IGF1 promotes osteogenic differentiation of mesenchymal stem cells derived from rat bone marrow by increasing TAZ expression

The role of YAP/TAZ on joint and arthritis

Osteoarthritis (OA) and rheumatoid arthritis (RA) are two common forms of arthritis with undefined etiology and pathogenesis. Yes-associated protein (YAP) and its homolog transcriptional coactivator with PDZ-binding motif (TAZ), which act as sensors for cellular mechanical and inflammatory cues, have been identified as crucial players in the regulation of joint homeostasis. Current studies also reveal a significant association between YAP/TAZ and the pathogenesis of OA and RA. The objective of this review is to elucidate the impact of YAP/TAZ on different joint tissues and to provide inspiration for further studying the potential therapeutic implications of YAP/TAZ on arthritis. Databases, such as PubMed, Cochran Library, and Embase, were searched for all available studies during the past two decades, with keywords "YAP," "TAZ," "OA," and "RA."

Dual-crosslinked network of polyacrylamide-carboxymethylcellulose hydrogel promotes osteogenic differentiation in vitro

In our previous study, we successfully designed a dual-crosslinked network hydrogel by introducing the monomers acrylamide (AM), carboxymethylcellulose (CMC), zeolitic imidazolate framework-8 (ZIF-8), and alendronate (Aln). With the simultaneous presentation of physical and chemical crosslinks, the fabricated hydrogel with 10 % concentration of Aln@ZIF-8 (PAM-CMC-10%Aln@ZIF-8) exhibited excellent mechanical characteristics, high Aln loading efficiency (63.83 %), and a slow release period (6 d). These results demonstrate that PAM-CMC-10%Aln@ZIF-8 is a potential carrier for delaying Aln. In this study, we mainly focused on the biocompatibility and osteogenic ability of PAM-CMC-10%Aln@ZIF-8 in vitro, which is a continuation of our previous work. First, this study investigated the biocompatibility of dual-crosslinked hydrogels using calcein-AM/Propidium Iodide and cell counting kit-8. The morphology of rat bone mesenchymal stem cells was assessed using FITC-phalloidin/DAPI and vinculin immunostaining. Finally, osteogenic induction ability in vitro was assessed via alkaline phosphatase expression and alizarin red S staining, which was also confirmed using real-time PCR at the gene level and immunofluorescence at the protein level. The results indicated that the introduction of Aln enabled a dual-crosslinked hydrogel with superior biocompatibility and outstanding osteogenic differentiation ability in vitro, providing a solid foundation for subsequent animal experiments in vivo.

TAZ promotes osteogenic differentiation of mesenchymal stem cells line C3H10T1/2, murine multi-lineage cells lines C2C12, and MEFs induced by BMP9

Bone morphogenetic protein 9 (BMP9), also named as growth differentiation factor 2 (GDF-2), is the strongest cytokine that promotes osteogenic differentiation in the BMP family, and has broad clinical application value. Nevertheless, the mechanism of BMP9 promotes osteogenic differentiation remain unclear. TAZ, a transcriptional co-activator, has great effects on cell proliferation, differentiation, and stem cell self-renewal. In this research, we investigated the effects of TAZ in BMP9-induced osteogenic differentiation of mesenchymal stem cell line C3H10T1/2 (MSCs) and murine multi-lineage cell lines C2C12 and MEFs (MMCs) and explored its possible mechanisms. This study has found that BMP9 induces the expression of TAZ and promotes its nuclear translocation. Meanwhile, our study found that Ad-TAZ and TM-25659, a TAZ agonist, can enhance the osteogenic differentiation of MSCs and MMCs induced by BMP9. Conversely, Ad-si-TAZ and verteporfin, an inhibitor of TAZ, have the contradictory effect. Likewise, the promotion of TAZ to the BMP9-induced ectopic bone formation in vivo was confirmed by the subcutaneous transplantation of MSCs in nude mice. Furthermore, we have detected that TAZ might increase the levels of the phosphorylation of Smad1/5/8, p38, ERK1/2, and JNK induced by BMP9. Additionally, we also found that TAZ increased the total protein level of β-catenin induced by BMP9. In summary, our results strongly indicated that TAZ will promote the osteogenic differentiation in MSCs and MMCs induced by BMP9 through multiple signal pathways.

Preparation, characterization, and osteogenic activity mechanism of casein phosphopeptide-calcium chelate

Casein phosphopeptides (CPPs) are good at calcium-binding and intestinal calcium absorption, but there are few studies on the osteogenic activity of CPPs. In this study, the preparation of casein phosphopeptide calcium chelate (CPP-Ca) was optimized on the basis of previous studies, and its peptide-calcium chelating activity was characterized. Subsequently, the effects of CPP-Ca on the proliferation, differentiation, and mineralization of MC3T3-E1 cells were studied, and the differentiation mechanism of CPP-Ca on MC3T3-E1 cells was further elucidated by RNA sequencing (RNA-seq). The results showed that the calcium chelation rate of CPPs was 23.37%, and the calcium content of CPP-Ca reached 2.64 × 10⁵ mg/kg. The test results of Ultraviolet–Visible absorption spectroscopy (UV) and Fourier transform infrared spectroscopy (FTIR) indicated that carboxyl oxygen and amino nitrogen atoms of CPPs might be chelated with calcium during the chelation. Compared with the control group, the proliferation of MC3T3-E1 cells treated with 250 μg/mL of CPP-Ca increased by 21.65%, 26.43%, and 28.43% at 24, 48, and 72 h, respectively, and the alkaline phosphatase (ALP) activity and mineralized calcium nodules of MC3T3-E1 cells were notably increased by 55% and 72%. RNA-seq results showed that 321 differentially expressed genes (DEGs) were found in MC3T3-E1 cells treated with CPP-Ca, including 121 upregulated and 200 downregulated genes. Gene ontology (GO) revealed that the DEGs mainly played important roles in the regulation of cellular components. The enrichment of the Kyoto Encyclopedia of Genes and Genomes Database (KEGG) pathway indicated that the AMPK, PI3K-Akt, MAPK, and Wnt signaling pathways were involved in the differentiation of MC3T3-E1 cells. The results of a quantitative real-time PCR (qRT-PCR) showed that compared with the blank control group, the mRNA expressions of Apolipoprotein D (APOD), Osteoglycin (OGN), and Insulin-like growth factor (IGF1) were significantly increased by 2.6, 2.0 and 3.0 times, respectively, while the mRNA levels of NOTUM, WIF1, and LRP4 notably decreased to 2.3, 2.1, and 4.2 times, respectively, which were consistent both in GO functional and KEGG enrichment pathway analysis. This study provided a theoretical basis for CPP-Ca as a nutritional additive in the treatment and prevention of osteoporosis.

Noncanonical Wnt5a Signaling Suppresses Hippo/TAZ-Mediated Osteogenesis Partly Through the Canonical Wnt Pathway in SCAPs

Purpose

Stem cells from the apical papilla (SCAPs) are promising seed cells for tissue regeneration medicine and possess the osteogenic differentiation potential. Wnt5a, a typical ligand of the noncanonical Wnt pathway, exhibits diverse roles in the regulation of osteogenesis. The transcriptional co-activator with PDZ-binding motif (TAZ, WWTR1) is a core regulator in the Hippo pathway and regulates stem behavior including osteogenic differentiation. This study aims to examine how Wnt5a regulates SCAPs osteogenesis and explore the precise mechanistic relationship between Wnt5a and TAZ.

Methods

SCAPs were isolated from developing apical papilla tissue of extracted human immature third molars in vitro. ALP staining, ALP activity and Alizarin red staining were used to evaluate osteogenic capacity. Osteogenic-related factors were assessed by qRT-PCR or Western blotting. Additionally, the receptor tyrosine kinase-like orphan receptor 2 (ROR2) was detected by immunocytofluorescence staining and silenced by small interfering RNA to verify the function of Wnt5a/ROR2 in TAZ-mediated osteogenesis. And we constructed TAZ-overexpression and β-catenin-overexpression SCAPs generated by lentivirus to explore the precise mechanistic relationship between Wnt5a and TAZ.

