Affiliations: Cellular Engineering Laboratory, Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA | Center for Molecular Orthopaedics, Department of Orthopaedic Surgery, Harvard Medical School, Boston, MA, USA | Orthopedic Biosciences Laboratory, Division of Orthopedic Surgery, University of Wisconsin, Madison, WI 53792, USA
Note: [] Address for correspondence: Clark T. Hung, Ph.D., Cellular Engineering Laboratory, Department of Biomedical Engineering, Columbia University, 351J Engineering Terrace, 1210 Amsterdam Avenue, New York, NY 10027, USA. Tel.: +1 212 854 6542; Fax: +1 212 854 8725; E‐mail: [email protected].
Abstract: The effects of hypotonic (180 mOsm) and hypertonic (580 mOsm) medium loading on chondrocyte aggrecan gene expression in 2D monolayer and 3D hydrogel culture (agarose or alginate) were studied. Aggrecan promoter activity was monitored using a luciferase reporter gene assay and transient transfection. Osmotic loading was observed to differentially affect promoter activity, with hypotonic loading generally producing at least a 40% elevation in promoter activity, except for the case of alginate where a 50% suppression was observed. Hypertonic loading produced at least a 35% decrease in activity for all cultures. Similar osmolality‐induced changes to aggrecan mRNA levels were observed in monolayer cells using qPCR. Deletion of exon 1 blocked the sensitivity of monolayer cells to hypertonic but not hypotonic medium changes. Confocal microscopy measurements suggested that the degree of hypotonic swelling in cells encapsulated in 3D matrix was restricted compared to monolayer cells whereas the degree of hypertonic shrinking was similar under both culture conditions.
Journal: Biorheology, vol. 40, no. 1-3, pp. 61-72, 2003
