Kouichi Takeuchi

An Increase in Circulating Mast Cell Colony-Forming Cells in Asthma

We compared a potential to generate mast cells among various sources of CD34+ peripheral blood (PB) cells in the presence of stem cell factor (SCF) with or without thrombopoietin (TPO), using a serum-deprived liquid culture system. From the time course of relative numbers of tryptase-positive and chymase-positive cells in the cultured cells grown by CD34+ PB cells of nonasthmatic healthy individuals treated with G-CSF, TPO appears to potentiate the SCF-dependent growth of mast cells without influencing the differentiation into mast cell lineage. CD34+ PB cells from asthmatic patients in a stable condition generated significantly more mast cells under stimulation with SCF alone or SCF+TPO at 6 wk of culture than did steady-state CD34+ PB cells of normal controls. Single-cell culture studies showed a substantial difference in the number of SCF-responsive or SCF+TPO-responsive mast cell progenitors in CD34+ PB cells between the two groups. In the presence of TPO, CD34+ PB cells from asthmatic children could respond to a suboptimal concentration of SCF to a greater extent, compared with the values obtained by those of normal controls. Six-week cultured mast cells of asthmatic subjects had maturation properties (intracellular histamine content and tryptase/chymase enzymatic activities) similar to those derived from mobilized CD34+ PB cells of nonasthmatic subjects. An increase in a potential of circulating hemopoietic progenitors to differentiate into mast cell lineage may contribute to the recruitment of mast cells toward sites of asthmatic mucosal inflammation.

STI571 inhibits growth and adhesion of human mast cells in culture

Stem cell factor (SCF)/c‐kit system is critical for human mast cell development. We thus examined the effects of STI571, an inhibitor of the c‐kit tyrosine kinase receptor, on the proliferation and function of human mast cells. STI571 at concentrations of 10−6 M or higher almost completely abolished the SCF‐dependent progeny generation from cord blood‐derived cultured mast cells through an inhibition of the tyrosine phosphorylation of c‐kit. The compound also suppressed the early phase of mast cell development. The extinction of mast cell growth induced by STI571 may be due largely to apoptosis according to the flow cytometric analysis and gel electrophoresis. Two‐hour exposure to STI571 that failed to influence the total viable cell number suppressed adhesion of the cells to fibronectin in the presence of SCF without altering the expressions of integrin molecules. Our results may provide a fundamental insight for the clinical application of STI571 in allergic disorders.

Establishment of a GM‐CSF‐dependent megakaryoblastic cell line with the potential to differentiate into an eosinophilic lineage in response to retinoic acids

We recently established a human granulocyte‐macrophage colony‐stimulating factor (GM‐CSF)‐dependent cell line (HML) from colony‐constituent cells grown by peripheral blood cells of a patient with acute megakaryoblastic leukaemia. The HML cells possessed megakaryocytic features, as determined by cytochemical, electron microscopic and flow cytometric analysis. In the present study we examined the effects of retinoic acid (RA) on the development of HML cells. All‐trans‐RA, 13‐cis‐RA and 9‐cis‐RA at 10−8 mol/l to 10−5 mol/l inhibited the GM‐CSF‐dependent cell growth. Some of the RA‐treated cells contained prominent azurophilic granules and were positive for peroxidase. They also reacted with Biebrich scarlet, Luxol fast blue and a monoclonal antibody against eosinophil peroxidase. In addition, exposure to RA increased the frequency and the intensity of major basic protein‐positive cells. However, eosinophil‐derived neurotoxin and eosinophil cationic protein were not detected or were only detected at a low level in the lysates of the HML cells treated with RA. Although IL‐5 alone could not stimulate cell growth, the addition of IL‐5 to the cultures containing stem cell factor + all‐trans‐RA was required for the expression of the eosinophilic phenotype. These results suggest that the HML cell line is a megakaryoblastic cell line with the potential to differentiate into the eosinophilic lineage. HML cells may be a useful model for elucidating the eosinophilic differentiation programme.

Megakaryocytes derived from CD34‐positive cord blood cells produce interleukin‐8

In a serum‐free liquid culture, thrombopoietin (TPO) selectively stimulated the growth of megakaryocytic cells from CD34‐positive cord blood cells. Using these cultured cells, we investigated cytokine production by human megakaryocytes. Day 10 megakaryocytes (2 × 105) secreted > 1000 pg/ml of interleukin (IL)‐8, in contrast to small amounts of IL‐1β and IL‐6. A time‐course study showed that the IL‐8 production of megakaryocytes occurred at the late phase of the culture period. The megakaryocyte‐conditioned medium had the chemotactic potential of polymorphonuclear leucocytes, which was abrogated by the addition of anti‐IL‐8 antibody, suggesting the secretion of biologically active IL‐8. The combination of TPO and IL‐1α was required for a significant augmentation of the IL‐8 secretion. Direct evidence for IL‐8 synthesis in megakaryocytes was provided by reverse transcription–polymerase chain reaction on purified CD41b+ cells and by the detection of intracellular IL‐8 in CD41b+ cells. These results suggest that TPO stimulates not only the proliferation and differentiation of the progenitors capable of megakaryocytic lineage expression but also IL‐8 release by the megakaryocytic cells with the aid of IL‐1.

