Synthesis and antimicrobial studies of cadasides analogues via on-resin esterification.

A series of cadasides analogues have been prepared via a combination of solid-phase peptide synthesis and solution-phase cyclization. Primary structure-activity relationship studies of cadasides have also been established and revealed the critical roles of unnatural amino acid residues, which will facilitate the further development of cadasides analogues with improved antimicrobial activities.

A large-cohort study of 2971 cases of epulis: focusing on risk factors associated with recurrence.

BACKGROUND: To analyze the clinicopathological features of different histological subtypes of epulis, and evaluate the risk factors associated with recurrence. MATERIALS AND METHODS: A retrospective study including 2971 patients was performed. The patients' sex, age, location, size, histological subtypes, recurrence information, oral hygiene habits, periodontitis symptoms and smoking history were retrieved from the patient medical records and follow-up information. RESULTS: Among the 2971 cases, focal fibrous hyperplasia (FFH) was the most common lesion (60.92%), followed by peripheral ossifying fibroma (POF) (29.32%), pyogenic granuloma (PG) (8.08%) and peripheral giant cell granuloma (PGCG) (1.68%). The peak incidence of epulis was in the third and fourth decade of life, with a mean age of 45.55 years. Female predominance was found in all types of lesions with a female to male ratio of 1.71:1. PG had the highest recurrence rate (17.18%), followed by POF (12.98%), FFH (9.55%) and PGCG (8.82%). Histological subtypes were significantly correlated with the recurrence of epulis (P = 0.013). Regular supportive periodontal therapy (P = 0.050) had a negative correlation with recurrence, whereas symptoms of periodontitis (P < 0.001) had a positive correlation with the recurrence of epulis. CONCLUSIONS: Controlling the periodontal inflammation and regular supportive periodontal therapy might help reduce the recurrence of epulis.

Periodontal Guided Tissue Regeneration Membranes: Limitations and Possible Solutions for the Bottleneck Analysis.

Guided tissue regeneration (GTR) is an important surgical method for periodontal regeneration. By placing barrier membrane on the root surface of the tooth to guide the adhesion and proliferation of periodontal ligament cells, periodontal tissue regeneration can be achieved. This review intends to analyze the current limitations of GTR membranes and to propose possible solutions for developing new ones. Limitations of current GTR membranes include nonabsorbable membranes and absorbable synthetic polymer membranes exhibit weak biocompatibility; when applying to a large defect wound, the natural collagen membrane with fast degradation rate have limited mechanical strength, and the barrier function may not be maintained well. Although the degradation time can be prolonged after cross-linking, it may cause foreign body reaction and affect tissue integration; The clinical operation of current barrier membranes is inconvenient. In addition, most of the barrier membranes lack bioactivity and will not actively promote periodontal tissue regeneration. Possible solutions include using electrospinning (ELS) techniques, nanofiber scaffolds, or developing functional gradient membranes to improve their biocompatibility; adding Mg, Zn, and/or other metal alloys, or using 3D printing technology to improve their mechanical strength; increasing the concentration of nanoparticles or using directional arrangement of membrane fibers to control the fiber diameter and porosity of the membrane, which can improve their barrier function; mixing natural and synthetic polymers as well as other biomaterials with different degradation rates in proportion to change the degradation rate and maintain barrier function; to improve the convenience of clinical operation, barrier membranes that meets personalized adhesion to the wound defect can be manufactured; developing local controlled release drug delivery systems to improve their bioactivity. Impact statement This review provides an up-to-date summary of commonly commercial periodontal guided tissue regeneration membranes, and analyze their limitations in clinical use. Using studies published recently to explore possible solutions from several perspectives and to raise possible strategies in the future. Several strategies have tested in vivo/in vitro, which will guide the way to propel clinical translation, meeting clinical needs.

Lipidomic analysis reveals altered lipid profiles of gingival tissues with periodontitis.

