Review of Signaling Pathways Governing MSC Osteogenic and Adipogenic Differentiation

The combined anti-osteoporotic effects of simvastatin and exercise in ovariectomized mice fed a high-fat diet

BACKGROUND

To evaluate and compare the effects of the combined intervention of simvastatin and exercise on the bone degeneration in a mice model of osteoporosis (OP) induced by obesity and estrogen deficiency.

METHODS

56 female 3-month-old C57BL/6 mice were given a standard diet or a high-fat diet after ovariectomy (OVX) or sham surgery. Drug administration and exercise training were initiated 72 h after surgical operation, which were treated with simvastatin (10 mg/kg/day) or exercise (15 m/min for 30 min/day) or combined with simvastatin and exercise at 72 h for 8 weeks. The pathology of OP was assessed by histomorphology analyses, immunohistochemistry (IHC), micro-computed tomography (Micro-CT), enzyme-linked immunosorbent assay (ELISA) and cell culture.

RESULTS

The coexistence of obesity and estrogen deficiency significantly further exacerbated OP pathology, and combined intervention showed a better significant anti-osteoporosis effect than monotherapy. In details, simvastatin combined with exercise ameliorated the abnormal bone mass, microstructure and bone marrow adipocyte differentiation, significantly increased osteoprotegerin (OPG), type 1 collagen (Col-I), RUNX2 and osteocalcin (OCN) expression, decreased the expression of receptor activator of nuclear factor-kappaB ligand (RANKL) and peroxisome proliferator-activated receptor γ (PPARγ). Furthermore, combined intervention markedly improved abnormal metabolic status, reduced the levels of serum glucose, insulin, triglycerides (TG), low-density lipoprotein (LDL), leptin, CTX-1 and IL-1β, and increased the level of OCN.

CONCLUSIONS

The coexistence of obesity and estrogen deficiency further aggravates bone tissue degeneration and abnormal metabolic pathology, which could be better inhibited by the combination with simvastatin and exercise instead of single intervention, suggesting that combined intervention may be a potential candidate for amelioration of the progression of OP.

Impact of Treadmill Interval Running on the Appearance of Zinc Finger Protein FHL2 in Bone Marrow Cells in a Rat Model: A Pilot Study

Although the benefits of physical exercise to preserve bone quality are now widely recognized, the intimate mechanisms leading to the underlying cell responses still require further investigations. Interval training running, for instance, appears as a generator of impacts on the skeleton, and particularly on the progenitor cells located in the bone marrow. Therefore, if this kind of stimulus initiates bone cell proliferation and differentiation, the activation of a devoted signaling pathway by mechano-transduction seems likely. This study aimed at investigating the effects of an interval running program on the appearance of the zinc finger protein FHL2 in bone cells and their anatomical location. Twelve 5-week-old male Wistar rats were randomly allocated to one of the following groups (n = 6 per group): sedentary control (SED) or high-intensity interval running (EX, 8 consecutive weeks). FHL2 identification in bone cells was performed by immuno-histochemistry on serial sections of radii. We hypothesized that impacts generated by running could activate, in vivo, a specific signaling pathway, through an integrin-mediated mechano-transductive process, leading to the synthesis of FHL2 in bone marrow cells. Our data demonstrated the systematic appearance of FHL2 (% labeled cells: 7.5%, p < 0.001) in bone marrow obtained from EX rats, whereas no FHL2 was revealed in SED rats. These results suggest that the mechanical impacts generated during high-intensity interval running activate a signaling pathway involving nuclear FHL2, such as that also observed with dexamethasone administration. Consequently, interval running could be proposed as a non-pharmacological strategy to contribute to bone marrow cell osteogenic differentiation.

BMP-2 Induced Signaling Pathways and Phenotypes: Comparisons Between Senescent and Non-senescent Bone Marrow Mesenchymal Stem Cells

The use of BMP-2 in orthopedic surgery is limited by uncertainty surrounding its effects on the differentiation of mesenchymal stem cells (MSCs) and how this is affected by cellular aging. This study compared the effects of recombinant human BMP-2 (rhBMP-2) on osteogenic and adipogenic differentiation between senescent and non-senescent MSCs. Senescent and non-senescent MSCs were cultured in osteogenic and adipogenic differentiation medium containing various concentrations of rhBMP-2. The phenotypes of these cells were compared by performing a calcium assay, adipogenesis assay, staining, real-time PCR, western blotting, and microarray analysis. rhBMP-2 induced osteogenic differentiation to a lesser extent (P < 0.001 and P = 0.005 for alkaline phosphatase activity and Ca²⁺ release) in senescent MSCs regardless of dose-dependent increase in both cells. However, the induction of adipogenic differentiation by rhBMP-2 was comparable between them. There was no difference between these two groups of cells in the adipogenesis assay (P = 0.279) and their expression levels of PPARγ were similar. Several genes such as CHRDL1, NOG, SMAD1, SMAD7, and FST encoding transcription factors were proposed to underlie the different responses of senescent and non-senescent MSCs to rhBMP-2 in microarray analyses. Furthermore, inflammatory, adipogenic, or cell death-related signaling pathways such as NF-kB or p38-MAPK pathways were upregulated by BMP-2 in senescent MSCs, whereas bone forming signaling pathways involving BMP, SMAD, and TGF- ß were upregulated in non-senescent MSCs as expected. This phenomenon explains bone forming dominance by non-senescent MSCs and possible frequent complications such as seroma, osteolysis, or neuritis in senescent MSCs during BMP-2 use in orthopedic surgery.

Growth Hormone Receptor Controls Adipogenic Differentiation of Chicken Bone Marrow Mesenchymal Stem Cells by Affecting Mitochondrial Biogenesis and Mitochondrial Function

Growth hormone receptor (GHR) can activate several signaling pathways after binding to growth hormone (GH) to regulate cell growth and development. Sex-linked dwarf (SLD) chickens, normal protein functions are prevented because of exon mutations in the GHR gene, have more severe fat deposition. However, the specific molecular mechanisms responsible for this phenotype remains unclear. We therefore investigated the effect of the GHR gene on adipogenic differentiation of chicken bone marrow mesenchymal stem cells (BMSCs). We found that bone marrow fat deposition was more severe in SLD chickens compared to normal chickens, and the expression of genes related to adipogenic differentiation was enhanced in SLD chicken BMSCs. We also detected enhanced mitochondrial function of BMSCs in SLD chickens. In vitro, overexpression of GHR in chicken BMSCs increased mitochondrial membrane potential but decreased reactive oxygen and ATP contents, oxidative phosphorylation complex enzyme activity, and mitochondrial number. Expression of genes associated with mitochondrial biogenesis and function was repressed during adipogenic differentiation in chicken BMSCs, the adipogenic differentiation capacity of chicken BMSCs was also repressed. With knockdown of GHR, opposite results were observed. We concluded that GHR inhibited adipogenic differentiation of chicken BMSCs by suppressing mitochondrial biogenesis and mitochondrial function.

Comparison of the Infant and Adult Adipose-Derived Mesenchymal Stem Cells in Proliferation, Senescence, Anti-oxidative Ability and Differentiation Potential

BACKGROUND

Infant adipose-derived mesenchymal stem cells (ADSCs) collected from excised polydactyly fat tissue, which was surgical waste, could be cultured and expanded in vitro in this study. In addition, the collecting process would not cause pain in the host. In this study, the proliferation, reduction of senescence, anti-oxidative ability, and differentiation potential in the infant ADSCs were compared with those in the adult ADSCs harvested from thigh liposuction to determine the availability of infant ADSCs.

METHODS

Proliferation was determined by detecting the fold changes in cell numbers and doubling time periods. Senescence was analyzed by investigating the age-related gene expression levels and the replicative stress. The superoxide dismutase (SOD) gene expression, adipogenic, neurogenic, osteogenic, and tenogenic differentiation were compared by RT-qPCR. The chondrogenic differentiation efficiency was also determined using RT-qPCR and immunohistochemical staining.

RESULTS

The proliferation, SOD (SOD1, SOD2 and SOD3) gene expression, the stemness-related gene (c-MYC) and telomerase reverse transcriptase of the infant ADSCs at early passages were enhanced compared with those of the adults'. Cellular senescence related genes, including p16, p21 and p53, and replicative stress were reduced in the infant ADSCs. The adipogenic genes (PPARγ and LPL) and neurogenic genes (MAP2 and NEFH) of the infant ADSC differentiated cells were significantly higher than those of the adults' while the expression of the osteogenic genes (OCN and RUNX) and tenogenic genes (TNC and COL3A1) of both demonstrated opposite results. The chondrogenic markers (SOX9, COL2 and COL10) were enhanced in the infant ADSC differentiated chondrogenic pellets, and the expression levels of SODs were decreased during the differentiation process.

CONCLUSION

Cultured infant ADSCs demonstrate less cellular senescence and replicative stress, higher proliferation rates, better antioxidant defense activity, and higher potential of chondrogenic, adipogenic and neurogenic differentiation.