Results

Wnt5a (100ng/mL) significantly suppressed ALP activity, mineralization nodules formation, expression of osteogenic-related factors. Meanwhile, it decreased the expression of TAZ mRNA and protein. TAZ overexpression promoted osteogenesis of SCAPs while Wnt5a could block TAZ-mediated osteogenesis. Furthermore, ROR2 siRNA (siROR2) was found to upregulate TAZ and canonical Wnt pathway signaling related molecules such as β-catenin, GSK3β and p-GSK3β. The suppression of Wnt5a/ROR2 on osteogenesis was significantly reversed by β-catenin overexpression through Wnt5a/ROR2/β-catenin/TAZ pathway.

Conclusion

Taken together, the present study demonstrates that Wnt5a suppresses TAZ-mediated osteogenesis of SCAPs and there may be a Wnt5a/ROR2/β-catenin/TAZ pathway regulating osteogenesis of SCAPs. Moreover, Wnt5a could be a candidate for regulators in tissue regeneration.

YAP/TAZ in Bone and Cartilage Biology

YAP and TAZ were initially described as the main regulators of organ growth during development and more recently implicated in bone biology. YAP and TAZ are regulated by mechanical and cytoskeletal cues that lead to the control of cell fate in response to the cellular microenvironment. The mechanical component represents a major signal for bone tissue adaptation and remodelling, so YAP/TAZ contributes significantly in bone and cartilage homeostasis. Recently, mice and cellular models have been developed to investigate the precise roles of YAP/TAZ in bone and cartilage cells, and which appear to be crucial. This review provides an overview of YAP/TAZ regulation and function, notably providing new insights into the role of YAP/TAZ in bone biology.

Curculigoside Ameliorates Bone Loss by Influencing Mesenchymal Stem Cell Fate in Aging Mice

Senile osteoporosis is characterized by increased bone loss and fat accumulation in marrow. Curculigoside (CCG) is the major bioactive component of Curculigo orchioides, which has been used as anti-osteoporosis therapy for elder patients since antiquity. We aimed to investigate the underlying mechanisms by which CCG regulated the bone-fat balance in marrow of aging mice. In our study, CCG treatment was identified to interfere with the stem cell lineage commitment both in vivo and in vitro. In vivo, CCG promoted the transcriptional co-activator with PDZ-binding motif (TAZ) expression to reverse age-related bone loss and marrow adiposity. In vitro, proper concentration of CCG upregulated TAZ expression to increase osteogenesis and decrease adipogenesis of bone marrow mesenchymal stem cells (BMSCs). This regulating effect was discounted by TAZ knockdown or the use of MEK-ERK pathway inhibitor, UO126. Above all, our study confirmed the rescuing effects of CCG on the differential shift from adipogenesis to osteogenesis of BMSCs in aging mice and provided a scientific basis for the clinical use of CCG in senile osteoporosis.

Study of Icaritin Films by Low-Energy Electron Beam Deposition

In this paper, icaritin film was prepared by low-energy beam electron beam deposition (EBD). The material test showed that the structure and composition of icaritin were not changed after electron beam deposition. Then, the film was sliced and immersed in simulated body fluids, it can be seen that the film was released quickly in the first 7 days. With the extension of soaking time, the release rate gradually slowed down, and the release amount exceeded 90% in about 20 days. In vitro cytotoxicity test showed that the relative cell viability rate of the film was still 92.32±1.30% (p<0.05), indicating that the film possessed excellent cytocompatibility.

Shared Genetic and Epigenetic Mechanisms between the Osteogenic Differentiation of Dental Pulp Stem Cells and Bone Marrow Stem Cells

OBJECTIVE

To identify the shared genetic and epigenetic mechanisms between the osteogenic differentiation of dental pulp stem cells (DPSC) and bone marrow stem cells (BMSC).

MATERIALS AND METHODS

The profiling datasets of miRNA expression in the osteogenic differentiation of mesenchymal stem cells from the dental pulp (DPSC) and bone marrow (BMSC) were searched in the Gene Expression Omnibus (GEO) database. The differential expression analysis was performed to identify differentially expressed miRNAs (DEmiRNAs) dysregulated in DPSC and BMSC osteodifferentiation. The target genes of the DEmiRNAs that were dysregulated in DPSC and BMSC osteodifferentiation were identified, followed by the identification of the signaling pathways and biological processes (BPs) of these target genes. Accordingly, the DEmiRNA-transcription factor (TFs) network and the DEmiRNAs-small molecular drug network involved in the DPSC and BMSC osteodifferentiation were constructed.

RESULTS

16 dysregulated DEmiRNAs were found to be overlapped in the DPSC and BMSC osteodifferentiation, including 8 DEmiRNAs with a common expression pattern (8 upregulated DEmiRNAs (miR-101-3p, miR-143-3p, miR-145-3p/5p, miR-19a-3p, miR-34c-5p, miR-3607-3p, miR-378e, miR-671-3p, and miR-671-5p) and 1 downregulated DEmiRNA (miR-671-3p/5p)), as well as 8 DEmiRNAs with a different expression pattern (i.e., miR-1273g-3p, miR-146a-5p, miR-146b-5p, miR-337-3p, miR-382-3p, miR-4508, miR-4516, and miR-6087). Several signaling pathways (TNF, mTOR, Hippo, neutrophin, and pathways regulating pluripotency of stem cells), transcription factors (RUNX1, FOXA1, HIF1A, and MYC), and small molecule drugs (curcumin, docosahexaenoic acid (DHA), vitamin D3, arsenic trioxide, 5-fluorouracil (5-FU), and naringin) were identified as common regulators of both the DPSC and BMSC osteodifferentiation.

CONCLUSION

Common genetic and epigenetic mechanisms are involved in the osteodifferentiation of DPSCs and BMSCs.

Circular RNA and Messenger RNA Expression Profile and Competing Endogenous RNA Network in Subchondral Bone in Osteonecrosis of the Femoral Head

Osteonecrosis of the femoral head (ONFH) is a common and destructive orthopedic disease, of which the pathogenesis mechanism remains elusive. Limited studies have been conducted to investigate the role of circular RNAs (circRNAs) in subchondral bone in ONFH. This study aimed to profile differential expression of circRNAs and messenger RNAs (mRNAs) in subchondral bone obtained from ONFH patients by next-generation sequencing, and explore the potential regulatory relationship of these molecules in ONFH by bioinformatics analysis. As a result, we detected 74 aberrantly expressed circRNAs and 121 differentially expressed mRNAs. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses indicated several vital biological processes and signaling pathways, which are primarily related to osteogenic capacity influenced by osteoblasts and osteoclasts. Furthermore, attempting construction of protein-protein interaction network with 57 aberrant genes and competing endogenous RNA network with 3 selected circRNAs preliminarily revealed the regulatory roles and the relationships of these molecules in ONFH. In addition, the potential association of circRNAs in our networks with the molecular mechanism of ONFH was validated by real time-quantitative PCR. In conclusion, our findings may promote understanding the mechanism of ONFH, and offer a novel insight into early diagnosis and intervention of ONFH.

miR-221-3p and miR-222-3p downregulation promoted osteogenic differentiation of bone marrow mesenchyme stem cells through IGF-1/ERK pathway under high glucose condition

OBJECTIVE

This study aims to investigate the roles of miR-221-3p and miR-222-3p in the regulation of osteogenic differentiation of bone marrow mesenchyme stem cells (BMSCs) under high glucose condition.

MATERIALS AND METHODS

The expreesions of miR-221-3p, miR-222-3p and insulin-like growth factor 1 (IGF-1) were detected by qRT-PCR. The protein levels of osteoblast-related proteins (Osterix, Runx-2 and Osteopontin) were detected by western blot. Whether miR-221-3p and miR-222-3p can target IGF-1 was assessed by dual luciferase reporter gene assay.

RESULTS

miR-221-3p and miR-222-3p were up-regulated in the mandibles of diabetic rats and BMSCs cultured in high glucose condition. Silencing miR-221-3p or/ and miR-222-3p increased ALP activity and up-regulated osteoblast-related protein levels, and the simultaneous silence the two miRNAs showed stronger effects on ALP activity and osteoblast-related protein levels. Next, we confirmed that miR-221-3p and miR-222-3p both targeted IGF-1 and cooperatively regulated its expression. Besides, miR-221-3p and miR-222-3p regulated ERK activation through IGF-1. Silencing miR-221-3p and miR-222-3p promoted osteogenic differentiation of BMSCs through IGF-1 under high glucose condition.

