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Skin irritation / corrosion

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Administrative data

Endpoint:
skin irritation: in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
13 September 2016 to 19 September 2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017
Report date:
2017

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method B.46 (In Vitro Skin Irritation: Reconstructed Human Epidermis Model Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Reference substance name:
Confidential
IUPAC Name:
Confidential
Test material form:
liquid: viscous
Details on test material:
- Appearance/physical state: Dark brown extremely viscous liquid
- Storage conditions: Room temperature in the dark

In vitro test system

Test system:
human skin model
Source species:
human
Cell type:
non-transformed keratinocytes
Cell source:
skin obtained from plastic surgery from multiple donors
Source strain:
other: adult
Vehicle:
unchanged (no vehicle)
Details on test system:
PURPOSE OF THE TEST
- The purpose of this test was to evaluate the skin irritation potential of the test item using the EPISKIN reconstructed human epidermis model after a treatment period of 15 minutes followed by a post-exposure incubation period of 42 1 hours (Fentem et al., 2001, Zuang et al., 2002, Cotovio et al., 2005, Portes et al., 2002 and Hartung, 2007). The actual post-exposure incubation period was 43.75 hours and was recorded as a deviation in the study file. The principle of the assay is based on the measurement of cytotoxicity in reconstructed human epidermal cultures following topical exposure to the test item by means of the colorimetric MTT reduction assay. Cell viability is measured by enzymatic reduction of the yellow MTT tetrazolium salt (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) to a blue formazan salt (within the mitochondria of viable cells) in the test item treated tissues relative to the negative controls. The concentration of the inflammatory mediator IL-1α in the culture medium retained following the 42-hour post-exposure incubation period may also be determined for
test items which are found to be borderline non-irritant based upon the MTT reduction endpoint. This complimentary end-point can be used to either confirm a non-irritant result or will be used to override the non-irritant result.
- The EPISKIN model is a three-dimensional reconstructed human epidermis model consisting of adult human-derived epidermal keratinocytes seeded on a dermal substitute consisting of a collagen type I matrix coated with type IV collagen. A highly differentiated and stratified epidermis model is obtained after a 13-Day culture period comprising of the main basal, supra basal, spinous and granular layers and a functional stratum corneum.
- Following a full validation study, the EpiSkin reconstructed human epidermis model showed evidence of being a reliable and relevant stand-alone test for predicting rabbit skin irritation when the endpoint is measured by MTT reduction and for being used as a replacement for the Draize Skin Irritation Test for the purpose of distinguishing between irritating and non-Irritating test items.
- The procedure followed was based on the recommended EpiSkin SOP, Version 1.8 (February 2009), ECVAM Skin Irritation Validation Study.
- Test items are applied topically as the dermal route is the most likely exposure route and the results of the study are believed to be of value in predicting the likely skin irritancy potential to man.
Control samples:
yes, concurrent negative control
yes, concurrent positive control
Amount/concentration applied:
10 μL (26.3 μL/cm2)
Duration of treatment / exposure:
15 minutes
Duration of post-treatment incubation (if applicable):
42 hours
Number of replicates:
Triplicate tissues

Results and discussion

In vitro

Results
Irritation / corrosion parameter:
% tissue viability
Run / experiment:
15-minute exposure
Value:
73.3
Vehicle controls validity:
not applicable
Negative controls validity:
valid
Positive controls validity:
valid
Other effects / acceptance of results:
DIRECT MTT REDUCTION
- The MTT solution containing the test item did not turn blue or purple which indicated that the test item did not directly reduce MTT.

ASSESSMENT OF COLOUR INTERFERENCE WITH THE MTT ENDPOINT
- The solution containing the test item was colourless.
- It was therefore unnecessary to run colour correction tissues.

TEST ITEM, POSITIVE CONTROL ITEM AND NEGATIVE CONTROL ITEM
- The individual and mean OD562 values, standard deviations and tissue viabilities for the test item, negative control item and positive control item are given in Appendix 1 (attached). The mean viabilities and standard deviations of the test item and positive control, relative to the negative control are also given in Appendix 1.
- The relative mean viability of the test item treated tissues was 73.3 % after a 15-minute exposure period and 42-hour post-exposure incubation period.
- It was considered unnecessary to perform IL-1α analysis as the results of the MTT test were unequivocal.

QUALITY CRITERIA
- The relative mean tissue viability for the positive control treated tissues was 11.7 % relative to the negative control treated tissues and the standard deviation value of the viability was 2.7 %. The positive control acceptance criteria were therefore satisfied.
- The mean OD562 for the negative control treated tissues was 0.772 and the standard deviation value of the viability was 2.0 %. The negative control acceptance criteria were therefore satisfied.
- The standard deviation calculated from individual tissue viabilities of the three identically test item treated tissues was 5.6 %. The test item acceptance criterion was therefore satisfied.

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Conclusions:
Relative to the concurrently treated negative control, the viability of the test item treated tissues was 73.3 %.
Executive summary:

GUIDELINE

The study was performed in compliance with OECD Guideline for the Testing of Chemicals No. 439 (adopted 28 July 2015) and Method B.46 in vitro skin irritation: Reconstructed Human Epidermis Model Test as described in Commission Regulation (EC) No. 761/2009, of 23 July 2009, amending, for the purpose of its adaption to technical progress, Regulation (EC) No 440/2008 laying down test methods pursuant to Regulation (EC) No. 1907/2006 of the European Parliament and of the Council on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH). The purpose of this test was to evaluate the skin irritation potential of the test item using the EPISKINT reconstructed human epidermis model after a treatment period of 15 minutes followed by a post-exposure incubation period of 42 hours. The principle of the assay was based on the measurement of cytotoxicity in reconstructed human epidermal cultures following topical exposure to the test item by means of the colorimetric MTT reduction assay. Cell viability is measured by enzymatic reduction of the yellow MTT tetrazolium salt (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) to a blue formazan salt (within the mitochondria of viable cells) in the test item treated tissues relative to the negative controls.

 

METHODS

Triplicate tissues were treated with the test item for an exposure period of 15 minutes. At the end of the exposure period each tissue was rinsed before incubating for 42 hours. At the end of the post-exposure incubation period each tissue was taken for MTT-loading. The maintenance medium from beneath each tissue was transferred to pre-labelled micro tubes and stored in a freezer for possible inflammatory mediator determination. After MTT-loading a total biopsy of each epidermis was made and placed into micro tubes containing acidified isopropanol for extraction of formazan crystals out of the MTT-loaded tissues. At the end of the formazan extraction period each tube was mixed thoroughly and duplicate 200 μL samples were transferred to the appropriate wells of a pre-labelled 96-well plate. The optical density was measured at 562 nm. Data were presented in the form of percentage viability (MTT reduction in the test item treated tissues relative to negative control tissues).

 

RESULTS

The relative mean viability of the test item treated tissues was 73.3 % after the 15-minute exposure period 42 hour post-exposure incubation period. The quality criteria required for acceptance of results in the test were satisfied.

 

CONCLUSION

Relative to the concurrently treated negative control, the viability of the test item treated tissues was 73.3 %.

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