The combination of dextran sulphate and polyvinyl alcohol prevents excess aggregation and promotes proliferation of pluripotent stem cells in suspension culture.

OBJECTIVES: For clinical applications of cell-based therapies, a large quantity of human pluripotent stem cells (hPSCs) produced in standardized and scalable culture processes is required. Currently, microcarrier-free suspension culture shows potential for large-scale expansion of hPSCs; however, hPSCs tend to aggregate during culturing leading to a negative effect on cell yield. To overcome this problem, we developed a novel protocol to effectively control the sizes of cell aggregates and enhance the cell proliferation during the expansion of hPSCs in suspension. MATERIALS AND METHODS: hPSCs were expanded in suspension culture supplemented with polyvinyl alcohol (PVA) and dextran sulphate (DS), and 3D suspension culture of hPSCs formed cell aggregates under static or dynamic conditions. The sizes of cell aggregates and the cell proliferation as well as the pluripotency of hPSCs after expansion were assessed using cell counting, size analysis, real-time quantitative polymerase chain reaction, flow cytometry analysis, immunofluorescence staining, embryoid body formation, teratoma formation and transcriptome sequencing. RESULTS: Our results demonstrated that the addition of DS alone effectively prevented hPSC aggregation, while the addition of PVA significantly enhanced hPSC proliferation. The combination of PVA and DS not only promoted cell proliferation of hPSCs but also produced uniform and size-controlled cell aggregates. Moreover, hPSCs treated with PVA, or DS or a combination, maintained the pluripotency and were capable of differentiating into all three germ layers. mRNA-seq analysis demonstrated that the combination of PVA and DS significantly promoted hPSC proliferation and prevented cell aggregation through improving energy metabolism-related processes, regulating cell growth, cell proliferation and cell division, as well as reducing the adhesion among hPSC aggregates by affecting expression of genes related to cell adhesion. CONCLUSIONS: Our results represent a significant step towards developing a simple and robust approach for the expansion of hPSCs in large scale.

Ceria nanocrystals decorated mesoporous silica nanoparticle based ROS-scavenging tissue adhesive for highly efficient regenerative wound healing.

Restoration of tissue integrity and tissue function of wounded skin are both essential for wound repair and regeneration, while synergistic promotion of the two remains elusive. Since elevated reactive oxygen species (ROS) production in the injured site has been implicated in triggering a set of deleterious effects such as cellular senescence, fibrotic scarring, and inflammation, it is speculated that alleviating oxidative stress in the microenvironment of injured site would be beneficial to promote regenerative wound healing. In this study, a highly versatile ROS-scavenging tissue adhesive nanocomposite is synthesized by immobilizing ultrasmall ceria nanocrystals onto the surface of uniform mesoporous silica nanoparticles (MSN). The ceria nanocrystals decorated MSN (MSN-Ceria) not only has strong tissue adhesion strength, but also significantly restricts ROS exacerbation mediated deleterious effects, which efficiently accelerates the wound healing process, and more importantly, the wound area exhibits an unexpected regenerative healing characteristic featured by marked skin appendage morphogenesis and limited scar formation. This strategy can also be adapted to other wound repair where both ROS-scavenging activity and tissue adhesive ability matter.

Synergistic effects of co-administration of suicide gene expressing mesenchymal stem cells and prodrug-encapsulated liposome on aggressive lung melanoma metastases in mice.

The success of conventional suicide gene therapy for cancer treatment is still limited because of lack of efficient delivery methods, as well as poor penetration into tumor tissues. Mesenchymal stem cells (MSCs) have recently emerged as potential vehicles in improving delivery issues. However, these stem cells are usually genetically modified using viral gene vectors for suicide gene overexpression to induce sufficient therapeutic efficacy. This approach may result in safety risks for clinical translation. Therefore, we designed a novel strategy that uses non-viral gene vector in modifying MSCs with suicide genes to reduce risks. In addition, these cells were co-administrated with prodrug-encapsulated liposomes for synergistic anti-tumor effects. Results demonstrate that this strategy is effective for gene and prodrug delivery, which co-target tumor tissues, to achieve a significant decrease in tumor colonization and a subsequent increase in survival in a murine melanoma lung metastasis model. Moreover, for the first time, we demonstrated the permeability of MSCs within tumor nests by using an in vitro 3D tumor spheroid model. Thus, the present study provides a new strategy to improve the delivery problem in conventional suicide gene therapy and enhance the therapeutic efficacy. Furthermore, this study also presents new findings to improve our understanding of MSCs in tumor-targeted gene delivery.