Co-Stimulation of AGEs and LPS Induces Inflammatory Mediators through PLCγ1/JNK/NF-κB Pathway in MC3T3-E1 Cells.

Advanced glycation end-products (AGEs) are increased under hyperglycemia in vivo and are associated with the onset of diabetes. According to previous studies, AGEs exacerbate inflammatory diseases. However, the mechanism by which AGEs aggravate osteoblast inflammation remains unknown. Therefore, the aim of this study was to determine the effects of AGEs on the production of inflammatory mediators in MC3T3-E1 cells and the underlying molecular mechanisms. Co-stimulation with AGEs and lipopolysaccharide (LPS) was found to increase the mRNA and protein levels of cyclooxygenase 2 (COX2), interleukin-1α (IL-1α), S100 calcium-binding protein A9 (S100A9), and the production of prostaglandin E2 (PGE2) compared to no stimulation (untreated control) or individual stimulation with LPS or AGEs. In contrast, the phospholipase C (PLC) inhibitor, U73122, inhibited these stimulatory effects. Co-stimulation with AGEs and LPS also increased the nuclear translocation of nuclear factor-kappa B (NF-κB) compared to no stimulation (untreated control) or individual stimulation with LPS or AGE. However, this increase was inhibited by U73122. Co-stimulation with AGEs and LPS-induced phosphorylated phospholipase Cγ1 (p-PLCγ1) and phosphorylated c-Jun N-terminal kinase (p-JNK) expression compared to no stimulation or individual stimulation with LPS or AGEs. U73122 inhibited the effects induced by co-stimulation. siPLCγ1 did not increase the expression of p-JNK and the translocation of NF-κB. Overall, co-stimulation with AGEs and LPS may promote inflammation mediators in MC3T3-E1 cells by activating the nuclear translocation of NF-κB via PLCγ1-JNK activation.

Growth Factor Delivery Using a Collagen Membrane for Bone Tissue Regeneration.

The use of biomaterials and bioactive agents has shown promise in bone defect repair, leading to the development of strategies for bone regeneration. Various artificial membranes, especially collagen membranes (CMs) that are widely used for periodontal therapy and provide an extracellular matrix-simulating environment, play a significant role in promoting bone regeneration. In addition, numerous growth factors (GFs) have been used as clinical applications in regenerative therapy. However, it has been established that the unregulated administration of these factors may not work to their full regenerative potential and could also trigger unfavorable side effects. The utilization of these factors in clinical settings is still restricted due to the lack of effective delivery systems and biomaterial carriers. Hence, considering the efficiency of bone regeneration, both spaces maintained using CMs and GFs can synergistically create successful outcomes in bone tissue engineering. Therefore, recent studies have demonstrated a significant interest in the potential of combining CMs and GFs to effectively promote bone repair. This approach holds great promise and has become a focal point in our research. The purpose of this review is to highlight the role of CMs containing GFs in the regeneration of bone tissue, and to discuss their use in preclinical animal models of regeneration. Additionally, the review addresses potential concerns and suggests future research directions for growth factor therapy in the field of regenerative science.

Real-time assessment of guided bone regeneration in critical size mandibular bone defects in rats using collagen membranes with adjunct fibroblast growth factor-2.

BACKGROUND/PURPOSE: Fibroblast growth factor-2 (FGF-2) regulates bone formation. The concept of guided bone regeneration using a resorbable collagen membrane (RCM) is generally accepted in implant dentistry. This study aimed to investigate the bone healing pattern in rat mandibular bone defects in real-time with and without RCM containing FGF-2 (RCM/FGF-2). MATERIALS AND METHODS: Critical-size circular bone defects (4.0 mm diameter) were created on both sides of the rat mandibular bone. The defects were randomly divided into the following groups: control, RCM alone, RCM containing low (0.5 µg) or high (2.0 µg) concentration of FGF-2. We performed real-time in vivo micro-computerized tomography scans at the baseline and at 2, 4, and 6 weeks, and measured the volume of newly formed bone (NFB), bone mineral density (BMD) of NFB, and the closure percentage of the NFB area. At 6 weeks, the mandibular specimens were assessed histologically and histomorphometrically to evaluate the area of new bone regeneration. RESULTS: Real-time assessment revealed a significant increase in the volume, BMD, and closure percentage of the NFB area in the RCM/FGF-2-treated groups than that in the control and RCM groups. In the H-FGF-2 group, the volume and BMD of NFB exhibited a significant increase at 6 weeks than that at the baseline. Histological evaluation revealed the presence of osteoblasts, osteocytes, and blood vessels within the NFB. CONCLUSION: The real-time in vivo experiment demonstrated that RCM/FGF-2 effectively promoted bone regeneration within the critical-size mandibular defects in rats and verified new bone formation starting in the early postoperative phase.

