Hyaluronan-Based Gel Promotes Human Dental Pulp Stem Cells Bone Differentiation by Activating YAP/TAZ Pathway

Electroconductive gelatin/hyaluronic acid/hydroxyapatite scaffolds for enhanced cell proliferation and osteogenic differentiation in bone tissue engineering

Addressing the challenge of bone tissue regeneration requires creating an optimal microenvironment that promotes both osteogenesis and angiogenesis. Electroconductive scaffolds have emerged as promising solutions for bone regeneration; however, existing conductive polymers often lack biofunctionality and biocompatibility. In this study, we synthesized poly(3,4-ethylenedioxythiophene) nanoparticles (PEDOT NPs) using chemical oxidation polymerization and incorporated them into gelatin/hyaluronic acid/hydroxyapatite (Gel:HA:HAp) scaffolds to develop Gel:HA:HAp:PEDOT-NP scaffolds. Morphological analysis by scanning electron microscopy (SEM) showed a honeycomb-like structure with pores of 228-250 μm in diameter. The addition of the synthesized PEDOT NPs increased the conductive capabilities of the scaffolds to 1 × 10-6 ± 1.3 × 10-7 S/cm. Biological assessment of PEDOT NP scaffolds using human foetal osteoblastic 1.19 cells (hFOB), and human bone marrow-derived mesenchymal stem cells (hBMSCs) revealed enhanced cell proliferation and viability compared to control scaffold without NPs, along with increased osteogenic differentiation, evidenced by higher levels of alkaline phosphatase activity, osteopontin (OPN), alkaline phosphatase (ALP), and osteocalcin (OCN) expression, as observed through immunofluorescence, and enhanced expression of osteogenic-related genes. The conductive scaffold shows interesting mineralization capacity, as shown by Alizarin red and Osteoimage staining. Furthermore, PEDOT-NP scaffolds promoted angiogenesis, as indicated by improved tube formation abilities of human umbilical vein endothelial cells (HUVECs), especially at the higher concentrations of NPs. Overall, our findings demonstrate that the integration of PEDOT NPs scaffold enhances their conductive properties and promotes cell proliferation, osteogenic differentiation, and angiogenesis. Gel:HA:HAp:PEDOT-NP scaffolds exhibit promising potential as efficient biomaterials for bone tissue regeneration, offering a potential engineered platform for clinical applications.

Progress of silk fibroin biomaterial use in oral tissue regeneration engineering

The field of tissue engineering has introduced novel prospects for the regeneration of oral tissues, wherein stent materials assume a pivotal role and have garnered increasing attention. As a natural protein with good biocompatibility and adjustable biodegradability, an increasing number of studies focus on the uses of silk fibroin (SF) biomaterials for medical tissue regeneration engineering. Solid evidence has been found for using SF biomaterials in various oral tissue regeneration fields, from endodontics and periodontics to regenerating the maxillofacial bone. In order to provide researchers with a systematic understanding of the application of SF biomaterials to oral tissue regeneration, the present work reviews in detail the common forms of SF biomaterials for oral tissue regeneration as well as their preparation methods. In addition, the common additives used in the corresponding materials are introduced.

Noggin Combined With Human Dental Pulp Stem Cells to Promote Skeletal Muscle Regeneration

A proper source of stem cells is key to muscle injury repair. Dental pulp stem cells (DPSCs) are an ideal source for the treatment of muscle injuries due to their high proliferative and differentiation capacities. However, the current myogenic induction efficiency of human DPSCs hinders their use in muscle regeneration due to the unknown induction mechanism. In this study, we treated human DPSCs with Noggin, a secreted antagonist of bone morphogenetic protein (BMP), and discovered that Noggin can effectively promote myotube formation. We also found that Noggin can accelerate the skeletal myogenic differentiation (MyoD) of DPSCs and promote the generation of Pax7+ satellite-like cells. Noggin increased the expression of myogenic markers and the transcriptional and translational abundance of satellite cell (SC) markers in DPSCs. Moreover, BMP4 inhibited Pax7 expression and activated p-Smad1/5/9, while Noggin eliminated BMP4-induced p-Smad1/5/9 in DPSCs. This finding suggests that Noggin antagonizes BMP by downregulating p-Smad and facilitates the MyoD of DPSCs. Then, we implanted Noggin-pretreated DPSCs combined with Matrigel into the mouse tibialis anterior muscle with volumetric muscle loss (VML) and observed a 73% reduction in the size of the defect and a 69% decrease in scar tissue. Noggin-treated DPSCs can benefit the Pax7+ SC pool and promote muscle regeneration. This work reveals that Noggin can enhance the production of satellite-like cells from the MyoD of DPSCs by regulating BMP/Smad signaling, and these satellite-like cell bioconstructs might possess a relatively fast capacity for muscle regeneration.

