Production of osteocalcin by human bone cells in vitro. Effects of 1,25(OH)2D3, 24,25(OH)2D3, parathyroid hormone, and glucocorticoids

IGF1 drives Wnt-induced joint damage and is a potential therapeutic target for osteoarthritis

Osteoarthritis is the most common joint disease and a global leading cause of pain and disability. Current treatment is limited to symptom relief, yet there is no disease-modifying therapy. Its multifactorial etiology includes excessive activation of Wnt signaling, but how Wnt causes joint destruction remains poorly understood. Here, we identify that Wnt signaling promotes the transcription of insulin-like growth factor 1 (IGF1) in articular chondrocytes and that IGF1 is a major driver of Wnt-induced joint damage. Male mice with cartilage-specific Igf1 deficiency are protected from Wnt-triggered joint disease. Mechanistically, Wnt-induced IGF1 transcription depends on β-catenin and binding of Wnt transcription factor TCF4 to the IGF1 gene promoter. In a clinically relevant mouse model of post-traumatic osteoarthritis, cartilage-specific deletion of Igf1 protects against the disease in male mice. IGF1 silencing in chondrocytes from patients with osteoarthritis restores a healthy molecular profile. Our findings reveal that reducing Wnt-induced IGF1 is a potential therapeutic strategy for osteoarthritis.

Estrogen receptor alpha and NFATc1 bind to a bone mineral density-associated SNP to repress WNT5B in osteoblasts

Genetic factors and estrogen deficiency contribute to the development of osteoporosis. The single-nucleotide polymorphism (SNP) rs2887571 is predicted from genome-wide association studies (GWASs) to associate with osteoporosis but has had an unknown mechanism. Analysis of osteoblasts from 110 different individuals who underwent joint replacement revealed that the genotype of rs2887571 correlates with WNT5B expression. Analysis of our ChIP-sequencing data revealed that SNP rs2887571 overlaps with an estrogen receptor alpha (ERα) binding site. Here we show that 17β-estradiol (E2) suppresses WNT5B expression and further demonstrate the mechanism of ERα binding at the enhancer containing rs2887571 to suppress WNT5B expression differentially in each genotype. ERα interacts with NFATc1, which is predicted to bind directly at rs2887571. CRISPR-Cas9 and ChIP-qPCR experiments confirm differential regulation of WNT5B between each allele. Homozygous GG has a higher binding affinity for ERα than homozygous AA and results in greater suppression of WNT5B expression. Functionally, WNT5B represses alkaline phosphatase expression and activity, decreasing osteoblast differentiation and mineralization. Furthermore, WNT5B increases interleukin-6 expression and suppresses E2-induced expression of alkaline phosphatase during osteoblast differentiation. We show that WNT5B suppresses the differentiation of osteoblasts via receptor tyrosine kinase-like orphan receptor 1/2 (ROR1/2), which activates DVL2/3/RAC1/CDC42/JNK/SIN3A signaling and inhibits β-catenin activity. Together, our data provide mechanistic insight into how ERα and NFATc1 regulate the non-coding SNP rs2887571, as well as the function of WNT5B on osteoblasts, which could provide alternative therapeutic targets for osteoporosis.

Determining the association between hypertension and bone metabolism markers in osteoporotic patients

The aim of the case study is to examine the association between hypertension and the level of bone metabolism markers in newly diagnosed osteoporotic patients.A cross-sectional study of 518 subjects was done to see the association between hypertension and the level of osteocalcin (OC), bone-specific alkaline phosphatase (B-ALP), Tartrate-resistant acid phosphatase (TRAP.5B), and 25-hydroxy vitamin D (25-OHD). There were 243 (46.9%) osteoporosis patients with hypertension. Both univariate and multivariate analysis have suggested that lower OC and 25-OHD levels were associated with hypertension. The potential confounders-adjusted OC level was significantly lower in hypertensive female group than that in the female without hypertension group [β = -0.20, 95% confidence interval (95% CI) = -0.37 to -0.03, P = .02 in final adjust model]. The potential confounders-adjusted 25-OHD level was significantly lower in hypertensive male group than that in male without hypertension group (β = -0.34, 95% CI = -0.58 to -0.10, P = .01 in final adjust model). The B-ALP and TRACP.5B levels were positively associated with hypertension in all patients or subgroup analysis. However, all the correlations had no statistical significance for the B-ALP and TRACP.5B.In conclusion, the hypertension was associated with low level of OC and 25-OHD. Hypertension probably led to low bone turnover, which may be one of the mechanisms of hypertension-related osteoporosis.

A review of in vitro cell culture testing methods for bioactive glasses and other biomaterials for hard tissue regeneration

Bioactive glasses are used to regenerate bone by a mechanism which involves surface degradation, the release of ions such as calcium, soluble silica and phosphate and the precipitation of a biomimetic apatite surface layer on the glass. One major area of bioactive glass research is the incorporation of therapeutically active ions to broaden the application range of these materials. When developing such new compositions, in vitro cell culture studies are a key part of their characterisation. However, parameters of cell culture studies vary widely, and depending on the intended use of bioactive glass compositions, different layouts, cell types and assays need to be used. The aim of this publication is to provide materials scientists, particularly those new to cell culture studies, with a tool for selecting the most appropriate assays to give insight into the properties of interest.

