title: Increased levels of xylosyltransferase I correlate with the mineralization of the extracellular matrix during osteogenic differentiation of mesenchymal stem cells.
abstract: Mesenchymal stem cells (MSCs) are multipotent adult stem cells capable to differentiate into osteoblasts. Therefore, they represent attractive cell sources for tissue engineering applications, especially for bone replacement. Proteoglycans (PGs) exhibit a crucial role for matrix assembly and remodeling. Nevertheless, since bone development is a highly dynamic and complex process, the regulation of the extracellular matrix (ECM) formation remains elusive. Consequently, the aim of this study was to investigate the mRNA expression levels of genes involved in PG assembly in different stages of osteogenesis. For the rate-limiting enzyme in glycosaminoglycan (GAG) biosynthesis xylosyltransferase I (XT-I), maximal mRNA expression levels (3.89 +/- 0.83-fold increase) and elevated enzyme activities (285 +/- 17 dpm/mug DNA) were observed 10 days after osteogenic induction, simultaneously to the beginning mineralization of the ECM, whereas the highly homologous protein XT-II showed no specific alterations. The differential expression of chondroitin sulfate, dermatan sulfate and heparan sulfate chains was determined by analyzing the mRNA expression of EXTL2 (alpha-1,4-N-acetylhexosaminyltransferase), GalNAcT (beta-1,4-N-acetylgalactosaminyltransferase), and GlcAC5E (glucuronyl C5-epimerase) as they represent crucial enzymes in GAG biosynthesis. Besides GlcAC5E, all key enzymes showed upregulated mRNA contents (up to 3.6-fold) around day 10. Except for decorin, which exhibited heightened mRNA levels even in the early stages of osteogenesis, we found similar upregulated mRNA contents (up to 14.6-fold) for all investigated PG core proteins. The synchronized expression profiles demonstrate the coordinated biosynthesis of the PGs during bone formation and osteogenic stem cell differentiation occurring in parallel to the mineralization of the extracellular matrix.
authors.affiliation: Institut für Laboratoriums- und Transfusionsmedizin, Herz- und Diabesteszentrum NRW, Universitätsklinik der Ruhr-Universität Bochum, Georgstrasse 11, 32545 Bad Oeynhausen, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Müller
authors.forename: Christian
authors.initials: C
authors.lastname: Prante
authors.forename: Martin
authors.initials: M
authors.lastname: Gastens
authors.forename: Joachim
authors.initials: J
authors.lastname: Kuhn
authors.forename: Knut
authors.initials: K
authors.lastname: Kleesiek
authors.forename: Christian
authors.initials: C
authors.lastname: Götting
mesh_terms: D000469:Alkaline Phosphatase / Q000235:genetics / Q000378:metabolism; D058578:Biglycan; D002113:Calcification, Physiologic / Q000235:genetics / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D002238:Carbohydrate Epimerases / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology*; D024042:Collagen Type I / Q000235:genetics; D058575:Decorin; D005109:Extracellular Matrix / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000235:genetics; D015870:Gene Expression; D053673:Glypicans / Q000235:genetics; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism*; D017350:N-Acetylgalactosaminyltransferases / Q000235:genetics; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D010012:Osteogenesis / Q000235:genetics / Q000502:physiology*; D053495:Osteopontin / Q000235:genetics; D010430:Pentosyltransferases / Q000235:genetics / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism; D011509:Proteoglycans / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053669:Syndecan-2 / Q000235:genetics; D053675:Versicans / Q000235:genetics; D000097608:UDP Xylose-Protein Xylosyltransferase
chemical_list: D000469:Alkaline Phosphatase; D058578:Biglycan; D002118:Calcium; D002238:Carbohydrate Epimerases; D024042:Collagen Type I; D058575:Decorin; D016326:Extracellular Matrix Proteins; D053673:Glypicans; D008565:Membrane Proteins; D017350:N-Acetylgalactosaminyltransferases; D017351:N-Acetylglucosaminyltransferases; D053495:Osteopontin; D010430:Pentosyltransferases; D010710:Phosphates; D011509:Proteoglycans; D053669:Syndecan-2; D053675:Versicans; D000097608:UDP Xylose-Protein Xylosyltransferase; C546884:BGN protein, human; C546878:DCN protein, human; C105937:GPC3 protein, human; C508245:SDC2 protein, human; C508322:VCAN protein, human; C110834:EXTL2 protein, human; C023220:(N-acetylneuraminyl)-galactosylglucosylceramide N-acetylgalactosaminyltransferase; C019591:heparosan N-sulfate D-glucuronosyl 5-epimerase