Potential Role of Integrin α₅β₁/Focal Adhesion Kinase (FAK) and Actin Cytoskeleton in the Mechanotransduction and Response of Human Gingival Fibroblasts Cultured on a 3-Dimension Lactide-Co-Glycolide (3D PLGA) Scaffold

The role and mechanism of compressive stress in tumor

Recent research has revealed the important role of mechanical forces in the initiation and progression of tumors. The interplay between mechanical and biochemical cues affects the function and behavior of tumor cells during the development of solid tumors, especially their metastatic potential. The compression force generated by excessive cell proliferation and the tumor microenvironment widely regulates the progression of solid tumor disease. Tumor cells can sense alterations in compressive stress through diverse mechanosensitive components and adapt their mechanical characteristics accordingly to adapt to environmental changes. Here, we summarize the current role of compressive stress in regulating tumor behavior and its biophysical mechanism from the mechanobiological direction.

Mechanisms of mechanical force in periodontal homeostasis: a review

Mechanical forces affect periodontal health through multiple mechanisms. Normally, mechanical forces can boost soft and hard tissue metabolism. However, excessive forces may damage the periodontium or result in irreversible inflammation, whereas absence of occlusion forces also leads to tissue atrophy and bone resorption. We systemically searched the PubMed and Web of Science databases and found certain mechanisms of mechanical forces on immune defence, extracellular matrix (ECM) metabolism, specific proteins, bone metabolism, characteristic periodontal ligament stem cells (PDLSCs) and non-coding RNAs (ncRNAs) as these factors contribute to periodontal homeostasis. The immune defence functions change under forces; genes, signalling pathways and proteinases are altered under forces to regulate ECM metabolism; several specific proteins are separately discussed due to their important functions in mechanotransduction and tissue metabolism. Functions of osteocytes, osteoblasts, and osteoclasts are activated to maintain bone homeostasis. Additionally, ncRNAs have the potential to influence gene expression and thereby, modify tissue metabolism. This review summarizes all these mechanisms of mechanical forces on periodontal homeostasis. Identifying the underlying causes, this review provides a new perspective of the mechanisms of force on periodontal health and guides for some new research directions of periodontal homeostasis.

Enriched Graphene Oxide-Polypropylene Suture Threads Buttons Modulate the Inflammatory Pathway Induced by Escherichia coli Lipopolysaccharide

Graphene oxide (GO), derived from graphene, has remarkable chemical–physical properties such as stability, strength, and thermal or electric conductivity and additionally shows antibacterial and anti-inflammatory properties. The present study aimed to evaluate the anti-inflammatory effects of polypropylene suture threads buttons (PPSTBs), enriched with two different concentrations of GO, in the modulation of the inflammatory pathway TLR4/MyD 88/NFκB p65/NLRP3 induced by the Escherichia coli (E. coli) lipopolysaccharide (LPS-E). The gene and the protein expression of inflammatory markers were evaluated in an in vitro model of primary human gingival fibroblasts (hGFs) by real-time PCR, western blotting, and immunofluorescence analysis. Both GO concentrations used in the polypropylene suture threads buttons-GO constructs (PPSTBs-GO) decreased the expression of inflammatory markers in hGFs treated with LPS-E. The hGFs morphology and adhesion on the PPSTBs-GO constructs were also visualized by inverted light microscopy, scanning electron microscopy (SEM), and real-time PCR. Together, these results suggest that enriched PPSTBs-GO modulates the inflammatory process through TLR4/MyD 88/NFκB p65/NLRP3 pathway.

