A novel transfection method for eukaryotic cells using polyethylenimine coated albumin microbubbles.

Albumin microbubbles have been intensively studied for their application in gene delivery. However, with negative surface potential, albumin microbubbles hardly bind plasmid DNA, which might contribute to their low transgene efficiency. In this study, we developed polyethylenimine (PEI) coated albumin microbubbles (PAMB) which were prepared by sonicating the mixture of human albumin, PEI, polyethylene glycol and glucose. CHO cells, COS cells and 293T cells were transfected with PEI, PEI+albumin, PAMB and Lipofectamine 2000, respectively. Our results showed that the surface potential was elevated and PAMB could bind plasmid DNA. The transgene efficiency of PAMB was higher than PEI and PEI+albumin (P<0.05), and PAMB performed the same transgene effect as Lipofectamine 2000 did but with lower cytotoxicity than Lipofectamine 2000. Albumin microbubbles modified by PEI has high transgene efficiency and low cytotoxicity even without ultrasound medication, making it a useful non-virus gene delivery method in vitro.

Amniotic fluid stem cells provide considerable advantages in epidermal regeneration: B7H4 creates a moderate inflammation microenvironment to promote wound repair.

The current treatments for severe skin injury all involve skin grafting. However, there is a worldwide shortage of donor skin tissue. In this study, we examined the advantages of using human amniotic fluid stem (hAFS) cells in skin wound healing. In vitro, hAFS cells differentiate into keratinocytes (termed hAFS-K). Like keratinocytes, hAFS-K cells express the markers K5, K14, K10 and involucrin; display typical cellular structure, including a tonofibril-rich cytoplasm; and construct a completely pluristratified epithelium in 3D culture. In vivo, in a mouse excisional wound model, GFP-positive hAFS cells participate in wound repair. Co-localization of GFP/K14 and GFP/K10 in the repaired epidermis demonstrated that hAFS cells can differentiate into keratinocytes. Real-time PCR results confirmed that hAFS cells can initiate and promote early-stage repair of skin damage. During wound repair, hAFS cells did not directly secrete repair-related factors, such as bFGF, VEGF, CXCL12, TGF-ß1 and KGF, and provided a moderate inflammation reaction with lower expression of IL-1ß, IL-6, TNF-α, Cox2 and Mac3. In hAFS cells, the negative co-stimulatory molecule B7H4 regulates low immunogenicity, which can provide a modest inflammatory reaction microenvironment for wound repair. Furthermore, with their uniquely high proliferation rate, hAFS cells offer a promising alternative for epidermal regeneration.

Different roles of PD-L1 and FasL in immunomodulation mediated by human placenta-derived mesenchymal stem cells.

Mesenchymal stem cells (MSCs) derived from either bone marrow (BMSCs) or placenta (PMSCs) have the capacity to suppress immune responses to mitogenic and allogeneic stimulations. Both cell contact and soluble factor dependent mechanisms have been proposed to explain this immunosuppression. This study explored the roles of some of cell surface molecules expressed on human PMSCs (hPMSCs) in hPMSC mediated immunomodulation. hPMSCs strongly suppressed mitogen and allogeneic peripheral mononuclear cells (PBMCs) induced T cell activation and proliferation. hPMSCs constituently expressed programmed death-ligand 1 (PD-L1) and Fas ligand (FasL) molecules. Neutralising antibodies to-PD-L1 and FasL significantly reduced the suppressive effect of hPMSCs on T cell proliferation. However, only anti-PD-L1 antibody partially restored early T cell activation suppressed by hPMSCs. Anti-FasL antibody but not anti-PD-L1 antibody reduced apoptosis of activated T cell indicating that FasL molecule plays a role in inducing apoptosis of activated T cells, although overall hPMSCs diminished T cell apoptosis. Different effects of PD-L1 and FasL molecules on T cell activation and activated T cell apoptosis suggest that these two molecules influence T cell response at different stages. hPMSCs significantly prevented activated T cells from going into S phase. Both antibodies to PD-L1 and FasL had significant effect on reversing the effect of hPMSCs on cell cycles. hPMSCs reduced INF-γ but increased IL-10 production by mitogen activated T cells. Both antibodies partially abolished the effect of hPMSCs on INF-γ and IL-10 production. These data demonstrated that PD-L1 and FasL molecules play significant roles in immunomodulation mediated by hPMSCs. This study provides a rational basis for modulation of negative costimulators on hPMSCs to increase their immunosuppressive properties in their therapeutic applications.

