Role of fibroblast growth factor receptors (FGFR) and FGFR like-1 (FGFRL1) in mesenchymal stromal cell differentiation to osteoblasts and adipocytes

Essential growth factor receptors for fibroblast homeostasis and activation: Fibroblast Growth Factor Receptor (FGFR), Platelet Derived Growth Factor Receptor (PDGFR), and Transforming Growth Factor β Receptor (TGFβR)

Fibroblasts are cells of mesenchymal origin that are found throughout the body. While these cells have several functions, their integral roles include maintaining tissue architecture through the production of key extracellular matrix components, and participation in wound healing after injury. Fibroblasts are also key mediators in disease progression during fibrosis, cancer, and other inflammatory diseases. Under these perturbed states, fibroblasts can activate into inflammatory fibroblasts or contractile myofibroblasts. Fibroblasts require various growth factors and mitogenic molecules for survival, proliferation, and differentiation. While the activity of mitogenic growth factors on fibroblasts in vitro was characterized as early as the 1970s, the proliferation and differentiation effects of growth factors on these cells in vivo are unclear. Recent work exploring the heterogeneity of fibroblasts raises questions as to whether all fibroblast cell states exhibit the same growth factor requirements. Here, we will examine and review existing studies on the influence of fibroblast growth factor receptors (FGFRs), platelet-derived growth factor receptors (PDGFRs), and transforming growth factor β receptor (TGFβR) on fibroblast cell states.

KLF2 regulates stemness of human mesenchymal stem cells by targeting FGFR3

Mesenchymal stem cells (MSCs) are an attractive source of pluripotent cells for regenerative therapy; however, maintaining stemness and self-renewal of MSCs during expansion ex vivo is challenging. For future clinical applications, it is essential to define the roles and signaling pathways that regulate the fate of MSCs. Based on our earlier finding that Krüppel-like factor 2 (KLF2) participates in maintaining stemness in MSCs, we examined further the role of this factor in intrinsic signaling pathways. Using a chromatin immunoprecipitation (ChIP)-sequence assay, we found that the FGFR3 gene is a KLF2 binding site. Knockdown of FGFR3 significantly decreased the levels of key pluripotency factors, enhanced the expression of differentiation-related genes and down-regulated colony formation of human bone marrow MSCs (hBMSCs). Using alizarin red S and oil red O staining, we found that knockdown of FGFR3 inhibited the osteogenic and adipogenic ability of MSCs under conditions of differentiation. The ChIP-qPCR assay confirmed that KLF2 interacts with the promoter regions of FGFR3. Our findings suggest that KLF2 promotes hBMSC stemness by direct regulation of FGFR. Our findings may contribute to enhanced MSC stemness by genetic modification of stemness-related genes.

FGFR families: biological functions and therapeutic interventions in tumors

There are five fibroblast growth factor receptors (FGFRs), namely, FGFR1-FGFR5. When FGFR binds to its ligand, namely, fibroblast growth factor (FGF), it dimerizes and autophosphorylates, thereby activating several key downstream pathways that play an important role in normal physiology, such as the Ras/Raf/mitogen-activated protein kinase kinase/extracellular signal-regulated kinase, phosphoinositide 3-kinase (PI3K)/AKT, phospholipase C gamma/diacylglycerol/protein kinase c, and signal transducer and activator of transcription pathways. Furthermore, as an oncogene, FGFR genetic alterations were found in 7.1% of tumors, and these alterations include gene amplification, gene mutations, gene fusions or rearrangements. Therefore, FGFR amplification, mutations, rearrangements, or fusions are considered as potential biomarkers of FGFR therapeutic response for tyrosine kinase inhibitors (TKIs). However, it is worth noting that with increased use, resistance to TKIs inevitably develops, such as the well-known gatekeeper mutations. Thus, overcoming the development of drug resistance becomes a serious problem. This review mainly outlines the FGFR family functions, related pathways, and therapeutic agents in tumors with the aim of obtaining better outcomes for cancer patients with FGFR changes. The information provided in this review may provide additional therapeutic ideas for tumor patients with FGFR abnormalities.

Genetic variants of FGFR family associated with height, hypertension, and osteoporosis

BACKGROUND

Hypertension and osteoporosis are the most common types of health problems. A recent study suggested that the fibroblast growth factor receptor-like protein 1 (FGFRL1) gene in giraffes is the most promising candidate gene that may have direct effects on both the skeleton and the cardiovascular system.

AIM

Our study purposed to replicate the finding that the FGFR5 gene is related to giraffe-related characteristics (height, hypertension, and osteoporosis), and to assess the associations between genetic variants of the FGFR family and three phenotypes.

SUBJECTS AND METHODS

An association study was performed to confirm the connections between hypertension, osteoporosis, and height and the FGFR family proteins (FGFR1 to FGFR5).

RESULTS

We identified a total of 192 genetic variants in the FGFR family and found six SNVs in the FGFR2, FGFR3, and FGFR4 genes that were associated with two phenotypes simultaneously. Also, the FGFR family was found to be involved in calcium signalling, and three genetic variants of the FGFR3 gene showed significant signals in the pituitary and hypothalamus.

