*2.1. Human Gingiva-Derived Stem Cells*

GDSCs were collected using a previously reported method [21]. Gingival tissue was collected from a 70-year-old female undergoing a second implant surgery. The institutional review board of Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea approved this study (KC19SESI0259), and written informed consent was obtained from the participant. All experiments were performed according to relevant guidelines and regulations specified in the Declaration of Helsinki.

Gingival tissue was de-epithelialized, minced into 1–2 mm2 fragments, and digested in an alpha-modified minimal essential medium (α-MEM; Gibco, Grand Island, NY, USA) containing dispase (1 mg/mL; Sigma-Aldrich, St. Louis, MO, USA) and collagenase IV (2 mg/mL; Sigma-Aldrich). Cells were incubated in a humidified incubator at 37 ◦C. Every 2–3 days nonadherent cells were rinsed with phosphate-buffered saline (PBS; Welgene, Daegu, South Korea) and placed in fresh medium.
