毛囊是哺乳類動物皮膚的附屬物，具有定期再生用以保溫的能力。在體內平衡期間，外部微環境與來自於上皮細胞和間充質細胞的信號會調控毛囊生長週期。此外，游離輻射會導致毛囊進入萎縮性週期，其中包括萎縮性生長期和萎縮性衰退期甚至於導致掉髮。然而目前依然不清楚游離輻射導致地在毛囊再生過程中毛囊細胞的行為表現。在本實驗當中，我們通過活體影像和組織學分析闡明了輻射損傷後毛囊再生的機制。我們證明在受到2戈雷和5.5戈雷輻射照射後基底膜會失去其完整性。而且我們還追蹤了同一根受到游離輻射照射後的毛囊並發現它會進入萎縮性生長期。此外，我們通過縮時攝影活體影像觀察再生過程中上皮細胞及其後代的行為。在早期階段，凋亡細胞出現在毛囊基質當中，而外根鞘細胞停留在最初的位置。在受到5.5戈雷游離輻射照射48小時後，外根鞘細胞開始向下遷移並且試圖脫離基底膜。在照射後72到84小時，由於大量的細胞凋亡導致毛囊球逐漸消失。與此同時，上皮細胞也出現了顯著性的變化。透過我們的實驗，我們認為外根鞘細胞的搖擺向下運動和脫離基底膜都是由於基底膜的不完整而造成的，這為探索毛囊再生的機制提供了一個新的思路。

Hair follicles are appendages of the mammalian skin with the capacity to regularly regenerate for temperature protection. During homeostasis, external microenvironment and intrinsic signals from epithelial cells and mesenchymal cells regulate hair cycle. Besides, radiation induces hair follicle dystrophies, including dystrophic catagen and dystrophic anagen, and even hair loss. However, the cellular behaviors in hair follicle regeneration from radiation remain unclear. In this study, we elucidate the mechanisms of hair follicle regeneration post-radiation injury using intravital imaging and histological analysis. We demonstrated that basement membrane loses its integrity after 2Gy and 5.5Gy radiation. After radiation, we also traced single hair follicle and found that the hair follicle entry dystrophic anagen. Also, we monitored the behavior of epithelial cells and their progeny during regeneration by long-term live imaging. In the early phase, apoptotic cells appeared in the matrix of the hair follicle and the outer root sheath cells stayed at the original position. After 48 hours after 5.5Gy radiation, the ORS cells began to migrate downward and attempted to escape from the basement membrane. Hair bulb gradually disappeared at 72-82 hours due to massive apoptosis. Meanwhile, the epithelial cell morphology dramatically changes. Our result suggesting that the swinging downward movement of ORS cells and the detachment of basement membrane are all due to the incompleteness of basement membrane, which brings a new thought to explore the mechanism of HF regeneration.

口試委員會審定書..........................................#
中文摘要..................................................i
ABSTRACT................................................ii
CONTENTS...............................................iii
LIST OF FIGURES..........................................v
LIST OF TABLES..........................................vi
Introduction.............................................1
The structure of hair follicle...........................1
The cycle of hair follicle...............................2
Niche (microenvironment) of hair follicle................2
Hair follicle dystrophic model by ionizing radiation.....3
Intravital imaging.......................................4
Materials and Methods....................................6
Mice.....................................................6
Synchronization of the hair follicle cycle...............6
Radiation................................................7
Immunofluorescence staining..............................7
Intravital imaging.......................................7
Animal prepares for live imaging.........................8
Imaging processing.......................................9
Results.................................................10
Hair follicle basement membrane integrity changed from anagen to catagen.......................................10
Hair follicle basement membrane was damaged after irradiation injury......................................12
Irradiation-induced HF dystrophic change can be observed through two-photon microscopy...........................13
ORS cells did not migrate significantly in dystrophic anagen during 12 to 24 hours after 5.5 Gy IR injury.....16
ORS cells migrated downward and also attempted to migrated inward to IRS during 48 to 60 hours after irradiation injury..................................................18
Hair bulb shrank gradually and accompanied by massive apoptotic fragment during 72 to 82 hours after 5.5 Gy IR injury..................................................20
Discussion..............................................22
References..............................................25

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