Megakaryocytes emperipolesis in bone marrow of the patients with non-Hodgkin's lymphoma

Emperipolesis of hematopoietic cells within the cytoplasm of the megakaryocytes was most often described in association with various pathologic conditions. The aim of the research was estimation of the incidence of emperipolesis in the bone marrow of the patients with non-Hodgkin's lymphoma (NHL). 30 patients with different histological types of NHL (chronic lymphocytic leukaemia--CLL, hairy cell leukaemia--HCL, multiple myeloma--MM) in compliance with clinical stage of the disease, patient's age and sex were analyzed. Trephine biopsies of the bone marrow were carried out in fixative solution and paraffin embedding. Hematoxylin and eosin and monoclonal antibody CD 61 were applied on thin sections. Phenomenon of megakaryocytic emperipolesis in human bone marrow was found in 6 cases: in 5 cases in CLL and in 1 case in HCL. In most of them emperipolesis was related to single megakaryocytes. We observed in the cytoplasm of the megakaryocytes single hematopietic cells-most often lymphocytes, rarely eosinophilic granulocytes. We found no correlations between histological types of NHL, clinical stage of the disease, patients' age, sex and the incidence of megakaryocytic emperipolesis.     

Emperipolesis and interrelations of megakaryocytes and neutrophilic granulocytes in the bone marrow of healthy dogs

Emperipolesis is an ability of one cell to penetrate into cytoplasm of another cell and to stay there for some time, or to pass through it. Unlike a common phagocytosis, not a cell interacting is damaged. Penetration of neutrophilic granulocytes into cytoplasm of megakaryocytes is also considered as emperipolesis, that is revealed in the bone marrow of healthy persons. Its occurrence becomes greater at various pathological states of tumorous and non-tumorous etiology. Histological investigation of the bone marrow of the rib, breast bone, vertebral body and iliac bone crest, performed in 10 healthy dogs makes it possible to state, that there are possible specific interrelations between megakaryocytes and neutrophilic granulocytes, that terminate in death of the former. Therefore, the phenomenon observed cannot be identified with emperipolesis. In this case we, evidently, deal with a morphological demonstration of cell cytotoxicity, when neutrophils, being killers, act as effector-cells, and megakaryocytes - as target-cells. Cell cytotoxicity is a natural phenomenon, that under certain physiological conditions is evidently connected with thrombocytopoiesis.     

Emperipolesis--a peculiar feature of megakaryocytes as evaluated in chronic myeloproliferative diseases by morphometry and ultrastructure

A combined morphometric and ultrastructural study was performed on so called emperipolesis or internal wandering of myeloid cells in the cytoplasm of large mature megakaryocytes. Measurements were made on material from a total of 115 patients comprising a normal control group and 5 groups with subtypes of chronic myeloproliferative diseases, including primary (essential, idiopathic) thrombocythemia (PTH). A significant increase in this peculiar phenomenon was noted in myeloproliferative disorders and especially in PTH where the frequency of emperipolesis showed a positive correlation with the number of anuclear cytoplasmic fragments sectioned, with the circular deviation of the shapes of megakaryocytes and with the extent to which the peripheral thrombocyte count was elevated. Electron microscopy in selected cases displayed the integrity of the plasma membranes of engulfed hematopoietic cells within the dilated cavities of the megakaryocytic demarcation membrane system (DMS) and no evidence of phagocytosis. Moreover there was a close relationship between engulfed myeloid cells and the presumptive sites of platelet shedding which had their openings from the cisternal lumina of the DMS. Our results demonstrate that emperipolesis of hematopoietic cells within megakaryocytes should not be regarded as a special nosological feature, but as an indication of enforced thrombocytogenetic activity which is expressed particularly in PTH.     

Emperipolesis of hematopoietic cells in myelocytic leukemia. Electron microscopic and phase contrast microscopic studies

In case of blast crisis of chronic myelocytic leukemia, the blast cells contained several kinds of normal hematopoietic cells. The peroxidase reaction was strongly positive in the neutrophilic granules of the engulfed neutrophils. These engulfed cells appeared to be normal and the limiting membranes of the engulfing cells seemed to be intact. We speculated therefore that this phenomenon might be emperipolesis. In a case of chronic myelocytic leukemia and a case of acute myelocytic leukemia, some megakaryoblasts showed the same phenomenon. These megakaryoblasts did not phagocytize latex particles. The limiting membranes of the engulfing megakaryoblasts were stained with ruthenium red but those of the engulfed hematopoietic cells were not stained. By phase microscopy, the engulfed cells were actively moving inside the megakaryoblasts and it was observed that the engulfed cells were actually living within the engulfing cells. These results demonstrated that this phenomenon was emperipolesis. Observations with an electron microscope and the phase microscope are indispensable for distinguishing emperipolesis from phagocytosis.     