A Novel Corn-Expressed Phytase Improves Daily Weight Gain, Protein Efficiency Ratio and Nutrients Digestibility and Alters Fecal Microbiota in Pigs Fed with Very Low Protein Diets

The objective of this study was to assess the effect of a novel corn-expressed phytase (CEP) on growth, nutrients digestibility, bone characteristics and fecal microbiota of pigs fed with very low-protein, -calcium (Ca) and -phosphorous (P) diets. Forty-eight barrows were subjected to 6 groups for 4 weeks: positive control-adequate protein (PC), negative control-reduced protein (NC), NC + low-dose CEP, i.e., 2000 FTU/kg (LD), NC + high-dose CEP, i.e., 4000 FTU/kg (HD), LD with 0.12% unit reduced Ca and 0.15% unit reduced available P (LDR), and HD with 0.12% unit reduced Ca and 0.15% unit reduced available P (HDR). Compared to NC, LD and HDR had a higher average daily gain (ADG) and gain:protein ratio (G:P), HD and HDR had greater apparent fecal digestibility of Ca and P and bone mineral density and LDR and HDR had lower serum osteocalcin. The feces of LD was enriched in Lachnospiraceae, while the HD had a higher abundance of Succinvibrio and LDR had a higher abundance of Bifidobacterium and Actinobacteria. In conclusion, supplementation of protein-restricted diets with a CEP decreased their negative effects on ADG and G:P ratio, increased the digestibility of Ca and P regardless of the levels of these minerals in the diet, improved bone characteristics and produced differential effects on fecal bacterial population.

Isolation and Generation of Osteoblasts

This chapter describes the isolation, culture, and staining of osteoblasts. The key advantages of this assay are that it allows direct measurement of bone matrix deposition and mineralization, as well as yielding good quantities of osteoblasts at defined stages of differentiation for molecular and histological analysis. An additional focus of this chapter will be the culture of osteoblasts from less conventional animal species.

Mummy Material Can Promote Differentiation of Adipose Derived Stem Cells into Osteoblast through Enhancement of Bone Specific Transcription Factors Expression

Purpose: Application of Mummy material for treatment of different diseases such as bone fracture, cutaneous wounds and joint inflammation has been advised since hundred years ago in Persian traditional medicine. Due to the claims of indigenous people and advice of traditional medicine for application of this material in healing of bone fractures, this study has been designed to evaluate whether Mummy material can promote the differentiation of mesenchymal stem cells into osteoblasts and enhance the expression of bone specific genes and proteins.

Methods: Adipose derived stem cells (ASCs) at fourth cell passage were divided into control, osteogenesis group (received osteogenic medium), Mummy group (received Mummy at concentration of 500 µg/ml). ASCs in the fourth group were treated with both osteogenic medium and Mummy (500µg/ml). Cells in all groups were harvested on days 7, 14 and 21 days for further evaluation through Real time RT-PCR, Von kossa staining, Immunocytochemistry and flowcytometery.

Results: Treatment of ASCs with Mummy at concentration of 500µg/ml promotes the expression level of Osteocalcin, RUNX-2 and β1-integrin genes in different time points but that of the Osterix did not changed. Furthermore the expression of Osteocalcin protein enhanced significantly in ASCs treated with Mummy detected by Immunocytochemistry and flowcytometery technique compared to the control groups. The results of this study also showed that treatment of ASCs with Mummy resulted in formation of mineral deposits which was evaluated by Von Kossa staining method.

Conclusion: Obtained data from this study reveals that Mummy is a potent enhancer for differentiation of ASCs into osteoblasts in in vitro system, probably through increasing the level of bone specific genes and proteins.

Altered Ethanol Consumption in Osteocalcin Null Mutant Mice

Osteocalcin (OC) is an abundant extracellular calcium-binding protein synthesized by osteoblasts. Although most OC is bound to hydroxyapatite mineral during bone formation, a consistent amount is released directly to circulation. Plasma OC (pOC) levels are highly sensitive to stressful stimuli that alter stress-responsive hormones, such as glucocorticoids (cortisol or corticosterone) and the catecholamines norepinephrine and epinephrine. To gain a better understanding of the apparent relationship of OC to the effects of ethanol (EtOH) and the stress responses, we compared mice that have OC (WT [OC+/+] and HET [OC+/-]) with OC null mutants (KO [OC-/-]), which have no OC in either plasma or in bone. One experiment included chronic unpredictable stress, a second was conducted in the absence of any known stressors other than EtOH, while a third imposed a more severe acute immobilization stress in addition to EtOH consumption. The data obtained confirmed significant differences in EtOH consumption in mice that previously experienced various stressful stimuli. We also determined that adrenal tyrosine-hydroxylase expression was inversely proportional to EtOH consumption and tended to be lower in KO than in WT. Data suggest that OC possesses the ability to modulate the adrenal gene expression of the catecholamine synthetic pathway. This modulation may be responsible for differences in EtOH consumption under stress.

DOT1L safeguards cartilage homeostasis and protects against osteoarthritis

Osteoarthritis is the most prevalent and crippling joint disease, and lacks curative treatment, as the underlying molecular basis is unclear. Here, we show that DOT1L, an enzyme involved in histone methylation, is a master protector of cartilage health. Loss of DOT1L disrupts the molecular signature of healthy chondrocytes in vitro and causes osteoarthritis in mice. Mechanistically, the protective function of DOT1L is attributable to inhibition of Wnt signalling, a pathway that when hyper-activated can lead to joint disease. Unexpectedly, DOT1L suppresses Wnt signalling by inhibiting the activity of sirtuin-1 (SIRT1), an important regulator of gene transcription. Inhibition of SIRT1 protects against osteoarthritis triggered by loss of DOT1L activity. Modulating the DOT1L network might therefore be a therapeutic approach to protect the cartilage against osteoarthritis.

