(D) RT-qPCR quantification of relative miR-21-3p levels in total skin of chronically irradiated (Chr-UV; +) and non-irradiated (-) Ppard +/+ and -/- mice. miR-21-3p: Ppard +/+ no UV vs Ppard +/+ Chr-UV P = 0.008, Ppard +/+ Chr-UV vs Ppard -/- Chr-UV P = 0.002, ns: non significant. N=4 animals per groups, one representative experiment is shown out of two independent replicates. 