Activation of β-catenin signaling in aggrecan-expressing cells in temporomandibular joint causes osteoarthritis-like defects

ABSTRACT β-Catenin plays a critical role in cartilage formation and development. To further understand the role of β-catenin in osteoarthritis (OA) development in temporomandibular joint

(TMJ), we have generated _β-catenin_ conditional activation mice (_β-cat_(_ex3_)_Agc1CreER_) by breeding _Agc1-CreER_ mice with _β-catenin__flox_(_ex3_)/_+_ mice. Results of histologic

analysis showed the progressive TMJ defects in 3- and 6-month-old _β-cat_(_ex3_)_Agc1CreER_ mice (tamoxifen induction was performed at 2 weeks of age), including decreased chondrocyte

numbers in the superficial layer associated with less Alcian blue staining, increased numbers of hypertrophic chondrocytes in deep layers, and rough articular surface. Compared to the TMJ

phenotype of _β-cat_(_ex3_)_Col2CreER_ mice, _β-cat_(_ex3_)_Agc1CreER_ mice showed much severe morphological defects in the superficial layer of TMJ. This may reflect that _Agc1-CreER_ mice

could efficiently target cells in the superficial layer of TMJ. Results of immunostaining showed significantly increased expression of MMP13, Col-X, Adamts4, and Adamts5 in TMJ of

_β-cat_(_ex3_)_Agc1CreER_ mice. Results of proliferating cell nuclear antigen (PCNA), Ki67, and terminal deoxinucleotidyl transferase-mediated dUTP-fluorescein nick end labeling (TUNEL)

staining further demonstrated that cell proliferation was decreased and cell apoptosis was increased in condylar cartilage of _β-cat_(_ex3_)_Agc1CreER_ mice. Our findings indicate that

abnormal upregulation of β-catenin in TMJ leads to defects assembling to OA-like phenotype, further demonstrating that β-catenin plays a critical role in TMJ pathogenesis. SIMILAR CONTENT

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GENDER-SPECIFIC ANABOLIC DIFFERENCES TO TMJ CARTILAGE Article Open access 19 November 2020 INTRODUCTION The temporomandibular joint (TMJ) is one of the most common sites affected by

osteoarthritis (OA). It has been reported that up to 10 million Americans suffer from TMJ disorders (TMDs) each year and 14.56% of mainland Chinese patients with TMD had radiographic signs

of OA.1,2 Among TMDs, OA is the most prevalent degenerative disease.3 TMJ OA is characterized by cartilage degradation, alterations of subchondral bone remodeling, chronic pain, and joint

dysfunction.4,5 Although TMJ OA is a common degenerative joint disease that affects TMJ cartilage during the aging process, the pathological mechanisms of this disease remain largely

unknown.6 Canonical Wnt/β-catenin signaling plays an important role in the development and progression in multiple forms of arthritis, such as OA,7 spondyloarthritis,8,9,10 and diffuse

idiopathic skeletal hyperostosis.11,12,13 It has been shown that conditional activation of β-catenin in knee joint cartilage and intervertebral disc cartilage leads to knee OA and disc

tissue degeneration.7,14 In most recent studies, we also found that activation of β-catenin signaling in facet joint also causes severe OA-like phenotype (unpublished data). Our goal is to

have comprehensive understanding of the role of Wnt/β-catenin signaling in the pathogenesis of arthritis. TMJ OA is one of the important forms of OA and is a common dental disease. The

pathological progression of TMJ OA is considered to be a similar disease as knee OA.15 In previous studies, we generated _β-cat_(_ex3_)_Col2CreER_ mouse model and demonstrated that

dysregulation of β-catenin causes OA-like cartilage degeneration in the TMJ tissue.16 We suggest that β_-_catenin is a critical molecule in OA pathogenesis. Interestingly, there is no

significant change in the superficial zone of TMJ in _β-cat_(_ex3_)_Col2CreER_ mice. And cell proliferation and apoptosis was not changed upon _β-catenin_ activation in this mouse model.16

