MT1-MMP downregulation via the PI3K/Akt signaling pathway is required for the mechanical stretching-inhibited invasion of bone-marrow-derived mesenchymal stem cells

Mobilization from the bone marrow and the migration of bone-marrow-derived mesenchymal stem cells (BMSCs) through the peripheral circulation to injured tissue sites are regulated by multiple mechanical and chemical factors. We previously demonstrated that mechanical stretching promotes the migration but inhibits the invasion of BMSCs. However, the involved mechanisms, especially the mechanism of stretching-inhibited BMSC invasion, have not been thoroughly elucidated to date. In this study, we found that mechanical stretching with a 10% amplitude at a 1-Hz frequency for 8 hr significantly reduces BMSC invasion and downregulates the expression of membrane type-1 matrix metalloproteinases (MT1-MMP) at both the messenger RNA and protein levels. The overexpression of MT1-MMP restores mechanical stretching-reduced BMSC invasion. Moreover, phosphatidylinositol 3-kinase (PI3K)-dependent Akt phosphorylation in BMSCs was found to be inactivated by mechanical stretching. Pharmacological inhibitors of PI3K/Akt signaling (LY294002 or A443654) reduced the expression of MT1-MMP and impaired BMSC invasion. In addition, the upregulation of Akt phosphorylation by a pharmacological activator (SC79) increased MT1-MMP expression and suppressed mechanical stretching-reduced BMSC invasion. Taken together, our results suggest that mechanical stretching inhibits BMSC invasion by downregulating MT1-MMP expression by suppressing the PI3K/Akt signaling pathway.     

Clonal analysis of synovial fluid stem cells to characterize and identify stable mesenchymal stromal cell/mesenchymal progenitor cell phenotypes in a porcine model: a cell source with enhanced commitment to the chondrogenic lineage

Background aimsPrevious studies have demonstrated that porcine synovial membrane stem cells can adhere to a cartilage defect in vivo through the use of a tissue-engineered construct approach. To optimize this model, we wanted to compare effectiveness of tissue sources to determine whether porcine synovial fluid, synovial membrane, bone marrow and skin sources replicate our understanding of synovial fluid mesenchymal stromal cells or mesenchymal progenitor cells from humans both at the population level and the single-cell level. Synovial fluid clones were subsequently isolated and characterized to identify cells with a highly characterized optimal phenotype.MethodsThe chondrogenic, osteogenic and adipogenic potentials were assessed in vitro for skin, bone marrow, adipose, synovial fluid and synovial membrane–derived stem cells. Synovial fluid cells then underwent limiting dilution analysis to isolate single clonal populations. These clonal populations were assessed for proliferative and differentiation potential by use of standardized protocols.ResultsPorcine-derived cells demonstrated the same relationship between cell sources as that demonstrated previously for humans, suggesting that the pig may be an ideal preclinical animal model. Synovial fluid cells demonstrated the highest chondrogenic potential that was further characterized, demonstrating the existence of a unique clonal phenotype with enhanced chondrogenic potential.ConclusionsPorcine stem cells demonstrate characteristics similar to those in human-derived mesenchymal stromal cells from the same sources. Synovial fluid–derived stem cells contain an inherent phenotype that may be optimal for cartilage repair. This must be more fully investigated for future use in the in vivo tissue-engineered construct approach in this physiologically relevant preclinical porcine model.     

Exosomes derived from SDF1-overexpressing mesenchymal stem cells inhibit ischemic myocardial cell apoptosis and promote cardiac endothelial microvascular regeneration in mice with myocardial infarction