CONCLUSION

miR-221-3p and miR-222-3p inhibited osteogenic differentiation of BMSCs via IGF-1/ERK pathway under high glucose condition.

Role of YAP/TAZ in Cell Lineage Fate Determination and Related Signaling Pathways

The penultimate effectors of the Hippo signaling pathways YAP and TAZ, are transcriptional co-activator proteins that play key roles in many diverse biological processes, ranging from cell proliferation, tumorigenesis, mechanosensing and cell lineage fate determination, to wound healing and regeneration. In this review, we discuss the regulatory mechanisms by which YAP/TAZ control stem/progenitor cell differentiation into the various major lineages that are of interest to tissue engineering and regenerative medicine applications. Of particular interest is the key role of YAP/TAZ in maintaining the delicate balance between quiescence, self-renewal, proliferation and differentiation of endogenous adult stem cells within various tissues/organs during early development, normal homeostasis and regeneration/healing. Finally, we will consider how increasing knowledge of YAP/TAZ signaling might influence the trajectory of future progress in regenerative medicine.

Polydatin improves osteogenic differentiation of human bone mesenchymal stem cells by stimulating TAZ expression via BMP2-Wnt/β-catenin signaling pathway

OBJECTIVES

Polydatin (PD), extracted from Polygonum cuspidatum, has shown potential therapeutic applications due to its antiosteoporotic and anti-inflammatory activities. Our previous study suggested that PD promotes the osteogenesis of human bone marrow stromal cells (hBMSCs) via the BMP2-Wnt/β-catenin pathway. The aim of our present study was to further explore the role of PD-mediated regulation of Tafazzin (TAZ), a transcriptional coactivator with a PDZ-binding motif, in osteogenesis.

MATERIALS AND METHODS

hBMSCs were isolated and treated with PD at various concentrations. Alizarin red staining and RT-qPCR were performed to identify calcium complex deposition in hBMSCs as well as the expression of specific osteoblast-related markers, respectively, in each group. Next, TAZ-silenced hBMSCs were generated by lentivirus-produced TAZ shRNA. After treatment with PD, the osteogenic abilities of the TAZ-silenced and control hBMSCs were estimated by ALP activity assay, and expression of the TAZ protein was detected by Western blot analysis and immunofluorescence staining. In vitro, an ovariectomized (OVX) mouse model was established and used to evaluate the effect of PD on bone destruction by micro-CT, immunohistochemistry, and ELISA.

RESULTS

In vitro, 30 μM PD significantly improved the proliferation and calcium deposition of hBMSCs and markedly stimulated the expression of the mRNAs RUNX2, Osteopontin, DLX5, β-catenin, TAZ, and Osteocalcin (OCN). Osteogenic differentiation induced by PD was blocked by lentivirus-mediated TAZ shRNA. Furthermore, Noggin (a regulator of bone morphogenic protein 2 (BMP2)) and DKK1 (an inhibitor of the Wnt/β-catenin pathway) were found to inhibit the increase in TAZ expression induced by PD. In vivo, PD prevented estrogen deficiency-induced bone loss in the OVX mouse model.

CONCLUSION

Taken together, our findings suggest that PD improved the osteogenic differentiation of hBMSCs and maintained the bone matrix in the OVX mouse model through the activation of TAZ, a potential target gene of the BMP2-Wnt/β-catenin pathway.

MiR-33a Controls hMSCS Osteoblast Commitment Modulating the Yap/Taz Expression Through EGFR Signaling Regulation

Mesenchymal stromal cells (hMSCs) display a pleiotropic function in bone regeneration. The signaling involved in osteoblast commitment is still not completely understood, and that determines the failure of current therapies being used. In our recent studies, we identified two miRNAs as regulators of hMSCs osteoblast differentiation driving hypoxia signaling and cytoskeletal reorganization. Other signalings involved in this process are epithelial to mesenchymal transition (EMT) and epidermal growth factor receptor (EGFR) signalings through the regulation of Yes-associated protein (YAP)/PDZ-binding motif (TAZ) expression. In the current study, we investigated the role of miR-33a family as a (i) modulator of YAP/TAZ expression and (ii) a regulator of EGFR signaling during osteoblast commitments. Starting from the observation on hMSCs and primary osteoblast cell lines (Nh-Ost) in which EMT genes and miR-33a displayed a specific expression, we performed a gain and loss of function study with miR-33a-5p and 3p on hMSCs cells and Nh-Ost. After 24 h of transfections, we evaluated the modulation of EMT and osteoblast genes expression by qRT-PCR, Western blot, and Osteoimage assays. Through bioinformatic analysis, we identified YAP as the putative target of miR-33a-3p. Its role was investigated by gain and loss of function studies with miR-33a-3p on hMSCs; qRT-PCR and Western blot analyses were also carried out. Finally, the possible role of EGFR signaling in YAP/TAZ modulation by miR-33a-3p expression was evaluated. Human MSCs were treated with EGF-2 and EGFR inhibitor for different time points, and qRT-PCR and Western blot analyses were performed. The above-mentioned methods revealed a balance between miR-33a-5p and miR-33a-3p expression during hMSCs osteoblast differentiation. The human MSCs phenotype was maintained by miR-33a-5p, while the maintenance of the osteoblast phenotype in the Nh-Ost cell model was permitted by miR-33a-3p expression, which regulated YAP/TAZ through the modulation of EGFR signaling. The inhibition of EGFR blocked the effects of miR-33a-3p on YAP/TAZ modulation, favoring the maintenance of hMSCs in a committed phenotype. A new possible personalized therapeutic approach to bone regeneration was discussed, which might be mediated by customizing delivery of miR-33a in simultaneously targeting EGFR and YAP signaling with combined use of drugs.

Calvarial osteoblast gene expression in patients with craniosynostosis leads to novel polygenic mouse model

Craniosynostosis is the premature fusion of the sutures of the calvaria and is principally designated as being either syndromic (demonstrating characteristic extracranial malformations) or non-syndromic. While many forms of syndromic craniosynostosis are known to be caused by specific mutations, the genetic etiology of non-syndromic, single-suture craniosynostosis (SSC) is poorly understood. Based on the low recurrence rate (4-7%) and the fact that recurrent mutations have not been identified for most cases of SSC, we propose that some cases of isolated, single suture craniosynostosis may be polygenic. Previous work in our lab identified a disproportionately high number of rare and novel gain-of-function IGF1R variants in patients with SSC as compared to controls. Building upon this result, we used expression array data from calvarial osteoblasts isolated from infants with and without SSC to ascertain correlations between high IGF1 expression and expression of other osteogenic genes of interest. We identified a positive correlation between increased expression of IGF1 and RUNX2, a gene known to cause SSC with increased gene dosage. Subsequent phosphorylation assays revealed that osteoblast cell lines from cases with high IGF1 expression demonstrated inhibition of GSK3β, a serine/threonine kinase known to inhibit RUNX2, thus activating osteogenesis through the IRS1-mediated Akt pathway. With these findings, we have utilized established mouse strains to examine a novel model of polygenic inheritance (a phenotype influenced by more than one gene) of SSC. Compound heterozygous mice with selective disinhibition of RUNX2 and either overexpression of IGF1 or loss of function of GSK3β demonstrated an increase in the frequency and severity of synostosis as compared to mice with the RUNX2 disinhibition alone. These polygenic mouse models reinforce, in-vivo, that the combination of activation of the IGF1 pathway and disinhibition of the RUNX2 pathway leads to an increased risk of developing craniosynostosis and serves as a model of human SSC.

