Proliferation and differentiation of osteoblasts and adipocytes in rat bone marrow stromal cell cultures: effects of dexamethasone and calcitriol

The Effects of Corticosteroid Administration and Treadmill Exercise on Marrow Adipose Tissue and Trabecular Bone after Anterior Cruciate Ligament Reconstruction in Rats

We aimed to investigate the effects of short-term corticosteroid administration after anterior cruciate ligament (ACL) reconstruction on marrow adipose tissue (MAT) and trabecular bone mass, as well as to examine whether treadmill exercise can mitigate MAT increase and trabecular bone deterioration caused by corticosteroid. ACL-reconstructed rats were divided into groups: no intervention, daily treadmill exercise (60 min/day), administration of the steroidal drug dexamethasone (250 μg/kg on days 0-5, 7, and 9 post-operatively), or dexamethasone administration combined with treadmill exercise. Untreated rats were served as controls. At day 10 or 30 post-operatively, histological assessments were performed in the proximal tibial epiphysis. MAT accumulation and trabecular bone loss were observed after ACL reconstruction. Dexamethasone promoted MAT accumulation at day 10 post-operatively but did not affect the trabecular bone loss. The MAT accumulation caused by dexamethasone reversed within 21 days after discontinuation. Treadmill exercise did not influence the changes in the MAT and trabecular bone areas. Short-term corticosteroid administration after ACL reconstruction promoted MAT accumulation while not affecting trabecular bone area. The MAT accumulation resulting from corticosteroid administration was reversible after discontinuation. Treadmill exercise could not mitigate the accumulation of MAT caused by corticosteroid administration and did not affect trabecular bone area.

The Role of Codon Usage, tRNA Availability, and Cell Proliferation in EBV Latency and (Re)Activation

Epstein–Barr nuclear antigen 1 (EBNA1) protein synthesis is inhibited during Epstein–Barr virus (EBV) latency and is resumed in EBV (re)activation. In analyzing the molecular mechanisms underpinning the translation of EBNA1 in the human host, this article deals with two orders of data. First, it shows that the heavily biased codon usage of the EBNA1 open reading frame cannot be translated due to its noncompliance with the human codon usage pattern and the corresponding tRNA pool. The EBNA1 codon bias resides in the sequence composed exclusively of glycine and alanine, i.e., the Gly-Ala repeat (GAR). Removal of the nucleotide sequence coding for GAR results in an EBNA1 codon usage pattern with a lower codon bias, thus conferring translatability to EBNA1. Second, the data bring cell proliferation to the fore as a conditio sine qua non for qualitatively and quantitatively modifying the host's tRNA pool as required by the translational needs of EBNA1, thus enabling viral reactivation. Taken together, the present work provides a biochemical mechanism for the pathogen's shift from latency to (re)activation and confirms the role of human codon usage as a first-line tool of innate immunity in inhibiting pathogens' expression. Immunologically, this study cautions against using codon optimization and proliferation-inducing substances such as glucocorticoids and adjuvants, which can (re)activate the otherwise quiescent, asymptomatic, and innocuous EBV infection. Lastly, the data pose the question whether the causal pathogenic role attributed to EBV should instead be ascribed to the carcinogenesis-associated cellular proliferation.

The Action of Vitamin D in Adipose Tissue: Is There the Link between Vitamin D Deficiency and Adipose Tissue-Related Metabolic Disorders?

Adipose tissue plays an important role in systemic metabolism via the secretion of adipocytokines and storing and releasing energy. In obesity, adipose tissue becomes dysfunctional and characterized by hypertrophied adipocytes, increased inflammation, hypoxia, and decreased angiogenesis. Although adipose tissue is one of the major stores of vitamin D, its deficiency is detective in obese subjects. In the presented review, we show how vitamin D regulates numerous processes in adipose tissue and how their dysregulation leads to metabolic disorders. The molecular response to vitamin D in adipose tissue affects not only energy metabolism and adipokine and anti-inflammatory cytokine production via the regulation of gene expression but also genes participating in antioxidant defense, adipocytes differentiation, and apoptosis. Thus, its deficiency disturbs adipocytokines secretion, metabolism, lipid storage, adipogenesis, thermogenesis, the regulation of inflammation, and oxidative stress balance. Restoring the proper functionality of adipose tissue in overweight or obese subjects is of particular importance in order to reduce the risk of developing obesity-related complications, such as cardiovascular diseases and diabetes. Taking into account the results of experimental studies, it seemed that vitamin D may be a remedy for adipose tissue dysfunction, but the results of the clinical trials are not consistent, as some of them show improvement and others no effect of this vitamin on metabolic and insulin resistance parameters. Therefore, further studies are required to evaluate the beneficial effects of vitamin D, especially in overweight and obese subjects, due to the presence of a volumetric dilution of this vitamin among them.

Differentiation of Mesenchymal Stem Cells Derived From Human Adipose Tissue Into Cholinergic-like Cells: An in Vitro Study

Introduction:

Cholinergic-associated diseases currently constitute a significant cause of neurological and neurodegenerative disabilities. As the drugs are not efficient in improving the suffered tissues, stem cell treatment is considered an effective strategy for substituting the lost cells.

Methods:

In the current study, we set out to investigate the differentiation properties of human Adipose-Derived Mesenchymal Stem Cells (AD-MSCs) into cholinergic-like cells by two morphogens of Retinoic Acid (RA) and Sonic Hedgehog (Shh) using a three-step in vitro procedure. The results were evaluated using real-time PCR, flow cytometry, and immunocytochemistry for two weeks.

Results:

Our data showed that the cells could express cholinergic specific markers, including Islet-1, Acetylcholinesterase (AChE), SMI-32, and Nestin, at mRNA and protein levels. We could also quantitatively evaluate the expression of Islet-1, AChE, and Nestin at 14 days post-induction using flow cytometry.

Conclusion:

Human AD-MSCs are potent cells to differentiate into cholinergic-like cells in the presence of RA and Shh through a three-step protocol. Thus, they could be a suitable cell candidate for the regeneration of cholinergic-associated diseases. However, more functional and electrophysiological analyses are needed in this regard.

Human Codon Usage: The Genetic Basis of Pathogen Latency

Infectious diseases pose two main compelling issues. First, the identification of the molecular factors that allow chronic infections, that is, the often completely asymptomatic coexistence of infectious agents with the human host. Second, the definition of the mechanisms that allow the switch from pathogen dormancy to pathologic (re)activation. Furthering previous studies, the present study (1) analyzed the frequency of occurrence of synonymous codons in coding DNA, that is, codon usage, as a genetic tool that rules protein expression; (2) described how human codon usage can inhibit protein expression of infectious agents during latency, so that pathogen genes the codon usage of which does not conform to the human codon usage cannot be translated; and (3) framed human codon usage among the front-line instruments of the innate immunity against infections. In parallel, it was shown that, while genetics can account for the molecular basis of pathogen latency, the changes of the quantitative relationship between codon frequencies and isoaccepting tRNAs during cell proliferation offer a biochemical mechanism that explains the pathogen switching to (re)activation. Immunologically, this study warns that using codon optimization methodologies can (re)activate, potentiate, and immortalize otherwise quiescent, asymptomatic pathogens, thus leading to uncontrollable pandemics.