Rivaroxaban significantly inhibits the stimulatory effects of bone-modulating hormones: In vitro study of primary female osteoblasts

BACKGROUND

Anticoagulant therapy is a mainstay of treatment subsequent to major orthopedic surgeries. Evidence linking anticoagulant therapy, osteoporosis, and delayed fracture healing is not conclusive. We have previously reported that rivaroxaban significantly inhibited cell growth and energy metabolism in a human osteoblastic cell line. This study analyzed the response of primary female osteoblast cells to rivaroxaban in combination with various bone-modulating hormones.

METHODS

Bone samples were taken from both premenopausal (pre-Ob) and postmenopausal (post-Ob) women. Cells were isolated from each sample and cultured to sub-confluence. Each sample was then treated with Rivaroxaban (10 µg/ml) in combination with the following hormones or with the hormones alone for 24 hours: 30nM estradiol-17β (E2), 390nM estrogen receptor α (ERα) agonist PPT, 420nM estrogen receptor β (ERβ) agonist DPN, 50nM parathyroid hormone (PTH), and 1nM of vitamin D analog JKF.

RESULTS

No effects were observed after exposure to rivaroxaban alone. When pre-Ob and post-Ob cells were exposed to the bone-modulating hormones as a control experiment, DNA synthesis and creatine kinase (CK)-specific activity was significantly stimulated with a greater response in the pre-Ob cells. When the cells were exposed to rivaroxaban in combination with bone-modulating hormones, the increased DNA synthesis and CK-specific activity previously observed were completely attenuated.

CONCLUSIONS

Rivaroxaban significantly inhibited the stimulatory effects of bone-modulating hormones in both pre-Ob and post-Ob primary human cell lines. This finding may have clinical relevance for patients at high risk of osteoporosis managed with rivaroxaban or other factor Xa inhibitors.

Osteocalcin, Vascular Calcification, and Atherosclerosis: A Systematic Review and Meta-analysis

BACKGROUND

Osteocalcin (OC) is an intriguing hormone, concomitantly being the most abundant non-collagenous peptide found in the mineralized matrix of bone, and expanding the endocrine function of the skeleton with far-reaching extra-osseous effects. A new line of enquiry between OC and vascular calcification has emerged in response to observations that the mechanism of vascular calcification resembles that of bone mineralisation. To date, studies have reported mixed results. This systematic review and meta-analysis aimed to identify any association between OC and vascular calcification and atherosclerosis.

METHODS AND RESULTS

Databases were searched for original, peer reviewed human studies. A total of 1,453 articles were retrieved, of which 46 met the eligibility criteria. Overall 26 positive, 17 negative, and 29 neutral relationships were reported for assessments between OC (either concentration in blood, presence of OC-positive cells, or histological staining for OC) and extent of calcification or atherosclerosis. Studies that measured OC-positive cells or histological staining for OC reported positive relationships (11 studies). A higher percentage of Asian studies found a negative relationship (36%) in contrast to European studies (6%). Studies examining carboxylated and undercarboxylated forms of OC in the blood failed to report consistent results. The meta-analysis found no significant difference between OC concentration in the blood between patients with "atherosclerosis" and control (p = 0.13, n = 1,197).

CONCLUSION

No definitive association was determined between OC and vascular calcification or atherosclerosis; however, the presence of OC-positive cells and histological staining had a consistent positive correlation with calcification or atherosclerosis. The review highlighted several themes, which may influence OC within differing populations leading to inconclusive results. Large, longitudinal studies are required to further current understanding of the clinical relevance of OC in vascular calcification and atherosclerosis.

Associations of Serum Osteocalcin and Polymorphisms of the Osteocalcin Gene with Bone Mineral Density in Postmenopausal and Elderly Chinese Women

BACKGROUND

The aims of this study were: (1) to evaluate the association of serum osteocalcin with bone mineral density (BMD) and markers of bone metabolism in postmenopausal and elderly Chinese women, and (2) to observe the relationships of single-nucleotide polymorphisms (SNPs) in and around the osteocalcin gene with osteocalcin and BMD.

METHODS

A cross-sectional study was conducted with 725 postmenopausal Chinese women. Five SNPs (rs1543294, rs1800247, rs759330, rs2842880, and rs933489) of the osteocalcin gene were genotyped. Serum osteocalcin and intact parathyroid hormone (PTH), 25-hydroxyvitamin D [25(OH)D], and type I collagen containing cross-linked C-telopeptide (β-CTX) were measured. The BMD of the lumbar spine and proximal femur was measured by dual-energy X-ray absorptiometry.

RESULTS

Osteocalcin was positively correlated with serum phosphorus (p = 0.001), alkaline phosphatase (ALP; p < 0.001), PTH (p = 0.002) and β-CTX (p < 0.001), and negatively correlated with BMD at the lumbar spine (p < 0.001) and total hip (p = 0.002). No significant association was obtained between the SNPs, haplotypes of the osteocalcin gene, and BMD or osteocalcin.

CONCLUSION

Our results suggest that osteocalcin was positively correlated with serum phosphorus, ALP, PTH, and β-CTX, but negatively correlated with BMD at the lumbar spine and total hip. Common genetic variants of the osteocalcin gene may not be a major contributor to variations in serum osteocalcin or BMD in postmenopausal and elderly Chinese women.

