SCARLESS SURGERY: ARE WE THERE YET?

Swathi Balaji and Swathi Balaji

Research Associate, Center for Molecular Fetal Therapy, Cincinnati Children's Hospital Medical Center, USA

Abstract

INTRODUCTION
More than 100 million patients acquire scars annually in the developed world, for which there is no effective therapy. The fetal response to cutaneous injury is regenerative and can be recapitulated in postnatal wounds by viral mediated over-expression of IL-10. We hypothesized that sustained delivery of biologically active recombinant IL-10 could be facilitated through a more clinically translatable hydrogel delivery system and used to promote regenerative healing in postnatal wounds.

METHODS
Optimal hydrogel composition for sustained IL-10 release was determined by evaluating in vitro multiple hydrogel formulations containing hyaluronan/heparin sulphate and collagen loaded with recombinant IL-10. IL-10 release was quantified (ELISA) and conditioned media from the gels were collected daily and used to treat adult dermal fibroblasts to quantify pericellular matrix (PCM) formation and migration. In vivo, an excisional wound model in C57BL/6J mice was used to evaluate the effects of hydrogel mediated IL-10 release on scar attenuation. 4mm wounds were evaluated at 28 days. Additional controls included, gel control, lentiviral IL-10 (LV-IL-10) and PBS (n=4/group). Histological evaluation (H&E) and capillary density (CD 31+ caps/HPF) of uninjured skin and scars were performed (n=20) and observed differences were used to establish a quantifiable parameters-based novel histologic scar scale, which was used to compare treatments. Data presented as mean+/-SD, p-values by ANOVA.

RESULTS
HH10, a gel made of 2:1:1 (hyaluronan conjugated with heparan sulphate, type-I collagen and polyethylene glycol diacrylate) and IL-10 (800ng/25ul) resulted in optimal sustained release of IL-10 in vitro, which is biologically active and increased PCM formation and migration by fibroblasts. In vivo, histologic analysis demonstrated significant differences between uninjured skin and scar in epidermal height and topography, nuclear orientation of the basal keratinocytes, scar area, dermal appendages and vascular density (column A vs.B; p<.01). HH10 treatment resulted in wound healing indistinguishable from surrounding skin, with significantly improved scar parameters compared to characteristic scar in PBS wounds (column D vs. B; p<.01). HH10 restores epidermal and dermal scar parameters to the levels observed in uninjured skin (column D vs. A; p=ns). Scar assessment reveals HH10 and viral over-expression of IL-10 are equally potent in achieving attenuation of scar (column D vs. C; p=ns). Gel treatment without IL-10 improves wound healing compared to PBS (column E vs. B; p<.05), but not to levels seen with HH10 or LV-IL-10 (column E vs. D or C; p<.05).

CONCLUSIONS
Our novel quantifiable method to assess scars histologically demonstrated that sustained release of biologically active recombinant IL-10 using a hyaluronan-based hydrogel (HH10) is capable of restoring epidermal and dermal parameters in postnatal wounds to the levels observed in unwounded skin, the benchmark of regenerative healing. HH10 obviates some of the translatable concerns with IL-10 gene therapy, and has broad potential applications beyond the cosmetic benefit, to any disease characterized by excessive fibroplasia.