Effects of FGF-2/-9 in calvarial bone cell cultures: differentiation stage-dependent mitogenic effect, inverse regulation of BMP-2 and noggin, and enhancement of osteogenic potential

Synergistic and sequential effects of BMP-2, bFGF and VEGF on osteogenic differentiation of rat osteoblasts

In the present study, the effects of bone morphogenetic protein-2 (BMP-2), vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) on regulation of rat osteoblast (ROB) maturation in vitro were investigated. It was found that the proliferation, differentiation and mineralization of ROBs were all dose-dependently increased at particular times in the case of treatment with only one growth factor. To investigate the effects of combined treatment, ROBs were treated with either a single application of a relatively high dose of each growth factor, or binary/triple combined applications of relatively low doses of the growth factors. Osteogenic differentiation was significantly promoted in the triple combination treatment of BMP-2, VEGF and bFGF compared with the single or binary combination treatments. The optimal timing of the triple combination to enhance osteogenesis was also tested. When bFGF and VEGF were added in the early stage, and BMP-2 and VEGF were added in the late stage, osteogenic differentiation of ROBs could be enhanced more effectively. These results could be used to construct bone tissue engineering scaffolds that release growth factors sequentially.

Developmental pathways hijacked by osteosarcoma

Cancer of any type often can be described by an arrest, alteration or disruption in the normal development of a tissue or organ, and understanding of the normal counterpart's development can aid in understanding the malignant state. This is certainly true for osteosarcoma and the normal developmental pathways that guide osteoblast development that are changed in the genesis of osteogenic sarcoma. A carefully regulated crescendo-decrescendo expression of RUNX2 accompanies the transition from mesenchymal stem cell to immature osteoblast to mature osteoblast. This pivotal role is controlled by several pathways, including bone morphogenic protein (BMP), Wnt/β-catenin, fibroblast growth factor (FGF), and protein kinase C (PKC). The HIPPO pathway and its downstream target YAP help to regulate proliferation of immature osteoblasts and their maturation into non-proliferating mature osteoblasts. This pathway also helps regulate expression of the mature osteoblast protein osteocalcin. YAP also regulates expression of MT1-MMP, a membrane-bound matrix metalloprotease responsible for remodeling the extracellular matrix surrounding the osteoblasts. YAP, in turn, can be regulated by the ERBB family protein Her-4. Osteosarcoma may be thought of as a cell held at the immature osteoblast stage, retaining some of the characteristics of that developmental stage. Disruptions of several of these pathways have been described in osteosarcoma, including BMP, Wnt/b-catenin, RUNX2, HIPPO/YAP, and Her-4. Further, PKC can be activated by several receptor tyrosine kinases implicated in osteosarcoma, including the ERBB family (EGFR, Her-2 and Her-4 in osteosarcoma), IGF1R, FGF, and others. Understanding these functions may aid in the understanding the mechanisms underpinning clinical observations in osteosarcoma, including both the lytic and blastic phenotypes of tumors, the invasiveness of the disease, and the tendency for treated tumors to ossify rather than shrink. Through a better understanding of the relationship between normal osteoblast development and osteosarcoma, we may gain insights into novel therapeutic avenues and improved outcomes.

Basic fibroblastic growth factor affects the osteogenic differentiation of dental pulp stem cells in a treatment-dependent manner

AIM

To determine how basic fibroblastic growth factor (bFGF) affected the osteogenic differentiation of human dental pulp stem cells (DPSCs) in vitro and in vivo.

METHODOLOGY

Basic fibroblastic growth factor stimulation of DPSCs was divided into a pre-treatment period and an osteogenic differentiation period. Alizarin red quantification experiments and alkaline phosphatase activity quantification assay were performed to examine the osteogenic differentiation of DPSCs after different bFGF stimulation. Quantification reverse transcription polymerase chain reaction was used to analyze the osteogenic gene expression of DPSCs after different bFGF stimulation. In addition, DPSCs that received the 1 and 2 weeks bFGF pre-treatments as in the in vitro experiments were mineralized for 1 week and seeded into hydroxyapatite/tricalcium phosphate (HA/TCP) pills and subcutaneously transplanted into naked mice for 2 or 3 months. The transplants were removed, sliced and stained using Modified Ponceau Trichrome Stain to observe the formation of mineralized tissue.

RESULTS

Basic fibroblastic growth factor stimulation in the osteogenic differentiation period decreased the in vitro osteogenic differentiation ability of DPSCs. One week pre-treatment with bFGF increased the in vitro osteogenic differentiation ability of DPSCs, whereas 2 weeks pre-treatment with bFGF decreased the in vitro osteogenic differentiation ability of DPSCs. The pre-treatment period was vital for the osteogenic differentiation of DPSCs in vitro. The in vivo results were similar to the in vitro results.

CONCLUSIONS

Basic fibroblastic growth factor affected the osteogenic differentiation of DPSCs in a treatment-dependent manner both in vitro and in vivo.

Induction of bone formation in abdominal implants constituted by collagen sponges embedded with plant-based human transforming growth factor family proteins in ectopic dog model

Background

Trauma, osteomyelitis, bone tumour resections and congenital deformities are the main causes of bone deficiency in which autologous graft is the preferred treatment, but usually the bone supplies are limited.

Methods

An experimental model of heterotopic bone formation in the subcutaneous abdominal area of dogs was developed. This model consists in omentum wrapped implants constituted by collagen type 1 sponges embedded with demineralized bone powder, calcium cloride, thrombin and platelet rich plasma; the implant is totally converted in trabecular bone after four months of implantation. This model was improved by accelerating bone production, after the isolation of the most conspicuous histological constituents (inflammatory, bone and adipose tissues) by laser microdisection and purified from them RNA that was used to determine by RT-PCR the gene expression kinetics of the most important growth bone factors. Then, the most abundant and rapidly synthesized factors were produced by genetic engineering in tobacco plants.

Results

Bone morphogenetic proteins 2 and 7 and transforming growth factor-β1were the most rapidly and highly synthesized factors, and they were efficiently produced in a genetic engineering plant based system in tobacco leaves. Their incorporation as recombinant proteins in the scaffold collagen sponge induced in just one month mature heterotopic bone.

Conclusion

This study demonstrates for the first time that this plant system is able to produce recombinant bone growth factors in high amount and at low cost, and they were highly efficient to rapidly induce bone formation in abdominal implants potentially useful for autotransplantation.

Odontogenic differentiation of human dental pulp cells by calcium silicate materials stimulating via FGFR/ERK signaling pathway

Bone healing needs a complex interaction of growth factors that establishes an environment for efficient bone formation. We examine how calcium silicate (CS) and tricalcium phosphate (β-TCP) cements influence the behavior of human dental pulp cells (hDPCs) through fibroblast growth factor receptor (FGFR) and active MAPK pathways, in particular ERK. The hDPCs are cultured with β-TCP and CS, after which the cells' viability and odontogenic differentiation markers are determined by using PrestoBlue® assay and western blot, respectively. The effect of small interfering RNA (siRNA) transfection targeting FGFR was also evaluated. The results showed that CS promoted cell proliferation and enhances FGFR expression. It was also found that CS increases ERK and p38 activity in hDPCs, and furthermore, raises the expression and secretion of DSP, and DMP-1. Additionally, statistically significant differences (p<0.05) have been found in the calcium deposition in si-FGFR transfection and ERK inhibitor between CS and β-TCP; these variations indicated that ERK/MAPK signaling is involved in the silicon-induced odontogenic differentiation of hDPCs. The current study shows that CS substrates play a key role in odontoblastic differentiation of hDPCs through FGFR and modulate ERK/MAPK activation.

