Expression of placenta growth factor in mouse hair follicle cycle

Aim. The hair follicle cycle comprises an anagen growth phase followed by a catagen regression phase and a telogen resting phase. During anagen neoangiogenesis events occur leading to a marked increase in the extension of the perifollicular vascular network. The aim of the present study was to evaluate the expression of the angiogenic cytokine placenta growth factor (PlGF) in hair follicle and its relationship with changes in perifollicular vascularization during hair cycle. Methods. A murine model of synchronized hair follicle cycling induced by depilation was employed to obtain skin samples at different time points of the hair cycle. The evaluation of PlGF expression and perifollicular vessels was performed by immunohistochemical analysis. A computer assisted morphometric analysis was used to quantify perifollicular vessel size and density. Results. Immunoreactivity for PlGF was detected during anagen in follicular keratinocytes of the outer root sheath, with maximum signal 8 days after depilation (middle anagen), while no PlGF staining was observed in catagen and telogen phases. Computer assisted morphometric analysis in perifollicular dermis showed a significant increase in average vessel size and in percentage of dermal area occupied by blood vessels during late anagen. Conclusion. The present study shows that PlGF protein is upregulated in anagen mouse hair follicles, immediately before the maximum peak of perifollicular angiogenesis. These results suggest a role for PlGF in modulation of hair follicle-associated angiogenesis events. PlGF might act in synergism with the closely related vascular endothelial growth factor (VEGF) which has recently been shown to promote anagen angiogenesis and hair growth.