Background. Immunological and infectious safety of blood components is considered to be a key condition for high-quality transfusion therapy. The progress of blood filtration methods contributes to the development of methods for the validation of residual leukocyte control in blood products.The aim of the study was to compare the efficiency of flow cytometer with hematology analyzer for counting residual leukocytes in blood productsMethods. In this study, we compared the efficiency of two analytical instruments for counting residual leukocytes in 191 blood plasma samples: a flow cytometer (Navios Beckman Coulter) with a LeukoSure commercial reagent kit and a Sysmex XT4000i hematology analyzer.Results. All the samples under investigation met technical regulation requirements. Most of the samples were characterized by a significantly low amount of residual leukocytes, which fact presented a particular scientific interest. The use of a Navios Beckman Coulter flow cytometer and a commercial reagent kit allowed us to detect 15 or lower cells per μL in 83 % of the samples. The use of a Sysmex XT- 4000i automatic hematology analyzer for the calculation of residual white blood cells in this range proved to be limited due to the sensitivity of the device and the absence of certified reference materials with a low white blood cell count.Conclusion. Our results show that a Navios Beckman Coulter flow cytometer with a commercial reagent kit is suitable for measuring residual leukocytes in blood plasma. This instrument is most appropriate for samples with a minimum number of cells. A significant variability of the amount of residual white blood cells in blood plasma confirms the importance of inspecting the content of leukocytes in all blood components.
Many research groups have developed various types of tissue-engineered cardiac constructs. However, the immunological properties of such artificial tissues are not yet fully understood. Previously, we developed microfiber scaffolds carrying human iPSC-derived cardiomyocytes (hiPSC-CM). In this work, we evaluated the ability of these tissue-engineered constructs to activate the expression of CD28 and CTLA-4 proteins on T lymphocytes, which are early markers of the immune response. For this purpose, electrospun PLA microfiber scaffolds were seeded with hiPSC-CM and cultured for 2 weeks. Allogeneic mononuclear cells were then co-cultured for 48 h with three groups of samples: bare scaffolds, pure cardiomyocyte culture and tissue-engineered constructs, followed by analysis of CD28/CTLA-4 expression on T lymphocytes using flow cytometry. PLA scaffolds and concanavalin A stimulation (positive control) statistically significantly increased CD28 expression on CD4+ T cells (up to 61.3% and 66.3%) CD8+ T cells (up to 17.8% and 21.7%). CD28/CTLA-4 expression was not increased when T lymphocytes were co-cultured with cardiac tissue-engineered constructs and iPSC-CM monolayers. Thus, iPSC-CM in monolayers and on PLA microfiber scaffolds did not induce T cell activation, which suggests that such cardiac constructs would not be a cause of rejection after implantation.
<p>Характерный маркер кардиальных стволовых клеток – тиразинкиназный рецептор c-kit. Клетки с фенотипом c-kit+ легко выделяются и культивируются in vitro. Однако истинным кардиомиогенным потенциалом обладают только кардиальные стволовые клетки, полученные из сердца постнатальных животных. Исследователи предполагают две популяции c-kit+ клеток в сердце различного происхождения в эмбриогенезе. Клетки c-kit+, способные дифференцироваться в кардиомиоциты, происходят из клеток первичного кардиального поля и исчезают вскоре после рождения, а те, что имеют проэпикардиальное происхождение, экспрессируют мезенхимальные маркеры и способны к дифференцировке в эндотелиальном, муральном и фибробластном направлениях. Ранее мы описали c-kit+ клетки, выделенные из фрагментов ушка правого предсердия, и исследовали их ангиогенный потенциал in vitro. В этом исследовании мы сравнили поверхностные маркеры мезенхимальных стволовых клеток костного мозга, кардиальных стволовых клеток и фибробластов кожи человека методом проточной цитометрии и полимеразной цепной реакции с обратной транскрипцией. Показали, что культура кардиальных стволовых клеток человека, полученная в результате магнитного сортинга с помощью антител на c-kit-рецептор является гетерогенной. В ней присутствуют клетки, несущие характерный набор поверхностных маркеров мезенхимальных стволовых клеток костного мозга, эндотелиальных и муральных клеток. Иммунофенотип фибробластов кожи также представлен характерным набором маркеров мезенхимальных стволовых клеток, за исключением дополнительного маркера CD10, соответствующего эластазе, нейтральной пептидазе. Кроме того, фибробласты кожи дифференцируются в остеогенном и адипогенном направлениях при использовании индукционных сред. Таким образом, фибробласты кожи человека, полученные согласно стандартным протоколам, являются мезенхимальными стволовыми клетками кожи. В соответствии с иммунофенотипом мезенхимальные стволовые клетки костного мозга, кардиальные стволовые клетки и фибробласты кожи экспрессируют гены паракринных факторов HGF, VEGF, PDGFb, ANG1, ANG2, IGF1, TGFb, обладающих кардиопротекторным и ангиогенным эффектами.</p>
We propose a calibration-free method to determine the number of receptors per cell, as well as the direct and the reverse reaction rate constants for a single receptor. The method is based on the analysis of the temporal evolution of the cells mean fluorescent intensity measured by a flow cytometer during the ligand-receptor (antigen-antibody) binding under the conditions of their comparable concentrations. We developed the kinetic approach accounting both for the delay between the dilution and the measurement and for the practical duration of the measurement itself. The method was applied to determine thenumber of CD14 receptors on human blood mononuclear (granulocytes, monocytes, lymphocytes) cells of several donors. We also obtained the direct ( (5.6 ± 0.2) × 10 M min ) and reverse ( (1.3 ± 0.2) × 10 min ) rate constants of ligand-receptor interaction, and estimated the size of the binding site as b = 0.5 nm. The latter allows one to recalculate the rate constants for a different ligand, fluorescent label, medium viscosity, and/or temperature. The knowledge of the rate constants is essential for the calibration-free determination of the number of receptors per cell from a single kinetic curve of the cells mean fluorescence intensity.
Different types of engineered cardiac constructs are being developed nowadays by many research groups. However, the immunological properties of such artificial tissues are not yet clearly understood. Previously, we have studied microfiber scaffolds carrying iPSC-derived cardiomyocytes. In this work, we evaluated the ability of these tissue-engineered constructs to activate the expression of CD28 and CTLA-4 proteins in T-lymphocytes which are early markers of the immune response. For this purpose electrospun PLA nanofibrous scaffolds were seeded with human iPSCs-CM and cultivated for 2 weeks. After, allogeneic mononuclear cells were co-cultured during 48 hours with 3 groups of samples that were tissue-engineered constructs, pure culture of cardiomyocytes and bare scaffolds followed by analysis of CD28/CTLA-4 expression on T-lymphocytes via flow cytometry. PLA scaffolds and concanavalin A (positive control) stimulation statistically significantly increased CD28 expression on CD4+ cells (up to 61.3% and 66.3%) and on CD8+ cells (up to 17.8% and 21.7%). CD28/CTLA-4 expression didn’t increase during co-cultivation of T-lymphocytes with cardiac engineered constructs and iPSC-CM monolayers. Thus, iPSCs-CM in monolayers and on PLA nanofibrous scaffolds didn’t cause T-cell activation, which allows us to expect that such cardiac constructs are not a cause of rejection after implantation.
Адрес для переписки:Шкода Ольга Сергеевна ФГБУ «Новосибирский научно-исследовательский институт патологии кровообращения имени академика Е.Н. Мешалкина» Министерства здравоохранения РФ 630055, Россия, г. Новосибирск, ул. Речкуновская, 15. Тел.: 8 (983) 309-02-39.
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