The protein kinase C pathway plays a central role in the fibroblast growth factor-stimulated expression and transactivation activity of Runx2

Unraveling the dynamics of osteoblast differentiation in MC3T3-E1 cells: Transcriptomic insights into matrix mineralization and cell proliferation

Unraveling the intricacies of osteoblast differentiation is crucial for advancing our comprehension of bone biology. This study investigated the complicated molecular events orchestrating osteoblast differentiation in MC3T3-E1 cells, a well-established in vitro culture model. Employing longitudinal RNA-sequencing analysis, we explored transcriptomic changes at the pivotal time points of 0, 1, 4, 7, 10, 14, and 21 days and categorized osteogenic differentiation into proliferation, matrix maturation, and mineralization stages. Notably, we observed a simultaneous increase in matrix mineralization and cell proliferation during the mineralization stage, accompanied by a positive correlation between proliferation-associated genes and those enriched in ossification. Additionally, we identified the presence of proliferating cells over the mineralizing matrix layers. These results could serve as a model for understanding the principles by which bone lining cells are formed on the calcified bone matrix and the mechanism by which new osteoblasts are recruited during the bone remodeling process.

Berberine Derivative Compound 13 as a Potent Promoter of Osteoblast Differentiation via Akt and PKC Signaling Pathways

Berberine has been widely studied for its biological functions in various diseases, including cancer, diabetes, and cardiovascular diseases. Nevertheless, structural modifications of berberine have been demonstrated to augment its pharmacological efficacy in specific biological processes, particularly osteogenesis. In this study, we aimed to explore new berberine derivatives with pro-osteogenic activity and molecular mechanisms. Our results demonstrated that compound 13 is the most effective among the tested compounds. Compound 13 significantly enhanced BMP4-induced alkaline phosphatase (ALP) staining and increased the transcriptional activity of osteogenic markers such as ALP, Runt-related gene 2 (Runx2), and Osterix at both the mRNA and protein levels. Furthermore, we found that the Akt and PKC signaling pathways play crucial roles in compound 13-induced osteogenesis via treatment with specific inhibitors. The molecular docking results supported the potential interaction between compound 13 and these kinases. These findings highlighted the regulatory role of compound 13 in osteoblast differentiation via the Akt and PKC signaling pathways. Overall, our study provides compelling evidence that compound 13 is a promising therapeutic candidate for the treatment of osteoporosis, with the potential for further development and optimization to improve bone health and strength.

Notch signaling pathway in osteogenesis, bone development, metabolism, and diseases

The skeletal system provides vital importance to support organ development and functions. The Notch signaling pathway possesses well-established functions in organ development and cellular homeostasis. The Notch signaling pathway comprises five typical ligands (JAG1, JAG2, DLL1, DLL3, and DLL4), four receptors (Notch1-4), and four intracellular domains (NICD1-4). Each component of the Notch signaling pathway has been demonstrated to be fundamental in osteoblast differentiation and bone formation. The dysregulation in the Notch signaling pathway is highly linked with skeletal disorders or diseases at the developmental and postnatal stages. Recent studies have highlighted the importance of the elements of the Notch signaling pathway in the skeletal system, as well as its interaction with signaling, such as Wnt/β-catenin, BMP, TGF-β, FGF, autophagy, and hedgehog (Hh) to construct a potential gene regulatory network to orchestrate osteogenesis and ossification. Our review has provided a comprehensive summary of the Notch signaling pathway in the skeletal system, as well as the insights targeting Notch signaling for innovative potential drug discovery targets or therapeutic interventions to treat bone disorders, such as osteoporosis and osteoarthritis. An in-depth molecular mechanistic strategy to modulate the Notch signaling pathway and its associated signaling pathway will be encouraged for consideration to trigger enhanced therapeutic approaches for bone disorders by defining Notch-regulating drugs for clinical use.

Impaired MC3T3-E1 osteoblast differentiation triggered by oncogenic HRAS is rescued by the farnesyltransferase inhibitor Tipifarnib

HRAS is a ubiquitously expressed protein and functions as a central regulator of cellular homeostasis. In somatic cells, mutations in this gene cause cancer, while germline mutations trigger a developmental disorder known as Costello syndrome (CS). Among numerous pathologies, adult CS patients develop osteoporosis. Previous studies revealed that HRAS is implicated in bone homeostasis by controlling osteoblast differentiation, adaptation to mechanical strain and repression of RANKL expression in mature osteoblasts, and by regulating osteoclast differentiation. However, the impact of HRAS on osteoblast differentiation is still debatable. In this study, we created stable doxycycline inducible cell lines overexpressing HRAS G12 mutants in MC3T3-E1 preosteoblast cell line and analyzed their impact on osteoblast differentiation. We demonstrated an inhibitory role of HRAS G12S and HRAS G12V mutants on osteogenic differentiation and identified an increased expression of Opn in an HRAS-dependent manner, which directly correlated with impaired osteogenesis, and was rescued by the farnesyl transferase inhibitor Tipifarnib. At the molecular level, Tipifarnib was not able to block HRAS activation, but impaired HRAS localization to the plasma membrane, and inhibited MAPK activation and Opn expression. Thus, HRAS abundance/activation and its potential crosstalk with OPN may be more critical for osteogenic differentiation than previously assumed.

The Tight Relationship Between the Tumoral Microenvironment and Radium-223

Radium-223 (223Ra) was the first radioactive isotope approved for treating castration-resistant prostate cancer (CRPC) with symptomatic bone metastases without visceral metastatic disease. To better understand the action of 223Ra, its role in the tumor microenvironment represents a crucial aspect. A literature search was conducted using the PubMed/MEDLINE database and studies regarding the relationship between 223Ra and the tumoral microenvironment were considered. The tumoral microenvironment is a complex setting in which complex interactions between cells and molecules occur. Radium-223, as an alpha-emitter, induces double-stranded DNA breaks; to potentiate this effect, it could be used in patients with genetic instability but also in combination with therapies which inhibit DNA repair, modulate the immune response, or control tumor growth. In conclusion, a few studies have taken into consideration the tumoral microenvironment in association with 223Ra. However, its understanding is a priority to better comprehend how to effectively exploit 223Ra and its action mechanism.

Protein kinase C signaling "in" and "to" the nucleus: Master kinases in transcriptional regulation

PKC is a multifunctional family of Ser-Thr kinases widely implicated in the regulation of fundamental cellular functions, including proliferation, polarity, motility, and differentiation. Notwithstanding their primary cytoplasmic localization and stringent activation by cell surface receptors, PKC isozymes impel prominent nuclear signaling ultimately impacting gene expression. While transcriptional regulation may be wielded by nuclear PKCs, it most often relies on cytoplasmic phosphorylation events that result in nuclear shuttling of PKC downstream effectors, including transcription factors. As expected from the unique coupling of PKC isozymes to signaling effector pathways, glaring disparities in gene activation/repression are observed upon targeting individual PKC family members. Notably, specific PKCs control the expression and activation of transcription factors implicated in cell cycle/mitogenesis, epithelial-to-mesenchymal transition and immune function. Additionally, PKCs isozymes tightly regulate transcription factors involved in stepwise differentiation of pluripotent stem cells toward specific epithelial, mesenchymal, and hematopoietic cell lineages. Aberrant PKC expression and/or activation in pathological conditions, such as in cancer, leads to profound alterations in gene expression, leading to an extensive rewiring of transcriptional networks associated with mitogenesis, invasiveness, stemness, and tumor microenvironment dysregulation. In this review, we outline the current understanding of PKC signaling "in" and "to" the nucleus, with significant focus on established paradigms of PKC-mediated transcriptional control. Dissecting these complexities would allow the identification of relevant molecular targets implicated in a wide spectrum of diseases.