Vitamin D in relation to bone health and muscle function in young female soccer players

The present work investigated serum vitamin D (25(OH)D) status in relation to bone and muscle qualities and functions in 19 female soccer players (13-16 years) resident at northern latitude with very low sun exposure (∼32-36 h/month) during winter season (late January to early March). Serum 25(OH)D, parathyroid hormone and bone turnover markers osteocalcin (OC) and beta carboxy-terminal collagen cross-links (β-Ctx), as well as body composition and muscle performance were examined. Hormones were tested using routine laboratory methods. Fat mass, lean mass, and bone mineral density in whole body, as well as femur and lumbar spine were evaluated with dual-energy X-ray absorptiometry. Muscle performance was assessed through isokinetic knee extension and flexion, countermovement jump, and sprint running. 25(OH)D was low (50.5 ±   12.8 nmol l^-1), whereas the values of bone turnover markers were markedly high (OC: 59.4 ±   18.6 µg l^-1; β-Ctx: 1075 ±   408 ng l^-1). All bone and muscle measurements were normal or above normal. 25(OH)D was not significantly correlated with most of the parameters of bone and muscle quality or function, except the knee extension time to peak torque (r   =   -0.50, p =   .03). In conclusion, the level of vitamin D is markedly low in adolescent female soccer players during the winter in Sweden. However, vitamin D levels did not significantly correlate with measures of bone and muscle except a moderate correlation in time to peak torque in the knee extensors. The practical implication of low vitamin D levels in young growing female athletes remains unclear.

Generation of rodent and human osteoblasts

This paper describes the isolation, culture and staining of primary osteoblasts from neonatal rodents and human samples. The calvaria and long-bone assays allow direct measurement of bone matrix deposition and mineralisation, as well as producing osteoblasts at defined stages of differentiation for molecular and histological analysis. Culture of human osteoblasts enables cell function to be investigated in targeted patient groups. The described methods will provide a step-by-step guide of what to expect at each stage of the culture and highlight the varied tissue culture conditions required to successfully grow osteoblasts from different sources. A special focus of this paper is the methods used for analysis of bone mineralisation and how to ensure that nonspecific mineral deposition or staining is not quantified.

Impact of extracellular matrix derived from osteoarthritis subchondral bone osteoblasts on osteocytes: role of integrinβ1 and focal adhesion kinase signaling cues

INTRODUCTION

Our recent study indicated that subchondral bone pathogenesis in osteoarthritis (OA) is associated with osteocyte morphology and phenotypic abnormalities. However, the mechanism underlying this abnormality needs to be identified. In this study we investigated the effect of extracellular matrix (ECM) produced from normal and OA bone on osteocytic cells function.

METHODS

De-cellularized matrices, resembling the bone provisional ECM secreted from primary human subchondral bone osteoblasts (SBOs) of normal and OA patients were used as a model to study the effect on osteocytic cells. Osteocytic cells (MLOY4 osteocyte cell line) cultured on normal and OA derived ECMs were analyzed by confocal microscopy, scanning electron microscopy (SEM), cell attachment assays, zymography, apoptosis assays, qRT-PCR and western blotting. The role of integrinβ1 and focal adhesion kinase (FAK) signaling pathways during these interactions were monitored using appropriate blocking antibodies.

RESULTS

The ECM produced by OA SBOs contained less mineral content, showed altered organization of matrix proteins and matrix structure compared with the matrices produced by normal SBOs. Culture of osteocytic cells on these defective OA ECM resulted in a decrease of integrinβ1 expression and the de-activation of FAK cell signaling pathway, which subsequently affected the initial osteocytic cell's attachment and functions including morphological abnormalities of cytoskeletal structures, focal adhesions, increased apoptosis, altered osteocyte specific gene expression and increased Matrix metalloproteinases (MMP-2) and -9 expression.

CONCLUSION

This study provides new insights in understanding how altered OA bone matrix can lead to the abnormal osteocyte phenotypic changes, which is typical in OA pathogenesis.

In vitro characterization and osteoblast responses to nanostructured photocatalytic TiO2 coated surfaces

The aims of the study were to characterize a nanostructured photoactive titanium dioxide (TiO(2)) coating and to compare the cellular response of human osteoblasts before and after ultraviolet (UV) irradiation of the coating. A specific nanostructured TiO(2) powder (Degussa P-25), which consists of approximately 80% anatase and 20% rutile, was spin-coated onto commercially pure titanium discs, and was heat-treated thereafter. After topographical, chemical and photocatalytic property characterizations, human osteoblasts were cultured on the coated discs before and after UV irradiation. Cell morphology was evaluated by scanning electron microscopy (SEM), and cell viability was analysed by 3-(4,5-dimethylthiazol)-2,5-diphenyltetrazolium bromide (MTT) assay. From the contact angle analysis, the wettability significantly improved after UV irradiation. The cultured cells were flattened with numerous elongated lammellipodia; however, no morphological differences were indicated between -UV and +UV surfaces. The MTT assay analysis showed that -UV surface presented significantly higher viability compared to the +UV surface except for one cell population group at 3h where there were no differences. The nanostructured photoactive TiO(2) surface improved its hydrophilicity by UV irradiation, however no enhancing effect in cell response was confirmed at the time tested compared to the non-irradiated surface.

Mesenchymal stem cells isolated from adipose and other tissues: basic biological properties and clinical applications

Mesenchymal stem cells (MSCs) are adult stem cells that were initially isolated from bone marrow. However, subsequent research has shown that other adult tissues also contain MSCs. MSCs originate from mesenchyme, which is embryonic tissue derived from the mesoderm. These cells actively proliferate, giving rise to new cells in some tissues, but remain quiescent in others. MSCs are capable of differentiating into multiple cell types including adipocytes, chondrocytes, osteocytes, and cardiomyocytes. Isolation and induction of these cells could provide a new therapeutic tool for replacing damaged or lost adult tissues. However, the biological properties and use of stem cells in a clinical setting must be well established before significant clinical benefits are obtained. This paper summarizes data on the biological properties of MSCs and discusses current and potential clinical applications.