Forkhead box C1 promotes the pathology of osteoarthritis in subchondral bone osteoblasts via the Piezo1/YAP axis

Subchondral bone sclerosis is a key characteristic of osteoarthritis (OA). Prior research has shown that Forkhead box C1 (FoxC1) plays a role in the synovial inflammation of OA, but its specific role in the subchondral bone of OA has not been explored. Our research revealed elevated expression levels of FoxC1 and Piezo1 in OA subchondral bone tissues. Further experiments on OA subchondral bone osteoblasts with FoxC1 or Piezo1 overexpression showed increased cell proliferation activity, expression of Yes-associated Protein 1 (YAP) and osteogenic markers, and secretion of proinflammatory factors. Mechanistically, the overexpression of FoxC1 through Piezo1 activation, in combination with downstream YAP signaling, led to increased levels of alkaline phosphatase (ALP), collagen type 1 (COL1) A1, RUNX2, Osteocalcin, matrix metalloproteinase (MMP) 3, and MMP9 expression. Notably, inhibition of Piezo1 reversed the regulatory function of FoxC1. The binding of FoxC1 to the targeted area (ATATTTATTTA, residues +612 to +622) and the activation of Piezo1 transcription were verified by the dual luciferase assays. Additionally, Reduced subchondral osteosclerosis and microangiogenesis were observed in knee joints from FoxC1-conditional knockout (CKO) and Piezo1-CKO mice, indicating reduced lesions. Collectively, our study reveals the significant involvement of FoxC1 in the pathologic process of OA subchondral bone via the Piezo1/YAP signaling pathway, potentially establishing a novel therapeutic target.

Multi-site enhancement of osteogenesis: peptide-functionalized GelMA hydrogels with three-dimensional cultures of human dental pulp stem cells

Human dental pulp stem cells (hDPSCs) have demonstrated greater proliferation and osteogenic differentiation potential in certain studies compared to other types of mesenchymal stem cells, making them a promising option for treating craniomaxillofacial bone defects. However, due to low extracting concentration and long amplifying cycles, their access is limited and utilization rates are low. To solve these issues, the principle of bone-forming peptide-1 (BFP1) in situ chemotaxis was utilized for the osteogenic differentiation of hDPSCs to achieve simultaneous and synergistic osteogenesis at multiple sites. BFP1-functionalized gelatin methacryloyl hydrogel provided a 3D culture microenvironment for stem cells. The experimental results showed that the 3D composite hydrogel scaffold constructed in this study increased the cell spread area by four times compared with the conventional GelMA scaffold. Furthermore, the problems of high stem cell dosage and low rate of utilization were alleviated by orchestrating the programmed proliferation and osteogenic differentiation of hDPSCs. In vivo, high-quality repair of critical bone defects was achieved using hDPSCs extracted from a single tooth, and multiple 'bone island'-like structures were successfully observed that rapidly induced robust bone regeneration. In conclusion, this study suggests that this kind of convenient, low-cost, island-like osteogenesis strategy involving a low dose of hDPSCs has great potential for repairing craniomaxillofacial critical-sized bone defects.

A comprehensive in vitro characterization of non-crosslinked, diverse tissue-derived collagen-based membranes intended for assisting bone regeneration

Collagen-based membranes are class III-medical devices widely used in dental surgical procedures to favour bone regeneration. Here, we aimed to provide biophysical and biochemical data on this type of devices to support their optimal use and design/manufacturing. To the purpose, four commercial, non-crosslinked collagen-based-membranes, obtained from various sources (equine tendon, pericardium or cortical bone tissues, and porcine skin), were characterized in vitro. The main chemical, biophysical and biochemical properties, that have significant clinical implications, were evaluated. Membranes showed similar chemical features. They greatly differed in morphology as well as in porosity and density and showed a diverse ranking in relation to these latter two parameters. Samples highly hydrated in physiological medium (swelling-ratio values in the 2.5-6.0 range) and, for some membranes, an anisotropic expansion during hydration was, for the first time, highlighted. Rheological analyses revealed great differences in deformability (150-1500kPa G') also alerting about the marked variation in membrane mechanical behaviour upon hydration. Samples proved diverse sensitivity to collagenase, with the cortical-derived membrane showing the highest stability. Biological studies, using human-bone-derived cells, supported sample ability to allow cell proliferation and to prompt bone regeneration, while no relevant differences among membranes were recorded. Prediction of relative performance based on the findings was discussed. Overall, results represent a first wide panel of chemical/biophysical/biochemical data on collagen-based-membranes that 1) enhances our knowledge of these products, 2) aids their optimal use by providing clinicians with scientific basis for selecting products based on the specific clinical situation and 3) represents a valuable reference for optimizing their manufacturing.

