Protumorogenic Potential of Pancreatic Adenocarcinoma-Derived Extracellular Vesicles.

Cancer development is a highly complicated process in which tumour growth depends on the development of its vascularization system. To support their own growth, tumour cells significantly modify their microenvironment. One of such modifications inflicted by tumours is stimulation of endothelial cell migration and proliferation. There is accumulating evidence that extracellular vesicles (EVs) secreted by tumour cells (tumour-derived EVs, TEVs) may be regarded as "messengers" with the potential for affecting the biological activities of target cells. Interaction of TEVs with different cell types occurs in an auto- and paracrine manner and may lead to changes in the function of the latter, e.g., promoting motility, proliferation, etc. This study analysed the proangiogenic activity of EVs derived from human pancreatic adenocarcinoma cell line (HPC-4, TEVHPC) in vitro and their effect in vivo on Matrigel matrix vascularization in severe combined immunodeficient (SCID) mice. TEVHPC enhanced proliferation of HPC-4 cells and induced their motility. Moreover, TEVHPC stimulated human umbilical vein endothelial cell (HUVEC) proliferation and migration in vitro. Additionally, TEVHPC influenced secretion of proangiogenic factors (IL-8, VEGF) by HUVEC cells and supported Matrigel matrix haemoglobinization in vivo. These data show that TEVs may support tumour propagation in an autocrine manner and may support vascularization of the tumour. The presented data are in line with the theory that tumour cells themselves are able to modulate the microenvironment via TEVs to maximize their growth potential.

Post mortem development of meat quality as related to changes in cytoskeletal proteins of chicken muscles.

1. A procedure was developed to separate high and medium molecular weight myofibrillar proteins from chicken muscular tissue with a high resolution by flat bed sodium-dodecyl-sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and subsequent detection by either a general protein stain or Western blotting. These procedures were used to analyse the degradation process of cytoskeletal proteins in chicken breast and leg muscles during meat ageing. 2. This study demonstrates the degradation of all the examined cytoskeletal proteins: titin, nebulin and desmin as well as vinculin, a protein component of the costamere structure. All the examined proteins were found to be degraded during ageing of chicken breast and leg muscles. 3. Degradation of titin, nebulin and desmin started at 3 h post mortem in breast muscle. Intact titin and nebulin disappeared within 1 d. Intact desmin and vinculin were not detectable after 3 d post mortem. In leg muscle, the degradation process of all the examined proteins evolved much more slowly than in breast chicken muscles. 4. The changes observed in shear force, myofibrillar fragmentation and cooking loss were related to changes in cytoskeletal proteins and used to identify marker proteins or degradation products for the purpose of monitoring the development of meat ageing. The ageing process was faster in breast muscle than in leg muscle. 5. Significant correlations were found between degradation processes of titin, nebulin, and desmin and shear force, as well as myofibril fragmentation index of breast and leg muscles.

Ergosterol as an indicator of the presence of microscopic fungi in eggs for human consumption produced in different husbandry systems.

Ergosterol (ERG) content, being an indicator of fungal biomass, was analyzed in samples of eggshell, egg white, and egg yolk from eggs from farms with intensive management systems of layer hens (i.e., cage and litter housing). Moreover, analogous samples were analyzed from eggs from farms in the western central part of Poland, where layer hens were kept in the organic system. In all samples, the highest ERG concentration was found in shells and the lowest in egg white, whereas ERG was not found in egg yolk. When comparing investigated housing systems, a higher concentration of the analyzed metabolite was detected in eggs from litter housing than in eggs from cage housing. Concentrations of ERG in samples of eggs from organic husbandry were highly varied, ranging from 2.44 to 42.67 mg/kg in shells and from 0.28 to 16.11 mg/kg in egg white.

The presence of B7-H4+ macrophages and CD25+CD4+ and FOXP3+ regulatory T cells in the microenvironment of nasal polyps - a preliminary report.