Transplantation of human amniotic mesenchymal stem cells in the treatment of focal cerebral ischemia.

Cerebrovascular injury is one of the three major causes of death and is the leading cause of adult disability. Despite the increasing progress in emergency treatment and early rehabilitation in patients with cerebrovascular injury, treatment options for neurological dysfunction that presents at a later stage are lacking. This study examined the potential of human amniotic mesenchymal stem cell (hAMSC) transplantation in the repair of neurological deficits in an experimental focal cerebral ischemia model. Following the isolation of hAMSCs, growth characteristics and surface antigen expression were observed. Butylated hydroxyanisole (BHA) was used to induce the cultured cells into neuron-like cells, which were identified by immunocytochemistry. The suture model was used to induce focal cerebral ischemia in rats, which were subsequently randomly divided into experimental and control groups for treatment with BrdU-labeled hAMSCs or PBS, respectively. Neurological deficits were assessed following transplantation using the neurological severity score, beam balance test and elevated body swing test. Eight weeks later, rat brain tissue was analyzed with H&E staining and BrdU immunohistochemistry, and the survival and spatial distribution of the transplanted hAMSCs were determined. The hAMSCs proliferated in vitro, and it was found that neuron-specific enolase (NSE) was expressed in neurons, whereas glial fibrillary acidic protein (GFAP) was expressed in astrocytes. The focal ischemia model caused varying degrees of left limb hemiplegia accompanied by right sided Horner's Syndrome. When examined 1, 3, 6 and 8 weeks later, significant recovery in neurological behavior was detected in the rats treated with hAMSC transplantation compared with the control (P<0.01). BrdU-labeled hAMSCs were concentrated near the graft site and surrounding areas, in certain cases migrating towards the ischemic lesion. Local gliosis and lymphocytic infiltration were not detected. hAMSCs exhibit great potential for proliferation and are induced to differentiate into NSE-expressing neuron-like cells following treatment with BHA. Moreover, hAMSC transplantation may improve neurological symptoms following focal cerebral ischemia.

The negative co-signaling molecule b7-h4 is expressed by human bone marrow-derived mesenchymal stem cells and mediates its T-cell modulatory activity.

Though experimental evidence shows that human bone marrow-derived mesenchymal stem cells (hBMSCs) are able to suppress T-cell activation and proliferation, the precise mechanisms are still not completely understood. Here, we investigated the role of the negative costimulatory molecule B7-H4 in the immunosuppressive effect of hBMSCs on T-cell activation. We showed that B7-H4 expresses abundantly on hBMSCs assessed by reverse transcription, immunofluorescence staining, and flow cytometric analysis. Further studies demonstrated that B7-H4 expressed on hBMSCs inhibits T-cell activation and proliferation via induction of cell cycle arrest and inhibition of NF-kappaB nuclear translocation. Blocking B7-H4 would decrease the secretion of transforming growth factor-beta1 (TGF-beta1) in the supernatant of activated T cells co-cultured with hBMSCs. Addition of neutralizing antibodies against B7-H4 significantly attenuated the inhibitory effects of hBMSCs on T-cells. Thus, our study established the novel role of B7-H4 molecule in the suppressive effect of hBMSCs on T-cell activation and proliferation. Taken together, these results highlight the complex role of hBMSCs in regulating the immune response, asserting the possibility of their therapeutic application in transplantation, the treatment of graft-versus-host disease (GVHD), and autoimmune diseases.