Megakaryocyte-stromal cell interactions: effect on megakaryocyte proliferation, proplatelet production, and survival

Bone marrow stromal cells provide a proper environment for the development of hematologic lineages. The incorporation of different stromal cells to in vitro culture systems would be an attractive model to study megakaryopoiesis and thrombopoiesis. Our objective was to evaluate the participation of different types of stromal cells on in vitro megakaryopoiesis, thrombopoiesis and megakaryocyte (MK) survival. CD34-positive progenitors from umbilical cord blood were differentiated into MK precursors and then co-cultured with umbilical vein endothelial cells (HUVEC), bone marrow mesenchymal stem cells (MSCs), skin fibroblasts (SF) (all human) or mouse fibroblast cell line (L929). The number of MKs (CD61-positive cells) was increased in the presence of HUVEC and SF while L929 cells decreased total and mature MK count. Concerning thrombopoiesis, HUVEC increased proplatelet (PP)-producing MKs, while MSCs, L929 and SF had the opposite effect (immunofluorescence staining and microscopic analysis).  MK survival was enhanced in MSC and SF co-cultures, as assessed by evaluation of pyknotic nuclei. However, HUVEC and L929 did not prevent apoptosis of MKs. Reciprocally, the cloning efficiency of MSCs was decreased in the presence of MKs, while the ability of stromal cells (either MSCs or SF) to produce the extracellular matrix proteins type III collagen, fibronectin, dermatan sulfate, heparan sulfate and P4HB was preserved. These data indicate that each stromal cell type performs distinctive functions, which differentially modulate MK growth and platelet production, and, at the same time, that MKs also modify stromal cells behavior. Overall, our results highlight the relevance of considering the influence of stromal cells in MK research as well as the close interplay of different cell types within the bone marrow milieu.

The Polycomb Protein Bmi1 Plays a Crucial Role in the Prevention of 1,25(OH)2 D Deficiency-Induced Bone Loss

We analyzed the skeletal phenotypes of heterozygous null Cyp27b1 (Cyp27b1^+/- ) mice and their wild-type (WT) littermates to determine whether haploinsufficiency of Cyp27b1 accelerated bone loss, and to examine potential mechanisms of such loss. We found that serum 1,25-dihydroxyvitamin D [1,25(OH)₂ D] levels were significantly decreased in aging Cyp27b1^+/- mice, which displayed an osteoporotic phenotype. This was accompanied by a reduction of expression of the B lymphoma Moloney murine leukemia virus (Mo-MLV) insertion region 1 (Bmi1) at both gene and protein levels. Using chromatin immunoprecipitation (ChIP)-PCR, electrophoretic mobility shift assay (EMSA) and a luciferase reporter assay, we then showed that 1,25(OH)₂ D₃ upregulated Bmi1 expression at a transcriptional level via the vitamin D receptor (VDR). To determine whether Bmi1 overexpression in mesenchymal stem cells (MSCs) could correct bone loss induced by 1,25(OH)₂ D deficiency, we overexpressed Bmi1 in MSCs using Prx1-driven Bmi1 transgenic mice (Bmi1^Tg ) mice. We then compared the bone phenotypes of Bmi1^Tg mice on a Cyp27b1^+/- background, with those of Cyp27b1^+/- mice and with those of WT mice, all at 8 months of age. We found that overexpression of Bmi1 in MSCs corrected the bone phenotype of Cyp27b1^+/- mice by increasing osteoblastic bone formation, reducing osteoclastic bone resorption, increasing bone volume, and increasing bone mineral density. Bmi1 overexpression in MSCs also corrected 1,25(OH)₂ D deficiency-induced oxidative stress and DNA damage, and cellular senescence of Cyp27b1^+/- mice by reducing levels of reactive oxygen species (ROS), elevating serum total superoxide dismutase levels, reducing the percentage of γH₂ A.X, p16, IL-1β, and TNF-α-positive cells and decreasing γH2A.X, p16, p19, p53, p21, IL-1β, and IL-6 expression levels. Furthermore, 1,25(OH)₂ D stimulated the osteogenic differentiation of MSCs, both ex vivo and in vitro, from WT mice but not from Bmi1^-/- mice and 1,25(OH)₂ D administration in vivo increased osteoblastic bone formation in WT, but not in Bmi1 ^-/- mice. Our results indicate that Bmi1, a key downstream target of 1,25(OH)₂ D, plays a crucial role in preventing bone loss induced by 1,25(OH)₂ D deficiency. © 2019 American Society for Bone and Mineral Research.

High-Dose TGF-β1 Impairs Mesenchymal Stem Cell-Mediated Bone Regeneration via Bmp2 Inhibition

Transforming growth factor-β1 (TGF-β1) is a key factor in bone reconstruction. However, its pathophysiological role in non-union and bone repair remains unclear. Here we demonstrated that TGF-β1 was highly expressed in both C57BL/6 mice where new bone formation was impaired after autologous bone marrow mesenchymal stem cell (BMMSC) implantation in non-union patients. High doses of TGF-β1 inhibited BMMSC osteogenesis and attenuated bone regeneration in vivo. Furthermore, different TGF-β1 levels exhibited opposite effects on osteogenic differentiation and bone healing. Mechanistically, low TGF-β1 doses activated smad3, promoted their binding to bone morphogenetic protein 2 (Bmp2) promoter, and upregulated Bmp2 expression in BMMSCs. By contrast, Bmp2 transcription was inhibited by changing smad3 binding sites on its promoter at high TGF-β1 levels. In addition, high TGF-β1 doses increased tomoregulin-1 (Tmeff1) levels, resulting in the repression of Bmp2 and bone formation in mice. Treatment with the TGF-β1 inhibitor SB431542 significantly rescued BMMSC osteogenesis and accelerated bone regeneration. Our study suggests that high-dose TGF-β1 dampens BMMSC-mediated bone regeneration by activating canonical TGF-β/smad3 signaling and inhibiting Bmp2 via direct and indirect mechanisms. These data collectively show a previously unrecognized mechanism of TGF-β1 in bone repair, and TGF-β1 is an effective therapeutic target for treating bone regeneration disability. © 2019 American Society for Bone and Mineral Research.

