The role of reactive oxygen species in mesenchymal stem cell adipogenic and osteogenic differentiation: a review

Three widely used pesticides and their mixtures induced cytotoxicity and apoptosis through the ROS-related caspase pathway in HepG2 cells

Difenoconazole, cypermethrin and triazophos are widely used pesticides in agricultural production and frequently detected in foods. The aim of this study was to determine the effect of these pesticides and their mixtures on cell viability, reactive oxygen species (ROS), lactate dehydrogenase (LDH) content, apoptosis rate and DNA fragmentation and synthesis in human hepatocellular carcinoma cells (HepG2). The order of inhibitory effects for the individual pesticides was ranked as difenoconazole > cypermethrin > triazophos. The enhanced expression of caspase-3, caspase-7 and PARP activity was observed in HepG2 cells, which was 1.7, 1.3 and 1.6-fold higher than the control, respectively, along with significant protein cleavage; and induced apoptosis in a concentration-dependent manner. Further, the pesticide mixtures significantly increased ROS level (up to 1.3-fold), induced DNA fragmentation (up to 1.8-fold), inhibited DNA synthesis (up to 53%), and damaged the cells by destroying the cell membrane and producing a large amount of LDH at concentration range of 10-30 μM. Specifically, mixtures containing difenoconazole showed stronger toxicities than individual pesticides, implying higher health risks associated with mixtures. Our results show that three widely used pesticides exhibited cytotoxicity and apoptosis through the ROS-related caspase pathway, providing a basis for evaluation of health risks from pesticide mixtures via food consumption.

Bioadaptation of implants to In vitro and In vivo oxidative stress pathological conditions via nanotopography-induced FoxO1 signaling pathways to enhance Osteoimmunal regeneration

Varieties of pathological conditions, including diabetes, are closely related to oxidative stress (OS), but the osseointegration or bioadaptation of implants to OS and the related mechanism remain poorly explored. In this study, the antioxidation and osteoimmune regeneration of titanium implants with micro/nanotopographies were evaluated under H₂O₂-, lipopolysaccharide (LPS)- and hyperglycemia-mediated cellular OS models and in diabetic rats as a representative animal model of OS. TiO₂ nanotube (TNT) coating on titanium implants directly induced superior osteogenic differentiation of bone mesenchymal stem cells (MSCs) and osseointegration compared with microscale sand blasted-acid etched topography (SLA) under OS, attributed to higher superoxide dismutase 2 activity, the neutralization of intracellular reactive oxygen species (ROS), and less apoptosis. Mechanistically, the oxidation resistance on TNT is driven by upregulated forkhead box transcription factor O1 (FoxO1), which is abolished after knockdown of FoxO1 via shRNA in MSCs. Indirectly, TNT also alleviates OS in macrophages, therefore inducing a higher portion of the M2 phenotype under OS with increased secretion of the anti-inflammatory cytokine IL-10, further promoting the osseoimmunity capacity compared with SLA. The current study not only suggests the potential application of TiO₂ nanotube-coated titanium implants in compromised conditions but also provides a systematic evaluation strategy for the future development of bone biomaterials.

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H₂O₂, lipopolysaccharide and hyperglycemia induced cellular oxidative stress models.

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TiO₂ nanotubes promote oxidation resistance and osteogenesis under oxidative stress.

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TiO₂ nanotubes activate forkhead box transcription factor O1 to enhance osteogenesis.

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TiO₂-nanotube-coated implants promote osseointegration in diabetic rats.

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TiO₂ nanotubes induce anti-inflammatory osteoimmunity under oxidative stress.

Mesenchymal Stem Cell-Based Therapy for Diabetes Mellitus: Enhancement Strategies and Future Perspectives

Diabetes mellitus (DM), a chronic disorder of carbohydrate metabolism, is characterized by the unbridled hyperglycemia resulted from the impaired ability of the body to either produce or respond to insulin. As a cell-based regenerative therapy, mesenchymal stem cells (MSCs) hold immense potency for curing DM duo to their easy isolation, multi-differentiation potential, and immunomodulatory property. However, despite the promising efficacy in pre-clinical animal models, naive MSC administration fails to exhibit clinically satisfactory therapeutic outcomes, which varies greatly among individuals with DM. Recently, numbers of innovative strategies have been applied to improve MSC-based therapy. Preconditioning, genetic modification, combination therapy and exosome application are representative strategies to maximize the therapeutic benefits of MSCs. Therefore, in this review, we summarize recent advancements in mechanistic studies of MSCs-based treatment for DM, and mainly focus on the novel approaches aiming to improve the anti-diabetic potentials of naive MSCs. Additionally, the potential directions of MSCs-based therapy for DM are also proposed at a glance.

Discrepancies on the Role of Oxygen Gradient and Culture Condition on Mesenchymal Stem Cell Fate

Over the past few years, mesenchymal stem (or stromal) cells (MSCs) have garnered enormous interest due to their therapeutic value especially for their multilineage differentiation potential leading to regenerative medicine applications. MSCs undergo physiological changes upon in vitro expansion resulting in expression of different receptors, thereby inducing high variabilities in therapeutic efficacy. Therefore, understanding the biochemical cues that influence the native local signals on differentiation or proliferation of these cells is very important. There have been several reports that in vitro culture of MSCs in low oxygen gradient (or hypoxic conditions) upregulates the stemness markers and promotes cell proliferation in an undifferentiated state, as hypoxia mimics the conditions the progenitor cells experience within the tissue. However, different studies report different oxygen gradients and culture conditions causing ambiguity in their interpretation of the results. In this progress report, it is aimed to summarize recent studies in the field with specific focus on conflicting results reported during the application of hypoxic conditions for improving the proliferation or differentiation of MSCs. Further, it is tried to decipher the factors that can affect characteristics of MSC under hypoxia and suggest a few techniques that could be combined with hypoxic cell culture to better recapitulate the MSC tissue niche.

TL1A/TNFR2 Axis Enhances Immunoregulatory Effects of Bone Marrow Derived Mesenchymal Stem Cell by Indian Hedgehog Signaling Pathway

Background and Objectives

The immunomodulatory potential of mesenchymal stem cells (MSCs) can be regulated by a variety of molecules, especially cytokines. The inflammatory cytokine, TNF-like ligand 1A (TL1A), has been reported as an inflammation stimulator in-multiple autoimmune diseases. Here, we studied the effects of TL1A/TNF-receptor 2 (TNFR2) pathway on the therapeutic potency of bone marrow-derived MSCs (BMSCs).

Methods and Results

BMSCs, fibroblast-like synoviocytes (FLSs), and H9 and jurkat human T lymphocytes were used in this study. BMSCs paracrine activities, differentiation, proliferation, and migration were investigated after stimulation with TL1A, and intervened with anti-TNFR2. Additionally, the effects of TL1A on BMSCs therapeutic potency were evaluated by treating RA-FLSs, and H9 and jurkat T cells with TL1A-stimulated BMSCs conditioned medium (CM). Indian hedgehog (IHH) involvement was determined by gene silencing and treatment by recombinant IHH (rIHH). TL1A induced BMSCs stemness-related genes, COX-2, IL-6, IDO, TGF-β and HGF through TNFR2. Also, TL1A corrected biased differentiation and increased proliferation, and migration through TNFR2. Meanwhile, CM of TL1A-stimulated BMSCs decreased the inflammatory markers of RA-FLSs and T cells. Moreover, TL1A-stimulated BMSCs experienced IHH up-regulation coupled with NF-κB and STAT3 signaling up-regulation, while p53 and oxidative stress were down-regulated. Furthermore, treatment of BMSCs by rIHH increased their anti-inflammatory effects. More importantly, knockdown of IHH decreased the ability of TL1A-stimulated BMSCs to alleviating the inflammation in RA-FLSs and T cells.

Conclusions

This study reports the effects of TL1A/TNFR2 pathway on the biological behaviors and therapeutic potency of BMSCs through IHH. These findings could introduce novel procedures to increase the stemness of MSCs in cellular therapy.

