Stem cells applications in bone and tooth repair and regeneration: New insights, tools, and hopes

The role of WWP1 and WWP2 in bone/cartilage development and diseases

Bone and cartilage diseases are often associated with trauma and senescence, manifested as pain and limited mobility. The repair of bone and cartilage lesion by mesenchymal stem cells is regulated by various transcription factors. WW domain-containing protein 1 (WWP1) and WW domain-containing protein 2 (WWP2) are named for WW domain which recognizes PPXY (phono Ser Pro and Pro Arg) motifs of substrate. WWP1and WWP2 are prominent components of the homologous to the E6-AP carboxyl terminus (HECT) subfamily, a group of the ubiquitin ligase. Recently, some studies have found that WWP1 and WWP2 play an important role in the pathogenesis of bone and cartilage diseases and regulate the level and the transactivation of various transcription factors through ubiquitination. Therefore, this review summarizes the distribution and effects of WWP1 and WWP2 in the development of bone and cartilage, discusses the potential mechanism and therapeutic drugs in bone and cartilage diseases such as osteoarthritis, fracture, and osteoporosis.

CA1 Modulates the Osteogenic Differentiation of Dental Follicle Stem Cells by Activating the BMP Signaling Pathway In Vitro

BACKGROUND

Carbonic anhydrase 1 (CA1) has been found to be involved in osteogenesis and osteoclast in various human diseases, but the molecular mechanisms are not completely understood. In this study, we aim to use siRNA and lentivirus to reduce or increase the expression of CA1 in Dental follicle stem cells (DFSCs), in order to further elucidate the role and mechanism of CA1 in osteogenesis, and provide better osteogenic growth factors and stem cell selection for the application of bone tissue engineering in alveolar bone fracture transplantation.

METHODS

The study used RNA interference and lentiviral vectors to manipulate the expression of the CA1 gene in DFSCs during in vitro osteogenic induction. The expression of osteogenic marker genes was evaluated and changes in CA1, alkaline phosphatase (ALP), Runt-related transcription factor 2 (RUNX2), and Bone morphogenetic proteins (BMP2) were measured using quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting (WB). The osteogenic effect was assessed through Alizarin Red staining.

RESULTS

The mRNA and protein expression levels of CA1, ALP, RUNX2, and BMP2 decreased distinctly in the si-CA1 group than other groups (p < 0.05). In the Lentivirus-CA1 (LV-CA1) group, the mRNA and protein expressions of CA1, ALP, RUNX2, and BMP2 were amplified to varying degrees than other groups (p < 0.05). Apart from CA1, BMP2 (43.01%) and ALP (36.69%) showed significant upregulation (p < 0.05). Alizarin red staining indicated that the LV-CA1 group produced more calcified nodules than other groups, with a higher optical density (p < 0.05), and the osteogenic effect was superior.

CONCLUSIONS

CA1 can impact osteogenic differentiation via BMP related signaling pathways, positioning itself upstream in osteogenic signaling pathways, and closely linked to osteoblast calcification and ossification processes.

C5L2 CRISPR KO enhances dental pulp stem cell-mediated dentinogenesis via TrkB under TNFα-induced inflammation

Background and Objectives: Dental caries is one of the most common human pathological conditions resulting from the invasion of bacteria into the dentin. Current treatment options are limited. In many cases, endodontic therapy leads to permanent pulp tissue loss. Dentin-pulp complex regeneration involves dental pulp stem cells (DPSCs) that differentiate into odontoblast-like cells under an inflammatory context. However, limited information is available on how DPSC differentiation processes are affected under inflammatory environments. We identified the crucial role of complement C5a and its receptor C5aR in the inflammation-induced odontoblastic DPSC differentiation. Methodology: Here, we further investigated the role of a second and controversial C5a receptor, C5L2, in this process and explored the underlying mechanism. Human DPSCs were examined during 7-, 10-, and 14-day odontogenic differentiation treated with TNFα, C5L2 CRISPR, and tyrosine receptor kinase B (TrkB) antagonist [cyclotraxin-B (CTX-B)]. Results: Our data demonstrate that C5L2 CRISPR knockout (KO) enhances mineralization in TNFα-stimulated differentiating DPSCs. We further confirmed that C5L2 CRISPR KO significantly enhances dentin sialophosphoprotein (DSPP) and dentin matrix protein-1 (DMP-1) expression after 14-day odontoblastic DPSC differentiation, and treatment with CTX-B abolished the TNFα/C5L2 CRISPR KO-induced DSPP and DMP-1 increase, suggesting TrkB's critical role in this process. Conclusion and Key applications: Our data suggest a regulatory role of C5L2 and TrkB in the TNFα-induced odontogenic DPSC differentiation. This study may provide a useful tool to understand the mechanisms of the role of inflammation in dentinogenesis that is required for successful DPSC engineering strategies.

Potential of Oral Cavity Stem Cells for Bone Regeneration: A Scoping Review

Bone loss is a common problem that ranges from small defects to large defects after trauma, surgery, or congenital malformations. The oral cavity is a rich source of mesenchymal stromal cells (MSCs). Researchers have documented their isolation and studied their osteogenic potential. Therefore, the objective of this review was to analyze and compare the potential of MSCs from the oral cavity for use in bone regeneration.

METHODS

A scoping review was carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines. The databases reviewed were PubMed, SCOPUS, Scientific Electronic Library Online (SciELO), and Web of Science. Studies using stem cells from the oral cavity to promote bone regeneration were included.

RESULTS

A total of 726 studies were found, of which 27 were selected. The MSCs used to repair bone defects were (I) dental pulp stem cells of permanent teeth, (II) stem cells derived from inflamed dental pulp, (III) stem cells from exfoliated deciduous teeth, (IV) periodontal ligament stem cells, (V) cultured autogenous periosteal cells, (VI) buccal fat pad-derived cells, and (VII) autologous bone-derived mesenchymal stem cells. Stem cells associate with scaffolds to facilitate insertion into the bone defect and to enhance bone regeneration. The biological risk and morbidity of the MSC-grafted site were minimal. Successful bone formation after MSC grafting has been shown for small defects with stem cells from the periodontal ligament and dental pulp as well as larger defects with stem cells from the periosteum, bone, and buccal fat pad.

CONCLUSIONS

Stem cells of maxillofacial origin are a promising alternative to treat small and large craniofacial bone defects; however, an additional scaffold complement is required for stem cell delivery.

Bioglass/collagen scaffolds combined with bone marrow stromal cells on bone healing in an experimental model in cranial defects in rats

This study aimed to develop bone regenerative therapeutic strategies, based on the addition of bone marrow stromal cells (BMSC) on bioglass/collagen (BG/COL) scaffolds. For this purpose, an in vivo study was conducted using tissue response of the BG/COL scaffolds combined with BMSC in a critical-size defects. Wistar rats were submitted to the surgical procedure to perform the cranial critical size bone defects and distributed in four groups (20 animals per group): Control Group (CG) (rats submitted to the cranial bone defect surgery without treatment), Bioglass Group (BG) (rats treated with BG), BG/COL Group (rats treated with BG/COL) and Bioglass/Collagen and BMSC Group (BG/COL/BMSC) (rats treated with BG/COL scaffolds enriched with BMSCs). Animals were euthanized 15 and 30 days after surgery. Scanning electron microscopy, histopathological and immunohistochemistry analysis were used. SEM analysis demonstrated that porous scaffolds were obtained, and Col fibers were successfully impregnated to BG matrices. The implantation of the BMSC on BG/COL based scaffolds was effective in stimulating newly bone formation and produced an increased immunoexpression of markers related to the bone repair. These results highlight the potential of BG/COL scaffolds and BMSCs to be used as a therapeutic approach for bone regeneration.