Thrombin-stimulated effects on megakaryocytopoiesis and pulmonary-platelet interactions

The effects of thrombin stimulation on megakaryocytopoiesis and pulmonary-platelet interactions were investigated before and after administration of the compound to 15 mongrel dogs. Each dog served as its own control. Thrombin was given to encourage the traffic of megakaryocytes into the lung and to study the thrombin-stimulated effects on megakaryocytopoiesis in the bone marrow. Our results showed that thrombin increased the numbers of bone marrow cells in general and megakaryocytes (MK) in particular. In addition, the maturation cycle of megakaryocytes was accelerated and the number of MK migrating into the central venous circulation was nearly doubled. Most of the circulating MK ultimately became sequestered in pulmonary capillaries, where platelets were shed into the arterial circulation. We conclude that thrombin has a major stimulatory effect on megakaryocytopoiesis in the bone marrow and that the lung plays an important role as a vascular filter and regulator of circulating platelet count.     

Localization of megakaryocytes in the bone marrow

In the bone marrow, megakaryocytes are located in the extravascular space, applied to the abluminal surface of endothelium. In this position, they send cytoplasmic projections into the lumen. Some of these projections are organelle free and may serve to anchor the cell to the endothelium. They could also serve to monitor the circulation and to receive information as to the requirement of the body for platelet formation. Megakaryocytes also send organelle containing projections into the lumen. This may be an early step in the migration of these cells into the lumen or, alternatively, part of the proplatelet formation. These proplatelets are 2.5 x 120 microns elongated structures that penetrate the lumen and can each subsequently make 1000 platelets. Each megakaryocyte can make six to eight proplatelets. In the perisinal position, megakaryocytes may subserve an adventitial function as well; many blood cells can then take a transmegakaryocytic route to reach the endothelium and enter the circulation.     

Phospholipid composition of rat megakaryocytes and its rearrangement in platelets

Rat platelets and their megakaryocyte precursors were examined for phospholipid composition. (1) The phospholipid composition of rat megakaryocytes, which were enriched and prepared from bone marrow cells, was almost identical to that of platelets. (2) The subclass composition of choline-containing glycerophospholipids (CGP) of rat megakaryocytes differed significantly from that of platelets: 1-alkenyl-2-acyl glycerophosphocholine (GPC) in megakaryocytes accounted for 29% of the total, whereas that in platelets was only 7%. (3) Rat platelets contained a larger amount of arachidonic acid than megakaryocytes, especially in ethanolamine-containing glycerophospholipids (EGP). (4) [32P]Phosphoric acid was significantly incorporated into megakaryocytes, whereas platelets showed little incorporation. On the other hand, the uptake of [3H]arachidonic acid into platelet phospholipids was about 15-times higher than that observed with megakaryocytes. (5) As reported previously for other blood cells, such as neutrophils and macrophages, the radioactivity of labeled arachidonic acid incorporated into CGP of platelets decreased, whereas that incorporated into EGP increased during a subsequent chase period. Hardly any such change was observed with megakaryocytes. These results suggest that the phospholipid composition of rat platelets is mainly determined at the time of thrombopoiesis, whereas the composition of molecular species is remodeled during circulation after thrombopoiesis.     

Platelet Changes in Acute Leukemia

Acute leukemia is a hematopoietic stem cell malignant disease, with abnormal proliferation of leukemic and immature cells that suppress the production of normal blood cells and extensively invade peripheral tissues. The bleeding complications are very common in acute leukemia and often lead to death. One major cause for hemorrhage is thrombocytopenia, which is caused by the replacement of normal bone marrow cells with leukemic cells and the inhibition of megakaryocytes functions. Declines in platelet count as well as in function in acute leukemia have been reported in many studies. Here, we reviewed the literatures concerning platelet changes in acute leukemia.     

Lycramine brilliant blue JL: a new stain for human megakaryocytes

Using the acrylic textile dye Lycramine brilliant blue JL, mature and immature megakaryocytes from human bone marrow specimens stained metachromatically bright lavender. This coloration was not observed in other types of bone marrow cells. After digestion with either diastase or ribonuclease, subsequent staining of marrow specimens did not reveal a significant diminution of the intensity of staining of megakaryocytes. However, after incubation with hyaluronidase followed by staining with Lycramine brilliant blue JL, staining of megakaryocyte cytoplasm was either imperceptible or very pale blue. Accordingly, at least one of the substances responsible for the staining reaction is acid mucopolysaccharide in the cytoplasm of megakaryocytes. With further experience and comparison with established immunologic and cytochemical techniques, staining of megakaryocytes with Lycramine brilliant blue JL may be a useful addition to the cytochemistry of blood and bone marrow cells.     