TMJ condylar cartilage is comprised of dense extracellular collagen fibers and proteoglycans.17 The condylar cartilage is divided into the superficial, middle, and deep layers.18 The

superficial and/or middle zones of condylar cartilage have been identified as regions enriched with highly proliferative cells.19 Mandibular condylar chondrocyte apoptosis and extracellular

matrix degradation play an important role in the development of cartilage degeneration in TMJ OA.20,21 Moreover, activation of chondrocyte hypertrophy with low metabolism followed by

apoptosis in the condylar cartilage is also considered to be part of the disease pathology associated with condylar cartilage degeneration.22 We propose that the _β-cat_(_ex3_)_Col2CreER_

mice might not be able to fully reveal the pathogenesis of TMJ OA. We have recently examined the targeting specificity and recombination efficiency of _Agc1-CreER__T2_ mice in TMJ tissue and

found that _Agc1-CreER__T2_ mice could efficiently target entire condylar cartilage, including superficial, middle, and deep layers. We decided to use this mouse model to re-evaluate the

functions of β-catenin in TMJ tissue using the new _β-cat_(_ex3_)_Agc1ER_ conditional activation mouse model. It has been suggested that mechanisms of the aggrecan- or collagen-induced

arthritis are very different.23 This may be related to the difference of their expression patterns in the condylar cartilage. Another advantage of using _Agc1-CreER__T2_ mice is that these

mice could target cartilage tissue in adult animals.24 In the present study, we have used _Agc1-CreER__T2_ mice to drive β-catenin overexpression and determined the pathogenesis caused by

β-catenin activation in the TMJ tissue. In our study, we explored whether overexpression of β-catenin in aggrecan_-_expressing chondrocytes could lead to cartilage matrix degradation and

affect cell proliferation and apoptosis, which may contribute to the OA phenotype observed in _β-cat_(_ex3_)_Agc1CreER_ mice. RESULTS HIGH CRE-RECOMBINATION EFFICIENCY AND _Β-CATENIN_

ACTIVATION IN _Β-CAT_(_EX3_)_AGC1CREER_ MICE To evaluate the _Agc1-Cre_ expression and recombination efficiency in the TMJ cartilage, _Agc1-CreER__T2_ mice were bred with _ROSA__mT/mG_

reporter mice to generate _Agc1-CreER__T2__; ROSA__mT/mG_ mice. Tamoxifen was administered when the mice were aged 2 weeks and TMJ samples were harvested at 1 month. The red fluorescent

image of condylar cartilage revealed no recombination in Cre-negative control mice (Fig. 1a). The green-labeled chondrocytes in _Agc1-CreER__T2__; ROSA__mT/mG_ mice showed _Agc1_-expressing

cells in the superficial, middle, and deep layers of condylar chondrocytes (Fig. 1a). We then generated _β-cat_(_ex3_)_Agc1CreER_ mice by crossing _Agc1-CreER__T2_ mice with

_β-catenin_(_ex3_)_flox/flox_ mice. Tamoxifen was administered to 2-week-old mice and condylar cartilage samples were harvested from these mice at 3 and 6 months of age. Immunohistochemical

(IHC) results showed that _β-catenin_ was overexpressed in the majority of condylar chondrocytes at 3- and 6-month-old mice (Fig. 1b, c). There were few β-catenin-positive cells in the

chondrocytes of Cre− mice. However, in _β-cat_(_ex3_)_Agc1CreER_ mice, _β-catenin_ expressed in the superficial, middle, and deep layers of condylar chondrocytes indicating that β-catenin in

the chondrocytes was significantly increased compared to the Cre− mice (Fig. 1b, c). The numbers of _β-catenin_-positive cells in TMJ cartilage were significantly higher in

_β-cat_(_ex3_)_Agc1CreER_ mice compared to Cre− mice (Fig. 1d). These results demonstrated that _Agc1-CreER__T2_ mice could target the chondrocytes of TMJ with high efficiency and drive

β-catenin activation in condylar chondrocytes. CONDITIONAL ACTIVATION OF _Β-CATENIN_ INDUCED CONDYLAR CARTILAGE DEFECTS The role of β-catenin in condylar cartilage was investigated in

_β-cat_(_ex3_)_Agc1CreER_ mice. Tamoxifen was administered to 2-week-old mice and TMJ samples were harvested from these mice at 3 and 6 months of age. The chondrocytes in the control mice

were well organized in the three layers: small and round cells in the top superficial layer; medium-sized cells were present in large numbers in the middle layer; and fewer, bigger,

hypertrophic, mature cells in the deep layer (Fig. 2a, b, left panels). In contrast, 3-month-old _β-cat_(_ex3_)_Agc1CreER_ mice presented early signs of TMJ OA: decreased chondrocyte numbers

in the superficial and middle layer accompanied with less Alcian blue staining in these areas, rough articular surface with numerous rounded chondrocytes often appearing as doublets, and

