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The presence of extracellular matrix alters the chondrocyte response to endoplasmic reticulum stress
Author(s) -
Nugent Ashleigh E.,
McBurney Denise L.,
Horton Walter E.
Publication year - 2011
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.23025
Subject(s) - unfolded protein response , endoplasmic reticulum , chondrocyte , extracellular matrix , tunicamycin , thapsigargin , apoptosis , microbiology and biotechnology , cartilage , extracellular , andrology , endocrinology , chemistry , medicine , western blot , biology , biochemistry , anatomy , gene
The objective of this study was to test the hypothesis that extracellular matrix (ECM) would alter the endoplasmic reticulum (ER) stress response of chondrocytes. Chondrocytes were isolated from calf knees and maintained in monolayer culture or suspended in collagen I to form spot cultures (SCs). Our laboratory has shown that bovine chondrocytes form cartilage with properties similar to native cartilage after 2–4 weeks in SCs. Monolayer cultures treated with ER stressors glucose withdrawal (–Glu), tunicamycin (TN), or thapsigargin (TG) up‐regulated Grp78 and Gadd153, demonstrating a complete ER stress response. SCs were grown at specific times from 1 day to 6 weeks before treatment with ER stressors. Additionally, SCs grown for 1, 2, or 6 weeks were treated with increasing concentrations of TN or TG. Western blotting of SCs for Grp78 indicated that increased ECM accumulation results in delayed expression; however, Grp78 mRNA is up‐regulated in response to ER stressors even after 6 weeks in culture. SCs treated with ER stressors did not up‐regulate Gadd153, suggesting that the cells experienced ER stress but would not undergo apoptosis. In fact, SCs undergo apoptosis upon ER stress treatment after 0–1 day of growth; however, after 4 days and to 6 weeks, apoptosis in treated samples was not different than controls. Pro‐survival molecules Bcl‐2 and Bag‐1 were up‐regulated upon ER stress in SCs. These results suggest that presence of ECM confers protection from ER stressors. Future studies involving chondrocyte physiology should focus on responses in conditions more closely mimicking the in vivo cartilage environment. J. Cell. Biochem. 112: 1118–1129, 2011. © 2011 Wiley‐Liss, Inc.