Gene Network Analysis for Osteoporosis, Sarcopenia, Diabetes, and Obesity in Human Mesenchymal Stromal Cells

The systemic gene interactions that occur during osteoporosis and their underlying mechanisms remain to be determined. To this end, mesenchymal stromal cells (MSCs) were analyzed from bone marrow samples collected from healthy individuals (n = 5) and patients with osteoporosis (n = 5). A total of 120 osteoporosis-related genes were identified using RNA-sequencing (RNA-seq) and Ingenuity Pathway Analysis (IPA) software. In order to analyze these genes, we constructed a heatmap of one-way hierarchical clustering and grouped the gene expression patterns of the samples. The MSCs from one control participant showed a similar expression pattern to that observed in the MSCs of three patients with osteoporosis, suggesting that the differentiating genes might be important genetic determinants of osteoporosis. Then, we selected the top 38 genes based on fold change and expression, excluding osteoporosis-related genes from the control participant. We identified a network among the top 38 genes related to osteoblast and osteoclast differentiation, bone remodeling, osteoporosis, and sarcopenia using the Molecule Activity Predictor program. Among them, 25 genes were essential systemic genes involved in osteoporosis. Furthermore, we identified 24 genes also associated with diabetes and obesity, among which 10 genes were involved in a network related to bone and energy metabolism. The study findings may have implications for the treatment and prevention of osteoporosis.

Recent Advances in Enhancement Strategies for Osteogenic Differentiation of Mesenchymal Stem Cells in Bone Tissue Engineering

Although bone is an organ that displays potential for self-healing after damage, bone regeneration does not occur properly in some cases, and it is still a challenge to treat large bone defects. The development of bone tissue engineering provides a new approach to the treatment of bone defects. Among various cell types, mesenchymal stem cells (MSCs) represent one of the most promising seed cells in bone tissue engineering due to their functions of osteogenic differentiation, immunomodulation, and secretion of cytokines. Regulation of osteogenic differentiation of MSCs has become an area of extensive research over the past few years. This review provides an overview of recent research progress on enhancement strategies for MSC osteogenesis, including improvement in methods of cell origin selection, culture conditions, biophysical stimulation, crosstalk with macrophages and endothelial cells, and scaffolds. This is favorable for further understanding MSC osteogenesis and the development of MSC-based bone tissue engineering.

Scaffold-Free Spheroids with Two-Dimensional Heteronano-Layers (2DHNL) Enabling Stem Cell and Osteogenic Factor Codelivery for Bone Repair

Scaffold-free spheroids offer great potential as a direct supply of cells for bottom-up bone tissue engineering. However, the building of functional spheroids with both cells and bioactive signals remains challenging. Here, we engineered functional spheroids with mesenchymal stem cells (MSCs) and two-dimensional heteronano-layers (2DHNL) that consisted of black phosphorus (BP) and graphene oxide (GO) to create a 3D cell-instructive microenvironment for large defect bone repair. The effects of the engineered 2D materials on the proliferation, osteogenic differentiation of stem cells was evaluated in an in vitro 3D spheroidal microenvironment. Excellent in vivo support of osteogenesis of MSCs, neovascularization, and bone regeneration was achieved after transplanting these engineered spheroids into critical-sized rat calvarial defects. Further loading of osteogenic factor dexamethasone (DEX) on the 2DHNL showed outstanding in vivo osteogenic induction and bone regrowth without prior in vitro culture in osteogenic medium. The shortened overall culture time would be advantageous for clinical translation. These functional spheroids impregnated with engineered 2DHNL enabling stem cell and osteogenic factor codelivery could be promising functional building blocks to provide cells and differential clues in an all-in-one system to create large tissues for time-effective in vivo bone repair.

Global Proteomic Analysis of Mesenchymal Stem Cells Derived from Human Embryonic Stem Cells via Connective Tissue Growth Factor Treatment under Chemically Defined Feeder-Free Culture Conditions

Stem cells can be applied usefully in basic research and clinical field due to their differentiation and self-renewal capacity. The aim of this study was to establish an effective novel therapeutic cellular source and create its molecular expression profile map to elucidate the possible therapeutic mechanism and signaling pathway. We successfully obtained a mesenchymal stem cell population from human embryonic stem cells (hESCs) cultured on chemically defined feeder-free conditions and treated with connective tissue growth factor (CTGF) and performed the expressive proteomic approach to elucidate the molecular basis. We further selected 12 differentially expressed proteins in CTGF-induced hESC-derived mesenchymal stem cells (C-hESC-MSCs), which were found to be involved in the metabolic process, immune response, cell signaling, and cell proliferation, as compared to bone marrow derived-MSCs(BM-MSCs). Moreover, these up-regulated proteins were potentially related to the Wnt/β-catenin pathway. These results suggest that C-hESC-MSCs are a highly proliferative cell population, which can interact with the Wnt/β-catenin signaling pathway; thus, due to the upregulated cell survival ability or downregulated apoptosis effects of C-hESC-MSCs, these can be used as an unlimited cellular source in the cell therapy field for a higher therapeutic potential. Overall, the study provided valuable insights into the molecular functioning of hESC derivatives as a valuable cellular source.

Alkbh1-mediated DNA N6-methyladenine modification regulates bone marrow mesenchymal stem cell fate during skeletal aging

Objectives

DNA N6‐methyladenine (N6‐mA) demethylase Alkbh1 participates in regulating osteogenic differentiation of mesenchymal stem cell (MSCs) and vascular calcification. However, the role of Alkbh1 in bone metabolism remains unclear.

Materials and Methods

Bone marrow mesenchymal stem cells (BMSCs)‐specific Alkbh1 knockout mice were used to investigate the role of Alkbh1 in bone metabolism. Western blot, qRT‐PCR, and immunofluorescent staining were used to evaluate the expression of Alkbh1 or optineurin (optn). Micro‐CT, histomorphometric analysis, and calcein double‐labeling assay were used to evaluate bone phenotypes. Cell staining and qRT‐PCR were used to evaluate the osteogenic or adipogenic differentiation of BMSCs. Dot blotting was used to detect the level of N6‐mA in genomic DNA. Chromatin immunoprecipitation (Chip) assays were used to identify critical targets of Alkbh1. Alkbh1 adeno‐associated virus was used to overexpress Alkbh1 in aged mice.

Results

Alkbh1 expression in BMSCs declined during aging. Knockout of Alkbh1 promoted adipogenic differentiation of BMSCs while inhibited osteogenic differentiation. BMSC‐specific Alkbh1 knockout mice exhibited reduced bone mass and increased marrow adiposity. Mechanistically, we identified optn as the downstream target through which Alkbh1‐mediated DNA m6A modification regulated BMSCs fate. Overexpression of Alkbh1 attenuated bone loss and marrow fat accumulation in aged mice.

Conclusions

Our findings demonstrated that Alkbh1 regulated BMSCs fate and bone‐fat balance during skeletal aging and provided a potential target for the treatment of osteoporosis.

Reduced Osteogenic Differentiation Potential In Vivo in Acute Myeloid Leukaemia Patients Correlates with Decreased BMP4 Expression in Mesenchymal Stromal Cells

The osteogenic differentiation potential of mesenchymal stromal cells (hMSCs) is an essential process for the haematopoiesis and the maintenance of haematopoietic stem cells (HSCs). Therefore, the aim of this work was to evaluate this potential in hMSCs from AML patients (hMSCs-AML) and whether it is associated with BMP4 expression. The results showed that bone formation potential in vivo was reduced in hMSCs-AML compared to hMSCs from healthy donors (hMSCs-HD). Moreover, the fact that hMSCs-AML were not able to develop supportive haematopoietic cells or to differentiate into osteocytes suggests possible changes in the bone marrow microenvironment. Furthermore, the expression of BMP4 was decreased, indicating a lack of gene expression committed to the osteogenic lineage. Overall, these alterations could be associated with changes in the maintenance of HSCs, the leukaemic transformation process and the development of AML.

Regulation of the mesenchymal stem cell fate by interleukin-17: Implications in osteogenic differentiation

Bone regeneration is a tightly regulated process that ensures proper repair and functionality after injury. The delicate balance between bone formation and resorption is governed by cytokines and signaling molecules released during the inflammatory response. Interleukin (IL)-17A, produced in the early phase of inflammation, influences the fate of osteoprogenitors. Due to their inherent capacity to differentiate into osteoblasts, mesenchymal stem/stromal cells (MSCs) contribute to bone healing and regeneration. This review presents an overview of IL-17A signaling and the leading cellular and molecular mechanisms by which it regulates the osteogenic differentiation of MSCs. The main findings demonstrating IL-17A’s influence on osteoblastogenesis are described. To this end, divergent information exists about the capacity of IL-17A to regulate MSCs’ osteogenic fate, depending on the tissue context and target cell type, along with contradictory findings in the same cell types. Therefore, we summarize the data showing both the pro-osteogenic and anti-osteogenic roles of IL-17, which may help in the understanding of IL-17A function in bone repair and regeneration.

Mesenchymal Stem Cell-Derived Extracellular Vesicle: A Promising Alternative Therapy for Osteoporosis

Osteoporosis is the chronic metabolic bone disease caused by the disturbance of bone remodeling due to the imbalance of osteogenesis and osteoclastogenesis. A large population suffers from osteoporosis, and most of them are postmenopausal women or older people. To date, bisphosphonates are the main therapeutic agents in the treatment of osteoporosis. However, limited therapeutic effects with diverse side effects caused by bisphosphonates hindered the therapeutic applications and decreased the quality of life. Therefore, an alternative therapy for osteoporosis is still needed. Stem cells, especially mesenchymal stem cells, have been shown as a promising medication for numerous human diseases including many refractory diseases. Recently, researchers found that the extracellular vesicles derived from these stem cells possessed the similar therapeutic potential to that of parental cells. To date, a number of studies demonstrated the therapeutic applications of exogenous MSC-EVs for the treatment of osteoporosis. In this article, we reviewed the basic back ground of EVs, the cargo and therapeutic potential of MSC-EVs, and strategies of engineering of MSC-EVs for osteoporosis treatment.