Periodontal tissue stem cells and mesenchymal stem cells in the periodontal ligament

Periodontal tissue stem cells, which play a crucial role in maintaining the homeostasis of periodontal tissues, are found in the periodontal ligament (PDL). These cells have long been referred to as mesenchymal stem/stromal cells (MSCs), and their clinical applications have been extensively studied. However, tissue stem cells in the PDL have not been thoroughly investigated, and they may be different from MSCs. Recent advances in stem cell biology, such as genetic lineage tracing, identification of label-retaining cells, and single-cell transcriptome analysis, have made it possible to analyze tissue stem cells in the PDL in vivo. In this review, we summarize recent findings on these stem cell populations in PDL and discuss future research directions toward developing periodontal regenerative therapy.

In situ regeneration of bone-to-tendon structures: Comparisons between costal-cartilage derived stem cells and BMSCs in the rat model

Bone-tendon interface (BTI), also called enthesis, is composed of the bone, fibrocartilage, and tendon/ligament with gradual structural characteristics. The unique gradient structure is particularly important for mechanical stress transfer between bone and soft tissues. However, BTI injuries result in fibrous scar repairs and high incidences of re-rupture, which is attributed to the lack of local stem cells with tenogenic and osteogenic potentials. In the rat model, we identified unique stem cells from costal cartilage (CDSCs) with a high in situ regeneration potential of BTI structures. Compared to bone-marrow mesenchymal stem cells (BMSCs), CDSCs exhibit higher self-renewal capacities, better adaptability to low-oxygen and low-nutrient post-transplantation environments, as well as strong bi-potent differentiation abilities of osteogenesis and tenogenesis. After transplantation, CDSCs can survive, proliferate, and in situ gradually regenerate BTI structures. Therefore, CDSCs have a great potential for tissue engineering regeneration in BTI injuries, and have future clinical application prospects. STATEMENT OF SIGNIFICANCE: Tissue engineering is a promising technique for bone-to-tendon interface (BTI) regeneration after injury, but it is still a long way from clinical application. One of the major reasons is the lack of suitable seed cells. This study found an ideal source of seed cells derived from costal cartilages (CDSCs). Compared to the traditional seed cell BMSCs, CDSCs have higher proliferation ability, strong chondrogenic and tenogenic differentiation potential, and better adaptability to low-oxygen and low nutrient conditions. CDSCs were able to survive, proliferate, and regenerate BTI structures in situ, in contrast to BMSCs. CDSCs transplantation showed strong BTI structures regeneration potential both histologically and biomechanically, making it a suitable seed cell for the tissue engineering regeneration of BTI.

Effects of Systemic or Local Administration of Mesenchymal Stem Cells from Patients with Osteoporosis or Osteoarthritis on Femoral Fracture Healing in a Mouse Model

The purpose of this study was to analyze the regenerative capacity of mesenchymal stem cells (MSCs) in the treatment of fractures. MSCs extracted from patients with osteoporotic hip fractures or hip osteoarthritis undergoing hip replacement surgeries were cultured and injected into mice with femoral fracture. Two experimental models were established, one for the systemic administration of MSCs (n = 29) and another one for local administration (n = 30). Fracture consolidation was assessed by micro-CT and histology. The degree of radiological consolidation and corticalization was better with MSCs from osteoporosis than from osteoarthritis, being significant after systemic administration (p = 0.0302 consolidation; p = 0.0243 corticalization). The histological degree of consolidation was also better with MSCs from osteoporosis than from osteoarthritis. Differences in histological scores after systemic infusion were as follows: Allen, p = 0.0278; Huo, p = 0.3471; and Bone Bridge, p = 0.0935. After local administration at the fracture site, differences in histological scores were as follows: Allen, p = 0.0764; Huo, p = 0.0256; and Bone Bridge, p = 0.0012. As osteoporosis and control groups were similar, those differences depended on an inhibitory influence by MSCs from patients with osteoarthritis. In conclusion, we found an unexpected impairment of consolidation induced by MSCs from patients with osteoarthritis. However, MSCs from patients with osteoporosis compared favorably with cells from patients with osteoarthritis. In other words, based on this study and previous studies, MSCs from patients with osteoporosis do not appear to have worse bone-regenerating capabilities than MSCs from non-osteoporotic individuals of similar age.

Posology and Serum-/Xeno-Free Engineered Adipose Stromal Cells Cell Sheets

Well-characterized adipose stem cells and chemically defined culture media are important factors that control the production of the cell sheet, used in translational medicine. In this study, we have developed and engineered multilayer adipose stem cell cell sheets (ASCCSs) using chemically defined/serum-free culture media: undifferentiated or differentiated into osteoblasts and chondrocytes. In addition, using the cell sheet transmittance, we estimated the number of cells per cell sheet. Undifferentiated ASCCSs were engineered in 10 days, using serum-free/xeno-free culture media. They were CD29⁺, CD73⁺, CD90⁺, CD105+, HLA-A+, and HLA-DR-. ASCCSs differentiated into chondrocytes and osteoblasts were also engineered using chemically defined and animal-free culture media, in only 14 days. The addition of an ROCK inhibitor improved the chondrocyte cell sheet engineering. The decrease in the cell sheet transmittance rate was higher for the osteoblast cell sheets due to the intracellular Ca²⁺ accumulation. The estimation of cell number per cell sheet was carried out with the transmittance, which will provide important information for cell sheet posology. In conclusion, three types of ASCCSs were engineered using serum-free, xeno-free culture media, expressing their specific markers. Their transmittance measurement allowed estimating the number of cells per cell sheet, with a non-invasive methodology.

Dental Pulp-Derived Stem Cells Are as Effective as Bone Marrow-Derived Mesenchymal Stromal Cells When Implanted into a Murine Critical Bone Defect

Background While bone marrow-derived mesenchymal stromal cells (BM-MSCs) have been used for many years in bone tissue engineering applications, the procedure still has drawbacks such as painful collection methods and damage to the donor site. Dental pulp-derived stem cells (DPSCs) are readily accessible, occur in high amounts and show a high proliferation and differentiation capability. Therefore, DPSCs may be a promising alternative for BM-MSCs to repair bone defects. Objective The aim of this study was to investigate the bone regenerative potential of DPSCs in comparison to BM-MSCs in vitro and in vivo. Methods In vitro investigations included analysis of cell doubling time as well as proliferation and osteogenic differentiation. For the in vivo study 36 male NMRI nude mice were randomized into 3 groups: 1) control (cell-free mineralized collagen matrix (MCM) scaffold), 2) MCM + DPSCs and 3) MCM + BM-MSCs. Critical size 2 mm bone defects were created at the right femur of each mouse and stabilized by an external fixator. After 6 weeks animals were euthanized and microcomputed tomography scans (µCT) and histological analyses were performed. Results In vitro DPSCs showed a 2-fold lower population doubling time and a 9-fold higher increase in proliferation when seeded onto MCM scaffolds as compared to BM-MSCs, but DPSCs showed a significantly lower osteogenic capability than BM-MSCs. In vivo, the healing of the critical bone defect in NMRI nude mice was comparable among all groups. Conclusions Pre-seeding of MCM scaffolds with DPSCs and BM-MSCs did not enhance bone defect healing. </p>.

Genetics and Epigenetics of Bone Remodeling and Metabolic Bone Diseases

Bone metabolism consists of a balance between bone formation and bone resorption, which is mediated by osteoblast and osteoclast activity, respectively. In order to ensure bone plasticity, the bone remodeling process needs to function properly. Mesenchymal stem cells differentiate into the osteoblast lineage by activating different signaling pathways, including transforming growth factor β (TGF-β)/bone morphogenic protein (BMP) and the Wingless/Int-1 (Wnt)/β-catenin pathways. Recent data indicate that bone remodeling processes are also epigenetically regulated by DNA methylation, histone post-translational modifications, and non-coding RNA expressions, such as micro-RNAs, long non-coding RNAs, and circular RNAs. Mutations and dysfunctions in pathways regulating the osteoblast differentiation might influence the bone remodeling process, ultimately leading to a large variety of metabolic bone diseases. In this review, we aim to summarize and describe the genetics and epigenetics of the bone remodeling process. Moreover, the current findings behind the genetics of metabolic bone diseases are also reported.