The Unmixing Problem: A Guide to Applying Single-Cell RNA Sequencing to Bone

Bone is composed of a complex mixture of many dynamic cell types. Flow cytometry and in vivo lineage tracing have offered early progress toward deconvoluting this heterogeneous mixture of cells into functionally well-defined populations suitable for further studies. Single-cell sequencing is poised as a key complementary technique to better understand the cellular basis of bone metabolism and development. However, single-cell sequencing approaches still have important limitations, including transcriptional effects of cell isolation and sparse sampling of the transcriptome, that must be considered during experimental design and analysis to harness the power of this approach. Accounting for these limitations requires a deep knowledge of the tissue under study. Therefore, with the emergence of accessible tools for conducting and analyzing single-cell RNA sequencing (scRNA-seq) experiments, bone biologists will be ideal leaders in the application of scRNA-seq to the skeleton. Here we provide an overview of the steps involved with a single-cell sequencing analysis of bone, focusing on practical considerations needed for a successful study. © 2019 American Society for Bone and Mineral Research.

The Role of the Nuclear Envelope Protein MAN1 in Mesenchymal Stem Cell Differentiation

Mutations in MAN1, a protein of the nuclear envelope, cause bone phenotypes characterized by hyperostosis. The mechanism of this pro-osteogenic phenotype remains unknown. We increased and decreased MAN1 expression in mesenchymal stem cells (MSC) upon which standard osteogenic and adipogenic differentiation were performed. MAN1 knockdown increased osteogenesis and mineralization. In contrast, osteogenesis remained stable upon MAN1 overexpression. Regarding a mechanism, we found that low levels of MAN1 facilitated the nuclear accumulation of regulatory smads and smads-related complexes, with a concurrently high expression of nuclear β-Catenin. In addition, we found adipogenesis to be decreased in both conditions, although predominantly affected by MAN1 overexpression. Finally, lamin A, a protein of the nuclear envelope that regulates MSC differentiation, was unaffected by changes in MAN1. In conclusion, our studies demonstrated that lower levels of MAN1 in differentiating MSC are associated with higher osteogenesis and lower adipogenesis. High levels of MAN1 only affected adipogenesis. These effects could have an important role in the understanding of the role of the proteins of the nuclear envelope in bone formation. J. Cell. Biochem. 118: 4425-4435, 2017. © 2017 Wiley Periodicals, Inc.

Functional and Structural Assessment of the Effect of Human Umbilical Cord Blood Mesenchymal Stem Cells in Doxorubicin-Induced Cardiotoxicity

Cardiomyopathy induced by doxorubicin (DOX) was recognized at an early stage and also several years after drug administration. Mesenchymal stem cells (MSCs) have many properties that make them suitable for preventive and/or regenerative therapies. In this study, we evaluated the effect of MSCs in the functional and the structural improvement of DOX-induced cardiomyopathy in rats. Ninety adult male albino rats were randomly divided into three equal groups of thirty rats each: Group I (control): rats received normal saline. Group II (DOX- group): rats received DOX. Group III (DOX-MSCs group): rats received DOX for 2 weeks then human umbilical cord blood mesenchymal stem cells (hUCB-MSCs). Rats in all groups were evaluated for: physical condition, electrocardiography (ECG), and hemodynamic parameters. Serum cardiac troponin I (cTnI), malondialdehyde (MDA), total antioxidant capacity (TAC), and DNA fragmentation on heart tissue isolated DNA were estimated for evaluation of the mechanism and the extent of the damage. Hearts were examined histopathologically for detection of MSCs homing, structural evaluation, with counting of the collagen fibers for evaluation of fibrosis. DOX-administered rats showed significant functional and structural deterioration. DOX-MSCs treated rats (group III) showed improved functional and structural criteria with restoration of all biochemical indicators of cardiac damage and reactive oxygen species (ROS) to normal, as well. In Conclusion, hUCB-MSCs significantly ameliorated the cardiotoxic manifestations as shown by biochemical, functional, and structural cardiac improvement. J. Cell. Biochem. 118: 3119-3129, 2017. © 2017 Wiley Periodicals, Inc.

Breast Cancer Stem Cell Therapeutics, Multiple Strategies Versus Using Engineered Mesenchymal Stem Cells With Notch Inhibitory Properties: Possibilities and Perspectives

Relapse cases of cancers are more vigorous and difficult to control due to the preponderance of cancer stem cells (CSCs). Such CSCs that had been otherwise dormant during the first incidence of cancer gradually appear as radiochemoresistant cancer cells. Hence, cancer therapeutics aimed at CSCs would be an effective strategy for mitigating the cancers during relapse. Alternatively, CSC therapy can also be proposed as an adjuvant therapy, along-with the conventional therapies. As regenerative stem cells (RSCs) are known for their trophic effects, anti-tumorogenicity, and better migration toward an injury site, this review aims to address the use of adult stem cells such as dental pulp derived; cord blood derived pure populations of regenerative stem cells for targeting CSCs. Indeed, pro-tumorogenicity of RSCs is of concern and hence has also been dealt with in relation to breast CSC therapeutics. Furthermore, as notch signaling pathways are upregulated in breast cancers, and anti-notch antibody based and sh-RNA based therapies are already in the market, this review focuses the possibilities of engineering RSCs to express notch inhibitory proteins for breast CSC therapeutics. Also, we have drawn a comparison among various possibilities of breast CSC therapeutics, about, notch1 inhibition. J. Cell. Biochem. 119: 141-149, 2018. © 2017 Wiley Periodicals, Inc.

