First report of reversal of organ dysfunction in sickle cell anemia by the use of hydroxyurea: splenic regeneration

Much of the morbidity associated with sickle cell anemia (SCA) is due to ongoing infarction resulting in organ dysfunction. Because the spleen is often the first organ damaged in this illness, there is a significant impairment of the immune system in these patients. Hydroxyurea (HU) has been shown to increase fetal hemoglobin (HbF) and decrease painful episodes in patients with this disease. It is unclear whether HU can prevent organ damage. We treated two SCA patients with HU for several years and found evidence of reversal of previously documented splenic dysfunction. Patient no. 1 was treated for 30 months with an increase in HbF to 30%. HU was stopped because of cytopenia. She developed left upper quadrant pain. A splenectomy was performed due to the possibility of splenic abscesses. A pathologic review found no evidence of infection and an enlarged spleen that showed active germinal centers. Patient no. 2 was treated for 24 months with HU before developing splenomegaly. His HbF levels were 25% to 30%, his pit counts averaged 2%, and his liver spleen scans showed uptake. These two cases show that chronic HU therapy may reverse splenic dysfunction in certain patients and suggest that this drug may have efficacy beyond the elimination of pain in SCA.

Use of spleen organ cultures to monitor hemopoietic progenitor cell regeneration following irradiation and marrow transplantation

After lethal irradiation of C57BL mice followed by the injection of 10(7) marrow cells, total cellularity and progenitor cell levels exceeded pretreatment levels within 12 days in the spleen, but regeneration remained incomplete in the marrow. The exceptional regenerative capacity of progenitor populations in the spleen was observed in organ cultures of spleen slices prepared 24 hr after irradiation and transplantation, excluding continuous repopulation from the marrow as a significant factor in splenic regeneration.