Zur Entwicklung einer mikroangiopathischhämolytischen Anämie am Modell des transplantablen Hämangioendothelioms der J-129-Maus

Abstract

Introduction In earlier reports we have described the morphological findings of microangiopathic hemolytic anemia (MHA) in autopsy cases. The aim of this publication is to show more exactly the close correlation between microangiopathy and intravascular hemolysis in a transplantable hemangioendothelioma of the mouse. This animal model is suitable for study of the MHA, which develops within short time, with various morphological and biochemical parameters. Material and methods 100 J 129 mice (Jackson Laboratory, Bar Harbor, Me) with transplanted hemangioendothelioma and 20 healthy controls were studied. For transplantation the tumors were removed in toto from donors and minced in 0.9% sterile saline; 0.7 ml of this tumor suspension was injected subcutaneously in the lateral flank of the recipients. The tests were started on the 5th, 10th, 15th and 20th day after tumor inoculation. Tissue for light microscopy (tumor, spleen, liver, kidney and bone marrow) was fixed in 6% buffered neutral formalin, embedded in paraffin, and 5μ sections were stained with hematoxylin-eosin, periodic acid Schiff reaction and Perls' iron stain. Tissue for transmission electron microscopy (hemangioendothelioma) was fixed in a aqueous solution of glutaraldehyde (6.25% in 0.1 m phosphate buffer of pH 7.2), twice washed in 0.2 M solution of saccharose (pH 7.2) and stored at 4° C for at least 18 hours in buffered 2% OsC 44-solution (pH 7.1), dehydrated in graded alcohol solutions and propylene oxide and embedded in Araldite. Thin sections were cut with an ultramicrotome and contrasted with uranyl acetate and basic lead oxide. Fragmented erythrocytes (schistocytes) were estimated in blood smears stained by Pappenhein's method. They were always smaller than normal erythrocytes and had lost their discoid forms. One or two spiny projections were typical features of fragmented red cells. Often they had a very bizarre appearence (Klein et al., 1975). The thrombocytes were counted in a Thoma chamber, in a hypotonic solution of procaine. Blood samples were obtained from the femoral vessels using the method of Young and Chambers (1973). The plasma hemoglobin was determined by the benzidine method of Crosby and Furth (1956). The following direct and indirect parameters of hemolysis were photometrically measured (micromethods) : serum iron (method of Trinder, 1956; Biochemica test combination of Boehringer/Mannheim, article No 15947), serum bilirubin (method of Jendrassik and Grof, 1938; Merckotest®, article No 3333), and hemoglobin of whole blood (method of van Kampen and Zijlstra, 1961; Biochemica test combination of Boehringer/Mannheim, article No 15927). Reticulocytes were counted in blood films stained with brillant cresyl blue. Results Tumors became palpable at about 5 days after transplantation, grew expansively and infiltrated the subcutaneous tissue. The tumors were composed of capillary and cavernous spaces (Fig. 1 and 2), lined by anaplastic endothelial cells. Often the blood spaces were narrowed or occluded by thrombi. Electronmicroscopically the neoplastic cells lining vascular spaces were very irregular. Often, deformed erythrocytes seemed to be trapped by various villus-like protrusions of tumor cells projecting into the blood spaces (Fig. 3). At other sites erythrocytes were enclosed and laced by fibrin strands (Fig. 4). Platelet aggregates attached to tumor cells were observed, too. In correlation with the tumor volume and with the extent of local intravascular coagulation in the hemangioendotheliomas, the thrombocytes decreased from 1,068 ± 275 × 10 3/mm 3 in the controls to 26 × 10 3/mm 3 in tumor bearing mice (Fig. 5). With increasing size of the tumor many schistocytes (up to 36%) appeared in the peripheral blood (Fig. 6 and 7); the plasma hemoglobin (up to 131 mg%) and bilirubin (up to 1.39 mg%) became elevated, too (Fig. 7) The tumor bearing mice always developed a siderosis of the kidney (“blue kidneys”). Deposition of siderin pigment was mainly found in the epithelial cells and less in the lumina of the proximal convoluted tubules. The amount of siderin pigment in the kidneys depended on tumor size and on the time after tumor cell inoculation (Fig. 9). The intravascular hemolysis caused a severe Coombs negative anemia with reticulocytosis up to 93% (controls 4.8 ± 5.1%). Serum iron remained normal. Hyperplastic extramedullary erythropoiesis developed in spleen (Fig. 10) and liver (Fig. 11), accompanied by proliferation of megakaryocytes in the spleen. Concluding remarks The morphological and biochemical investigations have shown that there is a good correlation between development of abnormal tumor vessels and so-called microangiopathic hemolytic anemia (MHA). The same type of anemia can be seen in patients with large hemangiomas or with metastasing (especially mucin-forming) tumors that have invaded blood vessels, with resulting thrombosis.