title: The effects of BMP6 overexpression on adipose stem cell chondrogenesis: Interactions with dexamethasone and exogenous growth factors.
abstract: Adipose-derived stem cells (ASCs) are multipotent progenitors that can be chondrogenically induced by growth factors such as bone morphogenetic protein 6 (BMP-6). We hypothesized that nonviral transfection of a BMP-6 construct (pcDNA3-BMP6) would induce chondrogenic differentiation of ASCs encapsulated in alginate beads and that differentiation would be enhanced by the presence of the synthetic glucocorticoid dexamethasone (DEX) or the combination of epidermal growth factor (EGF), fibroblast growth factor-2 (FGF-2), and transforming growth factor beta-1 (TGF-beta1), collectively termed expansion factors (EFs). Chondrogenesis was assessed using quantitative real-time polymerase chain reaction for types I, II, and X collagen, aggrecan, and BMP6. Immunohistochemistry was performed with antibodies for types I, II, and X collagen and chondroitin-4-sulfate. BMP6 overexpression alone induced a moderate chondrogenic response. The inclusion of EFs promoted robust type II collagen expression but also increased type I and X collagen deposition, consistent with a hypertrophic chondrocyte phenotype. Early gene expression data indicated that DEX was synergistic with BMP-6 for chondrogenesis, but immunohistochemistry at 28 days showed that DEX reduced glycosaminoglycan accumulation. These results suggest that chondrogenic differentiation of ASCs depends on complex interactions among various growth factors and media supplements, as well as the concentration and duration of growth factor exposure.
authors.affiliation: Orthopaedic Research Laboratories, Department of Surgery, Division of Orthopaedic Surgery, 375 MSRB, Box 3093, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: Brian O
authors.initials: BO
authors.lastname: Diekman
authors.forename: Bradley T
authors.initials: BT
authors.lastname: Estes
authors.forename: Farshid
authors.initials: F
authors.lastname: Guilak
mesh_terms: D000273:Adipose Tissue / Q000166:cytology*; D000328:Adult; D055418:Bone Morphogenetic Protein 6 / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D020219:Chondrogenesis / Q000187:drug effects* / Q000235:genetics; D002809:Chondroitin Sulfates / Q000378:metabolism; D003094:Collagen / Q000235:genetics / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D013234:Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism
chemical_list: D055418:Bone Morphogenetic Protein 6; D036341:Intercellular Signaling Peptides and Proteins; D003907:Dexamethasone; D002809:Chondroitin Sulfates; D003094:Collagen