Temporal Change of Alcian Blue-Stained Primo Vascular System in Lymph Vessels of Rats.

This study aims to investigate the temporal change of a vascular system now known as the primo vascular system (PVS). We used Alcian blue (AB) dye for imaging the distribution of the PVS in lymphatic vessels. The target lymph vessels were chosen as they are easily accessible from the skin, and long-term observation is possible with intact physiological conditions due to a minimal surgical procedure. AB solution was injected into the inguinal lymph node and the target lymph vessels were located along the superficial epigastric vessels. The imaging system allowed processing for extraction of images showing changes in the AB intensity of the visualized PVS components. This newly developed procedure can be used for further study on various dynamic processes of PVS in lymph vessels.

Visualization of the primo vascular system afloat in a lymph duct.

Because of the potential roles of the primo vascular system (PVS) in cancer metastasis, immune function, and regeneration, understanding the molecular biology of the PVS is desirable. The current state of PVS research is comparable to that of lymph research prior to the advent of Lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1). There is very little knowledge of the molecular biology of the PVS due to difficulties in identifying and isolating primo endothelial cells. Present investigations rely on the morphology and the use of differential staining procedures to identify the PVS within tissues, making detailed molecular studies all but impossible. To overcome such difficulties, one may emulate the explosive development of lymph molecular biology. For this purpose, there is a need for a reliable method to obtain PVS specimens to initiate the molecular investigation. One of the most reliable methods is to detect the primo vessels and primo nodes afloat in the lymph flow. The protocols for observation of the PVS in the large lymph ducts in the abdominal cavity and the thoracic cavity were reported earlier. These methods require a laparectomy and skillful techniques. In this work, we present a protocol to identify and harvest PVS specimens from the lymph ducts connecting the inguinal and the axillary nodes, which are located entirely in the skin. Thus, the PVS specimen is more easily obtainable. This method is a stepping-stone toward development of a system to monitor migration of cancer cells in metastasis from a breast tumor to the axillary nodes, where cancer cells use the PVS as a survival rope in hostile lymph flow.