Skin from the Factory

To be able to produce artificial skin as an in vitro test system for cosmetics and chemicals, the four Fraunhofer Institutes IGB, IPA, IPT, and IZI under the direction of Prof. Heike Walles, Fraunhofer IGB, have developed a fully automated production process for human skin equivalents and a production facility.

As part of the Fraunhofer Future Foundation funded project “Mass Customized Organ Replicates – Tissue Engineering on Demand”, the complete process chain for the production of skin models – from cell extraction, cell proliferation to the 3D tissue construction – was fully automated. Initially, the established production process was used to produce 3D skin equivalents (full skin model consisting of epidermis and dermis). Currently, the facility is being validated for epidermis models.

Skin equivalents as in vitro test systems for cosmetics, chemicals, and drugs are rare: Currently, the production of an in vitro skin test system requires six weeks and must be performed by trained personnel.

Since the manual productions is tedious and time consuming, the four Fraunhofer Institutes IGB, IPA, IPT, and IZI have taken up the challenge to develop a process and facility for the fully automated and standardized production of skin equivalents. The tolerance of cosmetics and the toxicity of chemicals can be realistically tested on these artificial tissues. This will make it possible to reduce animal experiments. Furthermore, in the long run the “skin factory” will open new perspectives in the area of skin transplantation.  

Automatable cultivation steps

Because the patented (Patent No. EP 1 290 145B1) three-dimensional (3D) skin model test system developed at Fraunhofer IGB is a well established system, it was perfectly suited as a first standard model for an automated system.

The first step in the development of automated process in tissue engineering was the analysis and understanding of all steps, from the skin biopsy to a 3D skin model, and to be able to translate them into machine processes and environments.

Within the project, the production of a synthetic collagen replacement of biocompatible and biodegradable polymers was also investigated. Another task was the development of a bioreactor for automated cell culture with a functionalized membrane for the expansion of the cells.

Validation as an alternative to animal experiments

In order for an in vitro test system to be accepted by the European Centre for the Validation of Alternative Methods (ECVAM), it must be shown that the test system is sufficiently sensitive, specific and reproducible to describe the toxicological properties of the tested substance. Manually produced epidermis models are currently being used in accordance with ECVAM guidelines as validated tests to replace animal experiments. The main objective now is therefore the validation of the first in vitro irritation skin test system (epidermis model) created from a fully automated system. We are benefitting from the existing data from previous validation studies and the existing experiences of the ECVAM with this test system. This should allow us to validate the test system within the shortest possible time period while preparing the models for commercial use.

Further information:

→ www.tissue-factory.com
→ www.igb.fraunhofer.de/en/competences/tissue-engineering/tissue-models/skin-from-the-factory.html

The fully automated manufacturing system to create a two-layer skin model (epidermis, dermis) was completed and successfully demonstrated within the three-year project deadline. It is important to note that the entire mechanical process is divided into individual modules. This allows the modules to be exchanged in order to meet the requirements of producing different tissue types.

Modular design of the fully automated production of skin equivalents

The automated process begins with the sterilization of skin biopsies. A gripper arm then transports the biopsies to a different module that separates the dermal cells and enzymes from the epidermal (Module B). These two different types of cells are then separated and seeded on cell culture surfaces and then cultured (Module C). The culture is monitored until the required numbers of cells have been grown. Once there are enough cells, the two cell types are combined to create a two-layer model. The cells forming the lower flexible dermis are then mixed with collagen (Module D). The model is then stored in a humid incubator set at body temperature for three weeks, after which the one centimeter diameter skin model is complete.

Automated, upscaled production of high-quality human epidermis

Within a few months, the Fraunhofer project consortium was able to establish the process for producing a human epidermis model for skin in an automated system. In this process, dermal cells (keratinocytes) are isolated, expanded and then cultured in specially designed and patented culture vessels to establish a properly structured epidermis. The system creates reproducible epidermis test models in large quantities that cannot be morphologically distinguished from manually prepared test models and we are currently investigating the physiological comparability between the two systems.