Aggravation of ADAMTS and matrix metalloproteinase production and role of ERK1/2 pathway in the interaction of osteoarthritic subchondral bone osteoblasts and articular cartilage chondrocytes -- possible pathogenic role in osteoarthritis

OBJECTIVE

Degradative enzymes, such as A disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) and matrix metalloproteinases (MMP), play key roles in development of osteoarthritis (OA). We investigated if crosstalk between subchondral bone osteoblasts (SBO) and articular cartilage chondrocytes (ACC) in OA alters the expression and regulation of ADAMTS5, ADAMTS4, MMP-1, MMP-2, MMP-3, MMP-8, MMP-9, and MMP-13, and also tested the possible involvement of mitogen-activated protein kinase (MAPK) signaling pathway during this process.

METHODS

ACC and SBO were isolated from normal and OA patients. An in vitro coculture model was developed to study the regulation of ADAMTS and MMP under normal and OA joint crosstalk conditions. The MAPK-ERK inhibitor PD98059 was applied to delineate the involvement of specific pathways during this interaction process.

RESULTS

Indirect coculture of OA SBO with normal ACC resulted in significantly increased expression of ADAMTS5, ADAMTS4, MMP-2, MMP-3, and MMP-9 in ACC, whereas coculture of OA ACC led to increased MMP-1 and MMP-2 expression in normal SBO. Upregulation of ADAMTS and MMP under these conditions was correlated with activation of the MAPK-ERK1/2 signaling pathway, and addition of the MAPK-ERK inhibitor PD98059 reversed the overexpression of ADAMTS and MMP in cocultures.

CONCLUSION

These results add to the evidence that in human OA, altered bidirectional signals between SBO and ACC significantly influence the critical features of both cartilage and bone by producing abnormal levels of ADAMTS and MMP. We have demonstrated for the first time that this altered crosstalk was mediated by the phosphorylation of MAPK-ERK1/2 signaling pathway.

Isolation and culture of human osteoblasts

The skeleton is a dynamic organ that is constantly active throughout life. The highly coordinated actions of bone cells early in life determine the body's shape and form, whilst the constant remodelling (bone resorption followed by an equal amount of bone formation) during adulthood helps to maintain skeletal mass and repair microdamage. When the balance of bone resorption and bone formation becomes unequal, bone diseases, such as osteoporosis, occur. In order to develop drugs to combat bone disease, it is important to know the regulatory systems involved in normal bone formation and resorption. In this chapter, we concentrate on bone formation, providing a detailed guide to isolating and culturing primary human osteoblasts in bone explant cultures, as well as the methodology used to characterise and monitor the function of osteoblasts. In combination, these methods provide a powerful tool in bone cell biology and in the development of new novel treatments for bone disease.

Primary human osteoblast cultures

Osteoblast cultures can be used to investigate the mechanisms of bone formation, to probe the cellular and molecular basis of bone disease, and to screen for potential therapeutic agents that affect bone formation. Here, we describe the methods for establishing and characterising primary human osteoblast cultures.

Global gene expression profile of osteoblast-like cells grown on polyester copolymer scaffolds

One of the principal goals in tissue engineering is to produce scaffold materials that will guide cells to differentiate and regenerate functional replacement tissue at the site of injury. Poly(l-lactide-co-1,5-dioxepan-2-one) [Poly(LLA-co-DXO)], a potential scaffolding material for bone tissue engineering, has high hydrophilicity. Previous in vitro studies using human osteoblast-like cells (HOBs) demonstrated greater cytocompatibility and enhanced osteogenic differentiation when HOBs were seeded onto Poly(LLA-co-DXO) compared to Poly(l-lactide) [P(LLA)] scaffolds. The aim of the study was to identify the gene expression profiles of HOBs obtained from alveolar bone and grown on Poly(LLA-co-DXO) biodegradable polymer scaffolds compared to P(LLA) one. Illumina HumanWG-6 v3.0 Expression BeadChips were used for the gene expression analysis. Several genes were found as differentially expressed at 24 h and at 21 days. Expression of genes related to cell adhesion, cytoskeleton, antiapoptosis, proliferation, and bone mineralization was influenced by adding the monomer 1,5-dioxepan-2-one to the L-lactide. Genes related to three biological pathways involving Integrin, Notch, and Ras were found to be upregulated. For selected genes, results were confirmed by quantitative reverse transcriptase-polymerase chain reaction. Further, calcium content analysis revealed a significant enhancement of calcium deposition on both tested scaffolds. This observation was confirmed by Von Kossa and Alizarin Red S staining. Findings of this study are relevant to a better understanding of the molecular mechanisms underlying the behavior of HOBs in bone regenerative procedure.

Comparison of Short-Run Cell Seeding Methods for Poly(L-Lactide-co-1,5-Dioxepan-2-one) Scaffold Intended for Bone Tissue Engineering

Constructs intended for bone tissue engineering are influenced by the initial cell seeding procedure. The seeding method should be rapid, convenient, improve cell spatial distribution, and have no negative effects on cellular viability and differentiation. This study aimed to compare the effect of short-run seeding methods (centrifuge and vortex) with a static method on the scaffolds prepared from poly(L-lactide-co-1,5-dioxepan-2-one) by solvent-casting particulate-leaching (SCPL) technique. Human osteoblast-like cells (HOB) were seeded by the three methods described above. The seeding efficiency was determined by attached cell numbers. Cellular proliferation was analyzed by WST-1 and dsDNA assay. Cell distribution was examined by scanning electron (SEM) and fluorescence microscopy. Expression of Alkaline Phosphatase (ALP), Collagen type I (Col I), Osteocalcin (OC) and Proliferating Cell Nuclear Antigen (PCNA) were determined by real time RT-PCR. Results indicated that centrifuge and vortex increased seeding efficiency and had no negative effects on cellular viability. The data obtained by the fluorescence microscope confirmed the SEM results that the vortex method improved cell distribution through the scaffolds more than the other two methods (p<0.05). The RT-PCR results showed no significant differences on the expression of mRNA between the three methods of the above markers. The vortex method was found to be a simple and feasible seeding method for the poly(L-lactide-co-1,5-dioxepan-2-one) scaffolds.