AIM: The role of lipids in periodontitis has not been well studied. Thus, this study aimed to explore periodontitis-associated lipid profile changes and identify differentially expressed lipid metabolites in gingival tissues. MATERIALS AND METHODS: Gingival tissues from 38 patients with periodontitis (periodontitis group) and 38 periodontally healthy individuals (control group) were collected. A ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry-based non-targeted metabolomics platform was used to identify and compare the lipid profiles of the two groups. The distribution and expression of related proteins were subsequently analysed via immunohistochemistry to further validate the identified lipids. RESULTS: Lipid profiles significantly differed between the two groups, and 20 differentially expressed lipid species were identified. Lysophosphatidylcholines (lysoPCs), diacylglycerols (DGs), and phosphatidylethanolamines (PEs) were significantly up-regulated, while triacylglycerols (TGs) were downregulated in the periodontitis group. Moreover, the staining intensity of ABHD5/CGI-58, secretory phospholipase A2 (sPLA2), and sPLA2-IIA was significantly stronger in the gingival tissues of patients with periodontitis than in those of healthy controls. CONCLUSIONS: LysoPCs, DGs, and PEs were significantly up-regulated, whereas TGs were down-regulated in gingival tissues of patients with periodontitis. Correspondingly, the immunohistochemical staining of ABHD5/CGI-58, sPLA2, and sPLA2-IIA in gingival tissues was consistent with the downstream production of lipid classes (lysoPCs, TGs, and DGs).

A novel cone-beam CT scanning technique for measuring periodontal soft tissues in the esthetic area.

PURPOSE: This study investigated and tested a novel cone-beam computed tomography (CBCT) scanning technique capable of obtaining clear contours of soft tissues in the esthetic area. METHODS: Twenty-three periodontally healthy participants underwent this novel CBCT scanning technique. Soft tissue morphological parameters were measured on the CBCT images obtained. Intraoral clinical data were also collected at the same locations, and the accuracy of the CBCT method was tested. RESULTS: The median (interquartile range [IQR]) of the supracrestal gingival tissue thickness as 0.91 (0.73-1.13) mm, and the thickness of the central incisors was significantly greater than that of the canines (P < 0.05). The median (IQR) of keratinized tissue thickness was 0.73 (0.55-0.91) mm, which also showed a significantly greater thickness in the central incisors than in the canines (P < 0.05). Bland-Altman analysis suggested that CBCT could be accurate for measuring soft tissues in the esthetic area. CONCLUSION: The novel CBCT technique described yields clear contours of soft tissues in the esthetic area without the need for auxiliary tools. Moreover, measurements of soft tissue morphological parameters on CBCT appear to be accurate.

High expression of aryl hydrocarbon receptor (AhR) plays an important role in the formation of fibrous epulis.

OBJECTIVES: Epulis is considered to be a massive reactive lesion rather than a true neoplasia. AhR is thought to be associated with inflammation and development of neoplasms. Here, we aimed to observe the expression of AhR in fibrous epulis and explore its role and possible mechanism in the pathogenesis of epulis. MATERIALS AND METHODS: Epulis and normal gingival tissues were collected, and AhR expression was detected at the mRNA and protein levels by quantitative polymerase chain reaction (qPCR) and immunohistochemistry, respectively. The expression levels of proinflammatory cytokines and apoptosis-related factor genes in human periodontal ligament cells (hPDLCs) and human gingival fibroblasts (hGFs) transfected with AhR short interfering RNA (siRNA) or negative control siRNA, upon stimulation with lipopolysaccharide of Porphyromonas gingivalis (Pg-LPS), were then examined. Finally, the expression levels of the proinflammatory cytokines and apoptosis-related factor genes in the epulis tissues were observed by qPCR. RESULTS: AhR expression in fibrous epulis was significantly increased at both the mRNA and protein levels. The expression of proinflammatory cytokines and apoptosis-related factor genes in hPDLCs transfected with AhR siRNA was significantly decreased when stimulated with Pg-LPS. The same trends were observed for hGFs. The opposite trend was detected in the epulis tissues. CONCLUSION: AhR may be a key factor in fibrous epulis pathogenesis that acts by regulating the expression of BCL2 family genes and inflammatory factor-related genes.

Evaluation of polydimethylsiloxane-based substrates for in vitro culture of human periodontal ligament cells.

