FAP and periodontitis: Specifically, OLN promotes bone formation by facilitating BMSC differentiation into mature osteoblasts,[37] while FAP inhibits bone formation by suppressing the Wnt/β‐catenin signaling pathway in BMSCs.[8] Additionally, FAP can impair BMSC osteogenic differentiation by activating the expression of histone lysine demethylase 7A.[38] Notably, we observed that FAP+ fibroblasts and OLN+ fibroblasts were predominantly localized near the alveolar bone surface, where bone resorption typically begins in periodontitis.