Animal Models for Photodiagnosis and Photodynamic Therapy

Abstract

A prerequisite for starting a clinical trial is evidence of a positive impact of the technique or drug in animals. The choice of the animal model is thus very important and should mimic as closely as possible the human situation. A variety of animal models have been validated for pharmaceutical trials. The situation in phototheranostics however is not fully clear. This is due to the very complex interplay of various elements such as vascularization, oxygenation, drug availability and biodistribution, light absorption, and scattering. The present paper will give general information on aspects of animal models that have to be considered in phototheranostics, as well as highlight some typical animal models that are useful for the investigation of light‐tissue interactions.

Photodynamic therapy in colorectal cancer treatment—The state of the art in preclinical research

“…The main question of photodynamic animal research is a choice of appropriate animal model that would mimic the human situation as closely as possible and would enable to translate animal research results into clinical benefit [88,89]. A variety of animal models validated for conventional drugs trials are inappropriate for photodynamic experiments due to the complex interplay between many physicochemical, morphological and physiological factors such as vascularization and oxygenation of CRC as an heterogenous "organoid" in dynamic state, as well as bioavailability and pharmacokinetics of photosensitizer which acts rather as catalyst of intracellular processes contrary to conventional anticancer drugs interacting with specific cell and tissue receptors [89,122,124].…”

“…A variety of animal models validated for conventional drugs trials are inappropriate for photodynamic experiments due to the complex interplay between many physicochemical, morphological and physiological factors such as vascularization and oxygenation of CRC as an heterogenous "organoid" in dynamic state, as well as bioavailability and pharmacokinetics of photosensitizer which acts rather as catalyst of intracellular processes contrary to conventional anticancer drugs interacting with specific cell and tissue receptors [89,122,124]. On the other hand, even in the case of conventional chemotherapeutics, the results of animal studies may not be replicated in the clinical domain, probably due to methodological biases and lack of uniform requirements for reporting animal data [88,127].…”

Photodynamic Therapy for Colorectal Cancer: An Update and a Look to the Future

“…A prerequisite for starting a clinical trial is evidence of a positive impact of the technique or drug on animals. The complexity of in vivo tumor microenvironments and the potential influence of factors such as blood flow, immune response, and tissue architecture require further studies to assess the full potential of PDT in the treatment of colon and rectal cancer [51,85]. The choice of animal model is therefore very important and should mimic the human situation as much as possible.…”

“…The choice of animal model is therefore very important and should mimic the human situation as much as possible. The most commonly studied animals are rats and mice [85,86]. The selection of an appropriate cell line is another crucial aspect.…”

“…The selection of an appropriate cell line is another crucial aspect. Many pharmacological studies use nude animals bearing humanderived tumors [85]. Nude animals, lacking a functional immune system, are commonly used to avoid immune rejection of human tumor cells.…”