High doses of synthetic antioxidants induce premature senescence in cultivated mesenchymal stem cells.

Stress-induced premature senescence program is known to be activated in cells by various genotoxic stressors, and oxidative stress is considered to be the main of those. To this end, many studies discover antioxidants as protective anti-aging agents. In the current study, we examined the effects of different antioxidants (Tempol, resveratrol, NAC, DPI) on the mesenchymal stem cells maintained in normal physiological conditions. We used high, but non-cytotoxic antioxidant doses which are widely used in laboratory practice to protect cells from oxidative damage. We show that these substances induce reversible block of cell proliferation and do not cause any genotoxic effects when applied to the quiescent cells. However, the same doses of the same substances, when applied to the proliferating cells, can induce irreversible cell cycle arrest, DNA strand breaks accumulation and DNA damage response activation. As a consequence, antioxidant-induced DNA damage results in the stress-induced premature senescence program activation. We conclude that high doses of antioxidants, when applied to the proliferating cells that maintain physiological levels of reactive oxygen species, can cause DNA damage and induce premature senescence which suggests to re-estimate believed unconditional anti-aging antioxidant properties.

Yeast red pigment modifies cloned human α-synuclein pathogenesis in Parkinson disease models in Saccharomyces cerevisiae and Drosophila melanogaster.

Recently, we identified the yeast red pigment (RP), a polymer of 1-(5'-Phosphoribosyl)-5-aminoimidazole, as a novel potential anti-amyloid agent for the therapy of neurodegenerative diseases. The purpose of this study was to further validate RP for treatment of Parkinson's disease (PD) and to clarify molecular mechanisms involved in the reduction of amyloid cytotoxicity. We investigated RP effects in vivo using Saccharomyces cerevisiae and Drosophila melanogaster PD models. Western blot analysis revealed reduction in the levels of insoluble α-synuclein in both models, while soluble α-synuclein decreased only in Drosophila. In both models RP significantly reduced α-synuclein cytotoxicity, as was revealed by immunohistochemistry in Drosophila (p < 0.001, n = 27 flies per genotype/assay) and by flow cytometry in yeast (p < 0.05). Data obtained from the yeast PD model suggests that RP antitoxic effects are associated with a drop in ROS accumulation, and slower cellular transition from the early to late apoptotic stage. Using Drosophila brain tissue sections, we have demonstrated that RP helps to compensate for an α-synuclein-mediated reduction in the number of dopaminergic neurons and leads to better performance in animal climbing tests (p < 0.001, n = 120-150 flies per genotype/assay). Taken together, these results demonstrate the potential of RP for the treatment of PD, at least in model systems.

Flow cytometric HyPer-based assay for hydrogen peroxide.

HyPer is a genetically encoded fluorogenic sensor for hydrogen peroxide which is generally used for the ratiometric imaging of H2O2 fluxes in living cells. Here, we demonstrate the advantages of HyPer-based ratiometric flow cytometry assay for H2O2, by using K562 and human mesenchymal stem cell lines expressing HyPer. We show that flow cytometry analysis is suitable to detect HyPer response to submicromolar concentrations of extracellularly added H2O2 that is much lower than concentrations addressed previously in the other HyPer-based assays (such as cell imaging or fluorimetry). Suggested technique is also much more sensitive to hydrogen peroxide than the widespread flow cytometry assay exploiting H2O2-reactive dye H2DCFDA and, contrary to the H2DCFDA-based assay, can be employed for the kinetic studies of H2O2 utilization by cells, including measurements of the rate constants of H2O2 removal. In addition, flow cytometry multi-parameter ratiometric measurements enable rapid and high-throughput detection of endogenously generated H2O2 in different subpopulations of HyPer-expressing cells. To sum up, HyPer can be used in multi-parameter flow cytometry studies as a highly sensitive indicator of intracellular H2O2.

Redox environment in stem and differentiated cells: A quantitative approach.

Stem cells are believed to maintain a specific intracellular redox status through a combination of enhanced removal capacity and limited production of ROS. In the present study, we challenge this assumption by developing a quantitative approach for the analysis of the pro- and antioxidant ability of human embryonic stem cells in comparison with their differentiated descendants, as well as adult stem and non-stem cells. Our measurements showed that embryonic stem cells are characterized by low ROS level, low rate of extracellular hydrogen peroxide removal and low threshold for peroxide-induced cytotoxicity. However, biochemical normalization of these parameters to cell volume/protein leads to matching of normalized values in stem and differentiated cells and shows that tested in the present study cells (human embryonic stem cells and their fibroblast-like progenies, adult mesenchymal stem cells, lymphocytes, HeLa) maintain similar intracellular redox status. Based on these observations, we propose to use ROS concentration averaged over the cell volume instead of ROS level as a measure of intracellular redox balance. We show that attempts to use ROS level for comparative analysis of redox status of morphologically different cells could lead to false conclusions. Methods for the assessment of ROS concentration based on flow cytometry analysis with the use of H2DCFDA dye and HyPer, genetically encoded probe for hydrogen peroxide, are discussed.

