Gingival and dermal fibroblasts: their similarities and differences revealed from gene expression

Guidance on the assessment of biocompatibility of biomaterials: Fundamentals and testing considerations

BACKGROUND

Assessing the biocompatibility of materials is crucial for ensuring the safety and well-being of patients by preventing undesirable, toxic, immune, or allergic reactions, and ensuring that materials remain functional over time without triggering adverse reactions. To ensure a comprehensive assessment, planning tests that carefully consider the intended application and potential exposure scenarios for selecting relevant assays, cell types, and testing parameters is essential. Moreover, characterizing the composition and properties of biomaterials allows for a more accurate understanding of test outcomes and the identification of factors contributing to cytotoxicity. Precise reporting of methodology and results facilitates research reproducibility and understanding of the findings by the scientific community, regulatory agencies, healthcare providers, and the general public.

AIMS

This article aims to provide an overview of the key concepts associated with evaluating the biocompatibility of biomaterials while also offering practical guidance on cellular principles, testing methodologies, and biological assays that can support in the planning, execution, and reporting of biocompatibility testing.

Biological Activities of Citrus-Derived Extracellular Vesicles on Human Cells: The Role of Preservation

Extracellular vesicles (EVs) have been identified as important mediators for cell-to-cell communication. Citrus-based EVs in particular offer an excellent platform for nutraceutical delivery systems, as their endemic cargo includes micronutrients (e.g., ascorbic acid), which contribute to their antioxidant capacity. Despite being extensively investigated as to their therapeutic and diagnostic potential, their cargo is inherently unstable and thus directly affected by their storage and preservation. In this study, EVs were isolated from citrus fruit using tangential flow filtration and evaluated for their physicochemical characteristics, antioxidant activity and effects on human cells. To assess how their isolation and preservation methods affect these properties, the EVs were tested immediately after isolation (from fresh and freeze-thawed juices) or following freeze-drying. A measurable biological effect of cryoprotection on citrus-derived EVs was evident, whether during or after isolation. This was more pronounced in the cell-based assays, ranging from -4% to +32% in human skin fibroblast proliferation. Nevertheless, the effects on human cancer cells varied depending on the cell line. Although these results should be considered preliminary observations, subject to further investigation, it is safe to state that any type of preservation is expected to impact the EVs' biological activity.

[Oral mesenchymal cells, a specific niche, from development to regeneration]

Oral buccal tissues, including bone and mucosa, have unique properties. Oral mucosal fibroblasts and jaw osteoblasts, both derived from Cranial Neural Crest cells, play a key role in healing and repair. These cells express a specific repertoire of genes with their regenerative properties, but also craniofacial diseases. Understanding these tissues holds clinical promise for tissue regeneration and repair of bone and mucosal defects. These multidisciplinary advances also offer potential for better management of periodontal-related conditions and improved oral health.

Differential molecular profiles and associated functionalities characterize connective tissue grafts obtained at different locations and depths in the human palate

The present study aimed to assess the molecular profiles of subepithelial connective tissue grafts (CTGs) obtained at different locations and depths in the human palate. Sixty-four CTGs belonging to anterior deep (AD), anterior superficial (AS), posterior deep (PD), and posterior superficial (PS) groups were subjected to RNA-Sequencing and their transcriptomes were analyzed computationally. Functional correlations characterizing the CTG groups were validated by cell biological experiments using primary human palatal fibroblasts (HPFs) extracted from the CTGs. A clearly more pronounced location-dependent than depth-dependent difference between the grafts, with a minimal number of genes (4) showing no dependence on the location, was revealed. Epithelial, endothelial, and monocytic cell migration was strongly (P < 0.001) potentiated by AD- and PS-HPFs. Moreover, significantly increased expression of genes encoding C-C and C-X-C motif chemokine ligands as well as significantly (P < 0.01) activated p38 signaling suggested immunomodulatory phenotype for AD- and PS-HPFs. Increased growth factor gene expression and significantly activated (P < 0.001) Erk and Akt signaling in HPFs originating from A-CTGs implied their involvement in cell survival, proliferation, and motility. Prominent collagen-rich expression profile contributing to high mechanical stability, increased osteogenesis-related gene expression, and strongly activated (P < 0.001) Smad1/5/8 signaling characterized HPFs originating from P-CTGs. The present data indicate that in humans, differences between palatal CTGs harvested from different locations and depths appear to be location- rather than depth-dependent. Our findings provide the basis for future personalization of the therapeutic strategy by selecting an optimal graft type depending on the clinical indications.

