Alteration of PBMC transcriptome profile after interaction with multipotent mesenchymal stromal cells under "physiological" hypoxia.

Multipotent mesenchymal stromal cells (MSCs) have demonstrated a pronounced immunosuppressive activity, the manifestation of which depends on the microenvironmental factors, including O2 level. Here we examined the effects of MSCs on transcriptomic profile of allogeneic phytohemagglutinin-stimulated peripheral blood mononuclear cells (PBMCs) after interaction at ambient (20%) or "physiological" hypoxia (5%) O2. As revealed with microarray analysis, PBMC transcriptome at 20% O2 was more affected, which was manifested as differential expression of more than 300 genes, whereas under 5% O2 220 genes were changed. Most of genes at 20% O2 were downregulated, while at hypoxia most of genes were upregulated. Altered gene patterns were only partly overlapped at different O2 levels. A set of altered genes at hypoxia only was of particular interest. According to Gene Ontology a part of above genes was responsible for adhesion, cell communication, and immune response. At both oxygen concentrations, MSCs demonstrated effective immunosuppression manifested as attenuation of T cell activation and proliferation as well as anti-inflammatory shift of cytokine profile. Thus, MSC-mediated immunosuppression is executed with greater efficacy at a "physiological" hypoxia, since the same result has been achieved through a change in the expression of a fewer genes in target PBMCs.

Changes Induced by Inflammatory-Activated Immune Cell Microenvironment in the Paracrine Profile of MSC.

We studied the influence of activated innate and adaptive immune cells on the production of growth factors by human adipose tissue multipotent mesenchymal stromal cells (MSC). MSC showed immunosuppressive properties in vitro: decreased activation and proliferation of stimulated immune cells. T-cell interaction with MSC resulted with increased secretion of EGF, PDGF-AB/BB, FGF-2, and VEGF growth factors. Co-culturing with natural killer cells also stimulated TGFα production. The intensity of the effect varied depending on the type of immune cells. Natural killer caused a more significant increase in PDGF-AB/BB and FGF-2 secretion, while VEGF secretion increased stronger after co-culturing with T cells. The obtained data indicate the possibility of increasing reparative potential of MSC under the influence of inflammatory microenvironment.

Сord blood hematopoietic stem cells ex vivo enhance the bipotential commitment of adipose mesenchymal stromal progenitors.

AIMS: Stroma-dependent ex vivo expansion of hematopoietic stem progenitor cells (HSPCs) is a valid approach for cell therapy needs. Our goal was to verify whether HSPCs can affect stromal cells to optimize their functions during ex vivo expansion. MAIN METHODS: HSPCs from cord blood (cb) were cocultured with growth-arrested adipose mesenchymal stromal cells (MSCs). Commitment-related transcriptional and secretory profiles as well as hematopoiesis-supportive activity of intact and osteo-induced MSCs were examined. KEY FINDINGS: During expansion, cbHSPCs affected the functional state of MSCs, contributing to the formation of early stromal progenitors with a bipotential osteo-adipogenic profile. This was evidenced by the upregulation of certain MSC genes of osteo- and adipodifferentiation (ALPL, RUNX2, BGLAP, CEBPA, ADIPOQ), as well as by elevated alkaline phosphatase activity and altered osteoprotein patterns. Joint paracrine profiles upon coculture were characterized by a balance of "positive" (GM-SCF) and "negative" (IP-10, MIP-1α, MCP-3) myeloid regulators, effectively supporting expansion of both committed and primitive cbHSPCs. Short-term (72 h) osteoinduction prior to coculture resulted in more pronounced shift of the bipotential transcriptomic and osteoprotein profiles. The increased proportions of late primitive CD133-/CD34+cbHSPCs and unipotent CFUs suggested that cbHSPCs after expansion on osteo-MSCs were more committed versus cbHSPCs from coculture with non-differentiated MSCs. SIGNIFICANCE: During ex vivo expansion, cbHSPCs can drive the bipotential osteo-adipogenic commitment of MSCs, providing a specific hematopoiesis-supportive milieu. Short-term preliminary osteo-induction enhanced the development of the bipotential profile, leading to more pronounced functional polarization of cbHSPCs, which may be of interest in an applied context.

