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The plasticity of gastric chief cells is exemplified by their ability to transdifferentiate into spasmolytic polypeptide-expressing metaplasia (SPEM) after parietal cell loss. We sought to determine if chief cell maturity is a limiting factor in the capacity to transdifferentiate. Mist1 - /- mice, previously shown to form only immature chief cells, were treated with DMP-777 or L635 to study the capability of these immature chief cells to transdifferentiate into a proliferative metaplastic lineage after acute parietal cell loss. Mist1 -/- mice treated with DMP-777 showed fewer chief cell to SPEM transitions. Mist1 -/- mice treated with L635 demonstrated significantly fewer proliferative SPEM cells compared with control mice. Thus immature chief cells were unable to transdifferentiate efficiently into SPEM after acute parietal cell loss. To determine whether chief cell age affects transdifferentiation into SPEM, we used tamoxifen to induce YFP expression in chief cells of Mist1 CreER/+ ;Rosa YFP mice and subsequently treated the cells with L635 to induce SPEM at 1 to 3.5 mo after tamoxifen treatment. After L635 treatment to induce acute parietal cell loss, 43% of all YFP-positive cells at 1 mo posttamoxifen were SPEM cells, of which 44% of these YFP-positive SPEM cells were proliferative. By 2 mo after tamoxifen induction, only 24% of marked SPEM cells were proliferating. However, by 3.5 mo after tamoxifen induction, only 12% of marked chief cells transdifferentiated into SPEM and none were proliferative. Thus, as chief cells age, they lose their ability to transdifferentiate into SPEM and proliferate. Therefore, both functional maturation and age limit chief cell plasticity., New & Noteworthy: Previous investigations have indicated that spasmolytic polypeptide-expressing metaplasia (SPEM) in the stomach arises from transdifferentiation of chief cells. Nevertheless, the intrinsic properties of chief cells that influence transdifferentiation have been largely unknown. We now report that the ability to transdifferentiate into SPEM is impaired in chief cells that lack full functional maturation, and as chief cells age, they lose their ability to transdifferentiate. Thus chief cell plasticity is dependent on both cell age and maturation.

Oxyntic atrophy in the stomach leads to chief cell transdifferentiation into spasmolytic polypeptide expressing metaplasia (SPEM). Investigations of preneoplastic metaplasias in the stomach are limited by the sole reliance on in vivo mouse models, owing to the lack of in vitro models for distinct normal mucosal lineages and metaplasias. Utilizing the Immortomouse, in vitro cell models of chief cells and SPEM were developed to study the characteristics of normal chief cells and metaplasia. Chief cells and SPEM cells isolated from Immortomice were cultured and characterized at both the permissive (33°C) and the nonpermissive temperature (39°C). Clones were selected on the basis of their transcriptional expression of specific stomach lineage markers (named ImChief and ImSPEM) and protein expression and growth were analyzed. The transcriptional expression profiles of ImChief and ImSPEM cells were compared further by using gene microarrays. ImChief cells transcriptionally express most chief cell markers and contain pepsinogen C and RAB3D-immunostaining vesicles. ImSPEM cells express the SPEM markers TFF2 and HE4 and constitutively secrete HE4. Whereas ImChief cells cease proliferation at the nonpermissive temperature, ImSPEM cells continue to proliferate at 39°C. Gene expression profiling of ImChief and ImSPEM revealed myelin and lymphocyte protein 2 (MAL2) as a novel marker of SPEM lineages. Our results indicate that the expression and proliferation profiles of the novel ImChief and ImSPEM cell lines resemble in vivo chief and SPEM cell lineages. These cell culture lines provide the first in vitro systems for studying the molecular mechanisms of the metaplastic transition in the stomach.