Laminin Production and Basement Membrane Deposition by Mesenchymal Stem Cells upon Adipogenic Differentiation |
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Authors: | Ariel Noro Tarvo Sillat Ismo Virtanen Sulev Ingerpuu Nils B?ck Yrj? T Konttinen Matti Korhonen |
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Institution: | Institute of Biomedicine/Anatomy, University of Helsinki, Helsinki, Finland (AN,TS,IV,NB,MK);Finnish Red Cross Blood Service, Helsinki, Finland (AN,MK);Department of Medicine, UH and HUCH, Helsinki, Finland (TS,YTK);Institute of Molecular and Cell Biology, University of Tartu, Tartu, Estonia (SI);Orton Orthopaedic Hospital of the Invalid Foundation, Helsinki, Finland (YTK);COXA Hospital for Joint Replacement, Tampere, Finland (YTK) |
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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. |
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Keywords: | adipocyte mesenchymal stem cell basement membrane differentiation laminin integrin |
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