Surface characteristics and in vitro biocompatibility of surface-modified titanium foils as a regenerative barrier membrane for guided bone regeneration

This study evaluated surface characteristics and biocompatibility of surface-modified thin titanium (Ti) foils as a regenerative barrier membrane for future application in guided bone regeneration (GBR) surgery to augment atrophic alveolar bone. Anodic oxidation and post-heat treatment were performed to prepare various Ti foil samples. Then, the in vitro soft and hard tissue compatibility of the samples was evaluated by examining the cell responses using primary human gingival fibroblasts (HGFs) and MG63 human osteoblast-like cells. Investigated Ti foil samples showed marked differences in physicochemical surface properties. Additional 400°C heat treatment applied to the anodized Ti surface led to formation of an anatase titanium dioxide structure and well-organized nanoscale protrusions, and significantly increased surface wettability. Anodization and heat treatment enhanced the growth of HGFs and MG63 cells in Ti foil samples. Additional heat treatment for 10 and 30 min further significantly improved the response of HGFs including spreading and proliferation, and upregulated the mRNA expression of cell adhesion- and maturation-related genes as well as the osteoblast differentiation of MG63 cells. Ti foil sample with thin oxide coating obtained by a 30 min heat treatment exhibited poor clinical plasticity as a regenerative barrier membrane, which showed complete coating failure in the bending test. Our results indicate that anatase Ti oxide coating of a specific film thickness with nanoscale surface protrusion morphology and hydrophilic characteristics obtained by anodization and post-heat treatment would be an effective approach as a biocompatible Ti regenerative membrane for inducing better regeneration of both gingival tissue and bone.

Focusing on Mechanoregulation Axis in Fibrosis: Sensing, Transduction and Effecting

Fibrosis, a pathologic process featured by the excessive deposition of connective tissue components, can affect virtually every organ and has no satisfactory therapy yet. Fibrotic diseases are often associated with organ dysfunction which leads to high morbidity and mortality. Biomechanical stmuli and the corresponding cellular response havebeen identified in fibrogenesis, as the fibrotic remodeling could be seen as the incapacity to reestablish mechanical homeostasis: along with extracellular matrix accumulating, the physical property became more “stiff” and could in turn induce fibrosis. In this review, we provide a comprehensive overview of mechanoregulation in fibrosis, from initialing cellular mechanosensing to intracellular mechanotransduction and processing, and ends up in mechanoeffecting. Our contents are not limited to the cellular mechanism, but further expand to the disorders involved and current clinical trials, providing an insight into the disease and hopefully inspiring new approaches for the treatment of tissue fibrosis.

In vitro behaviour of human gingival fibroblasts cultured on 3D-printed titanium alloy with hydrogenated TiO2 nanotubes

Selective laser melting (SLM), as one of the most common 3D-printed technologies, can form personalized implants, which after further surface modification can obtain excellent osseointegration. To study the surface properties of SLM titanium alloy (Ti6Al4V) with hydrogenated titanium dioxide (TiO₂)nanotubes (TNTs) and its influence on the biological behaviour of human gingival fibroblasts (HGFs), we used SLM to prepare 3D-printed titanium alloy samples (3D-Ti), which were electrochemically anodizing to fabricate 3D-TNTs and then further hydrogenated at high temperature to obtain 3D-H₂-TNTs. Polished cast titanium alloy (MP-Ti) was used as the control group. The surface morphology, hydrophilicity and roughness of MP-Ti, 3D-Ti, 3D-TNTs and 3D-H₂-TNTs were measured and analysed by scanning electron microscopy (SEM), contact angle metre, surface roughness measuring instrument and atomic force microscope, respectively. HGFs were cultured on the four groups of samples, and the cell morphology was observed by SEM. Fluorescence staining (DAPI) was used to observe the number of adhered cell nuclei, while a cell counting kit (CCK-8) was used to detect the early adhesion and proliferation of HGFs. Fluorescence quantitative real time polymerase chain reaction (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA) were used to detect the expression of adhesion-related genes and fibronectin (FN), respectively. The results of this in vitro comparison study indicated that electrochemical anodic oxidation and high-temperature hydrogenation can form a superhydrophilic micro-nano composite morphology on the surface of SLM titanium alloy, which can promote both the early adhesion and proliferation of human gingival fibroblasts and improve the expression of cell adhesion-related genes and fibronectin. Graphical abstract.

