Follicle and melanocyte stem cells, and their application in neuroscience A Web of Science-based literature analysis

OBJECTIVE: To identify global research trends of follicle and melanocyte stem cells, and their application in neuroscience. DATA RETRIEVAL: We performed a bibliometric analysis of studies from 2002 to 2011 on follicle and melanocyte stem cells, and their application in neuroscience, which were retrieved from the Web of Science, using the key words follicle stem cell or melanocyte stem cell, and neural, neuro or nerve. SELECTION CRITERIA: Inclusion criteria: (a) peer-reviewed published articles on follicle and melanocyte stem cells, and their application in neuroscience, which were indexed in the Web of Science; (b) original research articles, reviews, meeting abstracts, proceedings papers, book chapters, editorial material, and news items. Exclusion criteria: (a) articles that required manual searching or telephone access; (b) documents that were not published in the public domain; and (c) a number of corrected papers from the total number of articles. on follicle and melanocyte stem cells by years, journals, countries, institutions, institutions in China, and most cited papers. (2) Distribution of publications on the application of follicle and melanocyte stem cells in neuroscience by years, journals, countries, institutions, and most cited papers. RESULTS: Of the 348 publications from 2002 to 2011 on follicle and melanocyte stem cells, which were retrieved from the Web of Science, more than half were from American authors and institutes. The most prolific institutions in China for publication of papers on follicle and melanocyte stem cells were the Fourth Military Medical University and Third Military Medical University. The most prolific journals for publication of papers on follicle and melanocyte stem cells were the Journal of Investigative Dermatology , Pigment Cell & Melanoma Research . Of the 63 publications from 2002 to 2011 on the application of follicle and melanocyte stem cells in neuroscience, which were retrieved from the Web of Science, more than half were from American authors and institutes, and no papers were from Chinese authors and institutes. The most prolific journals for publication of papers on the application of follicle and melanocyte stem cells in neuroscience were the Journal of Investigative Dermatology , Pigment Cell & Melanoma Research . CONCLUSION: Based on our analysis of the literature and research trends, we found that follicle stem cells might offer further benefits in neural regenerative medicine. (2) We analyzed the publication year, journals, countries, institutions, and institutions in China. Specifically, we analyzed all the data on follicle and melanocyte stem cells, and their application in neuroscience.


INTRODUCTION
Skin covers the surface of the body, and is the largest of all organs. It is composed of the epidermis, dermis, and subcutaneous tissue and appendages. The antigenicity of skin stem cells is weak, and they not only have the ability to self-renew, they also have multipotency and a strong proliferative ability. Skin stem cells can differentiate into various cells to repair cutaneous deficiencies, such as the cells of the skin, hair follicles, and sweat and sebaceous glands [1][2][3] .
Follicle stem cells are located in the outer root sheath, i.e. the hair follicle bulge of the lower part of sebaceous glands. Follicle stem cells not only move downward to hair follicle roots to form hair follicles, but can also migrate upward from the hair follicle outer root sheath to generate the epidermis. These cells can even differentiate into neural crest stem cells and subsequently generate neurons and glial cells. Neural crest stem cells can also differentiate into melanocytes and smooth muscle cells, and can promote the repair of injured nerves. When neural crest stem cells in the hair follicle bulge are transplanted into injured peripheral nerves, they can promote axon growth and recovery of nerve functions. Thus, follicle stem cells can be used to repair spinal and auditory nerves to treat spinal cord injury and hearing disorders, respectively, and neurological degeneration [4][5][6][7][8] . Follicle stem cells proliferate rapidly in vitro and survive in long-term culture, do not show immunological rejection, and are not hindered by ethical issues. Thus, they can be used in regenerative medicine [9] . Melanocyte stem cells are also widely distributed in the hair follicle bulge. At present, there are relatively few studies of their application in neuroscience.
In this study, we analyzed the research trends of follicle and melanocyte stem cells, and their application in neuroscience, based on a bibliometric analysis of the papers in the Web of Science published from 2002 to 2011.