[CHARACTERISTIC OF THE CELLULAR SPHEROIDS, DERIVED FROM MESENCHYMAL STEM CELL LINES FROM BONE MARROW AND MUSCLE OF LIMB OF EARLY HUMAN EMBRYO].

Cellular spheroids were derived from mesenchymal stem cell lines derived from 5-6-weeks embryo from different tissues of 5-6-week human embryo: bone marrow (FetMSC) and muscle of limb (M-FetMSC). Comparative analysis of the characteristics of these lines has been performed with 2D culturing in monolayer and 3D culturing in spheroids. The characteristics of cellular spheroids were obtained after 48 h after their formation from monolayer cultures on the 6th passage after decryopreservation. Spheroids in contrast to monolayer cultures are heterogeneous cell populations composed of fibroblast-like and epithelioid cells. Two-day spheroids are actively proliferating structure. Cell surface markers were analyzed using flow cytometry. Both in the monolayer cultures and cellular spheroids, this analysis has revealed the presence of expression of surface antigens CDD44, CD73, CD9O, CD105, HLA-ABC that are characteristic of human MSC, and the absence of expression if CD34 and HLA-DR. Nevertheless, the level of expression of CD90 and CD105 antigens was significantly lower in the spheroids as compared with corresponding monolayer cultures. Immunofluorescence and flow cytometry analysis of the expression of transcriptions factors and surface antigens characteristic of human embryonic stem cells showed the presence of expression of Sox-2 and SSEA-4 in 2D and 3D cultures. Lack of expression of Oct-4 in 2D cultures and its significant increase in 3D cultures has been found. Immunofluorescence analysis showed the presence of the markers of early differentiation in the derivates of three germ layers characteristic of human embryonic stem cells in the cellular spheroids of both lines, which coincides with 2D cultures of these lines. The directed osteogenic, chondrogenic and adipogenic differentiation of these lines has been shown. However, a number of differences has been found between monolayer cultures and spheroids. Adipogenic differentiation was more active in the cellular spheroids from cell line M-FetMSC a compared with corresponding monolayer cultures. Differences between the 2D and 3D cultures of both lines have been shown by the character of chondrogenic differentiation. The results obtained confirm the status of MSC for the cellular spheroids derived from monolayer cultured of cell lines FetMSC and M-FetMSC and apparently indicate a partial extension of their differentiation capacity as compared to monolayer cultured.

Reactive Oxygen Species Are Required for Human Mesenchymal Stem Cells to Initiate Proliferation after the Quiescence Exit.

The present study focuses on the involvement of reactive oxygen species (ROS) in the process of mesenchymal stem cells "waking up" and entering the cell cycle after the quiescence. Using human endometrial mesenchymal stem cells (eMSCs), we showed that intracellular basal ROS level is positively correlated with the proliferative status of the cell cultures. Our experiments with the eMSCs synchronized in the G0 phase of the cell cycle revealed a transient increase in the ROS level upon the quiescence exit after stimulation of the cell proliferation. This increase was registered before the eMSC entry to the S-phase of the cell cycle, and elimination of this increase by antioxidants (N-acetyl-L-cysteine, Tempol, and Resveratrol) blocked G1-S-phase transition. Similarly, a cell cycle arrest which resulted from the antioxidant treatment was observed in the experiments with synchronized human mesenchymal stem cells derived from the adipose tissue. Thus, we showed that physiologically relevant level of ROS is required for the initiation of human mesenchymal stem cell proliferation and that low levels of ROS due to the antioxidant treatment can block the stem cell self-renewal.

[Dynamics of the cell cycle in human endothelial cell culture infected with influenza virus].