CONCLUSION

Taken together, these findings suggest that FGFR genes are associated with hypertension, height, and osteoporosis. In particular, the present study highlights the FGFR3 gene, which influences two fundamental regulators of bone remodelling.

The Metabolic Features of Osteoblasts: Implications for Multiple Myeloma (MM) Bone Disease

The study of osteoblast (OB) metabolism has recently received increased attention due to the considerable amount of energy used during the bone remodeling process. In addition to glucose, the main nutrient for the osteoblast lineages, recent data highlight the importance of amino acid and fatty acid metabolism in providing the fuel necessary for the proper functioning of OBs. Among the amino acids, it has been reported that OBs are largely dependent on glutamine (Gln) for their differentiation and activity. In this review, we describe the main metabolic pathways governing OBs' fate and functions, both in physiological and pathological malignant conditions. In particular, we focus on multiple myeloma (MM) bone disease, which is characterized by a severe imbalance in OB differentiation due to the presence of malignant plasma cells into the bone microenvironment. Here, we describe the most important metabolic alterations involved in the inhibition of OB formation and activity in MM patients.

Glucose transporters GLUT1, GLUT3, and GLUT4 have different effects on osteoblast proliferation and metabolism

Bone is an active tissue that undergoes constant remodeling. Bone formation requires energy and one of the energy sources of bone-forming osteoblasts is glucose, which is transported inside the cells via glucose transporters. However, the role of class I glucose transporters in the differentiation and metabolism of osteoblasts and their precursors, bone marrow mesenchymal stromal cells (BMSCs) remains inconclusive. Our aim was to characterize the expression and contribution of main class I glucose transporters, GLUT1, GLUT3, and GLUT4, during osteoblast proliferation and differentiation. To investigate the role of each GLUT, we downregulated GLUTs with siRNA technology in primary rat BMSCs. Live-cell imaging and RNA-seq analysis was used to evaluate downstream pathways in silenced osteoblasts. Glucose transporters GLUT1, GLUT3, and GLUT4 had distinct expression patterns in osteoblasts. GLUT1 was abundant in BMSCs, but rapidly and significantly downregulated during osteoblast differentiation by up to 80% (p < 0.001). Similar downregulation was observed for GLUT4 (p < 0.001). In contrast, expression levels of GLUT3 remained stable during differentiation. Osteoblasts lacked GLUT2. Silencing of GLUT4 resulted in a significant decrease in proliferation and differentiation of preosteoblasts (p < 0.001) and several pathways related to carbohydrate metabolism and cell signaling were suppressed. However, silencing of GLUT3 resulted in increased proliferation (p < 0.001), despite suppression of several pathways involved in cellular metabolism, biosynthesis and actin organization. Silencing of GLUT1 had no effect on proliferation and less changes in the transcriptome. RNA-seq dataset further revealed that osteoblasts express also class II and III glucose transporters, except for GLUT7. In conclusion, GLUT1, -3 and -4 may all contribute to glucose uptake in differentiating osteoblasts. GLUT4 expression was clearly required for osteoblast proliferation and differentiation. GLUT1 appears to be abundant in early precursors, but stable expression of GLUT3 suggest also a role for GLUT3 in osteoblasts. Presence of other GLUT members may further contribute to fine-tuning of glucose uptake. Together, glucose uptake in osteoblast lineage appears to rely on several glucose transporters to ensure sufficient energy for new bone formation.

FGFRL1 and FGF genes are associated with height, hypertension, and osteoporosis

Hypertension and osteoporosis are two major disorders, which interact with each other. Specific genetic signals involving the fibroblast growth factor receptor-like 1 (FGFRL1) gene are related to high blood pressure and bone growth in giraffes. FGFRL1 is associated with cardiovascular system and bone formation. We performed an association study to investigate the role of FGFRL1 in hypertension, osteoporosis, and height determination in humans. In addition, we identified three kinds of phenotypes in fibroblast growth factor (FGF) genes and examined their association with the FGFRL1 gene. We identified 42 SNPs in the FGFRL1 gene associated with each trait. We then analyzed the potential functional annotation of each SNP. The FGFRL1 gene was found to be associated with height, hypertension, and osteoporosis, consistent with the results of a previous study. In addition, the FGF2, FGF4, FGF10, FGF18, and FGF22 genes were found to interact with the FGFRL1 gene. Our study suggests that both FGFRL1 and FGFRL1-related genes may determine the height and the prevalence of osteoporosis and hypertension in the Korean population.