Cell sources for bone regeneration: the good, the bad, and the ugly (but promising)

Based on the extensive investigation of various ways to regenerate bone, bone marrow stromal cells, in conjunction with ceramic scaffolds, show great promise for application in human patients, and are already in use in a limited number of clinical trials. In preparing for clinical trials, scale-up current good manufacturing processes (cGMP) must incorporate the use of appropriate assays to ensure that the resulting cell product has maintained its biological activity. Future developments are needed to identify better scaffolds, and better ways to deliver cells with either injectable carriers, or by developing techniques to aide in their escape from the circulation and their incorporation into the pre-existing tissue. Lastly, development of methods that faithfully direct pluripotent stem cell differentiation into populations of osteogenic precursors (and ideally, containing skeletal stem cells) represents a new challenge in the field of bone regeneration, but also offer new opportunities to not only to study the biology of bone formation, but also to develop a robust cell source for bone regeneration.

A High Throughput System for Long Term Application of Intermittent Cyclic Hydrostatic Pressure on Cells in Culture

The process of bone remodeling is governed by mechanical stresses and strains. Studies on the effects of mechanical stimulation on cell response are often difficult to compare as the nature of the stimuli and differences in parameters applied vary greatly. Experimental systems for the investigation of mechanical stimuli are mostly limited in throughput or flexibility and often the sum of several stimuli is applied. In this work, a flexible system that allows the investigation of cell response to isolated intermittent cyclic hydrostatic pressure (icHP) on a high throughput level is shown. Human bone derived cells were cultivated with or without mechanical stimulus in the presence or absence of chemical cues triggering osteogenesis for 7–10 days. Cell proliferation and osteogenic differentiation were evaluated by cell counting and immunohistochemical staining for bone alkaline phosphatase as well as collagen 1, respectively. In either medium, both cell proliferation and level of differentiation were increased when the cultures were mechanically stimulated. These initial results therefore qualify the present system for studies on the effects of isolated icHP on cell fate and encourage further investigations on the details behind the observed effects.

Response of Bone and Periodontal Ligament Cells to Biodegradable Polymer Scaffolds In Vitro

In this in vitro study, the initial response of human periodontal ligament (PDL) cells and alveolar osteoblast-like cells (HOB) to three biodegradable polymers with varying pore size and different mechanical properties were evaluated. Scaffolds were synthesized from poly(L-lactide), [poly(LLA)], poly(L-lactide-co-1,5-dioxepan-2-one), [poly(LLA-co-DXO)], poly(L-lactide-co-ε-caprolactone), and [poly(LLA-co-CL)] with pore sizes greater or less than 90 µm by salt leaching. Cells were obtained from patients undergoing routine oral surgery. After 2—4 passages, the cells were grown on scaffolds and in culture plates (control) for 3 h (PDL cells), 3 days (PDL cells and HOB), 10 and 14 days (HOB), respectively. The cellular morphology and spreading were determined by scanning electron microscopy (SEM) and the attachment and proliferation were evaluated by MTT assays. The SEM images revealed heterogeneous cellular morphology and good spreading. Cellular attachment and proliferation were significantly higher on poly(LLA-co-DXO) and poly(LLA-co-CL) than on poly(LLA) scaffolds (p = 0.003) and highest for poly(LLA-co-DXO). Expression of bone formation markers, collagen-I (COL-I), transforming growth factor-β 1 (TGF-β1), and osteocalcin (OCN), was determined by ELISA. The expression of COL-1 was similar for HOB and PDL cells, but significantly higher for pore size >90 µm while the HOB expression of TGFβ 1 and OCN was greater on poly(LLA-co-CL) and poly(LLA-co-DXO) than on poly(LLA) scaffolds.

Polyester copolymer scaffolds enhance expression of bone markers in osteoblast-like cells

In tissue engineering, the resorbable aliphatic polyester poly(L-lactide) (PLLA) is used as scaffolds in bone regeneration. Copolymers of poly(L-lactide)-co-(epsilon-caprolactone) [poly(LLA-co-CL)] and poly(L-lactide)-co-(1,5-dioxepan-2-one) [poly(LLA-co-DXO)], with superior mechanical properties to PLLA, have been developed to be used as scaffolds, but the influence on the osteogenic potential is unclear. This in vitro study of test scaffolds of poly(LLA-co-CL) and poly(LLA-co-DXO) using PLLA scaffolds as a control demonstrates the attachment and proliferation of human osteoblast-like cells (HOB) as measured by SEM and a methylthiazol tetrazolium (MTT) colorimetric assay, and the progression of HOB osteogenesis for up to 3 weeks; expressed as synthesis of the osteoblast differentiation markers: collagen type 1 (Col 1), alkaline phosphatase, bone sialoprotein, osteocalcin (OC), osteopontin and runt related gene 2 (Runx2). Surface analysis disclosed excellent surface attachment, spread and penetration of the cells into the pores of the test scaffolds compared to the PLLA. MTT results indicated that test scaffolds enhanced the proliferation of HOBs. Cells grown on the test scaffolds demonstrated higher synthesis of Col 1 and OC and also increased bone markers mRNA expression. Compared to scaffolds of PLLA, the poly(LLA-co-CL) and poly(LLA-co-DXO) scaffolds enhanced attachment, proliferation, and expression of osteogenic markers by HOBs in vitro. Therefore, these scaffolds might be appropriate carriers for bone engineering.