Metabolic Oscillations in Co-Cultures of Hepatocytes and Mesenchymal Stem Cells: Effects of Seeding Arrangement and Culture Mixing

In vitro assembly of functional liver tissue is a prerequisite for the transplantation of tissue-engineered livers. There is an increasing demand for in vitro models that replicate complex events occurring in the liver. However, tissue engineering of implantable liver systems is currently limited by the difficulty of assembling three dimensional hepatocyte cultures of a useful size, while maintaining full cell viability. Recent reports have demonstrated that bone marrow mesenchymal stem cells (BM-MSCs) can provide a number of cues promoting hepatocyte growth and development. In this study, the effects of BM-MSCs co-culture on hepatocyte metabolism were evaluated as a function of scaffold seeding arrangement. BM-MSCs were co-cultured with hepatocytes in porous chitosan-heparin scaffolds using several seeding arrangements. The seeded scaffolds were subjected to orbital shaking to enhance mass transfer. BM-MSC-hepatocyte co-cultures exhibited higher rates of hepatocyte-specific functions, compared to hepatocyte-only cultures, regardless of the seeding arrangement. Cells formed smaller-compact spheroids in the heterotypic systems compared to mono-cultures of hepatocytes only. The spheroids exhibited reduction in size with time in all conditions except for the condition where BM-MSCs were seeded one day after seeding hepatocytes. In this condition, spheroids increased in size due to BM-MSC proliferation. Spheroid size reduction was hypothesized to be the result of cyclic shear stresses generated by the orbital shaking. Furthermore, results suggested that BM-MSC seeding onto preformed hepatocyte spheroids provide a degree of shear-protection and trophic stimuli. Overall, the results indicate that co-culturing hepatocytes with BM-MSCs enhanced their metabolic functions for the first week of culture. J. Cell. Biochem. 118: 3003-3015, 2017. © 2017 Wiley Periodicals, Inc.

Shielding Engineered Islets With Mesenchymal Stem Cells Enhance Survival Under Hypoxia

In the present study we focused on the improvisation of islet survival in hypoxia.The Islet like cell aggregates (ICAs) derived from wharton's jelly mesenchymal stem cells (WJ MSC) were cultured with and without WJ MSC for 48 h in hypoxia and normoxia and tested for their direct trophic effect on β cell survival. The WJ MSCs themselves secreted insulin upon glucose challenge and expressed the pancreatic markers at both transcription and translational level (C-peptide, Insulin, Glucagon, and Glut 2). Direct contact of MSCs with ICAs facilitated highest viability under hypoxia as evidenced by fluorescein diacetate/propidium iodide and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The cytokine analysis of the co-cultured ICAs revealed amplification of anti-inflammatory cytokine like TGFβ and TNFα accompanied by depletion of pro-inflammatory cytokines. The increment in VEGF and PDGFa was also seen showing their ability to vascularize upon transplantation. This was further accompanied by reduction in total reactive oxygen species, nitric oxide, and super oxide ions and down regulation of Caspase3, Caspase8, p53, and up regulation of Bcl2 confirming prevention of apoptosis in ICAs. The western blot analysis confirmed the cytoprotective effect of WJ MSC on ICAs as they enhanced the anti-apoptotic marker BCL2 and reduced the expression of apoptotic markers, Annexin 5 and Caspase 3. There was a significant reduction in the expression of p38 protein in the presence of MSCs making the ICAs responsive to glucose. Taken together our data demonstrate for the first time that the WJ MSC expressed pancreatic markers and their supplementation protected engineered islets against hypoxia and oxidative stress. J. Cell. Biochem. 118: 2672-2683, 2017. © 2017 Wiley Periodicals, Inc.

Long Non-Coding RNA MALAT1 Promotes Proliferation, Angiogenesis, and Immunosuppressive Properties of Mesenchymal Stem Cells by Inducing VEGF and IDO

Mesenchymal stem cells (MSCs) play an important role in regulating angiogenesis and immune balance. The abnormal MSCs in proliferation and function were reported at maternal fetal interface in patients with pre-eclampsia (PE). Long non-coding RNA MALAT1 was known to regulate the function of trophoblast cells. However, it is not clear whether MALAT1 regulates MSCs to be related to PE. In the present study, we found that the expression of MALAT1 was significantly reduced in both umbilical cord tissues and MSCs in patients with severe PE. MALAT1 did not affect the phenotype and differentiation of MSCs. Of note, transfection with MALAT1 plasmid into MSCs drove the cell cycle into G2/M phase and inhibited cell apoptosis. The supernatants from MALAT1-overexpressed MSCs promoted the migration of MSCs, invasion of HTR-8/SVneo and tube formation of HUVEC, while si-MALAT1 had the opposite effects. Moreover, we found that MALAT1-induced VEGF mediated these effects of MALAT1 on MSCs. Furthermore, we found that MALAT1-overexpressed MSCs promoted M2 macrophage polarization and this effect was mediated by MALAT1-induced IDO expression, suggesting that MALAT1 may enhance the immunosuppressive properties of MSCs in vivo. In addition, we also investigated the factors that inhibit MALAT1 expression in PE and found that peroxide was a cause for MALAT1 downregulation. Taken together, our data demonstrate that MALAT1 is an important endogenous regulator in the proliferation, angiogenesis, and immunosuppressive properties of MSCs, suggesting it may be involved in the pathogenesis of PE. J. Cell. Biochem. 118: 2780-2791, 2017. © 2017 Wiley Periodicals, Inc.

