To visualize capillary blood flow in animals, researchers have typically used fluorescent tracers that work as ‘chemical dyes’ in the blood plasma. While these molecules are popular as they don't induce an immunological response, they are limited in use as their signal intensity reduces within an hour of administration. This means additional injectoions are required for longer experiments, which may instigate unwanted stress among animals and increase the risk of an immune response.
To overcome these challenges, researchers developed a new tracking method involving fluorescent proteins. This new method enabled blood plasma to remain fluorescent- and hence trackable- for several months.
To create the fluorescent proteins, the researchers injected mice with a virus containing a fluorescent protein gene. Once in the body, the gene interacted with albumin, making it fluorescent. Hajime Hirase, professor at the Center for Translational Neuromedicine at the University of Copenhagen, said:
“Half of the blood is blood cells and the rest is fluid called plasma. My graduate students Xiaowen Wang and Christine Delle calculated that if we label a few percent of albumin, we should be able to see green fluorescent blood by microscopy.”
The researchers noted that their approach addresses two of the'‘3 R’s’ of ethical use of animals in research. While they are not able to replace animals with other methods, their new approach allows them to refine their testing of animals by eliminating stress from multiple injections. It also allows them to reduce the number of animals needed in research as the same animals could be studied for longer.
The researchers conclude that their novel genetic plasma labeling approach is both a versatile and cost-effective method for investigating vasculature conditions in the body as well as health and disease in animal models. They hope that their findings may faciliate research into conditions such as stroke to enable understanding and possible treatments.
Sources: Science Daily, Cell Reports Methods
