Project description:Development of systems allowing the maintenance of native properties of mesenchymal stromal cells (MSC) is a critical challenge for studying physiological functions of skeletal progenitors, as well as towards cellular therapy and regenerative medicine applications. Conventional stem cell culture in monolayer on plastic dishes (2D) is associated with progressive loss of functionality, likely due to the absence of a biomimetic microenvironment and the selection of adherent populations. Here we demonstrate that 2D MSC expansion can be entirely bypassed by culturing freshly isolated bone marrow cells within the pores of 3D scaffolds in a perfusion-based bioreactor system, followed by enzymatic digestion for cell retrieval. The 3D-perfusion system supported MSC growth while maintaining cells of the hematopoietic lineage, and thus generated a cellular environment mimicking some features of the bone marrow stroma. As compared to 2D-expansion, sorted CD45- cells derived from 3D-perfusion culture after the same time (3 weeks) or a similar extent of proliferation (7-8 doublings) maintained a 4.3-fold higher clonogenicity and exhibited a superior differentiation capacity towards all typical mesenchymal lineages, with similar immunomodulatory function in vitro. Transcriptomic analysis performed on MSC from 5 donors validated the robustness of the process and indicated a reduced inter-donor variability as well as a significant upregulation of multipotency-related gene clusters following 3D-perfusion as compared to 2D expansion. The described system offers a model to study how factors of a 3D engineered niche may regulate MSC function and, by streamlining conventional labor-intensive processes, is prone to automation and scalability within closed bioreactor systems. Nucleated cells were isolated from 5 fresh human bone marrow aspirates by means of red blood cells lyses buffer and then were seeded into a 3D perfusion bioreactor system using a pure hydroxyapatite 3D scaffold and in conventional Petri dishes (2D). After culture for 19 days, cells from both systems were enzymatically retrieved and sorted using anti-CD45-coated magnetic beads. Total RNA was extracted from CD45- cells, QCed and hybridized to Affymetrix microarrays.

Project description:Gene Expression analysis of a differentiation timeseries of human Mesenchymal Stem Cells (hMSCs) in the presence of adipogenic/osteogenic factors. hMSCs differentiate into fat cells when treated with dexamethasone (10^-6 M), insulin (10 ug/ml), rosiglitazone (10^-7 M) and IBMX (250 uM). TGFbeta (5 ng/ml) inhibits this process and redirects these cells to differentiate into bone cells. Introduction: Patients suffering from osteoporosis show an increased number of adipocytes in their bone marrow, concomitant with a reduction in the pool of human mesenchymal stem cells (hMSCs) that are able to differentiate into osteoblasts, thus leading to suppressed osteogenesis. Methods: In order be able to interfere with this process, we have investigated in vitro culture conditions whereby adipogenic differentiation of hMSCs is impaired and osteogenic differentiation is promoted. By means of gene expression microarray analysis, we have investigated genes which are potential targets for prevention of fat cell differentiation. Results: Our data show that BMP2 promotes both adipogenic and osteogenic differentiation of hMSCs, while TGFÎ² inhibits differentiation into both lineages. However, when cells are cultured under adipogenic differentiation conditions, which contains cAMP-enhancing agents such as IBMX of PGE2, TGFÎ² promotes osteogenic differentiation, while at the same time inhibiting adipogenic differentiation. Gene expression and immunoblot analysis indicated that cAMP-induced suppression of HDAC5 levels plays an important role in the inhibitory effect of TGFÎ² on osteogenic differentiation. By means of gene expression microarray analysis, we have investigated genes which are downregulated by TGFÎ² under adipogenic differentiation conditions and may therefore be potential targets for prevention of fat cell differentiation. We thus identified 9 genes for which FDA-approved drugs are available. Our results show that drugs directed against the nuclear hormone receptor PPARG, the metalloproteinase ADAMTS5 and the aldo-keto reductase AKR1B10 inhibit adipogenic differentiation in a dose-dependent manner, although in contrast to TGFÎ² they do not appear to promote osteogenic differentiation. Conclusions: The approach chosen in this study has resulted in the identification of new targets for inhibition of fat cell differentiation, which may not only be relevant for prevention of osteoporosis, but also of obesity. hMSCs were induced to differentiate in the presence dexamethasone, insulin and rosiglitazone, to which was added either 50 ng/ml BMP2; BMP2 + TGFbeta; BMP2 + IBMX; BMP2 + TGFbeta + IBMX.

Project description:Human mesenchymal stem cells (hMSC) have an extensive potential for clinical applications in cell therapy. However, very little is known of the specific molecular regulatory mechanisms that control the therapeutical properties of these cells. We aimed to identify microRNAs (miRNAs) that could be involved in controlling the transition between the self-renewing (undifferentiated) and the reparative (differentiated) phenotypes of hMSCs. MicroRNA microarrays were used to identify miRNAs that are upregulated in undifferentiated hMSCs. For that, we compared the miRNA expression profiles of undifferentiated bone marrow-derived hMSCs with the same primary cell lines after 9 days of in vitro adipogenic or osteogenic induction. We also compared the miRNA expression profiles of undifferentiated hMSCs with skin fibroblasts (a mesenchymal cell lineage with a more restricted differentiation potential). These experiments allowed us to identify miR-335 as the only miRNA downregulated upon MSC differentiation as well as in MSCs in comparison with skin fibroblasts. Gene expression microarrays were used to identify genes that are downregulated in hMSCs overexpressing miR-335. We compared the miRNA expression profiles of hMSCs transduced with a lentiviral vector encoding miR-335 with MSCs transduced with a control lentiviral vector. Our results suggest miR-335 downregulation could be one of the triggers for the initiation of MSCs activities involved in tissue repair and remodelling, including cell migration and differentiation. We compared the miRNA expression profiles of undifferentiated bone marrow-derived hMSCs with the same primary cell lines after 9 days of adipogenic or osteogenic induction, as well as with skin fibroblasts. A total of four independent samples were used for each condition. For the adipogenic/osteogenic vs. undifferentiated MSC comparison, the RNA samples were pooled (two independent samples/pool) before labeling. We also compared the miRNA expression profiles of hMSCs transduced with the lentiviral vector pLV-EmGFP-MIRN335 with MSCs transduced with the control vector pLV-EmGFP-Mock. For the gene expression microarrays, a total of three independent samples were used for each condition.

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