Rehmannia glutinosa Libosch Extracts Prevent Bone Loss and Architectural Deterioration and Enhance Osteoblastic Bone Formation by Regulating the IGF-1/PI3K/mTOR Pathway in Streptozotocin-Induced Diabetic Rats

Rehmanniae Radix Praeparata (RR, named as Shudihuang in traditional Chinese medicine), the steamed roots of Rehmannia glutinosa Libosch (Scrophulariaceae), has been demonstrated to have anti-diabetic and anti-osteoporotic activities. This study aimed to explore the protective effect and underlying mechanism of RR on diabetes-induced bone loss. It was found that RR regulated the alkaline phosphatase activity and osteocalcin level, enhanced bone mineral density, and improved the bone microarchitecture in diabetic rats. The catalpol (CAT), acteoside (ACT), and echinacoside (ECH) from RR increased the proliferation and differentiation of osteoblastic MC3T3-E1 cells injured by high glucose and promoted the production of IGF-1 and expression of related proteins in BMP and IGF-1/PI3K/mammalian target of rapamycin complex 1 (mTOR) signaling pathways. The verifying tests of inhibitors of BMP pathway (noggin) and IGF-1/PI3K/mTOR pathway (picropodophyllin) and molecular docking of IGF-1R further indicated that CAT, ACT, and ECH extracted from RR enhanced bone formation by regulating IGF-1/PI3K/mTOR signaling pathways. These findings suggest that RR may prove to be a promising candidate drug for the prevention and treatment of diabetes-induced osteoporosis.

Mechanism of Action of Icariin in Bone Marrow Mesenchymal Stem Cells

Osteoporosis, femoral head necrosis, and congenital bone defects are orthopedic disorders characterized by reduced bone generation and insufficient bone mass. Bone regenerative therapy primarily relies on the bone marrow mesenchymal stem cells (BMSCs) and their ability to differentiate osteogenically. Icariin (ICA) is the active ingredient of Herba epimedii, a common herb used in traditional Chinese medicine (TCM) formulations, and can effectively enhance BMSC proliferation and osteogenesis. However, the underlying mechanism of ICA action in BMSCs is not completely clear. In this review, we provide an overview of the studies on the role and mechanism of action of ICA in BMSCs, to provide greater insights into its potential clinical use in bone regeneration.

Sal B targets TAZ to facilitate osteogenesis and reduce adipogenesis through MEK-ERK pathway

Salvianolic acid B (Sal B), a major bioactive component of Chinese herb, was identified as a mediator for bone metabolism recently. The aim of this study is to investigate the underlying mechanisms by which Sal B regulates osteogenesis and adipogenesis. We used MC3T3-E1 and 3T3-L1 as the study model to explore the changes of cell differentiation induced by Sal B. The results indicated that Sal B at different concentrations had no obvious toxicity effects on cell proliferation during differentiation. Furthermore, Sal B facilitated osteogenesis but inhibited adipogenesis by increasing the expression of transcriptional co-activator with PDZ-binding motif (TAZ). Accordingly, TAZ knock-down offset the effects of Sal B on cell differentiation into osteoblasts or adipocytes. Notably, the Sal B induced up-expression of TAZ was blocked by U0126 (the MEK-ERK inhibitor), rather than LY294002 (the PI3K-Akt inhibitor). Moreover, Sal B increased the p-ERK/ERK ratio to regulate the TAZ expression as well as the cell differentiation. In summary, this study suggests for the first time that Sal B targets TAZ to facilitate osteogenesis and reduce adipogenesis by activating MEK-ERK signalling pathway, which provides evidence for Sal B to be used as a potential therapeutic agent for the management of bone diseases.

High-fat and high-glucose microenvironment decreases Runx2 and TAZ expression and inhibits bone regeneration in the mouse

BACKGROUND

Type 2 diabetes mellitus (T2DM) and hyperlipidemia are negatively related to bone regeneration. The aim of this study was to evaluate the effect of high-fat and high-glucose microenvironment on bone regeneration and to detect the expression of runt-related transcription factor 2 (Runx2) and transcriptional co-activator with PDZ-binding domain (TAZ) during this process.

METHODS

After establishing a high-fat and high-glucose mouse model, a 1 mm × 1.5 mm bone defect was developed in the mandible. On days 7, 14, and 28 after operation, bone regeneration was evaluated by hematoxylin-eosin staining, Masson staining, TRAP staining, and immunohistochemistry, while Runx2 and TAZ expression were detected by immunohistochemistry, RT-PCR, and Western blot analysis.

RESULTS

Our results showed that the inhibition of bone regeneration in high-fat and high-glucose group was the highest among the four groups. In addition, the expression of Runx2 in high-fat, high-glucose, and high-fat and high-glucose groups was weaker than that in the control group, but the expression of TAZ only showed a decreasing trend in the high-fat and high-glucose group during bone regeneration.

CONCLUSIONS

In conclusion, these results suggest that high-fat and high-glucose microenvironment inhibits bone regeneration, which may be related to the inhibition of Runx2 and TAZ expression.

IRS-1 targets TAZ to inhibit adipogenesis of rat bone marrow mesenchymal stem cells through PI3K-Akt and MEK-ERK pathways

Gene modification of mesenchymal stem cells (MSCs) offers a promising approach for clinical stem cell therapy. Transcriptional co-activator with PDZ-binding motif (TAZ) plays a vital role in MSCs' differentiation. We aim to explore the interaction of insulin receptor substrate-1 (IRS-1) with TAZ to regulate MSCs' adipogenesis in this study. Initially, IRS-1 and TAZ followed similar decreasing expression pattern at the early stage of adipogenesis. And, overexpression of IRS-1 decreased the CCAAT/enhancer binding protein β (C/EBPβ) and peroxi-some proliferator-activated receptor gamma (PPARγ) expression with TAZ upregulation. Accordingly, knockdown of IRS-1 induced the upexpression of C/EBPβ and PPARγ with TAZ downregulation. Indeed, IRS-1 targeted TAZ to downregulate the C/EBPβ and PPARγ expression, while knockdown of TAZ attenuated the IRS-1 inhibited adipogenesis. Furthermore, both LY294002 (the PI3K-Akt inhibitor) and U0126 (the MEK-ERK inhibitor) blocked the regulation of IRS-1 on TAZ during adipogenesis. Additionally, IRS-1 and TAZ influenced the cell proliferation in the above process. Taken together, this study suggests for the first time that IRS-1 is a key regulator of the MSCs' adipogenesis and may serve as a potential therapeutic target for differential alterations in bone marrow.

IRS-1 increases TAZ expression and promotes osteogenic differentiation in rat bone marrow mesenchymal stem cells

Whether insulin receptor substrate 1 (IRS-1) inhibits or promotes the osteogenic proliferation and differentiation in vitro remains controversial. Transcriptional co-activator with PDZ-binding motif (TAZ) plays a vital role in the osteogenesis of bone marrow mesenchymal stem cells (BMSCs), and strongly activates the expression of the osteogenic differentiation markers. In this study, we found that IRS-1 and TAZ followed similar increasing expression patterns at the early stage of osteogenic differentiation. Knocking down IRS-1 decreased the TAZ, RUNX2 and OCN expression, and overexpressing IRS induced the upregulation of the TAZ, RUNX2 and OCN expression. Furthermore, our results showed that it was LY294002 (the PI3K-Akt inhibitor), other than UO126 (the MEK-ERK inhibitor), that inhibited the IRS-1 induced upregulation of TAZ expression. Additionally, SiTAZ blocked the cell proliferation in G1 during the osteogenic differentiation of BMSCs. Taken together, we provided evidence to demonstrate that IRS-1 gene modification facilitates the osteogenic differentiation of rat BMSCs by increasing TAZ expression through the PI3K-Akt signaling pathway.This article has an associated First Person interview with the first author of the paper.

