title: Follistatin-like protein 1 regulates chondrocyte proliferation and chondrogenic differentiation of mesenchymal stem cells.
abstract: OBJECTIVE
  Chondrocytes, the only cells in the articular cartilage, play a pivotal role in osteoarthritis (OA) because they are responsible for maintenance of the extracellular matrix (ECM). Follistatin-like protein 1 (FSTL1) is a secreted protein found in mesenchymal stem cells (MSCs) and cartilage but whose function is unclear. FSTL1 has been shown to modify cell growth and survival. In this work, we sought to determine whether FSTL1 could regulate chondrogenesis and chondrogenic differentiation of MSCs.
  
  
  METHODS
  To study the role of FSTL1 in chondrogenesis, we used FSTL1 knockout (KO) mice generated in our laboratory. Proliferative capacity of MSCs, obtained from skulls of E18.5 embryos, was analysed by flow cytometry. Chondrogenic differentiation of MSCs was carried out in a pellet culture system. Gene expression differences were assessed by microarray analysis and real-time PCR. Phosphorylation of Smad3, p38 MAPK and Akt was analysed by western blotting.
  
  
  RESULTS
  The homozygous FSTL1 KO embryos showed extensive skeletal defects and decreased cellularity in the vertebral cartilage. Cell proliferation of FSTL1-deficient MSCs was reduced. Gene expression analysis in FSTL1 KO MSCs revealed dysregulation of multiple genes important for chondrogenesis. Production of ECM proteoglycans and collagen II expression were decreased in FSTL1-deficient MSCs differentiated into chondrocytes. Transforming growth factor β signalling in FSTL1 KO cells was significantly suppressed.
  
  
  CONCLUSIONS
  FSTL1 is a potent regulator of chondrocyte proliferation, differentiation and expression of ECM molecules. Our findings may lead to the development of novel strategies for cartilage repair and provide new disease-modifying treatments for OA.
authors.affiliation: Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA.
authors.forename: Yury
authors.initials: Y
authors.lastname: Chaly
authors.affiliation: Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA VA Medical Center, Pittsburgh, Pennsylvania, USA.
authors.forename: Harry C
authors.initials: HC
authors.lastname: Blair
authors.affiliation: Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA.
authors.forename: Sonja M
authors.initials: SM
authors.lastname: Smith
authors.affiliation: Department of Pediatrics, Children's Hospital of Pittsburgh of UPMC, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Bushnell
authors.affiliation: Department of Pediatrics, Children's Hospital of Pittsburgh of UPMC, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Marinov
authors.affiliation: Department of Pediatrics, Children's Hospital of Pittsburgh of UPMC, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Campfield
authors.affiliation: Department of Pediatrics, University of Iowa Carver College of Medicine, Iowa City, Iowa, USA.
authors.forename: Raphael
authors.initials: R
authors.lastname: Hirsch
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000502:physiology*; D049109:Cell Proliferation / Q000502:physiology*; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D020219:Chondrogenesis / Q000502:physiology*; D024043:Collagen Type II / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism; D038702:Follistatin-Related Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D023421:Models, Animal; D011509:Proteoglycans / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000494:pharmacology
chemical_list: D024043:Collagen Type II; D038702:Follistatin-Related Proteins; C448720:Fstl1 protein, mouse; D011509:Proteoglycans; D016212:Transforming Growth Factor beta
keywords: Chondrocytes; Cytokines; Osteoarthritis