Morpho-Functional Effect of a New Collagen-Based Medical Device on Human Gingival Fibroblasts: An In Vitro Study

Maintaining periodontal and peri-implant soft tissues health is crucial for the long-term health of teeth and dental implants. New biomedical strategies aimed at avoiding connective tissue alterations and related diseases (e.g., periodontitis and peri-implantitis) are constantly evolving. Among these, collagen-based medical products have proven to be safe and effective. Accordingly, the aim of the present study was to evaluate the effects of Dental SKIN BioRegulation (Guna S.p.a., Milan, Italy), a new injectable medical device composed of type I collagen of porcine origin, on primary cultures of human gingival fibroblasts (hGF). To this end, hGF were cultured on collagen-coated (COL, 100 µg/2 mL) or uncoated plates (CTRL) before evaluating cell viability (24 h, 48 h, 72 h, and 7 d), wound healing properties (3 h, 6 h, 12 h, 24 h, and 48 h), and the activation of mechanotransduction markers, such as FAK, YAP, and TAZ (48 h). The results proved a significant increase in cell viability at 48 h (p < 0.05) and wound closure at 24 h (p < 0.001) of hGF grown on COL, with an increasing trend at all time-points. Furthermore, COL significantly induced the expression of FAK and YAP/TAZ (p < 0.05), thereby promoting the activation of mechanotransduction signaling pathways. Overall, these data suggest that COL, acting as a mechanical bio-scaffold, could represent a useful treatment for gingival rejuvenation and may possibly help in the resolution of oral pathologies.

Key Challenges in Diamond Coating of Titanium Implants: Current Status and Future Prospects

Over past years, the fabrication of Ti-based permanent implants for fracture fixation, joint replacement and bone or tooth substitution, has become a routine task. However, it has been found that some degradation phenomena occurring on the Ti surface limits the life or the efficiency of the artificial constructs. The task of avoiding such adverse effects, to prevent microbial colonization and to accelerate osteointegration, is being faced by a variety of approaches in order to adapt Ti surfaces to the needs of osseous tissues. Among the large set of biocompatible materials proposed as an interface between Ti and the hosting tissue, diamond has been proven to offer bioactive and mechanical properties able to match the specific requirements of osteoblasts. Advances in material science and implant engineering are now enabling us to produce micro- or nano-crystalline diamond coatings on a variety of differently shaped Ti constructs. The aim of this paper is to provide an overview of the research currently ongoing in the field of diamond-coated orthopedic Ti implants and to examine the evolution of the concepts that are accelerating the full transition of such technology from the laboratory to clinical applications.

Investigating wound healing characteristics of gingival and skin keratinocytes in organotypic cultures

OBJECTIVES

The gingiva heals at an accelerated rate with reduced scarring when compared to skin. Potential well-studied factors include immune cell number, angiogenesis disparities and fibroblast gene expression. Differential keratinocyte gene expression, however, remains relatively understudied. This study explored the contrasting healing efficiencies of gingival and skin keratinocytes, alongside their differential gene expression patterns.

METHODS

3D organotypic culture models of human gingiva and skin were developed using temporarily immortalised primary keratinocytes. Models were wounded for visualisation of re-epithelialisation and analysis of keratinocyte migration to close the wound gap. Concurrently, differentially expressed genes between primary gingival and skin keratinocytes were identified, validated, and functionally assessed.

RESULTS

Characterisation of the 3D cultures of gingiva and skin showed differentiation markers that recapitulated organisation of the corresponding in vivo tissue. Upon wounding, gingival models displayed a significantly higher efficiency in re-epithelialisation and stratification versus skin, repopulating the wound gap within 24 hours. This difference was likely due to distinct patterns of migration, with gingival cells demonstrating a form of sheet migration, in contrast to skin, where the leading edge was typically 1-2 cells thick. A candidate approach was used to identify several genes that were differentially expressed between gingival and skin keratinocytes. Knockdown of PITX1 resulted in reduced migration capacity of gingival cells.

CONCLUSION

Gingival keratinocytes retain in vivo superior wound healing capabilities in in vitro 2D and 3D environments. Intrinsic gene expression differences could result in gingival cells being 'primed' for healing and play a role in faster wound resolution.

CLINICAL SIGNIFICANCE STATEMENT

The successful development of organotypic models, that recapitulate re-epithelialisation, will underpin further studies to analyse the oral response to wound stimuli, and potential therapeutic interventions, in an in vitro environment.

The Structure and Function of Next-Generation Gingival Graft Substitutes-A Perspective on Multilayer Electrospun Constructs with Consideration of Vascularization

There is a shortage of suitable tissue-engineered solutions for gingival recession, a soft tissue defect of the oral cavity. Autologous tissue grafts lead to an increase in morbidity due to complications at the donor site. Although material substitutes are available on the market, their development is early, and work to produce more functional material substitutes is underway. The latter materials along with newly conceived tissue-engineered substitutes must maintain volumetric form over time and have advantageous mechanical and biological characteristics facilitating the regeneration of functional gingival tissue. This review conveys a comprehensive and timely perspective to provide insight towards future work in the field, by linking the structure (specifically multilayered systems) and function of electrospun material-based approaches for gingival tissue engineering and regeneration. Electrospun material composites are reviewed alongside existing commercial material substitutes', looking at current advantages and disadvantages. The importance of implementing physiologically relevant degradation profiles and mechanical properties into the design of material substitutes is presented and discussed. Further, given that the broader tissue engineering field has moved towards the use of pre-seeded scaffolds, a review of promising cell options, for generating tissue-engineered autologous gingival grafts from electrospun scaffolds is presented and their potential utility and limitations are discussed.

