Effect of bFGF on the growth and matrix turnover of stem cells from human apical papilla: Role of MEK/ERK signaling

Genipin cross-linked gelatin hydrogel for encapsulating wharton jelly mesenchymal stem cells and basic fibroblast growth factor delivery in vocal fold regeneration

Approaches to regenerate vocal fold in glottic insufficiency remains to be a focus for exploration. This is attributed to the applications of cells or biological molecules alone result in fast degradation and inadequate for regeneration. Development of an injectable hydrogel for glottic insufficiency is challenging, as it needs to be non-cytotoxic, elastic yet possess good strength and easy to fabricate. This gap prompts us to study the feasibility of our genipin(gn)-crosslinked gelatin (G) hydrogel in encapsulating Wharton's Jelly Mesenchymal Stem Cells (WJMSCs) and basic fibroblast growth factor (bFGF) WJMSCs with the aim to provide regeneration in glottic insufficiency. WJMSCs was encapsulated into two optimised formulations with the density of 2,000,000 cells/mL. The encapsulated cells were tested for its morphology, cell viability, proliferation and migration. Then, the incorporation of basic fibroblast growth factor (bFGF) was done into a final formulation and was tested for the cellular response and in vitro inflammation. 6G 0.4gn demonstrated better cell viability after in vitro culturing for 7 day. After incorporation of bFGF into cell-laden 6G 0.4gn, encapsulated WJMSCs showed to have improved viability and migration. The inflammatory profile of the hydrogel was imperceptible and was regarded as minimal or no pro- and anti-inflammation. Altogether, we have first formulated 6G 0.4gn which is suitable to encapsulate WJMSCs and incorporation of bFGF. Current study fulfils the market need in vocal fold regeneration, by suggesting its rejuvenating potential in glottic insufficiency, yet this combined formulation should be studied further to justify its translation to clinical setting.

Fibroblast growth factor 2 promotes osteo/odontogenic differentiation in stem cells from the apical papilla by inhibiting PI3K/AKT pathway

Fibroblast growth factor 2 (FGF2) is a crucial factor in odontoblast differentiation and dentin matrix deposition, which facilitates pulpodentin repair and regeneration. Nevertheless, the specific biological function of FGF2 in odontoblastic differentiation remains unclear because it is controlled by complex signalling pathways. This study aimed to investigate the mechanism underlying the effect of FGF2 on osteo/odontogenic differentiation of stem cells from the apical papilla (SCAP). SCAP were pretreated with conditioned media containing FGF2 for 1 week, followed by culturing in induced differentiation medium for another week. RNA sequencing (RNA-seq) combined with quantitative reverse transcription polymerase chain reaction (RT-qPCR) was used to evaluate the pathways affected by FGF2 in SCAP. Osteo/odontogenic differentiation of SCAP was determined using Alizarin red S staining, alkaline phosphatase staining, RT-qPCR, and western blotting. Pretreatment with FGF2 for 1 week increased the osteo/odontogenic differentiation ability of SCAP. RNA-seq and Kyoto Encyclopedia of Genes and Genomes pathway analyses revealed that phosphatidylinositol 3-kinase (PI3K)/AKT signalling is involved in the osteogenic function of FGF2. RT-qPCR results indicated that SCAP expressed FGF receptors, and western blotting showed that p-AKT was reduced in FGF2-pretreated SCAP. The activation of the PI3K/AKT pathway partially reversed the stimulatory effect of FGF2 on osteo/odontogenic differentiation of SCAP. Our findings suggest that pretreatment with FGF2 enhances the osteo/odontogenic differentiation ability of SCAP by inhibiting the PI3K/AKT pathway.

Supra-Alveolar Bone Regeneration: Progress, Challenges, and Future Perspectives

Periodontitis is a highly prevalent disease that damages the supporting tissues of a tooth, including the alveolar bone. Alveolar bone loss owing to periodontitis is broadly categorized as supra-alveolar and intra-alveolar bone loss. In intra-alveolar bone loss, the defect has an angular or oblique orientation to the long axis of the tooth in an apical direction. In contrast, the defect is perpendicular to the long axis of the tooth in supra-alveolar bone loss. Unlike intra-alveolar bone defects, supra-alveolar bone defects lack supporting adjacent space, which makes supra-alveolar bone regeneration more challenging. In addition, the limited availability of resources in terms of vascularity and underlying tissues is another obstacle to supra-alveolar bone regeneration. Currently, supra-alveolar bone loss is the least predictable periodontal defect type in regenerative periodontal therapy. In addition, supra-alveolar bone loss is much more common than other alveolar bone loss. Despite its prevalence, research on supra-alveolar bone regeneration remains sparse, indicating an unmet need for significant research efforts in this area. This review summarize recent advances, obstacles, and future directions in the field of supra-alveolar bone regeneration. We discuss the biomaterials, bioactive molecules, and cells that have been tested for supra-alveolar bone regeneration, followed by pre-clinical and clinical approaches employed in this field. Additionally, we highlight obstacles and present future directions that will propel supra-alveolar bone research forward.

Growth Factor Immobilization to Synthetic Hydrogels: Bioactive bFGF-Functionalized Polyisocyanide Hydrogels

With its involvement in cell proliferation, migration and differentiation basic fibroblast growth factor (bFGF) has great potential for tissue engineering purposes. So far, however, clinical translation of soluble bFGF-based therapies is unsuccessful, because the required effective doses are often supraphysiological, which may cause adverse effects. An effective solution is growth factor immobilization, whereby bFGF retains its bioactivity at increased efficacy. Studied carriers include films, solid scaffolds, and particles, as well as natural and synthetic hydrogels. However, these synthetic hydrogels poorly resemble the characteristics of the native extracellular matrix (ECM). In this work, bFGF is covalently conjugated to the synthetic, but highly biocompatible, polyisocyanide-based hydrogel (PIC-bFGF), which closely mimics the architecture and mechanical properties of the ECM. The growth factor conjugation protocol is straightforward and readily extrapolated to other growth factors or proteins. The PIC-bFGF hydrogel shows a prolonged bioactivity up to 4 weeks although no clear effects on the ECM metabolism are observed. Beyond the future potential of the PIC-bFGF hydrogel toward various tissue engineering applications, this work underlines that simple biological conjugation procedures are a powerful strategy to induce additional bioactivity in 3D synthetic cell culture matrices.

