Maintenance of differentiation potential of human bone marrow mesenchymal stem cells immortalized by human telomerase reverse transcriptase gene despite of extensive proliferation

Senescence of skeletal stem cells and their contribution to age-related bone loss

Human aging is linked to bone loss, resulting in bone fragility and an increased risk of fractures. This is primarily due to an age-related decline in the function of bone-forming osteoblastic cells and accelerated cellular senescence within the bone microenvironment. Here, we provide a detailed discussion of the hypothesis that age-related defective bone formation is caused by senescence of skeletal stem cells, as they are the main source of bone forming osteoblastic cells and influence the composition of bone microenvironment. Furthermore, this review discusses potential strategies to target cellular senescence as an emerging approach to treat age-related bone loss.

Legumain is a paracrine regulator of osteoblast differentiation and mediates the inhibitory effect of TGF-β1 on osteoblast maturation

Transforming growth factor-beta 1 (TGF-β1) is a critical regulator of skeletal homeostasis and has diverse effects on osteoblastogenesis. To date, the mechanisms behind the intriguing inhibitory effect of TGF-β1 on osteoblast maturation are not fully understood. Here, we demonstrate a novel mechanism by which TGF-β1 modulates osteoblast maturation through the lysosomal protease legumain. We observed that addition of TGF-β1 to osteogenic cultures of human bone marrow derived mesenchymal stromal (stem) cells enhanced legumain activity and secretion, in-spite of decreased legumain mRNA expression, suggesting post-transcriptional regulation. We further showed that osteogenic cells internalize and activate prolegumain, associated with inhibited osteoblast maturation, revealing legumain as a paracrine regulator of osteoblast maturation. Interestingly, TGF-β1 treatment exacerbated legumain internalization and activity, and showed an additive effect on legumain-induced inhibition of osteoblast maturation. Importantly, pharmacological inhibition of legumain abolished the inhibitory effect of TGF-β1 on osteoblast maturation. Our findings reveal that TGF-β1 inhibits osteoblast maturation by stimulating secretion and activity of endogenous legumain, as well as enhancing internalization and activation of extracellular prolegumain. Therefore, our study provides a deeper understanding of the complex regulation of osteoblastogenesis and unveils a novel TGF-β1-legumain axis in regulation of osteoblast maturation, offering novel insights for possible therapeutic interventions related to bone diseases associated with aberrant TGF-β1 signaling.

Novel Chitosan-Gelatin Scaffold with Valproic Acid Augments In Vitro Osteoblast Differentiation of Mesenchymal Stem Cells

The study aimed to develop a biodegradable scaffold incorporating valproic acid (VPA) for improved human bone marrow-derived mesenchymal stem cell (hBMSC) proliferation, differentiation, and bone mineral synthesis. A chitosan-gelatin (CH-G) scaffold was fabricated and loaded with varying concentrations of VPA (1, 3, 5 mM/L). In vitro studies assessed drug release, cell proliferation, morphology, mineralization, and gene expression. VPA was rapidly released from the scaffold, with over 90% cumulative release within seven days. Cells cultured on VPA-loaded scaffolds exhibited significantly enhanced proliferation and mineralization compared to the control. VPA treatment upregulated osteocalcin and runt-related transcription factor 2 (Runx-2) expression, key markers of osteogenic differentiation. The CH-G scaffold, particularly with 1 mM/L VPA, demonstrates excellent biocompatibility and promotes hBMSC-mediated bone regeneration. This novel approach holds promise for future applications in bone tissue engineering.

Chitosan-Gelatin Scaffolds Loaded with Different Antibiotic Formulations for Regenerative Endodontic Procedures Promote Biocompatibility and Antibacterial Activity

BACKGROUND

This study investigated the biocompatibility and antibacterial efficacy of chitosan-gelatin (CH-G) scaffolds loaded with slow-releasing antibiotic formulations used in regeneration endodontic procedures (REPs).

METHODS

Scaffolds were fabricated using freeze drying and loaded with varying concentrations of augmentin or modified triple antibiotic paste (mTAP). High-resolution scanning electron microscopy (SEM) was used to characterize the scaffold, while drug release was monitored via UV-Vis spectrophotometry. Immortalized human mesenchymal stem cells (hMSCs) were cultured on CH-G scaffolds alone (control), either 0.1 mg/mL or 1 mg/mL of augmentin or mTAP, and 10 mg/mL calcium hydroxide (Ca(OH)2). Cell viability and proliferation were assessed using the Alamar Blue assay and SEM, respectively, and live/dead staining further corroborated cell viability. Antibacterial activity against Enterococcus faecalis was evaluated using the MTT assay and confocal laser scanning microscopy (CLSM).

RESULTS

Augmentin at 0.1 mg/mL appeared to promote better cell growth and attachment within the scaffolds than all other formulations, exhibiting acceptable viability. SEM revealed improved cell attachment in augmentin and mTAP groups compared to the Ca(OH)2 group. Augmentin at 1 mg/mL and mTAP groups significantly reduced viable bacteria compared to controls. Augmentin groups and mTAP at 1 mg/mL were highly effective in eliminating E. faecalis biofilms, with mTAP potentially causing more cell death within the remaining biofilm structures.

CONCLUSIONS

This study suggests that CH-G scaffolds loaded with augmentin and mTAP, particularly at a concentration of 1 mg/mL, offer promising advantages for REPs due to their biocompatibility, antibacterial efficacy, and ability to promote cell attachment. Further research may explore the long-term effects in clinical settings.

Advances in natural and synthetic macromolecules with stem cells and extracellular vesicles for orthopedic disease treatment

Serious orthopedic disorders resulting from myriad diseases and impairments continue to pose a considerable challenge to contemporary clinical care. Owing to its limited regenerative capacity, achieving complete bone tissue regeneration and complete functional restoration has proven challenging with existing treatments. By virtue of cellular regenerative and paracrine pathways, stem cells are extensively utilized in the restoration and regeneration of bone tissue; however, low survival and retention after transplantation severely limit their therapeutic effect. Meanwhile, biomolecule materials provide a delivery platform that improves stem cell survival, increases retention, and enhances therapeutic efficacy. In this review, we present the basic concepts of stem cells and extracellular vesicles from different sources, emphasizing the importance of using appropriate expansion methods and modification strategies. We then review different types of biomolecule materials, focusing on their design strategies. Moreover, we summarize several forms of biomaterial preparation and application strategies as well as current research on biomacromolecule materials loaded with stem cells and extracellular vesicles. Finally, we present the challenges currently impeding their clinical application for the treatment of orthopedic diseases. The article aims to provide researchers with new insights for subsequent investigations.

Imbalanced EphB4/EphrinB2 Signaling Modulates Bone Resorption in Periodontitis Induced by Porphyromonas gingivalis

Periodontitis, a chronic infectious disease in periodontal tissues, is characterized by an imbalance of alveolar bone resorption and remodeling, which eventually results in tooth loosening and even tooth loss. The etiology of periodontitis is polymicrobial synergy and dysbiosis, in which Porphyromonas gingivalis (P. gingivalis) is one of the primary pathogens responsible for periodontitis progression. The interplay of EphrinB2/EphB4 is crucial for osteoblast-osteoclast communication during bone remodeling and healing. This study investigates the mechanism of EphB4/EphrinB2 transduction modulating osteogenesis inhibition and bone resorption in periodontitis induced by P. gingivalis. An in vivo model of chronic periodontitis provoked by P. gingivalis was constructed, the inflammation and bone resorption were evaluated. The expression of EphB4 and EphrinB2 proteins in periodontal tissues was detected, which was also evaluated, respectively, in osteoblasts and osteoclasts infected with P. gingivalis in vitro. Then, a simulated coculture model of osteoblasts and osteoclasts was established to activate the forward and reverse pathways of EphB4/EphrinB2 with P. gingivalis infection. This study showed that P. gingivalis infection promoted alveolar bone resorption in rats and enhanced EphB4 and EphrinB2 expression in periodontal tissues. EphB4 and molecules associated with osteogenesis in osteoblasts infected with P. gingivalis were inhibited, while EphrinB2 and osteoclast differentiation-related markers in osteoclasts were activated. In conclusion, this study suggested that EphB4/EphrinB2 proteins were involved in alveolar bone remodeling in the process of periodontitis induced by P. gingivalis infection. Moreover, attenuated EphB4/EphrinB2 with P. gingivalis infection weakened osteoblast activity and enhanced osteoclast activity.

Apigenin and Rutaecarpine reduce the burden of cellular senescence in bone marrow stromal stem cells

Introduction

Osteoporosis is a systemic age-related disease characterized by reduced bone mass and microstructure deterioration, leading to increased risk of bone fragility fractures. Osteoporosis is a worldwide major health care problem and there is a need for preventive approaches.

Methods and results

Apigenin and Rutaecarpine are plant-derived antioxidants identified through functional screen of a natural product library (143 compounds) as enhancers of osteoblastic differentiation of human bone marrow stromal stem cells (hBMSCs). Global gene expression profiling and Western blot analysis revealed activation of several intra-cellular signaling pathways including focal adhesion kinase (FAK) and TGFβ. Pharmacological inhibition of FAK using PF-573228 (5 μM) and TGFβ using SB505124 (1μM), diminished Apigenin- and Rutaecarpine-induced osteoblast differentiation. In vitro treatment with Apigenin and Rutaecarpine, of primary hBMSCs obtained from elderly female patients enhanced osteoblast differentiation compared with primary hBMSCs obtained from young female donors. Ex-vivo treatment with Apigenin and Rutaecarpine of organotypic embryonic chick-femur culture significantly increased bone volume and cortical thickness compared to control as estimated by μCT-scanning.

