Histone deacetylase inhibition destabilizes the multi-potent state of uncommitted adipose-derived mesenchymal stromal cells

Exploring the therapeutic potential of regulatory T cell in rheumatoid arthritis: Insights into subsets, markers, and signaling pathways

Rheumatoid arthritis (RA) is a complex autoimmune inflammatory rheumatic disease characterized by an imbalance between immunological reactivity and immune tolerance. Regulatory T cells (Tregs), which play a crucial role in controlling ongoing autoimmunity and maintaining peripheral tolerance, have shown great potential for the treatment of autoimmune inflammatory rheumatic diseases such as RA. This review aims to provide an updated summary of the latest insights into Treg-targeting techniques in RA. We focus on current therapeutic strategies for targeting Tregs based on discussing their subsets, surface markers, suppressive function, and signaling pathways in RA.

Epigenetic regulators controlling osteogenic lineage commitment and bone formation

Bone formation and homeostasis are controlled by environmental factors and endocrine regulatory cues that initiate intracellular signaling pathways capable of modulating gene expression in the nucleus. Bone-related gene expression is controlled by nucleosome-based chromatin architecture that limits the accessibility of lineage-specific gene regulatory DNA sequences and sequence-specific transcription factors. From a developmental perspective, bone-specific gene expression must be suppressed during the early stages of embryogenesis to prevent the premature mineralization of skeletal elements during fetal growth in utero. Hence, bone formation is initially inhibited by gene suppressive epigenetic regulators, while other epigenetic regulators actively support osteoblast differentiation. Prominent epigenetic regulators that stimulate or attenuate osteogenesis include lysine methyl transferases (e.g., EZH2, SMYD2, SUV420H2), lysine deacetylases (e.g., HDAC1, HDAC3, HDAC4, HDAC7, SIRT1, SIRT3), arginine methyl transferases (e.g., PRMT1, PRMT4/CARM1, PRMT5), dioxygenases (e.g., TET2), bromodomain proteins (e.g., BRD2, BRD4) and chromodomain proteins (e.g., CBX1, CBX2, CBX5). This narrative review provides a broad overview of the covalent modifications of DNA and histone proteins that involve hundreds of enzymes that add, read, or delete these epigenetic modifications that are relevant for self-renewal and differentiation of mesenchymal stem cells, skeletal stem cells and osteoblasts during osteogenesis.

Cellular Enhancement of Frozen Meniscus Allograft Combining Native Meniscus and Mesenchymal Stromal Cell Injections

OBJECTIVE

This proof-of-concept study investigated an improved cell-based injection therapy combining mesenchymal stem cells (MSCs) and meniscus cells (MCs) to support superior meniscus allograft repopulation and early revival compared to injecting MSCs alone.

DESIGN

In this controlled laboratory study, frozen meniscus allograft samples were injected vertically with a cell suspension containing different ratios of MSCs and MCs or control (lactated ringers) and cultured for 28 days. Samples were analyzed weekly for cell viability, migration, and metabolism using histological and biochemical assays. Tissue medium was analyzed for matrix metalloproteinase (MMP) expression using zymography.

RESULTS

Cellular repopulation of frozen allografts injected with different cell suspensions was validated by immunohistochemistry. Significant higher DNA content was evidenced in grafts treated with suspensions of MCs or MC:MSC (1:4 ratio). Cell metabolic activity was significantly different between all treated groups and control group after 1 week. Allografts injected with MCs showed significantly more cell proliferation than injections with MSCs. MMP2 activity was detected in medium of all grafts cellularized with MCs with or without MSCs. Scanning electron microscopy (SEM) analysis showed resolution of the needle puncture, but not in the control group. Cell labeling of MCs upon injection of mixed MC:MSC suspensions revealed a gradual increase in the cell ratio.

CONCLUSIONS

The findings of this study establish that injection of MCs with or without MSCs enhances the cellularity of meniscus allograft to support early graft revival and remodeling.

HDAC11 deficiency resists obesity by converting adipose-derived stem cells into brown adipocyte-like cells

Obesity, with complications such as type 2 diabetes, dyslipidemia, and even cancer, is rampant worldwide. Histone deacetylases (HDACs) have been extensively studied as key players in the epigenetic regulation of cellular metabolism. However, the function of HDAC11 has long been focused on the immune and nervous systems and cancer development, and its potential role in obesity has been poorly studied. We found that the expression of HDAC11 was highly upregulated in the white adipose tissue (WAT) of obese mice and was closely related to the progression of obesity. Knockdown of HDAC11 by lentiviral injection in high-fat diet-fed mice attenuated the development of obesity. Furthermore, knockdown of HDAC11 ameliorated WAT hypertrophy and induced WAT browning. At the cellular level, silencing of HDAC11 promoted the differentiation of adipose-derived stem cells (ADSCs) into brown adipocyte-like cells and inhibited the proliferation of ADSCs. More interestingly, HDAC11 expression was elevated in ADSCs isolated from obese mice, and silencing of HDAC11 facilitated the spontaneous differentiation of ADSCs into mesoderm, which is the source of adipocytes. This also superficially and effectively demonstrates the exciting prospect of HDAC11 silencing in obesity research and treatment, as a valve for "energy saving and flow reduction".

Roles of Histone Acetyltransferases and Deacetylases in the Retinal Development and Diseases

The critical role of epigenetic modification of histones in maintaining the normal function of the nervous system has attracted increasing attention. Among these modifications, the level of histone acetylation, modulated by histone acetyltransferases (HATs) and histone deacetylases (HDACs), is essential in regulating gene expression. In recent years, the research progress on the function of HDACs in retinal development and disease has advanced remarkably, while that regarding HATs remains to be investigated. Here, we overview the roles of HATs and HDACs in regulating the development of diverse retinal cells, including retinal progenitor cells, photoreceptor cells, bipolar cells, ganglion cells, and Müller glial cells. The effects of HATs and HDACs on the progression of various retinal diseases are also discussed with the highlight of the proof-of-concept research regarding the application of available HDAC inhibitors in treating retinal diseases.

The Potential to Fight Obesity with Adipogenesis Modulating Compounds

Obesity is an increasingly severe public health problem, which brings huge social and economic burdens. Increased body adiposity in obesity is not only tightly associated with type 2 diabetes, but also significantly increases the risks of other chronic diseases including cardiovascular diseases, fatty liver diseases and cancers. Adipogenesis describes the process of the differentiation and maturation of adipocytes, which accumulate in distributed adipose tissue at various sites in the body. The major functions of white adipocytes are to store energy as fat during periods when energy intake exceeds expenditure and to mobilize this stored fuel when energy expenditure exceeds intake. Brown/beige adipocytes contribute to non-shivering thermogenesis upon cold exposure and adrenergic stimulation, and thereby promote energy consumption. The imbalance of energy intake and expenditure causes obesity. Recent interest in epigenetics and signaling pathways has utilized small molecule tools aimed at modifying obesity-specific gene expression. In this review, we discuss compounds with adipogenesis-related signaling pathways and epigenetic modulating properties that have been identified as potential therapeutic agents which cast some light on the future treatment of obesity.