Role of 25-Hydroxyvitamin D3 and 1,25-Dihydroxyvitamin D3 in Chicken Embryo Osteogenesis, Adipogenesis, Myogenesis, and Vitamin D3 Metabolism

A study was conducted to understand the effects of 25-hydroxyvitamin D₃ (25OHD) and 1,25-dihydroxyvitamin D₃ (1,25OHD) administration on the expression of key genes related to osteogenesis, adipogenesis, myogenesis, and vitamin D₃ metabolism in the chicken embryo. A total of 120 fertilized Cobb 500 eggs were used in the current study and were reared under standard incubation conditions. On embryonic day 3 (ED 3), PBS (C), PBS with 40ng 1,25OHD (1,25D-L), 200ng 1,25OHD (1,25D-H), 40ng 25OHD (25D-L), or 200ng 25OHD (25D-H) were injected into the dorsal vein of developing embryos. Whole embryos were harvested at 1, 3, and 6h post-injection for gene expression analyses (n=8). Gene expression for key osteogenesis markers (RUNX2: runt-related transcription factor 2; BMP2: bone morphogenetic protein 2; COL1A2: collagen type I alpha 2 chain; BGLAP: bone gamma-carboxyglutamate protein; SPP1: secreted phosphoprotein 1; and ALP: alkaline phosphatese), adipogenesis markers (PPAR-γ: peroxisome proliferator-activated receptor gamma; FASN: fatty acid synthase; and FABP4: fatty acid binding protein 4), myogenesis markers (MYOG: myogenin; MYOD1: myogenic differentiation 1; and MYF5: myogenic factor 5), and the enzyme responsible for vitamin D₃ inactivation (CYP24A1: cytochrome P450 family 24 subfamily A member 1) were measured using real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). Data were normalized by the ΔΔCT method and analyzed using a one-way ANOVA. Results indicated that at 1h post-injection, no differences were found among treatments. At 3h, the early osteogenesis differentiation marker, ALP, was increased by 1,25D-H and 25D-H, and 25D-H also stimulated the expression of adipogenesis markers (FAPB4 and FASN). In contrast, the expression of myogenesis markers (MYOD1 and MYF5) was suppressed by 25OHD or 1,25OHD treatments, respectively. At 6h, a late osteogenic differentiation marker, SPP1, was increased by 25D-H. MYOD1 and MYF5 were continuously suppressed by 25OHD treatments or 1,25D-H. The evidence of vitamin D₃ metabolite retention was assessed by measuring CYP24A1 expression. At 1h, there were no differences in CYP24A1 expression. At 3h, all treatments upregulated CYP24A1 expression relative to control (PBS) embryos. However, at 6h, only the 25D-H group retained higher CYP24A1 expression compared to the other treatments. In conclusion, the results suggested both 1,25OHD and 25OHD induced chicken embryo osteogenesis and adipogenesis, but inhibited myogenesis during early chicken embryo development. The higher dosage of 25OHD showed a possibility of a longer retention time in the embryos.

The Regulation of Marrow Fat by Vitamin D: Molecular Mechanisms and Clinical Implications

PURPOSE OF REVIEW

To review the available literature regarding a possible relationship between vitamin D and bone marrow adipose tissue (BMAT), and to identify future avenues of research that warrant attention.

RECENT FINDINGS

Results from in vivo animal and human studies all support the hypothesis that vitamin D can suppress BMAT expansion. This is achieved by antagonizing adipogenesis in bone marrow stromal cells, through inhibition of PPARγ2 activity and stimulation of pro-osteogenic Wnt signalling. However, our understanding of the functions of BMAT is still evolving, and studies on the role of vitamin D in modulating BMAT function are lacking. In addition, many diseases and chronic conditions are associated with low vitamin D status and low bone mineral density (BMD), but BMAT expansion has not been studied in these patient populations. Vitamin D suppresses BMAT expansion, but its role in modulating BMAT function is poorly understood.

Biomaterial based treatment of osteoclastic/osteoblastic cell imbalance - Gelatin-modified calcium/strontium phosphates

Osteoporotic bone represents - particularly in case of fractures - difficult conditions for its regeneration. In the present study, the focus was put on a degradable bone substitute material of gelatin-modified calcium and strontium phosphates facing the special demands of osteoporotic bone. The release of strontium ions from the material ought to stimulate osteoblastogenesis either direct by ion release or indirect after material resorption by increased presence and activity of osteoclasts, which subsequently stimulate osteoblasts. A new porous material was produced from calcium phosphate, strontium phosphate and a mixed phase of calcium/strontium phosphate precipitated in presence of gelatin. Initially, ion release was analyzed in standard‑calcium containing (2.0 mM) and low-calcium (0.4 mM) minimum essential medium. The cultivation of human peripheral blood mononuclear cells next to the material led to formation of osteoclast-like cells, able to migrate, fuse, and differentiate. Especially, the mixed gelatin-modified calcium/strontium phosphate allowed osteoclastogenesis as proven morphologically and by real-time quantitative polymerase chain reaction (RT-qPCR). It was precisely this material that led to the best osteoblastic reaction of human bone marrow stromal cells cultured on the material. The investigations of the bone substitute material indicate active involvement in the balance of cells of the bone morphogenetic unit.

Sulfated hyaluronic acid and dexamethasone possess a synergistic potential in the differentiation of osteoblasts from human bone marrow stromal cells

The development of novel bioactive biomaterials is urgently needed to meet the needs of an aging population. Both sulfated hyaluronic acid and dexamethasone are candidates for the functionalization of bone grafts, as they have been shown to enhance the differentiation of osteoblasts from bone marrow stromal cells in vitro and in vivo. However, the underlying mechanisms are not fully understood. Furthermore, studies combining different approaches to assess synergistic potentials are rare. In this study, we aim to gain insights into the mode of action of both sulfated hyaluronic acid and dexamethasone by a comprehensive analysis of the cellular fraction, released matrix vesicles, and the extracellular matrix, combining classical biochemical assays with mass spectrometry-based proteomics, supported by novel bioinformatical computations. We found elevated differentiation levels for both treatments, which were further enhanced by a combination of sulfated hyaluronic acid and dexamethasone. Single treatments revealed specific effects on osteogenic differentiation. Dexamethasone activates signalling pathways involved in the differentiation of osteoblasts, for example, CXC-motif chemokine receptor type 4 and mitogen-activated protein kinases. The effects of sulfated hyaluronic acid were predominantly linked to an alteration in the composition of the extracellular matrix, affecting the synthesis, secretion, and/or activity of fibrillary (fibronectin and thrombospondin-2) and nonfibrillary (transglutaminase-2, periostin, and lysyloxidase) extracellular matrix components, including proteases and their inhibitors (matrix metalloproteinase-2, tissue inhibitor of metalloproteinase-3). The effects were treatment specific, and less additive or contrary effects were found. Thus, we anticipate that the synergistic action of the treatment-specific effects is the key driver in elevated osteogenesis.

Simultaneous cell traction and growth measurements using light

Characterizing the effects of force fields generated by cells on proliferation, migration and differentiation processes is challenging due to limited availability of nondestructive imaging modalities. Here, we integrate a new real-time traction stress imaging modality, Hilbert phase dynamometry (HPD), with spatial light interference microscopy (SLIM) for simultaneous monitoring of cell growth during differentiation processes. HPD uses holographic principles to extract displacement fields from chemically patterned fluorescent grid on deformable substrates. This is converted into forces by solving an elasticity inverse problem. Since HPD uses the epi-fluorescence channel of an inverted microscope, cellular behavior can be concurrently studied in transmission with SLIM. We studied the differentiation of mesenchymal stem cells (MSCs) and found that cells undergoing osteogenesis and adipogenesis exerted larger and more dynamic stresses than their precursors, with MSCs developing the smallest forces and growth rates. Thus, we develop a powerful means to study mechanotransduction during dynamic processes where the matrix provides context to guide cells toward a physiological or pathological outcome.

Strontium ions promote in vitro human bone marrow stromal cell proliferation and differentiation in calcium-lacking media

In order to investigate the influence of calcium and strontium ion concentration on human bone marrow stromal cells and their differentiation to osteoblasts, different cell culture media have been used. Even though this study does not contain a bone substitute material, the reason for this study was the decrease of cation concentration by many biomaterials, due to induced apatite precipitation. As a consequence, the reduced calcium ion concentration is known to affect osteoblastic development. Therefore, the main focus was put on the question, whether an increased strontium concentration (in the range of mM) might be suitable to compensate the lack of calcium ions. The effect of solely strontium ions-with only calcium in the media resulting from fetal calf serum-was investigated. Commercially available calcium-free medium (modified α-MEM) was tested in comparison with media with varied calcium ion concentrations (0.9, 1.8, and 3.6 mM), or strontium ion concentration (0.4, 0.9, 1.8, and 3.6 mM). In case of calcium, higher concentrations cause increased proliferation, while differentiation was shifted to earlier points of time. Differentiation was increased by solely strontium ions only at 0.4-0.9 mM, while proliferation was highest for 0.9-1.8 mM. From these results, it can be concluded that strontium is able to compensate a lack of calcium to a certain degree. Thus, in contrast to calcium ion release, a strontium ion release from bone substitute materials might be applicable for stimulation of bone regeneration without influencing the media saturation.