Clinical classification of tooth position in the alveolar bone housing with periodontal defects.

A new classification of tooth position in the alveolar bone housing, which indicates the width of alveolar bone for buccolingual direction, with bone defects caused by periodontal disease is proposed. This classification highlights the importance of tooth position in the alveolar bone housing in terms of the progression of the regenerative process and the factors that may affect the prognosis of compromised teeth after regenerative surgery. Tooth positions were divided into two groups: (i) The whole tooth is centrally positioned in the existing alveolar bone housing (Grade I) and (ii) A part of the tooth is exposed out of the existing alveolar bone housing (Grade II). Grade II is further divided into two subgroups according to situations encountered in clinical practice. The following subclasses are suggested: Subgroup A, where the alveolar bone housing is broader than the tooth, and Subgroup B, where the alveolar bone housing is narrower than the tooth. These subgroups represent a discrepancy between tooth size and alveolar bone dimensions in the buccolingual orientation. This classification could be useful for planning the correct regenerative treatment for each type of the tooth position in the alveolar bone housing with periodontal defects.

Released fibroblast growth factor18 from a collagen membrane induces osteoblastic activity involved with downregulation of miR-133a and miR-135a.

We have developed a unique delivery system of growth factors using collagen membranes (CMs) to induce bone regeneration. We hypothesized that fibroblast growth factor18 (FGF-18), a pleiotropic protein that stimulates proliferation in several tissues, can be a good candidate to use our delivery system for bone regeneration. Cell viability, cell proliferation, alkaline phosphatase activity, mineralization, and marker gene expression of osteoblastic differentiation were evaluated after mouse preosteoblasts were cultured with a CM containing FGF-18, a CM containing platelet-derived growth factor, or a CM alone. Furthermore, expression of microRNA, especially miR-133a and miR-135a involving inhibition of osteogenic factors, was measured in preosteoblasts with CM/FGF-18 or CM alone. A sustained release of FGF-18 from the CM was observed over 21 days. CM/FGF-18 significantly promoted cell proliferation, alkaline phosphatase activity, and mineralization compared to CM alone. Gene expression of type I collagen, runt-related transcription factor 2, osteocalcin, Smad5, and osteopontin was significantly upregulated in CM/FGF-18 compared to CM alone, and similar to CM/platelet-derived growth factor. Additionally, CM/FGF-18 downregulated expression of miR-133a and miR-135a. These results suggested that released FGF-18 from a CM promotes osteoblastic activity involved with downregulation of miR-133a and miR-135a.

A collagen membrane containing osteogenic protein-1 facilitates bone regeneration in a rat mandibular bone defect.

OBJECTIVES: Osteogenic protein-1 (OP-1) has shown osteoinductive activities and is useful for clinical treatments, including bone regeneration. Regenerative procedures using a bioabsorbable collagen membrane (BCM) are well established in periodontal and implant dentistry. We evaluated the subsequent effects of the BCM in combination with OP-1 on bone regeneration in a rat mandibular circular critical-sized bone defect in vivo. DESIGN: We used 8 rats that received surgery in both sides of the mandible, and created the total 16 defects which were divided into 4 groups: Group 1; no treatment, as a control, Group 2; BCM alone, Group 3; BCM containing low dose 0.5µg of OP-1 (L-OP-1), and Group 4; BCM containing high dose 2.0µg of OP-1 (H-OP-1). Newly formed bone was evaluated by micro computed tomography (micro-CT) and histological analyses at 8 weeks postoperatively. In quantitative and qualitative micro-CT analyses of the volume of new bone formation, bone density, and percentage of new bone area was evaluated. RESULTS: BCM with rhOP-1 significantly increased and accelerated bone volume, bone mineral density, and percentage of new bone area compared to control and BCM alone at 8 weeks after surgery; these enhancements in bone regeneration in the OP-1-treated groups were dose-dependent. CONCLUSIONS: OP-1 delivered with a BCM may have effective osteoinductive potency and be a good combination for bone regeneration. The use of such a combination device for osteogenesis may result in safer and more predictable bone regenerative outcomes in the future.