Prevention of Oxygen Inhibition of PolyHIPE Radical Polymerization using a Thiol-based Crosslinker

Polymerized high internal phase emulsions (polyHIPEs) are highly porous constructs currently under investigation as tissue engineered scaffolds. We previously reported on the potential of redox-initiated polyHIPEs as injectable bone grafts that space fill irregular defects with improved integration and rapid cure. Upon subsequent investigation, the radical-initiated cure of these systems rendered them susceptible to oxygen inhibition with an associated increase in uncured macromer in the clinical setting. In the current study, polyHIPEs with increased resistance to oxygen inhibition were fabricated utilizing a tetrafunctional thiol, pentaerythritol tetrakis(3-mercaptoproprionate), and the biodegradable macromer, propylene fumarate dimethacrylate. Increased concentrations of the tetrathiol additive provided improved oxygen resistance as confirmed by polyHIPE gel fraction while retaining the requisite rapid cure rate, compressive properties, and pore architecture for use as an injectable bone graft. Additionally, thiol-methacrylate polyHIPEs exhibited increased degradation under accelerated conditions and supported critical markers of human mesenchymal stem cell activity. In summary, we have improved upon current methods of fabricating injectable polyHIPE grafts to meet translational design goals of improved polymerization kinetics under clinically relevant conditions without sacrificing key scaffold properties.

Real-Time H2 O2 Measurements in Bone Marrow Mesenchymal Stem Cells (MSCs) Show Increased Antioxidant Capacity in Cells From Osteoporotic Women

Oxidative stress (OS) derived from an increase in intracellular reactive oxygen species (ROS) is a major determinant of aging and lifespan. It has also been associated with several age-related disorders, like postmenopausal osteoporosis of Mesenchymal stem cells (MSCs). MSCs are the common precursors for osteoblasts and adipocytes; appropriate commitment and differentiation of MSCs into a specific phenotype is modulated, among other factors, by ROS balance. MSCs have shown more resistance to ROS than differentiated cells, and their redox status depends on complex and abundant anti-oxidant mechanisms. The purpose of this work was to analyze in real time, H₂ O₂ signaling in individual h-MSCs, and to compare the kinetic parameters of H₂ O₂ management by cells derived from both control (c-) and osteoporotic (o-) women. For these purposes, cells were infected with a genetically encoded fluorescent biosensor named HyPer, which is specific for detecting H₂ O₂ inside living cells. Subsequently, cells were sequentially challenged with 50 and 500 μM H₂ O₂ pulses, and the cellular response was recorded in real time. The results demonstrated adequate expression of the biosensor allowing registering fluorescence from HyPer at a single cell level. Comparison of the response of c- and o-MSCs to the oxidant challenges demonstrated improved antioxidant activity in o-MSCs. This was further corroborated by measuring the relative expression of mRNAs for catalase, superoxide dismutase-1, thioredoxine, and peroxiredoxine, as well as by cell-surviving capacity under short-term H₂ O₂ treatment. We conclude that functional differences exist between healthy and osteoporotic human MSCs. The mechanism for these differences requires further study. J. Cell. Biochem. 118: 585-593, 2017. © 2016 Wiley Periodicals, Inc.

3, 3', 5-triiodo-L-thyronine Increases In Vitro Chondrogenesis of Mesenchymal Stem Cells From Human Umbilical Cord Stroma Through SRC2

Our group focuses on the study of mesenchymal stem cells (MSCs) from human umbilical cord stroma or Warthońs jelly and their directed differentiation toward chondrocyte-like cells capable of regenerating damaged cartilage when transplanted into an injured joint. This study aimed to determine whether lactogenic hormone prolactin (PRL) or 3, 3', 5-triiodo-L-thyronine (T3), the active thyroid hormone, modulates chondrogenesis in our in vitro model of directed chondrogenic differentiation, and whether Wnt signalling is involved in this modulation. MSCs from human umbilical cord stroma underwent directed differentiation toward chondrocyte-like cells by spheroid formation. The addition of T3 to the chondrogenic medium increased the expression of genes linked to chondrogenesis like collagen type 2, integrin alpha 10 beta 1, and Sox9 measured by quantitative real time polymerase chain reaction (qRT-PCR) analysis. Levels of collagen type 2 and aggrecane analyzed by immunohistochemistry, and staining by Safranin O were increased after 14 days in spheroid culture with T3 compared to those without T3 or only with PRL. B-catenin, Frizzled, and GSK-3β gene expressions were significantly higher in spheroids cultured with chondrogenic medium (CM) plus T3 compared to CM alone after 14 days in culture. The increase of chondrogenic differentiation was inhibited when the cells were treated with T3 plus ML151, an inhibitor of the T3 steroid receptor. This work demonstrates, for first time, that T3 promotes differentiation towards chondrocytes-like cells in our in vitro model, that this differentiation is mediated by steroid receptor co-activator 2 (SRC2) and does not induce hypertrophy. J. Cell. Biochem. 117: 2097-2108, 2016. © 2016 Wiley Periodicals, Inc.

Neurogenic Differentiation of Mesenchymal Stem Cells Induces Alterations in Extracellular Nucleotides Metabolism

The presented results show for the first time that the neurogenic transdifferentiation of hUC-MSCs considerably changes the elements of purinergic signaling profile. Although, it has been demonstrated in the literature that extracellular nucleotides and nucleosides determine the fate of mesenchymal and neural stem cells, there is lack of comprehensive studies on the activity of ecto-enzymes metabolizing nucleotides on the surface of neurogenically induced cells. Our study shows that human UC-MSCs sense the microenvironment and adjust their response to the environmental signals for example, adenine nucleotides and nucleosides. Nucleotides, and not adenosine, signaling alters the biological potential of MSCs-decreases their proliferation rate, increases the neurogenic transdifferentiation efficiency expressed as the number of positively labeled NCAM⁺ and A2B5⁺ cells and simultaneously increases the ecto-nucleotidases activity on neural- and glial-committed precursors. Purines implication in the proliferative and neurogenic potential of hUC-MSCs is of strong importance for the in vitro propagation of hUC-MSCs and for their successive therapeutic applications. J. Cell. Biochem. 118: 478-486, 2017. © 2016 Wiley Periodicals, Inc.