Bi-phasic effect of gelatin in myogenesis and skeletal muscle regeneration

Skeletal muscle regeneration requires extracellular matrix (ECM) remodeling, including an acute and transient breakdown of collagen that produces gelatin. Although the physiological function of this process is unclear, it has inspired the application of gelatin to injured skeletal muscle for a potential pro-regenerative effect. Here, we investigated a bi-phasic effect of gelatin in skeletal muscle regeneration, mediated by the hormetic effects of reactive oxygen species (ROS). Low-dose gelatin stimulated ROS production from NADPH oxidase 2 (NOX2) and simultaneously upregulated the antioxidant system for cellular defense, reminiscent of the adaptive compensatory process during mild stress. This response triggered the release of the myokine IL-6, which stimulates myogenesis and facilitates muscle regeneration. By contrast, high-dose gelatin stimulated ROS overproduction from NOX2 and the mitochondrial chain complex, and ROS accumulation by suppressing the antioxidant system, triggering the release of TNFα, which inhibits myogenesis and regeneration. Our results have revealed a bi-phasic role of gelatin in regulating skeletal muscle repair mediated by intracellular ROS, the antioxidant system and cytokine (IL-6 and TNFα) signaling.

Summary: Application of high- and low-dose gelatin to skeletal muscle revealed a bi-phasic role of gelatin in regulating skeletal muscle repair, which has translational implications for regenerative medicine.

Contact Angle and Cell Adhesion of Micro/Nano-Structured Poly(lactic-co-glycolic acid) Membranes for Dental Regenerative Therapy

Biodegradable membranes are used in regenerative dentistry for guided tissue regeneration (GTR) and guided bone regeneration (GBR). In this study, patterned poly(lactic-co-glycolic acid) (PLGA) membranes with groove, pillar, and hole structures were successfully fabricated by thermal nanoimprinting. Their surfaces were evaluated for topography by scanning electron microscopy and laser microscopy, for hydrophobicity/hydrophilicity by contact angle analysis, and for MC3T3-E1 cell adhesion. The sizes of the patterns on the surfaces of the membranes were 0.5, 1.0, and 2.0 μm, respectively, with the height/depth being 1.0 μm. The pillared and holed PLGA membranes were significantly more hydrophobic than the non-patterned PLGA membranes (p < 0.05). However, the 0.5 μm- and 1.0 μm-grooved PLGA membranes were significantly more hydrophilic than the non-patterned PLGA membranes (p < 0.05). The 0.5 μm-grooved, pillared, and holed membranes exhibited significantly superior adhesion to the MC3T3-E1 cells than the non-patterned PLGA (p < 0.05). These results suggest that patterned PLGA membranes can be clinically used for GTR and GBR in the dental regeneration field.

The Open Cell Form of 3D-Printed Titanium Improves Osteconductive Properties and Adhesion Behavior of Dental Pulp Stem Cells

Titanium specimens have been proven to be safe and effective biomaterials in terms of their osseo-integration. To improve the bioactivity and develop customized implants titanium, the surface can be modified with selective laser melting (SLM). Moreover, the design of macro-porous structures has become popular for reaching a durable bone fixation. 3D-printed titanium (Titanium A, B, and C), were cleaned using an organic acid treatment or with electrochemical polishing, and were characterized in terms of their surface morphology using scanning electron microscopy. Next, Dental Pulp Stem Cells (DPSCs) were cultured on titanium in order to analyze their biocompatibility, cell adhesion, and osteoconductive properties. All tested specimens were biocompatible, due to the time-dependent increase of DPSC proliferation paralleled by the decrease of LDH released. Furthermore, data highlighted that the open cell form with interconnected pores of titanium A, resembling the inner structure of the native bone, allows cells to better adhere inside the specimen, being proteins related to cell adherence highly expressed. Likewise, titanium A displays more suitable osteoconductive properties, being the profile of osteogenic markers improved compared to titanium B and C. The present work has demonstrated that the inner design and post-production treatments on titanium surfaces have a dynamic influence on DPSC behavior toward adhesion and osteogenic commitment.