Osteogenic and Chondrogenic Potential of Periosteum-Derived Mesenchymal Stromal Cells: Do They Hold the Key to the Future?

The periosteum, with its outer fibrous and inner cambium layer, lies in a dynamic environment with a niche of pluripotent stem cells for their reparative needs. The inner cambium layer is rich in mesenchymal progenitors, osteogenic progenitors, osteoblasts, and fibroblasts in a scant collagen matrix environment. Their role in union and remodeling of fracture is well known. However, the periosteum as a source of mesenchymal stem cells has not been explored in detail. Moreover, with the continuous expansion of techniques, newer insights have been acquired into the roles and regulation of these periosteal cells. From a therapeutic standpoint, the periosteum as a source of tissue engineering has gained much attraction. Apart from its role in bone repair, analysis of the bone-forming potential of periosteum-derived stem cells is lacking. Hence, this article elucidates the role of the periosteum as a potential source of mesenchymal stem cells along with their capacity for osteogenic and chondrogenic differentiation for therapeutic application in the future.

Mechanical loading alleviated the inhibition of β2-adrenergic receptor agonist terbutaline on bone regeneration

The long-term use of adrenergic medication in treating various conditions, such as asthma, increases the chances of bone fracture. Dynamic mechanical loading at a specific time is a method for improving bone quality and promoting healing. Therefore, we hypothesized that precisely controlling the mechanical environment can contribute to the alleviation of the negative effects of chronic treatment with the common asthma drug terbutaline, which is a β2-adrenergic receptor agonist that facilitates bone homeostasis and defect repair through its anabolic effect on osteogenic cells. Our in vitro results showed that terbutaline can directly inhibit osteogenesis by impairing osteogenic differentiation and mineralization. Chronic treatment in vivo was simulated by administering terbutaline to C57BL/6J mice for 4 weeks before bone defect surgery and mechanical loading. We utilized a stabilized tibial defect model, which allowed the application of anabolic mechanical loading. During homeostasis, chronic terbutaline treatment reduced the bone formation rate, the fracture toughness of long bones, and the concentrations of bone formation markers in the sera. During defect repair, terbutaline decreased the bone volume, type H vessel, and total blood vessel volume. Terbutaline treatment reduced the number of osteogenic cells. Periostin, which was secreted mainly by Prrx1+ osteoprogenitors and F4/80+ macrophages, was inhibited by treating the bone defect with terbutaline. Interestingly, controlled mechanical loading facilitated the recovery of bone volume and periostin expression and the number of osteogenic cells within the defect. In conclusion, mechanical loading can rescue negative effects on new bone accrual and repair induced by chronic terbutaline treatment.

Circ_0134944 inhibits osteogenesis through miR-127-5p/PDX1/SPHK1 pathway

Introduction

Osteoporosis, a common skeletal disorder mainly affecting postmenopausal women, is characterized by the imbalance between osteogenesis and osteoclastogenesis. Circ_0134944 has been recently found to be upregulated in postmenopausal osteoporosis (PMOP) patients. However, its role in osteogenesis remains unknown. Here we aimed to explore the role of circ_0134944 in osteogenesis and reveal the underlying mechanism.

Methods

qRT-PCR was used to determine the expression of circ_0134944, miR-127-5p, PDX1 and SPHK1 in the blood mononuclear cells (BMCs) of PMOP patients. Bone marrow mesenchymal stem cells (BMSCs) were used as the cellular model. Western blotting and qRT-PCR were used to determine the expression of osteogenesis-related genes (Runx2, OPN, OCN). ALP and Alizarin Red S staining were performed to evaluate osteogenic differentiation. The interactions between circ_0134944 and miR-127-5p, miR-127-5p and PDX1, PDX1 and SPHK1 were determined by dual-luciferase reporter and ChIP assay.

Results

Circ_0134944, PDX1 and SPHK1 were upregulated while miR-127-5p was downregulated in PMOP patients. Enhanced expression of circ_0134944 suppressed osteogenesis, which was then reversed by miR-127-5p overexpression. The binding between circ_0134944 and miR-127-5p, PDX1 and miR-127-5p were confirmed by dual-luciferase reporter assay. Moreover, PDX1 was enriched in the promoter region of SPHK1, and SPHK1 overexpression prevented the promotion of osteogenesis induced by miR-127-5p overexpression.

Conclusions

Taken together, these results demonstrate that circ_0134944 inhibit osteogenesis via miR-127-5p/PDX1/SPHK1 axis. Thus, the present study offered evidence that circ_0134944/miR-127-5p/PDX1/SPHK1 axis could be a potential therapeutic target for PMOP.

Betulinic acid decreases lipid accumulation in adipogenesis-induced human mesenchymal stem cells with upregulation of PGC-1α and UCP-1 and post-transcriptional downregulation of adiponectin and leptin secretion

Background

Controlling cellular functions, including stem cell growth and differentiation, can be the key for the treatment of metabolic disorders, such as type II diabetes mellitus (T2DM). Previously identified as peroxisome proliferator-activated receptor gamma (PPARγ) antagonist, betulinic acid (BA) may have the capability to control stem cell homeostasis, benefiting T2DM treatment. In this study, the effects of BA on osteogenesis and adipogenesis mechanisms of human mesenchymal stem cells (hMSCs) were investigated.

Results

We observed that BA increased hMSC osteogenesis by enhancing the alkaline phosphatase activity, calcium deposition, and mRNA expressions of osteogenic markers, namely, runt-related transcription factor 2, osteocalcin, and osteopontin. In addition, BA decreased hMSC adipogenesis with the decrease in glycerol-3-phosphate dehydrogenase activity, reduced intracellular lipid accumulations, down-regulated CCAAT-enhancer-binding protein alpha, and suppressed post-transcriptional adiponectin and leptin secretion. BA increased the brown adipocyte characteristics with the increase in the ratio of small lipid droplets and glucose uptake. Furthermore, the mRNA expressions of brown adipocyte markers, namely, PPARγ coactivator one alpha, uncoupling protein 1, and interleukin-6 increased.

Conclusions

Our results uncovered the mechanisms of how BA improved glucose and lipid metabolisms by decreasing white adipogenesis and increasing brown adipogenesis. Altogether, BA may be used for balancing glucose metabolisms without the potential side effects on bone loss or weight gain.

PKD1 alleviates oxidative stress-inhibited osteogenesis of rat bone marrow-derived mesenchymal stem cells through TAZ activation

Oxidative stress is known to inhibit osteogenesis and PKD1 is implicated in bone remodeling and skeletogenesis. In the present study, we explored the role of PKD1 in osteogenesis under oxidative stress. H2 O2 was used to induce oxidative stress in rat bone marrow (BM)-mesenchymal stem cells (MSCs) during osteoblast differentiation. Alkaline phosphatase (ALP) activity, calcium deposits, and the RUNX2 marker were assayed to determine osteogenic differentiation. The correlation of PKD1, Sirt1, c-MYC, and TAZ was further confirmed by chromatin immunoprecipitation (ChIP) and dual-luciferase reporter assay. We found that H2 O2 induced the downregulation of PKD1 expression and the upregulation of c-MYC, and Sirt1 was accompanied by decreasing cell viability in BM-MSCs. During osteogenic differentiation, the expression of PKD1 was upregulated significantly whereas Sirt1 tended to be upregulated mildly under normal conditions. Both PKD1 and Sirt1 were upregulated upon oxidative stress. The positive correlation of PKD1 expression with osteogenic differentiation under normal conditions might be hindered by oxidative stress and PKD1 could interact with TAZ under oxidative stress to regulate osteogenic differentiation. Our results suggest that PKD1 may alleviate oxidative stress-inhibited osteogenesis of rat BM-MSCs through TAZ activation.

Phactr1 negatively regulates bone mass by inhibiting osteogenesis and promoting adipogenesis of BMSCs via RhoA/ROCK2

The imbalance between osteogenic and adipogenic differentiation of Bone marrow-derived mesenchymal stem cells (BMSCs) is involved in the occurrence and development of osteoporosis (OP). Previous studies have indicated the potential of phosphatase and actin regulator 1 (Phactr1) in regulating osteogenic and adipogenic differentiation of BMSCs. The present study aims to investigate the function and mechanism of Phactr1 in regulating osteogenic and adipogenic differentiation of BMSCs. Herein, the expression of Phactr1 in bone and adipose tissue of OP rats was determined by immunohistochemical. BMSCs were subjected to osteogenic and adipogenic differentiation, and transfected with Phactr1 overexpression lentivirus, small interference RNA (siRNA) and KD025 (selective ROCK2 inhibitor). The relationship between Phactr1 and ROCK2 was detected by Co-IP experiment. The expression of Phactr1, Runx2, C/EBPα, RhoA and ROCK2 was detected by Western blot. Calcium nodule and lipid droplets were determined by alizarin red and Oil red O staining. Interestingly, Phactr1 increased in both bone and adipose tissue of OP rats. During osteogenic differentiation, Phactr1 decreased and active RhoA, ROCK2 increased, while overexpression Phactr1 inhibits the increase of Runx2. Phactr1 increased and active RhoA decreased, ROCK2 did not changed during adipogenic differentiation. While, Knockdown Phactr1 inhibits the increase of C/EBPα. Phactr1 and ROCK2 were combined in osteogenic differentiation, but not in adipogenic differentiation. By using KD025, the decrease of Phactr1 and increase of Runx2 were inhibited respectively in osteogenic differentiation. Meanwhile, when ROCK2 was inhibited, Phactr1, C/EBPα were significantly increased in adipogenic differentiation. These findings indicated that Phactr1 negatively regulates bone mass by inhibiting osteogenesis and promoting adipogenesis of BMSCs by activating RhoA/ROCK2.