Leptin blocks the inhibitory effect of vitamin D on adipogenesis and cell proliferation in 3T3-L1 adipocytes

Recently, we demonstrated high serum leptin and 25(OH)D (calcidiol) in obese animals, with high C/EBP_β and PPAR_γ expression in adipose tissue. Since the role of vitamin D in adipogenesis remains controversial and hyperleptinemia is found in obesity, we asked if leptin could interfere in vitamin D action on adipocytes. Here, we studied the direct effect of these two hormones upon 3T3L1 preadipocytes incubated with or without 1,25(OH)2D (100 nM, 24 h) and with leptin (10^-7 M, 4 h later). RT-PCR (VDR and Cyp27b1/1α-hydroxylase), western blotting (VDR, Cyp27b1/1α-hydroxylase, ObR-b, C/EBP_β, PPAR_γ and Bax content), a cell proliferation assay and an Annexin V-FITC binding assay were performed. Incubation with 1,25(OH)2D decreased Cyp27b1/1α-hydroxylase and VDR. Co-incubation of 1,25(OH)2D and leptin did not change Cyp27b1/1α-hydroxylase and had no additive effect upon the decreased VDR mRNA. Incubation with 1,25(OH)2D decreased C/EBP_β and PPARγ. In the cell proliferation assay, 1,25(OH)2D decreased the number of 3T3L1 cells. No changes in OBR-b or apoptotic parameters (Bax and annexin-V) were observed. The 1,25(OH)2D decreased pro-adipogenic factors and proliferation of adipocytes. However, since it inhibits the conversion of 25(OH)D to 1,25(OH)2D and VDR mRNA long-term, it could decrease the vitamin D response in adipocytes, leading to greater adipogenesis. The co-incubation of both hormones, simulating what occurs in obesity, even neutralizing the effect on Cyp27b1/1α-hydroxylase, did not change the vitamin D sensitivity but decreased SOCS-3 and pSTAT-3. Thus, an excess of vitamin D and hyperleptinemia could decrease vitamin D sensitivity in adipocytes, contributing to increased adipogenesis.

Low-dose dexamethasone affects osteoblast viability by inducing autophagy via intracellular ROS

Glucocorticoids (GCs) are closely associated with the progression of GC-induced osteoporosis (GIOP) by inhibiting osteoblast viability. However, endogenous GCs are important for bone development. In addition, previous studies have demonstrated that GCs could induce autophagy, a cytoprotective process that is protective against various stressors. In the present study, the aim is to explore whether osteoblasts exhibited dose-dependent viability in the presence of GCs due to autophagy. hFOB 1.19 osteoblasts were treated with various doses of dexamethasone (DEX; 10⁻⁸-10⁻⁴ M) for 0, 24, 48 and 72 h. The results revealed a biphasic effect of DEX on the viability of hFOB 1.19 cells; a high dose of DEX (≥10⁻⁶ M) accelerated cell apoptosis, while a low dose of DEX (10⁻⁸ M) increased cell viability. Furthermore, significantly increased autophagy was observed in the low dose DEX treatment group, as indicated by the expression of the autophagy-associated proteins beclin 1 and microtubule-associated protein light chain 3, and the detection of autophagosomes. Another finding was that DEX upregulated intracellular reactive oxygen species (ROS), which was decreased by the autophagy agonist rapamycin. The increase in autophagy and cell viability associated with low-dose DEX (10⁻⁸ M) was suppressed by the ROS scavenger catalase and the autophagy inhibitor 3-methyladenine. In conclusion, the results revealed that GCs affected osteoblast viability in a dose-dependent manner. A low dose of GCs increased osteoblast viability by inducing autophagy via intracellular ROS. The results indicate that autophagy may be a novel mechanism by which osteoblasts survive GC exposure and provide a potential therapeutic target for treating GIOP.

Functional Hepatocyte-Like Cells Derived from Human Bone Marrow Mesenchymal Stem Cells on a Novel 3-Dimensional Biocompatible Nanofibrous Scaffold

Aim

To supporting growth and functional differentiation of adult stem cells into hepatocytes in a well-controlled manner, we performed differentiation of human bone marrow mesenchymal stem cells (hBMSCs) to hepatocytes-like cells on a constructed 3-dimensional (3D) nanofibrous biocompatible scaffold.

Methods

After characterization of the hBMSCs isolated from human bone marrow, the performance of the cells seeded and their proliferation on the scaffold was evaluated by scanning electron microscopy (SEM) and 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Different approaches such as immunocytochemistry, reverse transcriptase polymerase chain reaction (RT-PCR), and biochemical assays were used to estimate the ability of hBMSC-derived cells to express hepatocyte-specific markers.

Results

Scanning electron micrographs and MTT analysis revealed the cells were able to expand and remained biologically and metabolically active for 21 days. Immunocytochemical analysis of albumin and α-fetoprotein showing the accumulation of these markers in differentiated cells was confirmed by RT-PCR. Additional markers such as cytochrome P450 3A4, cytokeratin-18, and cytokeratin-19 detected by RT-PCR showed progressive expression during 3 weeks of differentiation on 3D scaffold. The hepatocyte-like cells displayed several characteristics of metabolic functions as judged by production of albumin, urea, transferrin, serum glutamic pyruvic transaminase (SGPT), and serum oxaloacetate aminotransferase (SGOT). Levels of above-mentioned markers, except SGOT in differentiated cells on scaffold, were found to be significantly greater than in the 2D culture system (p<0.05).

Conclusion

Overall data suggest that the engineered nanofibrous scaffold is a conductive matrix for functional hBMSC-derived hepatocyte-like cells and is promising for maintenance of hepatocytes suitable for implantation.

The role of vitamin D in adipogenesis

Vitamin D, a secosteroid predominately obtained by endogenous production, has in recent years been linked to obesity and its comorbidities. The purpose of this review is to draw conclusions from animal and human studies on the effects of vitamin D on adipogenesis to identify the molecular links between vitamin D and obesity. The information presented herein was obtained from 4 databases (PubMed, CINAHL, Cochrane Library, Scopus) using predefined search terms, as well as research literature and other reviews. The effects of vitamin D on adipogenesis have been researched in several animal models, and the majority of these studies suggest vitamin D plays an inhibitory role in adipogenesis. Studies into vitamin D status and obesity in humans are limited, with the majority being observational epidemiological studies that provide no conclusions on cause and effect or clear links on the molecular mechanisms. The few cell culture and supplementation studies that have investigated adipogenesis in human cells indicate that, in contrast to findings from rodent studies, vitamin D is proadipogenic. There is insufficient evidence to determine whether 1) vitamin D deficiency is associated with a lean or obese phenotype, 2) vitamin D deficiency is a consequence of obesity, or (3) the effects of vitamin D on fat tissue are due to interactions with calcium.

Spotlight on vitamin D receptor, lipid metabolism and mitochondria: Some preliminary emerging issues

Transcriptional control and modulation of calcium fluxes underpin the differentiating properties of vitamin D (1,25(OH)₂D₃). In the latest years however few studies have pointed out the relevance of the mitochondrial effects of the hormone. It is now time to focus on the metabolic results of vitamin D receptor (VDR) action in mitochondria, which can explain the pleiotropic effects of 1,25(OH)₂D₃ and may elucidate few contrasting aspects of its activity. The perturbation of lipid metabolism described in VDR knockout mice and vitamin D deficient animals can be revisited based on the newly identified mechanism of action of 1,25(OH)₂D₃ in mitochondria. From the same point of view, the controversial role of 1,25(OH)₂D₃ in adipogenesis can be better interpreted.