Surface Roughness of Titanium Orthopedic Implants Alters the Biological Phenotype of Human Mesenchymal Stromal Cells

Metal orthopedic implants are largely biocompatible and generally achieve long-term structural fixation. However, some orthopedic implants may loosen over time even in the absence of infection. In vivo fixation failure is multifactorial, but the fundamental biological defect is cellular dysfunction at the host-implant interface. Strategies to reduce the risk of short- and long-term loosening include surface modifications, implant metal alloy type, and adjuvant substances such as polymethylmethacrylate cement. Surface modifications (e.g., increased surface rugosity) can increase osseointegration and biological ingrowth of orthopedic implants. However, the localized responses of cells to implant surface modifications need to be better characterized. As an in vitro model for investigating cellular responses to metallic orthopedic implants, we cultured mesenchymal stromal/stem cells on clinical-grade titanium disks (Ti6Al4V) that differed in surface roughness as high (porous structured), medium (grit blasted), and low (bead blasted). Topological characterization of clinically relevant titanium (Ti) materials combined with differential mRNA expression analyses (RNA-seq and real-time quantitative polymerase chain reaction) revealed alterations to the biological phenotype of cells cultured on titanium structures that favor early extracellular matrix production and observable responses to oxidative stress and heavy metal stress. These results provide a descriptive model for the interpretation of cellular responses at the interface between native host tissues and three-dimensionally printed modular orthopedic implants, and will guide future studies aimed at increasing the long-term retention of such materials after total joint arthroplasty. Impact statement Using an in vitro model of implant-to-cell interactions by culturing mesenchymal stromal cells (MSCs) on clinically relevant titanium materials of varying topological roughness, we identified mRNA expression patterns consistent with early extracellular matrix (ECM) production and responses to oxidative/heavy metal stress. Implants with high surface roughness may delay the differentiation and ECM formation of MSCs and alter the expression of genes sensitive to reactive oxygen species and protein kinases. In combination with ongoing animal studies, these results will guide future studies aimed at increasing the long-term retention of widely used titanium materials after total joint arthroplasty.

Brd4 Inactivation Increases Adenoviral Delivery of BMP2 for Paracrine Stimulation of Osteogenic Differentiation as a Gene Therapeutic Concept to Enhance Bone Healing

Bromodomain (BRD) proteins are histone code interpreters that recognize acetylated lysines and link the dynamic state of chromatin with the transcriptional machinery. Here, we demonstrate that ablation of the Brd4 gene in primary mouse bone marrow–derived mesenchymal stem cells via a conditional Brd4^fl/fl allele suppresses osteogenic lineage commitment. Remarkably, loss of Brd4 function also enhances expression of genes in engineered adenoviral vectors, including Cre recombinase and green fluorescent protein (GFP). Similarly, vector‐based expression of BMP2 mRNA and protein levels are enhanced upon Brd4 depletion in cells transduced with an adenoviral vector that expresses BMP2 (Ad‐BMP2). Importantly, Brd4 depletion in MC3T3‐E1 and human adipose‐derived mesenchymal stem cells (AMSCs) transduced with Ad‐BMP2 enhances osteogenic differentiation of naïve MC3T3‐E1 cells via paracrine mechanisms based on transwell and conditioned medium studies. Our studies indicate that Brd4 depletion enhances adenoviral transgene expression in mammalian cells, which can be leveraged as a therapeutic strategy to improve viral vector‐based gene therapies. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Differences in Cytotoxicity of Lidocaine, Ropivacaine, and Bupivacaine on the Viability and Metabolic Activity of Human Adipose-Derived Mesenchymal Stem Cells

PURPOSE

We evaluated biological effects of distinct local anesthetics on human adipose-derived mesenchymal stem cells when applied to reduce periprocedural pain during mesenchymal stem cell injections.

METHODS AND MATERIALS

Metabolic activity (MTS assay), viability (Live/Dead stain), and gene expression (quantitative real-time reverse-transcriptase polymerase chain reaction) were measured in mesenchymal stem cells incubated with various concentrations of lidocaine, ropivacaine, or bupivacaine during a 12-hr time course.

RESULTS

Cell viability and metabolic activity decreased in a dose, time, and substance-specific manner after exposure to lidocaine, ropivacaine, and bupivacaine, with ropivacaine being the least cytotoxic. Cell viability decreases after brief exposure (<1.5 hrs) at clinically relevant concentrations (eg, 8 mg/ml of lidocaine, 2.5 mg/ml of ropivacaine or bupivacaine). Mesenchymal stem cells exposed to local anesthetics change their expression of mRNA biomarkers for stress response (EGR1, EGR2), proliferation (MKI67, HIST2H4A), ECM (COL1A1, COL3A1), and cell surface marker (CD105).

CONCLUSIONS

Local anesthetics are cytotoxic to clinical-grade human mesenchymal stem cells in a dose-, time-, and agent-dependent manner and change expression of ECM, proliferation, and cell surface markers. Lidocaine and bupivacaine are more cytotoxic than ropivacaine. Single-dose injections of local anesthetics may affect the biological properties of mesenchymal stem cells in vitro but may not affect the effective dose of MSCs in a clinical setting.

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

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

Relative mRNA and protein stability of epigenetic regulators in musculoskeletal cell culture models

Control of gene expression by epigenetic regulators is fundamental to tissue development and homeostasis. Loss-of-function (LOF) studies using siRNAs for epigenetic regulators require that RNA interference rapidly reduces the cellular levels of the corresponding mRNAs and/or proteins. The most abundant chromatin structural proteins (i.e., the core histones H2A, H2B, H3 and H4) have relatively long half-lives and do not turn over rapidly, although their mRNAs are labile. The question arises whether epigenetic regulatory enzymes (e.g., Ezh2) or proteins that interact with histones via selective modifications (e.g., Cbx1 to Cbx8, Brd4) are stable or unstable. Therefore, we performed classical α-amanitin and cycloheximide inhibition assays that block, respectively, mRNA transcription and protein translation in mouse MC3T3 osteoblasts, ATDC5 chondrocytes and C2C12 myoblasts. We find that mRNA levels of Cbx proteins and Ezh2 were significantly depleted after 24 hrs, while their corresponding proteins remained relatively stable. As positive control, the half-life of the labile cyclin D1 protein was found to be less than 1 hr. Our study suggests that histone code readers and writers are relatively stable chromatin-related proteins, which is consistent with their long-term activities in maintaining chromatin organization and phenotype identity. These findings have conceptual ramifications for the interpretation of RNAi experiments that reduce the mRNA but not protein levels of epiregulatory proteins. We propose that siRNAs for at least some epigenetic regulatory proteins may exert their biological effects by blocking translation and new protein synthesis rather than by decreasing pre-existing protein pools.

Cranial Neural Crest Cells and Their Role in the Pathogenesis of Craniofacial Anomalies and Coronal Craniosynostosis

Craniofacial anomalies are among the most common of birth defects. The pathogenesis of craniofacial anomalies frequently involves defects in the migration, proliferation, and fate of neural crest cells destined for the craniofacial skeleton. Genetic mutations causing deficient cranial neural crest migration and proliferation can result in Treacher Collins syndrome, Pierre Robin sequence, and cleft palate. Defects in post-migratory neural crest cells can result in pre- or post-ossification defects in the developing craniofacial skeleton and craniosynostosis (premature fusion of cranial bones/cranial sutures). The coronal suture is the most frequently fused suture in craniosynostosis syndromes. It exists as a biological boundary between the neural crest-derived frontal bone and paraxial mesoderm-derived parietal bone. The objective of this review is to frame our current understanding of neural crest cells in craniofacial development, craniofacial anomalies, and the pathogenesis of coronal craniosynostosis. We will also discuss novel approaches for advancing our knowledge and developing prevention and/or treatment strategies for craniofacial tissue regeneration and craniosynostosis.

Inhibition of the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) stimulates osteoblastogenesis by potentiating bone morphogenetic protein 2 (BMP2) responses

The catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) is a pleiotropic enzyme involved in DNA repair, cell cycle control, and transcription regulation. A potential role for DNA-PKcs in the regulation of osteoblastogenesis remains to be established. We show that pharmacological inhibition of DNA-PKcs kinase activity or gene silencing of Prkdc (encoding DNA-PKcs) in murine osteoblastic MC3T3-E1 cells and human adipose-derived mesenchymal stromal cells markedly enhanced osteogenesis and the expression of osteoblast differentiation marker genes. Inhibition of DNA-PKcs inhibited cell cycle progression and increased osteogenesis by significantly enhancing the bone morphogenetic protein 2 response in osteoblasts and other mesenchymal cell types. Importantly, in vivo pharmacological inhibition of the kinase enhanced bone biomechanical properties. Bones from osteoblast-specific conditional Prkdc-knockout mice exhibited a similar phenotype of increased stiffness. In conclusion, DNA-PKcs negatively regulates osteoblast differentiation, and therefore DNA-PKcs inhibitors may have therapeutic potential for bone regeneration and metabolic bone diseases.