Hedgehog Signaling Controls Chondrogenesis and Ectopic Bone Formation via the Yap-Ihh Axis

Fibrodysplasia ossificans progressiva (FOP) is a rare congenital disorder characterized by abnormal bone formation due to ACVR1 gene mutations. The identification of the molecular mechanisms underlying the ectopic bone formation and expansion in FOP is critical for the effective treatment or prevention of HO. Here we find that Hh signaling activation is required for the aberrant ectopic bone formation in FOP. We show that the expression of Indian hedgehog (Ihh), a Hh ligand, as well as downstream Hh signaling, was increased in ectopic bone lesions in Acvr1R206H; ScxCre mice. Pharmacological treatment with an Ihh-neutralizing monoclonal antibody dramatically reduced chondrogenesis and ectopic bone formation. Moreover, we find that the activation of Yap in the FOP mouse model and the genetic deletion of Yap halted ectopic bone formation and decreased Ihh expression. Our mechanistic studies showed that Yap and Smad1 directly bind to the Ihh promoter and coordinate to induce chondrogenesis by promoting Ihh expression. Therefore, the Yap activation in FOP lesions promoted ectopic bone formation and expansion in both cell-autonomous and non-cell-autonomous manners. These results uncovered the crucial role of the Yap-Ihh axis in FOP pathogenesis, suggesting the inhibition of Ihh or Yap as a potential therapeutic strategy to prevent and reduce HO.

Intradermal Injection of Hybrid Complexes of High- and Low-Molecular-Weight Hyaluronan: Where Do We Stand and Where Are We Headed in Regenerative Medicine?

Hyaluronic acid (HA) is a remarkably multifaceted biomacromolecule, playing a role in regulating myriad biological processes such as wound healing, tissue regeneration, anti-inflammation, and immunomodulation. Crosslinked high- and low-molecular-weight hyaluronic acid hydrogels achieve higher molar concentrations, display slower degradation, and allow optimal tissue product diffusion, while harnessing the synergistic contribution of different-molecular-weight hyaluronans. A recent innovation in the world of hyaluronic acid synthesis is represented by NAHYCO® Hybrid Technology, a thermal process leading to hybrid cooperative hyaluronic acid complexes (HCC). This review summarizes the current literature on the in vitro studies and in vivo applications of HCC, from facial and body rejuvenation to future perspectives in skin wound healing, dermatology, and genitourinary pathologies.

EID3 inhibits the osteogenic differentiation of periodontal ligament stem cells and mediates the signal transduction of TAZ-EID3-AKT/MTOR/ERK

Exploring the molecular mechanisms of cell behaviors is beneficial for promoting periodontal ligament stem cell (PDLSC)-mediated tissue regeneration. This study intends to explore the regulatory effects of EID3 on cell proliferation, apoptosis, and osteogenic differentiation and to preliminarily explore the regulatory mechanism of EID3. Here, EID3 was overexpressed or knocked down in PDLSCs by recombinant lentivirus. Then, cell proliferation activity was analyzed by colony-forming assay, EdU assay, and cell cycle assay. Cell apoptosis was detected by flow cytometry. The osteo-differentiation potential was analyzed using ALP activity assay, ALP staining, alizarin red staining, and mRNA and protein assay of osteo-differentiation related genes. The results showed that when EID3 was knocked down, the proliferation activity and osteogenic differentiation potential of PDLSCs decreased, while they increased when EID3 was overexpressed. The cell apoptosis rate decreased in PDLSCs with EID3 knockdown but increased in PDLSCs with EID3 overexpression. Moreover, EID3 inhibited the transduction of the AKT/MTOR and ERK signaling pathway. In addition, TAZ negatively regulated the expression of EID3, and the overexpression of EID3 partially reversed the promotive effects of TAZ on the osteogenic differentiation of PDLSCs. Taken together, EID3 inhibits the proliferation and osteogenic differentiation while promoting the apoptosis of PDLSCs. EID3 inhibits the transduction of the AKT/MTOR and ERK signaling pathways and mediates the regulatory effect of TAZ on PDLSC osteogenic differentiation.

Adult Mesenchymal Stem Cells in Presence of Glycosaminoglycans

The application of adult mesenchymal stem cells (MSCs) in the field of tissue regeneration is of increasing interest to the scientific community. In particular, scaffolds and/or hydrogel based on glycosaminoglycans (GAGs) play a pivotal role due to their ability to support the in vitro growth and differentiation of MSCs toward a specific phenotype. Here, we describe different possible approaches to develop GAGs-based biomaterials, hydrogel, and polymeric viscous solutions in order to assess/develop a suitable biomimetic environment. To sustain MSCs viability and promote their differentiation for potential therapeutic applications.

