Local delivery of recombinant human FGF7 enhances bone formation in rat mandible defects

Whole genome sequencing in families with oligodontia

BACKGROUND/OBJECTIVES

Tooth agenesis (TA) is among the most common malformations in humans. Although several causative mutations have been described, the genetic cause often remains elusive. Here, we test whether whole genome sequencing (WGS) could bridge this diagnostic gap.

METHODS

In four families with TA, we assessed the dental phenotype using the Tooth Agenesis Code after intraoral examination and radiographic and photographic documentation. We performed WGS of index patients and subsequent segregation analysis.

RESULTS

We identified two variants of uncertain significance (a potential splice variant in PTH1R, and a 2.1 kb deletion abrogating a non-coding element in FGF7) and three pathogenic variants: a novel frameshift in the final exon of PITX2, a novel deletion in PAX9, and a known nonsense variant in WNT10A. Notably, the FGF7 variant was found in the patient, also featuring the WNT10A variant. While mutations in PITX2 are known to cause Axenfeld-Rieger syndrome 1 (ARS1) predominantly featuring ocular findings, accompanied by dental malformations, we found the PITX2 frameshift in a family with predominantly dental and varying ocular findings.

CONCLUSION

Severe TA predicts a genetic cause identifiable by WGS. Final exon PITX2 frameshifts can cause a predominantly dental form of ARS1.

Primer on fibroblast growth factor 7 (FGF 7)

Fibroblast growth factor 7 (FGF7), also known as keratinocyte growth factor (KGF), is an important member of the FGF family that is mainly expressed by cells of mesenchymal origin while affecting specifically epithelial cells. Thus, FGF7 is widely expressed in diverse tissues, especially in urinary system, gastrointestinal tract (GI-tract), respiratory system, skin, and reproductive system. By interacting specifically with FGFR2-IIIb, FGF7 activates several downstream signal pathways, including Ras, PI3K-Akt, and PLCs. Previous studies of FGF7 mutants also have implicated its roles in various biological processes including development of essential organs and tissue homeostasis in adults. Moreover, more publications have reported that FGF7 and/or FGF7/FGFR2-IIIb-associated signaling pathway are involved in the progression of various heritable or acquired human diseases: heritable conditions like autosomal dominant polycystic kidney disease (ADPKD) and non-syndromic cleft lip and palate (NS CLP), where it promotes cyst formation and affects craniofacial development, respectively; acquired non-malignant diseases such as chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), mucositis, osteoarticular disorders, and metabolic diseases, where it influences inflammation, repair, and metabolic control; and tumorigenesis and malignant diseases, including benign prostatic hyperplasia (BPH), prostate cancer, gastric cancer, and ovarian cancer, where it enhances cell proliferation, invasion, and chemotherapy resistance. Targeting FGF7 pathways holds therapeutic potential for managing these conditions, underscoring the need for further research to explore its clinical applications. Having more insights into the function and underlying molecular mechanisms of FGF7 is warranted to facilitate the development of effective treatments in the future. Here, we discuss FGF7 genomic structure, signal pathway, expression pattern during embryonic development and in adult organs and mutants along with phenotypes, as well as associated diseases.

Regulation mechanism of endochondral ossification in Rana zhenhaiensis during metamorphosis based on histomorphology and transcriptome analyses

Endochondral ossification plays a crucial role in the limb development of amphibians. This study explored the ossification sequence in the hindlimb of Rana zhenhaiensis tadpoles and the correlation between thyroid hormones (THs) and endochondral ossification via histomorphology and transcriptional analyses. Our results suggest that ossification of the femur and tibiofibula was initiated during the period of high THs activity (metamorphosis climax). In addition, the results of differentially expressed gene analyses in the hindlimb and tail showed that systemic factors, transcription factors, and locally secreted factors interacted with each other during the metamorphosis climax to regulate the occurrence of endochondral ossification. These results will enrich the morphological data of anurans and provide scientific reference for the evolutionary history of vertebrates.

