N-cadherin and cadherin 11 modulate postnatal bone growth and osteoblast differentiation by distinct mechanisms

Single-cell transcriptomic resolution of osteogenesis during craniofacial morphogenesis

Craniofacial morphogenesis depends on complex cell fate decisions during the differentiation of post-migratory cranial neural crest cells. Molecular mechanisms of cell differentiation of mesenchymal cells to developing bones, cartilage, teeth, tongue, and other craniofacial tissues are still poorly understood. We performed single-cell transcriptomic analysis of craniofacial mesenchymal cells derived from cranial NCCs in mouse embryo. Using FACS sorting of Wnt1-Cre2 progeny, we carefully mapped the cell heterogeneity in the craniofacial region during the initial stages of cartilage and bone formation. Transcriptomic data and in vivo validations identified molecular determinants of major cell populations involved in the development of lower and upper jaw, teeth, tongue, dermis, or periocular mesenchyme. Single-cell transcriptomic analysis of Meis2-deficient mice revealed critical gene expression differences, including increased osteogenic and cell adhesion markers. This leads to affected mesenchymal cell differentiation and increased ossification, resulting in impaired bone, cartilage, and tongue formation.

RNA-Binding Proteins as Novel Effectors in Osteoblasts and Osteoclasts: A Systems Biology Approach to Dissect the Transcriptional Landscape

Bone health is ensured by the coordinated action of two types of cells-the osteoblasts that build up bone structure and the osteoclasts that resorb the bone. The loss of balance in their action results in pathological conditions such as osteoporosis. Central to this study is a class of RNA-binding proteins (RBPs) that regulates the biogenesis of miRNAs. In turn, miRNAs represent a critical level of regulation of gene expression and thus control multiple cellular and biological processes. The impact of miRNAs on the pathobiology of various multifactorial diseases, including osteoporosis, has been demonstrated. However, the role of RBPs in bone remodeling is yet to be elucidated. The aim of this study is to dissect the transcriptional landscape of genes encoding the compendium of 180 RBPs in bone cells. We developed and applied a multi-modular integrative analysis algorithm. The core methodology is gene expression analysis using the GENEVESTIGATOR platform, which is a database and analysis tool for manually curated and publicly available transcriptomic data sets, and gene network reconstruction using the Ingenuity Pathway Analysis platform. In this work, comparative insights into gene expression patterns of RBPs in osteoblasts and osteoclasts were obtained, resulting in the identification of 24 differentially expressed genes. Furthermore, the regulation patterns upon different treatment conditions revealed 20 genes as being significantly up- or down-regulated. Next, novel gene-gene associations were dissected and gene networks were reconstructed. Additively, a set of osteoblast- and osteoclast-specific gene signatures were identified. The consolidation of data and information gained from each individual analytical module allowed nominating novel promising candidate genes encoding RBPs in osteoblasts and osteoclasts and will significantly enhance the understanding of potential regulatory mechanisms directing intracellular processes in the course of (patho)physiological bone turnover.

Expression quantitative trait loci analysis in rheumatoid arthritis identifies tissue specific variants associated with severity and outcome

OBJECTIVE

Genome-wide association studies have successfully identified more than 100 loci associated with susceptibility to rheumatoid arthritis (RA). However, our understanding of the functional effects of genetic variants in causing RA and their effects on disease severity and response to treatment remains limited.

METHODS

In this study, we conducted expression quantitative trait locus (eQTL) analysis to dissect the link between genetic variants and gene expression comparing the disease tissue against blood using RNA-Sequencing of synovial biopsies (n=85) and blood samples (n=51) from treatment-naïve patients with RA from the Pathobiology of Early Arthritis Cohort.

RESULTS

This identified 898 eQTL genes in synovium and genes loci in blood, with 232 genes in common to both synovium and blood, although notably many eQTL were tissue specific. Examining the HLA region, we uncovered a specific eQTL at HLA-DPB2 with the critical triad of single-nucleotide polymorphisms (SNPs) rs3128921 driving synovial HLA-DPB2 expression, and both rs3128921 and HLA-DPB2 gene expression correlating with clinical severity and increasing probability of the lympho-myeloid pathotype.

CONCLUSIONS

This analysis highlights the need to explore functional consequences of genetic associations in disease tissue. HLA-DPB2 SNP rs3128921 could potentially be used to stratify patients to more aggressive treatment immediately at diagnosis.

Cdh11: Roles in different diseases and potential value in disease diagnosis and treatment

Cadherin is a homophilic, Ca2+-dependent cell adhesion glycoprotein that mediates cell-cell adhesion. Among them, Cadherin-11 (CDH11), as a classical cadherin, participates in and influences many crucial aspects of human growth and development. Furthermore, The involvement of CDH11 has been identified in an increasing number of diseases, primarily including various tumorous diseases, fibrotic diseases, autoimmune diseases, neurodevelopmental disorders, and more. In various tumorous diseases, CDH11 acts not only as a tumor suppressor but can also promote migration and invasion of certain tumors through various mechanisms. Likewise, in non-tumorous diseases, CDH11 remains a pivotal factor in disease progression. In this context, we summarize the specific functionalities and mechanisms of CDH11 in various diseases, aiming to gain a more comprehensive understanding of the potential value of CDH11 in disease diagnosis and treatment. This endeavor seeks to provide more effective diagnostic and therapeutic strategies for clinical management across diverse diseases.

Bone Metastasis Initiation Is Coupled with Bone Remodeling through Osteogenic Differentiation of NG2+ Cells

The bone microenvironment is dynamic and undergoes remodeling in normal and pathologic conditions. Whether such remodeling affects disseminated tumor cells (DTC) and bone metastasis remains poorly understood. Here, we demonstrated that pathologic fractures increase metastatic colonization around the injury. NG2+ cells are a common participant in bone metastasis initiation and bone remodeling in both homeostatic and fractured conditions. NG2+ bone mesenchymal stem/stromal cells (BMSC) often colocalize with DTCs in the perivascular niche. Both DTCs and NG2+ BMSCs are recruited to remodeling sites. Ablation of NG2+ lineage impaired bone remodeling and concurrently diminished metastatic colonization. In cocultures, NG2+ BMSCs, especially when undergoing osteodifferentiation, enhanced cancer cell proliferation and migration. Knockout of N-cadherin in NG2+ cells abolished these effects in vitro and phenocopied NG2+ lineage depletion in vivo. These findings uncover dual roles of NG2+ cells in metastasis and remodeling and indicate that osteodifferentiation of BMSCs promotes metastasis initiation via N-cadherin-mediated cell-cell interaction.

SIGNIFICANCE

The bone colonization of cancer cells occurs in an environment that undergoes constant remodeling. Our study provides mechanistic insights into how bone homeostasis and pathologic repair lead to the outgrowth of disseminated cancer cells, thereby opening new directions for further etiologic and epidemiologic studies of tumor recurrences. This article is highlighted in the In This Issue feature, p. 247.