CD4+CD25+FoxP3+ Regulatory Tregs inhibit fibrocyte recruitment and fibrosis via suppression of FGF-9 production in the TGF-β1 exposed murine lung

Pulmonary fibrosis is a difficult to treat, often fatal disease whose pathogenesis involves dysregulated TGF-β1 signaling. CD4+CD25+FoxP3+ Regulatory T cells (“Tregs”) exert important effects on host tolerance and arise from naïve CD4+ lymphocytes in response to TGF-β1. However, the precise contribution of Tregs to experimentally induced murine lung fibrosis remains unclear. We sought to better understand the role of Tregs in this context. Using a model of fibrosis caused by lung specific, doxycycline inducible overexpression of the bioactive form of the human TGF-β1 gene we find that Tregs accumulate in the lung parenchyma within 5 days of transgene activation and that this enhancement persists to at least 14 days. Anti-CD25 Antibody mediated depletion of Tregs causes increased accumulation of soluble collagen and of intrapulmonary CD45+Col Iα1 fibrocytes. These effects are accompanied by enhanced local concentrations of the classical inflammatory mediators CD40L, TNF-α, and IL-1α, along with the neuroimmune molecule fibroblast growth factor 9 (FGF-9, also known as “glial activating factor”). FGF-9 expression localizes to parenchymal cells and alveolar macrophages in this model and antibody mediated neutralization of FGF-9 results in attenuated detection of intrapulmonary collagen and fibrocytes without affecting Treg quantities. These data indicate that CD4+CD25+FoxP3+ Tregs attenuate TGF-β1 induced lung fibrosis and fibrocyte accumulation in part via suppression of FGF-9.

Role of FGF/FGFR signaling in skeletal development and homeostasis: learning from mouse models

Fibroblast growth factor (FGF)/fibroblast growth factor receptor (FGFR) signaling plays essential roles in bone development and diseases. Missense mutations in FGFs and FGFRs in humans can cause various congenital bone diseases, including chondrodysplasia syndromes, craniosynostosis syndromes and syndromes with dysregulated phosphate metabolism. FGF/FGFR signaling is also an important pathway involved in the maintenance of adult bone homeostasis. Multiple kinds of mouse models, mimicking human skeleton diseases caused by missense mutations in FGFs and FGFRs, have been established by knock-in/out and transgenic technologies. These genetically modified mice provide good models for studying the role of FGF/FGFR signaling in skeleton development and homeostasis. In this review, we summarize the mouse models of FGF signaling-related skeleton diseases and recent progresses regarding the molecular mechanisms, underlying the role of FGFs/FGFRs in the regulation of bone development and homeostasis. This review also provides a perspective view on future works to explore the roles of FGF signaling in skeletal development and homeostasis.

Fibroblast growth factor-2 isoform (low molecular weight/18 kDa) overexpression in preosteoblast cells promotes bone regeneration in critical size calvarial defects in male mice

Repair of bone defects remains a significant clinical problem. Bone morphogenetic protein 2 (BMP2) is US Food and Drug Administration-approved for fracture healing but is expensive and has associated morbidity. Studies have shown that targeted overexpression of the 18-kDa low-molecular-weight fibroblast growth factor 2 isoform (LMW) by the osteoblastic lineage of transgenic mice increased bone mass. This study tested the hypotheses that overexpression of LMW would directly enhance healing of a critical size calvarial bone defect in mice and that this overexpression would have a synergistic effect with low-dose administration of BMP2 on critical size calvarial bone defect healing. Bilateral calvarial defects were created in LMW transgenic male mice and control/vector transgenic (Vector) male mice and scaffold with or without BMP2 was placed into the defects. New bone formation was assessed by VIVA-computed tomography of live animals over a 27-week period. Radiographic and computed tomography analysis revealed that at all time points, healing of the defect was enhanced in LMW mice compared with that in Vector mice. Although the very low concentration of BMP2 did not heal the defect in Vector mice, it resulted in complete healing of the defect in LMW mice. Histomorphometric and gene analysis revealed that targeted overexpression of LMW in osteoblast precursors resulted in enhanced calvarial defect healing due to increased osteoblast activity and increased canonical Wnt signaling.

Crosstalk between tyrosine kinase receptors, GSK3 and BMP2 signaling during osteoblastic differentiation of human mesenchymal stem cells

Bone morphogenic proteins (BMPs) promote mesenchymal stem cell (MSC) osteogenic differentiation, whereas platelet derived growth factor (PDGF) and fibroblast growth factor (FGF) activate their proliferation through receptors tyrosine kinase (RTK). The effects of PDGF or FGF receptor signaling pathway on BMP2-induced osteoblastic differentiation was investigated in human MSC (HMSC). Inhibition of PDGF or/and FGF receptors enhanced BMP2-induced alkaline phosphatase (ALP) activity, expression of Osterix, ALP and Bone sialoprotein, and matrix calcification. These effects were associated with increased Smad-1 activity, indicating that mitogenic factors interfere with Smad signaling in HMSC differentiation. RTK activate MAPK and inhibit GSK3 through the PI3K/Akt pathway. Biochemical analysis indicated that MAPK JNK and GSK3 especially are potential signaling molecules regulating BMP-induced osteoblastic HMSC differentiation. These observations highlight that the osteogenic effects of BMP2 are modulated by mitogenic factors acting through RTK.

Genistein promotion of osteogenic differentiation through BMP2/SMAD5/RUNX2 signaling

To investigate the effects of Genistein on the osteogenic related gene expression profiles during osteoblastic differentiation of human bone marrow mesenchymal stem cell (hBMSC) cultures, the hBMSCs were cultured under osteogenic differentiation medium with the addition of Genistein (10(-8)∼10(-5) M) for 12 days. The cell proliferation was measured by BrdU incorporation, while the osteoblastic differentiation in hBMSC cultures was assessed by cellular alkaline phosphatase (ALP) activity. The cell apoptosis was determined by caspase 3/7 activation. GEArray Q series human osteogenesis gene array was used to analyze large-scale gene expression in Genistein-treated hBMSC cultures compared to the control group. Quantitative real-time RT-PCR, small interfering RNA (siRNA), and western blot analysis were used to confirm the microarray data in five representative transcripts. Genistein (10(-8)∼10(-6) M) dose- and time-dependently increased cell proliferation and cellular ALP activity, but had no significant effect on cell apoptosis in hBMSC cultures. The 96-gene array analysis indicated that 22 genes were upregulated more than 2-fold and 7 genes were downregulated at least 1.5-fold. The expressions of bone morphogenetic proteins (BMPs), small mothers against decapentaplegic homologs (SMADs), and Runt-related transcription factor 2 (RUNX2) were concomitantly increased under Genistein treatment while insulin-like growth factor 2 and inhibitory SMADs 6 and 7 expressions were significantly decreased. The results of the real-time RT-PCR had a correlation with the results of microarray analysis and were estrogen-receptor dependent. Specific gene siRNAs knock-down further confirmed the osteogenic effects of Genistein on BMP2, SMAD5 and RUNX2 protein expression. Genistein enhanced osteogenic differentiation in cultured hBMSCs mainly through the BMP-dependent SMADs and RUNX2 signaling.