Periodontal ligament (PDL) cells are regarded as the cell type with the highest potential for periodontal regeneration. Biophysical cues of the culture substrate are increasingly identified as vital parameters to affect cell behavior. Compared to traditional tissue culture polystyrene (TCPS), polydimethylsiloxane (PDMS) substrates corroborate more closely the elastic modulus values of the physiological environment. Consequently, the aim of this study was to evaluate the effect of PDMS-based substrates with different stiffness on cellular responses of human PDL cells. PDMS substrates with different stiffness were fabricated by varying the ratio of base to curing component. The influence of PDMS substrates on PDL cell spreading and cytoskeletal morphologies, motility, proliferation, stemness gene expression, and osteogenic differentiation was evaluated and compared to that on conventional TCPS. PDL cells cultured on PDMS substrates exhibited a smaller cell size and more elongated morphology, with less spreading area, fewer focal adhesions, and faster migration than cells on TCPS. Compared to TCPS, PDMS substrates promoted the rapid in vitro expansion of PDL cells without interfering with their self-renewal ability. In contrast, the osteogenic differentiation ability of PDL cells cultured on PDMS was lower in comparison to cells on TCPS. PDL cells on PDMS exhibited similar cell morphology, motility, proliferation, and self-renewal gene expression. The stiffer PDMS substrate increased the osteogenic gene expression of PDL cells compared to the soft PDMS group in one donor. These data indicate that PDMS-based substrates have the potential for the efficient PDL cell expansion.

Structural Parameters Optimization of Elastic Cell in a Near-Bit Drilling Engineering Parameters Measurement Sub.

The downhole engineering parameters measurement sub is a key component of the rotary steerable drilling system. To enable a measurement sub to serve reliably under downhole complex conditions, the structural parameters optimization of its key but weak elastic cell is systematically studied. First, the multiple relations among measurement sensitivities, structural stiffnesses, and strength during structural parameters design are summarized. Second, the selection of the structural parameters of the elastic cell is characterized as a multi-objective optimization model, which is solved using the non-dominated sorting genetic algorithm II (NSGA-II). Furthermore, the finite element method (FEM) is used to verify the measurement performance and static strength of the proposed structure. Finally, transient dynamics analysis is applied to investigate the dynamic strength of the designed structure. The results show that the proposed parameters optimization strategy can quickly obtain the database for the structural parameters design of an elastic cell. The static analysis results based on the FEM further verify the effectiveness of the proposed method. Transient dynamic analysis also reveals the relative rigor of the proposed methodology framework to some extent. This work has practical significance for improving the drilling efficiency and reducing drilling risks. In addition, this proposed methodology has good extensibility.

Formation of Human Periodontal Ligament Cell Spheroids on Chitosan Films.

Periodontal ligament (PDL) cells hold great promise for periodontal tissue regeneration. Conventionally, PDL cells are cultured on two-dimensional (2D) substrates such as tissue culture polystyrene (TCPS). However, characteristic changes of PDL cells have been observed during in vitro culture. This phenomenon is probably because the 2D TCPS differs from the in vivo three-dimensional (3D) microenvironment. Compared to cells cultured on 2D substrates, cells grown in a 3D microenvironment exhibit more similarities to in vivo cells. Therefore, 3D cell culture models provide a promising alternative for conventional 2D monolayer cell culture. To improve conventional PDL cell culture models, we have recently developed a 3D cell culture method, which is based on spheroid formation of PDL cells on chitosan films. Here, we present detailed cell spheroid culture protocols based on chitosan films. The 3D culture system of PDL cellular spheroids overcome some of the limitations related to conventional 2D monolayer cell culture, and thus may be suitable for producing PDL cells with an enhanced therapeutic efficacy for future periodontal tissue regeneration.

An unexpected dual-response pH probe based on acridine.

A new pH fluorescent probe 2,8-bis(acridin-9-ylethynyl)-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine (TBN), which has two acridine moieties attached to Tröger's base, is a useful fluorescent probe for monitoring extreme acidic and alkaline pH. TBN displays an excellent pH dependent behavior and responds linearly to extreme conditions in the pH ranges of 1.4-3.4 and 12.5-15.0. TBN can represent a novel type of fluorescent probe with perfect emission properties in extreme acidic and alkaline conditions by utilizing only one functional group.

Push Force Analysis of Anchor Block of the Oil and Gas Pipeline in a Single-Slope Tunnel Based on the Energy Balance Method.

In this paper, a single-slope tunnel pipeline was analysed considering the effects of vertical earth pressure, horizontal soil pressure, inner pressure, thermal expansion force and pipeline-soil friction. The concept of stagnation point for the pipeline was proposed. Considering the deformation compatibility condition of the pipeline elbow, the push force of anchor blocks of a single-slope tunnel pipeline was derived based on an energy method. Then, the theoretical formula for this force is thus generated. Using the analytical equation, the push force of the anchor block of an X80 large-diameter pipeline from the West-East Gas Transmission Project was determined. Meanwhile, to verify the results of the analytical method, and the finite element method, four categories of finite element codes were introduced to calculate the push force, including CAESARII, ANSYS, AutoPIPE and ALGOR. The results show that the analytical results agree well with the numerical results, and the maximum relative error is only 4.1%. Therefore, the results obtained with the analytical method can satisfy engineering requirements.