Stem Cells from the Apical Papilla (SCAPs): Past, Present, Prospects, and Challenges

Dental diseases occurring on young permanent teeth usually lead to the premature arrest of tooth root development. Sustained tooth root elongation is necessary to achieve the goal of long-term preservation of affected teeth. To this end, stem cell-based regenerative endodontic treatment has been regarded as one of the most promising strategies for treating young permanent teeth with pulp and periapical infections. Endogenous stem cells residing in the apical papilla, named stem cells from the apical papilla (SCAPs), have been intensively investigated due to their critical roles in pulp regeneration and root redevelopment. The present review summarizes advances in the field of SCAPs studies and discusses the challenges that need to be further addressed.

Promoting Immortalized Adipose-Derived Stem Cell Transdifferentiation and Proliferation into Neuronal-Like Cells through Consecutive 525 nm and 825 nm Photobiomodulation

Neuronal cells can be generated from adipose-derived stem cells (ADSCs) through biological or chemical inducers. Research has shown that this process may be optimized by the introduction of laser irradiation in the form of photobiomodulation (PBM) to cells. This in vitro study is aimed at generating neuronal-like cells with inducers, chemical or biological, and at furthermore treating these transdifferentiating cells with consecutive PBM of a 525 nm green (G) laser and 825 nm near-infrared (NIR) laser light with a fluence of 10 J/cm². Cells were exposed to induction type 1 (IT1): 3-isobutyl-1-methylxanthine (IBMX) (0.5 mM)+indomethacin (200 μM)+insulin (5 μg/ml) for 14 days, preinduced with β-mercaptoethanol (BME) (1 mM) for two days, and then incubated with IT2: β-hydroxyanisole (BHA) (100 μM)+retinoic acid (RA) (10-6 M)+epidermal growth factor (EGF) (10 ng/ml)+basic fibroblast growth factor (bFGF) (10 ng/ml) for 14 days and preinduced with β-mercaptoethanol (BME) (1 mM) for two days and then incubated with indomethacin (200 μM)+RA (1 μM)+forskolin (10 μM) for 14 days. The results were evaluated through morphological observations, viability, proliferation, and migration studies, 24 h, 48 h, and 7 days post-PBM. The protein detection of an early neuronal marker, neuron-specific enolase (NSE), and late, ciliary neurotrophic factor (CNTF), was determined with enzyme-linked immunosorbent assays (ELISAs). The genetic expression was also explored through real-time PCR. Results indicated differentiation in all experimental groups; however, cells that were preinduced showed higher proliferation and a higher differentiation rate than the group that was not preinduced. Within the preinduced groups, results indicated that cells treated with IT2 and consecutive PBM upregulated differentiation the most morphologically and physiologically.

bFGF stimulated plasminogen activation factors, but inhibited alkaline phosphatase and SPARC in stem cells from apical Papilla: Involvement of MEK/ERK, TAK1 and p38 signaling

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bFGF induced uPA, uPAR, PAI-1 production/expression in SCAP →

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bFGF induced decline of ALP and SPARC of SCAP →

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The effects of bFGF are regulated by ERK, p38, TAK1 and Akt signaling →

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Crucial for SCAP proliferation, matrix turnover and differentiation →

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These events are important for revascularization/root apexogenesis

Introduction

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The Regenerative Potential of bFGF in Dental Pulp Repair and Regeneration

Regenerative endodontic therapy intends to induce the host’s natural wound-healing process, which can restore the vitality, immunity, and sensitivity of the inflammatory or necrotic pulp tissue destroyed by infection or trauma. Myriads of growth factors are critical in the processes of pulp repair and regeneration. Among the key regulatory factors are the fibroblast growth factors, which have turned out to be the master regulators of both organogenesis and tissue homeostasis. Fibroblast growth factors, a family composed of 22 polypeptides, have been used in tissue repair and regeneration settings, in conditions as diverse as burns, ulcers, bone-related diseases, and spinal cord injuries. Meanwhile, in dentistry, the basic fibroblast growth factor is the most frequently investigated. Thereby, the aim of this review is 2-fold: 1) foremost, to explore the underlying mechanisms of the bFGF in dental pulp repair and regeneration and 2) in addition, to shed light on the potential therapeutic strategies of the bFGF in dental pulp–related clinical applications.

Unraveling the Role of the Apical Papilla During Dental Root Maturation

The apical papilla is a stem cell rich tissue located at the base of the developing dental root and is responsible for the progressive elongation and maturation of the root. The multipotent stem cells of the apical papilla (SCAP) are extensively studied in cell culture since they demonstrate a high capacity for osteogenic, adipogenic, and chondrogenic differentiation and are thus an attractive stem cell source for stem cell-based therapies. Currently, only few studies are dedicated to determining the role of the apical papilla in dental root development. In this review, we will focus on the architecture of the apical papilla and describe the specific SCAP signaling pathways involved in root maturation. Furthermore, we will explore the heterogeneity of the SCAP phenotype within the tissue and determine their micro-environmental interaction. Understanding the mechanism of postnatal dental root growth could further aid in developing novel strategies in dental root regeneration.