Transcriptional Biomarkers and Immunohistochemistry for Detection of Illicit Dexamethasone Administration in Veal Calves.

Corticosteroids such as Dexamethasone (DEX) are commonly licensed for therapy in meat animals due to their known pharmacological properties. However, their misuse aimed to achieve anabolic effects is often found by National Residues Control Plans. The setup of a complementary "biomarker based" methods to unveil such illicit practices is encouraged by current European legislation. In this study, the combined use of molecular and histological quantitative techniques was applied on formalin fixed paraffin embedded (FFPE) muscle samples to assess the effects of illicit DEX treatment on veal calves. A PCR array, including 28 transcriptional biomarkers related to DEX exposure, was combined with a histochemical analysis of muscle fiber. An analysis based on unsupervised (PCA) and supervised (PLS-DA and Kohonen's SOM) methods, was applied in order to define multivariate models able to classify animals suspected of illicit treatment by DEX. According to the conventional univariate approach, a not-significant reduction in type I fibres was recorded in the DEX-treated group, and only 12 out of 28 targeted genes maintained their expected differential expression, confirming the technical limitations of a quantitative analysis on FFPE samples. However, the multivariate models developed highlighted the possibility to establish complementary screening strategies, particularly when based on transcriptional biomarkers characterised by low expression profiles.

Regucalcin expression profiles in veal calf testis: validation of histological and molecular tests to detect sex steroids illicit administration.

BACKGROUND: Sex steroids administration in meat producing animals is forbidden within the EU to preserve consumers' safety, but continuous monitoring to identify resurgence of their misuse is needed. Among biomarkers related to sex steroids abuse in veal calves the regucalcin (RGN) mRNA perturbations in testis have been described in RNAlater samples. To setup novel diagnostic method, to update current tests available in National Residue Control Plans (NRCPs) and in legal dispute when illicit practices on farm animals are suspected, the reliability of RGN profiling was assessed by histological and molecular techniques. METHODS: Formalin fixed paraffin embedded (FFPE) testis samples, chosen being the most effective preservation strategy adopted by histological NRCPs and allowing easier retrospective analysis if required by legal disputes, were analyzed from veal calves treated with nandrolone, 17ß-estradiol and a cocktail of the two hormones. RGN levels were determined by quantitative Real Time PCR and Immunohistochemistry assays. Test performances were assessed and compared by multiple ROC curves. RESULTS: Both tests resulted sensitive and specific, allowing to enrich, in future field investigation, novel integrated diagnostic protocols needed to unveil sex steroid abuse. DISCUSSION: Developed RT-qPCR and IHC methods confirmed RGN as a useful and robust biomarker to detect illegal administration of sex steroid hormones in veal calves. The developed methods, successfully applied to ten years old FFPE blocks, could allow both retrospective analysis, when supplementary investigations are requested by authorities, and future implementation of current NRCPs.

Real-time PCR assay for detecting illicit steroid administration in veal calves allows reliable biomarker profiling of formalin-fixed, paraffin-embedded (FFPE) archival tissue samples.

In the context of mRNA biomarker profiling, formalin fixed paraffin embedded (FFPE) samples represent an interesting source for retrospective analysis. However, the implementation in routine analysis of FFPE samples, following legislation demands for validated and accredited methods, often requires critical revision and optimization. In the frame of an official control program the validation study of a molecular test for detection of sex steroids administration in calves, based on quantification of progesterone-Receptor mRNA in bulbo-urethral gland samples, was performed: analyses were made on FFPE tissues sections routinary used for histological investigations and compared with RNAlater tissue preservation. To overcome the limitations of original assays several modifications were tested. Obtained results confirmed how Progesterone-Receptor assay represent a useful tool to study suspected cases of sex steroid illicit administration in veal calves, complementary to histological and/or immune histochemical investigation, overcoming the limitation of field studies, where optimal pre-analytical condition cannot always be guarantee.