## 3 Results
### Cardiac LyV Density and Structural Remodeling
(**B**–**E,G**–**J**)—panels showing interstitial collagen deposits in Picrosirius-stained histological sections; (**B**), (**G**)—control; (**C,H**)—contr + Ang II; (**D,I**)—db/db; (**F,J**)—db/db + Ang II; scale bar—100 \(\mu\)m.  
Figure 8: Confocal microscopy images of cardiac LyVs in the control, Ang II-treated control, db/db, and Ang II-treated db/db mice. (**A–H**)—confocal microscopic images of myocardial sections stained with anti-LYVE (red), anti-CD31 (green), Alexa Fluor 388-conjugated WGA lectin (white), Hoechst 33,342 for nuclei (blue); (**A,E**)—control; (**B,F**)—control + Ang II; (**C,G**)—db/db; (**D,H**)—db/db + Ang II; (**A–D**)—pericornary LyVs; (**E–H**)—intramycardial LyVs; scale bar—50 μm; abnormally shaped LyVs in db/db mice (**C,G**, arrows), pericoronary LyVs are embedded in the enlarged/hypertrophied adventitial tissue of coronary arteries (**B,D** arrows); LyVs in intramycardial locations (**F**, white-edged arrows); pericoronary LyVs in Ang II-treated mice usually present open lumina (**D**, the white-edged arrow); number of tissue sections: 3–5 from each study group; scale bar—50 μm. Figure 7: Density of cardiac lymphatic vessels presented as the ratio between the number of LyVs and the number of cardiomyocytes within a given area of the myocardium. (**A**)—the LV, (**B**)—the RV, and (**C**)—the IVS. (**D,F**)—presented as the number of LyVs within various cardiac locations: subepicardial (**D**), pericoronary (**E**), and intramycardial (**F**) areas; pericoronary LyVs are calculated as the number of pericoronary LyVs to the number of all the cross-sectioned coronary arteries in a given tissue section (showed as percentage). The number of intramycardial LyVs decreased markedly in only the db/db and Ang II-treated db/db mice compared to the controls and to the Ang II-treated control mice. Statistics—\({}^{*}\)\(p\)\(<\) 0.05, \({}^{**}\)\(p\)\(<\) 0.02, \({}^{***}\)\(p\)\(<\) 0.001; number of samples = 3—tile scan sections from each study group. Moreover, collagen fibers were visible in the immediate vicinity of the flaps in the db/db mice and in both groups of Ang II-treated mice (Supplementary Figure S4B-D). These changes were accompanied by the altered distribution and structure of tufts with AnchFs that connect the LyV walls with the ECM. The AnchFs were shorter and formed abnormally oriented tufts in the Ang II-treated control and db/db mice compared to those visible in the control, and tufts were almost absent in the Ang II-treated db/db mice (Figure 11B-D, vs. Figure 11A). At the same time, there was also an increase in collagen deposits directly adjacent to the LyV walls in the experimental groups compared to the control, with the most dense masses of collagen in the Ang II-treated db/db mice (Figure 11D). The thickness of the BM surrounding the initial lymphatics was significantly increased in the db/db and Ang II-treated db/db mice compared to the control (Figure 10C). A significantly thicker BM surrounded the LyVs in the Ang II-treated db/db mice than in the Ang II-treated control mice (Figure 10C). Occasionally, the BM around the LyVs in the Ang II-treated db/db mice was multilayered (Figure 10D). Figure 9: Ultrastructure of myocardial initial LyVs. Details boxed in (panels **A–D**) are presented at higher magnifications in (panels **A’**–**D’). (**A**,**A’**)—control, (**B**,**B’**)—control + Ang II, (**C**,**C’**)—db/db, and (**D**,**D’**)—db/db + Ang II. LyV—lymphatic vessel lumina. Arrows in (**D’**) point to cytoplasmic protrusions extending into the LyV lumen. Scale bars: (**A–C**)—10 μm, (**D**)—5 μm, (**A’**–**D’**)—2 μm; number of samples from each study group = 6. In addition, transcellular transport, as assessed by the vesicular index, was significantly decreased in the db/db, Ang II-treated control, and Ang II-treated db/db mice compared to the control (Figure 10B), with the smallest number of cytoplasmic vesicles detected in the Ang II-treated db/db mice.