title: Extracellular Calcium Modulates Chondrogenic and Osteogenic Differentiation of Human Adipose-Derived Stem Cells: A Novel Approach for Osteochondral Tissue Engineering Using a Single Stem Cell Source.
abstract: We have previously shown that elevating extracellular calcium from a concentration of 1.8 to 8 mM accelerates and increases human adipose-derived stem cell (hASC) osteogenic differentiation and cell-mediated calcium accretion, even in the absence of any other soluble osteogenic factors in the culture medium. However, the effects of elevated calcium on hASC chondrogenic differentiation have not been reported. The goal of this study was to determine the effects of varied calcium concentrations on chondrogenic differentiation of hASC. We hypothesized that exposure to elevated extracellular calcium (8 mM concentration) in a chondrogenic differentiation medium (CDM) would inhibit chondrogenesis of hASC when compared to basal calcium (1.8 mM concentration) controls. We further hypothesized that a full osteochondral construct could be engineered by controlling local release of calcium to induce site-specific chondrogenesis and osteogenesis using only hASC as the cell source. Human ASC was cultured as micromass pellets in CDM containing transforming growth factor-β1 and bone morphogenetic protein 6 for 28 days at extracellular calcium concentrations of either 1.8 mM (basal) or 8 mM (elevated). Our findings indicated that elevated calcium induced osteogenesis and inhibited chondrogenesis in hASC. Based on these findings, stacked polylactic acid nanofibrous scaffolds containing either 0% or 20% tricalcium phosphate (TCP) nanoparticles were electrospun and tested for site-specific chondrogenesis and osteogenesis. Histological assays confirmed that human ASC differentiated locally to generate calcified tissue in layers containing 20% TCP, and cartilage in the layers with no TCP when cultured in CDM. This is the first study to report the effects of elevated calcium on chondrogenic differentiation of hASC, and to develop osteochondral nanofibrous scaffolds using a single cell source and controlled calcium release to induce site-specific differentiation. This approach holds great promise for osteochondral tissue engineering using a single cell source (hASC) and single scaffold.
authors.affiliation: 1 Joint Department of Biomedical Engineering at University of North Carolina at Chapel Hill, North Carolina State University , Raleigh, North Carolina.
authors.forename: Liliana F
authors.initials: LF
authors.lastname: Mellor
authors.affiliation: 1 Joint Department of Biomedical Engineering at University of North Carolina at Chapel Hill, North Carolina State University , Raleigh, North Carolina.
authors.forename: Mahsa
authors.initials: M
authors.lastname: Mohiti-Asli
authors.affiliation: 1 Joint Department of Biomedical Engineering at University of North Carolina at Chapel Hill, North Carolina State University , Raleigh, North Carolina.
authors.forename: John
authors.initials: J
authors.lastname: Williams
authors.affiliation: 1 Joint Department of Biomedical Engineering at University of North Carolina at Chapel Hill, North Carolina State University , Raleigh, North Carolina.
authors.forename: Arthi
authors.initials: A
authors.lastname: Kannan
authors.affiliation: 1 Joint Department of Biomedical Engineering at University of North Carolina at Chapel Hill, North Carolina State University , Raleigh, North Carolina.
authors.forename: Morgan R
authors.initials: MR
authors.lastname: Dent
authors.affiliation: 2 Departments of Orthopedic Surgery and Biomedical Engineering, Duke University Medical Center , Durham, North Carolina.
authors.forename: Farshid
authors.initials: F
authors.lastname: Guilak
authors.affiliation: 1 Joint Department of Biomedical Engineering at University of North Carolina at Chapel Hill, North Carolina State University , Raleigh, North Carolina.|3 Department of Materials Science and Engineering, North Carolina State University , Raleigh, North Carolina.
authors.forename: Elizabeth G
authors.initials: EG
authors.lastname: Loboa
mesh_terms: D000273:Adipose Tissue / Q000166:cytology*; D000328:Adult; D002113:Calcification, Physiologic / Q000187:drug effects; D002118:Calcium / Q000494:pharmacology*; D002130:Calcium Phosphates / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D020219:Chondrogenesis / Q000187:drug effects*; D005110:Extracellular Space / Q000737:chemistry; D005786:Gene Expression Regulation / Q000187:drug effects; D006025:Glycosaminoglycans / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D019344:Lactic Acid / Q000494:pharmacology; D010012:Osteogenesis / Q000187:drug effects*; D011091:Polyesters; D011108:Polymers / Q000494:pharmacology; D013234:Stem Cells / Q000166:cytology* / Q000187:drug effects / Q000648:ultrastructure; D023822:Tissue Engineering / Q000379:methods*; D054457:Tissue Scaffolds; D055815:Young Adult
chemical_list: D002130:Calcium Phosphates; D006025:Glycosaminoglycans; D011091:Polyesters; D011108:Polymers; D019344:Lactic Acid; C033616:poly(lactide); C018392:tricalcium phosphate; D002118:Calcium