[Role of Fibroblast Growth Factor 7 in Craniomaxillofacial Development]

Craniomaxillofacial development involves a series of highly ordered temporal-spatial cellular differentiation processes in which a variety of cell signaling factors, such as fibroblast growth factors, play important regulatory roles. As a classic fibroblast growth factor, fibroblast growth factor 7 (FGF7) serves a wide range of regulatory functions. Previous studies have demonstrated that FGF7 regulates the proliferation and migration of epithelial cells, protects them, and promotes their repair. Furthermore, recent findings indicate that epithelial cells are not the only ones subjected to the broad and powerful regulatory capacity of FGF7. It has potential effects on skeletal system development as well. In addition, FGF7 plays an important role in the development of craniomaxillofacial organs, such as the palate, the eyes, and the teeth. Nonetheless, the role of FGF7 in oral craniomaxillofacial development needs to be further elucidated. In this paper, we summarized the published research on the role of FGF7 in oral craniomaxillofacial development to demonstrate the overall understanding of FGF7 and its potential functions in oral craniomaxillofacial development.

Fibroblast growth factor 7 protects osteoblasts against oxidative damage through targeting mitochondria

The pathophysiology of osteoporosis is significantly influenced by the impaired functioning of osteoblasts, which is particularly caused by oxidative stress. Nevertheless, the underlying mechanisms responsible for this phenomenon are still not well understood. The objective of this study was to elucidate the impact of fibroblast growth factor 7 (FGF7) on the behavior of osteoblasts under conditions of oxidative stress. The osteoblast-like MC3T3 cells were pretreated with recombinant FGF7 in the presence of oxidative stress induced by hydrogen peroxide (H2 O2 ). We first provided the evidence that the endogenous FGF7 was significantly increased in osteoblasts in response to the increased H2 O2 levels. Recombined FGF7 demonstrated a remarkable capacity to resist the detrimental effects of H2 O2 -induced oxidative stress, including the increase in cell apoptosis, decrease in osteoblast viability, and impairment in osteogenic differentiation capacity, on osteoblasts. Furthermore, we extensively explored the mechanism underlying these protective effects and discovered a remarkable modulation of reactive oxygen species (ROS) homeostasis in H2 O2 -treated cells following the pronounced expression of FGF7, which significantly differed from the control group. Additionally, we observed that FGF7 exerted partial preservation on both the morphology and function of mitochondria when exposed to oxidative stress conditions. Furthermore, FGF7 exhibited the ability to enhance the activation of the p38/MAPK signaling pathway while concurrently suppressing the JNK/MAPK signaling pathway in response to oxidative stress. These results underscore the promising role and underlying mechanisms of FGF7 in preserving osteoblast homeostasis in the face of oxidative stress.

Single-cell RNA sequencing analysis of the temporomandibular joint condyle in 3 and 4-month-old human embryos

BACKGROUND

The temporomandibular joint (TMJ) is a complex joint consisting of the condyle, the temporal articular surface, and the articular disc. Functions such as mastication, swallowing and articulation are accomplished by the movements of the TMJ. To date, the TMJ has been studied more extensively, but the types of TMJ cells, their differentiation, and their interrelationship during growth and development are still unclear and the study of the TMJ is limited. The aim of this study was to establish a molecular cellular atlas of the human embryonic temporomandibular joint condyle (TMJC) by single-cell RNA sequencing, which will contribute to understanding and solving clinical problems.

RESULTS

Human embryos at 3 and 4 months of age are an important stage of TMJC development. We performed a comprehensive transcriptome analysis of TMJC tissue from human embryos at 3 and 4 months of age using single-cell RNA sequencing. A total of 16,624 cells were captured and the gene expression profiles of 15 cell clusters in human embryonic TMJC were determined, including 14 known cell types and one previously unknown cell type, "transition state cells (TSCs)". Immunofluorescence assays confirmed that TSCs are not the same cell cluster as mesenchymal stem cells (MSCs). Pseudotime trajectory and RNA velocity analysis revealed that MSCs transformed into TSCs, which further differentiated into osteoblasts, hypertrophic chondrocytes and tenocytes. In addition, chondrocytes (CYTL1^high + THBS1^high) from secondary cartilage were detected only in 4-month-old human embryonic TMJC.

CONCLUSIONS

Our study provides an atlas of differentiation stages of human embryonic TMJC tissue cells, which will contribute to an in-depth understanding of the pathophysiology of the TMJC tissue repair process and ultimately help to solve clinical problems.