FGFR2 accommodates osteogenic cell fate determination in human mesenchymal stem cells

The multilineage differentiation potential of human mesenchymal stem cells (hMSCs) underpins their clinical utility for tissue regeneration. Control of such cell-fate decisions is tightly regulated by different growth factors/cytokines and their cognate receptors. Fibroblast growth factors (FGFs) are among such factors critical for osteogenesis. However, how FGF receptors (FGFRs) help to orchestrate osteogenic progression remains to be fully elucidated. Here, we studied the protein levels of FGFRs during osteogenesis in human adult bone marrow-derived MSCs and discovered a positive correlation between FGFR2 expression and alkaline phosphatase (ALP) activity, an early marker of osteogenesis. Through RNA interference studies, we confirmed the role of FGFR2 in promoting the osteogenic differentiation of hMSCs. Knockdown of FGFR2 resulted in downregulation of pro-osteogenic genes and upregulation of pro-adipogenic genes and adipogenic commitment. Moreover, under osteogenic induction, FGFR2 knockdown resulted in upregulation of Enhancer of Zeste Homolog 2 (EZH2), an epigenetic enzyme that regulates MSC lineage commitment and suppresses osteogenesis. Lastly, we show that serial-passaged hMSCs have reduced FGFR2 expression and impaired osteogenic potential. Our study suggests that FGFR2 is critical for mediating osteogenic fate by regulating the balance of osteo-adipogenic lineage commitment. Therefore, examining FGFR2 levels during serial-passaging of hMSCs may prove useful for monitoring their multipotency.

Increased Expression and Altered Cellular Localization of Fibroblast Growth Factor Receptor-Like 1 (FGFRL1) Are Associated with Prostate Cancer Progression

Simple Summary

Prostate cancer (PCa) is one of the most frequently diagnosed malignancies in men. PCa is primarily regulated by androgens, but other mechanisms, such as fibroblast growth factor receptor (FGFR) signaling, are also involved. In some patients, PCa relapses after surgical removal of prostate, and androgen deprivation therapy (ADT) is used as the first-line treatment. Unfortunately, the patients often lose response to ADT and progress by other mechanisms to castration-resistant, currently non-curable PCa. In our study, we aimed to identify better diagnostic markers and therapeutic targets against PCa. We analyzed patient PCa tissue samples from radical prostatectomies and biopsies, and used physiologically relevant 3D organoids and mouse xenografts to study FGFR signaling in PCa. We found that FGFRL1, a protein belonging to the FGFR family, plays a role in PCa. Our results suggest that FGFRL1 has significant effects on PCa progression and has potential as a prognostic biomarker.

Abstract

Fibroblast growth factor receptors (FGFRs) 1–4 are involved in prostate cancer (PCa) regulation, but the role of FGFR-like 1 (FGFRL1) in PCa is unclear. FGFRL1 expression was studied by qRT-PCR and immunohistochemistry of patient tissue microarrays (TMAs) and correlated with clinical patient data. The effects of FGFRL1 knockdown (KD) in PC3M were studied in in vitro culture models and in mouse xenograft tumors. Our results showed that FGFRL1 was significantly upregulated in PCa. The level of membranous FGFRL1 was negatively associated with high Gleason scores (GSs) and Ki67, while increased cytoplasmic and nuclear FGFRL1 showed a positive correlation. Cox regression analysis indicated that nuclear FGFRL1 was an independent prognostic marker for biochemical recurrence after radical prostatectomy. Functional studies indicated that FGFRL1-KD in PC3M cells increases FGFR signaling, whereas FGFRL1 overexpression attenuates it, supporting decoy receptor actions of membrane-localized FGFRL1. In accordance with clinical data, FGFRL1-KD markedly suppressed PC3M xenograft growth. Transcriptomics of FGFRL1-KD cells and xenografts revealed major changes in genes regulating differentiation, ECM turnover, and tumor–stromal interactions associated with decreased growth in FGFRL1-KD xenografts. Our results suggest that FGFRL1 upregulation and altered cellular compartmentalization contribute to PCa progression. The nuclear FGFRL1 could serve as a prognostic marker for PCa patients.

FGF1 promotes the differentiation of goat intramuscular and subcutaneous preadipocytes

Fibroblast growth factor 1(FGF1) has been proved to bind to specific signal molecules and activate intracellular signal transduction, leading to proliferation or differentiation of cells. However, the role of FGF1 in goat adipocytes is still unclear. Here, we investigated its role in lipogenesis of goats, which depends on the activation of FGFRs. In goat intramuscular and subcutaneous adipocytes, we observed that adipocytes accumulation was inhibited by interfering of FGF1, the expression of C/EBPα, C/EBPβ, LPL, Pref-1, PPARγ, AP2, KLF4, KLF6, KLF10 and KLF17 were significantly down-regulated (p < 0.05). When the FGF1 was up-regulated, the opposite result was found, while the expression of C/EBPβ, LPL, PPARγ, SREBP1, AP2, KLF4, KLF7, KLF15, KLF16 and KLF17 were increased significantly (p < 0.05) in goat intramuscular and subcutaneous adipocytes. The expression level of FGFR1 was significantly and decreased with the interference of FGF1, and increased with the overexpression of FGF1. But in goat subcutaneous adipocytes, only the expression of FGFR2 was consistent with the expression of FGF1. Interference methods confirmed that FGFR1 or FGFR2 and FGF1 have the similarly promoting function in adipocytes differentiation. With the co-transfection technology, we confirmed that FGF1 promoted the differentiation of intramuscular and subcutaneous adipocytes might via FGFR1 or FGFR2, respectively.

