miRNAs are emerging as key regulators of complex biological systems in several developmental processes. qRT-PCR is a powerful tool to quantitatively assess the profiles and modulation of miRNA expression. In the emerging field of cartilage maturation studies, from precursor to hypertrophic chondrocytes, few data about miRNA regulation are available, and no consensus on the best reference gene (RG) has been reached. This is a crucial pitfall since reliable outcomes depend on proper data normalization. The aim of this work was to identify reliable and stable miRNA RGs, basing the analysis on available high throughput qRT-PCR miRNA data (from the NCBI Gene Expression Omnibus database, GSE49152) obtained from human embryonic cartilage tissues enriched in the precursor, differentiated, and hypertrophic chondrocytes. Four normalization approaches were used, and the stability was quantified by combining BestKeeper, delta-Ct, geNorm, and NormFinder statistical tools. An integrated approach allowed to identify miR-26a-5p as the most stable RG and miR-212-3p as the worst one. RNU44, used in original dataset analysis, performed as second best RG. Applications of different normalization strategies significantly impacted the profiles and modulation of miRNA expression. Herein presented results point out the crucial need of a consensus on data normalization studies aimed at dissecting miRNA role in human cartilage development, to avoid the postulation of unreliable biological conclusions.
Keywords: cartilage; chondrocyte; development; miRNA; qRT-PCR; reference gene.