CCCTC-binding factor is essential to the maintenance and quiescence of hematopoietic stem cells in mice

Hematopoiesis involves a series of lineage differentiation programs initiated in hematopoietic stem cells (HSCs) found in bone marrow (BM). To ensure lifelong hematopoiesis, various molecular mechanisms are needed to maintain the HSC pool. CCCTC-binding factor (CTCF) is a DNA-binding, zinc-finger protein that regulates the expression of its target gene by organizing higher order chromatin structures. Currently, the role of CTCF in controlling HSC homeostasis is unknown. Using a tamoxifen-inducible CTCF conditional knockout mouse system, we aimed to determine whether CTCF regulates the homeostatic maintenance of HSCs. In adult mice, acute systemic CTCF ablation led to severe BM failure and the rapid shrinkage of multiple c-Kit(hi) progenitor populations, including Sca-1⁺ HSCs. Similarly, hematopoietic system-confined CTCF depletion caused an acute loss of HSCs and highly increased mortality. Mixed BM chimeras reconstituted with supporting BM demonstrated that CTCF deficiency-mediated HSC depletion has both cell-extrinsic and cell-intrinsic effects. Although c-Kit(hi) myeloid progenitor cell populations were severely reduced after ablating Ctcf, c-Kit(int) common lymphoid progenitors and their progenies were less affected by the lack of CTCF. Whole-transcriptome microarray and cell cycle analyses indicated that CTCF deficiency results in the enhanced expression of the cell cycle-promoting program, and that CTCF-depleted HSCs express higher levels of reactive oxygen species (ROS). Importantly, in vivo treatment with an antioxidant partially rescued c-Kit(hi) cell populations and their quiescence. Altogether, our results suggest that CTCF is indispensable for maintaining adult HSC pools, likely by regulating ROS-dependent HSC quiescence.

Cyclooxygenase-2 blockade inhibits accumulation and function of myeloid-derived suppressor cells and restores T cell response after traumatic stress / 华中科技大学学报（医学）（英德文版）

Myeloid-derived suppressor cells (MDSCs) play a crucial role in T cell dysfunction, which is related to poor outcome in patients with severe trauma. Cyclooxygenase-2 (Cox-2) contributes to immune disorder in trauma and infection via production of prostaglandin E2. However, the role of Cox-2 in the accumulation and function of MDSCs after traumatic stress has not been fully elucidated. In the present study, we treated murine trauma model with NS398, a selective Cox-2 inhibitor. Then the percentages of CD11b+/Gr-1+ cells, proliferation and apoptosis of CD4+ T cells were determined. Arginase activity and arginase-1 (Arg-1) protein expression of splenic CD11b+/Gr-1+ cells, and delayed-type hypersensitivity (DTH) response were analyzed. The results showed that Cox-2 blockade significantly decreased the percentages of CD11b+/Gr-1+ cells in the spleen and bone marrow 48 and 72 h after traumatic stress. NS398 inhibited arginase activity and down-regulated the Arg-1 expression of splenic CD11b+/Gr-1+ cells. Moreover, NS398 could promote proliferation and inhibit apoptosis of CD4+ T cells. It also restored DTH response of traumatic mice. Taken together, our data revealed that Cox-2 might play a pivotal role in the accumulation and function of MDSC after traumatic stress.

Amplification of functional myeloid-derived suppressor cells during stem cell mobilization induced by granulocyte colony-stimulation-factor / 华中科技大学学报（医学）（英德文版）

The effects of granulocyte colony-stimulation-factor (G-CSF) on stem cell mobilization and its impact on the amplification of myeloid-derived suppressor cells (MDSCs) of donor mice were examined. A mouse model of stem cell mobilization was established by consecutive subcutaneous injection of 100 μg/kg G-CSF for 5 days. The blood from the donor mice was routinely examined during mobilization. Stem cells and MDSCs were analyzed by flow cytometry. The immunosuppressive molecules derived from MDSCs in serum and spleen, including hydrogen dioxide (H2O2) and nitric oxide (NO), and the activity of nitric oxide synthase (NOS) were determined during the mobilization. Apoptosis of T lymphocytes was assessed by using Annexin-V/PI. During stem cell mobilization, the number of lymphocytes and white blood cells in the peripheral blood was increased, and peaked on the 4th day. The number of stem cells in G-CSF-treated mice was significantly greater than that in controls (P<0.01). The expansions of MSDCs were also observed after G-CSF mobilization, with a more notable rate of growth in the peripheral blood than in the spleen. The activity of NOS and the production of NO were increased in the donor mice, and the serum H2O2 levels were approximately 4-fold greater than the controls. Consequently, apoptosis of T lymphocytes was increased and showed a positive correlation with the elevated percentage of MDSCs. It was concluded that G-CSF could provide sufficient peripheral blood stem cells for transplantation. Exogenous administration of G-CSF caused the accumulation of MDSCs in the peripheral blood and the spleen, which could lead to apoptosis of T lymphocytes and may offer a new strategy for the prevention and treatment of graft versus host disease.

