BCL-2 is a negative regulator of apoptosis [46] and we hypothesized that a reduced BCL2 expression by pPDLSCs can be due to the stress conditions in the periodontitis microenvironment, enriched with free oxygen radicals, indeed it has been demonstrated that PDLSCs treated with H2O2 showed inhibition of BCL2 [47]. This evidence concerns the gene BCL2 and periodontitis.