Validation of reliable reference genes for qPCR of CD4+ Tcells exposed to compressive strain.

Abstract

For accurate interpretation of quantitative real-time PCR (qPCR) data, stable reference genes are essential for normalization of target genes. To date, there is no information on reliable housekeeping genes in CD4+ Tcells in athree-dimensional (3D) matrix under pressure stimulation. This in vitro study describes for the first time amethod for pressure stimulation of CD4+ Tcells in a3D matrix in the context of orthodontic tooth movement (OTM) and identifies aset of reliable reference genes. CD4+ Tcells were isolated from murine spleen and activated with anti-CD3/-CD28 Dynabeads (Thermo Fisher, Langenselbold, Germany) on standard cell culture plates or in 3D scaffolds with or without compressive strain. Expression stability of nine potential reference genes was examined using four mathematical algorithms. Gene expression of Il2 was normalized to all potential reference genes to highlight the importance of correct normalization. Cell proliferation and the expression of the surface markers CD25 and CD69 were also determined. The 3D matrix did not inhibit proliferation after immunological activation of Tcells and embedded the cells sufficiently to expose them to pressure load. Expression of ubiquitin C (Ubc) and hypoxanthine phosphoribosyltransferase (Hprt) was the most stable under all conditions tested. Acombination of these two genes was suitable for normalization of qPCR data. Normalization of Il2 gene expression showed highly variable results depending on the reference gene used. Pressure reduced cell proliferation and the number of CD69-positive Tcells. This study provides abasis for performing valid and reliable qPCR experiments with CD4+ Tcells cultured in 3D scaffolds and exposed to compressive forces simulating OTM.