Exosomes extracted from mesenchymal stem cells (MSCs) was reported to reduce myocardial ischemia/reperfusion damage. Besides, stromal-derived factor 1 (SDF1a) functions as cardiac repair after myocardial infarction (MI). Therefore, the present study aims to identify whether exosomes (Exo) released from SDF1-overexpressing MSCs display a beneficial effect on ischemic myocardial infarction. Initially, a gain-of-function study was performed to investigate the function of SDF1 in ischemic myocardial cells and cardiac endothelial cells. Coculture experiments were performed to measure potential exosomic transfer of SDF1 from MSCs to ischemic myocardial cells and cardiac endothelial cells. During the coculture experiments, exosome secretion was disrupted by neutral sphingomyelinase inhibitor GW4869 and upregulated exosomal SDF1 using SDF1 plasmid. Effects of Exo-SDF1 on cardiac function in MI mice were investigated in vivo. MSCs suppressed myocardial cell apoptosis and promoted microvascular regeneration of endothelial cells through secretion of exosomes. The addition of GW4869 led to increased apoptotic capacity of myocardial cells, decreased microvascular formation ability of endothelial cells, enhanced autophagy ability, and elevated Beclin-1 level as well as ratio of LC3II/LC3I. Overexpression of SDF1 and Exo-SDF1 inhibited apoptosis and autophagy of myocardial cells, but promoted tube formation of endothelial cells. The interference of PI3K signaling pathway promoted apoptosis and autophagy of myocardial cells, but inhibited tube formation of endothelial cells. SDF1 activated the PI3K signaling pathway. Exo-SDF1 protected cardiac function of MI mice and inhibited myocardial tissue damage. This study provided evidence that SDF1 overexpression in MSCs-derived exosomes inhibited autophagy of ischemic myocardial cells and promoted microvascular production of endothelial cells.     

Endometrial stromal cells and decidualized stromal cells: Origins,transformation and functions

Decidualization of endometrium, which is characterized by endometrial stromal cell (ESC) decidualization, vascular reconstruction, immune cell recruitment, and plentiful molecule production, is a crucial step for uterus to become receptive for embryo. When implantation takes place, ESCs surround and directly interact with embryo. Decidualized stromal cells (DSCs) are of great importance in endometrial decidualization, having a broad function in regulating immune activity and vascular remodeling of uterus. DSCs are shown to have a higher metabolic level and looser cytoskeleton than ESCs. What's the origin of ESCs and how ESCs successfully transform into DSCs had puzzled scientists in the last decades. Breakthrough had been achieved recently, and many studies had elucidated some of the characters and functions of DSCs. However, several questions still remain unclear. This paper reviews current understanding of where ESCs come from and how ESCs differentiate into DSCs, summarizes some characters and functions of DSCs, analyzes current studies and their limitations and points out research areas that need further investigation.     

The cultivation conditions affect the aggregation and functionality of β‐cell lines alone and in coculture with mesenchymal stromal/stem cells

The manufacturing of viable and functional β‐cell spheroids is required for diabetes cell therapy and drug testing. Mesenchymal stromal/stem cells (MSCs) are known to improve β‐cell viability and functionality. We therefore investigated the aggregation behavior of three different β‐cell lines (rat insulinoma‐1 cell line [INS‐1], mouse insulinoma‐6 cell line [MIN6], and a cell line formed by the electrofusion of primary human pancreatic islets and PANC‐1 cells [1.1B4]), two MSC types, and mixtures of β‐cells and MSCs under different conditions. We screened several static systems to produce uniform β‐cell and MSC spheroids, finding cell‐repellent plates the most suitable. The three different β‐cell lines differed in their aggregation behavior, spheroid size, and growth in the same static environment. We found no major differences in spheroid formation between primary MSCs and an immortalized MSC line, although both differed with regard to the aggregation behavior of the β‐cell lines. All spheroids showed a reduced viability due to mass transfer limitations under static conditions. We therefore investigated three dynamic systems (shaking multi‐well plates, spinner flasks, and shaking flasks). In shaking flasks, there were no β‐cell‐line‐dependent differences in aggregation behavior, resulting in uniform and highly viable spheroids. We found that the aggregation behavior of the β‐cell lines changed in a static coculture with MSCs. The β‐cell/MSC coculture conditions must be refined to avoid a rapid segregation into distinct populations under dynamic conditions.     

The effects of retinoic acid on reversing the adipocyte differentiation into an osteoblastic tendency in ST2 cells, a murine bone marrow-derived stromal cell line

Although the mouse bone marrow stromal cell line ST2 has been known to be differentiated into osteoblasts, the differentiation characteristics of the cell into adipocyte and the concerned relationship between its adipogenesis and osteogenesis remains unknown. The adipogenic induction medium which is made up of insulin, dexamethasone (DEX) and 3-isobutyl-1-methylxanthine(IBMX), stimulated the expression of n early adipogenic marker PPAR γ and a late marker GPDH in ST2 cells. The triglyceride accumulation and lipid stain level generated by the induction medium in ST2 cells was inhibited by RA with IC₅₀ at about 1 nM. The induction medium up-regulated expression of PPARγ and GPDH was also inhibited by RA whereas RA (30 nM) exterted no effect on the cell growth. Interestingly, treatment of the cells with induction medium in the presense of RA caused a 3- or 10-fold higher in ALP activity respectively as compared to those treated with RA or the induction medium alone. RT-PCR analysis showed that such a synergistic effect of RA and the induction medium paralleled the process of inhibition on adipogenesis. Additional experiments showed that IBMX played a key role in increasing the effect of RA and ALP activity. Our results suggested that the relationship between adipogenesis and osteogenesis in ST2 cells was reciprocally interrelated and the process of adipogenesis could be potentially reversed into an osteoblastogenic tendency. This is the first report demonstrating that RA transforms adipogenic potential into an osteoblastic tendency. This revised version was published online in July 2006 with corrections to the Cover Date.     

