title: Extensive CD44-dependent hyaluronan coats on human bone marrow-derived mesenchymal stem cells produced by hyaluronan synthases HAS1, HAS2 and HAS3.
abstract: Hyaluronan (HA), a natural extracellular matrix component, has been considered as an important constituent of the stem cell niche, and successfully used as 3D scaffolds for the chondrogenic differentiation of stem cells. However, the expression levels of HA synthases (HAS1, 2 and 3) and the synthesis of HA by stem cells have remained unknown, and were studied here in the human bone marrow-derived mesenchymal stem cells (hMSCs). Nine hMSCs from different donors were cultured as monolayers with MSC culture medium supplemented with FGF-2. The amount of HA secreted into medium was studied by an ELISA-type assay, and HA bound to cell surface by live cell microscopy. The expression of HASs was analyzed by real time RT-PCR and immunostainings. The HA receptor CD44 was studied by immunocytochemistry. An intense HA coat surrounded the plasma membrane and its protrusions in all nine hMSCs. Displacement assay with HA oligosaccharides indicated that HA coat was at least partly dependent on CD44, which showed similar, relatively high expression in all hMSCs. All HAS isoenzymes were detected, HAS1 showing the largest and HAS3 the smallest range of expression levels between the hMSCs. The secretion of HA ranged between 22.5 and 397.4 ng/10,000 cells/24h, and could not be clearly assigned to the mRNA level of a certain HAS, or a combination of the isoenzymes. This suggests that post-transcriptional and post-translational factors were involved in the adjustment of the HA secretion. In conclusion, all hMSCs expressed high levels of HAS1-3, secrete large amounts of HA, and surround themselves with a thick HA coat bound to CD44. The results suggest that hMSC has the potential for autocrine maintenance of the HA niche, important for their stemness.
authors.affiliation: Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland; Biocenter Kuopio, University of Eastern Finland, Kuopio, Finland. Electronic address: chengjuan.qu@uef.fi.
authors.forename: Chengjuan
authors.initials: C
authors.lastname: Qu
authors.affiliation: Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland.
authors.forename: Kirsi
authors.initials: K
authors.lastname: Rilla
authors.affiliation: Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland.
authors.forename: Raija
authors.initials: R
authors.lastname: Tammi
authors.affiliation: Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland.
authors.forename: Markku
authors.initials: M
authors.lastname: Tammi
authors.affiliation: Department of Orthopaedics and Traumatology, Kuopio University Hospital, Kuopio, Finland; Bone and Cartilage Research Unit, Surgery, Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland.
authors.forename: Heikki
authors.initials: H
authors.lastname: Kröger
authors.affiliation: Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland; Biocenter Kuopio, University of Eastern Finland, Kuopio, Finland.
authors.forename: Mikko J
authors.initials: MJ
authors.lastname: Lammi
mesh_terms: D001854:Bone Marrow Cells / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D015870:Gene Expression; D014453:Glucuronosyltransferase / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D018960:Hyaluronan Receptors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D000076002:Hyaluronan Synthases; D006820:Hyaluronic Acid / Q000096:biosynthesis; D007150:Immunohistochemistry; D007527:Isoenzymes; D059630:Mesenchymal Stem Cells / Q000201:enzymology / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics
chemical_list: C497483:CD44 protein, human; D018960:Hyaluronan Receptors; D007527:Isoenzymes; D012333:RNA, Messenger; D006820:Hyaluronic Acid; D014453:Glucuronosyltransferase; D000076002:Hyaluronan Synthases
keywords: CD44; Human bone marrow-derived mesenchymal stem cells; Hyaluronan; Hyaluronan synthases (1, 2, 3); Stem cell niche