Lycramine Brilliant Blue Jl: A New Stain for Human Megakaryocytes

Using the acrylic textile dye Lycramine brilliant blue JL, mature and immature megakaryocytes from human bone marrow specimens stained metachromatically bright lavender. This coloration was not observed in other types of bone marrow cells. After digestion with either diastase or ribonuclease, subsequent staining of marrow specimens did not reveal a significant diminution of the intensity of staining of megakaryocytes. However, after incubation with hyaluronidase followed by staining with Lycramine brilliant blue JL, staining of megakaryocyte ctyoplasm was either imperceptible or very pale blue. Accordingly, at least one of the substances responsible for the staining reaction is acid mucopolysaccharide in the cytoplasm of megakaryocytes. With further experience and comparison with established immunologic and cytochemical techniques, staining of megakaryocytes with Lycramine brilliant blue JL may be a useful addition to the cytochemistry of blood and bone marrow cells.     

Ultrastructure and peroxidase cytochemistry of normal human leukocytes at birth

At birth, differential and white blood cell counts of normal newborn infants are strikingly different from those of adults in that the number of leukocytes is increased and immature cells course through the circulation. In this study, our intent was to examine normal neonatal cord blood by electron microscopy and peroxidase cytochemistry to determine whether any detectable differences exist in the leukocytes of neonatal and adult blood. This investigation was undertaken because newborn infants have an increased susceptibility to infection, and alterations in phagocyte function have been implicated as the cause. Cord blood was found to contain mature leukocytes of all kinds, similar in ultrastructure and peroxidase localization to those of adults. Moreover, as indicated earlier by light microscopy, immature forms (normally found only in adult bone marrow) were present in the blood of newborns. We found that nearly all cell lines were represented in the neonatal circulation by such developmental forms as promyelocytes, myelocytes, promonocytes, erythroblasts, megakaryocytes, rare unidentifiable blasts, and dividing cells—all resembling their counterparts in adult bone marrow. With the techniques used here, neonatal leukocytes were similar to those of the adult in ultrastructure and peroxidase localization, although some had been mobilized into the blood in a remarkably immature state. This study, the first of its kind, will serve as a helpful background for future investigations of acquired, genetic or neoplastic leukocyte abnormalities which may be discovered at birth.     

Eosinophils and Megakaryocytes Support the Early Growth of Murine MOPC315 Myeloma Cells in Their Bone Marrow Niches

Multiple myeloma is a bone marrow plasma cell tumor which is supported by the external growth factors APRIL and IL-6, among others. Recently, we identified eosinophils and megakaryocytes to be functional components of the micro-environmental niches of benign bone marrow plasma cells and to be important local sources of these cytokines. Here, we investigated whether eosinophils and megakaryocytes also support the growth of tumor plasma cells in the MOPC315.BM model for multiple myeloma. As it was shown for benign plasma cells and multiple myeloma cells, IL-6 and APRIL also supported MOPC315.BM cell growth in vitro, IL-5 had no effect. Depletion of eosinophils in vivo by IL-5 blockade led to a reduction of the early myeloma load. Consistent with this, myeloma growth in early stages was retarded in eosinophil-deficient ΔdblGATA-1 mice. Late myeloma stages were unaffected, possibly due to megakaryocytes compensating for the loss of eosinophils, since megakaryocytes were found to be in contact with myeloma cells in vivo and supported myeloma growth in vitro. We conclude that eosinophils and megakaryocytes in the niches for benign bone marrow plasma cells support the growth of malignant plasma cells. Further investigations are required to test whether perturbation of these niches represents a potential strategy for the treatment of multiple myeloma.     

