Signaling pathways implicated in hematopoietic progenitor cell proliferation and differentiation.

The objective of this study was to investigate the signal transduction pathways associated with the clonal development of myeloid and erythroid progenitor cells. The contribution of particular signaling molecules of protein tyrosine kinases (PTKs), mitogen-activated protein (MAP) kinase, and PI-3 kinase signaling to the growth of murine bone marrow colony forming unit-granulocyte-macrophage (CFU-GM) and erythroid (burst forming unit-erythroid [BFU-E] and colony forming unit-erythroid [CFU-E]) progenitors was examined in studies performed in the presence or absence of specific signal transduction inhibitors. The results clearly pointed to different signal transducing intermediates that are involved in cell proliferation and differentiation depending on the cell lineage, as well as on the progenitors' maturity. Lineage-specific differences were obtained when chemical inhibitors specific for receptor- or nonreceptor-PTKs, as well as for the main groups of distinctly regulated MAPK cascades, were used because all of these compounds suppressed the growth of erythroid progenitors, with no major effects on myeloid progenitors. At the same time, differential involvement of MEK/extracellular signal-regulated kinase (ERK) MAPK transduction pathway was observed in the proliferation and/or differentiation of early, BFU-E, and late, CFU-E, erythroid progenitor cells. The results also demonstrated that phosphatydylinositol (PI)-3 kinase and nuclear factor kappaB (NF-kappaB) transcriptional factor were required for maintenance of both myeloid and erythroid progenitor cell function. Overall, the data obtained indicated that committed hematopoietic progenitors express a certain level of constitutive signaling activity that participates in the regulation of normal steady-state hematopoiesis and point to the importance of evaluating the impact of signal transduction inhibitors on normal bone marrow when used as potential therapeutic agents.

Controlled-rate versus uncontrolled-rate freezing as predictors for platelet cryopreservation efficacy.

BACKGROUND: Cryobiologic variables responsible for cell injuries and freezing techniques applicable in medical cryopractice should be revised and/or reengineered for minimizing cryoinjuries and maximizing cell recovery. In this study, the efficacy of different cryopreservation protocols based on platelet (PLT) recovery was evaluated. STUDY DESIGN AND METHODS: PLTs (n = 33) were prepared from whole-blood units. Cell count and viability, PLT morphologic score (PMS), and hypotonic shock response were determined. PLT surface antigens were measured by flow cytometry. Controlled-rate (with compensated fusion heat) and uncontrolled-rate freezing methods combined with 6 percent dimethyl sulfoxide were used. RESULTS: PLT recovery was superior in the controlled-rate setting (91.0 +/- 5.5 vs. 86.0 +/- 6.5; p < 0.05). PMS was significantly better in controlled-rate freezing (p < 0.01). GPIb/CD42b expression was reduced in both freezing groups versus control. GP140/CD62p expression was significantly (p < 0.05) lower in the controlled-rate group and in both frozen groups was significantly higher than in the control groups. CONCLUSION: The use of strictly equalized (1 degrees C/min) controlled-rate freezing, combined with an intensified cooling rate (2 degrees C/min) during the liquid-to-solid-phase transition period, allows advanced quantitative and qualitative PLT recovery, even though the minor intergroup differences for some variables were observed.

Hematopoietic changes and altered reactivity to IL-17 in Syphacia obvelata-infected mice.

Pinworm parasites commonly infect laboratory mice with high prevalence even in well-managed animal colonies. Although often considered as irrelevant, these parasites if undetected may significantly interfere with the experimental settings and alter the interpretation of final results. There are a few reports documenting the effects of pinworms on research and the effects of pinworms on the host hematopoiesis have not yet been investigated. In this study we examined the changes within various hematopoietic cell lineages in the bone marrow, spleen, peripheral blood and peritoneal space during naturally acquired Syphacia obvelata infection in inbred CBA mice. The data obtained showed significant hematopoietic alterations, characterized by increased myelopoiesis and erythropoiesis in S. obvelata-infected animals. In order to additionally evaluate if this pinworm infection modifies hematopoietic cells' reactivity, we examined the effect of murine interleukin-17, T cell-derived cytokine implicated in the regulation of hematopoiesis and inflammation, on the growth of bone marrow progenitor cells and demonstrated that bone marrow myeloid and erythroid progenitors from S. obvelata-infected mice displayed altered sensitivity to IL-17 when compared to non-infected controls. Taken together the alterations presented pointed out that this rodent pinworm is an important environmental agent that might significantly modify the hosts' hematopoietic response, and therefore interfere with the experimental settings and alter the interpretation of the final results. However, the results obtained also contributed new data concerning the activity of IL-17 on bone marrow hematopoietic cells, supporting our previous reports that depending on physiological/pathological status of the organism IL-17 exerts differential effects on the growth of progenitor cells.

Interleukine-17-induced inhibitory effect on late stage murine erythroid bone marrow progenitors.

Recent studies have shown that the T cell-derived cytokine, interleukin-17 (IL-17), stimulates hematopoiesis, specifically granulopoiesis inducing expansion of committed and immature progenitors in bone marrow. Our previous results pointed to its role in erythropoiesis too, demonstrating significant stimulation of BFU-E and suppression of CFU-E growth in the bone marrow from normal mice. As different sensitivities of erythroid and myeloid progenitor cells to nitric oxide (NO) were found, we considered the possibility that the observed effects of IL-17 were mediated by NO. The effects of recombinant mouse IL-17, NO donor (sodium nitroprusside - SNP) and two NO synthases inhibitors (L-NAME and aminoguanidine) on erythroid progenitor cells growth, as well as the ability of IL-17 to induce nitric oxide production in murine bone marrow cells, were examined. In addition, we tested whether the inhibition of CFU-E colony formation by IL-17 could be corrected by erythropoietin (Epo), the principal regulator of erythropoiesis. We demonstrated that IL-17 can stimulate low level production of NO in murine bone marrow cells. Exogenously added NO inhibited CFU-E colony formation, whereas both L-NAME and aminoguanidine reversed the CFU-E suppression by IL-17 in a dose-dependent manner. The inhibition of CFU-E by IL-17 was also corrected by exposure to higher levels of Epo. The data obtained demonstrated that at least some of the IL-17 effects in bone marrow related to the inhibition of CFU-E, were mediated by NO generation. The fact that Epo also overcomes the inhibitory effect of IL-17 on CFU-E suggests the need for further research on their mutual relationship and co-signalling.