Intravital multiphoton microscopy as a novel tool in the field of immunopharmacology

Intravital microscopy with multiphoton excitation is a recently developed optical imaging technique for deep tissue imaging without fixation or sectioning, which permits examination of fundamental concepts regarding the dynamic nature of cells under physiological and pathological conditions in living animals. This novel technique also offers exciting opportunities for pharmacological research by providing new platforms for the study of cellular dynamics in response to drugs in vivo. Moreover, fluorescent chemical probes for functional or molecular analysis in single cells in vivo play important roles in pharmacology. For example, we have recently revealed the pharmacodynamic actions of different biological agents for the treatment of rheumatoid arthritis (RA) in vivo by directly visualizing drug-induced cellular behaviors and functions of osteoclasts on bone surfaces. This review focuses on the principles and advantages of intravital imaging for the dissection of pharmacological mechanisms, and discusses how such imaging can contribute to the drug development process, introducing recent trials that evaluated the in vivo pharmacological effects of various agents.