Background: The unique properties of mesenchymal stem cells (MSCs) have made them powerful tools in cell therapy and genetic engineering and Murine Mesenchymal stem cells are a suitable model for study in this field.Compared with human mesenchymal stem cells, murine mesenchymal stem cells have different features such as heterogeneity and slow growth rate. Several reports have shown that microRNAs are involved in many cell regulatory processes such as hypoxia. In this study, the effect of hypoxia was investigated on the expression of hypoxia related microRNA in murine mesenchymal stem cells isolated from adipose tissue (AD-MSC).Methods: AD-MSCs were cultured in two hypoxic and normoxic conditions. The expressions of mir-21 and mir-130a in the primary and immortality phase of AD-MSC were evaluated by using Real-time PCR technique.Also, the expression of MSCs surface markers were investigated by flow cytometry in the two mentioned phases.Findings: Our study showed the expression of mir-21 and mir-130a was increased in hypoxic conditions compared to normoxia. Also expressions of surface markers were different in primary and immortality phase.Conclusion: Considering that stem cells are sensitive to environmental oxygen levels, over-expression of mir-21 and mir-130a could promote the survival of MSCs exposed to hypoxia.

Introduction: An induction of osteogenic differentiation in rat bone marrow stromal cell cultures by dexamethasone was reported. Materials and Methods: The marrow stromal cells obtained from 4 to 6 weeks - old Spruge-Dawely male rats were grown in primary culture for 7 days and then subcultured for 20 days. The cells were cultured in either DMEM medium containing 15% fetal calf serum, antibiotics and ascorbic acid; or the above medium supplemented with either 10 mM Na-b glycerophosphate (Na-β GP), 10-8 M dexamethasone (Dex) or a combination of both. The cultures were stainded with cresyl violet, toluidine blue and alizarin red S and examined under phase-contrast microscopy. Results: Primary culture: The stromal cells in the primary culture formed cell colonies at day 5 and reached confluency by day 7. Subculture: The bone marrow stromal cells in the subculture formed cell colonies by day 2. All subcultures reached confluency after 3 to 5 days; except those cells grown in primary cultury and subculture in the presence of Dex or Dex and Na-bGP which failed to reach confluency at any time. The later cultures formed isolated islands of cells. At the 8th day, dense cultures of polygonal cells became evident in the centers of these islands. The cultures increased in size with time. Conclusion: Three-dimentional nodular structures developed in relation to the clusters at 10th to 11th days in the cultures containing both Dex and Na-bGP Introduction: An induction of osteogenic differentiation in rat bone marrow stromal cell cultures by dexamethasone was reported. Materials and Methods: The marrow stromal cells obtained from 4 to 6 weeks - old Spruge-Dawely male rats were grown in primary culture for 7 days and then subcultured for 20 days. The cells were cultured in either DMEM medium containing 15% fetal calf serum, antibiotics and ascorbic acid; or the above medium supplemented with either 10 mM Na-b glycerophosphate (Na-β GP), 10-8 M dexamethasone (Dex) or a combination of both. The cultures were stainded with cresyl violet, toluidine blue and alizarin red S and examined under phase-contrast microscopy. Results: Primary culture: The stromal cells in the primary culture formed cell colonies at day 5 and reached confluency by day 7. Subculture: The bone marrow stromal cells in the subculture formed cell colonies by day 2. All subcultures reached confluency after 3 to 5 days; except those cells grown in primary cultury and subculture in the presence of Dex or Dex and Na-βGP which failed to reach confluency at any time. The later cultures formed isolated islands of cells. At the 8th day, dense cultures of polygonal cells became evident in the centers of these islands. The cultures increased in size with time. Conclusion: Three-dimentional nodular structures developed in relation to the clusters at 10th to 11th days in the cultures containing both Dex and Na-βGP.

Germline and somatic stem cells are distinct types of stem cells that are dedicated to reproduction and somatic tissue regeneration, respectively. Germline stem cells (GSCs), which can self-renew and generate gametes, are unique stem cells in that they are solely dedicated to transmit genetic information from generation to generation. We developed a strategy for the establishment of germline stem cell lines from embryonic stem cells (ES). These cells are able to undergo meiosis, generate haploid male gametes in vitro and are functional, as shown by fertilization after intra-cytoplasmic injection into mouse oocytes. In other approach, we show that bone marrow stem (BMS) cells are able to trans-differentiate into male germ cells. BMS cell-derived germ cells expressed the known molecular markers of primordial germ cells. The ability to derive male germ cells from ES and BMS cells reveals novel aspects of germ cell development and opens the possibilities for use of these cells in reproductive medicine. Conversely, we showed that adult male germline stem cells, spermatogonial stem cells (SSCs), can be converted into embryonic stem cell like cells which can differentiate into the somatic stem cells of three germ layers. Understanding how SSC can give rise to pluripotent stem cells and how somatic stem cells differentiate into germ cells could give significant insights into the regulation of developmental totipotency as well as having important implications for male fertility and regenerative medicine.

The future development of medicine will greatly depend on research, knowledge and clinical application of stem cells. In recent years, stem cells especially; skin stem cells have been very interesting and amazing targets for study and scientific application in the following fields: 1- Cell-based therapy; 2- Regenerative medicine and tissue engineering; 3- Gene therapy; 4- Therapeutic cloning; 5- More efficient new drugs with fewer side effects.