Chondrogenic Differentiation of Human Mesenchymal Stem Cells Results in Substantial Changes of Ecto-Nucleotides Metabolism

Mesenchymal stem cells (MSCs) are population of adult stem cells and attractive candidates for cartilage repair due to their chondrogenic potential. Purinergic compounds (purinergic receptors and ecto-enzymes metabolizing nucleotides), together with nucleotides/nucleosides present in the extracellular environment, are known to play a key role in controlling the stem cells biological potential to proliferate and differentiate. Despite the available literature pointing to the importance of purinergic signaling in controlling the fate of MSCs, the research results linking nucleotides and ecto-nucleotidases with MSCs chondrogenic differentiation are indigent. Therefore, the aim of presented study was the characterization of the ecto-nucleotides hydrolysis profile and ecto-enzymes expression in human umbilical cord-derived MSCs and chondrogenically induced MSCs. We described substantial changes of ecto-nucleotides metabolism and ecto-enzymes expression profiles resulting from chondrogenic differentiation of human umbilical cord-derived MSCs. The increased rate of ADP hydrolysis, measured by ecto-nucleotidases activity, plays a pivotal role in the regulation of cartilage formation and resorption. Despite the increased level of NTPDase1 and NTPDase3 mRNA expression in chondrogenically induced MSCs, their activity toward ATP remains quite low. Supported by the literature data, we hypothesize that structure-function relationships in chondrogenic lineage dictate the direction of nucleotides metabolism. In early neocartilage tissue, the beneficial role of ATP in improving biomechanical properties of cartilage does not necessitate the high rate of enzymatic ATP degradation.

Lamin A/C Acts as an Essential Factor in Mesenchymal Stem Cell Differentiation Through the Regulation of the Dynamics of the Wnt/β-Catenin Pathway

Changes in the expression of lamin A/C, a fibrilar protein of the nuclear envelope, are associated with the cellular features of age-related bone loss. Reduced expression of lamin A/C inhibits osteoblastogenesis while facilitating adipogenic differentiation of mesenchymal stem cells (MSC) in vitro and in vivo. In this study we investigated the regulatory role that lamin A/C plays on the essential elements of the Wnt/β-catenin pathway, which are pivotal in MSC differentiation. Initially, we assessed the effect of lamin A/C gene (LMNA) overexpression on MSC differentiation while compared it to lamin A/C depleted MSC. Osteogenesis and gene expression of osteogenic factors were higher in LMNA-transfected MSC as compared to control. Conversely, adipogenesis and expression of adipogenic factors were significantly lower in LMNA transfected cells. Nuclear β-catenin was significantly higher (∼two fold) in MSC expressing higher levels of LMNA as compared to control with nuclear β-catenin levels being significantly lower (∼ -42%) in siRNA-treated MSC. Luciferase activity for β-catenin-mediated transcriptional activation was significantly higher in cells overexpressing LMNA. These data indicate that MSC overexpressing LMNA have higher osteogenic and lower adipogenic differentiation potential. In conclusion, our studies demonstrate that lamin A/C plays a significant role in the differentiation of both osteoblasts and adipocytes by regulating some of the elements of Wnt/β-catenin signaling during early MSC differentiation.

Differential Expression Profiles of Long Noncoding RNA and mRNA of Osteogenically Differentiated Mesenchymal Stem Cells in Ankylosing Spondylitis

OBJECTIVE

We previously demonstrated that mesenchymal stem cells (MSC) from patients with ankylosing spondylitis (AS; ASMSC) have a greater osteogenic differentiation capacity than MSC from healthy donors (HDMSC) and that this difference underlies the pathogenesis of pathological osteogenesis in AS. Here we compared expression levels of long noncoding RNA (lncRNA) and mRNA between osteogenically differentiated ASMSC and HDMSC and explored the precise mechanism underlying abnormal osteogenic differentiation in ASMSC.

METHODS

HDMSC and ASMSC were induced with osteogenic differentiation medium for 10 days. Microarray analyses were then performed to identify lncRNA and mRNA differentially expressed between HDMSC and ASMSC, which were then subjected to bioinformatics analysis and confirmed by quantitative real-time PCR (qRT-PCR) assays. In addition, coding-non-coding gene co-expression (CNC) networks were constructed to examine the relationships between the lncRNA and mRNA expression patterns.

RESULTS

A total of 520 lncRNA and 665 mRNA were differentially expressed in osteogenically differentiated ASMSC compared with HDMSC. Bioinformatics analysis revealed 64 signaling pathways with significant differences, including transforming growth factor-β signaling. qRT-PCR assays confirmed the reliability of the microarray data. The CNC network indicated that 4 differentially expressed lncRNA, including lnc-ZNF354A-1, lnc-LIN54-1, lnc-FRG2C-3, and lnc-USP50-2 may be involved in the abnormal osteogenic differentiation of ASMSC.

CONCLUSION

Our study characterized the differential lncRNA and mRNA expression profiles of osteogenically differentiated ASMSC and identified 4 lncRNA that may participate in the abnormal osteogenic differentiation of ASMSC. These results provide insight into the pathogenesis of pathological osteogenesis in AS.

Mesenchymal stem cells promote epithelial to mesenchymal transition and metastasis in gastric cancer though paracrine cues and close physical contact

Mesenchymal stem cells (MSCs) have been shown to integrate into the tumor stroma; however, the precise mechanisms of this process are still elusive. In this study, the EMT phenotype and the enhanced metastatic ability of tumor cells were observed using transwell and trans-endothelial migration assays, respectively, as well as by using electron and laser confocal microscopy. Critical genes were screened and validated using gene arrays and clinical samples, and the changes at the protein level were examined both in vitro and in vivo. Cancer cells acquired an "activated" carcinoma-associated fibroblasts (CAFs) phenotype after being in close contact with MSCs and enhancing tumor metastasis and growth in vivo. Paracrine signals also induced EMT and promoted transwell and trans-endothelial migration, the changes were dependent on β-catenin, MMP-16, snail and twist. Notably, the higher expression levels of β-catenin and MMP-16 were correlated with tumor invasion and distant organ and lymph node metastases in intestinal type gastric cancer. MSCs within the tumor niche significantly facilitated tumor growth and metastasis by paracrine cues and close physical connection. This occurred partly through snail, twist and its downstream targets, specifically β-catenin/MMP-16.