Effect of granulocyte colony stimulating factor EPC on cardiac function in patients with heart failure after myocardial infarction / 南方医科大学学报

<p><b>OBJECTIVE</b>To study the changes of cardiac function following treatment with granulocyte colony stimulating factor (G-CSF) in patients with heart failure after myocardial infarction.</p><p><b>METHODS</b>Thirty-eight patients with heart failure after myocardial infarction were randomized into G-CSF treatment group and control group. All the patients received conventional treatment (medication and interventional therapy), and the patients in treatment group were given additional G-CSF (600 µg/day) for 7 consecutive days. The plasma level of brain-type natriuretic peptide (BNP) and the number of endothelial progenitor cells (EPCs) in the peripheral blood were detected before and at 7 days and 4 months after the treatment. The cardiac functions (LVSD, EDV, and LVEF) were evaluated by ultrasonic imaging before and at 2 weeks and 4 months after the treatment.</p><p><b>RESULTS</b>The number of EPCs was significantly higher in the treatment group than in the control group after the treatment especially at 7 days (P<0.01). In both groups, BNP level was lowered significantly after the treatment to recover the normal level (P<0.01). The cardiac functions were improved in all the patients at 7 days and 4 months after the treatment, and the improvement was more obvious in the treatment group (P<0.05), especially in terms of LVEF at 4 months after the treatment (P<0.01).</p><p><b>CONCLUSION</b>EPC mobilization by G-CSF can effectively improve the cardiac functions and lessen ventricular remodeling in patients with heart failure after myocardial infarction.</p>

Diagnostic and therapeutic guideline for myeloproliferative neoplasm

The myeloproliferative neoplasm (MPN), polycythemia vera (PV), essential thrombocytosis (ET), and primary myelofibrosis (PMF) are clonal hematopoietic stem cell diseases that share in common overproduction of one or more of the formed elements of the blood with overlapping clinical features but exhibit different natural histories and different therapeutic requirements. Therefore, accuracy of diagnosis is the cornerstone of therapy. The World Health Organization diagnostic criteria for both the classic BCR-ABL-negative MPNs (that is PV, ET, and PMF) and chronic eosinophilic leukemia/hypereosinophilic syndrome have been revised in the 2008 edition, by incorporating new information on their V617F mutation in the Janus kinase 2 (JAK2) tyrosine kinase. The JAK2 V617F point mutation makes the normal hematopoietic progenitor cells hypersensitive to thrombopoietin, erythropoietin, and myeloid progenitor cells, leading to trilinear hematopoietic myeloproliferation. JAK2 V617F is found in most patients with PV, ET, or PMF and is, therefore, useful as a clonal marker when present. However their absence does not exclude the diagnosis of an MPN. The major complications of the MPN are thrombosis, hemorrhage and extramedullary hematopoiesis with massive splenomegaly and bone marrow failure. Myelofibrosis is classically listed as a complication of the MPN. Current treatment options are low dose aspirin, phlebotomy and cytoreductive therapy with hydroxyurea, anagrelide, and interferon for PV and ET but the most effective therapy is still bone marrow transplantation for PMF for the relief of symptoms and the prevention of complications. Drugs targeting JAK2 V617F are promising. This article reviews the changes in diagnostic criteria and algorithms, and also provides treatment guidelines that are tailored to routine clinical practice.

Inmunoterapia del cáncer: Importancia de controlar la inmunosupresión / Cancer immunotherapy: Importance of overcoming immune suppression

Es cada vez mayor la evidencia experimental y clínica de que el sistema inmunitario interviene activamente en la patogénesis y el control de la progresión tumoral. Una respuesta antitumoral efectiva depende de la correcta interacción de varios componentes del sistema inmunitario, como las células presentadoras de antígeno y diferentes sub-poblaciones de linfocitos T. Sin embargo, los tumores malignos desarrollan numerosos mecanismos para evadir el reconocimiento y su eliminación por parte del sistema inmunitario. En esta revisión discutiremos algunos de esos mecanismos y posibles estrategias terapéuticas para contrarrestarlos.