The Effect of Selenium Nanoparticles on the Osteogenic Differentiation of MC3T3-E1 Cells

Reactive oxygen species (ROS) regulate various functions of cells, including cell death, viability, and differentiation, and nanoparticles influence ROS depending on their size and shape. Selenium is known to regulate various physiological functions, such as cell differentiations and anti-inflammatory functions, and plays an important role in the regulation of ROS as an antioxidant. This study aims to investigate the effect of selenium nanoparticles (SeNPs) on the differentiation of osteogenic MC3T3-E1 cells. After fabrication of SeNPs with a size of 25.3 ± 2.6 nm, and confirmation of its oxidase-like activity, SeNPs were added to MC3T3-E1 cells with or without H₂O₂: 5~20 μg/mL SeNPs recovered cells damaged by 200 μM H₂O₂ via the intracellular ROS downregulating role of SeNPs, revealed by the ROS staining assay. The increase in osteogenic maturation with SeNPs was gradually investigated by expression of osteogenic genes at 3 and 7 days, Alkaline phosphatase activity staining at 14 days, and Alizarin red S staining at 28 days. Therefore, the role of SeNPs in regulating ROS and their therapeutic effects on the differentiation of MC3T3-E1 cells were determined, leading to possible applications for bone treatment.

The role and mechanism of mitochondrial functions and energy metabolism in the function regulation of the mesenchymal stem cells

Mesenchymal stem cells (MSCs) are multipotent cells that show self-renewal, multi-directional differentiation, and paracrine and immune regulation. As a result of these properties, the MSCs have great clinical application prospects, especially in the regeneration of injured tissues, functional reconstruction, and cell therapy. However, the transplanted MSCs are prone to ageing and apoptosis and have a difficult to control direction differentiation. Therefore, it is necessary to effectively regulate the functions of the MSCs to promote their desired effects. In recent years, it has been found that mitochondria, the main organelles responsible for energy metabolism and adenosine triphosphate production in cells, play a key role in regulating different functions of the MSCs through various mechanisms. Thus, mitochondria could act as effective targets for regulating and promoting the functions of the MSCs. In this review, we discuss the research status and current understanding of the role and mechanism of mitochondrial energy metabolism, morphology, transfer modes, and dynamics on MSC functions.

Changes in the extracellular microenvironment and osteogenic responses of mesenchymal stem/stromal cells induced by in vitro direct electrical stimulation

Electrical stimulation (ES) has potential to be an effective tool for bone injury treatment in clinics. However, the therapeutic mechanism associated with ES is still being discussed. This study aims to investigate the initial mechanism of action by characterising the physical and chemical changes in the extracellular environment during ES and correlate them with the responses of mesenchymal stem/stromal cells (MSCs). Computational modelling was used to estimate the electrical potentials relative to the cathode and the current density across the cell monolayer. We showed expression of phosphorylated ERK1/2, c-FOS, c-JUN, and SPP1 mRNAs, as well as the increased metabolic activities of MSCs at different time points. Moreover, the average of 2.5 μM of H₂O₂ and 34 μg/L of dissolved Pt were measured from the electrically stimulated media (ES media), which also corresponded with the increases in SPP1 mRNA expression and cell metabolic activities. The addition of sodium pyruvate to the ES media as an antioxidant did not alter the SPP1 mRNA expression, but eliminated an increase in cell metabolic activities induced by ES media treatment. These findings suggest that H₂O₂ was influencing cell metabolic activity, whereas SPP1 mRNA expression was regulated by other faradic by-products. This study reveals how different electrical stimulation regime alters cellular regenerative responses and the roles of faradic by-products, that might be used as a physical tool to guide and control cell behaviour.

Antiobesity effect of Brassica juncea cultivated in Jeongseon with optimized sinigrin content using 3T3-L1 adipocytes

In recent years, Brassica juncea has been selected as a special agricultural crop in Jeongseon, Gangwon-do, Korea, and is actively grown there. However, there have been no studies on B. juncea cultivated in Jeongseon (BJJ). Sinigrin, an index component of cruciferous vegetables, has been reported to have antiobesity effects. In this study, we developed a method for obtaining a BJJ extract with optimized sinigrin content, and investigate the antiobesity properties of the BJJ extract and sinigrin. The optimal extraction conditions for BJJ were found to be with 60% ethanol, at 70°C, for 3 hr. Lipid accumulation and ROS production were significantly suppressed in both the BJJ extract and sinigrin-treated groups. Furthermore, BJJ extract and sinigrin were effectively controlled the expression of proteins that regulate lipid accumulation, fatty acid oxidation, and energy metabolism. Thus, BJJ extract containing sinigrin may be used as a health functional food material. PRACTICAL APPLICATIONS: Brassica juncea has been reported to be rich in flavonoids, polyphenols, and glucosinolate, which are secondary vegetable metabolites. In this study, an extraction method to optimize the content of sinigrin in BJJ was established, and the antiobesity mechanism for the extract was confirmed. Lipid accumulation and ROS production were significantly suppressed in both the BJJ extract and sinigrin-treated groups in the study. It was confirmed that the expression of proteins that regulate lipid accumulation, lipid synthesis, fatty acid oxidation, heat generation, and energy metabolism was effectively controlled by the BJJ extract and sinigrin. Therefore, the ethanol extraction method of this study are considered to be useful for the preparation of extracts using cruciferous vegetables, and BJJ extract containing sinigrin have the potential to be used as a health functional food material for obesity.

Dynamic proteomic profiling of human periodontal ligament stem cells during osteogenic differentiation

Background

Human periodontal ligament stem cells (hPDLSCs) are ideal seed cells for periodontal regeneration. A greater understanding of the dynamic protein profiles during osteogenic differentiation contributed to the improvement of periodontal regeneration tissue engineering.

Methods

Tandem Mass Tag quantitative proteomics was utilized to reveal the temporal protein expression pattern during osteogenic differentiation of hPDLSCs on days 0, 3, 7 and 14. Differentially expressed proteins (DEPs) were clustered and functional annotated by Gene Ontology (GO) terms. Pathway enrichment analysis was performed based on the Kyoto Encyclopedia of Genes and Genomes database, followed by the predicted activation using Ingenuity Pathway Analysis software. Interaction networks of redox-sensitive signalling pathways and oxidative phosphorylation (OXPHOS) were conducted and the hub protein SOD2 was validated with western blotting.

Results

A total of 1024 DEPs were identified and clustered in 5 distinctive clusters representing dynamic tendencies. The GO enrichment results indicated that proteins with different tendencies show different functions. Pathway enrichment analysis found that OXPHOS was significantly involved, which further predicted continuous activation. Redox-sensitive signalling pathways with dynamic activation status showed associations with OXPHOS to various degrees, especially the sirtuin signalling pathway. SOD2, an important component of the sirtuin pathway, displays a persistent increase during osteogenesis. Data are available via ProteomeXchange with identifier PXD020908.

Conclusion

This is the first in-depth dynamic proteomic analysis of osteogenic differentiation of hPDLSCs. It demonstrated a dynamic regulatory mechanism of hPDLSC osteogenesis and might provide a new perspective for research on periodontal regeneration.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-020-02123-6.

Mitochondrial metabolism is a key regulator of the fibro-inflammatory and adipogenic stromal subpopulations in white adipose tissue

The adipose tissue stroma is a rich source of molecularly distinct stem and progenitor cell populations with diverse functions in metabolic regulation, adipogenesis, and inflammation. The ontology of these populations and the mechanisms that govern their behaviors in response to stimuli, such as overfeeding, however, are unclear. Here, we show that the developmental fates and functional properties of adipose platelet-derived growth factor receptor beta (PDGFRβ)+ progenitor subpopulations are tightly regulated by mitochondrial metabolism. Reducing the mitochondrial β-oxidative capacity of PDGFRβ+ cells via inducible expression of MitoNEET drives a pro-inflammatory phenotype in adipose progenitors and alters lineage commitment. Furthermore, disrupting mitochondrial function in PDGFRβ+ cells rapidly induces alterations in immune cell composition in lean mice and impacts expansion of adipose tissue in diet-induced obesity. The adverse effects on adipose tissue remodeling can be reversed by restoring mitochondrial activity in progenitors, suggesting therapeutic potential for targeting energy metabolism in these cells.