The Role of Long Non-Coding RNAs and Circular RNAs in Bone Regeneration: Modulating MiRNAs Function

Although bone is a self-healing organ and is able to repair and restore most fractures, large bone fractures, about 10%, are not repairable. Bone grafting, as a gold standard, and bone tissue engineering using biomaterials, growth factors, and stem cells have been developed to restore large bone defects. Since bone regeneration is a complex and multiple-step process and the majority of the human genome, about 98%, is composed of the non-protein-coding regions, non-coding RNAs (ncRNAs) play essential roles in bone regeneration. Recent studies demonstrated that long ncRNAs (lncRNAs) and circular RNAs (circRNAs), as members of ncRNAs, are widely involved in bone regeneration by interaction with microRNAs (miRNAs) and constructing a lncRNA or circRNA/miRNA/mRNA regulatory network. The constructed network regulates the differentiation of stem cells into osteoblasts and their commitment to osteogenesis. This review will present the structure and biogenesis of lncRNAs and circRNAs, the mechanism of bone repair, and the bone tissue engineering in bone defects. Finally, we will discuss the role of lncRNAs and circRNAs in osteogenesis and bone fracture healing through constructing various lncRNA or circRNA/miRNA/mRNA networks and the involved pathways. This article is protected by copyright. All rights reserved.

Proteoglycans and Glycosaminoglycans in Stem Cell Homeostasis and Bone Tissue Regeneration

Stem cells maintain a subtle balance between self-renewal and differentiation under the regulatory network supported by both intracellular and extracellular components. Proteoglycans are large glycoproteins present abundantly on the cell surface and in the extracellular matrix where they play pivotal roles in facilitating signaling transduction and maintaining stem cell homeostasis. In this review, we outline distinct proteoglycans profiles and their functions in the regulation of stem cell homeostasis, as well as recent progress and prospects of utilizing proteoglycans/glycosaminoglycans as a novel glycomics carrier or bio-active molecules in bone regeneration.

Potential of Bone-Marrow-Derived Mesenchymal Stem Cells for Maxillofacial and Periodontal Regeneration: A Narrative Review

Bone-marrow-derived mesenchymal stem cells (BM-MSCs) are one of the most widely studied postnatal stem cell populations and are considered to utilize more frequently in cell-based therapy and cancer. These types of stem cells can undergo multilineage differentiation including blood cells, cardiac cells, and osteogenic cells differentiation, thus providing an alternative source of mesenchymal stem cells (MSCs) for tissue engineering and personalized medicine. Despite the ability to reprogram human adult somatic cells to induced pluripotent stem cells (iPSCs) in culture which provided a great opportunity and opened the new door for establishing the in vitro disease modeling and generating an unlimited source for cell base therapy, using MSCs for regeneration purposes still have a great chance to cure diseases. In this review, we discuss the important issues in MSCs biology including the origin and functions of MSCs and their application for craniofacial and periodontal tissue regeneration, discuss the potential and clinical applications of this type of stem cells in differentiation to maxillofacial bone and cartilage in vitro, and address important future hopes and challenges in this field.

Comparing the Osteogenic Potential and Bone Regeneration Capacities of Dedifferentiated Fat Cells and Adipose-Derived Stem Cells In Vitro and In Vivo: Application of DFAT Cells Isolated by a Mesh Method

BACKGROUND

We investigated and compared the osteogenic potential and bone regeneration capacities of dedifferentiated fat cells (DFAT cells) and adipose-derived stem cells (ASCs).

METHOD

We isolated DFAT cells and ASCs from GFP mice. DFAT cells were established by a new culture method using a mesh culture instead of a ceiling culture. The isolated DFAT cells and ASCs were incubated in osteogenic medium, then alizarin red staining, alkaline phosphatase (ALP) assays, and RT-PCR (for RUNX2, osteopontin, DLX5, osterix, and osteocalcin) were performed to evaluate the osteoblastic differentiation ability of both cell types in vitro. In vivo, the DFAT cells and ASCs were incubated in osteogenic medium for four weeks and seeded on collagen composite scaffolds, then implanted subcutaneously into the backs of mice. We then performed hematoxylin and eosin staining and immunostaining for GFP and osteocalcin.

RESULTS

The alizarin red-stained areas in DFAT cells showed weak calcification ability at two weeks, but high calcification ability at three weeks, similar to ASCs. The ALP levels of ASCs increased earlier than in DFAT cells and showed a significant difference (p < 0.05) at 6 and 9 days. The ALP levels of DFATs were higher than those of ASCs after 12 days. The expression levels of osteoblast marker genes (osterix and osteocalcin) of DFAT cells and ASCs were higher after osteogenic differentiation culture.

CONCLUSION

DFAT cells are easily isolated from a small amount of adipose tissue and are readily expanded with high purity; thus, DFAT cells are applicable to many tissue-engineering strategies and cell-based therapies.

Decreased autophagy impairs osteogenic differentiation of adipose-derived stem cells via Notch signaling in diabetic osteoporosis mice

BACKGROUND

The osteogenic differentiation ability of adipose-derived stem cells (ASCs) is attenuated in type 2 diabetic osteoporosis (Dop) mice. Several studies suggest autophagy and Notch signaling pathway play vital roles in cell proliferation, differentiation, and osteogenesis. However, the mechanisms of autophagy and Notch signaling in the osteogenic differentiation of Dop ASCs were unclear. Thus, it is meaningful to reveal potential correlations between autophagy, Notch signaling, and osteogenesis, and explore involved molecular mechanisms in Dop ASCs.

MATERIALS AND METHODS

The diabetic osteoporosis C57BL/6 mouse model, which was confirmed by micro-CT and HE & Masson staining, was established through high-sugar and high-fat diet and streptozotocin injection. ASCs were obtained from the inguinal subcutaneous fat of Dop mice. The multi-differentiation potential of ASCs was evaluated by staining with Alizarin Red (osteogenesis), Oil Red O (adipogenesis), and Alcian blue (chondrogenesis). Cell viability was assessed by Cell Counting Kit-8 assay. Torin1, an inhibitor of mTOR, was used to stimulate the autophagy signaling pathway. DAPT, a γ-secretase inhibitor, was used to suppress Notch signaling pathway activity. Gene and protein expression of autophagy, Notch signaling pathway, and osteogenic factors were detected by real-time quantitative PCR, western blot, and immunofluorescence microscopy.

RESULTS

Our findings showed autophagy and osteogenic differentiation ability of Dop ASCs exhibited downward trends that were both rescued by Torin1. Notch signaling was suppressed in Dop ASCs, but upregulated when autophagy was activated. After activation of autophagy, DAPT treatment led to decreased Notch signaling pathway activation and attenuated osteogenic differentiation ability in Dop ASCs.

CONCLUSIONS

Downregulated autophagy suppressed Notch signaling, leading to a reduced osteogenic differentiation capacity of Dop ASCs, and Torin1 can rescue this process by activating autophagy. Our findings contribute to understanding the mechanism underlying impairment of the osteogenic differentiation ability of Dop ASCs.