Cell-Based Approaches in Periodontal Regeneration: A Systematic Review and Meta-Analysis of Periodontal Defect Models in Animal Experimental Work.

Various cell types have been assessed for experimental periodontal tissue regeneration in a variety of animal models. Nonetheless, the efficacy of cell-based approaches for periodontal regeneration is still controversial. Therefore, the purpose of this study was to systematically review cell-based approaches for periodontal regeneration in animal studies including a meta-analysis to obtain more clarity on their efficacy. The results of this systematic review and meta-analysis revealed that cell-based approaches have a favorable effect on periodontal tissue regeneration, as displayed by the positive effect of cell-based approaches on new bone, cementum, and periodontal ligament (PDL) formation in periodontal defects. Moreover, subgroup analysis showed a favorable effect on PDL formation by PDL-derived cells, but not by bone marrow mesenchymal stem cells (BMSCs). However, meta-analysis did not show any statistically significant differences in effect between PDL-derived cells and BMSCs. These results provide important information for the implementation of cell-based approaches in clinical practice as a routine treatment for periodontal regeneration in the future.

Influence of bone marrow-derived mesenchymal stem cells pre-implantation differentiation approach on periodontal regeneration in vivo.

AIM: The implantation of bone marrow-derived mesenchymal stem cells (MSCs) has previously been shown successful to achieve periodontal regeneration. However, the preferred pre-implantation differentiation strategy (e.g. maintenance of stemness, osteogenic or chondrogenic induction) to obtain optimal periodontal regeneration is still unknown. This in vivo study explored which differentiation approach is most suitable for periodontal regeneration. MATERIALS AND METHODS: Mesenchymal stem cells were obtained from Fischer rats and seeded onto poly(lactic-co-glycolic acid)/poly(ɛ-caprolactone) electrospun scaffolds, and then pre-cultured under different in vitro conditions: (i) retention of multilineage differentiation potential; (ii) osteogenic differentiation approach; and (iii) chondrogenic differentiation approach. Subsequently, the cell-scaffold constructs were implanted into experimental periodontal defects of Fischer rats, with empty scaffolds as controls. After 6 weeks of implantation, histomorphometrical analyses were applied to evaluate the regenerated periodontal tissues. RESULTS: The chondrogenic differentiation approach showed regeneration of alveolar bone and ligament tissues. The retention of multilineage differentiation potential supported only ligament regeneration, while the osteogenic differentiation approach boosted alveolar bone regeneration. CONCLUSION: Chondrogenic differentiation of MSCs before implantation is a useful strategy for regeneration of alveolar bone and periodontal ligament, in the currently used rat model.

Periodontal cell implantation contributes to the regeneration of the periodontium in an indirect way.

Periodontitis is the most common human infectious disease. Regeneration of bone and soft tissue defects after periodontitis remains challenging, although the transplantation of periodontal ligament (PDL) cells seems a liable strategy. However, little is known about the function of PDL cells after transplantation. In the current study, a combination of in vitro coculture systems and in vivo immunohistochemistry (IHC) was used to investigate the role of PDL cells in the regenerative process. First, a coculture method was used, in which mesenchymal cells (representing the host tissue) were brought into direct contact with PDL cells (representing the transplanted cell population). It was found that PDL cells significantly increased mineralized matrix formation and osteocalcin expression, whereas control cells did not. Similar results were obtained when a noncontact coculture system was applied separating PDL and mesenchymal cells. In an in vivo rat model, regeneration of alveolar bone and ligament was seen after PDL cell transplantation. Implanted PDL cells were found clustered along the newly formed tissues. IHC showed enhanced osteopontin expression and gap junction staining in areas neighboring implanted PDL cells. In conclusion, PDL cells enhance periodontal regeneration through a trophic factor stimulating the osteogenic activity of the surrounding host cells.

Periodontal tissue regeneration using enzymatically solidified chitosan hydrogels with or without cell loading.