Proinflammatory interleukins' production by adipose tissue‐derived mesenchymal stromal cells: the impact of cell culture conditions and cell‐to‐cell interaction

The impact of culture conditions and interaction with activated peripheral blood mononuclear cells on the interleukin (IL) gene expression profile and proinflammatory IL‐6 and IL‐8 production by adipose‐derived stromal cells (ASCs) was investigated. A microarray analysis revealed a wide range of IL genes either under standard (20%) or hypoxic (5%) O₂ concentrations, some highly up‐regulated at hypoxia. IL‐6 and IL‐8 production was inversely dependent on cell culture density. In early (first–third) passages, IL‐6 and IL‐8 concentration was higher at 20% O₂ and in late (8th‐12th) passages under 5% O₂. Interaction between ASCs and mononuclear cells in indirect setting was accompanied with a significant decrease of IL‐6 and did not result in the elevation of IL‐8 concentration. Thereby, the production of proinflammatory interleukins (IL‐6 and IL‐8) may be affected by the ASC intrinsic features (density in culture, and duration of expansion), as well as by microenvironmental factors, such as hypoxia and the presence of blood‐borne cells. These data are important for elucidating ASC paracrine activity regulation in vitro. They would also be on demand for optimisation of the cell therapy protocols, based on the application of ASC biologically active substances. Copyright © 2015 John Wiley & Sons, Ltd. SIGNIFICANCE PARAGRAPH Ex vivo expansion is widely used for increasing the number of adipose‐derived stromal cells (ASCs) and improving of their quality. The present study was designed to elucidate the particular factors influencing the interleukin production in ASCs. The presented data specified the parameters (i.e. cell density, duration of cultivation, hypoxia, etc.) that should be taken in mind when ASCs are intended to be used in protocols implying their paracrine activity. These data would be of considerable interest for researchers and clinicians working in the biomedical science.     

Differences in the expression of chromosome 1 genes between lung telocytes and other cells: mesenchymal stem cells,fibroblasts, alveolar type II cells,airway epithelial cells and lymphocytes

Telocytes (TCs) are a unique type of interstitial cells with specific, extremely long prolongations named telopodes (Tps). Our previous study showed that TCs are distinct from fibroblasts (Fbs) and mesenchymal stem cells (MSCs) as concerns gene expression and proteomics. The present study explores patterns of mouse TC‐specific gene profiles on chromosome 1. We investigated the network of main genes and the potential functional correlations. We compared gene expression profiles of mouse pulmonary TCs, MSCs, Fbs, alveolar type II cells (ATII), airway basal cells (ABCs), proximal airway cells (PACs), CD8⁺ T cells from bronchial lymph nodes (T‐BL) and CD8⁺ T cells from lungs (T‐LL). The functional and feature networks were identified and compared by bioinformatics tools. Our data showed that on TC chromosome 1, there are about 25% up‐regulated and 70% down‐regulated genes (more than onefold) as compared with the other cells respectively. Capn2, Fhl2 and Qsox1 were over‐expressed in TCs compared to the other cells, indicating that biological functions of TCs are mainly associated with morphogenesis and local tissue homoeostasis. TCs seem to have important roles in the prevention of tissue inflammation and fibrogenesis development in lung inflammatory diseases and as modulators of immune cell response. In conclusion, TCs are distinct from the other cell types.     