Chromium Oxide Nanoparticle Impaired Osteogenesis and Cellular Response to Mechanical Stimulus

Background

Release of metallic wear particles from hip replacement implants is closely associated with aseptic loosening that affects the functionality and survivorship of the prostheses. Chromium oxide nanoparticles (CrNPs) are the dominant form of the wear particles found in the periprosthetic tissues. Whether CrNPs play a role in the clinically observed particle-induced osteolysis, tissue inflammatory reactions and functional activities of human mesenchymal stem cells (MSCs) remain unknown.

Methods

A tibia-defect rat model, cytotoxicity assays and flow cytometry were applied to study the effect of CrNPs on MSCs survival and macrophage inflammatory response. Also, oscillatory fluid flow stimulation was used to analyse the osteogenic differentiation of MSCs while treated by CrNPs. In addition, the influence of CrNPs on MSC biomechanical properties was determined via atomic force microscope (AFM) and fluorescence microscopy.

Results

It was found that implantation of CrNPs significantly decreased bone formation in vivo. CrNPs had no obvious effects on inflammatory cytokines release of U937 macrophages. Additionally, CrNPs did not interfere with MSCs osteogenic differentiation under static culture. However, the upregulated osteogenic differentiation of MSCs due to fluid flow stimulation was reduced by CrNPs in a dose-dependent manner. Moreover, osteogenic gene expression of OPN, Cox2 and Rnux2 after mechanical stimulation was also decreased by CrNPs treatments. Furthermore, cell elasticity and adhesion force of MSCs were affected by CrNPs over 3 days of exposure. We further verified that these effects of CrNPs could be associated with its interruption on cell mechanical properties.

Conclusion

The results demonstrated that CrNPs impaired cellular response to mechanical stimulus and osteogenesis without noticeable effects on the survival of the human MSCs.

FBW7 couples structural integrity with functional output of primary cilia

Structural defects in primary cilia have robust effects in diverse tissues and systems. However, how disorders of ciliary length lead to functional outcomes are unknown. We examined the functional role of a ciliary length control mechanism of FBW7-mediated destruction of NDE1, in mesenchymal stem cell (MSC) differentiation. We show that FBW7 functions as a master regulator of both negative (NDE1) and positive (TALPID3) regulators of ciliogenesis, with an overall positive net effect on primary cilia formation, MSC differentiation to osteoblasts, and bone architecture. Deletion of Fbxw7 suppresses ciliation, Hedgehog activity, and differentiation, which are partially rescued in Fbxw7/Nde1-null cells. We also show that NDE1, despite suppressing ciliogenesis, promotes MSC differentiation by increasing the activity of the Hedgehog pathway by direct binding and enhancing GLI2 activity in a cilia-independent manner. We propose that FBW7 controls a protein-protein interaction network coupling ciliary structure and function, which is essential for stem cell differentiation.

Petsouki et al. dissect the importance of FBW7-mediated regulation of NDE1 and TALPID3 in mesenchymal stem cells (MSCs). They find that by modulating the abundance of negative (NDE1) and positive (TALPID3) cilia regulators, FBW7 contributes to both the assembly and signaling functions of primary cilia that are necessary for osteoblast differentiation.

Andrographolide Reduces Lipid Droplet Accumulation in Adipocytes Derived from Human Bone Marrow Mesenchymal Stem Cells by Suppressing Regulators of Adipogenesis

Obesity has become a major public health concern; so, a strategy to prevent or reduce obesity is a priority. The inhibition of lipid droplet accumulation and adipogenesis process provides a target for the treatment of obesity. Herein, the effect of andrographolide (AP) on lipid accumulation in adipocytes derived from human bone marrow mesenchymal stem cells (hBM-MSCs) was examined. AP at concentrations of 1, 2.5, 5, and 10 μM reduced lipid droplet accumulation in the adipocytes by suppressing the adipogenic differentiation of hBM-MSCs. Concurrently, the expressions of adipogenic marker genes and the level of adipokines secreted by adipocytes were suppressed. Gene screening analysis showed a negative regulation of genes involved in the adipogenesis process. In conclusion, we demonstrated for the first time an antilipid accumulation in adipocytes from hBM-MSCs by AP. The compound may potentially be a novel therapeutic agent for the treatment of obesity as well as obesity-related diseases.

Bone marrow adiposity inversely correlates with bone turnover in pediatric renal osteodystrophy

Bone marrow adiposity is associated with bone disease in the general population. Although chronic kidney disease (CKD) is associated with increased bone fragility, the correlation between marrow adiposity and bone health in CKD is unknown. We evaluated the relationship between bone marrow adipocytes and bone histomorphometry in 32 pediatric patients. We also evaluated the effects of growth hormone and calcitriol (1,25(OH)₂D₃)—two therapies commonly prescribed for pediatric bone disease—on marrow adiposity and bone histomorphometry. Finally, the adipogenic potential of primary human osteoblasts from CKD patients was assessed in vitro, both alone and in the presence of 1,25(OH)₂D₃. In cross-sectional analysis, marrow adipocyte number per tissue area (Adi.N/T.Ar) correlated with bone formation rate/bone surface (BFR/BS) in patients with high bone turnover (r = −0.55, p = 0.01) but not in those with low/normal bone turnover. Changes in bone formation rate correlated with changes Adi.N/T.Ar on repeat bone biopsy(r = −0.48, p = 0.02). In vitro, CKD and control osteoblasts had a similar propensity to transition into an adipocyte-like phenotype; 1,25(OH)₂D₃ had very little effect on this propensity. In conclusion, marrow adiposity correlates inversely with bone turnover in pediatric patients with high turnover renal osteodystrophy. The range of adiposity observed in pediatric patients with low/normal bone turnover is not explained by intrinsic changes to precursor cells or by therapies but may reflect the effects of circulating factors on bone cell health in this population.

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Marrow adipocyte numbers correlate with bone formation in high turnover renal osteodystrophy.

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Marrow adipocyte numbers do not correlate with osteoid accumulation in CKD.

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Circulating toxins may impair adipogenesis in low turnover osteodystrophy.

Wnt signalling inhibits adipogenesis in orbital fibroblasts from patients with Graves' orbitopathy

BACKGROUND/AIMS

To investigate the role of Wnt signalling in adipogenesis using an in vitro model of Graves' orbitopathy (GO).

METHODS

Orbital fat was obtained from patients with GO and non-GO participants for primary orbital fibroblast (OF) culture. Expression levels of Wnt5a, Wnt10b, β-catenin, phospho-β-catenin and cyclin D1 were compared between GO and non-GO OFs. These expression levels were also determined during adipogenesis of GO and non-GO OFs. The effects of a stimulator and inhibitor of Wnt signalling on adipogenesis of GO and non-GO OFs were investigated.

RESULTS

Western blotting analysis showed significant reductions in β-catenin and cyclin D1 and significant enhancement of phospho-β-catenin in OFs from patients with GO, compared with OFs from non-GO participants (p<0.05). Expression of Wnt5a, Wnt10b, β-catenin and cyclin D1 in OFs was highest on day 0, and then gradually declined after induction of adipogenic differentiation. The expression levels of PPARγ, C/EBPα and C/EBPβ were reduced in Wnt stimulator-treated OFs in a dose-dependent manner. Oil red O staining confirmed that a stimulator of Wnt inhibited adipogenesis in GO OFs.

CONCLUSION

These results indicate that Wnt signalling inhibits adipogenesis in OFs from patients with GO and non-GO participants. Further studies are required to examine the potential of Wnt signalling as a target for therapeutic strategies.

Pre-conditioning of Mesenchymal Stem Cells with Piper longum L. augments osteogenic differentiation

ETHNOPHARMACOLOGICAL RELEVANCE

The Indian Traditional Medicine, Ayurveda prescribes Piper longum L. popularly known as Long Pepper (Pippali) for the treatment of inflammatory and degenerative diseases. Therapeutic benefits of Piper longum L. are mainly attributed to the anti-inflammatory and arthritic potential.

AIM OF THE STUDY

This study was aimed to explore the activity of Piper longum L. fruit extract on proliferation and osteogenic differentiation of human Wharton's Jelly Mesenchymal Stem Cells (WJMSCs) to find out it's possible role as anti-osteoporotic agent.

MATERIALS AND METHODS

Proliferation of WJMSCs treated with Piper longum L. fruit extract was assessed by MTT assay and Cell Cycle Analysis. Effect of Piper longum L. preconditioning on osteogenic differentiation was performed. Ca2+ accumulation and matrix mineralization (Von Kossa and Alizarin Red Staining), alkaline phosphatase (ALP) activity and gene expression of key mRNA (RT PCR) was analyzed.

