title: Histone deacetylase 4 promotes TGF-beta1-induced synovium-derived stem cell chondrogenesis but inhibits chondrogenically differentiated stem cell hypertrophy.
abstract: The transforming growth factor-beta (TGF-beta) superfamily members play diverse roles in cartilage development and maintenance. TGF-beta up-regulates chondrogenic gene expression by enhancing transcription factor SRY (sex determining region Y)-box 9 (Sox9) and inhibits osteoblast differentiation by repressing runt-related transcription factor 2 (Runx2). Recently, histone deacetylases (HDACs) were reported to act as negative regulators of chondrocyte hypertrophy. It was speculated that HDAC4 may promote TGF-beta1-induced MSC chondrogenesis. In this study, the adenovirus-mediated HDAC4 gene (Ad.HDAC4) was utilized to infect synovium-derived stem cells (SDSCs). Adenovirus-mediated LacZ (Ad.LacZ) served as a control. The infected cells were centrifuged to form SDSC pellets followed by incubation in a serum-free chondrogenic medium for 15 days with or without 10ng/mL TGF-beta1. Transfection efficiency was determined in SDSCs using Ad.LacZ. Cytotoxicity was measured using lactate dehydrogenase assay. Histology, immunostaining, biochemical analysis, and real-time polymerase chain reaction were performed to assess chondrogenesis at protein and mRNA levels in infected SDSCs. Our data demonstrated that supplementation with TGF-beta1 could initiate and promote SDSC chondrogenesis; however, TGF-beta1 alone was insufficient to fully differentiate SDSCs into chondrocytes. Ad.HDAC4 could be efficiently transfected into SDSCs. Without TGF-beta1 treatment, HDAC4 had no effect on SDSC chondrogenesis; however, in the presence of TGF-beta1, HDAC4 could speed up and maintain a high level of chondrogenesis while down-regulating the hypertrophic marker - type X collagen expression. This study is the first report showing that HDAC4 overexpression promotes TGF-beta1-induced SDSC chondrogenesis but inhibits chondrogenically differentiated stem cell hypertrophy. The mechanism underlying this process needs further investigation.
authors.affiliation: Tissue Engineering Laboratory, Department of Orthopaedics, West Virginia University, PO Box 9196, Morgantown, WV 26506, USA. mpei@hsc.wvu.edu
authors.forename: Ming
authors.initials: M
authors.lastname: Pei
authors.forename: Demeng
authors.initials: D
authors.lastname: Chen
authors.forename: Jingting
authors.initials: J
authors.lastname: Li
authors.forename: Lei
authors.initials: L
authors.lastname: Wei
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D020219:Chondrogenesis; D005786:Gene Expression Regulation; D005819:Genetic Markers; D006655:Histone Deacetylases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006984:Hypertrophy; D012333:RNA, Messenger / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism*; D013552:Swine / Q000378:metabolism*; D013583:Synovial Membrane / Q000166:cytology* / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*
chemical_list: D005819:Genetic Markers; D012333:RNA, Messenger; D012097:Repressor Proteins; D053773:Transforming Growth Factor beta1; C400300:HDAC4 protein, human; D006655:Histone Deacetylases