Disrupting biological sensors of force promotes tissue regeneration in large organisms

Tissue repair and healing remain among the most complicated processes that occur during postnatal life. Humans and other large organisms heal by forming fibrotic scar tissue with diminished function, while smaller organisms respond with scarless tissue regeneration and functional restoration. Well-established scaling principles reveal that organism size exponentially correlates with peak tissue forces during movement, and evolutionary responses have compensated by strengthening organ-level mechanical properties. How these adaptations may affect tissue injury has not been previously examined in large animals and humans. Here, we show that blocking mechanotransduction signaling through the focal adhesion kinase pathway in large animals significantly accelerates wound healing and enhances regeneration of skin with secondary structures such as hair follicles. In human cells, we demonstrate that mechanical forces shift fibroblasts toward pro-fibrotic phenotypes driven by ERK-YAP activation, leading to myofibroblast differentiation and excessive collagen production. Disruption of mechanical signaling specifically abrogates these responses and instead promotes regenerative fibroblast clusters characterized by AKT-EGR1.


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The wounds were randomly assigned to receive either FAKI hydrogel (W_HF), blank hydrogel ('placebo', W_H), or no hydrogel (wounded control, W) (n=6-9 wounds per condition). We could only perform experiments on 1 to 3 pigs concurrently. Additional experiments were performed as necessary to detect the effect of treatment across a range of variables.
We performed collagen scaffold experiments based on the availability of human clinical samples, which corresponded to the frequency of plastic surgery cases. Additional experiments were performed as necessary to detect the effect of treatment across a range of variables.
No data were excluded.
To verify the reproducibility of our findings, we performed each major experiment multiple times in order to generate biological replicates. For pig studies, several pigs were used, with different treatment conditions distributed equally across each pig dorsum to minimize any interanimal effects. All attempts at replication were successful.
For human studies, human fibroblasts were isolated from several different patients to replicate and repeat all experiments, including scRNAseq (n=3), immunofluorescent staining (n=4), qPCR (n=6), western blot (n=4), and siRNA (n=3). This ensured that all findings were translatable and reproducible across different human samples. All attempts at replication were successful.
Up to eight wounds, approximately 5cm x 5cm in size, were created on each lateral flank. The wounds were randomly assigned to receive either FAKI hydrogel (W_HF), blank hydrogel ('placebo', W_H), or no hydrogel (wounded control, W).
For each human patient sample experiment, 3 collagen scaffolds were seeded with the patient fibroblasts. These 3 collagen scaffolds would be randomly assigned to either No Strain, Strain, or Strain+FAKI groups.
Days to wound closure were determined for each wound based on blinded assessment of gross photography. Quantification of scar metrics was performed using a Visual Analog Scale (VAS) for 5 components (vascularity, pigmentation, observer comfort, acceptability, and contour) by a panel of four blinded scar experts. Cutometer measurements were made blinded to wound assignment. Counting of hair follicles and glands were made blinded to the treatment allocation. Quantification of collagen staining as well as all immunofluorescent staining was made in an unbiased manner using MATLAB image processing to quantify the amount of stain in each sample. The same threshold was used for all images.
Picrosirius red staining quantification was made in an unbiased, quantitative manner using several previously published computer algorithms. The same threshold was used for all images.
qPCR was performed and quantified by a core facility (SFGF) blinded to the treatment allocation. Western blot quantification was made blinded to the lane allocation.
For scRNA-seq, cells were processed by a core facility (SFGF) blinded to treatment allocation. For analysis, data were normalized and processed according to the Seurat package in an unbiased manner.