Apoptosis of Erythroid Precursors under Stimulation with Thrombopoietin: Contribution to Megakaryocytic Lineage Choice

Although the effect of thrombopoietin (TPO) on megakaryocyte production is well established, its role in the commitment of multipotential hematopoietic progenitors to the megakaryocytic lineage remains to be determined. In the present study, we attempted to clarify the determination process of megakaryocytic lineage as a terminal differentiation pathway under stimulation with TPO. Day 7 cultured cells grown by TPO derived from cord blood CD34+ cells were divided into four subpopulations on the basis of CD34 and CD41 expression. The CD34−/CD41− cells showed the labeling pattern of anti‐CD42b and anti‐CD9 antibodies closer to that of the CD34+/CD41− cells than the CD34+/CD41+ cells. Replating experiments revealed that approximately 40% of the CD34−/CD41− cells proliferated in response to a combination of growth factors, and more than 80% of them were pure erythroid precursors. However, this subpopulation failed to grow/survive and fell into apoptosis in the presence of TPO alone. In contrast, the CD34+/CD41+ cells, which predominantly contained megakaryocytic precursors, exerted a low but significant proliferative potential in the presence of TPO. The insufficient response to TPO of the CD34−/CD41− cells may result from the apparently low expression of c‐Mpl, as determined by flow cytometric analysis and reverse transcription‐polymerase chain reaction analysis. Therefore, these results suggest that the apoptosis of hematopoietic precursors other than megakaryocytic precursors is related to the determination of the terminal differentiation under the influence of TPO.

Effect of the mutant microphthalmia-associated transcription factor found in Tietz syndrome on the in vitro development of mast cells.

Mutations in microphthalmia-associated transcription factor (MITF) lead to Waardenburg syndrome type 2 (WS2), a dominantly inherited disorder involving hearing loss and pigment disturbances caused by a lack of melanocytes. On rare occasions, mutations in MITF lead to Tietz syndrome (TS), which is characterized by a severe WS2 phenotype. The MITF gene is the human homolog of the mouse microphthalmia (mi) gene in some families. Mi/mi mice show decreased numbers and an abnormal phenotype of mast cells (MC). In contrast, the number and phenotype of MC in WS2/TS patients who also have an alteration in their MITF gene are unclear. In this study, we identified a mutation in the MITF gene, delR217, which was equivalent to that found in mi/mi mice, in a case of TS. None of the MITF isoforms with the mutation were able to transactivate the tyrosinase gene promoter. In addition, mutant MITF-M showed dominant negative activity toward wild-type MITF-M, inhibiting its transactivation of the tyrosinase gene promoter. The patients peripheral blood CD34+ cells showed no differences with respect to total cell number or their expression levels of tryptase mRNA in a serum-deprived liquid culture system for 6 weeks when compared with normal control cells. These findings suggest that MITF does not play a critical role in MC development in humans.

Transient Deformation of Neutrophils in Kawasaki Disease.

In the treatment of Kawasaki disease, resistance to high-dose immunoglobulin intravenous (IGIV) can occur. The neutrophil morphology analyses in 17 patients revealed that transient pseudo-Pelger-Huët anomaly was more frequently detected in the IGIV-resistant group. This finding may aid the prediction of IGIV resistance.

Transfusion-related acute lung injury in an infant

Ryu Yanagisawa, Kouichi Takeuchi, Takashi Kurata, Kazuo Sakashita, Shigetaka Shimodaira and Eizaburo Ishii Departments of Hematology/Oncology and General Pediatrics, Nagano Children’s Hospital, Azumino and Department of Pediatrics, Shinshu University School of Medicine, and Division of Blood Transfusion and Center for Advanced Cell Therapy, Shinshu University Hospital, Matsumoto and Department of Pediatrics, Nagano Prefectural Suzaka Hospital, Suzaka, Nagano, Japan

Hypoglycemia During the Temporary Interruption of Parenteral Nutrition Infusion in Pediatric Hematopoietic Stem Cell Transplantation.

Background: Parenteral nutrition (PN) is required with pediatric procedures such as hematopoietic stem cell transplantation (HSCT). However, risks associated with temporary PN infusion interruption remain unclear. Materials and Methods: We retrospectively analyzed in 22 children undergoing HSCT receiving PN with the same daily routine: temporary PN infusion interruption before breakfast for administering a saline-diluted acyclovir drip. After correcting patients’ glucose levels, we examined minimum blood glucose levels between preparative regimen initiation and post-HSCT day 30. Patients were divided into 2 groups according to a minimum glucose cutoff of 60 mg/dL. Patient background characteristics and hypoglycemia risk factors were compared between both groups. Results: The hypoglycemia group had a significantly lower body surface area, higher glucose infusion rate (GIR), lower cholinesterase levels, and higher zinc levels at the onset of the minimum blood glucose level (P < .05). Multivariate analyses revealed an association only between higher GIR (≥5 mg/kg/min) and hypoglycemia during the temporary PN infusion interruption. A time course analysis of blood glucose and immunoreactive insulin (IRI) levels in 1 patient revealed a combined high-caloric and saline flush before acyclovir initiation, causing temporary increased IRI, as the etiology for hypoglycemia. Conclusions: Particular attention and several precautions are required to prevent complications associated with temporary PN infusion interruption in children with higher GIR.

Effectiveness of subarachnoid drug infusion for pediatric tumor-related pain

Although the effectiveness of subarachnoid continuous drug infusion has been established in cancer pain management, its clinical use in children is rare. A 14‐year‐old girl with neurofibromatosis type I complained of right leg pain stemming from a growing tumor on her right buttock. Continuous and breakthrough right leg pain were unbearable, even at high doses of systemic opioids that caused severe constipation and deep sedation. Subsequent continuous infusion of bupivacaine and morphine through a subarachnoid catheter effectively relieved the girls pain. The corresponding decrease in systemic opioid also improved her activities of daily living. The patient eventually died of cachexia due to the rapidly growing buttock lesion that was pathologically confirmed post‐mortem as a malignant peripheral nerve sheath tumor. Subarachnoid continuous drug infusion may be very useful in controlling severe pain with few side‐effects, even in the field of pediatric palliative care.