Interplay between integrins and cadherins to control bone differentiation upon BMP-2 stimulation

Introduction: Upon BMP-2 stimulation, the osteoblastic lineage commitment in C2C12 myoblasts is associated with a microenvironmental change that occurs over several days. How does BMP-2 operate a switch in adhesive machinery to adapt to the new microenvironment and to drive bone cell fate is not well understood. Here, we addressed this question for BMP-2 delivered either in solution or physically bound of a biomimetic film, to mimic its presentation to cells via the extracellular matrix (ECM). Methods: Biommetics films were prepared using a recently developed automated method that enable high content studies of cellular processes. Comparative gene expressions were done using RNA sequencing from the encyclopedia of the regulatory elements (ENCODE). Gene expressions of transcription factors, beta chain (1, 3, 5) integrins and cadherins (M, N, and Cad11) were studied using quantitative PCR. ECM proteins and adhesion receptor expressions were also quantified by Western blots and dot blots. Their spatial organization in and around cells was studied using immuno-stainings. The individual effect of each receptor on osteogenic transcription factors and alkaline phosphatase expression were studied using silencing RNA of each integrin and cadherin receptor. The organization of fibronectin was studied using immuno-staining and quantitative microscopic analysis. Results: Our findings highlight a switch of integrin and cadherin expression during muscle to bone transdifferentiation upon BMP-2 stimulation. This switch occurs no matter the presentation mode, for BMP-2 presented in solution or via the biomimetic film. While C2C12 muscle cells express M-cadherin and Laminin-specific integrins, the BMP-2-induced transdifferentiation into bone cells is associated with an increase in the expression of cadherin-11 and collagen-specific integrins. Biomimetic films presenting matrix-bound BMP-2 enable the revelation of specific roles of the adhesive receptors depending on the transcription factor. Discussion: While β3 integrin and cadherin-11 work in concert to control early pSMAD1,5,9 signaling, β1 integrin and Cadherin-11 control RunX2, ALP activity and fibronectin organization around the cells. In contrast, while β1 integrin is also important for osterix transcriptional activity, Cadherin-11 and β5 integrin act as negative osterix regulators. In addition, β5 integrin negatively regulates RunX2. Our results show that biomimetic films can be used to delinate the specific events associated with BMP-2-mediated muscle to bone transdifferentiation. Our study reveals how integrins and cadherins work together, while exerting distinct functions to drive osteogenic programming. Different sets of integrins and cadherins have complementary mechanical roles during the time window of this transdifferentiation.

Cellular plasticity in bone metastasis

Metastasis is responsible for a large majority of death from malignant solid tumors. Bone is one of the most frequently affected organs in cancer metastasis, especially in breast and prostate cancer. Development of bone metastasis requires cancer cells to successfully complete a number of challenging steps, including local invasion and intravasation, survival in circulation, extravasation and initial seeding, and finally, formation of metastatic colonies after a period of dormancy or indolent growth. During this process, cancer cells often undergo a series of cellular and molecular changes to gain cellular plasticity that helps them adapt to various environments they encounter along the journey of metastasis. Understanding the mechanisms behind cellular plasticity and adaptation during the formation of bone metastasis is crucial for the development of novel therapies.

Only the Co-Transcriptional Activity of β-Catenin Is Required for the Local Regulatory Effects in Hypertrophic Chondrocytes on Developmental Bone Modeling

In hypertrophic chondrocytes, β-catenin has two roles. First, it locally suppresses the differentiation of osteoclasts at the chondro-osseous junction by maintaining the pro-osteoclastic factor receptor activator of NF-κB ligand (RANKL) at low levels. Second, it promotes the differentiation of osteoblast-precursors from chondrocytes. Yet, β-catenin is a dual-function protein, which can either participate in cell-cell adherens junctions or serve as a transcriptional co-activator in canonical Wnt signaling interacting with T-cell factor/lymphoid enhancer-binding factor (TCF/LEF) transcription factors. Hence, whenever studying tissue-specific requirements of β-catenin using a conventional conditional knockout approach, the functional mechanisms underlying the defects in the conditional mutants remain ambiguous. To decipher mechanistically which of the two molecular functions of β-catenin is required in hypertrophic chondrocytes, we used different approaches. We analyzed the long bones of newborn mice carrying either the null-alleles of Lef1 or Tcf7, or mice in which Tcf7l2 was conditionally deleted in the hypertrophic chondrocytes, as well as double mutants for Lef1 and Tcf7l2, and Tcf7 and Tcf7l2. Furthermore, we analyzed Ctnnb1 mutant newborns expressing a signaling-defective allele that retains the cell adhesion function in hypertrophic chondrocytes. None of the analyzed Tcf/Lef single or double mutants recapitulated the previously published phenotype upon loss of β-catenin in hypertrophic chondrocytes. However, using this particular Ctnnb1 allele, maintaining cell adhesion function, we show that it is the co-transcriptional activity of β-catenin, which is required in hypertrophic chondrocytes to suppress osteoclastogenesis and to promote chondrocyte-derived osteoblast differentiation. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Gain-of-Function Lrp5 Mutation Improves Bone Mass and Strength and Delays Hyperglycemia in a Mouse Model of Insulin-Deficient Diabetes

High fracture rate and high circulating levels of the Wnt inhibitor, sclerostin, have been reported in diabetic patients. We studied the effects of Wnt signaling activation on bone health in a mouse model of insulin-deficient diabetes. We introduced the sclerostin-resistant Lrp5^A214V mutation, associated with high bone mass, in mice carrying the Ins2^Akita mutation (Akita), which results in loss of beta cells, insulin deficiency, and diabetes in males. Akita mice accrue less trabecular bone mass with age relative to wild type (WT). Double heterozygous Lrp5^A214V /Akita mutants have high trabecular bone mass and cortical thickness relative to WT animals, as do Lrp5^A214V single mutants. Likewise, the Lrp5^A214V mutation prevents deterioration of biomechanical properties occurring in Akita mice. Notably, Lrp5^A214V /Akita mice develop fasting hyperglycemia and glucose intolerance with a delay relative to Akita mice (7 to 8 vs. 5 to 6 weeks, respectively), despite lack of insulin production in both groups by 6 weeks of age. Although insulin sensitivity is partially preserved in double heterozygous Lrp5^A214V /Akita relative to Akita mutants up to 30 weeks of age, insulin-dependent phosphorylated protein kinase B (pAKT) activation in vitro is not altered by the Lrp5^A214V mutation. Although white adipose tissue depots are equally reduced in both compound and Akita mice, the Lrp5^A214V mutation prevents brown adipose tissue whitening that occurs in Akita mice. Thus, hyperactivation of Lrp5-dependent signaling fully protects bone mass and strength in prolonged hyperglycemia and improves peripheral glucose metabolism in an insulin independent manner. Wnt signaling activation represents an ideal therapeutic approach for diabetic patients at high risk of fracture. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

CD271+CD51+PALLADIN- Human Mesenchymal Stromal Cells Possess Enhanced Ossicle-Forming Potential

Human mesenchymal stem/stromal cells (hMSCs), when engrafted into immunodeficient mice, can form ectopic bone organs with hematopoietic stem cell (HSC) supportive functions. However, the ability to do so, through a cartilage intermediate, appears limited to 30% of donor bone marrow samples. In this study, we characterize the heterogeneous nature of hMSCs and their ability to efficiently form humanized ossicles observed in "good donors" to correlate with the frequency and functionality of chondrocyte progenitors. Flow cytometry of putative hMSC markers was enriched in the CD271⁺CD51⁺ stromal cell subset, which also possessed enhanced hMSC activity as assessed by single-cell colony-forming unit fibroblast (CFU-F) and undifferentiated mesensphere formation. Transcriptome analysis of CD271⁺ cells presented upregulation of chondrogenesis-/osteogenesis-related genes and HSC/niche maintenance factors such as C-X-C motif chemokine 12 (CXCL12) and ANGIOPOIETIN 1. Among the candidate genes selected to enrich for subsets with greater chondrogenic ability, cells negative for the actin cross-linker PALLADIN displayed the greatest CFU-F potential. Our study contributes to a better characterization of ossicle-forming hMSCs and their efficient isolation for the optimized engineering of human bone organs.

Genome-wide association study reveals novel loci associated with feeding behavior in Pekin ducks

Background

Feeding behavior traits are an essential part of livestock production. However, the genetic base of feeding behavior traits remains unclear in Pekin ducks. This study aimed to determine novel loci related to feeding behavior in Pekin ducks.

Results

In this study, the feeding information of 540 Pekin ducks was recorded, and individual genotype was evaluated using genotyping-by-sequencing methods. Genome-wide association analysis (GWAS) was conducted for feeding behavior traits. Overall, thirty significant (P-value < 4.74E-06) SNPs for feeding behavior traits were discovered, and four of them reached the genome-wide significance level (P-value < 2.37E-07). One genome-wide significance locus associated with daily meal times was located in a 122.25 Mb region on chromosome 2, which was within the intron of gene ubiquitin-conjugating enzyme E2 E2 (UBE2E2), and could explain 2.64% of the phenotypic variation. This locus was also significantly associated with meal feed intake, and explained 2.72% of this phenotypic variation.

