Validation of Indocyanine Green-Methylene Blue Dye in the Lymphedema Rat Tail Model.

Background/

Objectives

Lymphedema is characterized by edema; in severe cases, skin changes and ulceration significantly impair patients' quality of life. Although several experimental rodent models for lymphedema have been established, a reproducible and practical model remains essential for evaluating new therapeutic and imaging agents. This study aimed to establish a lymphedema animal model and to evaluate the efficacy of a newly synthesized dual-mode imaging reagent as a potential alternative to indocyanine green (ICG).

Methods

Eleven Sprague-Dawley rats were classified into two groups. Full-thickness skin excision was performed on the tails of nine rats to induce lymphedema; two rats served as controls. Five rats received ICG injections for 1 week postoperatively, while the remaining six rats were administered tail injections of chemically synthesized indocyanine green-methylene blue (ICG-MB) reagent. Lymphatic flow was photographed using a SPY camera. After euthanasia, tail segments were analyzed by microcomputed tomography (micro-CT) to measure volume and by hematoxylin-eosin staining for histological evaluation.

Results

On postoperative day 7, lymphatic flow was confirmed in the ICG-MB group using the SPY Elite® fluorescence imaging system. On micro-CT scans, the preoperative rat tail volume was 3992.72 ± 144.80 mm3. Rat tail volume was 5216.71 ± 1131.88 and 4614.76 ± 468.29 mm3, respectively, at 1 and 2 weeks after lymphedema was induced. Histology revealed lymphocyte infiltration, inflammatory reaction, and thickened subcutaneous adipose tissue, with no significant difference between groups.

Conclusions

The rat tail lymphedema model proved valuable for studying lymphedema pathology and diagnostic agents. The ICG-MB reagents demonstrate stable performance and favorable biocompatibility.