title: Effects of Osmolarity on the Spontaneous Calcium Signaling of In Situ Juvenile and Adult Articular Chondrocytes.
abstract: Calcium is a universal second messenger that mediates the metabolic activity of chondrocytes in articular cartilage. Spontaneous intracellular calcium ([Ca(2+)]i) oscillations, similar to those in neurons and myocytes, have recently been observed in chondrocytes. This study analyzed and compared the effects of different osmotic environments (hypertonic, hypotonic, and isotonic) on the spontaneous [Ca(2+)]i signaling of in situ chondrocytes residing in juvenile and adult cartilage explants. In spite of a lower cell density, a significantly higher percentage of chondrocytes in adult cartilage under all osmotic environments demonstrated spontaneous [Ca(2+)]i oscillations than chondrocytes in juvenile cartilage. For both juvenile and adult chondrocytes, hypotonic stress increased while hypertonic stress decreased the response rates. Furthermore, the spatiotemporal characteristics of the [Ca(2+)]i peaks vary in an age-dependent manner. In the hypotonic environment, the [Ca(2+)]i oscillation frequency of responsive adult cells is almost tripled whereas the juvenile cells respond with an increased duration and magnitude of each [Ca(2+)]i peak. Both juvenile and adult chondrocytes demonstrated significantly slower [Ca(2+)]i oscillations with longer rising and recovery time under the hypertonic condition. Taken together, these results shed new insights into the interplay between age and osmotic environment that may regulate the fundamental metabolism of chondrocytes.
authors.affiliation: Department of Mechanical Engineering, University of Delaware, 130 Academy Street SPL126, Newark, DE, 19716, USA.
authors.forename: Yilu
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Department of Biomedical Engineering, University of Delaware, Newark, DE, 19716, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: David
authors.affiliation: Department of Mechanical Engineering, University of Delaware, 130 Academy Street SPL126, Newark, DE, 19716, USA.
authors.forename: Xingyu
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA.
authors.forename: Leo Q
authors.initials: LQ
authors.lastname: Wan
authors.affiliation: Department of Biological Sciences, University of Delaware, Newark, DE, 19716, USA.
authors.forename: Randall L
authors.initials: RL
authors.lastname: Duncan
authors.affiliation: Department of Mechanical Engineering, University of Delaware, 130 Academy Street SPL126, Newark, DE, 19716, USA.
authors.forename: Liyun
authors.initials: L
authors.lastname: Wang
authors.affiliation: Department of Mechanical Engineering, University of Delaware, 130 Academy Street SPL126, Newark, DE, 19716, USA. xlu@udel.edu.
authors.forename: X Lucas
authors.initials: XL
authors.lastname: Lu
mesh_terms: D000367:Age Factors; D000818:Animals; D020013:Calcium Signaling; D002358:Cartilage, Articular / Q000166:cytology; D002417:Cattle; D019902:Chondrocytes / Q000378:metabolism*; D009994:Osmolar Concentration
keywords: Age; Calcium; Cartilage; Chondrocyte; Osmotic; Signal transduction