Conclusions

This study is the first GWAS for feeding behavior traits in ducks. Our results provide a list of candidate genes associated with feeding behavior, and also help to better understand the genetic mechanisms of feeding behavior patterns in ducks.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07668-1.

Surface decoration of development-inspired synthetic N-cadherin motif via Ac-BP promotes osseointegration of metal implants

Research works on the synergistic effect of surface modified bioactive molecules and bone metal implants have been highlighted. N-cadherin is regarded as a key factor in directing cell-cell interactions during the mesenchymal condensation preceding the osteogenesis in the musculoskeletal system. In this study, the N-cadherin mimetic peptide (Cad) was biofunctionalized on the titanium metal surface via the acryloyl bisphosphonate (Ac-BP). To learn the synergistic effect of N-cadherin mimetic peptide, when tethered with titanium substrates, on promoting osteogenic differentiation of the seeded human mesenchymal stem cells (hMSCs) and the osseointegration at the bone-implant interfaces. Results show that the conjugation of N-cadherin mimetic peptide with Ac-BP promoted the osteogenic gene markers expression in the hMSCs. The biofunctionalized biomaterial surfaces promote the expression of the Wnt/β-catenin downstream axis in the attached hMSCs, and then enhance the in-situ bone formation and osseointegration at the bone-implant interfaces. We conclude that this N-cadherin mimetic peptide tethered on Ti surface promote osteogenic differentiation of hMSCs and osseointegration of biomaterial implants in vitro and in vivo. These findings demonstrate the importance of the development-inspired surface bioactivation of metal implants and shed light on the possible cellular mechanisms of the enhanced osseointegration.

N-cadherin in osteolineage cells modulates stromal support of tumor growth

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N-cadherin in osteolineage, Osterix+ cells restrains extraskeletal tumor growth.

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Osterix+ cells are present in the stromal microenvironment of extraskeletal tumors.

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Osterix+ cells are present in normal tissues frequent sites of metastasis.

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N-cadherin modulates pro-tumorigenic signaling in tumor associated Osterix+ cells.

Tumor growth and metastases are dependent on interactions between cancer cells and the local environment. Expression of the cell–cell adhesion molecule N-cadherin (Ncad) is associated with highly aggressive cancers, and its expression by osteogenic cells has been proposed to provide a molecular “dock” for disseminated tumor cells to establish in pre-metastatic niches within the bone. To test this biologic model, we conditionally deleted the Ncad gene (Cdh2) in osteolineage cells using Osx-cre (cKO). Contrary to expectations, the metastatic breast cancer cell line PyMT-BO1 was able to form tumors in bone and to induce osteolysis in cKO as well as in control mice. Despite absence of Ncad, bone marrow stromal cells isolated from cKO mice were able to engage in direct cell–cell interactions with tumor cells expressing either N- or E-cadherin. However, subcutaneous PyMT-BO1 and B16F10 tumors grew larger in cKO relative to control littermates. Cell tracking experiments using the Ai9 reporter revealed the presence of Osx+ and Ncad+ cells in the stroma of extra-skeletal tumors and in a small population of lung cells. Gene expression analysis by RNAseq of Osx+ cells isolated from extra-skeletal tumors revealed alterations of pro-tumorigenic signaling pathways in cKO cells relative to control Osx+ cells. Thus, Ncad in Osx+ cells is not necessary for the establishment of bone metastases, but in extra-skeletal tumors it regulates pro-tumorigenic support by the microenvironment.

Microarray analysis identification of key pathways and interaction network of differential gene expressions during osteogenic differentiation

BACKGROUND

Adult bone marrow-derived mesenchymal stem cells (BM-MSCs) are multipotent stem cells that can differentiate into three lineages. They are suitable sources for cell-based therapy and regenerative medicine applications. This study aims to evaluate the hub genes and key pathways of differentially expressed genes (DEGs) related to osteogenesis by bioinformatics analysis in three different days. The DEGs were derived from the three different days compared with day 0.

RESULTS

Gene expression profiles of GSE37558 were obtained from the Gene Expression Omnibus (GEO) database. A total of 4076 DEGs were acquired on days 8, 12, and 25. Gene ontology (GO) enrichment analysis showed that the non-canonical Wnt signaling pathway and lipopolysaccharide (LPS)-mediated signaling pathway were commonly upregulated DEGs for all 3 days. KEGG pathway analysis indicated that the PI3K-Akt and focal adhesion were also commonly upregulated DEGs for all 3 days. Ten hub genes were identified by CytoHubba on days 8, 12, and 25. Then, we focused on the association of these hub genes with the Wnt pathways that had been enriched from the protein-protein interaction (PPI) by the Cytoscape plugin MCODE.

CONCLUSIONS

These findings suggested further insights into the roles of the PI3K/AKT and Wnt pathways and their association with osteogenesis. In addition, the stem cell microenvironment via growth factors, extracellular matrix (ECM), IGF1, IGF2, LPS, and Wnt most likely affect osteogenesis by PI3K/AKT.

A genome-wide association analysis for body, udder, and leg conformation traits recorded in Murciano-Granadina goats

Morphological traits are of great importance to dairy goat production given their effect on phenotypes of economic interest. However, their underlying genomic architecture has not yet been extensively characterized. Herein, we aimed to identify genomic regions associated with body, udder, and leg conformation traits recorded in 825 Murciano-Granadina goats. We genotyped this resource population using the GoatSNP50 BeadChip (Illumina Inc., San Diego, CA) and performed genome-wide association analyses using the GEMMA software. We found 2 genome-wide significant associations between markers rs268273468 [Capra hircus (CHI) 16:69617700] and rs268249346 (CHI 28:18321523) and medial suspensory ligament. In contrast, we did not detect any genome-wide significant associations for body and leg traits. Moreover, we found 12, 19, and 7 chromosome-wide significant associations for udder, body, and leg traits, respectively. Comparison of our data with previous studies revealed a low level of positional concordance between regions associated with morphological traits. In addition to technical factors, this lack of concordance could be due to a substantial level of genetic heterogeneity among breeds or to the strong polygenic background of morphological traits, which makes it difficult to detect genetic factors that have small phenotypic effects.

Characterization of sexual size dimorphism and sex-biased genes expression profile in the olive flounder

Sexual size dimorphism (SSD) is a widespread phenomenon in fish species, including in the olive flounder. Although it is well established that female olive flounders acquire more bone mass than males, the underlying mechanism and timing of this SSD remains controversial. Here, the gene expression profiles of adult male and female olive flounder fish were explored to better understand the SSD mechanisms. Using RNA sequencing, a total of 4784 sex-biased differentially expressed genes (DEGs) in the fin with asymptotic growth after maturity were identified, among which growth-related factors were found. Gene ontology and pathway enrichment studies were performed to predict potential SSD-related genes and their functions. According to functional analysis, negative regulation of cell proliferation was significantly enriched in males, and anabolism related genes were highly expressed in females. In addition, pathway analysis using the Kyoto Encyclopedia of Genes and Genomes database revealed that five sexual dimorphism-related candidate genes (bambia, smurf1, dvl2, cul1a, and dvl3) were enriched in osteogenesis-contributing pathways. These results suggest that these five candidate genes may be relevant for skeletal development in olive flounders. Altogether, this study adds new knowledge for a better understanding of SSD-related growth traits in olive flounder, which can be used for enhancing aquaculture productivity with reduced production costs.

