Role of mast cells in ion transport abnormalities associated with intestinal anaphylaxis. Correction of the diminished secretory response in genetically mast cell-deficient W/Wv mice by bone marrow transplantation.

To investigate the role of mast cells in transport abnormalities during intestinal anaphylaxis, we examined responses to antigen in isolated intestinal preparations from ovalbumin-sensitized genetically mast cell-deficient WBB6F1-W/Wv (W/Wv) mice and congenic normal WBBGF1(-)+/+ (+/+) mice. Changes in ion transport (primarily secretion of chloride ions) were indicated by increases in short-circuit current (Isc). In tissues from +/+ mice, antigen caused increases in Isc which were significantly inhibited by antagonists to histamine (diphenhydramine) and serotonin (ketanserin), by a cyclooxygenase inhibitor (piroxicam) and by a neurotoxin (tetrodotoxin). In preparations from W/Wv mice, antigen-stimulated responses were approximately 30% of that in +/+ mice and were inhibited only by piroxicam. Responses to electrical transmural stimulation of nerves were approximately 50% in W/Wv versus +/+ mice, and were inhibited by antagonists of mast cell mediators in +/+ but not W/Wv mice. Reconstitution of mast cells in W/Wv mice by intravenous injection of +/+ bone marrow cells restored the normal responses to both antigen and nerve stimulation. Our results indicate that mast cell-dependent mechanisms are primarily responsible for the ion secretion associated with intestinal anaphylaxis, but that other cells are also involved. In addition, our data provide evidence for the functional importance of bidirectional communication between nerves and mast cells in the regulation of ion transport in the gastrointestinal tract.     

Role of mast cells in anaphylaxis. Evidence for the importance of mast cells in the cardiopulmonary alterations and death induced by anti-IgE in mice.

We used genetically mast cell-deficient WBB6F1-W/Wv and WCB6F1-S1/S1d mice and the congenic normal (+/+) mice to investigate the effects of intravenous infusion of goat antimouse IgE on heart rate (HR), pulmonary dynamic compliance (Cdyn), pulmonary conductance (GL), and survival. In WBB6F1-+/+ and WCB6F1-+/+ mice, anti-IgE induced extensive degranulation of tracheobronchial mast cells, as well as significant elevation of HR, significant reductions in Cdyn and GL and, in some cases, death. In contrast, W/Wv and S1/S1d mice exhibited little or no pathophysiological responses and no mortality after challenge with anti-IgE. In W/Wv mice reconstituted with mast cells by intravenous administration of bone marrow cells derived from congenic +/+ mice (+/+ BM----W/Wv mice), anti-IgE induced extensive mast cell degranulation, as well as pathophysiological responses and mortality similar to those observed in WBB6F1-+/+ mice. These findings suggest a critical role for mast cells in the development of the cardiopulmonary changes and mortality associated with anti-IgE-induced anaphylaxis.     

Regulation of human megakaryocytopoiesis. An in vito analysis.

We have recently described an assay system for human peripheral blood megakaryocyte colony-forming unit cells (CFU-M) using an anti-platelet glycoprotein antiserum probe to define megakaryocyte colonies grown in vitro. This system was applied to study the nature and regulation of human bone marrow CFU-M. In the absence of a specific megakaryocyte growth-promoting factor, 12.4 +/- 3.0 (means +/- SEM) megakaryocyte colonies were cloned per 5 X 10(5) cells cultured. Colonies were present after 6 d of incubation reaching peak numbers between days 10 and 14 and slowly decreasing thereafter. Erythropoietin in concentrations of up to 4 U/ml failed to augment colony numbers. Also failing to enhance megakaryocyte colony plating efficiency were media containing burst-promoting activity and colony-stimulating activity. A medium conditioned by human embryonic kidney cells, which has been previously demonstrated to contain thrombopoietin, also had no effect on megakaryocyte colony numbers. In contrast, sera from three patients with severe aplastic anemia produced significant enhancement of CFU-M-derived colony formation in vitro. Both the number of megakaryocyte colonies present and the number of megakaryocytes per colony were increased in proportion to the final concentration of aplastic anemia serum. In the presence of 10% aplastic anemia serum, cultured megakaryocyte colony numbers were linear with respect to the number of bone marrow mononuclear cells plated suggesting a clonal origin of each of the colonies. This in vitro assay for bone marrow CFU-M is a reliable means by which to study the regulation of human megakaryocytopoiesis. Initial data suggest that megakaryocyte production is stimulated by a factor detectable in aplastic anemia serum that may be distinct from other known hematopoietic stem cell regulators.     

