A Hyaluronic Acid-Rich Node and Duct System in Which Pluripotent Adult Stem Cells Circulate

Regenerative medicine is in demand of adult pluripotent stem cells (PSCs). The "Bonghan System (BHS)" was discovered and suggested to contain cells with regenerative capacity in the early 1960s. It had been ignored for a long time due to the lack of sufficient details of experiments, but about 37 years after the initial report, the BHS was rediscovered and named as the "primo vascular system." Recently, we have discovered a similar structure, which contained a high level of hyaluronic acid, and hence, named the structure as hyaluronic acid-rich node and duct system (HAR-NDS). Here we discuss the HAR-NDS concept starting from the discovery of BHS, and findings pointing to its importance in regenerative medicine. This HAR-NDS contained adult PSCs, called node and duct stem cells (NDSCs), which appeared to circulate in it. We describe the evidence that NDSCs can differentiate into hemangioblasts that further produced differentiated blood cells. The NDSCs had a potential to differentiate into neuronal cells and hepatocytes; thus, NDSCs had a capability to become cells from all three germ layers. This system appears to be a promising alternative source of adult stem cells that can be easily delivered to their target tissues and participate in tissue regeneration.