Performance of the Pollen Tube Growth Test in the COLIPA Validation Study on Alternatives to the Rabbit Eye Irritation Test.

In the present paper, we describe and analyse the performance and the results of the pollen tube growth (PTG) test applied to the COLIPA international validation study of in vitro alternatives to the Draize eye irritation test. The PTG test, based on photometric quantification of in vitro pollen tube mass production, was used by three independent laboratories to estimate the acute eye irritation potentials of 23 ingredients and 32 cosmetic formulations. Basing on historical Draize test data and on IC(50) values of previously tested cosmetic formulations, a mathematical formula was generated to predict rabbit eye irritation potentials from PTG test results. Statistical evaluation of the calculated modified maximal average scores (MMAS) revealed a high prediction capability of the PTG test in regard to the finished formulations but a relatively low one for alcohols, higher concentrated cationic surfactants, and acidic and alkaline materials. Furthermore, our results indicated that the PTG test was able to produce precise IC(50) values without any limitations from all of the 55 test substances with good intra- and interlaboratory reproducibility. From these findings we suggest that the PTG test is not a validated test at present but is considered to be a potent candidate for further validation processes. For this purpose an additional prediction model for ingredient classes as mentioned above must be generated.