Characterization and comparison of osteoblasts derived from mouse embryonic stem cells and induced pluripotent stem cells

New developments in stem cell biology offer alternatives for the reconstruction of critical-sized bone defects. One of these developments is the use of induced pluripotent stem (iPS) cells. These stem cells are similar to embryonic stem (ES) cells, but can be generated from adult somatic cells and therefore do not raise ethical concerns. Proper characterization of iPS-derived osteoblasts is important for future development of safe clinical applications of these cells. For this reason, we differentiated mouse ES and iPS cells toward osteoblasts using osteogenic medium and compared their functionality. Immunocytochemical analysis showed significant expression of bone markers (osteocalcin and collagen type I) in osteoblasts differentiated from ES and iPS cells on days 7 and 30. An in vitro mineralization assay confirmed the functionality of osteogenically differentiated ES and iPS cells. Gene expression arrays focusing on osteogenic differentiation were performed in order to compare the gene expression pattern in both differentiated and undifferentiated ES cells and iPS cells. We observed a significant upregulation of osteogenesis-related genes such as Runx2, osteopontin, collagen type I, Tnfsf11, Csf1, and alkaline phosphatase upon osteogenic differentiation of the ES and iPS cells. We further validated the expression of key osteogenic genes Runx2, osteopontin, osteocalcin, collagen type I, and osterix in both differentiated and undifferentiated ES and iPS cells by means of quantified real-time polymerase chain reaction. We conclude that ES and iPS cells are similar in their osteogenic differentiation capacities, as well as in their gene expression patterns.

Effectiveness and mode of action of a combination therapy for heterotopic ossification with a retinoid agonist and an anti-inflammatory agent

Heterotopic ossification (HO) consists of ectopic cartilage and bone formation following severe trauma or invasive surgeries, and a genetic form of it characterizes patients with Fibrodysplasia Ossificans Progressiva (FOP). Recent mouse studies showed that HO was significantly inhibited by systemic treatment with a corticosteroid or the retinoic acid receptor γ agonist Palovarotene. Because these drugs act differently, the data raised intriguing questions including whether the drugs affected HO via similar means, whether a combination therapy would be more effective or whether the drugs may hamper each other's action. To tackle these questions, we used an effective HO mouse model involving subcutaneous implantation of Matrigel plus rhBMP2, and compared the effectiveness of prednisone, dexamathaosone, Palovarotene or combination of. Each corticosteroid and Palovarotene reduced bone formation at max doses, and a combination therapy elicited similar outcomes without obvious interference. While Palovarotene had effectively prevented the initial cartilaginous phase of HO, the steroids appeared to act more on the bony phase. In reporter assays, dexamethasone and Palovarotene induced transcriptional activity of their respective GRE or RARE constructs and did not interfere with each other's pathway. Interestingly, both drugs inhibited the activity of a reporter construct for the inflammatory mediator NF-κB, particularly in combination. In good agreement, immunohistochemical analyses showed that both drugs markedly reduced the number of mast cells and macrophages near and within the ectopic Matrigel mass and reduced also the number of progenitor cells. In sum, corticosteroids and Palovarotene appear to block HO via common and distinct mechanisms. Most importantly, they directly or indirectly inhibit the recruitment of immune and inflammatory cells present at the affected site, thus alleviating the effects of key HO instigators.

Thiol-ene click hydrogels for therapeutic delivery

Hydrogels are of growing interest for the delivery of therapeutics to specific sites in the body. For use as a delivery vehicle, hydrophilic precursors are usually laden with bioactive moieties and then directly injected to the site of interest for in situ gel formation and controlled release dictated by precursor design. Hydrogels formed by thiol-ene click reactions are attractive for local controlled release of therapeutics owing to their rapid reaction rate and efficiency under mild aqueous conditions, enabling in situ formation of gels with tunable properties often responsive to environmental cues. Herein, we will review the wide range of applications for thiol-ene hydrogels, from the prolonged release of anti-inflammatory drugs in the spine to the release of protein-based therapeutics in response to cell-secreted enzymes, with a focus on their clinical relevance. We will also provide a brief overview of thiol-ene click chemistry and discuss the available alkene chemistries pertinent to macromolecule functionalization and hydrogel formation. These chemistries include functional groups susceptible to Michael type reactions relevant for injection and radically-mediated reactions for greater temporal control of formation at sites of interest using light. Additionally, mechanisms for the encapsulation and controlled release of therapeutic cargoes are reviewed, including i) tuning the mesh size of the hydrogel initially and temporally for cargo entrapment and release and ii) covalent tethering of the cargo with degradable linkers or affinity binding sequences to mediate release. Finally, myriad thiol-ene hydrogels and their specific applications also are discussed to give a sampling of the current and future utilization of this chemistry for delivery of therapeutics, such as small molecule drugs, peptides, and biologics.

Super pharmacological levels of calcitriol (1,25-(OH)2D3) inhibits mineral deposition and decreases cell proliferation in a strain dependent manner in chicken mesenchymal stem cells undergoing osteogenic differentiation in vitro

The biologically active form of vitamin D₃, calcitriol (1,25-(OH)₂D₃), plays a key role in mineral homeostasis and bone formation and dietary vitamin D₃ deficiency is a major cause of bone disorders in poultry. Supplementary dietary cholecalciferol (25-hydroxyvitamin D, 25-OH), the precursor of calcitriol, is commonly employed to combat this problem; however, dosage must be carefully determined as excess dietary vitamin D can cause toxicity resulting in a decrease in bone calcification, hypercalcinemia and renal failure. Despite much research on the therapeutic administration of dietary vitamin D in humans, the relative sensitivity of avian species to exogenous vitamin D has not been well defined. In order to determine the effects of exogenous 1,25-(OH)₂D₃ during avian osteogenesis, chicken bone marrow-derived mesenchymal stem cells (BM-MSCs) were exposed to varying doses of 1,25-(OH)₂D₃ during in vitro osteogenic differentiation and examined for markers of early proliferation and osteogenic induction. Similar to humans and other mammals, poultry BM-MSCs were found to be highly sensitive to exogenous 1,25-(OH)₂D₃ with super pharmacological levels exerting significant inhibition of mineralization and loss of cell proliferation in vitro. Strain related differences were apparent, with BM-MCSs derived from layers strains showing a higher level of sensitivity to 1,25-(OH)₂D₃ than those from broilers. These data suggest that understanding species and strain specific sensitivities to 1,25-(OH)₂D₃ is important for optimizing bone health in the poultry industry and that use of avian BM-MSCs are a useful tool for examining underlying effects of genetic variation in poultry.

Causes of Vitamin D Deficiency and Effect of Vitamin D Supplementation on Metabolic Complications in Obesity: a Review

Obese subjects are often characterized by low plasma 25-hydroxy-vitamin D (25OHD) levels. Many explanations for this association have been proposed. Low plasma 25OHD is associated with obesity-related comorbidities such as insulin resistance, type 2 diabetes mellitus, and low-grade inflammation. In this review, we discuss the proposed mechanisms for low 25OHD in obesity and explore the results of recent RCTs on vitamin D (VD) supplementation on obesity and its metabolic complications such as insulin resistance and type 2 diabetes. Although the results from these clinical randomized controlled trials vary, the general picture is that VD treatment of obese individuals does not seem to be an effective treatment of obesity-related metabolic complications.

Dysregulation of Mitochondrial Functions and Osteogenic Differentiation in Cisd2-Deficient Murine Induced Pluripotent Stem Cells

Wolfram syndrome 2 (WFS2) is a premature aging syndrome caused by an irreversible mitochondria-mediated disorder. Cisd2, which regulates mitochondrial electron transport, has been recently identified as the causative gene of WFS2. The mouse Cisd2 knockout (KO) (Cisd2(-/-)) recapitulates most of the clinical manifestations of WFS2, including growth retardation, osteopenia, and lordokyphosis. However, the precise mechanisms underlying osteopenia in WFS2 and Cisd2 KO mice remain unknown. In this study, we collected embryonic fibroblasts from Cisd2-deficient embryos and reprogrammed them into induced pluripotent stem cells (iPSCs) via retroviral transduction with Oct4/Sox2/Klf4/c-Myc. Cisd2-deficient mouse iPSCs (miPSCs) exhibited structural abnormalities in their mitochondria and an impaired proliferative capability. The global gene expression profiles of Cisd2(+/+), Cisd2(+/-), and Cisd2(-/-) miPSCs revealed that Cisd2 functions as a regulator of both mitochondrial electron transport and Wnt/β-catenin signaling, which is critical for cell proliferation and osteogenic differentiation. Notably, Cisd2(-/-) miPSCs exhibited impaired Wnt/β-catenin signaling, with the downregulation of downstream genes, such as Tcf1, Fosl1, and Jun and the osteogenic regulator Runx2. Several differentiation markers for tridermal lineages were globally impaired in Cisd2(-/-) miPSCs. Alizarin red S staining and flow cytometry analysis further revealed that Cisd2(-/-) miPSCs failed to undergo osteogenic differentiation. Taken together, our results, as determined using an miPSC-based platform, have demonstrated that Cisd2 regulates mitochondrial function, proliferation, intracellular Ca(2+) homeostasis, and Wnt pathway signaling. Cisd2 deficiency impairs the activation of Wnt/β-catenin signaling and thereby contributes to the pathogeneses of osteopenia and lordokyphosis in WFS2 patients.