Lipopolysaccharide from Escherichia coli stimulates osteogenic differentiation of human periodontal ligament stem cells through Wnt/β-catenin-induced TAZ elevation

Human periodontal ligament stem cells (PDLSCs), a type of dental tissue-derived mesenchymal stem cells (MSCs), can be clinically applied in periodontal tissue regeneration to treat periodontitis, which is initiated and sustained by bacteria. Lipopolysaccharide (LPS), the major component of the outer membrane of gram-negative bacteria, is a pertinent deleterious factor in the oral microenvironment. The aim of this study was to investigate the effect of LPS on the proliferation and osteogenic differentiation of PDLSCs, as well as the mechanisms involved. Proliferation and osteogenic differentiation of PDLSCs were detected under the stimulation of Escherichia coli-derived LPS. The data showed that E. coli-derived LPS did not affect the proliferation, viability, and cell cycle of PDLSCs. Furthermore, it promoted osteogenic differentiation with the activation of TAZ. Lentivirus-mediated depletion of TAZ (transcriptional activator with a PDZ motif) was used to determine the role of TAZ on LPS-induced enhancement of osteogenesis. PDLSCs cultured in osteogenic media with or without LPS and DKK1 (Wnt/β-catenin pathway inhibitor) were used to determine the regulatory effect of Wnt signaling. We found that TAZ depletion offset LPS-induced enhancement of osteogenesis. Moreover, treatment with DKK1 offset LPS-induced TAZ elevation and osteogenic promotion. In conclusion, E. coli-derived LPS promoted osteogenic differentiation of PDLSCs by fortifying TAZ activity. The elevation and activation of TAZ were mostly mediated by the Wnt/β-catenin pathway. PDLSC-governed alveolar bone tissue regeneration was not necessarily reduced under bacterial conditions and could be modulated by Wnt and TAZ.

Direct phenotypic conversion of human fibroblasts into functional osteoblasts triggered by a blockade of the transforming growth factor-β signal

A procedure to generate functional osteoblasts from human somatic cells may pave the way to a novel and effective transplantation therapy in bone disorders. Here, we report that human fibroblasts were induced to show osteoblast phenotypes by culturing with ALK5 i II, which is a specific inhibitor for activin-like kinase 5 (ALK5) (tumor growth factor-β receptor 1 (TGF-β R1)). Cells cultured with ALK5 i II expressed osteoblast-specific genes and massively produced calcified bone matrix, similar to the osteoblasts induced from mesenchymal stem cells (MSC-OBs). Treatment with vitamin D3 in addition to ALK5 i II induced more osteoblast-like characters, and the efficiency of the conversion reached approximately 90%. The chemical compound-mediated directly converted osteoblasts (cOBs) were similar to human primary osteoblasts in terms of expression profiles of osteoblast-related genes. The cOBs abundantly produced bone matrix in vivo and facilitated bone healing after they were transplanted into immunodeficient mice at an artificially induced defect lesion in femoral bone. The present procedure realizes a highly efficient direct conversion of human fibroblasts into transgene-free and highly functional osteoblasts, which might be applied in a novel strategy of bone regeneration therapy in bone diseases.

Osseointegration of layer-by-layer polyelectrolyte multilayers loaded with IGF1 and coated on titanium implant under osteoporotic condition

Purpose

Titanium implant is a widely used method for dental prosthesis restoration. Nevertheless, in patients with systemic diseases, including osteoporosis, diabetes, and cancer, the success rate of the implant is greatly reduced. This study investigates a new implant material loaded with insulin-like growth factor 1 (IGF1), which could potentially improve the implant success rate, accelerate the occurrence of osseointegration, and provide a new strategy for implant treatment in osteoporotic patients.

Materials and methods

Biofunctionalized polyelectrolyte multilayers (PEMs) with polyethylenimine as the excitation layer and gelatin/chitosan loaded with IGF1 were prepared on the surface of titanium implant by layer-by-layer self-assembly technique. The physical and chemical properties of the biofunctionalized PEMs, the biological characteristics of bone marrow mesenchymal stem cells (BMMSCs), and bone implant contact correlation test indexes were detected and analyzed in vitro and in vivo using osteoporosis rat model.

Results

PEMs coatings loaded with IGF1 (TNS-PEM-IGF1-100) implant promoted the early stage of BMMSCs adhesion. Under the action of body fluids, the active coating showed sustained release of growth factors, which in turn promoted the proliferation and differentiation of BMMSCs and the extracellular matrix. At 8 weeks from implant surgery, the new bone around the implants was examined using micro-CT and acid fuchsin/methylene blue staining. The new bone formation increased with time in each group, while the TNS-PEM-IGF1-100 group showed the highest thickness and continuity.

Conclusion

TNS-PEM-IGF1-100 new implants can promote osseointegration in osteoporotic conditions both in vivo and in vitro and provide a new strategy for implant repair in osteoporotic patients.

New pathway of icariin-induced MSC osteogenesis: transcriptional activation of TAZ/Runx2 by PI3K/Akt

Icariin has been demonstrated to stimulate mesenchymal stem cell (MSC) osteogensis and activate several signals, such as PI3K/Akt, but how the osteogenesis was sequentially mediated is unclear. Runx2 is one of the osteogenic regulators in MSC and is regulated by the TAZ gene. The purpose of this study was to investigate whether icariin-activated PI3K/Akt crosstalked with the TAZ-Runx2 pathway to regulate MSC osteogenesis. Adipose-derived MSCs were treated with icariin alone, together with TAZ silencing or PI3K/Akt inhibitor. Normal MSCs were used as a control. The activation of PI3K/Akt, expression of TAZ and downstream expression of Runx2 were analyzed. Induction of MSC osteogenesis under different treatments was detected. The results demonstrated that icariin treatment significantly activated PI3K/Akt and TAZ expression, as well as the downstream Runx2 expression. When activation of PI3K/Akt by icariin was inhibited by LY294002, upregulated TAZ expression was reversed, as well as the downstream expression of Runx2. Consequently, with the osteogenic counteracting effects of icariin on MSCs, inhibition of TAZ upregulation by siRNA did not significantly influence PI3K/ Akt activation in icariin-treated MSCs, but icariin-induced upregulation of Runx2 and osteogenic differentiation in MSCs was counteracted. It could be concluded from these findings that icariin treatment activated PI3K/Akt and further mediated the transcriptional activation of the TAZ/Runx2 pathway to induce osteogenic differentiation of MSCs.

Liraglutide, a glucagon-like peptide-1 receptor agonist, facilitates osteogenic proliferation and differentiation in MC3T3-E1 cells through phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT), extracellular signal-related kinase (ERK)1/2, and cAMP/protein kinase A (PKA) signaling pathways involving β-catenin

Previous studies have proven that glucagon-like peptide-1 (GLP-1) and its receptor agonist exert favorable anabolic effects on skeletal metabolism. However, whether GLP-1 could directly impact osteoblast-mediated bone formation is still controversial, and the underlying molecular mechanism remains to be elucidated. Thus in this paper, we investigated the effects of liraglutide, a glucagon-like peptide-1 (GLP-1) receptor agonist, on murine MC3T3-E1 preosteoblasts proliferation and differentiation and explored the potential cellular basis. Our study confirmed the presence of GLP-1R in MC3T3-E1, and demonstrated that liraglutide promotes osteoblasts proliferation at an intermediate concentration (100nM) and time (48h), upregulated the expression of osteoblastogenic biomarkers at various stages, and stimulated osteoblastic mineralization. Liraglutide also elevated the intracellular cAMP level and phosphorylation of AKT, ERK and β-catenin simultaneously with increased nuclear β-catenin content and transcriptional activity. Pretreatment of cells with the inhibitors LY294002, PD98059, H89 and GLP-1R and β-catenin siRNA partially blocked the liraglutide-induced signaling activation and attenuated the facilitating effect of liraglutide on MC3T3-E1 cells. Collectively, liraglutide was capable of acting upon osteoblasts directly through GLP-1R by activating PI3K/AKT, ERK1/2, cAMP/PKA/β-cat-Ser675 signaling to promote bone formation via GLP-1R. Thus, GLP-1 analogues may be potential therapeutic strategy for the treatment of osteoporosis in diabetics.