Comparison of Osteogenic Potentials of Dental Pulp and Bone Marrow Mesenchymal Stem Cells Using the New Cell Transplantation Platform, CellSaic, in a Rat Congenital Cleft-Jaw Model

Scaffolds stimulate cell proliferation and differentiation and play major roles in providing growth and nutrition factors in the repair of bone defects. We used the recombinant peptide Cellnest™ to prepare the three-dimensional stem cell complex, CellSaic, and evaluated whether CellSaic containing rat dental pulp stem cells (rDPSCs) was better than that containing rat bone marrow stem cells (rBMSCs). rDPSC-CellSaic or rBMSC-CellSaic, cultured with or without osteogenic induction medium, formed the experimental and control groups, respectively. Osteoblast differentiation was evaluated in vitro and transplanted into a rat model with a congenital jaw fracture. Specimens were collected and evaluated by microradiology and histological analysis. In the experimental group, the amount of calcium deposits, expression levels of bone-related genes (RUNX2, ALP, BSP, and COL1), and volume of mineralized tissue, were significantly higher than those in the control group (p < 0.05). Both differentiated and undifferentiated rDPSC-CellSaic and only the differentiated rBMSC-CellSaic could induce the formation of new bone tissue. Overall, rBMSC-CellSaic and rDPSC-CellSaic made with Cellnest™ as a scaffold, provide excellent support for promoting bone regeneration in rat mandibular congenital defects. Additionally, rDPSC-CellSaic seems a better source for craniofacial bone defect repair than rBMSC-CellSaic, suggesting the possibility of using DPSCs in bone tissue regenerative therapy.

Effects of iRoot SP on osteogenic differentiation of human stem cells from apical papilla

BACKGROUND

Research shows that nano-bioceramics can modulate the differentiation of dental stem cells. The novel ready-to-use calcium-silicate-based root-canal sealer iRoot SP is widely used in root filling. Accordingly, the aim of this study was to evaluate the effects of iRoot SP on proliferation and osteogenic differentiation in human stem cells from the apical papilla (hSCAPs).

METHODS

hSCAPs were isolated and characterized in vitro, then cultured with various concentrations of iRoot SP extract. Cell proliferation was assessed by CCK-8 assay, and scratch-wound-healing assays were performed to evaluate cell-migration capacity. hSCAPs were then cultured in osteogenic medium supplemented with iRoot SP extracts. Alkaline phosphatase (ALP) activity assay was used to evaluate ALP enzyme levels. Alizarin red staining and cetylpyridinium chloride (CPC) assays were performed to assess calcified-nodule formation and matrix-calcium accumulation of hSCAPs. The mRNA and protein expression levels of the osteogenic markers OCN, OSX, Runx2, and DSPP were determined by qRT-PCR and Western blotting. The data were analyzed using one-way ANOVA and LSD-t tests.

RESULTS

iRoot SP at low concentrations (2, 0.2, and 0.02 mg/mL) is nontoxic to hSCAPs. iRoot SP at concentrations of 0.02 and 0.2 mg/mL significantly increases cell-migration capacity. In terms of osteogenic differentiation, 0.2 mg/mL iRoot SP promotes intracellular ALP activity and the formation of mineralized nodules. Moreover, the expression of osteogenic markers at the mRNA and protein levels are upregulated by iRoot SP.

CONCLUSION

iRoot SP is an effective filling material for periapical bone regeneration.

Micro-Computed Tomography Analysis on Administration of Mesenchymal Stem Cells - Bovine Teeth Scaffold Composites for Alveolar Bone Tissue Engineering

The tissue engineering approach for periodontal tissue regeneration using a combination of stem cells and scaffold has been vastly developed. Mesenchymal Stem Cells (MSCs) seeded with Bovine Teeth Scaffold (BTSc) can repair alveolar bone damage in periodontitis cases. The alveolar bone regeneration process was analyzed by micro-computed tomography (µ-CT) to observe the structure of bone growth and to visualize the scaffold in 3-Dimensional (3D). The purpose of this study is to analyze alveolar bone regeneration by µ-CT following the combination of MSCs and bovine teeth scaffold (MSCs-BTSc) implantation in the Wistar rat periodontitis model. Methods. MSCs were cultured from adipose-derived mesenchymal stem cells of rats. BTSc was taken from bovine teeth and freeze-dried with a particle size of 150-355 µm. MSCs were seeded on BTSc for 24 hours and transplanted in a rat model of periodontitis. Thirty-five Wistar rats were made as periodontitis models with LPS induction from P. gingivalis injected to the buccal section of interproximal gingiva between the first and the second mandibular right-molar teeth for six weeks. There were seven groups (control group, BTSc group on day 7, BTSc group on day 14, BTSc group on day 28, MSCs-BTSc group on day 7, MSCs-BTSc group on day 14, MSCs-BTSc group on day 28). The mandibular alveolar bone was analyzed and visualized in 3D with µ-CT to observe any new bone growth. Statistical Analysis. Group data were subjected to the Kruskal Wallis test followed by the Mann-Whitney (p <0.05). The µ-CT qualitative analysis shows a fibrous structure, which indicates the existence of new bone regeneration. Quantitative analysis of the periodontitis model showed a significant difference between the control model and the model with the alveolar bone resorption (p <0.05). The bone volume and density measurements revealed that the MSCs-BTSc group on day 28 formed new bone compared to other groups (p <0.05). Administration of MSCs-BTSc combination has the potential to form new alveolar bone.

Comparative Proteomic and Metabolomic Analysis of Human Osteoblasts, Differentiated from Dental Pulp Stem Cells, Hinted Crucial Signaling Pathways Promoting Osteogenesis

Population aging has been a global trend for the last decades, which increases the pressure to develop new cell-based or drug-based therapies, including those that may cure bone diseases. To understand molecular processes that underlie bone development and turnover, we followed osteogenic differentiation of human dental pulp stem cells (DPSCs) using a specific induction medium. The differentiation process imitating in vivo osteogenesis is triggered by various signaling pathways and is associated with massive proteome and metabolome changes. Proteome was profiled by ultrahigh-performance liquid chromatography and comprehensively quantified by ion mobility-enhanced mass spectrometry. From 2667 reproducibly quantified and identified proteins, 432 were differentially abundant by strict statistic criteria. Metabolome profiling was carried out by nuclear magnetic resonance. From 27 detected metabolites, 8 were differentially accumulated. KEGG and MetaboAnalyst hinted metabolic pathways that may be involved in the osteogenic process. Enrichment analysis of differentially abundant proteins highlighted PPAR, FoxO, JAK-STAT, IL-17 signaling pathways, biosynthesis of thyroid hormones and steroids, mineral absorption, and fatty acid metabolism as processes with prominent impact on osteoinduction. In parallel, metabolomic data showed that aminoacyl-tRNA biosynthesis, as well as specific amino acids, likely promote osteodifferentiation. Targeted immunoassays validated and complemented omic results. Our data underlined the complexity of the osteogenic mechanism. Finally, we proposed promising targets for future validation in patient samples, a step toward the treatment of bone defects.

Three-dimensional Spheroid Culture Enhances Multipotent Differentiation and Stemness Capacities of Human Dental Pulp-derived Mesenchymal Stem Cells by Modulating MAPK and NF-kB Signaling Pathways

BACKGROUND

Three-dimensional (3D) culture of mesenchymal stem cells has become an important research and development topic. However, comprehensive analysis of human dental pulp-derived mesenchymal stem cells (DPSCs) in 3D-spheroid culture remains unexplored. Thus, we evaluated the cellular characteristics, multipotent differentiation, gene expression, and related-signal transduction pathways of DPSCs in 3D-spheroid culture via magnetic levitation (3DM), compared with 2D-monolayer (2D) and 3D-aggregate (3D) cultures.

METHODS

The gross morphology and cellular ultrastructure were observed in the 2D, 3D, and 3DM experimental groups using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Surface markers and trilineage differentiation were evaluated using flow cytometry and staining analysis. Quantitative reverse transcription-polymerase chain reaction and immunofluorescence staining (IF) were performed to investigate the expression of differentiation and stemness markers. Signaling transduction pathways were evaluated using western blot analysis.