Cysteine and glycine-rich protein 2 retards platelet-derived growth factor-BB-evoked phenotypic transition of airway smooth muscle cells by decreasing YAP/TAZ activity

Cysteine and glycine-rich protein 2 (Csrp2) has emerged as a key factor in controlling the phenotypic modulation of smooth muscle cells. The phenotypic transition of airway smooth muscle cells (ASMCs) is a pivotal step in developing airway remodeling during the onset of asthma. However, whether Csrp2 mediates the phenotypic transition of ASMCs in airway remodeling during asthma onset is undetermined. This work aimed to address the link between Csrp2 and the phenotypic transition of ASMCs evoked by platelet-derived growth factor (PDGF)-BB in vitro. The overexpression or silencing of Csrp2 in ASMCs was achieved through adenovirus-mediated gene transfer. The expression of mRNA was measured by quantitative real-time-PCR. Protein levels were determined through Western blot analysis. Cell proliferation was detected by EdU assay and Calcein AM assays. Cell cycle distribution was assessed via fluorescence-activated cell sorting assay. Cell migration was evaluated using the scratch-wound assay. The transcriptional activity of Yes-associated protein (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ) was measured using the luciferase reporter assay. A decline in Csrp2 level occurred in PDGF-BB-stimulated ASMCs. Increasing Csrp2 expression repressed the PDGF-BB-evoked proliferation and migration of ASMCs. Moreover, increasing Csrp2 expression impeded the phenotypic change of PDGF-BB-stimulated ASMCs from a contractile phenotype into a synthetic/proliferative phenotype. On the contrary, the opposite effects were observed in Csrp2-silenced ASMCs. The activity of YAP/TAZ was elevated in PDGF-BB-stimulated ASMCs, which was weakened by Csrp2 overexpression or enhanced by Csrp2 silencing. The YAP/TAZ activator could reverse Csrp2-overexpression-mediated suppression of the PDGF-BB-evoked phenotypic switching of ASMCs, while the YAP/TAZ suppressor could dimmish Csrp2-silencing-mediated enhancement on PDGF-BB-evoked phenotypic switching of ASMCs. In summary, Csrp2 serves as a determinant for the phenotypic switching of ASMCs. Increasing Csrp2 is able to impede PDGF-BB-evoked phenotypic change of ASMCs from a synthetic phenotype into a synthetic/proliferative phenotype through the effects on YAP/TAZ. This work implies that Csrp2 may be a key player in airway remodeling during the onset of asthma.

Low, medium, and high molecular weight hyaluronic acid effects on human dental pulp stem cells in vitro

Hyaluronic acid (HA), an extracellular biopolymer found throughout the human body, holds promise as a biocompatible and biodegradable scaffold material. High molecular weight (HMW) HA degrades, generating low molecular weight (LMW) fragments with distinct properties. These fragments can influence the behaviour of cells, including human dental pulp stem cells (hDPSCs) incorporated into HA-containing hydrogels or scaffolds. Therefore, a comprehensive examination of the impact of a range of HA molecular weights on hDPSCs is essential before designing HA-based scaffolds for these cells. hDPSC lines were cultured with LMW HA (800 Da, 1600 Da, 15 kDa), medium molecular weight HA (237 kDa), or HMW HA (1500 kDa) over six passages. The various molecular weights had negligible effects on hDPSCs viability, morphology, adhesion, or relative telomere length. Furthermore, the expression of key surface stemness markers (CD29, CD44, CD73, CD90) remained unaltered. HA did not induce osteogenic, chondrogenic, or adipogenic differentiation. Moreover, the potential for chondrogenic and osteogenic differentiation was not adversely affected by LMW or HMW HA. Various molecular weights of HA seem safe, biocompatible and therefore suitable components for hDPSCs-containing scaffolds. These findings affirm that the hDPCSs will not be negatively affected by HA fragments resulting from scaffold degradation.

The Effect of Hydrogel Hyaluronic Acid on Dentine Sialophosphoprotein Expression of Human Dental Pulp Stem Cells

OBJECTIVE

Hyaluronic acid (HA) is glycosaminoglycan and one of important factors in extracellular matrix. In an inflamed pulp, when niche biology is conducive, the recruitment of human dental pulp stem cells (hDPSCs) will take place and differentiate into odontoblast like cell, creating reparative dentine and expressing dentine sialophosphoprotein (DSPP). Therefore, the purpose of this study was to analyze the potential of hydrogel HA in various concentration towards hDPSCs differentiation via DSPP expression at day 7 and 14.

METHODS

After hDPSCs incubation reaching 80% confluence, cells were then starved for 24 hours. Then, culture media were supplemented with osteogenic media. hDPSCs planted into 96 well plate and HA 10 μg/mL, 20 μg/mL, and 30 μg/mL were added. DSPP expression was analysed using elisa reader at day 7 and 14, qualitative result was analysed using alizarin red at day 21. Data was analysed using one-way ANOVA.