Biocompatibility of Polyester Scaffolds with Fibroblasts and Osteoblast-like Cells for Bone Tissue Engineering

The aim of this study was to evaluate the in vitro cytotoxicity and cytocompatibility of the developed aliphatic polyester co-polymer scaffolds: poly(L-lactide-co-ε-caprolactone) and poly(L-lactide-co-1,5-dioxepan-2-one). The scaffolds were produced by solvent casting and particulate leaching, and tested by direct and indirect contact cytotoxicity assays on human osteoblast-like cells and mouse fibroblasts. Cell morphology was documented by light and scanning electron microscopy. Viability was assessed by the MTT, neutral red uptake, lactic dehydrogenase and apoptosis assays. Extraction tests confirmed that the scaffolds did not have a cytotoxic effect on the cells. The cells grew and spread well on the test scaffolds with good cellular attachment and viability. The scaffolds are noncytotoxic and biocompatible with the two cell types and warrant continued investigation as potential constructs for bone tissue engineering.

miR-29 modulates Wnt signaling in human osteoblasts through a positive feedback loop

Differentiation of human mesenchymal stem cells into osteoblasts is controlled by extracellular cues. Canonical Wnt signaling is particularly important for maintenance of bone mass in humans. Post-transcriptional regulation of gene expression, mediated by microRNAs, plays an essential role in the control of osteoblast differentiation. Here, we find that miR-29a is necessary for human osteoblast differentiation, and miR-29a is increased during differentiation in the mesenchymal precursor cell line hFOB1.19 and in primary cultures of human osteoblasts. Furthermore, the promoter of the expressed sequence tag containing the human miR-29a gene is induced by canonical Wnt signaling. This effect is mediated, at least in part, by two T-cell factor/LEF-binding sites within the proximal promoter. Furthermore, we show that the negative regulators of Wnt signaling, Dikkopf-1 (Dkk1), Kremen2, and secreted frizzled related protein 2 (sFRP2), are direct targets of miR-29a. Endogenous protein levels for these Wnt antagonists are increased in cells transfected with synthetic miR-29a inhibitor. In contrast, transfection with miR-29a mimic decreases expression of these antagonists and potentiates Wnt signaling. Overall, we demonstrate that miR-29 and Wnt signaling are involved in a regulatory circuit that can modulate osteoblast differentiation. Specifically, canonical Wnt signaling induces miR-29a transcription. The subsequent down-regulation of key Wnt signaling antagonists, Dkk1, Kremen2, and sFRP2, by miR-29a potentiates Wnt signaling, contributing to a gene expression program important for osteoblast differentiation. This novel regulatory circuit provides additional insight into how microRNAs interact with signaling molecules during osteoblast differentiation, allowing for fine-tuning of intricate cellular processes.

Bone tissue engineering with human stem cells

Treatment of extensive bone defects requires autologous bone grafting or implantation of bone substitute materials. An attractive alternative has been to engineer fully viable, biological bone grafts in vitro by culturing osteogenic cells within three-dimensional scaffolds, under conditions supporting bone formation. Such grafts could be used for implantation, but also as physiologically relevant models in basic and translational studies of bone development, disease and drug discovery. A source of human cells that can be derived in large numbers from a small initial harvest and predictably differentiated into bone forming cells is critically important for engineering human bone grafts. We discuss the characteristics and limitations of various types of human embryonic and adult stem cells, and their utility for bone tissue engineering.

Targeting subchondral bone for treating osteoarthritis: what is the evidence?

Over the past few decades, significant progress has been made with respect to new concepts about the pathogenesis of osteoarthritis (OA). This article summarises some of the knowledge we have today on the involvement of the subchondral bone in OA. It provides substantial evidence that changes in the metabolism of the subchondral bone are an integral part of the OA disease process and that these alterations are not merely secondary manifestations, but are part of a more active component of the disease. Thus, a strong rationale exists for therapeutic approaches that target subchondral bone resorption and/or formation, and data evaluating the drugs targeting bone remodelling raise the hope that new treatment options for OA may become available.

In vitro cellular response and in vivo primary osteointegration of electrochemically modified titanium

Anodic spark deposition (ASD) is an attractive technique for improving the implant-bone interface that can be applied to titanium and titanium alloys. This technique produces a surface with microporous morphology and an oxide layer enriched with calcium and phosphorus. The aim of the present study was to investigate the biological response in vitro using primary human osteoblasts as a cellular model and the osteogenic primary response in vivo within a short experimental time frame (2 and 4 weeks) in an animal model (rabbit). Responses were assessed by comparing the new electrochemical biomimetic treatments to an acid-etching treatment as control. The in vitro biological response was characterized by cell morphology, adhesion, proliferation activity and cell metabolic activity. A complete assessment of osteogenic activity in vivo was achieved by estimating static and dynamic histomorphometric parameters at several time points within the considered time frame. The in vitro study showed enhanced osteoblast adhesion and higher metabolic activity for the ASD-treated surfaces during the first days after seeding compared to the control titanium. For the ASD surfaces, the histomorphometry indicated a higher mineral apposition rate within 2 weeks and a more extended bone activation within the first week after surgery, leading to more extensive bone-implant contact after 2 weeks. In conclusion, the ASD surface treatments enhanced the biological response in vitro, promoting an early osteoblast adhesion, and the osteointegrative properties in vivo, accelerating the primary osteogenic response.

