Immunohistochemical localization of neuromarkers and neuropeptides in human fetal and neonatal urinary bladder.

Abstract

To use immunohistochemical techniques to determine the spatial and temporal distribution of a variety of neuropeptides in the human fetal and neonatal urinary bladder. Thirteen pre-natal specimens ranging in gestational age from 17 to 35 weeks were acquired following abortion or miscarriage. In addition two post-natal specimens aged 8 and 12 weeks were obtained at post-mortem and were included in this study. The overall innervation of each specimen was visualized using the general nerve marker protein gene product 9.5 (PGP). Localization of dopamine-beta-hydroxylase (DBH) and tyrosine hydroxylase (TH) revealed putative noradrenergic nerves. The neuropeptides studied included neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), substance P (SP), and calcitonin gene-related peptide (CGRP). At 17 weeks a rich plexus of PGP and NPY-containing nerves was present throughout the detrusor muscle coat. As gestational age increased, VIP, SP and CGRP-containing nerves were observed with increasing frequency although SP and CGRP were mainly confined to perivascular nerve plexuses. TH- and DBH-containing nerves were first observed in the intramural ureters at 30 weeks and the detrusor muscle at 35 weeks and were relatively numerous in the intramural ureters and muscle of the superficial trigone in the two post-natal specimens. PGP-containing nerves were first observed beneath the bladder epithelium at 23 weeks and gradually became more numerous with increasing age. Occasional NPY, VIP, SP and CGRP-containing nerves were observed in the submucosa but TH- and DBH-immunostained nerves were especially numerous in the mucosa of the trigone in the two post-natal specimens, many such nerves being unrelated to the vascular supply. The bladder detrusor possesses a rich autonomic innervation by 17 weeks of gestation and this presumptive cholinergic innervation is associated with NPY immunoreactivity. Presumptive noradrenergic nerves appear relatively late in pre-natal development and mainly supply the intramural ureters and superficial trigone. A submucosal plexus of nerves has been demonstrated, the functional significance of which remains uncertain.