HDAC inhibition induces expression of scaffolding proteins critical for tumor progression in pediatric glioma: focus on EBP50 and IRSp53

BACKGROUND

Diffuse midline glioma (DMG) is a pediatric malignancy with poor prognosis. Most children die less than one year after diagnosis. Recently, mutations in histone H3 have been identified and are believed to be oncogenic drivers. Targeting this epigenetic abnormality using histone deacetylase (HDAC) inhibitors such as panobinostat (PS) is therefore a novel therapeutic option currently evaluated in clinical trials.

METHODS

BH3 profiling revealed engagement in an irreversible apoptotic process of glioma cells exposed to PS confirmed by annexin-V/propidium iodide staining. Using proteomic analysis of 3 DMG cell lines, we identified 2 proteins deregulated after PS treatment. We investigated biological effects of their downregulation by silencing RNA but also combinatory effects with PS treatment in vitro and in vivo using a chick embryo DMG model. Electron microscopy was used to validate protein localization.

RESULTS

Scaffolding proteins EBP50 and IRSp53 were upregulated by PS treatment. Reduction of these proteins in DMG cell lines leads to blockade of proliferation and migration, invasion, and an increase of apoptosis. EBP50 was found to be expressed in cytoplasm and nucleus in DMG cells, confirming known oncogenic locations of the protein. Treatment of glioma cells with PS together with genetic or chemical inhibition of EBP50 leads to more effective reduction of cell growth in vitro and in vivo.

CONCLUSION

Our data reveal a specific relation between HDAC inhibitors and scaffolding protein deregulation which might have a potential for therapeutic intervention for cancer treatment.

Functional expression of ZNF467 and PCBP2 supports adipogenic lineage commitment in adipose-derived mesenchymal stem cells

Bone marrow-derived mesenchymal stromal/stem cells (BMSCs) have the potential to be employed in many different skeletal therapies. A major limitation to utilizing BMSCs as a therapeutic strategy in human disease and tissue regeneration is the low cell numbers obtained from initial isolation necessitating multiple cell passages that can lead to decreased cell quality. Adipose-derived mesenchymal stromal/stem cells (AMSCs) have been proposed as an alternative cell source for regenerative therapies; however the differentiation capacity of these cells differs from BMSCs. To understand the differences between BMSCs and AMSCs, we compared the global gene expression profiles of BMSCs and AMSCs and identified two genes, PCBP2 and ZNF467 that were differentially expressed between AMSCs and BMSCs. We demonstrate that PCBP2 and ZNF467 impact adipogenic but not osteogenic differentiation, further supporting evidence that AMSCs and BMSCs appear to be adapted to their microenvironment.

Concise Review: The Regulatory Mechanism of Lysine Acetylation in Mesenchymal Stem Cell Differentiation

Nowadays, the use of MSCs has attracted considerable attention in the global science and technology field, with the self-renewal and multidirectional differentiation potential for diabetes, obesity treatment, bone repair, nerve repair, myocardial repair, and so on. Epigenetics plays an important role in the regulation of mesenchymal stem cell differentiation, which has become a research hotspot in the medical field. This review focuses on the role of lysine acetylation modification on the determination of MSC differentiation direction. During this progress, the recruitment of lysine acetyltransferases (KATs) and lysine deacetylases (KDACs) is the crux of transcriptional mechanisms in the dynamic regulation of key genes controlling MSC multidirectional differentiation.

The epigenetic reader Brd4 is required for osteoblast differentiation

Transcription networks and epigenetic mechanisms including DNA methylation, histone modifications, and noncoding RNAs control lineage commitment of multipotent mesenchymal progenitor cells. Proteins that read, write, and erase histone tail modifications curate and interpret the highly intricate histone code. Epigenetic reader proteins that recognize and bind histone marks provide a crucial link between histone modifications and their downstream biological effects. Here, we investigate the role of bromodomain-containing (BRD) proteins, which recognize acetylated histones, during osteogenic differentiation. Using RNA-sequencing (RNA-seq) analysis, we screened for BRD proteins (n = 40) that are robustly expressed in MC3T3 osteoblasts. We focused functional follow-up studies on Brd2 and Brd4 which are highly expressed in MC3T3 preosteoblasts and represent "bromodomain and extra terminal domain" (BET) proteins that are sensitive to pharmacological agents (BET inhibitors). We show that small interfering RNA depletion of Brd4 has stronger inhibitory effects on osteoblast differentiation than Brd2 loss as measured by osteoblast-related gene expression, extracellular matrix deposition, and alkaline phosphatase activity. Similar effects on osteoblast differentiation are seen with the BET inhibitor +JQ1, and this effect is reversible upon its removal indicating that this small molecule has no lasting effects on the differentiation capacity of MC3T3 cells. Mechanistically, we find that Brd4 binds at known Runx2 binding sites in promoters of bone-related genes. Collectively, these findings suggest that Brd4 is recruited to osteoblast-specific genes and may cooperate with bone-related transcription factors to promote osteoblast lineage commitment and maturation.

Hypothermia and nutrient deprivation alter viability of human adipose-derived mesenchymal stem cells

PURPOSE

Adipose-derived mesenchymal stem cells (MSCs) are attractive biological agents in regenerative medicine. To optimize cell therapies, it is necessary to determine the most effective delivery method for MSCs. Therefore, we evaluated the biological properties of MSCs after exposure to various temperatures to define optimal storage conditions prior to therapeutic delivery of MSCs.

DESIGN

Prospective observational study.

METHODS AND MATERIALS

Adherent and non-adherent MSCs were incubated at multiple temperatures (i.e., 4, 23 and 37 °C) in Lactated Ringers (LR) solution lacking essential cell growth ingredients, or in culture media which is optimized for cell growth. Cells were assessed either after the temperature changes (4 h) or after recovery (24 h). Metabolic activity of MSCs, cell number and expression of representative mRNA biomarkers were evaluated to assess the biological effects of temperature. We monitored changes in mRNAs expression related to cytoprotective- or stress-related responses (e.g., FOS, JUN, ATF1, ATF4, EGR1, EGR2, MYC), proliferation (e.g., HIST2H4, CCNB2), and extracellular matrix production (ECM; e.g., COL3A1, COL1A1) by quantitative real time reverse-transcriptase polymerase chain reaction (RT-qPCR) analysis.

RESULTS

Our study demonstrates that storing MSCs in Lactated Ringers (LR) solution for 4 h decreases cell number and metabolic activity. The number of viable MSCs decreased significantly when cultured at physiological temperature (37 °C) and severe hypothermia (4 °C), while cells grown at ambient temperature (23 °C) exhibited the least detrimental effects. There were no appreciable biological differences in mRNA markers for proliferation or ECM deposition at any of the temperatures. However, biomarkers related to cytoprotective- or stress-responses were selectively elevated depending on temperature or media type (i.e., LR versus standard media).

CONCLUSION

The biological impact of nutrient-free media and temperature changes after 4 h exposure persists after a 24 h recovery period. Hence, storage temperature and media conditions should be optimized to improve effective dosing of MSCs.

Effect of Lidocaine on Viability and Gene Expression of Human Adipose-derived Mesenchymal Stem Cells: An in vitro Study

OBJECTIVE

To assess the biologic effects of lidocaine on the viability, proliferation, and function of human adipose tissue-derived mesenchymal stromal/stem cells (MSCs) in vitro.

