Cameron, TL and Gresshoff, IL and Bell, KM and Pirog, KA and Sampurno, L and Hartley, CL and Sanford, EM and Wilson, R and Ermann, J and Boot-Handford, RP and Glimcher, LH and Briggs, MD and Bateman, JF, Cartilage-specific ablation of XBP1 signaling in mouse results in a chondrodysplasia characterized by reduced chondrocyte proliferation and delayed cartilage maturation and mineralization, Osteoarthritis and Cartilage, 23, (4) pp. 661-670. ISSN 1063-4584 (2015) [Refereed Article]
© 2015 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.
Objective: To investigate the in vivo role of the IRE1/XBP1 unfolded protein response (UPR) signaling pathway in cartilage.
Design: Xbp1flox/flox.Col2a1-Cre mice (Xbp1CartΔEx2), in which XBP1 activity is ablated specifically from cartilage, were analyzed histomorphometrically by Alizarin red/Alcian blue skeletal preparations and X-rays to examine overall bone growth, histological stains to measure growth plate zone length, chondrocyte organization, and mineralization, and immunofluorescence for collagen II, collagen X, and IHH. Bromodeoxyuridine (BrdU) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) analyses were used to measure chondrocyte proliferation and cell death, respectively. Chondrocyte cultures and microdissected growth plate zones were analyzed for expression profiling of chondrocyte proliferation or endoplasmic reticulum (ER) stress markers by Quantitative PCR (qPCR), and of Xbp1 mRNA splicing by RT-PCR to monitor IRE1 activation.
RESULTS: Xbp1CartΔEx2 displayed a chondrodysplasia involving dysregulated chondrocyte proliferation, growth plate hypertrophic zone shortening, and IRE1 hyperactivation in chondrocytes. Deposition of collagens II and X in the Xbp1CartΔEx2 growth plate cartilage indicated that XBP1 is not required for matrix protein deposition or chondrocyte hypertrophy. Analyses of mid-gestation long bones revealed delayed ossification in Xbp1CartΔEx2 embryos. The rate of chondrocyte cell death was not significantly altered, and only minimal alterations in the expression of key markers of chondrocyte proliferation were observed in the Xbp1CartΔEx2 growth plate. IRE1 hyperactivation occurred in Xbp1CartΔEx2 chondrocytes but was not sufficient to induce regulated IRE1-dependent decay (RIDD) or a classical UPR.
CONCLUSION: Our work suggests roles for XBP1 in regulating chondrocyte proliferation and the timing of mineralization during endochondral ossification, findings which have implications for both skeletal development and disease.
|Item Type:||Refereed Article|
|Keywords:||ER stress, XBP1, chondrodysplasia, endochondral ossification, growth plate|
|Research Division:||Biomedical and Clinical Sciences|
|Research Group:||Clinical sciences|
|Research Field:||Rheumatology and arthritis|
|Objective Group:||Clinical health|
|Objective Field:||Clinical health not elsewhere classified|
|UTAS Author:||Wilson, R (Dr Richard Wilson)|
|Web of Science® Times Cited:||27|
|Deposited By:||Central Science Laboratory|
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