Cell cycle in a culture of endothelial cells EAhy 926 infected with influenza virus was investigated. Cytometric analysis of culture, synchronized using contact inhibition, has shown that the exposure to the influenza virus in cells EAhy 926 lengthened S-phase of the cell cycle. This result has been tested and proven on culture EAhy 926 treated with nocodazole. Compared with lung carcinoma cells A549, in which influenza virus provokes the arrest of G0/G1 phase of the cycle, elongation of S-phase of cycle at a similar infection of endothelial culture EAhy 926 indicates that the influenza virus differently affects the dynamics of the cell cycle according to the origin of the infected culture.

[INDUCTION OF DECIDUAL DIFFERENTIATION OF ENDOMETRIAL MESENCHYMAL STEM CELLS].

In this study, we compared the ability of human mesenchymal stem cells derived from menstrual blood (eMSCs) and mesenchymal stem cells (MSCs) from other tissues to differentiate into decidual cells in vitro. It was demonstrated that during differentiation secretion of decidualization markers (prolactin and insulin-like growth factor binding protein-1) increases in eMSCs from adipose tissue (MSC-AD). Thus, the ability of eMSCs to differentiate into decidual cells is much higher than MSC-BM or MSC-AD. It makes eMSCs promising for application in cellular therapy of infertility associated with decidualzation insufficiency.

[CHARACTERISTICS OF NEW MESENCHYMAL STEM CELL LINE DERIVED FROM HUMAN EMBRYONIC STEM CELLS].

New nonimmortalized fibroblast-like cell line SC6-MSC has been obtained from a line of human embryonic stem cells (ESC)--SC6. Numerical and structural karyotypic analysis has shown hypodiploidy karyotypic: 45, X0 in this line. The average cell population doublings time, for SC6-MSC is 26.0 ± 0.4 h at the 8th passage and 82.0 ± 9.2 h at the 18th passage. The growth curves showed active proliferation for 8-10 passages with a consequent gradual decrease of proliferative activity, which ended to 20th passage. To determine the line's status, the analysis of the surface markers by flow cytometry was carried out. We have revealed the expression of surface antigens CD44, CD73, CD90, CD105 and HLA-ABC characteristic for human MSC, and the absence of CD34 and HLA-DR expression. However, the level of expression of surface markers CD90 and CD105 was significantly lower in comparison with other MSC lines including the line SC5-MSC derived from the line human ESC-SC5. Immunofluorescence analysis of the expression of the surface markers and transcription factor Oct-4 characteristic for human embryonic stem cells showed the absence of Oct-4 expression and the presence of SSEA-4 and TRA-1-60 expression, which is characteristic for a number of MSC lines with normal karyotype. Immunofluorescence analysis has shown the presence of the markers of early differentiation in the derivates of three germ layers, characteristic for human ESC, which in corresponding microenvironments may allow MSC to be useful for reparation of tissue injures. The directed osteogenic and chondrogenic differentiation of line SC6-MSC has shown. However, no directed adipogenic differentiation of this line has been found. The obtained results with high probability may indicate what alteration of chromosomal and, accordingly, gene balance, in line SC6-MSC with karyotype 45, X0 resulted in decrease in differential potential, in expression CD90, associated in particular with the processes of differentiation and aging of cells.

[CHARACTERISTIC OF ENDOMETRIAL MESENCHYMAL STEM CELLS IN CULTURE OBTAINED FROM PATIENT WITH ADENOMYOSIS].

Adenomyosis is form of endometriosis, common diseases of female reproductive system, which can lead to infertility in women. in this study we are obtained and characterized cell line endometrial mesenchymal stem cells from a patient with adenomyosis, and compare obtained cells with the cell line of healthy donor. Aim of this study was to assesses the extent of differences between cells from donor with adenomyosis and cells from healthy donor. Was established that compared lines had morphology like fibroblasts, were differentiated in adipocytes, were expressed mesenchymal markers and didn't expressed haematopoietic markers. Cytogenetic analysis of differentially stained metaphase chromosomes on G-banding (passage 6-7) showed that healthy donor's cells had predominantly normal karyotype. The cellular line from a patient with diagnosis of "adenomyosis" had a lot of cells with changes in karyotype's structure. These changes were related with aneuploidy of cellular population and the presence non-random chromosomal breaks, often in chromosomes 7 and 11. Analysis of this data allows the cells from adenomyosis characterized physiological stability in culture and karyotypic instability with non-random involvement certain chromosomal set. The cellular line obtained from donor with adenomyosis showed signs destabilization of he genome, typical for cell transformation. Division of adenomyosis cells to the 26th passage is stopped and these cells entered into a phase of replicative aging. Based on this, we can conclude that founded karyotype's hanges do not lead to transformation and immortalization of cells in vitro.