Extrusion-based 3D printed biodegradable porous iron

Extrusion-based 3D printing followed by debinding and sintering is a powerful approach that allows for the fabrication of porous scaffolds from materials (or material combinations) that are otherwise very challenging to process using other additive manufacturing techniques. Iron is one of the materials that have been recently shown to be amenable to processing using this approach. Indeed, a fully interconnected porous design has the potential of resolving the fundamental issue regarding bulk iron, namely a very low rate of biodegradation. However, no extensive evaluation of the biodegradation behavior and properties of porous iron scaffolds made by extrusion-based 3D printing has been reported. Therefore, the in vitro biodegradation behavior, electrochemical response, evolution of mechanical properties along with biodegradation, and responses of an osteoblastic cell line to the 3D printed iron scaffolds were studied. An ink formulation, as well as matching 3D printing, debinding and sintering conditions, was developed to create iron scaffolds with a porosity of 67%, a pore interconnectivity of 96%, and a strut density of 89% after sintering. X-ray diffracometry confirmed the presence of the α-iron phase in the scaffolds without any residuals from the rest of the ink. Owing to the presence of geometrically designed macropores and random micropores in the struts, the in vitro corrosion rate of the scaffolds was much improved as compared to the bulk counterpart, with 7% mass loss after 28 days. The mechanical properties of the scaffolds remained in the range of those of trabecular bone despite 28 days of in vitro biodegradation. The direct culture of MC3T3-E1 preosteoblasts on the scaffolds led to a substantial reduction in living cell count, caused by a high concentration of iron ions, as revealed by the indirect assays. On the other hand, the ability of the cells to spread and form filopodia indicated the cytocompatibility of the corrosion products. Taken together, this study shows the great potential of extrusion-based 3D printed porous iron to be further developed as a biodegradable bone substituting biomaterial.

Effects of 20(S)-hydroxycholesterol on satellite cell proliferation and differentiation of broilers

In the modern poultry industry, with increasing product demand, muscle growth rate and meat yield in chickens have tremendously changed. Understanding the regulation of muscle development is important to maintain efficient growth and development in meat-type chickens. 20(S)-hydroxycholesterol (20S) is known as one of the naturally occurring osteogenic cholesterol derivatives due to its ability to induce osteogenic differentiation; however, no studies have evaluated myogenic response to 20S in chicken muscle cells. To determine the use of 20S in vitro for the proliferation and differentiation of chicken satellite cells, satellite cells were isolated from pectoralis major muscle of 4-week-old Ross 708 male chickens and subjected to 0.25, 0.5, and 1.0 μmol of 20S during their proliferation and differentiation stages. Cell proliferation and differentiation were measured every 24 h for 72 h by determining DNA concentration, the activity of creatine kinase, and the expressions of myogenic regulatory transcription factors. Together these results suggested that a lower concentration of 20S did not affect myogenesis but a high concentration of 1.0 μmol 20S can negatively affect proliferation and differentiation in chicken satellite cells.

Insights into the Role of Magnesium Ions in Affecting Osteogenic Differentiation of Mesenchymal Stem Cells

Bone marrow mesenchymal stem cells (MSCs) are multipotent stem cells with the ability to differentiate into bone-producing cells, which is essential for bone formation. Magnesium biomedical materials, such as biodegradable matters with osteoinductive properties, play a vital role in the osteogenic differentiation of MSCs. International and Chinese studies have shown that magnesium ions, which are produced by biodegradation, mainly achieve this effect by regulating the expression of genes and proteins associated with osteogenesis, activating multiple signal pathways, elevating autophagic activities, and adjusting the pH in the microenvironment. It is of great significance to study the regulatory mechanisms and identify the optimal conditions that how magnesium ions promote osteogenic differentiation of MSCs. In this study, we summarized the regulatory mechanisms noted above.

Aqueous Extract of Salvia miltiorrhiza Bunge-Radix Puerariae Herb Pair Attenuates Osteoporosis in Ovariectomized Rats Through Suppressing Osteoclast Differentiation

Traditional herb pair Salvia miltiorrhiza Bunge-Radix Puerariae (DG) owns various biological activities including anti-inflammatory and anti-oxidative stress. Oxidative stress is one high-risk factor for osteoporosis, then effect of DG on osteoporosis and underlying mechanisms was explored both in vivo and in vitro. Firstly, the predication from network pharmacology hinted that DG has the potential for ameliorating osteoporosis. Consistent with predication, DG significantly restored bone loss and deficiency of type II collagen, decreased TRAP and Cathepsin K positive areas in femur. Meanwhile it improved important characteristics of microarchitectural deterioration of tissue, reduced the numbers of NFATc1-positive osteoclast in the vertebra as well as decreased the serum osteoclast-specific cytokine RANKL and OPG release in OVX rats exhibiting its protective effect against osteoporosis. In vitro, DG noticeably decreased osteoclastic-special marker protein expressions of RANK, c-Fos and NFATc1. Furthermore, autophagy pathway p62/LC3B, ROS production and NF-κB were all activated by RANKL stimulation and blocked by DG pretreatment. Moreover, autophagy inhibitors, ROS scavenger, Ca²⁺ chelator and NF-κB inhibitor remarkably suppressed c-Fos and NFATc1 expressions. Taken together, DG may ameliorate osteoporosis by regulating osteoclast differentiation mediated by autophagy and oxidative stress. This study provided a mechanistic basis for DG treating osteoporosis and offered a safe dose for DG in preventing and improving bone diseases.

Evaluating the bio-application of biomacromolecule of lignin-carbohydrate complexes (LCC) from wheat straw in bone metabolism via ROS scavenging

Lignin-carbohydrate complexes (LCC) arebiomacromolecules that can be obtained from different biomass. Even some works have shown the LCC can efficiently scavenge the intracellular and endogenous reactive oxygen species (ROS), while little work has been carried out to investigate the potential application of LCC for ROS-related treatment in biological filed, especially for the treatment of periprosthetic osteolysis in vivo. In this work, Lignin-rich (LCC-A) and carbohydrate-rich (LCC-B) fractions in wheat straw are isolated and used as the ROS scavenger to promote osteoblast differentiation and inhibit osteoclast differentiation. The chemical composition and structures are characterized by high performance anion exchange chromatography (HPAEC) and nuclear magnetic resonance (NMR) technologies (quantitative ¹³C NMR and 2D-HSQC NMR), respectively. The results showed LCC-A possesses higher in vitro ROS-scavenging ability than LCC-B (89.8% vs 57.8%) and to inhibit osteoclast differentiation, whereas LCC-B more significantly activates cellular antioxidant activities via the KEAP1-NRF2-ARE pathway (218.5% vs 438.0% in the level of HO-1), thus promoting osteoblast differentiation in an inflammatory environment. Moreover, the therapeutic administration of LCC-A and LCC-B for Ti-particle-induced osteolytic murine calvariae showed both of them positively regulate and restore the bone metabolism, while preventing calvaria impairment. Hence, LCC from wheat straw exhibits efficient bone protective effects, suggesting it may be used as the promising ROS scavenger for clinical treatment of periprosthetic osteolysis.

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.

Mtu1 defects are correlated with reduced osteogenic differentiation

Accumulating evidence has revealed that mitochondria dynamics and function regulation is essential for the successful mesenchymal stem cell (MSC) differentiation. In the present study, the researchers reported for the first time that Mtu1 defects are correlated with reduced osteogenic differentiation. Using in vitro cultured bone marrow MSCs and stromal cell line MS5, we demonstrated that depressed Mtu1 expression was associated with reduced 2-thiouridine modification of the U34 of mitochondrial tRNA^Gln, tRNA^Glu, and tRNA^Lys, which led to respiratory deficiencies and reduced mitochondrial ATP production, and finally suppressed osteogenic differentiation. As expected, these Mtu1-deficient mice exhibited obvious osteopenia. Therefore, our findings in this study provide new insights into the pathophysiology of osteopenia.

