Positive-feedback regulation of subchondral H-type vessel formation by chondrocyte promotes osteoarthritis development in mice.
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| Abstract | :  Vascular-invasion-mediated interactions between activated articular chondrocytes and subchondral bone are essential for osteoarthritis (OA) development. Here, we determined the role of nutrient sensing mechanistic target of rapamycin complex 1 (mTORC1) signaling in the crosstalk across the bone cartilage interface and its regulatory mechanisms. Then mice with chondrocyte-specific mTORC1 activation (Tsc1 CKO and Tsc1 CKOER ) or inhibition (Raptor CKOER ) and their littermate controls were subjected to OA induced by destabilization of the medial meniscus (DMM) or not. DMM or Tsc1 CKO mice were treated with bevacizumab, a vascular endothelial growth factor (VEGF)-A antibody that blocks angiogenesis. Articular cartilage degeneration was evaluated using the Osteoarthritis Research Society International score. Immunostaining and western blotting were conducted to detect H-type vessels and protein levels in mice. Primary chondrocytes from mutant mice and ADTC5 cells were treated with interleukin-1β to investigate the role of chondrocyte mTORC1 in VEGF-A secretion and in vitro vascular formation. Clearly, H-type vessels were increased in subchondral bone in DMM-induced OA and aged mice. Cartilage mTORC1 activation stimulated VEGF-A production in articular chondrocyte and H-type vessel formation in subchondral bone. Chondrocyte mTORC1 promoted OA partially through formation of VEGF-A-stimulated subchondral H-type vessels. In particular, vascular-derived nutrients activated chondrocyte mTORC1, and stimulated chondrocyte activation and production of VEGF, resulting in further angiogenesis in subchondral bone. Thus a positive-feedback regulation of H-type vessel formation in subchondral bone by articular chondrocyte nutrient-sensing mTORC1 signaling is essential for the pathogenesis and progression of OA. This article is protected by copyright. All rights reserved. | 
| Year of Publication | :  2018 | 
| Journal | :  Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research | 
| Date Published | :  2018 | 
| ISSN Number | :  0884-0431 | 
| DOI | :  10.1002/jbmr.3388 | 
| Short Title | :  J Bone Miner Res | 
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