RESULTS

Significant increase in the proliferation of WJMSCs was observed upon treatment of Piper longum L. at 5 μg/mL (P < 0.001) which can be attributed to the significant decrease in apoptotic cells (P < 0.05) as evidenced by cell cycle analysis. Preconditioning of Piper longum L. (10-100 μg/mL) enhanced Ca2+ accumulation and matrix mineralization as observed by Von Kossa and Alizarin Red staining where ALP activity was elevated 3.6 folds as compared to untreated WJMSCs (P < 0.001). RT-PCR analysis exhibited up regulation of Runx2, Osterix, ALP and OPN mRNAs.

CONCLUSIONS

We demonstrate for the first time that Piper longum L. fruit extract enhanced osteogenic differentiation of WJMSCs. This finding can be clinically translated into development of an anti-osteoporotic agent.

CGRP Regulates the Age-Related Switch Between Osteoblast and Adipocyte Differentiation

Osteoporosis is a chronic age-related disease. During aging, bone marrow-derived mesenchymal stem cells (BMSCs) display increased adipogenic, along with decreased osteogenic, differentiation capacity. The aim of the present study was to investigate the effect of calcitonin gene-related peptide (CGRP) on the osteogenic and adipogenic differentiation potential of BMSC-derived osteoblasts. Here, we found that the level of CGRP was markedly lower in bone marrow supernatant from aged mice compared with that in young mice. In vitro experiments indicated that CGRP promoted the osteogenic differentiation of BMSCs while inhibiting their adipogenic differentiation. Compared with vehicle-treated controls, aged mice treated with CGRP showed a substantial promotion of bone formation and a reduction in fat accumulation in the bone marrow. Similarly, we found that CGRP could significantly enhance bone formation in ovariectomized (OVX) mice in vivo. Together, our results suggested that CGRP may be a key regulator of the age-related switch between osteogenesis and adipogenesis in BMSCs and may represent a potential therapeutic strategy for the treatment of age-related bone loss.

The effects of locomotion on bone marrow mesenchymal stem cell fate: insight into mechanical regulation and bone formation

Bone marrow mesenchymal stem cells (BMSCs) refer to a heterogeneous population of cells with the capacity for self-renewal. BMSCs have multi-directional differentiation potential and can differentiate into chondrocytes, osteoblasts, and adipocytes under specific microenvironment or mechanical regulation. The activities of BMSCs are closely related to bone quality. Previous studies have shown that BMSCs and their lineage-differentiated progeny (for example, osteoblasts), and osteocytes are mechanosensitive in bone. Thus, a goal of this review is to discuss how these ubiquious signals arising from mechanical stimulation are perceived by BMSCs and then how the cells respond to them. Studies in recent years reported a significant effect of locomotion on the migration, proliferation and differentiation of BMSCs, thus, contributing to our bone mass. This regulation is realized by the various intersecting signaling pathways including RhoA/Rock, IFG, BMP and Wnt signalling. The mechanoresponse of BMSCs also provides guidance for maintaining bone health by taking appropriate exercises. This review will summarize the regulatory effects of locomotion/mechanical loading on BMSCs activities. Besides, a number of signalling pathways govern MSC fate towards osteogenic or adipocytic differentiation will be discussed. The understanding of mechanoresponse of BMSCs makes the foundation for translational medicine.

Histomorphometric Evaluation of Socket Preservation Using Autogenous Tooth Biomaterial and BM-MSC in Dogs

This study is aimed at assessing the dimensional alterations occurring in the alveolar bone after premolar extraction in dogs with histomorphometric and histological analysis. After atraumatic premolar extraction, tooth-derived bone graft material was grafted in the extraction socket of the premolar region in the lower jaws of six dogs in two experimental groups. In the second experimental group, BM-MSCs were added together with the graft. The control was left untreated on the opposite side. After twelve weeks, all six animals were sacrificed. Differences in alveolar bone height crests lingually and buccally, and alveolar bone width at 1, 3, and 5 mm infracrestally, were examined. Histologic study revealed osteoconductive properties of tooth biomaterial. A statistically significant difference was detected between the test and control groups. In the test groups, a reduced loss of vertical and horizontal alveolar bone dimensions compared with the control group was observed. Tooth bone graft material may be considered useful for alveolar ridge preservation after tooth extraction, as it could limit the natural bone resorption process.

The Role of Adipose Stem Cells in Bone Regeneration and Bone Tissue Engineering

Bone regeneration is a complex process that is influenced by tissue interactions, inflammatory responses, and progenitor cells. Diseases, lifestyle, or multiple trauma can disturb fracture healing, which might result in prolonged healing duration or even failure. The current gold standard therapy in these cases are bone grafts. However, they are associated with several disadvantages, e.g., donor site morbidity and availability of appropriate material. Bone tissue engineering has been proposed as a promising alternative. The success of bone-tissue engineering depends on the administered cells, osteogenic differentiation, and secretome. Different stem cell types offer advantages and drawbacks in this field, while adipose-derived stem or stromal cells (ASCs) are in particular promising. They show high osteogenic potential, osteoinductive ability, and immunomodulation properties. Furthermore, they can be harvested through a noninvasive process in high numbers. ASCs can be induced into osteogenic lineage through bioactive molecules, i.e., growth factors and cytokines. Moreover, their secretome, in particular extracellular vesicles, has been linked to fracture healing. The aim of this review is a comprehensive overview of ASCs for bone regeneration and bone tissue engineering.

Wnt7a promotes the osteogenic differentiation of human mesenchymal stem cells

Mesenchymal stem cells (MSCs) have the ability of differentiating into osteoblasts. Elucidating the molecular mechanisms of MSC differentiation into osteoblasts may provide novel therapeutic strategies for bone‑related diseases. Increasing evidence has confirmed that Wnt signaling plays the key role in osteoblast differentiation; however, the role of individual Wnt proteins in osteogenesis needs to be investigated. The present study thus aimed to explore the role of Wnt7a in bone formation. For this purpose, human bone‑derived MSCs were identified by flow cytometry and the cell differentiation potential, including osteogenic and adipogenic differentiation was examined. In order to explore the role of Wnt7a in MSC osteogenic differentiation, Wnt7a expression was measured at the mRNA and protein level following treatment with the osteogenic inducer, bone morphogenetic protein (BMP)4/7, and following the induction of osteogenic or adipogenic differentiation. The ectopic expression of Wnt7a in MSCs was confirmed and its influence on MSC osteogenic differentiation was detected using osteocyte markers and by Alizarin Red S staining. Mechanistically, the influence of Wnt7a on Runt‑related transcription factor 2 (RUNX2) expression was examined at the mRNA and protein level. The regulatory effects of Wnt7a on RUNX2 promoter activities were examined by promoter reporter assay, and by examining the binding of TCF1, a downstream target of Wnt, to the RUNX2 promoter by ChIP assay. The results revealed that the knockdown of Wnt7a in MSCs decreased the expression of osteocyte markers and inhibited osteogenic differentiation. In accordance, the overexpression of Wnt7a in MSCs increased the expression of osteocyte markers and promoted osteogenic differentiation. Mechanistically, the knockdown of Wnt7a in MSCs reduced RUNX2 expression and the overexpression of Wnt7a in MSCs promoted RUNX2 expression. Furthermore, it was confirmed that Wnt7a regulated RUNX2 promoter activities by promoter report assay, and by examining the binding of TCF1 to the RUNX2 promoter by ChIP assay. On the whole, the present study demonstrates that Wnt7a plays a key role in MSC differentiation into osteoblasts and the findings presented herein may provide a promising therapy target for bone‑related diseases.

Long Non-coding RNAs and MicroRNAs Interplay in Osteogenic Differentiation of Mesenchymal Stem Cells

Long non-coding RNAs (lncRNAs) have gained great attention as epigenetic regulators of gene expression in many tissues. Increasing evidence indicates that lncRNAs, together with microRNAs (miRNAs), play a pivotal role in osteogenesis. While miRNA action mechanism relies mainly on miRNA-mRNA interaction, resulting in suppressed expression, lncRNAs affect mRNA functionality through different activities, including interaction with miRNAs. Recent advances in RNA sequencing technology have improved knowledge into the molecular pathways regulated by the interaction of lncRNAs and miRNAs. This review reports on the recent knowledge of lncRNAs and miRNAs roles as key regulators of osteogenic differentiation. Specifically, we described herein the recent discoveries on lncRNA-miRNA crosstalk during the osteogenic differentiation of mesenchymal stem cells (MSCs) derived from bone marrow (BM), as well as from different other anatomical regions. The deep understanding of the connection between miRNAs and lncRNAs during the osteogenic differentiation will strongly improve knowledge into the molecular mechanisms of bone growth and development, ultimately leading to discover innovative diagnostic and therapeutic tools for osteogenic disorders and bone diseases.