Fibroblast Growth Factor 2 Regulates High Mobility Group A2 Expression in Human Bone Marrow-Derived Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are an excellent source for numerous cellular therapies due to their simple isolation, low immunogenicity, multipotent differentiation potential and regenerative secretion profile. However, over-expanded MSCs show decreased therapeutic efficacy. This shortcoming may be circumvented by identifying methods that promote self-renewal of MSCs in culture. HMGA2 is a DNA-binding protein that regulates self-renewal in multiple types of stem cells through chromatin remodeling, but its impact on human bone marrow-derived MSCs is not known. Using an isolation method to obtain pure MSCs within 9 days in culture, we show that expression of HMGA2 quickly decreases during early expansion of MSCs, while let-7 microRNAs (which repress HMGA2) are simultaneously increased. Remarkably, we demonstrate that FGF-2, a growth factor commonly used to promote self-renewal in MSCs, rapidly induces HMGA2 expression in a time- and concentration-dependent manner. The signaling pathway involves FGF-2 receptor 1 (FGFR1) and ERK1/2, but acts independent from let-7. By silencing HMGA2 using shRNAs, we demonstrate that HMGA2 is necessary for MSC proliferation. However, we also show that over-expression of HMGA2 does not increase cell proliferation, but rather abrogates the mitogenic effect of FGF-2, possibly through inhibition of FGFR1. In addition, using different methods to assess in vitro differentiation, we show that modulation of HMGA2 inhibits adipogenesis, but does not affect osteogenesis of MSCs. Altogether, our results show that HMGA2 expression is associated with highly proliferating MSCs, is tightly regulated by FGF-2, and is involved in both proliferation and adipogenesis of MSCs. J. Cell. Biochem. 117: 2128-2137, 2016. © 2016 Wiley Periodicals, Inc.

Placenta Mesenchymal Stem Cell Derived Exosomes Confer Plasticity on Fibroblasts

Mesenchymal stem cell (MSC)-conditioned medium (MSC-CM) has been reported to enhance wound healing. Exosomes contain nucleic acids, proteins, and lipids, and function as an intercellular communication vehicle for mediating some paracrine effects. However, the function of MSC-derived exosomes (MSC-exo) remains elusive. In this study, we isolated human placenta MSC (PlaMSC)-derived exosomes (PlaMSC-exo) and examined their function in vitro. PlaMSCs were isolated from human term placenta using enzymatic digestion. PlaMSC-exo were prepared from the conditioned medium of PlaMSC (PlaMSC-CM) by ultracentrifugation. The expression of stemness-related genes, such as OCT4 and NANOG, in normal adult human dermal fibroblasts (NHDF) after incubation with PlaMSC-exo was measured by real-time reverse transcriptase PCR analysis (real-time PCR). The effect of PlaMSC-exo on OCT4 transcription activity was assessed using Oct4-EGFP reporter mice-derived dermal fibroblasts. The stimulating effects of PlaMSC-exo on osteoblastic and adipocyte-differentiation of NHDF were evaluated by alkaline phosphatase (ALP), and Alizarin red S- and oil red O-staining, respectively. The expression of osteoblast- and adipocyte-related genes was also assessed by real-time PCR. The treatment of NHDF with PlaMSC-exo significantly upregulated OCT4 and NANOG mRNA expression. PlaMSC-exo also enhanced OCT4 transcription. The NHDF treated with PlaMSC-exo exhibited osteoblastic and adipocyte-differentiation in osteogenic and adipogenic induction media. PlaMSC-exo increase the expression of OCT4 and NANOG mRNA in fibroblasts. As a result, PlaMSC-exo influence the differentiation competence of fibroblasts to both osteoblastic and adipocyte-differentiation. It shows a new feature of MSCs and the possibility of clinical application of MSC-exo. J. Cell. Biochem. 117: 1658-1670, 2016. © 2015 Wiley Periodicals, Inc.

Mesenchymal Stem Cells Respond to Hypoxia by Increasing Diacylglycerols

Mesenchymal stem cells (MSC) are currently being tested clinically for a plethora of conditions, with most approaches relying on the secretion of paracrine signals by MSC to modulate the immune system, promote wound healing, and induce angiogenesis. Hypoxia has been shown to affect MSC proliferation, differentiation, survival and secretory profile. Here, we investigate changes in the lipid composition of human bone marrow-derived MSC after exposure to hypoxia. Using mass spectrometry, we compared the lipid profiles of MSC derived from five different donors, cultured for two days in either normoxia (control) or hypoxia (1% oxygen). Hypoxia induced a significant increase of total triglycerides, fatty acids and diacylglycerols (DG). Remarkably, reduction of DG levels using the phosphatidylcholine-specific phospholipase C inhibitor D609 inhibited the secretion of VEGF and Angiopoietin-2, but increased the secretion of interleukin-8, without affecting significantly their respective mRNA levels. Functionally, incubation of MSC in hypoxia with D609 inhibited the potential of the cells to promote migration of human endothelial cells in a wound/scratch assay. Hence, we show that hypoxia induces in MSC an increase of DG that may affect the angiogenic potential of these cells.