Comprehending fibroblast growth factor receptor like 1: Oncogene or tumor suppressor?

Fibroblast Growth Factor Receptor Like 1 (FGFRL1) signaling has crucial role in a multitude of processes during genetic diseases, embryonic development and various types of cancer. Due to its partial structural similarity with its classical Fibroblast Growth Factor Receptor [FGFR] counterparts and lack of tyrosine kinase domain, FGFRL1 was thought to work as a decoy receptor in FGF/FGFR signaling. Later on, growing number evidences showed that expression of FGFRL1 affects major pathways like ERK1/2, Akt and others, which are dysfunctional in a wide range of human cancers. In this review, we provide an overview of the current understanding of FGFRL1 and its roles in cell differentiation, adhesion and proliferation pathways . Overexpression of FGFRL1 might lead to tumor progression and invasion. In this context, inhibitors for FGFRL1 might have therapeutic benefits in human cancer prognosis.

Cytokines regulate stemness of mesenchymal stem cells via miR-628-5p during periodontal regeneration

BACKGROUND

Cytokines play key roles in stimulating periodontal regeneration; however, their exact mechanisms of action remain unclear. Mesenchymal stem cells (MSCs) are multipotent cells that have self-renewal abilities and can differentiate into periodontal tissues such as bone, cementum, and periodontal ligaments following transplantation, like periodontal progenitor cells. Here, we used MSCs to identify the regulatory genes induced by periodontal regenerative cytokines.

METHODS

Human MSCs (hMSCs) were cultured under conditions of periodontal regenerative cytokine stimulation or silencing of undifferentiated hMSC transcription factors. To characterize the changes associated with periodontal regenerative cytokine-regulated microRNAs (miRNAs), miRNA, and mRNA expression was evaluated using miRNA arrays and quantitative real-time polymerase chain reaction, respectively. One of the identified miRNAs, miR-628-5p, was then overexpressed or suppressed in hMSCs during osteogenesis; the effect of these changes on osteogenesis was investigated.

RESULTS

Cytokine-stimulated MSCs showed characteristic miRNA profiles and mRNA levels of undifferentiated hMSC transcription factors ETV1, SOX11, and GATA6. Next, we silenced these transcription factors in MSCs and examined the miRNA profiles. The levels of miR-628-5p were decreased upon all cytokine treatments and were increased upon silencing of ETV1, SOX11, and GATA6. Overexpression of miR-628-5p suppressed osteogenesis; however, its inhibition enhanced OPN, ALP, OC, BMP2, and RUNX2 mRNA levels, and bone matrix mineralization, but not OSX mRNA or ALP activity.

CONCLUSIONS

miR-628-5p negatively regulates MSC stemness during periodontal regeneration. Periodontal regenerative cytokines act as miR-628-5p suppressors to support periodontal regeneration. Thus, selection of effective cytokines for different MSCs, based on miRNA profiling, is important for advancing regenerative therapies.

Epigenetic landscape in blood leukocytes following ketosis and weight loss induced by a very low calorie ketogenic diet (VLCKD) in patients with obesity

BACKGROUND

The molecular mechanisms underlying the potential health benefits of a ketogenic diet are unknown and could be mediated by epigenetic mechanisms.

OBJECTIVE

To identify the changes in the obesity-related methylome that are mediated by the induced weight loss or are dependent on ketosis in subjects with obesity underwent a very-low calorie ketogenic diet (VLCKD).

METHODS

Twenty-one patients with obesity (n = 12 women, 47.9 ± 1.02 yr, 33.0 ± 0.2 kg/m²) after 6 months on a VLCKD and 12 normal weight volunteers (n = 6 women, 50.3 ± 6.2 yrs, 22.7 ± 1.5 kg/m²) were studied. Data from the Infinium MethylationEPIC BeadChip methylomes of blood leukocytes were obtained at time points of ketotic phases (basal, maximum ketosis, and out of ketosis) during VLCKD (n = 10) and at baseline in volunteers (n = 12). Results were further validated by pyrosequencing in representative cohort of patients on a VLCKD (n = 18) and correlated with gene expression.

RESULTS

After weight reduction by VLCKD, differences were found at 988 CpG sites (786 unique genes). The VLCKD altered methylation levels in patients with obesity had high resemblance with those from normal weight volunteers and was concomitant with a downregulation of DNA methyltransferases (DNMT)1, 3a and 3b. Most of the encoded genes were involved in metabolic processes, protein metabolism, and muscle, organ, and skeletal system development. Novel genes representing the top scoring associated events were identified, including ZNF331, FGFRL1 (VLCKD-induced weight loss) and CBFA2T3, C3orf38, JSRP1, and LRFN4 (VLCKD-induced ketosis). Interestingly, ZNF331 and FGFRL1 were validated in an independent cohort and inversely correlated with gene expression.