cells in the middle and deep layers illustrated increased numbers of hypertrophic cells. In addition to decreased cellularity of the middle layers of cartilage, clustering of hypertrophic

chondrocytes appeared more frequently in the deeper layer; cartilage area scattering and subchondral bone sclerosis were also observed in the _β-cat_(_ex3_)_Agc1CreER_ mice compared with

age-matched control group (Fig. 2a, right panel). At 6 months of age, increased severity of defects, such as clustering chondrocytes in the superficial and deeper layer, the increasing

numbers of hypertrophic chondrocytes, and subchondral new bone formation in condylar cartilage were observed in _β-cat_(_ex3_)_Agc1CreER_ mice (Fig. 2b, right panel). We also analyzed the

histology sections using the scoring system recommended by the Osteoarthritis Research Society International (OARSI) as previously described.27,29 We found that _β-cat_(_ex3_)_Agc1CreER_

mice had significantly higher scores for OA damage compared to Cre− mice (Fig. 2c). The histomorphometric analysis also showed significant reductions in articular cartilage area in 3- and

6-month-old _β-cat_(_ex3_)_Agc1CreER_ mice (Fig. 2d). CHANGES IN THE EXPRESSION OF GENES ENCODING FOR MATRIX-DEGRADATION ENZYMES IN _Β-CAT_(_EX3_)_AGC1ER_ MICE We have previously observed

significant upregulation of _Mmp13_ and _Adamts5_ expression in _β-cat_(_ex3_)_Col2CreER_ mice and demonstrated that both matrix metalloproteinase 13 (MMP13) and Adamts5 play important roles

in the TMJ OA development in these mice.16 We propose that _Mmp13_ and _Adamts5_ might be the key downstream target genes of β-catenin during TMJ OA development. To further test this

hypothesis, we performed IHC and immunofluorescence (IF) assays to determine changes in the expression of these collagenase and aggrecanases. Results of IHC revealed increased MMP13

expression in the _β-cat_(_ex3_)_Agc1CreER_ mice, especially in the superficial layer and deeper layer of the condylar cartilage in 3- and 6- month-old mice compared to controls (Fig. 3a,

b). In addition, IF results showed significant increased ColX expression in chondrocytes of entire condylar cartilage in _β-cat_(_ex3_)_Agc1CreER_ mice compared to controls, indicating that

the chondrocytes underwent hypertrophy at this stage (Fig. 4a, b). Furthermore, the expression of cartilage-degrading enzymes, such as Adamts4, and Adamts5 was also increased, especially in

the superficial layer of TMJ chondrocytes in _β-cat_(_ex3_)_Agc1CreER_ mice (Fig. 4c–f). These results suggest that the activation of β-catenin signaling could lead to chondrocyte

hypertrophy and degenerative defects. ALTERATIONS OF CELL PROLIFERATION AND APOPTOSIS IN _Β-CAT_(_EX3_)_AGC1CREER_ MICE To further investigate the pathological process in _β-

cat_(_ex3_)_Agc1CreER_ mice, proliferating cell nuclear antigen (PCNA), Ki67, and terminal deoxinucleotidyl transferase-mediated dUTP-fluorescein nick end labeling (TUNEL) staining was

performed to assess changes in chondrocyte proliferation and apoptosis. In control mice, especially at the 3-month-old, results of PCNA staining showed that abundant proliferating cells were

present in the entire TMJ cartilage. However, the PCNA-positive cells were dramatically reduced in the condylar cartilage of 3- and 6-month-old _β-cat_(_ex3_)_Agc1CreER_ mice (Fig. 5a). To

further analyze changes in cell proliferation, we also performed Ki67 staining and found that numbers of Ki67-positive cells in the middle zones of condylar cartilage were significantly

reduced in 3-month-old _β-cat_(_ex3_)_Agc1CreER_ mice (Fig. 5b, c). These results suggest that overexpression of _β-catenin_ in aggrecan-expressing condylar chondrocytes significantly

affects cell proliferation. Data of TUNEL staining demonstrated the increased apoptotic cells, mostly in the deeper layers of the condylar cartilage of the mutant mice compared to that in

control mice (Fig. 5d, e). In the control group, only few scattered apoptotic cells were detected in the deeper layer of the condylar cartilage in the mice at 6 months of age. Taking

together, these results indicate that conditional activation of _β-catenin_ in the TMJ tissue induced degenerative defects that might be partly due to changes in cell proliferation and