The nasal polyp (NP) seems to represent the end-stage of longstanding inflammation in patients with chronic rhinosinusitis. The aim of our study has been to evaluate the presence of two regulatory cell populations in the microenvironment of NP: CD4+CD25high Foxp3+ (Treg) cells and B7-H4-expressing macrophages. Treg cells are actively able to inhibit T lymphocytes, while the population of B7-H4-expressing macrophages has recently been described as characterized by a regulatory function similar to that of Treg cells. For our study, we evaluated 14 NP tissue samples. The samples were divided into two main groups, eosinophilic (NP) and lymphocytic (NP), according to the predominant type of immune cell infiltration. The presence of Treg cells and B7-H4 positive macrophages in the samples was analyzed by FACS. Treg cells and B7-H4-expressing macrophages were identified in all the examined nasal polyps. The percentages of both Treg cells and of B7H4 positive cells found in the eosinophilic nasal polyps were higher than those found in the lymphocytic nasal polyps. Treg cells and B7H4+ macrophage subpopulations were present in the NP microenvironment and the alterations in their percentages were related to a distinct pattern of immune cell infiltration.

High anti tumor activity against rhabdomyosarcoma cells and low normal cells cytotoxicity of heat shock protein 90 inhibitors, with special emphasis on 17-[2-(pyrrolidin-1-yl)ethyl]-aminno-17-demethoxygeldanamycin.

Rhabdomyosarcoma is a highly metastatic tumor, mostly observed in children and adolescence. When diagnosed at early stages it is mostly curable. However, in advanced or metastatic stages the 5-years survival rate is below 20%. Thus, new treatment strategies for this tumor are needed. In this paper we showed that HSP90 inhibitors, geldanamycin and its analogs, can profoundly affect proliferation of rhabdomyosarcoma cells. We also showed that blocking of HSP90 function induces apoptosis of tumor cells and downregulates expression of anti apoptotic protein AKT. Cells exposed to geldanamycin and its analogs exhibit strong reduction of MET receptor expression and subsequent inhibition of HGF-dependent tumor cells migration and invasion. Interestingly, at concentrations sufficient to block tumor cells growth and motility, the 17AEP-GA, 17AAG and 17DMAP-GA were not toxic or only slightly toxic toward normal hematopoietic, mesenchymal and endothelial cells. This could be due to low HSP90 expression both at mRNA and protein level in these cells. Collectively, our findings suggest that blocking HSP90 action through geldanmycins could be in the future a part of new therapeutic strategies in rhabdomyosarcoma treatment.

Physical and chemical characteristics and acceptability of home style beef jerky.

Properties of snack foods from comminuted, seasoned beef, dried under laboratory conditions at a temperature of 55±2°C were analyzed in this study. Samples were collected after 3, 4, 5, 6 and 7h of drying. The jerky products were evaluated by selected physicochemical and sensory methods. A significant influence of thermal treatment on the sample colour (L(∗), a(∗), b(∗)-values) was observed. Results of sensory examination of selected attributes of the analyzed product performed by a trained panel confirmed that dried snack products obtained from beef under non-commercial conditions had the most desirable texture attributes, i.e. high chewiness at such a dryness that the moisture-to-protein ratio (MPR) was 0.5. At this value tensile work was the largest (757.77N×mm). Such a product is an attractive offer for those consumers who are willing to accept original, convenience products meeting at the same time their growing requirements concerning high organoleptic and nutritive value.

Remaining problems and controversies in the management of childhood head and neck soft tissue sarcomas: Retrospective (national) Multicenter Study of the Polish Pediatric Solid Tumors Group.

