Figure 4.

Bioluminescence imaging of ATP, Ca²⁺ and oxygen during chondrogenesis. (A) Right panel: Bioluminescence imaging at the single-cell level shows that bioluminescent intensities of Actin-Phrixothrix hirtus red luciferase (PxRe) to report intracellular ATP levels in individual cells oscillate collectively by intercellular synchronization during chondrogenesis. Left panel: Time course data of P_ACTIN-PxRe intensities of individual cells indicated by red squares after chondrogenic induction. Reproduced with permission from [65]. (B) Simultaneous monitoring of intracellular oxygen (blue line) and ATP (red line) levels during chondrogenesis in the micromass culture of mesenchymal stem cells (MSCs) by using an oxygen reporter (P_ACTIN-Rluc) and ATP reporter (P_ACTIN-PxRe). Reproduced with permission from [65]. (C) Simultaneous monitoring of intracellular Ca²⁺ (blue line) and ATP (red line) levels during chondrogenesis in micromass culture of ATDC5 cells using a calcium reporter (aequorin) and ATP reporter (P_ACTIN-PxRe). Reproduced with permission from [67].