CDR1as regulated by hnRNPM maintains stemness of periodontal ligament stem cells via miR-7/KLF4

CDR1as is a well‐identified circular RNA with regulatory roles in a variety of physiological processes. However, the effects of CDR1as on stemness of periodontal ligament stem cells (PDLSCs) and the underlying mechanisms remain unclear. In this study, we detect CDR1as in human PDLSCs, and subsequently demonstrate that CDR1as maintains PDLSC stemness. Knockdown of CDR1as decreases the expression levels of stemness‐related genes and impairs the cell's multi‐differentiation and cell migration abilities, while overexpression of CDR1as increases the expression levels of stemness‐related genes and enhances these abilities. Furthermore, our results indicate that the RNA‐binding protein hnRNPM directly interacts with CDR1as and regulates its expression in PDLSCs. In addition, we show that CDR1as promotes the expression of stemness‐related genes in PDLSCs by inhibiting miR‐7‐mediated suppression of KLF4 expression. Collectively, our results demonstrate that CDR1as participates in the molecular circuitry that regulates PDLSC stemness.

GSK3β rephosphorylation rescues ALPL deficiency-induced impairment of odontoblastic differentiation of DPSCs

Background

Premature exfoliation of the deciduous teeth is a common manifestation in childhood patients with hypophosphatasia (HPP), which is an autosomal inherited disease caused by ALPL mutations. Dysplasia of the cementum, dentin, and alveolar bone has been proposed to be the main reasons for the exfoliation of teeth, while the extraordinarily complex intracellular mechanisms remain elusive. Dental pulp stem cells (DPSCs) have been demonstrated to successfully regenerate functional pulp-dentin-like tissue. Dental pulp cells derived from HPP patients impaired mineralization; however, insight into the deeper mechanism is still unclear.

Methods

The effects of ALPL on odontoblastic differentiation of DPSCs from HPP patient were assessed by Alizarin Red staining, immunofluorescent staining, Western blot and RT-PCR, and micro-CT assays.

Result

Here, we found DPSCs from HPP patient exhibited low ALP activity and impaired odontoblastic differentiation. Meanwhile, we found that loss of function of ALPL reduced phosphorylation of GSK3β in DPSCs. While GSK3β rephosphorylation improved odontoblastic differentiation of HPP DPSCs with LiCl treatment. Finally, we demonstrated systemic LiCl injection ameliorated tooth-associated defects in ALPL^+/− mice by enhanced phosphorylation of GSK3β in the teeth.

Conclusions

Our study indicates that ALPL regulates odontoblastic differentiation of DPSCs and provides useful information for understanding how ALPL deficiency led to tooth dysplasia and, ultimately, may inform efforts at improvement tooth defects in HPP patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02235-7.

Development of a Biomaterial Scaffold Integrated with Osteoinductive Oxysterol Liposomes to Enhance Hedgehog Signaling and Bone Repair

Bone repair requires the tightly regulated control of multiple intrinsic and extrinsic cell types and signaling pathways. One of the positive regulatory signaling pathways in membranous and endochondral bone healing is the Hedgehog (Hh) signaling family. Here, a novel therapeutic liposomal delivery vector was developed by self-assembly of an Hh-activating cholesterol analog with an emulsifier, along with the addition of Smoothened agonist (SAG) as a drug cargo, for the enhancement of Hh signaling in bone regeneration. The drug-loaded nanoparticulate agonists of Hh signaling were immobilized onto trabecular bone-mimetic apatite-coated 3D scaffolds using bioinspired polydopamine adhesives to ensure favorable microenvironments for cell growth and local therapeutic delivery. Results showed that SAG-loaded liposomes induced a significant and dose-dependent increase in Hh-mediated osteogenic differentiation, as evidenced by in vitro analysis of bone marrow stromal cells, and in vivo calvarial bone healing, as evidenced using all radiographic parameters and histomorphometric analyses. Moreover, favorable outcomes were achieved in comparison to standards of care, including collagen sponge-delivered rBMP2 or allograft bone. In summary, this study demonstrates using a nanoparticle packaged Hh small molecule as a widely applicable bone graft substitute for robust bone repair.

Synergistic Effect of rhBMP-2 Protein and Nanotextured Titanium Alloy Surface to Improve Osteogenic Implant Properties

One of the major limitations during titanium (Ti) implant osseointegration is the poor cellular interactions at the biointerface. In the present study, the combined effect of recombinant human Bone Morphogenetic Protein-2 (rhBMP-2) and nanopatterned Ti6Al4V fabricated with Directed irradiation synthesis (DIS) is investigated in vitro. This environmentally-friendly plasma uses ions to create self-organized nanostructures on the surfaces. Nanocones (≈36.7 nm in DIS 80°) and thinner nanowalls (≈16.5 nm in DIS 60°) were fabricated depending on DIS incidence angle and observed via scanning electron microscopy. All samples have a similar crystalline structure and wettability, except for sandblasted/acid-etched (SLA) and acid-etched/anodized (Anodized) samples which are more hydrophilic. Biological results revealed that the viability and adhesion properties (vinculin expression and cell spreading) of DIS 80° with BMP-2 were similar to those polished with BMP-2, yet we observed more filopodia on DIS 80° (≈39 filopodia/cell) compared to the other samples (<30 filopodia/cell). BMP-2 increased alkaline phosphatase activity in all samples, tending to be higher in DIS 80°. Moreover, in the mineralization studies, DIS 80° with BMP-2 and Anodized with BMP-2 increased the formation of calcium deposits (>3.3 fold) compared to polished with BMP-2. Hence, this study shows there is a synergistic effect of BMP-2 and DIS surface modification in improving Ti biological properties which could be applied to Ti bone implants to treat bone disease.

Co-transfection with BMP2 and FGF2 via chitosan nanoparticles potentiates osteogenesis in human adipose-derived stromal cells in vitro

OBJECTIVE

To investigate if co-transfection of human bone morphogenetic protein 2 (BMP-2, BMP2) and human fibroblast growth factor 2 (FGF2, FGF2) via chitosan nanoparticles promotes osteogenesis in human adipose tissue-derived stem cells (ADSCs) in vitro.

MATERIALS AND METHODS

Recombinant BMP2 and/or FGF2 expression vectors were constructed and packaged into chitosan nanoparticles. The chitosan nanoparticles were characterized by atomic force microscopy. Gene and protein expression levels of BMP-2 and FGF2 in ADSCs in vitro were evaluated by real-time polymerase chain reaction (PCR), western blot, and enzyme-linked immunosorbent assay. Osteocalcin (OCN) and bone sialoprotein (BSP) gene expression were also evaluated by real-time PCR to assess osteogenesis.

RESULTS

The prepared chitosan nanoparticles were spherical with a relatively homogenous size distribution. The BMP2 and FGF2 vectors were successfully transfected into ADSCs. BMP-2 and FGF2 mRNA and protein levels were significantly up-regulated in the co-transfection group compared with the control group. OCN and BSP mRNA levels were also significantly increased in the co-transfection group compared with cells transfected with BMP2 or FGF2 alone, suggesting that co-transfection significantly enhanced osteogenesis.

CONCLUSIONS

Co-transfection of human ADSCs with BMP2/FGF2 via chitosan nanoparticles efficiently promotes the osteogenic properties of ADSCs in vitro.

Ligustrum japonicum Thunb. Fruits Exert Antiosteoporotic Properties in Bone Marrow-Derived Mesenchymal Stromal Cells via Regulation of Adipocyte and Osteoblast Differentiation

Ligustrum japonicum fruits have been used as a part of traditional medicinal practices and supplements in Korea and Japan. It has been reported to possess various bioactivities, but its antiosteoporotic potential and active substances have not been reported yet. The present study followed an ALP activity and lipid accumulation-guided screening of L. japonicum fruits for antiosteoporotic compounds and isolated salidroside as an active compound. Antiosteoporotic effects of L. japonicum fruits and salidroside were examined in mesenchymal stromal cells by their ability to enhance osteoblast formation by increased ALP activity and osteogenic marker gene expression while suppressing adipogenesis by inhibition of lipid accumulation and adipocyte marker gene expressions. Results showed that salidroside was able to enhance osteoblast differentiation via Wnt/BMP signaling pathway overactivation and suppress the PPARγ-mediated adipocyte differentiation, both through the MAPK pathway. In conclusion, L. japonicum fruits were suggested to possess antiosteoporotic activities and to be a source of antiosteoporotic substances such as salidroside.

Direct conversion of osteosarcoma to adipocytes by targeting TNIK

Osteosarcoma (OS) is an aggressive mesenchymal tumor for which no molecularly targeted therapies are available. We have previously identified TRAF2- and NCK-interacting protein kinase (TNIK) as an essential factor for the transactivation of Wnt signal target genes and shown that its inhibition leads to eradication of colorectal cancer stem cells. The involvement of Wnt signaling in the pathogenesis of OS has been implicated. The aim of the present study was to examine the potential of TNIK as a therapeutic target in OS. RNA interference or pharmacological inhibition of TNIK suppressed the proliferation of OS cells. Transcriptome analysis suggested that a small-molecule inhibitor of TNIK upregulated the expression of genes involved in OS cell metabolism and downregulated transcription factors essential for maintaining the stem cell phenotype. Metabolome analysis revealed that this TNIK inhibitor redirected the metabolic network from carbon flux toward lipid accumulation in OS cells. Using in vitro and in vivo OS models, we confirmed that TNIK inhibition abrogated the OS stem cell phenotype, simultaneously driving conversion of OS cells to adipocyte-like cells through induction of PPARγ. In relation to potential therapeutic targeting in clinical practice, TNIK was confirmed to be in an active state in OS cell lines and clinical specimens. From these findings, we conclude that TNIK is applicable as a potential target for treatment of OS, affecting cell fate determination.