Discussion

Our data revealed that Apigenin and Rutaecarpine enhance osteoblastic differentiation, bone formation, and reduce the age-related effects of hBMSCs. Therefore, Apigenin and Rutaecarpine cellular treatment represent a potential strategy for maintaining hBMSCs health during aging and osteoporosis.

Adipose-Derived Mesenchymal Stem Cell (MSC) Immortalization by Modulation of hTERT and TP53 Expression Levels

Mesenchymal stem cells (MSCs) are pivotal players in tissue repair and hold great promise as cell therapeutic agents for regenerative medicine. Additionally, they play a significant role in the development of various human diseases. Studies on MSC biology have encountered a limiting property of these cells, which includes a low number of passages and a decrease in differentiation potential during in vitro culture. Although common methods of immortalization through gene manipulations of cells are well established, the resulting MSCs vary in differentiation potential compared to primary cells and eventually undergo senescence. This study aimed to immortalize primary adipose-derived MSCs by overexpressing human telomerase reverse transcriptase (hTERT) gene combined with a knockdown of TP53. The research demonstrated that immortalized MSCs maintained a stable level of differentiation into osteogenic and chondrogenic lineages during 30 passages, while also exhibiting an increase in cell proliferation rate and differentiation potential towards the adipogenic lineage. Long-term culture of immortalized cells did not alter cell morphology and self-renewal potential. Consequently, a genetically stable line of immortalized adipose-derived MSCs (iMSCs) was established.

Development of an Effective Functional Lipid Anchor for Membranes (FLAME) for the Bioorthogonal Modification of the Lipid Bilayer of Mesenchymal Stromal Cells

The glycosylation of cellular membranes is crucial for the survival and communication of cells. As our target is the engineering of the glycocalyx, we designed a functionalized lipid anchor for the introduction into cellular membranes called Functional Lipid Anchor for MEmbranes (FLAME). Since cholesterol incorporates very effectively into membranes, we developed a twice cholesterol-substituted anchor in a total synthesis by applying protecting group chemistry. We labeled the compound with a fluorescent dye, which allows cell visualization. FLAME was successfully incorporated in the membranes of living human mesenchymal stromal cells (hMSC), acting as a temporary, nontoxic marker. The availability of an azido function─a bioorthogonal reacting group within the compound─enables the convenient coupling of alkyne-functionalized molecules, such as fluorophores or saccharides. After the incorporation of FLAME into the plasma membrane of living hMSC, we were able to successfully couple our molecule with an alkyne-tagged fluorophore via click reaction. This suggests that FLAME is useful for the modification of the membrane surface. Coupling FLAME with a galactosamine derivative yielded FLAME-GalNAc, which was incorporated into U2OS cells as well as in giant unilamellar vesicles (GUVs) and cell-derived giant plasma membrane vesicles (GPMVs). With this, we have shown that FLAME-GalNAc is a useful tool for studying the partitioning in the liquid-ordered (Lo) and the liquid-disordered (Ld) phases. The molecular tool can also be used to analyze the diffusion behavior in the model and the cell membranes by fluorescence correlation spectroscopy (FCS).

Distinctions in bone matrix nanostructure, composition, and formation between osteoblast-like cells, MG-63, and human mesenchymal stem cells, UE7T-13

Osteoblast-like cells and human mesenchymal stem cells (hMSCs) are frequently employed as osteoprogenitor cell models for evaluating novel biomaterials in bone healing and tissue engineering. In this study, the characterization of UE7T-13 hMSCs and MG-63 human osteoblast-like cells was examined. Both cells can undergo osteogenesis and produce calcium extracellular matrix; however, calcium nodules produced by MG-63 lacked a central mass and appeared flatter than UE7T-13. The absence of growing calcium nodules in MG-63 was discovered by SEM-EDX to be associated with the formation of alternating layers of cells and calcium extracellular matrix. The nanostructure and composition analysis showed that UE7T-13 had a finer nanostructure of calcium nodules with a higher calcium/phosphate ratio than MG-63. Both cells expressed high intrinsic levels of collagen type I alpha 1 chain, while only UE7T-13 expressed high levels of alkaline phosphatase, biomineralization associated (ALPL). High ALP activity in UE7T-13 was not further enhanced by osteogenic induction, but in MG-63, low intrinsic ALP activity was greatly induced by osteogenic induction. These findings highlight the differences between the two immortal osteoprogenitor cell lines, along with some technical notes that should be considered while selecting and interpreting the pertinent in vitro model.

Inhibition of GSK-3β Enhances Osteoblast Differentiation of Human Mesenchymal Stem Cells through Wnt Signalling Overexpressing Runx2

Small-molecule-inhibitor-based bone differentiation has been recently exploited as a novel approach to regulating osteogenesis-related signaling pathways. In this study, we identified 1-Azakenpaullone, a highly selective inhibitor of glycogen synthase kinase-3β (GSK-3β), as a powerful inducer of osteoblastic differentiation and mineralization of human mesenchymal stem cells (MSCs). GSK-3β is a serine-threonine protein kinase that plays a major role in different disease development. GSK-3β is a key regulator of Runx2 activity in osteoblastic formation. We evaluated alkaline phosphatase activity and staining assays to assess osteoblast differentiation and Alizarin Red staining to assess the mineralization of cultured human MSCs. Gene expression profiling was assessed using an Agilent microarray platform, and bioinformatics were performed using Ingenuity Pathway Analysis software. Human MSCs treated with 1-Azakenpaullone showed higher ALP activity, increased in vitro mineralized matrix formation, and the upregulation of osteoblast-specific marker gene expression. Global gene expression profiling of 1-Azakenpaullone-treated human MSCs identified 1750 upregulated and 2171 downregulated mRNA transcripts compared to control cells. It also suggested possible changes in various signaling pathways, including Wnt, TGFβ, and Hedgehog. Further bioinformatics analysis employing Ingenuity Pathway Analysis recognized significant enrichment in the 1-Azakenpaullone-treated cells of genetic networks involved in CAMP, PI3K (Complex), P38 MAPK, and HIF1A signaling and functional categories associated with connective tissue development. Our results suggest that 1-Azakenpaullone significantly induced the osteoblastic differentiation and mineralization of human MSCs mediated by the activation of Wnt signaling and the nuclear accumulation of β-catenin, leading to the upregulation of Runx2, a key transcription factor that ultimately promotes the expression of osteoblast-specific genes. Thus, 1-Azakenpaullone could be used as an osteo-promotor factor in bone tissue engineering.

miR-126 mitigates the osteogenic differentiation of human bone marrow-derived mesenchymal stem cells by targeting the ERK1/2 and Bcl-2 pathways

Human bone marrow mesenchymal stem cells (hBMMSCs) are a promising cell source for bone engineering owing to their high potential to differentiate into osteoblasts. The objective of the present study is to assess microRNA-126 (miR-126) and examine its effects on the osteogenic differentiation of hBMMSCs. In this study, we investigate the role of miR-126 in the progression of osteogenic differentiation (OD) as well as the apoptosis and inflammation of hBMMSCs during OD induction. OD is induced in hBMMSCs, and matrix mineralization along with other OD-associated markers are evaluated by Alizarin Red S (AR) staining and quantitative PCR (qPCR). Gain- and loss-of-function studies are performed to demonstrate the role of miR-126 in the OD of hBMMSCs. Flow cytometry and qPCR-based cytokine expression studies are performed to investigate the effect of miR-126 on the apoptosis and inflammation of hBMMSCs. The results indicate that miR-126 expression is downregulated during the OD of hBMMSCs. Gain- and loss-of function assays reveal that miR-126 upregulation inhibits the differentiation of hBMMSCs into osteoblasts, whereas the downregulation of miR-126 promotes hBMMSC differentiation, as assessed by the determination of osteogenic genes and alkaline phosphatase activity. Furthermore, the miR-126 level is positively correlated with the production of inflammatory cytokines and apoptotic cell death. Additionally, our results suggest that miR-126 negatively regulates not only B-cell lymphoma 2 (Bcl-2) expression but also the phosphorylation of extracellular signal‑regulated protein kinase (ERK) 1/2. Moreover, restoring ERK1/2 activity and upregulating Bcl-2 expression counteract the miR-126-mediated suppression of OD in hBMMSCs by promoting inflammation and apoptosis, respectively. Overall, our findings suggest a novel molecular mechanism relevant to the differentiation of hBMMSCs into osteoblasts, which can potentially facilitate bone formation by counteracting miR-126-mediated suppression of ERK1/2 activity and Bcl-2 expression.