Low-intensity pulsed ultrasound inhibits lipopolysaccharide-induced IL-6 and RANKL expression in osteoblasts.

Periodontal disease is caused by inflammation induced by Porphyromonas gingivalis (P.g.) lipopolysaccharide (LPS) and involves expression of proinflammatory cytokines such as interleukin (IL)-1, IL-6, tumor necrosis factor-α, and receptor activator of nuclear factor kappa B ligand (RANKL), which are implicated in bone resorption. Low-intensity pulsed ultrasound (LIPUS) is commonly used in the treatment of bone fracture. However, the mechanisms by which LIPUS inhibits LPS-induced inflammatory cytokines are poorly understood. Therefore, we investigated the effects of LIPUS on LPS-induced expression of the proinflammatory cytokines IL-6 and RANKL. MC3T3-E1 cells were incubated in the presence or absence of P.g. LPS and then stimulated with LIPUS for 30 min/day for a maximum of 14 days. LPS increased mRNA and protein expressions of IL-6 and RANKL on day 14. In addition, mRNA expression of COX-2 LPS was higher after 3 and 7 days of LIPUS treatment. PGE2 was induced by LPS after 7 and 14 days of culture. LIPUS suppressed all stimulatory effects of LPS. These results suggest that LIPUS inhibits LPS-induced expression of inflammation cytokines by suppressing PGE2 production and might thus have potential applications in the treatment of periodontitis.

The potential of stromal cell-derived factor-1 delivery using a collagen membrane for bone regeneration.

Stromal cell-derived factor-1 (SDF-1) is a cytokine that is important in stem and progenitor cell recruitment in tissue repair after injury. Regenerative procedures using collagen membranes (CMs) are presently well established in periodontal and implant dentistry. The objective of this study is to test the subsequent effects of the released SDF-1 from a CM on bone regeneration compared to platelet-derived growth factor (PDGF) in vitro and in vivo. For in vitro studies, cell proliferation, alkaline phosphatase activity, and osteoblastic differentiation marker genes were assessed after MC3T3-E1 mouse preosteoblasts were cultured with CMs containing factors. In vivo effects were investigated by placement of CMs containing SDF-1 or PDGF using a rat mandibular bone defect model. At 4 weeks after the surgery, the new bone formation was measured using micro-computed tomography (µCT) and histological analysis. The results of in vitro studies revealed that CM delivery of SDF-1 significantly induced cell proliferation, ALP activity, and gene expression of all osteogenic markers compared to the CM alone or control, similar to PDGF. Quantitative and qualitative µCT analysis for volume of new bone formation and the percentage of new bone area showed that SDF-1-treated groups significantly increased and accelerated bone regeneration compared to control and CM alone. The enhancement of bone formation in SDF-1-treated animals was dose-dependent and with levels similar to those measured with PDGF. These results suggest that a CM with SDF-1 may be a great candidate for growth factor delivery that could be a substitute for PDGF in clinical procedures where bone regeneration is necessary.

Ex vivo nonviral gene delivery of µ-opioid receptor to attenuate cancer-induced pain.

