C29-24 Alterations in Structure and Function of Pleural Lymphatic and Blood Vessels in Pleurodesis Mouse Models

Abstract Rationale To treat pleural diseases, such as pleural effusion, we often induce pleural adhesions by chemical pleurodesis. Representative chemical pleurodesis agents include OK-432, minocycline, and talc. Pleural effusion is drained through pleural lymphatic vessels (lymphatics) and produced through pleural capillaries. Lymphatic endothelial cells are connected by 2 types of intercellular junctions: discontinuous button-like junctions, which facilitate fluid uptake, and continuous zipper-like junctions, which impair absorption. However, the effects of pleurodesis agents on the morphology and function of pleural lymphatics and blood vessels remain unclear. This study aimed to investigate the effects of OK-432, minocycline, and talc on pathological changes in pleural vasculatures and lymphatic drainage function. Methods Each agent was intrapleurally injected into C57BL/6 mice 4 times over 2 weeks. Whole-mount chest wall immunofluorescence staining was performed using the lymphatic marker anti-LYVE-1, blood vessel marker anti-CD31, and lymphatic endothelial junction marker anti-VE-cadherin antibodies, followed by confocal microscopy observation. Evans blue dye was intrapleurally injected to evaluate lymphatic drainage function. Results OK-432 and minocycline mildly induced lymphangiogenesis and blood vessel remodeling, whereas talc massively induced lymphangiogenesis and blood vessel remodeling, confirmed by area densities of lymphatics and blood vessels. The drainage function is improved by the greater number of button-like junctions in the lymphatics and impaired by the greater number of zipper-like junctions. The number of button-like junctions was more abundant in the OK-432-treated group and was reduced in the minocycline- and talc-treated groups. The number of zipper-like junctions was decreased in the OK-432- and minocycline-treated groups but increased in the talc-treated group. These findings predicted that lymphatic drainage function would be maintained in the OK-432-treated group, whereas drainage function would deteriorate in the minocycline- and talc-treated groups. Indeed, OK-432 showed the better drainage function, followed by minocycline, and then talc, measured by evans blue. Conclusion Our results suggest that, in terms of pleural effusion absorption, OK-432 has advantage compared with minocycline and talc. Understanding these drug characteristics may be important for more effective pleural effusion control. This abstract is funded by: This research was supported by Japan Society for the Promotion of Science (JSPS) KAKENHI (24K02778, and 25K22899 to S.E.; 24K10581 to T.E.), Japan Agency for Medical Research and Development (25zf0127001h0005 to S.E.), Japan Science and Technology Agency (JST) Strategic International Collaborative Research Program (SICORP) (JPMJSC2308 to S.E.).