| ObjectiveFeline Leukemia Virus, Subgroup C (FLVCR) is a cytoplasmic heme exporter and is highly expressed in human hematopoietic cells. Retroviral interference with FLVCR display results in a loss of erythroid progenitors(CFU-E) and severe anemia in cats .In order to explore the importance of FLVCR for effective erythropoiesis in human cells, we studied the expression of FLVCR in childhood thalassemia , other hemolytic anemia and non-anemia controls and evaluated the relationship of expression of FLVCR and the clinical parameters.MethodsSamples of bone marrow of 50 children with thalassemia,other hemolytic anemia and non-anemia controls were collected in our hospital from March, 2005 to August, 2006. Mononucleaed red cells from BM of 21 thalassemic patients, 17 other other hemolytic anemia and 12 non-anemia controls were isolated by Ficoll-Hypaque centrifugation. Expression of FLVCR protein and mRNA on these two populations of proerythroblasts (CD71 bright, CD117+) and late erythroid precursors (CD71 bright, CD117 negative cells) were determined by 3 color flow cytometry and quantitative Real-time PCR with sorting these two populations . The correlation between the expression of FLVCR and the clinical and iron metabolic parameters were evaluated.Results1. FLVCR cell surface protein expression in nucleated red cells of three research groups as following:.(1) Positive rate and mean fluorecence intensity of FLVCR cell surface protein expression in CD71 bright, CD117+ cells of thalassemia, other hemolytic anemia and non-anemia controls were 78.9%, 84.2%, 74.85% and 306, 347, 291.5 respectively; while in CD71 bright, CD117 negative cells were 8.8%, 10.6%, 6.9% and 150,122,119 respectively, which indicate expression of FLVCR in proerythroblasts was significantly higher than that of more late erythroid precursors, P<0.01.(2) Positive rate and mean fluorecence intensity of FLVCR cell surface protein expression in CD71 bright, CD117+ cells of thalassemia were 78.9% and 306, which showed a higher tendency , as compared with cells of non-anemia controls ( 74.85% and 291.5) , but there were no statistic difference, P>0.05.(3) Positive rate and mean fluorecence intensity of FLVCR cell surface protein expression in CD71 bright, CD117+ cells of other hemolytic anemia were 84.2% and 347 respectively ,there were no statistical significance compared with that of non-anemia controls (74.85%, 291.5), P>0.05.(4) Positive rate and mean fluorecence intensity of FLVCR cell surface protein expression in CD71 bright, CD117 negative cells of thalassemia were 8.8%, and 150 respectively, which showed higher levels of expression, as compared with to cells of non-anemia controls (6.9% ,119) P<0.05.(5) Positive rate and mean fluorecence intensity of FLVCR cell surface protein expression in CD71 bright, CD117 negative cells of other hemolytic anemia were 10.6%, and 122 respectively, there were no statistical significance compared with that of non-anemia controls(6.9% ,119), P>0.05.2. FLVCR mRNA expression in nucleated red cells of three research groups as following:Of 10 samples, expression of FLVCR mRNA(mean rank 5.44 )in CD71 bright, CD117+ cells was lower than that of CD71 bright, CD117 negative cells(mean rank 6.00) with statistical significance, P=0.028.3. The correlation between expression of FLVCR and the clinical parameters: The hemolytic anemia patients with higher expression of FLVCR had higher retic count, higher percentage of more late erythroblast and lower LDH. The hemolytic anemia patients and thalassemic patients with higher expression of FLVCR had higher percentage of sideroblasts and serum ferritin level.Conclusions1. Our study found that the expression of FLVCR cell surface protein of three research groups was higher in proerythroblasts (CD71 bright, CD117+ cells), and decreased as erythropoiesis proceeds, combined with other studies in vitro and identification of FLVCR as a human heme exporter, which indicate that FLVCR plays an important role in developing erythroid cells to protect them from heme toxicity.2. There was no significantly compensatory up-regulation in FLVCR protein expression in proerythroblasts (CD71 bright, CD117+ cells) of thalassemia, indicating probably other ways exist in regulating heme metabolic balance in proerythroblasts together with FLVCR; The expression of FLVCR in more late erythroid precursors of thalassemia was higher than that of non-anemia group, which hint that FLVCR up-regulates with compensation and plays the role of effective erythropoiesis3. The disparity between FLVCR protein and mRNA may reflect postthanscriptional regulation of protein level. FLVCR cell surface protein performs inportant function in erythropoiesis4. The patients with higher expression of FLVCR have more effective erythropoiesis, FLVCR expression has close relation with iron metabolic parameters...
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