CONCLUSIONS

The beneficial effects of VLCKD therapy on obesity involve a methylome more suggestive of normal weight that could be mainly mediated by the VLCKD-induced ketosis rather than weight loss.

Scaling a Dpp Morphogen Gradient through Feedback Control of Receptors and Co-receptors

Gradients of decapentaplegic (Dpp) pattern Drosophila wing imaginal discs, establishing gene expression boundaries at specific locations. As discs grow, Dpp gradients expand, keeping relative boundary positions approximately stationary. Such scaling fails in mutants for Pentagone (pent), a gene repressed by Dpp that encodes a diffusible protein that expands Dpp gradients. Although these properties fit a recent mathematical model of automatic gradient scaling, that model requires an expander that spreads with minimal loss throughout a morphogen field. Here, we show that Pent's actions are confined to within just a few cell diameters of its site of synthesis and can be phenocopied by manipulating non-diffusible Pent targets strictly within the Pent expression domain. Using genetics and mathematical modeling, we develop an alternative model of scaling driven by feedback downregulation of Dpp receptors and co-receptors. Among the model's predictions is a size beyond which scaling fails-something we observe directly in wing discs.

Identification of novel mRNA isoforms associated with meat tenderness using RNA sequencing data in beef cattle

The Warner-Bratzler shear force (WBSF) and myofibrillar fragmentation index (MFI) are complementary methodologies used to measure beef tenderness. Longissimus thoracis samples from the 20 most extreme bulls (out of 80 bulls set) for WBSF (tender (n = 10) and tough (n = 10)) and MFI (high (n = 10) and low (n = 10)) traits were collected to perform transcriptomic analysis using RNA-Sequencing. All analysis were performed through CLC Genomics Workbench. A total of 39 and 27 transcripts for WBSF and MFI phenotypes were DE, respectively. The possible DE novel mRNA isoforms, for WBSF and MFI traits, are myosin encoders (e.g. MYL1 and MYL6). In addition, we identified potential mRNA isoforms related to genes affecting the speed fibers degradation during the meat aging process. The DE novel transcripts are transcripted by genes with biological functions related to oxidative process, energy production and striated muscle contraction. The results suggest that the identified mRNA isoforms could be used as potential candidate to select animals in order to improve meat tenderness.

Actomyosin and the MRTF-SRF pathway downregulate FGFR1 in mesenchymal stromal cells

Both biological and mechanical signals are known to influence cell proliferation. However, biological signals are mostly studied in two-dimensions (2D) and the interplay between these different pathways is largely unstudied. Here, we investigated the influence of the cell culture environment on the response to bFGF, a widely studied and important proliferation growth factor. We observed that human mesenchymal stromal cells (hMSCs), but not fibroblasts, lose the ability to respond to soluble or covalently bound bFGF when cultured on microfibrillar substrates. This behavior correlated with a downregulation of FGF receptor 1 (FGFR1) expression of hMSCs on microfibrillar substrates. Inhibition of actomyosin or the MRTF/SRF pathway decreased FGFR1 expression in hMSCs, fibroblasts and MG63 cells. To our knowledge, this is the first time FGFR1 expression is shown to be regulated through a mechanosensitive pathway in hMSCs. These results add to the sparse literature on FGFR1 regulation and potentially aid designing tissue engineering constructs that better control cell proliferation.

Identification and characterization of adipose surface epitopes

Adipose tissue is a central regulator of metabolism and an important pharmacological target to treat the metabolic consequences of obesity, such as insulin resistance and dyslipidemia. Among the various cellular compartments, the adipocyte cell surface is especially appealing as a drug target as it contains various proteins that when activated or inhibited promote adipocyte health, change its endocrine function and eventually maintain or restore whole-body insulin sensitivity. In addition, cell surface proteins are readily accessible by various drug classes. However, targeting individual cell surface proteins in adipocytes has been difficult due to important functions of these proteins outside adipose tissue, raising various safety concerns. Thus, one of the biggest challenges is the lack of adipose selective surface proteins and/or targeting reagents. Here, we discuss several receptor families with an important function in adipogenesis and mature adipocytes to highlight the complexity at the cell surface and illustrate the problems with identifying adipose selective proteins. We then discuss that, while no unique adipocyte surface protein might exist, how splicing, posttranslational modifications as well as protein/protein interactions can create enormous diversity at the cell surface that vastly expands the space of potentially unique epitopes and how these selective epitopes can be identified and targeted.

Fibroblast growth factors signaling in bone metastasis

Many solid tumors metastasize to bone, but only prostate cancer has bone as a single, dominant metastatic site. Recently, the FGF axis has been implicated in cancer progression in some tumors and mounting evidence indicate that it mediates prostate cancer bone metastases. The FGF axis has an important role in bone biology and mediates cell-to-cell communication. Therefore, we discuss here basic concepts of bone biology, FGF signaling axis, and FGF axis function in adult bone, to integrate these concepts in our current understanding of the role of FGF axis in bone metastases.