Increasing evidence indicates that the immune system is involved in the control of tumor progression. Effective antitumor immune response depends on the interaction between several components of the immune system, including antigen-presenting cells and different T cell subsets. However, tumor cells develop a number of mechanisms to escape recognition and elimination by the immune system. In this review we discuss these mechanisms and address possible therapeutic approaches to overcome the immune suppression generated by tumors.

High incidence of zidovudine induced anaemia in HIV infected patients in eastern India.

Background & objectives: Zidovudine (ZDV) is the preferred nucleoside reverse transcriptase inhibitor in the first line antiretroviral regimen in India. It is known to be associated with life threatening toxicity like anaemia. This study was aimed at determining the prevalence of ZDV induced anaemia in HIV infected patients initiated on ZDV containing antiretroviral therapy regimen and also to find out the correlates, if any, for causing ZDV induced anaemia. Methods: This retrospective study was carried in ART Centre, Sir Sunderlal Hospital, Banaras Hindu University, Varanasi between March 2005 to December 2007. HIV infected patients registered at ART Centre were treated according to guidelines of National AIDS Control Organization (NACO). Patients (n=1256) with haemoglobin (Hb) >8 g/dl were prescribed ZDV based antiretroviral therapy regimens. Patients developing anaemia (<8 g/dl) with other causes of anaemia excluded were recorded. Correlation of baseline characteristics (age, gender, haemoglobin levels, weight, CD4 counts and WHO clinical stage) with risk of developing anaemia was also calculated. Results: Two hundred three (16.2%) patients on ZDV regimen developed anaemia (<8 g%); 7.9 per cent (n=100) of these developed severe anaemia (<6.5 g%). Females were more prone to develop anaemia (P=0.026). Age, weight, WHO clinical stage and CD4 counts had no relation to development of anaemia. Interpretation & conclusion: High incidence of ZDV induced anaemia seen in this study indicates regular monitoring of patients, particularly women on ZDV based antiretroviral regimens.

Cytogenetic studies of acute myeloid leukemia

Acute myeloid leukemia [AML] describes as a group of hematopoietic stem cell disorders characterized by expansion of undifferentiated myeloid progenitors. Acquired chromosomal anomaly particularly reciprocal translocations constitute one of the major events contribute to leukemogenesis. 45 untreated, newly diagnosed patients with de novo AML were enrolled in the present study, and subjected to cytogenetic analysis. Four ml of heparinized peripheral blood were collected for 72 hours synchronized culture, and then chromosome G- banding analysis was performed using standard methods. The karyotypes were designated according to the International System for Human Cytogenetic Nomenclature [ISCN]. The collected data were analyzed statistically. Cytogenetic analysis and karyotype results were obtained in 45 patients with de novo AML. Males constituted 33.3%, and females constituted 66.7% of this group. The patients' age ranged from 17-60 years. Chromosomal anomalies have been detected in 21 out of 45 patients [46.7%]. However five different types of chromosome anomalies have been detected; where seven cases [33.3%] carrying t[15;17]] q22;q21]; six cases [28.5%] carrying t[8;21][q22;q22]; three cases [14.3%] had trisomy 8; three cases [[14.3%] had monosomy 7; and lastly two cases [9.5%] carrying inv[3][q21q26]. Conventional cytogenetic analysis reliability detects chromosomal abnormalities in AML patients at the time of diagnosis. Chromosomal anomalies detected in Egyptian AML patients, are similar to some extent to those recorded in other areas of the world

Forward genetic screening for zebrafish mutants defective in myelopoiesis / 南方医科大学学报

