Building a Better Scar: Re-engineering Extracellular Matrix Structure in Dermal Scars

Introduction

Cutaneous scars represent a common surgical complication, yet no effective drug therapy for scar treatment currently exists despite huge patient and physician demand. A connexin 43 (Cx43) carboxyl terminus (CT) mimetic peptide, alpha Connexin Carboxy-Terminus 1 (αCT1), has demonstrated efficacy in improving long-term scar appearance in pre-clinical and clinical trials. However, current understanding of the mechanism-of-action by which αCT1 improves long-term scar appearance with early intervention treatment is not well understood.

Methods

In vivo: Scar biopsies from 1) human, 2) Sprague-Dawley rat, and 3) IAF Hairless guinea pig trials of αCT1 were examined for collagen matrix structure at 4 weeks (all models), and 2 and 6 weeks (rat and guinea pig models only). Collagen matrix variables examined included local disorganization of the fibers, a variable that is higher in unwounded skin compared to scar tissue, and density of the fibers, which is higher in scar tissue but can also be used as an early temporal marker of the rate of healing.

In vitro: Primary murine dermal fibroblasts were isolated from the whole dermis of 3-4 week old transgenic mice expressing collagen 1(α2) GFP-tpz. Cells were sorted for expression via FACS and plated on prealigned collagen substrate for 7 days under conditions favorable to generating extracellular matrix.

Results: All in vivo scar biopsies demonstrated some level of altered collagen matrix structure with αCT1 treatment. Treated scars had higher local disorganization of the collagen fibers within the wound, and an increase in collagen matrix density compared to control at certain earlier timepoints that tended to decrease or disappear at later timepoints. The IAF Hairless guinea pig, a novel splinted wound healing model presented herein, was found to closely replicate the human dermal collagen profile and changes in collagen profile spurred by αCT1, significantly outperforming the traditional rat model. Primary dermal murine fibroblasts treated in vitro with αCT1 significantly increased synthesis of procollagen 1, the precursor of collagen 1 necessary for constructing the extracellular matrix, suggesting that at least part of the reason for higher collagen density at early in vivo timepoints is due to increased collagen synthesis by fibroblasts.

Conclusion: αCT1 treatment in the early stages of wound healing prompts individual fibroblasts to increase their output of collagen and create a more disorganized early collagen matrix. These early changes potentially spur the long-term scar appearance improvements seen in clinical trials, and provide a basis for future work to discover the cellular pathways to alter in order to improve wound healing and cutaneous scarring outcomes.