Scalp bacterial species influence SIRT1 and TERT expression in keratinocytes

Scalp bacteria on the human scalp and scalp hair comprise distinct community structures for sites and individuals. To evaluate their effect on human keratinocyte cellular activity, including that of the hair follicular keratinocytes, the expression of several longevity genes was examined using HaCaT cells. A screening system that uses enhanced green fluorescent protein (EGFP) fluorescence was established to identify scalp bacteria that enhance silent mating type information regulation 2 homolog-1 (SIRT1) promoter activity in transformed HaCaT cells (SIRT1p-EGFP). The results of quantitative polymerase chain reaction revealed that several predominant scalp bacteria enhanced (Cutibacterium acnes and Pseudomonas lini) and repressed (Staphylococcus epidermidis) the expressions of SIRT1 and telomerase reverse transcriptase (TERT) genes in HaCaT cells. These results suggest that the predominant scalp bacteria are related to the health of the scalp and hair, including repair of the damaged scalp and hair growth, by regulating gene expression in keratinocytes.