Safety of terminally gamma-ray-sterilized screws coated with fibroblast growth factor 2-calcium phosphate composite layers in non-human primates

Screws coated with fibroblast growth factor 2 (FGF-2)-calcium phosphate (CP) composite layers exhibit enhanced soft tissue and bone formation and angiogenesis because of the biological activity of FGF-2. Furthermore, the mitogenic activity of the FGF-2 within the composite layers remains unchanged after gamma-ray sterilization, which may improve the storage stability prior to clinical use. However, the in vivo safeties of these screws as spinal implants remain unknown. Here, a randomized controlled trial, involving non-human primates, investigated the safety of using FGF-2-CP composite layer-coated screws after either gamma-ray sterilization or aseptic processing. Titanium alloy screws coated with FGF-2-CP composite layers and subjected to either gamma-ray sterilization at 25 kGy (GS group) or aseptic storage (AS group) were implanted into the vertebral bodies of two cynomolgus monkeys exceeding 12 weeks (day 99). Physiological, histological, and radiographic investigations were performed to evaluate the safeties of the screws. There were no serious adverse events, such as surgical site infection, significant loss of body weight, or abnormal blood test results. No radiolucent areas were observed around the screws from the GS or AS group throughout the study. In the intraosseous region, no significant differences were observed in bone and fibrous tissue apposition rates and rate of bone formation between the two groups (p = 0.49, 0.77, and 0.11, respectively). Neither tumor lesions nor accumulation of lymphocytes and neutrophils were observed in either group. Our data suggest that FGF-2-CP composite layer-coated screws subjected to terminal gamma-ray sterilization are as safe as those fabricated in aseptic processing.

Elucidating Fibroblast Growth Factor-Induced Kinome Dynamics Using Targeted Mass Spectrometry and Dynamic Modeling

Fibroblast growth factors (FGFs) are paracrine or endocrine signaling proteins that, activated by their ligands, elicit a wide range of health and disease-related processes, such as cell proliferation and the epithelial-to-mesenchymal transition. The detailed molecular pathway dynamics that coordinate these responses have remained to be determined. To elucidate these, we stimulated MCF-7 breast cancer cells with either FGF2, FGF3, FGF4, FGF10, or FGF19. Following activation of the receptor, we quantified the kinase activity dynamics of 44 kinases using a targeted mass spectrometry assay. Our system-wide kinase activity data, supplemented with (phospho)proteomics data, reveal ligand-dependent distinct pathway dynamics, elucidate the involvement of not earlier reported kinases such as MARK, and revise some of the pathway effects on biological outcomes. In addition, logic-based dynamic modeling of the kinome dynamics further verifies the biological goodness-of-fit of the predicted models and reveals BRAF-driven activation upon FGF2 treatment and ARAF-driven activation upon FGF4 treatment.

The enhancing effects of heparin on the biological activity of FGF-2 in heparin-FGF-2-calcium phosphate composite layers

Orthopedic and dental implants coated with fibroblast growth factor-2 (FGF-2)-calcium phosphate composite layers promote dermis formation, bone formation, and angiogenesis because of the biological activity of FGF-2. Enhancing the biological activity of FGF-2 in the composite layers is important for its wider application in orthopedics and dentistry. This study incorporated low-molecular-weight heparin (LMWH) into the FGF-2-calcium phosphate composite layers and clarified the enhancing effects of LMWH on the biological activity of FGF-2 in the composite layers in vitro. LMWH-FGF-2-calcium phosphate composite layers were successfully formed on zirconia in supersaturated calcium phosphate solutions. The composite layers comprised continuous and macroscopically homogeneous layers and particles smaller than 500 nm in size composed of amorphous calcium phosphate. The amounts of Ca and P deposited on zirconia remained almost unchanged with the addition of LMWH under the presence of FGF-2 in the supersaturated calcium phosphate solution. The LMWH in the supersaturated calcium phosphate solution increased the stability of FGF-2 in the solution and the amount of FGF-2 in the composite layers. The LMWH in the composite layers increased the mitogenic and endothelial tube-forming activities of FGF-2, and FGF-2 activity of inducing osteogenic differentiation gene expression pattern in the composite layers. Our results indicate that the enhanced biological activity of FGF-2 in the LMWH-FGF-2-calcium phosphate composite layers is attributed to an LMWH-mediated increase in the amount of FGF-2, which maintains its biological activity in the supersaturated calcium phosphate solution and the composite layers. The LMWH-FGF-2-calcium phosphate composite layer is a promising coating for orthopedic and dental implants. STATEMENT OF SIGNIFICANCE: Orthopedic and dental implants coated with fibroblast growth factor-2 (FGF-2)-calcium phosphate composite layers promote dermis formation, bone formation, and angiogenesis because of the biological activity of FGF-2. Enhancing the biological activity of FGF-2 in the layers is important for wider its application in orthopedics and dentistry. This study demonstrates the enhancing effects of low-molecular-weight heparin (LMWH) contained within LMWH-FGF-2-calcium phosphate composite layers on the biological activity of FGF-2 in vitro. Our results indicate that the enhanced biological activity of FGF-2 within the composite layers arises from an LMWH-mediated increase in the amount of FGF-2, which maintains its biological activity in the LMWH-FGF-2-calcium phosphate composite layers and supersaturated calcium phosphate solutions used for coating the composite layers.

Anosmin-1-Like Effect of UMODL1/Olfactorin on the Chemomigration of Mouse GnRH Neurons and Zebrafish Olfactory Axons Development

The impairment of development/migration of hypothalamic gonadotropin-releasing hormone (GnRH) neurons is the main cause of Kallmann's syndrome (KS), an inherited disorder characterized by hypogonadism, anosmia, and other developmental defects. Olfactorin is an extracellular matrix protein encoded by the UMODL1 (uromodulin-like 1) gene expressed in the mouse olfactory region along the migratory route of GnRH neurons. It shares a combination of WAP and FNIII repeats, expressed in complementary domains, with anosmin-1, the product of the ANOS1 gene, identified as the causative of KS. In the present study, we have investigated the effects of olfactorin in vitro and in vivo models. The results show that olfactorin exerts an anosmin-1-like strong chemoattractant effect on mouse-immortalized GnRH neurons (GN11 cells) through the activation of the FGFR and MAPK pathways. In silico analysis of olfactorin and anosmin-1 reveals a satisfactory similarity at the N-terminal region for the overall arrangement of corresponding WAP and FNIII domains and marked similarities between WAP domains’ binding modes of interaction with the resolved FGFR1–FGF2 complex. Finally, in vivo experiments show that the down-modulation of the zebrafish z-umodl1 gene (orthologous of UMODL1) in both GnRH3:GFP and omp2k:gap-CFPrw034 transgenic zebrafish strains leads to a clear disorganization and altered fasciculation of the neurites of GnRH3:GFP neurons crossing at the anterior commissure and a significant increase in olfactory CFP + fibers with altered trajectory. Thus, our study shows olfactorin as an additional factor involved in the development of olfactory and GnRH systems and proposes UMODL1 as a gene worthy of diagnostic investigation in KS.

Excessive osteoclast activation by osteoblast paracrine factor RANKL is a major cause of the abnormal long bone phenotype in Apert syndrome model mice

The fibroblast growth factor (FGF)/FGF receptor (FGFR) signaling pathway plays important roles in the development and growth of the skeleton. Apert syndrome caused by gain‐of‐function mutations of FGFR2 results in aberrant phenotypes of the skull, midface, and limbs. Although short limbs are representative features in patients with Apert syndrome, the causative mechanism for this limb defect has not been elucidated. Here we quantitatively confirmed decreases in the bone length, bone mineral density, and bone thickness in the Apert syndrome model of gene knock‐in Fgfr2^S252W/+ (EIIA‐Fgfr2^S252W/+) mice. Interestingly, despite these bone defects, histological analysis showed that the endochondral ossification process in the mutant mice was similar to that in wild‐type mice. Tartrate‐resistant acid phosphatase staining revealed that trabecular bone loss in mutant mice was associated with excessive osteoclast activity despite accelerated osteogenic differentiation. We investigated the osteoblast–osteoclast interaction and found that the increase in osteoclast activity was due to an increase in the Rankl level of osteoblasts in mutant mice and not enhanced osteoclastogenesis driven by the activation of FGFR2 signaling in bone marrow‐derived macrophages. Consistently, Col1a1‐Fgfr2^S252W/+ mice, which had osteoblast‐specific expression of Fgfr2 S252W, showed significant bone loss with a reduction of the bone length and excessive activity of osteoclasts was observed in the mutant mice. Taken together, the present study demonstrates that the imbalance in osteoblast and osteoclast coupling by abnormally increased Rankl expression in Fgfr2^S252W/+ mutant osteoblasts is a major causative mechanism for bone loss and short long bones in Fgfr2^S252W/+ mice.