The role of fibroblast growth factor 7 in cartilage development and diseases

Fibroblast growth factor 7 (FGF7), also known as keratinocyte growth factor (KGF), shows a crucial biological significance in tissue development, wound repair, tumorigenesis, and immune reconstruction. In the skeletal system, FGF7 directs the cellular synaptic extension of individual cells and facilities functional gap junction intercellular communication of a collective of cells. Moreover, it promotes the osteogenic differentiation of stem cells via a cytoplasmic signaling network. For cartilage, reports have indicated the potential role of FGF7 on the regulation of key molecules Cx43 in cartilage and Runx2 in hypertrophic cartilage. However, the molecular mechanism of FGF7 in chondrocyte behaviors and cartilage pathological process remains largely unknown. In this review, we systematically summarize the recent biological function of FGF7 and its regulatory role on chondrocytes and cartilage diseases, especially through the hot focus of two key molecules, Runx2 and Cx43. The current knowledge of FGF7 on the physiological and pathological processes of chondrocytes and cartilage provides us new cues for wound repair of cartilage defect and therapy of cartilage diseases.

Differential expression and effect analysis of lncRNA-mRNA in congenital pseudarthrosis of the tibia

Background: To analyze the lncRNA-mRNA differential expression and co-expression network of periosteal stem cells (PSCs) from congenital pseudarthrosis of the tibia (CPT) and normal patients, and to explore the role of key lncRNAs. Methods: Differentially expressed lncRNAs and mRNAs in PSCs were obtained by sequencing, and biological functions of differentially expressed mRNAs were detected by gene ontology (GO), Kyoto encyclopedia of genes and genomes (KEGG) pathway and protein -protein interaction (PPI) analysis. The co-expression network of lncRNA-mRNA was constructed by correlation analysis of differentially expressed lncRNAs and mRNAs, and the key lncRNAs were screened according to the connectivity degree. After that, the cis-regulated target genes of differential expressed lncRNAs and mRNAs were predicted. Results: A total of 194 differentially expressed lncRNAs were identified, including 73 upregulated and 121 downregulated genes. A total of 822 differentially expressed mRNAs were identified, including 311 upregulated and 511 downregulated genes. GO, KEGG and PPI enrichment analysis showed that the regulatory function of differentially expressed mRNAs were mainly gathered in skeletal system development and tissue morphogenesis. The co-expression network with 226 nodes and 3,390 edges was constructed based on correlation analysis. A total of 10 key lncRNAs, including FAM227B, POM121L9P, AF165147 and AC103702, were screened according to connectivity degree. Prediction of target genes indicated that FAM227B-FGF7 and AC103702-HOXB4/5/6 may play an important role in the pathogenesis of CPT. Conclusion: A total of 10 key lncRNAs, including FAM227B, POM121L9P, AF165147, and AC103702, occupy the core position in the co-expression network, suggesting that these lncRNAs and their target genes may play an important role in the pathogenesis of CPT.

TET enzymes regulate skeletal development through increasing chromatin accessibility of RUNX2 target genes

The Ten-eleven translocation (TET) family of dioxygenases mediate cytosine demethylation by catalyzing the oxidation of 5-methylcytosine (5mC). TET-mediated DNA demethylation controls the proper differentiation of embryonic stem cells and TET members display functional redundancy during early gastrulation. However, it is unclear if TET proteins have functional significance in mammalian skeletal development. Here, we report that Tet genes deficiency in mesoderm mesenchymal stem cells results in severe defects of bone development. The existence of any single Tet gene allele can support early bone formation, suggesting a functional redundancy of TET proteins. Integrative analyses of RNA-seq, Whole Genome Bisulfite Sequencing (WGBS), 5hmC-Seal and Assay for Transposase-Accessible Chromatin (ATAC-seq) demonstrate that TET-mediated demethylation increases the chromatin accessibility of target genes by RUNX2 and facilities RUNX2-regulated transcription. In addition, TET proteins interact with RUNX2 through their catalytic domain to regulate cytosine methylation around RUNX2 binding region. The catalytic domain is indispensable for TET enzymes to regulate RUNX2 transcription activity on its target genes and to regulate bone development. These results demonstrate that TET enzymes function to regulate RUNX2 activity and maintain skeletal homeostasis.

Here the authors investigate the role of the TET family of DNA demethylases in mammalian skeletal development. They find that loss of TETs leads to hypermethylation that results in decreased chromatin accessibility of RUNX2 target genes, repressing osteoblast differentiation and leading to skeletal defects in mouse such as short limbs.

