Partially oxygenated sickled cells: sickle-shaped red cells found in circulating blood of patients with sickle cell disease.

A previously uncharacterized type of sickled cell was found in venous blood of patients with sickle cell disease when blood was collected without exposure to air and fixed immediately with 1% glutaraldehyde solution equilibrated with 5% oxygen. These cells were either elongated, resembling irreversibly sickled cells (ISCs), or nonelongated, with a raisin-like shape. Both types assumed a normal discoidal shape upon full oxygenation. Since these cells exist only under partially oxygenated conditions, they are described as partially oxygenated sickled cells (POSCs). POSCs are morphologically distinct from partially deoxygenated sickled cells formed during deoxygenation by having rounded edges, while the latter have sharp edges. Transmission electron microscopy of POSCs revealed various amounts of misaligned Hb S polymers. Investigations in vitro demonstrated the formation of POSC-like cells by partial oxygenation of deoxygenated cells. Since POSCs contain intracellular fibers and sickle readily upon deoxygenation, they may have clinical and pathological significance.

Red blood cell membrane and density changes under ambient and hypoxic conditions in transgenic mice producing human sickle hemoglobin.

Red blood cells (RBC) from patients with sickle cell disease (SCD) are characterized by membrane lesions caused by cell sickling and oxidative damage due to denatured hemichromes. We have developed three lines of transgenic human sickle hemoglobin (Hb S) mice, which produce 30, 50, and 80% human beta sickle globin (h beta S), by crossing transgenic progeny with nonthalassemic, heterozygous, or homozygous beta-thalassemic mice, respectively. Transgenic mice that produce Hb A, developed in a similar fashion, were used as controls. RBC from each transgenic line were examined for pathologic changes. RBC from 50 and 80% h beta S mice sickle upon deoxygenation in vitro while RBC from 30% h beta S mice and all Hb A mice do not. Density gradients of RBC from each Hb S line, including those from 30% h beta S that do not sickle, show broad distributions with increased dense fractions, similar to those of patients with SCD. RBC from Hb S lines exhibit elevated membrane-associated denatured hemoglobin (MADH) levels (0.250 +/- 0.080%) when compared to RBC from nontransgenic (0.073 +/- 0.021%) and transgenic Hb A (0.062 +/- 0.033%) mice. Elevated MADH levels in RBC from the 30% h beta S line suggest that membrane changes occur even though these cells do not sickle. These Hb S-dependent pathologic changes suggest that transgenic Hb S lines may be useful for the study of not only RBC sickling in vivo but also membrane oxidative damage and other chronic changes attributed to abnormal properties of both oxygenated and deoxygenated Hb S.