Epidermal α3β1 is required for efficient wound healing and is downregulated in aged skin

Introduction

Epidermal integrin α3β1 has emerged as a promising therapeutic target in impaired wound healing as it has been shown to be highly expressed during wound healing and has been linked to keratinocyte migration in vitro. However, its role in re-epithelialization in vivo has remained unclear. This study aims to clarify this role by using a novel inducible epidermis-specific α3 knockout (iα3eKO) murine model.

Methods

Young (8-week-old) and aged (22-month-old) iα3eKO mice were treated topically with tamoxifen (4OHT) to induce α3 knockout, or with vehicle control (acetone) 5 and 3 days prior to wounding. The backs of the mice were shaved, disinfected, then wounded with 4mm full-thickness biopsy punches. Frozen sections were prepared and immunostained with anti-integrin α3, anti-K14, anti-Ki67, and DAPI. Keratinocyte proliferation and wound re-epithelialization were assessed in each age group.

Results

Young 4OHT-treated mice exhibited markedly reduced wound re-epithelialization compared to their vehicle-treated counterparts (p<0.0001). Keratinocyte proliferation was also decreased in wound-distal hair follicles in young animals (p = 0.0235), suggesting a lack of proliferating keratinocytes contributes to the reduced wound re-epithelialization. Keratinocyte proliferation was similarly decreased in aged mice, and 4OHT treatment did not further reduce healing parameters. Additionally, our findings indicate that epidermal α3β1 levels naturally decline with advanced murine age, and preliminary results indicate that this may also occur during human aging. Therefore, we hypothesize that reduced levels of α3β1 contribute to reduced capacity for wound healing observed in the aged population.

Conclusions

Overall, our work indicates that integrin α3β1 promotes wound re-epithelialization and declines with chronological age, suggesting that wound healing mechanisms may be impaired in the elderly due to a natural decrease in α3β1 levels. Future studies will reveal whether therapeutic promotion of integrin α3β1 function will aid in wound closure in the elderly and/or in hard-to-heal wounds, in general.