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Effect of CBX7 deficiency on the socket healing after tooth extractions

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CBX7 is shown to down-regulate the expression of osteopontin (OPN) that is associated with osteoblast function. Here, we studied the role of CBX7 in the wound healing of tooth extraction socket in which osteoblast activity is critical via comparison between CBX7-knockout (CBX7−/−) mice and their wild-type (WT) counterparts of 6 weeks old with maxillary first molar extracted. Mice were euthanized at 7, 14, and 21 days after extractions, and alveolar sockets were assessed by semi-quantitative histomorphometry for hard tissue healing, including new bone fill (Masson’s trichrome staining), osteoblast activity (OPN/osterix, Osx), osteoclast activity (tartrate-resistant acid phosphatase, TRAP), and for soft tissue healing, including blood vessels (alpha smooth muscle actin, α-SMA). Also, the bone microarchitecture was evaluated by micro-CT. In radiological analysis, CBX7−/− mice increased bone mass significantly more than WT mice did. Consistently, both the amount of new bone fill and OPN/Osx-immunopositive cells in the extraction sockets were significantly increased in CBX7−/− mice at each time point with respect to their WT siblings, while osteoclast number exhibited a trend of more increase in CBX7−/− mice at all time points as well. In agreement with enhanced bone formation during socket healing, significantly elevated α-SMA-immunopositive area was noted in CBX7−/− mice in contrast to WT mice. Taken together, these data suggest that CBX7 deficiency has a positive effect on tooth extraction socket healing.

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This study was supported in part by the National Basic Research Program of China (2012CB966902), the National Natural Science Foundation of China (81670966), the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD, 2014-37) and the Project of Invigorating College through Science and Education.

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Correspondence to Zhixuan Zhou or Ning Chen.

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Fig. S1

Tooth extraction of mouse upper left first molar. a Preparation of mouse and instruments. b Position of the elevator blade between 1st and 2nd molars. c Morphology of tooth extraction socket. The yellow dotted lines depict the locations of three roots, including mesio-, distobuccal and distopalatal root (M, DB and DP). d Shape of mouse upper left first molar without any fractures (JPEG 4219 kb)

Fig. S2

CBX7 expression in post-extraction sockets of WT mice. Representative photomicrograph of extraction wound sections stained immunochemically for CBX7. Bar, 100 μm (JPEG 628 kb)

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Jiang, F., Yang, X., Meng, X. et al. Effect of CBX7 deficiency on the socket healing after tooth extractions. J Bone Miner Metab 37, 584–593 (2019).

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