METHODS

Adipose-derived MSCs from three donors were exposed to lidocaine at various dilutions (2 mg/mL to 8 mg/mL) and exposure times (0.5 to 4 hours). Cell number and viability, mitochondrial activity, and real-time reverse-transcriptase quantitative polymerase chain reaction (RT-qPCR) were analyzed at 0 (immediate effects) or 24 and 48 hours (recovery effects) after treatment with lidocaine.

RESULTS

Trypan blue staining showed that increasing concentrations of lidocaine decreased the number of observable viable cells. 3-[4,5,dimethylthiazol-2-yl]-5-[3-carboxymethoxy-phenyl]-2-[4-sulfophenyl]-2H-tetrazolium (MTS) assays revealed a concentration- and time- dependent decline of mitochondrial activity and proliferative ability. Gene expression analysis by RT-qPCR revealed that adipose-derived MSCs exposed to lidocaine express robust levels of stress response/cytoprotective genes. However, higher concentrations of lidocaine caused a significant downregulation of these genes. No significant differences were observed in expression of extracellular matrix (ECM) markers COL1A1 and DCN except for COL3A1 (P < .05). Levels of messenger RNA (mRNA) for proliferation markers (CCNB2, HIST2H4A, P < .001) and MKI67 (P < .001) increased at 24 and 48 hours. Expression levels of several transcription factors- including SP1, PRRX1, and ATF1-were modulated in the same manner. MSC surface markers CD44 and CD105 demonstrated decreased expression immediately after treatment, but at 24 and 48 hours postexposure, the MSC markers showed no significant difference among groups.

CONCLUSION

Lidocaine is toxic to MSCs in a dose- and time- dependent manner. MSC exposure to high (4-8 mg/mL) concentrations of lidocaine for prolonged periods can affect their biologic functions. Although the exposure time in vivo is short, it is essential to choose safe concentrations when applying lidocaine along with MSCs to avoid compromising the viability and potency of the stem cell therapy.

A Simple Dynamic Strategy to Deliver Stem Cells to Decellularized Nerve Allografts

BACKGROUND

The addition of adipose-derived mesenchymal stromal cells to decellularized nerve allografts may improve outcomes of nerve reconstruction. Prior techniques used for cell seeding are traumatic to both the mesenchymal stromal cells and nerve graft. An adequate, reliable, and validated cell seeding technique is an essential step for evaluating the translational utility of mesenchymal stromal cell-enhanced decellularized nerve grafts. The purpose of this study was to develop a simple seeding strategy with an optimal seeding duration.

METHODS

A dynamic bioreactor was used to seed rat and human mesenchymal stromal cells separately onto rat and human decellularized nerve allografts. Cell viability was evaluated by MTS assays and cellular topology after seeding was determined by scanning electron microscopy. Cell density and distribution were determined by Live/Dead assays and Hoechst staining at four different time points (6, 12, 24, and 72 hours). The validity and reliability of the seeding method were calculated.

RESULTS

Cells remained viable at all time points, and mesenchymal stromal cells exhibited exponential growth in the first 12 hours of seeding. Seeding efficiency increased significantly from 79.5 percent at 6 hours to 89.2 percent after 12 hours of seeding (p = 0.004). Both intrarater reliability (r = 0.97) and interrater reliability (r = 0.92) of the technique were high.

CONCLUSIONS

This study describes and validates a new method of effectively seeding decellularized nerve allografts with mesenchymal stromal cells. This method is reproducible, distributes cells homogenously over the graft, and does not traumatize the intraneural architecture of the allograft. Use of this validated seeding technique will permit critical comparison of graft outcomes.

Loss of histone methyltransferase Ezh2 stimulates an osteogenic transcriptional program in chondrocytes but does not affect cartilage development

Ezh2 is a histone methyltransferase that suppresses osteoblast maturation and skeletal development. We evaluated the role of Ezh2 in chondrocyte lineage differentiation and endochondral ossification. Ezh2 was genetically inactivated in the mesenchymal, osteoblastic, and chondrocytic lineages in mice using the Prrx1-Cre, Osx1-Cre, and Col2a1-Cre drivers, respectively. WT and conditional knockout mice were phenotypically assessed by gross morphology, histology, and micro-CT imaging. Ezh2-deficient chondrocytes in micromass culture models were evaluated using RNA-Seq, histologic evaluation, and Western blotting. Aged mice with Ezh2 deficiency were also evaluated for premature development of osteoarthritis using radiographic analysis. Ezh2 deficiency in murine chondrocytes reduced bone density at 4 weeks of age but caused no other gross developmental effects. Knockdown of Ezh2 in chondrocyte micromass cultures resulted in a global reduction in trimethylation of histone 3 lysine 27 (H3K27me3) and altered differentiation in vitro RNA-Seq analysis revealed enrichment of an osteogenic gene expression profile in Ezh2-deficient chondrocytes. Joint development proceeded normally in the absence of Ezh2 in chondrocytes without inducing excessive hypertrophy or premature osteoarthritis in vivo In summary, loss of Ezh2 reduced H3K27me3 levels, increased the expression of osteogenic genes in chondrocytes, and resulted in a transient post-natal bone phenotype. Remarkably, Ezh2 activity is dispensable for normal chondrocyte maturation and endochondral ossification in vivo, even though it appears to have a critical role during early stages of mesenchymal lineage commitment.

Tissue-Nonspecific Alkaline Phosphatase Is Required for MC3T3 Osteoblast-Mediated Protection of Acute Myeloid Leukemia Cells from Apoptosis

The bone marrow microenvironment harbors and protects leukemic cells from apoptosis-inducing agents via mechanisms that are incompletely understood. We previously showed SDF-1 (CXCL-12), a chemokine readily abundant within the bone marrow microenvironment, induces apoptosis in acute myeloid leukemia (AML) cells that express high levels of the SDF-1 receptor CXCR4. However, differentiating osteoblasts found within this niche protect cocultured AML cells from apoptosis. Additionally, this protection was abrogated upon treatment of the differentiating osteoblasts with histone deacetylase inhibitors (HDACi). In this study, we begin to characterize and target the molecular mechanisms that mediate this osteoblast protection. Quantitative RT-PCR revealed that HDACi treatment of differentiating osteoblasts (mouse MC3T3 osteoblast cell line) reduced expression of multiple genes required for osteoblast differentiation, including genes important for producing mineralized bone matrix. Interestingly, pretreating differentiating osteoblasts with cyclosporine A, a drug known to inhibit osteoblast differentiation, similarly impaired osteoblast-mediated protection of cocultured AML cells (KG1a and U937 human AML cell lines). Both HDACi and cyclosporine A reduced osteoblast expression of the key mineralization enzyme tissue-nonspecific alkaline phosphatase (TNAP; encoded by Alpl). Moreover, specifically reducing TNAP expression or activity in differentiating osteoblasts significantly impaired the ability of the osteoblasts to protect cocultured AML cells. Together, our results indicate that inhibiting osteoblast matrix mineralization by specifically targeting TNAP is sufficient to significantly impair osteoblast-mediated protection of AML cells. Therefore, designing combination therapies that additionally target the osteoblast-produced mineralized bone matrix may improve treatment of AML by reducing the protection of leukemic cells within the bone marrow microenvironment.

Cytotoxic Effects of Nonionic Iodinated Contrast Agent on Human Adipose-Derived Mesenchymal Stem Cells

BACKGROUND

Transplantation of mesenchymal stem cells (MSCs) is a promising therapy for degenerative spine conditions. However, cell therapy for painful spine degeneration presently requires use of contrast agents during fluoroscopy-guided injections, and the effects of these agents on MSCs represents a gap in knowledge.

OBJECTIVE

To investigate the biological effects of contrast media (CM) that are coinjected with MSCs.

DESIGN

Prospective observational study.

SETTING

Academic medical center.

PARTICIPANTS

Patient-derived clinical-grade culture expanded MSCs.

INTERVENTIONS

Iohexol (Omnipaque300) was reduced to 12.5%, 25%, 50%, and 100% of the stock solution and incubated with MSCs for 30 minutes, 4 hours, and 48 hours. We also used complete media and 12.5%, 25%, 50%, 100% of phosphate-buffered saline as a control group.

