Collagen-Binding Peptidoglycans Inhibit MMP Mediated Collagen Degradation and Reduce Dermal Scarring

Scarring of the skin is a large unmet clinical problem that is of high patient concern and impact. Wound healing is complex and involves numerous pathways that are highly orchestrated, leaving the skin sealed, but with abnormal organization and composition of tissue components, namely collagen and proteoglycans, that are then remodeled over time. To improve healing and reduce or eliminate scarring, more rapid restoration of healthy tissue composition and organization offers a unique approach for development of new therapeutics. A synthetic collagen-binding peptidoglycan has been developed that inhibits matrix metalloproteinase-1 and 13 (MMP-1 and MMP-13) mediated collagen degradation. We investigated the synthetic peptidoglycan in a rat incisional model in which a single dose was delivered in a hyaluronic acid (HA) vehicle at the time of surgery prior to wound closure. The peptidoglycan treatment resulted in a significant reduction in scar tissue at 21 days as measured by histology and visual analysis. Improved collagen architecture of the treated wounds was demonstrated by increased tensile strength and transmission electron microscopy (TEM) analysis of collagen fibril diameters compared to untreated and HA controls. The peptidoglycan's mechanism of action includes masking existing collagen and inhibiting MMP-mediated collagen degradation while modulating collagen organization. The peptidoglycan can be synthesized at low cost with unique design control, and together with demonstrated preclinical efficacy in reducing scarring, warrants further investigation for dermal wound healing

Collagen Fibril Diameter by TEM.

<p>Representative TEM images of collagen fibrils from wounded areas and histograms of fibril diameters. There was a broader distribution of collagen fibril diameters in untreated and HA treated incisions. The DS-SILY treated wounds more closely resembled intact skin with a narrower distribution of collagen fibril diameters. Graph inserts indicate treatment type, average fibril diameter (nm), and the total range of fibril diameters (nm).</p

Tensile Strength.

<p>Mean breaking strength of healed incisions from each group of rats 21 days after surgery. ** denotes that DS-SILY treated wounds were significantly stronger than both non treated controls (NT) (p<0.001) and those receiving the HA excipient (HA) (p = 0.0178). n = 12 tissue samples (3 rats in each group).</p

Comparison of effects of decorin and DS-SILY peptidoglycan in wound healing.

<p>Comparison of effects of decorin and DS-SILY peptidoglycan in wound healing.</p

Collagen degradation by MMP.

<p>Intact collagen bands, shown above the dotted line, were quantified and used to determine the amount of collagen degraded, while collagen degradation products appear below the dotted line. Collagen degradation with MMP-1 was decreased with pre-incubation of DS-SILY from 18% to 1% (columns 2 and 3). Collagen degradation with MMP-13 was decreased with pre-incubation of DS-SILY from 55% to 15% (columns 5 and 6). Intact collagen not incubated with MMP-1 or MMP-13 (columns 1 and 4) was used for comparison.</p

Visible Scar Length.

<p>Graph comparing the visible scar lengths remaining 21 days after surgery in 3 groups of rats. The average scar length remaining from wounds receiving no treatment (NT) was set to a length of 1.0 and the visible lengths of the other wounds were expressed as fractions of the average NT length. * denotes that wounds receiving no treatment had significantly high visible scars as compared to wounds receiving HA (p = 0.0005). ** denotes that wounds receiving DS-SILY decreased the visible scar compared to both NT (p<0.0001) and to HA (p = 0.0372). n = 45 measurements.</p

Histology.

<p>Representative Mason Trichrome stained microscopic sections of healed incisions in rats at 21 days. Arrows indicate the outer limit of the granulation tissue area with no treatment (NT), HA excipient (HA), and peptidoglycan-treated wounds (DS-SILY). In each group, note the marked differences in collagen organization and maturity in the granulation tissue area. The area of granulation tissue in each image was measured in ImageJ. * denotes that DS-SILY treatment resulted in significantly smaller wound areas as compared to untreated wounds (NT) (p = 0.0109). n = 11 tissue samples.</p