CD44v9 and Cystine‐Glutamate Transporter xCT Potentiate the Defense Against ROS to Allow for Effective Healing in Response to Gastric Injury
Authors: Teal Emma L. , Chakrabarti Jayati L. , Steele Nina , Sundaram Nambirajan , Hawkins Jennifer , Wang Jiang L. , Helmrath Michael A. , Diwan Tayyab L. , Zavros Yana L. 
Published: June 2021

Background

Cluster‐of‐differentiation gene 44 (CD44) is an alternatively spliced cell surface protein that coordinates normal as well as metaplastic epithelial cell proliferation and migration. CD44 variant isoform 9 (CD44v9) is spliced by the epithelial cell‐type‐specific splicing regulator ESRP1 and has been shown to emerge transiently during gastric repair. CD44v9 stabilizes the cystine‐glutamate transporter, xCT, which provides defense against reactive oxygen species (ROS) build up and redox imbalance. ROS produced during injury is a criticial event for the development of epithelial apoptosis leading to ulceration.

Hypothesis

CD44v9 stabilizes the xCT transporter to potentiate defense against ROS to establish an environment conducive to efficient wound repair.

Methods

Acetic acid injury was induced in C57BL/6 (BL6) mice and then animals were treated with sulfasalazine (SSZ), an inhibitor of xCT‐dependent cystine transport. Mice were anlayzed between 1–30 days post‐injury. Ulcer size was measured, and CD44v9, xCT and ESRP1 expression and histology was anlayzed. Human‐derived gastric organoids from elderly (>55 years) or young (14–20 years) patients were generated. A novel scratch‐wound assay generated from 3D organoids derived from human stomachs and transferred to a 2D gastric epithelial cell monolayer (huGEM) culture was treated with SSZ. Wound closure was measured by images captured during time‐lapse microscopy and changes in CD44v9 and xCT analzyed by immunofluorescence.

Results

1) CD44v9 and xCT co‐expressing cells emerge at the ulcer margin: In BL6 mice, CD44v9‐xCT co‐expressing cells emerged at the ulcer margin within 3‐days post‐injury. Compared to control mice, BL6 mice treated with SSZ showed impaired wound healing in response to acetic acid injury. A human gastric ulcer tissue array revealed robust expression of CD44v9/xCT co‐expressing cells in the ulcerated tissue. Expression of CD44v9/xCT was not observed in biopsies collected from elderly patients. 2) Sulfasalazine inhibited wound healing in huGEM scratch wound assays: HuGEM cultures exhibited a cellular composition reflective of primary gastric tissue that included the expression of parietal, chief, and mucous neck and pit cells. CD44v9/xCT co‐expressing cells emerged at the wound edge in huGEM cultures in response to a scratch wound. HuGEM cultures treated with SSZ exhibited significantly delayed wound healing in response to a wound.

Conclusion

CD44v9 and xCT emerge during gastric regeneration which may potentiate defense against ROS to allow for effective healing. Current studies address the loss of CD44v9/xCT mechanism in the aged stomach using huGEM cultures generated from elderly patients.

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.