Age-related changes in the myenteric plexus of the porcine bowel

Myenteric plexus (MP) is well recognized as an important regulator of peristaltic activity. Knowledge regarding prenatal and postnatal normal morphological changes is important when interpreting histopathologic findings in motility disorders of childhood. The aim of this study was to determine the neuronal density and morphology of the myenteric plexus (MP) of the porcine bowel from fetal life to adulthood.

Small and large bowel whole-mount preparations of the MP were stained using NADPH diaphorase histochemistry in animals from 6 different age groups (60 and 90 days of gestation, newborn, 4-week and 12-week-old, and adult pigs). Using light microscopy, above parameters was quantified, and cell/nucleus sizes were measured. Results were analyzed using 1-way analysis of variance test.

There were significant regional and age-related differences in cell numbers per ganglia noted in MP throughout the lifetime of a pig. There was an abrupt increase in cell numbers per ganglia from the newborn to 4-week-old animals, which then stabilized in most parts of the bowel, except in the distal large bowel, where it continued to increase. Ganglion density and ganglia cell density both decreased steadily with advancing age. Cell size increased with age, mostly secondary to increase in the cytoplasm.

Our results show that significant changes occur in the MP in relation to age and the region of the bowel. These changes are most evident in the immediate period after birth but continue throughout life. Such age-related changes must be taken into account during morphological evaluation of biopsy specimens taken from infants who had constipation.