Hyperlipidemia Impairs Osseointegration via the ROS/Wnt/β-Catenin Pathway

The influence of hyperlipidemia on titanium implant osseointegration and the underlying mechanisms is not well understood. This study investigates the changes in osseointegration and explores the potential mechanisms in hyperlipidemia conditions. In vivo, specialized titanium implants were implanted in the femurs of diet-induced or genetic hyperlipidemia mice. In vitro, primary murine osteoblasts were cultured on the titanium surface in high-fat medium. Results showed that hyperlipidemia led to poor osseointegration in both types of mice in vivo, and high-fat medium impaired the osteogenic differentiation of primary osteoblasts on the titanium surface in vitro. In addition, high-fat medium caused significant overproduction of reactive oxygen species (ROS) and inhibition of the Wnt/β-catenin pathway in osteoblasts. Both N-acetyl-L-cysteine (NAC, an ROS antagonist) and Wnt3a (an activator of the Wnt/β-catenin pathway) attenuated the poor osteogenic ability of osteoblasts. In addition, NAC reactivated the Wnt/β-catenin pathway in osteoblasts under high-fat stimulation. These results demonstrate that hyperlipidemia impairs osseointegration via the ROS/Wnt/β-catenin pathway and provide support for the ROS or Wnt/β-catenin pathway as a promising therapeutic target for the development of novel drugs or implant materials to improve the osseointegration of implants in hyperlipidemic patients.

Synergistic Treatment of Obesity via Locally Promoting Beige Adipogenesis and Antioxidative Defense in Adipose Tissues

Obesity is a primary risk factor for type 2 diabetes, cardiovascular diseases, cancer, and other chronic diseases. Current antiobesity medications need frequent administration and show limited efficacy with severe side effects. Herein, browning agent rosiglitazone (Rsg) and antioxidant manganese tetroxide nanoparticles (MnNPs, around 250 nm) are integrated into electrospun short fibers (SF@Rsg-Mn) with a 1.5 μm width and a 20 μm length. Upon injection into inguinal adipose tissues, SF@Rsg-Mn are well retained in the local depots to sustainably release Rsg in 30 days for adipose tissue browning, while MnNPs on the fiber surface continuously scavenge adipose reactive oxygen species (ROS) for an extended period of time. Synergistic inhibition of fat accumulation through ROS scavenging and white adipocyte browning has been demonstrated for the first time, and the optimal synergistic ratio of Rsg and MnNPs is determined to be 1/14 via combination index examination. SF@Rsg-Mn inhibit lipid accumulation through downregulation of adipogenic gene PPARγ while promoting energy expenditure through upregulation of brown-specific gene UCP1 and mitochondrial function gene COX7A1. In a diet-induced obesity mouse model, a single injection of SF@Rsg-Mn into inguinal adipose tissues has accomplished a synergistic effect on body weight loss, fat reduction, glucose, and lipid metabolic improvement while minimizing adverse effects on other tissues, thereby paving the way to efficacious, safe, and practical treatment of obesity.

An NRF2 Perspective on Stem Cells and Ageing

Redox and metabolic mechanisms lie at the heart of stem cell survival and regenerative activity. NRF2 is a major transcriptional controller of cellular redox and metabolic homeostasis, which has also been implicated in ageing and lifespan regulation. However, NRF2's role in stem cells and their functioning with age is only just emerging. Here, focusing mainly on neural stem cells, which are core to adult brain plasticity and function, we review recent findings that identify NRF2 as a fundamental player in stem cell biology and ageing. We also discuss NRF2-based molecular programs that may govern stem cell state and function with age, and implications of this for age-related pathologies.

Blood Impairs Viability of Fat Grafts and Adipose Stem Cells: Importance of Washing in Fat Processing

BACKGROUND

Fat processing plays a pivotal role in graft survival. Each component of the blood in lipoaspirate affects fat survival in different ways, but the mechanisms are not clear.

OBJECTIVES

The aim of this study was to investigate, by various experimental methods, the effect of blood on the viability of fat grafts and adipose stem cells (ASCs).

METHODS

Blood and fat samples were obtained from 6 female patients undergoing aesthetic liposuction. For the in vivo experiment, we compared fat mixed with normal saline or various ratios of blood in nude mice. The samples were explanted at 2 and 8 weeks to evaluate the gross volume retention and histologic and immunohistochemical characteristics. For in vitro experiments, ASCs were pretreated with hemoglobin at different concentrations and for different times. We then assessed the proliferation, migration, adipogenesis, and reactive oxygen species production of ASCs.

RESULTS

Blood in the graft led to a decrease in graft viability, as evaluated by general observation and histologic and immunohistochemical morphology in vivo. In vitro experiments showed inhibited proliferation, migration, and adipogenesis, and increased reactive oxygen species production in ACSs, after hemoglobin treatment, suggesting impaired ASC viability.

CONCLUSIONS

This study suggests that blood impairs the viability of fat grafts and ASCs and provides evidence that washing to remove blood is important in fat processing.

Mesenchymal Stem Cells Early Response to Low-Dose Ionizing Radiation

Introduction

Mesenchymal stem cells (MSCs) are applied as the therapeutic agents, e.g., in the tumor radiation therapy.

Purpose of the Study

To evaluate the human adipose MSC early response to low-dose ionizing radiation (LDIR).

Materials and Methods

We investigated different LDIR (3, 10, and 50 cGy) effects on reactive oxygen species production, DNA oxidation (marker 8-oxodG), and DNA breaks (marker ɣ H2AX) in the two lines of human adipose MSC. Using reverse transcriptase-polymerase chain reaction, fluorescence-activated cell sorting, and fluorescence microscopy, we determined expression of genes involved in the oxidative stress development (NOX4), antioxidative response (NRF2), antiapoptotic and proapoptotic response (BCL2, BCL2A1, BCL2L1, BIRC2, BIRC3, and BAX1), in the development of the nuclear DNA damage response (DDR) (BRCA1, BRCA2, ATM, and P53). Cell cycle changes were investigated by genes transcription changes (CCND1, CDKN2A, and CDKN1A) and using proliferation markers KI-67 and proliferating cell nuclear antigen (PCNA).

Results

Fifteen to 120 min after exposure to LDIR in MSCs, transient oxidative stress and apoptosis of the most damaged cells against the background of the cell cycle arrest were induced. Simultaneously, DDR and an antiapoptotic response were found in other cells of the population. The 10-cGy dose causes the strongest and fastest DDR following cell nuclei DNA damage. The 3-cGy dose induces a less noticeable and prolonged response. The maximal low range dose, 50 cGy, causes a damaging effect on the MSCs.

Conclusion

Transient oxidative stress and the death of a small fraction of the damaged cells are essential components of the MSC population response to LDIR along with the development of DDR and antiapoptotic response. A scheme describing the early MSC response to LDIR is proposed.

Adipose-specific BMP and activin membrane-bound inhibitor (BAMBI) deletion promotes adipogenesis by accelerating ROS production

With the improvement of people's living standards, the number of obese patients has also grown rapidly. It is reported that the level of oxidative stress in obese patients has significantly increased, mainly caused by the increase in reactive oxygen species (ROS) levels in adipose tissue. Studies have shown that the use of siRNA to interfere with bone morphogenetic protein and activin membrane-bound inhibitor (BAMBI) expression could promote adipocyte differentiation, and under hypoxic conditions, BAMBI could act as a regulator of HIF1α to regulate the polarity damage of epithelial cells. In view of these results, we speculated that BAMBI may regulate adipogenesis by regulating the level of ROS. In this study, we generated adipose-specific BAMBI knockout mice (BAMBI AKO) and found that compared with control mice, BAMBI AKO mice showed obesity when fed with high-fat diet, accompanied by insulin resistance, glucose intolerance, hypercholesterolemia, and increased inflammation in adipose tissue. Interestingly, adipose-specific deficiency of BAMBI could cause an increase in the expression level of Nox4, thereby promoting ROS production in cytoplasm and mitochondria and the DNA-binding activity of C/EBPβ and ultimately promoting adipogenesis. Consistently, our findings indicated that BAMBI may be a reactive oxygen regulator to affect adipogenesis, thereby controlling obesity and metabolic syndrome.

