Hypoxia Inducible Factor (HIF)‐1 accelerates epithelial wound healing through integrin regulation
Authors: Goggins Bridie Jane , Minahan Kyra , Outteridge Noah , Knight Darryl , Horvat Jay , Keely Simon 
Published: November 2023

Inflammatory Bowel Disease (IBD) affects over 5 million people worldwide and the rate of incidence is increasing. IBD is characterized by chronic, immune‐mediated inflammation of the gastrointestinal tract, which contributes to repeated cycles of epithelial wounding and repair. In healthy individuals, the epithelium functions as a selective barrier, critical for mucosal protection. During intestinal inflammation, loss of the epithelial barrier contributes to vascular damage, leading to reduced oxygen availability (hypoxia) at the mucosa. Wound healing processes, such as epithelial restitution occur in this hypoxic environment and are critical for the restoration of barrier integrity and gut homeostasis. This is facilitated by the transcription factor; hypoxia‐inducible factor (HIF)‐1, a key regulator of mucosal protection and wound healing during hypoxia. HIF‐1 mediates an array of protective mechanisms that promote cell survival and tissue repair. Previous work has shown that pharmacological stabilisation of HIF‐1α by prolyl hydroxylase inhibitors (PHDi) is protective in murine models of colitis. Importantly, our work has identified HIF‐1‐mediated induction of integrin‐β1 at the mucosa, as critical to this process. As integrin αβ heterodimers are key mediators of epithelial migration, we hypothesized that pharmacological HIF‐1α stabilisation accelerates epithelial restitution through integrin‐dependent pathways.

The aim of this study was to investigate the functional role of epithelial α integrin subunits dimerizing with integrin‐β1 to promote HIF‐1‐mediated wound healing and examine their post‐translational activity during HIF‐1 stabilisation.

Cell migration and inhibition scratch assays were performed on T84 monolayers to examine the functional role of HIF‐1‐induced integrins in vitro. Cells were incubated in hypoxic conditions (1% O2) and/or PHDi (AKB‐4924, 100μM) and rate of wound closure was monitored over 24 hours. Monolayers were stained by immunofluorescence for α integrin subunits at 12 hours post wound. Novel biopsy‐wound models were used to extend the study of PHDi‐mediated wound healing in vivo.

T84 monolayers displayed accelerated wound closure when treated with PHDi, which was inhibited by antibodies functionally targeting integrin‐α3. Immunofluorescent imaging of cell monolayers at 12 hours post‐wound showed both PHDi treatments and hypoxic conditions significantly increased expression of integrin‐α3 in lamellipodia localized at the leading edge of the wound. PHDi treatment also significantly accelerated mucosal wound closure in the colons of mice receiving biopsy wounds.

These data suggest that PHDi‐mediated HIF‐1 stabilization promotes mucosal healing through regulation of epithelial integrins, in particular α3β1. Integrin‐α3β1 is a key regulator of epithelial cytoskeletal organization therefore PHDi compounds may be enhancing wound closure through integrin‐α3β1‐mediated re‐organization of the cytoskeleton.

Support or Funding Information

The work was supported by an Emlyn and Jennie Thomas Postgraduate Medical Research Scholarship and National Health and Medical Research Council Project Grant APP1021582.