Stem cells are the cells having some distinguishing characteristics like longevity, high capacity of self-renewal and differentiation, quiescence and highly error-free proliferation. Almost all stem cells have the potential of lineage reprogramming, i.e. inter-conversion of cell lineages. They also have the potential to differentiate into almost all kinds of cells. These cells have been found in almost every organs of human body. Pool of stem cells found in epidermis is termed as Epidermal Stem Cells. Many researchers around the world have reported different kinds of stem cells in skin, based on their cell surface makers, while they have not categorized these cells chronically. It is worth mentioning here that all kinds of stem cells reported in skin, i.e. keratinocyte stem cells, limbal stem cells, hair follicle and bulge stem cells, SG (sebaceous gland) stem cells, and spinous keratinocytes express specific types of cytokeratin protein (e.g. K1, K3, K5, K10, K12, K14, K15, K19 etc.) on their surfaces. Biologists have defined that almost all of these stem cells share single origin, i.e. Basal Layer of Embryonic Skin. As the embryonic skin passes the developmental stages, the basal layer produces two mother stem cells of skin, keratinocyte stem cells, and so called Limbal Stem Cells (in cornea). Keratinocyte stem cells give rise to the cells expressing Cytokeratin proteins on their surfaces. So, all the cells expressing cytokeratin are tracked back to these stem cells in origin, while undergone natural lineage reprogramming or differentiation. The stem cells in the basal-layer give rise to keratinocyte stem cells which can be found in the basal layer of the adult skin. During the developmental stages, this basal layer, containing keratinocyte stem cells, gives rise to limbal invagination of corneal region, a linage conversion mechanism happens, and the keratinocyte stem cells are naturally reprogramed into the limbal stem cells. In basal layer of the epidermis, the keratinocyte stem cells give rise to bulge, hair follicle, and SG stem cells when placode formation takes place. In future, we need studies to find out which kind of cytokeratin protein is expressed early in these cells. In another word it would be helpful to define the order of cytokeratin expression regarding these lineage developmental processes from embryonic to mature skin and from embryonic basal layer to the formation of cornified epithelial cells.

Dental tissues provide an alternate source of stem cells compared with bone marrow and have a similar potency as that of bone marrow derived mesenchymal stem cells. It has been established there are six types of dental stem cells: Dental pulp stem cells, stem cells from human exfoliated deciduous teeth, stem cells from apical papilla, periodontal ligament stem cells, dental follicle progenitor cells, oral periosteum stem cells and recently gingival connective tissue stem cells. Most of the dental tissues have a common developmental pathway; thus, it is relevant to understand whether stem cells derived from these closely related tissues are programmed differently. The present review analyzes whether stem cells form dental tissues depict distinct characteristics by gaining insight into differences in their immunophenotype. In addition, to explore the possibility of establishing a unique phenotypic fingerprint of these stem cells by identifying the unique markers that can be used to isolate these stem cells. This, in future will help in developing better techniques and markers for identification and utilization of these stem cells for regenerative therapy.

Bone marrow microenviroment contains cellular and acellular compartments. Cellular compartment contains hematopoetic stem cells, mesenchymal stem cells and some other kinds of stromal cells while acellular compartment includes scaffold proteins known as an extra cellular matrix. Hematopoietic stem cells resided in the bone marrow interact with a bone marrow microenvironment called the stem cell niche. Hematopoietic stem cells (HSCs) are able to produce the variety of blood cells and bone marrow microenvironment plays a supportive role for the cells in this process. Recent studies over in-vitro models demonstrating the essential role of stromal cells in hematopoiesis reflected the view that cell-cell contact in the marrow microenvironment is critical for hematopoietic stem cells normal function and differentiation. Direct cell-cell contacts and cytokines secreted by mesenchymal stem cells play a critical role in the coculture of hematopoetic stem cells and mesenchymal stem cells and the determination of the fate of hematopoetic stem cells. Several studies demonstrate the effect of mesenchymal stem cells on self renewal, expansion, proliferation and differentiation of hematopoetic stem cells in vitro that lead to different and contradictory results. In this paper, we will investigate the effect of mesenchymal stem cells on differentiation of hematopoietic stem cells in vitro. The data of the present article were obtained through the review of many papers published on the effect of stem cells. The review of different studies has shown the necessity to survey the effect of mesenchymal stem cells on differentiation of different cell lines as a laboratory model. Direct cell-cell contact between mesenchymal stem cells and hematopoietic stem cells and the signaling pathways activated by this interaction enable proliferation and expansion of HSCs in the undifferentiated state.