Adipose-derived stromal cell immunosuppression of T cells is enhanced under "physiological" hypoxia.

Multipotent mesenchymal stromal cells (MSCs) are characterized by immunomodulatory properties along with the high proliferative and paracrine activity, as well as multilineage potency. The effects of MSCs on the T cell adaptive immunity are of a special interest. Low O2 level (1-7 %) is known to be typical for the putative site of the MSC - T cell interactions. A comparative evaluation of the effects of adipose tissue derived MSC (ASCs) on the mitogen-stimulated T cells at the ambient (20 %) and tissue-related (5 %) O2 levels demonstrated reduced T cell activation by the HLA-DR expression, decreased pro-inflammatory and increased anti-inflammatory cytokine production in co-culture, inhibited T cell proliferation, with the effects increased at hypoxia. T cell interactions with ASCs resulted in the up-regulation of PDCD1, Foxp3, and TGFß1 known to play an important role in the immune response suppression, and in the down-regulation of genes involved in the inflammatory reaction (IL2, IFNG). These changes were significantly increased under hypoxia. At the same time, neither ASCs nor the reduced O2 level had negative effects on the viability of T cells.

Evaluation of committed and primitive cord blood progenitors after expansion on adipose stromal cells.

Umbilical cord blood mononuclear fraction is a valuable source of hematopoietic stem and progenitor cells (CB HSPCs). The rarity of this population is a serious limitation of its application in cell therapy. Ex vivo expansion enables to significantly amplify the number of hematopoietic precursors of different commitment. Here, we expand CB MNCs in co-culture with human adipose tissue-derived stromal cells (ASCs) to enrich HSPCs and describe phenotypic features of newly formed hematopoietic populations. The CD34+-HSPCs demonstrated 6-fold enrichment with 9000 CFUs per 50 × 103 HSPCs on average. A part of the floating HSPCs were bearing lineage markers, while others were primitive precursors (CD133-/CD34+). Among ASC-associated HSPCs, two subsets of cord blood-borne cells were revealed: СD90+/СD45- and СD90+/СD45+. The proportion of CD3+/CD8+ and NK-T as well as CD25+ and HLA-DR+ Т cells among СD90+/СD45- cells was significantly higher compared to MNCs and floating HSPCs. More than 80% of CD45+/СD90+ HSPCs were identified as late primitive precursors (CD133-/CD34+). Thus, CB MNC expansion in the presence of ASCs provides the generation of both lineage committed lymphoid progenitors and CD34+/CD133- primitive HSPCs. Substantially enriched with primitive precursors, ASC-associated HSPCs could be considered as a perspective tool for a long-term restoration of hematopoiesis in various hematologic disorders.

[EFFECT OF STROMAL CELLS AND OXYGEN CONCENTRATION ON THE MAINTENANCE OF CORD BLOOD HEMATOPOIETIC PRECURSORS].

The paper analyses the morphological and functional features of cord blood cells (CBCs) in the co-culture with multipotent mesenchymal stromal cells (MMSCs) from human adipose tissue under tissue-related oxygen. We have established that MMSCs effectively maintained viability of CBCs at different oxygen concentrations (1, 5 and 20%). According to the data obtained, the oxygen concentration affected the number of colony-forming units (CFUs) formed by CBCs in selective medium. In particular, not co-cultured CBCs the 1 and 5% O2 than at 20% O2. After co-culture with MMSCs, the CFUs numbers were similar at 1 and 20% O2 and increased by 30 at 5% O2. Tissue related O2 concentrations had an impact on the proportion of lineage-resctricted CFCs among CBCs: the number of more committed progenitors--CFU-G and CFU-M, increased, and multi and bipotent--CFU-GEMM and CFU-GM, decreased at low oxygen concentrations. This effect was more pronounced after co-culture compared to that of initial CBCs. Thus, the presence of stromal cells and tissue-related oxygen jointly and severally influenced CBCs in vitro.

[Bone marrow mononuclear cells from murine tibia after the space flight on biosatellite "Bion-M1"].

