Laminin Production and Basement Membrane Deposition by Mesenchymal Stem Cells upon Adipogenic Differentiation

• Published in: The journal of histochemistry and cytochemistry Vol. 61; no. 10; pp. 719 - 730
• Main Authors: Noro, Ariel, Sillat, Tarvo, Virtanen, Ismo, Ingerpuu, Sulev, Bäck, Nils, Konttinen, Yrjö T., Korhonen, Matti
• Format: Journal Article
• Language: English
• Published: Los Angeles, CA SAGE Publications 01.10.2013
• Subjects: Adipocytes - cytology; Adipocytes - metabolism; Adipogenesis; Adult; Azo Compounds - metabolism; Basement Membrane - metabolism; Gene Expression Regulation; Humans; Laminin - biosynthesis; Laminin - genetics; Laminin - metabolism; Mesenchymal Stromal Cells - cytology; Mesenchymal Stromal Cells - metabolism; Protein Transport; mesenchymal stem cell; laminin; basement membrane; differentiation; integrin; adipocyte
• ISSN: 0022-1554; 1551-5044
• DOI: 10.1369/0022155413502055

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.