Figure 6.

Modular mix‐and‐match toolbox to build fit‐for‐purpose autologous WAT‐on‐chip models. a) To create WAT‐on‐chip models specifically tailored to certain scientific questions, the authors propose a spectrum of on‐chip culture conditions with varying degrees of complexity ranging from simple adipocyte‐only systems (A) to highly complex full WAT‐on‐chip models (ASE). b) Structural characterization of the full WAT‐on‐chip model (ASE) on d12. Anti‐CD31 immunofluorescence staining showed a tight endothelial barrier on the chip's membrane. To visualize the membrane area over the adipocyte‐filled tissue chambers, the chip had to be inverted (i). Adipocytes are displayed by staining their lipid droplets. To uncover stromovascular cells, SVF is labeled with a cell tracker prior to injection into the chip. SVF is 3D distributed among the adipocytes in the tissue chamber (adipocytes not shown for better visibility of SVF) (ii; orthogonal view). Moreover, a tracking of SVF motion within the first 6 h after injection revealed dynamic migration for some of the labeled cells while others remained stationary (ii; Video S1, Supporting Information). Scale bars equal 200 µm (one‐chamber view) and 100 µm (zoomed‐in orthogonal view and video). c) Monitoring of FA trafficking properties for A, AS, and AE systems uncovered noticeable differences in FA uptake comparing A and AS to AE. Representative images of A and AE conditions at time points 0, 10.5, 38.5, and 52.5 min. d) Comparison of adipokine release by different co‐/multi‐culture WAT‐on‐chips from the same patient, measured from media effluents collected for 24 h from d10 to d11 of on‐chip culture. Even though the analyzed adipokines are exclusively produced by adipocytes, there are considerable differences in their release regarding the models’ cellular composition. e) Identification of on‐chip ATMs by visualizing CD11c and Trem2 (i), CD86 and CD45 (ii), and CD206 and CD45 (iii) expression. ATMs are positive for the investigated markers and clustered to, sometimes even enwrapping, mature adipocytes. Moreover, intracellular lipid droplets in CD86⁺‐cells might be an indicator of lipid scavenging activity. Z‐stack imaging data are also represented as supplemental videos (Videos S2–S4, Supporting Information) to ensure full elucidation of all events in one stack. Scale bars equal 50 µm.