MT1-MMP down-regulates the glucose 6-phosphate transporter expression in marrow stromal cells: a molecular link between pro-MMP-2 activation, chemotaxis, and cell survival

Bone marrow-derived stromal cells (BMSC) are avidly recruited by experimental vascularizing tumors, which implies that they must respond to tumor-derived growth factor cues. In fact, BMSC chemotaxis and cell survival are regulated, in part, by the membrane type-1 matrix metalloproteinase (MT1-MMP), an MMP also involved in pro-MMP-2 activation and in degradation of the extracellular matrix (ECM). Given that impaired chemotaxis was recently observed in bone marrow cells isolated from a glucose 6-phosphate transporter-deficient (G6PT-/-) mouse model, we sought to investigate the potential MT1-MMP/G6PT signaling axis in BMSC. We show that MT1-MMP-mediated activation of pro-MMP-2 by concanavalin A (ConA) correlated with an increase in the sub-G1 cell cycle phase as well as with cell necrosis, indicative of a decrease in BMSC survival. BMSC isolated from Egr-1-/- mouse or MT1-MMP gene silencing in BMSC with small interfering RNA (siMT1-MMP) antagonized both the ConA-mediated activation of pro-MMP-2 and the induction of cell necrosis. Overexpression of recombinant full-length MT1-MMP triggered necrosis and this was signaled through the cytoplasmic domain of MT1-MMP. ConA inhibited both the gene and protein expression of G6PT, while overexpression of recombinant G6PT inhibited MT1-MMP-mediated pro-MMP-2 activation but could not rescue BMSC from ConA-induced cell necrosis. Cell chemotaxis in response to the tumorigenic growth factor sphingosine 1-phosphate was significantly abrogated in siMT1-MMP BMSC and in chlorogenic acid-treated BMSC. Altogether, we provide evidence for an MT1-MMP/G6PT signaling axis that regulates BMSC survival, ECM degradation, and mobilization. This may lead to optimized clinical applications that use BMSC as a platform for the systemic delivery of therapeutic or anti-cancer recombinant proteins in vivo.     

STRO-1, HOP-26 (CD63), CD49a and SB-10 (CD166) as markers of primitive human marrow stromal cells and their more differentiated progeny: a comparative investigation in vitro

There is widespread interest in the use of bone marrow stromal cells (BMSC) for tissue reconstruction and repair and for gene therapy. BMSC represent the differentiated progeny of CFU-F, which however comprise a developmentally heterogeneous population as is reflected in the cellular heterogeneity of the cell populations to which they give rise. We have compared the efficacy of monoclonal antibodies recognising a series of stromal antigens, viz. STRO-1, HOP-26, CD49a and SB-10/CD166, as tools for the enrichment of CFU-F prior to culture and as developmental markers for culture-expanded BMSC. In freshly isolated bone marrow mononuclear cells (BMMNC), the proportion of antigen-positive cells was 27%, 46%, 5% and 19% for STRO-1, HOP-26, CD49a and CD166, respectively. All CD49a⁺ cells co-expressed STRO-1. The degree of CFU-F enrichment obtained with anti-CD49a (~18-fold) by a one-pass immunoselection strategy was significantly greater than that of all other antibodies tested. BMSC expressed higher levels of all antigens investigated (except for HOP-26) compared with BMMNC. Expression of STRO-1 and CD49a remained restricted to a subset of BMSC, whereas all BMSC were SB-10/CD166 positive. Treatment with dexamethasone (10 nM), which promotes the differentiation and further maturation of cells of the osteogenic lineage in this cell culture system, increased the expression of CD49a and HOP-26. The CD49a⁺ and HOP-26⁺ fractions of BMSC were further subdivided by dual-labelling with anti-STRO-1 and B4–78 (an antibody recognising the B/L/K isoform of the enzyme alkaline phosphatase), respectively. By using a variety of criteria, the HOP-26 antigen was identified as CD63, a member of the tetraspanin family of proteins thought to modulate integrin compartmentalisation and signalling.K.S., S.W., C.M.J. and J.A.L. gratefully acknowledge the financial support of the University Bath, the Arthritis Research Campaign and the Wellcome Trust     

S14 protein in breast cancer cells: direct evidence of regulation by SREBP-1c, superinduction with progestin, and effects on cell growth