Silver Nanoparticles Alone or in Combination with Calcium Hydroxide Modulate the Viability, Attachment, Migration, and Osteogenic Differentiation of Human Mesenchymal Stem Cells

This study aimed to evaluate the effect of silver nanoparticles (AgNPs) alone or in combination with calcium hydroxide (Ca(OH)2) on the proliferation, viability, attachment, migration, and osteogenic differentiation of human mesenchymal stem cells (hMSCs). Different concentrations of AgNPs alone or mixed with Ca(OH)2 were prepared. Cell proliferation was measured using AlamarBlue, and hMSCs attachment to dentin disks was evaluated using scanning electron microscopy. Live-dead imaging was performed to assess apoptosis. Wound healing ability was determined using the scratch-migration assay. To evaluate osteogenic differentiation, the expression of Runt-related transcription factor (RUNX2), Transforming growth factor beta-1 (TGF-β1), Alkaline Phosphatase (ALP), and Osteocalcin (OCN) were measured using real-time reverse transcriptase polymerase chain reaction. ALP staining and activity were also performed as indicators of osteogenic differentiation. AgNPs alone seemed to favor cell attachment. Lower concentrations of AgNPs enhanced cell proliferation. AgNP groups showed markedly less apoptosis. None of the medicaments had adverse effects on wound closure. The expression of TGF-β1 was significantly upregulated in all groups, and OCN was highly expressed in the AgNP groups. AgNPs 0.06% showed the most enhanced ALP gene expression levels, activity, and marked cytochemical staining. In conclusion, AgNPs positively affect hMSCs, making them a potential biomaterial for various clinical applications.

Improved Protocol to Study Osteoblast and Adipocyte Differentiation Balance

Adipogenesis-osteoblastogenesis balance-rupture is relevant in multiple diseases. Current human mesenchymal stem cells (hMSCs) in vitro differentiation models are expensive, and are hardly reproducible. Their scarcity and variability make an affordable and reliable method to study adipocyte-osteoblast-equilibrium difficult. Moreover, media composition has been inconstant throughout the literature. Our aims were to compare improved differentiation lab-made media with consensus/commercial media, and to identify a cell-line to simultaneously evaluate both MSCs differentiations. Lab-made media were compared with consensus and commercial media in C3H10T1/2 and hMSC, respectively. Lab-made media were tested on aged women primary pre-osteoblast-like cells. To determine the optimum cell line, C3H10T1/2 and hMSC-TERT cells were differentiated to both cell fates. Differentiation processes were evaluated by adipocytic and osteoblastic gene-markers expression and staining. Lab-made media significantly increased consensus medium induction and overcame commercial media in hMSCs differentiation to adipocytes and osteoblasts. Pre-osteoblast-like cells only properly differentiate to adipocyte. Lab-made media promoted adipocyte gene-markers expression in C3H10T1/2 and hMSC-TERT, and osteoblast gene-markers in C3H10T1/2. Oil Red O and Alizarin Red staining supported these findings. Optimized lab-made media were better at differentiating MSCs compared to consensus/commercial media, and evidenced the adipogenic commitment of pre-osteoblast-like cells from aged-women. C3H10T1/2 is an optimum MSC line by which to study adipocyte-osteoblast differentiation balance.

Novel thiazolidinedione analog reduces a negative impact on bone and mesenchymal stem cell properties in obese mice compared to classical thiazolidinediones

Objective

The use of thiazolidinediones (TZDs) as insulin sensitizers has been shown to have side effects including increased accumulation of bone marrow adipocytes (BMAds) associated with a higher fracture risk and bone loss. A novel TZD analog MSDC-0602K with low affinity to PPARγ has been developed to reduce adverse effects of TZD therapy. However, the effect of MSDC-0602K on bone phenotype and bone marrow mesenchymal stem cells (BM-MSCs) in relation to obesity has not been intensively studied yet.

Methods

Here, we investigated whether 8-week treatment with MSDC-0602K has a less detrimental effect on bone loss and BM-MSC properties in obese mice in comparison to first generation of TZDs, pioglitazone. Bone parameters (bone microstructure, bone marrow adiposity, bone strength) were examined by μCT and 3-point bending test. Primary BM-MSCs were isolated and measured for osteoblast and adipocyte differentiation. Cellular senescence, bioenergetic profiling, nutrient consumption and insulin signaling were also determined.

Results

The findings demonstrate that MSDC-0602K improved bone parameters along with increased proportion of smaller BMAds in tibia of obese mice when compared to pioglitazone. Further, primary BM-MSCs isolated from treated mice and human BM-MSCs revealed decreased adipocyte and higher osteoblast differentiation accompanied with less inflammatory and senescent phenotype induced by MSDC-0602K vs. pioglitazone. These changes were further reflected by increased glycolytic activity differently affecting glutamine and glucose cellular metabolism in MSDC-0602K-treated cells compared to pioglitazone, associated with higher osteogenesis.

Conclusion

Our study provides novel insights into the action of MSDC-0602K in obese mice, characterized by the absence of detrimental effects on bone quality and BM-MSC metabolism when compared to classical TZDs and thus suggesting a potential therapeutical use of MSDC-0602K in both metabolic and bone diseases.

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MSDC-0602K improves bone quality and increases proportion of smaller BMAds in obese mice.

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MSDC-0602K-treated mice show lower adipogenic differentiation with less senescent phenotype in primary BM-MSCs.

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MSDC-0602K induces higher glycolytic activity in BM-MSCs compared to pioglitazone.

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MSDC-0602-treated BM-MSCs prefer glutamine over glucose uptake in comparison to AT-MSCs.

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Beneficial effect of MSDC-06002K in BM-MSCs manifests by absence of MPC inhibition.

Effects of mesenchymal stem cell transplantation on spinal cord injury patients

Spinal cord injury (SCI) is a traumatic injury with sensory and motor deficits that more than 1 million patients worldwide suffer from disability due to it. Many pharmacological therapies help reduce SCI-related injury and protect CNS from more damage but no current therapy could improve the axonal repair. In this regard, stem cell therapy is considered a regenerative method for SCI patient treatment. The neurotrophic and immunomodulatory factor secretion, differentiation, neuroprotecting, and remyelinating properties have made mesenchymal stem cells (MSCs) principally useful in this field. There are studies on the role of MSCs in patients suffering from SCI. However, low number of SCI patients and the lack of control groups in these studies, the cell transplantation appropriate methods, including cell source, dose, route of delivery, and transplantation timing, are various in trials. This study reviews the beneficial effects of MSC transplantation in SCI clinical studies with a special focus on the MSC properties and limitations of MSC transplantation.

β-Ecdysterone Enhanced Bone Regeneration Through the BMP-2/SMAD/RUNX2/Osterix Signaling Pathway

Bone defects are a global public health problem. However, the available methods for inducing bone regeneration are limited. The application of traditional Chinese herbs for bone regeneration has gained popularity in recent years. β-ecdysterone is a plant sterol similar to estrogen, that promotes protein synthesis in cells; however, its function in bone regeneration remains unclear. In this study, we investigated the function of β-ecdysterone on osteoblast differentiation and bone regeneration in vitro and in vivo. MC3T3-E1 cells were used to test the function of β-ecdysterone on osteoblast differentiation and bone regeneration in vitro. The results of the Cell Counting Kit-8 assay suggested that the proliferation of MC3T3-E1 cells was promoted by β-ecdysterone. Furthermore, β-ecdysterone influenced the expression of osteogenesis-related genes, and the bone regeneration capacity of MC3T3-E1 cells was detected by polymerase chain reaction, the alkaline phosphatase (ALP) test, and the alizarin red test. β-ecdysterone could upregulate the expression of osteoblastic-related genes, and promoted ALP activity and the formation of calcium nodules. We also determined that β-ecdysterone increased the mRNA and protein levels of components of the BMP-2/Smad/Runx2/Osterix pathway. DNA sequencing further confirmed these target effects. β-ecdysterone promoted bone formation by enhancing gene expression of the BMP-2/Smad/Runx2/Osterix signaling pathway and by enrichment biological processes. For in vivo experiments, a femoral condyle defect model was constructed by drilling a bone defect measuring 3 mm in diameter and 4 mm in depth in the femoral condyle of 8-week-old Sprague Dawley male rats. This model was used to further assess the bone regenerative functions of β-ecdysterone. The results of micro-computed tomography showed that β-ecdysterone could accelerate bone regeneration, exhibiting higher bone volume, bone surface, and bone mineral density at each observation time point. Immunohistochemistry confirmed that the β-ecdysterone also increased the expression of collagen, osteocalcin, and bone morphogenetic protein-2 in the experiment group at 4 and 8 weeks. In conclusion, β-ecdysterone is a new bone regeneration regulator that can stimulate MC3T3-E1 cell proliferation and induce bone regeneration through the BMP-2/Smad/Runx2/Osterix pathway. This newly discovered function of β-ecdysterone has revealed a new direction of osteogenic differentiation and has provided novel therapeutic strategies for treating bone defects.

