Cre-GFP Adeno-associated virus(AAV Serotype 6)

Scarring is more severe when the subcutaneous fascia beneath the dermis is damaged by surgery or trauma. Here, researchers performed a detailed analysis of fascia cell mobilization in acute surgical wounds, fibroblast lineage-specific transgenic mice, and skin fascia explants (scar-like tissue in a dish - SCAD) using deep tissue intravital live imaging. They observed that injury triggers swarming-like collective cell migration of fascia fibroblasts, which progressively contract the skin and form scars. Swarming is unique to fascia fibroblasts and requires upregulation of N-cadherin. Fibroblasts from the upper skin and oral mucosa have neither clustering nor N-cadherin expression, and these tissues repair wounds with minimal scarring. Blocking N-cadherin binding inhibits swarming and skin contraction, and reduces scarring in SCADs and in animals. Thus, fibroblast swarming and N-cadherin offer therapeutic avenues to inhibit fascia mobilization and pathological fibrotic responses in a range of medical settings.

Here, the researchers injected AAV6 viral particles expressing Cre recombinase (AAV6-Cre-GFP) into the fascia surrounding wounds of N-cadherin floxed mice (Ncad^fl/fl), which contains loxP sites flanking exon 1 of the N-cadherin gene. Thereafter, Cre-expressing fascial fibroblasts transduced around the wound lost N-cadherin. Compared with the control virus, the Cre-expressing virus (AAV6-Cre-GFP) led to a 65% reduction in N-cadherin expression in the scar region (Figure 1a, b) and reduced scar area and width, as confirmed by overall macroscopic and histological analysis (Figure 1c-f). More importantly, transverse histological views of the scars clearly demonstrated that the centripetal pattern of collagen fibers around the center of the scar was disrupted by N-cadherin plaque knockout (Figure 1e). Fractal analysis measurements of control scars showed that scars had typically higher fractal dimension (FD) and lower lacunarity (L) values compared to adjacent normal skin (Figure 1g). The lattice of N-cadherin knockout scars was significantly more porous and less complex (Figure 1g), suggesting that the absence of N-cadherin improves wound quality.

Figure 1. N-cadherin is crucial for scar formation in vivo. N-cadherin was locally knockout around wounds on Ncad^fl/fl mice by injection of Cre-expressing AAV6-Cre-GFP virus. AAV6-GFP virus served as control. (Jiang D, et al., 2020)