Alterations in cell cycle dynamics in human endothelium cell culture infected with influenza virus.

The cell cycle of endothelium EAhy 926 cell culture infected with influenza virus has been studied. Cytometric analysis of cell culture synchronized by contact inhibition revealed the elongation of the S phase of the cell cycle in EAhy 926 cells under the influence of influenza virus. This result was shown in an EAhy 926 culture infected with influenza virus and treated with nocodazole. Comparison of a lung carcinoma A549 cell line in which influenza virus causes G0/G1 arrest and of an endothelial EAhy 926 cell line in which the same infection leads to S-phase elongation allows it to be suggested that different effects of influenza virus on cell cycle dynamics depend on the origin of infected cells.

[Comparative characteristics of the stem cells isolated from subcutaneous and subepicardial adipose tissue].

BACKGROUND: Stem cells (SCs) considerably vary in morphological, immunophenotypic, proliferative, and differentiation characteristics depending on their tissue source. The comparative analysis of their biological properties is essential for the optimal choice of SCs for regenerative therapies. METHODS: Using immunocytochemistry, flow cytometry, histochemistry and real-time RT-PCR, we have investigated SCs obtained from human subepicardial (SEC-AT) and subcutaneous (SC-AT) adipose tissue and cultured under similar culture conditions without any differentiation-promoting factors. RESULTS: The cultures were similar in the high proportion of proliferating cell nuclear antigen (PCNA)-positive cells. In both cultures, immunophenotyping has revealed high expression of mesenchymal stem cell surface markers CD29, CD44, CD73, and CD105, low expression of CD31, CD34 and CD45, and wide variability in CD117, CD146 and CD309 expression. The only distinction in CD marker profile was significantly lower expression of CD90 in SCs from SEC-AT. Histochemical analysis has shown the lack of Oil Red O-positive cells in both cultures and about ten-fold higher number of alkaline phosphatase-positive cells among SCs from SC-AT. In the both cultures, immunocytochemistry has detected similar low expression of slow myosin heavy chain marker MAB1628 and smooth muscle actin marker α-hSMA. Gap junctional protein Connexin-43 expression was markedly higher in SCs from SC-AT, and epithelial cell marker Cytokeratin-19 expression was detected only in these cells. By RT-PCR, GATA4 mRNA was found to be highly expressed only in SCs from SEC-AT. CONCLUSIONS: Our results suggest that SC-AT, as compared with SEC-AT, is richer in epithelial cell and osteogenic progenitors. In turn, SEC-AT possesses cardiomyogenic SCs, and can be considered as an alternative to SC-AT as a source of SCs for cell cardiotherapy.

Intracellular oxidation of hydroethidine: compartmentalization and cytotoxicity of oxidation products.

Hydroethidine (HE) is a blue fluorescent dye that is intracellularly converted into red-emitting products on two-electron oxidation. One of these products, namely 2-hydroxyethidium, is formed as the result of HE superoxide anion-specific oxidation, and so HE is widely used for the detection of superoxide in cells and tissues. In our experiments we exploited three cell lines of different origin: K562 (human leukemia cells), A431 (human epidermoid carcinoma cells), and SCE2304 (human mesenchymal stem cells derived from endometrium). Using fluorescent microscopy and flow cytometry analysis, we showed that HE intracellular oxidation products accumulate mostly in the cell mitochondria. This accumulation provokes gradual depolarization of mitochondrial membrane, affects oxygen consumption rate in HE-treated cells, and causes cellular apoptosis in the case of high HE concentrations and/or long cell incubations with HE, as well as a high rate of HE oxidation in cells exposed to some stimuli.

[Comparative characteristics of mesenchymal stem cell lines derived from bone marrow and muscle of limb of early human embryo].