<p><b>OBJECTIVE</b>To identify zebrafish mutants with myelopoiesis defects by ENU mutagenesis and large-scale forward genetic screening.</p><p><b>METHODS</b>Male zebrafish were mutagenized with N-ethyl N-nitrosourea to induce mutations in the spermatogonial cells to generate the founders, which were outcrossed with AB to raise F1 fish. The F1 fish from different founders were mated to generate the F2 families. The F3 embryos from F2 sibling crosses were screened by Sudan black B staining and neutral red staining.</p><p><b>RESULTS</b>A total of 350 F2 families from F1 sibling crosses were screened, and 1424 F2 crosses were analyzed. Six mutations were identified resulting in abnormal Sudan black B staining and neutral red staining, indicating the involvement of neutrophil deficiency or macrophage abnormalities.</p><p><b>CONCLUSION</b>It is simple and cheap to induce and screen myelopoiesis deficiency in zebrafish by ENU chemical mutagenesis and Sudan black B staining and neutral red staining. These mutants shed light on the identification of the genes important to myelopoiesis in zebrafish.</p>

Leukemic stromal hematopoietic microenvironment negatively regulates the normal hematopoiesis in mouse model of leukemia / 癌症

<p><b>BACKGROUND AND OBJECTIVE</b>Leukemic microenvironment has a major role in the progression of leukemia. Leukemic cells can induce reversible changes in microenvironmental components, especially the stromal function which results in improved growth conditions for maintaining the malignant leukemic cells. This study aimed to investigate the survival advantage of leukemic cells over normal hematopoietic cells in stromal microenvironment in long term.</p><p><b>METHODS</b>The mice were injected intraperitoneally with N-N' ethylnitrosourea (ENU) to induce leukemia; the mice received injection of normal saline were used as control. At 180 days after ENU induction, the mice were killed and the bone marrows were cultured for 19 days. Colony-forming assays were used to analyze the formation of various cell colonies. The expression of Sca-1, CD146, VEGFR2, CD95, pStat3, pStat5, and Bcl-xL in marrow cells were detected by flow cytometry.</p><p><b>RESULTS</b>Long-term leukemic bone marrow culture showed abnormal elongated stromal fibroblasts with almost absence of normal hematopoietic cells. Adherent cell colonies were increased, but CFU-F and other hematopoietic cell colonies were significantly decreased in leukemia group (P<0.001). Primitive progenitor-specific Sca-1 receptor expression was decreased with subsequent increased expression of CD146 and VEGFR-2 in leukemic bone marrow cells. Decreased Fas antigen expression with increased intracellular pStat3, pStat5 and Bcl-xL proteins were observed in leukemic bone marrow cells.</p><p><b>CONCLUSIONS</b>Stromal microenvironment shows altered morphology and decreased maturation in leukemia. Effective progenitor cells are decreased in leukemia with increased leukemia-specific cell population. Leukemic microenvironment plays a role in promoting and maintaining the leukemic cell proliferation and survivability in long term.</p>

Hexane-Soluble Fraction of the Common Fig, Ficus carica, Inhibits Osteoclast Differentiation in Murine Bone Marrow-Derived Macrophages and RAW 264.7 Cells

Osteoclasts, derived from multipotent myeloid progenitor cells, play homeostatic roles in skeletal modeling and remodeling, but may also destroy bone in pathological conditions such as osteoporosis and rheumatoid arthritis. Osteoclast development depends critically on a differentiation factor, the receptor activator of NF-kappaB ligand (RANKL). In this study, we found that the hexane soluble fraction of the common fig Ficus carica (HF6-FC) is a potent inhibitor of osteoclastogenesis in RANKL-stimulated RAW264.7 cells and in bone marrow-derived macrophages (BMMs). HF6-FC exerts its inhibitory effects by suppression of p38 and NF-kappaB but activation of ERK. In addition, HF6-FC significantly decreased the expression of NFATc1 and c-Fos, the master regulator of osteoclast differentiation. The data indicate that components of HF6-FC may have therapeutic effects on bone-destructive processes such as osteoporosis, rheumatoid arthritis, and periodontal bone resorption.

Experimental study on spinal fusion induced by hBMP-4 gene modified tissue engineered bone / 中华外科杂志