The Potential of FGF-2 in Craniofacial Bone Tissue Engineering: A Review

Bone is a hard-vascularized tissue, which renews itself continuously to adapt to the mechanical and metabolic demands of the body. The craniofacial area is prone to trauma and pathologies that often result in large bone damage, these leading to both aesthetic and functional complications for patients. The "gold standard" for treating these large defects is autologous bone grafting, which has some drawbacks including the requirement for a second surgical site with quantity of bone limitations, pain and other surgical complications. Indeed, tissue engineering combining a biomaterial with the appropriate cells and molecules of interest would allow a new therapeutic approach to treat large bone defects while avoiding complications associated with a second surgical site. This review first outlines the current knowledge of bone remodeling and the different signaling pathways involved seeking to improve our understanding of the roles of each to be able to stimulate or inhibit them. Secondly, it highlights the interesting characteristics of one growth factor in particular, FGF-2, and its role in bone homeostasis, before then analyzing its potential usefulness in craniofacial bone tissue engineering because of its proliferative, pro-angiogenic and pro-osteogenic effects depending on its spatial-temporal use, dose and mode of administration.

Bovine milk extracellular vesicles induce the proliferation and differentiation of osteoblasts and promote osteogenesis in rats

Bone is constantly balanced between the formation of new bone by osteoblasts and the absorption of old bone by osteoclasts. To promote bone growth and improve bone health, it is necessary to promote the proliferation and differentiation of osteoblasts. Although bovine milk is known to exert a beneficial effect on bone formation, the study on the effect of bovine milk extracellular vesicles (EVs) on osteogenesis in osteoblasts is limited. In this study, we demonstrated that bovine milk EVs promoted the proliferation of human osteogenic Saos-2 cells by increasing the expression of cell cycle-related proteins. In addition, bovine milk EVs also induced the differentiation of Saos-2 cells by increasing the expression of RUNX2 and Osterix which are key transcription factors for osteoblast differentiation. Oral administration of milk EVs did not cause toxicity in Sprague-Dawley rats. Furthermore, milk EVs promoted longitudinal bone growth and increased the bone mineral density of the tibia. Our findings suggest that milk EVs could be a safe and powerful applicant for enhancing osteogenesis. PRACTICAL APPLICATIONS: Until now, calcium and vitamin D have been prescribed to promote bone formation or to prevent bone diseases such as osteoporosis. Recently, several studies to find bioactive molecules that regulate cellular functions of osteoblasts or osteoclasts are actively underway. Milk basic proteins and lactoferrin present in milk are known to promote bone formation, but they exist in small quantities and the isolation of these proteins is complicated making mass production difficult. Recently, it has been found that milk contains large quantities of EVs, and that they promote bone formation. Studies on the effect of Milk EVs on osteoblasts during osteogenesis will help in the development of biomaterials for osteogenesis.

Transcriptional Programming in Arteriosclerotic Disease: A Multifaceted Function of the Runx2 (Runt-Related Transcription Factor 2)

Despite successful therapeutic strategies in the prevention and treatment of arteriosclerosis, the cardiovascular complications remain a major clinical and societal issue worldwide. Increased vascular calcification promotes arterial stiffness and accelerates cardiovascular morbidity and mortality. Upregulation of the Runx2 (Runt-related transcription factor 2), an essential osteogenic transcription factor for bone formation, in the cardiovascular system has emerged as an important regulator for adverse cellular events that drive cardiovascular pathology. This review discusses the regulatory mechanisms that are critical for Runx2 expression and function and highlights the dynamic and complex cross talks of a wide variety of posttranslational modifications, including phosphorylation, acetylation, ubiquitination, and O-linked β-N-acetylglucosamine modification, in regulating Runx2 stability, cellular localization, and osteogenic transcriptional activity. How the activation of an array of signaling cascades by circulating and local microenvironmental factors upregulates Runx2 in vascular cells and promotes Runx2-mediated osteogenic transdifferentiation of vascular smooth muscle cells and expression of inflammatory cytokines that accelerate macrophage infiltration and vascular osteoclast formation is summarized. Furthermore, the increasing appreciation of a new role of Runx2 upregulation in promoting vascular smooth muscle cell phenotypic switch, and Runx2 modulated by O-linked β-N-acetylglucosamine modification and Runx2-dependent repression of smooth muscle cell-specific gene expression are discussed. Further exploring the regulation of this key osteogenic transcription factor and its new perspectives in the vasculature will provide novel insights into the transcriptional regulation of vascular smooth muscle cell phenotype switch, reprograming, and vascular inflammation that promote the pathogenesis of arteriosclerosis.

Biological Characteristics and Osteogenic Differentiation of Ovine Bone Marrow Derived Mesenchymal Stem Cells Stimulated with FGF-2 and BMP-2

Cell-based therapies using mesenchymal stem cells (MSCs) are a promising tool in bone tissue engineering. Bone regeneration with MSCs involves a series of molecular processes leading to the activation of the osteoinductive cascade supported by bioactive factors, including fibroblast growth factor-2 (FGF-2) and bone morphogenetic protein-2 (BMP-2). In this study, we examined the biological characteristics and osteogenic differentiation potential of sheep bone marrow MSCs (BM-MSCs) treated with 20 ng/mL of FGF-2 and 100 ng/mL BMP-2 in vitro. The biological properties of osteogenic-induced BM-MSCs were investigated by assessing their morphology, proliferation, phenotype, and cytokine secretory profile. The osteogenic differentiation was characterized by Alizarin Red S staining, immunofluorescent staining of osteocalcin and collagen type I, and expression levels of genetic markers of osteogenesis. The results demonstrated that BM-MSCs treated with FGF-2 and BMP-2 maintained their primary MSC properties and improved their osteogenic differentiation capacity, as confirmed by increased expression of osteocalcin and collagen type I and upregulation of osteogenic-related gene markers BMP-2, Runx2, osterix, collagen type I, osteocalcin, and osteopontin. Furthermore, sheep BM-MSCs produced a variety of bioactive factors involved in osteogenesis, and supplementation of the culture medium with FGF-2 and BMP-2 affected the secretome profile of the cells. The results suggest that sheep osteogenic-induced BM-MSCs may be used as a cellular therapy to study bone repair in the preclinical large animal model.

Nicotinamide Improves Delayed Tooth Eruption in Runx2+/- Mice

Patients with cleidocranial dysplasia (CCD) caused by mutations in RUNX2 have severe dental anomalies, including delayed or absent eruption of permanent teeth. This requires painful and expensive surgical/orthodontic intervention because of the absence of medicine for this condition. Here, we demonstrate that nicotinamide, a vitamin B3 and class III histone deacetylase inhibitor, significantly improves delayed tooth eruption in Runx2^+/- mice, a well-known CCD animal model, through the restoration of decreased osteoclastogenesis. We also found that Csf1 mRNA and protein levels were significantly reduced in Runx2^+/- osteoblasts as compared with wild type whereas RANKL and OPG levels had no significant difference between wild type and Runx2^+/- osteoblasts. The nicotinamide-induced restoration of osteoclastogenesis of bone marrow-derived macrophages in Runx2^+/- mice was due to the increased expression of RUNX2 and CSF1 and increased RANKL/OPG ratio. RUNX2 directly regulated Csf1 mRNA expression via binding to the promoter region of the Csf1 gene. In addition, nicotinamide enhanced the RUNX2 protein level and transacting activity posttranslationally with Sirt2 inhibition. Taken together, our study shows the potential and underlying molecular mechanism of nicotinamide for the treatment of delayed tooth eruption by using the Runx2^+/- murine model, suggesting nicotinamide as a candidate therapeutic drug for dental abnormalities in patients with CCD.

