Hematopoietic and endothelial progenitor cell trafficking in patients with myeloproliferative diseases.

BACKGROUND AND OBJECTIVES: The presence of circulating hematopoietic progenitor cells in patients with myeloproliferative diseases (MPD) has been described. However, the exact nature of such progenitor cells has not been specified until now. The aim of this work was to investigate the presence of endothelial precursor cells in the blood of patients with MPD and to assess the role of the endothelial cell lineage in the pathophysiology of this disease. DESIGN AND METHODS: Endothelial progenitor cell marker expression (CD34, prominin (CD133), kinase insert domain receptor (KDR) or vascular endothelial growth factor receptor 2 (VEGFR2), and von Willebrand factor) was assessed in the blood of 53 patients with MPD by quantitative polymerase chain reaction. Clonogenic stem cell assays were performed with progenitor cells and monocytes to assess differentiation towards the endothelial cell lineage. The patients' were divided according to whether they had essential thrombocythemia (ET, n=17), polycythemia vera (PV, n=21) or chronic idiopathic myelofibrosis (CIMF, n=15) and their data compared with data from normal controls (n=16) and patients with secondary thrombo- or erythrocytosis (n=17). RESULTS: Trafficking of CD34-positive cells was increased above the physiological level in 4/17 patients with ET, 5/21 patients with PV and 13/15 patients with CIMF. A subset of patients with CIMF co-expressed the markers CD34, prominin (CD133) and KDR, suggesting the presence of endothelial precursors among the circulating progenitor cells. Clonogenic stem cell assays confirmed differentiation towards both the hematopoietic and the endothelial cell lineage in 5/10 patients with CIMF. Furthermore, the molecular markers trisomy 8 and JAK2 V617F were found in the grown endothelial cells of patients positive for trisomy 8 or JAK2 V617F in the peripheral blood, confirming the common clonal origin of both hematopoietic and endothelial cell lineages. INTERPRETATION AND CONCLUSIONS: Endothelial precursor cells are increased in the blood of a subset of patients with CIMF, and peripheral endothelial cells bear the same molecular markers as hematopoietic cells, suggesting a primary role of pathological endothelial cells in this disease.

Progenitor cell trafficking in physiologic conditions and in myeloproliferative diseases: quantification of CD34+ cells by polymerase chain reaction.

BACKGROUND AND OBJECTIVES: Previous studies using flow cytometry have shown that CD34+ cell trafficking is increased in patients with chronic idiopathic myelofibrosis. Few data exist on physiologic CD34 + cell trafficking and the quantification of very low cell ranges requires reliable and sensitive measurement techniques. The aim of this study was to establish a quantitative polymerase chain reaction (PCR) technique for studying CD34+ cell trafficking in physiologic conditions, and in patients with myeloproliferative diseases. DESIGN AND METHODS: CD34+ cell trafficking was measured in 56 controls [(healthy controls (n=21), patients with ischemic cardiopathy (n=21), patients with secondary thrombocytosis or erythrocytosis (n=14)], and in 37 untreated patients with myeloproliferative diseases diagnosed according to the WHO-criteria [(essential thrombocythemia (n=10), polycythemia vera (n=14) and chronic idiopathic myelofibrosis (n=13)]. Quantitative PCR was used to determine CD34 mRNA expression in peripheral blood samples. RESULTS: Physiologic CD34 mRNA expression ranges were determined in the healthy control group. Mean CD34 mRNA expression was within the physiologic range in patients with ischemic cardiopathy, secondary thrombocytosis or erythrocytosis, essential thrombocythemia and polycythemia vera (p=0.146), but was significantly increased in patients with chronic idiopathic myelofibrosis (p<0.001). When analyzed individually, 12/13 patients with chronic idiopathic myelofibrosis and 3/14 patients with polycythemia vera showed CD34 mRNA expression above the physiologic range. INTERPRETATION AND CONCLUSIONS: This is a first report about CD34+ cell trafficking measured by quantitative PCR. Quantitative PCR is a reliable method suitable for the quantification of very low cell populations. Our study confirms the significant increase of CD34+ cell trafficking in patients with chronic idiopathic myelofibrosis, and in a subset of patients with polycythemia vera. Prospective studies are underway to characterize these circulating CD34+ cells and to investigate their role in the pathophysiology of myeloproliferative diseases.

Cloning, characterization and analysis by RNA interference of various genes of the Chelonus inanitus polydnavirus.

Successful parasitism of some endoparasitic wasps depends on an obligately symbiotic association with polydnaviruses. These unique viruses have a segmented genome consisting of circles of double-stranded (ds) DNA and do not replicate in the parasitized host. They are produced in the wasp's ovary and injected into the host along with the egg. Chelonus inanitus is an egg-larval parasitoid; its polydnavirus (CiV) has been shown to protect the parasitoid larva from the host's immune system and to induce developmental arrest in the prepupal stage. The genome of CiV consists of at least 10-12 segments and five have been sequenced up to now. Here, the complete (CiV12g2) or partial (CiV12g1, CiV16.8g1) cloning of three new CiV genes is reported. All three occur only on one viral segment and have no similarity to other known polydnavirus genes, with the exception of a high similarity of CiV12g1 to CiV14g1 and CiV12g2 to CiV14g2. Furthermore, the first attempt of in vivo application of RNA interference to study the function of polydnavirus genes is shown. Injection of dsRNA of two late- and one early- and late-expressed CiV genes into CiV/venom-containing host eggs partially rescued last-instar larvae from developmental arrest. Injection of the same dsRNAs into parasitized eggs partially reduced parasitoid survival, mainly by preventing the successful emergence of the parasitoid from the host. These viral genes thus seem to be involved in inducing developmental arrest and in keeping the cuticle soft, which appears to be necessary for parasitoid emergence and host feeding.

Ovary development and polydnavirus morphogenesis in the parasitic wasp Chelonus inanitus. I. Ovary morphogenesis, amplification of viral DNA and ecdysteroid titres.

Polydnaviruses are unique symbiotic viruses that are replicated in the calyx cells of the ovary of some parasitic wasps. They have a segmented genome of circular double-stranded DNA and are injected along with the wasp's egg into the host, where they are essential for successful parasitism. Polydnaviruses replicate from integrated proviral DNA, and after excision of viral segments, flanking DNA is rejoined. Little is known about ovarian morphogenesis, the mode of amplification of the viral DNA and the involvement of ecdysteroids. Here we have analysed these parameters in the course of pupal-adult development in the braconid wasp Chelonus inanitus. Immediately after pupation, ovarian cells proliferated and calyx cells began to differentiate; at this stage ecdysteroids, in particular 20-hydroxyecdysone, were highest. Thereafter, calyx cells began to increase in size and DNA content and eventually became gigantic. Amplification of non-viral DNA (actin) and viral DNA in its integrated and excised form and of corresponding rejoined flanking regions was measured by quantitative real-time PCR. In the early phase of calyx cell differentiation, copy numbers of actin and integrated viral DNA increased to a similar extent. This, along with the increase in nuclear volume and DNA content in the absence of extensive cell proliferation, suggested polyploidization of the early stage calyx cells. In the following phase, integrated viral DNA was selectively and intensively amplified and eventually excised and circularized. As copy numbers of excised circular viral DNA and rejoined flanking DNA reached similarly high levels, excised viral DNA appeared not to replicate. After adult eclosion, amplification of viral DNA declined.