Effect of myenteric denervation on intestinal epithelium proliferation and migration of suckling and weanling rats

Abstract

The effects of myenteric denervation on the cell kinetics of the intestinal epithelium of suckling and weanling rats were investigated. The myenteric plexus of an ileal segment was partially ablated by serosal application of benzalkonium chloride (BAC) in three groups of rats: those that underwent surgery at 13 days and were killed 15 (13/28-day-old) or 23 (13/36-day-old) days after treatment, and those that were operated at 21 days (21/36-day-old) and were killed 15 days after treatment. The extent of denervation was assessed in whole-mount preparations. The cell bodies of myenteric neurones were stained by NADH-diaphorase histochemical technique. Cell proliferation was estimated by the mitotic index (MI) and morphometric analysis of villus and crypt lengths using an image analysis system. Thickness of the muscle layers was also assessed by morphometry. Cell migration on the villi was estimated by the position of the leading labelled cell 24 h after tritiated thymidine injection. The number of neurones was reduced by around 80% in rats operated at 13 days, and reduced by 98% in those operated at 21 days. The thickness of the muscle layers was increased in all groups of treated animals. MI was significantly higher 15 days after BAC-treatment in the 13/28 group. Morphological changes in the intestinal mucosa were observed 15 days after BAC-treatment, when there was an increase in villus height (13/28 group) and crypt depth (13/28 and 21/36 groups). Cell migration rate was accelerated in the 21/36 group. No differences where found in the 13/36 group. These results show the strong effect of myenteric ablation on cell proliferation and migration in the ileal epithelium in the first 15 days of treatment in suckling and in weanling rats, and the subsequent recovery of intestinal mucosa homeostasis later on.

Figure 1

Effect of BAC‐treatment on body weight (g). *P < 0.05 compared to control, using Student's t‐test for paired observations); n = number of animals.

Figure 2

Photomicrographs of whole‐mount preparations of the muscle layer of rat ileum stained by NADH‐diaphorase to detect myenteric neurones.(a) Control rat (13/36‐day‐old), note the sharp outline of the neuronal perikarya and the unstained nuclei (×900) and(b) BAC‐treated rat (13/36 group), an area with few perikarya (×900).

Figure 3

Mitotic index (%) of the ileum in saline and BAC‐treated rats; n = 5; *P < 0.05 compared to control, using Student's t‐test for paired observations.

Figure 4

Villus height (µm) and crypt depth (µm) of the ileum in saline and BAC‐treated rats. *P < 0.05 compared to control, using Student's t‐test for paired observations; n = 5 or 6 when indicated.

Figure 5

Photomicrographs of longitudinal sections of ileal crypts and muscle layers of (a) control rats (13/28‐day‐old) and (b) BAC‐treated rats (13/28 group). Enlarged crypts and muscle layers in treated rats. Arrows indicate limit between crypt and villi. haematoxylin and eosin, ×150.

Figure 6

Muscular layer thickness (µm) in the ileum in saline and BAC‐treated rats; n = 5. *P < 0.05 compared to control, using Student's t‐test for paired observations.