Impact of warm ischemia on gene expression analysis in surgically removed biosamples

Surgically removed samples of high quality provide more accurate and reliable results in downstream molecular assays. Some factors, including the type of anesthesia, surgical manipulation, transport time and mode, preservation method, storage length, and number of freeze-thaw cycles, can affect biosample quality and the subsequent gene expression analysis. Warm ischemia resulting from these factors has a substantial effect on biosample quality and is the focus of this mini review. We classified the effects of warm ischemia on gene expression as (i) warm ischemia-induced metabolic activity (WIMA) in living cells and (ii) warm ischemia-induced RNA degradation (WIRD). The differential effects of WIMA and WIRD on gene expression analysis appear to depend on the period after surgical removal. WIMA predominantly affects gene expression during the early stage after surgery, whereas WIRD has a more significant effect after tissue thawing. By a literature review, we also found that RNA isolated from surgically removed biopsies is stable, and high-quality RNA can be obtained for most nonfixed human tissue maintained at room temperature during the early period after surgery. Understanding these characteristics of gene expression variation should help biomedical researchers to avoid misleading gene expression results.