Comparing to healthy PDLSCs, PTCSC3 was significantly downregulated (Fig. 1a), while TLR4 mRNA was significantly upregulated (Fig. 1b) in periodontitis-affected PDLSCs (p < 0.05), indicating the involvement of PTCSC3 and TLR4 in the pathogenesis of periodontitis. The gene discussed is TLR4; the disease is periodontitis.