Effect of spleen cell conditioned medium on megakaryocytopoiesis in a short-term bone marrow culture system

The effect of pokeweed mitogen-stimulated spleen cell conditioned medium (PWCM) on the proliferation of megakaryocytes and megakaryocyte progenitor cells (CFU-M) was studied with a short-term liquid culture (STLC) system. Adherent and nonadherent cells were sampled daily for acetylcholinesterase-positive cells and CFU-M. The proliferative capacity of CFU-M was determined by culturing cells from STLC in secondary methylcellulose cultures and counting the number of megakaryocytes per colony. Positive dose-related effects were observed between the number of megakaryocytes and CFU-M in liquid culture and the concentration of PWCM in the culture. In contrast, the proliferative capacity of CFU-M was lower in cultures containing high concentrations of PWCM compared with cultures containing low concentrations of PWCM. Furthermore, mean megakaryocyte diameter was significantly smaller in cultures containing high levels of PWCM compared with cultures with low concentrations. These data suggest that at low levels of conditioned medium, megakaryocytopoiesis is characterized by production of fewer CFU-M with a higher proliferative capacity and fewer large megakaryocytes. In turn, high concentrations of PWCM promote the production of a greater number of CFU-M with reduced proliferative capacity and an increased number of small megakaryocytes.     

Mast cell mediators regulate vascular permeability changes in Arthus reaction.

Plasma exudation characterizes the early phase of acute inflammation. The possible role of mast cells and their mediators in this event in immune complex-induced injury was studied. Dye exudation was assessed from 5 min to 2 hr after initiating reverse passive Arthus reaction in mast cell-deficient mice, WBB6F1-W/Wv (W/Wv), and their normal congenic controls, WBB6F1-+/+ (+/+). The response to antibody (10, 30 and 100 micrograms/site, i.d.) was dose- and time-dependent in both groups of mice. At the lower doses of antibody, 10 and 30 micrograms/site, exudation was significantly less (30% and 40%, respectively) in W/Wv as compared to +/+ mice between 15 to 45 min. With 100 micrograms of antibody/site, significant differences between W/Wv and +/+ mice were noted only at 15 and 30 min. The deficit in permeability changes in W/Wv mice was reversed by local mast cell reconstitution. In +/+ mice, pyrilamine and methysergide pretreatment reduced vascular permeability to the same extent by 70, 60 and 35% when stimulated for 30 min with 10, 30 and 100 micrograms of antibody/site, respectively. An equivalent inhibition was observed with the 5-lipoxygenase inhibitor A-63162. None of the inhibitors decreased plasma permeation in W/Wv mice. These results indicate that the mast cell mediators histamine and serotonin regulate vascular permeability early during an immune complex-mediated inflammation. The data also suggest the involvement of leukotrienes and the importance of mast cells in their synthesis. The profile of inhibition in +/+ mice agrees well with the difference in exudation observed between normal and mast cell-deficient mice.     

Interleukin 3 perfusion in W/Wv mice allows the development of macroscopic hematopoietic spleen colonies and restores cutaneous mast cell number

The genetically anemic W/Wv mice are characterized by the inability of their bone marrow cells to form macroscopic pluripotent hematopoietic colonies in the spleen of irradiated recipients upon transfer (colony-forming units). Furthermore, they almost totally lack mast cells, notably in the skin. In the present study, we have tested the effect of recombinant murine interleukin 3 (rmIL-3) on W/Wv mice hematopoiesis. Transfer of W/Wv bone marrow cells into lethally irradiated recipients perfused with rmIL-3 is followed by the appearance of macroscopic spleen colonies. Moreover, perfusion of rmIL-3 in W/Wv mice: (a) restores almost normal total numbers of hematopoietic precursors (colony-forming cells), but without modification of anemia; and (b) leads to the appearance of a normal number of mastocytes in the skin.     

