Figure 2.

Ultrastructure of fibroblasts in the bladder wall as revealed by transmission electron microscopy. A: cross section through the suburothelial (SU) region showing the layered nature of fibroblasts under the urothelium (Ut) and their numerous cell extensions (CE) and protrusions. A portion of a blood vessel (BV) is found at the right. Surrounding the cells and their extensions is a collagen-rich matrix (light gray material). The dashed boxed regions are magnified in B and E. In all images, the nuclei of presumptive fibroblasts are marked with red circles. B: suburothelial fibroblast with prominent rough endoplasmic reticulum (RER) in its cytoplasm. The nucleolus (Nucl) of a fibroblast nucleus is marked. Bundles of collagen (Col) are found in the matrix. The dashed boxed region is magnified in the inset. C: suburothelial fibroblast with readily discernable Golgi (Go). The cell is surrounded by collagen fibrils. D: cell-cell adhesion complex between two fibroblasts (false colored red or green). The dashed boxed region is magnified in the inset. The site of cell-cell adhesion, including cytoplasmic densities on either side, is indicated by the arrow. Collagen surrounds the cells. E: close proximity of fibroblast extensions to a nerve fascicle (NF) composed of nonmyelinated axons and surrounded by collagen. F: fibroblast in the outer lamina propria (OLP) near the border of smooth muscle cells (SMC). The dashed boxed region is magnified in the inset. G: fibroblast in the intermuscular region (IM) between adjacent smooth muscle cells, surrounded by collagen, and near an unmyelinated nerve fascicle (NF). H: serosal (Se) fibroblast within the thin collagen matrix between smooth muscle cells and mesothelial cells (MC), which form the mesothelium. A free axon (Ax) is present. Images are representative of experiments performed in three mice.