Autologous Multilayered Fibroblast Sheets Can Reinforce Bronchial Stump in a Rat Model

Bronchopleural fistula is one of the most serious postoperative complications caused by the incomplete healing of a bronchial stump. Fibroblasts play an important role in wound healing by facilitating connective tissue formation and inducing angiogenesis. We developed a method for production of multilayered fibroblast sheets that secreted some growth factors and promoted wound healing. The present study aimed to assess the treatment effect of multilayered fibroblast sheets on bronchial stump healing. In this rat model, left pneumonectomy was performed, and multilayered fibroblast sheets derived from autologous oral mucosal tissues were transplanted to the bronchial stump. The changes in the bronchial stump were examined macroscopically, histologically, and mechanically. The fibroblast sheets promoted the formation of thick connective tissues around the bronchial stump. The formed connective tissues were accompanied by new blood vessels, and fibrosis was observed over time. Then, 7 days after the transplantation of the fibroblast sheets, the bronchial wall became significantly thicker, and the area of the blood vessels for the bronchial wall tissues was significantly larger in the experimental group than in the control group. In addition, the burst pressure in the bronchial stump was significantly higher in the experimental group than in the control group. Bronchial stumps were reinforced by the transplantation of multilayered fibroblast sheets derived from autologous oral mucosal tissues.

Hydrogen-Generating Silica Material Prevents UVA-ray-Induced Cellular Oxidative Stress, Cell Death, Collagen Loss and Melanogenesis in Human Cells and 3D Skin Equivalents

Ultraviolet-A (UVA) irradiation induces harmful effects on skin cells and accelerates skin aging through oxidative stress. In this study, the effects of a hydrogen-generating silica material named ULH-002 against UVA injuries in human cells and 3D skin equivalents were investigated. The oxygen radical absorption capacity (ORAC) assay showed that both freshly prepared ULH-002 solutions and 7-day-old solutions exhibited equal peroxyl radical (ROO·) scavenging activities concentration-dependently. CellROX^® green/orange staining showed that ULH-002 could reduce UVA-induced oxidative stress in human keratinocytes HaCaT and human gingival fibroblasts (HGFs). ULH-002 significantly prevented UVA-induced apoptotic/necrotic cell death and cell-viability decline in HGFs and keratinocytes, as shown by Annexin V/PI apoptosis assay and PrestoBlue assay, respectively. Immunostaining showed that ULH-002 prevented the UVA-induced deterioration of expression of both type IV and I collagens in the 3D skin equivalents, and similarly in monolayer HGFs. UVA-enhanced melanogenesis was observed in human melanocytes HMV-II and HMV-II cell-containing 3D skin equivalents, but markedly prevented by ULH-002 as demonstrated by Fontana–Masson’s staining. In conclusion, our data suggested that ULH-002 could protect human keratinocytes and fibroblasts from UVA-induced injuries, prevent the loss of type IV and I collagens, as well as reduce melanogenesis. ULH-002 might be developed as a skin care reagent in the cosmetic industry.

New Gene Markers Involved in Molecular Processes of Tissue Repair, Response to Wounding and Regeneration Are Differently Expressed in Fibroblasts from Porcine Oral Mucosa during Long-Term Primary Culture

Simple Summary

Wound healing and vascularization mechanisms are key steps in the complex morphological process of tissue reconstruction. Additionally, these processes in the oral cavity are more rapid than in the skin and result in less scar formation. Epithelial cells and fibroblasts play an important role in the process of wound healing. In our study, we focused on fibroblasts and monitored changes in gene expression during their in vitro culture. Based on the analysis, we distinguished three groups of processes that play important roles in tissue regeneration: response to wounding, wound healing and vascularization. We identified genes that were involved in all three processes. These genes could be selected as tissue specific repair markers for oral fibroblasts.

Abstract

The mechanisms of wound healing and vascularization are crucial steps of the complex morphological process of tissue reconstruction. In addition to epithelial cells, fibroblasts play an important role in this process. They are characterized by dynamic proliferation and they form the stroma for epithelial cells. In this study, we have used primary cultures of oral fibroblasts, obtained from porcine buccal mucosa. Cells were maintained long-term in in vitro conditions, in order to investigate the expression profile of the molecular markers involved in wound healing and vascularization. Based on the Affymetrix assays, we have observed three ontological groups of markers as wound healing group, response to wounding group and vascularization group, represented by different genes characterized by their expression profile during long-term primary in vitro culture (IVC) of porcine oral fibroblasts. Following the analysis of gene expression in three previously identified groups of genes, we have identified that transforming growth factor beta 1 (TGFB1), ITGB3, PDPN, and ETS1 are involved in all three processes, suggesting that these genes could be recognized as markers of repair specific for oral fibroblasts within the porcine mucosal tissue.