Biological characteristics of megakaryocytes: specific lineage commitment and associated disorders

Megakayocytes (Megakaryocytes) are among the rarest type of haematopoietic cells and highly specialized precursors for platelets. Normal mature megakaryocytes are, perhaps, the largest cells in the marrow. In contrast, their annucleated platelets progeny are the smallest subcellular fragments in the circulation, which in spite of their size, play crucial roles in thrombostasis and haemostasis. Megakaryopoiesis involves complicated and multi-step biological processes. Research over the last decade has resulted in certain important new discoveries, such as the specific megakaryocyte-forming haematopoietic stem cell (HSC) subpopulation, thrombopoietin (Tpo), formation and release of platelets, etc. Substantial understanding of the specific lineage commitment, differentiation, and the molecular regulatory mechanisms of megakaryopoiesis has also been achieved. Despite existing controversies and questions, megakaryopoiesis remains an exciting field in biomedical research. Certain recent biological findings as well as future research in megakaryopoiesis are summarised in this article. Certain pathological changes associated with megakaryocytes, such as immune thrombocytopenia purpura (ITP), acute megakayoblastic leukaemia, etc., are also discussed in this article.     

Subpopulations of mouse blood monocytes differ in maturation stage and inflammatory response

Blood monocytes are well-characterized precursors for macrophages and dendritic cells. Subsets of human monocytes with differential representation in various disease states are well known. In contrast, mouse monocyte subsets have been characterized minimally. In this study we identify three subpopulations of mouse monocytes that can be distinguished by differential expression of Ly-6C, CD43, CD11c, MBR, and CD62L. The subsets share the characteristics of extensive phagocytosis, similar expression of M-CSF receptor (CD115), and development into macrophages upon M-CSF stimulation. By eliminating blood monocytes with dichloromethylene-bisphosphonate-loaded liposomes and monitoring their repopulation, we showed a developmental relationship between the subsets. Monocytes were maximally depleted 18 h after liposome application and subsequently reappeared in the circulation. These cells were exclusively of the Ly-6C(high) subset, resembling bone marrow monocytes. Serial flow cytometric analyses of newly released Ly-6C(high) monocytes showed that Ly-6C expression on these cells was down-regulated while in circulation. Under inflammatory conditions elicited either by acute infection with Listeria monocytogenes or chronic infection with Leishmania major, there was a significant increase in immature Ly-6C(high) monocytes, resembling the inflammatory left shift of granulocytes. In addition, acute peritoneal inflammation recruited preferentially Ly-6C(med-high) monocytes. Taken together, these data identify distinct subpopulations of mouse blood monocytes that differ in maturation stage and capacity to become recruited to inflammatory sites.     

Changes in the composition of canine respiratory cells obtained by bronchial lavage following irradiation or drug immunosuppression.

Canine respiratory cells, obtained by bronchial lavage, and blood leukocytes were monitored to observe cellular changes following acute and chronic immunosuppression. Irradiation (350 R) produced bone marrow suppression and prompt peripheral blood leukopenia, but did not affect recovery of pulmonary alveolar macrophages or lymphocytes for 12 days after. Treatment for 6 weeks with daily methylprednisolone (1 mg/kg) caused a progressive decrease in the number of recoverable respiratory lymphocytes, whereas alternate day methylprednisolone (2 mg/kg) had less effect. Cyclophosphamide in combination with steroids generally augmented the progressive loss of blood and respiratiory lymphocytes. Recovery of alveolar macrophages was not changed appreciably. Thus, the population of lung macrophages, sampled by pulmonary lavage, withstood acute and chronic forms of immunosuppression very well. In contrast, canine lymphocytes seem more susceptible to injury, especially to drug regimens containing steroids.     

A mathematical model of thrombopoiesis in rats

A mathematical model of thrombopoiesis in rats is presented. This has four compartments; stem cells, megakaryocytes, thrombocytes and thrombopoietin. A high thrombopoietin concentration influences bone marrow proliferation in three ways. Firstly the stem cells are stimulated and a slow increase in megakaryocyte number follows. Secondly there are additional endomitoses in the (early) megakaryocytes resulting in an increase in megakaryocyte volume. Thirdly the megakaryocyte maturation time is shortened. The parameters of the model are determined from experimental values for the normal, maximum and minimum proliferation rates, maturation times and destruction rates. The model is tested by comparing simulated results for acute and chronic thrombocytopenia and thrombocytosis with experimental curves from the literature. The model and data agree within the limits of experimental error. Not all of the thrombopoietic regulatory system is known yet, so some important alternative hypotheses are investigated and compared with the model. Several hypotheses have been excluded in this way.     

Long-term preservation of canine bone marrow: in vitro studies.

