Beta‐catenin regulates wound size and mediates the effect of TGF‐beta in cutaneous healing

Abstract

After cutaneous injury, a variety of cell types are activated to reconstitute the epithelial and dermal components of the skin. beta-Catenin plays disparate roles in keratinocytes and fibroblasts, inhibiting keratinocyte migration and activating fibroblast proliferation, suggesting that beta-catenin could either inhibit or enhance the healing process. How beta-catenin functions in concert with other signaling pathways important in the healing process is unknown. Wound size was examined in mice expressing conditional null or conditional stabilized alleles of beta-catenin, regulated by an adenovirus expressing cre-recombinase. The size of the wounds in the mice correlated with the protein level of beta-catenin. Using mice expressing these conditional alleles, we found that the wound phenotype imparted by Smad3 deficiency and by the injection of TGFbeta before wounding is mediated in part by beta-catenin. TGFbeta was not able to regulate proliferation in beta-catenin null fibroblasts, whereas keratinocyte proliferation rate was independent of beta-catenin. When mice are treated with lithium, beta-catenin-mediated signaling was activated in cutaneous wounds, which healed with a larger size. These results demonstrate a crucial role for beta-catenin in regulating cutaneous wound size. Furthermore, these data implicate mesenchymal cells as playing a critical role regulating wound size.

A Quantitative Approach to Scar Analysis

“…Previous studies have used only the width of the fibrotic area as a measure of scar size and did not delineate the entire scar area. 29,30 By dividing the scar area by the corresponding average scar thickness, our methodology not only measures the entire scar area but is also able to account for variability in skin thickness. Using this approach, we demonstrated that in addition to anatomic regional differences, various other factors such as age, sex, and scar age could influence dermal thickness.…”

Fibronectin and β-Catenin Act in a Regulatory Loop in Dermal Fibroblasts to Modulate Cutaneous Healing

“…NaCl or LiCl was added to the drinking water to a final concentration of 0.014 M. This dosage was previously shown to elevate ␤-catenin in mesenchymal cells in mice (6,36). An adenovirus that expresses DKK-1 (32), CRE-recombinase, or GFP as a control (6), was administered to wild type or genetically modified mice 4 days prior to wounding.…”

“…NaCl or LiCl was added to the drinking water to a final concentration of 0.014 M. This dosage was previously shown to elevate ␤-catenin in mesenchymal cells in mice (6,36). An adenovirus that expresses DKK-1 (32), CRE-recombinase, or GFP as a control (6), was administered to wild type or genetically modified mice 4 days prior to wounding. The mice were injected subcutaneously with the adenovirus at a titer of 1 ϫ 10 8 plaque-forming units at the future wound site, and also intraperitoneally, as previously reported (6,37,38); Eda Fn Ϫ/Ϫ ; Catnb tm1Tak mice were injected with a dose of 5 ϫ 10 7 plaqueforming units/site of an adenovirus driving expression of CRErecombinase, or GFP, as previously reported (6).…”

“…An adenovirus that expresses DKK-1 (32), CRE-recombinase, or GFP as a control (6), was administered to wild type or genetically modified mice 4 days prior to wounding. The mice were injected subcutaneously with the adenovirus at a titer of 1 ϫ 10 8 plaque-forming units at the future wound site, and also intraperitoneally, as previously reported (6,37,38); Eda Fn Ϫ/Ϫ ; Catnb tm1Tak mice were injected with a dose of 5 ϫ 10 7 plaqueforming units/site of an adenovirus driving expression of CRErecombinase, or GFP, as previously reported (6). Wounds were harvested at either 5, 7, 12, or 14 days after injury, and the wounds were examined for size, cellularity, and ␤-catenin protein levels.…”

“…Wound fibroblasts have elevated ␤-catenin protein levels and exhibit ␤-catenin-mediated T-cell factor (Tcf)-dependent 3 transcriptional activity during the proliferative phase of healing. Furthermore, ␤-catenin levels correlate with the size of the scar that forms, and genetic stabilization of ␤-catenin leads to hyperplastic scars in mice (3,6). ␤-Catenin acts as a transcriptional co-activator but also associates with cadherins at adherens junctions to maintain cell-cell contacts (7).…”