**4. Barriers and Sensory Web of the Bladder Mucosa and Submucosa**

The bladder wall has four layers: Mucosa, submucosa (lamina propria and muscularis mucosae), detrusor muscle, and serous layer (tunica serosa) [12]. The transitional urothelium extends from the renal pelvis to the ureter and inner bladder wall. The urothelial apical surface lines a sulfated polysaccharide glycosaminoglycan layer, which acts as a non-specific anti-adherence factor and as a defense mechanism against infection. The urothelium is composed of three layers: A basal cell layer, an intermediate layer, and a superficial layer containing polarized umbrella cells (diameters of 25–250 μm). The uroplakin membrane and tight junction complexes of the umbrella cell layer play important roles in the barrier function of the urothelium. The apical uroplakin membrane may reduce the permeability of the cells to small molecules (e.g., water, urea, and protons). The tight junction complexes can reduce the movement of ions and solutes between cells and specialized lipid molecules. The intermediate spindle cells, found beneath the umbrella layer, have up to five strata, and they can rapidly differentiate into umbrella cells when the barrier is disrupted. The single-layer mononuclear basal cells adhere to the intermediate cells and to the basement membrane. The suburothelial layer consists of interstitial cells, myofibroblasts, blood vessels, and afferent sensory nerve endings at the lamina propria beneath the basal membrane.

In addition to the barrier function, the mucosa layer serves as a sensory web, which comprises the urothelium and sensory afferent and efferent nerves linked by gap junctions, which amplify and transmit the signals among the mucosa, nervous, and muscular systems [3,12]. The unmyelinated C-fiber endings are widespread in the urothelium and lamina propria. Parasympathetic nerve cells and intramural ganglion cells are also embedded among the lamina propria. The schematic diagram of the bladder mucosa and submucosa are illustrated in Figure 2.

**Figure 2.** Schematic diagram of barriers and sensory web of the bladder mucosa. Impermissible bladder barrier consists of the glycosaminoglycan (GAG) layer, uroplakins, and tight junction. The sensory web was innervated by neuron-like urothelium.

#### **5. Intravesical Delivery of onaBoNTA**
