Demonstration of neuronal networks in the human upper urinary tract using confocal laser scanning microscopy

To our knowledge innervation of the upper urinary tract and its role in motility and sensation are not clearly understood. The whole mount preparation technique provides 3-dimensional (D) morphology of the innervation and its relationship of branching and interconnecting nerve fibers to each other and to the neighboring tissues. Confocal laser scanning microscopy provides dramatic optical advantages for detecting 3-D structures in thick specimens. We investigated the distribution and morphology of the neuronal structures in the human upper urinary tract using the whole mount preparation technique and confocal laser scanning microscopy.

Whole mount preparations of the human renal pelvis and ureter were stained by standard immunohistochemical method using various neuronal markers (protein gene product 9.5, neuron specific enolase and neurofilament). The 3-D architecture of the specimens was investigated with the help of confocal laser scanning microscopy.

We detected 2 mesh-like neuronal networks or plexus in the human upper urinary tract. The first and more prominent plexus was located in the submucosa between the lamina propria and tunica muscularis, and the second neuronal network was found between the smooth muscle fibers of the ureteral wall. There were frequent interconnections between the 2 networks in the ureteral wall.

To our knowledge our study shows for the first time that there are 2 well formed mesh-like neuronal plexus in the human upper urinary tract. Our findings suggest that the autonomic nervous system of the human upper urinary tract may have a significant role in the propagation, coordination and modulation of ureteropelvic peristalsis.