Effect Of AnxA1 On Apoptosis Of Hair Follicle Cells In Hair Follicle Growth Cycle And Its Mechanism

Annexin A1(AnxA1),as a calcium-dependent phospholipid binding protein,exists in eukaryotic cells and have a hand in many life activities.Apoptosis is a continuous activity during the growth of hair follicles(HFs).AnxA1 is one of the relevant factors affecting the growth and development of HFs and also affects the transcription and translation of the apoptotic genes TNF-? and Caspase3.We speculate that AnxA1 may have an effect on the apoptosis of hair follicle cells(HFCs)during the periodic growth.In order to explore the influence of AnxA1 on HFs apoptosis,this study used the AnxA1 gene Knock out(KO)and Overexpression(OE)mice and Wild type(WT)mice back skin tissue as experimental materials.The effects of AnxA1 on HFCs apoptosis,the main action period of AnxA1 on HFCs apoptosis and the molecular mechanism of the process were investigated by TUNEL,RT-qPCR,Western blot,HE staining and immunofluorescence.1.Comparison of HFs structure in the back skin of AnxA1 KO,OE and WT miceIn this study,the artificial depilation was used to construct a synchronous mouse model and the back skin HFs sections of the first natural cycle mice were dyed with HE to observe the HFs structure throughout the growth cycle.There was no significant change in HFs growth in WT,AnxA1 KO and OE mice during anagen and telogen.Compared with WT mice,the vertical longitude of HFs and the shrinkage degree of HFs were stronger in AnxA1 KO mice during the catagen stage,and the epidermal layer was thinner,and the decrease degree of hair papilla was deeper.There were no significant changes in the vertical longitude of hair bulb,epidermis,dermis and HFs between AnxA1 OE mice and WT mice.2.The effect of AnxA1 on HFCs apoptosis and its main action periodNuclear DNA breakage was detected by TUNEL assay.The DNA breakage occurred mainly in the inner root sheath,outer root sheath,epidermis and dermis of WT,AnxA1 KO and OE mice during anagen.Catagen is an active period of apoptosis.DNA breakage occurred in the inner root sheath and outer root sheath,epidermis and dermis of mice.Compared with WT mice,DNA breakage in the HFCs of AnxA1 KO mice was stronger than that of WT mice,and DNA breakage occurred in the HF bulb of WT mice.There was no dramatic difference between WT and AnxA1 OE mice.At telogen,DNA breaks were mainly in the outer root sheaths of the three kinds of mice,and there was no dramatic difference.Detection of Caspase3 gene transcription and translation level showed that the expression of Caspase3 gene was up-regulated in AnxA1 KO mice during the catagen,and there was no dramatic difference in the expression of Caspase3 gene between WT and AnxA1 OE mice.Therefore,it is speculated that AnxA1 affects HFCs apoptosis mainly in catagen,and may inhibit HFCs apoptosis.3.The molecular mechanism of AnxA1 affecting HFCs apoptosisIn order to study how AnxA1 affects HFCs apoptosis,the apoptotic factors Bcl2,Bax and P53 were firstly detected.At the early stage of catagen,the expression of Bcl2 and P53 in KO mice were higher than those in WT and OE mice,while the expression of Bax were lower than those in WT and OE mice,and there was no dramatic difference between AnxA1 OE and WT mice.At the late stage of catagen,there was no dramatic difference in the expression levels of the three mice.The results showed that AnxA1 may inhibit the apoptosis of HFs through the apoptotic factors Bcl2,Bax and P53.In order to study the effect of PI3K/ AKT signaling pathway on HFs apoptosis,phosphorylated PI3 K,AKT and its downstream molecules Foxo1 and Mdm2 were detected.Compared with WT mice,the phosphorylation levels of PI3 K and AKT in AnxA1 KO mice decreased the expression of Mdm2 at the early stage of catagen.There was no dramatic difference in the phosphorylation level and Mdm2 expression between WT and AnxA1 OE mice.The phosphorylation levels of PI3 K and AKT and the expression levels of Mdm2 in AnxA1 KO and OE mice were not significantly different from those in WT mice at the late stage of catagen.Foxo1 expression in KO and OE mice was higher than that in WT mice at the early stage of catagen.There was no significant difference in Foxo1 expression between AnxA1 KO and WT mice in the late catagen,and the expression of Foxo1 in OE mice was higher than WT mice.The results indicated that AnxA1 may inhibit HFs apoptosis through PI3K/AKT signaling pathway.