Evaluation of a hyaluronic acid hydrogel (Restylane Lyft) as a scaffold for dental pulp regeneration in a regenerative endodontic organotype model

Scaffolds are crucial elements for dental pulp regeneration. Most of the currently used scaffolds in regenerative endodontic procedures (REPs) are unsuitable for chairside clinical use. This study aimed to evaluate the effect of an injectable synthetic scaffold (Restylane Lyft) on human bone marrow mesenchymal stem cell (hBMSC) viability, proliferation, and osteo/dentinogenic differentiation in a regenerative endodontic organotype model (REM). hBMSC were loaded in an REM either alone (hBMSC group) or mixed with the Restylane Lyft scaffold (Restylane/hBMSC group) and cultured in basal culture medium (n = 9/group). hMSC on culture plates served as controls. Cell viability and proliferation were measured using AlamarBlue assay. The loaded REM was cultured in an osteogenic differentiation medium to measure alkaline phosphatase activity (ALP) and examine the expression of the osteo/dentinogenic markers using real-time reverse transcriptase polymerase chain reaction. Cell viability in all groups increased significantly over 5 days. The Restylane/hBMSC group showed significantly higher ALP activity and dentin sialophosphoprotein, osteocalcin, and bone sialoprotein genes expression than the hBMSC and the control groups. Restylane Lyft, a hyaluronic acid (HA) injectable, FDA-approved hydrogel, maintained cell viability and proliferation and promoted osteo/dentinogenic differentiation of hBMSC when cultured in an REM. Henceforth, it could be a promising chairside scaffold material for REPs.

Transcriptomic profiling of the telomerase transformed Mesenchymal stromal cells derived adipocytes in response to rosiglitazone

Background

Differentiation of Immortalized Human Bone Marrow Mesenchymal Stromal Cells - hTERT (iMSC3) into adipocytes is in vitro model of obesity. In our earlier study, rosiglitazone enhanced adipogenesis particularly the brown adipogenesis of iMSC3. In this study, the transcriptomic profiles of iMSC3 derived adipocytes with and without rosiglitazone were analyzed through mRNA sequencing.

Results

A total of 1508 genes were differentially expressed between iMSC3 and the derived adipocytes without rosiglitazone treatment. GO and KEGG enrichment analyses revealed that rosiglitazone regulates PPAR and PI3K-Akt pathways. The constant rosiglitazone treatment enhanced the expression of Fatty Acid Binding Protein 4 (FABP4) which enriched GO terms such as fatty acid binding, lipid droplet, as well as white and brown fat cell differentiation. Moreover, the constant treatment upregulated several lipid droplets (LDs) associated proteins such as PLIN1. Rosiglitazone also activated the receptor complex PTK2B that has essential roles in beige adipocytes thermogenic program. Several uniquely expressed novel regulators of brown adipogenesis were also expressed in adipocytes derived with rosiglitazone: PRDM16, ZBTB16, HOXA4, and KLF15 in addition to other uniquely expressed genes.

Conclusions

Rosiglitazone regulated several differentially regulated genes and non-coding RNAs that warrant further investigation about their roles in adipogenesis particularly brown adipogenesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12863-022-01027-z.

HIF-1α and Pro-Inflammatory Signaling Improves the Immunomodulatory Activity of MSC-Derived Extracellular Vesicles

Despite the strong evidence for the immunomodulatory activity of mesenchymal stromal cells (MSCs), clinical trials have so far failed to clearly show benefit, likely reflecting methodological shortcomings and lack of standardization. MSC-mediated tissue repair is commonly believed to occur in a paracrine manner, and it has been stated that extracellular vesicles (EVs) secreted by MSCs (EVMSC) are able to recapitulate the immunosuppressive properties of parental cells. As a next step, clinical trials to corroborate preclinical studies should be performed. However, effective dose in large mammals, including humans, is quite high and EVs industrial production is hindered by the proliferative senescence that affects MSCs during massive cell expansion. We generated a genetically modified MSC cell line overexpressing hypoxia-inducible factor 1-alpha and telomerase to increase the therapeutic potency of EVMSC and facilitate their large-scale production. We also developed a cytokine-based preconditioning culture medium to prime the immunomodulatory response of secreted EVs (EV_MSC-T-HIF^c). We tested the efficacy of this system in vitro and in a delayed-type hypersensitivity mouse model. MSC-T with an HIF-1α-GFP lentiviral vector (MSC-T-HIF) can be effectively expanded to obtain large amounts of EVs without major changes in cell phenotype and EVs composition. EV_MSC-T-HIF^c suppressed the proliferation of activated T-cells more effectively than did EVs from unmodified MSC in vitro, and significantly blunted the ear-swelling response in vivo by inhibiting cell infiltration and improving tissue integrity. We have developed a long-lived EV source that secretes high quantities of immunosuppressive EVs, facilitating a more standard and cost-effective therapeutic product.

Evaluation of the regenerative potential of decellularized skeletal muscle seeded with mesenchymal stromal cells in critical-sized bone defect of rat models

Background

The morbidities and complications reported in the reconstruction of large bony defects have inspired progression in the field of bioengineering, with a recent breakthrough for the use of decellularized skeletal muscle grafts (DSMG).

Aim

To assess the osteogenic potentials of seeded DSMG in vitro and to investigate bone regeneration in critical size defect in vivo.

Materials and Methods

Assessment of cell viability and characterization was carried out on seeded DSMG for different intervals in vitro. For in vivo experiments, histological analysis was performed for rat cranial defects for the following groups: (A) non-treated DSMG and (B) seeded DSMG after a period of 8 weeks.

Results

The in vitro experiment demonstrated the lack of cytotoxicity and inert properties of seeded DSMG; these facilitated the osteogenic differentiation and significant gene expressions, particularly of COL1A1, RUNX2, and OPN (1.9174 ± 0.11673, 1.1806 ± 0.02383, and 1.1802 ± 0.00775, respectively). In the in vivo experiment, superior results were detected in the seeded DSMG group which showed highly vascularized and cellular dense connective tissue with deposited bone matrix and multiple scattered islets of newly formed bone.

Conclusion

Our results demonstrated the promising aspects of DSMG; however, there is a lack of studies to support further implications.

Metabolic Glycoengineering in hMSC-TERT as a Model for Skeletal Precursors by Using Modified Azide/Alkyne Monosaccharides

Metabolic glycoengineering enables a directed modification of cell surfaces by introducing target molecules to surface proteins displaying new features. Biochemical pathways involving glycans differ in dependence on the cell type; therefore, this technique should be tailored for the best results. We characterized metabolic glycoengineering in telomerase-immortalized human mesenchymal stromal cells (hMSC-TERT) as a model for primary hMSC, to investigate its applicability in TERT-modified cell lines. The metabolic incorporation of N-azidoacetylmannosamine (Ac₄ManNAz) and N-alkyneacetylmannosamine (Ac₄ManNAl) into the glycocalyx as a first step in the glycoengineering process revealed no adverse effects on cell viability or gene expression, and the in vitro multipotency (osteogenic and adipogenic differentiation potential) was maintained under these adapted culture conditions. In the second step, glycoengineered cells were modified with fluorescent dyes using Cu-mediated click chemistry. In these analyses, the two mannose derivatives showed superior incorporation efficiencies compared to glucose and galactose isomers. In time-dependent experiments, the incorporation of Ac₄ManNAz was detectable for up to six days while Ac₄ManNAl-derived metabolites were absent after two days. Taken together, these findings demonstrate the successful metabolic glycoengineering of immortalized hMSC resulting in transient cell surface modifications, and thus present a useful model to address different scientific questions regarding glycosylation processes in skeletal precursors.

JAK2 Inhibition by Fedratinib Reduces Osteoblast Differentiation and Mineralisation of Human Mesenchymal Stem Cells

Several signalling pathways, including the JAK/STAT signalling pathway, have been identified to regulate the differentiation of human bone marrow skeletal (mesenchymal) stem cells (hBMSCs) into bone-forming osteoblasts. Members of the JAK family mediate the intracellular signalling of various of cytokines and growth factors, leading to the regulation of cell proliferation and differentiation into bone-forming osteoblastic cells. Inhibition of JAK2 leads to decoupling of its downstream mediator, STAT3, and the subsequent inhibition of JAK/STAT signalling. However, the crucial role of JAK2 in hBMSCs biology has not been studied in detail. A JAK2 inhibitor, Fedratinib, was identified during a chemical biology screen of a small molecule library for effects on the osteoblastic differentiation of hMSC-TERT cells. Alkaline phosphatase activity and staining assays were conducted as indicators of osteoblastic differentiation, while Alizarin red staining was used as an indicator of in vitro mineralised matrix formation. Changes in gene expression were assessed using quantitative real-time polymerase chain reaction. Fedratinib exerted significant inhibitory effects on the osteoblastic differentiation of hMSC-TERT cells, as demonstrated by reduced ALP activity, in vitro mineralised matrix formation and downregulation of osteoblast-related gene expression, including ALP, ON, OC, RUNX2, OPN, and COL1A1. To identify the underlying molecular mechanisms, we examined the effects of Fedratinib on a molecular signature of several target genes known to affect hMSC-TERT differentiation into osteoblasts. Fedratinib inhibited the expression of LIF, SOCS3, RRAD, NOTCH3, TNF, COMP, THBS2, and IL6, which are associated with various signalling pathways, including TGFβ signalling, insulin signalling, focal adhesion, Notch Signalling, IL-6 signalling, endochondral ossification, TNF-α, and cytokines and inflammatory response. We identified a JAK2 inhibitor (Fedratinib) as a powerful inhibitor of the osteoblastic differentiation of hMSC-TERT cells, which may be useful as a therapeutic option for treating conditions associated with ectopic bone formation or osteosclerotic metastases.