MAIN OUTCOME MEASURES

We examined cytotoxicity of iohexol at different concentrations and exposure duration, as well as the potential for recovery over time. Cell counts, mitochondrial activity, and quantitative real time reverse-transcriptase polymerase chain reaction of related genes were analyzed immediately after exposure (day 0) and after 2 days of exposure (day 2).

RESULTS

Human MSCs exhibit a time- and concentration-dependent cytotoxic response to iodinated CM. A brief, 30-minute exposure did not affect MSCs function and viability. However, extended treatment with iohexol for 4 hours at 50% or higher concentration had a significant impact on both viability and gene expression in MSCs.

CONCLUSIONS

CM (Omnipaque300) is cytotoxic to MSCs in a time-and concentration-dependent manner. Hence, the concentration of CM that accompanies MSC injections should be carefully considered during MSC therapy for disk-degenerative diseases.

LEVEL OF EVIDENCE

To be determined.

Osteogenic Stimulation of Human Adipose-Derived Mesenchymal Stem Cells Using a Fungal Metabolite That Suppresses the Polycomb Group Protein EZH2

Strategies for musculoskeletal tissue regeneration apply adult mesenchymal stem/stromal cells (MSCs) that can be sourced from bone marrow- and lipo-aspirates. Adipose tissue-derived MSCs are more easily harvested in the large quantities required for skeletal tissue-engineering approaches, but are generally considered to be less osteogenic than bone marrow MSCs. Therefore, we tested a new molecular strategy to improve their osteogenic lineage-differentiation potential using the fungal metabolite cytochalasin D (CytoD). We show that CytoD, which may function by redistributing the intracellular location of β-actin (ACTB), is a potent osteogenic stimulant as reflected by significant increases in alkaline phosphatase activity, extracellular matrix mineralization, and osteoblast-related gene expression (e.g., RUNX2, ALPL, SPARC, and TGFB3). RNA sequencing analyses of MSCs revealed that acute CytoD treatment (24 hours) stimulates a broad program of osteogenic biomarkers and epigenetic regulators. CytoD decreases mRNA and protein levels of the Polycomb chromatin regulator Enhancer of Zeste Homolog 2 (EZH2), which controls heterochromatin formation by mediating trimethylation of histone 3 lysine 27 (H3K27me3). Reduced EZH2 expression decreases cellular H3K27me3 marks indicating a global reduction in heterochromatin. We conclude that CytoD is an effective osteogenic stimulant that mechanistically functions by blocking both cytoplasmic actin polymerization and gene-suppressive epigenetic mechanisms required for the acquisition of the osteogenic phenotype in adipose tissue-derived MSCs. This finding supports the use of CytoD in advancing the osteogenic potential of MSCs in skeletal regenerative strategies. Stem Cells Translational Medicine 2018;7:197-209.

Molecular Signatures Associated with Treatment of Triple-Negative MDA-MB231 Breast Cancer Cells with Histone Deacetylase Inhibitors JAHA and SAHA

Jay Amin hydroxamic acid (JAHA; N8-ferrocenylN¹-hydroxy-octanediamide) is a ferrocene-containing analogue of the histone deacetylase inhibitor (HDACi) suberoylanilide hydroxamic acid (SAHA). JAHA's cytotoxic activity on MDA-MB231 triple negative breast cancer (TNBC) cells at 72 h has been previously demonstrated with an IC₅₀ of 8.45 μM. JAHA's lethal effect was found linked to perturbations of cell cycle, mitochondrial activity, signal transduction, and autophagy mechanisms. To glean novel insights on how MDA-MB231 breast cancer cells respond to the cytotoxic effect induced by JAHA, and to compare the biological effect with the related compound SAHA, we have employed a combination of differential display-PCR, proteome analysis, and COMET assay techniques and shown some differences in the molecular signature profiles induced by exposure to either HDACis. In particular, in contrast to the more numerous and diversified changes induced by SAHA, JAHA has shown a more selective impact on expression of molecular signatures involved in antioxidant activity and DNA repair. Besides expanding the biological knowledge of the effect exerted by the modifications in compound structures on cell phenotype, the molecular elements put in evidence in our study may provide promising targets for therapeutic interventions on TNBCs.

Histone deacetylase inhibitors reduce differentiating osteoblast-mediated protection of acute myeloid leukemia cells from cytarabine

The bone marrow microenvironment protects acute myeloid leukemia (AML) cells during chemotherapy and is a major factor in relapse. Here, we examined which type(s) of bone marrow cells are responsible for the relapse of AML following treatment with cytarabine (Ara-C), and we identified a means to inhibit this protection. To determine the protective cell type(s), AML cells were treated with Ara-C, and AML cell survival in the presence or absence of osteoblast lineage cells was assessed. Cultured AML cells and patient bone marrow isolates were each significantly protected from Ara-C-induced apoptosis by co-culture with differentiating osteoblasts. Moreover, pretreating differentiating osteoblasts with the histone deacetylase inhibitors (HDACi) vorinostat and panobinostat abrogated the ability of the differentiating osteoblasts to protect AML cells. Together, our results indicate that differentiating osteoblasts have the potential to promote residual AML in the bone marrow following standard chemotherapy and act via a mechanism requiring HDACi-sensitive gene expression. Using HDACi to target the leukemic microenvironment in combination with Ara-C could potentially improve treatment of AML. Moreover, other strategies for manipulating bone marrow osteoblasts may also help eradicate AML cells and reduce relapse.

Histone acetylation favours the cardiovascular commitment of adipose tissue-derived stromal cells

BACKGROUND

Although adipose stromal cells (ASCs) retain the ability to transdifferentiate at low rate towards the cardiac lineage, the potential mechanisms underlying such process have still to be elucidated.

METHODS

Since chromatin state modifications are involved in several processes regulating the cellular cell fate commitment, we aimed at evaluating the role of histone protein acetylation in the cardiovascular-like transdifferentiation of ASCs.

RESULTS

We found a clear increase of histone 3 acetylation status paralleled by a significant upregulation of cardiac TnI gene expression, in ASCs treated with the conditioned medium of primary cardiomyocyte cell cultures for 72h. This result suggests that histone acetylation contributes to the transdifferentiation of ASCs towards the cardiac lineage. In order to directly test this hypothesis, ASCs cultured with regular medium were treated with SAHA, a pan histone deacetylase inhibitor. We found that SAHA enhanced the cardiac permissive state of ASCs, increasing both mRNA and protein expression of cardiovascular genes, particularly cTnI. This suggests that histone acetylation induction is sufficient to promote cardiovascular transdifferentiation.

CONCLUSIONS

The control of ASC fate by epigenetic regulators might be an interesting tool to boost both cardiac commitment and regenerative capacities of ASCs.

Integrated transcriptomic and proteomic analysis of the molecular cargo of extracellular vesicles derived from porcine adipose tissue-derived mesenchymal stem cells

Background

Mesenchymal stromal/stem cell (MSC) transplantation is a promising therapy for tissue regeneration. Extracellular vesicles (EVs) released by MSCs act as their paracrine effectors by delivering proteins and genetic material to recipient cells. To assess how their cargo mediates biological processes that drive their therapeutic effects, we integrated miRNA, mRNA, and protein expression data of EVs from porcine adipose tissue-derived MSCs.

Methods

Simultaneous expression profiles of miRNAs, mRNAs, and proteins were obtained by high-throughput sequencing and LC-MS/MS proteomic analysis in porcine MSCs and their daughter EVs (n = 3 each). TargetScan and ComiR were used to predict miRNA target genes. Functional annotation analysis was performed using DAVID 6.7 database to rank primary gene ontology categories for the enriched mRNAs, miRNA target genes, and proteins. STRING was used to predict associations between mRNA and miRNA target genes.