TGF-β1 regulates the expression and transcriptional activity of TAZ protein via a Smad3-independent, myocardin-related transcription factor-mediated mechanism

Hippo pathway transcriptional coactivators TAZ and YAP and the TGF-β1 (TGFβ) effector Smad3 regulate a common set of genes, can physically interact, and exhibit multilevel cross-talk regulating cell fate-determining and fibrogenic pathways. However, a key aspect of this cross-talk, TGFβ-mediated regulation of TAZ or YAP expression, remains uncharacterized. Here, we show that TGFβ induces robust TAZ but not YAP protein expression in both mesenchymal and epithelial cells. TAZ levels, and to a lesser extent YAP levels, also increased during experimental kidney fibrosis. Pharmacological or genetic inhibition of Smad3 did not prevent the TGFβ-induced TAZ up-regulation, indicating that this canonical pathway is dispensable. In contrast, inhibition of p38 MAPK, its downstream effector MK2 (e.g. by the clinically approved antifibrotic pirferidone), or Akt suppressed the TGFβ-induced TAZ expression. Moreover, TGFβ elevated TAZ mRNA in a p38-dependent manner. Myocardin-related transcription factor (MRTF) was a central mediator of this effect, as MRTF silencing/inhibition abolished the TGFβ-induced TAZ expression. MRTF overexpression drove the TAZ promoter in a CC(A/T-rich)₆GG (CArG) box-dependent manner and induced TAZ protein expression. TGFβ did not act by promoting nuclear MRTF translocation; instead, it triggered p38- and MK2-mediated, Nox4-promoted MRTF phosphorylation and activation. Functionally, higher TAZ levels increased TAZ/TEAD-dependent transcription and primed cells for enhanced TAZ activity upon a second stimulus (i.e. sphingosine 1-phosphate) that induced nuclear TAZ translocation. In conclusion, our results uncover an important aspect of the cross-talk between TGFβ and Hippo signaling, showing that TGFβ induces TAZ via a Smad3-independent, p38- and MRTF-mediated and yet MRTF translocation-independent mechanism.

Effects of TAZ on human dental pulp stem cell proliferation and migration

Transcriptional coactivator with PDZ‑binding motif (TAZ) acts as the key downstream regulatory target in the Hippo signaling pathway. TAZ overexpression has been reported to promote cellular proliferation and induce epithelial‑mesenchymal transition in human mammary epithelial cells. However, the effects of TAZ in the regulation of human dental pulp stem cell (hDPSC) proliferation and migration, as well as the molecular mechanisms underlying its actions, remain to be elucidated. The present study demonstrated that TAZ was expressed in hDPSCs. TAZ silencing, following hDPSC transfection with TAZ‑specific small interfering (si)RNA (siTAZ), inhibited cellular proliferation and migration in vitro. These effects appeared to be associated with the downregulation of connecting tissue growth factor (CTGF) and cysteine‑rich angiogenic inducer (Cyr) 61 expression. Further investigation of the mechanisms underlying the actions of TAZ in hDPSCs revealed that TAZ silencing suppressed CTGF and Cyr61 expression by interfering with transforming growth factor (TGF)‑β signaling pathways. The present results suggested that TAZ may be implicated in the proliferation and migration of hDPSCs, through the modulation of CTGF and Cyr61 expression via a TGF‑β‑dependent signaling pathway.

ETS (E26 transformation-specific) up-regulation of the transcriptional co-activator TAZ promotes cell migration and metastasis in prostate cancer

Prostate cancer is a very common malignant disease and a leading cause of death for men in the Western world. Tumorigenesis and progression of prostate cancer involves multiple signaling pathways, including the Hippo pathway. Yes-associated protein (YAP) is the downstream transcriptional co-activator of the Hippo pathway, is overexpressed in prostate cancer, and plays a vital role in the tumorigenesis and progression of prostate cancer. However, the role of the YAP paralog and another downstream effector of the Hippo pathway, transcriptional co-activator with PDZ-binding motif (TAZ), in prostate cancer has not been fully elucidated. Here, we show that TAZ is a basal cell marker for the prostate epithelium. We found that overexpression of TAZ promotes the epithelial-mesenchymal transition (EMT), cell migration, and anchorage-independent growth in the RWPE1 prostate epithelial cells. Of note, knock down of TAZ in the DU145 prostate cancer cells inhibited cell migration and metastasis. We also found that SH3 domain binding protein 1 (SH3BP1), a RhoGAP protein that drives cell motility, is a direct target gene of TAZ in the prostate cancer cells, mediating TAZ function in enhancing cell migration. Moreover, the prostate cancer-related oncogenic E26 transformation-specific (ETS) transcription factors, ETV1, ETV4, and ETV5, were required for TAZ gene transcription in PC3 prostate cancer cells. MAPK inhibitor U0126 treatment decreased TAZ expression in RWPE1 cells, and ETV4 overexpression rescued TAZ expression in RWPE1 cells with U0126 treatment. Our results show a regulatory mechanism of TAZ transcription and suggest a significant role for TAZ in the progression of prostate cancer.

miR-1827 inhibits osteogenic differentiation by targeting IGF1 in MSMSCs

We recently reported that maxillary sinus membrane stem cells (MSMSCs) have osteogenic potential. However, the biological mechanisms of bone formation remain unclear. In this study, we investigated the role and mechanisms of microRNAs (miRNAs) in the osteogenic differentiation of MSMSCs. The expression of miRNAs was determined in differentiated MSMSCs by comprehensive miRNA microarray analysis and quantitative RT-PCR (qRT-PCR). We selected miR-1827 for functional follow-up studies to explore its significance in MSMSCs. Here, miR-1827 was found to be up-regulated during osteogenic differentiation of MSMSCs. Over expression of miR-1827 inhibited osteogenic differentiation of MSMSCs in vitro, whereas the repression of miR-1827 greatly promoted cell differentiation. Further experiments confirmed that insulin-like growth factor 1 (IGF1) is a direct target of miR-1827. miR-1827 inhibited osteogenic differentiation partially via IGF1, which in turn is a positive regulator of osteogenic differentiation. Moreover, miR-1827 suppressed ectopic bone formation and silencing of miR-1827 led to increased bone formation in vivo. In summary, this study is the first to demonstrate that miR-1827 can regulate osteogenic differentiation. The increase in miR-1827 expression observed during osteogenesis is likely a negative feedback mechanism, thus offering a potential therapeutic target to address inadequate bone volume for dental implantation through inhibiting miR-1827.

Insulin-like growth factor-1 (IGF-1) enhances the osteogenic activity of bone morphogenetic protein-6 (BMP-6) in vitro and in vivo, and together have a stronger osteogenic effect than when IGF-1 is combined with BMP-2

Bone morphogenetic protein-2 (BMP-2) is widely used in orthopedic surgery and bone tissue engineering because of its strong osteogenic activity. However, BMP-2 treatments have several drawbacks and many groups are actively exploring alternatives. Since BMP-6 has been demonstrated to be more osteoinductive, its use, either alone or together with other growth factors, might be an interesting option. In this work, we have compared the effect of BMP-2, BMP-6, or insulin-like growth factor-1 (IGF-1), either alone or in combination. Murine preosteoblasts were treated with 15 nM IGF-1 and/or 6 nM BMP-2 or -6 and the expression of osteogenic marker genes, proliferation, and alkaline phosphatase (ALP) activity in vitro were analyzed. The results showed that IGF-1 greatly enhanced the BMP-induced osteogenic differentiation of these cells in general and that the ALP activity in the cultures was higher when the combination was made with BMP-6 than with BMP-2. Furthermore, we tested the osteogenic potential of these treatments in vivo by loading 25 pmoles of IGF-1 and/or 10 pmoles of BMP-2 or -6 onto absorbable collagen sponges and implanting them into an ectopic bone formation model in rats. This study revealed that only BMP-6 was able to induce bone formation at the used dose and that the addition of IGF-1 contributed to an increase of the mineralization in the implants. Hence, the combination of BMP-6 with IGF-1 might be a better alternative than BMP-2 for orthopedic surgery or bone tissue engineering approaches. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1867-1875, 2017.

