In an effort to reduce the use of animals for toxicity testing, companies have developed in vitro skin models or equivalents to replace the Draize skin irritation test. This development has been further pushed by the European Union regulation that has prohibited the use of animals for collecting toxicological data on cosmetic ingredients that began 2009. Supply of these engineered tissues skin equivalents is a significant issue that can be solved by development of effective cryopreservation methods. Presently, these constructs are made to order and require a lead time of several weeks before they can be used. A cryopreserved product would be available when needed eliminating lead time required to manufacture the product. Additionally, performance of quality control checks for stock that is ready to be shipped could be performed and large batches could be manufactured providing a cost savings to suppliers. A cryopreserved skin model would also provide the end- user greater flexibility for scheduling of experiments without concern regarding availability of the constructs and it would be possible to order from the same batch of product in order to have better control of uniformity within research studies. In Phase I, our alternate strategy, vitrification was used to successfully cryopreserve the skin construct Epiderm with a viability of 91%.
Three specific aims are proposed for Phase II. The vitrification protocol will be optimized for epithelial tissue constructs in well inserts to include not only Epiderm but other epithelial tissue constructs relevant to toxicity testing. In addition, experiments are planned to scale up the vitrification process for larger numbers of samples and determine optimum storage and shipping conditions. This optimized process would also be applicable to other tissue engineered tissue constructs, such as cardiovascular tissue equivalents.
Tissue constructs like Epiderm, have been developed by several companies to be used as in vitro replacements for the in vivo skin irritation and corrosivity tests. A preservation method for these type of constructs for skin and other tissues will insure that these constructs are readily available when needed, providing a less expensive, consistent, quality controlled product. Success in this project will help reduce the number of animals employed for research, reduce cost of tissue equivalent constructs and increase availability of human test models that may be more predictive of toxicity in humans than current live animal models.