The phenotype of gingival fibroblasts and their potential use in advanced therapies

Advanced therapies in medicine use stem cells, gene editing, and tissues to treat a wide range of conditions. One of their goals is to stimulate endogenous repair of tissues and organs by manipulating stem cells and their niche, as well as to optimize the intrinsic characteristics and plasticity of differentiated cells in adult tissues. In this context, fibroblasts emerge as an alternative source to stem cells because they share phenotypic and regenerative characteristics. Specifically, fibroblasts of the oral mucosae have been shown to have improved regenerative capacity compared to other fibroblast populations. Additionally, their easy access by means of minimally invasive procedures without generating aesthetic problems, with easy and rapid in vitro expansion and with great capacity to respond to extrinsic factors, make oral fibroblasts an attractive and interesting resource for regenerative medicine. This review summarizes current concepts regarding the phenotypic and functional aspects of human Gingival Fibroblasts and their niche, differentiating them from other fibroblast populations of oral-lining mucosa and skin fibroblasts. Furthermore, some applications are presented in regenerative medicine, emphasizing on the biological potential of human Gingival Fibroblasts.

Distinct differences in hypoxic responses between human oral mucosa and skin fibroblasts in a 3D collagen matrix

The differences between oral mucosa and skin wound healing involving hypoxic responses of fibroblasts are poorly elucidated. In this study, we aimed to study the different hypoxic responses between oral and skin fibroblasts embedded in a three-dimensional (3D) collagen matrix to address the early stage of wound healing. Primary oral mucosa fibroblasts (OMFs) obtained from the retromolar area and skin fibroblasts (SFs) obtained from the abdomen were cultured in the 3D 'floating model' under either 21%, 5% or 1% O₂ for 2 days. Cell viability under hypoxia was higher in the OMFs than in the SFs. Collagen gel contraction was suppressed under hypoxic conditions in both fibroblasts, consistent with the reduction of alpha smooth muscle actin expression, except for SFs under 1% O₂. Subsequently, their gene expression profiles between 21 and 1% O₂ concentrations were compared via microarray technology, and the expression profiles of the extracellular matrix (ECM)-associated proteins, including matrix metalloproteinases and collagens, were evaluated. The OMFs were more susceptible to 1% O₂, and more of their genes were downregulated than the SFs'. Although the production and expression levels of ECM-associated proteins in both fibroblasts diminished under hypoxia, those levels in OMFs were significantly higher than those in SFs. In the case of single origin OMFs and SFs, our findings suggest that OMFs possess a higher baseline production capacity of several ECM-associated proteins than SFs, except type III collagen. The intrinsic hypoxic responses of OMFs may be attributed to a more favourable wound healing in oral mucosa.

Fibroblast Interaction with Different Abutment Surfaces: In Vitro Study

Background: Attaining an effective mucosal attachment to the transmucosal part of the implant could protect the peri-implant bone. Aim: To evaluate if chair side surface treatments (plasma of Argon and ultraviolet light) may affect fibroblast adhesion on different titanium surfaces designed for soft tissue healing. Methods: Grade 5 titanium discs with four different surface topographies were subdivided into 3 groups: argon-plasma; ultraviolet light, and no treatment. Cell morphology and adhesion tests were performed at 20 min, 24 h, and 72 h. Results: Qualitative observation of the surfaces performed at the SEM was in accordance with the anticipated features. Roughness values ranged from smooth (MAC Sa = 0.2) to very rough (XA Sa = 21). At 20 min, all the untreated surfaces presented hemispherical cells with reduced filopodia, while the cells on treated samples were more spread with broad lamellipodia. However, these differences in spreading behavior disappeared at 24 h and 72 h. Argon-plasma, but not UV, significantly increased the number of fibroblasts independently of the surface type but only at 20 min. Statistically, there was no surface in combination with a treatment that favored a greater cellular adhesion. Conclusions: Data showed potential biological benefits of treating implant abutment surfaces with the plasma of argon in relation to early-stage cell adhesion.

Characterization of spontaneous spheroids from oral mucosa-derived cells and their direct comparison with spheroids from skin-derived cells

Background

Our group has developed a novel method for spontaneous spheroid formation using a specific low-adherence culture plate with around 90° water contact angle. In this study, this method was applied for oral mucosa-derived cells. First, the feasibility of spontaneous spheroid formation was tested. Next, the characteristics of spontaneous spheroids from oral mucosa- and skin-derived cells were compared with special focus on the stemness and neuronal differentiation capability.

Methods

Oral mucosal cells were obtained from the palate and buccal mucosa of C57BL/6J mice. Similarly, skin cells were obtained from the back of the same mouse strain. Passage 2–3 cells were inoculated into the specific low-adherence culture plates to form spontaneous spheroids. The effect of basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), and B27 supplement on spheroid formation and maintenance was assessed. Immunofluorescence and quantitative reverse transcription polymerase chain reaction (qRT-PCR) were performed to investigate the expression of pluripotency markers, cell proliferation and apoptosis markers, and neurogenic differentiation markers.