Virus-mediated gene delivery shows promise for the treatment of chronic pain. However, viral vectors have cytotoxicity. To avoid toxicities and limitations of virus-mediated gene delivery, we developed a novel nonviral hybrid vector: HIV-1 Tat peptide sequence modified with histidine and cysteine residues combined with a cationic lipid. The vector has high transfection efficiency with little cytotoxicity in cancer cell lines including HSC-3 (human tongue squamous cell carcinoma) and exhibits differential expression in HSC-3 (∼45-fold) relative to HGF-1 (human gingival fibroblasts) cells. We used the nonviral vector to transfect cancer with OPRM1, the µ-opioid receptor gene, as a novel method for treating cancer-induced pain. After HSC-3 cells were transfected with OPRM1, a cancer mouse model was created by inoculating the transfected HSC-3 cells into the hind paw or tongue of athymic mice to determine the analgesic potential of OPRM1 transfection. Mice with HSC-3 tumors expressing OPRM1 demonstrated significant antinociception compared with control mice. The effect was reversible with local naloxone administration. We quantified ß-endorphin secretion from HSC-3 cells and showed that HSC-3 cells transfected with OPRM1 secreted significantly more ß-endorphin than control HSC-3 cells. These findings indicate that nonviral delivery of the OPRM1 gene targeted to the cancer microenvironment has an analgesic effect in a preclinical cancer model, and nonviral gene delivery is a potential treatment for cancer pain.

LIPUS suppressed LPS-induced IL-1α through the inhibition of NF-κB nuclear translocation via AT1-PLCß pathway in MC3T3-E1 cells.

Inflammatory cytokines, interleukin (IL)-1, IL-6, and TNF-α, are involved in inflammatory bone diseases such as rheumatoid osteoarthritis and periodontal disease. Particularly, periodontal disease, which destroys alveolar bone, is stimulated by lipopolysaccharide (LPS). Low-intensity pulsed ultrasound (LIPUS) is used for bone healing in orthopedics and dental treatments. However, the mechanism underlying effects of LIPUS on LPS-induced inflammatory cytokine are not well understood. We therefore aimed to investigate the role of LIPUS on LPS-induced IL-1α production. Mouse calvaria osteoblast-like cells MC3T3-E1 were incubated in the presence or absence of LPS (Porphyromonas gingivalis), and then stimulated with LIPUS for 30 min/day. To investigate the role of LIPUS, we determined the expression of IL-1α stimulated with LIPUS and treated with an angiotensin II receptor type 1 (AT1) antagonist, Losartan. We also investigate to clarify the pathway of LIPUS, we transfected siRNA silencing AT1 (siAT1) in MC3T3-E1. LIPUS inhibited mRNA and protein expression of LPS-induced IL-1α. LIPUS also reduced the nuclear translocation of NF-κB by LPS-induced IL-1α. Losartan and siAT1 blocked all the stimulatory effects of LIPUS on IL-1α production and IL-1α-mediated NF-κB translocation induced by LPS. Furthermore, PLCß inhibitor U73122 recovered NF-κB translocation. These results suggest that LIPUS inhibits LPS-induced IL-1α via AT1-PLCß in osteoblasts. We exhibit that these findings are in part of the signaling pathway of LIPUS on the anti-inflammatory effects of IL-1α expression.

Low-intensity pulsed ultrasound-induced ATP increases bone formation via the P2X7 receptor in osteoblast-like MC3T3-E1 cells.

Low-intensity pulsed ultrasound (LIPUS) is used for bone healing in orthopedics and dentistry. It has been shown that LIPUS induces the secretion of extracellular adenosine triphosphate (ATP), a key mediator of osteoblast response to mechanical stimuli. However, the detailed mechanism of LIPUS-induced osteogenesis has been elusive. In this study, we investigated the role of the P2X7 receptor in LIPUS-induced osteogenesis. LIPUS induced the release of extracellular ATP, differentiation of osteoblasts and osteogenesis via the P2X7 receptor, without affecting the activity of alkaline phosphatase (ALPase). These results suggest that LIPUS-induced extracellular ATP promotes bone formation via the osteoblast P2X7 receptor independently of ALPase.

Nanometer-scale features on micrometer-scale surface texturing: a bone histological, gene expression, and nanomechanical study.

