Isolation and differentiation of mouse embryonic stem cells

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.