In vitro studies were performed on canine bone marrow frozen with DMSO and stored in liquid nitrogen for 2 to 6 months. The results are compared with previously reported parallel in vivo experiments that demonstrated no loss of stem cells. When studies were performed immediately after thawing, there was no substantial drop in the count of nucleated cells and, except for megakaryocytes, there was no alteration of the bone marrow morphology. After two washes, and removal of DMSO, the nucleated cell count dropped to 50% of its previous value. Optic and electron microscopy showed severe damage in mature myeloid elements. In some instances, the cells had a condensed nucleus similar to the red-purple inclusion body of LE cells (as observed in systemic lupus erythematosus), and electron microscopy showed heavy chromatin clumping. On the other hand, both optic and electron microscopy showed a good preservation of lymphocytes, plasmocytes, and erythroid precursors. Two-hour DNA synthesis slightly dropped after storage, and this drop appeared more consistent when related to a constant volume of bone marrow (50 microliters) rather than to a constant number of nucleated cells (10(6)). In five instances frozen and thawed bone marrow was grown in short-term cultures, and analysis of 98 metaphases showed no major aberrations of the chromosomes and only 2% of minor aberrations, such as breakages and fragments. These data, compared with the results of previous in vivo experiments that showed no loss of stem cells after 5 months storage, suggest that stem cells are less sensitive to freezing and thawing injury than myeloid elements and/or that it might be safer for the thawed bone marrow not to be manipulated before infusion.     

The effect of food and water deprivation on the peripheral blood parameters of the mouse

Various peripheral blood and bone marrow parameters were determined during food and water deprivation and during food deprivation alone in order to obtain base lines that may be used to make comparisons with similar data from irradiated mice. The peripheral blood parameters following food and water deprivation were similar to those following food deprivation alone. The mean survival time was about 5 days and the weight loss 40% of the control weight. There was an absolute decrease in the total circulating lymphocyte and platelet counts, while the total granulocyte count remained unchanged or increased. The blood volume decreased, while the hematocrit and specific gravity of the blood increased. The bone marrow parameters following food and water deprivation showed that erythropoiesis was more markedly depressed than myelopoiesis. The tritiated thymidine labeling index for granulopoietic cells and megakaryocytes decreased progressively during starvation. The variations in the white blood count and the bone marrow parameters are not comparable with those found in irradiated mice having the G.I. syndrome; the changes in mean survival time, weight loss, hematocrit, and blood volume are similar.     

Dualism of mixed chimerism between hematopoiesis and stroma in chronic idiopathic myelofibrosis after allogeneic stem cell transplantation

Scant knowledge exists concerning lineage-restricted mixed chimerism (mCh) after allogeneic peripheral blood stem cell transplantation (PSCT) in patients with chronic idiopathic myelofibrosis (CIMF). Following a sex-mismatched PSCT, a combined immunopheno- and genotyping by fluorescence in-situ hybridization (FISH) was performed on sequential bone marrow (BM) biopsies at standardized intervals. Results were compared with PCR analysis of corresponding peripheral blood samples in five patients. According to FISH, pretransplant specimens revealed a gender congruence of more than 99%, while in the first three months the total BM exhibited a persistent fraction of host cells (30% to 40%) with a tendency to decline after about one year. It is noteworthy that the majority of endothelial cells maintained a recipient origin, whereas CD34+ progenitors and especially CD61+ megakaryocytes exhibited only very few host-derived cells. In keeping with the prevalence of donor cells in the hematopoietic compartment, PCR analysis of peripheral blood cells displayed a non-significant degree of mCh. In conclusion, according to FISH and PCR analysis, successful PSCT in CIMF results in an almost complete chimeric (donor-derived) state of the hematopoietic cell population. The non-transplantable stromal compartment includes the vascular endothelium with a predominance of recipient cells. The minimal mCh of this population implies probably a donor-derived origin (endothelial progenitor cells).     

A MATHEMATICAL MODEL OF THROMBOPOIESIS IN RATS

A mathematical model of thrombopoiesis in rats is presented. This has four compartments; stem cells, megakaryocytes, thrombocytes and thrombopoietin. A high thrombopoietin concentration influences bone marrow proliferation in three ways. Firstly the stem cells are stimulated and a slow increase in megakaryocyte number follows. Secondly there are additional endomitoses in the (early) megakaryocytes resulting in an increase in megakaryocyte volume. Thirdly the megakaryocyte maturation time is shortened. The parameters of the model are determined from experimental values for the normal, maximum and minimum proliferation rates, maturation times and destruction rates. The model is tested by comparing simulated results for acute and chronic thrombocytopenia and thrombocytosis with experimental curves from the literature. The model and data agree within the limits of experimental error. Not all of the thrombopoietic regulatory system is known yet, so some important alternative hypotheses are investigated and compared with the model. Several hypotheses have been excluded in this way.