TNF and periodontal disorder: It seems that in the response to the inflammation which caused by TNF-α, the expression of miR-142 significantly increases in HGECs.37 It seems that, the expression of miR-17 is in association with diminished expression of IL-8.38 IL-8 is an important chemokine involved in the recruitment of immune cells, so it is useful to study the association between miR-17 expression in HGECs and IL-8 secretion in periodontal disease.