Background: Recently, embryonic stem (ES) cells have become very important resources in basic medical researches. These cells can differetiate into derivatives of all primary germ layers. Objectives: In order to isolate embryonic stem cells in vitro, the blastocyst were cultured and the morphological aspects, population doubling time, alkalin phosphatse and DIFFERENTIATION properties of the cells were investigated.Materials and Methods: The balstocysts from NMRI mice were cultured for 3 days up to time that inner cell mass (ICM) reach to the outgrowth stage. The cells were disaggregated and trypsinized every 3 days until the appearance of the colonies of ES cells. The colony positive cells were fixed and stained for alkaline phosphatase. The ES cells were cultured in suspension state for 5 days, at the same time Leukaemia Inhibitory Factor (LIF) was removed from media to form embryoid bodies(EBs). The EBs were cultured for 8 - 20 days on collagen coated dish to induce the spontaneouse DIFFERENTIATION.Results: During the 6-9 days after the disaggregation of ICM in the expansion stage, the colony of ES cells appeared as a flat monolayer mass with strike boundaries and nondistinguish cytoplasm including a few nuclei. In colony formation stage, the morphology changed from flat monolayer to round multilayer with strike define boundaries. Undifferentiated cells were seen as intensely small cells attached together compactly with high nucleus/cytoplasm (N/C) ratio. The cells of colonies tend to differetiate by separation from each other and became larger and diffused on substrate by attaching to dish. The positive alkaline phosphatase cells were seen in typical morphology of ES colonies. The EBs cells were seen in culture after 5 days in suspension and began to spontaneously differentiate into various types of cells such as nerve and hematopoitic lineages.Conclusion: Despite strike morphology of ES colonies, it is difficult to distinguish the differentiated from undifferentiated cell colonies in the colony formation stage. New ES cells are capable to give rise into EBs and are susceptible of spontaneously DIFFERENTIATION in various type of cells.

The advent of regenerative medicine has brought us the opportunity to regenerate, modify and restore human organs function. Stem cells, a key resource in regenerative medicine, are defined as clonogenic, self-renewing, progenitor cells that can generate into one or more specialized cell types. Human dental pulp stem cells (HDPSCs) are ectodermal-derived stem cells, originating from migrating neural crest cells and are capable of providing enough cells for potential cell-based therapies. During last decade, HDPSCs have received extensive attention in the field of tissue engineering and regenerative medicine due to their accessibility and ability to differentiate in several cell phenotypes. In this review, we have described the potential of HDPSCs to differentiate into odontoblasts, osteoblasts, hepatocytes, neuroblasts and angioblasts in response to different bioactive factors. Therefore, the culture and selective DIFFERENTIATION of HDPSCs should provide further understanding of dental pulp progenitors and their potential use for new therapeutic approaches in regenerative medicine.

Objective: To show whether or not calreticulin modulates adipogenesis.Materials and Methods: ES cells.Results: Calreticulin, an endoplasmic reticulumresident protein, affects many critical cellular functions including protein folding and calcium-homeostasis. Using embryonic stem cells and 3T3-L1 preadipocytes, we show that calreticulin modulates adipogenesis. We find that calreticulin-deficient cells show increased potency for adipogenesis when compared to wild-type or calreticulin overexpressing cells. In the highly adipogenic crt-/- cells, the endoplasmic reticulum lumenal calcium concentration was reduced. Increasing the endoplasmic reticulum lumenal calcium concentration lead to a decrease in adipogenesis. In calreticulin-deficient cells, the calmodulin/CaMKII pathway was upregulated and inhibition of CaMKII reduced adipogenesis. Calreticulin inhibits adipogenesis via a negative-feedback mechanism whereby the expression of calreticulin is initially upregulated by PPARγ. This abundance of calreticulin subsequently negatively regulates the expression of PPARg, LPL, C/ EBPa and aP2.Conclusion: Calreticulin appears to function as a Ca2+-dependent molecular switch that regulates commitment to adipocyte DIFFERENTIATION by preventing the expression and transcriptional activation of critical pro-adipogenic transcription factors.