Fig. 3.

(a) Representative magnetic resonance whole-body images from a control (injected with PBS) and treated (injected with either ^GWT or ^GKO microcapsules into visceral fat depot) mice were obtained using 9.4 T MRI scanner. Dark elliptical structures with long T1 relaxation time were identified as microcapsules (C, orange) when the signal to noise ratio (SNR) ratio was lower than in adipose (fat) and muscle tissues (M), indicating low proton density of microcapsules’ interior (b). Insert shows 3D MR image reconstruction of identified microcapsules (C, blue) interspersed within visceral (vis), but not subcutaneous fat. Adipose and muscle tissues are shown in yellow and red, respectively (see 3D image in Suppl. video). (c) Representative sections of visceral fat isolated from control and injected with ^GWT and ^GKO capsule mice. Visceral fat was dissected 80 days after injection. Paraffin embedded sections were stained with hematoxylin&eosin (H&E) to visualize all cells in the adipose tissue. In the same slide GFP-labeling indicates implanted microcapsules (C), containing green encapsulated cells (CC), but not host adipocytes (A). The larger, 40×, magnification shows multiple engineered cells (CC) on the border of a capsule. Due to the fact that GFP-positive cells were equally spread and adherent to the inner side of APL polymer shell (invincible), the microcapsules were observed as circular fluorescent structures in the fluorescence images. Pink eosin staining indicated a protein matrix within the microcapsules that was not present in vitro (Fig. 2c). Lower, 10× magnification shows the whole capsule within the capsule’s cluster. Host adipocytes were smaller in size than the microcapsules (‘A’ vs. ‘C’).