Results

Differential expression analysis revealed 4 miRNAs, 255 mRNAs, and 277 proteins enriched in EVs versus MSCs (fold change >2, p<0.05). EV-enriched miRNAs target transcription factors (TFs) and EV-enriched mRNAs encode TFs, but TF proteins are not enriched in EVs. Rather, EVs are enriched for proteins that support extracellular matrix remodeling, blood coagulation, inflammation, and angiogenesis.

Conclusions

Porcine MSC-derived EVs contain a genetic cargo of miRNAs and mRNAs that collectively control TF activity in EVs and recipient cells, as well as proteins capable of modulating cellular pathways linked to tissue repair. These properties provide the fundamental basis for considering therapeutic use of EVs in tissue regeneration.

Profiling of human epigenetic regulators using a semi-automated real-time qPCR platform validated by next generation sequencing

Epigenetic mechanisms control phenotypic commitment of mesenchymal stromal/stem cells (MSCs) into osteogenic, chondrogenic or adipogenic lineages. To investigate enzymes and chromatin binding proteins controlling the epigenome, we developed a hybrid expression screening strategy that combines semi-automated real-time qPCR (RT-qPCR), next generation RNA sequencing (RNA-seq), and a novel data management application (FileMerge). This strategy was used to interrogate expression of a large cohort (n>300) of human epigenetic regulators (EpiRegs) that generate, interpret and/or edit the histone code. We find that EpiRegs with similar enzymatic functions are variably expressed and specific isoforms dominate over others in human MSCs. This principle is exemplified by analysis of key histone acetyl transferases (HATs) and deacetylases (HDACs), H3 lysine methyltransferases (e.g., EHMTs) and demethylases (KDMs), as well as bromodomain (BRDs) and chromobox (CBX) proteins. Our results show gender-specific expression of H3 lysine 9 [H3K9] demethylases (e.g., KDM5D and UTY) as expected and upregulation of distinct EpiRegs (n>30) during osteogenic differentiation of MSCs (e.g., HDAC5 and HDAC7). The functional significance of HDACs in osteogenic lineage commitment of MSCs was functionally validated using panobinostat (LBH-589). This pan-deacetylase inhibitor suppresses osteoblastic differentiation as evidenced by reductions in bone-specific mRNA markers (e.g., ALPL), alkaline phosphatase activity and calcium deposition (i.e., Alizarin Red staining). Thus, our RT-qPCR platform identifies candidate EpiRegs by expression screening, predicts biological outcomes of their corresponding inhibitors, and enables manipulation of the human epigenome using molecular or pharmacological approaches to control stem cell differentiation.

Safety Studies for Use of Adipose Tissue-Derived Mesenchymal Stromal/Stem Cells in a Rabbit Model for Osteoarthritis to Support a Phase I Clinical Trial

Adipose‐derived mesenchymal stem cells (AMSCs) offer potential as a therapeutic option for clinical applications in musculoskeletal regenerative medicine because of their immunomodulatory functions and capacity for trilineage differentiation. In preparation for a phase I clinical trial using AMSCs to treat patients with osteoarthritis, we carried out preclinical studies to assess the safety of human AMSCs within the intra‐articular joint space. Culture‐expanded human AMSCs grown in human platelet‐lysate were delivered via intra‐articular injections into normal healthy rabbit knees and knees at risk for the development of osteoarthritis after bilateral medial anterior hemimeniscectomy. Treatment outcomes and safety were evaluated by assessing the general health, function, and behavior of the animals. Joint tissues were analyzed by x‐ray, magnetic resonance imaging, and histopathology. Intra‐articular AMSC therapy was well tolerated in this study. We did not observe adverse systemic reactions, nor did we find evidence of damage to intra‐articular joint tissues. Thus, the data generated in this study show a favorable safety profile for AMSCs within the joint space in support of a phase I clinical trial evaluating the clinical utility of AMSCs to treat osteoarthritis. Stem Cells Translational Medicine2017;6:910–922

Neuropeptide Y mediates glucocorticoid-induced osteoporosis and marrow adiposity in mice

Increased neuropeptide Y (NPY) expression occurred in the glucocorticoid-induced osteoporotic skeleton. NPY knockout mice exhibited a minor response to the glucocorticoid-mediated exacerbation of bone accretion and fatty marrow pathogenesis. NPY deletion restored SITR1 signaling and enhanced PPARγ ubiquitination of bone tissue, an alternative strategy for ameliorating glucocorticoid-induced skeletal deterioration.

INTRODUCTION

Glucocorticoid excess is observed to worsen the pathogenesis of osteoporosis and fatty marrow. This study was undertaken to investigate the contribution of neuropeptide Y (NPY) to glucocorticoid-induced bone loss and marrow adiposity.

METHODS

NPY knockout and wild-type mice were administered methylprednisolone for four consecutive weeks. Bone mineral density, microarchitecture, and calcein-labeled mineral acquisition were quantified by μCT, dual energy X-ray absorptiometry, and histomorphometry. Expression of osteogenic and adipogenic markers and acetylation states of PPARγ were detected by RT-quantitative PCR, immunoprecipitation, and immunoblotting.

RESULTS

High NPY levels were associated with glucocorticoid-induced trabecular bone deterioration and marrow fat accumulation. Mice lacking NPY had high bone mass concomitant with spacious trabecular and cortical bone microstructure. NPY deletion shielded skeletal tissues from the glucocorticoid-induced impediment of bone mass, trabecular morphometric characteristics, mineral accretion activity, and fatty marrow development. Ex vivo, NPY deficiency sustained osteogenic differentiation capacity and curtailed the glucocorticoid-mediated escalation of adipocyte formation reactions of primary bone-marrow mesenchymal cells. NPY deletion appeared to modulate Y1 and Y2 receptors, sirtuin 1, ERK, and p38 signaling pathways, an effect that facilitated hypoacetylation and ubiquitination of adipogenic transcription factor PPARγ in the skeletal tissues exposed to glucocorticoid stress.

CONCLUSIONS

NPY mediates the glucocorticoid-induced disturbance of mineral accretion and marrow adipogenesis through post-translational modification of PPARγ. This study brings a new molecular insight into the disintegration of adipogenic and osteogenic activities within glucocorticoid-mediated osteoporotic skeletons. Control of NPY is an alternative strategy to ameliorate glucocorticoid-induced bone destruction and fatty marrow.

Osteogenic potential of human adipose-tissue-derived mesenchymal stromal cells cultured on 3D-printed porous structured titanium

Integration of porous metal prosthetics, which restore form and function of irreversibly damaged joints, into remaining healthy bone is critical for implant success. We investigated the biological properties of adipose-tissue-derived mesenchymal stromal/stem cells (AMSCs) and addressed their potential to alter the in vitro microenvironment of implants. We employed human AMSCs as a practical source for musculoskeletal applications because these cells can be obtained in large quantities, are multipotent, and have trophic paracrine functions. AMSCs were cultured on surgical-grade porous titanium disks as a model for orthopedic implants. We monitored cell/substrate attachment, cell proliferation, multipotency, and differentiation phenotypes of AMSCs upon osteogenic induction. High-resolution scanning electron microscopy and histology revealed that AMSCs adhere to the porous metallic surface. Compared to standard tissue culture plastic, AMSCs grown in the porous titanium microenvironment showed differences in temporal expression for genes involved in cell cycle progression (CCNB2, HIST2H4), extracellular matrix production (COL1A1, COL3A1), mesenchymal lineage identity (ACTA2, CD248, CD44), osteoblastic transcription factors (DLX3, DLX5, ID3), and epigenetic regulators (EZH1, EZH2). We conclude that metal orthopedic implants can be effectively seeded with clinical-grade stem/stromal cells to create a pre-conditioned implant.