Prostate-specific antigen modulates the osteogenic differentiation of MSCs via the cadherin 11-Akt axis

BACKGROUND

A high prevalence of osteoblastic bone metastases is characteristic of prostate cancer. Prostate-specific antigen (PSA) is a serine protease uniquely produced by prostate cancer cells and is an important serological marker for prostate cancer. However, whether PSA modulates the osteogenic process remains largely unknown. In this study, we explored the effect of PSA on modulating the osteoblastic differentiation of mesenchymal stem cells (MSCs). In this study, we used flow cytometry, CCK-8 assay, Alizarin red S (ARS) staining and quantification, alkaline phosphatase (ALP) activity and staining, Western blotting, and quantitative real-time PCR (qRT-PCR) to explore the effect of PSA on osteogenic differentiation of MSCs.

RESULTS

We first demonstrated that although PSA did not affect the proliferation, morphology, or phenotype of MSCs, it significantly promoted the osteogenic differentiation of MSCs in a concentration-dependent manner. Furthermore, we demonstrated that PSA promoted the osteogenic differentiation of MSCs by elevating the expression of Cadherin 11 in MSCs and, thus, activating the Akt signaling pathway.

CONCLUSIONS

In conclusion, we demonstrated that PSA could promote the osteogenesis of MSCs through Akt signaling pathway activation by elevating the expression of cadherin-11 in MSCs. These findings imply a possible role of PSA in osteoblastic bone metastases in prostate cancer.

Cell-cell junctions in developing and adult tendons

Tendons connect muscles to bones to transfer the forces necessary for movement. Cell-cell junction proteins, cadherins and connexins, may play a role in tendon development and injury. In this review, we begin by highlighting current understanding of how cell-cell junctions may regulate embryonic tendon development and differentiation. We then examine cell-cell junctions in postnatal tendon, before summarizing the role of cadherins and connexins in adult tendons. More information exists regarding the role of cell-cell junctions in the formation and homeostasis of other musculoskeletal tissues, namely cartilage and bone. Therefore, to inform future tendon studies, we include a brief survey of cadherins and connexins in chondrogenesis and osteogenesis, and summarize how cell-cell junctions are involved in some musculoskeletal tissue pathologies. An enhanced understanding of how cell-cell junctions participate in tendon development, maintenance, and disease will benefit future regenerative strategies.

Novel variants in CDH2 are associated with a new syndrome including Peters anomaly

Peters anomaly (PA) is a congenital corneal opacity associated with corneo-lenticular attachments. PA can be isolated or part of a syndrome with most cases remaining genetically unsolved. Exome sequencing of a trio with syndromic PA and 145 additional unexplained probands with developmental ocular conditions identified a de novo splicing and three novel missense heterozygous CDH2 variants affecting the extracellular cadherin domains in four individuals with PA. Syndromic anomalies were seen in three individuals and included left-sided cardiac lesions, dysmorphic facial features, and decreasing height percentiles; brain magnetic resonance imaging identified agenesis of the corpus callosum and hypoplasia of the inferior cerebellar vermis. CDH2 encodes for N-cadherin, a transmembrane protein that mediates cell-cell adhesion in multiple tissues. Immunostaining in mouse embryonic eyes confirmed N-cadherin is present in the lens stalk at the time of separation from the future cornea and in the developing lens and corneal endothelium at later stages, supporting a possible role in PA. Previous studies in animal models have noted the importance of Cdh2/cdh2 in the development of the eye, heart, brain, and skeletal structures, also consistent with the patient features presented here. Examination of CDH2 in additional patients with PA is indicated to confirm this association.

Mesenchymal Stem Cells in the Adult Human Liver: Hype or Hope?

Chronic liver diseases constitute a significant economic, social, and biomedical burden. Among commonly adopted approaches, only organ transplantation can radically help patients with end-stage liver pathologies. Cell therapy with hepatocytes as a treatment for chronic liver disease has demonstrated promising results. However, quality human hepatocytes are in short supply. Stem/progenitor cells capable of differentiating into functionally active hepatocytes provide an attractive alternative approach to cell therapy for liver diseases, as well as to liver-tissue engineering, drug screening, and basic research. The application of methods generally used to isolate mesenchymal stem cells (MSCs) and maintain them in culture to human liver tissue provides cells, designated here as liver MSCs. They have much in common with MSCs from other tissues, but differ in two aspects-expression of a range of hepatocyte-specific genes and, possibly, inherent commitment to hepatogenic differentiation. The aim of this review is to analyze data regarding liver MSCs, probably another type of liver stem/progenitor cells different from hepatic stellate cells or so-called hepatic progenitor cells. The review presents an analysis of the phenotypic characteristics of liver MSCs, their differentiation and therapeutic potential, methods for isolating these cells from human liver, and discusses issues of their origin and heterogeneity. Human liver MSCs are a fascinating object of fundamental research with a potential for important practical applications.

Screening of perfused combinatorial 3D microenvironments for cell culture

Biomaterials combining biochemical and biophysical cues to establish close-to-extracellular matrix (ECM) models have been explored for cell expansion and differentiation purposes. Multivariate arrays are used as material-saving and rapid-to-analyze platforms, which enable selecting hit-spotted formulations targeting specific cellular responses. However, these systems often lack the ability to emulate dynamic mechanical aspects that occur in specific biological milieus and affect physiological phenomena including stem cells differentiation, tumor progression, or matrix modulation. We report a tailor-made strategy to address the combined effect of flow and biochemical composition of three-dimensional (3D) biomaterials on cellular response. We suggest a simple-to-implement device comprising (i) a perforated platform accommodating miniaturized 3D biomaterials and (ii) a bioreactor that enables the incorporation of the biomaterial-containing array into a disposable perfusion chamber. The system was upscaled to parallelizable setups, increasing the number of analyzed platforms per independent experiment. As a proof-of-concept, porous chitosan scaffolds with 1 mm diameter were functionalized with combinations of 5 ECM and cell-cell contact-mediating proteins, relevant for bone and dental regeneration, corresponding to 32 protein combinatorial formulations. Mesenchymal stem cells adhesion and production of an early osteogenic marker were assessed on-chip on static and under-flow dynamic perfusion conditions. Different hit-spotted biomaterial formulations were detected for the different flow regimes using direct image analysis. Cell-binding proteins still poorly explored as biomaterials components - amelogenin and E-cadherin - were here shown as relevant cell response modulators. Their combination with ECM cell-binding proteins - fibronectin, vitronectin, and type 1 collagen - rendered specific biomaterial combinations with high cell adhesion and ALP production under flow. The developed versatile system may be targeted at widespread tissue regeneration applications, and as a disease model/drug screening platform. STATEMENT OF SIGNIFICANCE: A perfusion system that enables cell culture in arrays of three-dimensional biomaterials under dynamic flow is reported. The effect of 31 cell-binding protein combinations in the adhesion and alkaline phosphatase (ALP) production of mesenchymal stem cells was assessed using a single bioreactor chamber. Flow perfusion was not only assessed as a classical enhancer/accelerator of cell growth and early osteogenic differentiation. We hypothesized that flow may affect cell-protein interactions, and that key components driving cell response may differ under static or dynamic regimes. Indeed, hit-spotted formulations that elicited highest cell attachment and ALP production on static cell culture differed from the ones detected for dynamic flow assays. The impacting role of poorly studied proteins as E-cadherin and amelogenin as biomaterial components was highlighted.

Cooperative Contraction Behaviors of a One-Dimensional Cell Chain

Collective behaviors of multiple cells play important roles in various physiological and pathological processes, but the mechanisms of coordination among cells are highly unknown. Here, we build a one-dimensional cell-chain model to quantitatively study cell cooperativity. Combining experimental and theoretical approaches, we showed that the matrix stiffness, intercellular adhesion strength, and cell-chain length have a significant effect on the cooperative contraction of the cell chains. Cells have strong cooperativity, i.e., exhibiting a united contraction mode, in shorter cell chains or on softer matrix or with higher intercellular adhesion strength. In contrast, cells would exhibit a divided contraction when the cell chain was long or on stiffer matrix or with weaker adhesion strength. In addition, our quantitative results indicated that the cooperativity of cells is regulated by the coupling between matrix stiffness and intercellular adhesion, which can be quantified by an explicit parameter group. These results may provide guidelines for regulating the cooperativity of cells in their collective behaviors in tissue morphogenesis and tissue engineering in biomedical applications.

