T0026

Two human gingiva KC cell lines and one human gingiva fibroblast cell line were used. Cell lines were used for experiments up to passage 50. Human gingiva KC cell line, OKG4/bmi1/TERT, was immortalized by expression of Telomerase Reverse Transcriptase (purchased from Rheinwald laboratory).^{29 (link),30 (link)} In our study, it is referred to as KC-TERT. Human gingiva KC were immortalized with the human papillomavirus type 16 as described previously (University Medical Center Freiburg) and are referred to in this study as KC-HPV.^{25 (link),31 (link),32 (link)} Both KC cell lines were cultured in KC medium as described above. The human gingiva fibroblast cell line was TERT immortalized (T0026, purchased from ABM) and referred to in this study as Fib-TERT. It was cultured in fibroblast medium as described above.

Healthy human gingiva tissue was used in an anonymous fashion in accordance with the “Human Tissue and Medical Research: Code of conduct for responsible use” as formulated by the Federation of Dutch Medical Scientific Societies (www.federa.org). Primary human gingiva fibroblasts were isolated as previously described (Buskermolen et al., 2016). In short, after enzymatic separation of the epithelium and lamina propria, the lamina propria was digested in collagenase type II (Gibco, Grand Island, NY) for 3 hr. After passing the tissue suspension through a 40 μm cell strainer (Corning, Oneonta, NY) and washing with PBS, the cells were cultured in fibroblast medium consisting of DMEM (Gibco), supplemented with 5% Fetal Clone III (GE, Logan, UT) and 1% penicillin‐streptomycin (Gibco). Fibroblasts were used between passage 2 and 4. The hTERT‐immortalized human gingiva fibroblasts (T0026, purchased from ABM, Richmond, BC, Canada) were also cultured in fibroblast medium and used until passage 30.