Results

Using this culture plate, spontaneous spheroid formation was feasible. This process depended on the presence of serum but was independent of the additives such as bFGF, EGF, and B27 supplement, although they improved the efficiency and were essential for spheroid maintenance. This result was confirmed by the higher expression of Caspase7 in the spheroids cultured without the additives than that with the additives. The spheroids from oral mucosa-derived cells expressed stem cell markers, such as Sox2, SSEA1, Oct4, Nanog, and Nestin. The expression of Sox2 in spheroids from oral mucosal cells was higher than that in spheroids from skin-derived cells. Both spheroid-forming cell types had the ability to differentiate into neural and Schwann cells after neurogenic induction, although significantly higher MAP 2, MBP, Nestin, and Nurr1 gene expression was noted in the cells from oral mucosa-derived spheroids.

Conclusions

The results showed that spontaneous spheroids from oral mucosa-derived cells contain highly potent stem cells, which were as good as skin-derived stem cells. The high expression of certain neuronal marker genes suggests an advantage of these cells for regeneration therapy for neuronal disorders.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1283-0) contains supplementary material, which is available to authorized users.

Impact of Nano-Crystalline Diamond Enhanced Hydrophilicity on Cell Proliferation on Machined and SLA Titanium Surfaces: An In-Vivo Study in Rodents

By coating surfaces with nano-crystalline diamond (NCD) particles, hydrophilicity can be altered via sidechain modifications without affecting surface texture. The present study aimed to assess the impact of NCD hydrophilicity on machined and rough SLA titanium discs on soft tissue integration, using a rodent model simulating submerged healing. Four different titanium discs (machined titanium = M Titanium, NCD-coated hydrophilic machined titanium = M-O-NCD, sand blasted acid etched (SLA Titanium) titanium, and hydrophilic NCD-coated SLA titanium = SLA O-NCD) were inserted in subdermal pockets of 12 Wistar rats. After one and four weeks of healing, the animals were sacrificed. Biopsies were embedded in methyl methacrylate (MMA), and processed for histology. The number of cells located within a region of interest (ROI) of 10 µm around the discs were counted and compared statistically. Signs of inflammation were evaluated descriptively employing immunohistochemistry. At one week, M-O-NCD coated titanium discs showed significantly higher amounts of cells compared to M Titanium, SLA Titanium, and SLA-O-NCD (p < 0.001). At four weeks, significant higher cell counts were noted at SLA-O-NCD surfaces (p < 0.01). Immunohistochemistry revealed decreased inflammatory responses at hydrophilic surfaces. Within the limits of an animal study, M-O-NCD surfaces seem to stimulate cell proliferation in the initial healing phase, whereas SLA-O-NCD surfaces appeared advantageous afterwards.

Involvement of neural crest and paraxial mesoderm in oral mucosal development and healing

Tissue engineering therapies using adult stem cells derived from neural crest have sought accessible tissue sources of these cells because of their potential pluripotency. In this study, the gingiva and oral mucosa and their associated stem cells were investigated. Biopsies of these tissues produce neither scarring nor functional problems and are relatively painless, and fresh tissue can be obtained readily during different chairside dental procedures. However, the embryonic origin of these cells needs to be clarified, as does their evolution from the perinatal period to adulthood. In this study, the embryonic origin of gingival fibroblasts were determined, including gingival stem cells. To do this, transgenic mouse models were used to track neural crest derivatives as well as cells derived from paraxial mesoderm, spanning from embryogenesis to adulthood. These cells were compared with ones derived from abdominal dermis and facial dermis. Our results showed that gingival fibroblasts are derived from neural crest, and that paraxial mesoderm is involved in the vasculogenesis of oral tissues during development. Our in vitro studies revealed that the neuroectodermal origin of gingival fibroblasts (or gingival stem cells) endows them with multipotential properties as well as a specific migratory and contractile phenotype which may participate to the scar-free properties of the oral mucosa. Together, these results illustrate the high regenerative potential of neural crest-derived stem cells of the oral mucosa, including the gingiva, and strongly support their use in cell therapy to regenerate tissues with impaired healing.

Human gingival fibroblast response to enamel matrix derivative, porcine recombinant 21.3-kDa amelogenin and 5.3-kDa tyrosine-rich amelogenin peptide