FAK Shutdown: Consequences on Epithelial Morphogenesis and Biomarker Expression Involving an Innovative Biomaterial for Tissue Regeneration

By employing an innovative biohybrid membrane, the present study aimed at elucidating the mechanistic role of the focal adhesion kinase (FAK) in epithelial morphogenesis in vitro over 4, 7, and 10 days. The consequences of siRNA-mediated FAK knockdown on epithelial morphogenesis were monitored by quantifying cell layers and detecting the expression of biomarkers of epithelial differentiation and homeostasis. Histologic examination of FAK-depleted samples showed a significant increase in cell layers resembling epithelial hyperplasia. Semiquantitative fluorescence imaging (SQFI) revealed tissue homeostatic disturbances by significantly increased involucrin expression over time, persistence of yes-associated protein (YAP) and an increase of keratin (K) 1 at day 4. The dysbalanced involucrin pattern was underscored by ROCK-II^Ser1366 activity at day 7 and 10. SQFI data were confirmed by quantitative PCR and Western blot analysis, thereby corroborating the FAK shutdown-related expression changes. The artificial FAK shutdown was also associated with a significantly higher expression of filaggrin at day 10, sustained keratinocyte proliferation, and the dysregulated expression of K19 and vimentin. These siRNA-induced consequences indicate the mechanistic role of FAK in epithelial morphogenesis by simultaneously considering prospective biomaterial-based epithelial regenerative approaches.

Calreticulin silencing inhibits extracellular matrix synthesis of human gingival fibroblasts cultured on three-dimensional poly(lactic-co-glycolic acid) scaffolds by inhibiting the calcineurin/nuclear factor of activated T cells 3 signalling pathway

BACKGROUND

The retraction and compression of gingival tissue have a significant impact on the efficiency and stability of orthodontic treatment, but the underlying molecular mechanism has not been fully elucidated. The aim of the current study was to investigate the effects of mechanical forces on the expression level of calreticulin (CRT), the activity of the calcineurin (CaN)/nuclear factor of activated T cells (NFAT) 3 signalling pathway, and extracellular matrix (ECM) synthesis in human gingival fibroblasts (HGFs) cultured on three-dimensional (3D) poly(lactic-co-glycolic acid) (PLGA) scaffolds and to further explore the mechanical transduction pathways that may be involved.

MATERIALS AND METHODS

A mechanical force of 25 g/cm² was applied to HGFs for 0, 6, 24, 48, or 72 h. The expression of CRT, CaN, NFAT3, phosphorylated NFAT3 (p-NFAT3) and type I collagen (COL-I) were detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting. Subsequently, small interfering RNA (siRNA) was used to knock down the expression of CRT in HGFs, and the impacts of the applied force on the expression levels of CaN, NFAT3, p-NFAT3, and COL-I were also evaluated by RT-qPCR and western blotting.

RESULTS

The application of mechanical force on HGFs cultured on 3D PLGA scaffolds led to a significant increases in CRT, CaN, and COL-I expression as well as a decrease in p-NFAT3 expression. However, the effects of mechanical force on CaN, p-NFAT3, and COL-I expression were reversed following downregulation of CRT and displayed a significant decrease in CaN/NFAT3 activity and COL-I synthesis.

CONCLUSION

This study showed that the CaN/NFAT3 signalling pathway and CRT appear to be involved in the mechanotransduction of HGFs, and downregulation of CRT inhibits COL-I synthesis potentially via the CaN/NFAT3 signalling pathway. Taken together, these findings ultimately provide novel insight into the mechanisms underlying mechanical force-induced ECM synthesis, which may be conducive to the development of targeted therapeutics to treat fibrotic diseases, including gingival fibrosis caused by orthodontic treatment.

