الفهرس 
Introduction & Aim of the workOnly 14 pages are availabe for public view
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Abstract
Hair growth is a unique cyclic regeneration phenomenon where the HFs undergo successive growth cycles of anagen (active growth), catagen (cessation of growth and regression), telogen (period of relative quiescence) and exogen (shedding of the old hair fiber) (Plikus and Chuong, 2008).
HF has a stem cell niche called the bulge that acts as a reservoir of multipotent stem cells that could give rise to all epithelial lineages of the skin, including epidermal and follicular keratinocytes and sebocytes, it undergoes dramatic morphological and molecular changes during the different phases of the hair cycle, as stem cells in the niche become activated and proliferate only during the anagen phase of the hair cycle (Inoue et al.,2009).
Wound repair is a biological well-coordinated process that involves the integrated interaction of different cell types. It comprises of three main phases; an initial phase that leads to hemostasis and an inflammatory reaction, a second proliferative phase and a third phase that comprises tissue remodeling and regeneration (Gainza et al.,2015).
Humans and other adult mammals have a limited capacity to regenerate and restore their tissues and organs. This can be obtained through the attraction of somatic stem cells located in a niche or by inducing differentiated cells to proliferate (Borena et al., 2015)
HF stem cells have a significant contribution to wound healing mediated by recruitment of cells from wound-adjacent HFs as re-epithelialization classically occurs from the periphery (Vagnozzi et al., 2015),this came from the observation that areas with higher follicle densities, such as the mice back skin or human scalp heals better than other non-hair-bearing areas(Ito and Cotsarelis, 2008).
Also, it has been demonstrated that wounding of mice during the anagen phase of hair cycle resulted in accelerated skin repair, accompanied with significantly pronounced reduction in wound area compared with wounding in the catagen or telogen hair cycle stage (Ansell et al., 2011).
Wound care has traditionally been relied on dressings, comprising both natural and synthetic materials (Boateng et al., 2008) but they did not achieve the desired results(Chen et al., 2015), Therefore, there is an urge to develop more effective therapeutic strategies that encourage the body’s natural repair mechanisms that promotes tissue regeneration (Eming et al., 2014).
This study has been conducted at The Ohio State University, Wexner Medical center, USA. All animal studies were performed in accordance with protocols approved by the Laboratory Animal Care and Use Committee of The Ohio State University. This study has been conducted on 42 Male C57BL/6 and 20 Male mice homozygous +/+ Leprdb/J, or db/db mice. Mice were randomly assigned in to two groups TRF and PBO.
In the present study, we first tested the ability of TRF to induce anagen hair cycling in C57Bl/6 mice (TRF group; n=21, PBO group n=21), we applied TRF or PBO was applied topically into shaved and depilated dorsal skin of 8 weeks old mice at a dose of 200μl / mouse thrice per weektill d7, d14 and d21 with 7 mice in each group at each time point. Mice have been sacrificed and biopsy collected at each time point. While the PBO mice group remained in telogen phase noted by the pink dorsal skin, the TRF mice group showed anagen induction noted by the black dorsal skin starting at d7 and reached the maximum effect at d21 of application confirmed by histological examination that showed statistically significant increase (d7, P=0.02; d14, P=0.0004; d21, P=0.0002 ) in the anagen HFs score in TRF treated group compared with PBO group which remained in telogen, accompanied with statistically significant increase (d7, P=0.002; d14, P=0.01; d21, P=3.81E05 ) in subcutaneous fat layer thickness in anagen skin TRF group compared to telogen skin PBO group.
After optimizing the effect of TRF on anagen induction to be maximum at d21, we tested the effect of TRF on db/db mice hair cycling, We noticed that the TRF mice group (n=10) showed anagen induction at d21 compared to PBO group (n=10) which remained in telogen confirmed by histological examination that showed significant increase (P=0.007) in anagen HFs score in TRF group compared to PBO group. Also, we noticed the anagen wave extending beyond the area of TRF application as anagen follicles in the propagating phase send activators into the inter-follicular macro-environment to facilitate the anagen entry of adjacent competent telogen follicles(Plikus et al., 2009).