ABSTRACT
INTRODUCTION: Understanding how extracellular matrix (ECM) protein composition regulates the process of human induced pluripotent stem cell (hiPSC) colony formation may facilitate the design of optimal cell culture environments. In this study, we investigated the effect of migratory behaviors on hiPSC colony formation on various ECM-coated surfaces. METHODS: To quantify how different ECM proteins affect migratory behavior during the colony formation process, single cells were seeded onto surfaces coated with varying concentrations of different ECM proteins. Cell behavior was monitored by time-lapse observation, and quantitative analysis of migration rates in relation to colony formation patterns was performed. Actin cytoskeleton, focal adhesions, and cell-cell interactions were detected by fluorescence microscopy. RESULTS: Time-lapse observations revealed that different mechanisms of colony formation were dependent upon the migratory behavior of cells on different ECM surfaces. HiPSCs formed tight colonies on concentrated ECM substrates, while coating with dilute concentrations of ECM yielded more motile cells and colonies capable of splitting into single cells or small clusters. Enhanced migration caused a reduction of cell-cell contacts that enabled splitting or merging between cells and cell clusters, consequently reducing the efficiency of clonal colony formation. High cell-to-cell variability in migration responses to ECM surfaces elicited differential focal adhesion formation and E-cadherin expression within cells and colonies. This resulted in variability within focal adhesions and further loss of E-cadherin expression by hiPSCs. CONCLUSIONS: Migration is an important factor affecting hiPSC colony-forming patterns. Regulation of migratory behavior can be an effective way to improve the expansion of hiPSCs while improving the process of clonal colony formation. We believe that this investigation provides a valuable method for understanding cell phenotypes and heterogeneity during colony formation in culture.
ABSTRACT
IL-2 is a potent immunostimulant and has been tested for clinical use, including in immunotherapy for cancers and HIV infection. Here we show that a widely used neutralizing anti-murine IL-2 mAb (S4B6) exhibits unexpected activities that enhance the treatment effects of IL-2 in vivo. Coinjection of the anti-IL-2 mAb with a plasmid carrying murine IL-2 cDNA significantly increased the serum IL-2 levels and induced a substantial increase in the division of CD8+ T and NK1.1(high) cells in vivo. Injection of the mAb premixed with recombinant murine IL-2 showed the same enhanced effect. A 5-day treatment with the anti-IL-2 mAb alone gradually increased the CD44(high)CD8+ population, and the increased population was maintained for >300 days, suggesting that the mAb can gradually maintain and potentially enhance the bioactivity of endogenous IL-2 for extended periods. Furthermore, combined treatment with the anti-IL-2 mAb plus the IL-2 plasmid markedly enhanced Ag-specific CTL activity in vivo and partially protected mice from tumor metastasis to the lungs, compared with the anti-IL-2 mAb or IL-2 plasmid alone. These results demonstrated IL-2-enhancing effects of the anti-IL-2 mAb in vivo and suggest that combining a neutralizing anti-IL-2 Ab with IL-2 gene delivery might be used effectively to enhance IL-2 functions in clinical applications.