Multipotent mesenchymal stromal cells are fully permissive for human cytomegalovirus infection

Congenital human cytomegalovirus (HCMV) infection is a leading infectious cause of birth defects. Previous studies have reported birth defects with multiple organ maldevelopment in congenital HCMV-infected neonates. Multipotent mesenchymal stromal cells (MSCs) are a group of stem/progenitor cells that are multi-potent and can self-renew, and they play a vital role in multi-organ formation. Whether MSCs are susceptible to HCMV infection is unclear. In this study, MSCs were isolated from Wharton's jelly of the human umbilical cord and identified by their plastic adherence, surface marker pattern, and differentiation capacity. Then, the MSCs were infected with the HCMV Towne strain, and infection status was assessed via determination of viral entry, replication initiation, viral protein expression, and infectious virion release using western blotting, immunofluorescence assays, and plaque forming assays. The results indicate that the isolated MSCs were fully permissive for HCMV infection and provide a preliminary basis for understanding the pathogenesis of HCMV infection in non-nervous system diseases, including multi-organ malformation during fetal development.

Human Adipose-Derived Mesenchymal Stromal/Stem Cells Remain Viable and Metabolically Active Following Needle Passage

OBJECTIVE

To assess the biological effects of passage through clinically relevant needles on the viability and metabolic activity of culture-expanded, human adipose tissue-derived mesenchymal stromal/stem cells (AMSCs).

DESIGN

Prospective observational pilot study.

SETTING

Academic medical center.

PARTICIPANTS

Patient-derived clinical-grade culture expanded AMSCs.

INTERVENTIONS

AMSCs were passed through syringes without a needle attached (control), with an 18-gauge (25.4-mm) needle attached and with a 30-gauge (19-mm) needle attached at a constant injection flow rate and constant cell concentrations. Each injection condition was completed in triplicate.

MAIN OUTCOME MEASURES

Cell number and viability, proliferative capacity, metabolic activity, and acute gene expression as measured by cell counts, mitochondrial activity, and quantitative real time reverse-transcription polymerase chain reaction on day 0 (immediately), day 1, and day 4 after injection.

RESULTS

AMSC viability was not significantly affected by injection, and cells proliferated normally regardless of study group. Postinjection, AMSCs robustly expressed both proliferation markers and extracellular matrix proteins. Stress-response mRNAs were markedly but transiently increased independently of needle size within the first day in culture postinjection.

CONCLUSIONS

Human, culture-expanded AMSCs maintain their viability, proliferative capacity, and metabolic function following passage through needles as small as 30-gauge at constant flow rates of 4 mL/min, despite an early, nonspecific stress/cytoprotective response. These initial findings suggest that culture-expanded AMSCs should tolerate the injection process during most cell-based therapeutic interventions.

Anabolic and Antiresorptive Modulation of Bone Homeostasis by the Epigenetic Modulator Sulforaphane, a Naturally Occurring Isothiocyanate

Bone degenerative pathologies like osteoporosis may be initiated by age-related shifts in anabolic and catabolic responses that control bone homeostasis. Here we show that sulforaphane (SFN), a naturally occurring isothiocyanate, promotes osteoblast differentiation by epigenetic mechanisms. SFN enhances active DNA demethylation viaTet1andTet2and promotes preosteoblast differentiation by enhancing extracellular matrix mineralization and the expression of osteoblastic markers (Runx2,Col1a1,Bglap2,Sp7,Atf4, andAlpl). SFN decreases the expression of the osteoclast activator receptor activator of nuclear factor-κB ligand (RANKL) in osteocytes and mouse calvarial explants and preferentially induces apoptosis in preosteoclastic cells via up-regulation of theTet1/Fas/Caspase 8 and Caspase 3/7 pathway. These mechanistic effects correlate with higher bone volume (∼20%) in both normal and ovariectomized mice treated with SFN for 5 weeks compared with untreated mice as determined by microcomputed tomography. This effect is due to a higher trabecular number in these mice. Importantly, no shifts in mineral density distribution are observed upon SFN treatment as measured by quantitative backscattered electron imaging. Our data indicate that the food-derived compound SFN epigenetically stimulates osteoblast activity and diminishes osteoclast bone resorption, shifting the balance of bone homeostasis and favoring bone acquisition and/or mitigation of bone resorptionin vivo Thus, SFN is a member of a new class of epigenetic compounds that could be considered for novel strategies to counteract osteoporosis.

Obesity and diabetes: the link between adipose tissue dysfunction and glucose homeostasis

Obesity and type 2 diabetes mellitus (T2DM) epidemics, which have already spread, imply the possibility of both conditions being closely related. Thus, the goal of the present review was to draw a parallel between obesity, adipose tissue (AT) changes, and T2DM development. To this end, a search was conducted in PubMed, MEDLINE and SciELO databases, using the following key words and their combinations: obesity; diabetes; insulin resistance; diet; weight loss; adipocin; inflammation markers; and interleukins. Based on a literature review, AT dysfunction observed in obesity is characterised by adipocyte hypertrophy, macrophage infiltration, impaired insulin signalling and insulin resistance. In addition, there is release of inflammatory adipokines and an excessive amount of NEFA promoting ectopic fat deposition and lipotoxicity in muscle, liver and pancreas. Recent evidence supports the hypothesis that the conception of AT as a passive energy storage organ should be replaced by a dynamic endocrine organ, which regulates metabolism through a complex adipocyte communication with the surrounding microenvironment. The present review demonstrates how glucose homeostasis is changed by AT dysfunction. A better understanding of this relationship enables performing nutritional intervention strategies with the goal of preventing T2DM.

Chromatin modifiers and histone modifications in bone formation, regeneration, and therapeutic intervention for bone-related disease

Post-translational modifications of chromatin such as DNA methylation and different types of histone acetylation, methylation and phosphorylation are well-appreciated epigenetic mechanisms that confer information to progeny cells during lineage commitment. These distinct epigenetic modifications have defined roles in bone, development, tissue regeneration, cell commitment and differentiation, as well as disease etiologies. In this review, we discuss the role of these chromatin modifications and the enzymes regulating these marks (methyltransferases, demethylases, acetyltransferases, and deacetylases) in progenitor cells, osteoblasts and bone-related cells. In addition, the clinical relevance of deregulated histone modifications and enzymes as well as current and potential therapeutic interventions targeting chromatin modifiers are addressed.

Histone Deacetylase Inhibitors Target the Leukemic Microenvironment by Enhancing a Nherf1-Protein Phosphatase 1α-TAZ Signaling Pathway in Osteoblasts

Disrupting the protective signals provided by the bone marrow microenvironment will be critical for more effective combination drug therapies for acute myeloid leukemia (AML). Cells of the osteoblast lineage that reside in the endosteal niche have been implicated in promoting survival of AML cells. Here, we investigated how to prevent this protective interaction. We previously showed that SDF-1, a chemokine abundant in the bone marrow, induces apoptosis of AML cells, unless the leukemic cells receive protective signals provided by differentiating osteoblasts (8, 10). We now identify a novel signaling pathway in differentiating osteoblasts that can be manipulated to disrupt the osteoblast-mediated protection of AML cells. Treating differentiating osteoblasts with histone deacetylase inhibitors (HDACi) abrogated their ability to protect co-cultured AML cells from SDF-1-induced apoptosis. HDACi prominently up-regulated expression of the Nherf1 scaffold protein, which played a major role in preventing osteoblast-mediated protection of AML cells. Protein phosphatase-1α (PP1α) was identified as a novel Nherf1 interacting protein that acts as the downstream mediator of this response by promoting nuclear localization of the TAZ transcriptional modulator. Moreover, independent activation of either PP1α or TAZ was sufficient to prevent osteoblast-mediated protection of AML cells even in the absence of HDACi. Together, these results indicate that HDACi target the AML microenvironment by enhancing activation of the Nherf1-PP1α-TAZ pathway in osteoblasts. Selective drug targeting of this osteoblast signaling pathway may improve treatments of AML by rendering leukemic cells in the bone marrow more susceptible to apoptosis.

