Atlas of Prenatal Hair Follicle Morphogenesis Using the Pig as a Model System

Yao Jiang,Xiangdong Ding,Yi Wang,Quan Zou,Bo Liu,Tianlong Liu,Shujuan Li

doi:10.3389/fcell.2021.721979

Abstract

The pig is an increasingly popular biomedical model, but only a few in depth data exist on its studies in hair follicle (HF) morphogenesis and development. Hence, the objective of this study was to identify the suitability of the pig as an animal model for human hair research. We performed a classification of pig HF morphogenesis stages and hair types. All four different hair types sampled from 17 different body parts in pig were similar to those of human. The Guard_2 sub-type was more similar to type II human scalp hair while Guard_1, Awl, Auchene, and Zigzag were similar to type I scalp hair. Based on morphological observation and marker gene expression of HF at 11 different embryonic days and six postnatal days, we classified pig HF morphogenesis development from E41 to P45 into three main periods – induction (E37–E41), organogenesis (E41–E85), and cytodifferentiation (>E85). Furthermore, we demonstrated that human and pig share high similarities in HF morphogenesis occurrence time (early/mid gestational) and marker gene expression patterns. Our findings will facilitate the study of human follicle morphogenesis and research on complex hair diseases and offer researchers a suitable model for human hair research.

Highlights

Hair follicles (HFs) are one of the most important appendages of the skin
The mouse is the most commonly used animal model for research on human HF development, the classification of hair types in human has been implemented in different ways, mainly depending on the body parts with scalp hair being the most studied hair type (Duverger and Morasso, 2009; Buffoli et al, 2014)
Similarities could still be explored between pig and human scalp hair

Summary

Introduction

Hair follicles (HFs) are one of the most important appendages of the skin. Their development is divided into prenatal HF morphogenesis development and postnatal HF cycle development (Schneider et al, 2009). HF morphogenesis development in the prenatal stage is critically important, which determines HF cycle development in the postnatal stage. Several classical genetic markers such as SOX2 (Saxena et al, 2019), LEF1 (Boras-Granic et al, 2006), SOX9 (Nguyen et al, 2018), and KRT15 (Miyachi et al, 2018) have been established as critical genes involved in each step of morphogenesis, and studies on these genes have enabled a fine-toothed dissection of the cellular and molecular dynamics of HF morphogenesis (Sennett et al, 2015; Tomann et al, 2016)

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Conclusion