A Murine Tail Lymphedema Model

Lymphedema is a chronic condition with no cure. It affects one third of patients who have had an axillary lymph node surgery and radiation in the treatment of breast cancer. Having a valid animal model facilitates understanding the mechanism and development of novel treatment strategies.

The mouse tail model of lymphedema is reliable and reproducible with the rapid onset. It exhibits histological changes consistent with human lymphedema. Demonstrating the procedure will be Dr.Ganesh Mohan, a post-doctorate from my laboratory.

To begin, position the eight week old sedated mouse sternally and prep the tail with 70%isopropyl alcohol. Use a caliper to measure the tail diameter at five millimeter increments starting 20 millimeters from the base of the tail. Mark a three millimeter circumferential excision on the tail 20 millimeters from the base.

Under surgical microscopic magnification, perform a meticulous three millimeter full thickness skin excision leaving all the underlying vasculature intact. Incise the superior circumferential mark first through the dermis followed by a circumferential full thickness incision three millimeters distal to the first incision. Make a perpendicular full thickness vertical incision to connect the two incisions, then use a toothed fine pickup to grasp a leading edge and dissect deep within the avascular plane to the dermis and superficial to the vein adventitia with micro scissors.

Inject 0.1 milliliter of 1%isosulfan blue subcutaneously proximal to the tip of the tail. Identify the two lymphatic channels appearing blue due to the injection adjacent to the lateral tail veins. Transect the lymphatics carefully, dissecting a plane between the lateral vein and the lymphatic with straight microsurgical scissors.

Pass the tip of one scissor blade between the lymphatic vessel and the lateral vein and close the blades to transect the lymphatic vessel. When finished, dress the tail wound with a sterile adherent clear addressing. Administer indocyanine green 0.1 milliliter subcutaneously into the distal mouse tail near the tip.

Dim the room lights then place near infrared laser angiography in buffering setting and perform live imaging. After administration of isosulfan blue into the tail tip, the lymphatics exhibited blue color. The lymphatics were disrupted while adjacent lateral veins were preserved.

The progressive swelling and sustained persistent lymphedema in the mouse tail after lymphedema induction is shown here. The mouse tail volume as calculated by a truncated cone equation, peaked at week four and plateaued to week six followed by gradual improvement that was sustained until week 15. High-resolution laser speckle contrast imaging was done to confirm mouse tail perfusion in the lymphedema tail model showing injured lateral veins and intact lateral veins for assessment of tail vasculature patency.

Near infrared laser lymphangiography demonstrated preoperative intact lymphatics and no ICG transit beyond surgical site post-operatively, thereby confirming that swelling was caused by lymphatic disfunction. The efficiency of genetic cargo delivery using tissue nanotransfection technology was demonstrated by delivering fluorescein amidite labeled DNA to the murine tail. Using adaptations for the mouse tail lymphedema model and ICG near infrared laser angiography is a clinically translatable and exciting animal model with treatment implications.