Lineage-specific differentiation of osteogenic progenitors from pluripotent stem cells reveals the FGF1-RUNX2 association in neural crest-derived osteoprogenitors

Human pluripotent stem cells (hPSCs) can provide a platform to model bone organogenesis and disease. To reflect the developmental process of the human skeleton, hPSC differentiation methods should include osteogenic progenitors (OPs) arising from three distinct embryonic lineages: the paraxial mesoderm, lateral plate mesoderm, and neural crest. Although OP differentiation protocols have been developed, the lineage from which they are derived, as well as characterization of their genetic and molecular differences, has not been well reported. Therefore, to generate lineage-specific OPs from human embryonic stem cells and human induced pluripotent stem cells, we employed stepwise differentiation of paraxial mesoderm-like cells, lateral plate mesoderm-like cells, and neural crest-like cells toward their respective OP subpopulation. Successful differentiation, confirmed through gene expression and in vivo assays, permitted the identification of transcriptomic signatures of all three cell populations. We also report, for the first time, high FGF1 levels in neural crest-derived OPs-a notable finding given the critical role of fibroblast growth factors (FGFs) in osteogenesis and mineral homeostasis. Our results indicate that FGF1 influences RUNX2 levels, with concomitant changes in ERK1/2 signaling. Overall, our study further validates hPSCs' power to model bone development and disease and reveals new, potentially important pathways influencing these processes.

RUNX2-modifying enzymes: therapeutic targets for bone diseases

RUNX2 is a master transcription factor of osteoblast differentiation. RUNX2 expression in the bone and osteogenic front of a suture is crucial for cranial suture closure and membranous bone morphogenesis. In this manner, the regulation of RUNX2 is precisely controlled by multiple posttranslational modifications (PTMs) mediated by the stepwise recruitment of multiple enzymes. Genetic defects in RUNX2 itself or in its PTM regulatory pathways result in craniofacial malformations. Haploinsufficiency in RUNX2 causes cleidocranial dysplasia (CCD), which is characterized by open fontanelle and hypoplastic clavicles. In contrast, gain-of-function mutations in FGFRs, which are known upstream stimulating signals of RUNX2 activity, cause craniosynostosis (CS) characterized by premature suture obliteration. The identification of these PTM cascades could suggest suitable drug targets for RUNX2 regulation. In this review, we will focus on the mechanism of RUNX2 regulation mediated by PTMs, such as phosphorylation, prolyl isomerization, acetylation, and ubiquitination, and we will summarize the therapeutics associated with each PTM enzyme for the treatment of congenital cranial suture anomalies.

Myristoylated alanine-rich C-kinase substrate effector domain peptide improves sex-specific recovery and axonal regrowth after spinal cord injury

Myristoylated alanine-rich C-kinase substrate (MARCKS) is an intracellular receptor for polysialic acid. MARCKS supports development, synaptic plasticity, and regeneration after injury. MARCKS binds with its functionally essential effector domain (ED) to polysialic acid. A 25-mer peptide comprising the ED of MARCKS stimulates neuritogenesis of primary hippocampal neurons after addition to the culture. This motivated us to investigate whether ED peptide has similar effects in spinal cord injury. ED peptide supported recovery and regrowth of monoaminergic axons in female, but not in male mice. Sex-specific differences in response to ED peptide application also occurred in cultured neurons. In female but not male neurons, the ED peptide enhanced neurite outgrowth that could be suppressed by inhibitors of the estrogen receptors α and β, fibroblast growth factor receptor-1, protein kinase C, and matrix metalloproteinase 2. In addition, we observed female-specific elevation of phosphorylated MARCKS levels after ED peptide treatment. In male neurons, the ED peptide enhanced neuritogenesis in the presence of an androgen receptor inhibitor to the extent seen in ED peptide-treated female neurons. However, inhibition of androgen receptor did not lead to increased phosphorylation of MARCKS. These results provide insights into the functions of a novel compound contributing to gender-dependent regeneration.

The FGF/FGFR system in the physiopathology of the prostate gland

Fibroblast growth factors (FGFs) are a family of proteins possessing paracrine, autocrine, or endocrine functions in a variety of biological processes, including embryonic development, angiogenesis, tissue homeostasis, wound repair, and cancer. Canonical FGFs bind and activate tyrosine kinase FGF receptors (FGFRs), triggering intracellular signaling cascades that mediate their biological activity. Experimental evidence indicates that FGFs play a complex role in the physiopathology of the prostate gland that ranges from essential functions during embryonic development to modulation of neoplastic transformation. The use of ligand- and receptor-deleted mouse models has highlighted the requirement for FGF signaling in the normal development of the prostate gland. In adult prostate, the maintenance of a functional FGF/FGFR signaling axis is critical for organ homeostasis and function, as its disruption leads to prostate hyperplasia and may contribute to cancer progression and metastatic dissemination. Dissection of the molecular landscape modulated by the FGF family will facilitate ongoing translational efforts directed toward prostate cancer therapy.

Functional Characteristics of Novel FGFR1 Mutations in Patients with Isolated Gonadotropin-Releasing Hormone Deficiency

BACKGROUND

Isolated gonadotropin-releasing hormone (GnRH) deficiency (IGD) has a wide phenotypic spectrum including Kallmann syndrome (KS) and normosmic idiopathic hypogonadotropic hypogonadism (nIHH). FGFR1 mutations have been identified in 3-10% of patients with KS or nIHH. This study was performed to investigate clinical phenotypes and functional characteristics of FGFR1 mutations in patients with IGD.

METHODS

This study included 8 patients (from 7 families) with FGFR1 mutations identified by targeted gene panel sequencing or whole exome sequencing (WES). The impact of the identified mutations on FGFR1 function was assessed using in vitro studies.

RESULTS

Seven heterozygous mutations in FGFR1 were identified in 8 patients from 7 independent families. The patients exhibited a wide spectrum of pubertal development, including anosmia in a prepubertal boy (n=1), delayed puberty (n=2), nIHH (n=3), and KS (n=2). Four of the mutations were classified as likely pathogenic, and the other three were variants of uncertain significance. FGF8-FGFR1 signaling activities for the novel FGFR1 variants (p.Y339H, p.S681I, and p.N185Kfs*16) were reduced by in vitro functional assay, indicating loss-of-function mutations.

CONCLUSIONS

This study identified seven rare sequence variants in FGFR1 in patients with KS and nIHH. Probands with an FGFR1 mutations displayed a wide phenotypic spectrum ranging from KS to anosmia. A prepubertal male with anosmia should be followed up to assess pubertal development because they can manifest hypogonadotropic hypogonadism after puberty. These results expand the phenotypic spectrum of FGFR1 mutations and suggest a broader biologic role of FGFR1 in reproduction.

Post-Translational Regulations of Transcriptional Activity of RUNX2

Runt-related transcription factor 2 (RUNX2) is a key transcription factor for bone formation and osteoblast differentiation. Various signaling pathways and mechanisms that regulate the expression and transcriptional activity of RUNX2 have been thoroughly investigated since the involvement of RUNX2 was first reported in bone formation. As the regulation of Runx2 expression by extracellular signals has recently been reviewed, this review focuses on the regulation of post-translational RUNX2 activity. Transcriptional activity of RUNX2 is regulated at the post-translational level by various enzymes including kinases, acetyl transferases, deacetylases, ubiquitin E3 ligases, and prolyl isomerases. We describe a sequential and linear causality between post-translational modifications of RUNX2 by these enzymes. RUNX2 is one of the most important osteogenic transcription factors; however, it is not a suitable drug target. Here, we suggest enzymes that directly regulate the stability and/or transcriptional activity of RUNX2 at a post-translational level as effective drug targets for treating bone diseases.