Most breast cancers exhibit brisk lipogenesis, and require it for growth. S14 is a lipogenesis-related nuclear protein that is overexpressed in most breast cancers. Sterol response element-binding protein-1c (SREBP-1c) is required for induction of lipogenesis-related genes, including S14 and fatty acid synthase (FAS), in hepatocytes, and correlation of SREBP-1c and FAS expression suggested that SREBP-1c drives lipogenesis in tumors as well. We directly tested the hypothesis that SREBP-1c drives S14 expression and mediates lipogenic effects of progestin in T47D breast cancer cells. Dominant-negative SREBP-1c inhibited induction of S14 and FAS mRNAs by progestin, while active SREBP-1c induced without hormone and superinduced in its presence. Changes in S14 mRNA were reflected in protein levels. A lag time and lack of progestin response elements indicated that S14 and FAS gene activation by progestin is indirect. Knockdown of S14 reduced, whereas overexpression stimulated, T47D cell growth, while nonlipogenic MCF10a mammary epithelial cells were not growth-inhibited. These data directly demonstrate that SREBP-1c drives S14 gene expression in breast cancer cells, and progestin magnifies that effect via an indirect mechanism. This supports the prediction, based on S14 gene amplification and overexpression in breast tumors, that S14 augments breast cancer cell growth and survival.     

Transforming growth factor-beta3 promotes mesenchymal cell proliferation and angiogenesis mediated by the enhancement of cyclin D1, Flk-1, and CD31 gene expression during CL/Fr mouse lip fusion

BACKGROUND: Cleft lip with or without cleft palate is the most common congenital anomaly in the craniofacial region. Knowledge of the molecular mechanisms behind normal lip fusion can contribute to better intervention and improved functional clinical outcome. Transforming growth factor-beta3 (TGF-beta3) has been implicated in lip morphogenesis. Therefore, we hypothesized that TGF-beta3 functions during lip fusion through regulation of angiogenesis and mesenchymal cell cycle progression during early developmental stages. METHODS: To test this hypothesis we used the CL/Fraser mouse model, which has a high incidence of cleft lip. Lips isolated from embryonic day (ED) 11.5 mouse embryos were allowed to develop in serum-free organ cultures in the presence or absence of TGF-beta3. The lips that developed in these cultures fused in 2 days. RESULTS: During normal development, we detected positive immunoreactions for TGF-beta3 at the site of fusion. We also detected mesenchymal cells that were immunopositive for Flk-1 and CD31, which are markers for endothelial cell precursors. Exogenous TGF-beta3 accelerated lip fusion in culture. This enhancement was associated with an increase in the number of capillary blood vessels in the lips cultured in the presence of TGF-beta3, in comparison with controls. In tandem, TGF-beta3 increased the level of expression of both Flk-1 and CD31. Our data suggest that an elevated level of TGF-beta3 may promote angiogenesis in developing lips that is mediated by increased Flk-1 and CD31 expression. We also detected increased cyclin D1 expression (a marker for cell proliferation) in the presence of TGF-beta3, which suggests that TGF-beta3 promoted cell proliferation. CONCLUSIONS: TGF-beta3 promoted cell proliferation and angiogenesis in lip mesenchymal tissues. These events led to enhanced lip fusion in the presence of TGF-beta3.     

Biological effects of a relatively low concentration of 1-b-D-arabinofuranosylcytosine in K562 cells: Alterations of the cell cycle,erythroid-differentiation,and apoptosis

Therapeutic strategies for leukemia are directed to induction of differentiation and apoptosis as well as growth inhibition. One of the key antileukemic agents, 1--D-arabinofuranosylcytosine (ara C), is clinically applied according to these therapeutic aims. However, the molecular effects of 0.1 g/ml of ara C, a concentration that corresponds to the serum level in leukemic patients on a conventional dose of ara C, have not been well disclosed. Here, we addressed these issues using K562 cells which derived from a blastic crisis of chronic myeloid leukemia. DNA synthesis of treated cells was suppressed from 1-6 h. But, it recovered at 12 h and no further inhibition was observed. The number of cells was not decreased but DNA fragmentation was observed at 72 h. The number of erythroid-differentiated cells also increased to 30% at 72 h. Along with treatment, no marked alteration of mRNAs for cell cycle-regulating genes was found and the retinoblastoma gene product remained hyperphosphorylated throughout treatment. The expression of mRNAs for apoptosis-regulating genes also remained unchanged, except for slight down-regulation of Bax. c-myc protein was not found later than 48 h, and Max mRNA was downregulated. c-jun was immediately induced, followed by the fluctuated expression level along with treatment. These findings suggest that the 0.1 g/ml ara C changed the proliferation, differentiation and death of K562 cells in a biphasic manner. In the early phase, DNA synthesis was inhibited without altering the expression of cell cycle regulating-genes. In the latter phase, cell death and erythroid- differentiation occurred in accordance with the down-regulation of c-myc.