In this work, we have carried out a comparative analysis of the characteristics of mesenchymal stem cell lines isolated from different tissues of 5-6-weeks homan embryo: bone marrow (line FetMSC) and muscle of limb (line M-FetMSC). The basic characteristics of these lines were obtained at the 6th passage. Average population doubling time was 33.0 ± 1.4 h (FetMSC) and 25.0 ± 0.1 h (M-FetMSC). Growth curves also indicated active proliferation of cells of both lines. Numerical and structural karyotypic analysis showed that both lines have a normal karyotype: 46, XY. In order to determine the status of the lines, cell surface markers were analyzed by flow cytometry. The analysis revealed the presence of surface antigens specific for human MSCs, CD44, CD73, CD90, CD105, HLA-ABC, vimentin, and the lack of CD34 and HLA-DR, in both lines. The ability to differentiate into osteogenic, chondrogenic and adipogenic directions has been also shown for both lines. Im- munofluorescence and flow cytometry analysis has detected no expression of the surface antigen TRA-1-60 in both lines, but has revealed high expression of the surface antigen SSEA-4 and low expression of transcription factor Oct-4 characteristic of human embryonic stem cells. In these lines, immunofluorescence analysis has shown the presence of the markers of early differentiation in the derivates of three germ layers characteristic of human embryonic stem cells, which provides significant opportunities for MSC to be useful, in corresponding microenvironments, for repair of tissue injures. Dispite confirming MSC status for FetMSC and M-FetMSC lines, a number of interlinear differences related to growth characteristics and differentiation potential were revealed. Adipogenic differentiatiation potential of M-FetMSC line was reduced compared with FetMSC line. Immunofluorescence analysis showed that, in the process of skeletal-muscle differentiation, Z-disks were revealed only in sarcomeres of M-FetMSC line. These findings suggest the possible influence of different microenvironments in which the cells are in the body before their transfer in vitro.

[Mesenchymal stem cells of human endometrium do not undergo spontaneous transformation during long-term cultivation].

Mesenchymal stem cells isolated from human endometrium (eMSC) are perspective source of stem cells for regenerative medicine. Large amount of these cells accumulated by in vitro cultivation is usually required for transplantation into patients. We established several cell eMSC lines and cultivated them during long period of time to examine the possibility of their spontaneous transformation. All cell lines demonstrate limited lifespan, undergo replicative senescence and die. Karyotypic analysis on different passages reveals that most cells display karyotypic stability. Thus, extended in vitro cultivation of eMSCs does not lead to spontaneous transformation that makes therapeutic application of these cells safety for patients. During long-term cultivation eMSCs sustain the expression of surface markers.

[Ability of the influenza viruses and their envelope proteins to stimulates endothelial cells apoptosis in vitro].

The ability of the modern epidemic strains of influenza virus type A (subtypes H5N1, H3N2, H1N1pdm) and their surface proteins, hemagglutinin (HA) and neuraminidase to cause the activation of the cellular protein caspase-3 and stimulate the emergence of phosphatidylserine on the membrane of human endothelial cell line EAhy926 has been studied. It was questioned how the viruses and their surface proteins that were studied cause the activation of caspase-3 after 0.5 h of exposure that recorded immunogistotsitohimicheski. The test viruses and neuraminidase (concentration 10 µg/ml) led to the appearance of phosphatidylserine on the cell membrane in a time interval of 2-8 h from the beginning of the treatment, which was recorded by flow cytometry. The death of endothelial cells when exposed to the HA (in a concentration of 50 µg/ml) and in the same time frame was not accompanied by the appearance of phosphatidylserine. The specific feature of apoptotic cell death during the reproduction of the virus are described, as well as the effects of viral proteins.

[The STAT5 signaling in the expression of alpha-subunit of interleukin-2 receptor in human blood lymphocytes].

The comparative study of the STAT3 and STAT5 activity (as assessed by tyrosine phosphorylation level) and the expression of a α-subunit of interleukin-2 receptor (as examined by cytophotometric evaluation of the number of CD25+ cells) during the phytohemagglutinin (PHA)-induced proliferation of human blood lymphocytes (HBL) have been made. It has been revealed that the level of STAT3 phosphorylation is high in both res ting and competent HBL and remains unchanged in the presence of PHA or interleukin-2 (IL-2). In contrast to STAT3, phosphorylation of STAT5 was not seen in both resting and competent HBL. We observed phosphorylation of STAT5 no earlier than 5 h after PHA stimulation and the maximum phosphorylation was detected following 24 h. Exogenous IL-2 induced high level of STAT5 phosphorylation in the competent HBL as early as at 30 min and this level of STAT5 phosphorylation kept in the next 24-48 h. The correlation between alterations in tyrosine phosphorylation level of STAT5 and the expression of CD25 has been established. WHI-P131, an inhibitor of JAK3 kinase, prevents STAT5 activation, cell surface expression of CD25 and lymphocyte proliferation. It has been concluded that JAK3/STAT5 signaling via IL-2 receptor is necessary to maintain the long-term expression of the high-affinity αßγ(c)-receptor of IL-2 and optimal proliferation of HBL.

[Developing of a new feeder-free system and characterization of human embryonic stem cell sublines derived in this system under autogenic and allogenic culturing].