apoptosis. DISCUSSION In this study, we generated _β-cat_(_ex3_)_Agc1CreER_ mouse model and demonstrated that overexpression of _β-catenin_ in aggrecan-expressing chondrocytes leads to

degenerative defects resembling an OA-like phenotype in condylar cartilage. The TMJ OA is a degenerative disease with age-related joint disorder.25 Meanwhile, TMJ disorders mostly affect

young women according to recent researches.26,27 The _Agc1-CreER__T2_ transgenic mouse model is a valuable tool to investigate the postnatal OA development, allowing chondrocyte-specific

gene targeting in an inducible manner.24 To determine the role of β-catenin in TMJ OA development in postnatal mice, we decided to induce β-catenin expression in 2-week-old mice. β-Catenin

was activated specifically in mature chondrocytes. _β-cat_(_ex3_)_Agc1CreER_ mice exhibited TMJ phenotype similar to that of human TMJ OA, including increased chondrocyte hypertrophy

observed in the superficial zone of the condylar cartilage, severe loss of articular cartilage at the margins of cartilage tissue, and subchondral sclerosis. In _β-catenin_ conditional

activation mice, the accelerated catabolic effects (matrix degradation and hypertrophy) may contribute to the eventual loss of the condylar cartilage in this mouse model. In previous

studies, we demonstrated that _β-cat_(_ex3_) _Co12CreER_ mice also showed TMJ OA-like phonotype.16 Compared to middle and deep layers, the superficial area of the condylar cartilage is

relatively normal. This is probably because the _Col2_ gene is not expressed in cells of the superficial layer. _Col2_ is mainly expressed in the middle and deep layers,28 so the condylar

cartilage was not the most efficiently targeted by _Co12-CreER__T2_ mice.3,29,30 In the present study, we specifically determine the role of β-catenin signaling in _Agc1-CreER__T2_ targeting

cells. Interestingly, we observed that activation of β-catenin signaling in aggrecan-expressing cells leads to dramatic damage in the superficial zone of condylar cartilage. This finding

indicates that the superficial zone of the condylar cartilage could be more efficiently targeted by _Agc1-CreER__T2_ mice. Our findings using both transgenic mice clearly demonstrated that

the proper level of β-catenin activity is critical for maintaining the integrity of the condylar cartilage in TMJ. In this study, we also observed significant increases in the expression of

collagenase (MMP13) and aggrecanases (Adamts4 and Adamts5) in _β-cat_(_ex3_)_Agc1CreER_ mice. In addition, there is a significant increase in the expression of ColX, the most specific marker

of hypertrophic chondrocytes, in _β-cat_(_ex3_)_Agc1CreER_ mice. Consistent with this, increased numbers of hypertrophic chondrocytes were observed in the condylar cartilage in

_β-cat_(_ex3_)_Agc1CreER_ mice. MMP13 and Adamts5 are the primary enzymes leading to cartilage degradation.31,32 β-Catenin may serve as an important regulator of MMP13 and Adamts5 in

hypertrophic chondrocytes. In our study, we used two different β-catenin activation mouse models to demonstrate that proper levels of β-catenin are critical in maintaining condylar cartilage

integrity; however, it remains unknown how β-catenin signaling is upregulated during the development of TMJ OA. Previous reports revealed that cell proliferation and apoptosis in condylar

cartilage could also be involved in OA development.20,33 The rat TMJ OA model showed histological changes, including reduced chondrocytes proliferation and increased chondrocytes

apoptosis.34 It has also been reported that the OA is caused by excessive chondrocyte apoptosis.35 The superficial and/or middle zones of normal condylar cartilage have been identified as

regions enriched in cells that are highly proliferative.19 In the present study, in addition to the cartilage degradation we also demonstrated decreased chondrocyte proliferation and

increased chondrocyte apoptosis in _β-cat_(_ex3_)_Agc1CreER_ mice. These changes could also contribute to the development of TMJ OA. The increased numbers of TUNEL-positive chondrocytes may

reflect the enhancement of chondrocyte differentiation in the middle zone of the condylar cartilage in _β-cat_(_ex3_)_Agc1CreER_ mice.36 This is consistent with the notion that cell

apoptosis of mandibular condylar could be responsible for the development and progression of TMJ OA.20,34 In summary, our study revealed that, in addition to changes in the middle and deep

zones, the morphology and function of the superficial zone of cartilage could also be regulated by β-catenin signaling. We suggest that β-catenin may play important roles in chondrocyte

proliferation, differentiation, and apoptosis in the condylar cartilage. Dysregulation of β-catenin signaling in chondrocytes of condylar cartilage may cause significant changes in

chondrocyte function, leading to TMJ OA development. TMJ β-catenin signaling may be served as a potential therapeutic target for the development of drugs to treat TMJ OA. MATERIALS AND

METHODS ANIMALS _Agc1-CreER__T2_ transgenic mice24 and _ROSA__mT/mG_ (membrane-Tomato/membrane-Green) reporter mice37 were obtained from Jackson Laboratories (Bar Harbor, ME, USA).