The stem cell possesses two distinct traits: self-renewal and differentiation capacity. The stem cell population is comprised of two main cell types: embryonic stem cells and adult stem cells. Researches on the stem cells provoked ways to utilize their potential for therapeutic treatments of multiple neurological disorders. There are three different approaches in neural repair with the usage of stem cells: cell replacements, neuroprotection and gene delivery which are highly developed in treating neurological disorders such as Parkinson and multiple sclerosis but these approaches have their own problems. In comparison with embryonic stem cells, adult stem cells have more application in neural repair, because the usage of embryonic stem cells raises ethical issues, and will involve allograft transplantation and are of much risk for tumor formation. Taking all of this into account, utilizing adult stem cells are in priority. Furthermore, injection of molecules such as bFGF and EGF leads to induction of neurogenesis that can be helpful in neural repair.

Stem cell therapy has been applied for the treatment of degenerative diseases encompassing corneal disorders.This consideration is regarding the unique characteristics of stem cells including self-renewal and pluripotency. Some corneal diseases result from deficiencies in the limbal region. In these conditions, limbal stem cell therapy is considered in which limbal stem cells are cultured in vitro and transplanted. However, allograft stem cell transplants may be rejected and the use of immonosuppressors may have adverse effects.Patient’s epithelial cells are suggested as a source for corneal stem cells. Animal studies have shown successful differentiation of hair follicle, dental pulp, bone marrow, oral mucus and mesenchymal stem cells to corneal epithelial cells. In this revie warticle, the corneal stem cells are first introduced. Various stem cell cultures are then discussed and the possibility of using other stem cell sources for the treatment of corneal disorders is evaluated.

Bone marrow microenvironment contains cellular and acellular compartments. The cellular compartment includes hematopoietic stem cells, mesenchymal stem cells and some other stromal cell types, while the acellular compartment is composed of scaffold proteins known as the extra cellular matrix. Direct cell-cell contact as well as cytokines secreted by mesenchymal stem cells during coculture of hematopoietic stem cells and mesenchymal stem cells play a critical role in hematopoiesis, and determines the fate of hematopoietic stem cells. Several studies have demonstrated the impact of mesenchymal stem cells on self-renewal, expansion, proliferation and differentiation of hematopoietic stem cells in vitro, which have shown different and contradictory results. In this paper, we will investigate the effect of mesenchymal stem cells on differentiation of hematopoietic stem cells in vitro.

The 3T3 feeder layer cells are commonly used for stem cell maintenance and expansion. Although feeder free systems are recently being developed for embryonic stem cells culture, deciphering the ability of new sources of feeder cells is still important for accurate expansion of epithelial stem cells. This study was aimed to introduce a new feeder layer for the culture of human limbal stem cells which can be applied for therapeutic corneal regeneration. For this purpose, the potential of unrestricted somatic stem cells (USSCs) isolated from umbilical cord blood was investigated. Human limbal stem cells were co-cultured with mouse 3T3 fibroblasts in addition with human unrestricted somatic stem cell (USSC), isolated from full term-pregnant women. The expression of surface markers including CD73, CD90, CD105, CD45, CD34, and CD44was evaluated using flowcytometry. Lmbal stem cells were cultured on two feeder layers in which mitotic activities were inhibited using mitomycin C. The morphology of cultured cells was assessed using phase-contrast microscopy. Furthermore, stem cell characteristics were assessed using immunocytochemistry and real-time PCR for stem cell markers including p63, KRT19, KRT3, Cx43, vimentin, involucrin and ABCG2. Additionally, chromosomal karyotype analysis was preformed. Cord blood somatic stem cells with spindle-shaped morphology can be quickly split up. The results demonstrated that limbal stem cells cultured on USSC surface were positive for ABCG2, 63 and KRT19. These results were confirmed by real-time PCR analysis. Limbal stem cells grown on a USSC feeder layer maintained a stem cell-like phenotype, comparable to cells grown on a 3T3 feeder layer. Karyotype analysis of USSCs and Limbal stem cells represented a normal 44XX karyotype. USSC could successfully support the growth of human limbal stem cells even better than 3T3 feeder cells. Since USSC are derived from human beings, it has an advantage over 3T3.