FGF-2 enhances Runx-2/Smads nuclear localization in BMP-2 canonical signaling in osteoblasts

Bone morphogenetic protein 2 (BMP-2) is one of the most potent regulators of osteoblast differentiation and bone formation. R-Smads (Smads 1/5/8) are the major transducers for BMPs receptors and, once activated, they are translocated in the nucleus regulating transcription target genes by interacting with various transcription factors. Runx-2 proteins have been shown to interact through their C-terminal segment with Smads and this interaction is required for in vivo osteogenesis. In particular, recruitment of Smads to intranuclear sites is Runx-2 dependent, and Runx-2 factor may accommodate the dynamic targeting of signal transducer to active transcription sites. Previously, we have shown, by in vitro and in vivo experiments, that BMP-2 up-regulated FGF-2 which is important for the maximal responses of BMP-2 in bone. In this study, we found that endogenous FGF2 is necessary for BMP-2 induced nuclear accumulation and co-localization of Runx-2 and phospho-Smads1/5/8, while Runx/Smads nuclear accumulation and co-localization was reduced in Fgf2-/- osteoblasts. Based on these novel data, we conclude that the impaired nuclear accumulation of Runx-2 in Fgf2-/- osteoblasts reduces R-Smads sub-nuclear targeting with a consequent decreased expression of differentiating markers and impaired bone formation in Fgf2 null mice.

Regulation of bone morphogenetic protein signalling and cranial osteogenesis by Gpc1 and Gpc3

From birth, the vault of the skull grows at a prodigious rate, driven by the activity of osteoblastic cells at the fibrous joints (sutures) that separate the bony calvarial plates. One in 2500 children is born with a medical condition known as craniosynostosis because of premature bony fusion of the calvarial plates and a cessation of bone growth at the sutures. Bone morphogenetic proteins (BMPs) are potent growth factors that promote bone formation. Previously, we found that Glypican-1 (GPC1) and Glypican-3 (GPC3) are expressed in cranial sutures and are decreased during premature suture fusion in children. Although glypicans are known to regulate BMP signalling, a mechanistic link between GPC1, GPC3 and BMPs and osteogenesis has not yet been investigated. We now report that human primary suture mesenchymal cells coexpress GPC1 and GPC3 on the cell surface and release them into the media. We show that they inhibit BMP2, BMP4 and BMP7 activities, which both physically interact with BMP2 and that immunoblockade of endogenous GPC1 and GPC3 potentiates BMP2 activity. In contrast, increased levels of GPC1 and GPC3 as a result of overexpression or the addition of recombinant protein, inhibit BMP2 signalling and BMP2-mediated osteogenesis. We demonstrate that BMP signalling in suture mesenchymal cells is mediated by both SMAD-dependent and SMAD-independent pathways and that GPC1 and GPC3 inhibit both pathways. GPC3 inhibition of BMP2 activity is independent of attachment of the glypican on the cell surface and post-translational glycanation, and thus appears to be mediated by the core glypican protein. The discovery that GPC1 and GPC3 regulate BMP2-mediated osteogenesis, and that inhibition of endogenous GPC1 and GPC3 potentiates BMP2 responsiveness of human suture mesenchymal cells, indicates how downregulation of glypican expression could lead to the bony suture fusion that characterizes craniosynostosis.

Biological activities of phosphocitrate: a potential meniscal protective agent

Phosphocitrate (PC) inhibited meniscal calcification and the development of calcium crystal-associated osteoarthritis (OA) in Hartley guinea pigs. However, the mechanisms remain elusive. This study sought to examine the biological activities of PC in the absence of calcium crystals and test the hypothesis that PC is potentially a meniscal protective agent. We found that PC downregulated the expression of many genes classified in cell proliferation, ossification, prostaglandin metabolic process, and wound healing, including bloom syndrome RecQ helicase-like, cell division cycle 7 homolog, cell division cycle 25 homolog C, ankylosis progressive homolog, prostaglandin-endoperoxide synthases-1/cyclooxygenase-1, and plasminogen activator urokinase receptor. In contrast, PC stimulated the expression of many genes classified in fibroblast growth factor receptor signaling pathway, collagen fibril organization, and extracellular structure organization, including fibroblast growth factor 7, collagen type I, alpha 1, and collagen type XI, alpha 1. Consistent with its effect on the expression of genes classified in cell proliferation, collagen fibril organization, and ossification, PC inhibited the proliferation of OA meniscal cells and meniscal cell-mediated calcification while stimulating the production of collagens. These findings indicate that PC is potentially a meniscal-protective agent and a disease-modifying drug for arthritis associated with severe meniscal degeneration.

A review of hedgehog signaling in cranial bone development

During craniofacial development, the Hedgehog (HH) signaling pathway is essential for mesodermal tissue patterning and differentiation. The HH family consists of three protein ligands: Sonic Hedgehog (SHH), Indian Hedgehog (IHH), and Desert Hedgehog (DHH), of which two are expressed in the craniofacial complex (IHH and SHH). Dysregulations in HH signaling are well documented to result in a wide range of craniofacial abnormalities, including holoprosencephaly (HPE), hypotelorism, and cleft lip/palate. Furthermore, mutations in HH effectors, co-receptors, and ciliary proteins result in skeletal and craniofacial deformities. Cranial suture morphogenesis is a delicate developmental process that requires control of cell commitment, proliferation and differentiation. This review focuses on both what is known and what remains unknown regarding HH signaling in cranial suture morphogenesis and intramembranous ossification. As demonstrated from murine studies, expression of both SHH and IHH is critical to the formation and fusion of the cranial sutures and calvarial ossification. SHH expression has been observed in the cranial suture mesenchyme and its precise function is not fully defined, although some postulate SHH to delay cranial suture fusion. IHH expression is mainly found on the osteogenic fronts of the calvarial bones, and functions to induce cell proliferation and differentiation. Unfortunately, neonatal lethality of IHH deficient mice precludes a detailed examination of their postnatal calvarial phenotype. In summary, a number of basic questions are yet to be answered regarding domains of expression, developmental role, and functional overlap of HH morphogens in the calvaria. Nevertheless, SHH and IHH ligands are integral to cranial suture development and regulation of calvarial ossification. When HH signaling goes awry, the resultant suite of morphologic abnormalities highlights the important roles of HH signaling in cranial development.

Fibroblast growth factor-2 and bone morphogenetic protein-2 have a synergistic stimulatory effect on bone formation in cell cultures from elderly mouse and human bone

Combined regimens of fibroblast growth factor-2 (FGF-2) and bone morphogenetic protein-2 (BMP-2) were investigated to stimulate osteogenic differentiation. In young mouse calvaria-derived cells, FGF-2 (0.16ng/mL) in combination with BMP-2 (50ng/mL) did not enhance mineralization, but in old mouse cells it resulted in more mineralization than BMP-2 alone. In young long bone mouse cultures, FGF-2 enhanced mineralization relative to BMP-2 alone, but in old cultures, lower dose of FGF-2 (0.016ng/mL) was necessary. In neonatal mouse calvarial cells, sequential delivery of low-dose FGF-2 and low-dose BMP-2 (5ng/mL) was more stimulatory than co-delivery. In young human cultures, 0.016ng/mL of FGF-2 did not enhance mineralization, in combination with 5ng/mL of BMP-2, but in older cultures, codelivery of FGF-2 and BMP-2 was superior to BMP-2 alone. In conclusion, BMP-2 treatment alone was sufficient for maximal mineralization in young osteoblast cultures. However, coadministration of FGF-2 and BMP-2 increases mineralization more than BMP-2 alone in cultures from old and young mouse long bones and old humans but not in young mouse calvarial cultures.

