Abstract 2532: Utilization of longitudinal ultrasound imaging as a novel pharmacodynamic marker of graft versus host disease progression in mice

Abstract Graft versus host disease (GvHD) is a potentially life-threatening condition that occurs most commonly after allogeneic transplantation of bone marrow or stem cells, and less frequently after organ/tissue transplantation. GvHD can present as an acute disease, or it can develop more slowly, resulting in a chronic condition affecting multiple tissues and organs. Allogeneic (acute and chronic) and xenogeneic GvHD models have been developed in mice that aim to replicate some of the clinical manifestations seen in human disease. However, endpoints such as GvHD scoring which are commonly used to track disease progression are subjective and difficult to replicate consistently. In addition, terminal sampling as well as longitudinal blood sampling for biomarker analysis often requires the use of satellite groups which is costly and at odds with the principles of 3R animal usage. To overcome these challenges, we describe the novel use of a Vega ultrasound imaging system (Revvity, Waltham, MA, USA), to monitor longitudinal changes in splenic volume, a well-known biomarker associated with GvHD and other diseases. To determine the feasibility of this workflow, a two-phase pilot study was conducted. The first phase of the pilot study utilized N=15 mice split into 3 groups of 5 mice each. Group 1 mice were controls while groups 2-3 were affected by chronic GvHD. Each mouse was imaged with 3-D high-frequency B-mode ultrasound using the Vega on day 100, 106, and 114 post transfer of splenocytes and bone marrow cells into irradiated recipient mice. Spleens were manually segmented from each image to measure spleen volume. The second phase of the pilot study was focused on tracking changes in an acute model of GvHD. For this phase, N=8 mice were split into 4 groups of 2 mice each. Group 1 were controls, while groups 2-4 received 3e6 to 5e6 dose of splenocytes and 1e7 bone marrow cells. Mice were imaged on day 10, 21, and 31 using the Vega, and spleen volumes were again determined via manual segmentation. In the chronic model, spleen volumes in affected animals were significantly reduced (37.9 ± 11.5 mm3) compared to control animals (84.8 ± 15.3 mm3). In the acute model, we observed an initial phase of splenomegaly followed by a drastic shrinkage of the spleens to roughly 50% of the control volumes. In summary, this study suggests the use of 3D non-invasive ultrasound imaging for assessing organ size and structure differences in GvHD model that will facilitate the discovery of new therapies. Citation Format: Bincy John, Thomas Kierski, Tomek Czernuszewicz, Fei Zhao, Daniele Repetto, Jessica Neil, David Harris. Utilization of longitudinal ultrasound imaging as a novel pharmacodynamic marker of graft versus host disease progression in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2532.