Osteoarthritic cartilage chondrocytes alter subchondral bone osteoblast differentiation via MAPK signalling pathway involving ERK1/2

Osteoarthritic subchondral bone is characterized by abnormal bone density and enhanced production of bone turnover markers, an indication of osteoblast dysfunction. Several studies have proposed that pathological changes in articular cartilage influence the subchondral bone changes, which are typical of the progression of osteoarthritis; however, direct evidence of this has yet to be reported. The aim of the present study was to investigate what effects articular cartilage cells, isolated from normal and osteoarthritic joints, may have on the subchondral bone osteoblast phenotype, and also the potential involvement of the mitogen activated protein kinase (MAPK) signalling pathway during this process. Our results suggest that chondrocytes isolated from a normal joint inhibited osteoblast differentiation, whereas chondrocytes isolated from an osteoarthritic joint enhanced osteoblast differentiation, both via a direct and indirect cell interaction mechanisms. Furthermore, the interaction of subchondral bone osteoblasts with osteoarthritic chondrocyte conditioned media appeared to significantly activate ERK1/2 phosphorylation. On the other hand, conditioned media from normal articular chondrocytes did not affect ERK1/2 phosphorylation. Inhibition of the MAPK-ERK1/2 pathways reversed the phenotype changes of subchondral bone osteoblast, which would otherwise be induced by the conditioned media from osteoarthritic chondrocytes. In conclusion, our findings provide evidence that osteoarthritic chondrocytes affect subchondral bone osteoblast metabolism via an ERK1/2 dependent pathway.

Differentiation of fetal osteoblasts and formation of mineralized bone nodules by 45S5 Bioglass conditioned medium in the absence of osteogenic supplements

Bioactive glasses bond strongly to bone in vivo and their ionic dissolution products have previously been shown to have stimulatory properties on adult and fetal osteoblasts and to induce the differentiation of embryonic stem cells towards the osteoblastic lineage in vitro. In the present study, the effect of 45S5 Bioglass conditioned medium with two different Si concentrations (15 microg/ml (BGCM/15) and 20 microg/ml (BGCM/20)) on human fetal osteoblast growth, differentiation and extracellular matrix production and mineralization was investigated. In the first instance, primary fetal osteoblasts were examined for the osteoblast phenotypic markers alkaline phosphatase (ALP), collagen type I (Col I) and OB Cadherin (Cadherin 11) (OB Cad) as well as for the mesenchymal stem cell markers CD105 and CD166. At passage 0 more than 50% of the population was positive for Col I and ALP, but at passage 2, the proportion of cells expressing ALP increased. In addition at passage 0 more than 50% of the fetal osteoblasts expressed the mesenchymal stem cell surface markers CD105 and CD166. Treatment with BGCM/15 and BGCM/20 in the absence of osteogenic supplements increased the gene expression of the bone extracellular matrix proteins alkaline phosphatase, osteonectin and bone sialoprotein as determined by quantitative real time reverse transcriptase-polymerase chain reaction (rt RT-PCR) analysis. Extracellular matrix production was also enhanced in the absence of osteogenic supplements by the 45S5 Bioglass conditioned medium as demonstrated by ALP enzymatic activity, osteocalcin and Col I protein synthesis. Furthermore, BGCM/15 and BGCM/20 significantly enhanced the formation of mineralized nodules, based on alizarin red histochemical staining, without necessitating the addition of beta-glycerophosphate, l-ascorbate-2-phosphate or dexamethasone (commonly used osteogenic supplements).

A novel spectrofluorometric technique for specific biocompatibility testing of implantable materials by cell culture. Report on use for multiparameter analysis of human osteoblasts cultured on commercially pure titanium and hydroxyapatite

The authors describe a novel spectrofluorometric technique based on double-labelled fluorescence imaging using immunoconjugates labelled with fluorochromes. Following isolation and characterization, cells are seeded on the surface of disks of the material(s) to be tested. After application of a primary antibody and an antibody bearing a fluorochrome, the signal emitted by the molecules in the extracellular matrix on the surface of the test disks is measured by spectrofluorimetry. Measurement is thus independent of the surface characteristics of the test material. Measured values are compared with pre-established standard curves. This technique facilitates determination of the characteristic molecules expressed by a given cell type,thus allowing accurate evaluation of the response of pertinent biological samples to implantable biomaterials.

Therapeutic touch affects DNA synthesis and mineralization of human osteoblasts in culture

Complementary and alternative medicine (CAM) techniques are commonly used in hospitals and private medical facilities; however, the effectiveness of many of these practices has not been thoroughly studied in a scientific manner. Developed by Dr. Dolores Krieger and Dora Kunz, Therapeutic Touch is one of these CAM practices and is a highly disciplined five-step process by which a practitioner can generate energy through their hands to promote healing. There are numerous clinical studies on the effects of TT but few in vitro studies. Our purpose was to determine if Therapeutic Touch had any effect on osteoblast proliferation, differentiation, and mineralization in vitro. TT was performed twice a week for 10 min each on human osteoblasts (HOBs) and on an osteosarcoma-derived cell line, SaOs-2. No significant differences were found in DNA synthesis, assayed by [(3)H]-thymidine incorporation at 1 or 2 weeks for SaOs-2 or 1 week for HOBs. However, after four TT treatments in 2 weeks, TT significantly (p = 0.03) increased HOB DNA synthesis compared to controls. Immunocytochemistry for Proliferating Cell Nuclear Antigen (PCNA) confirmed these data. At 2 weeks in differentiation medium, TT significantly increased mineralization in HOBs (p = 0.016) and decreased mineralization in SaOs-2 (p = 0.0007), compared to controls. Additionally, Northern blot analysis indicated a TT-induced increase in mRNA expression for Type I collagen, bone sialoprotein, and alkaline phosphatase in HOBs and a decrease of these bone markers in SaOs-2 cells. In conclusion, Therapeutic Touch appears to increase human osteoblast DNA synthesis, differentiation and mineralization, and decrease differentiation and mineralization in a human osteosarcoma-derived cell line.