RESULTS

At day 7, there was a statistically significant different potential of HA conditioned media in various concentration (p<0.05) towards hDPSCs differentiation via expression of DSPP with HA 30 μg/mL being the most potential concentration to increase DSPP expression.

CONCLUSION

HA have the potential to increase odontoblast differentiation process via expression of DSPP, with HA 30 μg/mL being the optimum concentration for hDPSCs. (EEJ-2022-12-169).

Resistin targets TAZ to promote osteogenic differentiation through PI3K/AKT/mTOR pathway

Osteogenic differentiation (OD) of bone marrow mesenchymal stem cells (BMSCs) contributes significantly to the regeneration of bone defects. Resistin, an adipose tissue-specific secretory factor, has been shown to involve many different functions, including metabolism, inflammation, cancer, and bone remodeling. However, the effects and mechanisms of resistin on OD of BMSCs remain unclear. Herein, we demonstrated that resistin was highly expressed in BMSCs with OD. Upregulation of resistin contributed to the progression of OD of BMSCs by activating PI3K/AKT/mTOR signaling pathway. In addition, resistin facilitated OD by targeting transcriptional co-activator with PDZ-binding motif (TAZ). In a rat femoral condyle bone defect model, local injection of resistin significantly promoted bone repair and improved bone formation. This work contributes to better understanding the mechanism of resistin directly involved in the OD and might provide a new therapeutic strategy for bone defect regeneration.

Emerging Roles of YAP/TAZ in Tooth and Surrounding: from Development to Regeneration

Yes associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) are ubiquitous transcriptional co-activators that control organ development, homeostasis, and tissue regeneration. Current in vivo evidence suggests that YAP/TAZ regulates enamel knot formation during murine tooth development, and is indispensable for dental progenitor cell renewal to support constant incisor growth. Being a critical sensor for cellular mechano-transduction, YAP/TAZ lays at the center of the complex molecular network that integrates mechanical cues from the dental pulp chamber and surrounding periodontal tissue into biochemical signals, dictating in vitro cell proliferation, differentiation, stemness maintenance, and migration of dental stem cells. Moreover, YAP/TAZ-mediated cell-microenvironment interactions also display essential regulatory roles during biomaterial-guided dental tissue repair and engineering in some animal models. Here, we review recent advances in YAP/TAZ functions in tooth development, dental pulp, and periodontal physiology, as well as dental tissue regeneration. We also highlight several promising strategies that harness YAP/TAZ activation for promoting dental tissue regeneration.

KIAA1199 deficiency enhances skeletal stem cell differentiation to osteoblasts and promotes bone regeneration

Upon transplantation, skeletal stem cells (also known as bone marrow stromal or mesenchymal stem cells) can regulate bone regeneration by producing secreted factors. Here, we identify KIAA1199 as a bone marrow stromal cell-secreted factor in vitro and in vivo. KIAA1199 plasma levels of patients positively correlate with osteoporotic fracture risk and expression levels of KIAA1199 in patient bone marrow stromal cells negatively correlates with their osteogenic differentiation potential. KIAA1199-deficient bone marrow stromal cells exhibit enhanced osteoblast differentiation in vitro and ectopic bone formation in vivo. Consistently, KIAA1199 knockout mice display increased bone mass and biomechanical strength, as well as an increased bone formation rate. They also exhibit accelerated healing of surgically generated bone defects and are protected from ovariectomy-induced bone loss. Mechanistically, KIAA1199 regulates osteogenesis by inhibiting the production of osteopontin by osteoblasts, via integrin-mediated AKT and ERK-MAPK intracellular signaling. Thus, KIAA1199 is a regulator of osteoblast differentiation and bone regeneration and could be targeted for the treatment or management of low bone mass conditions.

The effect of hyaluronic acid conditioned media on hDPSCs differentiation through CD44 and transforming growth factor-β1 expressions

Hyaluronic acid (HA) has the capability to influence dentin niche which is important in regenerative process. The CD44 as a specific receptor of HA was found to be related to dentin mineralization process. Meanwhile, transforming growth factor β1 (TGF-β1) has a vital role in the transition from proliferation into the differentiation of human dental pulp stem cell human dental pulp stem cells (hDPSCs) to become odontoblast cells and dentin mineralization. This study aims to analyzed HA's effect on dentin mineralization through CD44 and TGF-β1 expressions. Stem cells were cultured in four different supplemented conditioned media (control, +10 μg/mL, +20 μg/mL, and + 30 μg/mL of HA). Evaluation of CD44 expression was analyzed using flow cytometry and TGF-β1 was analyzed using enzyme-linked immunosorbent assay reader. Qualitative result using Alizarin red test after 21 days was done to confirm the formation of mineralization nodules. It was shown that HA expression of CD44 and TGF-β1 on hDPSCs were higher in AH groups compared to the control group and 30 μg/mL HA induced the highest TGF-β1 expression on hDPSCs. Alizarin red test also showed the highest mineralization nodules in the same group. Therefore, from this study, we found that supplemented 30 μg/mL of HA was proved in initiating hDPSCs differentiation process and promote dentin mineralization.