Genetic analysis reveals cell type-specific regulation of receptor tyrosine kinase c-Kit by the protein tyrosine phosphatase SHP1

Receptor protein tyrosine kinases (RTKs) transmit downstream signals via interactions with secondary signaling molecules containing SH2 domains. Although many SH2-phosphotyrosyl interactions have been defined in vitro, little is known about the physiological significance of specific RTK/SH2 interactions in vivo. Also, little is known about the mechanisms by which specific RTKs interact with and/or are regulated by specific protein tyrosine phosphatases (PTPs). To address such issue, we carried out a genetic analysis of the previously reported biochemical interaction between the RTK c-Kit, encoded at the W locus, and the SH2-containing non-transmembrane PTP SHP1, encoded at the motheaten (me) locus (1). Mice carrying a kinase-defective allele of c-Kit (Wv/+) were crossed with me/+ mice, which carry one effectively null allele of SHP1, and then backcrossed to generate all possible allelic combinations. Our results indicate strong intergenic complementation between these loci in hematopoietic progenitor cells. Compared to progenitors purified from normal mice, bone marrow progenitor cells (lin-) from me/me mice markedly hyper-proliferated in response to Kit ligand (KL). stimulation. Superimposition of the me/me genotype increased the number of one marrow-derived CFU-E from Wv/+ mice. Conversely, the presence of one or two copies of Wv decreased the number of macrophages and granulocytes in me/me lung, skin, peripheral blood and bone marrow, thereby decreasing the severity of the me/me phenotype. The decrease in dermal mast cells in Wv/Wv mice was rescued to levels found in Wv/+mice by superimposition of the me/me genotype. Surprisingly, however, the presence or absence of SHP1 had no effect on the proliferative response of bone marrow-derived cultured mast cells to KL or IL3 ex vivo. Nevertheless, the immediate-early response to KL stimulation, as measured by KL-induced tyrosyl phosphorylation, was substantially increased in mast cells from Wv/+:me/me compared to Wv/ +:+/+ mice, strongly suggesting that SHP1 directly dephosphorylates and regulates c-Kit. Taken together, our results establish that SHP1 negatively regulates signaling from c-Kit in vivo, but in a cell type- specific manner.     

In vivo and in vitro modulation of megakaryocytopoiesis and stromal colony formation by lithium

The ability of lithium to influence in vivo and in vitro megakaryocytopoiesis and the hematopoietic microenvironment from marrow and splenic tissues was investigated. For three consecutive days, mice were injected intraperitoneally with ultrapure lithium chloride (1.6 mg/kg body weight). Animals were killed on days 1 through 4 and thereafter on alternating days until day 16. Megakaryocytopoiesis was evaluated by culturing marrow and splenic cells for their megakaryocyte stem cell (CFU-M) content. The marrow and splenic microenvironment was determined by measuring stromal colonies. Increases in marrow CFU-M were noted on the first 3 days after Li, with the maximum effect on day 2 (180% of control). A second wave of megakaryocytopoiesis began on day 6 and peaked on day 10 (165% of control). Splenic megakaryocytopoiesis was also stimulated by Li; maximum production occurred on day 10 (330% of control). Splenic stromal colony formation was elevated on the 12 days after Li. Numbers of marrow stromal colonies were elevated on days 6, 10, and 12. The increased numbers of marrow- and splenic-derived CFU-M elevated the level of circulating platelets for 10 days after Li. Dose-response Li (0.01 to 10 mmol/L) studies performed in vitro demonstrate that Li effectively increased the number of both CFU-M and stromal colony-forming cells in the presence of optimal concentrations of conditioned media used to stimulate the formation of CFU-M. Furthermore, when stromal colonies were used as feeder layers overlaid with normal nonadherent marrow cells, Li-stimulated stromal colonies supported a greater number of CFU-Ms than did normal, non-Li-treated stromal cultures.(ABSTRACT TRUNCATED AT 250 WORDS)     

Megakaryocytopoiesis and granulopoiesis after murine cytomegalovirus infection

Thrombopoiesis and granulopoiesis following murine cytomegalovirus infection were investigated by studying changes in megakaryocytes, megakaryocyte and granulocyte-macrophage progenitor cells, and spleen colony-forming cells. The soft gel in vitro culture system was used to assay for megakaryocyte and granulocyte-macrophage progenitor cells in marrow and spleen. Murine cytomegalovirus produced a mild thrombocytopenia to 90% of control values 1 day after infection at a time when marrow megakaryocyte levels were normal, suggesting a mild direct toxic effect of the virus on platelets. A reduction of megakaryocytes, megakaryocyte and granulocyte-macrophage progenitor cells, and spleen colony-forming cells to 40% to 60% of control values occurred within 24 to 48 hours of infection in association with an additional decrease in platelets to 58% of control levels on day 4. In vitro inoculation of marrow cell cultures with murine cytomegalovirus also resulted in a reduction of megakaryocyte- and granulocyte-macrophage colony-forming cells within 24 to 48 hours, suggesting that murine cytomegalovirus-induced thrombocytopenia and granulocytopenia may be in part caused by direct infection of precursor cells. The recovery of cells in the spleen was followed by a striking seven- to 10-fold increase in spleen colony-forming cells and megakaryocyte and granulocyte-macrophage progenitor cells in the spleen. These marked increases followed significant increases in spleen cell production of colony-stimulating activities within 2 days of murine cytomegalovirus infection, suggesting that hematopoietic cell recovery is mediated by increased local production of colony-stimulating activities in the spleen.     