Enamel matrix derivative (EMD) containing a variety of protein fractions has been used for periodontal tissue regeneration. It is suggested that the proteins contained in EMD positively influence gingival fibroblasts migration and proliferation. Effects of EMD as well as of porcine recombinated 21.3-kDa amelogenin (prAMEL) and 5.3-kDa tyrosine-rich amelogenin peptide (prTRAP) on human gingival fibroblast (HGF-1, ATCC; USA) cell line were investigated. Real-time cell analysis (xCELLigence system; Roche Applied Science) was performed to determine the effects of EMD, prAMEL and prTRAP (12.5–50 μg/mL) on HGF-1 cell proliferation and migration. The effect of treatment on cell cycle was determined using flow cytometry. EMD significantly increased HGF-1 cell proliferation after 24- and 48-h incubation. Individually, prAMEL and prTRAP also increased HGF-1 cell proliferation; however, the difference was significant only for prAMEL 50 µg/mL. prAMEL and TRAP significantly increased HGF-1 cell migration after 60- and 72-h incubation. Cell cycle analysis showed significant decrease of the percentage of cells in the G0/G1 phase and a buildup of cells in the S and M phase observed after EMD and prAMEL stimulation. This process was ligand and concentration-dependent. The various molecular components in the enamel matrix derivative might contribute to the reported effects on gingival tissue regeneration; however, biologic effects of prAMEL and prTRAP individually were different from that of EMD.

Comparative proteomics of paired vocal fold and oral mucosa fibroblasts

Injuries of the vocal folds frequently heal with scar formation, which can have lifelong detrimental impact on voice quality. Current treatments to prevent or resolve scars of the vocal fold mucosa are highly unsatisfactory. In contrast, the adjacent oral mucosa is mostly resistant to scarring. These differences in healing tendency might relate to distinct properties of the fibroblasts populating oral and vocal fold mucosae. We thus established the in vitro cultivation of paired, near-primary vocal fold fibroblasts (VFF) and oral mucosa fibroblasts (OMF) to perform a basic cellular characterization and comparative cellular proteomics. VFF were significantly larger than OMF, proliferated more slowly, and exhibited a sustained TGF-β1-induced elevation of pro-fibrotic interleukin 6. Cluster analysis of the proteomic data revealed distinct protein repertoires specific for VFF and OMF. Further, VFF displayed a broader protein spectrum, particularly a more sophisticated array of factors constituting and modifying the extracellular matrix. Conversely, subsets of OMF-enriched proteins were linked to cellular proliferation, nuclear events, and protection against oxidative stress. Altogether, this study supports the notion that fibroblasts sensitively adapt to the functional peculiarities of their respective anatomical location and presents several molecular targets for further investigation in the context of vocal fold wound healing.

BIOLOGICAL SIGNIFICANCE

Mammalian vocal folds are a unique but delicate tissue. A considerable fraction of people is affected by voice problems, yet many of the underlying vocal fold pathologies are sparsely understood at the molecular level. One such pathology is vocal fold scarring - the tendency of vocal fold injuries to heal with scar formation -, which represents a clinical problem with highly suboptimal treatment modalities. This study employed proteomics to obtain comprehensive insight into the protein repertoire of vocal fold fibroblasts, which are the cells that predominantly synthesize the extracellular matrix in both physiological and pathophysiological conditions. Protein profiles were compared to paired fibroblasts from the oral mucosa, a neighboring tissue that is remarkably resistant to scarring. Bioinformatic analyses of the data revealed a number of pathways as well as single proteins (e.g. ECM-remodeling factors, transcription factors, enzymes) that were significantly different between the two fibroblast types. Thereby, this study has revealed novel interesting molecular targets which can be analyzed in the future for their impact on vocal fold wound healing.

Transcriptome analysis of periodontitis-associated fibroblasts by CAGE sequencing identified DLX5 and RUNX2 long variant as novel regulators involved in periodontitis

Periodontitis is affecting over half of the adult population, and represents a major public health problem. Previously, we isolated a subset of gingival fibroblasts (GFs) from periodontitis patients, designated as periodontitis-associated fibroblasts (PAFs), which were highly capable of collagen degradation. To elucidate their molecular profiles, GFs isolated form healthy and periodontitis-affected gingival tissues were analyzed by CAGE-seq and integrated with the FANTOM5 atlas. GFs from healthy gingival tissues displayed distinctive patterns of CAGE profiles as compared to fibroblasts from other organ sites and characterized by specific expression of developmentally important transcription factors such as BARX1, PAX9, LHX8, and DLX5. In addition, a novel long non-coding RNA associated with LHX8 was described. Furthermore, we identified DLX5 regulating expression of the long variant of RUNX2 transcript, which was specifically active in GFs but not in their periodontitis-affected counterparts. Knockdown of these factors in GFs resulted in altered expression of extracellular matrix (ECM) components. These results indicate activation of DLX5 and RUNX2 via its distal promoter represents a unique feature of GFs, and is important for ECM regulation. Down-regulation of these transcription factors in PAFs could be associated with their property to degrade collagen, which may impact on the process of periodontitis.