Integration of multiple signaling pathways determines differences in the osteogenic potential and tissue regeneration of neural crest-derived and mesoderm-derived calvarial bones

The mammalian skull vault, a product of a unique and tightly regulated evolutionary process, in which components of disparate embryonic origin are integrated, is an elegant model with which to study osteoblast biology. Our laboratory has demonstrated that this distinct embryonic origin of frontal and parietal bones confer differences in embryonic and postnatal osteogenic potential and skeletal regenerative capacity, with frontal neural crest derived osteoblasts benefitting from greater osteogenic potential. We outline how this model has been used to elucidate some of the molecular mechanisms which underlie these differences and place these findings into the context of our current understanding of the key, highly conserved, pathways which govern the osteoblast lineage including FGF, BMP, Wnt and TGFβ signaling. Furthermore, we explore recent studies which have provided a tantalizing insight into way these pathways interact, with evidence accumulating for certain transcription factors, such as Runx2, acting as a nexus for cross-talk.

BMP-2, VEGF and bFGF synergistically promote the osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) were treated with bone morphogenetic protein-2 (BMP-2), vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) dose-dependently and time-dependently. Together they caused a strong synergistic effect on the osteogenic differentiation of MSCs, with lower concentrations of each factor being enough to show the synergistic promotion (50 ng BMP-2/ml, 1 ng VEGF/ml and 10 ng bFGF/ml). When both VEGF and bFGF were added in the early proliferating stage (the first 7 days) and BMP-2 was added in the late differentiation stage (the last 7 days), osteogenic differentiation of MSCs could be enhanced more effectively.

Phenotype profile of a genetic mouse model for Muenke syndrome

PURPOSE

The Muenke syndrome mutation (FGFR3 (P250R)), which was discovered 15 years ago, represents the single most common craniosynostosis mutation. Muenke syndrome is characterized by coronal suture synostosis, midface hypoplasia, subtle limb anomalies, and hearing loss. However, the spectrum of clinical presentation continues to expand. To better understand the pathophysiology of the Muenke syndrome, we present collective findings from several recent studies that have characterized a genetically equivalent mouse model for Muenke syndrome (FgfR3 (P244R)) and compare them with human phenotypes.

CONCLUSIONS

FgfR3 (P244R) mutant mice show premature fusion of facial sutures, premaxillary and/or zygomatic sutures, but rarely the coronal suture. The mice also lack the typical limb phenotype. On the other hand, the mutant mice display maxillary retrusion in association with a shortening of the anterior cranial base and a premature closure of intersphenoidal and spheno-occipital synchondroses, resembling human midface hypoplasia. In addition, sensorineural hearing loss is detected in all FgfR3 (P244R) mutant mice as in the majority of Muenke syndrome patients. It is caused by a defect in the mechanism of cell fate determination in the organ of Corti. The mice also express phenotypes that have not been previously described in humans, such as reduced cortical bone thickness, hypoplastic trabecular bone, and defective temporomandibular joint structure. Therefore, the FgfR3 (P244R) mouse provides an excellent opportunity to study disease mechanisms of some classical phenotypes of Muenke syndrome and to test novel therapeutic strategies. The mouse model can also be further explored to discover previously unreported yet potentially significant phenotypes of Muenke syndrome.

Leader genes in osteogenesis: a theoretical study

Little is still known about the molecular mechanisms involved in the process of osteogenesis. In this paper, the leader genes approach, a new bioinformatics method which has already been experimentally validated, is adopted in order to identify the genes involved in human osteogenesis. Interactions among genes are then calculated and genes are ranked according to their relative importance in this process. In total, 167 genes were identified as being involved in osteogenesis. Genes were divided into 4 groups, according to their main function in the osteogenic processes: skeletal development; cell adhesion and proliferation; ossification; and calcium ion binding. Seven genes were consistently identified as leader genes (i.e. the genes with the greatest importance in osteogenesis), while 14 were found to have slightly less importance (class B genes). It was interesting to notice that the larger part of leader and class B genes belonged to the cell adhesion and proliferation or to the ossification sub-groups. This finding suggested that these two particular sub-processes could play a more important role in osteogenesis. Moreover, among the 7 leader genes, it is interesting to notice that RUNX2, BMP2, SPARC, PTH play a direct role in bone formation, while the 3 other leader genes (VEGF, IL6, FGF2) seem to be more connected with an angiogenetic process. Twenty-nine genes have no known interactions (orphan genes). From these results, it may be possible to plan an ad hoc experimentation, for instance by microarray analyses, focused on leader, class B and orphan genes, with the aim to shed new light on the molecular mechanisms underlying osteogenesis.

Cholesteryl group- and acryloyl group-bearing pullulan nanogel to deliver BMP2 and FGF18 for bone tissue engineering

To create a drug delivery system that allows the controlled release of proteins, such as growth factors, over a long-term period, cholesteryl group- and acryloyl group-bearing pullulan (CHPOA) nanogels were aggregated to form fast-degradable hydrogels (CHPOA/hydrogels) by cross-linking with thiol-bearing polyethylene glycol. The gold standard of clinical bone reconstruction therapy with a physiologically active material is treatment with recombinant human bone morphogenetic protein 2 (BMP2); however, this approach has limitations, such as inflammation, poor cost-efficiency, and varying interindividual susceptibility. In this study, two distinct growth factors, BMP2 and recombinant human fibroblast growth factor 18 (FGF18), were applied to a critical-size skull bone defect for bone repair by the CHPOA/hydrogel system. The CHPOA-FGF18/hydrogel displayed identical results to the control CHPOA-PBS/hydrogel, and the CHPOA-BMP2/hydrogel treatment imperfectly induced bone repair. By contrast, the CHPOA-FGF18 + BMP2/hydrogel treatment strongly enhanced and stabilized the BMP2-dependent bone repair, inducing osteoprogenitor cell infiltration inside and around the hydrogel. This report indicates that the CHPOA/hydrogel system can successfully deliver two different proteins to the bone defect to induce effective bone repair. The combination of the CHPOA/hydrogel system with the growth factors FGF18 and BMP2 might be a step towards efficient bone tissue engineering.

FGF/FGFR signaling in bone formation: progress and perspectives

Fibroblast growth factors (FGFs) are important molecules that control bone formation. FGF act by activating FGF receptors (FGFRs) and downstream signaling pathways that control cells of the osteoblast lineage. Recent advances have been made in the identification of FGF/FGFR signaling pathways that control osteogenesis. Indeed, studies of mouse and human models provided novel insights into the signaling pathways that control bone formation. Genomic studies also highlighted the implication of molecular targets of FGF/FGFR signaling regulating osteoblastogenesis. Recent studies further revealed the important role of crosstalks between FGF/FGFR signaling and other signaling pathways in the regulation of osteogenesis. Finally, the importance of the mechanisms modulating FGFR degradation in the control of osteoblast differentiation has been recently revealed. This short review summarizes the recently described mechanisms underlying FGF/FGFR signaling that are involved in the control of osteoblastogenesis. This knowledge may have potential therapeutic implications in skeletal disorders characterized by abnormal bone formation.

