Megakaryocytic differentiation of human progenitor cells is negatively influenced by direct contact with stroma

The recently defined ligand for the Mpl receptor, thrombopoietin (TPO), has been found to be the principal regulatory cytokine of megakaryocytopoiesis. Furthermore, it has been hypothesized that direct interaction between stroma or stroma-derived extracellular matrix (ECM) and human progenitor cells (HPC) may modulate megakaryocytopoiesis. For that purpose, we studied megakaryocytic development of HPC, obtained from patients with hematological malignancies in complete remission or solid tumors without bone marrow involvement, under the influence of megakaryocyte growth and development factor (MGDF, a pegylated, truncated molecule related to the endogenous Mpl ligand). The megakaryocytic development of HPC cultured in contact with a stromal layer (contact cultures) was compared with cultures in which HPC were grown separated from a stromal layer by a microporous membrane (non-contact cultures). A significantly lower number of megakaryocytes (CD41- and CD61-positive cells) was obtained from contact cultures compared to non-contact cultures. Furthermore, the expression of CD42b was higher in non-contact cultures, as compared to contact cultures, indicating an increase in megakaryocyte maturation in non-contact cultures. In contrast, no difference in clonogenic capacity was observed (CFU-GM, BFU-E, CFU-Mk). The possibility that direct contact between HPC and stroma induces the production of a soluble inhibitory cytokine as an explanation for the diminished megakaryocytic development in contact cultures, was excluded by performing transwell experiments in which HPC were cultured in direct contact and in a transwell simultaneously. The percentage of megakaryocytes raised from HPC present in the transwell did not decrease, irrespective of the presence of HPC simultaneous below the transwell in direct contact with stroma. It is concluded that both megakaryocytic development out of HPC and megakaryocytic differentiation is reduced in contact cultures, as compared to non-contact cultures. This is due to modulation by adhesive interactions with stroma, stroma-derived ECM or cytokines bound to the membrane of stromal cells, rather than resulting from the production of diffusible cytokines by stromal cells.

G-CSF (filgrastim)-stimulated whole blood kept unprocessed at 4 degrees C does support a BEAM-like regimen in bad-risk lymphoma

The purpose of this study was to demonstrate the reconstitutive potential of granulocyte colony-stimulating factor (G-CSF) (filgrastim; Neupogen-primed unprocessed whole blood after myelotoxic therapy in bad-risk lymphoma. Nine patients with resistant lymphoma were treated with BAM: a BEAM regimen modified to a 72 h course consisting of BCNU 300 mg/m2 i.v. (day 1), Ara-C 3000 mg/m2 i.v. q 12 h (day 2) and melphalan 140 mg/m2 i.v. (day 3). After 5 days stimulation with G-CSF (10 micrograms/kg) 1l of blood was drawn, kept unprocessed for 3 days and reinfused 24 h after completion of chemotherapy. Back-up peripheral stem cells were available for all patients. The neutrophil count reached 0.5 x 10(9)/l at a median of 16 days (range 11-25) and a platelet count of 10 x 10(9)/l was reached at a median of 20 days (range 11-NR (not reached)). The median length of hospital stay was short in these patients with a median of 19 days (range 17-33). In three patients platelet transfusion independence did not occur before day 28. Those patients received their back-up stem cells. Antibiotics had to be used in two patients. The median number of reinfused CD34+ cells was 0.28 x 10(6)/kg (range 0.01-0.59). When more than 0.2 x 10(6)/kg CD34+ cells were reinfused the time to recovery was comparable to that observed after 'classical PBSCT'. In conclusion, the use of G-CSF-stimulated unprocessed whole blood is easy to perform and a cheap technique to mobilize and collect stem cells that can serve as a stem cell source after severe myelotoxic therapy in bad-risk malignant lymphoma.

[Hepatosplenic candidiasis in patients treated for hemato-oncological disorders]

Hepatosplenic candidiasis is increasingly observed in patients with a haematological malignancy who have received chemotherapy. A case history is described of a male aged 45 who developed symptoms of hepatosplenic candidiasis caused by Candida tropicalis after treatment for acute myeloid leukaemia. The disease is characterized by persistent fever after recovery of the leukopenia induced by the chemotherapy. Echographic and computer-tomographic examination may reveal abscess patterns specific of Candida in the liver. Treatment consists of amphotericin B intravenously or fluconazole orally. Protracted treatment is frequently required.

Giant-cell arteritis with normal erythrocyte sedimentation rate: case report and review of the literature

A high Erythrocyte Sedimentation Rate (ESR) is often seen as a sine qua non for the diagnosis of giant-cell arteritis. The percentages of histopathologically proven giant-cell arteritis associated with a normal ESR, however, are variously reported as 5 to 30%. We describe a patient with histopathologically proven giant-cell arteritis and a normal ESR. A review of literature identified 34 cases of giant-cell arteritis who showed a normal ESR. Their clinical symptoms and signs are compared with the characteristics of patients with giant cell arteritis and an elevated ESR. No distinctive clinical features were found. A normal ESR cannot be used to exclude the diagnosis of giant-cell arteritis.