Micro- and nanoscale surface modifications have been the focus of multiple studies in the pursuit of accelerating bone apposition or osseointegration at the implant surface. Here, we evaluated histological and nanomechanical properties, and gene expression, for a microblasted surface presenting nanometer-scale texture within a micrometer-scale texture (MB) (Ossean Surface, Intra-Lock International, Boca Raton, FL) versus a dual-acid etched surface presenting texture at the micrometer-scale only (AA), in a rodent femur model for 1, 2, 4, and 8weeks in vivo. Following animal sacrifice, samples were evaluated in terms of histomorphometry, biomechanical properties through nanoindentation, and gene expression by real-time quantitative reverse transcription polymerase chain reaction analysis. Although the histomorphometric, and gene expression analysis results were not significantly different between MB and AA at 4 and 8 weeks, significant differences were seen at 1 and 2 weeks. The expression of the genes encoding collagen type I (COL-1), and osteopontin (OPN) was significantly higher for MB than for AA at 1 week, indicating up-regulated osteoprogenitor and osteoblast differentiation. At 2 weeks, significantly up-regulated expression of the genes for COL-1, runt-related transcription factor 2 (RUNX-2), osterix, and osteocalcin (OCN) indicated progressive mineralization in newly formed bone. The nanomechanical properties tested by the nanoindentation presented significantly higher-rank hardness and elastic modulus for the MB compared to AA at all time points tested. In conclusion, the nanotopographical featured surfaces presented an overall higher host-to-implant response compared to the microtextured only surfaces. The statistical differences observed in some of the osteogenic gene expression between the two groups may shed some insight into the role of surface texture and its extent in the observed bone healing mechanisms.

Efficient in vivo gene delivery using modified Tat peptide with cationic lipids.

A combination of modified HIV-1 Tat (mTat) peptide and cationic lipids, FuGENE HD (FH), dramatically enhanced transfection efficiency across a range of cell lines when compared to mTat or FH alone (Biomaterials 35:1705-1715 2014). The efficiency of this Tat peptide combination was significantly higher than many commercial non-viral vectors. In this present study, we tested the feasibility of this non-viral vector, mTat/FH, in vivo using plasmid DNA encoding a luciferase gene. The results of the in vivo studies showed that animals administered mTat/FH/DNA intramuscularly had significantly higher and longer luciferase expression (≈7 months) than those with mTat/DNA, FH/DNA, or DNA alone. Histological evaluation showed little immune response in the muscles, livers, and kidneys of mice administered with the mTat/FH. The combination of mTat with FH could significantly improve transfection efficiency, expanding the potential use of non-viral gene vectors in vivo.

The effect of a bioactive collagen membrane releasing PDGF or GDF-5 on bone regeneration.

Regenerative procedures using barrier membrane technology are presently well established in periodontal/endodontic surgery. The objective of this study was to compare the subsequent effects of the released platelet-derived growth factor (PDGF) and growth/differentiation factor 5 (GDF-5) from collagen membranes (CMs) on bone regeneration in vitro and in vivo. In vitro studies were conducted using MC3T3-E1 mouse preosteoblasts cultured with or without factors. Cell viability, cell proliferation, alkaline phosphatase (ALP) activity and bone marker gene expression were then measured. In vivo studies were conducted by placing CMs with low or high dose PDGF or GDF-5 in rat mandibular defects. At 4 weeks after surgery new bone formation was measured using µCT and histological analysis. The results of in vitro studies showed that CM/GDF-5 significantly increased ALP and cell proliferation activities without cytotoxicity in MC3T3-E1 cells when compared to CM/PDGF or CM alone. Gene expression analysis revealed that Runx2 and Osteocalcin were significantly increased in CM/GDF-5 compared to CM/PDGF or control. Quantitative and qualitative µCT and histological analysis for new bone formation revealed that although CM/PDGF significantly enhanced bone regeneration compared to CM alone or control, CM/GDF-5 significantly accelerated bone regeneration to an even greater extent than CM/PDGF. The results also showed that GDF-5 induced new bone formation in a dose-dependent manner. These results suggest that this strategy, using a CM carrying GDF-5, might lead to an improvement in the current clinical treatment of bone defects for periodontal and implant therapy.

