Assessment of the use of RNA quality metrics for the screening of articular cartilage specimens from clinically normal dogs and dogs with osteoarthritis

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Abstract
Objective—To assess 2 methods of RNA purification by use of different quality metrics and identify the most useful metric for quality assessment of RNA extracted from articular cartilage from dogs with osteoarthritis. Sample Population—40 articular cartilage specimens from the femoral heads of 3 clinically normal dogs and 37 dogs with osteoarthritis. Procedures—RNA was extracted from articular cartilage by 2 purification methods. Quality metrics of each sample were determined and recorded by use of a UV spectrophotometer (Spec I; to determine the 260 to 280 nm absorbance ratio [A260:A280 ratio]), a second UV spectrophotometer (Spec II; to determine A260:A280 and A260:A230 absorbance ratios), and a microfluidic capillary electrophoresis analyzer (to determine the ribosomal peak ratio [RR], degradation factor [DF], and RNA integrity number [RIN]). The RNA was extracted from affected (osteoarthritic) articular cartilage and assessed with the same quality metrics. Metric results were compared with visual analysis of the electropherogram to determine the most useful RNA quality metric. Results—No differences in methods of RNA purification were determined by use of quality metrics. The RNA extracted from unaffected (normal) cartilage was of higher quality than that extracted from affected (osteoarthritic) cartilage, as determined by the RIN and Spec II A260:A230 ratio. The RIN and RR were the most sensitive metrics for determining RNA quality, whereas the DF was most specific. A significant proportion (32%) of RNA extracted from osteoarthritic articular cartilage specimens was determined as being of low quality. Conclusions and Clinical Relevance—No single metric provided a completely sensitive and specific assessment of the quality of RNA recovered from articular cartilage.