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Title: Molecular and functional differences of cells cultured under human Multipotent Adult Progenitor Cell, Mesenchymal Stem Cell and Mesoangioblast conditions
Other Titles: Moleculaire en functionele verschillen van cellen gecultiveerd onder humane Multipotente Adulte Progenitor Cel, Mesenchymale Stamcel en Mesoangioblast condities
Authors: Roobrouck, Valerie
Issue Date: 24-Mar-2011
Abstract: Adult stem cells can be obtained from different somatic tissues and have the capacity to self-renew and differentiate into multiple cell types. Several adherent adult stem cells have been described with different phenotypic and functional properties. As many of these cells are being considered for clinical therapies, it is of great importance that the identity and potency of these products is validated. In 2002, our lab described the derivation of Multipotent Adult Progenitor Cells (MAPC) from postnatal bone marrow (BM), which can be long-term expanded and differentiated towards cells from the three germ layers. Another class of adult stem cells derived from BM are Mesenchymal Stem Cells (MSC), which differentiate towards bone, cartilage, fat, smooth muscle, connective tissue and hematopoietic supportive stroma. Recent studies have suggested that human (h)MSC may be a subpopulation of pericytes. A second population of cells, also thought to be a subpopulation of pericytes, is Mesoangioblasts (Mab). Human Mab are commonly isolated from skeletal muscle tissue and differentiate with high efficiency towards skeletal myofibers both in vitro and in vivo following transplantation in mice with muscular dystrophy. The first objective of this thesis was to compare, in a side by side study, the phenotypic, functional and molecular characteristics of hMSC, hMab and hMAPC using uniform standardized methods. Human MSC and hMAPC were isolated from bone and hMab from skeletal muscle following standard protocols and several independent donors were used to perform the experiments. Human MAPC could be expanded in vitro significantly longer than hMSC and hMab, consistent with a higher and more sustained telomerase activity in hMAPC. Human MAPC, hMSC and hMab were phenotypically distinct and the cell surface antigen CD140b could discriminate among the three cell types, being highly expressed on hMSC, at low levels on hMab and not expressed on hMAPC. Differentiation capacity towards adipocytes, osteoblasts, chondrocytes and smooth muscle cells in vitro was similar among the three cell types. However, only hMab differentiated to skeletal myocytes, while only hMAPC differentiated to endothelium in vitro and in vivo. A comparative transcriptome analysis confirmed that the three cell populations are distinct and revealed gene signatures that correlated with their specific functional properties. Human MSC expressed gene networks involved in the organization of fibrils and filaments and the development of smooth muscle cells. They also expressed gene networks involved in neovascularization, consistent with the notion that BM-MSC may promote postnatal vessel formation. Human Mab were characterized by genes involved in skeletal muscle development and cardiogenesis while hMAPC, consistent with their endothelial potential, expressed genes involved in endothelial differentiation and angiogenesis. The second objective of this thesis was to determine if the phenotypic, functional and molecular features of hMSC, hMab and hMAPC are mediated by the culture conditions. Therefore, cells isolated under one of the three culture conditions were switched to a different condition and grown for a minimum of three passages under the new culture conditions. The comparison was made between hMAPC and hMab and between hMAPC and hMSC, as transcriptome analysis had revealed that the gene expression profiles of hMab and hMSC clustered more closely together. Human MSC and hMab cultured under MAPC conditions became capable of generating endothelial-like cells, whereas hMab lost some of their ability to generate myotubes. By contrast, hMAPC cultured under MSC conditions lost their endothelial differentiation capacity, while this was retained when cultured under Mab conditions. However, myogenic capacity was not gained when hMAPC were cultured under Mab conditions. Furthermore, the global expressed gene profile of hMSC and hMab cultured under MAPC conditions became more similar to that of hMAPC. Likewise, the transcriptome of hMAPC cultured under MSC or Mab conditions became more similar to that of hMSC and hMab, respectively. In conclusion, this study has demonstrated clear phenotypic and in vitro and in vivo functional differences among cultured hMSC, hMab and hMAPC, which was reflected in their transcriptome. Moreover, the study has indicated that the phenotypic and functional properties, as well as the expressed gene profile of these cell populations was not solely determined by cell intrinsic characteristics, but influenced by changes in the culture conditions.
Publication status: published
KU Leuven publication type: TH
Appears in Collections:Interdepartemental Stem Cell Institute (-)
Hematology Section (-)

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