SiRNA-Mediated Inhibition Of FGF5 And FGF18 And Redulation Of Hair Follicle Cycle

Both Fibroblast growth factor 5(FGF5)and Fibroblast growth factor 18(FGF18)are key regulators of hair follicle(HF)cycling.FGF5 is highly expressed in late anagen phase to induce onset of catagen phase of HF cycle,thereby stopping the hair growth.FGF18 is strongly expressed in telogen HF to maintain the telogen phase,while simultaneously inhibiting the anagen phase.Therefore,FGF5 and FGF18 may serves as potential targets for HF cycle modulation and hair growth promotion.The present study is aimed to modulate HF cycling and promote hair growth with small interfering RNA(si RNA)-mediated gene silencing of FGF5 and FGF18.The candidate si RNAs were designed using Si Direct,Oligowalk and Si RNA online software and screened in NIH/3T3 cells transfected with recombinant plasmid expressing FGF5 or FGF18,through examining their inhibitory effects on FGF5 or FGF18 expression with q PCR.The inhibition on FGF5 by cell-penetrating peptide-delivered si RNA and cholesterol-modified si RNA were compared both in vitro and in vivo,and it was found that cholesterol-modified si RNA exhibits a more effective and stable inhibitory effects.The modulating effect of FGF5-targeting si RNA on HF cycling was investigated in a depilation-induced hair growth mouse model.The m RNA and protein levels of FGF5 in skin tissues were assayed by q PCR and Western blotting.The HF cycling stage was determined by observing the morphologic changes of HF in H&E-stained skin sections.The result shows that intradermal injection of cholesterol-modified si RNA results in down-regulation of FGF5 expression in skin tissues and a delayed entry of hair follicle into catagen and extension of anagen phase.The modulating effect of FGF18-targeting si RNA on HF cycling was investigated in a hair-shaving telogenic mouse model.The result shows that both intradermal injection and topical cream application of cholesterol-modified si RNA result in a remarkable down-regulation of FGF18 expression in skin tissues and an earlier initiation of anagen phase.To summarize,the present study confirmed that the cholesterol-modified si RNA is able to silence FGF5 and FGF18 both in vitro and in vivo,and capable of modulating HF cycling,si RNA-mediated FGF5 silencing prolong the anagen phase whereas si RNA-mediated FGF18 silencing promote an earlier entry of HF into anagen phase and increase hair elongation.These finding suggest that the targeting of cutaneous regulators of HF cycling such as FGF5 and FGF18 by si RNA might may be a promising strategy in the treatment of alopecia.