Splenic thrombopoiesis after bone marrow ablation with radiostrontium: a murine model

Murine platelet production is normally supported by high-ploidy bone marrow megakaryocytes without significant contribution from splenic megakaryocytes with predominantly low-ploidy levels. We produced sustained bone marrow ablation using radiostrontium, and examined the processes by which splenic platelet production is initiated and maintained in the absence of bone marrow function. Bone marrow hematopoiesis, measured by total nucleated cell number and viability, megakaryocyte colony-forming cells, and granulocyte-macrophage colony-forming cells, was rapidly ablated in mice by using yttrium 90-free strontium 90. Platelet count declined from normal (1224 x 10(3)/microliters) to a nadir (98 x 10(3)/microliters) 11 days after 90Sr, and then rose to a stable level (705 x 10(3)/microliters) on days 20 through 115. Peripheral leukocyte concentration decreased rapidly and remained below 25% of normal in contrast to hemoglobin levels, which were minimally lowered. Mean spleen weight rose rapidly after 90Sr to 66% above normal. Splenic megakaryocyte frequency, measured by two-color fluorescence-activated flow cytometry, rose from basal levels (0.09% +/- 0.06%) to 0.15% +/- 0.07% (p less than 0.001), total spleen nucleated cells fell to 71% of normal, and the absolute number of spleen megakaryocytes was unchanged. Total spleen megakaryocyte colony-forming cells were not significantly increased above normal whereas total spleen granulocyte-macrophage colony-forming cells increased abruptly after day 13 to 10 times normal levels. Splenectomy after hematopoietic recovery from 90Sr bone marrow ablation resulted in a rapid decline of platelet levels, followed by death. Although the spleen became the sole site of platelet production, the splenic megakaryocyte ploidy distribution was only minimally changed from normal, and the modal ploidy class remained 2N. In contrast to experimental thrombocytopenia in mice with intact bone marrow, in which megakaryocyte ploidy is increased, thrombocytopenia associated with sustained bone marrow ablation does not result in upward regulation of splenic megakaryocyte ploidy as a compensatory mechanism.     

Hematopoietic Stem Cells with High Proliferative Potential: ASSAY OF THEIR CONCENTRATION IN MARROW BY THE FREQUENCY AND DURATION OF CURE OF W/Wv MICE

This study was designed to approach two primary questions concerning hematopoietic stem cells (HSC) in mice: what is the concentration of HSC with extensive proliferative potential in marrow, and how long can an HSC continue to function in an intact animal? The assay system was the W/W^v mouse, a mouse with an inherited HSC defect, reflected in a reduction in all myeloid tissue and most particularly in a macrocytic anemia.A single chromosomally marked HSC will reconstitute the defective hematopoietic system of the W/W^v. The concentration of HSC in normal littermate (+/+) marrow was assayed by limiting dilution calculation using cure of W/W^v as an end point (correction of anemia and erythrocytes'' macrocytosis) and found to be ∼10/10⁵. This is significantly less than spleen colony forming cell (CFU-S) concentration: ∼220/10⁵ in +/+ and ranging from 50 to 270/10⁵ in various other studies. Blood values were studied at selected intervals for as long as 26 mo. Of 24 initially cured mice, which were observed for at least 2 yr, 75% remained cured. However, of all cured mice, 17 lost the cure, returning to a macrocytic anemic state. Cured mice had normal numbers of nucleated and granulocytic cells per humerus and a normal concentration of CFU-S. However, cure of secondary W/W^v recipients by this marrow was inefficient compared with the original +/+ marrow. These studies suggest the CFU-S assay over-estimates extensively proliferating HSC or perhaps does not assay such a cell. A single such HSC can not only cure a W/W^v, but can sustain the cure for 2 yr or more, despite a relative deficit of cells capable of curing other W/W^v. However, the duration of sustained cure may be finite.     