RESULTS

The morphology of cell aggregates and spheroids was largely influenced by the types of cell culture plates and initial cell seeding density. SEM and TEM experiments confirmed that the solid and firm structure of spheroids was quickly formed in the 3DM-medium without damaging cells. In addition, these three groups all expressed multilineage differentiation capabilities and surface marker expression. The trilineage differentiation capacities of the 3DM-group were significantly superior to the 2D and 3D-groups. The osteogenesis, angiogenesis, adipogenesis, and stemness-related genes were significantly enhanced in the 3D and 3DM-groups. The IF analysis showed that the extracellular matrix expression, osteogenesis, and angiogenesis proteins of the 3DM-group were significantly higher than those in the 2D and 3D-groups. Finally, 3DM-culture significantly activated the MAPK and NF-kB signaling transduction pathways and ameliorated the apoptosis effects of 3D-culture.

CONCLUSIONS

This study confirmed that 3DM-spheroids efficiently enhanced the therapeutic efficiency of DPSCs.

CDR1as regulated by hnRNPM maintains stemness of periodontal ligament stem cells via miR-7/KLF4

CDR1as is a well‐identified circular RNA with regulatory roles in a variety of physiological processes. However, the effects of CDR1as on stemness of periodontal ligament stem cells (PDLSCs) and the underlying mechanisms remain unclear. In this study, we detect CDR1as in human PDLSCs, and subsequently demonstrate that CDR1as maintains PDLSC stemness. Knockdown of CDR1as decreases the expression levels of stemness‐related genes and impairs the cell's multi‐differentiation and cell migration abilities, while overexpression of CDR1as increases the expression levels of stemness‐related genes and enhances these abilities. Furthermore, our results indicate that the RNA‐binding protein hnRNPM directly interacts with CDR1as and regulates its expression in PDLSCs. In addition, we show that CDR1as promotes the expression of stemness‐related genes in PDLSCs by inhibiting miR‐7‐mediated suppression of KLF4 expression. Collectively, our results demonstrate that CDR1as participates in the molecular circuitry that regulates PDLSC stemness.

MiR-105 enhances osteogenic differentiation of hADSCs via the targeted regulation of SOX9

OBJECTIVE

To investigate whether miR-105 can regulate the osteogenic differentiation of human adipose-derived mesenchymal stem cells (hADSCs) by targeting SOX9.

METHODS

The hADSCs were grouped for subsequent transfection and induction of osteogenic differentiation as follows: control, miR-NC, miR-105 mimics, miR-105 inhibitors, SOX9, SOX9 siRNA, miR-105 mimics + SOX9 and miR-105 inhibitors + SOX9 siRNA groups. Next, hADSCs were stained for alkaline phosphatase (ALP), and Alizarin Red S staining (ARS) was performed. Osteogenic differentiation-related genes and miR-105 expression were assessed by qRT-PCR, while SOX9 protein expression was determined by Western blotting.

RESULTS

MiR-105 expression was increased and SOX9 protein expression was decreased during the osteogenic differentiation of hADSCs. A dual-luciferase reporter assay confirmed SOX9 to be a target gene of miR-105. Compared with the control group, the miR-105 mimics and SOX9 siRNA groups had elevated BMP2, OPN, OCN, BSP, Osx and Runx2 mRNA expression with reduced SOX9 expression, as well as increased ARS intensity and ALP activity. After transfection of miR-105 inhibitors/SOX9 into hADSCs, the results were the opposite. Overexpressing SOX9 reversed the effect of miR-105 in promoting the osteogenic differentiation of hADSCs.

CONCLUSION

MiR-105 could target SOX9 to improve the expression of osteogenic differentiation genes and thus enhance the osteogenic differentiation of hADSCs.

Calcium Hydroxide Increases Human Umbilical Cord Mesenchymal Stem Cells Expressions of Apoptotic Protease-Activating Factor-1, Caspase-3 and Caspase-9

Purpose

Calcium hydroxide is a gold standard dental material generally used for pulpal and periapical therapy including regenerative endodontic procedures because of its positive properties. However, evaluation about this material on stem cells is limited. Human umbilical cord mesenchymal stem cells (HUCMSCs) are potential to be used in regenerative therapy. Regenerative therapy needs a sustainable cell supply to maintain its regenerative capacity. The aim of this study was to ascertain the apoptosis result of calcium hydroxide on HUCMSCs through the expression of apoptotic protease-activating factor-1 (APAF-1), caspase-3, and caspase-9.

Materials and Methods

This study used a thawed frozen stock of passage 5 HUCMSCs, grown in minimum essential medium (MEM) alpha containing calcium hydroxide at concentration of 0.1 microgram/mL for 1, 3 and 7 days. Polyclonal antibody with fluorescence isothiocyanate (FITC) label was used to evaluate the expressions. APAF-1, caspase-3, and caspase-9 expressions were recorded and compared on every observation day using fluorescence microscope. Analysis of variance was performed to analyze the significance among the results of treatment groups. The results were concluded significant if p<0.05.

Results

The addition of calcium hydroxide in MEM alpha medium increases HUCMSCs expression of APAF-1, caspase-3 and caspase-9 significantly, compared to the control group without calcium hydroxide (p<0.05) in all the times. Day 1 showed the lowest increase followed by higher expressions on day 3 and day 7.

Conclusion

HUCMSCs express increased APAF-1, caspase-3 and caspase-9 after in-vitro calcium hydroxide exposure. This should be considered when using calcium hydroxide on HUCMSCs for regenerative procedures with regard to other positive properties.

Role and application of stem cells in dental regeneration: A comprehensive overview

Recently, a growing attention has been observed toward potential advantages of stem cell (SC)-based therapies in regenerative treatments. Mesenchymal stem/stromal cells (MSCs) are now considered excellent candidates for tissue replacement therapies and tissue engineering. Autologous MSCs importantly contribute to the state-of-the-art clinical strategies for SC-based alveolar bone regeneration. The donor cells and immune cells play a prominent role in determining the clinical success of MSCs therapy. In line with the promising future that stem cell therapy has shown for tissue engineering applications, dental stem cells have also attracted the attention of the relevant researchers in recent years. The current literature review aims to survey the variety and extension of SC-application in tissue-regenerative dentistry. In this regard, the relevant English written literature was searched using keywords: "tissue engineering", "stem cells", "dental stem cells", and "dentistry strategies". According to the available database, SCs application has become increasingly widespread because of its accessibility, plasticity, and high proliferative ability. Among the growing recognized niches and tissues containing higher SCs, dental tissues are evidenced to be rich sources of MSCs. According to the literature, dental SCs are mostly present in the dental pulp, periodontal ligament, and dental follicle tissues. In this regard, the present review has described the recent findings on the potential of dental stem cells to be used in tissue regeneration.

Distinct Osteogenic Potentials of BMP-2 and FGF-2 in Extramedullary and Medullary Microenvironments

Bone morphogenetic protein-2 (BMP-2) and fibroblast growth factor-2 (FGF-2) have been regarded as the major cytokines promoting bone formation, however, several studies have reported unexpected results with failure of bone formation or bone resorption of these growth factors. In this study, BMP-2 and FGF-2 adsorbed into atellocollagen sponges were transplanted into bone defects in the bone marrow-scarce calvaria (extramedullary environment) and bone marrow-abundant femur (medullary environment) for analysis of their in vivo effects not only on osteoblasts, osteoclasts but also on bone marrow cells. The results showed that BMP-2 induced high bone formation in the bone marrow-scarce calvaria, but induced bone resorption in the bone marrow-abundant femurs. On the other hand, FGF-2 showed opposite effects compared to those of BMP-2. Analysis of cellular dynamics revealed numerous osteoblasts and osteoclasts present in the newly-formed bone induced by BMP-2 in calvaria, but none were seen in either control or FGF-2-transplanted groups. On the other hand, in the femur, numerous osteoclasts were observed in the vicinity of the BMP-2 pellet, while a great number of osteoblasts were seen near the FGF-2 pellets or in the control group. Of note, FCM analysis showed that both BMP-2 and FGF-2 administrated in the femur did not significantly affect the hematopoietic cell population, indicating a relatively safe application of the two growth factors. Together, these results indicate that BMP-2 could be suitable for application in extramedullary bone regeneration, whereas FGF-2 could be suitable for application in medullary bone regeneration.