Aberrant Activation of TGF-β in Subchondral Bone at the Onset of Rheumatoid Arthritis Joint Destruction

Rheumatoid arthritis (RA) is an autoimmune disease that often leads to joint destruction. A myriad of drugs targeting the immune abnormalities and downstream inflammatory cascades have been developed, but the joint destruction is not effectively halted. Here we report that aberrant activation of TGF-β in the subchondral bone marrow by immune response increases osteoprogenitors and uncoupled bone resorption and formation in RA mouse/rat models. Importantly, either systemic or local blockade of TGF-β activity in the subchondral bone attenuated articular cartilage degeneration in RA. Moreover, conditional deletion of TGF-β receptor II (Tgfbr2) in nestin-positive cells also effectively halted progression of RA joint destruction. Our data demonstrate that aberrant activation of TGF-β in the subchondral bone is involved at the onset of RA joint cartilage degeneration. Thus, modulation of subchondral bone TGF-β activity could be a potential therapy for RA joint destruction.

MiR-124 inhibits myogenic differentiation of mesenchymal stem cells via targeting Dlx5

MicroRNAs (miRNAs), including miR-1, miR-133, and miR-206, play a crucial role in muscle development by regulating muscle cell proliferation and differentiation. The aim of the present study was to define the effect of miR-124 on myogenic differentiation of mesenchymal stem cells (MSCs). The expression level of miR-124 in skeletal muscles was much lower than those in primary cultured bone marrow-derived MSCs and the bone, fat and brain tissues obtained from C57BL/6 mice. Myogenic stimuli significantly decreased the expression levels of miR-124 in mouse bone marrow-derived MSCs and C2C12 cells. Forced expression of miR-124 suppressed the expression of myogenic marker genes such as Myf5, Myod1, myogenin and myosin heavy chain and multinucleated myotube formation. Blockade of endogenous miR-124 with a hairpin inhibitor enhanced myogenic marker gene expression and myotube formation. During myogenic differentiation of MSCs and C2C12 cells, the levels of Dlx5, a known target of miR-124, were inversely regulated with those of miR-124. Furthermore, overexpression of Dlx5 increased myogenic differentiation, whereas knockdown of Dlx5 using siRNA inhibited myogenesis in C2C12 cells. These results suggest that miR-124 is a negative regulator of myogenic differentiation of MSCs and that upregulation of Dlx5 accompanied with downregulation of miR-124 by myogenic stimuli is necessary for the proper progression of myogenic differentiation.

Human umbilical cord mesenchymal stem cells alleviate nasal mucosa radiation damage in a guinea pig model

Nasal complications after radiotherapy severely affect the quality of life of nasopharyngeal carcinoma patients, and there is a compelling need to find novel therapies for nasal epithelial cell radiation damage. Therefore, we investigated the therapeutic effect of human umbilical cord mesenchymal stem cells (hUC-MSCs) in guinea pig model of nasal mucosa radiation damage and explored its therapeutic mechanism. Cultured hUC-MSCs were injected intravenously immediately after radiation in the nasal mucosa-radiation-damage guinea pig model. Migration of hUC-MSCs into the nasal mucosa and the potential for differentiation into nasal epithelial cells were evaluated by immunofluorescence. The therapeutic effects of hUC-MSCs were evaluated by mucus clearance time (MCT), degree of nasal mucosa edema, and the nasal mucosa cilia form and coverage ratio. Results indicate that the hUC-MSCs migrated to the nasal mucosa lamina propria and did not differentiate into nasal epithelial cells in this model. The MCT and degree of mucosal edema were improved at 1 week and 1 month after radiation, respectively, but no difference was found at 3 months and 6 months after radiation. The nasal mucosa cilia form and coverage ratio was not improved 6 months after radiation. Thus, hUC-MSCs can migrate to the nasal mucosa lamina propria and improve MCT and mucosa edema within a short time period, but these cells are unable to differentiate into nasal epithelial cells and improve nasal epithelial regeneration in the nasal mucosa radiation damage guinea pig model.

Mesenchymal stem cell trials for pulmonary diseases

All adult tissues, including the lung, have some capacity to self-repair or regenerate through the replication and differentiation of stem cells resident within these organs. While lung resident stem cells are an obvious candidate cell therapy for lung diseases, limitations exist regarding our knowledge of the biology of these cells. In contrast, there is considerable interest in the therapeutic potential of exogenous cells, particularly mesenchymal stem/stromal cells (MSCs), for lung diseases. Bone marrow derived-MSCs are the most studied cell therapy for these diseases. Preclinical studies demonstrate promising results using MSCs for diverse lung disorders, including emphysema, bronchopulmonary dysplasia, fibrosis, and acute respiratory distress syndrome. This mini-review will summarize ongoing clinical trials using MSCs in lung diseases, critically examine the data supporting their use for this purpose, and discuss the next steps in the translational pathway for MSC therapy of lung diseases.

Surface density of vascular endothelial growth factor modulates endothelial proliferation and differentiation

Therapeutic strategies aim to regulate vasculature either by encouraging vessel growth for tissue engineering or inhibiting vascularization around a tumor. Vascular endothelial growth factor (VEGF) is essential to these processes, and there are several strategies that manipulate VEGF signaling. Here we develop a method to control the surface density of VEGF, which is covalently attached to tissue culture polystyrene (TCPS), and explore cellular responses to surfaces with varying VEGF densities. We show that the crosslinker reduces but does not eliminate the biological activity of soluble VEGF as measured by endothelial proliferation. However, endothelial cells cultured on surfaces of covalently bound VEGF did not proliferate in response to surface cues. Interestingly, compared to cells incubated with soluble VEGF (10 ng/ml) and cultured on TCPS, lower cell proliferation was observed when endothelial cells were cultured on high VEGF surface densities (5.9 ng/cm(2)), whereas higher cell proliferation occurred when cells were cultured on low surface densities (0.04 ng/cm(2)). High density surfaces (5.9 ng/cm(2)) also acted in synergy with an inhibitor of VEGF receptors to further suppress endothelial cell proliferation. We also examined the effect of VEGF surfaces on endothelial differentiation of mesenchymal stem cells. No effect was observed when cells were cultured on VEGF surfaces; however, the VEGF surfaces acted in synergy with an inhibitor of VEGF receptors to decrease the ability of differentiated cells to form vascular networks. Together, these results suggest that surface density of bound VEGF can be used to modulate cell behavior and inhibit an angiogenic response.