Dexamethasone in osteogenic medium strongly induces adipocyte differentiation of mouse bone marrow stromal cells and increases osteoblast differentiation

BACKGROUND

Osteoblasts and adipocytes share a common mesenchymal stem cell origin. Therefore, it has been suggested that the accumulation of marrow adipocytes observed in bone loss is caused by a shift in the commitment of mesenchymal stem cells from the osteogenic pathway to the adipogenic pathway. Supporting this hypothesis the competition between adipogenic and osteogenic lineages was widely demonstrated on partially homogeneous cell populations. However, some data from mouse models showed the existence of an independent relationship between bone mineral content and bone marrow adiposity. Therefore, the combination of adipogenesis and osteogenesis in primary culture would be helpful to determine if this competition would be observed on a whole bone marrow stromal cell population in a culture medium allowing both lineages. In this aim, mouse bone marrow stromal cells were cultured in a standard osteogenic medium added with different concentrations of Dexamethasone, known to be an important regulator of mesenchymal progenitor cell differentiation.

RESULTS

Gene expression of osteoblast and adipocyte markers, biochemical and physical analyses demonstrated the presence of both cell types when Dexamethasone was used at 100 nM. Overall, our data showed that in this co-differentiation medium both differentiation lineages were enhanced compared to classical adipogenic or osteogenic culture medium. This suggests that in this model, adipocyte phenotype does not seem to increase at the expense of the osteoblast lineage.

CONCLUSION

This model appears to be a promising tool to study osteoblast and adipocyte differentiation capabilities and the interactions between these two processes.

Effect of glucocorticoid-induced oxidative stress on the expression of Cbfa1

Glucocorticoids therapy is strongly limited since extended glucocorticoids can cause serious side effects, including increased susceptibility to develop the bone disease osteoporosis. Despite its side effects recognized importance to clinicians, seldom is known about how glucocorticoids directly impact bone-forming osteoblasts. Previous studies showed that dexamethasone (DEX) induces excessive production of reactive oxygen species (ROS), and causes oxidative stress in rat hippocampal slice cultures. To assess the implications and investigate the mechanisms of glucocorticoid-elicited osteoporosis, we hypothesize that DEX exposure induces oxidative stress which leads to decreased Cbfa1 mRNA expression, and predict that the antioxidant N-acetylcysteine (NAC) mitigates the damaging effects of DEX. Oxidative stress is implicated in osteoporosis. Furthermore, the osteoblast transcriptional factor Cbfa1 is reported to play a protective role against osteoporosis in postmenopausal women. Cells treated with (0.1, 1, 10μM) DEX exhibited signs of oxidative damages including depletion in total antioxidant capacity (T-AOC), increased ROS formation, and enhanced lipid peroxidation. Cbfa1 mRNA expression, by RT-PCR, was significantly reduced after exposure to (0.1, 1, 10μM) DEX. Pretreatment with the antioxidant NAC (2mM) prevented DEX-induced decrease in Cbfa1 mRNA. This study provides insight into the underlying mechanisms of high dose DEX-induced osteotoxicity. DEX (0.1, 1, 10μM) decreases the expression of Cbfa1 mRNA and inhibits differentiation and function of osteoblasts by inducing oxidative stress. The antioxidant NAC can mitigate the oxidative stress damaging effects of DEX. In addition, this study distinguishes itself by identifying Cbfa1 as a target for high dose DEX-induced osteotoxicity.

Induction of STEAP4 correlates with 1,25-dihydroxyvitamin D3 stimulation of adipogenesis in mesenchymal progenitor cells derived from human adipose tissue

The vitamin D receptor (VDR) is expressed in human adipocytes and is transiently induced during early adipogenesis in mesenchymal progenitor cell models. VDR null mice exhibit enhanced energy expenditure and reduced adiposity even when fed high fat diets. Adipocyte-specific transgenic-expression of human VDR in mice enhances adipose tissue mass, indicating that VDR activation in adipocytes enhances lipid storage in vivo. In these studies, we conducted genomic profiling and differentiation assays in primary cultures of human adipose-derived mesenchymal progenitor cells to define the role of the VDR and its ligand 1,25-dihydroxyvitamin D3 (1,25D) in adipogenesis. In the presence of adipogenic media, 1,25D promoted lipid accumulation and enhanced the expression of FABP4, FASN, and PPARγ. Mesenchymal cells derived from 6-month old VDR null mice exhibited impaired adipogenesis ex vivo but differentiation was restored by stable expression of human VDR. STEAP4, a gene that encodes a metalloreductase linked to obesity, insulin sensitivity, metabolic homeostasis and inflammation, was highly induced in human adipose cells differentiated in the presence of 1,25D but was minimally affected by 1,25D in undifferentiated precursors. These studies provide a molecular basis for recent epidemiological associations between vitamin D status, body weight and insulin resistance which may have relevance for prevention or treatment of metabolic syndrome and obesity.

Bisphosphonate- and statin-induced enhancement of OPG expression and inhibition of CD9, M-CSF, and RANKL expressions via inhibition of the Ras/MEK/ERK pathway and activation of p38MAPK in mouse bone marrow stromal cell line ST2

Osteoclast differentiation is influenced by receptor activator of the NF-κB ligand (RANKL), macrophage colony-stimulating factor (M-CSF), and CD9, which are expressed on bone marrow stromal cells and osteoblasts. In addition, osteoprotegerin (OPG) is known as an osteoclastogenesis inhibitory factor. In this study, we investigated whether bisphosphonates and statins increase OPG expression and inhibit the expression of CD9, M-CSF, and RANKL in the bone marrow-derived stromal cell line ST2. We found that bisphosphonates and statins enhanced OPG mRNA expression and inhibited the expression of CD9, M-CSF, and RANKL mRNA. Futhermore, bisphosphonates and statins decreased the membrane localization of Ras and phosphorylated ERK1/2, and activated the p38MAPK. This indicates that bisphosphonates and statins enhanced OPG expression, and inhibited the expression of CD9, M-CSF, and RANKL through blocking the Ras/ERK pathway and activating p38MAPK. Accordingly, we believe that its clinical applications will be investigated in the future for the development of osteoporosis therapy.

EGb 761 promotes osteoblastogenesis, lowers bone marrow adipogenesis and atherosclerotic plaque formation

AIM OF THE STUDY

Our earlier study has demonstrated that EGb 761 (standardized extract of Ginkgo) has the bone sparing effect on the estrogen deficiency induced bone loss model. In the present study, we have addressed the question whether treatment of osteoporosis benefits arterial calcification or vice versa, because both adipocyte and osteoblast originate from the same mesenchymal cell of the bone marrow cell (BMC) population.

MATERIALS AND METHODS

Bone marrow cells were isolated to study the effect of EGb 761 on osteoblast and adipocytes. For in vivo effect hamsters were fed high fat diet and the effect of EGb 761 studied on atherosclerotic plaque formation and endothelial function.

RESULTS

BMC's undergoing induced osteogenic or adipogenic differentiations in the presence of EGb 761 show increase and decrease in mineralization and adipogenesis respectively. Osteogenic and adipogenic mRNAs, reveal lineage dependent expression patterns. Runx-2 (osteoblast transcription factor) showed a progressive increase, whereas PPAR-γ (adipogenic regulator) was attenuated, with same pattern of expression being for late osteogenic and adipogenic genes. EGb 761 led to increase in apoptotic cells and ROS, an important upstream signal. In vivo experiments in hamsters after induction with high cholesterol diet (HCD) show improvement in endothelial function by EGb 761 with lowering in total plasma cholesterol levels. EGb 761 led to vascular preservation of the aortic lumen with impairment of the endothelium dependent relaxation which was corroborated by micro-CT and histological sections of the thoracic region of the aorta.

