Polycythemia and oxygen sensing
Abstract
Polycythemias can be differentiated based on the responsiveness of erythroid progenitors to circulating cytokines. Primary polycythemias are characterized by an augmented response due to acquired somatic or inherited germ-line mutations that are expressed within hematopoietic progenitors causing increased proliferation or decreased apoptosis and resulting in accumulation of red blood cells. In terms of oxygen requirements, primary polycythemias can be viewed as the production of hemoglobin fully dissociated from the tissue oxygen needs and from the oxygen sensing pathway. Polycythemia vera (PV) is the most common primary polycythemia. PV bone marrow progenitors cells can form erythroid colonies in the absence of exogenous erythropoietin in vitro. These endogenous erythroid colonies (EEC) are useful in differentiating PV and secondary polycythemias. They also can differentiate PV where this feature is independent of Epo signalling from primary familial and congenital polycythemia. In this autosomal dominant primary polycythemia, at variance with PV, EEC formation is abolished by anti-Epo and anti-Epo receptor neutralising antibodies. Mutations of the EPOR have been described and resulted in nine cases in truncated EPORs lacking ...Continue Reading
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Apoptosis
Apoptosis is a specific process that leads to programmed cell death through the activation of an evolutionary conserved intracellular pathway leading to pathognomic cellular changes distinct from cellular necrosis