In vivo visualization of Bonghan ducts inside blood vessels of mice by using an Alcian blue staining method

An in vivo method using Alcian blue (AB) was developed for visualizing floating threadlike tissues inside blood vessels of mice. These novel structures called intravascular Bonghan ducts (IBHDs) are considered as extension of acupuncture meridians. For in vivo imaging of IBHDs, AB solution (pH 7.4) that stains mucopolysaccharides like hyaluronic acid was used. After injecting AB solution into the femoral vein of a mouse, the threadlike structures, stained deep blue, inside the inferior vena cava. The histological results, such as hematoxylin, eosin, and AB staining, show the compositions of the cells and the extracellular matrix in the IBHD. Further studies are needed to investigate their physiological functions, especially in relation with those of other circulatory systems.