Exosomes Derived From M2 Macrophages Facilitate Osteogenesis and Reduce Adipogenesis of BMSCs

Bone regeneration is a complex process that requires the coordination of osteogenesis and osteoclastogenesis. The balance between osteogenesis and adipogenesis of bone marrow mesenchymal stem cells (BMSCs) plays a major role in the process of bone formation. Recently, intercellular communication between bone cells and surrounding cells has been gradually recognized, and macrophages on the surface of bone have been proven to regulate bone metabolism. However, the underlying mechanisms have not been fully elucidated. Recent studies have indicated that exosomes are vital messengers for cell-cell communication in various biological processes. In this experiment, we found that exosomes derived from M2 macrophages (M2D-Exos) could inhibit adipogenesis and promote osteogenesis of BMSCs. M2D-Exo intervention increased the expression of miR-690, IRS-1, and TAZ in BMSCs. Additionally, miR-690 knockdown in M2 macrophages with a miR-690 inhibitor partially counteracted the effect of M2D-Exos on BMSC differentiation and the upregulation of IRS-1 and TAZ expression. Taken together, the results of our study indicate that exosomes isolated from M2 macrophages could facilitate osteogenesis and reduce adipogenesis through the miR-690/IRS-1/TAZ axis and might be a therapeutic tool for bone loss diseases.

NRF2 function in osteocytes is required for bone homeostasis and drives osteocytic gene expression

Osteocytes, the most abundant bone cell type, are derived from osteoblasts through a process in which they are embedded in an osteoid. We previously showed that nutrient restriction promotes the osteocyte transcriptional program and is associated with increased mitochondrial biogenesis. Here, we show that increased mitochondrial biogenesis increase reactive oxygen species (ROS) levels and consequently, NRF2 activity during osteocytogenesis. NRF2 activity promotes osteocyte-specific expression of Dmp1, Mepe, and Sost in IDG-SW3 cells, primary osteocytes, and osteoblasts, and in murine models with Nfe2l2 deficiency in osteocytes or osteoblasts. Moreover, ablation of Nfe2l2 in osteocytes or osteoblasts generates osteopenia and increases osteoclast numbers with marked sexual dimorphism. Finally, treatment with dimethyl fumarate prevented the deleterious effects of ovariectomy in trabecular bone masses of mice and restored osteocytic gene expression. Altogether, we uncovered the role of NRF2 activity in osteocytes during the regulation of osteocyte gene expression and maintenance of bone homeostasis.

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ROS levels and NRF2 activity are increased during osteocytogenesis.

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NRF2 drives osteocyte specification and activate the transcription of osteocyte-specific genes.

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NRF2 in osteocytes has a fundamental role in bone homeostasis and its deletion induces osteopenia.

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Activation of NRF2 with dimethyl fumarate prevents osteopenia induced by ovariectomy.

Simulated Microgravity Suppresses Osteogenic Differentiation of Mesenchymal Stem Cells by Inhibiting Oxidative Phosphorylation

Studies showed that energy metabolism plays a pivotal role in the differentiation of stem cells. Previous studies revealed that simulated microgravity (SMG) inhibits osteogenic differentiation of mesenchymal stem cells (MSCs). However, the underlying relationship between osteogenesis and energy metabolism under SMG conditions is not fully understood. In the present study, we investigated mitochondrial oxidative phosphorylation (OXPHOS) by assessing the level of peroxisome proliferator activated receptor γ coactivator 1α (PGC-1α), mitochondrial DNA (mtDNA) copy number, mitochondrial mass and oxygen consumption rate (OCR) during osteogenesis of MSCs under SMG conditions. We found that SMG inhibited osteogenic differentiation and OXPHOS of MSCs. Moreover, the expression of sirtuin 1 (Sirt1), an important energy sensor, significantly decreased. After upregulating the expression of Sirt1 using resveratrol, an activator of Sirt1, SMG-inhibited OXPHOS and osteogenic differentiation of MSCs were recovered. Taken together, our results suggest that SMG suppresses osteogenic differentiation of MSCs by inhibiting OXPHOS, indicating that OXPHOS might serve as a potential therapeutic target for repairing bone loss under microgravity conditions.

Stem cell spheroid engineering with osteoinductive and ROS scavenging nanofibers for bone regeneration

Stem cell spheroids have been widely investigated to accelerate bone tissue regeneartion. However, the directed differentiation of stem cells into osteoblastic lineage and the prevention of cells from damage by reactive oxygen species (ROS) remain challenge. Here, we developed osteoinductive and ROS scavenging extracellular matrix (ECM)-mimicking synthetic fibers based on epigallocatechin gallate (EGCG) coating. They were then utilized to fabricate engineered spheroids with human adipose-derived stem cells (hADSCs) for bone tissue regeneation. The EGCG-mineral fibers (EMF) effectively conferred osteoinductive and ROS scavenging signals on the hADSCs within spheroids, demonstrating relative upregulation of antioxidant genes (SOD-1 (25.8±2.1) and GPX-1 (3.3±0.1) and greater level of expression of osteogenic markers, RUNX2 (5.8±0.1) and OPN (5.9±0.1), compared to hADSCs in the spheroids without EMF. The in vitro overexpression of osteogenic genes from hADSCs was achieved from absence of osteogenic supplenments. Furthermore, in vivo transplantation of hADSCs spheroids with the EMF significantly promoted calvarial bone regeneration (48.39±9.24%) compared to that from defect only (17.38±6.63%), suggesting that the stem cell spheroid biofabrication system with our novel mineralization method described here is a promising tool for bone tissue regeneration.

Bile acid-based dual-functional prodrug nanoparticles for bone regeneration through hydrogen peroxide scavenging and osteogenic differentiation of mesenchymal stem cells

A high level of reactive oxygen species (ROS) such as hydrogen peroxide (H₂O₂) upregulates pro-inflammatory cytokines and inhibits the osteogenic differentiation of mesenchymal stem cells (MSCs), which are key factors in bone regeneration. Ursodeoxycholic acid (UDCA), a hydrophilic bile acid, has antioxidant and anti-inflammatory activities and also plays beneficial roles in bone regeneration by stimulating the osteogenic differentiation of MSCs while suppressing their adipogenic differentiation. Despite its remarkable capacity for bone regeneration, multiple injections of UDCA induce adverse side effects such as mechanical stress and contamination in bone defects. To fully exploit the beneficial roles of UDCA, a concept polymeric prodrug was developed based on the hypothesis that removal of overproduced H₂O₂ will potentiate the osteogenic functions of UDCA. In this work, we report bone regenerative nanoparticles (NPs) formulated from a polymeric prodrug of UDCA (PUDCA) with UDCA incorporated in its backbone through H₂O₂-responsive peroxalate linkages. The PUDCA NPs displayed potent antioxidant and anti-inflammatory activities in MSCs and induced osteogenic rather than adipogenic differentiation of the MSCs. In rat models of bone defect, the PUDCA NPs exhibited significantly better bone regeneration capacity and anti-inflammatory effects than equivalent amounts of UDCA. We anticipate that PUDCA NPs have tremendous translational potential as bone regenerative agents.

Enhanced viability and function of mesenchymal stromal cell spheroids is mediated via autophagy induction

Mesenchymal stromal cells (MSCs) have received attention as promising therapeutic agents for the treatment of various diseases. However, poor post-transplantation viability is a major hurdle in MSC-based therapy, despite encouraging results in many inflammatory disorders. Recently, three dimensional (3D)-cultured MSCs (MSC_3D) were shown to have higher cell survival and enhanced anti-inflammatory effects, although the underlying mechanisms have not yet been elucidated. In this study, we investigated the molecular mechanisms by which MSC_3D gain the potential for enhanced cell viability. Herein, we found that macroautophagy/autophagy was highly induced and ROS production was suppressed in MSC_3D as compared to 2D-cultured MSCs (MSC_2D). Interestingly, inhibition of autophagy induction caused decreased cell viability and increased apoptotic activity in MSC_3D. Furthermore, modulation of ROS production was closely related to the survival and apoptosis of MSC_3D. We also observed that HMOX1 (heme oxygenase 1) was significantly up-regulated in MSC_3D. In addition, gene silencing of HMOX1 caused upregulation of ROS production and suppression of the genes related to autophagy. Moreover, inhibition of HIF1A (hypoxia inducible factor 1 subunit alpha) caused suppression of HMOX1 expression in MSC_3D, indicating that the HIF1A-HMOX1 axis plays a crucial role in the modulation of ROS production and autophagy induction in MSC_3D. Finally, the critical role of autophagy induction on improved therapeutic effects of MSC_3D was further verified in dextran sulfate sodium (DSS)-induced murine colitis. Taken together, these results indicated that autophagy activation and modulation of ROS production mediated via the HIF1A-HMOX1 axis play pivotal roles in enhancing the viability of MSC_3D.List of abbreviations:3D: three dimensional; 3MA: 3 methlyadenine; AMPK: AMP-activated protein kinase; Baf A₁: bafilomycin A₁; CFSE: carboxyfluorescein succinimidyl ester; CoCl₂: cobalt chloride; CoPP: cobalt protoporphyrin; DSS: dextran sulfate sodium; ECM: extracellular matrix; FOXO3/FOXO3A: forkhead box O3; HIF1A: hypoxia inducible factor 1 subunit alpha; HMOX1/HO-1: heme oxygenase 1; HSCs: hematopoietic stem cells; IL1A/IL-1α: interleukin 1 alpha; IL1B/IL-1β: interleukin 1 beta; IL8: interleukin 8; KEAP1: kelch like ECH associated protein 1; LAMP1: lysosomal associated membrane protein 1; LAMP2: lysosomal associated membrane protein 2; MSC_2D: 2D-cultured MSCs; MSC_3D: 3D-cultured MSCs; MSCs: mesenchymal stromal cells; NFE2L2/NRF2: nuclear factor, erythroid 2 like 2; PGE2: prostaglandin E2; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PINK1: PTEN induced kinase 1; ROS: reactive oxygen species; siRNA: small interfering RNA; SIRT1: sirtuin 1; SOD2: superoxide dismutase 2; SQSTM1/p62: sequestosome 1; TGFB/TGF-β: transforming growth factor beta.