Tuning Thermal Dosage to Facilitate Mesenchymal Stem Cell Osteogenesis in Pro-Inflammatory Environment

Mesenchymal stem cells (MSCs) are multipotent cells that can replicate and differentiate to different lineages, potentiating their use as integral components in regenerated mesenchymal tissues. Our previous work and other studies have indicated that mild heat shock enhances osteogenesis. However, the influence of pro-inflammatory cytokines on osteogenic differentiation during mildly elevated temperature conditions remains to be fully explored. In this study, human MSCs (hMSCs) were cultured with tumor necrosis factor-alpha (TNF-α), an important mediator of the acute phase response, and interleukin-6 (IL-6) which plays a role in damaging chronic inflammation, then heat shocked at 39 °C in varying frequencies-1 h per week (low), 1 h every other day (mild), and 1 h intervals three times per day every other day (high). DNA data showed that periodic mild heating inhibited suppression of cell growth caused by cytokines and induced maximal proliferation of hMSCs while high heating had the opposite effect. Quantitative osteogenesis assays show significantly higher levels of alkaline phosphatase (ALP) activity and calcium precipitation in osteogenic cultures following mild heating compared to low heating or nonheated controls. These results demonstrate that periodic mild hyperthermia may be used to facilitate bone regeneration using hMSCs, and therefore may influence the design of heat-based therapies in vivo.

Conditional Reprogramming Inducing Clinical Cells Proliferation: New Research Tools in Tumor and Inflammatory-related Diseases

In the era of precision medicine, establishing a patient-derived cell model is crucial, whether in vitro or in vivo. Compared to the traditional cell lines, patient-derived primary cells represent precise genetic features from specific patients, but poor proliferative activity of human primary cells restricts their popular application. Conditional reprogramming (CR) is a new cell culture technique to achieve rapid growth of patient-derived cells in vitro, making it possible to identify the individual difference and screen drugs sensitivity. In this review, we will summarize the application and limitation of CR in tumor and inflammatory-related diseases, indicating the prospect of this technique for preclinical research.

Tankyrase inhibitor XAV-939 enhances osteoblastogenesis and mineralization of human skeletal (mesenchymal) stem cells

Tankyrase is part of poly (ADP-ribose) polymerase superfamily required for numerous cellular and molecular processes. Tankyrase inhibition negatively regulates Wnt pathway. Thus, Tankyrase inhibitors have been extensively investigated for the treatment of clinical conditions associated with activated Wnt signaling such as cancer and fibrotic diseases. Moreover, Tankyrase inhibition has been recently reported to upregulate osteogenesis through the accumulation of SH3 domain-binding protein 2, an adaptor protein required for bone metabolism. In this study, we investigated the effect of Tankyrase inhibition in osteoblast differentiation of human skeletal (mesenchymal) stem cells (hMSCs). A Tankyrase inhibitor, XAV-939, identified during a functional library screening of small molecules. Alkaline phosphatase activity and Alizarin red staining were employed as markers for osteoblastic differentiation and in vitro mineralized matrix formation, respectively. Global gene expression profiling was performed using the Agilent microarray platform. XAV-939, a Tankyrase inhibitor, enhanced osteoblast differentiation of hBMSCs as evidenced by increased ALP activity, in vitro mineralized matrix formation, and upregulation of osteoblast-related gene expression. Global gene expression profiling of XAV-939-treated cells identified 847 upregulated and 614 downregulated mRNA transcripts, compared to vehicle-treated control cells. It also points towards possible changes in multiple signaling pathways, including TGFβ, insulin signaling, focal adhesion, estrogen metabolism, oxidative stress, RANK-RANKL (receptor activator of nuclear factor κB ligand) signaling, Vitamin D synthesis, IL6, and cytokines and inflammatory responses. Further bioinformatic analysis, employing Ingenuity Pathway Analysis identified significant enrichment in XAV-939-treated cells of functional categories and networks involved in TNF, NFκB, and STAT signaling. We identified a Tankyrase inhibitor (XAV-939) as a powerful enhancer of osteoblastic differentiation of hBMSC that may be useful as a therapeutic option for treating conditions associated with low bone formation.

Generation of Inducible CRISPRi and CRISPRa Human Stromal/Stem Cell Lines for Controlled Target Gene Transcription during Lineage Differentiation

Background

Human bone marrow stromal/stem cells (hMSCs, also known as the skeletal stem cells or mesenchymal stem cells) are being employed to study lineage fate determination to osteoblasts, adipocytes, and chondrocytes. However, mechanistic studies employing hMSC have been hampered by the difficulty of deriving genetically modified cell lines due to the low and unstable transfection efficiency.

Methods

We infected hMSC with a CRISPR/Cas9 lentivirus system, with specific inducible dCas9-coupled transcription activator or repressor: dCas9-KRAB or dCas9-VP64, respectively, and established two hMSC lines (hMSC-CRISPRi and hMSC-CRISPRa) that can inhibit or activate gene expression, respectively. The two cell lines showed similar cell morphology, cell growth kinetics, and similar lineage differentiation potentials as the parental hMSC line. The expression of KRAB-dCas9 or VP64-dCas9 was controlled by the presence or absence of doxycycline (Dox) in the cell culturing medium. To demonstrate the functionality of the dCas9-effector hMSC system, we tested controlled expression of alkaline phosphatase (ALP) gene through transfection with the same single ALP sgRNA.

Results

In the presence of Dox, the expression of ALP showed 60-90% inhibition in hMSC-CRISPRi while ALP showed more than 20-fold increased expression in hMSC-CRISPRa. As expected, the ALP was functionally active and the cells showed evidence for inhibition or enhancement of in vitro osteoblast differentiation, respectively.

Conclusion

hMSC-CRISPRi and hMSC-CRISPRa are useful resources to study genes and genetic pathways regulating lineage-specific differentiation of hMSC.

In vitro Differentiation of Human TERT-Transfected Multi-Lineage Progenitor Cells (MLPC) into Immortalized Hepatocyte-Like Cells

Background

Research directed towards drug development, metabolism, and liver functions often utilize primary hepatocytes (PH) for preliminary in vitro studies. Variability in the in vitro functionality of PH and the unsuitability of hepatocarcinoma cells for these studies have driven researchers to look to ESC, iPS, and other stem cell types using differentiation protocols to provide more reliable and available cells. This study describes the development of hepatocyte-like cells through the in vitro differentiation of human TERT-immortalized cord blood-derived multi-lineage progenitor cells (MLPC). The E12 clonal cell line derived from polyclonal TERT-transfected cells was used throughout the study.

Methods

E12 MLPC were subjected to a three-step differentiation protocol using alternating combinations of growth factors, cytokines, and maturational factors. Cells at various stages of differentiation were analyzed for consistency with PH by morphology, immunohistochemistry, urea production, and gene expression.

Results

E12 MLPC were shown to significantly change morphology with each stage of differentiation. Coincidental with the morphological changes in the cells, immunohistochemistry data documented the differentiation to committed endoderm by the expression of SOX-17 and GATA-4; the progression to committed hepatocyte-like cells by the expression of a large number of markers including α-fetoprotein and albumin; and the final differentiation by the expression of nuclear and cytoplasmic HNF4. Fully differentiated cells demonstrated gene expression, urea production, and immunohistochemistry consistent with PH. A methodology and medium formulation to continuously expand the E12-derived hepatocyte-like cells is described.

Conclusion

The availability of immortalized hepatocyte-like cell lines could provide a consistent tool for the study of hepatic diseases, drug discovery, and the development of cellular therapies for liver disorders. Utilization of these techniques could provide a basis for the development of bridge therapies for liver failure patients awaiting transplant.

Obesity-Associated Hypermetabolism and Accelerated Senescence of Bone Marrow Stromal Stem Cells Suggest a Potential Mechanism for Bone Fragility

Obesity is associated with increased risk for fragility fractures. However, the cellular mechanisms are unknown. Using a translational approach combining RNA sequencing and cellular analyses, we investigated bone marrow stromal stem cells (BM-MSCs) of 54 men divided into lean, overweight, and obese groups on the basis of BMI. Compared with BM-MSCs obtained from lean, obese BM-MSCs exhibited a shift of molecular phenotype toward committed adipocytic progenitors and increased expression of metabolic genes involved in glycolytic and oxidoreductase activity. Interestingly, compared with paired samples of peripheral adipose tissue-derived stromal cells (AT-MSCs), insulin signaling of obese BM-MSCs was enhanced and accompanied by increased abundance of insulin receptor positive (IR+) and leptin receptor positive (LEPR+) cells in BM-MSC cultures. Their hyper-activated metabolic state was accompanied by an accelerated senescence phenotype. Our data provide a plausible explanation for the bone fragility in obesity caused by enhanced insulin signaling leading to accelerated metabolic senescence of BM-MSCs.

Immortalizing Mesenchymal Stromal Cells from Aged Donors While Keeping Their Essential Features

Human bone marrow-derived mesenchymal stromal cells (MSCs) obtained from aged patients are prone to senesce and diminish their differentiation potential, therefore limiting their usefulness for osteochondral regenerative medicine approaches or to study age-related diseases, such as osteoarthiritis (OA). MSCs can be transduced with immortalizing genes to overcome this limitation, but transduction of primary slow-dividing cells has proven to be challenging. Methods for enhancing transduction efficiency (such as spinoculation, chemical adjuvants, or transgene expression inductors) can be used, but several parameters must be adapted for each transduction system. In order to develop a transduction method suitable for the immortalization of MSCs from aged donors, we used a spinoculation method. Incubation parameters of packaging cells, speed and time of centrifugation, and valproic acid concentration to induce transgene expression have been adjusted. In this way, four immortalized MSC lines (iMSC#6, iMSC#8, iMSC#9, and iMSC#10) were generated. These immortalized MSCs (iMSCs) were capable of bypassing senescence and proliferating at a higher rate than primary MSCs. Characterization of iMSCs showed that these cells kept the expression of mesenchymal surface markers and were able to differentiate towards osteoblasts, adipocytes, and chondrocytes. Nevertheless, alterations in the CD105 expression and a switch of cell fate-commitment towards the osteogenic lineage have been noticed. In conclusion, the developed transduction method is suitable for the immortalization of MSCs derived from aged donors. The generated iMSC lines maintain essential mesenchymal features and are expected to be useful tools for the bone and cartilage regenerative medicine research.

