Quantitative monitoring of the mRNA expression pattern of the TGF-β-isoforms (β1, β2, β3) during transdifferentiation of hepatic stellate cells using a newly developed real-time SYBR Green PCR

Current methods to determine the mRNA of the TGF-β-isoforms, β1, β2, and β3, are not sensitive enough to detect small alterations in the expression levels. Therefore, we established a SYBR Green I-based real-time quantitative PCR procedure with fragment-specific standards. The advantage of gene-specific quantification is the possibility to be abstain from the need to compare results with a house-keeping gene having a different sequence and PCR efficiency. Reproducibility of the results and analytical variances of the real-time PCR assays were tested. In transdifferentiating rat hepatic stellate cells (HSC) the TGF-β1-mRNA was found to be the predominant isoform expressed followed by TGF-β3 and low amounts of TGF-β2-mRNA. An alteration of the TGF-β1,-β2, and -β3 ratio during HSC transdifferentiation could not be detected. Furthermore, the GAPDH mRNA expression varied during HSC activation, and thus is not recommended as a standard in real-time PCR quantifications.