Soft tissue sarcomas in children are a heterogeneous group of malignant diseases. Among these, tumors localized in the head and neck region are especially difficult to treat. While multidisciplinary care has dramatically improved the prognosis of sarcoma patients, their treatment remains uncertain because of demand on radical surgical resection of the tumor. Achieving cure without deforming or mutilating the child remains the primary goal of treatment. This study is the multicenter (nationwide, 11 Polish centers) retrospective analysis of the treatment results in children having soft tissue sarcoma in the head and neck region during the previous decade (from 1991 to 2001). Late effects of the treatment are documented in long-term survivals. Eighty-five children from 1 to 212 months of age were included. Different multimodal treatment protocols were utilized (CWS-91, SIOP-MMT-91, and CWS-96). The median observation time was 25 months. Data on long-term effects were collected in 34 long-term survivals. Complete remission was achieved in 68 (80%) patients. Primary treatment failure occurred in 13 (15.3%) patients, all of whom succumbed in disease progression. Relapse occurred in 21 (30.9%) patients primarily achieving complete remission. Second primary neoplasm occurred in 3 children. The estimated 5-year event-free survival and the 5-year total survival rates for the whole group are 0.38 and 0.55, respectively. The main late effect documented in long-term survivals were cosmetic defects in 12 (35.3%) and visual field deficit or blindness in 8 (26.5%). Despite substantial improvement of the prognosis of pediatric soft tissue sarcomas, the multimodal treatment of head and neck region tumors remains controversial. Improved long-term outcome and focusing on psychosocial difficulties raise the important and difficult problem of functional results and cosmesis. Tumors localized in the orbit carry an excellent prognosis. However, the main late sequela is vision impairment and cosmetic defect due to the therapy given many years earlier. Two other tumor localizations--the parameningeal and nonparameningeal ones--still have bad prognosis. The observations made in this study confirm that main prognostic factors are the size of the primary tumor and the tumor stage. The worst prognosis remains invasive tumor (T2-stage) with a size over 5 cm. Individually adjusted multimodal therapy, which imperatively needs to be radical, though not mutilating, might minimize the late effects. Psychosocial problems in long-term survivors need to be focused on at the national level and better support must be provided in the future, involving a team of different medical and paramedical profiles.

Effect of selected commercial substances with cryoprotective activity on the quality of mechanically recovered, washed and frozen stored poultry meat.

Investigations were conducted on mechanically recovered poultry meat (MRPM) and on protein preparation obtained from MRPM by washing it first with 1% water solution of sodium chloride and with water afterwards. The raw materials were frozen at the temperature of -23 C. The effect of added stabilizers on the quality of gels produced from fresh raw materials, and after freezing and frozen storage was assessed. The following additives were used: 1% pork hydrolizate (Pork Stock), 0.5% Cremodan containing carrageens, and 1.5% bovine blood plasma (AMP 600N). Freezing and frozen storage caused a significant reduction of functional properties of MRPM and its protein preparation. None of the examined additives protected simultaneously all the investigated functional properties of the frozen samples. The amount of thermal drip, the gel texture and the amount of protein transition heat were determined by scanning differential calorimetry. The lowest thermal drip in gels obtained from frozen-stored samples was observed when bovine blood plasma was used as a stabilizer. On the other hand, the most advantageous protective effect on the proteins of the frozen MRPM and on the preparation, determined by mechanical strain resistance of the gels, was found with 1% pork hydrolizate added. The results of thermodynamic investigations of proteins revealed that the best protective effect on the frozen preparation was observed with 1.5% blood plasma added. No protective activity of added Cremodan on proteins of the frozen protein preparation was noted.

New T-lymphocytic cell lines for studying cell infectability by human immunodeficiency virus.