Long-term efficient gene delivery using polyethylenimine with modified Tat peptide.

Polyethylenimine (PEI), a cationic polymer, has been widely studied and shown great promise as an efficient gene delivery vehicle. Likewise, the HIV-1 Tat peptide, a cell-permeable peptide, has been successfully used for intracellular gene delivery. To improve the favorable properties of these two vectors, we combine PEI with the modified Tat peptide sequence bearing histidine and cysteine residues (mTat). In vitro mTat/PEI-mediated transfection was evaluated by luciferase expression plasmid in two cell types. mTat/PEI produced significant improvement (≈5-fold) in transfection efficiency of both cell lines with little cytotoxicity when compared to mTat alone, PEI alone, or four commercial reagents. The particle size of mTat/PEI/DNA complex was significantly smaller than mTat or PEI alone, and it was correlated with higher transfection efficiency. Filipin III, an inhibitor of caveolae-mediated endocytosis, significantly inhibited mTat/PEI transfection. In contrast, chlorpromazine, an inhibitor of clathrin-mediated endocytosis, did not. This suggested caveolae-mediated endocytosis as the transfection mechanism. Furthermore, the results of in vivo studies showed that animals administered mTat/PEI/DNA intramuscularly had significantly higher and longer luciferase expression (≈7 months) than those with mTat/DNA, PEI/DNA, or DNA alone, without any associated toxicity. The combination of mTat with PEI could significantly improve transfection efficiency, expanding the potential use as a non-viral gene vector both in vitro and in vivo.

Daily low-intensity pulsed ultrasound stimulates production of bone morphogenetic protein in ROS 17/2.8 cells.

Although daily low-intensity pulsed ultrasound (LIPUS) can accelerate osteogenic differentiation of the rat clonal cell line ROS 17/2.8, the molecular mechanism that underlies this phenomenon is unclear. The purpose of this study was to determine which molecules exposed to daily LIPUS treatment stimulate osteogenic differentiation. The cells were cultured in the presence and absence (control) of LIPUS stimulation. LIPUS treatments consisted of 1.5-MHz ultrasound administered at an intensity of 30 mW/cm(2), 20 min daily for 7 days. The expression of bone morphogenetic proteins (BMPs) and their receptors involved in osteogenesis were measured using real-time PCR and/or Western blot analysis. Phosphorylation of the mothers against decapentaplegic 1 (Smad1) protein was determined by Western blotting. Daily LIPUS treatment significantly increased the expression of BMP-2, -4, and -7 and their receptors, and also phosphorylation of Smad1. Noggin markedly inhibited the daily LIPUS-induced phosphorylation of Smad1. Our findings demonstrate that the osteogenic activity of daily LIPUS may be mediated by BMPs in ROS 17/2.8 cells.

Daily low-intensity pulsed ultrasound-mediated osteogenic differentiation in rat osteoblasts.

There were few studies investigating the effects of the mechanical stimulation provided by daily low-intensity pulsed ultrasound (LIPUS) treatment. LIPUS is known to accelerate bone mineralization and regeneration; however, the precise cellular mechanism is unclear.Our purpose was to determine how daily LIPUS treatment affected cell viability, alkaline phosphatase activity, osteogenesis-related gene expression, and mineralized nodule formation in osteoblasts. The typical osteoblastic cell line ROS 17/2.8 cells were cultured in the absence or presence of LIPUS stimulation. Daily LIPUS treatments (1.5 MHz; 20 min) were administered at an intensity of 30 mW/cm(2) for 14 days. Expression of osteogenesis-related genes was examined at mRNA levels using real-time polymerase chain reaction and at protein levels using western blotting analysis. LIPUS stimulation did not affect the rate of cell viability. Alkaline phosphatase activity was increased after 10 days of culture with daily LIPUS stimulation. LIPUS significantly increased the expression of mRNAs encoding Runx2, Msx2, Dlx5, osterix, bone sialoprotein, and bone morphogenetic protein-2, whereas it significantly reduced the expression of mRNA encoding the transcription factor AJ18. Mineralized nodule formation was markedly increased on Day 14 of LIPUS stimulation. LIPUS stimulation directly affected osteogenic cells, leading to mineralized nodule formation. LIPUS is likely to have a fundamental influence on key functional activities of osteoblasts in alveolar bone.