Identification of a single-nucleotide polymorphism within CDH2 gene associated with bone morbidity in childhood acute lymphoblastic leukemia survivors

Aim: To identify genetic markers associated with late treatment-related skeletal morbidity in survivors of childhood acute lymphoblastic leukemia (ALL). Patients & methods: To this end, we measured the association between reduction in bone mineral density or vertebral fractures prevalence and variants from 1039 genes derived through whole exome sequencing in 242 childhood ALL survivors. Top-ranking variants were confirmed through genotyping, and further explored with stratified analyses and multivariable models. Results: The minor allele of rs1944294 in CDH2 gene was associated with bone geometrical parameter, trabecular cross-sectional area (p = 0.001). The association was modulated by radiation therapy (p = 0.001) and post-treatment time (p = 0.0002). Conclusion: The variant in CDH2 gene is a potential novel risk factor of bone morbidity in survivors of childhood ALL.

TGFβ2-induced tenogenesis impacts cadherin and connexin cell-cell junction proteins in mesenchymal stem cells

Tenogenic differentiation of stem cells is needed for tendon tissue engineering approaches. A current challenge is the limited information on the cellular-level changes during tenogenic induction. Tendon cells in embryonic and adult tendons possess an array of cell-cell junction proteins that include cadherins and connexins, but how these proteins are impacted by tenogenic differentiation is unknown. Our objective was to explore how tenogenic induction of mesenchymal stem cells (MSCs) using the transforming growth factor (TGF)β2 impacted protein markers of tendon differentiation and protein levels of N-cadherin, cadherin-11 and connexin-43. MSCs were treated with TGFβ2 for 21 days. At 3 days, TGFβ2-treated MSCs developed a fibroblastic morphology and significantly decreased levels of N-cadherin protein, which were maintained through 21 days. Similar decreases in protein levels were found for cadherin-11. Connexin-43 protein levels significantly increased at 3 days, but then decreased below control levels, though not significantly. Protein levels of scleraxis and tenomodulin were significantly increased at day 14 and 21, respectively. Taken together, our results indicate that TGFβ2 is an inducer of tendon marker proteins (scleraxis and tenomodulin) in MSCs and that tenogenesis alters the protein levels of N-cadherin, cadherin-11 and connexin-43. These findings suggest a role for connexin-43 early in tenogenesis, and show that early-onset and sustained decreases in N-cadherin and cadherin-11 may be novel markers of tenogenesis in MSCs.

Neural crest contributions to the ear: Implications for congenital hearing disorders

Congenital hearing disorders affect millions of children worldwide and can significantly impact acquisition of speech and language. Efforts to identify the developmental genetic etiologies of conductive and sensorineural hearing losses have revealed critical roles for cranial neural crest cells (NCCs) in ear development. Cranial NCCs contribute to all portions of the ear, and defects in neural crest development can lead to neurocristopathies associated with profound hearing loss. The molecular mechanisms governing the development of neural crest derivatives within the ear are partially understood, but many questions remain. In this review, we describe recent advancements in determining neural crest contributions to the ear, how they inform our understanding of neurocristopathies, and highlight new avenues for further research using bioinformatic approaches.

Analysis of the association between CDH2 gene polymorphism and osteoarthritis risk

OBJECTIVE

to define the cadherin 2 (CDH2) gene polymorphism in Chinese osteoarthritis and control populations and to explore the correlation between CDH2 gene polymorphism and the risk of osteoarthritis.

METHOD

a total of 476 patients with osteoarthritis were collected and 380 control subjects were included in the study. Clinical data such as gender, age and functional score were collected. The blood and tissue samples were collected and genotyped by PCR. Data analysis was performed using SPSS 19.0, Hapioview 4.2 and SNPstats softwares.

RESULTS

the association of rs11083271 and osteoarthritis was initially validated in this study population (P = 0.016, OR = 1.43 (1.07- 1.93)]. The risk of OA was significantly higher in heterozygous T/C than in homozygous T/T and C/C in rs11083271. By adjusting the age, according to gender stratification analysis, the heterozygous T/C genotype in rs11083271 significantly increased the risk of OA incidence in males [p = 0.011, 3.40 (1.55-7.43)]. The remaining rs sites were not significantly associated with OA. Notably, the association of rs11564299 with OA, regardless of genotyping, gene frequency and RNA expression levels in the study population, was not confirmed.

CONCLUSION

in this study, we have analyzed the association between CDH2 gene polymorphism and OA in Chinese population. We found that rs11083271 heterozygous T/C genotype significantly increases the risk of OA and the severity of the disease. By contrast, the rs11564299 locus and OA have no significant correlation in the Chinese population. The role of rs11083271 in the regulation of CDH2 expression levels and the mechanisms by which it impacts OA remain to be further studied.

Gga-miR-205a Affecting Myoblast Proliferation and Differentiation by Targeting CDH11

Non-coding RNAs especially miRNAs have been found to play important roles during skeletal muscle development. Our previous RNA-Seq performed on breast muscle tissue from 7 weeks old Recessive White Rock and Xinhua Chicken and leg muscle tissue from female Xinghua Chicken at three development time points (11 embryo age, 16 embryo age, and 1 day post hatch) (accession number GSE62971 and GSE89355, respectively) showed that miR-205a and CDH11 were differentially expressed genes. In this study, we found that overexpression of CDH11 significantly facilitated Quail muscle clone (QM7) and chicken primary myoblast (CPM) proliferation and hampered CPM differentiation. MiR-205a can directly binding to the 3'UTR of CDH11 and the overexpression of miR-205a could inhibit both cell lines (QM7) and CPM proliferation, at the meantime promote the differentiation of myoblasts. The Dual-Luciferase Reporter Assay results and qRT-PCR results showed that myogenin (MyoG) could regulate the expression of miR-205a by binding to the active region of miR-205a. Altogether our data suggest that MyoG could stimulate miR-205a expression to suppress CDH11, which promotes myoblasts proliferation while represses the differentiation.

A novel mutation in CDH11, encoding cadherin-11, cause Branchioskeletogenital (Elsahy-Waters) syndrome

Cadherins are cell-adhesion molecules that control morphogenesis, cell migration, and cell shape changes during multiple developmental processes. Until now four distinct cadherins have been implicated in human Mendelian disorders, mainly featuring skin, retinal and hearing manifestations. Branchio-skeleto-genital (or Elsahy-Waters) syndrome (BSGS) is an ultra-rare condition featuring a characteristic face, premature loss of teeth, vertebral and genital anomalies, and intellectual disability. We have studied two sibs with BSGS originally described by Castori et al. in 2010. Exome sequencing led to the identification of a novel homozygous nonsense variant in the first exon of the cadherin-11 gene (CDH11), which results in a prematurely truncated form of the protein. Recessive variants in CDH11 have been recently demonstrated in two other sporadic patients and a pair of sisters affected by BSGS. Although the function of this cadherin (also termed Osteoblast-Cadherin) is not completely understood, its prevalent expression in osteoblastic cell lines and up-regulation during differentiation suggest a specific function in bone formation and development. This study identifies a novel loss-of-function variant in CDH11 as a cause of BSGS and supports the role of cadherin-11 as a key player in axial and craniofacial malformations.

