BACKGROUND:Biological and morphological characteristics of neural stem/progenitor cells (NSPCs) have been widely investigated. OBJECTIVE:To explore the ultrastructure of human embryo-derived NSPCs and neurospheres cultivated in vitro using electron microscopy. DESIGN,TIME AND SETTING:A cell biology experiment was performed at the Brain Tumor Laboratory of Soochow University,and Jiangsu Province Key Laboratory of Neuroregeneration, Nantong University between August 2007 and April 2008. MATERIALS:Human fetal brain tissue was obtained from an 8-week-old aborted fetus;serum-free Dulbecco’s modified Eagle’s medium/F_(12) culture medium was provided by Gibco,USA;scanning electron microscope was provided by Hitachi Instruments,Japan;transmission electron microscope was provided by JEOL,Japan. METHODS:NSPCs were isolated from human fetal brain tissue and cultivated in serum-free Dulbecco’s modified Eagle’s medium/F_(12) culture medium.Cells were passaged every 5-7 days. After three passages,NSPCs were harvested and used for ultrastructural examination. MAIN OUTCOME MEASURES:Ultrastructural examination of human NSPCs and adjacent cells in neurospheres. RESULTS:Individual NSPCs were visible as spherical morphologies with rough surfaces under scanning electron microscope.Generally,they had large nuclei and little cytoplasm.Nuclei were frequently globular with large amounts of euchromatin and a small quantity of heterochromatin,and most NSPCs had only one nucleolus.The Golgi apparatus and endoplasmic reticulum were underdeveloped;however,autophagosomes were clearly visible.The neurospheres were made up of NSPCs and non-fixiform material inside.Between adjacent cells and at the cytoplasmic surface of apposed plasma membranes,there were vesicle-like structures.Some membrane boundaries with high permeabilities were observed between some contiguous NSPCs in neurospheres,possibly attributable to plasmalemmal fusion between adjacent cells. CONCLUSION:A large number of autophagosomes were observed in NSPCs and gap junctions were visible between adjacent NSPCs. BACKGROUND: Biological and morphological characteristics of neural stem / progenitor cells (NSPCs) have been widely investigated. OBJECTIVE: To explore the ultrastructure of human embryo-derived NSPCs and neurospheres cultivated in vitro using electron microscopy. DESIGN, TIME AND SETTING: A cell biology experiment was performed at the Brain Tumor Laboratory of Soochow University, and Jiangsu Key Laboratory of Neuroregeneration, Nantong University between August 2007 and April 2008. MATERIALS: Human fetal brain tissue was obtained from an 8-week-old aborted fetus; serum-free Dulbecco’s modified Eagle’s medium / F_ ​​(12) culture medium was provided by Gibco, USA; scanning electron microscope was provided by Hitachi Instruments, Japan; transmission electron microscope was provided by JEOL, Japan. METHODS: NSPCs were isolated from human fetal brain tissue and cultivated in serum-free Dulbecco’s modified Eagle’s medium / F (12) culture medium. Cells were passaged every 5-7 days. After three passages, NS PCs were harvested and used for ultrastructural examination. MAIN OUTCOME MEASURES: Ultrastructural examination of human NSPCs and adjacent cells in neurospheres. RESULTS: Individual NSPCs were visible as spherical morphologies with rough surfaces under scanning electron microscope. General, they had large nuclei and little cytoplasm .Nuclei were frequently globular with large amounts of euchromatin and a small quantity of heterochromatin, and most NSPCs had only one nucleolus. The Golgi apparatus and endoplasmic reticulum were underdeveloped; however, autophagosomes were clearly visible. The neurospheres were made up of NSPCs and non -fixiform material inside.Between adjacent cells and at the cytoplasmic surface of apposed plasma membranes, there were were vesicle-like structures.Some membrane boundaries with high permeabilities were observed between some contiguous NSPCs in neurospheres, possibly attributable to plasmalemmal fusion between adjacent cells. : A large number of autophagosomeswere observed in NSPCs and gap junctions were visible between adjacent NSPCs.