Effect of miR-381-3p/FGF7 axis on the osteogenic differentiation of bone marrow mesenchymal stem cells through MEK/ERK signaling pathway

Although microRNAs (miRNAs) exert an important role in the osteogenesis of mesenchymal stem cells (MSCs), the effect of miR-381-3p on the osteogenic differentiation in MBD‑MSCs is still unclear. The BMMSCs from patients with MBD (MBD‑MSC) or normal participants (Normal‑MSC) were isolated and induced to differentiation with dexamethasone. BMMSCs were transfected with miR-381-3p mimic, miR-381-3p inhibitor, and FGF7 siRNA to regulate the expression of miR-381-3p or FGF7. The direct binding between miR-381-3p and FGF7 was predicted and confirmed by bioinformatics prediction and luciferase reporter assay. The effect of miR-381-3p on the osteogenic differentiation of BMMSCs was assessed by RT‑qPCR, alizarin Red S staining and western blot assays. Isolated BMMSCs showed the regular morphology, and were positive for CD44, CD90 and CD105 but negative for CD34 and CD45 markers. The calcium deposition and the relative mRNA expression levels of ALP, OC and OPN after induction were markedly enhanced. MiR-381-3p was upregulated in BMMSCs. Also, inhibition of miR-381-3p notably promoted osteogenic differentiation, vice versa. Besides, miR-381-3p could directly target FGF7 and negatively modulate the expression of FGF7. Moreover, inhibition of FGF7 attenuated the increase of the calcium deposition, and the relative mRNA expression of ALP, OC and OPN caused by the downregulation of miR-381-3p. In addition, the miR-381-3p inhibitor-induced the enhancement of the relative protein expressions of FGFR2, p-MEK and p-ERK1/2 were significantly reduced by the co-transfection of si-FGF7. Furthermore, the application of LY3214996, the inhibitor of ERK also verified these outcomes. MiR-381-3p directly targeting FGF7 modulated the osteogenic differentiation via MEK/ERK signaling pathway in BMMSCs.

Roles of the fibroblast growth factor signal transduction system in tissue injury repair

Following injury, tissue autonomously initiates a complex repair process, resulting in either partial recovery or regeneration of tissue architecture and function in most organisms. Both the repair and regeneration processes are highly coordinated by a hierarchy of interplay among signal transduction pathways initiated by different growth factors, cytokines and other signaling molecules under normal conditions. However, under chronic traumatic or pathological conditions, the reparative or regenerative process of most tissues in different organs can lose control to different extents, leading to random, incomplete or even flawed cell and tissue reconstitution and thus often partial restoration of the original structure and function, accompanied by the development of fibrosis, scarring or even pathogenesis that could cause organ failure and death of the organism. Ample evidence suggests that the various combinatorial fibroblast growth factor (FGF) and receptor signal transduction systems play prominent roles in injury repair and the remodeling of adult tissues in addition to embryonic development and regulation of metabolic homeostasis. In this review, we attempt to provide a brief update on our current understanding of the roles, the underlying mechanisms and clinical application of FGFs in tissue injury repair.

FGF7-induced E11 facilitates cell-cell communication through connexin43

Fibroblast growth factors (FGFs) include a large family of growth factors that play a critical role in maintaining bone homeostasis, but the specific role of its members such as FGF7 does not well understand. Osteoblasts are a kind of major cells essential for bone formation. Osteoblasts interact with one another to create the unique structure of osteons. The well-connected osteons constitute the cortical bone. As an early osteocyte marker that triggers actin cytoskeleton dynamics, E11 is essential for osteoblasts' dendrites formation. However, the upstream which regulates E11 is mainly unknown. The purpose of this study was to examine the influence of FGF7 on the expression and the distribution of E11 in osteoblasts, which mediated osteoblasts' processes formation and gap junctional intercellular communication (GJIC) partly through connexin43 (Cx43). We first demonstrated that FGF7 increased the expression of E11 in osteoblasts. We then showed that FGF7 promoted osteoblasts' dendrites elongation and functional gap junctions formation. Furthermore, E11 interacted directly with Cx43 in primary osteoblasts. MAPK pathway and PI3K-AKT pathway were involved in the effect of FGF7. Our results shed light on the unique role of FGF7 on osteoblasts, which may indicate that FGF7 plays a more significant role in the later stages of bone development and homeostasis.