Physical contact between mesenchymal stem cells and endothelial precursors induces distinct signatures with relevance to the very early phase of regeneration

Multipotent adult stem cells/precursor cells, especially of the mesenchymal and endothelial lineage, may have great potential for bone tissue engineering. Although their potential is highly recognized, not much is known about the underlying molecular mechanisms that initiate the regeneration process, connect osteogenesis, and angiogenesis and, finally, orchestrate renewal of bone tissue. Our study addressed these questions by generating two in vitro cell culture models to examine the changes in the global gene expression patterns of endothelial precursor cells and mesenchymal stem cells after 24 hours of either humoral (conditioned medium) or direct cell-cell interaction (co-culture). Endothelial precursor cells were isolated from human buffy coat and mesenchymal stem cells from the bone marrow of the femoral head. The comparison of the treated and control cells by microarray analyses revealed in total more than 1500 regulated genes, which were analyzed for their affiliation to angiogenesis and osteogenesis. Expression array analyses at the RNA and protein level revealed data with respect to regulated genes, pathways and targets that may represent a valid basis for further dissection of the systems biology of regeneration processes. It may also be helpful for the reconstitution of the natural composition of a regenerative microenvironment when targeting tissue regeneration both in vitro and in situ.

Tuning surface properties of bone biomaterials to manipulate osteoblastic cell adhesion and the signaling pathways for the enhancement of early osseointegration

Osteoblast cell adhesion is the initial step of early osseointegration responding to bone material implants. Enhancing the osteoblastic cell adhesion has become one of the prime aims when optimizing the surface properties of bone biomaterials. The traditional strategy focuses in improving the physical attachment of osteoblastic cells onto the surfaces of biomaterials. However, instead of a simple cell physical attachment, the osteoblastic cell adhesion has been revealed to be a sophisticated system. Despite the well-documented effect of bone biomaterial surface modifications on adhesion, few studies have focused on the underlying molecular mechanisms. Physicochemical signals from biomaterials can be transduced into intracellular signaling network and further initiate the early response cascade towards the implants, which includes cell survival, migration, proliferation, and differentiation. Adhesion is vital in determining the early osseointegration between host bone tissue and implanted bone biomaterials via regulating involving signaling pathways. Therefore, the modulation of early adhesion behavior should not simply target in physical attachment, but emphasize in the manipulation of downstream signaling pathways, to regulate early osseointegration. This review firstly summarized the basic biological principles of osteoblastic cell adhesion process and the activated downstream cell signaling pathways. The effects of different biomaterial physicochemical properties on osteoblastic cell adhesion were then reviewed. This review provided up-to-date research outcomes in the adhesion behavior of osteoblastic cells on bone biomaterials with different physicochemical properties. The strategy is optimised from traditionally focusing in physical cell adhesion to the proposed strategy that manipulating cell adhesion and the downstream signaling network for the enhancement of early osseointegration.

Dorsal root ganglion neurons regulate the transcriptional and translational programs of osteoblast differentiation in a microfluidic platform

Innervation by the sensory nervous system plays a key role in skeletal development and in orchestration of bone remodeling and regeneration. However, it is unclear how and in which bone cells can sensory nerves act to control these processes. Here, we show a microfluidic coculture system comprising dorsal root ganglion (DRG) neurons and mesenchymal stem cells (MSCs) that more faithfully represents the in vivo scenario of bone sensory innervation. We report that DRG neurons promote the osteogenic differentiation capacity of MSCs, by mediating the increase of alkaline phosphatase activity and the upregulation of osteoblast-specific genes. Furthermore, we show that DRG neurons have a positive impact on Cx43 levels in MSCs during osteoblastogenesis, especially at an early stage of this process. Conversely, we described a negative impact of DRG neurons on MSCs N-cadherin expression at a later stage. Finally, we demonstrate a cytoplasmic accumulation of β-catenin translocation into the nucleus, and subsequently Lymphoid Enhancer Binding Factor 1—responsive transcriptional activation of downstream genes in cocultured MSCs. Together, our study provides a robust body of evidence that the direct interaction of DRG neurons with MSCs in a bone-like microenvironment leads to an enhancement of osteoblast differentiation potential of MSCs. The osteogenic effect of DRG neurons on MSCs is mediated through the regulation of Cx43 and N-cadherin expression and activation of the canonical/β-catenin Wnt signaling pathway.

Heterozygous deletion of both sclerostin (Sost) and connexin43 (Gja1) genes in mice is not sufficient to impair cortical bone modeling

Connexin43 (Cx43) is the main gap junction protein expressed in bone forming cells, where it modulates peak bone mass acquisition and cortical modeling. Genetic ablation of the Cx43 gene (Gja1) results in cortical expansion with accentuated periosteal bone formation associated with decreased expression of the Wnt inhibitor sclerostin. To determine whether sclerostin (Sost) down-regulation might contribute to periosteal expansion in Gja1 deficient bones, we took a gene interaction approach and crossed mice harboring germline null alleles for Gja1 or Sost to generate single Gja1^+/–and Sost^+/–and double Gja1^+/–;Sost^+/–heterozygous mice. In vivo μCT analysis of cortical bone at age 1 and 3 months confirmed increased thickness in Sost^–/–mice, but revealed no cortical abnormalities in single Gja1^+/–or Sost^+/–mice. Double heterozygous Gja1^+/–Sost^+/–also showed no differences in mineral density, cortical thickness, width or geometry relative to wild type control mice. Likewise, 3-point bending measurement of bone strength revealed no significant differences between double Gja1^+/–;Sost^+/–or single heterozygous and wild type mice. Although these data do not exclude a contribution of reduced sclerostin in the cortical expansion seen in Gja1 deficient bones, they are not consistent with a strong genetic interaction between Sost and Gja1 dictating cortical modeling.

Homozygous indel mutation in CDH11 as the probable cause of Elsahy-Waters syndrome

Two sisters from a consanguineous couple were seen in genetics department for facial dysmorphic features and glaucoma. They both had broad foreheads, hypertelorism, megalocorneas, thick eyebrows with synophrys, flat malar regions, broad and bulbous noses, and mild prognathism. Both had glaucoma, younger one also had cataracts and phthisis bulbi. Other findings included bilateral partial cutaneous syndactyly of 2nd and 3rd fingers, history of impacted teeth with dentigerous cyst in the elder one, and intellectual disability (mild and borderline). The sisters were considered to have Elsahy-Waters syndrome. In order to elucidate the underlying molecular cause, sisters and their healthy parents were genotyped by SNP arrays, followed by homozygosity mapping. Homozygous regions were further analyzed by exome sequencing in one affected individual. A homozygous indel variant segregating with the condition was detected in CDH11 (c.1116_1117delinsGATCATCAG, p.(Ile372MetfsTer9)), which was then validated by using Sanger sequencing. CDH11 encodes cadherin 11 (osteo-cadherin) that regulates cell-cell adhesion, cell polarization and migration, as well as osteogenic differentiation. Further experiments revealed that CDH11 expression was decreased in patient-derived fibroblasts as compared to the heterozygous parent and another healthy donor. Immunostaining showed absence of the protein expression in patient fibroblasts. In addition, cell proliferation rate was slow and osteogenic differentiation potential was delayed. We consider that this study reveals loss-of-function mutations in CDH11 as a probable cause of this phenotype. Next generation sequencing in further patients would both prove this gene as causative, and finely delineate this clinical spectrum further contributing in identification of other possibly involved gene(s).