The potential of GMP-compliant platelet lysate to induce a permissive state for cardiovascular transdifferentiation in human mediastinal adipose tissue-derived mesenchymal stem cells

Human adipose tissue-derived mesenchymal stem cells (ADMSCs) are considered eligible candidates for cardiovascular stem cell therapy applications due to their cardiac transdifferentiation potential and immunotolerance. Over the years, the in vitro culture of ADMSCs by platelet lysate (PL), a hemoderivate containing numerous growth factors and cytokines derived from platelet pools, has allowed achieving a safe and reproducible methodology to obtain high cell yield prior to clinical administration. Nevertheless, the biological properties of PL are still to be fully elucidated. In this brief report we show the potential ability of PL to induce a permissive state of cardiac-like transdifferentiation and to cause epigenetic modifications. RTPCR results indicate an upregulation of Cx43, SMA, c-kit, and Thy-1 confirmed by immunofluorescence staining, compared to standard cultures with foetal bovine serum. Moreover, PL-cultured ADMSCs exhibit a remarkable increase of both acetylated histones 3 and 4, with a patient-dependent time trend, and methylation at lysine 9 on histone 3 preceding the acetylation. Expression levels of p300 and SIRT-1, two major regulators of histone 3, are also upregulated after treatment with PL. In conclusion, PL could unravel novel biological properties beyond its routine employment in noncardiac applications, providing new insights into the plasticity of human ADMSCs.

Histone Deacetylases in Bone Development and Skeletal Disorders

Histone deacetylases (Hdacs) are conserved enzymes that remove acetyl groups from lysine side chains in histones and other proteins. Eleven of the 18 Hdacs encoded by the human and mouse genomes depend on Zn(2+) for enzymatic activity, while the other 7, the sirtuins (Sirts), require NAD2(+). Collectively, Hdacs and Sirts regulate numerous cellular and mitochondrial processes including gene transcription, DNA repair, protein stability, cytoskeletal dynamics, and signaling pathways to affect both development and aging. Of clinical relevance, Hdacs inhibitors are United States Food and Drug Administration-approved cancer therapeutics and are candidate therapies for other common diseases including arthritis, diabetes, epilepsy, heart disease, HIV infection, neurodegeneration, and numerous aging-related disorders. Hdacs and Sirts influence skeletal development, maintenance of mineral density and bone strength by affecting intramembranous and endochondral ossification, as well as bone resorption. With few exceptions, inhibition of Hdac or Sirt activity though either loss-of-function mutations or prolonged chemical inhibition has negative and/or toxic effects on skeletal development and bone mineral density. Specifically, Hdac/Sirt suppression causes abnormalities in physiological development such as craniofacial dimorphisms, short stature, and bone fragility that are associated with several human syndromes or diseases. In contrast, activation of Sirts may protect the skeleton from aging and immobilization-related bone loss. This knowledge may prolong healthspan and prevent adverse events caused by epigenetic therapies that are entering the clinical realm at an unprecedented rate. In this review, we summarize the general properties of Hdacs/Sirts and the research that has revealed their essential functions in bone forming cells (e.g., osteoblasts and chondrocytes) and bone resorbing osteoclasts. Finally, we offer predictions on future research in this area and the utility of this knowledge for orthopedic applications and bone tissue engineering.

Epigenetic Control of Skeletal Development by the Histone Methyltransferase Ezh2

Epigenetic control of gene expression is critical for normal fetal development. However, chromatin-related mechanisms that activate bone-specific programs during osteogenesis have remained underexplored. Therefore, we investigated the expression profiles of a large cohort of epigenetic regulators (>300) during osteogenic differentiation of human mesenchymal cells derived from the stromal vascular fraction of adipose tissue (AMSCs). Molecular analyses establish that the polycomb group protein EZH2 (enhancer of zeste homolog 2) is down-regulated during osteoblastic differentiation of AMSCs. Chemical inhibitor and siRNA knockdown studies show that EZH2, a histone methyltransferase that catalyzes trimethylation of histone 3 lysine 27 (H3K27me3), suppresses osteogenic differentiation. Blocking EZH2 activity promotes osteoblast differentiation and suppresses adipogenic differentiation of AMSCs. High throughput RNA sequence (mRNASeq) analysis reveals that EZH2 inhibition stimulates cell cycle inhibitory proteins and enhances the production of extracellular matrix proteins. Conditional genetic loss of Ezh2 in uncommitted mesenchymal cells (Prrx1-Cre) results in multiple defects in skeletal patterning and bone formation, including shortened forelimbs, craniosynostosis, and clinodactyly. Histological analysis and mRNASeq profiling suggest that these effects are attributable to growth plate abnormalities and premature cranial suture closure because of precocious maturation of osteoblasts. We conclude that the epigenetic activity of EZH2 is required for skeletal patterning and development, but EZH2 expression declines during terminal osteoblast differentiation and matrix production.

Control of bone development by P2X and P2Y receptors expressed in mesenchymal and hematopoietic cells

Bone development and homeostasis require the interplay between several cell types, including mesenchymal osteoblasts and osteocytes, as well as hematopoietic osteoclasts. Recent evidence suggests that cell proliferation, differentiation and apoptosis of both mesenchymal and hematopoietic stem cells, which are fundamental for tissue regeneration and treatment of degenerative diseases, are controlled by P2 receptors (i.e., P2X and P2Y receptors). Both types of P2 receptors are versatile transducers of diverse signals activated by extracellular nucleotides like ATP that are released in response to tissue injury, infection or shear stress. The P2X family of receptors has been shown to mediate multiple signaling events including the influx of calcium, activation of mitogen activated protein kinases (MAPKs) and induction of AP-1 family members known to regulate bone development. Support for the significance of P2X7 in regulating bone development and homeostasis has been provided by several studies focusing on animal models and single nucleotide polymorphisms. P2 receptors are functionally expressed in both bone forming osteoblasts and bone resorbing osteoclasts, while recent findings also suggest that these receptors translate mechanical stimuli in osteocytes. Their ability to respond to external nucleotide analogs renders these cell surface proteins excellent targets for skeletal regenerative therapies. This overview summarizes mechanisms by which nucleotide receptors control skeletal cells and contribute to bone tissue development remodeling and repair.

MicroRNA and mRNA cargo of extracellular vesicles from porcine adipose tissue-derived mesenchymal stem cells

Mesenchymal stromal/stem cells (MSCs) are clinically useful for cell-based therapy, but concerns regarding their ability to replicate limit their human application. MSCs release extracellular vesicles (EVs) that mediate at least in part the paracrine effects of the parental cells. To understand the molecular basis of their biological properties, we characterized the RNA cargo of EVs from porcine adipose-tissue derived MSCs. Comprehensive characterization of mRNA and miRNA gene expression using high-throughput RNA sequencing (RNA-seq) revealed that EVs are selectively enriched for distinct classes of RNAs. For example, EVs preferentially express mRNA for transcription factors (e.g. MDFIC, POU3F1, NRIP1) and genes involved in angiogenesis (e.g. HGF, HES1, TCF4) and adipogenesis (e.g. CEBPA, KLF7). EVs also express Golgi apparatus genes (ARRB1, GOLGA4) and genes involved in TGF-β signaling. In contrast, mitochondrial, calcium signaling, and cytoskeleton genes are selectively excluded from EVs, possibly because these genes remain sequestered in organelles or intracellular compartments. RNA-seq generated reads for at least 386 annotated miRNAs, but only miR148a, miR532-5p, miR378, and let-7f were enriched in EVs compared to MSCs. Gene ontology analysis indicates that these miRNAs target transcription factors and genes that participate in several cellular pathways, including angiogenesis, cellular transport, apoptosis, and proteolysis. Our data suggest that EVs transport gene regulatory information to modulate angiogenesis, adipogenesis, and other cell pathways in recipient cells. These observations may contribute to development of regenerative strategies using EVs to overcome potential complications of cell-based therapy.