Therapeutic potential of mesenchymal stem cells in treating both types of diabetes mellitus and associated diseases

Diabetes mellitus is a common lifestyle disease which can be classified into type 1 diabetes mellitus and type 2 diabetes mellitus. While both result in hyperglycemia due to lack of insulin action and further associated chronic ailments, there is a marked distinction in the cause for each type due to which both require a different prophylaxis. As observed, type 1 diabetes is caused due to the autoimmune action of the body resulting in the destruction of pancreatic islet cells. On the other hand, type 2 diabetes is caused either due to insulin resistance of target cells or lack of insulin production as per physiological requirements. Attempts to cure the disease have been made by bringing drastic changes in the patients' lifestyle; parenteral administration of insulin; prescription of drugs such as biguanides, meglitinides, and amylin; pancreatic transplantation; and immunotherapy. While these attempts cause a certain degree of relief to the patient, none of these can cure diabetes mellitus. However, a new treatment strategy led by the discovery of mesenchymal stem cells and their unique immunomodulatory and multipotent properties has inspired therapies to treat diabetes by essentially reversing the conditions causing the disease. The current review aims to enumerate the role of various mesenchymal stem cells and the different approaches to treat both types of diabetes and its associated diseases as well.

Sclerostin Regulation, Microarchitecture, and Advanced Glycation End-Products in the Bone of Elderly Women With Type 2 Diabetes

Increased circulating sclerostin and accumulation of advanced glycation end-products (AGEs) are two potential mechanisms underlying low bone turnover and increased fracture risk in type 2 diabetes (T2D). Whether the expression of the sclerostin-encoding SOST gene is altered in T2D, and whether it is associated with AGEs accumulation or regulation of other bone formation-related genes is unknown. We hypothesized that AGEs accumulate and SOST gene expression is upregulated in bones from subjects with T2D, leading to downregulation of bone forming genes (RUNX2 and osteocalcin) and impaired bone microarchitecture and strength. We obtained bone tissue from femoral heads of 19 T2D postmenopausal women (mean glycated hemoglobin [HbA1c] 6.5%) and 73 age- and BMI-comparable nondiabetic women undergoing hip replacement surgery. Despite similar bone mineral density (BMD) and biomechanical properties, we found a significantly higher SOST (p = .006) and a parallel lower RUNX2 (p = .025) expression in T2D compared with non-diabetic subjects. Osteocalcin gene expression did not differ between T2D and non-diabetic subjects, as well as circulating osteocalcin and sclerostin levels. We found a 1.5-fold increase in total bone AGEs content in T2D compared with non-diabetic women (364.8 ± 78.2 versus 209.9 ± 34.4 μg quinine/g collagen, respectively; p < .001). AGEs bone content correlated with worse bone microarchitecture, including lower volumetric BMD (r = -0.633; p = .02), BV/TV (r = -0.59; p = .033) and increased trabecular separation/spacing (r = 0.624; p = .023). In conclusion, our data show that even in patients with good glycemic control, T2D affects the expression of genes controlling bone formation (SOST and RUNX2). We also found that accumulation of AGEs is associated with impaired bone microarchitecture. We provide novel insights that may help understand the mechanisms underlying bone fragility in T2D. © 2020 American Society for Bone and Mineral Research (ASBMR).

Parathyroid hormone ameliorates osteogenesis of human bone marrow mesenchymal stem cells against glucolipotoxicity through p38 MAPK signaling

Diabetes mellitus (DM)-induced glucolipotoxicity is a factor strongly contributing to alveolar bone deficiency. Parathyroid hormone (PTH) has been identified as a main systemic mediator to balance physiological calcium in bone. This study aimed to uncover PTH's potential role in ameliorating the osteogenic capacity of human bone marrow mesenchymal stem cells (HBMSCs) against glucolipotoxicity. Optimal PTH concentrations and high glucose and palmitic acid (GP) were administered to cells, followed by alkaline phosphatase (ALP) staining and ALP activity assay. Quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) and Immunoblot were carried out for assessing mRNA and protein amounts, respectively. Cell counting kit-8 (CCK-8) and flow cytometry were performed for quantitating cell proliferation. Osteogenesis and oxidative stress were determined, and the involvement of mitogen-activated protein kinase (MAPK) signaling was further verified. About 1-50 mmol/ml GP significantly inhibited the osteogenic differentiation of HBMSCs. 10^-9 mol/L PTH was found to be the optimal concentration for HBMSC induction. PTH had no effects on HBMSC proliferation, with or without GP treatment. PTH reversed inadequate osteogenesis and excessive oxidative stress in GP-treated HBMSCs. Mechanistically, PTH activated p38 MAPK signaling, while inhibiting p38 MAPK-suppressed PTH's beneficial impacts on HBMSCs. Collectively, PTH promotes osteogenic differentiation in HBMSCs against glucolipotoxicity via p38 MAPK signaling.

Gingiva-derived Mesenchymal Stem Cells and Their Potential Applications in Oral and Maxillofacial Diseases

BACKGROUND

Stem cells are undifferentiated cells with multilineage differentiation potential. They can be collected from bone marrow, fat, amniotic fluid, and teeth. Stem cell-based therapies have been widely used to treat multiple diseases, such as cardiac disease, and hematological disorders. The cells may also be beneficial for controlling the disease course and promoting tissue regeneration in oral and maxillofacial diseases. Oral-derived gingival mesenchymal stem cells are easy to access and the donor sites heal rapidly without a scar. Such characteristics demonstrate the beneficial role of GMSCs in oral and maxillofacial diseases.

OBJECTIVE

We summarize the features of GMSCs, including their self-renewal, multipotent differentiation, immunomodulation, and anti-inflammation properties. We also discuss their applications in oral and maxillofacial disease treatment and tissue regeneration.

CONCLUSION

GMSCs are easily harvestable adult stem cells with outstanding proliferation, differentiation, and immunomodulation characteristics. A growing body of evidence indicates that GMSCs have strong potential use in accelerating wound healing and promoting the regeneration of bone defects, periodontium, oral neoplasms, salivary glands, peri-implantitis, and nerves. Moreover, alginate, polylactic acid and polycaprolactone can be used as biodegradable scaffolds for GMSC encapsulation. Various growth factors can be applied to the corresponding scaffolds to obtain the desired GMSC differentiation and phenotypes. Three-dimensional spheroid culture systems could optimize GMSC properties and improve the performance of the cells in tissue engineering. The immunomodulatory property of GMSCs in controlling oral and maxillofacial inflammation needs further research.