Development of immortalized human hepatocyte-like hybrid cells by fusion of multi-lineage progenitor cells with primary hepatocytes

Human primary hepatocytes (PHs) are critical to studying liver functions, drug metabolism and toxicity. PHs isolated from livers that are unacceptable for transplantation have limited expansion and culture viability in vitro, in addition to rapidly deteriorating enzymatic functions. The unsuitability of immortalized hepato-carcinoma cell lines for this function has prompted studies to develop hepatocyte-like cells from alternative sources like ESC, iPS, and other stem cell types using differentiation protocols. This study describes a novel technique to produce expandable and functional hepatocyte-like cells from the fusion of an immortalized human umbilical cord blood derived cell line (E12 MLPC) to normal human primary hepatocytes. Multi-lineage progenitor cells (MLPC) comprise a small subset of mesenchymal-like cells isolated from human umbilical cord blood. MLPC are distinguishable from other mesenchymal-like cells by their extended expansion capacity (up to 80 cell doublings before senescence) and the ability to be differentiated into cells representative of endo-, meso- and ectodermal origins. Transfection of MLPC with the gene for telomerase reverse transcriptase (TERT) resulted in clonal cell lines that were capable of differentiation to different cellular outcomes while maintaining their functional immortality. A methodology for the development of immortalized hepatocyte-like hybrid cells by the in vitro fusion of human MLPC with normal human primary hepatocytes is reported. The resultant hybrid cells exhibited homology with hepatocytes by morphology, immunohistochemistry, urea and albumin production and gene expression. A medium that allows stable long-term expansion of hepatocyte-like fusion cells is described.

Resveratrol inhibits adipocyte differentiation and cellular senescence of human bone marrow stromal stem cells

Bone marrow adipose tissue (BMAT) is a unique adipose depot originating from bone marrow stromal stem cells (BMSCs) and regulates bone homeostasis and energy metabolism. An increased BMAT volume is observed in several conditions e.g. obesity, type 2 diabetes, osteoporosis and is known to be associated with bone fragility and increased risk for fracture. Therapeutic approaches to decrease the accumulation of BMAT are clinically relevant. In a screening experiment of natural compounds, we identified Resveratrol (RSV), a plant-derived antioxidant mediating biological effects via sirtuin- related mechanisms, to exert significant effects of BMAT formation. Thus, we examined in details the effects RSV on adipocytic and osteoblastic differentiation of tolermerized human BMSCs (hBMSC-TERT). RSV (1.0 μM) enhanced osteoblastic differentiation and inhibited adipocytic differentiation of hBMSC-TERT when compared with control and Sirtinol (Sirtuin inhibitor). Global gene expression profiling and western blot analysis revealed activation of a number of signaling pathways including focal adhesion kinase (FAK). Pharmacological inhibition of FAK using (PF-573228) and AKT inhibitor (LY-294002) (5μM), diminished RSV-induced osteoblast differentiation. In addition, RSV reduced the levels of senescence-associated secretory phenotype (SASP), gene markers associated with senescence (P53, P16, and P21), intracellular ROS levels and increased gene expression of enzymes protecting cells from oxidative damage (HMOX1 and SOD3). In vitro treatment of primary hBMSCs from aged patients characterized with high adipocytic and low osteoblastic differentiation ability with RSV, significantly enhanced osteoblast and decreased adipocyte formation when compared to hBMSCs from young donors. RSV targets hBMSCs and inhibits adipogenic differentiation and senescence-associated phenotype and thus a potential agent for treating conditions of increased BMAT formation.

Class I and II Histone Deacetylase Inhibitor LBH589 Promotes Endocrine Differentiation in Bone Marrow Derived Human Mesenchymal Stem Cells and Suppresses Uncontrolled Proliferation

Mesenchymal stem cells are useful tools employed in clinical and preclinical medicine. Their beneficial potential in especially degenerative as well as autoimmune diseases is a constant focus of research. Regarding diabetes mellitus, transplantation of stem cells is seen as a possible therapeutic approach to overcome the loss of endocrine pancreatic cells. It was reported that co-transplantation of mesenchymal stem cells with pancreatic islet cells improves function and survival of the graft. However, these multipotent progenitors may be able to form tumors, especially under immunosuppressed conditions. Histone deacetylase inhibitors might offer the potential to overcome this issue. These small molecules can induce cell differentiation and control proliferation. Their potential to control lineage development of stem cells has been distinctly demonstrated in the treatment of cancer, mainly in hematopoietic neoplasias.In this study, we demonstrate that human bone marrow-derived mesenchymal stem cells exhibit low carcinogenic potential in an immunosuppressed condition in vivo. Further, the effect of histone deacetylase inhibitors LBH589, MS-275, and MGCD0103 was examined after normalizing histone deacetylase activities in culture. Interestingly, transcripts of insulin gene enhancer protein and paired-box-gene 6, two markers of pancreatic endocrine differentiation were constitutively expressed in the cell line. The broad spectrum inhibitor of class I and class II histone deacetylases LBH589 upregulated the expression of these transcription factors in a significant way, whereas addition of selective class I histone deacetylase inhibitors MS-275 and MGCD0103 did not result in significant changes in gene expression.In conclusion, we deliver evidence that a combined class I and II histone deacetylase inhibition is able to modulate the transcripts of differentiation markers of mesenchymal stem cells. The treatment holds the capability to facilitate endocrine differentiation in future approaches to replace endocrine cells by stem cell therapy.

Establishment and characterization of an immortalized human chondrocyte cell line

OBJECTIVES

Following a specific number of mitotic divisions, primary chondrocytes undergo proliferative senescence, thwarting efforts to expand sufficient populations in vitro suitable to meet the needs of scientific research or medical therapies. Therefore, the human telomerase reverse transcriptase (TERT) was used to immortalize human chondrocyte and establish a cell line that escape from cellular senescence.

RESULTS

The human chondrocytes were successfully immortalized by ectopic stable expression of TERT. The established TERT-Chondrocyte cell line showed robust proliferation capacity, even in late passages up to P20, and displayed little cellular senescence. Moreover, TERT-Chondrocyte cells at 20th passage showed similar chondrocyte properties to normal chondrocytes at early passages.

CONCLUSIONS

Ectopic stable expression of TERT is an effective way to immortalized human chondrocyte. The immortalized chondrocytes displayed little cellular senescence, showed promise as an in vitro model to investigate osteoarthritis, and may be a promising resource for cell-based therapy for damaged cartilage.

Overexpression of RPN2 promotes osteogenic differentiation of hBMSCs through the JAK/STAT3 pathway

Osteoporosis is characterized by decreased bone mass and degenerating bone structure, which cause severe bone fragility and increase the risk for fractures. Human bone mesenchymal stem cells (hBMSCs) differentiate into osteoblasts through osteogenesis, and disturbances in the balance between bone generation and degeneration underlie the pathogenesis of senile osteoporosis. The highly conserved glycoprotein Ribophorin II (RPN2) is involved in multiple biological reactions, but the role of RPN2 in the osteogenic differentiation of hBMSCs and their molecular etiology is incompletely understood. Here, we show that RPN2 expression is up‐regulated in hBMSCs during osteogenic differentiation. In vitro assays revealed that silencing of RPN2 inhibited hBMSC differentiation into osteoblasts. Moreover, RPN2 overexpression enhanced the expression of linked genes and resulted in high alkaline phosphatase activity. Our results suggest that RPN2 targets Janus kinase 1 (JAK1), and RPN2 overexpression was observed to induce JAK1 ubiquitination. Depletion of JAK1 facilitated osteogenic differentiation of RPN2‐silenced hBMSCs. Moreover, western blot analysis revealed that RPN2 silencing suppressed the stimulation and nuclear translocation of the downstream signal transducer and activator of transcription 3 sensor; this could be reversed via RPN2 overexpression. This research sheds light on an innovative molecular mechanism that is associated with hBMSC differentiation into osteoblasts and may facilitate bone anabolism through RPN2.

