title: Changes of chondrocyte expression profiles in human MSC aggregates in the presence of PEG microspheres and TGF-β3.
abstract: Biomaterial microparticles are commonly utilized as growth factor delivery vehicles to induce chondrogenic differentiation of mesenchymal stem/stromal cells (MSCs). To address whether the presence of microparticles could themselves affect differentiation of MSCs, a 3D co-aggregate system was developed containing an equal volume of human primary bone marrow-derived MSCs and non-degradable RGD-conjugated poly(ethylene glycol) microspheres (PEG-μs). Following TGF-β3 induction, differences in cell phenotype, gene expression and protein localization patterns were found when compared to MSC aggregate cultures devoid of PEG-μs. An outer fibrous layer always found in differentiated MSC aggregate cultures was not formed in the presence of PEG-μs. Type II collagen protein was synthesized by cells in both culture systems, although increased levels of the long (embryonic) procollagen isoforms were found in MSC/PEG-μs aggregates. Ubiquitous deposition of type I and type X collagen proteins was found in MSC/PEG-μs cultures while the expression patterns of these collagens was restricted to specific areas in MSC aggregates. These findings show that MSCs respond differently to TGF-β3 when in a PEG-μs environment due to effects of cell dilution, altered growth factor diffusion and/or cellular interactions with the microspheres. Although not all of the expression patterns pointed toward improved chondrogenic differentiation in the MSC/PEG-μs cultures, the surprisingly large impact of the microparticles themselves should be considered when designing drug delivery/scaffold strategies.
authors.affiliation: Department of Orthopaedic Surgery, Washington University School of Medicine, 660 South Euclid Avenue, St Louis, MO 63110, USA.
authors.forename: Soumya
authors.initials: S
authors.lastname: Ravindran
authors.forename: Jacob L
authors.initials: JL
authors.lastname: Roam
authors.forename: Peter K
authors.initials: PK
authors.lastname: Nguyen
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Hering
authors.forename: Donald L
authors.initials: DL
authors.lastname: Elbert
authors.forename: Audrey
authors.initials: A
authors.lastname: McAlinden
mesh_terms: D000199:Actins / Q000378:metabolism; D002454:Cell Differentiation; D002478:Cells, Cultured; D019902:Chondrocytes / Q000378:metabolism*; D024043:Collagen Type II / Q000378:metabolism; D024121:Collagen Type X / Q000378:metabolism; D020869:Gene Expression Profiling; D006801:Humans; D007150:Immunohistochemistry; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism*; D008863:Microspheres; D009842:Oligopeptides / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry*; D011509:Proteoglycans / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D053782:Transforming Growth Factor beta3 / Q000096:biosynthesis / Q000378:metabolism*
chemical_list: C541116:ACTA2 protein, human; D000199:Actins; D024043:Collagen Type II; D024121:Collagen Type X; D009842:Oligopeptides; D011509:Proteoglycans; D053782:Transforming Growth Factor beta3; D011092:Polyethylene Glycols; C047981:arginyl-glycyl-aspartic acid