Andrographolide promotes proliferative and osteogenic potentials of human placenta-derived mesenchymal stem cells through the activation of Wnt/β-catenin signaling

Introduction

The in vitro expansion and differentiation of mesenchymal stem cells derived from bone marrow (BM-hMSCs) are considered as potential therapeutic tools for clinical applications in bone tissue engineering and regenerative medicine. However, invasive sampling and reduction in number and proliferative capacity with age are the major limitations of BM-hMSCs. Recently, human placenta-derived MSCs (PL-hMSCs) obtained by a non-invasive procedure have attracted much interest. Attempts to increase the potential of PL-hMSCs would be an important paradigm in regenerative medicine. Herein, we examined the proliferative and osteogenic effect of andrographolide (AP) on PL-hMSCs.

Methods

Mesenchymal stem cells were isolated from full-term normal human placentas and were characterized before using. Cell cytotoxicity and proliferative effect of AP were examined by MTT and BrdU assay, respectively. The non-toxicity concentrations of AP were further assessed for osteogenic effect determined by alkaline phosphatase (ALP) expression and activity, alizarin red staining, and osteoblast-specific gene expressions. Screening of genes involved in osteogenic differentiation-related pathways modulated by AP was explored by a NanoString nCounter analysis.

Results

PL-hMSCs generated in this study met the MSC criteria set by the International Society of Cellular Therapy. The non-cytotoxic concentrations of AP on PL-hMSCs are up to 10 μM. The compound increased PL-hMSC proliferation concomitant with increases in Wnt/β-catenin level and activity. It also enhanced osteogenic differentiation in association with osteoblast-specific mRNA expression. Further, AP promoted bone formation and increased bone structural protein level, osteocalcin, in osteoblastic cells. Gene screening analysis showed the upregulation of genes related to Wnt/β-catenin, TGFβ/BMP, SMAD, and FGF signaling pathways.

Conclusion

We demonstrated, for the first time, the potential role of AP in promoting proliferation, osteogenic differentiation, and osteoblast bone formation of PL-hMSCs. This study suggests that AP may be an effective novel agent for the improvement of PL-hMSCs and stem cell-based therapy for bone regeneration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02312-x.

Osteogenic potential of the growth factors and bioactive molecules in bone regeneration

The growing need for treatment of the impaired bone tissue has resulted in the quest for the improvement of bone tissue regeneration strategies. Bone tissue engineering is trying to create bio-inspired systems with a coordinated combination of the cells, scaffolds, and bioactive factors to repair the damaged bone tissue. The scaffold provides a supportive matrix for cell growth, migration, and differentiation and also, acts as a delivery system for bioactive factors. Bioactive factors including a large group of cytokines, growth factors (GFs), peptides, and hormonal signals that regulate cellular behaviors. These factors stimulate osteogenic differentiation and proliferation of cells by activating the signaling cascades related to ossification and angiogenesis. GFs and bioactive peptides are significant parts of the bone tissue engineering systems. Besides, the use of the osteogenic potential of hormonal signals has been an attractive topic, particularly in osteoporosis-related bone defects. Due to the unstable nature of protein factors and non-specific effects of hormones, the engineering of scaffolds to the controlled delivery of these bioactive molecules has paramount importance. This review updates the growth factors, engineered peptides, and hormones that are used in bone tissue engineering systems. Also, discusses how these bioactive molecules may be linked to accelerating bone regeneration.

FGF/FGFR signaling in health and disease

Growing evidences suggest that the fibroblast growth factor/FGF receptor (FGF/FGFR) signaling has crucial roles in a multitude of processes during embryonic development and adult homeostasis by regulating cellular lineage commitment, differentiation, proliferation, and apoptosis of various types of cells. In this review, we provide a comprehensive overview of the current understanding of FGF signaling and its roles in organ development, injury repair, and the pathophysiology of spectrum of diseases, which is a consequence of FGF signaling dysregulation, including cancers and chronic kidney disease (CKD). In this context, the agonists and antagonists for FGF-FGFRs might have therapeutic benefits in multiple systems.