PIN1 Attenuation Improves Midface Hypoplasia in a Mouse Model of Apert Syndrome

Premature fusion of the cranial suture and midface hypoplasia are common features of syndromic craniosynostosis caused by mutations in the FGFR2 gene. The only treatment for this condition involves a series of risky surgical procedures designed to correct defects in the craniofacial bones, which must be performed until brain growth has been completed. Several pharmacologic interventions directed at FGFR2 downstream signaling have been tested as potential treatments for premature coronal suture fusion in a mouse model of Apert syndrome. However, there are no published studies that have targeted for the pharmacologic treatment of midface hypoplasia. We used Fgfr2^S252W/+ knock-in mice as a model of Apert syndrome and morphometric analyses to identify causal hypoplastic sites in the midface region. Three-dimensional geometric and linear analyses of Fgfr2^S252W/+ mice at postnatal day 0 demonstrated distinct morphologic variance. The premature fusion of anterior facial bones, such as the maxilla, nasal, and frontal bones, rather than the cranium or cranial base, is the main contributing factor toward the anterior-posterior skull length shortening. The cranial base of the mouse model had a noticeable downward slant around the intersphenoid synchondrosis, which is related to distortion of the airway. Within a skull, the facial shape variance was highly correlated with the cranial base angle change along Fgfr2 S252W mutation-induced craniofacial anomalies. The inhibition of an FGFR2 downstream signaling enzyme, PIN1, via genetic knockdown or use of a PIN1 inhibitor, juglone, attenuated the aforementioned deformities in a mouse model of Apert syndrome. Overall, these results indicate that FGFR2 signaling is a key contributor toward abnormal anterior-posterior dimensional growth in the midface region. Our study suggests a novel therapeutic option for the prevention of craniofacial malformations induced by mutations in the FGFR2 gene.

Previous, Current, and Future Pharmacotherapy and Diagnosis of Prostate Cancer-A Comprehensive Review

Prostate cancer (PCa) is one of the most common cancers in men that usually develops slowly. Since diagnostic methods improved in the last decade and are highly precise, more cancers are diagnosed at an early stage. Active surveillance or watchful waiting are appealing approaches for men diagnosed with low-risk prostate cancer, and they are an antidote to the overtreatment problem and unnecessary biopsies. However, treatment depends on individual circumstances of a patient. Older hormonal therapies based on first generation antiandrogens and steroids were widely used in metastatic castration-resistant prostate cancer (mCRPC) patients prior to the implementation of docetaxel. Nowadays, accordingly to randomized clinical trials, abiraterone, enzalutamide, apalutamide. and docetaxel became first line agents administrated in the treatment of mCRPC. Furthermore, radium-223 is an optional therapy for bone-only metastasis patients. Sipuleucel-T demonstrated an overall survival benefit. However, other novel immunotherapeutics showed limitations in monotherapy. Possible combinations of new vaccines or immune checkpoint blockers with enzalutamide, abiraterone, radium-223, or docetaxel are the subject of ongoing rivalry regarding optimal therapy of prostate cancer.

The synergistic effects of graphene-contained 3D-printed calcium silicate/poly-ε-caprolactone scaffolds promote FGFR-induced osteogenic/angiogenic differentiation of mesenchymal stem cells

Graphene-contained calcium silicate (CS)/polycaprolactone (PCL) scaffold (GCP) provides an alternative solution that can bring several bone formation properties, such as osteoinductive. This study finds out the optimal percentage of graphene additive to calcium silicate and polycaprolactone mixture for excellent in vitro and in vivo bone-regeneration ability, in addition, this scaffold could fabricate by 3D printing technology and demonstrates distinct mechanical, degradation, and biological behavior. With controlled structure and porosity by 3D printing, osteogenesis and proliferation capabilities of Wharton's Jelly derived mesenchymal stem cells (WJMSCs) were significantly enhanced when cultured on 3D printed GCP scaffolds. In this study, it was also discovered that fibroblast growth factor receptor (FGFR) plays an active role in modulating differentiation behavior of WJMSCs cultured on GCP scaffolds. The validation has been proved by analyzed the decreased cell proliferation, osteogenic-related protein (ALP and OC), and angiogenic-related protein (VEGF and vWF) with FGFR knockdown on all experimental groups. Moreover, this study infers that the GCP scaffold could induce the effects of proliferation, differentiation and related protein expression on WJMSCs through FGFR pathway. In summary, this research indicated the 3D-printed GCP scaffolds own the dual bioactivities to reach the osteogenesis and vascularization for bone regeneration.

PIN1 is a new therapeutic target of craniosynostosis

Gain-of-function mutations in fibroblast growth factor receptors (FGFRs) cause congenital skeletal anomalies, including craniosynostosis (CS), which is characterized by the premature closure of craniofacial sutures. Apert syndrome (AS) is one of the severest forms of CS, and the only treatment is surgical expansion of prematurely fused sutures in infants. Previously, we demonstrated that the prolyl isomerase peptidyl-prolyl cis-trans isomerase interacting 1 (PIN1) plays a critical role in mediating FGFR signaling and that Pin1+/- mice exhibit delayed closure of cranial sutures. In this study, using both genetic and pharmacological approaches, we tested whether PIN1 modulation could be used as a therapeutic regimen against AS. In the genetic approach, we crossbred Fgfr2S252W/+, a mouse model of AS, and Pin1+/- mice. Downregulation of Pin1 gene dosage attenuated premature cranial suture closure and other phenotypes of AS in Fgfr2S252W/+ mutant mice. In the pharmacological approach, we intraperitoneally administered juglone, a PIN1 enzyme inhibitor, to pregnant Fgfr2S252W/+ mutant mice and found that this treatment successfully interrupted fetal development of AS phenotypes. Primary cultured osteoblasts from Fgfr2S252W/+ mutant mice expressed high levels of FGFR2 downstream target genes, but this phenotype was attenuated by PIN1 inhibition. Post-translational stabilization and activation of Runt-related transcription factor 2 (RUNX2) in Fgfr2S252W/+ osteoblasts were also attenuated by PIN1 inhibition. Based on these observations, we conclude that PIN1 enzyme activity is important for FGFR2-induced RUNX2 activation and craniofacial suture morphogenesis. Moreover, these findings highlight that juglone or other PIN1 inhibitors represent viable alternatives to surgical intervention for treatment of CS and other hyperostotic diseases.

Regulation of Proliferation, Differentiation and Functions of Osteoblasts by Runx2

Runx2 is essential for osteoblast differentiation and chondrocyte maturation. During osteoblast differentiation, Runx2 is weakly expressed in uncommitted mesenchymal cells, and its expression is upregulated in preosteoblasts, reaches the maximal level in immature osteoblasts, and is down-regulated in mature osteoblasts. Runx2 enhances the proliferation of osteoblast progenitors by directly regulating Fgfr2 and Fgfr3. Runx2 enhances the proliferation of suture mesenchymal cells and induces their commitment into osteoblast lineage cells through the direct regulation of hedgehog (Ihh, Gli1, and Ptch1), Fgf (Fgfr2 and Fgfr3), Wnt (Tcf7, Wnt10b, and Wnt1), and Pthlh (Pthr1) signaling pathway genes, and Dlx5. Runx2 heterozygous mutation causes open fontanelle and sutures because more than half of the Runx2 gene dosage is required for the induction of these genes in suture mesenchymal cells. Runx2 regulates the proliferation of osteoblast progenitors and their differentiation into osteoblasts via reciprocal regulation with hedgehog, Fgf, Wnt, and Pthlh signaling molecules, and transcription factors, including Dlx5 and Sp7. Runx2 induces the expression of major bone matrix protein genes, including Col1a1, Spp1, Ibsp, Bglap2, and Fn1, in vitro. However, the functions of Runx2 in differentiated osteoblasts in the expression of these genes in vivo require further investigation.

PKC regulates the production of fibroblast growth factor 23 (FGF23)

Serine/threonine protein kinase C (PKC) is activated by diacylglycerol that is released from membrane lipids by phospholipase C in response to activation of G protein-coupled receptors or receptor tyrosine kinases. PKC isoforms are particularly relevant for proliferation and differentiation of cells including osteoblasts. Osteoblasts/osteocytes produce fibroblast growth factor 23 (FGF23), a hormone regulating renal phosphate and vitamin D handling. PKC activates NFκB, a transcription factor complex controlling FGF23 expression. Here, we analyzed the impact of PKC on FGF23 synthesis. Fgf23 expression was analyzed by qRT-PCR in UMR106 osteoblast-like cells and in IDG-SW3 osteocytes, and FGF23 protein was measured by ELISA. Phorbol ester 12-O-tetradecanoylphorbol-13-acetate (PMA), a PKC activator, up-regulated FGF23 production. In contrast, PKC inhibitors calphostin C, Gö6976, sotrastaurin and ruboxistaurin suppressed FGF23 formation. NFκB inhibitor withaferin A abolished the stimulatory effect of PMA on Fgf23. PKC is a powerful regulator of FGF23 synthesis, an effect which is at least partly mediated by NFκB.