Fe3O4@GO magnetic nanocomposites protect mesenchymal stem cells and promote osteogenic differentiation of rat bone marrow mesenchymal stem cells

Fe₃O₄ nanoparticles (Fe₃O₄ NPs) are typical magnetic materials for bone tissue regeneration. However, the accompanying oxidative stress during the reaction process of Fe₃O₄ NPs and H₂O₂ in bone remodeling and disease may hinder their application. In order to reduce this side effect, we selected graphene oxide (GO) to modify Fe₃O₄ NPs. We showed that Fe₃O₄@GO magnetic nanocomposites (Fe₃O₄@GO MNCs) eliminated 30% of H₂O₂ in 3 h, and reduced the amount of ˙OH, the intermediate product of the Fenton reaction. The cellular study demonstrated that Fe₃O₄@GO MNCs reduced the cell damage caused by reactive oxygen species (ROS) and improved the activity of mesenchymal stem cells (MSCs). Moreover, when the magnetic field and bone morphogenetic protein-2 (BMP2) delivered by Fe₃O₄@GO MNCs worked together, osteogenic differentiation of MSCs in vitro was well promoted.

Inspired by nature: facile design of nanoclay-organic hydrogel bone sealant with multifunctional properties for robust bone regeneration

Bone repair is a complex process involving the sophisticated interplay of osteogenic stem cells, extracellular matrix, and osteoinductive factors, and it is affected by bacterial toxins and oxidative stress. Inspired by the nature of plant-derived phytochemicals and inorganic-organic analogues of the bone extracellular matrix, we report herein the facile design of a nanoclay-organic hydrogel bone sealant (NoBS) that integrates multiple physico-chemical cues for bone regeneration into a single system. Assembly of phytochemical-modified organic chitosan and silica-rich inorganic nanoclay serves as highly biocompatible and osteoconductive extracellular matrix mimics. The decorated phytochemical exerts inherent bactericidal and antioxidant activities, and acts as an intermolecular networking precursor for gelation with injectable and self-healing capabilities. Moreover, the NoBS exerts osteoinductive effects mediated by the nanoclay, which regulates the Wnt/β-catenin pathway, along with the addition of osteoinductive signals, resulting in bone regeneration in a non-healing cranial defect. Engineering of this integrated bone graft substitute with multifunctional properties inspired by natural materials may suggest a promising and effective approach for creating a favorable microenvironment for optimal bone healing.

TRIM16 protects human periodontal ligament stem cells from oxidative stress-induced damage via activation of PICOT

Periodontitis is a chronic inflammatory disease that result in severe loss of supporting structures and substantial tooth loss. Oxidative stress is tightly involved in the progression of periodontitis. Tripartite Motif 16 (TRIM16) has been identified as a novel regulatory protein in response to oxidative and proteotoxic stresses. The present study aimed to investigate the role of TRIM16 in human periodontal ligament stem cells (hPDLSCs) under oxidative stress. First, we found that the expression of TRIM16 decreased after exposure to H₂O₂. Then TRIM16 overexpression alleviated H₂O₂-induced oxidative stress by enhancing antioxidant capacity and reducing the amount of intracellular reactive oxygen species (ROS) and reactive nitrogen species (RNS). TRIM16 increased cell viability, inhibited cell apoptosis and the depolarization of the mitochondrial membrane potential in hPDLSCs. Furthermore, TRIM16 attenuated H₂O₂-induced suppression of osteogenic differentiation. Mechanistically, TRIM16 promoted the activation of protein kinase C (PKC)-interacting cousin of thioredoxin (PICOT), p-Akt and Nrf2, while knockdown of PICOT reversed TRIM16-mediated ROS resistance and decreased the expression of p-Akt and Nrf2. In conclusion, TRIM16 alleviated oxidative damage in hPDLSCs via the activation of PICOT/Akt/Nrf2 pathway, suggesting that TRIM16 could be a promising target to develop effective therapies for periodontitis.

Chitosan-coated hydroxyapatite and drug-loaded polytrimethylene carbonate/polylactic acid scaffold for enhancing bone regeneration

Biocompatible polymers and drug-delivery scaffolds have driven development in bone regeneration. In this study, we fabricated a chitosan (CS)-coated polytrimethylene carbonate (PTMC)/polylactic acid (PLLA)/oleic acid-modified hydroxyapatite (OA-HA)/vancomycin hydrochloride (VH) microsphere scaffold for drug release with excellent biocompatibility. The incorporation of PLLA, OA-HA, and VH into PTMC microspheres not only slowed the biodegradability of the scaffold but also enhanced its mechanical properties and surface properties. Moreover, the CS coating stimulated extensive adhesion of osteoblasts before OA-HA incorporation, which facilitated the controlled release of OA-HA. The scaffolds were characterized via scanning electron microscopy, in vitro comprehensive performance testing, cell culturing, and microcomputer tomography scanning. The results indicated that the surface of the composite microsphere scaffold was suitable for osteoblast adhesion. Additionally, the release of OA-HA stimulated osteogenic proliferation. Our findings suggest that the CS-PTMC/PLLA/OA-HA/VH microsphere scaffold is promising for bone tissue engineering applications.

Oxidative stress resulting from the removal of endogenous catalase induces obesity by promoting hyperplasia and hypertrophy of white adipocytes

Obesity is regarded as an abnormal expansion and excessive accumulation of fat mass in white adipose tissue. The involvement of oxidative stress in the development of obesity is still unclear. Although mainly present in peroxisomes, catalase scavenges intracellular H₂O₂ at toxic levels. Therefore, we used catalase-knockout (CKO) mice to elucidate the involvement of excessive H₂O₂ in the development of obesity. CKO mice with C57BL/6J background gained more weight with higher body fat mass with age than age-matched wild-type (WT) mice fed with either chow or high-fat diets. This phenomenon was attenuated by concomitant treatment with the antioxidants, melatonin or N-acetyl cysteine. Moreover, CKO mouse embryonic fibroblasts (MEFs) appeared to differentiate to adipocytes more easily than WT MEFs, showing increased H₂O₂ concentrations. Using 3T3-L1-derived adipocytes transfected with catalase-small interfering RNA, we confirmed that a more prominent lipogenesis occurred in catalase-deficient cells than in WT cells. Catalase-deficient adipocytes presented increased nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4) expression but decreased adenosine monophosphate-activated protein kinase (AMPK) expression. Treatment with a NOX4 inhibitor or AMPK activator rescued the propensity for obesity of CKO mice. These findings suggest that excessive H₂O₂ and related oxidative stress increase body fat mass via both adipogenesis and lipogenesis. Manipulating NOX4 and AMPK in white adipocytes may be a therapeutic tool against obesity augmented by oxidative stress.

NADPH oxidases in bone and cartilage homeostasis and disease: A promising therapeutic target

Reactive oxygen species (ROS) generated by the NADPH oxidase (Nox) enzymes are important short-range signaling molecules. They have been extensively studied in the physiology and pathophysiology of the cardiovascular system, where they have important roles in vascular inflammation, angiogenesis, hypertension, cardiac injury, stroke, and aging. Increasing evidence demonstrates that ROS and Nox enzymes also affect bone homeostasis and osteoporosis, and more recent studies implicate ROS and Nox enzymes in both inflammatory arthritis and osteoarthritis. Mechanistically, this connection may be through the effects of ROS on signal transduction. ROS affect both transforming growth factor-β/Smad signaling, interleukin-1β/nuclear factor-kappa B signaling, and the resulting changes in matrix metalloproteinase expression. The purpose of this review is to describe the role of Nox enzymes in the physiology and pathobiology of bone and joints and to highlight the potential of therapeutically targeting the Nox enzymes.

Factors inducing transdifferentiation of myoblasts into adipocytes

Fat infiltration in skeletal muscle is observed in several myopathies, is associated with muscular dysfunction, and is strongly correlated with insulin resistance, diabetes, obesity, and aging. In animal production, skeletal muscle fat (also known as intermuscular and intramuscular fat) is positively related to meat quality including tenderness, flavor, and juiciness. Thus, understanding the cell origin and regulation mechanism of skeletal muscle fat infiltration is important for developing therapies against human myopathies as well as for improving meat quality. Notably, age, sarcopenia, oxidative stress, injury, and regeneration can activate adipogenic differentiation potential in myoblasts and affect fat accumulation in skeletal muscle. In addition, several transcriptional and nutritional factors can directly induce transdifferentiation of myoblasts into adipocytes. In this review, we focused on the recent progress in understanding the muscle-to-adipocyte differentiation and summarized and discussed the genetic, nutritional, and physiological factors that can induce transdifferentiation of myoblasts into adipocytes. Moreover, the regulatory roles and mechanisms of these factors during the transdifferentiation process were also discussed.

