Abstract
Aims and objectives
The use of autologous tissue-engineered skin substitutes is a promising approach to cover large skin defects in patients. Preclinical investigation is pivotal to test and improve the quality of these bio-engineered substitutes. In the skin, the epidermis, formed mainly by keratinocytes, provides the first physical barrier protecting from the environment. Proper keratinocyte differentiation and, thus, formation of a stratified epidermis is essential for this function. Keratins, the main structural support of keratinocytes, play a vital role regarding differentiation of keratinocytes. Here, we examined the expression pattern of a recently described keratinocyte differentiation marker, namely Keratin 24, in our skin substitutes.
Materials and Methods
Human epidermal keratinocytes, melanocytes, dermal fibroblasts, palmar fibroblasts or sweat gland cells were used to prepare skin substitutes. Fibroblast-containing collagen hydrogels were prepared, and keratinocytes or sweat gland cells and melanocytes were seeded onto the hydrogels. The generated tissue-engineered dermo-epidermal skin analogs were transplanted onto full-thickness skin wounds created on the back of immuno-incompetent rats. The skin substitutes were excised at different time points and histologically examined with regard to Keratin 24 expression.
Results
We observed the expression of Keratin 24 in keratinocytes of the upper stratum spinosum of the epidermis. In particular, we observed an intensified expression of Keratin 24 13 weeks after transplantation compared to 4 weeks after transplantation. Importantly, we noticed a markedly higher presence of Keratin 24 in more spinous layers if we used palmar fibroblasts or sweat gland cells in our skin substitutes compared non-palmar fibroblasts or epidermal keratinocytes.
Conclusion
Our observations prove that the keratinocyte differentiation marker Keratin 24 is expressed in our dermo-epidermal skin substitutes in a normal pattern. This highlights that our bio-engineered skin analogs mature and reach homeostasis in an in vivo assay. These findings harbor favorable implications regarding future clinical application.
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Acknowledgements
This work was financially supported by EU-FP6 project EuroSTEC (soft tissue engineering for congenital birth defects in children: contract: LSHB-CT-2006-037409), by the EU-FP7 project EuroSkinGraft (FP7/2007–2013: Grant agreement no. 279024), and the Clinical Research Priority Programs (CRPP) of the Faculty of Medicine of the University of Zurich. We are particularly grateful to the Foundation Gaydoul and the sponsors of “DonaTissue” (Thérèse Meier, Robert Zingg, the Vontobel Foundation, and the Werner Spross Foundation) for their generous financial support and interest in our work.
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ER and MM are co-founding members and shareholders of “Cutiss AG”, a company to fund the further development of the tissue-engineered skin substitutes. All other authors declare that they have no conflict of interest.
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Klar, A.S., Michalak, K., Böttcher-Haberzeth, S. et al. The expression pattern of keratin 24 in tissue-engineered dermo-epidermal human skin substitutes in an in vivo model. Pediatr Surg Int 34, 237–244 (2018). https://doi.org/10.1007/s00383-017-4198-9
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DOI: https://doi.org/10.1007/s00383-017-4198-9