Hyaluronic acid-based hydrogels: As an exosome delivery system in bone regeneration

Exosomes are extracellular vesicles (EVs) containing various ingredients such as DNA, RNA, lipids and proteins, which play a significant role in intercellular communication. Numerous studies have demonstrated the important role of exosomes in bone regeneration through promoting the expression of osteogenic-related genes and proteins in mesenchymal stem cells. However, the low targeting ability and short circulating half-life of exosomes limited their clinical application. In order to solve those problems, different delivery systems and biological scaffolds have been developed. Hydrogel is a kind of absorbable biological scaffold composed of three-dimensional hydrophilic polymers. It not only has excellent biocompatibility and superior mechanical strength but can also provide a suitable nutrient environment for the growth of the endogenous cells. Thus, the combination between exosomes and hydrogels can improve the stability and maintain the biological activity of exosomes while achieving the sustained release of exosomes in the bone defect sites. As an important component of the extracellular matrix (ECM), hyaluronic acid (HA) plays a critical role in various physiological and pathological processes such as cell differentiation, proliferation, migration, inflammation, angiogenesis, tissue regeneration, wound healing and cancer. In recent years, hyaluronic acid-based hydrogels have been used as an exosome delivery system for bone regeneration and have displayed positive effects. This review mainly summarized the potential mechanism of HA and exosomes in promoting bone regeneration and the application prospects and challenges of hyaluronic acid-based hydrogels as exosome delivery devices in bone regeneration.

Topographic Cues of a PLGA Scaffold Promote Odontogenic Differentiation of Dental Pulp Stem Cells through the YAP/β-Catenin Signaling Axis

PURPOSE

The underlying mechanism of how topographic cues of artificial scaffolds regulate cell function remains poorly understood. Yes-associated protein (YAP) and β-catenin signaling have both been reported to play important roles in mechano-transduction and dental pulp stem cells (DPSCs) differentiation. We investigated the effects of YAP and β-catenin in spontaneous odontogenic differentiation of DPSCs induced by topographic cues of a poly(lactic-co-glycolic acid) (PLGA) membrane.

METHODS

The topographic cues and function of a fabricated PLGA scaffold were explored via scanning electron microscopy (SEM), alizarin red staining (ARS), reverse transcription-polymerase chain reaction (RT-PCR), and pulp capping. Immunohistochemistry (IF), RT-PCR, and western blotting (WB) were used to observe the activation of YAP and β-catenin when DPSCs were cultured on the scaffolds. Further, YAP was inhibited or overexpressed on either side of the PLGA membrane, and YAP, β-catenin, and odontogenic marker expression were analyzed using IF, ARS, and WB.

RESULTS

The closed side of the PLGA scaffold promoted spontaneous odontogenic differentiation and nuclear translocation of YAP and β-catenin in vitro and in vivo compared to the open side. The YAP antagonist verteporfin inhibited β-catenin expression, nuclear translocation, and odontogenic differentiation on the closed side, but the effects were rescued by LiCl. YAP overexpressing DPSCs on the open side activated β-catenin signaling and promoted odontogenic differentiation.

CONCLUSION

The topographic cue of our PLGA scaffold promotes odontogenic differentiation of DPSCs and pulp tissue through the YAP/β-catenin signaling axis.

Hyaluronic acid hydrogels support to generate integrated bone formation through endochondral ossification in vivo using mesenchymal stem cells

Engineered cartilage tissue from differentiated mesenchymal stem cells (MSCs) can generate bone in vivo through endochondral ossification (ECO). This ECO-mediated approach has the potential to circumvent the severe problems associated with conventional MSC-based bone tissue engineering techniques that lack mechanisms to induce angiogenesis. Hyaluronic acid (HA) is a key component in the cartilage extracellular matrix. However, the ECO-supporting properties of HA remain largely unclear. This study aimed to compare the ability of HA and collagen hydrogels to support in vitro differentiation of MSC-based hypertrophic cartilage tissues and to promote endochondral bone formation in vivo. Following the chondrogenic and hypertrophic differentiation in vitro, both HA and collagen constructs accumulated sulfated glycosaminoglycan (sGAG) and type 1, type II, and type X collagen. However, HA hydrogels exhibited a more uniform distribution of sGAG, type 1 collagen, type X collagen, and osteocalcin proteins; in addition, the cells embedded in the hydrogels had more rounded cell morphologies than those in the collagen constructs. At week 5 of in vitro culture, two to three constructs were implanted into a subcutaneous pocket in nude mice and harvested after 4 and 8 weeks. Both HA and collagen constructs promoted endochondral bone formation with vascularization and bone marrow development; however, the HA constructs fused to form integrated bone tissues and the bone marrow developed along the space between the two adhered grafts in all implanted pockets (n = 5). In the collagen constructs, the integration was observed in 40% of the pockets (n = 5). Microcomputer CT analysis revealed that the bone volume of HA constructs was larger than that of collagen constructs. In conclusion, compared to collagen hydrogels, HA hydrogels had superior potential to generate integrated bone with vascularization and bone marrow development. This study provides valuable insights for applying ECO-mediated bone tissue engineering approaches for the repair of critical-sized bone defects.