CONCLUSION

From this data, it can be implied that EGb 761 controls bone loss, adiposity and lowers atherogenic risk factor after HCD induction.

Age-related skeletal dynamics and decrease in bone strength in DNA repair deficient male trichothiodystrophy mice

Accumulation of DNA damage caused by oxidative stress is thought to be one of the main contributors of human tissue aging. Trichothiodystrophy (TTD) mice have a mutation in the Ercc2 DNA repair gene, resulting in accumulation of DNA damage and several features of segmental accelerated aging. We used male TTD mice to study the impact of DNA repair on bone metabolism with age. Analysis of bone parameters, measured by micro-computed tomography, displayed an earlier decrease in trabecular and cortical bone as well as a loss of periosteal apposition and a reduction in bone strength in TTD mice with age compared to wild type mice. Ex vivo analysis of bone marrow differentiation potential showed an accelerated reduction in the number of osteogenic and osteoprogenitor cells with unaltered differentiation capacity. Adipocyte differentiation was normal. Early in life, osteoclast number tended to be increased while at 78 weeks it was significantly lower in TTD mice. Our findings reveal the importance of genome stability and proper DNA repair for skeletal homeostasis with age and support the idea that accumulation of damage interferes with normal skeletal maintenance, causing reduction in the number of osteoblast precursors that are required for normal bone remodeling leading to a loss of bone structure and strength.

TAZ is downregulated by dexamethasone during the differentiation of 3T3-L1 preadipocytes

TAZ (transcriptional co-activator with PDZ binding motif) is a transcriptional modulator of mesenchymal stem cell differentiation. We have found that TAZ was expressed in postconfluent 3T3-L1 preadipocytes and downregulated during differentiation. Downregulation of TAZ was specifically mediated by dexamethasone (DEX), one component of induction cocktails routinely used in adipocyte differentiation. DEX repressed the transcription of TAZ by direct binding of the glucocorticoid receptor (GR) to the GR binding element in its promoter. More importantly, overexpression of TAZ inhibited adipogenesis and promoted the trans-differentiation of preadipocytes into osteocytes. This establishes a new functional interaction between DEX and TAZ that contributes to the mechanism of adipogenesis.

Proteome analysis of rat bone marrow mesenchymal stem cell differentiation

Bone marrow multipotent stromal cells (or mesenchymal stem cells; MSCs) have the capacity for renewal and the potential to differentiate in culture into several cell types including osteoblasts, chondrocytes, adipocytes, cardiomyocytes, and neurons. This study was designed to investigate the protein expression profiles of rat bone marrow MSCs during differentiation into adipogenic (by dexamethasone, isobutylmethylxanthine, insulin, and indomethacin), cardiomyogenic (by 5-azacytidine), chondrogenic (by ascorbic acid, insulin-transferrin-selenous acid, and transforming growth factor-β1), and osteogenic (by dexamethasone, β-glycerophosphate, and ascorbic acid) lineages by well-known differentiation inducers. Proteins extracted from differentiated MSCs were separated using two-dimensional gel electrophoresis (2-DE) and protein spots were detected using Sypro Ruby dye. Protein spots that were determined to be up- or down-regulated when the expression of corresponding spots (between weeks 1 and 2, 1 and 3, 1 and 4) showed an increase (≥2-fold) or decrease (≤0.5-fold) were successfully identified by MALDI-TOF-MS. In summary, 23 new proteins were identified either up- or down-regulated during differentiation experiments.

Bone grafts engineered from human adipose-derived stem cells in perfusion bioreactor culture

We report engineering of half-centimeter-sized bone constructs created in vitro using human adipose-derived stem cells (hASCs), decellularized bone scaffolds, and perfusion bioreactors. The hASCs are easily accessible, can be used in an autologous fashion, are rapidly expanded in culture, and are capable of osteogenic differentiation. hASCs from four donors were characterized for their osteogenic capacity, and one representative cell population was used for tissue engineering experiments. Culture-expanded hASCs were seeded on fully decellularized native bone scaffolds (4 mm diameter x 4 mm thick), providing the necessary structural and mechanical environment for osteogenic differentiation, and cultured in bioreactors with medium perfusion. The interstitial flow velocity was set to a level necessary to maintain cell viability and function throughout the construct volume (400 microm/s), via enhanced mass transport. After 5 weeks of cultivation, the addition of osteogenic supplements (dexamethasone, sodium-beta-glycerophosphate, and ascorbic acid-2-phosphate) to culture medium significantly increased the construct cellularity and the amounts of bone matrix components (collagen, bone sialoprotein, and bone osteopontin). Medium perfusion markedly improved the distribution of cells and bone matrix in engineered constructs. In summary, a combination of hASCs, decellularized bone scaffold, perfusion culture, and osteogenic supplements resulted in the formation of compact and viable bone tissue constructs.

Signalling strategies for osteogenic differentiation of human umbilical cord mesenchymal stromal cells for 3D bone tissue engineering

Human umbilical cord mesenchymal stromal cells (hUCMSCs) have recently shown the capacity to differentiate into multiple cell lineages in all three embryonic germ layers. The osteogenic differentiation of hUCMSCs in monolayer culture has been reported, while the differentiation in three-dimensional biomaterials has not yet been reported for tissue-engineering applications. Thus, the aim of this study was to evaluate the feasibility of using hUCMSCs for bone tissue engineering. hUCMSCs were cultured in poly(L-lactic acid) (PLLA) scaffolds in osteogenic medium (OM) for 3 weeks, after which the scaffolds were exposed to several different media, including the OM, a mineralization medium (MM) and the MM with either 10 or 100 ng/ml insulin-like growth factor (IGF)-1. The osteogenic differentiation was confirmed by the up-regulation of Runx2 and OCN, calcium quantification and bone histology. Switching from the OM to the MM promoted collagen synthesis and calcium content per cell, while continuing in the OM retained more cells in the constructs and promoted higher osteogenic gene expression. The addition of IGF-1 into the MM had no effect on cell proliferation, differentiation and matrix synthesis. In conclusion, hUCMSCs show significant potential for bone tissue engineering and culturing in the OM throughout the entire period is beneficial for osteogenic differentiation of these cells.

Osteoblastogenic effects of dexamethasone through upregulation of TAZ expression in rat mesenchymal stem cells

Transcriptional coactivator with PDZ-binding motif (TAZ), a beta-catenin-like molecule, drives mesenchymal stem cell (MSC) to differentiate into osteoblast lineage through co-activation of Runx2-dependent gene transcription and repression of peroxisome proliferator-activated receptorgamma (PPARgamma)-dependent gene transcription. Dexamethasone (DEX), a synthetic and widely used glucocorticoid, affects osteogenesis. However, the signaling pathway by which DEX affects osteoblastic differentiation remains obscure. In this study, we found that DEX at the concentration of 10(-8)M enhanced calcium deposition, TAZ, bone morphogenetic protein 2 (BMP-2) and alkaline phosphatase (ALP) expression during osteoblastic differentiation. RU486, an antagonist of glucocorticoid receptor, blocked the improvement of TAZ expression while MSCs were treated with 10(-8)M DEX. Moreover, higher concentration (10(-7)M) of DEX robustly suppressed TAZ and ALP expression in MSCs. These findings suggest that TAZ is not only involved in the signal pathway of BMP-2-induced osteoblastic differentiation, but also involved in the signaling pathway of DEX-induced osteoblastic differentiation, supporting the notion that TAZ is a convergence point of two signaling pathways, BMP-2 signaling pathway and Wnt-beta-catenin signaling pathway.