Fibroblast growth factor receptor 2 expression in apical periodontitis in mice

AIM

To investigate the presence, localization and the possible correlation of the fibroblast growth factor receptor-2 (FGFR2) with inflammatory resorption of cementum, periodontal ligament and alveolar bone during development of apical periodontitis in mice.

METHODOLOGY

Apical periodontitis was experimentally induced in mandibular first molars of mice by pulp exposure to the oral environment. Healthy teeth without pulp exposure were used as controls. At 7, 21 and 42 days following pulp exposure, the animals were euthanized and the jaws were prepared for analysis under conventional and fluorescence microscopy, immunohistochemistry (FGFR2), RT-PCR (RNAm levels of RANK, RANKL, OPG, Runx2 and cathepsin K) and enzyme histochemistry (cementoclasts and osteoclasts). Statistical analysis was performed by Kruskal-Wallis tests and Dunn's post hoc tests for multiple comparisons (α = 0.05) using SAS 9.4 software.

RESULTS

FGFR2-positive cells were not observed in the tissues surrounding healthy teeth but were observed in teeth with periapical lesions from seven days after root canal contamination. At days 21 and 42 after endodontic infection, the increase in periapical lesion size was accompanied by significantly enhanced expression of FGFR2 (P < 0.0001), significantly increased intensity of inflammatory cells, number of osteoclasts (P < 0.0001) and cementoclasts (P < 0.0001), and significantly enhanced RNAm levels of RANK/RANKL/OPG, Runx2 and cathepsin K compared to day 0 (P < 0.0001). At 21 and 42 days, FGFR2 was also expressed on osteoblasts, fibroblasts and inside enlarged lacunae of cementocytes along with acute and chronic inflammatory cells (macrophages, plasma cells and neutrophils). At all periods and cells, FGFR2 expression was observed in the cell membrane and cytoplasm, but not in the nucleus.

CONCLUSION

In mice, FGFR2 was not expressed in tissues surrounding healthy teeth but was expressed in apical periodontitis, specifically in the membrane and cytoplasm of osteoblasts, fibroblasts, lacunae of cementocytes, and acute and chronic inflammatory cells (macrophages, plasma cells and neutrophils). Its expression was correlated with the size of the periapical lesions.

NPY1R-targeted peptide-mediated delivery of a dual PPARα/γ agonist to adipocytes enhances adipogenesis and prevents diabetes progression

Objective

PPARα/γ dual agonists have been in clinical development for the treatment of metabolic diseases including type 2 diabetes and dyslipidemia. However, severe adverse side effects led to complications in clinical trials. As most of the beneficial effects rely on the compound activity in adipocytes, the selective targeting of this cell type is a cutting-edge strategy to develop safe anti-diabetic drugs. The goal of this study was to strengthen the adipocyte-specific uptake of the PPARα/γ agonist tesaglitazar via NPY₁R-mediated internalization.

Methods

NPY₁R-preferring peptide tesaglitazar-[F⁷, P³⁴]-NPY (tesa-NPY) was synthesized by a combination of automated SPPS and manual couplings. Following molecular and functional analyses for proof of concept, cell culture experiments were conducted to monitor the effects on adipogenesis. Mice treated with peptide drug conjugates or vehicle either by gavage or intraperitoneal injection were characterized phenotypically and metabolically. Histological analysis and transcriptional profiling of the adipose tissue were performed.

Results

In vitro studies revealed that the tesaglitazar-[F⁷, P³⁴]-NPY conjugate selectively activates PPARγ in NPY₁R-expressing cells and enhances adipocyte differentiation and adiponectin expression in adipocyte precursor cells. In vivo studies using db/db mice demonstrated that the anti-diabetic activity of the peptide conjugate is as efficient as that of systemically administered tesaglitazar. Additionally, tesa-NPY induces adipocyte differentiation in vivo.

Conclusions

The use of the tesaglitazar-[F7, P34]-NPY conjugate is a promising strategy to apply the beneficial PPARα/γ effects in adipocytes while potentially omitting adverse effects in other tissues.

•

Tesaglitazar-NPY targets adipocytes via NPY₁R receptor-mediated internalization.

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Peptide-drug conjugate is specifically delivered to NPY₁R-expressing cells.

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Release of tesaglitazar in adipocytes activates PPARγ.

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Drug delivery enhances adipocyte differentiation and adiponectin expression.

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Peptide conjugate exhibits antidiabetic activity in vivo.

Genome-wide DNA methylation profiling of hip articular cartilage identifies differentially methylated loci associated with osteonecrosis of the femoral head

OBJECTIVE

Recent studies demonstrated a critical role of hip articular cartilage destruction in the development of osteonecrosis of the femoral head (ONFH). The aim of this study was to characterize the genome-wide DNA methylation profile of hip cartilage obtained from patients with ONFH and healthy subjects.