From the Matrix to the Nucleus and Back: Mechanobiology in the Light of Health, Pathologies, and Regeneration of Oral Periodontal Tissues

Among oral tissues, the periodontium is permanently subjected to mechanical forces resulting from chewing, mastication, or orthodontic appliances. Molecularly, these movements induce a series of subsequent signaling processes, which are embedded in the biological concept of cellular mechanotransduction (MT). Cell and tissue structures, ranging from the extracellular matrix (ECM) to the plasma membrane, the cytosol and the nucleus, are involved in MT. Dysregulation of the diverse, fine-tuned interaction of molecular players responsible for transmitting biophysical environmental information into the cell's inner milieu can lead to and promote serious diseases, such as periodontitis or oral squamous cell carcinoma (OSCC). Therefore, periodontal integrity and regeneration is highly dependent on the proper integration and regulation of mechanobiological signals in the context of cell behavior. Recent experimental findings have increased the understanding of classical cellular mechanosensing mechanisms by both integrating exogenic factors such as bacterial gingipain proteases and newly discovered cell-inherent functions of mechanoresponsive co-transcriptional regulators such as the Yes-associated protein 1 (YAP1) or the nuclear cytoskeleton. Regarding periodontal MT research, this review offers insights into the current trends and open aspects. Concerning oral regenerative medicine or weakening of periodontal tissue diseases, perspectives on future applications of mechanobiological principles are discussed.

Modulation of Human Mesenchymal Stem Cells by Electrical Stimulation Using an Enzymatic Biofuel Cell

Enzymatic biofuel cells (EBFCs) have excellent potential as components in bioelectronic devices, especially as active biointerfaces to regulate stem cell behavior for regenerative medicine applications. However, it remains unclear to what extent EBFC-generated electrical stimulation can regulate the functional behavior of human adipose-derived mesenchymal stem cells (hAD-MSCs) at the morphological and gene expression levels. Herein, we investigated the effect of EBFC-generated electrical stimulation on hAD-MSC cell morphology and gene expression using next-generation RNA sequencing. We tested three different electrical currents, 127 ± 9, 248 ± 15, and 598 ± 75 nA/cm2, in mesenchymal stem cells. We performed transcriptome profiling to analyze the impact of EBFC-derived electrical current on gene expression using next generation sequencing (NGS). We also observed changes in cytoskeleton arrangement and analyzed gene expression that depends on the electrical stimulation. The electrical stimulation of EBFC changes cell morphology through cytoskeleton re-arrangement. In particular, the results of whole transcriptome NGS showed that specific gene clusters were up- or down-regulated depending on the magnitude of applied electrical current of EBFC. In conclusion, this study demonstrates that EBFC-generated electrical stimulation can influence the morphological and gene expression properties of stem cells; such capabilities can be useful for regenerative medicine applications such as bioelectronic devices.

Responses of human gingival fibroblasts to superhydrophilic hydrogenated titanium dioxide nanotubes

Soft tissue integration is critical for the long-term retention of dental implants. The surface properties including topography and wettability can impact soft tissue sealing. In our work, a thermal hydrogenation technique was applied to modify anodized titanium dioxide nanotubes (TNTs). However, the effects of the hydrogenated surface on soft-tissue cells remain unclear. The aim of the present study was to investigate the bioactivities of human gingival fibroblasts (HGFs) on structured surfaces, which determine the early formation of soft tissue sealing. Three groups were examined: commercially pure titanium (Ti), anodized TNTs (air-TNTs) and hydrogenated TNTs (H₂-TNTs). Scanning electron microscopy showed the nanotubular topography on the titanium surfaces after anodization. Then, hydrogenation ensured that the H₂-TNTs were superhydrophilic with a contact angle of 3.5 ± 0.8°. In vitro studies such as cell adhesion assays, cell morphology, immunocytochemistry, wound healing assays, real-time PCR and enzyme-linked immunosorbent assays displayed enhanced adhesion, migration, relative gene expression levels, and extracellular matrix synthesis of the HGFs on H₂-TNTs. Interestingly, focal adhesion kinase activation and integrin-mediated adhesion seemed to be induced by the H₂-TNT surface. Our results revealed that a superhydrophilic nanostructure modified by anodization and hydrogenation can improve the bioactivity of HGFs and connective tissue regeneration, which will further promote and expand the application of titanium dioxide nanotubes in dental implants.