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

Abstract

The CD44 gene encodes several protein isoforms due to alternative splicing and post translational modifications. Given that CD44 variant isoform 9 (CD44v9) is expressed within Spasmolytic Polypeptide/TFF2-Expressing Metaplasia (SPEM) glands during repair, CD44v9 may be play a functional role during the process of regeneration of the gastric epithelium. Here we hypothesize that CD44v9 marks a regenerative cell lineage responsive to infiltrating macrophages during regeneration of the gastric epithelium. Ulcers were induced in CD44-decient (CD44KO) and C57BL/6 (BL6) mice by a localized application of acetic acid to the serosal surface of the stomach. Gastric organoids expressing CD44v9 were derived from mouse stomachs and transplanted at the ulcer site of CD44KO mice. Ulcers, CD44v9 expression, proliferation and histology were measured 1, 3, 5 and 7-days post-injury. Human-derived gastric organoids were generated from stomach tissue collected from elderly (>55 years) or young (14–20 years) patients. Organoids were transplanted into the stomachs of NOD scid gamma (NSG) mice at the site of injury. Gastric injury was induced in NRG-SGM3 (NRGS) mice harboring human-derived immune cells (hnNRGS) and the immune profile analyzed by CyTOF. CD44v9 expression emerged within regenerating glands the ulcer margin in response to injury. While ulcers in BL6 mice healed within 7-days post-injury, CD44KO mice exhibited loss of repair and epithelial regeneration. Ulcer healing was promoted in CD44KO mice by transplanted CD55v9-expressing gastric organoids. NSG mice exhibited loss of CD44v9 expression and gastric repair. Transplantation of human-derived gastric organoids from young, but not aged stomachs promoted repair in NSG mouse stomachs in response to injury. Finally, compared to NRGS mice, huNRGS animals exhibited reduced ulcer sizes, an infiltration of human CD162+ macrophages and an emergence of CD44v9 expression in SPEM. Thus, during repair of the gastric epithelium CD44v9 emerges within a regenerative cell lineage t hat coincides with macrophage infiltration within the injured mucosa.

Pyloric metaplasia, pseudopyloric metaplasia, ulcer‐associated cell lineage and spasmolytic polypeptide‐expressing metaplasia: reparative lineages in the gastrointestinal mucosa

“…While SPEM and pseudopyloric metaplasia can be identified by pink rather than carmine diastase-resistant-PAS histological staining [38], one cannot determine the molecular nature of the lineage as reparative versus pre-neoplastic based on histological staining alone. SPEM arises in the setting of acute injury or ulceration [32,[39][40][41]. The observation of SPEM emerging rapidly after acute parietal cell loss induced by DMP777, L635 or high-dose tamoxifen is consistent with this lineage performing a role in the response to injury [41][42][43].…”

“…SPEM arises in the setting of acute injury or ulceration [32,39–41]. The observation of SPEM emerging rapidly after acute parietal cell loss induced by DMP777, L635 or high dose tamoxifen is consistent with this lineage performing a role in the response to injury [41–43].…”

“…SPEM appears to resolve following resolution of injury and can often appear as a highly localized phenomenon [29,41,43]. Thus, acute ulceration injury in the stomach is associated with the appearance of SPEM around ulcers and SPEM contributes to the healing of these lesions [32,39,44]. As was noted decades ago for healing duodenal ulcers, local areas of gastric injury lead to the evolution of a pyloric type metaplasia, SPEM, that resolves after healing.…”

“…Since its initial description, the SPEM lineage has been further characterized as a diastase PAS-positive lineage that expresses TFF2 and Muc6 as well GSII-lectin binding, similar to the mucinous secreting cells of the deep antral gland [30]. This lineage also expresses a number of other antral lineage markers including CD44 variant 9 (CD44v9) and clusterin [31][32][33]. One marker that is present uniquely in SPEM, but not in the antrum, is the protease inhibitor HE4 (WFDC2) [34,35].…”

Endogenous glucocorticoids prevent gastric metaplasia by suppressing spontaneous inflammation

“…Loss of parietal cells, downregulation of the mature chief cell marker MIST1, and renewed proliferation of post-mitotic cells localized at the base of the gastric glands are hallmarks of SPEM (19). To examine the effects of adrenalectomy on SPEM development we performed immunostaining for the de novo SPEM marker genes CD44 variant 9 (CD44v9) and SOX9 (22)(23)(24). CD44v9 was not detectable in the gastric corpus of control animals, but was robustly induced and colocalized with GSII 2 months after adrenalectomy ( Figure 2B).…”