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Title: Mechanosensitive Control of Articular Cartilage and Subchondral Bone Homeostasis in Mice Requires Osteocytic Transforming Growth Factor β Signaling
Objective

Transforming growth factor β (TGFβ) signaling plays a complex tissue‐specific and nonlinear role in osteoarthritis (OA). This study was conducted to determine the osteocytic contributions of TGFβ signaling to OA.

Methods

To identify the role of osteocytic TGFβ signaling in joint homeostasis, we used 16‐week‐old male mice (n = 9–11 per group) and female mice (n = 7–11 per group) with an osteocyte‐intrinsic ablation of TGFβ receptor type II (TβRIIocy−/−mice) and assessed defects in cartilage degeneration, subchondral bone plate (SBP) thickness, and SBP sclerostin expression. To further investigate these mechanisms in 16‐week‐old male mice, we perturbed joint homeostasis by subjecting 8‐week‐old mice to medial meniscal/ligamentous injury (MLI), which preferentially disrupts the mechanical environment of the medial joint to induce OA.

Results

In all contexts, independent of sex, genotype, or medial or lateral joint compartment, increased SBP thickness and SBP sclerostin expression were spatially associated with cartilage degeneration. Male TβRIIocy−/−mice, but not female TβRIIocy−/−mice, had increased cartilage degeneration, increased SBP thickness, and higher levels of SBP sclerostin compared with control mice (allP< 0.05), demonstrating that the role of osteocytic TGFβ signaling on joint homeostasis is sexually dimorphic. With changes in joint mechanics following injury, control mice had increased SBP thickness, subchondral bone volume, and SBP sclerostin expression (allP< 0.05). TβRIIocy−/−mice, however, were insensitive to subchondral bone changes with injury, suggesting that mechanosensation at the SBP requires osteocytic TGFβ signaling.

Conclusion

Our results provide new evidence that osteocytic TGFβ signaling is required for a mechanosensitive response to injury, and that osteocytes control SBP homeostasis to maintain cartilage health, identifying osteocytic TGFβ signaling as a novel therapeutic target for OA.

 
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Award ID(s):
1636331
NSF-PAR ID:
10453299
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Arthritis & Rheumatology
Volume:
73
Issue:
3
ISSN:
2326-5191
Page Range / eLocation ID:
p. 414-425
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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