Effects of VEGF and FGF-2 on proliferation and differentiation of human periodontal ligament stem cells

Human periodontal ligament stem cells (PDLSCs) from extracted third molar teeth are a type of adult stem cell originating from dental tissue. PDLSCs are known to have a self-renewal capacity and multi-lineage differentiation potential. Vascular endothelial growth factor (VEGF), an angiogenic/vasculogenic factor, has been shown to stimulate endothelial cell mitogenesis and cell migration. Another growth factor, fibroblast growth factor-2 (FGF-2), a mitogenic factor, enhances osteogenesis in mesenchymal stem cells (MSCs). This study examines the effects of VEGF and FGF-2 on PDLSCs in vitro and in vivo compared with those on bone marrow stem cells (BMSCs) as a positive control. Treatment of PDLSCs with VEGF increases the accumulation of calcium nodules, alkaline phosphatase (ALP) activity and the formation of hard tissue and up-regulates the mRNA level of runt-related transcription factor 2 (Runx2). In contrast, FGF-2 enhances the proliferation of PDLSCs in vitro in cell culture, where it significantly decreases calcium accumulation and ALP activity and down-regulates the expression of osteogenic gene markers (i.e., Runx2, ALP, type I collagen) involved in osteogenic induction. We have also transplanted PDLSCs with hydroxyapatite/tricalcium phosphate particles (HA/TCP) as carriers for each factor (VEGF, FGF-2) into nude mice and, after 8 weeks, observed the in vivo formation of hard tissue at the dorsal surface. Based on our results, we suggest that VEGF has positive effects on odonto-/osteogenic differentiation in vitro and on the formation of mineralized structure in vivo. FGF-2 might be a powerful promoter of the proliferation of progenitor cells in hard tissue regeneration but exogenous FGF-2 might inhibit terminal differentiation.

Changes in proliferation and osteogenic differentiation of stem cells from deep caries in vitro

INTRODUCTION

It is suggested that dental pulp stem cells are involved in tooth regeneration and play an important role in maintaining pulp homeostasis. Previously, normal dental pulps were more widely used for experimental models than carious dental pulps. The aim of this study was to isolate and culture the dental pulp stem cells from carious and normal teeth and to evaluate stem cell parameters.

METHODS

Pulp tissues were obtained and dissociated from normal and carious teeth. Single-cell suspensions were seeded into 6-well plates and purified by collecting multiple colonies. Normal dental pulp stem cells (DPSCs) and carious dental pulp stem cells (CDPSCs) were compared for morphologic appearance and for their capacity to differentiate into 3 lineages. Colony-forming and MTT assays, cell cycle analysis, gene expression, and alkaline phosphatase activity were also evaluated.

RESULTS

Stem cells were cultured successfully from normal and carious dental pulps. CDPSCs displayed increased proliferation ability compared with DPSCs. CDPSCs also showed enhanced ALP activity, mineralization ability, and expression of osteogenesis/dentinogenesis-related genes. All cultures differentiated into 3 cell types.

CONCLUSIONS

Our data suggest that caries as a local microenvironment should be taken into account when DPSCs are intended to be used for investigations and application. Furthermore, the mechanism of the underlying changes in cell properties requires further study.

The Muenke syndrome mutation (FgfR3P244R) causes cranial base shortening associated with growth plate dysfunction and premature perichondrial ossification in murine basicranial synchondroses

Muenke syndrome caused by the FGFR3(P250R) mutation is an autosomal dominant disorder mostly identified with coronal suture synostosis, but it also presents with other craniofacial phenotypes that include mild to moderate midface hypoplasia. The Muenke syndrome mutation is thought to dysregulate intramembranous ossification at the cranial suture without disturbing endochondral bone formation in the skull. We show in this study that knock-in mice harboring the mutation responsible for the Muenke syndrome (FgfR3(P244R)) display postnatal shortening of the cranial base along with synchondrosis growth plate dysfunction characterized by loss of resting, proliferating and hypertrophic chondrocyte zones and decreased Ihh expression. Furthermore, premature conversion of resting chondrocytes along the perichondrium into prehypertrophic chondrocytes leads to perichondrial bony bridge formation, effectively terminating the postnatal growth of the cranial base. Thus, we conclude that the Muenke syndrome mutation disturbs endochondral and perichondrial ossification in the cranial base, explaining the midface hypoplasia in patients.

Bone-metastatic prostate carcinoma favors mesenchymal stem cell differentiation toward osteoblasts and reduces their osteoclastogenic potential

Bone homeostasis is achieved by the balance between osteoclast-dependent bone resorption and osteoblastic events involving differentiation of adult mesenchymal stem cells (MSCs). Prostate carcinoma (PC) cells display the propensity to metastasize to bone marrow where they disrupt bone homeostasis as a result of mixed osteolytic and osteoblastic lesions. The PC-dependent activation of osteoclasts represents the initial step of tumor engraftment into bone, followed by an accelerated osteoblastic activity and exaggerated bone formation. However, the interactions between PC cells and MSCs and their participation in the disease progression remain as yet unclear. In this study, we show that bone metastatic PC-3 carcinoma cells release factors that increase the expression by human (h)MSCs of several known pro-osteoblastic commitment factors, such as α5/β1 integrins, fibronectin, and osteoprotegerin. As a consequence, as shown in an osteogenesis assay, hMSCs treated with conditioned medium (C(ed) M) derived from PC-3 cells have an enhanced potential to differentiate into osteoblasts, as compared to hMSCs treated with control medium or with C(ed) M from non-metastatic 22RV1 cells. We demonstrate that FGF-9, one of the factors produced by PC-3 cells, is involved in this process. Furthermore, we show that PC-3 C(ed) M decreases the pro-osteoclastic activity of hMSCs. Altogether, these findings allow us to propose clues to understand the mechanisms by which PC favors bone synthesis by regulating MSC outcome and properties.

TGF-β and BMP signaling in osteoblast differentiation and bone formation

Transforming growth factor-beta (TGF-β)/bone morphogenic protein (BMP) signaling is involved in a vast majority of cellular processes and is fundamentally important throughout life. TGF-β/BMPs have widely recognized roles in bone formation during mammalian development and exhibit versatile regulatory functions in the body. Signaling transduction by TGF-β/BMPs is specifically through both canonical Smad-dependent pathways (TGF-β/BMP ligands, receptors and Smads) and non-canonical Smad-independent signaling pathway (e.g. p38 mitogen-activated protein kinase pathway, MAPK). Following TGF-β/BMP induction, both the Smad and p38 MAPK pathways converge at the Runx2 gene to control mesenchymal precursor cell differentiation. The coordinated activity of Runx2 and TGF-β/BMP-activated Smads is critical for formation of the skeleton. Recent advances in molecular and genetic studies using gene targeting in mice enable a better understanding of TGF-β/BMP signaling in bone and in the signaling networks underlying osteoblast differentiation and bone formation. This review summarizes the recent advances in our understanding of TGF-β/BMP signaling in bone from studies of genetic mouse models and human diseases caused by the disruption of TGF-β/BMP signaling. This review also highlights the different modes of cross-talk between TGF-β/BMP signaling and the signaling pathways of MAPK, Wnt, Hedgehog, Notch, and FGF in osteoblast differentiation and bone formation.