Usefulness of Mesenchymal Cell Lines for Bone and Cartilage Regeneration Research

The unavailability of sufficient numbers of human primary cells is a major roadblock for in vitro repair of bone and/or cartilage, and for performing disease modelling experiments. Immortalized mesenchymal stromal cells (iMSCs) may be employed as a research tool for avoiding these problems. The purpose of this review was to revise the available literature on the characteristics of the iMSC lines, paying special attention to the maintenance of the phenotype of the primary cells from which they were derived, and whether they are effectively useful for in vitro disease modeling and cell therapy purposes. This review was performed by searching on Web of Science, Scopus, and PubMed databases from 1 January 2015 to 30 September 2019. The keywords used were ALL = (mesenchymal AND ("cell line" OR immortal*) AND (cartilage OR chondrogenesis OR bone OR osteogenesis) AND human). Only original research studies in which a human iMSC line was employed for osteogenesis or chondrogenesis experiments were included. After describing the success of the immortalization protocol, we focused on the iMSCs maintenance of the parental phenotype and multipotency. According to the literature revised, it seems that the maintenance of these characteristics is not guaranteed by immortalization, and that careful selection and validation of clones with particular characteristics is necessary for taking advantage of the full potential of iMSC to be employed in bone and cartilage-related research.

Hedgehog Signaling Inhibition by Smoothened Antagonist BMS-833923 Reduces Osteoblast Differentiation and Ectopic Bone Formation of Human Skeletal (Mesenchymal) Stem Cells

Background

Hedgehog (Hh) signaling is essential for osteoblast differentiation of mesenchymal progenitors during endochondral bone formation. However, the critical role of Hh signaling during adult bone remodeling remains to be elucidated.

Methods

A Smoothened (SMO) antagonist/Hedgehog inhibitor, BMS-833923, identified during a functional screening of a stem cell signaling small molecule library, was investigated for its effects on the osteoblast differentiation of human skeletal (mesenchymal) stem cells (hMSC). Alkaline phosphatase (ALP) activity and Alizarin red staining were employed as markers for osteoblast differentiation and in vitro mineralization capacity, respectively. Global gene expression profiling was performed using the Agilent® microarray platform. Effects on in vivo ectopic bone formation were assessed by implanting hMSC mixed with hydroxyapatite-tricalcium phosphate granules subcutaneously in 8-week-old female nude mice, and the amount of bone formed was assessed using quantitative histology.

Results

BMS-833923, a SMO antagonist/Hedgehog inhibitor, exhibited significant inhibitory effects on osteoblast differentiation of hMSCs reflected by decreased ALP activity, in vitro mineralization, and downregulation of osteoblast-related gene expression. Similarly, we observed decreased in vivo ectopic bone formation. Global gene expression profiling of BMS-833923-treated compared to vehicle-treated control cells, identified 348 upregulated and 540 downregulated genes with significant effects on multiple signaling pathways, including GPCR, endochondral ossification, RANK-RANKL, insulin, TNF alpha, IL6, and inflammatory response. Further bioinformatic analysis employing Ingenuity Pathway Analysis revealed significant enrichment in BMS-833923-treated cells for a number of functional categories and networks involved in connective and skeletal tissue development and disorders, e.g., NFκB and STAT signaling.

Conclusions

We identified SMO/Hedgehog antagonist (BMS-833923) as a powerful inhibitor of osteoblastic differentiation of hMSC that may be useful as a therapeutic option for treating conditions associated with high heterotopic bone formation and mineralization.

Biphasic Dose-Response and Hormetic Effects of Stress Hormone Hydrocortisone on Telomerase-Immortalized Human Bone Marrow Stem Cells In Vitro

Although high levels of stress hormones are associated with well-known negative health outcomes, their low levels can have health-promoting effects by virtue of the phenomenon of mild stress-induced hormesis. We have studied the effects of a wide range (between 100 nmol/L and 150 μmol/L) of hydrocortisone (HC) on human bone marrow stem cells in vitro. Telomerase-immortalized human mesenchymal stem cells (hTERT-MSCs) were exposed to various doses of HC for different durations (1-6 days) and analyzed for survival and metabolic activity by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, for cell migratory ability by a wound-healing assay and for osteoblastic and adipogenic differentiation abilities in vitro. Our findings indicate that hTERT-MSCs exposed to HC resulted in a biphasic hormetic dose–response in some measures but not all. Although the mitochondrial and metabolic MTT activity assay clearly showed low-level stimulatory (between 0.1 and 1 µmol/L) and high-level inhibitory effects (from about 10 µmol/L onward), the cytostatic and differentiation-inducing effects were mostly linear at concentrations between 1 and 100 µmol/L. Further long-term studies will elucidate whether chronic or intermittent exposure of human cells to stress hormones has physiologically beneficial hormetic effects.

Inhibitory Effect of Sirtuin6 (SIRT6) on Osteogenic Differentiation of Bone Marrow Mesenchymal Stem Cells

BACKGROUND The imbalance between bone resorption and formation is the basic mechanism underlying osteoporosis in the elderly. Osteogenesis is the differentiation of human mesenchymal stem cells (hMSCs) into osteoblasts. Sirtuin6 (SIRT6) regulates various biological functions, including differentiation. Transient receptor potential cation channel subfamily V member 1 (TRPV1) is a non-selective cation channel that can be activated by physical and chemical stimulation. However, experimental data supporting the role of SIRT6 in osteogenic differentiation (OD) of hMSCs are lacking. MATERIAL AND METHODS Differentiation of hMSCs was induced. The expressions of SIRT6, TRPV1, and CGRP were detected by Q-PCR, Western blot, and ELISA, respectively. SIRT6 was overexpressed in hMSCs by transfection. ALP activity and Alizarin Red staining were utilized to detect the effect of SIRT6 on hMSC OD. Then, capsaicin and capsazepine, the TRPV1 agonist and antagonist, respectively, were administrated to assess the role of TRPV1. RESULTS SIRT6 expression was downregulated during hMSC differentiation. SIRT6 overexpression was accompanied by reduced expression of specific genes and alkaline phosphatase (ALP) activity in osteoblasts. Furthermore, TRPV1 channel was also reduced by SIRT6 overexpression via ubiquitinating TRPV1. Capsaicin was utilized in SIRT6-overexpressed cells. Capsaicin therapy counteracted the effect of SIRT6 overexpression on OD, and markedly decreased OD. CONCLUSIONS The SIRT6-TRPV1-CGRP signal axis is the key to regulating OD in hMSCs, which could be a potential therapeutic target for osteoporosis and bone loss-related diseases.

Increased Gene Expression of RUNX2 and SOX9 in Mesenchymal Circulating Progenitors Is Associated with Autophagy during Physical Activity

Lack of physical exercise is considered an important risk factor for chronic diseases. On the contrary, physical exercise reduces the morbidity rates of obesity, diabetes, bone disease, and hypertension. In order to gain novel molecular and cellular clues, we analyzed the effects of physical exercise on differentiation of mesenchymal circulating progenitor cells (M-CPCs) obtained from runners. We also investigated autophagy and telomerase-related gene expression to evaluate the involvement of specific cellular functions in the differentiation process. We performed cellular and molecular analyses in M-CPCs, obtained by a depletion method, of 22 subjects before (PRE RUN) and after (POST RUN) a half marathon performance. In order to prove our findings, we performed also in vitro analyses by testing the effects of runners' sera on a human bone marrow-derived mesenchymal stem (hBM-MSC) cell line. PCR array analyses of PRE RUN versus POST RUN M-CPC total RNAs put in evidence several genes which appeared to be modulated by physical activity. Our results showed that physical exercise promotes differentiation. Osteogenesis-related genes as RUNX2, MSX1, and SPP1 appeared to be upregulated after the run; data showed also increased levels of BMP2 and BMP6 expressions. SOX9, COL2A1, and COMP gene enhanced expression suggested the induction of chondrocytic differentiation as well. The expression of telomerase-associated genes and of two autophagy-related genes, ATG3 and ULK1, was also affected and correlated positively with MSC differentiation. These data highlight an attractive cellular scenario, outlining the role of autophagic response to physical exercise and suggesting new insights into the benefits of physical exercise in counteracting chronic degenerative conditions.

Notch Signaling Inhibition by LY411575 Attenuates Osteoblast Differentiation and Decreased Ectopic Bone Formation Capacity of Human Skeletal (Mesenchymal) Stem Cells

Background

Chemical biology approaches using small molecule inhibitors targeting specific signaling pathways are useful tools to dissect the molecular mechanisms governing stem cell differentiation and for their possible use in therapeutic interventions.

Methods

Stem cell signaling small molecule library functional screen was performed employing human bone marrow skeletal (mesenchymal) stem cells (hBMSCs). Alkaline phosphatase (ALP) activity and formation of mineralized matrix visualized by Alizarin red staining were employed as markers for osteoblastic differentiation. Global gene expression profiling was conducted using the Agilent microarray platform, and data normalization and bioinformatics were performed using GeneSpring software. Pathway analyses were conducted using the Ingenuity Pathway Analysis (IPA) tool. In vivo ectopic bone formation was performed using hBMSC mixed with hydroxyapatite–tricalcium phosphate granules that were implanted subcutaneously in 8-week-old female nude mice. Hematoxylin and eosin staining and Sirius red staining were performed to identify bone formation in vivo.

Results

Among the tested molecules, LY411575, a potent γ-secretase and Notch signaling inhibitor, exhibited significant inhibitory effects on osteoblastic differentiation of hBMSCs manifested by reduced ALP activity, mineralized matrix formation, and decreased osteoblast-specific gene expression as well as in vivo ectopic bone formation. Global gene expression profiling of LY411575-treated cells revealed changes in multiple signaling pathways, including focal adhesion, insulin, TGFβ, IL6, and Notch signaling, and decreased the expression of genes associated with functional categories of tissue development. Among the affected signaling networks were TGFβ1, SPP1, and ERK regulatory networks.