Differences in the expression of the cardiopulmonary alterations associated with anti-immunoglobulin E-induced or active anaphylaxis in mast cell-deficient and normal mice. Mast cells are not required for the cardiopulmonary changes associated with certain fatal anaphylactic responses.

We compared the changes in heart rate (HR), pulmonary dynamic compliance (Cdyn), and pulmonary conductance (GL) associated with three different models of anaphylaxis in genetically mast cell-deficient WBB6F1-W/Wv and congenic normal (+/+) mice. Intravenous infusion of a monoclonal rat anti-mouse IgE produced a marked tachycardia, diminutions in Cdyn and GL, and death in +/+ but not W/Wv mice, and +/+ mice sensitized to develop high circulating levels of IgE exhibited HR, Cdyn, and GL responses to rat anti-IgE challenge which were significantly less intense than those in nonimmunized +/+ mice. By contrast, virtually identical cardiopulmonary responses were observed in either +/+ or W/Wv mice challenged to elicit pure active anaphylactic responses or simultaneous active and anti-IgE-dependent anaphylaxis. These findings show that anaphylactic responses associated with significant tachycardia, reductions in Cdyn and GL, and death can occur in the virtual absence of tissue mast cells. This is true even though, in normal mice, such responses are associated with extensive degranulation of tissue mast cells. By contrast, certain models of anaphylaxis, such as that induced in nonsensitized mice by anti-mouse IgE, can not be elicited in the absence of mast cells.     

Megakaryocyte growth and development factor. Analyses of in vitro effects on human megakaryopoiesis and endogenous serum levels during chemotherapy-induced thrombocytopenia.

The present study shows that recombinant human megakaryocyte growth and development factor (r-HuMGDF) behaves both as a megakaryocyte colony stimulating factor and as a differentiation factor in human progenitor cell cultures. Megakaryocyte colony formation induced with r-HuMGDF is synergistically affected by stem cell factor but not by interleukin 3. Megakaryocytes stimulated with r-HuMGDF demonstrate progressive cytoplasmic and nuclear maturation. Measurable levels of megakaryocyte growth and development factor in serum from patients undergoing myeloablative therapy and transplantation are shown to be elaborated in response to thrombocytopenic stress. These data support the concept that megakaryocyte growth and development factor is a physiologically regulated cytokine that is capable of supporting several aspects of megakaryopoiesis.     

Mast cells mediate complement activation after acid aspiration.

A significant role for the alternative complement pathway in acid aspiration has been demonstrated by the observation that C3 but not C4 genetic knockout mice are protected from permeability edema. Using mast cell-deficient mice (W/Wv), we tested the hypothesis that mast cells mediate complement activation after acid aspiration. Tracheostomy tubes were placed in anesthetized mice and 2 mL/kg 0.1 N HCL was instilled in the trachea. After 4 h, extravasation of 125I-albumin was used to calculate lung vascular permeability. The serum alternative complement pathway hemolytic activity was examined, and lung immunohistochemistry was performed. Lung permeability in W/Wv mice was 62% less than that of mast cell sufficient (+/+) animals and similar to +/+ mice treated with the chymase inhibitor chymostatin (65% decrease). Treatment of +/+ mice with D-PRO2,D-TRP(7,9)-Substance P, an antagonist to the neuropeptide substance P, reduced injury by 66%. Serum complement hemolytic activity was intact in injured w/wv mice and +/+ animals treated with chymostatin or dpdt-sp, but was decreased to 65% in the injured untreated +/+ group. Alveolar C3 deposition was intense in injured untreated +/+ mice but absent in the other groups. We interpret these data to indicate that mast cells mediate complement activation, via chymase degranulation, after acid aspiration. This mast cell activity likely is regulated by the release of substance P.     

Purification and partial characterization of a megakaryocyte colony-stimulating factor from human plasma.