Fibroblast growth factors in skeletal development

Fibroblast growth factors (FGFs) and their receptors (FGFRs) are expressed throughout all stages of skeletal development. In the limb bud and in cranial mesenchyme, FGF signaling is important for formation of mesenchymal condensations that give rise to bone. Once skeletal elements are initiated and patterned, FGFs regulate both endochondral and intramembranous ossification programs. In this chapter, we review functions of the FGF signaling pathway during these critical stages of skeletogenesis, and explore skeletal malformations in humans that are caused by mutations in FGF signaling molecules.

A tale of two cities: The genetic mechanisms governing calvarial bone development

The skull bones must grow in a coordinated, three-dimensional manner to coalesce and form the head and face. Mammalian skull bones have a dual embryonic origin from cranial neural crest cells (CNCC) and paraxial mesoderm (PM) and ossify through intramembranous ossification. The calvarial bones, the bones of the cranium which cover the brain, are derived from the supraorbital arch (SOA) region mesenchyme. The SOA is the site of frontal and parietal bone morphogenesis and primary center of ossification. The objective of this review is to frame our current in vivo understanding of the morphogenesis of the calvarial bones and the gene networks regulating calvarial bone initiation in the SOA mesenchyme.

Overexpression of Fgfr2c causes craniofacial bone hypoplasia and ameliorates craniosynostosis in the Crouzon mouse

FGFR2c regulates many aspects of craniofacial and skeletal development. Mutations in the FGFR2 gene are causative of multiple forms of syndromic craniosynostosis, including Crouzon syndrome. Paradoxically, mouse studies have shown that the activation (Fgfr2cC342Y; a mouse model for human Crouzon syndrome), as well as the removal (Fgfr2cnull), of the FGFR2c isoform can drive suture abolishment. This study aims to address the downstream effects of pathogenic FGFR2c signalling by studying the effects of Fgfr2c overexpression. Conditional overexpression of Fgfr2c (R26RFgfr2c;βact) results in craniofacial hypoplasia as well as microtia and cleft palate. Contrary to Fgfr2cnull and Fgfr2cC342Y, Fgfr2c overexpression is insufficient to drive onset of craniosynostosis. Examination of the MAPK/ERK pathway in the embryonic sutures of Fgfr2cC342Y and R26RFgfr2c;βact mice reveals that both mutants have increased pERK expression. The contrasting phenotypes between Fgfr2cC342Y and R26RFgfr2c;βact mice prompted us to assess the impact of the Fgfr2c overexpression allele on the Crouzon mouse (Fgfr2cC342Y), in particular its effects on the coronal suture. Our results demonstrate that Fgfr2c overexpression is sufficient to partially rescue craniosynostosis through increased proliferation and reduced osteogenic activity in E18.5 Fgfr2cC342Y embryos. This study demonstrates the intricate balance of FGF signalling required for correct calvarial bone and suture morphogenesis, and that increasing the expression of the wild-type FGFR2c isoform could be a way to prevent or delay craniosynostosis progression.

Extracellular calcium increases fibroblast growth factor 2 gene expression via extracellular signal-regulated kinase 1/2 and protein kinase A signaling in mouse dental papilla cells

We previously reported that elevated extracellular calcium (Ca²⁺) levels increase bone morphogenetic protein 2 expression in human dental pulp (hDP) cells. However, it is unknown whether extracellular Ca²⁺ affects the expression of other growth factors such as fibroblast growth factor 2 (FGF2).

Role of FGFR2b expression and signaling in keratinocyte differentiation: sequential involvement of PKCδ and PKCα

The tumor suppressor epithelial isoform of the fibroblast growth factor receptor 2 (FGFR2b) induces human keratinocyte early differentiation. Moreover, protein kinases C (PKCs) are known to regulate the differentiation program in several cellular contexts, including keratinocytes. Therefore, in this paper we propose to clarify if FGFR2b could play a role also in the late steps of keratinocyte differentiation and to assess if this receptor-induced process would sequentially involve PKCδ and PKCα isoforms. Immunofluorescence, biochemical, and molecular approaches, performed on 2D cultures or 3D organotypic rafts of human keratinocytes overexpressing FGFR2b by stable transduction, showed that receptor signaling induced the precocious onset and an accelerated progression of keratinocyte differentiation, indicating that FGFR2b is a crucial regulator of the entire program of keratinocyte differentiation. In addition, the use of specific inhibitors and gene silencing approaches through specific siRNA demonstrated that PKCδ controls the onset of FGFR2b-triggered differentiation, while PKCα plays a role restricted to the terminal stages of the process. Molecular analysis revealed that the two PKC isoforms sequentially act via induction of KLF4 and DLX3, two transcription factors linked by negative loops to p63, suggesting that p63 would represent the hub molecule at the crossroad of an intricate signaling network downstream FGFR2b, involving multiple PKC-induced transcription factors.

Redox-Dependent Bone Alkaline Phosphatase Dysfunction Drives Part of the Complex Bone Phenotype in Mice Deficient for Memo1

Mediator of ErbB2-driven cell Motility 1 (MEMO1) is an intracellular redox protein that integrates growth factors signaling with the intracellular redox state. We have previously reported that mice lacking Memo1 displayed higher plasma calcium levels and other alterations of mineral metabolism, but the underlying mechanism was unresolved and the bone phenotype was not described. Here, we show that Cre/lox-mediated MEMO1 deletion in the whole body of C57Bl/6 mice (Memo cKO) leads to severely altered trabecular bone and lower mineralization, with preserved osteoblast and osteoclast number and activity, but altered osteoblast response to epidermal growth factor (EGF) and FGF2. More strikingly, Memo cKO mice display decreased alkaline phosphatase (ALP) activity in serum and in bone, while ALPL expression level is unchanged. Bone intracellular redox state is significantly altered in Memo cKO mice and we inferred that ALP dimerization was reduced in Memo cKO mice. Indeed, despite similar ALP oxidation, we found increased ALP sensitivity to detergent in Memo cKO bone leading to lower ALP dimerization capability. Thus, we report a severe bone phenotype and dysfunctional bone ALP with local alteration of the redox state in Memo cKO mice that partially mimics hypophosphatasia, independent of ALPL mutations. These findings reveal Memo as a key player in bone homeostasis and underline a role of bone redox state in controlling ALP activity.

Intermittent Administration of Parathyroid Hormone 1-34 Enhances Osteogenesis of Human Mesenchymal Stem Cells by Regulating Protein Kinase Cδ

Human mesenchymal stem cells (hMSCs) can differentiate into osteoblasts and are regulated by chemical cues. The recombinant N-terminal (1–34 amino acids) fragment of the parathyroid hormone (PTH (1–34)) is identified to promote osteogenesis. The osteoanabolic effects of intermittent PTH (1–34) treatment are linked to a complex consisting of signaling pathways; additionally, protein kinase C (PKC) act as mediators of multifunctional signaling transduction pathways, but the role of PKC δ (PKCδ), a downstream target in regulating osteoblast differentiation during intermittent administration of PTH (1–34) is less studied and still remains elusive. The purpose of this study is to examine the role of PKCδ during intermittent and continuous PTH (1–34) administration using osteoblast-lineage-committed hMSCs. Relative gene expression of osteoblast-specific genes demonstrated significant upregulation of RUNX2, type I Collagen, ALP, and Osterix and increased alkaline phosphatase activity in the presence of PTH (1–34). Intermittent PTH (1–34) administration increased PKC activity at day 7 of osteogenic differentiation, whereas inhibition of PKC activity attenuated these effects. In addition, the specific isoform PKCδ was activated upon treatment. These findings demonstrate that intermittent PTH (1–34) treatment enhances the osteogenesis of hMSCs by upregulating osteoblast-specific genes via PKCδ activation.