Trends in extracellular matrix biology

Extracellular matrixes (ECMs) are intricate 3-dimensional macromolecular networks of unique architectures with regulatory roles in cell morphology and functionality. As a dynamic native biomaterial, ECM undergoes constant but tightly controlled remodeling that is crucial for the maintenance of normal cellular behavior. Under pathological conditions like cancer, ECM remodeling ceases to be subjected to control resulting in disease initiation and progression. ECM is comprised of a staggering number of molecules that interact not only with one another, but also with neighboring cells via cell surface receptors. Such interactions, too many to tally, are of paramount importance for the identification of novel disease biomarkers and more personalized therapeutic intervention. Recent advances in big data analytics have allowed the development of online databases where researchers can take advantage of a stochastic evaluation of all the possible interactions and narrow them down to only those of interest for their study, respectively. This novel approach addresses the limitations that currently exist in studies, expands our understanding on ECM interactions, and has the potential to advance the development of targeted therapies. In this article we present the current trends in ECM biology research and highlight its importance in tissue integrity, the main interaction networks, ECM-mediated cell functional properties and issues related to pharmacological targeting.

Cultivation of Cryopreserved Human Dental Pulp Stem Cells—A New Approach to Maintaining Dental Pulp Tissue

Human dental pulp stem cells (hDPSCs) are multipotent mesenchymal stem cells (MSCs) that are capable of self-renewal with multilineage differentiation potential. After being cryopreserved, hDPSCs were reported to maintain a high level of proliferation and multi-differentiation abilities. In order to optimize cryopreservation techniques, decrease storage requirements and lower contamination risks, the feasibility of new whole-tooth cryopreservation and its effects on hDPSCs were tested. The survival rates, morphology, proliferation rates, cell activity, surface antigens and differentiation abilities of hDPSCs isolated from fresh teeth were compared with those of one-month cryopreserved teeth in 5% and 10% DMSO. The data of the present study indicated that the new cryopreservation approach did not reduce the capabilities or stemness of hDPSCs, with the exception that it extended the first appearance time of hDPSCs in the teeth that were cryopreserved in 10% DMSO, and reduced their recovery rate. With the novel strategy of freezing, the hDPSCs still expressed the typical surface markers of MSCs and maintained excellent proliferation capacity. Three consecutive weeks of osteogenic and adipogenic induction also showed that the expression of the key genes in hDPSCs, including lipoprotein lipase (LPL), peroxisome proliferator-activated receptor-γ (PPAR-γ), alkaline phosphatase (ALP), runt-related transcription factor 2 (RUNX2), type I collagen (COL I) and osteocalcin (OSC) was not affected, indicating that their differentiation abilities remained intact, which are crucial parameters for hDPSCs as cell-therapy candidates. These results demonstrated that the new cryopreservation method is low-cost and effective for the good preservation of hDPSCs without compromising cell performance, and can provide ideas and evidence for the future application of stem-cell therapies and the establishment of dental banks.

Photocross-linked silk fibroin/hyaluronic acid hydrogel loaded with hDPSC for pulp regeneration

The construction of suitable biomaterials for pulp regeneration has always been a major challenge in the field of stomatology. Considering the complex and irregular anatomy of the root canal system, injectable hydrogels have received extensive attention as cell carriers in dental pulp regeneration. Here, we developed an injectable photocrosslinked methacrylylated silk fibroin (RSFMA)/methacrylylated hyaluronic acid (MeHA) composite hydrogel and characterized its physicochemical properties. The biocompatibility of encapsulated human dental pulp stem cells (hDPSCs) was subsequently investigated. With the addition of RSFMA, the pore size of the scaffolds became more regular with negligible change in porosity and exhibited excellent mechanical properties. Furthermore, the low concentration of RSFMA hydrogel in the composite hydrogel had higher cross-linking efficiency. In contrast to MeHA hydrogels, hDPSCs were encapsulated in hydrogels either in the absence or presence of high concentrations of RSFMA. The results indicated that cells in low-concentration RSFMA composite gel presented better growth ability, proliferation ability and osteogenic differentiation ability. This injectable photocrosslinked silk fibroin/hyaluronic acid hydrogel shows great potential in the field of dental pulp tissue engineering.