Effects of lactoferrin on the differentiation of pluripotent mesenchymal cells.

Lactoferrin accelerates bone formation, but the precise cellular mechanism behind this is still unclear. We examined the effect of lactoferrin on the differentiation of pluripotent mesenchymal cells using a typical pluripotent mesenchymal cell line, C2C12. Cells were cultured in low-mitogen differentiation medium to induce cell differentiation, with or without the addition of lactoferrin. The cell lineage was determined by alkaline phosphatase (ALPase) activity, mRNA expression of cellular phenotype-specific markers using real-time polymerase chain reaction (PCR), and protein synthesis using Western blotting. The expression of low-density lipoprotein lipase receptor-related proteins (LRPs) 1 and 2, both lactoferrin receptors, was determined by reverse transcription-PCR. ALPase activity increased after the addition of lactoferrin. The mRNA expression of Runx2, osteocalcin, and Sox9 increased markedly as a result of lactoferrin treatment, whereas the expression of MyoD, desmin, and PPARgamma decreased significantly. Western blots showed that lactoferrin stimulation increased Runx2 and Sox9 proteins, whereas it decreased MyoD and PPARgamma synthesis. C2C12 cells expressed the LRP1 lactoferrin receptor. These results indicate that lactoferrin treatment converts the differentiation pathway of C2C12 cells into the osteoblastic and chondroblastic lineage.

Lactoferrin suppress the adipogenic differentiation of MC3T3-G2/PA6 cells.

Lactoferrin accelerates the differentiation of osteogenic and chondrogenic lineage cells, whereas it inhibits the myogenic and adipogenic differentiation of pluripotent mesenchymal cells; however, the effect of lactoferrin on the differentiation of preadipocytes is unknown. In this study, we examined the effect of lactoferrin on adipogenic differentiation using a mouse preadipocyte cell line, MC3T3-G2/PA6. The cells were cultured in differentiation medium with or without lactoferrin to induce cellular differentiation. The cell lineage was then determined by Oil Red O staining, real-time PCR screening for the mRNA expression of phenotype-specific markers, and Western blot analysis. The number of Oil Red O-positive lipid droplets decreased following treatment with lactoferrin, as did the mRNA expression of C/EBPalpha, PPARgamma, aP2, and adiponectin. Furthermore, our Western blot data revealed a decrease in PPARgamma expression attributable to lactoferrin exposure. These results suggest that lactoferrin suppresses the adipogenic differentiation of MC3T3-G2/PA6 cells.

The in vitro osteogenetic characteristics of primary osteoblastic cells from a rabbit calvarium.

Previously, we showed that recombinant human bone morphogenetic protein-2 (rhBMP-2) increased bone augmentation beyond the skeletal envelope within a titanium cap in a rabbit calvarium; many cuboidal osteoblastic cells were observed histologically. These results suggested that the new osteoblastic cells might have differentiated and matured via stimulation by rhBMP-2. To date, however, no studies have reported the characteristics of osteoblastic cells derived from adult rabbit calvarium, after addition of rhBMP-2. To determine the effects of rhBMP-2 on osteoblastic cells, we observed morphological characteristics and alkaline phosphatase activity of osteoblastic cells from an adult rabbit calvarium. The expression of proteins in the BMP signaling pathway and extracellular matrix were analyzed, and mineralized nodule formation was assessed. The alkaline phosphatase activity increased significantly after rhBMP-2 stimulation. The protein levels of phosphorylated-Smad1, Runx2, osteocalcin, osteopontin, and type I collagen were augmented by rhBMP-2 stimulation using Western blotting or ELISA; rhBMP-2 also stimulated mineralized nodule formation with alizarin red staining. The results suggest that primary osteoblastic cells derived from a rabbit calvarium have osteogenetic characteristics in vitro, underscoring the potential use of these cells as a model for studying bone formation. These cells may play an important role in in vivo bone augmentation in a rabbit experimental model.