_β-catenin_(_ex3_)_flox/flox_ mice were originally reported by Harada et al.,38 and we have used these mice in our previous studies.7,14,16 _β-cat_(_ex3_)_Agc1CreER_ mice and the

Cre-negative littermates were generated. Tamoxifen (Sigma, St. Louis, MO, USA) was administered into 2-week-old mice by intraperitoneal (i.p.) injection (1 mg per 10 g body weight for 5

consecutive days), _n_ = 5 in each group. The animal protocol of this study has been approved by the IACUC of the Rush University and all experimental methods and procedures were carried out

in accordance with the approved guidelines. CRE-RECOMBINATION EFFICIENCY _ROSA__mT/mG_ mice contain two _loxP_ sites on either side of the mT cassette. Mice express red fluorescence in all

cell types and tissues before Cre-recombination and green fluorescence signal can be detected after Cre-recombination.37 _Agc1-CreER__T2_ mice were bred with _ROSA__mT/mG_ mice to generate

_Agc1-CreER__T2__; ROSA__mT/mG_ mice. Tamoxifen was administered into 2-week-old mice by i.p. injection (1 mg per 10 g body weight for 5 days). Skulls were dissected after the mice were

sacrificed at age 1 month, fixed in 0.2% glutaraldehyde at 4 °C for 2 days, followed by washing three times with phosphate buffered saline (PBS). Samples were decalcified in 14% EDTA for 3

weeks, cryo-protected in 30% sucrose at 4 °C for 3 days and then embedded and processed for frozen sections. Three-μm-thick sections were imaged with a fluorescence microscope. HISTOLOGY AND

HISTOMORPHOMETRY We dissected the skulls from _β-cat_(_ex3_)_Agc1CreER_ mice and their corresponding Cre-negative control mice. Samples were fixed in 10% neutral buffered formalin (VWR,

Radnor, PA, USA) for 3 days, then decalcified with formic acid (Decal Chemical Corp., Suffern, NY, USA) for 14 days. Samples were processed and embedded in paraffin. Three-μm-thick

mid-sagittal sections at three different levels (50 μm apart) were cut from the medial compartment of the TMJ. The sections were stained with Alcian blue/hematoxylin and eosin for

morphologic analysis. Three slides per mouse, five mice per group, were analyzed in the experiment. The histology data were further analyzed with OARSI scoring system as previously

described.39,40 We also quantified the cartilage area using the OsteoMeasure software (OsteoMetrics, Inc., Atlanta, GA, USA). IHC AND IF The paraffin sections were baked at 65 °C overnight.

Slides were then deparaffinized and rehydrated. Dako endogenous blocking reagent (S2003, Dako, Carpinteria, CA, USA) was then used to quench endogenous peroxidase for 15 min. Non-specific

binding sites were blocked with 1:10 normal horse/goat serum (S-2000, Vector Laboratories, Burlingame, CA, USA) for 30 min at room temperature. Primary antibodies: 1:400 dilution of MMP13

(ab39012, Abcam, Cambridge, UK), 1:1 000 dilution of ColX (ab49945, Abcam, Cambridge, UK); 1:400 dilution of Admts4 (ABT178, Millipore, Billerica, MA), and 1:500 dilution of Adamts5 (ab41037

Abcam, Cambridge, UK) were added, and the slides were incubated at 4 °C overnight. For IHC assays, the secondary biotinylated goat anti-mouse antibody (BA-9200, Vector Laboratories) at the

dilution of 1:200 was added for 30 min on the second day, followed by incubation with 1:250 streptavidin (21130, Pierce, Rockford, IL, USA) for 30 min. Positive staining was detected by

Romulin AEC Chromagen (Biocare Medical RAEC810L, Concord, CA, USA). For IF staining, an appropriate secondary antibody conjugated to a fluorescence probe was added, incubated at room

temperature for 1 h, rinsed in PBS, and mounted in an anti-fading mounting media (Vector Laboratories, Burlingame, CA). Results were obtained using an Olympus BX43 upright microscope

