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Published in eBiology: A LifeSciences Journal on Wed Sep 25 2019 05:40:23 GMT-0400 (Eastern Daylight Time)
Vol: 1, No: 4, Page: 10-19
DOI: 10.0001/JCMR.123

Skin Stem Cells; Definition, Function, Importance and Methods of Isolation in cell therapy

Mina Mashhadi , Mahnaz Jahani , Mina Mohammadi , Mina Mashhadi *

Dr. Mina Mashhadi , Department of Biology
Department of Neontology, Mashhad University of Medical Sciences, Iran

Stem cells (SCs) are a population of undifferentiated cells with high self-renewing and differentiation potency. On the basis of origin, SCs are divided into four main groups: embryonic stem cells (ESCs), fetal stem cells (FSCs), induced pluripotent stem cells (iPSCs), and adult stem cells (ASCs). Interestingly, in different literatures, ASCs are considered as unipotent progenitor cells, multipotent stem cells or even pluripotent stem cells with variety of differentiation potential. ASCs reside in many adult tissues such as liver, bone marrow, adipose tissue, neural tissues, skin and etc. Among adult tissues, skin is considered as a fast self-renewing tissue which is capable to reconstruct itself during skin homeostasis and injuries. In fact, skin is mentioned as a pool of different types of SCs including keratinocyte stem cells (KSCs), hair follicle stem cells (HFSCs) and sebaceous gland stem cells (SGSCs). During skin regeneration, cooperation between these stem cells is essential for reconstruction of skin. Among these SCs, KSCs are most common cells in epidermis layer (mostly in basal layer) which are the important population of SCs for regeneration of epidermis. Herein, we reviewed different methods for skin stem cells isolation and characterization, and their potential for clinical application.

Epidermal stem cells, Keratinocytes, Hair follicle, Characterization, Clonal conversion, Holoclone, Paraclone, Meroclone, Clinical application. ,

Full Text

Stem cells (SCs) are a population of unspecialized cells with self-renewal ability and differentiation potential [ 1, 2]. SCs are able to proliferate and differentiate into many cell lineages of tissue of origin that they are derived from [2]. Therefore, applying of SCs has been considering for addressing issues like tissue regeneration, drug screening and organogenesis [3]. Typically, SCs are divided into four main groups based on their tissue of origin: embryonic stem cells (ESCs), fetal stem cells (FSCs), induced pluripotent stem cells (iPSCs), and adult stem cells (ASCs) [2–4]. ESCs are totipotent cells which are derived from the inner cell mass (ICM) of blastocyst  and capable to make an entire organism and various cells of three main germ layers (mesoderm, endoderm and ectoderm) [5]. In contrast, ASCs have been considered as unipotent, multipotent and even pluripotent cells which are limited in their differentiation potential rather than ESCs, FSCs, and iPSCs [2, 3, 6–8]. In spite of high differentiation potential of ESCs, their applications have been limited due to ethical concerns, tumorigenic potential and difficulties in controlling of their rate of differentiation [2, 9]. Therefore, using of ASCs, as a most promising source for clinical practice and trials, has been developed because represent evidence of safety [9–11]. Generally, ASCs are multipotent cells which are derived from many adult tissues such as liver, bone marrow, adipose, neural tissue, and skin which are essential for regeneration of tissues/organs during various damages [12, 13]. Epidermal SCs, endothelial stem cells (EPCs), hematopoietic stem cells (HSCs), bone marrow stem cells (BMSCs) and neural stem cells (NSCs) are most common ASCs have been employed for therapeutic applications in tissue regeneration [9, 14]. Among different types of ASCs, epidermal or skin SCs are most common cells which are employed for skin repair [15, 16]. As a result, development of scientific knowledge about nature, biological function and importance of epidermal SCs in skin regeneration are required for development of call-based approaches in skin tissue engineering.


100 mM trehalose cause an accumulation of starch in source and depletion in sink tissues   

Supply of the 100 mM trehalose to the Arabidopsis seedlings (WT) led to the growth arrest and development arrest in leaves. In WT seedlings, the root length was very short (1.9± 0.6 mm after 14 days) and emergence of primary leaves was entirely inhibited. The trehalase expressing seedlings (TreF, line 46.2) had 12 times longer roots than WT ones after 14 days growth on 100 mM trehalose. TreF seedling root lengths on trehalose were as long as them on the sorbitol osmoticum control (figure 1).


Figure 1. The effect of 100 mM trehalose on the root growth of WT seedlings. WT seeds were germinated and grown under long day conditions on ½ MS medium with 100 mM trehalose or sorbitol. Root length was measured after 14 days. Each experiment was repeated three times. Error bars indicate Standard deviation. The abbreviations are WT (Wild type), tre (trehalose), and sorb (sorbiyol).


Trehalose in the medium led to an accumulation of large amounts of starch in the seedling source tissue, cotyledon, and to a depletion of starch in the colummella cells of the root cap, a sink tissue (figure 2a-c). Confocal microscopy of the seedling roots stained with propidium iodine revealed swelling as well as lysis of the cells in the extension zone of roots grown on 100 mM trehalose but not on 100 mM sorbitol (figure 2d-f). In addition to altered starch distribution and reduced root growth, trehalose appeared to alter cell wall elasticity compared with sorbitol.


Distribution of starch in TreF and WT was studied in 14 d seedlings using Lugol staining. Staining revealed that the reaction to trehalose was not fully homogenous when examining a large number of WT seedlings: 72% of the seedlings responded with massive trehalose accumulation in the cotyledons whilst 28% failed to stain. The response to trehalose of seedlings expressing E.coli trehalase (TreF line) was homogenous, as cotyledons of these seedlings did not stain with Lugol. Seedlings of the TreF line displayed starch in the columnella cells of the root tips (not shown).

Quantification of starch in the WT and TreF seedlings on trehalose is shown in figure 2 g. WT seedlings contained 11 mg.g-1 FW (fresh weight) starch on medium with 100 mM sorbitol. On trehalose, the starch level in WT was increased to 52 mg.g-1 FW. TreF seedlings on trehalose contained the same amount of starch as WT on


Generally, adult tissues for example liver, intestine and blood undergo rapid self-renewal during life time of animals. In common with these tissues, the human skin is a self-renewing tissue which reconstructs itself during skin injuries. As a matter of fact, the skin is considered as a stem cell pool which variety of SC niches is embedded in it. Among different types of SCs within skin, KSCs play crucial role in epidermis permanent regeneration. As a result, development of isolation, characterization and cultivation methods of KSCs can accelerate clinical applications of KSCs for treatment of skin disorders and injuries. In spite of key role of KSCs in skin repair, application of these cells face with some difficulties and limitations, such as long culturing time, high cost, the probably of highly significant scaring in deep burn injuries which are treated by cultured keratinocytes. With these limitations in mind, application of some strategies such as: recruitment of KSCs along with epidermis layer in order to prevention of high significant scaring, combination of KSCs with scaffolds or skin substitutes as a cell delivery system and integration of melanocytes, endothelial cells even different types of ASCs like mesenchymal SCs and adipose derived-SCs into keratinocyte culture are most promising approaches for development of cell-based therapeutic methods in an improved treatment of burns, chronic wounds and hereditary skin disorders.

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