Fibroblast heterogeneity and its implications for engineering organotypic skin models in vitro

Advances in cell culture methods, multidisciplinary research, clinical need to replace lost skin tissues and regulatory need to replace animal models with alternative test methods has led to development of three dimensional models of human skin. In general, these in vitro models of skin consist of keratinocytes cultured over fibroblast-populated dermal matrices. Accumulating evidences indicate that mesenchyme-derived signals are essential for epidermal morphogenesis, homeostasis and differentiation. Various studies show that fibroblasts isolated from different tissues in the body are dynamic in nature and are morphologically and functionally heterogeneous subpopulations. Further, these differences seem to be dictated by the local biological and physical microenvironment the fibroblasts reside resulting in "positional identity or memory". Furthermore, the heterogeneity among the fibroblasts play a critical role in scarless wound healing and complete restoration of native tissue architecture in fetus and oral mucosa; and excessive scar formation in diseased states like keloids and hypertrophic scars. In this review, we summarize current concepts about the heterogeneity among fibroblasts and their role in various wound healing environments. Further, we contemplate how the insights on fibroblast heterogeneity could be applied for the development of next generation organotypic skin models.

Human Gingival Integration-Free iPSCs; a Source for MSC-Like Cells

Mesenchymal stem cells (MSCs) are considered a potential autologous therapy for tissue engineering. The available procedures for MSC retrieval from patients are invasive, and their limited in vitro proliferation restricts their use in the treatment of damaged tissues. Therefore, it is important to establish an alternative and safe source of MSCs. The objective of this study was to demonstrate induced pluripotent stem cell (iPSC) generation from a combination of an accessible source tissue and an integration-free method; we also attempted the differentiation of iPSCs into MSC-like cells (MSLCs) for future autologous tissue engineering. iPSCs were derived from human gingival tissues, which are easily accessible in the field of dentistry, via the use of non-integrating episomal plasmids. Established iPSCs expressed embryonic stem (ES) cell-specific markers, as assessed by gene analysis and immunocytochemistry. Embryoid bodies and teratoma formation were formed from iPSCs, showing their capacity to differentiate into three germ layers. Furthermore, we were successful in differentiating iPSCs into MSLCs. They tested positively for their capacity of trilineage differentiation. Our results demonstrate that human gingival integration-free iPSCs, readily accessible stem cells generated using episomal plasmid vectors, are a promising source of MSLCs, which can be used in tissue regeneration.

Genotoxicity assessment of reactive and disperse textile dyes using human dermal equivalent (3D cell culture system)

Thousands of dyes are marketed daily for different purposes, including textile dyeing. However, there are several studies reporting attributing to dyes deleterious human effects such as DNA damage. Humans may be exposed to toxic dyes through either ingestion of contaminated waters or dermal contact with colored garments. With respect to dermal exposure, human skin equivalents are promising tools to assess in vitro genotoxicity of dermally applied chemicals using a three-dimensional (3D) model to mimic tissue behavior. This study investigated the sensitivity of an in-house human dermal equivalent (DE) for detecting genotoxicity of textile dyes. Two azo (reactive green 19 [RG19] and disperse red 1[DR1]) dyes and one anthraquinone (reactive blue 2 [RB2]) dye were analyzed. RG19 was genotoxic for DE in a dose-responsive manner, whereas RB2 and DR1 were nongenotoxic under the conditions tested. These findings are not in agreement with previous genotoxicological assessment of these dyes carried out using two-dimensional (2D) cell cultures, which showed that DR1 was genotoxic in human hepatoma cells (HepG2) and RG19 was nongenotoxic for normal human dermal fibroblasts (NHDF). These discrepant results probably may be due to differences between metabolic activities of each cell type (organ-specific genotoxicity, HepG2 and fibroblasts) and the test setup systems used in each study (fibroblasts cultured at 2D and three-dimensional [3D] culture systems). Genotoxicological assessment of textile dyes in context of organ-specific genotoxicity and using in vitro models that more closely resemble in vivo tissue architecture and physiology may provide more reliable estimates of genotoxic potential of these chemicals.

Distinct phenotype and therapeutic potential of gingival fibroblasts

Gingiva of the oral mucosa provides a practical source to isolate fibroblasts for therapeutic purposes because the tissue is easily accessible, tissue discards are common during routine clinical procedures and wound healing after biopsy is fast and results in complete wound regeneration with very little morbidity or scarring. In addition, gingival fibroblasts have unique traits, including neural crest origin, distinct gene expression and synthetic properties and potent immunomodulatory functions. These characteristics may provide advantages for certain therapeutic approaches over other more commonly used cells, including skin fibroblasts, both in intraoral and extra-oral sites. However, identity and phenotype of gingival fibroblasts, like other fibroblasts, are still not completely understood. Gingival fibroblasts are phenotypically heterogeneous, and these…fibroblast subpopulations may play different roles in tissue maintenance, regeneration and pathologies. The purpose of this review is to summarize what is currently known about gingival fibroblasts, their distinct potential for tissue regeneration and their potential therapeutic uses in the future.