The differentiation of human placenta-derived mesenchymal stem cells into dopaminergic cells in vitro

Mesenchymal stem cells (MSCs) constitute an interesting cellular source to promote brain regeneration after Parkinson's disease. MSCs have significant advantages over other stem cell types, and greater potential for immediate clinical application. The aim of this study was to investigate whether MSCs from the human placenta could be induced to differentiate into dopaminergic cells. MSCs from the human placenta were isolated by digestion and density gradient fractionation, and their cell surface glycoproteins were analyzed by flow cytometry. These MSCs were cultured under conditions promoting differetiation into adipocytes and osteoblasts. Using a cocktail that includes basic fibroblast growth factor (bFGF), all trans retinoic acid (RA), ascorbic acid (AA) and 3-isobutyl-1-methylxanthine (IBMX), the MSCs were induced in vitro to become dopamine (DA) neurons. Then, the expression of the mRNA for the Nestin and tyrosine hydroxylase (TH) genes was assayed via RT-PCR. The expression of the Nestin, dopamine transporter (DAT), neuronal nuclear protein (NeuN) and TH proteins was determined via immunofluorescence. The synthesized and secreted DA was determined via ELISA. We found that MSCs from the human placenta exhibited a fibroblastoid morphology. Flow cytometric analyses showed that the MSCs were positive for CD44 and CD29, and negative for CD34, CD45, CD106 and HLA-DR. Moreover, they could be induced into adipocytes and osteocytes. When the MSCs were induced with bFGF, RA, AA and IBMX, they showed a change in morphology to that of neuronal-like cells. The induced cells expressed Nestin and TH mRNA, and the Nestin, DAT, NeuN and TH proteins, and synthesized and secreted DA. Our results suggest that MSCs from the human placenta have the ability to differentiate into dopaminergic cells.

Effects of arachidonic acid and docosahexaenoic acid on differentiation and mineralization of MC3T3-E1 osteoblast-like cells

Osteoblasts in culture can differentiate into mature mineralizing osteoblasts when stimulated with osteogenic agents. Clinical trials and in vivo animal studies suggest that specific polyunsaturated fatty acids (PUFAs) may benefit bone health. The aim of this study was to investigate whether arachidonic acid (AA) and docosahexaenoic acid (DHA) affect osteogenesis in osteoblasts and the transdifferentiation into adipocytes. Results from this study show that long-term exposure to AA inhibited alkaline phosphatase (ALP) activity in these cells, which might be prostaglandin E(2) (PGE(2))-mediated. DHA exposure also inhibited ALP activity which was evident after both short- and long-term exposures. The mechanism whereby DHA inhibits ALP activity is not clear and needs to be investigated. Although long-term exposure to PUFAs inhibited ALP activity, the mineralizing properties of these cells were not compromised. Furthermore, PUFA exposure did not induce adipocyte-like features in these cells as evidenced by the lack of cytoplasmic triacylglycerol accummulation. More research is required to elucidate the cellular mechanisms of action of PUFAs on bone.

Lean phenotype and resistance to diet-induced obesity in vitamin D receptor knockout mice correlates with induction of uncoupling protein-1 in white adipose tissue

Increased adiposity is a feature of aging in both mice and humans, but the molecular mechanisms underlying age-related changes in adipose tissue stores remain unclear. In previous studies, we noted that 18-month-old normocalcemic vitamin D receptor (VDR) knockout (VDRKO) mice exhibited atrophy of the mammary adipose compartment relative to wild-type (WT) littermates, suggesting a role for VDR in adiposity. Here we monitored body fat depots, food intake, metabolic factors, and gene expression in WT and VDRKO mice on the C57BL6 and CD1 genetic backgrounds. Regardless of genetic background, both sc and visceral white adipose tissue depots were smaller in VDRKO mice than WT mice. The lean phenotype of VDRKO mice was associated with reduced serum leptin and compensatory increased food intake. Similar effects on adipose tissue, leptin and food intake were observed in mice lacking Cyp27b1, the 1alpha-hydroxylase enzyme that generates 1,25-dihydroxyvitamin D(3), the VDR ligand. Although VDR ablation did not reduce expression of peroxisome proliferator-activated receptor-gamma or fatty acid synthase, PCR array screening identified several differentially expressed genes in white adipose tissue from WT and VDRKO mice. Uncoupling protein-1, which mediates dissociation of cellular respiration from energy production, was greater than 25-fold elevated in VDRKO white adipose tissue. Consistent with elevation in uncoupling protein-1, VDRKO mice were resistant to high-fat diet-induced weight gain. Collectively, these studies identify a novel role for 1,25-dihydroxyvitamin D(3) and the VDR in the control of adipocyte metabolism and lipid storage in vivo.

Isolation of osteoprogenitors from murine bone marrow by selection of CD11b negative cells

Selection of cells having the most osteogenic potential is a strategy used in bone tissue engineering. Preclinical studies using murine bone marrow cells must consider the large amount of hematopoietic cells in the adherent fraction. The aim of this study was to enrich a murine bone marrow cell population with osteoprogenitors by using a simple and reliable method. Bone marrow from C57Bl/6 mice was extracted and cells which adhered onto plastic were expanded in primary culture for 14 days. Immunolabeling of the CD11b surface antigen was performed and the CD11b(-) cell fraction was isolated by FACS. Sorted and unsorted populations were analyzed for gene expression of osteoblast differentiation, alkaline phosphatase (AlkP) activity and matrix mineralization capacities. Selection of CD11b(-) cells increased the number of AlkP(+) cells from the plastic adherent fraction from 6.3% +/- 0.8 to 56% +/- 3.3 with a sevenfold increase in AlkP activity. mRNA analysis revealed a significant increase in the CD11b(-) fraction for Osterix (41-fold), RANKL (17-fold), M-CSF (8-fold) and Runx-2 (8-fold). An osteogenic population was obtained with improved capacities to produce a mineralized extracellular matrix in vitro, independently of the presence of glucocorticoids in the culture medium.

The biological roles of extracellular and intracytoplasmic glucocorticoids in skeletal cells

Osteoporosis is the most common metabolic disease characterized by loss of the normal density of bone, resulting in fragile bone and a higher risk of fractures. Patients under glucocorticoids treatment are susceptible to glucocorticoid-induced osteoporosis (GIO). The normal bone turnover depends on a balance between osteoblasts and osteoclasts. The skeletal cells including osteoblasts, osteoclasts, osteocytes and their precursors demonstrate altered features while they are cocultured with different extracellular glucocorticoids, or their intracytoplasmic glucocorticoids modified by genetic manipulation of 11beta-HSD isozyme. However, recent studies have also demonstrated different or even contradictive outcomes on whether the glucocorticoids inhibit or increase biological activity of these skeletal cells. Focusing on the roles of extracellular glucorticoids, intracytoplasmic glucocorticoids and the mechanism of transmembrane passage of the glucocorticoids, this review reveals that glucocorticoids may exert either inhibitive or enhancing influence on these skeletal cells, but relying on the difference in cell origins, methodology, and types of glucocorticoids. In addition, the effects of glucocorticoids may be dose- and time-dependent.

Rat bone marrow mesenchymal stem cells differentiate into hepatocyte-like cells in vitro

AIM: To investigate differentiation of rat bone marrow mesenchymal stem cells (MSCs) into hepatocyte-like cells.

METHODS: A total of 24 Wistar rats were randomly divided into 3 groups: normal group, hepatic fibrosis model group and Chinese medicine treatment group. The model of liver fibrosis was induced by subcutaneous injection of CCl₄. After the model was successfully developed, and the rats in Chinese medicine treatment group were fed with Danjin Shugan capsule. At the end of treatment, the rats were killed and the livers were obtained. Histopathological changes were evaluated by hematoxylin and eosin staining. MSCs were isolated by gradient density centrifugation and plastic adherence and then purified. The purified MSCs in each group were cultured with hepatocyte growth factor (HGF) and fibroblast growth factor-4 (FGF-4). The levels of alpha-fetoprotein (AFP) and albumin (Alb) in the supernatant were determined by radioimmunoassay on days 15, 21 and 27. On day 27, the cells were collected for glycogen staining and CK-18 immunocytochemical analysis.

RESULTS: Compared with those in the non-induced MSCs among the three groups, the levels of AFP in the induced-MSCs were higher on days 15, 21, and 27, and reached to the peak value on day 21 (hepatic fibrosis model group: 48.94 ± 0.08 vs 9.90 ± 0.09; Chinese medicine treatment group: 49.86 ± 0.29 vs 8.69 ± 0.62; normal group: 38.65 ± 0.33 vs 9.04 ± 0.11; all P< 0.01). There were significant differences in Alb levels on days 21 and 27 between the induced and non-induced MSCs (1.11 ± 0.08 vs 0.32 ± 0.00, 1.25 ± 0.04 vs 0.32 ± 0.00, 1.06 ± 0.03 vs 0.33 ± 0.00; 1.52 ± 0.02 vs 0.33 ± 0.00, 1.79 ± 0.01 vs 0.31 ± 0.03, 1.63 ± 0.04 vs 0.32 ± 0.01; all P < 0.01), but not on day 15; the peak level of Alb was on day 27. Both glycogen and CK-18 were positive on day 27 in the induced MSCs. According to AFP and Alb levels, the induced effects of Chinese medicine group were superior to those of the other two groups.