We identified five human T-lymphoid cell lines (PB-1, Sez-4, C19PL, HUT 102B and ATL-2) which highly express CD4 in addition to CXCR4 and CCR5. In order to evaluate if these cells are infectabile by human immunodeficiency virus (HIV) and could be employed as a model in HIV research we exposed these cell lines to X4 (T-cell tropic) and R5 (macrophage tropic) and subsequently tried to correlate their infectability with (i) level of chemokine coreceptor (CXCR4 and CCR5) expression, (ii) coreceptor functionality (calcium flux, chemotaxis and phosphorylation of MAPK p42/44 and AKT) and (iii) endogenous expression and secretion of HIV-related chemokines which compete with the virus for binding to CXCR4 (SDF-1/CXCL12) or CCR5 (MIP-1beta/CCL4, MIP-1alpha/CCL3, RANTES/CCL5, MCP-2/CCL8, MCP-3/CCL7 and MCP-4/CCL13). We demonstrated that while PB-1 cells are infectable by both X4 and R5 HIV, Sez-4, C91PL, HUT 102B and ATL-2 cells were infected by X4 HIV only. Moreover, we noticed that the susceptibility of these cells to HIV did not correspond either with the level of surface expression or with the functionality of CXCR4 or CCR5; however, it was modulated to some degree by the endogenously secreted HIV-related chemokines. Thus all five mature T-cell lines described here may provide useful new models for studying various aspects of HIV infection. In addition we demonstrate that the infectability of cells by HIV is modulated by so far unidentified intrinsic factors as well as some already known endogenously secreted chemokines. The identification of these factors may be important for developing new strategies to protect cells from HIV infection.

Platelet-derived microparticles bind to hematopoietic stem/progenitor cells and enhance their engraftment.

Because human CD34+ and murine Sca-1+ hematopoietic stem-progenitor cells (HSPCs) express platelet-binding sialomucin P-selectin (CD162) and integrin Mac-1 (CD11b-CD18) antigen, it was inferred that these cells might interact with platelets. As a result of this interaction, microparticles derived from platelets (PMPs) may transfer many platelet antigens (CD41, CD61, CD62, CXCR4, PAR-1) to the surfaces of HSPCs. To determine the biologic significance of the presence of PMPs on human CD34+ and murine Sca-1+ cells, their expressions on mobilized peripheral blood (mPB) and on nonmobilized PB- and bone marrow (BM)-derived CD34+ cells were compared. In addition, the effects of PMPs on the proliferation of CD34+ and Sca-1+ cells and on adhesion of HSPCs to endothelium and immobilized SDF-1 were studied. Finally, the hematopoietic reconstitution of lethally irradiated mice receiving transplanted BM mononuclear cells covered or not covered with PMPs was examined. It was found that PMPs are more numerous on mPB than on BM CD34+ cells, do not affect the clonogenicity of human and murine HSPCs, and increase adhesion of these cells to endothelium and immobilized SDF-1. Moreover, murine BM cells covered with PMPs engrafted lethally irradiated mice significantly faster than those not covered, indicating that PMPs play an important role in the homing of HSPCs. This could explain why in a clinical setting human mPB HSPCs (densely covered with PMPs) engraft more rapidly than BM HSPCs (covered with fewer PMPs). These findings indicate a new role for PMPs in stem cell transplantation and may have clinical implications for the optimization of transplantations.

Biological significance of MAPK, AKT and JAK-STAT protein activation by various erythropoietic factors in normal human early erythroid cells.

The aim of this study was to identify signal transduction pathways activated by erythropoietin (EpO) and erythropoietin co-stimulatory factors (kit ligand), insulin-like growth factor, thrombopoietin, interleukin 3 and granulocyte-macrophage colony-stimulating factor) in normal human bone marrow CD34(+) cells and d 11 erythroid burst forming unit derived glycophorin+ cells. The activation of these signal transduction pathways was further correlated with various biological effects such as (i) cell proliferation, (ii) inhibition of apoptosis, (iii) activation of adhesion and (iv) secretion of the matrix metalloproteinases (MMPs) MMP-9 and MMP-2, and vascular endothelial growth factor (VEGF). We found that in human CD34(+) cells and erythroblasts erythropoietic factors may activate similar but different signalling pathways, and that activation of each of the JAK-STAT, MAPK p42/44 or PI-3K-AKT axes alone is not sufficient either to stimulate cell proliferation or inhibit apoptosis, suggesting that these processes are regulated by orchestrated activation of multiple signalling cascades. Accordingly, we found that although cell proliferation was more related to simultaneous activation of JAK-STAT and MAPK p42/44, the effect on cell survival correlated with activation of PI-3K-AKT, MAPK p42/44 and JAK-STAT proteins. We also demonstrated that differentiating normal human erythroid cells lose their adhesive properties and secrete angiopoietic factors such as MMP-9, MMP-2 and VEGF, and we postulate that this secretion by early erythroid cells may play a role in their maturation and egress from the haematopoietic niches of the bone marrow.

