(622f) Identifying Primo Vascular System inside the Lymphatic Vessel Using Hollow Gold Nanoparticle

Primo Vascular System (PVS) is newly recognized vascular system in the mammalian body. It was first discovered by Bonghan Kim in early 1960s in North Korea. In 2010, the system is officially named as the PVS by the group led by Kwang-Sup Soh, in South Korea. The PVS consists of primo vessels (PVs), primo nodes (PNs), and fluid flowing inside. The major composition of the fluid is various biochemicals and cells related to immune functions and special type of stem cells. PVS is present in the entire mammalian body, including inside the blood and lymphatic systems, on the surface of internal organs, on the brain tissue and continued through the spinal canal, and under the skin. Recent reports confirmed Kim’s findings in 1960s on the role of the unique type of stem cells stored in the system performing the non-marrow based hematopoiesis and repairing damaged cells. These findings imply that the system is fundamental to maintaining mammalian lives. During cancer proliferation, the system also appears to have a role in the metastasis, and potentially storing cancer stem cells. The most important scientific claim on this system may be that it is to be the acupuncture meridian, although more studies are needed to done to confirm.

The PVS is very small (PV diameter, 20-50 mm; PN, 500-1500 mm) and translucent, highly challenging to identify it on/in the tissues with abundance of hemoglobin, which is a strong chromophore. Since biomarkers specific to the PVS is still not known, targeted contrast on its biomarker is still not possible. Harvesting a sufficient amount of PVS for further characterization has been, therefore, difficult. The Internal PVS subtype, one of the six PVS subtypes that Kim categorized, runs inside the blood and lymphatic vessels. Because these vessels are long, if it is successfully identified, the PVS harvested from them can potentially provide sufficient amount of samples. Out of two vessel types, the lymphatic vessel (LV) is a better candidate because its vessel wall is transparent and, with a help of a proper contrast agent, the PVS can be seen through its wall.

Over the years, several PVS scientists have attempted to develop techniques to identify PVS inside the LVs (intra lymphatic PVS; IL-PVS). The method currently used the most is using Alcian blue as the optical contrast agent, but this method is rather tedious in preparation and the repeatability is rather low even for the PVS experts. Our approach for developing a method for identifying the IL-PVS was utilizing the particular anatomical nature of the LV and IL-PVS within. The outer layer of a PV has pores in the size range of 2-5 mm, unlike blood or lymphatic vessels. Inside a PV, there are several sub-PVs and the interstitial space between the sub-PVs is filled with a polymer-like matrix. If nano-sized particles smaller than the PV pores but large enough to be trapped in the matrix are applied to the LV containing PVS, then the particles would be retained in the PVS and then generate the contrast by their colors.

Hollow gold nanospheres (HGNs) were found to be excellent for our purpose because of their variability in color and size, and good dispersity in bio-fluids. When a major LV is filled with the appropriately sized HGNs the spheres can get into the PVS inside the LV via the pores on its vessel wall. After a while the HNGs in the LVs are cleared by the natural flow of the lymphatic fluid and HGNs retaining PVS can be identified through the LV wall. The HGNs at a size range 50-125 nm, with a green to blue color range, allowed us to identify the PVS, within 15 minutes at a 95% success rate.

Currently, we are harvesting the PVS from the LVs for proteomics of PVS, as an effort to identify PVS specific protein biomarkers, which will be helpful for mapping the system in the body.