METHODS

Hip articular cartilage specimens were collected from 15 ONFH patients (including 11 males and 4 females) and 15 control subjects (including 11 males and 4 females) with femoral neck fracture. The average ages of the ONFH patients and control subjects were 50.27 ± 5.27 years and 61.67 ± 3.38 years, respectively. Genome-wide DNA methylation profiles of 5 ONFH and 5 control cartilages were determined by Illumina HumanMethylation850 array. Differential methylation analysis of DNA methylation profiles were performed by the empirical Bayes moderated t-test of the limma package. Mass spectrograph (MS) analysis of 10 ONFH cartilages and 10 normal cartilages were performed to validate the results of genome-wide DNA methylation profiling. Immunohistochemistry (IHC) of 4 ONFH cartilages and 4 control cartilages were conducted to evaluate the expression levels of proteins encoded by identified differentially methylated genes. t-test was used to assess the significance of protein expression differences between ONFH patients and controls in IHC.

RESULTS

We identified a total of 2872 differentially methylated CpG sites, annotated to 480 hypermethylated genes and 1335 hypomethylated genes for ONFH. The results of MS validation were consistent with that of genome-wide DNA methylation profiling. IHC further confirmed the increased protein expression of CARS (mean and 95%CI of superficial zone 59.67% [48.46, 56.14], and deep zone 31% [25.85, 30.61]), PDE4D (superficial zone 50.33% [33.64, 40.68] and deep zone 28.67% [10.81, 36.47]), ADAMTS12 (superficial zone 53.67% [36.01, 40.93] and deep zone 34.67% [22.56, 37.18]), LRP5 (superficial zone 59.63% [27.32, 39.61] and deep zone 22.95% [5.28, 19.29]), RUNX2 (superficial zone 52.58% [11.64, 31.33] and deep zone 35.01% [10.03, 27.44]) in ONFH articular cartilage.

CONCLUSION

Our results suggest the implication of DNA methylation alterations in the development of ONFH, and provide novel clues for pathogenetic and therapeutic studies of ONFH.

Dovitinib dilactic acid reduces tumor growth and tumor-induced bone changes in an experimental breast cancer bone growth model

Advanced breast cancer has a high incidence of bone metastases. In bone, breast cancer cells induce osteolytic or mixed bone lesions by inducing an imbalance in bone formation and resorption. Activated fibroblast growth factor receptors (FGFRs) are important in regulation of tumor growth and bone remodeling. In this study we used FGFR1 and FGFR2 gene amplifications containing human MFM223 breast cancer cells in an experimental xenograft model of breast cancer bone growth using intratibial inoculation technique. This model mimics bone metastases in breast cancer patients. The effects of an FGFR inhibitor, dovitinib dilactic acid (TKI258) on tumor growth and tumor-induced bone changes were evaluated. Cancer-induced bone lesions were smaller in dovitinib-treated mice as evaluated by X-ray imaging. Peripheral quantitative computed tomography imaging showed higher total and cortical bone mineral content and cortical bone mineral density in dovitinib-treated mice, suggesting better preserved bone mass. CatWalk gait analysis indicated that dovitinib-treated mice experienced less cancer-induced bone pain in the tumor-bearing leg. A trend towards decreased tumor growth and metabolic activity was observed in dovitinib-treated mice quantified by positron emission tomography imaging with 2-[¹⁸F]fluoro-2-deoxy-D-glucose at the endpoint. We conclude that dovitinib treatment decreased tumor burden, cancer-induced changes in bone, and bone pain. The results suggest that targeting FGFRs could be beneficial in breast cancer patients with bone metastases.

Targeting Cellular Trafficking of Fibroblast Growth Factor Receptors as a Strategy for Selective Cancer Treatment

Fibroblast growth factor receptors (FGFRs) in response to fibroblast growth factors (FGFs) transmit signals across the cell membrane, regulating important cellular processes, like differentiation, division, motility, and death. The aberrant activity of FGFRs is often observed in various diseases, especially in cancer. The uncontrolled FGFRs' function may result from their overproduction, activating mutations, or generation of FGFRs' fusion proteins. Besides their typical subcellular localization on the cell surface, FGFRs are often found inside the cells, in the nucleus and mitochondria. The intracellular pool of FGFRs utilizes different mechanisms to facilitate cancer cell survival and expansion. In this review, we summarize the current stage of knowledge about the role of FGFRs in oncogenic processes. We focused on the mechanisms of FGFRs' cellular trafficking-internalization, nuclear translocation, and mitochondrial targeting, as well as their role in carcinogenesis. The subcellular sorting of FGFRs constitutes an attractive target for anti-cancer therapies. The blocking of FGFRs' nuclear and mitochondrial translocation can lead to the inhibition of cancer invasion. Moreover, the endocytosis of FGFRs can serve as a tool for the efficient and highly selective delivery of drugs into cancer cells overproducing these receptors. Here, we provide up to date examples how the cellular sorting of FGFRs can be hijacked for selective cancer treatment.

