Real-Time PCR as a New in vitro Biocompatibility Method to Measure Leukocyte Response to Surface Contact in Dialysis Filter Devices

Abstract

The mortality risk of dialysis patients is still elevated. Even though there is continuous improvement in the biocompatibility of dialysis devices and treatments, there is clinical evidence of a negative inflammatory impact. One dialysis-related risk factor to be considered in this regard may be the repeated blood exposure to foreign filter surfaces. Standard test methods do not allow differences to be shown between most of the common dialysis devices. A new highly sensitive in vitro test system was developed by analyzing the response of leukocytes to surface contact in dialysis filter devices by means of quantitative real time PCR and flow cytometry. Membrane surface studies provided additional physical data. An increase in the transcription level of specific pro-inflammatory genes, particularly IL-1b, TNF alpha, and IL-8, was observed after blood contact to the filter devices. In two sets of pairwise filter comparisons, radiation-sterilized filters showed stronger cell activation, more hydrophilic membranes, and rougher surfaces. Quantitative real time RT-PCR was shown to be a new in vitro test method with increased sensitivity for detecting differences in activation levels of leukocytes upon membrane contact. Correlating leukocyte activation levels with surface properties opens new opportunities for understanding leukocyte activation upon membrane contact and thus guides further improvements in the biocompatibility of dialysis filter devices.