Systematic scoping review of mandibular bone tissue engineering

Tissue engineering is a promising alternative that may facilitate bony regeneration in small defects in compromised host tissue as well as large mandibular defects. This scoping systematic review was therefore designed to assess in vivo research on its use in the reconstruction of mandibular defects in animal models. A total of 4524 articles were initially retrieved using the search algorithm. After screening of the titles and abstracts, 269 full texts were retrieved, and a total of 72 studies included. Just two of the included studies employed osteonecrosis as the model of mandibular injury. All the rest involved the creation of a critical defect. Calcium phosphates, especially tricalcium phosphate and hydroxyapatite, were the scaffolds most widely used. All the studies that used a scaffold reported increased formation of bone when compared with negative controls. When combined with scaffolds, mesenchymal stem cells (MSC) increased the formation of new bone and improved healing. Various growth factors have been studied for their potential use in the regeneration of the maxillofacial complex. Bone morphogenic proteins (BMP) were the most popular, and all subtypes promoted significant formation of bone compared with controls. Whilst the studies published to date suggest a promising future, our review has shown that several shortfalls must be addressed before the findings can be translated into clinical practice. A greater understanding of the underlying cellular and molecular mechanisms is required to identify the optimal combination of components that are needed for predictable and feasible reconstruction or regeneration of mandibular bone. In particular, a greater understanding of the biological aspects of the regenerative triad is needed before we can to work towards widespread translation into clinical practice.

Macrophage MSR1 promotes BMSC osteogenic differentiation and M2-like polarization by activating PI3K/AKT/GSK3β/β-catenin pathway

Approximately 10% of bone fractures do not heal satisfactorily, leading to significant clinical and socioeconomic implications. Recently, the role of macrophages in regulating bone marrow stem cell (BMSC) differentiation through the osteogenic pathway during fracture healing has attracted much attention. Methods: The tibial monocortical defect model was employed to determine the critical role of macrophage scavenger receptor 1 (MSR1) during intramembranous ossification (IO) in vivo. The potential functions and mechanisms of MSR1 were explored in a co-culture system of bone marrow-derived macrophages (BMDMs), RAW264.7 cells, and BMSCs using qPCR, Western blotting, immunofluorescence, and RNA sequencing. Results: In this study, using the tibial monocortical defect model, we observed delayed IO in MSR1 knockout (KO) mice compared to MSR1 wild-type (WT) mice. Furthermore, macrophage MSR1 mediated PI3K/AKT/GSK3β/β-catenin signaling increased ability to promote osteogenic differentiation of BMSCs in the co-culture system. We also identified proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) as the target gene for macrophage MSR1-activated PI3K/AKT/GSK3β/β-catenin pathway in the co-culture system that facilitated M2-like polarization by enhancing mitochondrial oxidative phosphorylation. Conclusion: Our findings revealed a previously unrecognized function of MSR1 in macrophages during fracture repair. Targeting MSR1 might, therefore, be a new therapeutic strategy for fracture repair.

Application of a Bioactive/Bioresorbable Three-Dimensional Porous Uncalcined and Unsintered Hydroxyapatite/Poly-D/L-lactide Composite with Human Mesenchymal Stem Cells for Bone Regeneration in Maxillofacial Surgery: A Pilot Animal Study

A novel three-dimensional (3D) porous uncalcined and unsintered hydroxyapatite/poly-d/l-lactide (3D-HA/PDLLA) composite demonstrated superior biocompatibility, osteoconductivity, biodegradability, and plasticity, thereby enabling complex maxillofacial defect reconstruction. Mesenchymal stem cells (MSCs)-a type of adult stem cell-have a multipotent ability to differentiate into chondrocytes, adipocytes, and osteocytes. In a previous study, we found that CD90 (Thy-1, cluster of differentiation 90) and CD271 (low-affinity nerve growth factor receptor) double-positive cell populations from human bone marrow had high proliferative ability and differentiation capacity in vitro. In the present study, we investigated the utility of bone regeneration therapy using implantation of 3D-HA/PDLLA loaded with human MSCs (hMSCs) in mandibular critical defect rats. Microcomputed tomography (Micro-CT) indicated that implantation of a 3D-HA/PDLLA-hMSC composite scaffold improved the ability to achieve bone regeneration compared with 3D-HA/PDLLA alone. Compared to the sufficient blood supply in the mandibular defection superior side, a lack of blood supply in the inferior side caused delayed healing. The use of Villanueva Goldner staining (VG staining) revealed the gradual progression of the nucleated cells and new bone from the scaffold border into the central pores, indicating that 3D-HA/PDLLA loaded with hMSCs had good osteoconductivity and an adequate blood supply. These results further demonstrated that the 3D-HA/PDLLA-hMSC composite scaffold was an effective bone regenerative method for maxillofacial boney defect reconstruction.