The Role of Melanotransferrin (CD228) in the regulation of the differentiation of Human Bone Marrow-Derived Mesenchymal Stem Cells (hBM-MSC)

Melanotransferrin (CD228), firstly reported as a melanoma-associated antigen, is a membrane-bound glycoprotein of an iron-binding transferrin homolog. CD228 was found to be expressed significantly higher in human bone marrow-derived mesenchymal stem cells (hBM-MSC) than in human embryonic fibroblasts (FB) by RT-PCR, western blotting and flow cytometry. The expression of CD228 declined in aged hBM-MSC as osteogenesis-related genes did. We examined a possible role for CD228 in the regulation of osteogenesis and adipogenesis of hBM-MSC. Surprisingly, siRNA-mediated CD228 knockdown increased the expression of the transcription factor DLX5 and enhanced osteogenesis of hBM-MSC evidenced by an increased expression of the runt-related transcription factor 2 (RUNX2), osterix (Osx), and osteocalcin (OC), as well as higher alkaline phosphatase (ALP) activity and extracellular calcium deposition. Interestingly, hBM-MSC transfected with CD228 siRNA also showed an increase in intracellular lipid level during adipogenesis, indicated by oil red O staining of differentiated adipocytes. Overall, our study unveils CD228 as a cell surface molecule expressed by young hBM-MSC, but not by FB. It also provides evidence to suggest a role for CD228 as a negative regulator of osteogenesis and of lipid accumulation during adipogenesis in hBM-MSC in vitro.

The role of HDAC11 in obesity-related metabolic disorders: A critical review

At present, metabolic diseases, such as obesity and diabetes, have become the world's top health threats. These diseases are closely related to the abnormal development and function of adipocytes and metabolic inflammation associated with obesity. Histone deacetylase 11 (HDAC11), with a relatively unique structure and function in the HDAC family, plays a vital role in regulating cell growth, migration, and cell death. Currently, research on new key regulatory functions of HDAC11 in metabolic homeostasis is receiving more and more attention, and HDAC11 has also become a potential therapeutic target in the treatment of obesity and obesity-related diseases. Here, we summarized the latest literature on the role of HDAC11 in regulating the progress of obesity-related metabolic disorders.

Erythropoietin in bone homeostasis-Implications for efficacious anemia therapy

Bone homeostasis and hematopoiesis are irrevocably linked in the hypoxic environment of the bone marrow. Erythropoietin (Epo) regulates erythropoiesis by binding to its receptor, Epor, on erythroid progenitor cells. The continuous process of bone remodeling is achieved by the finely balanced activity of osteoblasts in bone synthesis and osteoclasts in bone resorption. Both osteoblasts and osteoclasts express functional Epors, but the underlying mechanism of Epo‐Epor signaling in bone homeostasis is incompletely understood. Two recent publications have provided new insights into the contribution of endogenous Epo to bone homeostasis. Suresh et al examined Epo‐Epor signaling in osteoblasts in bone formation in mice and Deshet‐Unger et al investigated osteoclastogenesis arising from transdifferentiation of B cells. Both groups also studied bone loss in mice caused by exogenous human recombinant EPO‐stimulated erythropoiesis. They found that either deletion of Epor in osteoblasts or conditional knockdown of Epor in B cells attenuates EPO‐driven bone loss. These findings have direct clinical implications because patients on long‐term treatment for anemia may have an increased risk of bone fractures. Phase 3 trials of small molecule inhibitors of the PHD enzymes (hypoxia inducible factor‐prolyl hydroxylase inhibitors [HIF‐PHIs]), such as Roxadustat, have shown improved iron metabolism and increased circulating Epo levels in a titratable manner, avoiding the supraphysiologic increases that often accompany intravenous EPO therapy. The new evidence presented by Suresh and Deshet‐Unger and their colleagues on the effects of EPO‐stimulated erythropoiesis on bone homeostasis seems likely to stimulate discussion on the relative merits and safety of EPO and HIF‐PHIs.

Selenium Nanoparticles by Moderating Oxidative Stress Promote Differentiation of Mesenchymal Stem Cells to Osteoblasts

Purpose

Redox homeostasis plays an important role in the osteogenic differentiation of human mesenchymal stem cells (hMSCs) for bone engineering. Oxidative stress (OS) is believed to induce osteoporosis by changing bone homeostasis. Selenium nanoparticles (SeNPs), an antioxidant with pleiotropic pharmacological activity, prevent bone loss. However, the molecular mechanism underlying the osteogenic activity during hMSC–SeNP interaction is unclear.

Methods

This study assessed the effects of different concentrations (25, 50, 100, and 300 ng/mL) of SeNPs on the cell viability and differentiation ability of human embryonic stem cell-derived hMSCs. In addition, we analyzed OS markers and their effect on mitogen-activated protein kinase (MAPK) and Forkhead box O3 (FOXO3) during osteogenesis.

Results

SeNPs increased the cell viability of hMSCs and induced their differentiation toward an osteogenic over an adipogenic lineage by enhancing osteogenic transcription and mineralization, while inhibiting Nile red staining and adipogenic gene expression. By preventing excessive reactive oxygen species accumulation, SeNPs increased antioxidant levels in hMSCs undergoing osteogenesis compared to untreated cells. In addition, SeNPs significantly upregulated the gene and protein expression of phosphorylated c-Jun N-terminal kinase (JNK) and FOXO3a, with no significant change in the expression levels of extracellular signal-related kinase (ERK) and p38 MAPK.

Conclusion

The results approved that low concentrations of SeNPs might enhance the cell viability and osteogenic potential of hMSCs by moderating OS. Increased JNK and FOXO3a expression shows that SeNPs might enhance osteogenesis via activation of the JNK/FOXO3 pathway. In addition, SeNP co-supplementation might prevent bone loss by enhancing osteogenesis and, thus, can be an effective candidate for treating osteoporosis through cell-based therapy.

Sclareol inhibits RANKL-induced osteoclastogenesis and promotes osteoblastogenesis through promoting CCN1 expression via repressing the MAPK pathway

Osteoclasts are crucial cellular components of bone and are the cause of various bone problems like osteoporosis. Various biological activities such as anti-tumorous, anti-inflammatory, antibacterial, and immunomodulatory function are influenced by Sclareol, as a natural diterpene compound. However, studies on the effect and mechanism of Sclareol on osteoporosis are rare. In the current research, the influence of Sclareol on osteoclastogenesis and osteoblastogenesis was targeted to be discovered in ovariectomy (OVX)-induced animal models and in vitro. The expression levels of osteoclast-related genes such as c-Fos, NFATc1, and CTSK were detected by RT-qPCR and western blotting to understand the inhibition of Sclareol on the creation of osteoclast. The influence of Sclareol on osteoblastogenesis and the expression of osteoblastogenic markers were also examined. Sclareol inhibited the osteoclastogenesis caused by receptor activator of nuclear factor-κB ligand (RANKL) which promoted osteoblastogenesis through upregulating the expression of cysteine-rich protein 61 (CYR61/CCN1), which is a matricellular protein of the CCN family. The p-ERK and p-P38 protein expression levels were considerably downregulated by Sclareol. Furthermore, CCN1 overexpression partially mimicked the inhibitory effect of Sclareol, while the opposite results were obtained after CCN1 silencing. Additionally, Sclareol protected against loss of bones in an osteoporosis mouse model generated by OVX. The acquired results indicated that Sclareol represses RANKL-induced osteoclastogenesis and promotes osteoblastogenesis via promoting the expression of CCN1 by constraining the mitogen-activated protein kinase (MAPK) pathway. Our findings proposed that for the avoidance and treatment of osteoclast-linked disorders, Sclareol is a potentially effective drug. A proposed model for mediated regulation of osteoclastogenesis and osteoblastogenesis by Sclareol. The basic model of the process by which Sclareol prevents osteoclastogenesis and promotes osteoblastogenesis. Sclareol may increase the expression of CCN1 through inhibiting the MAPK pathway, thereby inhibiting osteoclast differentiation and attenuating bone resorption. Sclareol represses the expression of c-Fos, which stimulates the formation of osteoclast. In contrast, Sclareol promotes osteoblast differentiation by upregulating Runx2 expression, thereby improving the formation of bones. Consequently, Sclareol protects against loss of bones by regulating the stability of bone makeover via inhibition of bone formation and stimulation of bone resorption. Graphical Headlights 1. Sclareol represses RANKL-induced osteoclastogenesis. 2. Sclareol promotes osteoblast differentiation. 3. Sclareol inhibits the MAPK pathway through induction of CCN1. 4. Sclareol protects against bone loss by regulating the balance of bone remodeling via inhibition of bone formation and stimulation of bone resorption.

Deconstructing transcriptional variations and their effects on immunomodulatory function among human mesenchymal stromal cells

Background

Mesenchymal stromal cell (MSC)-based therapies are being actively investigated in various inflammatory disorders. However, functional variability among MSCs cultured in vitro will lead to distinct therapeutic efficacies. Until now, the mechanisms behind immunomodulatory functional variability in MSCs are still unclear.

Methods

We systemically investigated transcriptomic variations among MSC samples derived from multiple tissues to reveal their effects on immunomodulatory functions of MSCs. We then analyzed transcriptomic changes of MSCs licensed with INFγ to identify potential molecular mechanisms that result in distinct MSC samples with different immunomodulatory potency.