Preconditioning mesenchymal stem cells with caspase inhibition and hyperoxia prior to hypoxia exposure increases cell proliferation

Myocardial infarction is a leading cause of mortality and morbidity worldwide. Occlusion of a coronary artery produces ischemia and myocardial necrosis that leads to left ventricular (LV) remodeling, dysfunction, and heart failure. Stem cell therapy may decrease infarct size and improve LV function; the hypoxic environment, however, following a myocardial infarction may result in apoptosis, which in turn decreases survival of transplanted stem cells. Therefore, the effects of preconditioned mesenchymal stem cells (MSC) with hyperoxia (100% oxygen), Z-VAD-FMK pan-caspase inhibitor (CI), or both in a hypoxic environment in order to mimic conditions seen in cardiac tissue post-myocardial infarction were studied in vitro. MSCs preconditioned with hyperoxia or CI significantly decreased apoptosis as suggested by TUNEL assay and Annexin V analysis using fluorescence assisted cell sorting. These effects were more profound when both, hyperoxia and CI, were used. Additionally, gene and protein expression of caspases 1, 3, 6, 7, and 9 were down-regulated significantly in MSCs preconditioned with hyperoxia, CI, or both, while the survival markers Akt1, NF-κB, and Bcl-2 were significantly increased in preconditioned MSCs. These changes ultimately resulted in a significant increase in MSC proliferation in hypoxic environment as determined by BrdU assays compared to MSCs without preconditioning. These effects may prove to be of great clinical significance when transplanting stem cells into the hypoxic myocardium of post-myocardial infarction patients in order to attenuate LV remodeling and improve LV function.

Aberrant CpG islands' hypermethylation of ABCB1 in mesenchymal stem cells of patients with steroid-associated osteonecrosis

OBJECTIVE

Patients carrying an ABCB1 polymorphism have a higher risk of developing osteonecrosis of the femoral head (ONFH). We investigated whether aberrant dinucleotide CpG islands' hypermethylation of ABCB1 gene existed in mesenchymal stem cells (MSC) of patients with ONFH, which results in cell dysfunction.

METHODS

Bone marrow was collected from the proximal femur of patients with glucocorticoid (GC)-associated ONFH (n = 22) and patients with new femoral neck fractures (n = 25). MSC were isolated by density gradient centrifugation. We investigated cell viability, intracellular reactive oxygen species (ROS) level, mitochondrial membrane potential (MMP), the amount of P-glycoprotein (P-gp) and ABCB1 transcripts, and methylation at CpG islands of ABCB1 promoter from both the femoral neck fractures group and the GC-associated ONFH group treated with or without the DNA methyltransferase inhibitor, 5'-Aza-2-deoxycytidine (5'-Aza-dC).

RESULTS

We observed that MSC from GC-associated ONFH groups showed reduced proliferation ability, elevated ROS levels, and depressed MMP when compared with the other 2 groups. Low levels of P-gp and ABCB1 transcript, as well as ABCB1 gene hypermethylation, in patients with GC-associated ONFH were also noted. Treatment with 5'-Aza-dC rapidly restored ABCB1 expression. Analysis of general expression revealed that aberrant CpG islands' hypermethylation of ABCB1 caused sensitivity to GC and induced changes in the proliferation and oxidative stress of MSC under GC administration.

CONCLUSION

These data suggest that aberrant CpG islands' hypermethylation of ABCB1 gene may be responsible for individual differences in the development of GC-associated ONFH.

Ubiquitin E3 ligase Wwp1 negatively regulates osteoblast function by inhibiting osteoblast differentiation and migration

Ubiquitin E3 ligase-mediated protein degradation promotes proteasomal degradation of key positive regulators of osteoblast functions. For example, the E3 ligases--SMAD-specific E3 ubiquitin protein ligase 1 (Smurf1), Itch, and WW domain-containing E3 ubiquitin protein ligase 1 (Wwp1)--promote degradation of Runt-related transcription factor 2 (Runx2), transcription factor jun-B (JunB), and chemokine (C-X-C) receptor type 4 (CXCR-4) proteins to inhibit their functions. However, the role of E3 ligases in age-associated bone loss is unknown. We found that the expression level of Wwp1, but not Smurf1 or Itch, was significantly increased in CD45-negative (CD45(-)) bone marrow-derived mesenchymal stem cells from 6-month-old and 12-month-old wild-type (WT) mice. Wwp1 knockout (Wwp1(-/-)) mice developed increased bone mass as they aged, associated with increased bone formation rates and normal bone resorption parameters. Bone marrow stromal cells (BMSCs) from Wwp1(-/-) mice formed increased numbers and areas of alkaline phosphatase(+) and Alizarin red(+) nodules and had increased migration potential toward chemokine (C-X-C motif) ligand 12 (CXCL12) gradients. Runx2, JunB, and CXCR-4 protein levels were significantly increased in Wwp1(-/-) BMSCs. Wwp1(-/-) BMSCs had increased amount of ubiquitinated JunB protein, but Runx2 ubiquitination was no change. Knocking down JunB in Wwp1(-/-) BMSCs returned Runx2 protein levels to that in WT cells. Thus, Wwp1 negatively regulates osteoblast functions by affecting both their migration and differentiation. Mechanisms designed to decrease Wwp1 levels in BMSCs may represent a new approach to prevent the decrease in osteoblastic bone formation associated with aging.