Background and Angiogenesis provides proper nutrition and helps to the development and spread of cancer cells. Cancer stem cells are a rare population of tumor cells responsible for initiation, spreading and growth of cancer. Angiogenesis occurs more in cancer stem cells compared with other cancer cells. Ibuprofen, as a member of nonsteroidal anti-inflammatory drugs (NSAIDs) group is used for prevention and treatment of certain cancers. In the present study, we investigated the effect of ibuprofen on angiogenesis in gastric cancer stem cells.
Gastric cancer stem cells of MKN45 cell line was isolated by spheroid colony formation technique. Gastric cancer stem cells were treated with various concentrations of ibuprofen. The angiogenic properties in gastric cancer stem cells treated with ibuprofen was compared with control cells using two-dimensional angiogenesis.
Angiogenesis reduced in the cancer stem cells treated with ibuprofen compared with the control cancer stem cells.
Ibuprofen decreased angiogenesis in gastric cancer stem cells.

Conducting research on the stem cell lines might bring some worthy good to public. Human Stem Cells (hSCs) research has provided opportunities for scientific progresses and new therapies, but some complex ethical matters should be noticed to ensure that stem cell research is carried out in an ethically appropriate manner. The aim of this review article is to discuss the importance of stem cell research, code of ethics for stem cell research in Iran and ethical recommendation. Generation of stem cells for research from human embryo or adult stem cells, saving, maintenance and using of them are the main ethical, legal and jurisprudence concerns in Iran. Concerns regarding human reproduction or human cloning, breach of human dignity, genetic manipulation and probability of tumorogenisity are observed in adult/somatic stem cells. Destruction of embryo to generate stem cell is an important matter in Iran. In this regards, obtaining stem cell from donated frozen embryos through infertility treatment that would be discarded is an acceptable solution in Iran for generation of embryo for research. Ethical, legal, and jurisprudence strategies for using adult/somatic stem cells are determination of ownership of stem cells, trade prohibition of human body, supervision on bio banks and information of Oversight Committee on Stem Cell Research. Recommendations to handle ethical issues for conducting stem cell research are well-designed studies, compliance codes of ethics in biomedical research (specifically codes of ethics on stem cell research, codes of ethics on clinical trials studies and codes of ethics on animals studies), appropriate collaboration with ethics committees and respecting of rights of participants (including both of human and animal rights) in research. In addition, there is a necessity for extending global networks of bioethics for strengthening communications within organizations at both the regional and international level, strengthening legislation systems, designing and establishing convenient collaborative educational courses at ifferent levels.

Stem cells are undifferentiated and multi pluripotent cells which can differentiate into a variety of mature cells and tissues such as nervous tissue, muscle tissue, epithelial tissue, skeletal tissue and etc. Stem cells from all different source have three unique features: 1) Proliferative capability: Stem cells are capable of self dividing and self renewing for long periods or more than six months at least that called immortalization. 2) Undifferentiated nature: It’s considered as one of the essential characteristics of stem cell, so it doesnt have any tissue-specific construction. 3) Differentiation to the different cells from all organs: This ability can Induced by tissue specific transcription factors. Because of that, they are so important in prevention and treatment of human disease. Depending on the sources from which they derive, they have different types which can be used to produce special cells and tissues. The most significant types of stem cells are; embryonic stem cells (ESCs) which are derived from embryos, adult stem cells (ASCs) which are derived from differentiated cells in a specific tissue, induced pluripotent stem cells (iPSs) which are produced from adult differentiated cells that have been genetically reprogrammed to act resemble to an embryonic stem cell and cord blood stem cells which contains haematopoietic stem cells and derived from the umbilical cord after gestation. By providing a medium containing of special growth factor, it is possible to orientated stem cell differentiation pathway and gained certain cells from them. The important uses of stem cells includes damaged heart tissue cells improvements and bone tissue repairing, cancer treatment, damaged neurological and spinal tissue repairing, improving burns and injuries and the treatment of diabetes, infertility and spermatogenesis dysfunction. Furthermore, the application of them in gene therapy is an important issue in the modern medicine science due to the role of them in transferring gene into different cells. Today, this method have had considerable progress in the treatment of many disease. In this review study, some aspect of stem cells like types and characteristic, origin, derivation techniques, storage conditions and differentiation to target tissues, current clinical usage and their therapeutic capabilities will be discussed.