Identification of Genes Differentially Expressed in Simvastatin-Induced Alveolar Bone Formation

Local delivery of simvastatin (SIM) has exhibited potential in preventing inflammation and limiting bone loss associated with experimental periodontitis. The primary aim of this study was to analyze transcriptome changes that may contribute to SIM's reduction of periodontal inflammation and bone loss. We evaluate the global genetic profile and signaling mechanisms induced by SIM on experimental periodontitis bone loss and inflammation. Twenty mature female Sprague Dawley rats were subjected to ligature-induced experimental periodontitis around maxillary second molars (M2) either unilaterally (one side untreated, n = 10) or bilaterally (n = 10). After the ligature removal at day 7, sites were injected with either carrier, pyrophosphate (PPi ×3), 1.5-mg SIM-dose equivalent SIM-pyrophosphate prodrug, or no injection. Three days after ligature removal, animals were euthanized; the M1-M2 interproximal was evaluated with μCT, histology, and protein expression. M2 palatal gingiva was harvested for RNA sequencing. Although ligature alone caused upregulation of proinflammatory and bone catabolic genes and proteins, seen in human periodontitis, SIM-PPi upregulated anti-inflammatory (IL-10, IL-1 receptor-like 1) and bone anabolic (insulin-like growth factor, osteocrin, fibroblast growth factor, and Wnt/ β-catenin) genes. The PPi carrier alone did not have these effects. Genetic profile and signaling mechanism data may help identify enhanced pharmacotherapeutic approaches to limit or regenerate periodontitis bone loss. © 2018 The Authors. JBMR Plus Published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

Materials Science and Design Principles of Growth Factor Delivery Systems in Tissue Engineering and Regenerative Medicine

Growth factors (GFs) are signaling molecules that direct cell development by providing biochemical cues for stem cell proliferation, migration, and differentiation. GFs play a key role in tissue regeneration, but one major limitation of GF-based therapies is dosage-related adverse effects. Additionally, the clinical applications and efficacy of GFs are significantly affected by the efficiency of delivery systems and other pharmacokinetic factors. Hence, it is crucial to design delivery systems that provide optimal activity, stability, and tunable delivery for GFs. Understanding the physicochemical properties of the GFs and the biomaterials utilized for the development of biomimetic GF delivery systems is critical for GF-based regeneration. Many different delivery systems have been developed to achieve tunable delivery kinetics for single or multiple GFs. The identification of ideal biomaterials with tunable properties for spatiotemporal delivery of GFs is still challenging. This review characterizes the types, properties, and functions of GFs, the materials science of widely used biomaterials, and various GF loading strategies to comprehensively summarize the current delivery systems for tunable spatiotemporal delivery of GFs aimed for tissue regeneration applications. This review concludes by discussing fundamental design principles for GF delivery vehicles based on the interactive physicochemical properties of the proteins and biomaterials.

Novel magnetic calcium phosphate-stem cell construct with magnetic field enhances osteogenic differentiation and bone tissue engineering

Superparamagnetic iron oxide nanoparticles (IONPs) are promising bioactive additives to fabricate magnetic scaffolds for bone tissue engineering. To date, there has been no report on osteoinductivity of IONP-incorporated calcium phosphate cement (IONP-CPC) scaffold on stem cells using an exterior static magnetic field (SMF). The objectives of this study were to: (1) develop a novel magnetic IONP-CPC construct for bone tissue engineering, and (2) investigate the effects of IONP-incorporation and SMF application on the proliferation, osteogenic differentiation and bone mineral synthesis of human dental pulp stem cells (hDPSCs) seeded on IONP-CPC scaffold for the first time. The novel magnetic IONP-CPC under SMF enhanced the cellular performance of hDPSCs, yielding greater alkaline phosphatase activities (about 3-fold), increased expressions of osteogenic marker genes, and more cell-synthesized bone minerals (about 2.5-fold), compared to CPC control and nonmagnetic IONP-CPC. In addition, IONP-CPC induced more active osteogenesis than CPC control in rat mandible defects. These results were consistent with the enhanced cellular performance by magnetic IONP in media under SMF. Moreover, nano-aggregates were detected inside the cells by transmission electron microscopy (TEM). Therefore, the enhanced cell performance was attributed to the physical forces generated by the magnetic field together with cell internalization of the released magnetic nanoparticles from IONP-CPC constructs.

