title: Laminin production and basement membrane deposition by mesenchymal stem cells upon adipogenic differentiation.
abstract: The aim was to study laminin (LM) synthesis, integration, and deposition into the basement membrane (BM) during adipogenesis. Human bone marrow-derived mesenchymal stromal cells (MSCs) were induced along the adipogenic lineage. LM chain mRNA and protein levels were followed using quantitative real-time polymerase chain reaction (qRT-PCR), immunofluorescence (IF) staining, transmission electron microscopy (TEM), and immunoprecipitation. MSCs produced low levels of LM mRNAs but were not surrounded by BM in IF and TEM imaging. LM-α4, LM-β1, and LM-γ1 mRNAs increased during adipogenesis 3.9-, 5.8-, and 2.8-fold by day 28. LM-411 was immunoprecipitated from the ECM of the differentiated cells. Immunostaining suggested deposition of LM-411 and some LM-421. BM build-up was probably organized in part by integrin (Int) α6β1. At day 28, TEM images revealed BM-like structures around fat droplet-containing cells. The first signs of BM formation and Int α6β1 were seen using IF imaging at day 14. Laminin-411 and Int α6β1 were expressed in vivo in mature human subcutaneous fat tissue. Undifferentiated human MSCs did not organize LM subunits into BM, whereas LM-411 and some LM-421 are precipitated in the BM around adipocytes. This is the first demonstration of LM-411 precipitation during hMSC adipogenesis around adipocytes as a structural scaffold and Int-regulated signaling element.
authors.affiliation: Institute of Biomedicine/Anatomy, University of Helsinki, Helsinki, Finland (AN,TS,IV,NB,MK).
authors.forename: Ariel
authors.initials: A
authors.lastname: Noro
authors.forename: Tarvo
authors.initials: T
authors.lastname: Sillat
authors.forename: Ismo
authors.initials: I
authors.lastname: Virtanen
authors.forename: Sulev
authors.initials: S
authors.lastname: Ingerpuu
authors.forename: Nils
authors.initials: N
authors.lastname: Bäck
authors.forename: Yrjö T
authors.initials: YT
authors.lastname: Konttinen
authors.forename: Matti
authors.initials: M
authors.lastname: Korhonen
mesh_terms: D017667:Adipocytes / Q000166:cytology* / Q000378:metabolism; D050156:Adipogenesis; D000328:Adult; D001391:Azo Compounds / Q000378:metabolism; D001485:Basement Membrane / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D007797:Laminin / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism*; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism*; D021381:Protein Transport
chemical_list: D001391:Azo Compounds; D007797:Laminin; C011049:oil red O
keywords: adipocyte; basement membrane; differentiation; integrin; laminin; mesenchymal stem cell
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