CD44 variant isoform 9 emerges in response to injury and contributes to the regeneration of the gastric epithelium

Cluster-of-differentiation gene 44, in particular CD44 variant isoform 9 (CD44v9), emerges during regeneration of the gastric epithelium in response to injury. In particular, CD44v9 is expressed within Spasmolytic Polypeptide/TFF2-Expressing Metaplasia (SPEM) glands during gastric repair, but the function is unknown. Here we tested the hypothesis that age dependent expression of CD44v9 marks a regenerative cell lineage responsive to infiltrating macrophages during regeneration of the gastric epithelium. Acetic acid injury was induced in CD44-deficient (CD44KO) and C57BL/6 (BL6) mice. Mouse-derived gastric organoids expressing CD44v9 were transplanted at the ulcer site of CD44KO mice. Ulcers, CD44v9 expression, proliferation and histology were measured at days 1, 3, 5 and 7 post-injury. Human-derived gastric organoids from elderly patients (>55 years) or young patients (14–20 years) were generated and transplanted into the stomachs of NOD scid gamma (NSG) mice post-injury. Ulcers were induced in NRG-SGM3 (NRGS) mice harboring human-derived immune cells (huNRGS) and the immune phenotype was analyzed by CyTOF. CD44v9 expression emerged at the ulcer margin during gastric ulcer repair. Compared to BL6 mice that healed ulcers within 7 days post-injury, CD44KO mice exhibited loss of ulcer repair and gastric epithelial regeneration. CD44v9-expressing gastric organoids transplanted into the stomachs of CD44KO mice promoted ulcer repair. Compared to NSG mice exhibiting loss of CD44v9 expression and gastric repair in response to injury, transplantation of human-derived gastric organoids from young, but not aged stomachs promoted repair. Finally, compared to NRGS mice, huNRGS animals exhibited smaller ulcer sizes and an infiltration of human CD163+ macrophages that correlated with an emergence of CD44v9 expression in SPEM. Thus, CD44v9 marks a regenerative cell lineage, and macrophages infiltrating the injured gastric mucosa are associated with the emergence of CD44v9 in epithelial cells during regeneration.