IGFBP-2 and -3 co-ordinately regulate IGF1 induced matrix mineralisation of differentiating human dental pulp cells

Human dental pulp cells (DPCs), which are known to contain a subset of stem cells capable of reforming a dentin and pulp-like complex upon in vivo transplantation, were isolated from third molars of three healthy donors and differentiated to a matrix mineralisation phenotype using by culture in dexamethasone and l-ascorbic acid. qRT-PCR analysis of insulin-like growth factor ( IGF) axis gene expression indicated that all genes, except insulin-like growth factor 1 (IGF1) and insulin-like growth factor binding protein-1 ( IGFBP-1), were expressed in DPCs. During differentiation upregulation of insulin-like growth factor binding protein-2 (IGFBP-2) and downregulation of insulin-like growth factor binding protein-3 (IGFBP-3) expression was observed. Changes in IGFBP-2 and IGFBP-3 mRNA expression were confirmed at the protein level by ELISA of DPC conditioned medium functional analysis indicated that IGF1 stimulated the differentiation of DPCs and that the activity of the growth factor was enhanced by pre-complexation with IGFBP-2 but inhibited by pre-complexation with IGFBP-3. Therefore changes in IGFBP-2 and -3 expression during differentiation form part of a co-ordinated functional response to enhance the pro-differentiative action of IGF1 and represent a novel mechanism for the regulation of DPC differentiation.

Design of Decorated Self-Assembling Peptide Hydrogels as Architecture for Mesenchymal Stem Cells

Hydrogels from self-assembling ionic complementary peptides have been receiving a lot of interest from the scientific community as mimetic of the extracellular matrix that can offer three-dimensional supports for cell growth or can become vehicles for the delivery of stem cells, drugs or bioactive proteins. In order to develop a 3D “architecture” for mesenchymal stem cells, we propose the introduction in the hydrogel of conjugates obtained by chemoselective ligation between a ionic-complementary self-assembling peptide (called EAK) and three different bioactive molecules: an adhesive sequence with 4 Glycine-Arginine-Glycine-Aspartic Acid-Serine-Proline (GRGDSP) motifs per chain, an adhesive peptide mapped on h-Vitronectin and the growth factor Insulin-like Growth Factor-1 (IGF-1). The mesenchymal stem cell adhesion assays showed a significant increase in adhesion and proliferation for the hydrogels decorated with each of the synthesized conjugates; moreover, such functionalized 3D hydrogels support cell spreading and elongation, validating the use of this class of self-assembly peptides-based material as very promising 3D model scaffolds for cell cultures, at variance of the less realistic 2D ones. Furthermore, small amplitude oscillatory shear tests showed that the presence of IGF-1-conjugate did not alter significantly the viscoelastic properties of the hydrogels even though differences were observed in the nanoscale structure of the scaffolds obtained by changing their composition, ranging from long, well-defined fibers for conjugates with adhesion sequences to the compact and dense film for the IGF-1-conjugate.

Inhibiting PPARγ by erythropoietin while upregulating TAZ by IGF1 synergistically promote osteogenic differentiation of mesenchymal stem cells

Erythropoietin (EPO) is reported to promote osteogenesis and inhibit adipogenesis of mesenchymal stem cells (MSC) through inhibiting PPARγ, while insulin-like growth factor 1 (IGF1) is able to enhance osteogenesis via upregulating transcriptional coactivator with PDZ-binding motif (TAZ). The different targets of EPO and IGF1 suggested their potential synergism to enhance osteogenesis. In this study, we aimed to determine the potential synergism of EPO and IGF1 and its efficacy on MSC differentiation. Rat adipose-derived mesenchymal stem cells (ADSCs) were separately treated with EPO, IGF1 and EPO/IGF1. It was observed that the co-treatment using EPO and IGF1 was able to potently promote the osteogenic differentiation of rat ADSCs compared with EPO or IGF1 alone, which offered a promising effective option to strengthen bone tissue regeneration for bone defects. Further, we demonstrated that the enhanced osteogenic differentiation by EPO and IGF1 co-treatment was almost counteracted by activating PPARγ through PPARγ agonist, RSG, and blocking TAZ through TAZ silencing RNA, siTAZ. Thus, it could be concluded that EPO and IGF1 possessed a potent synergism in promoting osteogenic differentiation, and the synergism was mainly attributed to co-regulation of different osteogenic regulators PPARγ and TAZ, which were targeted genes of EPO and IGF1 respectively.

Enoxaparin and rivaroxaban have different effects on human mesenchymal stromal cells in the early stages of bone healing

Objectives

Venous thromboembolism (VTE) is a major potential complication following orthopaedic surgery. Subcutaneously administered enoxaparin has been used as the benchmark to reduce the incidence of VTE. However, concerns have been raised regarding the long-term administration of enoxaparin and its possible negative effects on bone healing and bone density with an increase of the risk of osteoporotic fractures. New oral anticoagulants such as rivaroxaban have recently been introduced, however, there is a lack of information regarding how these drugs affect bone metabolism and post-operative bone healing.

Methods

We measured the migration and proliferation capacity of mesenchymal stem cells (MSCs) under enoxaparin or rivaroxaban treatment for three consecutive weeks, and evaluated effects on MSC mRNA expression of markers for stress and osteogenic differentiation.

Results

We demonstrate that enoxaparin, but not rivaroxaban, increases the migration potential of MSCs and increases their cell count in line with elevated mRNA expression of C-X-C chemokine receptor type 4 (CXCR4), tumor necrosis factor alpha (TNFα), and alpha-B-crystallin (CryaB). However, a decrease in early osteogenic markers (insulin-like growth factors 1 and 2 (IGF1, IGF2), bone morphogenetic protein2 (BMP2)) indicated inhibitory effects on MSC differentiation into osteoblasts caused by enoxaparin, but not by rivaroxaban.

Conclusions

Our findings may explain the adverse effects of enoxaparin treatment on bone healing. Rivaroxaban has no significant impact on MSC metabolism or capacity for osteogenic differentiation in vitro.

Cite this article: Dr H. Pilge. Enoxaparin and rivaroxaban have different effects on human mesenchymal stromal cells in the early stages of bone healing. Bone Joint Res 2016;5:95–100. DOI: 10.1302/2046-3758.53.2000595.

TWIST1 silencing enhances in vitro and in vivo osteogenic differentiation of human adipose-derived stem cells by triggering activation of BMP-ERK/FGF signaling and TAZ upregulation

Mesenchymal stem cells (MSCs) show promise for cellular therapy and regenerative medicine. Human adipose tissue-derived stem cells (hASCs) represent an attractive source of seed cells in bone regeneration. How to effectively improve osteogenic differentiation of hASCs in the bone tissue engineering has become a very important question with profound translational implications. Numerous regulatory pathways dominate osteogenic differentiation of hASCs involving transcriptional factors and signaling molecules. However, how these factors combine with each other to regulate hASCs osteogenic differentiation still remains to be illustrated. The highly conserved developmental proteins TWIST play key roles for transcriptional regulation in mesenchymal cell lineages. This study investigates TWIST1 function in hASCs osteogenesis. Our results show that TWIST1 shRNA silencing increased the osteogenic potential of hASCs in vitro and their skeletal regenerative ability when applied in vivo. We demonstrate that the increased osteogenic capacity observed with TWIST1 knockdown in hASCs is mediated through endogenous activation of BMP and ERK/FGF signaling leading, in turn, to upregulation of TAZ, a transcriptional modulator of MSCs differentiation along the osteoblast lineage. Inhibition either of BMP or ERK/FGF signaling suppressed TAZ upregulation and the enhanced osteogenesis in shTWIST1 hASCs. Cosilencing of both TWIST1 and TAZ abrogated the effect elicited by TWIST1 knockdown thus, identifying TAZ as a downstream mediator through which TWIST1 knockdown enhanced osteogenic differentiation in hASCs. Our functional study contributes to a better knowledge of molecular mechanisms governing the osteogenic ability of hASCs, and highlights TWIST1 as a potential target to facilitate in vivo bone healing.

Telomerase activity promotes osteoblast differentiation by modulating IGF-signaling pathway

The contribution of deficient telomerase activity to age-related decline in osteoblast functions and bone formation is poorly studied. We have previously demonstrated that telomerase over-expression led to enhanced osteoblast differentiation of human bone marrow skeletal (stromal) stem cells (hMSC) in vitro and in vivo. Here, we investigated the signaling pathways underlying the regulatory functions of telomerase in osteoblastic cells. Comparative microarray analysis and Western blot analysis of telomerase-over expressing hMSC (hMSC-TERT) versus primary hMSC revealed significant up-regulation of several components of insulin-like growth factor (IGF) signaling. Specifically, a significant increase in IGF-induced AKT phosphorylation and alkaline phosphatase (ALP) activity were observed in hMSC-TERT. Enhanced ALP activity was reduced in presence of IGF1 receptor inhibitor: picropodophyllin. In addition, telomerase deficiency caused significant reduction in IGF signaling proteins in osteoblastic cells cultured from telomerase deficient mice (Terc(-/-)). The low bone mass exhibited by Terc(-/-) mice was associated with significant reduction in serum levels of IGF1 and IGFBP3 as well as reduced skeletal mRNA expression of Igf1, Igf2, Igf2r, Igfbp5 and Igfbp6. IGF1-induced osteoblast differentiation was also impaired in Terc(-/-) MSC. In conclusion, our data demonstrate that impaired IGF/AKT signaling contributes to the observed decreased bone mass and bone formation exhibited by telomerase deficient osteoblastic cells.