Polydatin Incorporated in Polycaprolactone Nanofibers Improves Osteogenic Differentiation

Polycaprolactone nanofibers are used as scaffolds in the field of tissue engineering for tissue regeneration or drug delivery. Polycaprolactone (PCL) is a biodegradable hydrophobic polyester used to obtain implantable nanostructures, which are clinically applicable due to their biological safety. Polydatin (PD), a glycosidic precursor of resveratrol, is known for its antioxidant, antitumor, antiosteoporotic, and bone regeneration activities. We aimed to use the osteogenic capacity of polydatin to create a biomimetic innovative and patented scaffold consisting of PCL-PD for bone tissue engineering. Both osteosarcoma cells (Saos-2) and mesenchymal stem cells (MSCs) were used to test the in vitro cytocompatibility of the PD-PCL scaffold. Reverse-phase (RP) HPLC was used to evaluate the timing release of PD from the PCL-PD nanofibers and the MTT assay, scanning electron microscopy, and alkaline phosphatase (ALP) activity were used to evaluate the proliferation, adhesion, and cellular differentiation in both osteosarcoma and human mesenchymal stem cells (MSCs) seeded on PD-PCL nanofibers. The proliferation of osteosarcoma cells (Saos-2) on the PD-PCL scaffold decreased when compared to cells grown on PLC nanofibers, whereas the proliferation of MSCs was comparable in both PCL and PD-PCL nanofibers. Noteworthy, after 14 days, the ALP activity was higher in both Saos-2 cells and MSCs cultivated on PD-PCL than on empty scaffolds. Moreover, the same cells showed a spindle-shaped morphology after 14 days when grown on PD-PCL as shown by SEM. In conclusion, we provide evidence that nanofibers appropriately coated with PD support the adhesion and promote the osteogenic differentiation of both human osteosarcoma cells and MSCs.

Hypes and Hopes of Stem Cell Therapies in Dentistry: a Review

One of the most exciting advances in life science research is the development of 3D cell culture systems to obtain complex structures called organoids and spheroids. These 3D cultures closely mimic in vivo conditions, where cells can grow and interact with their surroundings. This allows us to better study the spatio-temporal dynamics of organogenesis and organ function. Furthermore, physiologically relevant organoids cultures can be used for basic research, medical research, and drug discovery. Although most of the research thus far focuses on the development of heart, liver, kidney, and brain organoids, to name a few, most recently, these structures were obtained using dental stem cells to study in vitro tooth regeneration. This review aims to present the most up-to-date research showing how dental stem cells can be grown on specific biomaterials to induce their differentiation in 3D. The possibility of combining engineering and biology principles to replicate and/or increase tissue function has been an emerging and exciting field in medicine. The use of this methodology in dentistry has already yielded many interesting results paving the way for the improvement of dental care and successful therapies.

Bio-functionalization and in-vitro evaluation of titanium surface with recombinant fibronectin and elastin fragment in human mesenchymal stem cell

Titanium is a biomaterial that meets a number of important requirements, including excellent mechanical and chemical properties, but has low bioactivity. To improve cellular response onto titanium surfaces and hence its osseointegration, the titanium surface was bio-functionalized to mimic an extracellular matrix (ECM)-like microenvironment that positively influences the behavior of stem cells. In this respect, fibronectin and elastin are important components of the ECM that regulate stem cell differentiation by supporting the biological microenvironment. However, each native ECM is unsuitable due to its high production cost and immunogenicity. To overcome these problems, a recombinant chimeric fibronectin type III_9-10 and elastin-like peptide fragments (FN9-10_ELP) was developed herein and applied to the bio-functionalized of the titanium surface. An evaluation of the biological activity and cellular responses with respect to bone regeneration indicated a 4-week sustainability on the FN9-10_ELP functionalized titanium surface without an initial burst effect. In particular, the adhesion and proliferation of human mesenchymal stem cells (hMSCs) was significantly increased on the FN9-10_ELP coated titanium compared to that observed on the non-coated titanium. The FN9-10_ELP coated titanium induced osteogenic differentiation such as the alkaline phosphatase (ALP) activity and mineralization activity. In addition, expressions of osteogenesis-related genes such as a collagen type I (Col I), Runt-related transcription factor 2 (RUNX2), osteopontin (OPN), osteocalcin (OCN), bone sialo protein (BSP), and PDZ-binding motif (TAZ) were further increased. Thus, in vitro the FN9-10_ELP functionalization titanium not only sustained bioactivity but also induced osteogenic differentiation of hMSCs to improve bone regeneration.