The FOXP2-Driven Network in Developmental Disorders and Neurodegeneration

The transcription repressor FOXP2 is a crucial player in nervous system evolution and development of humans and songbirds. In order to provide an additional insight into its functional role we compared target gene expression levels between human neuroblastoma cells (SH-SY5Y) stably overexpressing FOXP2 cDNA of either humans or the common chimpanzee, Rhesus monkey, and marmoset, respectively. RNA-seq led to identification of 27 genes with differential regulation under the control of human FOXP2, which were previously reported to have FOXP2-driven and/or songbird song-related expression regulation. RT-qPCR and Western blotting indicated differential regulation of additional 13 new target genes in response to overexpression of human FOXP2. These genes may be directly regulated by FOXP2 considering numerous matches of established FOXP2-binding motifs as well as publicly available FOXP2-ChIP-seq reads within their putative promoters. Ontology analysis of the new and reproduced targets, along with their interactors in a network, revealed an enrichment of terms relating to cellular signaling and communication, metabolism and catabolism, cellular migration and differentiation, and expression regulation. Notably, terms including the words "neuron" or "axonogenesis" were also enriched. Complementary literature screening uncovered many connections to human developmental (autism spectrum disease, schizophrenia, Down syndrome, agenesis of corpus callosum, trismus-pseudocamptodactyly, ankyloglossia, facial dysmorphology) and neurodegenerative diseases and disorders (Alzheimer's, Parkinson's, and Huntington's diseases, Lewy body dementia, amyotrophic lateral sclerosis). Links to deafness and dyslexia were detected, too. Such relations existed for single proteins (e.g., DCDC2, NURR1, PHOX2B, MYH8, and MYH13) and groups of proteins which conjointly function in mRNA processing, ribosomal recruitment, cell-cell adhesion (e.g., CDH4), cytoskeleton organization, neuro-inflammation, and processing of amyloid precursor protein. Conspicuously, many links pointed to an involvement of the FOXP2-driven network in JAK/STAT signaling and the regulation of the ezrin-radixin-moesin complex. Altogether, the applied phylogenetic perspective substantiated FOXP2's importance for nervous system development, maintenance, and functioning. However, the study also disclosed new regulatory pathways that might prove to be useful for understanding the molecular background of the aforementioned developmental disorders and neurodegenerative diseases.

N-cadherin Regulation of Bone Growth and Homeostasis Is Osteolineage Stage-Specific

N-cadherin inhibits osteogenic cell differentiation and canonical Wnt/β-catenin signaling in vitro. However, in vivo both conditional Cdh2 ablation and overexpression in osteoblasts lead to low bone mass. We tested the hypothesis that N-cadherin has different effects on osteolineage cells depending upon their differentiation stage. Embryonic conditional osteolineage Cdh2 deletion in mice results in defective growth, low bone mass, and reduced osteoprogenitor number. These abnormalities are prevented by delaying Cdh2 ablation until 1 month of age, thus targeting only committed and mature osteoblasts, suggesting they are the consequence of N-cadherin deficiency in osteoprogenitors. Indeed, diaphyseal trabecularization actually increases when Cdh2 is ablated postnatally. The sclerostin-insensitive Lrp5^A214V mutant, associated with high bone mass, does not rescue the growth defect, but it overrides the low bone mass of embryonically Cdh2-deleted mice, suggesting N-cadherin interacts with Wnt signaling to control bone mass. Finally, bone accrual and β-catenin accumulation after administration of an anti-Dkk1 antibody are enhanced in N-cadherin-deficient mice. Thus, although lack of N-cadherin in embryonic and perinatal age is detrimental to bone growth and bone accrual, in adult mice loss of N-cadherin in osteolineage cells favors bone formation. Hence, N-cadherin inhibition may widen the therapeutic window of osteoanabolic agents. © 2017 American Society for Bone and Mineral Research.

A nano-scaled and multi-layered recombinant fibronectin/cadherin chimera composite selectively concentrates osteogenesis-related cells and factors to aid bone repair

Easily accessible and effective bone grafts are in urgent need in clinic. The selective cell retention (SCR) strategy, by which osteogenesis-related cells and factors are enriched from bone marrow into bio-scaffolds, holds great promise. However, the retention efficacy is limited by the relatively low densities of osteogenesis-related cells and factors in marrow; in addition, a lack of satisfactory surface modifiers for scaffolds further exacerbates the dilemma. To address this issue, a multi-layered construct consisting of a recombinant fibronectin/cadherin chimera was established via a layer-by-layer self-assembly technique (LBL-rFN/CDH) and used to modify demineralised bone matrix (DBM) scaffolds. The modification was proven stable and effective. By the mechanisms of physical interception and more importantly, chemical recognition (fibronectin/integrins), the LBL-rFN/CDH modification significantly improved the retention efficacy and selectivity for osteogenesis-related cells, e.g., monocytes, mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs), and bioactive factors, e.g., bFGF, BMP-2 and SDF-1α. Moreover, the resulting composite (designated as DBM-LBL-rFN/CDH) not only exhibited a strong MSC-recruiting capacity after SCR, but also provided favourable microenvironments for the proliferation and osteogenic differentiation of MSCs. Eventually, bone repair was evidently improved. Collectively, DBM-LBL-rFN/CDH presented a suitable biomaterial for SCR and a promising solution for tremendous need for bone grafts.

STATEMENT OF SIGNIFICANCE

There is an urgent need for effective bone grafts. With the potential of integrating osteogenicity, osteoinductivity and osteoconductivity, selective cell retention (SCR) technology brings hope for developing ideal grafts. However, it is constrained by low efficacy and selectivity. Thus, we modified demineralized bone matrix with nano-scaled and multi-layered recombinant fibronectin/cadherin chimera (DBM-rFN/CDH-LBL), and evaluate its effects on SCR and bone repair. DBM-rFN/CDH-LBL significantly improved the efficacy and selectivity of SCR via physical interception and chemical recognition. The post-enriched DBM-rFN/CDH-LBL provided favourable microenvironments to facilitate the migration, proliferation and osteogenic differentiation of MSCs, thus accelerating bone repair. Conclusively, DBM-rFN/CDH-LBL presents a novel biomaterial with advantages including high cost-effectiveness, more convenience for storage and transport and can be rapidly constructed intraoperatively.

The critical role of the ZNF217 oncogene in promoting breast cancer metastasis to the bone

Bone metastasis affects >70% of patients with advanced breast cancer. However, the molecular mechanisms underlying this process remain unclear. On the basis of analysis of clinical datasets, and in vitro and in vivo experiments, we report that the ZNF217 oncogene is a crucial mediator and indicator of bone metastasis. Patients with high ZNF217 mRNA expression levels in primary breast tumours had a higher risk of developing bone metastases. MDA-MB-231 breast cancer cells stably transfected with ZNF217 (MDA-MB-231-ZNF217) showed the dysregulated expression of a set of genes with bone-homing and metastasis characteristics, which overlapped with two previously described 'osteolytic bone metastasis' gene signatures, while also highlighting the bone morphogenetic protein (BMP) pathway. The latter was activated in MDA-MB-231-ZNF217 cells, and its silencing by inhibitors (Noggin and LDN-193189) was sufficient to rescue ZNF217-dependent cell migration, invasion or chemotaxis towards the bone environment. Finally, by using non-invasive multimodal in vivo imaging, we found that ZNF217 increases the metastatic growth rate in the bone and accelerates the development of severe osteolytic lesions. Altogether, the findings of this study highlight ZNF217 as an indicator of the emergence of breast cancer bone metastasis; future therapies targeting ZNF217 and/or the BMP signalling pathway may be beneficial by preventing the development of bone metastases. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Increased Bone Mass in Female Mice Lacking Mast Cell Chymase

Here we addressed the potential impact of chymase, a mast-cell restricted protease, on mouse bone phenotype. We show that female mice lacking the chymase Mcpt4 acquired a persistent expansion of diaphyseal bone in comparison with wild type controls, reaching a 15% larger diaphyseal cross sectional area at 12 months of age. Mcpt4-/- mice also showed increased levels of a bone anabolic serum marker and higher periosteal bone formation rate. However, they were not protected from experimental osteoporosis, suggesting that chymase regulates normal bone homeostasis rather than the course of osteoporosis. Further, the absence of Mcpt4 resulted in age-dependent upregulation of numerous genes important for bone formation but no effects on osteoclast activity. In spite of the latter, Mcpt4-/- bones had increased cortical porosity and reduced endocortical mineralization. Mast cells were found periosteally and, notably, bone-proximal mast cells in Mcpt4-/- mice were degranulated to a larger extent than in wild type mice. Hence, chymase regulates degranulation of bone mast cells, which could affect the release of mast cell-derived factors influencing bone remodelling. Together, these findings reveal a functional impact of mast cell chymase on bone. Further studies exploring the possibility of using chymase inhibitors as a strategy to increase bone volume may be warranted.

