title: Adipose stem cells can secrete angiogenic factors that inhibit hyaline cartilage regeneration.
abstract: BACKGROUND
  Adipose stem cells (ASCs) secrete many trophic factors that can stimulate tissue repair, including angiogenic factors, but little is known about how ASCs and their secreted factors influence cartilage regeneration. Therefore, the aim of this study was to determine the effects ASC-secreted factors have in repairing chondral defects.
  
  
  METHODS
  ASCs isolated from male Sprague Dawley rats were cultured in monolayer or alginate microbeads supplemented with growth (GM) or chondrogenic medium (CM). Subsequent co-culture, conditioned media, and in vivo cartilage defect studies were performed.
  
  
  RESULTS
  ASC monolayers and microbeads cultured in CM had decreased FGF-2 gene expression and VEGF-A secretion compared to ASCs cultured in GM. Chondrocytes co-cultured with GM-cultured ASCs for 7 days had decreased mRNAs for col2, comp, and runx2. Chondrocytes treated for 12 or 24 hours with conditioned medium from GM-cultured ASCs had reduced sox9, acan, and col2 mRNAs; reduced proliferation and proteoglycan synthesis; and increased apoptosis. ASC-conditioned medium also increased endothelial cell tube lengthening whereas conditioned medium from CM-cultured ASCs had no effect. Treating ASCs with CM reduced or abolished these deleterious effects while adding a neutralizing antibody for VEGF-A eliminated ASC-conditioned medium induced chondrocyte apoptosis and restored proteoglycan synthesis. FGF-2 also mitigated the deleterious effects VEGF-A had on chondrocyte apoptosis and phenotype. When GM-grown ASC pellets were implanted in 1 mm non-critical hyaline cartilage defects in vivo, cartilage regeneration was inhibited as evaluated by radiographic and equilibrium partitioning of an ionic contrast agent via microCT imaging. Histology revealed that defects with GM-cultured ASCs had no tissue ingrowth from the edges of the defect whereas empty defects and defects with CM-grown ASCs had similar amounts of neocartilage formation.
  
  
  CONCLUSIONS
  ASCs must be treated to reduce the secretion of VEGF-A and other factors that inhibit cartilage regeneration, which can significantly influence how ASCs are used for repairing hyaline cartilage.
authors.forename: Christopher Sd
authors.initials: CS
authors.lastname: Lee
authors.forename: Olivia A
authors.initials: OA
authors.lastname: Burnsed
authors.forename: Vineeth
authors.initials: V
authors.lastname: Raghuram
authors.forename: Jonathan
authors.initials: J
authors.lastname: Kalisvaart
authors.forename: Barbara D
authors.initials: BD
authors.lastname: Boyan
authors.forename: Zvi
authors.initials: Z
authors.lastname: Schwartz
mesh_terms: D000273:Adipose Tissue / Q000166:cytology*; D043925:Angiogenesis Inducing Agents / Q000378:metabolism*; D000818:Animals; D002357:Cartilage Diseases / Q000000981:diagnostic imaging / Q000473:pathology / Q000628:therapy; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D018920:Coculture Techniques; D017077:Culture Media, Conditioned / Q000494:pharmacology; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism / Q000494:pharmacology; D051457:Hyaline Cartilage / Q000000981:diagnostic imaging / Q000473:pathology / Q000502:physiology*; D008297:Male; D019899:Paracrine Communication; D012333:RNA, Messenger / Q000378:metabolism; D011859:Radiography; D051381:Rats; D017207:Rats, Sprague-Dawley; D012038:Regeneration; D033581:Stem Cell Transplantation; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism / Q000494:pharmacology
chemical_list: D043925:Angiogenesis Inducing Agents; D017077:Culture Media, Conditioned; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D016222:Fibroblast Growth Factor 2