unique opportunities to enhance the predictability of current regenerative surgical approaches and inspire development of novel treatment strategies.

Induced Pluripotent Stem Cells and Periodontal Regeneration

Periodontitis is a chronic inflammatory disease which leads to destruction of both the soft and hard tissues of the periodontium. Tissue engineering is a therapeutic approach in regenerative medicine that aims to induce new functional tissue regeneration via the synergistic combination of cells, biomaterials, and/or growth factors. Advances in our understanding of the biology of stem cells, including embryonic stem cells and mesenchymal stem cells, have provided opportunities for periodontal tissue engineering. However, there remain a number of limitations affecting their therapeutic efficiency. Due to the considerable proliferation and differentiation capacities, recently described induced pluripotent stem cells (iPSCs) provide a new way for cell-based therapies for periodontal regeneration. This review outlines the latest status of periodontal tissue engineering and highlights the potential use of iPSCs in periodontal tissue regeneration.

Synergistic Effects of a Calcium Phosphate/Fibronectin Coating on the Adhesion of Periodontal Ligament Stem Cells onto Decellularized Dental Root Surfaces

This study aimed to enhance the attachment of periodontal ligament stem cells (PDLSCs) onto the decellularized dental root surface using surface coating with fibronectin and/or calcium phosphate (CaP) and to evaluate the activity of PDLSCs attached to a coated dental root surface following tooth replantation. PDLSCs were isolated from five dogs, and the other dental roots were used as a scaffold for carrying PDLSCs and then assigned to one of four groups according to whether their surface was coated with CaP, fibronectin, CaP/fibronectin, or left uncoated (control). Fibronectin increased the adhesion of PDLSCs onto dental root surfaces compared to both the control and CaP-coated groups, and simultaneous surface coating with CaP and fibronectin significantly accelerated and increased PDLSC adhesion compared to the fibronectin-only group. On in vivo tooth replantation, functionally oriented periodontal new attachment was observed on the CaP/fibronectin-coated dental roots to which autologous PDLSCs had adhered, while in the control condition, dental root replantation was associated only with root resorption and ankylosis along the entire root length. CaP and fibronectin synergistically enhanced the attachment of PDLSCs onto dental root surfaces, and autologous PDLSCs could produce de novo periodontal new attachment in an experimental in vivo model.

Periodontal ligament stem cells: current status, concerns, and future prospects

Periodontal ligament stem cells (PDLSCs), which reside in the perivascular space of the periodontium, possess characteristics of mesenchymal stem cells and are a promising tool for periodontal regeneration. Recently, great progress has been made in PDLSC transplantation. Investigators are attempting to maximize the proliferation and differentiation potential of PDLSCs by modifying culture conditions and applying growth factors. Nevertheless, problems remain. First, incomparability among different studies must be minimized by establishing standard guidelines for culture and identification of PDLSCs. Notably, attention should be paid to the biological safety of PDLSC transplantation. The present review updates the latest findings regarding PDLSCs and discusses standard criteria for culture and identification of PDLSCs. Finally, the review calls for careful consideration of PDLSC transplantation safety.

Tissue engineering in periodontal tissue

Periodontitis, a recognized disease worldwide, is bacterial infection-induced inflammation of the periodontal tissues that results in loss of alveolar bone. Once it occurs, damaged tissue cannot be restored to its original form, even if decontaminating treatments are performed. For more than half a century, studies have been conducted to investigate true periodontal regeneration. Periodontal regeneration is the complete reconstruction of the damaged attachment apparatus, which contains both hard tissue (alveolar bone and cementum) and soft tissue (periodontal ligament). Several treatments, including bone grafts, guided tissue regeneration with physical barriers for epithelial cells, and growth factors have been approved for clinical use; however, their indications and outcomes are limited. To overcome these limitations, the concept of "tissue engineering" was introduced. Combination treatment using cells, growth factors, and scaffolds, has been studied in experimental animal models, and some studies have been translated into clinical trials. In this review, we focus on recent progressive tissue engineering studies and discuss future perspectives on periodontal regeneration.

Enhanced periodontal tissue regeneration by periodontal cell implantation

AIM

Due to a lack of regenerative potential, current treatments for periodontal defects do not always provide satisfactory clinical results. Previously, the implantation of a biomaterial scaffold-cell construct has been suggested as a clinically achievable approach. In this study, it was aimed to investigate the contribution of implanted periodontal ligament (PDL) cells to periodontal tissue regeneration.

MATERIALS & METHODS

Gelatin sponges were seeded with green fluorescent protein (GFP) transfected PDL or gingival fibroblasts (GF) cells, and implanted into a surgically created rat intrabony periodontal defect model. After six weeks, decalcified maxillae were used for histomorphometrical and immunohistochemical analyses.

RESULTS

After six weeks, animals that had received the PDL cells exhibited significantly more functional bone and ligament. Furthermore, there were remarkable differences in the distribution of the transplanted cells. Periodontal ligament cells were always located directly lining the newly regenerated areas. In contrast, GF cells dispersed over the whole defect area, and did not provide a favourable effect on the regeneration of the periodontal tissues.

CONCLUSION

We concluded that PDL cells transplanted into a periodontal defect survive and favour regeneration of periodontium, possibly in a paracrine manner.