Effects of osteogenic growth factors on bone marrow stromal cell differentiation in a mineral-based delivery system

Delivering growth factors from bone-like mineral combines osteoinductivity with osteoconductivity. The effects of individual and sequential exposure of BMP-2 and FGF-2 on osteogenic differentiation, and their release from apatite were studied to design a dual delivery system. Bone marrow stromal cells were seeded on TCPS with the addition of FGF-2 (2.5, 10, 40 ng/ml) or BMP-2 (50, 150, 450 ng/ml) for 6 days. DNA content and osteogenic response were examined weekly for 3 weeks. FGF-2 increased DNA content; however, high concentrations of FGF-2 inhibited/delayed osteogenic differentiation, while a threshold concentration of BMP-2 was required for significant osteogenic enhancement. The sequence of delivery of BMP-2 (300 ng/ml) and FGF-2 (2.5 ng/ml) also had a significant impact on osteogenic differentiation. Delivery of FGF-2 followed by BMP-2 or delivery of BMP-2 followed by BMP-2 and FGF-2 enhanced osteogenic differentiation compared to the simultaneous delivery of both factors. Release of BMP-2 and FGF-2 from bone-like mineral was significantly affected by the concentration used during coprecipitation. BMP-2 also demonstrated a higher "burst" release compared to FGF-2. By integrating the results of the sequential delivery of BMP-2 and FGF-2 in solution, with the release of individual growth factors from mineral, an organic/inorganic delivery system based on coprecipitation can be designed for multiple biomolecules.

Reproductive toxicity of Rhizoma Sparganii (Sparganium stoloniferum Buch.-Ham.) in mice: mechanisms of anti-angiogenesis and anti-estrogen pharmacologic activities

ETHNOPHARMACOLOGICAL RELEVANCE

Indications and preliminary studies of Rhizoma Sparganii (RS) suggest its pharmacological mechanism is involved with endocrine/angiogenesis functions. We therefore studied its potential toxicity on reproduction in mice.

MATERIALS AND METHODS

Reproductive toxicity of 100, 200 and 400 mg/kg RS extract were studied in pregnant ICR mice and its offspring. The embryos' fibroblast growth factor-1 (FGF-1), vascular endothelial growth factor (VEGF) and estrogen receptor-α (ER-α) were evaluated as targets of endocrine/angiogenesis by immunohistochemical test.

RESULTS

The offspring of treated mice (100, 200 and 400 mg/kg RS extract) during their pregnancy had various pathological conditions, suggesting an abnormal FGF signaling phenomenon during pregnancy. Embryos from the 400 mg/kg group had significantly depressed levels of FGF-1 (P < 0.01) and VEGF (P < 0.05) expression levels as compared to controls by immunohistochemical test. Dysplasia in the heart (12.9%), craniofacial region (18.3%) and vertebrae (32.5%) presented in embryos of the 400 mg/kg group. Furthermore, the ER-α expression was inversely proportional to FGF-1 levels in the same embryo (P < 0.01).

CONCLUSIONS

These results implicate a FGF signaling abnormality in vivo and indicate that RS has anti-angiogenesis and anti-estrogen toxicity effects in pregnant rodents.

Effects of FGF2 and FGF9 on osteogenic differentiation of bone marrow-derived progenitors

Bone repair is a major concern in reconstructive surgery. Transplants containing osteogenically committed mesenchymal stem cells (MSCs) provide an alternative source to the currently used autologous bone transplants which have limited supply and require additional surgery to the patient. A major drawback, however is the lack of a critical mass of cells needed for successful transplantation. The purpose of the present study was to test the effects of FGF2 and FGF9 on expansion and differentiation of MSCs in order to establish an optimal culture protocol resulting in sufficient committed osteogenic cells required for successful in vivo transplantation. Bone marrow-derived MSCs cultured in αMEM medium supplemented with osteogenic supplements for up to three passages (control medium), were additionally treated with FGF2 and FGF9 in various combinations. Cultures were evaluated for viability, calcium deposition and in vivo osteogenic capacity by testing subcutaneous transplants in nude mice. FGF2 had a positive effect on the proliferative capacity of cultured MSCs compared to FGF9 and control medium treated cultures. Cultures treated with FGF2 followed by FGF9 showed an increased amount of extracted Alizarin red indicating greater osteogenic differentiation. Moreover, the osteogenic capacity of cultured cells transplanted in immunodeficient mice revealed that cells that were subjected to treatment with FGF2 in the first two passages and subsequently to FGF9 in the last passage only, were more successful in forming new bone. It is concluded that the protocol using FGF2 prior to FGF9 is beneficial to cell expansion and commitment, resulting in higher in vivo bone formation for successful bone tissue engineering.

Activation of FGF signaling mediates proliferative and osteogenic differences between neural crest derived frontal and mesoderm parietal derived bone

Background

As a culmination of efforts over the last years, our knowledge of the embryonic origins of the mammalian frontal and parietal cranial bones is unambiguous. Progenitor cells that subsequently give rise to frontal bone are of neural crest origin, while parietal bone progenitors arise from paraxial mesoderm. Given the unique qualities of neural crest cells and the clear delineation of the embryonic origins of the calvarial bones, we sought to determine whether mouse neural crest derived frontal bone differs in biology from mesoderm derived parietal bone.

Methods

BrdU incorporation, immunoblotting and osteogenic differentiation assays were performed to investigate the proliferative rate and osteogenic potential of embryonic and postnatal osteoblasts derived from mouse frontal and parietal bones. Co-culture experiments and treatment with conditioned medium harvested from both types of osteoblasts were performed to investigate potential interactions between the two different tissue origin osteoblasts. Immunoblotting techniques were used to investigate the endogenous level of FGF-2 and the activation of three major FGF signaling pathways. Knockdown of FGF Receptor 1 (FgfR1) was employed to inactivate the FGF signaling.

Results

Our results demonstrated that striking differences in cell proliferation and osteogenic differentiation between the frontal and parietal bone can be detected already at embryonic stages. The greater proliferation rate, as well as osteogenic capacity of frontal bone derived osteoblasts, were paralleled by an elevated level of FGF-2 protein synthesis. Moreover, an enhanced activation of FGF-signaling pathways was observed in frontal bone derived osteoblasts. Finally, the greater osteogenic potential of frontal derived osteoblasts was dramatically impaired by knocking down FgfR1.

Conclusions

Osteoblasts from mouse neural crest derived frontal bone displayed a greater proliferative and osteogenic potential and endogenous enhanced activation of FGF signaling compared to osteoblasts from mesoderm derived parietal bone. FGF signaling plays a key role in determining biological differences between the two types of osteoblasts.

Regulation of osteoblast and osteoclast functions by FGF-6

Fibroblast growth factor-6 (FGF-6) is known to be the key ligand for fibroblast growth factor receptor 4 (FGFR4) during muscle regeneration but its role in bone has yet to be verified. FGFR signaling is known to be important in the initiation and regulation of osteogenesis, so in this study the actions of FGF-6 on human osteoblasts and osteoclasts were investigated. Human primary osteoblasts (hOB) were used to study the effect of FGF-6 on proliferation (by ATP quantification), signal transduction (by ERK and AKT phosphorylation), differentiation (by alkaline phosphatase activity, APA), and mineralization (by calcein staining). To study FGF-6 activity on osteoclast differentiation, human bone marrow cells were used and tartrate-resistant acid phosphatase (TRAP) multinucleated cells together with actin filaments arrangements were quantified. Human primary mature osteoclasts were used to evaluate the effect of FGF-6 on osteoclast reabsorbing activity by reabsorbed pit measurements. FGF-6 >10(-9) M as FGF-2 10(-7) M induced hOB proliferation mediated by pERK together with a reduction in APA and reduced mineralization of the treated cells. Moreover FGF-6 increased the formation of TRAP-positive multinucleated cells in a dose-dependent manner (maximal effect at 10(-8) M). FGF-6-treated cells showed also a greater percentage of cells that formed typical osteoclast sealing zones. Mature osteoclasts cultured on dentine slice increased the area of reabsorption with a maximal effect of FGF-6 at 10(-12) M. FGF-6 may be considered a regulator of bone metabolism as shown by its activity on both osteoblasts and osteoclasts.