MicroRNA and Human Bone Health

The small non‐coding microRNAs (miRNAs) are post‐transcription regulators that modulate diverse cellular process in bone cells. Because optimal miRNA targeting is essential for their function, single‐nucleotide polymorphisms (SNPs) within or proximal to the loci of miRNA (miR‐SNPs) or mRNA (PolymiRTS) could potentially disrupt the miRNA‐mRNA interaction, leading to changes in bone metabolism and osteoporosis. Recent human studies of skeletal traits using miRNA profiling, genomewide association studies, and functional studies started to decipher the complex miRNA regulatory network. These studies have indicated that miRNAs may be a promising bone marker. This review focuses on human miRNA studies on bone traits and discusses how genetic variants affect bone metabolic pathways. Major ex vivo investigations using human samples supported with animal and in vitro models have shed light on the mechanistic role of miRNAs. Furthermore, studying the miRNAs’ signatures in secondary osteoporosis and osteoporotic medications such as teriparatide (TPTD) and denosumab (DMab) have provided valuable insight into clinical management of the disease. © 2018 The Authors. JBMR Plus Published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research

Endowing iPSC-Derived MSCs with Angiogenic and Keratinogenic Differentiation Potential: A Promising Cell Source for Skin Tissue Engineering

Induced pluripotent stem cells (iPSC) hold tremendous potential for personalized cell-based therapy for skin regeneration. Aiming to establish human iPSCs as a potential cell source for skin tissue engineering, we expect to obtain an epidermal-like cell line with angiogenic and keratinogenic differentiation potential via inducing iPSC-derived mesenchymal stem cells (iPSC-MSCs) with basic fibroblast growth factor (bFGF) and/or keratinocyte growth factor (KGF). The results show that iPSC-MSCs were successfully induced with a positive FGFR/KGFR expression on the cell surface. BFGF/KGF induction could significantly increase the expression of vascularization marker CD31 and keratinization marker CK10, respectively, while when combined together, although CD31 and CK10 were still positively expressed, their expressions were lower than that of the single induction group, suggesting that the effects of the two growth factors interfered with each other. This cell line with angiogenic and keratinogenic differentiation potential provides a promising new source of cells for the construction of well vascularized and keratinized tissue engineered skin, furthermore establishing an effective strategy for iPSC-based therapy in skin tissue engineering.

miR-210 promotes human osteosarcoma cell migration and invasion by targeting FGFRL1

Osteosarcoma is a common bone tumor and a frequently occuring cancer-associated threat to children. Notably, the prognosis of osteosarcoma is very poor when it is diagnosed with metastasis. A growing number of studies have indicated that various microRNAs (miRs) serve important regulatory roles in the pathogeny of different types of cancer. However, the functions of miR-210 in osteosarcoma need to be elucidated comprehensively. The aim of the present study was to investigate the potential roles of miR-210 in osteosarcoma by targeting fibroblast growth factor receptor-like 1 (FGFRL1). Reverse transcription-quantitative polymerase chain reaction results revealed that the expression of miR-210 was highly elevated while FGFRL1 expression was reduced inversely in osteosarcoma tissues compared with matched normal tissues. The results of Transwell assays showed that miR-210 promoted osteosarcoma cell migration and invasion. Furthermore, the luciferase reporter assay results suggested that miR-210 could directly bind to FGFRL1 in osteosarcoma cells. In addition, the present findings demonstrated that miR-210 could negatively regulate FGFRL1 expression by targeting the 3′untranslated region. In conclusion, the findings of the present study suggested that miR-210 exerted tumor carcinogenic functions in osteosarcoma by targeting FGFRL1. The findings of this study demonstrated that FGFRL1 was a direct target of miR-210 in osteosarcoma involved in the promoting functions mediated by miR-210 in the invasion and migration of osteosarcoma, suggesting that miR-210/FGFRL1 may be promising for discovering diagnostic and prognostic biomarkers for the therapies of osteosarcoma.

Cutting to the Chase: How Matrix Metalloproteinase-2 Activity Controls Breast-Cancer-to-Bone Metastasis

Bone metastatic breast cancer is currently incurable and will be evident in more than 70% of patients that succumb to the disease. Understanding the factors that contribute to the progression and metastasis of breast cancer can reveal therapeutic opportunities. Matrix metalloproteinases (MMPs) are a family of proteolytic enzymes whose role in cancer has been widely documented. They are capable of contributing to every step of the metastatic cascade, but enthusiasm for the use of MMP inhibition as a therapeutic approach has been dampened by the disappointing results of clinical trials conducted more than 20 years ago. Since the trials, our knowledge of MMP biology has expanded greatly. Combined with advances in the selective targeting of individual MMPs and the specific delivery of therapeutics to the tumor microenvironment, we may be on the verge of finally realizing the promise of MMP inhibition as a treatment strategy. Here, as a case in point, we focus specifically on MMP-2 as an example to show how it can contribute to each stage of breast-cancer-to-bone metastasis and also discuss novel approaches for the selective targeting of MMP-2 in the setting of the bone-cancer microenvironment.