Cellularity, viability and immunophenotype of mononuclear cells derived from the tibial marrow of C57bL/6 mice were measured after the 30-day "Bion-M1" space flight and subsequent 7-day recovery. Cell number in the flight group was significantly less than in the group of vivarium control. There was no difference in the parameter between the flight and control groups after the recovery. Viability of mononuclear cells was more than 95% in all examined groups. Flow cytometric analysis failed to show differences in bone marrow cell immunophenotype (CD45, CD34, CD90.1 (Thy1); however, the flight animals had more large-sized CD45+ mononuclears than the control groups of mice. These results indicate that spaceflight factors did not have significant damaging effects on the number or immunophenotype of murine bone marrow mononuclears. These observations are consistent with the previously made assumption of a moderate and reversible stress reaction of mammals to space flight.

In vitro study of interactions between silicon-containing nanoparticles and human peripheral blood leukocytes.

The effects of silicon dioxide-based nanoparticles on the viability and proliferative activity of human peripheral blood cultured lymphocytes were studied. All nanoparticles in a concentration of 100 µg/ml produced a significant cytotoxic effect, its intensity depending on particles' structure: SiO2 nanoparticles were least toxic, while Ce3(+)-intercaled montmorillonite nanoparticles were most toxic. The cells died mainly by apoptosis and postapoptotic necrosis. Incubation with nanoparticles in a concentration of 100 µg/ml for 72 h caused death of all phytohemagglutinin-activated lymphocytes, while in concentrations of 1 and 10 µg/ml the nanoparticles had no effect of proliferative activity of cells. The results suggest that the effects of nanoparticles on cells are determined by the nanoparticle concentration and size, as well as by their structure.

[Alteration of MMSC's immunosupression at reduced o2: direct cell-to-cell contacts and paracrine regulation].

During last two decades multipotent mesenchymal stromal (stem) cells (MMSCs) were not only identified and isolated from many tissues, but their immunopriviledge and immunosupressive potential along with high proliferative activity and multilineage differentiation were demonstrated. At the same time there is an increasing evidence of the MMSC plasticity due to a wide range of microenvironmental factors: extracellular matrix, cell-to-cell interactions, oxygen content, etc. In this paper, a comparative study of direct cell-to-cell and paracrine effects of MMSCs on human PHA-activated peripheral blood mononuclear cells (MNCs) in the standard (20%) and reduced to 5% O2 concentration in the culture medium was conducted. It is shown that after coculture with MMSCs the proliferative activity of PHA-MNCs, the share of HLA-DR(+) -T cells and IL-6, -8 and TNF-alpha concentrations were reduced, but IL-10 and IFN-gamma were increased in the medium. Potentiating effect on the MMSC immunomodulating properties was noted at low oxygen, which is of great importance for increasing the efficiency of immunosuppression.

[Human lymphocyte immunophenotype after interaction with mesenchymal stromal cells].

Human multipotent mesenchymalstromal cells were cocultured for 72h with allogeneic blood-borne mononuclear cells (MNCs) of different maturity (lymphocytes from adult peripheral blood and umbilical cord blood) and functional state (intact and PHA-activated human peripheral blood lymphocytes): After coculture with MMSCs the share ofB-cells among MNCs and cbMNCs decreased. The proportion ofT- and NK cells declined only among cbMNCs (p < 0.05). Only T-NK subpopulation reduced among MNC and cbMNC T-cells. The drop of CD8+ cells was detected in coculture of MMSCs and PHA-MNCs. Activated HLA-DR+ cells declined, CD25+ cells increased compared to monoculture of PHA-MNCs. MMSCs supported MNC, PHA-MNC and cbMNC viability. These results are important for understanding the physiology of the allogeneic cell-to-cell interaction in connection of potential clinical application of allogeneic cell products of blood-borne and stroinal origin.

Immunosuppressive effects of multipotent mesenchymal stromal cells in cultures with different O2 content in the medium.

We studied the effects of multipotent mesenchymal stromal cells isolated from the adipose tissue on proliferation and viability of immunocompetent cells at different concentration of O(2) (5 and 20%) in culture medium. It was shown that co-culturing with multipotent mesenchymal stromal cells 3-fold reduced proliferative index of phytohemagglutinin-activated lymphocytes, while their viability remained unchanged and did not depend on partial oxygen pressure in the medium. These findings suggest that low O(2)concentration in tissues will not affect immunosuppressive properties of multipotent mesenchymal stromal cells, which is very important for their application in regenerative medicine.