Results

MSCs were clustered into distinct groups showing different functional enrichment according to transcriptomic patterns. Differential expression analysis indicated that different groups of MSCs deploy common regulation networks in response to inflammatory stimulation, while expression variation of genes in the networks could lead to different immunosuppressive capability. These different responsive genes also showed high expression variability among unlicensed MSC samples. Finally, a gene panel was derived from these different responsive genes and was able to regroup unlicensed MSCs with different immunosuppressive potencies.

Conclusion

This study revealed genes with expression variation that contribute to immunomodulatory functional variability of MSCs and provided us a strategy to identify candidate markers for functional variability assessment of MSCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-020-02121-8.

Advances in mesenchymal stem cell transplantation for the treatment of osteoporosis

Osteoporosis is a systemic metabolic bone disease with characteristics of bone loss and microstructural degeneration. The personal and societal costs of osteoporosis are increasing year by year as the ageing of population, posing challenges to public health care. Homing disorders, impaired capability of osteogenic differentiation, senescence of mesenchymal stem cells (MSCs), an imbalanced microenvironment, and disordered immunoregulation play important roles during the pathogenesis of osteoporosis. The MSC transplantation promises to increase osteoblast differentiation and block osteoclast activation, and to rebalance bone formation and resorption. Preclinical investigations on MSC transplantation in the osteoporosis treatment provide evidences of enhancing osteogenic differentiation, increasing bone mineral density, and halting the deterioration of osteoporosis. Meanwhile, the latest techniques, such as gene modification, targeted modification and co-transplantation, are promising approaches to enhance the therapeutic effect and efficacy of MSCs. In addition, clinical trials of MSC therapy to treat osteoporosis are underway, which will fill the gap of clinical data. Although MSCs tend to be effective to treat osteoporosis, the urgent issues of safety, transplant efficiency and standardization of the manufacturing process have to be settled. Moreover, a comprehensive evaluation of clinical trials, including safety and efficacy, is still needed as an important basis for clinical translation.

Bisecting GlcNAc Protein N-Glycosylation Is Characteristic of Human Adipogenesis

Human adipose tissue contains a major source of adipose-derived stem cells (ADSCs) that have the ability to differentiate into various cell types: in vitro, ADSCs can differentiate into mesenchymal lineages including adipocytes, while in vivo, ADSCs become mature adipocytes. Protein glycosylation has been shown to change in stem cell differentiation, and while ADSCs have been acknowledged for their therapeutic potential, little is known about protein glycosylation during human ADSC adipogenic differentiation. In the present study, the global membrane protein glycosylation of native adipocytes was compared to ADSCs from the same individuals as a model of in vivo adipogenesis. For in vitro adipogenesis, ADSCs were adipogenically differentiated in cell culture using an optimized, large-scale differentiation procedure. The membrane glycome of the differentiated ADSCs (dADSCs) was compared with mature adipocytes and the progenitor ADSCs. A total of 137 glycan structures were characterized across the three cell types using PGC-LC coupled with negative-ion electrospray ionization mass spectrometry (ESI-MS)/MS. Significantly higher levels of bisecting GlcNAc-type N-glycans were detected in mature adipocytes (32.1% of total glycans) and in in vitro dADSC progeny (1.9% of total glycans) compared to ADSCs. This was further correlated by the mRNA expression of the MGAT3 gene responsible for the enzymatic synthesis of this structural type. The bisecting GlcNAc structures were found on the majority of human native adipocyte membrane proteins, suggesting an important role in human adipocyte biology. Core fucosylation was also significantly increased during in vivo adipogenesis but did not correlate with an increase in Fut8 gene transcript. Unexpectedly, low abundance structures carrying rare β-linked Gal-Gal termini were also detected. Overall, the N-glycan profiles of the in vitro differentiated progeny did not reflect native adipocytes, and the results show that bisecting GlcNAc structures are a characteristic feature of human adipocyte membrane protein N-glycosylation. Raw MS files are available on GlycoPOST (ID: GPST000153 https://glycopost.glycosmos.org/).

[Research progress in the osteogenetic mechanism of strontium]

Strontium (Sr) is an essential trace element and widely exists in nature. It plays an important role in the in vivo regulation of bone metabolism. Sr locates below Fe in the periodic table, and its chemical structure and polarity are similar to those of Ca. It can induce bone mesenchymal stem cells to differentiate into osteoblasts by inhibiting the activity of osteoclasts and reducing bone resorption. It promotes bone formation through a series of related pathways. The mechanism of Sr regulation of bone metabolism has been extensively researched in recent years. The current study aims to investigate the mechanism of Sr and provide a theoretical basis for its clinical application.

Regulation of bone marrow mesenchymal stem cell fate by long non-coding RNA

Bone mesenchymal stem cells (BMSCs) are progenitor cells isolated from bone marrow, which keep potential to differentiate into several kinds of cells including osteoblasts and adipocytes. A dynamic mutual regulation exists between osteogenesis and adipogenesis processes. Long non-coding RNA (lncRNA) performs diverse functions in biological activities including regulation of BMSCs commitment. Evidence has shown that lncRNA regulates key signaling pathways including TGFβ/BMP, Wnt and Notch pathways, and several transcription factors in BMSCs differention. Dysregulation of lncRNA in BMSCs leads to disruption of osteo-adipogenesis difffrentiation and results in impairment of bone homeostasis. In this review, we focus on the role of lncRNA in several critical signaling pathways that involved in regulation of osteo-adipogenesis of BMSC and prospects the potential clinical application of lncRNA.

Resistin mitigates stemness and metabolic profile of human adipose-derived mesenchymal stem cells via insulin resistance

During obesity adipose tissue abundantly secrete pro-inflammatory adipokines like Tumour Necrosis factor-alpha (TNFα), resistin, leptin, etc. but reduced anti-inflammatory adipokines like adiponectin, interleukin (IL)-10, and IL-4. In our recent clinical study, it was observed that both gene expressions and stored levels of resistin were elevated in adipose tissue of metabolically obese Indians. Resistin profoundly increases obesity, mitigates lipid metabolism, and causes peripheral insulin resistance. It dysregulates the metabolism of human adipocytes but, its effects on human adipose-derived mesenchymal stem cells (hADSC) are sparsely explored. Therefore, the present study was designed to explore the repercussion of resistin on stemness and metabolic profile of hADSC. hADSC were isolated from a healthy individual followed by immunophenotyping. Purified cells were treated with resistin and proliferation was monitored by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and Cell Cycle experiments. Gene expressions of pluripotent markers, inflammatory mediators, and lipogenic genes were scrutinized. Insulin sensitivity was examined by western blot and glucose uptake assay. Further, consequences of resistin on differentiation potentials of hADSC were examined by temporal expressions of phospho (p)SMAD1/5/8 protein complex, non-phosphorylated beta (β) catenin, and their dependent adipogenic transcription factors (ATF) and osteogenic transcription factors (OTF). MTT and cell cycle analysis revealed that resistin hampered proliferation of hADSC. Expressions of inflammatory markers and lipogenic genes were elevated. Resistin impaired insulin sensitivity and thus embarked insulin resistance in hADSC. Resistin increased adipogenesis and osteogenesis by altering expressions of activated pSMAD1/5/8 complex, activated β catenin, ATF and OTF temporally. Downregulation of CCAAT/enhancer-binding proteins (C/EBP)α and adiponectin in adipocytes and Sirtuin (SIRT)1 in osteocytes denote that resistin induces immaturity and insulin resistance in adipocytes and osteocytes. This is the first study which, reports that resistin mitigates the stemness of hADSC by reducing proliferation, inducing insulin resistance, and hampering maturation of adipocyte and osteocyte which could lead to metabolic disorders.

Microarray analysis identification of key pathways and interaction network of differential gene expressions during osteogenic differentiation

BACKGROUND

Adult bone marrow-derived mesenchymal stem cells (BM-MSCs) are multipotent stem cells that can differentiate into three lineages. They are suitable sources for cell-based therapy and regenerative medicine applications. This study aims to evaluate the hub genes and key pathways of differentially expressed genes (DEGs) related to osteogenesis by bioinformatics analysis in three different days. The DEGs were derived from the three different days compared with day 0.

RESULTS

Gene expression profiles of GSE37558 were obtained from the Gene Expression Omnibus (GEO) database. A total of 4076 DEGs were acquired on days 8, 12, and 25. Gene ontology (GO) enrichment analysis showed that the non-canonical Wnt signaling pathway and lipopolysaccharide (LPS)-mediated signaling pathway were commonly upregulated DEGs for all 3 days. KEGG pathway analysis indicated that the PI3K-Akt and focal adhesion were also commonly upregulated DEGs for all 3 days. Ten hub genes were identified by CytoHubba on days 8, 12, and 25. Then, we focused on the association of these hub genes with the Wnt pathways that had been enriched from the protein-protein interaction (PPI) by the Cytoscape plugin MCODE.

CONCLUSIONS

These findings suggested further insights into the roles of the PI3K/AKT and Wnt pathways and their association with osteogenesis. In addition, the stem cell microenvironment via growth factors, extracellular matrix (ECM), IGF1, IGF2, LPS, and Wnt most likely affect osteogenesis by PI3K/AKT.