PDGFA in Cashmere Goat: A Motivation for the Hair Follicle Stem Cells to Activate

SIMPLE SUMMARY: Cashmere goats are the most important goat breed due to the high yield and fineness of the fibers that they produce. Cashmere fiber is a luxury product since it is soft, light and warm. The development of this fiber depends on the hair follicle (HF) cyclical activity, which is characterized by the succession of growth and regressive phases. In the transition between telogen and anagen phases, many growth factors work to activate the HF stem cells and to allow the growth of a new cashmere fiber. As several factors involved in the stem cell activation, Platelet-Derived Growth Factor A (PDGFA), Bone Morphogenetic Protein 2 (BMP2) and Lim-Homeobox gene 2 (LHX2) were analyzed in this work to evaluate their activity during the cashmere HF cycle. These molecules were studied using different approaches and finally, PDGFA and BMP2 appeared to have higher levels of expression during the cycle activation phase with respect to the LHX2, which suggests that they play a main role in the development of a new cashmere fiber. The obtained data will improve the knowledge of the HF cycle in the cashmere goat and they could be a useful tool for improving cashmere fiber production. ABSTRACT: The cashmere hair follicle (HF) perpetually goes through cycles of growth, involution and rest. The photoperiod is the main factor in the control of seasonal coat change in cashmere goats while stem cells play a crucial role in the HF growth. Several factors, including Platelet-Derived Growth Factor A (PDGFA), Bone Morphogenetic Protein 2 (BMP2) and Lim-Homeobox gene 2 (LHX2) are implicated in HF morphogenesis and cycle. In this work, the mentioned molecules were investigated to evaluate their role in follicular cycle activation. The study was performed on skin samples collected at different periods of HF cycle and the molecular expression of PDGFA, BMP2 and LHX2 was evaluated by Real-Time PCR (qPCR) at each time point. Since PDGFA showed the most variation, the goat PDGFA gene was sequenced and the protein localization was investigated by immunohistochemistry together with PDGF receptor α (PDGFRα). PDGFA immunostaining was observed in the basal layer of the HF outer root sheath and the immunoreaction appeared stronger in the regressive HFs compared to those in the anagen phase according to qPCR analysis. PDGFRα was observed in the HF epithelium, proving the effect of PDGFA on the follicular structure. The data obtained suggest that PDGFA and BMP2 are both implicated in HF cycle in goat. In particular, PDGFA secreted by the HF is involved in the anagen activation.