Sprouty2 is involved in the control of osteoblast proliferation and differentiation through the FGF and BMP signaling pathways

Fibroblast growth factor (FGF) and bone morphogenetic protein (BMP) play essential roles in bone formation and osteoblast activity through the extracellular signal-regulated kinase 1/2 (ERK1/2) and Smad pathways. Sprouty family members are intracellular inhibitors of the FGF signaling pathway, and four orthologs of Sprouty have been identified in mammals. In vivo analyses have revealed that Sprouty2 is associated with bone formation. However, the mechanism by which the Sprouty family controls bone formation has not been clarified. In this study, we investigated the involvement of Sprouty2 in osteoblast proliferation and differentiation. We examined Sprouty2 expression in MC3T3-E1 cells, and found that high levels of Sprouty2 expression were induced by basic FGF stimulation. Overexpression of Sprouty2 in MC3T3-E1 cells resulted in suppressed proliferation compared with control cells. Sprouty2 negatively regulated the phosphorylation of ERK1/2 after basic FGF stimulation, and of Smad1/5/8 after BMP stimulation. Furthermore, Sprouty2 suppressed the expression of osterix, alkaline phosphatase, and osteocalcin mRNA, which are markers of osteoblast differentiation. Additionally, Sprouty2 inhibited osteoblast matrix mineralization. These results suggest that Sprouty2 is involved in the control of osteoblast proliferation and differentiation by downregulating the FGF-ERK1/2 and BMP-Smad pathways, and suppresses the induction of markers of osteoblast differentiation.

Interplay between FGFR2b-induced autophagy and phagocytosis: role of PLCγ-mediated signalling

Signalling of the epithelial splicing variant of the fibroblast growth factor receptor 2 (FGFR2b) induces both autophagy and phagocytosis in human keratinocytes. Here, we investigated, in the cell model of HaCaT keratinocytes, whether the two processes might be related and the possible involvement of PLCγ signalling. Using fluorescence and electron microscopy, we demonstrated that the FGFR2b-induced phagocytosis and autophagy involve converging autophagosomal and phagosomal compartments. Moreover, the forced expression of FGFR2b signalling mutants and the use of specific inhibitors of FGFR2b substrates showed that the receptor-triggered autophagy requires PLCγ signalling, which in turn activates JNK1 via PKCδ. Finally, we found that in primary human keratinocytes derived from light or dark pigmented skin and expressing different levels of FGFR2b, the rate of phagocytosis and autophagy and the convergence of the two intracellular pathways are dependent on the level of receptor expression, suggesting that FGFR2b signalling would control in vivo the number of melanosomes in keratinocytes, determining skin pigmentation.

Radium 223 dichloride for prostate cancer treatment

Prostate cancer is the most common malignant disease in men. Several therapeutic agents have been approved during the last 10 years. Among them, radium-223 dichloride (Xofigo^®) is a radioactive isotope that induces irreversible DNA double-strand breaks and consequently tumor cell death. Radium-223 dichloride is a calcium-mimetic agent that specifically targets bone lesions. Radium-223 dichloride has been approved for the treatment of metastatic castration-resistant prostate cancer with symptomatic bone metastases, without known visceral metastases. In this review, first we summarize the interplay between prostate tumor cells and bone microenvironment; then, we discuss radium-223 dichloride mechanism of action and present the results of the available clinical trials and future developments for this new drug.

[Research progress in osteogenesis and osteogenic mechanism of heparan sulfate]

Objective

To discuss the role of heparan sulfate (HS) in bone formation and bone remodeling and summarize the research progress in the osteogenic mechanism of HS.

Methods

The domestic and abroad related literature about HS acting on osteoblast cell line in vitro, HS and HS composite scaffold materials acting on the ani-mal bone defect models, and the effect of HS proteoglycans on bone development were summarized and analyzed.

Results

Many growth factors involved in fracture healing especially heparin-binding growth factors, such as fibroblast growth factors, bone morphogenetic protein, and transforming growth factor β, are connected noncovalently with long HS chains. HS proteoglycans protect these proteins from protease degradation and are directly involved in the regulation of growth factors signaling and bone cell function. HS can promote the differentiation of stem cells into osteoblasts and enhance the differentiation of osteoblasts. In bone matrix, HS plays a significant role in promoting the formation, maintaining the stability, and accelerating the mineralization.

Conclusion

The osteogenesis of HS is pronounced. HS is likely to become the clinical treatment measures of fracture nonunion or delayed union, and is expected to provide more choices for bone tissue engineering with identification of its long-term safety.

Connexin43 and Runx2 Interact to Affect Cortical Bone Geometry, Skeletal Development, and Osteoblast and Osteoclast Function

The coupling of osteoblasts and osteocytes by connexin43 (Cx43) gap junctions permits the sharing of second messengers that coordinate bone cell function and cortical bone acquisition. However, details of how Cx43 converts shared second messengers into signals that converge onto essential osteogenic processes are incomplete. Here, we use in vitro and in vivo methods to show that Cx43 and Runx2 functionally interact to regulate osteoblast gene expression and proliferation, ultimately affecting cortical bone properties. Using compound hemizygous mice for the Gja1 (Cx43) and Runx2 genes, we observed a skeletal phenotype not visible in wild-type or singly hemizygous animals. Cortical bone analysis by micro-computed tomography (μCT) revealed that 8-week-old male, compound Gja1^+/- Runx2^+/- mice have a marked increase in cross-sectional area, endosteal and periosteal bone perimeter, and an increase in porosity compared to controls. These compound Gja1^+/- Runx2^+/- mice closely approximate the cortical bone phenotypes seen in osteoblast-specific Gja1-conditional knockout models. Furthermore, μCT analysis of skulls revealed an altered interparietal bone geometry in compound hemizygotes. Consistent with this finding, Alizarin red/Alcian blue staining of 2-day-old Gja1^+/- Runx2^+/- neonates showed a hypomorphic interparietal bone, an exacerbation of the open fontanelles, and a further reduction in the hypoplastic clavicles compared to Runx2^+/- neonates. Expression of osteoblast genes, including osteocalcin, osterix, periostin, and Hsp47, was markedly reduced in tibial RNA extracts from compound hemizygous mice, and osteoblasts from compound hemizygous mice exhibited increased proliferative capacity. Further, the reduced osteocalcin expression and hyperproliferative nature of osteoblasts from Cx43 deficient mice was rescued by Runx2 expression. In summary, these findings provide evidence that Cx43 and Runx2 functionally intersect in vivo to regulate cortical bone properties and affect osteoblast differentiation and proliferation, and likely contributes to aspects of the skeletal phenotype of Cx43 conditional knockout mice. © 2017 American Society for Bone and Mineral Research.

An HDAC Inhibitor, Entinostat/MS-275, Partially Prevents Delayed Cranial Suture Closure in Heterozygous Runx2 Null Mice

Cleidocranial dysplasia (CCD) is an autosomal dominant skeletal disorder caused by mutations in RUNX2, coding a key transcription factor of early osteogenesis. CCD patients suffer from developmental defects in cranial bones. Despite numerous investigations and clinical approaches, no therapeutic strategy has been suggested to prevent CCD. Here, we show that fetal administration of Entinostat/MS-275, a class I histone deacetylase (HDAC)-specific inhibitor, partially prevents delayed closure of cranial sutures in Runx2^+/- mice strain of C57BL/6J by two mechanisms: 1) posttranslational acetylation of Runx2 protein, which stabilized the protein and activated its transcriptional activity; and 2) epigenetic regulation of Runx2 and other bone marker genes. Moreover, we show that MS-275 stimulates osteoblast proliferation effectively both in vivo and in vitro, suggesting that delayed skeletal development in CCD is closely related to the decreased number of progenitor cells as well as the delayed osteogenic differentiation. These findings provide the potential benefits of the therapeutic strategy using MS-275 to prevent CCD. © 2017 American Society for Bone and Mineral Research.