In vitro expansion of human megakaryocytes as a tool for studying megakaryocytic development and function.

Research on normal human megakaryopoiesis has been limited by technical problems in obtaining megakaryocytic cells in sufficient quantities for experimental purposes. We describe here an ex vivo serum-free liquid culture system to expand normal human megakaryoblasts from purified bone marrow-, cord blood- or peripheral blood-derived CD34(+) cells. The early megakaryocytic cells are expanded in the presence of recombinant thrombopoietin (TpO) and interleukin-3 (IL-3), and if necessary further purified by employing anti-CD61 immunomagnetic beads. Our expansion system generates normal human megakaryoblasts in quantities sufficient to perform various functional studies on these cells as well as to isolate from them proteins and mRNA for molecular analysis. Megakaryocytic cells isolated from these cultures (i) express several markers characteristic of this lineage (CD41, CD61, CD62 P, CXCR-4, PAR-1, etc.), (ii) respond by calcium flux and phosphorylation of various intracellular proteins to stimulation by thrombin and (iii) adhere to fibrinogen and vitronectin. However, human megakaryoblasts derived from the cultures supplemented with TpO + IL-3, in contrast to murine megakaryocytic cells cultured under similar conditions, display poor polyploidization and do not release platelets. Since IL-3 has been reported to inhibit final maturation of megakaryocytic cells, we recently modified our expansion strategy. In this new approach CD34(+) cells are first expanded for 11 days in the presence of TpO + IL-3. Then megakaryoblasts derived are expanded for an additional 7 days supplemented with TpO only. We found that megakaryocytic cells expanded in this 'two step culture' model are more differentiated, are polyploid and release platelets. The model described here provides normal human megakaryoblasts in adequate numbers, to study megakaryopoiesis and megakaryocyte function.

Biological significance of chemokine receptor expression by normal human megakaryoblasts.

The aim of this study was to learn more on the role of chemokines in the regulation of human megakryopoiesis. Normal human megakaryoblasts were expanded in serum-free liquid cultures and subsequently (1) phenotyped for expression of various chemokine receptors, (2) evaluated if chemokine receptors which they express are functional after stimulation by chemokines (calcium flux assay, chemotaxis, phosphorylation of MAPK-p42/44 and AKT proteins), and (3) investigated for expression and secretion of selected chemokines by employing RT-PCR and ELISA assays, respectively. In addition we also phenotyped peripheral blood platelets for expression of chemokine receptors and chemokines. We found that while human megakaryoblasts express several chemokine receptors (CXCR4, CCR6, CCR8, CCR5, CCR2 and CXCR3), CXCR4 was the only receptor detectable by FACS on human platelets. Moreover, among various chemokines tested, only SDF-1 (CXCR4 ligand) stimulated calcium flux and chemotaxis in normal human megakaryoblasts and phosphorylated MAPK-p42/44 and AKT in these cells. Although mRNAs for several chemokines were detectable by RT-PCR in normal human megakaryoblasts, only RANTES, IL-8, MCP-1 and PF-4 were found to be secreted by these cells. Finally we noticed that no chemokine tested in this study affected CFU-Meg colony formation by human CD34+ cells in serum-free cultures. We conclude that from all the chemokine receptor-chemokine axes tested, only SDF-1-CXCR4 axis was functional in assays employed in our studies, which further support the view that this axis plays a privileged role in regulating normal human megakaryopoiesis.

The SDF-1-CXCR4 axis stimulates VEGF secretion and activates integrins but does not affect proliferation and survival in lymphohematopoietic cells.