CONCLUSION: MSCs can differentiate into hepatocyte-like cells with hepatic phenotype and function in the presence of HGF and FGF-4, which may be used as a kind of cell resources to treat severe hepatic disease. Chinese medicine may optimize the induction of MSCs differentiation in vitro.

Human osteogenic protein-1 induces osteogenic differentiation of adipose-derived stem cells harvested from mice

OBJECTIVE

Osteogenic protein-1 (OP-1) has been shown to stimulate undifferentiated cells to produce mineralized tissue. Adipose tissue is a rich source of undifferentiated cells for tissue engineering purposes. The purpose of this study was to investigate the effect of OP-1 on osteogenic differentiation of adipose-derived stem cells and the production of bony tissue in vitro.

DESIGN

Adipose-derived stem cells (ADSCs) were isolated from inguinal fat pads of adult mice. Following cell expansion the cells were plated in 8-well chambered slides. The cells received one of four treatments: Group 1 cells were maintained in control medium, Group 2 cells were cultured in a common osteogenic medium, Group 3 cells were cultured in osteogenic medium supplemented with 250ng/mL of OP-1, and Group 4 cells were cultured with 250ng/mL of OP-1 added to control medium. Osteogenic differentiation of ADSCs was determined by estimating the number and size of mineralized nodules, and the amount of extracellular osteopontin secreted into cell culture medium. Mineralized nodule production was assessed at day 21 with von Kossa staining. Extracellular osteopontin release was measured after 8 and 21 days by enzyme-linked immunosorbant assay (ELISA). ANOVA/Tukey tests were used to identify differences among the four treatment groups for mineralized nodule production and osteopontin release (p<or=0.05).

RESULTS

Deposition of calcified nodules and osteopontin secretion was significantly greater for cell cultures incubated with OP-1 (p<or=0.05). At day 21, no significant differences in osteopontin secretion were noted among groups incubated with osteogenic nutrients and/or OP-1 (p>0.05), which were significantly higher than the group incubated in cell growth medium only (p<or=0.05). No significant differences in osteopontin secretion were noted between 8 and 21 days for any group (p>0.05). Linear regression analysis demonstrated a linear relationship was present between the presence of calcified nodules and the amount of osteopontin released (p<or=0.05).

CONCLUSIONS

OP-1 is a powerful inducer of osteogenic differentiation of adult adipose-derived stem cells.

Modulation of Dickkopf-1 attenuates glucocorticoid induction of osteoblast apoptosis, adipocytic differentiation, and bone mass loss

Long-term glucocorticoid treatment impairs the survival and bone formation of osteogenic cells, leading to bone mass loss. The Wnt inhibitor Dickkopf-1 (DKK1) acts as a potent bone-remodeling factor that mediates several types of skeletal disorders. Whereas excess glucocorticoid is known to disturb Wnt signaling in osteogenic cells, modulation of the skeletally deleterious effects of DKK1 to alleviate glucocorticoid induction of bone loss has not been tested. In this study, knockdown of DKK1 expression by end-capped phosphorothioate DKK1 antisense oligonucleotide (DKK1-AS) abrogated dexamethasone suppression of alkaline phosphatase activity and osteocalcin expression in MC3T3-E1 preosteoblasts. Exogenous DKK1-AS treatment alleviated dexamethasone suppression of mineral density, trabecular bone volume, osteoblast surface, and bone formation rate in bone tissue and ex vivo osteogenesis of primary bone-marrow mesenchymal cells. The DKK1-AS inhibited adipocyte volume in the marrow cavity of steroid-treated bone tissue. Immunohistochemical observation revealed that DKK1-AS abrogated dexamethasone-induced DKK1 expression and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling of osteoblasts adjacent to trabecular bone. Knocking down DKK1 abrogated dexamethasone-modulated expression of nuclear beta-catenin and phosphorylated Ser(473)-Akt and survival of osteoblasts and adipocytic differentiation of mesenchymal progenitor cell cultures. Taken together, knocking down DKK1 alleviated the deleterious effect of glucocorticoid on bone microstructure. The DKK1-AS treatment appeared to protect bone tissue by modulating beta-catenin and Akt-mediated survival as well as the osteogenic and adipogenic activities of glucocorticoid-stressed osteoprogenitor cells. Interference with the osteogenesis-inhibitory action of DKK1 has therapeutic potential for preventing glucocorticoid induction of osteopenia.

Proliferative capacity and osteogenic potential of novel dura mater stem cells on poly-lactic-co-glycolic acid

The rational design of biomimetic structures for the regeneration of damaged or missing tissue is a fundamental principle of tissue engineering. Multiple variables must be optimized, ranging from the scaffold type to the selection and properties of implanted cell(s). In this study, the osteogenic potential of a novel stem cell was analyzed on biodegradable poly(lactic-co-glycolic acid) (PLGA) biomaterials as a step toward creating new cell-materials constructs for bony regeneration. Dura mater stem cells (DSCs), isolated from rat dura mater, were evaluated and compared to bone marrow stem cells (BMSCs) for proliferative and differentiative properties in vitro. Experiments were carried out on both tissue culture plastic (TCP) and 2D planar films of PLGA. Proliferation of DSCs on both TCP and PLGA films increased over 21 days. Positive fold inductions in all five bone marker genes were observed at days 7, 14, 21 in all experimental samples compared with day 0 controls. DSCs demonstrated greater cell coverage and enhanced matrix staining on 2D PLGA films when compared with BMSCs. These cells can be isolated and expanded in culture and can subsequently attach, proliferate, and differentiate on both TCP and PLGA films to a greater extent than BMSCs. This suggests that DSCs are promising for cell-based bone tissue engineering therapies, particularly those applications involving regeneration of cranial bones.

Enhanced effects of 1,25(OH)(2)D(3) plus genistein on adipogenesis and apoptosis in 3T3-L1 adipocytes

OBJECTIVE

To investigate the ability of 1,25(OH)(2)D(3) (D) and genistein (G), alone and in combination, to inhibit adipogenesis and induce apoptosis in 3T3-L1 adipocytes.

METHODS AND PROCEDURES

3T3-L1 preadipocytes and mature adipocytes were incubated with various concentrations of D and G, alone and in combination, for 48 h. Viability was determined using the Cell Titer 96 Aqueous One Solution Cell Proliferation Assay. Post-confluent preadipocytes were incubated with D and G for up to 6 days during adipogenesis and lipid content was quantified by Nile Red dye; apoptosis was quantified by measurement of single-stranded DNA. Expression of adipocyte-specific proteins and VDR was analyzed by western blotting.

RESULTS

Combining D and G did not cause an enhanced effect on cell viability in either preadipocytes or mature adipocytes. In maturing preadipocytes, D at 0.5 nmol/l (D0.5) increased apoptosis by 47 +/- 10.25% (P < 0.05) and inhibited lipid accumulation by 28 +/- 10% (P < 0.001), while G at 25 micromol/l (G25) had no significant effect. However, D+G caused an enhanced apoptosis by 136 +/- 12.6% (P < 0.001) and enhanced inhibition of lipid accumulation by 82.46 +/- 2.95% (P < 0.001). Similarly, D0.5 alone decreased adipose-specific gene 422 (aP2) expression to 34.2 +/- 2.3% and increased VDR expression levels by 41.8 +/- 11% (P < 0.001), but G25 showed no effect. However, D0.5+G25 decreased aP2 expression to 52 +/- 4.2% (P < 0.05) and increased VDR expression levels by 131 +/- 14.5% (P < 0.0001).

DISCUSSION

These findings suggest that combining 1,25(OH)(2)D(3) with genistein results in an enhanced inhibition of lipid accumulation and induction of apoptosis in maturing 3T3-L1 preadipocytes.