Different endogenous threshold levels of Fibroblast Growth Factor-ligands determine the healing potential of frontal and parietal bones

In the skull vault, neural crest derived frontal bones have an increased healing capacity and higher expression levels of Fibroblast Growth Factor-ligands as compared to mesoderm-derived parietal bones. Thus, we asked whether Fibroblast Growth Factor-ligands are responsible for the superior healing potential of frontal bones. Parietal defects in juvenile and adult mice treated with Fibroblast Growth Factor-2, -9 and -18 showed increased bone regeneration, comparable to frontal defects. Immunohistochemistry revealed increased recruitment of osteoprogenitors and activation of FGF-signaling pathways in FGF-treated parietal defects. Conversely, calvarial defects in Fgf-9(+/-) and Fgf-18(+/-) mice showed impaired calvarial healing which could be rescued by exogenous Fibroblast Growth Factor-ligands. Moreover, by utilizing Wnt1Cre/R26R mice, the migration and contribution of dura mater and pericranium cells to calvarial healing could be demonstrated. Taken together our results demonstrated that different endogenous threshold levels of Fibroblast Growth Factor-ligands in frontal and parietal bones have a profound impact on calvarial regeneration. The present study thereby opens new avenues for translational medicine.

Enhanced bone formation using hydroxyapatite ceramic coated with fibroblast growth factor-2

Our objective was to develop a bone substitute coated with fibroblast growth factor-2 (FGF-2) that subsequently releases FGF-2. We investigated the use of our system of bone substitutes to induce bone formation. Hydroxyapatite ceramic buttons (HAP-CBs) were coated with FGF-2 by precipitation in supersaturated calcium phosphate solution. HAP-CBs were coated with high or low doses of FGF-2, denoted as FGF-H and FGF-L. The release of FGF-2 from FGF-H and FGF-L was evaluated using its release profile and bioactivity. The efficacy of the subsequent bone formation was quantified using rats with round-shaped bone defects (5mm in diameter) of the right parietal bone. Group 1 was treated only with HAP-CBs, group 2 with HAP-CBs and drops of FGF-2 solution, group 3 with FGF-L and group 4 with FGF-H. To detect the release of FGF-2 in vivo, the expression of bone morphogenic protein-2 (BMP-2) was measured in the defective bone tissue. FGF-2 was released in vitro from FGF-H and FGF-L, and maintained its bioactivity. Rats treated with FGF-L showed better bone formation than rats from the other groups. BMP-2 expression was detected in the defective bone tissues of group 3 at 14 days, which might indicate in vivo FGF-2 release during this period. A specific FGF-2 concentration may be needed for bone formation, and our system can release FGF-2 at adequate concentrations to induce bone formation.

Pulsed electromagnetic fields accelerate proliferation and osteogenic gene expression in human bone marrow mesenchymal stem cells during osteogenic differentiation

Osteogenesis is a complex series of events involving the differentiation of mesenchymal stem cells to generate new bone. In this study, we examined the effect of pulsed electromagnetic fields (PEMFs) on cell proliferation, alkaline phosphatase (ALP) activity, mineralization of the extracellular matrix, and gene expression in bone marrow mesenchymal stem cells (BMMSCs) during osteogenic differentiation. Exposure of BMMSCs to PEMFs increased cell proliferation by 29.6% compared to untreated cells at day 1 of differentiation. Semi-quantitative RT-PCR indicated that PEMFs significantly altered temporal expression of osteogenesis-related genes, including a 2.7-fold increase in expression of the key osteogenesis regulatory gene cbfa1, compared to untreated controls. In addition, exposure to PEMFs significantly increased ALP expression during the early stages of osteogenesis and substantially enhanced mineralization near the midpoint of osteogenesis. These results suggest that PEMFs enhance early cell proliferation in BMMSC-mediated osteogenesis, and accelerate the osteogenesis.

Effect of nicotine on gene expression of angiogenic and osteogenic factors in a rabbit model of bone regeneration

PURPOSE

This study aims to evaluate the influence of nicotine on the gene expression of osteogenic and angiogenic factors in bone regeneration by use of a nicotine-compromised rabbit model of mandibular lengthening.

MATERIALS AND METHODS

Thirty adult New Zealand white rabbits were randomly assigned to the nicotine group or the control group. The total nicotine or placebo exposure time for all animals was 7 weeks. Unilateral mandibular distraction osteogenesis was performed. Five animals in each group were sacrificed at day 5, day 11, and day 18, respectively, after commencement of active distraction. The distraction regenerate samples were harvested, and the messenger ribonucleic acid expression of bone transforming growth factor beta(1), platelet-derived growth factor A, and basic fibroblast growth factor was assayed by real-time polymerase chain reaction analysis.

RESULTS

The messenger ribonucleic acid expression of transforming growth factor beta(1), platelet-derived growth factor A, and basic fibroblast growth factor was significantly inhibited by nicotine exposure at a variety of time points.

CONCLUSIONS

The presence of nicotine inhibited the gene expression of angiogenic and osteogenic factors resulting in compromised bone regeneration.

Src family kinase/abl inhibitor dasatinib suppresses proliferation and enhances differentiation of osteoblasts

Dasatinib, a dual Src family kinase and Abl inhibitor, is being tested clinically for the treatment of prostate cancer bone metastasis. Bidirectional interactions between osteoblasts and prostate cancer cells are critical in the progression of prostate cancer in bone, but the effect of dasatinib on osteoblasts is unknown. We found that dasatinib inhibited proliferation of primary mouse osteoblasts isolated from mouse calvaria and the immortalized MC3T3-E1 cell line. In calvarial osteoblasts from Col-luc transgenic mice carrying osteoblast-specific Col1alpha1 promoter reporter, luciferase activity was inhibited. Dasatinib also inhibited fibroblast growth factor-2-induced osteoblast proliferation, but strongly promoted osteoblast differentiation, as reflected by stimulation of alkaline phosphatase activity, osteocalcin secretion and osteoblast mineralization. To determine how dasatinib blocks proliferative signaling in osteoblasts, we analyzed the expression of a panel of tyrosine kinases, including Src, Lyn, Fyn, Yes and Abl, in osteoblasts. In the Src family kinases, only Src was activated at a high level. Abl was expressed at a low level in osteoblasts. Phosphorylation of Src-Y419 or Abl-Y245 was inhibited by dasatinib treatment. Knockdown of either Src or Abl by lenti-shRNA in osteoblasts enhances osteoblast differentiation, suggesting that dasatinib enhances osteoblast differentiation through inhibition of both Src and Abl.