To better define the role HIV-related chemokine receptor-chemokine axes play in human hematopoiesis, we investigated the function of the CXCR4 and CCR5 receptors in human myeloid, T- and B-lymphoid cell lines selected for the expression of these receptors (CXCR4(+), CXCR4(+) CCR5(+), and CCR5(+) cell lines). We evaluated the phosphorylation of MAPK p42/44, AKT, and STAT proteins and examined the ability of the ligands for these receptors (stromal-derived factor-1 [SDF-1] and macrophage inflammatory protein-1beta [MIP-1beta]) to influence cell growth, apoptosis, adhesion, and production of vascular endothelial growth factors (VEGF), matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in these cell lines. We found that A) SDF-1, after binding to CXCR4, activates multiple signaling pathways and that in comparison with the MIP-1beta-CCR5 axis, plays a privileged role in hematopoiesis; B) SDF-1 activation of the MAPK p42/44 pathway and the PI-3K-AKT axis does not affect proliferation and apoptosis but modulates integrin-mediated adhesion to fibronectin, and C) SDF-1 induces secretion of VEGF, but not of MMPs or TIMPs. Thus the role of SDF-1 relates primarily to the interaction of lymphohematopoietic cells with their microenvironment and does not directly influence their proliferation or survival. We conclude that perturbation of the SDF-1-CXCR4 axis during HIV infection may affect interactions of hematopoietic cells with the hematopoietic microenvironment.

Heparinized cadaveric organ donors (HCOD)--a potential source of hematopoietic cells for transplantation and gene therapy.

BACKGROUND: Hematopoietic stem cells (HSC) from unrelated HLA-matched heparinized cadaveric organ donors (HCOD) are a new potential source of cells for transplantation and gene therapy. In addition, these cells could also be used as adjuvant therapy to increase microchimerism and graft tolerance after transplantations of various solid organs. Our purpose was to develop an efficient method for harvesting hematopoietic cells from HCODs, METHODS: Bone marrow cells were harvested from pelvic bones and/or vertebral bodies from 50 adult HCODs before or up to 3 hr after disconnecting the donor from the respirator. Subsequently, we evaluated the hematological and gasometric parameters of aspirated marrow samples as well as the proliferative potential, viability, and expression of CD34 and AC133 antigens on these cells. RESULTS: We noticed that up to 2-3 hr after disconnecting the donor from the respirator bone marrow cavities do not clot and remain uninfected and that it is possible to aspirate bone marrow mononuclear cells in quantities sufficient to perform allotransplantation. Nevertheless, due to the developing hypoxia and acidosis of the hematopoietic microenvironment the number and proliferative potential of CD34+ and AC133+ cells gradually decreases. Hence, to obtain viable early hematopoietic cells, bone marrow should be aspirated without delay; optimally before HCOD is disconnected from the respirator or at the very latest 2 hr after organ harvest. CONCLUSIONS: Collectively, our results show that early hemopoietic cells may be efficiently harvested from HCOD in large quantities and used for research and/or transplantation purposes. We postulate to create an international network of banks in which hemopoietic stem cells from HCODs could be preserved for therapeutic purposes.

Optimization of conditions for myofibril preparation from mechanically recovered chicken meat.

The influence of various conditions affecting the isolation of a myofibrillar preparation (MP) from chicken mechanically recovered meat (MRM), i.e. the time of additional chopping in a bowel chopper, washing time, the number of washings, and the water to MRM ratio, on the recovery of dry matter and myofibrillar protein, and fat content in the preparation was investigated. The following particular steps were determined to be the most desirable parameters: chopping MRM for 10 minutes, washing time of 15 minutes, 3 (or 2) consecutive washings, 3:1 water to MRM ratio (v/w). Under these conditions a significant decrease of fat content (93% on average) was found in comparison to the content in MRM. The removal of fat, sarcoplasmic protein and connective tissue increased the concentration of myofibrillar protein. The number of aqueous washings of MRM had the biggest influence on the protein and fat content in the concentrate. Electrophoretic analysis (SDS-PAGE) of protein in the preparation obtained under optimal conditions showed that myosin heavy chains (MHC) and actin constituted approximately 50% of all the proteins in the preparation.

