title: Gene expression profiling of primary human articular chondrocytes in high-density micromasses reveals patterns of recovery, maintenance, re- and dedifferentiation.
abstract: The high-density micromass culture has been widely applied to study chondrocyte cell physiology and pathophysiological mechanisms. Since an integrated image has not been established so far, we analyzed the phenotypic alterations of human articular chondrocytes in this model on the broad molecular level. Freshly isolated chondrocytes were assembled as micromasses and maintained up to 6 weeks in medium containing human serum. Formation of cartilaginous extracellular matrix (ECM) was evaluated by histological and immunohistochemical staining. At 0, 3 and 6 weeks, chondrocyte micromasses were subjected to gene expression analysis using oligonucleotide microarrays and real-time RT-PCR. Micromasses developed a cartilaginous ECM rich in proteoglycans and type II collagen. On gene expression level, time-dependent expression patterns was observed. The induction of genes associated with cartilage-specific ECM (COL2A1 and COL11A1) and developmental signaling (GDF5, GDF10, ID1, ID4 and FGFR1-3) indicated redifferentiation within the first 3 weeks. The repression of genes related to stress response (HSPA1A and HSPA4), apoptotic events (HYOU1, NFKBIA and TRAF1), and degradation (MMP1, MMP10 and MMP12) suggested a recovery of chondrocytes. Constant expression of other chondrogenic (ACAN, FN1 and MGP) and hypertrophic markers (COL10A1, ALPL, PTHR1 and PTHR2) indicated a pattern of phenotypic maintenance. Simultaneously, the expression of chondrogenic growth (BMP6, TGFA, FGF1 and FGF2) and transcription factors (SOX9, EGR1, HES1 and TGIF1), and other cartilage ECM-related genes (COMP and PRG4) was consistently repressed and expression of collagens related to dedifferentiation (COL1A1 and COL3A1) was steadily induced indicating a progressing loss of cartilage phenotype. Likewise, a steady increase of genes associated with proliferation (GAS6, SERPINF1, VEGFB and VEGFC) and apoptosis (DRAM, DPAK1, HSPB, GPX1, NGFRAP1 and TIA1) was observed. Sequence and interplay of identified expression patterns suggest that chondrocyte micromass cultures maintain a differentiated phenotype up to 3 weeks in vitro and might be useful for studying chondrocyte biology, pathophysiology and differentiation. Cultivation longer than 6 weeks leads to progressing dedifferentiation of chondrocytes that should be considered on long-term evaluations.
authors.affiliation: Tissue Engineering Laboratory and Berlin-Brandenburg Center for Regenerative Therapies, Department of Rheumatology and Clinical Immunology, Charité-Universitätsmedizin Berlin, Tucholskystrasse 2, 10117 Berlin, Germany. tilo.dehne@charite.de
authors.forename: Tilo
authors.initials: T
authors.lastname: Dehne
authors.forename: Rita
authors.initials: R
authors.lastname: Schenk
authors.forename: Carsten
authors.initials: C
authors.lastname: Perka
authors.forename: Lars
authors.initials: L
authors.lastname: Morawietz
authors.forename: Axel
authors.initials: A
authors.lastname: Pruss
authors.forename: Michael
authors.initials: M
authors.lastname: Sittinger
authors.forename: Christian
authors.initials: C
authors.lastname: Kaps
authors.forename: Jochen
authors.initials: J
authors.lastname: Ringe
mesh_terms: D053674:Aggrecans; D051792:Basic Helix-Loop-Helix Proteins; D002135:Calcium-Binding Proteins; D002356:Cartilage / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D002454:Cell Differentiation / Q000235:genetics*; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D003094:Collagen / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D024043:Collagen Type II / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D016326:Extracellular Matrix Proteins; D015870:Gene Expression; D020869:Gene Expression Profiling / Q000379:methods*; D018398:Homeodomain Proteins; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D007596:Joints / Q000378:metabolism; D046228:Microarray Analysis; D020411:Oligonucleotide Array Sequence Analysis; D011509:Proteoglycans / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000072056:Transcription Factor HES-1; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D000097568:Matrix Gla Protein; D000099255:Growth Arrest-Specific Protein 6; D000099158:Proteoglycan 4
chemical_list: D053674:Aggrecans; D051792:Basic Helix-Loop-Helix Proteins; D002135:Calcium-Binding Proteins; D003094:Collagen; D024043:Collagen Type II; D016326:Extracellular Matrix Proteins; D018398:Homeodomain Proteins; D036341:Intercellular Signaling Peptides and Proteins; D011509:Proteoglycans; D000072056:Transcription Factor HES-1; D014157:Transcription Factors; D000097568:Matrix Gla Protein; D000099255:Growth Arrest-Specific Protein 6; C508319:ACAN protein, human; C419197:PRG4 protein, human; D000099158:Proteoglycan 4; C078493:HES1 protein, human