The Role of Tryptophan Metabolites in Musculoskeletal Stem Cell Aging

Although aging is considered a normal process, there are cellular and molecular changes that occur with aging that may be detrimental to health. Osteoporosis is one of the most common age-related degenerative diseases, and its progression correlates with aging and decreased capacity for stem cell differentiation and proliferation in both men and women. Tryptophan metabolism through the kynurenine pathway appears to be a key factor in promoting bone-aging phenotypes, promoting bone breakdown and interfering with stem cell function and osteogenesis; however, little data is available on the impact of tryptophan metabolites downstream of kynurenine. Here we review available data on the impact of these tryptophan breakdown products on the body in general and, when available, the existing evidence of their impact on bone. A number of tryptophan metabolites (e.g., 3-hydroxykynurenine (3HKYN), kynurenic acid (KYNA) and anthranilic acid (AA)) have a detrimental effect on bone, decreasing bone mineral density (BMD) and increasing fracture risk. Other metabolites (e.g., 3-hydroxyAA, xanthurenic acid (XA), picolinic acid (PIA), quinolinic acid (QA), and NAD+) promote an increase in bone mineral density and are associated with lower fracture risk. Furthermore, the effects of other tryptophan breakdown products (e.g., serotonin) are complex, with either anabolic or catabolic actions on bone depending on their source. The mechanisms involved in the cellular actions of these tryptophan metabolites on bone are not yet fully known and will require further research as they are potential therapeutic targets. The current review is meant as a brief overview of existing English language literature on tryptophan and its metabolites and their effects on stem cells and musculoskeletal systems. The search terms used for a Medline database search were: kynurenine, mesenchymal stem cells, bone loss, tryptophan metabolism, aging, and oxidative stress.

The Effect of Hyperbaric Oxygen Therapy on Human Adipose-Derived Stem Cells

BACKGROUND

Adipose-derived stem cells are considered as candidate cells for regenerative plastic surgery. Measures to influence cellular properties and thereby direct their regenerative potential remain elusive. Hyperbaric oxygen therapy-the exposure to 100% oxygen at an increased atmospheric pressure-has been propagated as a noninvasive treatment for a multitude of indications and presents a potential option to condition cells for tissue-engineering purposes. The present study evaluates the effect of hyperbaric oxygen therapy on human adipose-derived stem cells.

METHODS

Human adipose-derived stem cells from healthy donors were treated with hyperbaric oxygen therapy at 2 and 3 atm. Viability before and after each hyperbaric oxygen therapy, proliferation, expression of surface markers and protein contents of transforming growth factor (TGF)-β, tumor necrosis factor-α, hepatocyte growth factor, and epithelial growth factor in the supernatants of treated adipose-derived stem cells were measured. Lastly, adipogenic, osteogenic, and chondrogenic differentiation with and without use of differentiation-inducing media (i.e., autodifferentiation) was examined.

RESULTS

Hyperbaric oxygen therapy with 3 atm increased viability, proliferation, and CD34 expression and reduced the CD31/CD34/CD45 adipose-derived stem cell subset and endothelial progenitor cell population. TGF-β levels were significantly decreased after two hyperbaric oxygen therapy sessions in the 2-atm group and decreased after three hyperbaric oxygen therapy sessions in the 3-atm group. Hepatocyte growth factor secretion remained unaltered in all groups. Although the osteogenic and chondrogenic differentiation were not influenced, adipogenic differentiation and autodifferentiation were significantly enhanced, with osteogenic autodifferentiation significantly alleviated by hyperbaric oxygen therapy with 3 atm.

CONCLUSION

Hyperbaric oxygen therapy with 3 atm increases viability and proliferation of adipose-derived stem cells, alters marker expression and subpopulations, decreases TGF-β secretion, and skews adipose-derived stem cells toward adipogenic differentiation.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

Energy metabolism: A newly emerging target of BMP signaling in bone homeostasis

Energy metabolism is the process of generating energy (i.e. ATP) from nutrients. This process is indispensable for cell homeostasis maintenance and responses to varying conditions. Cells require energy for growth and maintenance and have evolved to have multiple pathways to produce energy. Both genetic and functional studies have demonstrated that energy metabolism, such as glucose, fatty acid, and amino acid metabolism, plays important roles in the formation and function of bone cells including osteoblasts, osteocytes, and osteoclasts. Dysregulation of energy metabolism in bone cells consequently disturbs the balance between bone formation and bone resorption. Metabolic diseases have also been reported to affect bone homeostasis. Bone morphogenic protein (BMP) signaling plays critical roles in regulating the formation and function of bone cells, thus affecting bone development and homeostasis. Mutations of BMP signaling-related genes in mice have been reported to show abnormalities in energy metabolism in many tissues, including bone. In addition, BMP signaling correlates with critical signaling pathways such as mTOR, HIF, Wnt, and self-degradative process autophagy to coordinate energy metabolism and bone homeostasis. These findings will provide a newly emerging target of BMP signaling and potential therapeutic strategies and the improved management of bone diseases. This review summarizes the recent advances in our understanding of (1) energy metabolism in regulating the formation and function of bone cells, (2) function of BMP signaling in whole body energy metabolism, and (3) mechanistic interaction of BMP signaling with other signaling pathways and biological processes critical for energy metabolism and bone homeostasis.

Lipidomics of mesenchymal stem cell differentiation

Mesenchymal stem cells (MSCs), such as adipose-derived stem cells (ADSCs) and skeletal muscle-derived stem cells (MDSCs), are potential sources for cell-based therapeutic strategies. However, there is little knowledge about the lipid composition of these stem cells and the mechanisms of their differentiation. Lipids have important biological and physiological functions that are critical for understanding the regulation and control of stem cell fate. This study sought to analyze the lipidome of rabbit ADSCs and MDSCs and their adipogenic and osteogenic differentiation. The MSCs were isolated and were characterized by flow cytometry. Lipids were extracted from both MSCs and differentiated cells, and the lipids were subsequently analyzed with a hybrid triple quadrupole time-of-flight mass spectrometer. The results showed a total of 1687 lipid species. MSCs exhibited different lipid profiles as well as changes in lipid composition after differentiation. Furthermore, the expression levels of N-acyl-phosphatidylethanolamine (NAPE) 54:7+NH4 (-FA 17:0(NH4)) and phosphatidylcholine (PC) 42:6+Na were higher in the adipogenic lineages in of both MSC types, and NAPE 58:2+NH4 (-FA 17:0 (NH4)) and NAPE 56:2+NH4 (-FA 17:0 (NH4)) had higher levels in the osteogenic lineages, suggesting lipid similarities in cells differentiated from different stem cell sources.

Nanovibrational Stimulation of Mesenchymal Stem Cells Induces Therapeutic Reactive Oxygen Species and Inflammation for Three-Dimensional Bone Tissue Engineering

There is a pressing clinical need to develop cell-based bone therapies due to a lack of viable, autologous bone grafts and a growing demand for bone grafts in musculoskeletal surgery. Such therapies can be tissue engineered and cellular, such as osteoblasts, combined with a material scaffold. Because mesenchymal stem cells (MSCs) are both available and fast growing compared to mature osteoblasts, therapies that utilize these progenitor cells are particularly promising. We have developed a nanovibrational bioreactor that can convert MSCs into bone-forming osteoblasts in two- and three-dimensional, but the mechanisms involved in this osteoinduction process remain unclear. Here, to elucidate this mechanism, we use increasing vibrational amplitude, from 30 nm (N30) to 90 nm (N90) amplitudes at 1000 Hz and assess MSC metabolite, gene, and protein changes. These approaches reveal that dose-dependent changes occur in MSCs' responses to increased vibrational amplitude, particularly in adhesion and mechanosensitive ion channel expression and that energetic metabolic pathways are activated, leading to low-level reactive oxygen species (ROS) production and to low-level inflammation as well as to ROS- and inflammation-balancing pathways. These events are analogous to those that occur in the natural bone-healing processes. We have also developed a tissue engineered MSC-laden scaffold designed using cells' mechanical memory, driven by the stronger N90 stimulation. These mechanistic insights and cell-scaffold design are underpinned by a process that is free of inductive chemicals.