<p><b>OBJECTIVE</b>To evaluate the efficacy of hBMP-4 gene modified tissue engineered bone graft in the enhancement of rabbit spinal fusion and find an ideal kind of substitute for the autograft bone.</p><p><b>METHODS</b>Rabbit BMSCs were cultured and transfected with AAV-hBMP-4 using different MOI value. The optimal MOI value were determined by observing cell's morphology change. BMSCs were then transfected with AAV-hBMP4 and AAV-EGFP respectively, following which the transfected cells were evenly suspended in a collagen sponge I, and implanted to either side of the L5,6 intertransverse spaces posterolateral in the New Zealand rabbits to induce spinal fusion. Fourteen rabbits were randomly divided into 2 groups. Group 1: AAV-hBMP-4 transfected BMSCs in the right side (hBMP-4 side) and autograft bone in the left side. Group 2: AAV-hBMP-4 transfected BMSCs in the right side (hBMP-4 side) and AAV-EGFP transfected BMSCs in the left side (EGFP side). Radiographs and three-dimensional CT of the spine, manual palpation, gross and histological examination of the fusion masses for all the animals were performed subsequent to animals having been sacrificed at 12 weeks after surgery.</p><p><b>RESULTS</b>Evaluation has been taken in 12 New Zealand rabbits delivered into 2 groups which meet the criterion after operation. Eleven in 12 implemented sides involved hBMP-4 achieved bony fusion, to which 5 in 6 autografted sides was similar. But only 2 in 6 sides in EGFP-group achieved bony fusion meanwhile. Three-dimensional CT scan and palpation also evidenced the results. Bone formation was observed obviously on specimen both in hBMP4 sides and autografted ones. EGFP-group also got bony integration, but the quantity was small.</p><p><b>CONCLUSION</b>Tissue-engineered bone graft constructed from application of hBMP4 is a fine substitute for autograft. Effective enhancement of bony integration in spinal fusion surgery has been evidenced in vivo.</p>

Extragastic Pedunculated Giant Gastrointestinal Stromal Tumor of the Stomach

Gastrointestinal stromal tumors (GISTs) are a mesenchymal tumor of the digestive tract and they have various clinical characteristics. We report here on the largest extragastric pedunculated GIST of the stomach that has been seen in Korea. The patient was a 67-year-old man with a giant abdominal mass occupying the whole abdomen, and both leg showed swelling for the previous several months. On computed tomography (CT) and magnetic resonance imaging (MRI), this appeared as a septated cystic tumor with a solid component. Laparotomy revealed a giant extragastric tumor arising from the lesser curvature of the stomach that measured 47x34x23 cm and it weighed about 40 kg. Surgical treatment was performed to remove both the giant mass and the gastric wall where the tumor was attached to a 3-cm pedicle. On immunohistochemistry, the tumor was positive for myeloid stem cell antigen (CD34) and c-kit (CD117). The final diagnosis was a pedunculated extragastric type GIST arising from the stomach. The postoperative course was uneventful and the swelling in both legs resolved.

Myeloma stem/progenitor cells as new targets for therapy of multiple myeloma--review / 中国实验血液学杂志

Multiple myeloma (MM) is characterized by a population of functionally heterogeneous cells, in which identifying the target cells causing molecular lesion is a fundamental issue. The resultant tumor stem/progenitor cells comprise only a minor portion of the myeloma cells, which give rise through differentiation to more committed progenitors as well as differentiated blasts that constitute the bulk of the tumor. Although they are rare as compared with fully differentiated plasma cells, MM stem/progenitor cells are likely responsible for the maintenance and progression of disease through the production of new tumor cells. Thus, this is the cell population which must be eradicated for successful treatment. This article reviewed apparently conflicting evidence pertaining to the cellular origins of MM and proposed that myeloma may originate in more cellular components. In this article, the nature of the target cells, the identification and phenotypic analyses of clonogenic myeloma cells, the signaling pathways within myeloma stem/progenitor cells and the target therapy related were reviewed as well.

Experimental study of maxillary sinus lifting with tissue engineered bone / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the effect of tissue engineering bone in maxillary sinus lifting.</p><p><b>METHODS</b>The marrow stromal stem cells of dog were cultured in DMEM containing 100 m1/L fetal bovine serum and induced to differentiate to osteoblasts, which were then inoculated together with Bio-Oss for 5 days. Sixteen dog's bilateral maxillary sinus were elevated. One side was grafted with a compound of BMSC and Bio-Oss and the other side grafted with Bio-Oss alone. The samples were studied by gross, CT, histomorphology and histomorphometrical analysis at the 30th, 90th day after the operation. t-test was used for statistical analysis.</p><p><b>RESULTS</b>In gross view and CT, new bone formation was observed in all maxillary sinus after 30 and 90 days respectively. Histomorphometrical analysis showed much more new callus in BMSC-Bio-Oss group than in Bio-Oss group (P < 0.05).</p><p><b>CONCLUSIONS</b>A better effect of new bone formation could be obtained with tissue engineered bone in maxillary sinus lifting.</p>