Conclusions

We identified γ-secretase inhibitor (LY411575) as a potent regulator of osteoblastic differentiation of hBMSC that may be useful as a therapeutic option for treating conditions associated with ectopic bone formation.

A review on different methods to increase the efficiency of mesenchymal stem cell-based wound therapy

Mesenchymal stem cells (MSCs) accelerate wound healing but the harsh environment of wound site limits the engraftment, retention, and survival rate of transplanted cells. There are multiple approaches that amplify the therapeutic potential of MSCs. The MSCs derived from medical waste material, provide comparable regenerative abilities compared to traditional sources. The application of different scaffolds increases MSC delivery and migration into the wound. The spheroid culture of MSC increases the paracrine effects of the entrapped cells and the secretion of pro-angiogenic and anti-inflammatory cytokines. The MSC pretreating and preconditioning enhances the cell migration, proliferation, and survival rate, which lead to higher angiogenesis, re-epithelialization, wound closure, and granulation tissue formation. Moreover, genetic modification has been performed in order to increase MSC angiogenesis, differentiation potential, as well as the cell life span. Herein, we review the results of aforementioned approaches and provide information accommodating to the continued development of MSC-based wound therapy in the future.

Rosiglitazone Enhances Browning Adipocytes in Association with MAPK and PI3-K Pathways During the Differentiation of Telomerase-Transformed Mesenchymal Stromal Cells into Adipocytes

Obesity is a major risk for diabetes. Brown adipose tissue (BAT) mediates production of heat while white adipose tissue (WAT) function in the storage of fat. Roles of BAT in the treatment of obesity and related disorders warrants more investigation. Peroxisome proliferator activator receptor gamma (PPAR-γ) is the master regulator of both BAT and WAT adipogenesis and has roles in glucose and fatty acid metabolism. Adipose tissue is the major expression site for PPAR-γ. In this study, the effects of rosiglitazone on the brown adipogenesis and the association of MAPK and PI3K pathways was investigated during the in vitro adipogenic differentiation of telomerase transformed mesenchymal stromal cells (iMSCs). Our data indicate that 2 µM rosiglitazone enhanced adipogenesis by over-expression of PPAR-γ and C/EBP-α. More specifically, brown adipogenesis was enhanced by the upregulation of EBF2 and UCP-1 and evidenced by multilocular fatty droplets morphology of the differentiated adipocytes. We also found that rosiglitazone significantly activated MAPK and PI3K pathways at the maturation stage of differentiation. Overall, the results indicate that rosiglitazone induced overexpression of PPAR-γ that in turn enhanced adipogenesis, particularly browning adipogenesis. This study reports the browning effects of rosiglitazone during the differentiation of iMSCs into adipocytes in association with the activation of MAPK and PI3K signaling pathways.

Convergence of TGFβ and BMP signaling in regulating human bone marrow stromal cell differentiation

Targeting regulatory signaling pathways that control human bone marrow stromal (skeletal or mesenchymal) stem cell (hBMSC) differentiation and lineage fate determination is gaining momentum in the regenerative medicine field. Therefore, to identify the central regulatory mechanism of osteoblast differentiation of hBMSCs, the molecular phenotypes of two clonal hBMSC lines exhibiting opposite in vivo phenotypes, namely, bone forming (hBMSC^+bone) and non-bone forming (hBMSC^−Bone) cells, were studied. Global transcriptome analysis revealed significant downregulation of several TGFβ responsive genes, namely, TAGLN, TMP1, ACTA2, TGFβ2, SMAD6, SMAD9, BMP2, and BMP4 in hBMSC^−Bone cells and upregulation on SERPINB2 and NOG. Transcriptomic data was associated with marked reduction in SMAD2 protein phosphorylation, which thereby implies the inactivation of TGFβ and BMP signaling in those cells. Concordantly, activation of TGFβ signaling in hBMSC^−Bone cells using either recombinant TGFβ1 protein or knockdown of SERPINB2 TGFβ-responsive gene partially restored their osteoblastic differentiation potential. Similarly, the activation of BMP signaling using exogenous BMP4 or via siRNA-mediated knockdown of NOG partially restored the differentiation phenotype of hBMSC^−Bone cells. Concordantly, recombinant NOG impaired ex vivo osteoblastic differentiation of hBMSC^+Bone cells, which was associated with SERBINB2 upregulation. Our data suggests the existence of reciprocal relationship between TGFB and BMP signaling that regulates hBMSC lineage commitment and differentiation, whilst provide a plausible strategy for generating osteoblastic committed cells from hBMSCs for clinical applications.

Isocytosine deaminase Vcz as a novel tool for the prodrug cancer therapy

Background

The cytosine deaminase (CD)/5-fluorocytosine (5-FC) system is among the best explored enzyme/prodrug systems in the field of the suicide gene therapy. Recently, by the screening of the environmental metagenomic libraries we identified a novel isocytosine deaminase (ICD), termed Vcz, which is able of specifically converting a prodrug 5-fluoroisocytosine (5-FIC) into toxic drug 5-fluorouracil (5-FU). The aim of this study is to test the applicability of the ICD Vcz / 5-FIC pair as a potential suicide gene therapy tool.

Methods

Vcz-expressing human glioblastoma U87 and epithelial colorectal adenocarcinoma Caco-2 cells were treated with 5-FIC, and the Vcz-mediated cytotoxicity was evaluated by performing an MTT assay. In order to examine anti-tumor effects of the Vcz/5-FIC system in vivo, murine bone marrow-derived mesenchymal stem cells (MSC) were transduced with the Vcz-coding lentivirus and co-injected with 5-FIC or control reagents into subcutaneous GL261 tumors evoked in C57/BL6 mice.

Results

5-FIC alone showed no significant toxic effects on U87 and Caco-2 cells at 100 μM concentration, whereas the number of cells of both cell lines that express Vcz cytosine deaminase gene decreased by approximately 60% in the presence of 5-FIC. The cytotoxic effects on cells were also induced by media collected from Vcz-expressing cells pre-treated with 5-FIC. The co-injection of the Vcz-transduced mesenchymal stem cells and 5-FIC have been shown to augment tumor necrosis and increase longevity of tumorized mice by 50% in comparison with control group animals.

Conclusions

We have confirmed that the novel ICD Vcz together with the non-toxic prodrug 5-FIC has a potential of being a new enzyme/prodrug system for suicide gene therapy.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5409-7) contains supplementary material, which is available to authorized users.

NOTCH Signaling Is Activated through Mechanical Strain in Human Bone Marrow-Derived Mesenchymal Stromal Cells

Skeletal development and remodeling of adult bone are critically controlled by activated NOTCH signaling in genetically modified mice. It is yet unclear whether NOTCH signaling is activated by mechanical strain sensed by bone cells. We found that expression of specific NOTCH target genes is induced after in vivo tibial mechanical loading in wild-type mice. We further applied mechanical strain through cyclic stretching in human bone marrow-derived mesenchymal stromal cells (BMSCs) in vitro by using a bioreactor system and detected upregulation of NOTCH target gene expression. Inhibition of the NOTCH pathway in primary BMSCs as well as telomerase-immortalized human BMSCs (hMSC-TERT) through the gamma-secretase inhibitor GSI XII blocked mechanotransduction and modulated actin cytoskeleton organization. Short-hairpin RNA gene silencing identified NOTCH2 as the key receptor mediating NOTCH effects on hMSC-TERT cells. Our data indicate a functional link between NOTCH activation and mechanotransduction in human BMSCs. We suggest that NOTCH signaling is an important contributor to molecular mechanisms that mediate the bone formation response to mechanical strain.

MicroRNA-224 enhances the osteoblastic differentiation of hMSCs via Rac1

Osteogenesis is the differentiation of mesenchymal stem cells (MSCs) into osteoblasts. MicroRNAs (miRNAs) are short noncoding RNAs that target specific genes to mediate translational activities. In this study, we investigated how miR-224 regulates the osteoblastic differentiation of human MSCs (hMSCs) as well as the underlying mechanism. The results revealed the upregulation of miR-224 during hMSC differentiation. In vitro experiments showed that the downregulation of miR-224 suppressed the differentiation of hMSCs into osteoblasts. However, upregulation of miR-224 was concomitant with increased expression of relevant genes and augmented activity of alkaline phosphatase. Furthermore, the results indicated that Rac1 acted as the bona fide target of miR-224 and that Rac1 depletion promoted osteogenic differentiation in miR-224-silenced hMSCs. In addition, we found that both JAK/STAT3 and Wnt/β-catenin pathways were repressed by Rac1 depletion using quantitative reverse transcription polymerase chain reaction (qRT-PCR), western blotting, and immunofluorescence. Our data indicate a novel molecular mechanism in relation to hMSCs differentiation into osteoblasts, which may facilitate bone anabolism via miR-224. SIGNIFICANCE OF THE STUDY: In this study, we mainly explored the effects of miR-224 on hMSCs differentiation into osteoblasts. We find that induced miR-224 expression in hMSCs is considered closely associated with specific osteogenesis-related genes, alkaline phosphatase activity, and matrix mineralization, indicating that miR-224 may serve as a promising biomarker for osteogenic differentiation. Our data indicate a novel molecular mechanism in relation to hMSCs differentiation into osteoblasts, which may facilitate bone anabolism via miR-224.