This study is aimed to evaluate the in vivo biocompatibility and periodontal regenerative potential of enzymatically solidified chitosan hydrogels with or without incorporated periodontal ligament cells (PDLCs). To this end, chitosan hydrogels, with (n=8; CHIT+CELL) or without (n=8; CHIT) fluorescently labeled PDLCs, were prepared and transplanted into rat intrabony periodontal defects; untreated defects were used as empty controls (n=8; EMPTY). After 4 weeks, maxillae were harvested, decalcified, and used for histological, histomorphometrical, and immunohistochemical assessments. The results showed that PDLCs remained viable upon encapsulation within chitosan hydrogels before transplantation. Histological analysis demonstrated that the chitosan hydrogels were largely degraded after 4 weeks of implantation, without any adverse reaction in the surrounding tissue. In terms of periodontal regeneration, alveolar bone height, alveolar bone area, and epithelial downgrowth were comparable for CHIT, CHIT+CELL, as well as EMPTY groups. In contrast, both CHIT and CHIT+CELL showed a significant increase in functional ligament length compared with EMPTY. From a cellular perspective, the contribution of chitosan hydrogel-incorporated cells to the periodontal regeneration could not be ascertained, as no signal from transplanted PDLCs could be detected at 4 weeks posttransplantation. The results demonstrated that enzymatically solidified chitosan hydrogels are highly biocompatible and biodegradable. Moreover, chitosan hydrogels without cell loading can improve periodontal regeneration in terms of functional ligament length, indicating the great potential of this hydrogel in clinical applications. Further work on the use of chitosan hydrogels as cell carriers is required.

Human periodontal ligament derived progenitor cells: effect of STRO-1 cell sorting and Wnt3a treatment on cell behavior.

OBJECTIVES: STRO-1 positive periodontal ligament cells (PDLCs) and unsorted PDLCs have demonstrated potential for periodontal regeneration, but the comparison between unsorted cells and the expanded STRO-1 sorted cells has never been reported. Additionally, Wnt3a is involved in cell proliferation thus may benefit in vitro PDLC expansion. The aim was to evaluate the effect of STRO-1 cell sorting and Wnt3a treatment on cell behavior of human PDLCs (hPDLCs). MATERIALS AND METHODS: STRO-1 positive hPDLCs were sorted and the sorted cells were expanded and compared with their unsorted parental cells. Thereafter, hPDLCs were treated with or without Wnt3a and the cell proliferation, self-renewal, and osteogenic differentiation were evaluated. RESULTS: No differences were measured between the expanded STRO-1-sorted cells and unsorted parental cells in terms of proliferation, CFU, and mineralization capacity. Wnt3a enhanced the proliferation and self-renewal ability of hPDLCs significantly as displayed by higher DNA content values, a shorter cell population doubling time, and higher expression of the self-renewal gene Oct4. Moreover, Wnt3a promoted the expansion of hPDLCs for 5 passages without affecting cell proliferation, CFU, and osteogenic capacity. CONCLUSIONS: Expanded STRO-1-sorted hPDLCs showed no superiority compared to their unsorted parental cells. On the other hand, Wnt3a promotes the efficient hPDLC expansion and retains the self-renewal and osteogenic differentiation capacity.

Enzymatic control of chitosan gelation for delivery of periodontal ligament cells.

The aim of this study is to optimize enzymatic control over gelation of chitosan-based hydrogels for the delivery of periodontal ligament cells (PDLCs). The results reveal that the gelation time, strength, and degradation rate of the chitosan hydrogels can be controlled precisely by variation of the urea and urease concentrations. PDLCs remain viable inside these hydrogels for up to 30 days. Cells released from the hydrogel upon degradation and collected after 3, 15, and 30 days are able to form colonies and osteogenically differentiate. In conclusion, the enzymatic control over the gelation of chitosan hydrogels offers options for the delivery of PDLCs.

Biomaterial strategies for stem cell maintenance during in vitro expansion.

Stem cells, having the potential for self-renewal and multilineage differentiation, are the building blocks for tissue/organ regeneration. Stem cells can be isolated from various sources but are, in general, available in too small numbers to be used directly for clinical purpose without intermediate expansion procedures in vitro. Although this in vitro expansion of undifferentiated stem cells is necessary, stem cells typically diminish their ability to self-renew and proliferate during passaging. Consequently, maintaining the stemness of stem cells has been recognized as a major challenge in stem cell-based research. This review focuses on the latest developments in maintaining the self-renewal ability of stem cells during in vitro expansion by biomaterial strategies. Further, this review highlights what should be the focus for future studies using stem cells for regenerative applications.