FGF-7 Dictates Osteocyte Cell Processes Through Beta-Catenin Transduction

It is well recognized that osteocytes communicate with each other via gap junctions and that connxin43 (Cx43) shows its great potential in gap junction for the contribution enabling transmission of small molecules and operating in an autocrine/a paracrine manner. Fibroblast growth factors (FGFs) play significant roles in new bone formation and adult bone remodeling, and FGF signaling is regulated by the precise spatiotemporal approaches. However, the influence of FGF7 on osteocyte cell processes is not well elucidated. In this study, we aimed to examine the impact of FGF7 on osteocyte cell processes by characterizing the expression of Cx43 and to reveal the underlying mechanism regulating this cell process. We first found that the mRNA level of FGF7 was higher relative to other FGF family members both in osteocytes cell line (MLO-Y4) and bone tissue. We then demonstrated that FGF7 could increase the expression of Cx43 in osteocytes and promote the cell processes in the form of gap junctions between osteocytes. This modulation was due to the FGF7-induced cytoplasmic accumulation and resultant nuclear translocation of β-catenin. Our results could help us to further understand the importance of FGF7 on bone cell behavior and bone physiology and even pathology.

Micro-CT - a digital 3D microstructural voyage into scaffolds: a systematic review of the reported methods and results

BACKGROUND

Cell behavior is the key to tissue regeneration. Given the fact that most of the cells used in tissue engineering are anchorage-dependent, their behavior including adhesion, growth, migration, matrix synthesis, and differentiation is related to the design of the scaffolds. Thus, characterization of the scaffolds is highly required. Micro-computed tomography (micro-CT) provides a powerful platform to analyze, visualize, and explore any portion of interest in the scaffold in a 3D fashion without cutting or destroying it with the benefit of almost no sample preparation need.

MAIN BODY

This review highlights the relationship between the scaffold microstructure and cell behavior, and provides the basics of the micro-CT method. In this work, we also analyzed the original papers that were published in 2016 through a systematic search to address the need for specific improvements in the methods section of the papers including the amount of provided information from the obtained results.

CONCLUSION

Micro-CT offers a unique microstructural analysis of biomaterials, notwithstanding the associated challenges and limitations. Future studies that will include micro-CT characterization of scaffolds should report the important details of the method, and the derived quantitative and qualitative information can be maximized.

Nano-biphasic calcium phosphate/polyvinyl alcohol composites with enhanced bioactivity for bone repair via low-temperature three-dimensional printing and loading with platelet-rich fibrin

Background and aim

As a newly emerging three-dimensional (3D) printing technology, low-temperature robocasting can be used to fabricate geometrically complex ceramic scaffolds at low temperatures. Here, we aimed to fabricate 3D printed ceramic scaffolds composed of nano-biphasic calcium phosphate (BCP), polyvinyl alcohol (PVA), and platelet-rich fibrin (PRF) at a low temperature without the addition of toxic chemicals.

Methods

Corresponding nonprinted scaffolds were prepared using a freeze-drying method. Compared with the nonprinted scaffolds, the printed scaffolds had specific shapes and well-connected internal structures.

Results

The incorporation of PRF enabled both the sustained release of bioactive factors from the scaffolds and improved biocompatibility and biological activity toward bone marrow-derived mesenchymal stem cells (BMSCs) in vitro. Additionally, the printed BCP/PVA/PRF scaffolds promoted significantly better BMSC adhesion, proliferation, and osteogenic differentiation in vitro than the printed BCP/PVA scaffolds. In vivo, the printed BCP/PVA/PRF scaffolds induced a greater extent of appropriate bone formation than the printed BCP/PVA scaffolds and nonprinted scaffolds in a critical-size segmental bone defect model in rabbits.

Conclusion

These experiments indicate that low-temperature robocasting could potentially be used to fabricate 3D printed BCP/PVA/PRF scaffolds with desired shapes and internal structures and incorporated bioactive factors to enhance the repair of segmental bone defects.