Human plasma obtained from patients with hypomegakaryocytic thrombocytopenia contains a factor that promotes megakaryocyte colony formation by normal human marrow cells. This megakaryocyte colony-stimulating factor was purified from such a plasma specimen. A four-step purification scheme which included ammonium sulfate precipitation, diethylaminoethyl-Sepharose chromatography, affinity chromatography on wheat germ lectin-Sepharose 6MB, and reverse-phase high performance liquid chromatography resulted in a recovery of 16.6% of the initial biological activity and an increase in specific activity by 3,489-fold. The purified protein produced a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Purified megakaryocyte colony-stimulating factor was capable of promoting megakaryocyte colony formation at a concentration of 7.6 X 10(-8) M. Megakaryocyte colony-stimulating factor was shown to be a glycoprotein and had an apparent 46,000 mol wt. Deglycosylation of megakaryocyte colony-stimulating factor by treatment with trifluoromethane-sulfonate resulted in the loss of its ability to promote megakaryocyte colony formation. Megakaryocyte colony-stimulating factor appears to be an important regulator of in vitro human megakaryocytopoiesis at the level of the colony-forming unit megakaryocyte and may be of importance physiologically.     

Fate of bone marrow-derived cultured mast cells after intracutaneous, intraperitoneal, and intravenous transfer into genetically mast cell- deficient W/Wv mice. Evidence that cultured mast cells can give rise to both connective tissue type and mucosal mast cells

Both connective tissue mast cells and mast cells grown in vitro are derived from multipotential hematopoietic stem cells, but these two mast cell populations exhibit many differences in morphology, biochemistry, and function. We investigated whether the phenotype of cultured mast cells or their progeny was altered when the cells were transferred into different locations in vivo. Cultured mast cells were immature by ultrastructure, and stained with alcian blue but with neither safranin or berberine sulfate, a fluorescent dye that binds to the heparin of connective tissue mast cell granules. By contrast, mast cells recovered from the peritoneal cavity of congenitally mast cell-deficient (WB X C57BL/6)F1-W/Wv (WBB6F1-W/Wv) mice 10 wk after intraperitoneal injection of cultured WBB6F1-+/+ or C57BL/6-bgJ/bgJ mast cells stained with both safranin and berberine sulfate. Staining with berberine sulfate was prevented by treatment of the cells with heparinase but not chondroitinase ABC, suggesting that the adoptively transferred mast cell population had acquired the ability to synthesize and store heparin. Furthermore, the recovered mast cells were indistinguishable by ultrastructure from the normal mature peritoneal mast cells of WBB6F1-+/+ mice, and contained substantially more histamine than mast cells studied directly from culture. Intravenous injection of cultured mast cells resulted in the development of safranin-and berberine sulfate-positive mast cells in the peritoneal cavity, spleen, skin, and glandular stomach muscularis propria. Mast cells also developed on the glandular stomach mucosa, but these cells stained with alcian blue rather than safranin, and did not stain with berberine sulfate. This result suggests that cultured mast cells can give rise to mast cells of either the connective tissue type or mucosal phenotype, depending on anatomical location. Furthermore, transplantation of cultured mast cells into WBB6F1-W/Wv mice had no measurable effect on the anemia of the recipient mice, suggesting a possible strategy for repairing the mast cell deficiency of WBB6F1-W/Wv mice without affecting other bone marrow-derived populations such as erythrocytes. Intravenous injection of representative connective tissue type mast cells (30-50% pure peritoneal mast cells derived from WBB6F1-+/+ mice) gave results similar to those obtained with cultured mast cells: mast cells developing in the peritoneal cavity, skin, spleen, and glandular stomach muscularis propria of WBB6F1-W/Wv recipients stained with safranin and berberine sulfate, whereas mast cells developing in the mucosa of the glandular stomach stained only with alcian blue.(ABSTRACT TRUNCATED AT 400 WORDS)     

原发性血小板增多症巨核系祖细胞体外自主性生长及Tpo作用的探讨

目的：研究原发性血小板增多症（ET）巨核系祖细胞的体外自主性生长以及Tpo对其生长的作用,方法：用ET患者骨髓纯化CD^ 34细胞以不同浓度的骨髓和外周血单个核细胞进行体外培养,检测其对自发性CFU－MK形成的影响,用RT－PCR技术检测液体培养自发性生长细胞的Tpo的自主分泌和旁分泌,观察CD^ 34细胞培养中加入Tpo对CFU－MK形成的影响,结果：体外培养纯倾CD^ 34细胞无自发性CFU－MK形成,单个核细胞稀释到一定浓度（10^4/ml或10^3/ml）时自发性集落消失,液体培养自发性生长细胞无Tpo mRNA的表达,CD^ 34细胞培养中加入Tpo后可形杨CFU－MK,结论：ET患者的体外自发性CFU－MK形成并非巨核系祖细胞的自主性生长所,民Tpo的自主分泌或旁分泌也无关,ET的巨核系祖细胞可能对Tpo或其他细胞因子敏感。     