PS1/γ-Secretase-Mediated Cadherin Cleavage Induces β-Catenin Nuclear Translocation and Osteogenic Differentiation of Human Bone Marrow Stromal Cells

Bone marrow stromal cells (BMSCs) are considered a promising tool for bone bioengineering. However, the mechanisms controlling osteoblastic commitment are still unclear. Osteogenic differentiation of BMSCs requires the activation of β-catenin signaling, classically known to be regulated by the canonical Wnt pathway. However, BMSCs treatment with canonical Wnts in vitro does not always result in osteogenic differentiation and evidence indicates that a more complex signaling pathway, involving cadherins, would be required to induce β-catenin signaling in these cells. Here we showed that Wnt3a alone did not induce TCF activation in BMSCs, maintaining the cells at a proliferative state. On the other hand, we verified that, upon BMSCs osteoinduction with dexamethasone, cadherins were cleaved by the PS1/γ-secretase complex at the plasma membrane, and this event was associated with an enhanced β-catenin translocation to the nucleus and signaling. When PS1/γ-secretase activity was inhibited, the osteogenic process was impaired. Altogether, we provide evidence that PS1/γ-secretase-mediated cadherin cleavage has as an important role in controlling β-catenin signaling during the onset of BMSCs osteogenic differentiation, as part of a complex signaling pathway responsible for cell fate decision. A comprehensive map of these pathways might contribute to the development of strategies to improve bone repair.

N-cadherin restrains PTH repressive effects on sclerostin/SOST by regulating LRP6-PTH1R interaction

Sclerostin/SOST is a robust negative regulator of bone formation. Loss-of-function mutations of the sclerostin gene (SOST) cause sclerosteosis and Van Buchem disease characterized by bone overgrowth. Mediated by myocyte enhancer factor 2 (MEF2) transcription factors, parathyroid hormone (PTH) suppresses SOST expression through formation of complexes of parathyroid hormone-parathyroid hormone-related peptide receptor 1 (PTH1R) and lipoprotein receptor-related protein 6 (LRP6). N-cadherin has been shown to negatively regulate Wnt/β-catenin and PTH induced, protein kinase-dependent β-catenin signaling. Here, we investigated whether N-cadherin mediates the inhibitory effects of PTH on sclerostin/SOST. In vitro, overexpression of N-cadherin resulted in blunted PTH suppressive effects on sclerostin/SOST expression, as detected by immunoblot and qPCR analysis; PTH-induced downregulation of MEF2A, C, and D was impaired by N-cadherin; and N-cadherin reduced LRP6-PTHR1 interaction and endocytosis in response to PTH. In vivo, intermittent PTH (iPTH)-induced suppression of sclerostin/SOST was accentuated in Dmp1-cre; Cdh2^f/f (Cdh2^ΔDmp1 ) mice, compared with Cdh2^f/f mice. Additionally, iPTH had greater bone anabolic effects in Cdh2^ΔDmp1 mice compared to Cdh2^f/f mice. These data indicate that N-cadherin negatively mediates PTH suppressive effects on sclerostin/SOST by regulating LRP6-PTHR1 interaction, ultimately influencing PTH anabolic effects on bone.

Cadherin-11 Overexpression Induces Extracellular Matrix Remodeling and Calcification in Mature Aortic Valves

OBJECTIVE

Calcific aortic valve (AoV) disease is a significant clinical problem for which the regulatory mechanisms are poorly understood. Enhanced cell-cell adhesion is a common mechanism of cellular aggregation, but its role in calcific lesion formation is not known. Cadherin-11 (Cad-11) has been associated with lesion formation in vitro, but its function during adult valve homeostasis and pathogenesis is not known. This study aims to elucidate the specific functions of Cad-11 and its downstream targets, RhoA and Sox9, in extracellular matrix remodeling and AoV calcification.

APPROACH AND RESULTS

We conditionally overexpressed Cad-11 in murine heart valves using a novel double-transgenic Nfatc1(Cre);R26-Cad11(TglTg) mouse model. These mice developed hemodynamically significant aortic stenosis with prominent calcific lesions in the AoV leaflets. Cad-11 overexpression upregulated downstream targets, RhoA and Sox9, in the valve interstitial cells, causing calcification and extensive pathogenic extracellular matrix remodeling. AoV interstitial cells overexpressing Cad-11 in an osteogenic environment in vitro rapidly form calcific nodules analogous to in vivo lesions. Molecular analyses revealed upregulation of osteoblastic and myofibroblastic markers. Treatment with a Rho-associated protein kinase inhibitor attenuated nodule formation, further supporting that Cad-11-driven calcification acts through the small GTPase RhoA/Rho-associated protein kinase signaling pathway.

CONCLUSIONS

This study identifies one of the underlying molecular mechanisms of heart valve calcification and demonstrates that overexpression of Cad-11 upregulates RhoA and Sox9 to induce calcification and extracellular matrix remodeling in adult AoV pathogenesis. The findings provide a potential molecular target for clinical treatment.

Gene expression profiles in guided bone regeneration using combinations of different biomaterials: a pilot animal study

OBJECTIVES

The aim of this study was to investigate the gene expression profile related to guided bone regeneration (GBR) at the early healing stage while using combinations of different biomaterials.

MATERIALS AND METHODS

Cranial defects in 4 New Zealand rabbits were filled with A) biphasic calcium phosphate/experimental pericardium-derived collagen membrane, B) Bio-Oss^® /Bio-Gide^® , C) biphasic calcium phosphate/strontium hydroxyapatite-containing collagen membrane and D) Bio-Oss^® /strontium hydroxyapatite-containing collagen membrane. Seven days after surgery, one animal was subjected to histological observation and histomorphometric analysis, and three animals to real-time quantitative reverse transcription polymerase chain reaction (PCR). An RT² Profiler PCR Array (PANZ-026Z, QIAGEN, QIAGEN Sciences, Germantown, MD, USA) was conducted to observe the gene expression profile of groups A, C and D as compared with the control group B.

RESULTS

The analysis showed 9 of the 84 genes on the array to be significantly different in the three experimental groups (six genes in group D, four in group C and one in group A). Group D demonstrated the most changes in gene expression profile at day 7. Genes that were significantly down-regulated (AHSG, EGF) or up-regulated (CDH11, MMP13, GLI1 and MCSF) are responsible for early-stage bone formation, bone remodeling and pre-osteoclast development. The gene expression profile of this group correlated with the histological findings, as this group showed the higher formation of osteoid as compared with the other groups.

CONCLUSION

Gene expression patterns at early-stage healing of GBR-treated defects appear to be related to the biomaterial used. The combination of Bio-Oss^® and strontium hydroxyapatite-containing collagen membrane showed the most pro-osteogenic gene regulation profile (group D), implying the stimulation of key transcriptional factors, which appeared to translate into the up-regulation of the osteogenic process and earlier bone formation.

Hydrogels functionalized with N-cadherin mimetic peptide enhance osteogenesis of hMSCs by emulating the osteogenic niche

N-cadherin is considered to be the key factor in directing cell-cell interactions during mesenchymal condensation, which is essential to osteogenesis. In this study, hyaluronic acid (HA) hydrogels are biofunctionalized with an N-cadherin mimetic peptide to mimic the pro-osteogenic niche in the endosteal space to promote the osteogenesis of human mesenchymal stem cells (hMSCs). Results show that the conjugation of the N-cadherin peptide in the HA hydrogels enhances the expression of the osteogenic marker genes in the seeded hMSCs. Furthermore, the biofunctionalized HA hydrogels promote the alkaline phosphatase activity, type I collagen deposition, and matrix mineralization by the seeded hMSCs under both in vitro and in vivo condition. We postulate that the biofunctionalized hydrogels emulates the N-cadherin-mediated homotypic cell-cell adhesion among MSCs and the "orthotypic" interaction between the osteoblasts and MSCs. These findings demonstrate that the biofunctionalized HA hydrogels provide a supportive niche microenvironment for the osteogenesis of hMSCs.