Human gingival fibroblasts display a non-fibrotic phenotype distinct from skin fibroblasts in three-dimensional cultures

Scar formation following skin injury can be a major psychosocial and physiological problem. However, the mechanisms of scar formation are still not completely understood. Previous studies have shown that wound healing in oral mucosa is faster, associates with a reduced inflammatory response and results to significantly reduced scar formation compared with skin wounds. In the present study, we hypothesized that oral mucosal fibroblasts from human gingiva are inherently distinct from fibroblasts from breast and abdominal skin, two areas prone to excessive scar formation, which may contribute to the preferential wound healing outcome in gingiva. To this end, we compared the phenotype of human gingival and skin fibroblasts cultured in in vivo-like three-dimensional (3D) cultures that mimic the cells' natural extracellular matrix (ECM) niche. To establish 3D cultures, five parallel fibroblast lines from human gingiva (GFBLs) and breast skin (SFBLs) were seeded in high density, and cultured for up to 21 days in serum and ascorbic acid containing medium to induce expression of wound-healing transcriptome and ECM deposition. Cell proliferation, morphology, phenotype and expression of wound healing and scar related genes were analyzed by real-time RT-PCR, Western blotting and immunocytochemical methods. The expression of a set of genes was also studied in three parallel lines of human abdominal SFBLs. Findings showed that GFBLs displayed morphologically distinct organization of the 3D cultures and proliferated faster than SFBLs. GFBLs expressed elevated levels of molecules involved in regulation of inflammation and ECM remodeling (MMPs) while SFBLs showed significantly higher expression of TGF-β signaling, ECM and myofibroblast and cell contractility-related genes. Thus, GFBLs display an inherent phenotype conducive for fast resolution of inflammation and ECM remodeling, characteristic for scar-free wound healing, while SFBLs have a profibrotic, scar-prone phenotype.

Gingiva as a source of stem cells with therapeutic potential

Postnatal connective tissues contain phenotypically heterogeneous cells populations that include distinct fibroblast subpopulations, pericytes, myofibroblasts, fibrocytes, and tissue-specific mesenchymal stem cells (MSCs). These cells play key roles in tissue development, maintenance, and repair and contribute to various pathologies. Depending on the origin of tissue, connective tissue cells, including MSCs, have different phenotypes. Understanding the identity and specific functions of these distinct tissue-specific cell populations may allow researchers to develop better treatment modalities for tissue regeneration and find novel approaches to prevent pathological conditions. Interestingly, MSCs from adult oral mucosal gingiva possess distinct characteristics, including neural crest origin, multipotent differentiation capacity, fetal-like phenotype, and potent immunomodulatory properties. These characteristics and an easy, relatively noninvasive access to gingival tissue, and fast tissue regeneration after tissue biopsy make gingiva an attractive target for cell isolation for therapeutic purposes aiming to promote tissue regeneration and fast, scar-free wound healing. The purpose of this review is to discuss the identity, phenotypical heterogeneity, and function of gingival MSCs and summarize what is currently known about their properties, role in scar-free healing, and their future therapeutic potential.

Detrimental dermal wound healing: what can we learn from the oral mucosa?

Wounds in adults are frequently accompanied by scar formation. This scar can become fibrotic due to an imbalance between extracellular matrix (ECM) synthesis and ECM degradation. Oral mucosal wounds, however, heal in an accelerated fashion, displaying minimal scar formation. The exact mechanisms of scarless oral healing are yet to be revealed. This review highlights possible mechanisms involved in the difference between scar-forming dermal vs. scarless oral mucosal wound healing. Differences were found in expression of ECM components, such as procollagen I and tenascin-C. Oral wounds contained fewer immune mediators, blood vessels, and profibrotic mediators but had more bone marrow-derived cells, a higher reepithelialization rate, and faster proliferation of fibroblasts compared with dermal wounds. These results form a basis for further research that should be focused on the relations among ECM, immune cells, growth factors, and fibroblast phenotypes, as understanding scarless oral mucosal healing may ultimately lead to novel therapeutic strategies to prevent fibrotic scars.

IL-4 inhibition of IL-1 induced Matrix metalloproteinase-3 (MMP-3) expression in human fibroblasts involves decreased AP-1 activation via negative crosstalk involving of Jun N-terminal kinase (JNK)

Matrix metalloproteinase-3 (MMP-3) over-expression is associated with tissue destruction in the context of chronic inflammation. Previous studies showed that IL-4 inhibits induction of MMP-3 by IL-1β, and suggested that AP-1 might be involved. Here we show that IL-1 induced binding of transcription factor AP-1 to the MMP-3 promoter consists primarily of c-Jun, JunB, and c-Fos and that binding of c-Jun and c-Fos is inhibited by the combination of cytokines while binding of Jun B is not. Mutation of the AP-1 site in the MMP-3 promoter decreased the ability of IL-4 to inhibit its transcription in transfected MG-63 cells. Western blotting showed that both cytokines activate Jun N-terminal kinase (JNK), but with somewhat different kinetics, and that activation of JNK by both cytokines individually is inhibited by the combination. These results indicate that IL-4 inhibition of MMP-3 expression is associated with reduction of IL-1 induced binding of active forms of the AP-1 dimer, while less active JunB-containing dimers remain, and suggest that these changes are associated with decreased activation of JNK.