A new feeder-free culture system for human embryonic stem cells (hESC) was developed. It consist of extracellular matrix proteins synthesized by feeder cells--mesenchymal stem cell line SC5-MSC, which was derived from initial hESC line SC5. The major ECM proteins--fibronectin and laminin--that maintain hESC growth in feeder-free system were identified. An essential component of this system is a SC5-MSC-conditioned medium. Two hESC sublines were derived. The subline SC5-FF was cultured in autogenic and subline SC7-FF in allogenic system. Sublines SC5-FF and SC7-FF passed through more than 300 and 115 cell population doublings, retained normal diploid karyotype and an ability of in vitro differentiation into derivates of three germ layers. These sublines express markers of undifferentiated hESC: alkaline phosphatase, Oct-4, SSEA-4, TRA-1-81 and multidrug resistance transporter--ABCG2. The RT-PCR analysis revealed that undifferentiated cells SC5-FF subline, like cells of initial feeder-maintained hESC line SC5, expressed genes OCT4 and NANOG, and germ line specific genes such as DPPA3/STELLA and DAZL. An expression of OCT4, NANOG, DPPA3/STELLA ans DAZL was down-regulated during embryonic bodies differentiation, whereas expression of somatic lineages specific genes like GATA4 and AFP (extra embryonic and embryonic endoderm), PAX6 (neuroectoderm) and BRY (mesoderm) was up-regulated. The comparative analysis of some typical features (karyotype structure, the average population doubling time and the number of undifferentiated cells in populations) did not reveal essential differences between initial SC5 and SC7 lines and their sublines SC5-FF and SC7-FF. This shows that feeder-free culture systems, which are much more stable than any feeder systems, do not break main hESC features during long cultivation and can be recommended for fundamental, biomedicine and pharmacological investigations, using hESCs.

[Comparative characteristics of new mesenchymal stem cell lines derived from human embryonic stem cells, bone marrow and foreskin].

New nonimmortalized fibroblast-like cell lines SC5-MSC and SC3a-MSC, FetMSC, FRSN were obtained from human embryonic stem cells (ESC), bone marrow of a 5-6-days embryo and foreskin of a 3-years-old boy, respectively. All the lines are successfully used as the feeder at human ESC cultivation. It is determined that the average cell population doublings time varies from 25.5 h for ISC5-MSC to 38.8 h for SC3a-MSC. Active proliferation of all the lines is also shown by the corresponding growth curves. Numerical and structural karyotypic analysis showed that these lines had normal karyotype: 46,XX (SC5-MSC and SC3a-MSC) and 46,XY (FetMSC and FRSN). To determine the status of the lines, their cell surface markers were analyzed by flow cytometry. This analysis revealed the presence of surface antigens CD44, CD73, CD90, CD105 and HLA-ABC, characteristic of human MSC, and the absence of CD34 and HLA-DR. Different lines were found to express CD117(c-kit) to a different level. Immunofluorescence and flow cytometry analysis did not detect TRA-1-60 and Oct-4, characteristic of human embryonic stem cells, and revealed interlinear variations in the level of SSEA, which did not depend on the cell origin. It is not clear yet whether these interlinear variations affect functional MSC status. In all the lines, immunofluorescence analysis showed the presence of the markers of early differentiation in the derivates of three germ layers which may allow MSC to be useful, in corresponding microenvironments, for reparation of tissue injures. Adipogenic and osteogenic differentiatiation of all cell lines has been shown.

[The surface expression of CD25 at different stages of proliferative response in human lymphocytes. I. The role of JAK and Src tyrosine kinases as revealed by inhibitory analysis].

The long-lasting expression of an alpha-subunit of interleukin-3 receptor (IL-2Ralpha) was found to accompany the PHA-induced proliferation of human blood lymphocytes (HBL), so that to the end of the second day of mitogenic stimulation only, the large blasts may express the high affinity alphabetagamma(c) receptor for IL-2. With the selective pharmacological drugs to JAK (WHI-P131) and Src (PP2) it is shown that the non-receptor tyrosine kinases are involved in the surface CD25 expression. It is revealed that the PP-2-inhibitable expression of CD25 is timely associated with the initial stage of T cell activation, whereas WHI-P131-inhibitable expression was present during the whole G0/G1/S transition. These data indicate that at the early, antigen-dependent stage the expression of IL-2Ralpha is induced via Src-dependent signaling pathway, and prolonged increase in IL-2Ralpha expression is regulated by IL-2/IL-2 receptor interaction via JAK-dependent signaling pathway.