Mineralization behavior with mesenchymal stromal cells in a biomimetic hyaluronic acid-based scaffold

A biomimetic hyaluronic acid (HA)-based polymer scaffold was analysed in vitro for its characteristics and potential to support mineralization as carrier-vehicle. Biomimetic apatite crystal nucleation on the scaffold surface was obtained by a fine control of the pH level that increased ionic solubility thus controlling apatite formation kinetic. Different concentrations of human mesenchymal stromal cells (h-MSCs) were seeded on the scaffold, osteogenesis was induced in the presence or absence of fibroblast growth factor -2 and mineralization was analysed at different time points. We found that only at the highest h-MSCs concentration tested, the cells were uniformly distributed inside and outside the scaffold and proliferation started to decrease from day 7. Electron microscopy analysis evidenced that h-MSCs produced extracellular matrix but did not establish a direct contact with the scaffold. We found mineralized calcium-positive areas mainly present along the backbone of the scaffold starting from day 21 and increasing at day 35. FGF-2 treatment did not accelerate or increase mineralization. Non-biomimetic HA-based control scaffold showed immature mineralized areas only at day 35. Our data demonstrate that the biomimetic treatment of an HA-based scaffold promotes a faster mineralization process suggesting its possible use in clinics as a support for improving bone repair.

Repressive BMP2 gene regulatory elements near the BMP2 promoter

The level of bone morphogenetic protein 2 (BMP2) profoundly influences essential cell behaviors such as proliferation, differentiation, apoptosis, and migration. The spatial and temporal pattern of BMP2 synthesis, particular in diverse embryonic cells, is highly varied and dynamic. We have identified GC-rich sequences within the BMP2 promoter region that strongly repress gene expression. These elements block the activity of a highly conserved, osteoblast enhancer in response to FGF2 treatment. Both positive and negative gene regulatory elements control BMP2 synthesis. Detecting and mapping the repressive motifs is essential because they impede the identification of developmentally regulated enhancers necessary for normal BMP2 patterns and concentration.

Lysyl oxidase propeptide inhibits FGF-2-induced signaling and proliferation of osteoblasts

Pro-lysyl oxidase is secreted as a 50-kDa proenzyme and is then cleaved to a 30-kDa mature enzyme (lysyl oxidase (LOX)) and an 18-kDa propeptide (lysyl oxidase propeptide (LOX-PP)). The presence of LOX-PP in the cell layers of phenotypically normal osteoblast cultures led us to investigate the effects of LOX-PP on osteoblast differentiation. Data indicate that LOX-PP inhibits terminal mineralization in primary calvaria osteoblast cultures when added at early stages of differentiation, with no effects seen when present at later stages. LOX-PP was found to inhibit serum- and FGF-2-stimulated DNA synthesis and FGF-2-stimulated cell growth. Enzyme-linked immunosorbent assay and Western blot analyses show that LOX-PP inhibits FGF-2-induced ERK1/2 phosphorylation, signaling events that mediate the FGF-2-induced proliferative response. LOX-PP inhibits FGF-2-stimulated phosphorylation of FRS2alpha and FGF-2-stimulated DNA synthesis, even after inhibition of sulfation of heparan sulfate proteoglycans. These data point to a LOX-PP target at or near the level of fibroblast growth factor receptor binding or activation. Ligand binding assays on osteoblast cell layers with (125)I-FGF-2 demonstrate a concentration-dependent inhibition of FGF-2 binding to osteoblasts by LOX-PP. In vitro binding assays with recombinant fibroblast growth factor receptor protein revealed that LOX-PP inhibits FGF-2 binding in an uncompetitive manner. We propose a working model for the respective roles of LOX enzyme and LOX-PP in osteoblast phenotype development in which LOX-PP may act to inhibit the proliferative response possibly to allow cells to exit from the cell cycle and progress to the next stages of differentiation.

Loss of proliferation and differentiation capacity of aged human periodontal ligament stem cells and rejuvenation by exposure to the young extrinsic environment

The application of periodontal ligament stem cells (PDLSCs) may be effective for periodontal regenerative therapy. As tissue regenerative potential may be negatively regulated by aging, whether aging and its microenvironment modify human PDLSCs remains a question. In this study, we compared the proliferation and differentiation capacity of PDLSCs obtained from young and aged donors. Then, we exposed aged PDLSCs to young periodontal ligament cell-conditioned medium (PLC-CM), and young PDLSCs were exposed to aged PLC-CM. Morphological appearance, colony-forming assay, cell cycle analysis, osteogenic and adipogenic induction media, gene expression of cementoblast phenotype, and in vivo differentiation capacities of PDLSCs were evaluated. PDLSCs obtained from aged donors exhibited decreased proliferation and differentiation capacity when compared with those from young donors. Young PLC-CM enhanced the proliferation and differentiation capacity of PDLSCs from aged donors. Aged PDLSCs induced by young PLC-CM showed enhanced tissue-regenerative capacity to produce cementum/periodontal ligament-like structures, whereas young PDLSCs induced by aged PLC-CM transplants mainly formed connective tissues. To our knowledge, this is the first study to mimic the developmental microenvironment of PDLSCs in vitro, and our data suggest that age influences the proliferation and differentiation potential of human PDLSCs, and that the activity of human PDLSCs can be modulated by the extrinsic microenvironment.

Stem cell property of postmigratory cranial neural crest cells and their utility in alveolar bone regeneration and tooth development

The vertebrate neural crest is a multipotent cell population that gives rise to a variety of different cell types. We have discovered that postmigratory cranial neural crest cells (CNCCs) maintain mesenchymal stem cell characteristics and show potential utility for the regeneration of craniofacial structures. We are able to induce the osteogenic differentiation of postmigratory CNCCs, and this differentiation is regulated by bone morphogenetic protein (BMP) and transforming growth factor-beta signaling pathways. After transplantation into a host animal, postmigratory CNCCs form bone matrix. CNCC-formed bones are distinct from bones regenerated by bone marrow mesenchymal stem cells. In addition, CNCCs support tooth germ survival via BMP signaling in our CNCC-tooth germ cotransplantation system. Thus, we conclude that postmigratory CNCCs preserve stem cell features, contribute to craniofacial bone formation, and play a fundamental role in supporting tooth organ development. These findings reveal a novel function for postmigratory CNCCs in organ development, and demonstrate the utility of these CNCCs in regenerating craniofacial structures.

Effect of combined application of bFGF and inorganic polyphosphate on bioactivities of osteoblasts and initial bone regeneration

Basic fibroblast growth factor (bFGF) and inorganic polyphosphate (poly(P)) have been recognized as therapeutic agents that enhance bone regeneration. It has also been shown that poly(P) may enhance the mitogenic activity of bFGF. The purpose of this study is to evaluate the combined effect of bFGF and poly(P) on bioactivities of osteoblasts and initial bone regeneration in vitro and in vivo. MC3T3-E1 cells were treated with bFGF, poly(P) or bFGF+poly(P), then subjected to cell proliferation assay, alkaline phosphatase (ALP) activity measurement, quantitative real-time reverse transcription-polymerase chain reaction and Alizarin S Red staining. In an in vivo study, bFGF-, poly(P)- and bFGF+poly(P)-modified interconnected porous hydroxyapatite (IPHA) complexes were fabricated, and placed into the femurs of rabbits to evaluate new bone formation histologically and histomorphometrically. The highest enhancement of cell proliferation were observed in those treated with bFGF+poly(P) on days 5 and 7. Cells treated with bFGF+poly(P) also exhibited increased ALP activity on days 5 and 10, up-regulated mRNA levels of osteocalcin and osteopontin, and enhanced calcification when compared to the non-treated cells. In vivo, the highest bone formation ratio was observed in bFGF+poly(P)-modified IPHA complexes. This study indicated that co-application of bFGF and poly(P) may provide enhanced bone formation by modulating cell proliferation and the mineralization process. It is anticipated that a combined application of bFGF and poly(P) can provide a novel method for bone regeneration in clinical use.