Data retrieval
This study used bibliometric analyses to quantitatively and qualitatively investigate research trends of studies on follicle and melanocyte stem cells, and their application in neuroscience. We searched the Web of Science, a research database of publications and citations selected and evaluated by the Institute for Scientific Information in Philadelphia, PA, USA, using the keywords follicle stem cell or melanocyte stem cell, and neural, neuro or nerve. We limited the publication period from 2002 to 2011, and compiled a bibliography of all articles related to follicle melanocyte stem cells, and their application in neuroscience. We downloaded the data on September 4 th , 2012.

Inclusion criteria
The inclusion criteria are as follows: (1) published peer-reviewed articles on follicle and melanocyte stem cells, and their application in neuroscience, including original research articles, reviews, meeting abstracts, proceedings papers, book chapters, editorial material, and news items, which were indexed in the Web of Science; (2) the years of publication were 2002-2011; and (3) the citation database was Science Citation Index Expanded.

Exclusion criteria
We excluded articles that required manual searching or telephone access, documents that were not published in the public domain, and a number of corrected papers from the total number of articles analyzed.
The outcomes of all articles referring to skin stem cells were assessed using the following criteria.

Distribution of output by country for publications on follicle and melanocyte stem cells in the Web of Science from 2002 to 2011
The analysis of the contributions of different countries/states to publications was based on journal articles in which the address and affiliation of at least one author were provided ( Figure 2). Figure 2, it was clear that most papers on follicle and melanocyte stem cells were published in the USA (191 papers), followed by Japan (79 papers). China published 12 papers and ranked 6 th . The other prolific countries were the UK, Germany, Canada, Switzerland, France, Australia, and Italy.

Distribution of output by institution for publications on follicle and melanocyte stem cells in the Web of Science from 2002 to 2011
The University of California system and University of Pennsylvania in the USA were the most prolific research institutes ( Table 2). Eight of the top 11 research institutes publishing in this field were in the USA, and the other three institutes were in Japan, the UK and Germany, respectively.   (Table 3) As shown in Table 3    Implanted hair follicle stem cells form Schwann cells that support repair of severed peripheral nerves [19] Amoh Y, Li L, Campillo R, et al.

Distribution of output by country for publications on the application of follicle and melanocyte stem cells in neuroscience in the Web of Science from 2002 to 2011
The analysis of the contributions of different countries/ states to publications was based on journal articles in which the address and affiliation of at least one author were provided ( Figure 4).
As shown in Figure 4, it was clear that most papers on the application of follicle and melanocyte stem cells in neuroscience were published in the USA (37 papers), followed by Japan (25 papers). The other prolific countries were Germany, the UK, and Switzerland. There is no paper in this area that was published in China.

Distribution of output by institution for publications on the application of follicle and melanocyte stem cells in neuroscience in the Web of Science from 2002 to 2011
Anticancer Inc and the University of California system in the USA were the most prolific research institutes ( Table 6).
Seven of the top 15 research institutes publishing in this field were in the USA, four were in Japan, two were in Germany, and the other two institutes were in Switzerland and the UK, respectively.   Sciences of the United States of America [17] , was cited 150 times, which was more citations than any other paper.  (Table 7).   At present, scholars have made some achievements in the study of follicle and melanocyte stem cells, and their application in neuroscience [27][28][29][30][31][32][33] , which provides new hope for treatments of nervous system disease by autologous cell transplantation and gene therapy. The technology to induce the differentiation of follicle stem cell is still at an experimental stage, and has not been widely or successfully used in clinical practice. Nevertheless, follicle stem cells have some advantages over other types of stem cells. Follicle stem cells can be obtained easily, proliferate rapidly in vitro, survive in long-term culture, do not undergo immunological rejection, and are not hindered by ethical issues [34][35][36][37] . Therefore, these cells are one of the best candidates for cell therapy of nervous system diseases. We have reason to believe that the research prospects in this area are long range. At present, there are relatively few studies on the application of melanocyte stem cells in neuroscience, and their availability has yet to be confirmed.

DISCUSSION
Author contributions: Weifu Wu retrieved the references, extracted the data, conceived and designed the study, and wrote the manuscript. The author approved the final manuscript.

Conflicts of interest: None declared.
Author statements: The manuscript is original, has not been submitted to or is not under consideration by another publication, has not been previously published in any language or any form, including electronic, and contains no disclosure of confidential information or authorship/patent application disputations.