体外诱导人类诱导性多能干细胞分化为造血干 / 祖细胞的研究简

本研究探讨体外诱导人诱导性多能干细胞（induced pluripotent stem cell,iPSC）分化为造血干/祖细胞的能力.在体外用小鼠骨髓基质细胞OP9与人类iPSC共培养的方法,将iPSC诱导分化为造血干/祖细胞;用流式细胞术检测造血干/祖细胞表面标志物的表达水平;用实时定量PCR检测分化过程中iPSC及造血干/祖细胞的相关基因mRNA表达水平的变化;用免疫磁珠法分离CD34＋造血干/祖细胞并进行半固体集落形成实验检测细胞的集落形成能力.结果表明,iPSC与OP9细胞共培养诱导造血分化的第4天即可观察到iPSC形态变化;流式细胞术检测显示,分化得到的细胞表达已知的造血干/祖细胞相关表面标志物CD34和CD43分子.在体外分化过程中多能性的标志基因Oct4的表达逐渐下降,造血相关转录因子Gata-2的表达逐渐升高,而Runx-1的表达量则呈波浪式变化,CD34表达量逐渐升高.集落培养14 d能够得到红系集落（CFU-E）,粒系集落（CFU-G）,巨核系集落（CFU-M）,粒-巨核系集落（CFU-GM）和混合系集落（CFU-GEMM）.结论：iPSC细胞能够在体外通过与OP9细胞共培养分化为造血干/祖细胞.     

α干扰素直接抑制血小板生成素刺激的巨核细胞增殖和分化

目的：探讨α干扰素对Tpo刺激的巨核细胞的巨核细胞增殖和分化的影响及特点,方法：以三种不同细胞分离方法制备的正常小鼠骨髓巨细胞为研究对象,进行体外兰固休集落培养和液体培养,观察α干扰素对巨细胞集落形成单位（CFU－MK）,巨核细胞乙酰胆碱酯酶活性（AChE)以及巨核细胞计数,细胞直径和DNA含量的影响,结果：α干扰素抑制CFU－MK的形成,降低巨核细胞AChE,抑制作用与α干扰素剂量呈正相关,增加Tpo剂量或去除骨髓辅助细胞都不能抵消或改变这一作用,α干扰素对巨核细胞增殖和分化的各方面均有影响,巨核细胞计数减少,平均细胞直径减小,几何平均多倍体降低,结论：α干扰素以剂量依赖方式直接抑制Tpo刺激的巨核细胞增殖和分化。     

Histologic studies of splenic megakaryocytes after bone marrow ablation with strontium 90.

We previously showed that purified strontium 90 produced sustained bone marrow ablation in mice, lowering platelet levels to less than 10% of normal 11 days after administration. Platelet levels later rose exclusively from splenic production and were maintained at a stable level (58% of normal) from 20 to 115 days after injection. However, there was no change in the total number or ploidy distribution of splenic megakaryocytes, as immunologically detected by flow cytometry. To further study the characteristics of splenic thrombopoiesis after bone marrow ablation by 90Sr, we measured the frequency, cross-sectional area, and endomitotic figures of histologically recognizable megakaryocytes (as well as bare megakaryocyte nuclei) in mouse spleen sections. During the hematopoietic nadir 9 days after injection of yttrium 90-free 90Sr, the size (area) of megakaryocyte cross-sections (mean +/- SD, 1079.3 +/- 661.6 microns 2; normal, 398.7 +/- 192.8 microns 2) was greater than for any other time studied, but megakaryocyte frequency (corrected for size) did not increase until day 16. Overall, splenic megakaryocytes in marrow-ablated mice 16 or more days after 90Sr injection showed substantial increases (p = 0.001 for both comparisons) in mean area (707.5 +/- 386.2 microns 2) and sectional frequency (mean +/- SEM, 4.52 +/- 0.20 per 1.83 mm2; normal, 0.78 +/- 0.06 per 1.83 mm2). Megakaryocyte bare nuclei and endomitotic figures were also more numerous after 90Sr, injection, suggesting acceleration of megakaryocyte maturation and platelet production. The induction of splenic platelet production after bone marrow ablation is associated with increased size of recognizable megakaryocytes, despite lack of change in overall splenic megakaryocyte ploidy.