Reduced number of epithelial tuft cells and density of LGR5 expression in the myenteric plexus of the ageing human colon.

BACKGROUND: Tuft cells are specialised chemosensory epithelial cells involved in mucosal immunity and epithelial homeostasis, while leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5) regulates Wnt signalling, essential for post-mitotic neuronal maintenance. However, within the human colon the impact of ageing on tuft cell abundance in the mucosa and LGR5 distribution in the ganglionic area remains poorly characterised. The aims of this study were to quantify tuft cell populations in the adult human colonic epithelium and assess LGR5 presence within the ganglionic area. METHODS: Colonic tissue samples were obtained from younger adults (Ascending colon: AC, n = 6, aged 30-52 years; Descending colon: DC, n = 10, aged 42-60 years) and older adults (AC: n = 12, aged 70-89 years; DC: n = 5, aged 67-82 years). Immunolabelling was performed on formalin-fixed, paraffin-embedded sections using antibodies against cyclooxygenase-1 (COX-1) to identify tuft cells within epithelial crypts and LGR5 presence within the myenteric ganglia. RESULTS: Tuft cells exhibited a characteristic flask-shaped morphology with intense apical COX-1 staining. Their numbers per crypt and also per mucosal area were higher in younger adults compared with older adults (respectively, mean numbers per mm2 mucosal area: AC, 109.7 ± 8.9 vs. 44.9 ± 2.1; DC, 103.2 ± 5.1 vs. 58.6 ± 3.7; P < 0.05 each), with a more pronounced decline in the AC. LGR5-positive structures were consistently observed within myenteric ganglia located between the circular and longitudinal muscle layers in both colonic regions. Compared with younger adults LGR5-positive structures within the ganglia was markedly reduced in the ageing AC (younger: 0.63 ± 0.07 ×10-3, older: 0.26 ± 0.03 ×10-3 per ganglionic area; P < 0.05) but not clearly in the DC (younger: 0.83 ± 0.05 ×10-3, older: 0.58 ± 0.05 ×10-3 per ganglionic area; P > 0.05). CONCLUSION: In both regions of human colon, ageing reduced tuft cell abundance in the mucosal epithelium. Ageing also reduced LGR5-IR structures within the ganglionic area in the AC. These structural changes may contribute to age-dependent impairments of neuromodulatory functions of the epithelium and the mechanisms for maintaining myenteric ganglion homeostasis.