Figure 1.

IGMs and their characterization in CX3CR1^GFPmouse colon. Double immunolabeling of semithin sections with agrin and GFP was performed on distal (A) and proximal (B) colon sections of adult CX3CR1^GFP mice. GFP+ IGMs (red) are present inside the agrin+ basement membrane of the enteric ganglia (brown). Immunofluorescent staining with agrin (ganglionic basement membrane), Hu (enteric neurons), and GFP (macrophages) shows spatially distinct populations of MMs, with IGMs labeled with arrowheads and MyMs in the PGS with arrows (C). GFP+ IGM in physical contact with an enteric neuron (D, arrowhead). Agrin and Col4 immunolabeling shows the ECM capsule surrounding the enteric ganglia (E). The periganglionic space (E, asterisks) is present between the Col4-expressing smooth muscle basement membrane and the Col4+/agrin+ expressing ganglionic basement membrane. Super-resolution imaging of IGMs and the PGS shows a MyM penetrating the ganglionic basement membrane (G, dotted line) and entering the enteric ganglion (F and G, arrowheads). The smooth muscle basement membrane again shows expression of Col4, but not agrin (G, dashed line). cm, circular muscle layer; lm, longitudinal muscle layer.