## 3 Results
### Selected DAMP Sensors mRNA Detection in HGT, HGK, or HGF  
Messenger RNAs encoding TLR1, TLR2, TLR3, TLR5, TLR6, NOD1, NOD2, or NLRP1 were detectable among all HGT biopsies, HGK, and HGF cell explants investigated (Table 1). TLR4 or NLRP2 mRNA were not detected in every cell sample, with TLR4 being detectable in only 12/27 HGK (44.4% healthy gingival keratinocyte explants), or NLRP2 in only 5/27 HGF (18.5% healthy gingival fibroblasts explants), respectively. However, TLR4 expression in HGF and NLRP2 expression in HGK were observable in all samples followed. TLR7, TLR8 or TLR10 mRNAs were detectable among all HGT biopsies but were not detectable in any of the HGK or HGF explants. TLR9 mRNA was undetectable in HGT, HGK, or HGF (Figure 2). Quantities of Selected DAMP Sensor Transcripts from HGK or HGF under Hypoxia or E. coli LPS Stimulation  
The quantity of transcripts expression of DAMP sensors detectable by RT-qPCR from HGK/HGF explants, i.e., TLR1-6, NOD1, NOD2, NLRP1, or NLRP2 (Figure 2), under 1% or 18% O\({}_{2}\), 24 h, or 2 ug/mL _E. coli_ LPS under normoxia at 24 h, was followed (Table 4). Except TLR4 and NLRP2, the selected DAMP sensor mRNAs of interest were detectable from all HGK or HGF explants at both oxygen tensions tested at 24 h. The former, even if detectable from some cell explant samples, was persistently at low relative quantities in HGK (TLR4) or HGF (NLRP2), while the corresponding TLR4 mRNA in HGF or NLRP2 mRNA in HGK relative expression levels remained similar to other DAMP sensors investigated (Table 4). Under 2 ug/mL _E. coli_ LPS at normoxia at 24 h, all ten DAMP sensor mRNAs of interest were detectable (Table 4). Figure 2: Selected DAMP sensors mRNA detection from HGT, or HGK/HGF primary cultures. By reverse transcription, PCR, TLR1-6, NOD1/2 and NLRP1/2 were detectable in HGT, HGK, and HGF with TLR4 or NLRP2 detectable in some but not all samples investigated (please refer to text and Table 4 for details). TLR7/8/10 mRNAs were only detectable from HGTs. THP-1 cell line was utilized as the positive control for TLR9 mRNA detection. HGF—human gingival fibroblasts, HGK—human gingival keratinocytes, HGT—human gingival tissue. Apparently, under 1% O\({}_{2}\), 24 h, mRNA expression of TLR1-3, TLR6, NOD1/2 and NLRP1/2 in HGK were significantly increased at up to 4.6-fold for NOD2, while concerning HGF, TLR1-5, NOD1 and NLRP1 mRNAs seemed to be increased in hypoxia, up to 5.1-fold for TLR2 (Table 4). With the presence of 2 ug/mL E. coli LPS at normoxia at 24 h, only TLR2 and NOD2 expressions on HGK appeared significantly increased at up to 4.0 times for NOD2, compared to untreated controls. For HGF, the same LPS treatment seemed able to upregulate signals for TLR1, TLR2, TLR6 and NOD2, at up to 6.3-fold for NOD2 (Table 4). Levels of Selected DAMP Sensor Proteins from HGK or HGF under Hypoxia and/or E. coli LPS Stimulation  
DAMP sensor proteins observable from immunohistochemistry (Figure 1) were followed in HGK/HGF explants in vitro. Both cells were also subjected to 24 h 1% O\({}_{2}\) and/or 2 ug/mL _E. coli_ LPS treatment. In brief, TLR1-6, NOD1/2 or NLRP1/2 appeared readily detectable on both cell explants in hypoxia and/or _E. coli_ LPS challenge (Figure 3A). Semiquantitative analysis of DAMP sensors under various experimental conditions were also reported (Figure 3B,C). In brief, TLR1, TLR6 and NOD2 proteins appeared significantly increased after HGF treated by 1% O\({}_{2}\) and/or 2 ug/mL _E. coli_ LPS at 24 h (Figure 3C), while the same appeared observable for TLR6 only on HGK cells (Figure 3B). For the latter, TLR1 or NOD2 peptide appeared significantly increased upon 1% O\({}_{2}\) or 1% O\({}_{2}\) and 2 ug/mL _E. coli_ LPS at 24 h treatment, respectively (Figure 3B).