Figure 6. Time course of TNT exchange of lysosomes between co-cultured EPC and GC-stressed HUVEC and preservation of lysosomal pH gradient in the process of exchange. (A) A typical FACS analysis distribution of Celltracker and Lysotracker in the cells. Double-labeled cells indicated successful transfer. (B) Time-course of lysosomal transfer from EPC to stressed HUVEC. An increase in exchange rate occurred with time of co-culture. Asterisks depict p< 0.05; n=4. (C) Acridine orange labeling the low-pH compartment in EPC (orange), but lysosmal pH in stressed HUVEC is collapsed (green, upper panel). pH gradient persisted during the transfer of lysosomes to stressed HUVEC (upper panel). The lower panel illustrates the conclusion steps of lysosomal transfer with the restoration of lysosomal pH gradient in stressed HUVEC. Bars 20 μm.