Comparison of advanced therapy medicinal product gingiva and skin substitutes and their in vitro wound healing potentials.

Skin and oral mucosa substitutes are a therapeutic option for closing hard-to-heal skin and oral wounds. Our aim was to develop bi-layered skin and gingiva substitutes, from 3 mm diameter biopsies, cultured under identical conditions, which are compliant with current European regulations for advanced therapy medicinal products. We present in vitro mode of action methods to (i) determine viability: epithelial expansion, proliferation (Ki-67), metabolic activity (MTT assay); (ii) characterize skin and gingiva substitutes: histology and immunohistochemistry; and (iii) determine potency: soluble wound healing mediator release (enzyme-linked immunosorbent assay). Both skin and gingiva substitutes consist of metabolically active autologous reconstructed differentiated epithelium expanding from the original biopsy sheet on a fibroblast populated connective tissue matrix (donor dermis). Gingival epithelium expanded 1.7-fold more than skin epithelium during the 3 week culture period. The percentage of proliferating Ki-67-positive cells located in the basal layer of the gingiva substitute was >1.5-fold higher than in the skin substitute. Keratins 16 and 17, which are upregulated during normal wound healing, were expressed in both the skin and gingiva substitutes. Notably, the gingiva substitute secreted higher amounts of key cytokines involved in mitogenesis, motogenesis and chemotaxis (interleukin-6 > 23-fold, CXCL8 > 2.5-fold) as well as higher amounts of the anti-fibrotic growth factor, hepatocyte growth factor (>7-fold), compared with the skin substitute. In conclusion, while addressing the viability, characterization and potency of the tissue substitutes, important intrinsic differences between skin and gingiva were discovered that may explain in part the superior quality of wound healing observed in the oral mucosa compared with skin.

Autologous skin substitute for hard-to-heal ulcers: retrospective analysis on safety, applicability, and efficacy in an outpatient and hospitalized setting.

Chronic ulcers ((arterio)venous, decubitus, or postoperative) have no tendency to heal within a period of at least 3 months despite optimal therapy according to internationally accepted guidelines. This retrospective study evaluates the safety and efficacy of an autologous, dermal-epidermal skin substitute (SS) for treating ulcers of various origins. Ulcers were treated within 7 Dutch centers over 5 years. Sixty-six ulcers (size: 0.75-150 cm²; duration: 0.25-32 years) with a follow-up time of 24 weeks after a single-skin substitute application were assessed. Wound-bed preparation consisted of vacuum-assisted-closure-therapy (5 days, hospitalized) or application of acellular dermis (5-7 days, outpatient). Time to heal, adverse events, and recurrence 1 year after complete healing were recorded. Complete ulcer healing occurred in 36 of 66 ulcers (55%) at 24 weeks. At that time point, a further 29% of ulcers showed decrease in ulcer size between 50 and 99%. No difference was observed between the hospitalized vs. outpatient treatment with complete healing. There were 32 of 36 healed ulcers that were available for follow-up 1 year after complete closure, of which 27 (84%) were still closed. Only two minor/moderate possibly related adverse events were recorded. This retrospective analysis shows that SS provides a safe and successful treatment for particularly chronic ulcers of various origins.