Fig. 1: Early cathepsin K (Ctsk) activation in the ligature-induced periodontitis in mice. | Communications Biology

Fig. 1: Early cathepsin K (Ctsk) activation in the ligature-induced periodontitis in mice.

From: Oral microbial extracellular DNA initiates periodontitis through gingival degradation by fibroblast-derived cathepsin K in mice

Fig. 1

a The ligature (5.0 silk suture) was placed around the maxillary second molar (M2). Representative microCT images of the maxilla taken from the lateral view at the 1, 3, and 7 days after ligature placement. b Alveolar bone loss was measured at the middle of the second molar from cementoenamel junction (CEJ) to the alveolar bone crest (ABC) (n = 9). c The Osteoadsorptive Fluorogenic Sentinel (OFS) probe. OFS binds strongly to bone, where it remains quenched until activation by Ctsk through cleavage of a linker region containing the Ctsk substrate motif. d Day 4 of ligature placement, OFS-1 signal was detected but the fluorescent signal was not detected from a commercially available Ctsk FRET probe without a bisphosphonate bone anchoring element (SensoLyte 520, Anaspec, Fremont, CA) (n = 6). e Representative images showing Ctsk activation of OFS-3 fluorescence detected by an IVIS Spectrum system at 0, 1, 3, and 7 days after ligature placement. Quantification of the fluorescent signal was performed by region-of-interest placement to capture the entire palate, and results were represented as the total fluorescent signal (n = 4–5). f Immunohistochemical staining for Ctsk, counterstaining with methylene blue, and HE staining of the periodontal tissue at the 1 and 7 days after ligature placement. Yellow arrows indicate the Ctsk positive cells in the gingival and periodontal ligament connective tissue. White arrows indicate the Ctsk-positive osteoclasts on the alveolar bone and osteoclastic lacunae. Yellow asterisks indicate disintegrated gingival connective tissue. g A high-magnification photomicrograph of Day 7 IHC depicting Ctsk+ osteoclasts (while arrows). The insert shows TRAP+ osteoclasts. h A high-magnification photomicrograph of Day 7 IHC depicting Ctsk+ connective tissue cells (yellow arrows). i The number of Ctsk+ cells in gingival connective tissue (n = 3). ANOVA with Tukey’s multiple-comparison test (b, e, i) and Student’s t test (d). Data are presented as mean values ± SD; p < 0.05 was considered significant. The source data are provided in Supplementary Data 1, b, d, e, i.

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