Pin1, the Master Orchestrator of Bone Cell Differentiation

Pin1 is an enzyme that specifically recognizes the peptide bond between phosphorylated serine or threonine (pS/pT-P) and proline. This recognition causes a conformational change of its substrate, which further regulates downstream signaling. Pin1^-/- mice show developmental bone defects and reduced mineralization. Pin1 targets RUNX2 (Runt-Related Transcription Factor 2), SMAD1/5, and β-catenin in the FGF, BMP, and WNT pathways, respectively. Pin1 has multiple roles in the crosstalk between different anabolic bone signaling pathways. For example, it controls different aspects of osteoblastogenesis and increases the transcriptional activity of Runx2, both directly and indirectly. Pin1 also influences osteoclastogenesis at different stages by targeting PU.1 (Purine-rich nucleic acid binding protein 1), C-FOS, and DC-STAMP. The phenotype of Pin1^-/- mice has led to the recent identification of multiple roles of Pin1 in different molecular pathways in bone cells. These roles suggest that Pin1 can be utilized as an efficient drug target in congenital and acquired bone diseases. J. Cell. Physiol. 232: 2339-2347, 2017. © 2016 Wiley Periodicals, Inc.

Vitamin D Impacts the Expression of Runx2 Target Genes and Modulates Inflammation, Oxidative Stress and Membrane Vesicle Biogenesis Gene Networks in 143B Osteosarcoma Cells

Osteosarcoma (OS) is an aggressive malignancy of bone affecting children, adolescents and young adults. Understanding vitamin D metabolism and vitamin D regulated genes in OS is an important aspect of vitamin D/cancer paradigm, and in evaluating vitamin D as adjuvant therapy for human OS. Vitamin D treatment of 143B OS cells induced significant and novel changes in the expression of genes that regulate: (a) inflammation and immunity; (b) formation of reactive oxygen species, metabolism of cyclic nucleotides, sterols, vitamins and mineral (calcium), quantity of gap junctions and skeletogenesis; (c) bone mineral density; and (d) cell viability of skeletal cells, aggregation of bone cancer cells and exocytosis of secretory vesicles. Ingenuity pathway analysis revealed significant reduction in Runx2 target genes such as fibroblast growth factor -1, -12 (FGF1 and FGF12), bone morphogenetic factor-1 (BMP1), SWI/SNF related, matrix associated actin dependent regulator of chromatin subfamily a, member 4 (SMARCA4), Matrix extracellular phosphoglycoprotein (MEPE), Integrin, β4 (ITGBP4), Matrix Metalloproteinase -1, -28 (MMP1 and MMP28), and signal transducer and activator of transcription-4 (STAT4) in vitamin D treated 143B OS cells. These genes interact with the inflammation, oxidative stress and membrane vesicle biogenesis gene networks. Vitamin D not only inhibited the expression of Runx2 target genes MMP1, MMP28 and kallikrein related peptidase-7 (KLK7), but also migration and invasion of 143B OS cells. Vitamin D regulated Runx2 target genes or their products represent potential therapeutic targets and laboratory biomarkers for applications in translational oncology.

Bone morphogenetic protein-2 enhances the osteogenic differentiation capacity of mesenchymal stromal cells derived from human bone marrow and umbilical cord

Mesenchymal stromal cells (MSCs) are multipotent cells that can give rise to different cell types of the mesodermal lineages. They are powerful sources for cell therapy in regenerative medicine as they can be isolated from various tissues, and can be expanded and induced to differentiate into multiple lineages. Recently, the umbilical cord has been suggested as an alternative source of MSCs. Although MSCs derived from the umbilical cord can be induced to differentiate into osteoblasts with a phenotypic similarity to that of bone marrow-derived MSCs, the differentiation ability is not consistent. In addition, MSCs from the umbilical cord require a longer period of time to differentiate into osteoblasts. Previous studies have demonstrated the benefits of bone morphogenetic protein-2 (BMP-2) in bone tissue regeneration. In addition, several studies have supported the use of BMP-2 in periodontal regeneration, sinus lift bone-grafting and non-unions in oral surgery. Although the use of BMP-2 for bone tissue regeneration has been extensively investigated, the BMP-2-induced osteogenic differentiation of MSCs derived from the umbilical cord has not yet been fully examined. Therefore, in this study, we aimed to examine the effects of BMP-2 on the osteogenic differentiation of MSCs derived from umbilical cord compared to that of MSCs derived from bone marrow. The degree of osteogenic differentiation following BMP-2 treatment was determined by assessing alkaline phosphatase (ALP) activity, and the expression profiles of osteogenic differentiation marker genes, osterix (Osx), Runt-related transcription factor 2 (Runx2) and osteocalcin (Ocn). The results revealed that BMP-2 enhanced the osteogenic differentiation capacity of MSCs derived from both bone marrow and umbilical cord as demonstrated by increased ALP activity and the upregulation of osteogenic differentiation marker genes. The enhancement of the osteogenic differentiation capacity of MSCs by BMP-2 suggests that these MSCs may be used as alternative sources for bone engineering or cell therapy in regenerative medicine.

Deformed Skull Morphology Is Caused by the Combined Effects of the Maldevelopment of Calvarias, Cranial Base and Brain in FGFR2-P253R Mice Mimicking Human Apert Syndrome

Apert syndrome (AS) is a common genetic syndrome in humans characterized with craniosynostosis. Apert patients and mouse models showed abnormalities in sutures, cranial base and brain, that may all be involved in the pathogenesis of skull malformation of Apert syndrome. To distinguish the differential roles of these components of head in the pathogenesis of the abnormal skull morphology of AS, we generated mouse strains specifically expressing mutant FGFR2 in chondrocytes, osteoblasts, and progenitor cells of central nervous system (CNS) by crossing Fgfr2^+/P253R-Neo mice with Col2a1-Cre, Osteocalcin-Cre (OC-Cre), and Nestin-Cre mice, respectively. We then quantitatively analyzed the skull and brain morphology of these mutant mice by micro-CT and micro-MRI using Euclidean distance matrix analysis (EDMA). Skulls of Col2a1-Fgfr2^+/P253R mice showed Apert syndrome-like dysmorphology, such as shortened skull dimensions along the rostrocaudal axis, shortened nasal bone, and evidently advanced ossification of cranial base synchondroses. The OC-Fgfr2^+/P253R mice showed malformation in face at 8-week stage. Nestin-Fgfr2^+/P253R mice exhibited increased dorsoventral height and rostrocaudal length on the caudal skull and brain at 8 weeks. Our study indicates that the abnormal skull morphology of AS is caused by the combined effects of the maldevelopment in calvarias, cranial base, and brain tissue. These findings further deepen our knowledge about the pathogenesis of the abnormal skull morphology of AS, and provide new clues for the further analyses of skull phenotypes and clinical management of AS.

Inhibition of connexin 43 prevents trauma-induced heterotopic ossification

Heterotopic ossification (HO) can result from traumatic injury, surgery or genetic diseases. Here, we demonstrate that overexpression of connexin 43 (Cx43) is critical for the development and recurrence of traumatic HO in patients. Inhibition of Cx43 by shRNA substantially suppressed the osteogenic differentiation of MC-3T3 cells and the expression of osteogenic genes. We employed a tenotomy mouse model to explore the hypothesis that Cx43 is vital to the development of HO. Inhibition of Cx43 by a specific shRNA decreased extraskeletal bone formation in vivo. In addition, we demonstrated that ERK signaling activated by Cx43 plays an important role in promoting HO. ERK signaling was highly activated in HO tissue collected from patient and mouse models. Importantly, de novo soft tissue HO was significantly attenuated in mice treated with U0126. Inhibition of Cx43 and ERK led to decreased expressions of Runx2, BSP and Col-1 in vivo and in vitro. Moreover, HO patients with low Cx43 expression or ERK activation had a lower risk of recurrence after the lesions were surgically removed. Our findings indicate that Cx43 promotes trauma-induced HO formation by activating the ERK pathway and enhances the expression of osteogenic markers.