Examining the Characteristics and Applications of Mesenchymal, Induced Pluripotent, and Embryonic Stem Cells for Tissue Engineering Approaches across the Germ Layers

The field of regenerative medicine utilizes a wide array of technologies and techniques for repairing and restoring function to damaged tissues. Among these, stem cells offer one of the most potent and promising biological tools to facilitate such goals. Implementation of mesenchymal stem cells (MSCs), induced pluripotent stem cells (iPSCs), and embryonic stem cells (ESCs) offer varying advantages based on availability and efficacy in the target tissue. The focus of this review is to discuss characteristics of these three subset stem cell populations and examine their utility in tissue engineering. In particular, the development of therapeutics that utilize cell-based approaches, divided by germinal layer to further assess research targeting specific tissues of the mesoderm, ectoderm, and endoderm. The combinatorial application of MSCs, iPSCs, and ESCs with natural and synthetic scaffold technologies can enhance the reparative capacity and survival of implanted cells. Continued efforts to generate more standardized approaches for these cells may provide improved study-to-study variations on implementation, thereby increasing the clinical translatability of cell-based therapeutics. Coupling clinically translatable research with commercially oriented methods offers the potential to drastically advance medical treatments for multiple diseases and injuries, improving the quality of life for many individuals.

Bone regeneration capacities of alveolar bone mesenchymal stem cells sheet in rabbit calvarial bone defect

Mesenchymal stem cells sheets have been verified as a promising non-scaffold strategy for bone regeneration. Alveolar bone marrow mesenchymal stem cells, derived from neural crest, have the character of easily obtained and strong multi-differential potential. However, the bone regenerative features of alveolar bone marrow mesenchymal stem cells sheets in the craniofacial region remain unclear. The purpose of the present study was to compare the osteogenic differentiation and bone defect repairment characteristics of bone marrow mesenchymal stem cells sheets derived from alveolar bone (alveolar bone marrow mesenchymal stem cells) and iliac bone (Lon-bone marrow mesenchymal stem cells) in vitro and in vivo. Histology character, osteogenic differentiation, and osteogenic gene expression of human alveolar bone marrow mesenchymal stem cells and Lon-bone marrow mesenchymal stem cells were compared in vitro. The cell sheets were implanted in rabbit calvarial defects to evaluate tissue regeneration characteristics. Integrated bioinformatics analysis was used to reveal the specific gene and pathways expression profile of alveolar bone marrow mesenchymal stem cells. Our results showed that alveolar bone marrow mesenchymal stem cells had higher osteogenic differentiation than Lon-bone marrow mesenchymal stem cells. Although no obvious differences were found in the histological structure, fibronectin and integrin β1 expression between them, alveolar-bone marrow mesenchymal stem cells sheet exhibited higher mineral deposition and expression levels of osteogenic marker genes. After being transplanted in the rabbit calvarial defects area, the results showed that greater bone volume and trabecular thickness regeneration were found in bone marrow mesenchymal stem cells sheet group compared to Lon-bone marrow mesenchymal stem cells group at both 4 weeks and 8 weeks. Finally, datasets of bone marrow mesenchymal stem cells versus Lon-bone marrow mesenchymal stem cells, and periodontal ligament mesenchymal stem cells (another neural crest derived mesenchymal stem cells) versus umbilical cord mesenchymal stem cells were analyzed. Total 71 differential genes were identified by overlap between the 2 datasets. Homeobox genes, such as LHX8, MKX, PAX9, MSX, and HOX, were identified as the most significantly changed and would be potential specific genes in neural crest mesenchymal stem cells. In conclusion, the Al-bone marrow mesenchymal stem cells sheet-based tissue regeneration appears to be a promising strategy for craniofacial defect repair in future clinical applications.

Current Trends in Research on Bone Regeneration: A Bibliometric Analysis

Background

Bone regeneration is a frequent research topic in clinical studies, but macroscopic studies on the clinical application of bone regeneration are rare. We conducted a bibliometric analysis, using international databases, to explore the clinical application and mechanism of bone regeneration, to highlight the relevant research hotspots and prospects. Material and Methods. Scientific reports on bone regeneration published during 2009–2019 were retrieved from PubMed. VOSviewer for cooccurrence keywords and authorship analysis. BICOMB software was used to retrieve high-frequency words and construct a text/coword matrix. The matrix was inputted into gCLUTO software, managed by biclustering analysis, in order to identify hotspots, which could achieve mountain and matrix visualizations. The matrix was also analyzed by using Ucinet 6 software for social network analysis. A strategic diagram was used for further analysis of the research hotspots of bone regeneration by “SCIMAT” software. We searched the Web of Science for relevant articles.

Results

Eighty-nine high-frequency major MeSH terms were obtained from 10237 articles and were divided into 5 clusters. We generated a network visualization map, an overlay visualization mountain map, and a social network diagram. Then, the MeSH terms were subdivided into 7 categories according to each diagram; current research hotspots were identified as scaffold, drug effect, osseointegration in dental implant, guided bone regeneration, factors impacting bone regeneration, treatment of bone and tissue loss, and bone regeneration in dental implants.

Conclusion

BICOMB, VOSviewer, and other bibliometric tools revealed that dental implants, scaffolds, and factors impacting bone regeneration are hot research topics, while scaffolds also hold promise from the perspective of bone tissue regeneration.

Cervicovertebral anomalies and/or normal variants in patients with congenitally bilateral absent maxillary lateral incisors

OBJECTIVE

To determine whether there is a relationship between congenitally bilaterally absent maxillary lateral incisors (BAMLIs) and skeletal anomalies and/or normal variants.

MATERIALS AND METHODS

The records of 86 patients (62 girls, 24 boys; age 12-17 years) with congenitally BAMLIs and 86 patients (55 girls, 34 boys; age 13-18 years) without any dental or skeletal anomalies were collected and evaluated retrospectively. The study was based on the evaluation of lateral cephalometric and orthopantomographic radiographs. Posterior arch deficiency of the atlas bone (PADA); atlanto-occipital ligament calcification, known as "ponticulus posticus" (PP); and interclinoid ligament calcification, known as "sella turcica bridging" were recorded for each participant. Pearson χ2 and Fisher exact tests were used to evaluate and compare skeletal anomalies and/or normal variants between patients with BAMLIs and the control group.

RESULTS

The prevalence of cervicovertebral anomalies and/or normal variants seen in the lateral cephalometric radiographs was higher in patients with BAMLI than in the control group. The prevalence of PP was lower and that of PADA was higher in patients with BAMLIs than in the control group (P < .05).

CONCLUSION

The prevalence of PADA was increased and that of PP formation was decreased in patients with BAMLIs. There was a significant relationship between skeletal anomalies and/or normal variants.