[Results of treatment of osteosarcoma in children according to the SFOP-94 protocol in the experience of the Polish Paediatric Solid Tumour Study Group]. / Wyniki leczenia dzieci chorych na miesaka kosciopochodnego wedlug protokolu SFOP-94 w materiale Polskiej Grupy Pediatry Cznej ds. Leczenia Guzów Litych.

Between April 1994 and December 1999, 34 children aged from 5 to 20 years (23 females and 11 males) suffering from osteosarcoma, were treated according to the SFOP-94 protocol. The primary preoperative chemotherapy consists of adriamycin and high-dose methotrexate administration. There were 28 patients with non-metastatic tumours of the extremities and 6 children presented disseminated disease with pulmonary metastases. The primary localization included femur - 20 patients, tibia - 9 patients and humerus - 5 patients. In 26 patients limb-salvage surgery was applied. The programme of chemotherapy was changed in 4 children because of toxicity of methotrexate (1 patient) and progression of disease (3 patients). 26 out of 34 (76,5 %) children are alive including 24 out of 28 patients with localized disease. EFS calculated according to Kaplan-Meier analysis was 60 % at 67 months.

Short-term storage of human haematopoietic cells. Influence of air and deoxyribonuclease I.

The aim of this study was to optimize strategy for ex vivo short-term storage of human cord blood and bone marrow haematopoietic cells. We report that the presence of air in the vials (1/2 of their volume), in which hematopoietic cells are stored, improves the survival of clonogenic progenitors. We observed that presence of air prevented a rapid decrease in the pH of storage medium. Similarly, a beneficial effect on cell survival and recovery also had an addition of Deoxyribonuclease I (DNase I). We observed that DNase I efficiently prevented cell clumping, and moreover, did not affect the clonogenecity of the haematopoietic progenitors. Therefore containers, in which haematopoietic cells are stored, should contain enough air (source of oxygen) and the storage medium itself should be supplemented with DNase I.

Evidence that human haematopoietic stem cells (HSC) do not reside within the CD34+KIT- cell population.

Contradictory reports are published concerning the c-kit receptor (KIT) expression on human haematopoietic stem cells (HHSC). Therefore, the aim of this study was to reevaluate the expression of KIT on human early haematopoietic cells, and to study the distribution of HHSC among bone marrow mononuclear KIT+ and KIT- cells. First, we found that the detection sensitivity of the KIT expression on human HEL cells as well as CD34+ depends on the type of fluorochrome employed for the immunostaining (Cy5 > PE > FITC). Based on this observation, in our strategy for isolating human HHSC we employed a Cy-5 conjugated alpha-KIT MoAbs, which stained CD34+ cells in our preliminary studies the brightest. Accordingly, we labeled human BMMNC with PE-alpha-CD34 and Cy5-alpha-KIT MoAbs and subsequently sorted various subsets of labeled cells (CD34+KIT+, CD34+KIT- and CD34-KIT-). Cells sorted by FACS were then evaluated for their ability to engraft in the immunodeficient SCID mice model. We report here that only CD34+KIT+ cells, but not CD34+KIT- or CD34-KIT- were able to establish a human-murine haematopoietic chimerism in these animals. We found that SCID mice transplanted with CD34+ KIT+ cells, possessed approximately 5-11% of mononuclear cells, which expressed human CD45 antigen 4-5 weeks after transplantation in their bone marrow and, more importantly, early human haematopoietic progenitors from the myeloid and B-lymphoid lineages. Based on these results we conclude that KIT (CD117) is a very useful marker for identifying HHSC, and that HHSC, at least in our hands, are found in the KIT+ population of CD34+ cells.