P1B-14 Evaluation of Therapy Effect on Lymph Node Size with 24 MHz Ultrasound in Transgenic Mice

Currently, modifications of lymph node (LN) size in mice are evaluated using invasive characterization of LN cell- count and weight after dissection. This work evaluated the use of 24-MHz ultrasound to discriminate modifications of LN size in vivo. The sub-iliac LN are very small organs (long axis approximately two millimeters for adult C57BL/6 mice) situated about one millimeter beneath the skin. Receptor activator of nuclear factor kappa B (RANK) transgenic mice presenting enlarged LN were studied. An experimental peptide was used to block RANK signaling, and ultrasound at 24-MHz center frequency was used to scan the sub-iliac LN during treatment. In-house software was made to visualize the scan sequence, to select and to automatically estimate the area of the transverse plane with maximum cross-section. We investigated size variation of LN: 1) between wild type C57BL/6 (WT) and transgenic mice (Tg); 2) during therapy with cutaneous application of the peptide in WT mice and 3) during therapy with interperitonial (IP) administration of the same peptide in WT and Tg mice. Statistically significant changes between LN area in treated and control groups were observed for IP (p < 0.04) but not for cutaneous treatment groups. The LN modifications induced by therapy in this study were relatively subtle, implying that UBM could also be sufficiently sensitive to provide in vivo assessment of LN modifications due to lymphoma and anti-cancer treatments in mice.