Wnt-induced, TRP53-mediated Cell Cycle Arrest of Precursors Underlies Interstitial Cell of Cajal Depletion During Aging.

Background & Aims: Gastric dysfunction in the elderly may cause reduced food intake, frailty, and increased mortality. The pacemaker and neuromodulator cells interstitial cells of Cajal (ICC) decline with age in humans, and their loss contributes to gastric dysfunction in progeric klotho mice hypomorphic for the anti-aging Klotho protein. The mechanisms of ICC depletion remain unclear. Klotho attenuates Wnt (wingless-type MMTV integration site) signaling. Here, we examined whether unopposed Wnt signaling could underlie aging-associated ICC loss by up-regulating transformation related protein TRP53 in ICC stem cells (ICC-SC).
Methods: Mice aged 1-107 weeks, klotho mice, APC ^Δ468 mice with overactive Wnt signaling, mouse ICC-SC, and human gastric smooth muscles were studied by RNA sequencing, reverse transcription-polymerase chain reaction, immunoblots, immunofluorescence, histochemistry, flow cytometry, and methyltetrazolium, ethynyl/bromodeoxyuridine incorporation, and ex-vivo gastric compliance assays. Cells were manipulated pharmacologically and by gene overexpression and RNA interference.
Results: The klotho and aged mice showed similar ICC loss and impaired gastric compliance. ICC-SC decline preceded ICC depletion. Canonical Wnt signaling and TRP53 increased in gastric muscles of klotho and aged mice and middle-aged humans. Overstimulated canonical Wnt signaling increased DNA damage response and TRP53 and reduced ICC-SC self-renewal and gastric ICC. TRP53 induction persistently inhibited G ₁ /S and G ₂ /M cell cycle phase transitions without activating apoptosis, autophagy, cellular quiescence, or canonical markers/mediators of senescence. G ₁ /S block reflected increased cyclin-dependent kinase inhibitor 1B and reduced cyclin D1 from reduced extracellular signal-regulated kinase activity.
Conclusions: Increased Wnt signaling causes age-related ICC loss by up-regulating TRP53, which induces persistent ICC-SC cell cycle arrest without up-regulating canonical senescence markers.
(Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)