Stem cells are taken from all except-

Reference :Robbins basic pathology 9th edition pg no 74: stem cells are rare and very dif cult to isolate to purity. Fuhermore, they occur in specialized microenvi- ronments within the organ called stem cell niches. Appar- ently, signals from other cells in such niches keep the stem cells quiescent and undifferentiated. Stem cell niches have been identi ed in many organs. In the brain, neural stem cells occur in the subventricular zone and dentate gyrus; in the skin, tissue stem cells are found in the bulge region of the hair follicle; and in the cornea, they are found at the limbus. Perhaps the most extensively studied tissue stem cells are hematopoietic stem cells found in the bone marrow. Although rare, they can be puri ed to viual purity based on cell surface markers. Hematopoietic stem cells can be isolated from bone marrow as well as from the peripheral blood after mobilization by administration of ceain cytokines such as granulocyte colony-stimulating factor (G-CSF).