Preliminary study on immunologic tolerance for hetero-skin graft induced by chimeric donors / 中华烧伤杂志

<p><b>OBJECTIVE</b>To explore the feasibility of transplanting the skin from chimeric rats to rabbits.</p><p><b>METHODS</b>Chimeric rats were produced by transplanting the haematopoietic stem cells (HSCs) from rabbit marrows into fetal rats in uterus and followed by injecting the HSCs into the livers of the rats at newborn stage. After six weeks, the skin from chimeric rats was transplanted to the rabbits. In group A, the skin grafts from chimeric rat donors were transplanted to the HSCs donating rabbits, with the skin from non-chimeric rat to normal rabbits were used as control. In group B, the skin grafts from chimeric and non-chimeric rats were transplanted to the HSCs donating rabbits at the same time. Gross observation and the surviving time of heterogenic-skin graft were observed. The wound healing time was also recorded.</p><p><b>RESULTS</b>In group A, the surviving time and the wound healing time of non-chimeric grafts were (9.3 +/- 1.8) days and (20.9 +/- 2.1) days, respectively, while those in chimeric grafts were (15.1 +/- 2.6) and (18.5 +/-1.3) days, respectively. In group B, the surviving time and the wound healing time of non-chimeric grafts were similar to those of group A. Compared with those in non-chimeric grafts, the surviving time of chimeric grafts in both groups were prolonged (P < 0.01), and the wound healing time shortened (P < 0.05 or 0.01). Most of the wounds healed quickly after rejection of chimeric grafts, while the wounds with non-chimeric grafts were re-opened with exudation and some necrotic tissue.</p><p><b>CONCLUSION</b>Immunologic tolerance for skin graft can be induced by the skin from chimeric donors, which can prolong the surviving time of skin grafts and shorten the wound healing time.</p>

Study of cryopreservation of differentiated hepatocyte derived from human bone marrow stem cells / 中华外科杂志

<p><b>OBJECTIVE</b>To observe the viability and function of human bone marrow stem cell-derived hepatocytes following cryopreservation in vitro.</p><p><b>METHODS</b>Human bone marrow cells were induced to differentiate into hepatocytes in the presence of multiple factors. Mature hepatocytes were cryopreserved in 90% FBS and 10% DMSO (Group A), 10% FBS, 30% glycerol and 60% conditioned medium (Group B), and 10% FBS, 10% DMSO, and 80% UW solution (Group C). The cells were thawed after 4 weeks, and the cell viability and the albumin level were determined.</p><p><b>RESULTS</b>The human bone marrow derived hepatocytes maintained functional morphology after thawing. The viabilities in Group A, B and C were (60.0 +/- 3.3)%, (91.0 +/- 2.6)%, and (89.0 +/- 1.4)%, respectively. After culturing for 24 h, the albumin levels in Group A, B and C were (0.210 +/- 0.005) g/L, (0.340 +/- 0.020) g/L and (0.330 +/- 0.030) g/L, respectively.</p><p><b>CONCLUSIONS</b>Human bone marrow stem cell-derived hepatocytes can maintain the viability and function after cryopreservation. These cells may contribute to an important source of hepatocytes for clinical hepatocyte transplantation and artificial liver support system.</p>

Hematopoietic features and apoptosis in the bone marrow of severe Plasmodium falciparum-infected patients: preliminary study.

The mechanism of anemia in severe falciparum malaria is still not completely understood. The purpose of this study was to determine whether apoptosis in the erythroid lineage causes anemia in falciparum malaria. Bone marrow aspirated from 8 severe falciparum malaria patients, 3 normal volunteers and 5 retrospective normal bone marrow smears were investigated. By light microscopic study, 5 of 8 hyperparasitemic patients had hypocellular bone marrows and erythroid hypoplasia, whereas the other 3 patients had normal cellularity. The mean myeloid : erythroid ratio of these 5 patients was significantly (p < or = 0.05) higher than normal. Apoptosis of bone marrow nucleated cells (BMNC) could be determined from the exposure of phosphatidylserine (PS) on the cell membrane but not DNA fragmentation (180-250 bp) or ultrastructural morphology. The percentages of apoptotic BMNC and apoptotic erythroid cells in bone marrow from each patient and controls varied from low to high, and were not associated with parasitemia. This study suggests that destruction of erythroid lineage, particularly through apoptosis regulation, cannot solely account for anemia in falciparum malaria.