Induction of Lymphangiomas by Freund's Incomplete Adjuvant (FIA) in Fatty Acid Binding Protein (FABP)‐3, 5 and 7 Knock‐out Mice

Abstract

IntroductionIn an FIA‐induced benign lymphangioma model (Mancardi et al., 1999), we have suggested a sequential transformation from peritoneal mesothelial cells to functional lymphatic vessels via fat storing tumor cells after the FIA stimulation (EB2009 & 2015). However, the actual mechanism of the tumorigenesis and cellular involvement have yet to be established. FABPs are known to be involved in the promotion of cellular uptake and transport of fatty acids and the targeting of them to specific metabolic pathways. The aim of this study is, therefore, to investigate the possible involvement of FABPs during the FIA‐induced tumor development using FABP KO mice.Materials & MethodsLymphangiomas were induced in C57BL/6 (B6) mice and FABP3, 5 and 7 KO mice by an intraperitoneal injection of FIA (0.2 ml emulsion). For histological analyses, tissue cryosections were made and immunostained with various antibodies against FABP3, 4, 5, 7, and various lymphatic markers, such as podoplanin (PDPN), LYVE‐1 and LA102.Results & ConclusionsAfter FIA injection, peritoneal mesothelial cells became tall in height losing their polarity and gradually formed stratified cell masses on the peritoneal surface in B6 mice. The tumors became honeycomb‐like lymphangiomas consisted of ring‐like fat storing cells with various sizes. Some fat storing cells fused with each other and gradually formed either tubular structures like lymphatic vessels or huge follicles. These cells were strongly positive for PDPN, F4/80 and FABP5, but negative for FABP4. The follicular structures mainly consisted of FABP7+ cells. Interestingly, only the functional lymphatic vessel‐like structures expressed LYVE‐1 and LA102. In FABP‐KO mice, there was no significant difference in the incidence of tumors as compared with normal B6 mice. However, tumors developed more vigorously in FABP7 KO mice than other KO strains. Among FABP KO mice, relatively smaller fat storing cells were seen in FABP3 KO mice, whereas follicular type structures were more commonly found in FABP5 KO mice. In contrast, the tumors in FABP7 KO mice showed less fat storing cells with more inflammatory and fibrous components. In conclusion, a close relationship between the extrinsic FIA metabolism and the lymphatic system may be suggested in this tumor model, although the actual role and biological significance of each FABP in the tumorigenesis remain to be further clarified.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.