IGF1 Promotes Adipogenesis by a Lineage Bias of Endogenous Adipose Stem/Progenitor Cells

Adipogenesis is essential for soft tissue reconstruction following trauma or tumor resection. We demonstrate that CD31(-)/34(+)/146(-) cells, a subpopulation of the stromal vascular fraction (SVF) of human adipose tissue, were robustly adipogenic. Insulin growth factor-1 (IGF1) promoted a lineage bias towards CD31(-)/34(+)/146(-) cells at the expense of CD31(-)/34(+)/146(+) cells. IGF1 was microencapsulated in poly(lactic-co-glycolic acid) scaffolds and implanted in the inguinal fat pad of C57Bl6 mice. Control-released IGF1 induced remarkable adipogenesis in vivo by recruiting endogenous cells. In comparison with the CD31(-)/34(+)/146(+) cells, CD31(-)/34(+)/146(-) cells had a weaker Wnt/β-catenin signal. IGF1 attenuated Wnt/β-catenin signaling by activating Axin2/PPARγ pathways in SVF cells, suggesting IGF1 promotes CD31(-)/34(+)/146(-) bias through tuning Wnt signal. PPARγ response element (PPRE) in Axin2 promoter was crucial for Axin2 upregulation, suggesting that PPARγ transcriptionally activates Axin2. Together, these findings illustrate an Axin2/PPARγ axis in adipogenesis that is particularly attributable to a lineage bias towards CD31(-)/34(+)/146(-) cells, with implications in adipose regeneration.

The role of catecholamines in mesenchymal stem cell fate

Mesenchymal stem cells (MSCs) are multipotent stem cells found in many adult tissues, especially bone marrow (BM) and are capable of differentiation into various lineage cells such as osteoblasts, adipocytes, chondrocytes and myocytes. Moreover, MSCs can be mobilized from connective tissue into circulation and from there to damaged sites to contribute to regeneration processes. MSCs commitment and differentiation are controlled by complex activities involving signal transduction through cytokines and catecholamines. There has been an increasing interest in recent years in the neural system, functioning in the support of stem cells like MSCs. Recent efforts have indicated that the catecholamine released from neural and not neural cells could be affected characteristics of MSCs. However, there have not been review studies of most aspects involved in catecholamines-mediated functions of MSCs. Thus, in this review paper, we will try to describe the current state of catecholamines in MSCs destination and discuss strategies being used for catecholamines for migration of these cells to damaged tissues. Then, the role of the nervous system in the induction of osteogenesis, adipogenesis, chondrogenesis and myogenesis from MSCs is discussed. Recent progress in studies of signaling transduction of catecholamines in determination of the final fate of MSCs is highlighted. Hence, the knowledge of interaction between MSCs with the neural system could be applied towards the development of new diagnostic and treatment alternatives for human diseases.

FGF2 stimulates osteogenic differentiation through ERK induced TAZ expression

TAZ (transcriptional coactivator with PDZ-binding motif) is a transcriptional modulator that regulates mesenchymal stem cell differentiation. It stimulates osteogenic differentiation while inhibiting adipocyte differentiation. FGFs (fibroblast growth factors) stimulate several signaling proteins to regulate their target genes, which are involved in cell proliferation, differentiation, and cell survival. Within this family, FGF2 stimulates osteoblast differentiation though a mechanism that is largely unknown. In this report, we show that TAZ mediates FGF2 signaling in osteogenesis. We observed that FGF2 increases TAZ expression by stimulating its mRNA expression. Depletion of TAZ using small hairpin RNA blocked FGF2-mediated osteogenic differentiation. FGF2 induced TAZ expression was stimulated by ERK (extracellular signal-regulated kinase) activation and the inhibition of ERK blocked TAZ expression. FGF2 increased nuclear localization of TAZ and, thus, facilitated the interaction of TAZ and Runx2, activating Runx2-mediated gene transcription. Taken together, these results suggest that TAZ is an important mediator of FGF2 signaling in osteoblast differentiation.

COMP-Ang1 promotes chondrogenic and osteogenic differentiation of multipotent mesenchymal stem cells through the Ang1/Tie2 signaling pathway

Mesenchymal stem cells (MSCs) are pleiotrophic cells that differentiate to chondrocytes, osteoblasts, or adipocytes, as a result of crosstalk by specific signaling pathways including MAPK pathway. Recently cartilage oligomeric matrix protein angiopoietin1 (COMP-Ang1), an Ang1 variant which is more potent than native Ang1 in phosphorylating Tie2 receptor was developed. The Ang1/Tie2 signaling system not only plays a pivotal role in vessel growth, remodeling, and maturation, but also protective and recruit effect on MSCs. Thus, the aim of the present study was to investigate the differentiate effect of Ang1/Tie2 signaling on MSCs in the presence of chondrogenic, osteogenic and adipogenic induction medium, and to determine the possible mechanisms. Our results clearly demonstrated that MSCs cultured in each induction medium with COMP-Ang1 revealed strongly chondrogenic and osteogenic morphological change (3.5- and 2-fold, respectively) as well as up-regulate each gene, except for adipogenic differentiation. Accordingly, we found that phosphorylation of Tie2 expression lead to phosphorylation of p38 and AKT and then accelerating each differentiation of MSCs to chondrocytes and osteoblasts. Therefore, our findings suggest that COMP-Ang1 present a portal to promote MSCs differentiation to chondrocytes and osteoblasts through Ang1/Tie2 signaling pathway and provide insights into novel therapies for bone diseases.

Growth factor gene expression profiles of bone morphogenetic protein-2-treated human adipose stem cells seeded on calcium phosphate scaffolds in vitro

The secretome of stem cells strongly determines the outcome of tissue engineering strategies. We investigated how the secretome of human adipose stem cells (hASCs) can be affected by substrate, BMP-2 treatment, and degree of differentiation. We hypothesized that as differentiation progresses, hASCs produce increasingly more gene products associated with processes such as angiogenesis and bone remodeling. Human ASCs were treated for 15 min with BMP-2 (10 ng/ml) to enhance osteogenic differentiation, or with vehicle. Subsequently, hASCs were seeded on plastic or on biphasic calcium phosphate (BCP) consisting of 60% hydroxyapatite and 40% β-tricalcium phosphate. A PCR array for ~150 trophic factors and differentiation-related genes was performed at day 21 of culture. A limited set of factors was quantified by qPCR at days 0, 4, 14 and 21, and/or ELISA at day 21. Compared to plastic, BCP-cultured hASCs showed ≥2-fold higher expression of ~20 factors, e.g. cytokines such as IL-6, growth factors such as FGF7 and adhesion molecules such as VCAM1. Expression of another ~50 genes was decreased ≥2-fold on BCP vs. plastic, even though hASCs differentiate better on BCP than on plastic. BMP-2-treatment increased the expression of ~30 factors by hASCs seeded on BCP, while it decreased the expression of only PGF, PPARG and PTN. Substrate affected hASC secretion of Activin A and seemed to affect P1NP release. No clear association between hASC osteogenic differentiation and growth factor expression pattern was observed. Considering our observed lack of association between the degree of differentiation and the expression of factors associated with angiogenesis and bone remodeling by hASCs, future bone regeneration studies should focus more on systematically orchestrating the secretome of stem cells, rather than on inducing osteogenic differentiation of stem cells only. Short incubation with BMP-2 may be a promising treatment to enhance both osteogenic differentiation and environmental modulation.