Alveolar bone repair of rhesus monkeys by using BMP-2 gene and mesenchymal stem cells loaded three-dimensional printed bioglass scaffold

Over the past years, the study about bone tissue engineering in the field of regenerative medicine has been a main research topic. Using three-dimensional (3D) porous degradable scaffold complexed with mesenchymal stem cells (MSCs) and growth factor gene to improve bone tissue repair and regeneration has raised much interest. This study mainly evaluated the osteogenesis of alveolar bone defects of animal in the following experimental groups: sham-operated (SO), 3D printed bioglass (3D-BG), 3D-BG with BMP-2 gene loaded CS (3D-BG + BMP/CS) and 3D-BG with rhesus marrow bone MSCs and BMP/CS (3D-BG + BMP/CS + rBMSCs). Simulated human bone defect with critical size of 10 × 10 × 5 mm were established in quadrumana - rhesus monkeys, and in vivo osteogenesis was characterized by X-ray, micro-Computed Tomography (mCT) and history. Our results revealed that 3D-BG + rBMSCs + BMP/CS scaffold could improve bone healing best by showing its promote osteogenic properties in vivo. Considering the great bone repair capacity of 3D-BG + BMP/CS + rBMSCs in humanoid primate rhesus monkeys, it could be a promising therapeutic strategy for surgery trauma or accidents, especially for alveolar bones defects.

Adult Stem Cells for Bone Regeneration and Repair

The regeneration of bone fractures, resulting from trauma, osteoporosis or tumors, is a major problem in our super-aging society. Bone regeneration is one of the main topics of concern in regenerative medicine. In recent years, stem cells have been employed in regenerative medicine with interesting results due to their self-renewal and differentiation capacity. Moreover, stem cells are able to secrete bioactive molecules and regulate the behavior of other cells in different host tissues. Bone regeneration process may improve effectively and rapidly when stem cells are used. To this purpose, stem cells are often employed with biomaterials/scaffolds and growth factors to accelerate bone healing at the fracture site. Briefly, this review will describe bone structure and the osteogenic differentiation of stem cells. In addition, the role of mesenchymal stem cells for bone repair/regrowth in the tissue engineering field and their recent progress in clinical applications will be discussed.

Comparing the Osteogenic Potentials and Bone Regeneration Capacities of Bone Marrow and Dental Pulp Mesenchymal Stem Cells in a Rabbit Calvarial Bone Defect Model

The bone regeneration efficiency of bone marrow mesenchymal stem cells (BMSCs) and dental pulp mesenchymal stem cells (DPSCs) combined with xenografts in the craniofacial region remains unclear. Accordingly, this study commenced by comparing the cell morphology, cell proliferation, trilineage differentiation, mineral synthesis, and osteogenic gene expression of BMSCs and DPSCs in vitro. Four experimental groups (empty control, Bio-Oss only, Bio-Oss+BMSCs, and Bio-Oss+DPSCs) were then designed and implanted in rabbit calvarial defects. The BMSCs and DPSCs showed a similar morphology, proliferative ability, surface marker profile, and trilineage-differentiation potential in vitro. However, the BMSCs exhibited a higher mineral deposition and expression levels of osteogenic marker genes, including alkaline phosphatase (ALP), runt related transcription factor 2 (RUNX2), and osteocalcin (OCN). In the in vivo studies, the bone volume density in both MSC groups was significantly greater than that in the empty control or Bio-Oss only group. Moreover, the new bone formation and Collagen I / osteoprotegerin protein expressions of the scaffold+MSC groups were higher than those of the Bio-Oss only group. Finally, the Bio-Oss+BMSC and Bio-Oss+DPSC groups had a similar bone mineral density, new bone formation, and osteogenesis-related protein expression. Overall, the DPSCs seeded on Bio-Oss matched the bone regeneration efficacy of BMSCs in vivo and hence appear to be a promising strategy for craniofacial defect repair in future clinical applications.

Transforming Growth Factor-β3/Chitosan Sponge (TGF-β3/CS) Facilitates Osteogenic Differentiation of Human Periodontal Ligament Stem Cells

Periodontal disease is the main reason for tooth loss in adults. Tissue engineering and regenerative medicine are advanced technologies used to manage soft and hard tissue defects caused by periodontal disease. We developed a transforming growth factor-β3/chitosan sponge (TGF-β3/CS) to repair periodontal soft and hard tissue defects. We investigated the proliferation and osteogenic differentiation behaviors of primary human periodontal ligament stem cells (hPDLSCs) to determine the bioactivity and potential application of TGF-β3 in periodontal disease. We employed calcein-AM/propidium iodide (PI) double labeling or cell membranes (CM)-Dil labeling coupled with fluorescence microscopy to trace the survival and function of cells after implantation in vitro and in vivo. The mineralization of osteogenically differentiated hPDLSCs was confirmed by measuring alkaline phosphatase (ALP) activity and calcium content. The levels of COL I, ALP, TGF-βRI, TGF-βRII, and Pp38/t-p38 were assessed by western blotting to explore the mechanism of bone repair prompted by TGF-β3. When hPDLSCs were implanted with various concentrations of TGF-β3/CS (62.5-500 ng/mL), ALP activity was the highest in the TGF-β3 (250 ng/mL) group after 7 d (p < 0.05 vs. control). The calcium content in each group was increased significantly after 21 and 28 d (p < 0.001 vs. control). The optimal result was achieved by the TGF-β3 (500 ng/mL) group. These results showed that TGF-β3/CS promotes osteogenic differentiation of hPDLSCs, which may involve the p38 mitogen-activated protein kinase (MAPK) signaling pathway. TGF-β3/CS has the potential for application in the repair of incomplete alveolar bone defects.

Bone Repair and Regenerative Biomaterials: Towards Recapitulating the Microenvironment

Biomaterials and tissue engineering scaffolds play a central role to repair bone defects. Although ceramic derivatives have been historically used to repair bone, hybrid materials have emerged as viable alternatives. The rationale for hybrid bone biomaterials is to recapitulate the native bone composition to which these materials are intended to replace. In addition to the mechanical and dimensional stability, bone repair scaffolds are needed to provide suitable microenvironments for cells. Therefore, scaffolds serve more than a mere structural template suggesting a need for better and interactive biomaterials. In this review article, we aim to provide a summary of the current materials used in bone tissue engineering. Due to the ever-increasing scientific publications on this topic, this review cannot be exhaustive; however, we attempted to provide readers with the latest advance without being redundant. Furthermore, every attempt is made to ensure that seminal works and significant research findings are included, with minimal bias. After a concise review of crystalline calcium phosphates and non-crystalline bioactive glasses, the remaining sections of the manuscript are focused on organic-inorganic hybrid materials.

Clinical application of mesenchymal stem cells in periodontal regeneration: A systematic review and meta-analysis

OBJECTIVE

To evaluate the potential efficacy of mesenchymal stem cells (MSCs) in periodontal regeneration in humans on the following main outcomes: clinical attachment level (CAL), probing depth (PD), and gingival recession (GR).

BACKGROUND

The clinical application of stem cells in periodontal regeneration has begun in recent years, but clinical practices are not yet standardized and no recommendations are available at this time.

METHODS

Electronic database searches and hand searches were conducted. All types of studies, case series, and case reports were qualitatively described. Double-blind randomized controlled trials (RCTs) evaluating MSCs in periodontal regeneration were included in a meta-analysis if they compared administration of MSCs vs application of stem cell-free therapy in the control group, in healthy patients with periodontal defects, with a minimum of three mo of follow-up.

RESULTS

Fifteen reports were included in qualitative analysis, involving 123 patients and 158 periodontal defects. Only two small RCTs at high risk of bias, with a total of 59 patients and 70 periodontal defects, were included in the meta-analysis. A small but significant difference between test and control groups was found for CAL at three mo (-0.90 mm, 95% CI [-1.51; -0.29]), but not for PD and GR.

CONCLUSION

Low-quality evidence suggests that MSC-based therapy may have a small impact on periodontal regeneration. However, due to the monocentric character, the small sample size, and potential heterogeneity across the two included RCTs, these results must not be considered as definitive. High-quality RCTs are needed before any clinical use of MSCs in periodontal regeneration.

