title: Digoxin and adenosine triphosphate enhance the functional properties of tissue-engineered cartilage.
abstract: Toward developing engineered cartilage for the treatment of cartilage defects, achieving relevant functional properties before implantation remains a significant challenge. Various chemical and mechanical stimuli have been used to enhance the functional properties of engineered musculoskeletal tissues. Recently, Ca(2+)-modulating agents have been used to enhance matrix synthesis and biomechanical properties of engineered cartilage. The objective of this study was to determine whether other known Ca(2+) modulators, digoxin and adenosine triphosphate (ATP), can be employed as novel stimuli to increase collagen synthesis and functional properties of engineered cartilage. Neocartilage constructs were formed by scaffold-free self-assembling of primary bovine articular chondrocytes. Digoxin, ATP, or both agents were added to the culture medium for 1 h/day on days 10-14. After 4 weeks of culture, neocartilage properties were assessed for gross morphology, biochemical composition, and biomechanical properties. Digoxin and ATP were found to increase neocartilage collagen content by 52-110% over untreated controls, while maintaining proteoglycan content near native tissue values. Furthermore, digoxin and ATP increased the tensile modulus by 280% and 180%, respectively, while the application of both agents increased the modulus by 380%. The trends in tensile properties were found to correlate with the amount of collagen cross-linking. Live Ca(2+) imaging experiments revealed that both digoxin and ATP were able to increase Ca(2+) oscillations in monolayer-cultured chondrocytes. This study provides a novel approach toward directing neocartilage maturation and enhancing its functional properties using novel Ca(2+) modulators.
authors.affiliation: 1 Department of Biomedical Engineering, University of California Davis , Davis, California.
authors.forename: Eleftherios A
authors.initials: EA
authors.lastname: Makris
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Huang
authors.forename: Jerry C
authors.initials: JC
authors.lastname: Hu
authors.forename: Ye
authors.initials: Y
authors.lastname: Chen-Izu
authors.forename: Kyriacos A
authors.initials: KA
authors.lastname: Athanasiou
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001696:Biomechanical Phenomena / Q000187:drug effects; D020013:Calcium Signaling / Q000187:drug effects; D002356:Cartilage / Q000033:anatomy & histology / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D002417:Cattle; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology / Q000187:drug effects; D003094:Collagen / Q000378:metabolism; D019245:Compressive Strength / Q000187:drug effects; D004077:Digoxin / Q000494:pharmacology*; D055119:Elastic Modulus / Q000187:drug effects; D006025:Glycosaminoglycans / Q000378:metabolism; D023822:Tissue Engineering / Q000379:methods*
chemical_list: D000596:Amino Acids; D006025:Glycosaminoglycans; C015484:pyridinoline; D004077:Digoxin; D000255:Adenosine Triphosphate; D003094:Collagen