(Olympus Optical, Tokyo, Japan). CELL PROLIFERATION AND APOPTOSIS ASSAYS We dissected TMJ tissues from _β-cat_(_ex3_) _Agc1CreER_ mice and Cre-negative controls. Samples were fixed in 10%

formalin, decalcified, and embedded in paraffin. The condyles were sectioned into serial sections at 3-μm-thick in an anterior–posterior direction. Cell proliferation was carried out using

anti-PCNA and anti-Ki67 antibodies at the dilution of 1:200 (abl8197, ab16667, Abcam, Cambridge, UK) and 1:2 000, respectively, as previously described.16 Apoptosis assay was carried out

using a TUNEL Assay Kit according to the manufacturer’s instructions (G3250, Promega, Madison, WI, USA). STATISTICAL ANALYSIS The values are presented as mean ± standard error. Statistical

difference between groups was evaluated using one-way analysis of variance followed by Tukey–Kramer test and Student’s _t_-test with the SPSS13.0 statistical software. *_P < _0.05 and

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PubMed Central  Google Scholar  Download references ACKNOWLEDGEMENTS We would like to express our gratitude to Ms. Lily Yu for her help in processing and staining histological samples. This

work was supported by the National Institutes of Health Grants R01 AR054465 and R01 AR070222 to D.C. This work was also partially supported by the Natural Science Foundation of China (NSFC)

(grant # 81371999) to D.C. T.H. was partially supported by the State Scholarship Fund (No. 201406240061), China. J.L. was partially sponsored by a grant from Shenzhen Science and Technology

Innovation Committee (JCYJ20160331114205502 and JCYJ20150626090344603), and T.W. was partially supported by NSFC grants (grant # 81301531 and 81572104), China. AUTHORS CONTRIBUTIONS D.C.

contributed to the experimental design and data interpretation. T.H., L.Z., S.Z., Y.Z., L.L., T.W., and J.G. carried out all experiments. T.H. contributed to the manuscript preparation. D.C.

and L.Y. contributed to the revision of the manuscript. AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * Department of Pediatric Dentistry, Peking University School and Hospital of

Stomatology, Beijing, China Tianqian Hui * State Key Laboratory of Oral Diseases & National Clinical Research Center for Oral Diseases & West China Hospital of Stomatology, Sichuan

University, Chengdu, China Tianqian Hui & Ling Ye * Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, USA Tianqian Hui, Yachuan Zhou, Jun Li, Shanxing Zhang, 

Lifan Liao, Jianhong Gu, Lan Zhao & Di Chen * Department of Pharmacy, Shanghai Ninth People’s Hospital, Shanghai JiaoTong University School of Medicine, Shanghai, China Tingyu Wang *

Department of Medical Cell Biology and Genetics, Shenzhen Key Laboratory and the Center for Anti-Ageing and Regenerative Medicine, Shenzhen University Medical School, Shenzhen, China Jun Li

Authors * Tianqian Hui View author publications You can also search for this author inPubMed Google Scholar * Yachuan Zhou View author publications You can also search for this author

inPubMed Google Scholar * Tingyu Wang View author publications You can also search for this author inPubMed Google Scholar * Jun Li View author publications You can also search for this

author inPubMed Google Scholar * Shanxing Zhang View author publications You can also search for this author inPubMed Google Scholar * Lifan Liao View author publications You can also search

for this author inPubMed Google Scholar * Jianhong Gu View author publications You can also search for this author inPubMed Google Scholar * Ling Ye View author publications You can also

search for this author inPubMed Google Scholar * Lan Zhao View author publications You can also search for this author inPubMed Google Scholar * Di Chen View author publications You can also

search for this author inPubMed Google Scholar CORRESPONDING AUTHOR Correspondence to Di Chen. ETHICS DECLARATIONS COMPETING INTEREST The authors declare no competing interests. RIGHTS AND

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Wang, T. _et al._ Activation of β-catenin signaling in aggrecan-expressing cells in temporomandibular joint causes osteoarthritis-like defects. _Int J Oral Sci_ 10, 13 (2018).

https://doi.org/10.1038/s41368-018-0016-z Download citation * Accepted: 06 February 2018 * Published: 23 April 2018 * DOI: https://doi.org/10.1038/s41368-018-0016-z SHARE THIS ARTICLE Anyone

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