Altered Gene & MiRNA Regulation in Pediatric Acute Myeloid Leukemia

Abstract

The life-span of blood cells differs from very long – a maximum of 120 days for erythrocytes- to very short -8 hours for granulocytes-. Hence, to preserve the cell numbers required for normal function, hematopoiesis is a continuous process of blood cell maturation and proliferation. Hematopoiesis occurs in different organs and tissues during the first months of embryonic life. It starts in the yolk sac during early developmental stages of an embryo, is taken over mainly by the liver and in a very limited extent by the spleen during the second trimester of pregnancy while the bone marrow is the most important organ involved in hematopoiesis in the third trimester of pregnancy. The bone marrow will take over hematopoiesis as most important organ from birth onwards, retaining this function throughout life. In children, the bone marrow of the long bones such as the femur and the tibia is the most important in hematopoiesis, while in adults hematopoiesis occurs mainly in flat bones: the pelvis, cranium, vertebrae and sternum. All hematopoietic cells originate from the pluripotent hematopoietic stem cell. Normal function of blood cells can be roughly divided in three categories: delivery of oxy-gen to tissues by red blood cells, inflammation and wound healing by neutrophils, monocytes, lymphocytes, eosinophils, basophils, and fibroblasts, and continuous surveillance of blood vessels, blood clot formation and initiation of tissue repair by platelets.