Dual delivery of encapsulated BM-MSCs and BMP-2 improves osteogenic differentiation and new bone formation

Stem cell-based therapies provide a promising approach for bone repair. In the present work, we developed a novel 3D vehicle system for dual-delivery of encapsulated bone marrow mesenchymal stem cells (BM-MSCs) and bone morphogenetic protein-2 (BMP-2) for treatment of large bone defects. The vehicle system consists of sodium alginate microcapsules and polylactic acid (PLLA) microspheres. BM-MSCs are encapsulated in the microcapsules, and BMP-2 proteins are encapsulated in the PLLA microspheres. This vehicle system acted as a multicore structure for sustained release of BMP-2, which enabled pulsed dosing induction of osteogenic differentiation of the co-embedded BM-MSCs. in vitro experiments showed that the loaded BMP-2 was constitutively released up to 30 days. Bioactivity of the incorporated BMP-2 in the microspheres was preserved and osteogenic differentiation of the BM-MSCs in the microcapsules was improved. In vivo, osteogenesis studies demonstrated that satisfactory degree of repair of a rat calvarial defect was achieved with the delivery of either encapsulated BM-MSCs alone or encapsulated BMP-2 alone. Transplantation of encapsulated both BM-MSCs and BMP-2 exhibited the greatest repair potential following 4- or 8-weeks treatment. In conclusion, microencapsulation of BM-MSCs and BMP-2 promoted the maturity of newly generated bone and improved new bone formation. Transplantation of BM-MSCs and BMP-2 in our novel 3-D vehicle system is a promising strategy for regenerative therapies of large bone defects.

IL-33 guides osteogenesis and increases proliferation and pluripotency marker expression in dental stem cells

Objectives

Soluble IL‐33 (interleukin (IL)‐1‐like cytokine) acts as endogenous alarm signal (alarmin). Since alarmins, besides activating immune system, act to restore tissue homeostasis, we investigated whether IL‐33 exerts beneficial effects on oral stem cell pull.

Materials and Methods

Clonogenicity, proliferation, differentiation and senescence of stem cells derived from human periodontal ligament (PDLSCs) and dental pulp (DPSCs) were determined after in vitro exposure to IL‐33. Cellular changes were detected by flow cytometry, Western blot, immunocytochemistry and semiquantitative RT‐PCR.

Results

IL‐33 stimulated proliferation, clonogenicity and expression of pluripotency markers, OCT‐4, SOX‐2 and NANOG, but it inhibited ALP activity and mineralization in both PDLSCs and DPSCs. Higher Ki67 expression and reduced β‐galactosidase activity in IL‐33‐treated cells were demonstrated, whereas these trends were more conspicuous in osteogenic medium. However, after 7‐day IL‐33 pretreatment, differentiation capacity of IL‐33‐pretreated cells was retained, and increased ALP activity was observed in both cell types. Results showed that IL‐33 regulates NF‐κB and β‐catenin signalling, indicating the association of these molecules with changes observed in IL‐33‐treated PDLSCs and DPSCs, particularly their proliferation, pluripotency‐associated marker expression and osteogenesis.

Conclusions

IL‐33 treatment impairs osteogenesis of PDLSCs and DPSCs, while increases their clonogenicity, proliferation and pluripotency marker expression. After exposure to IL‐33, osteogenic capacity of cells stayed intact. NF‐κB and β‐catenin are implicated in the effects achieved by IL‐33 in PDLSCs and DPSCs.

Computational approaches for predicting key transcription factors in targeted cell reprogramming (Review)

There is a need for specific cell types in regenerative medicine and biological research. Frequently, specific cell types may not be easily obtained or the quantity obtained is insufficient for study. Therefore, reprogramming by the direct conversion (transdifferentiation) or re‑induction of induced pluripotent stem cells has been used to obtain cells expressing similar profiles to those of the desired types. Therefore, a specific cocktail of transcription factors (TFs) is required for induction. Nevertheless, identifying the correct combination of TFs is difficult. Although certain computational approaches have been proposed for this task, their methods are complex, and corresponding implementations are difficult to use and generalize for specific source or target cell types. In the present review four computational approaches that have been proposed to obtain likely TFs were compared and discussed. A simplified view of the computational complexity of these methods is provided that consists of three basic ideas: i) The definition of target and non‑target cell types; ii) the estimation of candidate TFs; and iii) filtering candidates. This simplified view was validated by analyzing a well‑documented cardiomyocyte differentiation. Subsequently, these reviewed methods were compared when applied to an unknown differentiation of corneal endothelial cells. The generated results may provide important insights for laboratory assays. Data and computer scripts that may assist with direct conversions in other cell types are also provided.

Semaphorin 3A receptor inhibitor as a novel therapeutic to promote innervation of bioengineered teeth

The sensory innervation of the dental pulp is essential for tooth function and protection. It is mediated by axons originating from the trigeminal ganglia and is spatio-temporally regulated. We have previously shown that the innervation of bioengineered teeth can be achieved only under immunosuppressive conditions. The aim of this study was to develop a model to determine the role of Semaphorin 3A (Sema3A) in the innervation of bioengineered teeth. We first analysed innervation of the dental pulp of mandibular first molars in newborn (postnatal day 0: PN0) mice deficient for Sema3A (Sema3A^-/- ), a strong inhibitor of axon growth. While at PN0, axons detected by immunostaining for peripherin and NF200 were restricted to the peridental mesenchyme in Sema3A^+/+ mice, they entered the dental pulp in Sema3A^-/- mice. Then, we have implanted cultured teeth obtained from embryonic day-14 (E14) molar germs of Sema3A^-/- mice together with trigeminal ganglia. The dental pulps of E14 cultured and implanted Sema3A^-/- teeth were innervated, whereas the axons did not enter the pulp of E14 Sema3A^+/+ cultured and implanted teeth. A "Membrane Targeting Peptide NRP1," suppressing the inhibitory effect of Sema3A, has been previously identified. The injection of this peptide at the site of implantation allowed the innervation of the dental pulp of bioengineered teeth obtained from E14 dental dissociated mesenchymal and epithelial cells reassociations of ICR mice. In conclusion, these data show that inhibition of only one axon repellent molecule, Sema3A, allows for pulp innervation of bioengineered teeth.

Role of the Inferior Alveolar Nerve in Rodent Lower Incisor Stem Cells

In developing teeth, the sequential and reciprocal interactions between epithelial and mesenchymal tissues promote stem/progenitor cell differentiation. However, the origin of the stem/progenitor cells has been the subject of considerable debate. According to recent studies, mesenchymal stem cells originate from periarterial cells and are regulated by neurons in various organs. The present study examined the role of innervation in tooth development and rodent incisor stem/progenitor cell homeostasis. Rodent incisors continuously grow throughout their lives, and the lower incisors are innervated by the inferior alveolar nerve (IAN). In this study, we resected the IAN in adult rats, and the intact contralateral side served as a nonsurgical control. Sham control rats received the same treatment as the resected rats, except for the resection process. The extent of incisor eruption was measured, and both mesenchymal and epithelial stem/progenitor cells were visualized and compared between the IAN-resected and sham-operated groups. One week after surgery, the IAN-resected incisors exhibited a chalky consistency, and the eruption rate was decreased. Micro–computed tomography and histological analyses performed 4 wk after surgery revealed osteodentin formation, disorganized ameloblast layers, and reduced enamel thickness in the IAN-resected incisors. Immunohistochemical analysis revealed a reduction in the CD90- and LRIG1-positive mesenchymal cell ratio in the IAN-resected incisors. However, the p40-positive epithelial stem/progenitor cell ratio was comparable between the 2 groups. Thus, mesenchymal stem/progenitor cell homeostasis is more related to IAN innervation than to epithelial stem/progenitor cells. Furthermore, sensory nerve innervation influences subsequent incisor growth and formation.