Reporter skin: In-vitro skin models for the detection of cell stress

Cosmetic and medical ingredients are subjected to risk assessment prior to their approval to guarantee consumer safety of preparations.

Standardized testing of substances for animal-free safety assessment: Next-Generation Risk Assessment (NGRA)

Ethical, regulatory and scientific reasons have led to the development of Next Generation Risk Assessment (NGRA), a hypothesis-driven, modern and, most importantly, animal-free risk assessment. Consequently, there is an urgent need for in-vivo mimicking in-vitro alternatives to replace previous tests for the safety assessment of substances.

Reporters skin models: Precise substance testing on living in-vitro tissue

At Fraunhofer IGB, we have established a set of in-vivo 3D reporter skin models (Burger-Kentischer et al., in-vitro 3D reporter skin model, EP 2 041 172) that represent the complex physiology of the skin, including the intact skin barrier.

Our unique selling point: Specific reporter genes make cell reactions visible by activating a signaling cascade, thus enabling rapid and precise evaluation of cell reactions in a living model - without the time-consuming preparation of histological sections for microscopic examination.

In this way, the reporter skin models can be used to determine the toxicological potential of a substance as well as to specifically and rapidly read out the activation of various cellular stress signaling pathways by the test substance in the same model. Thus, these models considerably outperform the test systems available on the market in terms of applicability and relevance.

© Fraunhofer IGB, Created with BioRender.com
Schematic representation of the principle of the 3D in-vitro reporter skin models. TF = transcription factor

Advantages

Reporter gene enables rapid and precise evaluation of cell responses in a living model
Test substances can be applied both systemically and topically to the reporter skin models.
This allows to investigate the skin penetration of a substance in addition to the skin stress potential and cytotoxicity.

Application areas

To date, various reporter skin models are available for testing skin stress, which assess parameters such as inflammatory responses in the skin. The reporter skin model set can be used to investigate potentially inflammatory allergy and ER stress inducing factors.

© Fraunhofer IGB
Querschnitt durch ein 3D In-vitro-Reporterhautmodell. Die Epidermis mit Hornschicht (pink) wird auf einer Trägermembran (grün) kultiviert.

Development and establishment of reproducible in-vivo mimickinig in-vitro reporter skin models

The organotypic reporter skin models are based on primary, immortalized keratinocytes, which guarantees a high donor-independent reproducibility. The activation of a specific cellular stress signaling pathway in these primary immortalized keratinocytes can be read out rapidly and easily by using a reporter protein that has been stably integrated into the genome via a reporter construct. These reporter keratinocytes form a multilayered epidermis in vitro. Analysis of the epidermis demonstrated a full physiological skin barrier function as well as a unique match of characteristic differentiation markers of the models with native human skin.

Customized adaptation

With our patented reporter skin models we offer a modern perspective to screen ingredients of preparations potentially coming into contact with the skin for their skin stress potential in a state-of-the-art in-vitro test system.

Upon customer request, the reporter test system can be extended to additional cellular signaling pathways and can also be applied to other organs.

Reporter systems for fast identification of immunomodulatory substances

For the identification and validation of immunomodulatory substances for the control of infections and immunological diseases, we have also introduced reporter systems for the activation of receptors of the innate immune system (PRRs) into different cell types of the 3D skin infection model. These 3D reporter skin models make it possible to measure the activation and inhibition of central signaling pathways of the innate immune system in the three-dimensional tissue context.